A method for treatment of biomass

Abstract

A method and system for treatment of biomass / organic material in which steam, generated by evaporative or vacuum / evaporative cooling of a thermally pre-treated biomass / organic material, is used for steam stripping of an anaerobically digested biomass / organic material or reject water from dewatering. In the present invention, steam resulting from evaporative or vacuum / evaporative cooling of biomass / organic material treated in a thermal pretreatment step, e.g. comprising THP, HTC, Wet Oxidation, HTL and / or SCWO, "Upstream" of a biological process, e.g., an anaerobic digestion, is used to carry out steam stripping for removal of ammonia from a digestate "Downstream" of an anaerobic digestion.

Description

[0001] A METHOD FOR TREATMENT OF BIOMASS

[0002] Field of the invention

[0003] The pre-treatment of biomass / organic materials at elevated temperatures prior to the subsequent conversion / processing of the biomass / organic material in downstream biological processes, such as anaerobic digestion, is becoming increasingly popular.

[0004] Known treatments at elevated temperatures can, depending on the temperature, be divided into three main categories.

[0005] • Treatment of the biomass / organic material at relatively high temperatures, typically above 100 °C, and pressures, such as by THP (Thermal Hydrolysis ProcessP), HTC (Hydrothermal Carbonization), partial Wet Oxidation, , aimed at optimizing the conversion / processing of the biomass / organic material in downstream biological process steps, such as anaerobic digestion.

[0006] • Treatment of the biomass / organic material at a temperature, which is sufficiently low to allow for a specific desired biological activity, e.g., thermophilic digestion at 45°C to 65°C and / or thermophile acid fermentation at 50°C to 70°C, which specific biological activity is aimed at optimizing the conversion / processing of the biomass / organic material in downstream biological process steps, such as an anaerobic digestion.

[0007] • Treatment of the biomass / organic material at a sufficiently high temperature to allow for hygenization at 70°C to 135°C, e.g., pasteurization (whether in the form of High-Temperature Short Time, (HTST), Extended Shelf Life (ESL) or Ultra-High Temperature (UHT) treatment), of the biomass / organic material but not otherwise aimed at optimizing the conversion / processing of the biomass / organic material in downstream biological process steps, such as anaerobic digestion.

[0008] Such a thermal pre-treatment of the biomass / organic material (such as by e.g., the above-mentioned THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or hygenization / pasteurization), in most embodiments will involve a need for cooling the biomass / organic material after the thermal pre-treatment and prior to subjecting it to further treatment in downstream biological processes, i.e., it will involve a need for cooling “Upstream” of the biological processes, if these operate at lower temperatures.

[0009] In case of downstream biological processes in the form of anaerobic digestion, e.g., in the production of biogas, these can operate under different temperature regimes, each supporting various communities of microorganisms. The two primary temperature ranges for anaerobic digestion are mesophilic and thermophilic digestion. As regards mesophilic digestion a typical temperature range is from 30°C to 45°C, with the most common operating temperature being around 37-40°C. Mesophilic digestion is widely used because it offers a good balance between operational stability and efficiency. The mesophilic microorganisms are relatively tolerant of changes in environmental conditions, making this range popular for many anaerobic digestion applications. Thermophilic digestion is typically performed in a temperature range from 50°C to 60°C, and some systems might operate at up to 70°C for specific substrates or to achieve higher pathogen reduction. Thermophilic digestion may in itself lead to higher biogas yields and faster processing times compared to mesophilic digestion, as well as enhanced pathogen reduction in the resulting end-product. However, it requires more energy for heating and can be more sensitive to operational upsets. The choice between mesophilic and thermophilic digestion often depends on the specific goals of the anaerobic digestion process, such as the desired biogas production rate, feedstock characteristics, and requirements for pathogen reduction.

[0010] As of today, several methods are used for such “Upstream” cooling steps, some of which are concomitantly aimed at recovering energy released as part of the cooling. Commonly used methods involve traditional liquid / liquid heat exchangers of either the tube-in-tube, shell and tube, or spiral type.

[0011] When designing a liquid-liquid heat exchanger, several factors must be considered to ensure optimal performance, including thermal performance, pressure drop, material selection, flow arrangement (co-current, counter-current, or cross-flow). Likewise, both the initial cost and the operating costs over the lifetime of the heat exchanger must be considered. Hence, the specific design of a liquid-liquid heat exchanger is highly dependent on its intended application, the properties of the fluids involved, and the required thermal performance.

[0012] Biomass / organic material used for biological processes, such as anaerobic digestion, commonly have much higher viscosity than water and have a water content below 97%, such as 92-96%, typically between 88 and 95%, and sometimes even as low as 75-87%, such as between 77 and 85%, such as between 78 and 83%, such as 80%, corresponding to dry matter concentrations from 2-4%, typically between 5 and 12%, and sometimes even as high as 13-25 %, such as between 15 and 23%, such as between 17 and 22%, such as 20%. Consequently, it is necessary to have turbulent flow to achieve high heat transfer coefficients in a liquid-liquid heat-exchanger and this becomes increasingly difficult with more viscous fluids. Thus, due to high viscosities and relatively low flow rates possible with the biomass / organic material processed in practice, heat exchangers for these types of processes are commonly designed with relatively low heat transfer coefficients, typically in the range between 150 to 650 [W / (m2*K)] and most commonly near 300 [W / (m2*°K)]. Liquid-liquid heat exchangers with low heat transfer coefficients results in large heat transfer surfaces but does allow for lower flow velocities. Also, even if increased heat transfer coefficients can be achieved, this typically involves increased pumping demands and reduced cooler dimensions. Thus, in addition to challenges resulting in low heat transfer coefficients, liquid-liquid heat exchangers for these processes often suffer from fouling and clogging resulting in high maintenance needs.

[0013] Evaporative cooling of thermally treated biomass / organic material to reduce the temperature of the material and to recover heat, has previously been described in e.g. WO2016066752 A1 , in which thermal hydrolysis is performed at a temperature above 140°C, and is followed by a wet explosion, carried out by means of reducing the pressure from 5-35 bar to a pressure below 2 bar, preferably approximately 1 bar, i.e. atmospheric pressure, thereby resulting in an intermediate product having a dry matter concentration above 25% and a temperature above 90°C and steam. WO2016066752 A1 describes that this steam (being at either atmospheric pressure or above) can be indirectly recovered in e.g. a condenser cooler, and that this heat may be used to either heat or pasteurize other process streams comprising materials of organic origin that are to be added to the pre-treated material prior to digestion, e.g. liquid manure, or pre-heat the biomass in a pre-heating tank before the biomass is subjected to thermal hydrolysis. WO2016066752 Alalso describes that the steam from the wet-explosion step may be used to pre-heat the biomass in a pre-heating tank before the biomass is pumped to the reactor(s).

[0014] Recently, also evaporative / vacuum cooling of thermally treated biomass / organic material to reduce the temperature of the material and to recover heat, has been demonstrated at commercial scale. Hence, e.g., W02021018780 A1 describes a process for the treatment of biomass / organic material which comprises the steps of: (1) performing a thermal pre-treatment of said biomass / organic material, thereby providing a thermally pre-treated biomass / organic material, (2) cooling said thermally pre-treated biomass / organic material, thereby providing a cooled pre-treated biomass / organic material and a vapor phase comprising steam, and (3) subjecting said cooled pre-treated biomass / organic material to further biological processing, wherein the cooling (of step 2) is performed using a evaporative / vacuum cooling step.

[0015] In a vapor phase, the substances exist in a gaseous form, distinct from their liquid or solid phases under specific conditions of temperature and pressure. Hence, from a physical standpoint, the vapor phase is characterized by the state in which particles (atoms or molecules) have enough kinetic energy to overcome intermolecular forces that keep them in a liquid or solid state. This phase is typically observed above the boiling point of a substance at atmospheric pressure, but it can also exist at lower temperatures as evaporation occurs from the surface of a liquid. The transition to the vapor phase is governed by factors like temperature, pressure and chemical potential’. For example, at boiling point, the vapor pressure of a liquid equals the external pressure, facilitating the transition of liquid molecules into the vapor phase. Chemically, the vapor phase refers to the composition and behavior of substances in their gaseous form. This includes the reactions and interactions that occur between gas-phase molecules, which can be significantly different from those in liquid or solid states due to the increased distance and freedom of movement of the atoms or molecules. In mixtures, a vapor phase composition can vary widely and is often described by partial pressures of each component, according to Dalton’s Law of Partial Pressures.

[0016] Hence, as should be clear from the above one form of vapor, which may form part of a vapor phase, is water vapor, which is, e.g., formed when water evaporates from surfaces, boils, or sublimates from a solid state (ice) directly into a gas, bypassing the liquid phase. The amount of water vapor atmospheric air can hold depends on the temperature, with warmer air capable of holding more water vapor than cooler air. Steam is water vapor produced when water boils and transforms from liquid to gas at or above its boiling point (100°C at atmospheric pressure at sea level). Steam carries significant amounts of thermal energy, in the form of latent heat, making it useful in heating and power generation. Steam can exist in different states, including saturated steam (where liquid water and steam exist in equilibrium at the boiling point) and superheated steam (heated beyond the boiling point at a given pressure, without the presence of water droplets).

[0017] Both evaporative cooling (as e.g. described in WO2016066752) and vacuum / evaporative cooling (as e.g. described in W02021018780 A1) of a biomass / organic material will involve removal of water vapor, i.e. steam, thereby released from the biomass / organic material. In the processes described in e.g. W02021018780 A1 , biomass / organic material is introduced into a vessel, which is connected to a vacuum pump, and it is described that the vapor, i.e. steam, produced in the cooling step (2) may be indirectly condensed in other unit operations, e.g. condenser heat exchangers, or that it may be condensed directly and used to pre-heat biomass / organic material entering either the thermal pretreatment step (1), e.g. by direct injection of the recovered steam produced in the evaporative / vacuum cooling step (2) into the biomass / organic material, or other pretreatment steps.

[0018] Apart from water (steam), applying vacuum conditions after a thermal pretreatment of a biomass / organic material, e.g., by THP, HTC and / or partial Wet Oxidation, can lead to the evaporation of various components, substances, and gases from the material. The application of a vacuum reduces the boiling points of these components, facilitating their separation from the treated biomass. The specific substances that evaporate under these conditions typically include Volatile Organic Compounds (VOCs), Ammonia (NH3), Hydrogen Sulfide (H2S), Carbon Dioxide (CO2), Light Hydrocarbons, such as alkanes (e.g. methane (CH4), ethane (C2H6), propane (C3H8), and butane (C4HI0)), alkenes (such as ethylene (C2H4) and propylene (C3H6)), alkynes (such as acetylene (C2H2), though it's less commonly found in natural hydrocarbon sources compared to alkanes and alkenes) and aromatics (such as benzene (C6H6). The evaporation of these components under vacuum may from an overall point of view be beneficial for reducing the volume of the material to be further treated, removing potentially harmful substances, and improving the overall efficiency of the intended process. However, the management of the evaporated gases and compounds, particularly those that are odorous, toxic, or greenhouse gases, is, nonetheless a critical consideration in the design and operation of the treatment facility.

[0019] Thus, a vapor phase resulting from subjecting a thermally pretreated (e.g., by THP, HTC and / or partial Wet Oxidation,) biomass / organic material to vacuum / evaporative cooling, may be made up partly or entirely of water vapor, which water vapor may be steam. The design of condenser heat exchangers for indirect condensation as described in W02021018780 A1 focuses on efficiently transferring heat from the vapor phase, comprising steam, to a cooling medium (often water), thereby causing the vapor, i.e. , primarily the steam, to condense. There are several types of condenser heat exchangers, each tailored to specific applications and working fluids. The most common types include shell and tube condensers, plate condensers, and air-cooled condensers. Key design considerations in case of condenser heat exchangers are the choice of cooling medium, thermal performance, material selection, pressure drop, condensate removal, fouling and cleaning, and energy efficiency. Designing for a minimal pressure drop on both the vapor and cooling medium sides is essential to maintain system efficiency and reduce energy costs. In many applications, the efficiency of the condenser directly impacts the overall energy efficiency of the system. Optimizing heat transfer and minimizing losses are crucial.

[0020] In relation to the biomass / organic materials of relevance to the present invention and the methods and systems described in, e.g., W02021018780 A1, it needs to be considered that the boiling point for water, which will be the most abundant constituent of any vapor phase in the context of the present invention, decreases with decreasing pressure. Hence, for most biomass / organic materials relevant to the methods and systems described in, e.g., WO2021018780 A1, it will typically be necessary to maintain the evaporative / vacuum cooling system well below ambient pressure to be able to remove heat from the liquid biomass / organic material through evaporation of water which can then be condensed in a condenser heat exchanger.

[0021] As mentioned above, the water vapor, i.e., steam, created in evaporative / vacuum cooling is most frequently removed by indirect condensation. Also, as the biomass / organic material is not in direct contact with the surface of any applicable heat exchanger, the risk of fouling and abrasion of such a heat exchanger is considerably reduced compared to traditional liquid-liquid heat exchangers, just like the need to overcome large pressure losses associated with pumping highly viscous fluids through a heat exchanger is avoided.

[0022] In indirect condensation in a condenser heat exchanger, the vapor, which comprises steam, and the cooling water are kept separate by a solid barrier which most commonly is a metal with sufficient strength and sufficient heat conductivity. The most common barrier materials are different grades of stainless steel (whether Austenitic, Ferritic, Martensitic, Precipitation Hardening, Duplex, Nitronic, A286, Alloy 20 or Super duplex), brass, and titanium. However, other metals and non-metallic materials, e.g., glass, can be used. Condensers of this type typically achieve heat transfer coefficients greater than 1000 W / (m2*K). To handle the condensate formed on the vapor side of the condenser cooler, such coolers are commonly built as plate or shell and tube heat exchangers where the force of gravity facilitates condensate to flow out from the condenser cooler. Plate and shell and tube heat exchanger designs are often the most economical options for achieving large surface areas and small footprints for condenser coolers.

[0023] For direct condensers, vapors from the liquid (which is cooled) may be brought in direct contact with a cooling medium. The heat transfer coefficients in direct condensers can therefore potentially be significantly higher than indirect condenser heat exchangers. This is possible to be achieved because the heat transfer is not limited by the heat conductivity of the solid barrier required for indirect condenser heat exchangers.

[0024] As mentioned above, solid organic material in the liquid biomass / organic material will in liquid-liquid heat exchangers be in direct contact with the heating or cooling surface. This is not the case for neither evaporative nor evaporative / vacuum cooling, where the liquid is cooled through heat of evaporation and the resulting vapor is brought in contact with, e.g., a cooling surface. Some organic material may be carried with the vapors transferred to, e.g., the condenser heat exchanger, but this will primarily be specific constituents of the biomass / organic material and also the amounts will be minor compared to that for liquid-liquid heat exchangers. Hence, the risk for fouling and abrasion is greatly reduced when using condenser coolers instead of liquid-liquid heat exchangers.

[0025] A potential drawback with evaporative / vacuum cooling is that any non-condensable gasses (NCG) in the vapor must be removed from the vacuum system.

[0026] Removal of NCG is a challenge in cooling systems applying indirect cooling using condenser coolers if the biomass / organic material contains large amounts of entrained or dissolved gases which are released and are non-condensable under the conditions present in the condenser cooler. The density of NCG decreases with decreasing pressure. Even if the volume of NCG that the vacuum system must remove may be minimized by efficient removal of the condensable gases in the vapor through condensation, the volume of any NCG will increase significantly at low temperature and low pressure, which tends to increase the costs and energy demand for the applicable vacuum system. Equipment for removal of NCG typically has a capacity measured in volume. With decreasing density, the required volumetric capacity increases. This results in larger capacity requirements and increased energy costs for maintaining condenser coolers at lower temperatures and pressures. Equipment used for removing NCG can be of an ejector type, but vacuum pumps such as liquid ring are more commonly used.

[0027] In case a cooled pre-treated biomass / organic material is intended to be processed in a biological process in the form of anaerobic digestion, the upper limit as regards how much of a biomass / biological material can be treated in a given system is, apart from viscosity-derived limitations, often limited by the total ammoniacal nitrogen (TAN) concentration reached in the digester. For most biomass / organic materials relevant in the context of, e.g., W02021018780 A1, and always for biomass / organic materials in the form of wastewater treatment plant sludges, the viscosity increases with increasing solid concentrations. With increasing viscosity, it becomes more challenging to maintain sufficient digester mixing and this sets a practical limit for digester solid feed concentrations for most plants without thermal pre-treatment technology. Through thermal pre-treatments, such as THP, HTC and / or partial Wet Oxidation, the viscosity of a biomass / organic material is significantly reduced. This shifts the limit for digester feed concentrations to a higher level.

[0028] However, as thermal pre-treatments of organic material results both in an increase in the maximum overall conversion of the biomass / organic material in the biological process and in a reduction of the viscosity of the material, applying a thermal pretreatment in relation to an anaerobic digestion will often result in the total ammoniacal nitrogen (TAN) concentration being the true limiting factor of the maximum possible feed (concentration) to the digester.

[0029] Hence, for most pre-treated biomass / organic materials in the form of sludges originating from wastewater treatment plants, viscosity and digester mixing will not be limiting factors. Instead, nitrogen released in the form of ammonium and ammonia becomes limiting. Biomass / organic materials in the form of municipal sludges pretreated with, e.g., THP, HTC and / or partial Wet Oxidation, are more easily converted into biogas. Not only are conversion rates higher, but under the practical constraints for design of anaerobic digesters, more of the solids can potentially, depending on process conditions, be converted into biogas. Practical limitations aimed at here are factors such as not allowing for infinite residence time in the digesters. Through the biological conversion in the anaerobic digester, nitrogen present in the biomass is mineralized and released in the form of ammonia or ammonium. More ammonium and ammonia are released with higher solid conversion levels. High levels of ammonium inhibit the micro-organisms producing methane, resulting in buildup of acids leading to an eventual collapse of the microbial community responsible for the conversion of organic acids into methane. As a result of higher solids feed concentrations and higher conversion levels, ammonia and ammonium concentrations are typically significantly higher in digesters with pre-treatment, such as THP, HTC and / or partial Wet Oxidation, compared to plants without thermal pre-treatment. For most full-scale plants in operation today which are equipped with THP and / or HTC and / or partial Wet Oxidation, for treatment of biomass / organic materials in the form of municipal sludge, the digester feed concentration is limited to between 8 and 12 %DS to avoid ammonia inhibition while viscosity and digester mixing are not limiting. In comparison, conventional plants without pre-treatment typically have a solids feed concentration between 2 to 8 %DS, depending on process design and the type of sludge that is treated.

[0030] The Increased conversion of biomass / organic material achievable with thermal treatments in the context of municipal wastewater results in increased ammonia return loads from the sludge treatment line back to the inlet of the wastewater treatment plant. The increased return load can be centrate or filtrate returned to the wastewater treatment plant before this is discharged or subjected to other further wastewater purification methods for removing or recovering specific compounds. It can also be centrate or filtrate that is returned to upstream of the process and reused as dilution water or process water with or without further purification, depending on the required water quality. An increased release of ammonia during anaerobic digestion, will in many cases result in increased treatment cost and often also require different dedicated side stream treatments, which will result in higher operational costs for the water treatment line at the wastewater treatment plant and increased capacity requirements for nitrogen removal. In several cases, it is therefore decided to build dedicated treatment plants based on technology such as Annamox for treatment of the return stream from anaerobic digestion processes equipped with thermal pretreatment.

[0031] In the Anammox process, however, the ammonia is converted to N2and N2O, the latter of which is a greenhouse gas, and the potential fertilizer value of the nitrogen is lost. As part of efforts to reduce the overall carbon footprint and operational costs, several wastewater treatment plants have chosen to invest in ammonia recovery systems. The most common process for achieving this is based on ammonia stripping followed by absorption columns to produce ammonia sulphate or similar products. There are two major types of ammonia stripping: air stripping and steam stripping, which may both include the addition of chemical additives to increase pH. Steam stripping is commonly considered to be the most capable stripping process for ammonia removal. However, this process typically consumes large amounts of heat energy, and thus steam stripping is typically not feasible at Water Resource Recovery Facilities (WRRF) if no waste heat is available. Hence, due to lower energy demands air stripping is the most commonly used method to recover ammonia at Waste Water Treatment Plants (WWTP’s). For both air stripping and steam stripping, capital expenditure (CAPEX) requirements are high. Particularly, the space requirements for air stripping are high.

[0032] Thus, due to both technological and economic challenges, neither ammonia steam stripping nor ammonia air stripping is widely used commercially at WRRFs today.

[0033] Hence, it would be desirable in such systems to be able to treat processed biomass / organic material, i.e., “Downstream” of the biological processes, in side streams in the form of alternative ammonia recovery systems.

[0034] In particular, it would be desirable to be able to treat the digested biomass / organic material “Downstream” from an anaerobic digester, commonly referred to as digestate, in side streams in the form of an alternative ammonia recovery system. Likewise, it would be desirable to be able to treat part of e.g. a digestate, e.g. the liquid fraction of a digestate, which has been subjected to a liquid / solid separation step generating a solid fraction and a liquid fraction with a reduced content of solids, in side streams in the form of an alternative ammonia recovery system. Such a liquid fraction, also sometimes referred to as “reject water”, "centrate” or “filtrate" could in principle be any liquid that is separated from the solid fraction of a material at any stage during the various treatment processes of a process involving the pre-treatment of biomass / organic materials at elevated temperatures prior to the subsequent conversion / processing of the biomass / organic material in downstream biological processes, such as anaerobic digestion. In some scenarios it could be the reject water from the so-called final dewatering, i.e. the last step in many sludge treatment processes, where water is removed from the resulting sludge to reduce its volume and weight, making it easier and more cost-effective to handle, transport, and dispose of or use. This is achieved through various methods such as centrifugation, belt filter presses, screw presses, or filter presses. The goal is to separate the sludge / biomass / organic material into a fraction with increased solids content, producing a cake-like material, and a liquid fraction with decreased solids content. The choice of dewatering technology can depend on several factors, including the desired dryness of the material, the specific characteristics of the material, operational costs, and environmental regulations.

[0035] In light of the above, the present invention provides such a method / system using excess heat from “Upstream” thermal pre-treatment of a biomass / organic material, such as by THP, HTC and / or partial Wet Oxidation for the removal of ammonia from a digestate or the liquid or solid fraction of a digestate, which has been subjected to a liquid / solid separation step, e.g. in the form of the reject water from a final dewatering step, “Downstream” of an anaerobic digestion.

[0036] Background of the invention

[0037] As will be clear from the below, the methods and systems described in the prior art differ significantly from the methods and systems of the present invention.

[0038] WO2020126397A1 describes a system / method to reduce the steam consumption for THP of biomass / organic material by using steam from evaporative / vacuum cooling of the biomass / organic material after the THP reactor to preheat biomass / organic material before the THP reactor. In the system described the first preheating tank / pulper is placed below atmospheric pressure. The first pulper is directly connected to the headspace of a second flash tank. A differential pressure between the first pulper and the second flash tank drives vapor from the second flash tank to the first pulper. In the first pulper the vapor is brought into contact with the biomass / organic material. This leads to condensation of part of the vapor and at the same time increases the temperature of the biomass / organic material. The biomass / organic material is then transferred to a second pulper at above atmospheric pressure connected to the head space of a first flash tank. The process described leads to both reduced steam consumption for the THP process by improved heat integration and at the same time a cooling of the hydrolyzed biomass / organic material before further biological treatment. WO2020126397A1 does not in any way describe that the vapor from the second (vacuum) flash tank, i.e. “Upstream” of the biological treatment, could be used "Downstream” of the biological treatment to facilitate e.g. ammonia stripping. As already mentioned above WO2016066752 A1 describes methods and systems for thermal hydrolysis of biomass / organic material having a dry matter content in the range from 25% to 90%DS, or above 45%DS (typical for several cellulosic materials), in which the thermal hydrolysis is performed at a temperature above 140°C, and is followed by wet explosion, carried out by means of reducing the pressure from 5-35 bar to a pressure below 2 bar, preferably approximately 1 bar, i.e. atmospheric pressure, thereby resulting in an intermediate product having a dry matter concentration above 25% and a temperature above 90°C, which intermediate product is subsequently fermented in a digestion tank, by mixing it into part of the content of said digestion tank, which is being transported in a recirculation loop emerging from said digestion tank. According to WO2016066752 A1 this makes it possible to achieve solid (SRT) and hydraulic retention times (HRT), the latter being a measure of the average length of time a soluble compound remains in the digestion tank, in the order of 10-40 days (SRT), preferably 20-40 days (SRT), 10-40 days (HRT), preferably 15- 30 days (HRT), thereby ensuring a longer exposure of and thus an increased Volatile Solids Reduction (VSR) of hard degradable solids present in the biomass.

[0039] WO2016066752 A1 also describes how heat from the steam from the wet explosion can be indirectly recovered in e.g. a condenser cooler, and that this heat may be used to either (e.g. if the intermediate product has a temperature above 100°C) heat or pasteurize other process streams comprising materials of organic origin that are to be added to the pre-treated material prior to digestion, e.g. liquid manure, or pre-heat the biomass in a pre-heating tank before the biomass is subjected to thermal hydrolysis. WO2016066752 A1 also describes how heat from the steam from the wet explosion can be recovered by returning flash steam from the wet-explosion step performed in one or more pressure relief tanks to be used to pre-heat biomass in a pre-heating tank before the biomass is pumped to the reactor. Hence, WO2016066752 A1 describes using energy recovered by evaporative cooling of a thermally pretreated biomass / organic material to preheat biomass / organic material upstream of the thermal pretreatment. However, WO2016066752 A1 does not describe that vapor released from the evaporative cooling of a thermally pre-treated biomass / organic material “Upstream” of a biological treatment process could be used “Downstream” of the biological treatment of such a biomass / organic material to facilitate ammonia stripping.

[0040] As also already mentioned above W02021018780A1 describes a system / method for cooling biomass / organic material after a thermal process before subjecting it to a biological treatment. The system described utilizes evaporative / vacuum cooling to cool the thermally pretreated biomass / organic material and uses direct condensation of the vapor thereby released in a subsequent condenser to preheat an incoming flow of biomass / organic material before the thermal pre-treatment. W02021018780A1 does not describe the possibility of recovering ammonia from the vapor used for the (pre)heating process. Also, the process described exclusively involves biomass / organic material, which has not yet been subjected to an anaerobic digestion. Therefore, the amount of ammonia in the material is low, as this has not yet been fully released / created from the degradation of proteins. Furthermore, W02021018780A1 does not describe the possible use of a de-gasser before the flash tank. This will significantly increase the size and energy consumption of the equipment for generating the vacuum.

[0041] Hence, both W02021018780A1 and WO2020126397A1 describe using energy recovered by evaporative / vacuum cooling of a thermally pretreated biomass / organic material to preheat biomass / organic material upstream of the thermal pretreatment. However, neither WO2021018780A1 nor WO2020126397A1 describe that the vapor released from the vacuum / evaporative cooling of a thermally pre-treated biomass / organic material “Upstream” of a biological treatment process could be used “Downstream” of the biological treatment of such a biomass / organic material to facilitate ammonia stripping.

[0042] WO2023225278A1 describes a system / method with a thermal treatment above 121 ° C (THP) of biomass / organic material (in the form of sludge) followed by anaerobic digestion. A vacuum is applied either upstream of, downstream of or directly on the anaerobic digester. The vacuum applied will cause water and volatile components (ammonia and VFA’s are mentioned) to evaporate, which is then recovered by condensation, regardless of whether the vacuum is applied upstream of, downstream of or directly on the anaerobic digester. The technical effects described in WO2023225278A1 is that it enables the decoupling of hydraulic retention time and solid retention time, by the removal of the water, and that it facilitates the separation and recovery of resources such as ammonia and VFAs, while simultaneously enhancing sludge thickening. The heat needed for the evaporation is transferred to the biomass / organic material by indirect heat exchangers. Again, WO2023225278A1 does not describe recovering heat to be used indirectly or directly for a “Downstream” stripping / evaporation of ammonia by applying vacuum on the thermally pre-treated biomass / organic material “Upstream” of the anaerobic digestion and transferring the vapor thereby produced to the "Downstream” stripping / evaporation process. Likewise, Farokh Laqa Kakar, Frances Okoye, Hussain Aqeel, Steven N. Liss, Elsayed Elbeshbishy, 2023, “Integrating Hydrothermal Pre-treatment and Vacuum Fermentation for Volatile Fatty Acids and Methane Recovery from Municipal Sludge. Proceeding at WEF / IWA Residuals and biosolids conference 2023”, describes a system / method that involves feeding a biomass / organic material to a hydrothermal pre-treatment apparatus for heating at a temperature of 121° C or more, and subsequently feeding the hydrothermally treated biomass / organic material to a vacuum integrated fermenter or digester, subjecting the particulate fraction thereof to fermentation or anaerobic digestion, while at the same time subjecting the biomass / organic material to vacuum pressure either upstream of, downstream of or during the fermentation or anaerobic digestion, to collect at least a portion of the soluble fraction of the biomass / organic material (including water and gases) as condensate and residual gases in order to thicken the remaining portion of biomass / organic material, and then recovering the thickened biomass / organic material. The recovered thickened biomass / organic material is then subjected to further processing comprising e.g. dewatering and post-pasteurization. The condensate is subjected to further processing comprising denitrification or biomethanization. Preferably the biomass / organic material is waste activated sludge having solid content of 1-16%. The vacuum pressure is preferably 10-750 mbar. A key element in the methods / systems described is that the fermentation or anaerobic digestion is performed under vacuum conditions (i.e. that it is “vacuum integrated”). This requires specialized and rather expensive design of the reactors that works well in a laboratory but which can, however, be expected to become a big hurdle for commercialization of large applications. Likewise, the transfer of heat / energy from a thermal pretreatment system upstream of the anaerobic digestion to the ammonia stripping downstream of the anaerobic digestion, as in the systems / methods of the present invention, which is necessary to allow for a heat and energy efficient process, is not described. This represents major differences from the methods / systems of the present invention that do not require that the anaerobic digestion is performed under vacuum. Instead, the methods / systems of the present invention apply a separate vacuum / evaporative cooling system, where the vacuum is applied on the pre-treated material “Upstream” of an anaerobic digestion, and the heat recovered is applied in an ammonia stripping process “Downstream of the anaerobic digestion, where the stripping of the ammonia is enabled, under controlled conditions.

[0043] US2021171986A1 describes a system / method involving a thermophilic fermentation as pre-treatment upstream of an anaerobic digestion. The possibility for heat integration between the upstream thermophilic fermentation and the downstream anaerobic digestion is described. In one of the specific examples a thermal hydrolysis (THP) is also part of the system and it is illustrated how heat integration between the different systems can be performed and how the methods may include conventional means for ammonia stripping. US2021171986A1, however, only describes heat integration by means of indirect heat exchangers. Likewise, US2021171986A1 does not describe heat recovery from the thermally pre-treated biomass / organic material by vacuum / evaporative cooling “Upstream” of anaerobic digestion and it does not describe that ammonia stripping can be performed by steam stripping “Downstream” of the anaerobic digestion, i.e. on the anaerobically digested biomass / organic material.

[0044] W02009012779A2 describes a system for thermal hydrolysis of a biomass / organic material before enzymatic hydrolysis and fermentation to ethanol. The system includes an option for using vacuum / evaporative cooling to reduce the temperature of the thermally pre-treated material before further processing this. The invention describes the possibility to use the vapor generated by the vacuum / evaporative cooling as energy supply for an evaporator system in which e.g. liquid flows, which are taken out of the system, may be concentrated. W02009012779A2 does not describe using vapor from the “Upstream” vacuum / evaporative cooling of the thermally pre-treated material for steam stripping of ammonia “Downstream” of an anaerobic digestion.

[0045] US2020346960A1 describes a system / method for degassing of biomass / organic material downstream of an anaerobic digester by use of a degassing unit comprising a vacuum pump or a gas compressor. The degassing unit removes part of the CO2 and CH4. The removal of CO2 facilitates struvite precipitation by MgCh addition. The system is operated in the range of 50-400 mbar corresponding to water boiling temperature of 33 ° C to 76 ° C. US2020346960A1 does neither describe that a condensation system could be installed as part of the degassing unit nor that the biomass / organic material should be subjected to a pre-heating step prior to the anaerobic digestion. Also, US2020346960A1 does not in any way describe that the gasses removed from the biomass / organic material by the degassing unit should contain ammonia or that this could be recovered. Finally, US2020346960A1 does not describe introducing energy (neither from upstream nor from downstream of the anaerobic digestion) into the system to facilitate steam stripping of ammonia from the anaerobically digested material. Based on the explicit disclosure of US2020346960A1 a skilled person would not assume that a significant evaporation of ammonia from the anaerobically digested material was intended or expected. Consequently, the systems / methods disclosed in US2020346960A1 do therefore neither involve the use of heat generated by cooling of a pre-heated material “Upstream” of the anaerobic digestion nor does the degassing “Downstream” of the anaerobic digestion described result in the stripping of ammonia as described in the present invention.

[0046] Anayo T Ukwuani and Wendong Tao, 2016, “Developing a vacuum thermal stripping - acid absorption process for ammonia recovery from anaerobic digester effluent”, presents an ammonia recovery process that couples vacuum thermal stripping with acid absorption. Ammonia is stripped out of a digestate from an anaerobic digestion boiling at a temperature below the normal boiling point due to vacuum. Stripped ammonia is then absorbed to a sulfuric acid solution, forming ammonium sulfate crystals as a marketable product. It is not in any way described, however, that the material, which is anaerobically digested should necessarily have been subjected to thermal pre-treatment. Consequently, neither it is described that the “Downstream” ammonia stripping could be combined with a vacuum / evaporative cooling system used to cool the product from an “Upstream” thermal pre-treatment process.

[0047] US2017291825 describes a process for recovering ammonia sulfate from organic material downstream an anaerobic digester. A system where part of the ammonia is extracted by heating and applying vacuum to a side stream from the anaerobic digester and then returning the organic material with reduced total ammoniacal nitrogen (TAN) concentration back to the anaerobic digester is described. The organic material is heated to the boiling point at the applied (vacuum)pressure. Water droplets are removed from the ammonia stream leaving the vacuum tank by a demister. The system described both recover an ammonia fraction and at the same time reduces the total ammoniacal nitrogen (TAN) concentration in the anaerobic digester. The heat / energy used to heat the organic material before the ammonia stripping is recovered in the anaerobic digester by recycling the organic material back to the anaerobic digester after stripping of the ammonia. In some embodiments, biogas produced in the anaerobic digester is used to heat the organic material.

[0048] US2017291825 does not describe that any additional heat recovered from elsewhere in the process may be used to evaporate part of the organic material. Also, the stripping time mentioned is in the range of 11 to 3 hours. A skilled person would therefore not assume that the system could include a steam stripping system where excess steam was used to recover ammonia in a vapor phase from the organic material. In conclusion, US2017291825 does not disclose the possibility to recover energy / steam from an ’’Upstream” thermal pre-treatment of biomass / organic material to be used for ammonia stripping “Downstream” of an anaerobic digestion of biomass / organic material.

[0049] Summary of the invention

[0050] In the present invention, steam resulting from evaporative / vacuum or evaporative cooling of biomass / organic material treated in a thermal pretreatment step, e.g. comprising THP, HTC and / or partial Wet Oxidation “Upstream” of a biological process, e.g., an anaerobic digestion, is used to carry out steam stripping for removal of ammonia from a digestate “Downstream” of an anaerobic digestion.

[0051] The steam stripping for removal of ammonia may be performed on the digestate or on part of such a digestate, e.g., the liquid fraction of such a digestate, which has been subjected to a liquid / solid separation step generating a solid fraction and a liquid fraction with a reduced content of solids.

[0052] The kinds of biomass / organic materials typically treated in methods / systems according to the present invention include sewage sludge, food waste, agricultural waste, industrial organic waste, so-called FOG and so-called OFMSW.

[0053] Sewage sludge from municipal wastewater treatment plants contains a mix of organic matter, pathogens, and nutrients.

[0054] Commercial and household food waste includes leftovers, vegetable trimmings, and expired food products.

[0055] Agricultural Waste includes manure from livestock and other agricultural residues, such as crop straw.

[0056] Industrial Organic Wastes includes organic waste streams from industries such as food processing, breweries, and paper mills.

[0057] Fats, Oils, and Greases (FOG) are often collected from food service establishments and can be challenging to treat due to their high lipid content.

[0058] Organic Fraction of Municipal Solid Waste (OFMSW) is an organic component of municipal solid waste, separated at the source or through mechanical biological treatment plants. In general, pre-treatment of the above-mentioned biomass / organic materials, e.g., by THP and / or HTC, enhances the anaerobic digestion process by increasing the rate of hydrolysis, which is often the rate-limiting step in digestion. Partial Wet Oxidation may increase biogas production by opening up the structure making cellulose or hemicellulose available to the microbial community in the anaerobic digester.

[0059] The typical dry matter content of biomass / organic materials treated in systems / methods according to the present invention can vary widely depending on the source of the biomass and the specific application. For wastewater treatment applications, particularly for the treatment of sewage sludge, the dry matter content of the material entering e.g. the THP can range from about 8 % to about 30% such as e.g. from about 15% to about 20% dry matter (DM) for thickened waste activated sludge and up to 30% or higher for more concentrated sludges or those that have been pre-conditioned or dewatered. Typically, the dry matter content of biomass / organic materials treated in systems / methods according to the present invention will be above 3%, such as above 4%, such as above 5%, such as above 6%, such as above 7%, such as above 8%, such as above 9%, such as above 10%, such as above 11%, such as above 12%, such as above 13%, such as above 14%, such as above 15%.

[0060] The dry matter content of biomass / organic material is typically determined by drying a known weight of the sample to remove all moisture and then measuring the weight of the dry residue. The process involves a) weighing a fresh sample (i.e. , a known volume or weight of the sludge or biomass sample is collected), b) drying the sample in an oven at a set temperature (usually around 105°C) for a prescribed period, often 8 hours or more, to remove all moisture, i.e. until there is no change in weight for a given period of time (the specific drying conditions, however, need to be carefully controlled to account for the loss of any so-called volatile solids), and c) weighing the dry sample. The dry matter content can then be calculated by comparing the weight of the dry sample to the original weight of the fresh sample, usually expressed as a percentage:

[0061] Dry Matter Content (%) = (Weight of Dry Sample / Weight of Fresh Sample) x 100

[0062] This method is straightforward and widely used due to its simplicity and reliability. However, it requires careful sample handling to avoid changes in the sample composition other than water loss, and the drying temperature must be chosen to prevent the decomposition of organic matter. For more volatile samples, alternative methods that operate at lower temperatures or use lyophilization (freeze-drying) might be employed to more accurately measure the dry matter content without losing volatile components.

[0063] A digestate or part of a digestate treated in the ammonia removal system described in the present invention can be sent to dewatering or be introduced back into the anaerobic digestion. The liquid fraction from a liquid / solid separation step, also sometimes referred to as dewatering processes, is commonly referred to as centrate or filtrate. A centrate is the liquid product obtained from a centrifugation process. In wastewater treatment and various industrial processes, centrifugation is used to separate solids from liquids. The solid component, often referred to as sludge or cake, is retained by the centrifuge, while the centrate is the clarified liquid that has been separated from the solids. The centrate can contain dissolved substances and very fine particles that remain suspended in the liquid. The quality and composition of centrate depend on the nature of the original mixture and the efficiency of the centrifugation process. A filtrate is the liquid that has passed through a filter, leaving the solid particles behind. The filtration process can vary in complexity from simple gravity-fed systems to sophisticated membrane technologies. The purpose of filtration is to remove particulate matter and other impurities from a liquid, producing a clear filtrate. The characteristics of the filtrate, such as its clarity, chemical composition, and the absence or presence of specific contaminants, are determined by the efficiency of the filtration medium and the nature of the filtered substance. Filtrate is commonly found in laboratory practices, water treatment, brewing, and various manufacturing processes where the separation of solids from liquids is required. Sending treated digestate to dewatering will help to reduce the nitrogen load in the centrate. Alternatively, the treated digestate can be introduced back to the anaerobic digester and this will help to reduce the nitrogen concentration in the digester and therefore also ultimately the nitrogen load in the centrate from dewatering. The present invention also describes recovery of ammonia in the form of ammonium-nitrate, ammoniumsulfate or other ammonia salts and ammonia water. However, as would be known to the skilled person it is possible to recover ammonia using different methods than the specific ones described here, and this should not limit the present invention. The recovered nitrogen can be used as fertilizer, fuel or feedstock for other processes. The operating expenses (OPEX) of the system described in the present invention is favorable because excess heat from the thermal pretreatment step, e.g. THP, HTC and / or partial Wet Oxidation, “Upstream” of a biological process, e.g., anaerobic digestion, covers the heat demand for steam stripping of ammonia “Downstream” of a biological process. Furthermore, the systems of the present invention at the same time allows for the necessary cooling of biomass / organic material treated in the thermal pretreatment step, e.g. THP, HTC and / or partial Wet Oxidation, reduces the nitrogen load in the centrate from final dewatering, and can also be used to lower the nitrogen content in the connected anaerobic digestion process. The methods / systems of the present invention thereby allow for a higher organic loading rate of the digesters without the concomitant increase in the nitrogen load seen for the prior art systems / methods. Hence, by the removal of ammonia from the digested biomass / organic material and the recycling of this ammonia reduced biomass / organic material to upstream of the digester, the systems / methods of the present invention could enable a higher reduction of volatile solids and thereby enables the construction of more compact anaerobic digestion systems. The recycling of the ammonia reduced biomass / organic material can be done to the digester or to upstream of the digester, e.g. to the upstream thermal pre-treatment process, which could further enhance the volatile solids degradation rate.

[0064] Alternatively, the centrate or filtrate of a digestate (or part of a digestate) fromanaerobic digestion can be treated directly in an ammonia stripping system according to the present invention. In such an embodiment there will be no reduction in the digester total ammoniacal nitrogen (TAN) concentration, but the nitrogen return load will be reduced. Hence, there will be a reduction in the return load of nitrogen from centrate or filtrate returned to the wastewater treatment plant before this is being discharged, or subjected to other further wastewater purification method for removing or recovering specific compounds. The same will apply if centrate or filtrate is returned to upstream of the process and reused as dilution water or process water with or without further purification, depending on the required dilution water quality.

[0065] Due to the high partial pressure of CO2 in an anaerobic digester, digestate typically contains large amounts of carbonic acid. Furthermore, digestate also contains dissolved and entrained gases such as CO2, CH4, and H2S. The significantly lower pressure in the evaporative / vacuum cooler, de-gasser and steam stripper of methods / systems according to the present invention will facilitate transfer of dissolved gases such as CO2 to the gas phase and this will greatly reduce the carbonic acid concentration in the digestate. This results in increased pH of the digestate, which in itself is favorable for ammonia stripping processes. As shown in figure 1 , the equilibrium between NH4+and NH3 shifts towards NH3 with increasing temperature and pH.

[0066] Likewise, the transfer of dissolved CO2 to the gas phase and the concomitant increase in pH in the digestate from an anaerobic digestion process in a method and system according to the present invention can significantly influence the precipitation of struvite (magnesium ammonium phosphate, MgNH4PO4'6H2O) from the digestate. Struvite precipitation is pH-dependent, with optimal formation occurring in a pH range of approximately 8.0 to 9.5. An increase in the pH of the digestate can therefore enhance the conditions favorable for struvite formation. This is because at higher pH levels, the availability of free ammonia (NH3) and phosphate ions (PO43"), which are necessary for struvite formation, increases.

[0067] Also, the shift of the equilibrium between ammonium ions (NH4+) and ammonia (NH3) towards the latter shown in Figure 1 gives rise to an increased availability of ammonia. Since struvite precipitation involves the reaction of magnesium (Mg2+), ammonia (NH3), and phosphate (PO43") ions, an increase in available ammonia due to a higher pH will facilitate more struvite formation. In addition, the solubility of struvite itself decreases as the pH increases within the optimal range. This means that once formed, struvite is less likely to dissolve back into the solution, making precipitation more favorable. In summary, the increase in the pH of a digestate from an anaerobic digestion process following as a consequence of the significantly lower pressure in the evaporative / vacuum cooler and steam stripper (and possible de-gasser) of methods / systems according to the present invention, and the concomitant transfer of dissolved CO2 to gas phase, will significantly promote the precipitation of struvite by enhancing the availability of the necessary ions for its formation and by creating conditions under which struvite is less soluble.

[0068] Likewise, an increase in pH in the digestate from an anaerobic digestion process in a method and system according to the present invention can significantly influence the precipitation of vivianite (Fe3(PO4)2'8 H2O).

[0069] Hence, the precipitation of struvite or vivianite from sludge treated in a wastewater treatment facility is influenced by a combination of chemical, operational, and environmental factors. These factors determine which of the two minerals precipitates by affecting the solubility and availability of the ions necessary for each compound's formation. As mentioned above struvite precipitation is favored in a slightly alkaline pH range, where phosphate, ammonium, and magnesium ions are more likely to combine. In contrast, vivianite forms in a more neutral to slightly acidic pH range, as ferrous ions (Fe2+) are more soluble and available for reaction with phosphate under these conditions.

[0070] The concentrations of magnesium, ammonium, and phosphate ions are critical for struvite formation, whereas vivianite formation requires a high concentration of ferrous ions) and phosphate. Hence, the relative availability of these ions can dictate which mineral is more likely to precipitate. For example, a high ratio of magnesium and phosphate favors struvite, whereas a high ratio of ferrous ions to phosphate favors vivianite.

[0071] Higher temperatures can influence the rate of struvite formation due to enhanced solubility of phosphate and increased reaction kinetics.

[0072] Oxygen levels influence the redox potential of the sludge. Aerobic conditions can oxidize Fe2+to Fe3+, making it less available for vivianite formation and potentially favoring phosphate removal through other mechanisms. Anaerobic conditions, on the other hand, can increase the availability of Fe2+by reducing Fe3+, favoring vivianite formation.

[0073] Biological phosphorus removal processes may release phosphate into the sludge, while chemical treatment with iron salts can provide the necessary iron for vivianite.

[0074] The presence of seed crystals can facilitate the precipitation of either mineral by providing a surface for crystal growth. The availability of seed crystals of struvite or vivianite can influence which mineral precipitates.

[0075] The presence of competing ions or substances that can complex with magnesium, ammonium, phosphate, or iron can affect the precipitation of struvite or vivianite. For example, high concentrations of calcium can compete with magnesium, potentially influencing the formation of struvite.

[0076] In summary, the precipitation of struvite or vivianite from sludge treated in a wastewater treatment facility depends on a complex interplay of chemical composition, operational factors, and environmental conditions. The specific conditions within a treatment facility will determine which of these minerals is more likely to form, influencing the approach to managing phosphorus removal and recovery.

[0077] Compared to the processes of the prior art the characteristic features of a system / method according to the present invention can be divided into features in the form of a) process steps performed on biomass / organic material that has been subjected to thermal pre-treatment before it is subjected to biological treatment, i.e. , “Upstream” of the applicable biological process, which is subsequently to be performed on said pre-treated biomass / organic material, and b) features in the form of process steps performed on biomass / organic material, which has been subjected to biological treatment, i.e., “Downstream” of the applicable biological process.

[0078] It should be stressed, however, that it is not a requirement for a system / method according to the present invention that there is a (or for that matter that there is a certain) biological process between the "Upstream” and “Downstream” processes / systems. Likewise, it is entirely possible to combine a system / method according to the present invention with biological process steps performed on the biomass / organic material before the “Upstream” processes (i.e., in addition to the thermal pre-treatment). In one example this could involve processes / systems in which a thermal hydrolysis unit is installed downstream of an anaerobic digestion unit, e.g. immediately prior to a dewatering step. In such an example the resulting centrate, now high in biodegradable COD, may be recycled to the digester inlet.

[0079] Thus, in its most general sense, “Upstream” processes according to the present invention amounts to energy recovery obtained through evaporative or vacuum / evaporative cooling of a thermally pre-treated biomass / organic material, and “Downstream” processes according to the present invention amounts to recovery of ammonia by steam stripping in the course of which energy recovered in the “Upstream” processes is utilized. As mentioned above, this steam stripping may include the addition of chemical additives to increase pH.

[0080] “Upstream” processes: In a system / method according to the present invention the “Upstream” system preferably includes a vacuum / evaporative cooler, in which the pretreated biomass / organic material is cooled by evaporative cooling at below atmospheric pressure. In some embodiments, the pre-treated biomass / organic material may be pre-cooled before entering the vacuum / evaporative cooler. Typical pressure in the vacuum / evaporative cooler is in the range of 55 mbar to 700 mbar. Typical temperatures are 35 ° C to 90 ° C, however, the exact conditions for the vacuum stage can vary significantly depending on the specific design and objectives of the treatment process.

[0081] Generally, the pressures are below atmospheric pressure, but the exact value can vary widely based on the specific process and equipment used. Hence, pressures can range from slightly below atmospheric to much lower values, often measured in millibars (mbar). For example, pressures might be in the range of 100 to 600 mbar, or even 200 to 500 mbar depending on the process goals, rather than in the broad range from 55 mbar to 700 mbar.

[0082] Likewise, also the temperature will depend on the specific process and the goal of the vacuum stage. As the vacuum is used for cooling, however, the temperature will be lower than during the thermal pre-treatment step, e.g., THP stage. If achieving a certain evaporative effect (apart from merely cooling) is essential, the temperature will depend on the boiling point of the water or other volatile components under the reduced pressure of the vacuum. It's important to note that the use of a vacuum in processes aimed at the biological processing of biomass / organic material, especially if combined with THP pretreatment processes, is highly specific to the technology and the design of the individual plant. As such, the exact pressures and temperatures can vary based on the equipment and operational practices of the facility in question. In most methods and systems according to the present invention, the average temperature of the cooled pre-treated biomass / organic material will be is at least 10 ° C lower than the average temperature of said thermally pre-treated biomass / organic material, such as at least 20 ° C lower, such as at least 30 ° C lower, such as at least 40 ° C lower, such as at least 50 ° C lower, such as at least 60 ° C lower, such as at least 70 ° C lower, such as at least 68 ° C lower, such as at least 69 ° C lower, such as at least 71 ° C lower, such as at least 41 ° C lower, such as at least 42 ° C lower, such as at least 43 ° C lower, such as at least 44 ° C lower, such as at least 45 ° C lower, such as at least 46 ° C lower, such as at least 47 ° C lower, such as at least 48 ° C lower, such as at least 49 ° C lower, such as at least 50 ° C lower, such as at least 51 ° C lower, such as at least 52 ° C lower, such as at least 53 ° C lower, such as at least 54 ° C lower, such as at least 55 ° C lower such as at least 56 ° C lower, such as at least 57 ° C lower, such as at least 58 ° C lower, such as at least 59 ° C lower, such as at least 60 ° C lower, such as at least 61 ° C lower, such as at least 62 ° C lower, such as at least 63 ° C lower, such as at least 64 ° C lower, such as at least 65 ° C lower, such as at least 66 ° C lower, such as at least 67 ° C lower, such as at least 68 ° C lower, such as at least 69 ° C lower, such as at least 70 ° C lower, such as at least 71 C lower, such as at least 72 ° C lower, such as at least 73 ° C lower.

[0083] As mentioned above, a vapor phase resulting from subjecting a thermally pretreated (e.g., by THP, HTC and / or partial Wet Oxidation) biomass / organic material to vacuum / evaporative cooling, may be made up partly or entirely of water vapor, which water vapor may be steam. In some methods and systems according to the present invention, the vapor phase resulting from the vacuum / evaporative cooling will, apart from water (steam), also typically include Volatile Organic Compounds (VOCs), Ammonia (NH3), Hydrogen Sulfide (H2S), Carbon Dioxide (CO2), Light Hydrocarbons, such as alkanes (e.g. methane (CH4), ethane (C2H6), propane (C3H8), and butane (C4H10)), alkenes (such as ethylene (C2H4) and propylene (C3H6)), alkynes (such as acetylene (C2H2), though it is less commonly found in natural hydrocarbon sources compared to alkanes and alkenes) and aromatics (such as benzene (C6H6).

[0084] In preferred embodiments of the methods and systems according to the present invention, the vapor phase resulting from the vacuum / evaporative cooling will typically comprise at least 90% steam W / W, such as at least 91% steam W / W, such as at least 92% steam W / W, such as at least 93% steam W / W, such as at least 94% steam W / W, such as at least 95% steam W / W, such as at least 96% steam W / W, such as at least 97% steam W / W, such as at least 98% steam W / W, such as at least 99% steam W / W.

[0085] The cooled material is either transferred directly to an applicable biological process, preferably an anaerobic digestion, or is subjected to further cooling and / or processing, e.g., the addition of dilution water, prior to being transferred to an applicable biological process. If applicable, components of the pre-treated biomass / organic material that partly enter the vapor phase in the cooling step and therefore leave the vacuum / evaporative cooler with the vapor may be recovered from the vapor in a scrubber / distillation process.

[0086] “Downstream” processes: In a system / method according to the present invention, the vapor resulting from the “Upstream” vacuum / evaporative cooler of the methods / systems can be used directly in units / steps for steam stripping placed "Downstream” of an applicable biological process, which is preferably an anaerobic digestion. The transfer can be in batch but is preferably continuous or semicontinuous. Vapor is continuously removed from the steam stripper for subsequent recovery processes in scrubber / recovery units by differential pressure.

[0087] In preferred embodiments of the methods and systems according to the present invention, the vapor phase used in units / steps for steam stripping placed "Downstream” of an applicable biological process, which is preferably an anaerobic digestion will typically comprise at least 90% steam W / W, such as at least 91% steam W / W, such as at least 92% steam W / W, such as at least 93% steam W / W, such as at least 94% steam W / W, such as at least 95% steam W / W, such as at least 96% steam W / W, such as at least 97% steam W / W, such as at least 98% steam W / W, such as at least 99% steam W / W.

[0088] The vapor will, depending on the conditions of the applicable biological processes, contain compounds like ammonia / organic acids or alcohols and other volatile compounds with low boiling temperature, but preferably contains ammonia. In preferred embodiments of the methods and systems according to the present invention, the vapor phase resulting from the above-mentioned steam stripping will, depending on the conditions of the applicable biological processes, contain at least 10% of the ammonia content of processed biomass / organic material subjected to steam stripping, i.e. , the processed biomass / organic material will be stripped of at least 10% of the ammonia content in the steam stripping step, such as at least 11%, such as at least 12%, such as at least 13%, such as at least 14%, such as at least 15%, such as at least 16%, such as at least 17%, such as at least 18%, such as at least 19%, such as at least 20%, such as at least 21%, such as at least 22%, such as at least 23%, such as at least 24%, such as at least 25%, such as at least 26%, such as at least 27%, such as at least 28%, such as at least 29%, such as at least 30%, such as at least 31 %, such as at least 32%, such as at least 33%, such as at least 34%, such as at least 35%, such as at least 36%, such as at least 37%, such as at least 38%, such as at least 39%, such as at least 40%, such as at least 41 %, such as at least 42%, such as at least 43%, such as at least 44%, such as at least 45%, such as at least 46%, such as at least 47%, such as at least 48%, such as at least 49%, such as at least 50%, such as at least 51 %, such as at least 52%, such as at least 53%, such as at least 54%, such as at least 55%, such as at least 56%, such as at least 57%, such as at least 58%, such as at least 59%, such as at least 60%, such as at least 61 %, such as at least 62%, such as at least 63%, such as at least 64%, such as at least 65%, such as at least 66%, such as at least 67%, such as at least 68%, such as at least 69%, such as at least 70%, such as at least 71 %, such as at least 72%, such as at least 73%, such as at least 74%, such as at least 75%, such as at least 76%, such as at least 77%, such as at least 78%, such as at least 79%, such as at least 80%, such as at least 81 %, such as at least 82%, such as at least 83%, such as at least 84%, such as at least 85%, such as at least 86%, such as at least 87%, such as at least 88%, such as at least 89%, such as at least 90%, such as at least 91 %, such as at least 92%, such as at least 93%, such as at least 94%, such as at least 95%, such as 65-95%, such as 70-95%, such as 75-95%, such as 80-95%, such as 85-95%, such as 90-95%.

[0089] The components in the vapor phase resulting from the above-mentioned steam stripping, including the ammonia, are recovered from the vapor in the scrubber / recovery unit. As an example, a sulfuric acid scrubber can be used to recover ammonia as ammonia sulphate.

[0090] Hence, in a first aspect the present invention relates to a method for treatment of biomass / organic material having a dry matter content of at least 3% comprising the steps of: subjecting said biomass / organic material to a thermal pre-treatment, comprising one or more of THP, HTC and / or partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, thereby obtaining a thermally pre-treated biomass / organic material subjecting said thermally pre-treated biomass / organic material to cooling by use of vacuum / evaporative cooling thereby generating: o a first vapor phase comprising at least 90% W / W steam, and o a cooled pre-treated biomass / organic material the average temperature of which is at least 10 °C lower than the average temperature of said thermally pre-treated biomass / organic material, subjecting a biomass / organic material, optionally said cooled thermally pretreated biomass / organic material, to a processing step in the form of an anaerobic digestion process, thereby obtaining a processed biomass / organic material, subjecting at least part of said processed biomass / organic material to a steam stripping step by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed biomass / organic material stripped of at least part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said method being characterized in that: said second vapor phase comprising steam used for said steam stripping of said at least part of said processed biomass / organic material comprises at least part of said first vapor phase comprising steam generated by said vacuum / evaporative cooling of said thermally pre-treated biomass / organic material, and said at least part of said processed biomass / organic material is stripped of at least 10% of its ammonia content in said steam stripping step.

[0091] In an alternative first aspect the present invention relates to a method for treatment of biomass / organic material having a dry matter content of at least 3% comprising the steps of: subjecting said biomass / organic material to a thermal pre-treatment, comprising one or more of THP, HTC and / or partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, thereby obtaining a thermally pre-treated biomass / organic material subjecting said thermally pre-treated biomass / organic material to cooling by use of evaporative cooling thereby generating: o a first vapor phase comprising at least 90% W / W steam, and o a cooled pre-treated biomass / organic material the average temperature of which is at least 10 °C lower than the average temperature of said thermally pre-treated biomass / organic material, subjecting a biomass / organic material, optionally said cooled thermally pretreated biomass / organic material, to a processing step in the form of an anaerobic digestion process, thereby obtaining a processed biomass / organic material, subjecting at least part of said processed biomass / organic material to a steam stripping step by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed biomass / organic material stripped of at least part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said method being characterized in that: said second vapor phase comprising steam used for said steam stripping of said at least part of said processed biomass / organic material comprises at least part of said first vapor phase comprising steam generated by said evaporative cooling of said thermally pre-treated biomass / organic material, and said at least part of said processed biomass / organic material is stripped of at least 10% of its ammonia content in said steam stripping step.

[0092] In a preferred embodiment of said first aspect of the present invention, said method is further characterized in that said biomass / organic material processed in said anaerobic digestion comprises at least part of said thermally pre-treated biomass / organic material.

[0093] In another preferred embodiment of said first aspect of the present invention, said method is further characterized in that at least part of said ammonia comprised in said third vapor phase is recovered from said third vapor phase, e.g., by scrubbing or distillation.

[0094] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that at least part of said first vapor phase comprising steam generated by said vacuum / evaporative cooling is continuously or semi- continuously transferred from said vacuum / evaporative cooling to said steam stripping step.

[0095] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that the part of said first vapor phase generated by use of said vacuum / evaporative cooling, which is comprised by said second vapor phase, which is used for said steam stripping step, and said third vapor phase generated in said steam stripping step are continuously transferred by differential pressure to said subsequent processes for recovery of said ammonia.

[0096] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that part of said pre-treated biomass / organic material, e.g., in the form of VOC’s, CO2, NH3, CH4, C2H6, C3H8, C4HI0, C2H4, C3H6, C2H2, C6H6and / or H2S contained therein, enters said first vapor phase, when said pretreated biomass / organic material is subjected to cooling by use of vacuum / evaporative cooling, and is recovered by a scrubber / distillation process before being used in said steam stripping step as part of said second vapor phase.

[0097] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized that at least part of said pre-treated biomass / organic material, e.g. in the form of VOC’s, CO2, NH3, CH4, C2H6, C3H8, C4HI0, C2H4, C3H6, C2H2, C6H6and / or H2S contained therein, which enters said first vapor phase, is part of, said part of, said first vapor phase, which is comprised by said second vapor phase, which is used for said steam stripping step and is recovered by a scrubber / distillation performed on said third vapor phase generated in said steam stripping step.

[0098] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that said vacuum / evaporative cooling is performed at below atmospheric pressure, such as from 55 mbar to 700 mbar.

[0099] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that said vacuum / evaporative cooling is performed at a temperature from 35° C to 90° C.

[0100] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that said at least part of said processed biomass / organic material, which is subjected to said steam stripping step, is the liquid part of at least part of said processed biomass / organic material having been subjected to a liquid / solid separation step.

[0101] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that said pre-treated biomass / organic material is pre-cooled before being subjected to vacuum / evaporative cooling.

[0102] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that said cooled pre-treated biomass / organic material is subjected to further cooling and / or processing, e.g. by the addition of dilution water.

[0103] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that at least part of said processed biomass / organic material is subjected to a liquid / solid separation process by which at least part of the solids, preferably suspended solids, are removed before said processed biomass / organic material is subjected to said steam stripping step.

[0104] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that at least part of said steam stripped processed biomass / organic material and / or at least part of any solid part of said at least part of said processed biomass / organic material is returned to either said thermal pretreatment or said anaerobic digestion process, thereby contributing to reducing the average concentration of ammonia in the material being subjected to said thermal pretreatment or said anaerobic digestion process.

[0105] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that said recovery of said ammonia is achieved by:

[0106] - scrubbing of said third vapor phase by use of acid and said ammonia is recovered in the form of an ammonium salt, or

[0107] - distillation of said third vapor phase and said ammonia is recovered in the form of ammonia water.

[0108] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that CO2, whether dissolved or in the form of bubbles, in said pre-treated biomass / organic material enters the vapor phase and becomes part of said first vapor phase when said thermally pre-treated biomass / organic material is subjected to said cooling by use of vacuum / evaporative cooling, which contributes to an increase in the pH of said cooled pre-treated biomass / organic material compared to the pH of said thermally pre-treated biomass / organic material.

[0109] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that at least part of any CO2, whether dissolved or in the form of bubbles, in said processed biomass / organic material enters the vapor phase and becomes part of said third vapor phase when said processed biomass / organic material is subjected to said stream stripping, which contributes to an increase in the pH of said steam stripped processed biomass / organic material compared to said processed biomass / organic material.

[0110] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that at least part of any CO2, whether dissolved or in the form of bubbles, in said processed biomass / organic material is removed by a separate de-gassing step before said processed biomass / organic material is subjected to said steam stripping.

[0111] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that said de-gassing step is performed by use of a dedicated vacuum generating system.

[0112] In yet another preferred embodiment of said first aspect of the present invention is further characterized in that at least part of said ammonia comprised in said third vapor phase is recovered from said third vapor phase, e.g., by scrubbing or distillation, and in that said third vapor phase, after removal of part of said ammonia, is used to directly or indirectly heat said processed biomass / organic material in said de-gasser

[0113] In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that it includes adding chemical additives to said biomass / organic material, said pre-treated biomass / organic material, said cooled pretreated biomass / organic material and / or said processed biomass / organic material to increase the pH of said processed biomass / organic material being subjected to or having been subjected to said steam stripping step. In yet another preferred embodiment of said first aspect of the present invention, said method is further characterized in that it includes adding chemical additives to said biomass / organic material, said pre-treated biomass / organic material, said cooled pretreated biomass / organic material and / or said processed biomass / organic material to facilitate phosphorus precipitation from said processed biomass / organic material being subjected to or having been subjected to said steam stripping step.

[0114] In yet an alternative first aspect of the present invention, it relates to a method for treatment of biomass / organic material having a dry matter content of at least 3% comprising the steps of: subjecting said biomass / organic material to a thermal pre-treatment step, comprising one or more of THP, HTC, partial Wet Oxidation, , thermophilic digestion, thermophile acid fermentation and / or pasteurization, thereby obtaining a thermally pre-treated biomass / organic material, subjecting at least part of said thermally pre-treated biomass / organic material to processing in the form of an anaerobic digestion process, thereby obtaining a processed biomass / organic material, subjecting at least part of said processed biomass / organic material to concomitant cooling and steam stripping by use of vacuum / evaporative cooling thereby generating: o a steam stripped and cooled processed biomass / organic material stripped of at least part of the ammonia content, and o a vapor phase comprising steam and ammonia, said method being characterized in that: at least part of said thermally pre-treated biomass / organic material is transferred directly from said thermal pre-treatment step to said processing step in the form of an anaerobic digestion process, without an interposed cooling step, said concomitant cooling and steam stripping by use of vacuum / evaporative cooling of at least part of said processed biomass / organic material is achieved by flash stripping, and said at least part of said processed biomass / organic material is stripped of at least 10% of its ammonia content in said steam stripping step.

[0115] In a second aspect the present invention relates to a system for treatment of biomass / organic material comprising: one or more thermal pre-treatment units, such as units for THP, HTC, partial Wet Oxidation, , thermophilic digestion, thermophile acid fermentation and / or pasteurization, for producing a thermally pre-treated biomass / organic material a vacuum / evaporative cooling unit for subjecting said thermally pre-treated biomass / organic material to cooling thereby generating: o a first vapor phase comprising steam, and o a cooled pre-treated biomass / organic material, a processing unit in the form of an anaerobic digestion unit, for subjecting a biomass / organic material, optionally said cooled thermally pre-treated biomass / organic material, to a biological process in the form of an anaerobic digestion to obtain a processed anaerobically digested biomass / organic material, a steam stripping unit for subjecting at least part of said processed anaerobically digested biomass / organic material to steam stripping by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed anaerobically digested biomass / organic material stripped of part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said system being characterized in that: it comprises tubing and equipment, which tubing and equipment allows for at least part of said first vapor phase, comprising steam, generated in said vacuum / evaporative cooling unit, to be transferred to be part of said second vapor phase, comprising steam, used in said steam stripping unit.

[0116] In a preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises tubing and equipment, which tubing and equipment allows for at least part of said thermally pre-treated biomass / organic material to be transferred to said anaerobic digestion unit.

[0117] In an alternative second aspect the present invention relates to a system for treatment of biomass / organic material comprising: one or more thermal pre-treatment units, such as units for THP, HTC, partial Wet Oxidation, , thermophilic digestion, thermophile acid fermentation and / or pasteurization, for producing a thermally pre-treated biomass / organic material an evaporative cooling unit for subjecting said thermally pre-treated biomass / organic material to cooling thereby generating: o a first vapor phase comprising steam, and o a cooled pre-treated biomass / organic material, a processing unit in the form of an anaerobic digestion unit, for subjecting a biomass / organic material, optionally said cooled thermally pre-treated biomass / organic material, to a biological process in the form of an anaerobic digestion to obtain a processed anaerobically digested biomass / organic material, a steam stripping unit for subjecting at least part of said processed anaerobically digested biomass / organic material to steam stripping by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed anaerobically digested biomass / organic material stripped of part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said system being characterized in that: it comprises tubing and equipment, which tubing and equipment allows for at least part of said first vapor phase, comprising steam, generated in said evaporative cooling unit, to be transferred to be part of said second vapor phase, comprising steam, used in said steam stripping unit.

[0118] In a preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises tubing and equipment, which tubing and equipment allows for at least part of said processed biomass / organic material to be subjected to a liquid / solid separation step, and for the liquid part of at least part of said processed biomass / organic material, having been subjected to said liquid / solid separation step, to be the part of said at least part of said processed biomass / organic material, which is subjected to said steam stripping step.

[0119] In another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises an ammonia scrubbing or distillation unit, which is connected to said steam stripping unit by tubing and equipment, which tubing and equipment allows for transfer of at least part of said third vapor phase from said steam stripping unit to said ammonia scrubbing or distillation unit.

[0120] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises tubing and equipment, which tubing and equipment allows for the continuous or semi-continuous transfer of at least part of said first vapor phase, comprising steam, generated by said vacuum / evaporative cooling unit, to said steam stripping unit.

[0121] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises tubing and equipment, which tubing and equipment allows for continuous transfer of at least part of said first vapor phase generated by use of said vacuum / evaporative cooling unit and at least part of said third vapor phase generated in said steam stripping unit by differential pressure to one or more scrubbing or distillation units, including said ammonia scrubbing or distillation unit.

[0122] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises a pre-cooling unit and tubing and equipment, which tubing and equipment allows for transfer of said pre-treated biomass / organic material from said pretreatment unit to said pre-cooling unit and transfer of material from said pre-cooling unit to said vacuum / evaporative cooling unit.

[0123] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises tubing and equipment, which tubing and equipment allows for further cooling and / or processing of said cooled pretreated biomass / organic material, e.g. by the addition of dilution water.

[0124] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises tubing and equipment, which tubing and equipment allows for the return of at least part of said processed biomass / organic material, possibly in the form of part of said processed biomass / organic material having been subjected to a solid / liquid separation step, stripped of ammonia from said steam stripping unit to said anaerobic digestion unit.

[0125] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises a de-gasser vessel placed downstream of said anaerobic digestion unit and upstream of said steam stripping unit and tubing and equipment, which tubing and equipment allows for transfer of material from said anaerobic digestion unit to said de-gasser vessel and from said de-gasser vessel to said steam stripping unit.

[0126] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that said de-gasser vessel is connected by tubing and equipment to a dedicated vacuum generating system.

[0127] In yet another preferred embodiment of said second aspect of the present invention, said system is further characterized in that it comprises tubing and equipment, which tubing and equipment allows for the return of at least part of said processed biomass / organic material, possibly in the form of part of said processed biomass / organic material having been subjected to a solid / liquid separation step, stripped of ammonia from said steam stripping unit, to upstream of either said anaerobic digestion unit or upstream of said thermal pre-treatment units.

[0128] In yet an alternative second aspect of the present invention it relates to a system for treatment of biomass / organic material comprising: one or more thermal pre-treatment units, such as units for THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, for producing a thermally pre-treated biomass / organic material, a processing unit in the form of an anaerobic digestion unit, for subjecting said thermally pre-treated biomass / organic material to processing in the form of an anaerobic digestion process, to obtain a processed biomass / organic material, a flash stripping unit for subjecting at least part of said processed biomass / organic material to concomitant cooling and steam stripping by use of vacuum / evaporative cooling thereby generating: o a steam stripped and cooled processed biomass / organic material stripped of at least part of the ammonia content, and o a vapor phase comprising steam and ammonia, said system being characterized in that: it comprises tubing and equipment, which tubing and equipment allows for at least part of said thermally pre-treated biomass / organic material to be transferred directly from said thermal pre-treatment units to said processing unit in the form of an anaerobic digestion unit, without an interposed cooling unit, it comprises tubing and equipment, which tubing and equipment allows for at least part of said steam stripped and cooled processed biomass / organic material, stripped of at least part of the ammonia content, generated in said flash stripping unit to be returned to said a processing unit in the form of an anaerobic digestion unit.

[0129] In a third aspect the present invention relates to a method of refurbishing an existing Water Resource Recovery Facility (WRRF), Waste Water Treatment Plant (WWTP) or anaerobic digestion plant for farm or industrial waste to ensure that said WRRF, WWTP or anaerobic digestion plant for farm or industrial waste comprises the units of a system according to the second aspect or any of the alternative second aspects of the present invention. As the skilled person will appreciate any of the above-mentioned aspects and / or preferred embodiments of the present invention may be combined with any other of the above-mentioned aspects and / or preferred embodiments of the present invention.

[0130] The present invention presents several benefits over the prior art, which will be described in the following.

[0131] Ammonia removal in “Downstream” digester side stream using steam stripper with energy from “Upstream” thermal pre-treatment

[0132] Today the most common way to cool biomass / organic material from an “Upstream” thermal process is to use indirect heat exchangers. Only a part of the heat can be utilized for heating purposes, and only if there is a need for energy. Most of the heat is lost as low temperature cooling water. Indirect heat exchangers require a high flow to secure turbulent flow and good heat transfer. Both CAPEX and OPEX for the indirect heat exchangers are high, especially in hot regions where cooling water temperatures are high. Systems to cool biomass / organic material after upstream thermal processes and utilizing the heat for preheating the biomass / organic material before the upstream thermal processes have been described in the prior art. However, this does not include a system to strip ammonia from a digestate or a system to reduce the total ammoniacal nitrogen (TAN) concentration in the processed biomass / organic material downstream of the anaerobic digester.

[0133] As mentioned above, it is known that anaerobic digestion will be inhibited by the concentration of free ammonia. No specific concentration for ammonia where the inhibition starts has been established. However, there is a general understanding that the concentration preferably should be maintained below 3000 mg / l ammonia- N for mesophilic anaerobic digestion. There are, however, examples of higher ammonia concentrations such as 4000, 5000 and 7000 mg / l and even higher and the field is currently the subject of further research. Older results by Schnurer and Nordberg strongly suggest that a shift in the methane producing population could be achieved through adaptation over time enabling a syntrophic acetate oxidation. Syntrophic acetate oxidation involves hydrogenotrophic methanogen, tolerating higher levels of ammonia, enabling methane production from acetate to proceed even though the acetotrophic methanogens are inhibited (A. Schnurer and A. Nordberg, 2008. Ammonia, a selective agent for methane production by syntrophic acetate oxidation at mesophilic temperature). Schnurer also demonstrated that the shift from aceticlastic methane production pathway to a syntrophic pathway is by thermodynamic necessity a much slower process, indicating need for longer residence time in mesophilic digesters operating at such elevated ammonia concentrations. This finding can explain the general understanding that ammonia concentrations should be kept below 3000mg / l for mesophilic anaerobic digestion to enable short retention times. Applying thermal hydrolysis to biomass / organic material in the form of municipal sludge is known to increase the conversion of organic material including proteins. This also increases mineralization of nitrogen. THP, HTC, and / or partial Wet Oxidation reduces the viscosity of treated municipal sludge and therefore it is possible to increase the TS to the anaerobic digester. The increased mineralization of nitrogen and increased TS to the anaerobic digester results in the digester loading often being limited by the total ammoniacal nitrogen (TAN) concentration.

[0134] Air stripping of ammonia from the liquid fraction after dewatering has been used in the industry previously. The technology often uses heating or chemicals to adjust pH to facilitate the ammonia stripping. The system is operated under atmospheric pressure, and thus normally not all of the CO2 is removed and the dosing of base necessary to increase the pH is high. For some systems, struvite or vivianite precipitation prior to the ammonia stripping is also required. On an industrial scale, air stripping is in most cases only used after the anaerobic digester and will therefore not normally reduce the ammonia concentration inside the digester. Systems for inline steam stripping of ammonia with recirculation to the anaerobic digester is presented in the literature. The overall effect of the inline steam stripping on ammonia concentration is the same as for the methods / systems of the present invention. The systems described in the prior art, however, use indirect heat transfer in heat exchangers or falling film evaporators. As described above, the use of indirect heat exchangers for heating biomass / organic material in the form of sludge has the challenge of fouling in the heat exchangers.

[0135] The ammonia released in the anaerobic digester will in the prior art methods end in the liquid fraction after dewatering and must be treated at the wastewater treatment plant. When the release of ammonia is increased due to the THP, HTC and / or partial Wet Oxidation, it will increase the cost of removing this ammonia from the wastewater. In some cases, the existing wastewater treatment plant cannot handle the increased load, so a dedicated side stream treatment must be installed to remove the ammonia. This can account for a significant total CAPEX and OPEX when implementing THP, HTC, and / or partial Wet Oxidation. The methods and systems of the present invention solves all the above challenges in one solution.

[0136] The present invention combines a solution for cooling the biomass / organic material, e.g., in the form of sludge, after “Upstream” thermal processes using an evaporative or evaporative / vacuum cooler with “Downstream” stripping of ammonia. The heat (vapor) from the cooling “Upstream” is utilized “Downstream” to facilitate the ammonia stripping in a steam stripper. The steam stripper uses the vapor from the evaporative or evaporative / vacuum cooler directly in the ammonia stripping and costly heat exchangers are therefore avoided. To the extent that the processed biomass / organic material is not subjected to a liquid / solid separation step prior to the steam stripping step, the steam stripper will be able to operate without heat exchangers and at temperatures close to that of the anaerobic digester, and it is therefore possible to recirculate a relatively large flow from the digester across the steam stripper. The higher the ammonia concentration in the media in a stripper, the easier it is to strip off a specific amount of ammonia. The large recirculation flow reduces the relative reduction in ammonia in the biomass / organic material (e.g., sludge) in the steam stripper, and therefore improves the overall recovery of ammonia in the steam stripper. The recovery of ammonia directly on a recirculation flow on the digester will reduce the ammonia concentration in the digester and potentially make it possible to increase the DS in the feed to the digester. The recovery of ammonia in the system can offset the increase in ammonia return load to the wastewater treatment plant and potentially eliminate the need for costly separate side stream treatment. Hence, the return load of ammonia from centrate or filtrate returned to the wastewater treatment plant before this is discharged to, or subjected to any other further wastewater purification method for removing or recovering specific compounds, will decrease. Similarly, the ammonia return load from centrate or filtrate that is returned to upstream of the process and reused as dilution water or process water, with or without further purification depending on the required dilution water quality, will decrease.

[0137] Effect of adding de-gasser

[0138] As mentioned above, the prior art does not describe methods / systems in which the heat (vapor) from an evaporative or evaporative / vacuum cooling of a pretreated material “Upstream” of an anaerobic digestion is utilized “Downstream” of an anaerobic digestion to facilitate ammonia stripping in a steam stripper. Also, in addition to the fact that the prior art does describe both systems using evaporative / vacuum cooler or evaporative / vacuum cooling with direct heat recovery and systems using vacuum steam stripping on a recirculation flow on digesters to reduce ammonia concentration in the digester, none of the prior art systems describe an accompanying de-gassing step. As described above, the energy consumption for removing NCG is a significant part of the OPEX cost of an ammonia recovery system operated under vacuum.

[0139] It is known that ammonia recovery can be improved if the pH is increased in the ammonia stripper system. The buffer capacity of biomass / organic material in the form of sludge from an anaerobic digester is high and therefore a larger amount of base is required to increase the pH. The buffering capacity of the digestate is partly due to the carbonate system with the dissolved CO2.

[0140] In embodiments of the present invention including a de-gasser, the energy effectiveness for generating the vacuum and, hence, of the overall system will significantly improve.

[0141] By including a de-gasser to work on the biomass / organic material in the form of sludge from the anaerobic digester it is possible to significantly reduce the CAPEX and OPEX of the vacuum pumps by reducing the volume of NCG gas to be removed.

[0142] Including a de-gasser before the stripping system will remove a large fraction of the dissolved CO2 in the sludge and thereby reduce the buffering capacity and slightly increase the pH of the processed biomass / organic material.

[0143] It is known that increasing the temperature will reduce the solubility of CO2 in the sludge. Therefore, preheating the sludge with an indirect heat exchanger between the anaerobic digester and de-gasser will facilitate the de-gassing.

[0144] To further improve the heat transfer, a recirculation loop may be used in certain embodiments of the present invention. On such a recirculation loop, an indirect heat exchanger can be installed to use waste heat to add additional energy to the biomass / organic material (e.g., sludge). This is in the range of 5-50% of the total energy input from the “Upstream” evaporative / vacuum cooler. This will further increase temperature out of the de-gasser and thereby the amount of excess vapor that can be used for steam stripping. Effect of steam stripper and preheater

[0145] The fraction of free ammonia significantly increases with increasing temperature. Steam stripping and any flash stripping will therefore become more efficient with increasing temperature. Therefore, heating the biomass / organic material (e.g., sludge) before stripping will be an advantage. Using indirect heat exchange for the heating of the processed material from the anaerobic digester with high solid content is as described above connected to high CAPEX and OPEX.

[0146] The methods and system of the present invention simultaneously increases the fraction of free ammonia and reduces the use of indirect heat exchangers.

[0147] By using a direct condenser / heat exchanger for preheating the media “Downstream” of the anaerobic digester / de-gasser with the vapor from the “Upstream” evaporative or evaporative / vacuum cooler, the use of indirect heat exchangers is avoided for recovery of the energy from the evaporative or evaporative / vacuum cooler.

[0148] To further improve the heat transfer, a recirculation loop may be used in certain embodiments of the present invention. On such a recirculation loop, an indirect heat exchanger can be installed to use waste heat to add additional energy to the biomass / organic material (e.g. sludge). This is in the range of 5-50% of the total energy input from the “Upstream” evaporative / vacuum cooler. This will further increase the amount of excess vapor that can be used for steam stripping. Also, in some embodiments, base may be added on the recirculation loop to increase pH for further increasing the fraction of free ammonia and thereby the effect of the steam stripping. In embodiments including a de-gasser, any base is added after the de-gasser, and hence less base would be required to achieve the same pH increase compared to a system without a de-gasser.

[0149] Effect of flash stripper with struvite precipitation and two outlets

[0150] Using the steam stripper and preheater described above will in most cases result in the evaporative / vacuum cooler operating at a temperature above what is required for the anaerobic digester. If the biomass / organic material (e.g., sludge) from the evaporative / vacuum cooler is sent directly to the anaerobic digester, then cooling of the digester will be required. At the same time, the energy from cooling can’t be utilized for the ammonia stripping. Uncontrolled struvite precipitation in the downstream system after anaerobic digestion can be a challenge for some wastewater treatment plants. At the same time, phosphorus released in the anaerobic digester will be recycled back to the wastewater treatment plant in the liquid fraction after dewatering.

[0151] In some embodiments, the methods and systems of the present invention combines cooling of media with increased ammonia recovery and struvite precipitation.

[0152] A flash stripper is operated at a lower pressure compared to the preheater and the stream stripper. When the biomass / organic material, e.g., in the form of sludge, enters a flash stripper, water will instantaneously flash off from the biomass / organic material (e.g., sludge) and reach an equilibrium between pressure and boiling temperature of water. Combining a preheater and steam stripper with a flash stripper will give an even higher recovery of ammonia compared to only using a steam stripper.

[0153] Struvite (NH4MgPO4) formation is facilitated by dosing MgCh to the biomass / organic material (e.g., sludge). Struvite formation after anaerobic digesters is normally limited by the concentration of Mg or PO4, and not by NH4. In embodiments of the methods and systems of the present invention including a flash stripper, MgCh may be added right before the inlet to the flash stripper. This will secure good mixing during the flash. Compared to the flash process taking place when the biomass / organic material (e.g., sludge) enters a flash stripper, the reaction producing struvite is relatively slow.

[0154] Therefore, most of the ammonia stripping occurs before ammonia is consumed for the reaction creating struvite. It is an advantage for the overall reduction of ammonia that the concentration during the stripping is as high as possible.

[0155] The amount of free ammonia is dependent on temperature and the amount of steam from the evaporative / vacuum cooler to a preheater and the flash stripper is directly linked to the pressure in a preheater and the steam stripper. Combining a preheater and the steam stripper with a flash stripper has the additional advantage that the pressure and temperature in the preheater and the stream stripper can be controlled precisely to maximize the overall ammonia recovery of the system.

[0156] In a particularly preferred embodiment, the lower part of a flash stripper includes a vertical plate separating the tank into two compartments. The media from the evaporative / vacuum cooler is injected to the flash stripper in the one compartment. The material from the preheater and steam stripper is injected to the top of a flash stripper distributing into both compartments. Near the bottom of the tank there is an opening in the plate, resulting in one liquid phase between the media from the evaporative / vacuum cooler and from the preheater and steam stripper. With this design, it is possible to use a flash stripper to cool the media from the evaporative / vacuum cooler to the same temperature as a flash stripper temperature. The flash steam from the media from evaporative / vacuum cooler will facilitate the stripping of ammonia in a flash stripper by increasing the total amount of vapor. The separation of the tank will make it possible to extract a fraction of the processed material where part of the ammonia has been removed from the system that is not mixed with unprocessed material from the evaporative / vacuum cooler. This fraction, where struvite is precipitated, methane and CO2 are removed, and part of the ammonia is stripped, is then sent to further downstream processing (like dewatering).

[0157] Detailed description of individual elements of embodiments of the invention

[0158] In one embodiment the present novel evaporative or evaporative / vacuum cooling and ammonia stripping system combines the cooling of the biomass / organic material after thermal pre-treatment with a possibility to inter alia reduce the TAN concentration in a digester and possible side streams, and in such an embodiment provides for the recovery of ammonia in a form, which can be used as fertilizer or source for other industrial processes. Hence, by combining cooling of the pre-treated biomass / organic material with ammonia recovery it is possible to utilize excess energy from the thermal pre-treatment to facilitate ammonia removal in a steam stripping system, rather than in an ammonia air stripper or an Anammox system. This will contribute to significantly reduce both the Capital expenditures (CapEx) and the operating expenses (OpEx) of the system. In addition, in this embodiment, a evaporative or evaporative / vacuum cooler and ammonia stripping method according to the present invention also makes use of the fact that part of the CO2 otherwise dissolved in the pre-treated biomass / organic material will, due to the vacuum, enter the gas phase in the steam stripper, which will contribute to an increase in pH that will again further facilitate ammonia stripping. After the steam stripping, part (or all) of the organic material may be returned back to the anaerobic digester, thereby reducing the concentration of ammonia in the anaerobic digester.

[0159] In an alternative set-up the present novel evaporative or evaporative / vacuum cooler and ammonia stripping system / method could be applied to combine the cooling of the biomass / organic material after thermal pre-treatment with a possibility to inter alia reduce the concentration of a fermentation end product in a fermenter and possible side streams, and in such a set-up would provide for the recovery of fermentation product by steam stripping. Hence, by combining cooling of the pre-treated biomass / organic material with recovery of the desired fermentation end product it is possible to utilize excess energy from the thermal pre-treatment to facilitate fermentation end product removal in a steam stripping system. Like in relation to ammonia stripping this would contribute to reduce both the Capital expenditures (CapEx) and the operating expenses (OpEx) of the system.

[0160] The aim of the evaporative or evaporative / vacuum cooling system is to cool thermally treated biomass / organic material to a desired temperature. In most cases, the biomass / organic material cooled in the evaporative or evaporative / vacuum cooler is introduced to a biological treatment step such as anaerobic digestion, which then in turn decides to which temperature it is desired to cool the biomass / organic material. Typically, the biomass / organic material contains nitrogen which upon biological conversion is released into the liquid phase in the form of NH3or NH The liquid from the biological treatment where ammonia and ammonium are formed is introduced to the ammonia stripping process. In the present invention, heat made available from the evaporative or evaporative / vacuum cooler is used to facilitate ammonia stripping.

[0161] The ammonia stripping process will always receive material from a biological process where ammonia and ammonium are formed, such as e.g. an anaerobic digestion. The heat will always be made available from a thermal treatment step for which it is desired to cool the thermally treated biomass / organic material. The process for thermal treatment can be installed in several different configurations in combination with biological process steps. Some of the possible arrangements are to treat all or parts of the feedstock prior to the biological process, a different configuration is with biological treatment prior to the thermal treatment process which later is followed by an additional biological treatment step (l-THP), or biological treatment followed by thermal treatment and dewatering where only the liquid fraction is returned to the biological treatment step. Furthermore, it is possible to carry out biological treatment followed by thermal treatment and all the thermally treated material is returned to the biological treatment (Eliquio Stultz THP). The thermal treatment step can also be THP, HTC and / or partial Wet Oxidation, or an acid phase thermophile fermentation or any other biological or thermo-chemical pretreatment method.

[0162] Here, we refer to “Upstream” processes as those that are prior to biological treatment while “Downstream” processes are after biological treatment. The “Upstream” processes are performed at a temperature above the temperature of the biological treatment. In all cases, ammonia stripping is “Downstream” biological treatment while the thermal treatment with evaporative or evaporative / vacuum cooling can be either “Upstream” or “Downstream” of a biological treatment step.

[0163] Anaerobic digester

[0164] For most embodiments, there will be thermal treatment “Upstream” and ammonia steam stripping “Downstream” of a biological process such as anaerobic digestion. In the anaerobic digester, part of the material is converted into, e.g., biogas. This biological conversion generates wanted and unwanted digestion products. For anaerobic digestion, biogas is generated and continuously removed from the digester. However, the conversion of material will also result in high concentrations of ammonia which will inhibit the digestion process. The anaerobic digestion can be in the mesophilic, thermophilic, or extreme thermophilic temperature rage or any temperature in between. This invention will continuously remove parts of the digestion products by treating a side stream from the digester in a downstream system, utilizing heat made available from the evaporative or evaporative / vacuum cooler treating biomass / organic material from the thermal treatment process.

[0165] Upstream system

[0166] Thermal pretreatment

[0167] As mentioned above the process for thermal pretreatment can be any biological or thermo-chemical pretreatment method. One possible arrangement is to treat all or parts of the feedstock biomass / organic material prior to the biological process in a thermal pretreatment step, e.g. by THP (Thermal Hydrolysis Process), HTC (Hydrothermal Carbonization) and / or partial Wet Oxidation.

[0168] THP (Thermal Hydrolysis Process): This method involves heating under high pressure. The heat and pressure break down the cell walls of organic material, making it more biodegradable and enhancing the efficiency of subsequent processes like anaerobic digestion.

[0169] HTC (Hydrothermal Carbonization): HTC is a process that mimics the natural formation of coal but at a significantly accelerated rate. It involves treating organic materials with water under high pressure and temperature. The process converts the material into a coal-like substance, known as hydrochar, which can be used as a solid fuel or soil amendment. It's particularly useful for wet biomass and can help reduce the volume of waste.

[0170] Partial Wet Oxidation: This is a process where organic compounds in organic material are partially oxidized in the presence of water using oxygen (air) under high temperatures and pressures. It effectively opens the biomass structure to increase accessibility of organic material to the microbial community in anaerobic digesters for production of biogas.

[0171] A different configuration is to have a biological pretreatment prior to a thermal pretreatment process, or a biological pretreatment followed by a thermal pretreatment and dewatering where the liquid fraction is returned to the biological pretreatment step. Likewise, it is possible to carry out biological pretreatment followed by thermal pretreatment where all the thermally pretreated material is returned to the biological pretreatment. Another possibility is to have a thermal / biological pretreatment step in the form of an acid phase thermophile fermentation.

[0172] A thermal hydrolysis process (THP) for processing biomass / organic material, such as in the treatment of sewage sludge, typically operates under temperatures between 100°C and 230°C, such as between 120°C and 180°C, depending on the specific system and the desired outcomes of the process. To maintain water in a liquid state at these high temperatures, the process is carried out under high pressure, typically around 4 to 12 bar, such as 6 to 8 bar.

[0173] Thermophilic digestion, a process used in the treatment of waste and for biogas production, operates at higher temperatures compared to mesophilic digestion. The typical temperature range for thermophilic digestion is between 45°C and 65°C, such as between 50°C and 60°C. Some systems may operate slightly outside this range, depending on specific process design and objectives.

[0174] Thermophilic acid fermentation, a stage in the breakdown of organic material under high temperatures by thermophilic microorganisms, typically occurs at temperatures similar to those used in thermophilic digestion processes. For acid fermentation specifically, the temperature range is often between 50°C and 65°C. The exact temperature can vary based on the specific type of thermophiles involved and the substrate being fermented. Hygienization and pasteurization are thermal processes aimed at reducing or eliminating pathogens in various materials, including food organic waste, each with its typical temperature ranges tailored to achieve specific safety standards. Hygienization is commonly used in the treatment of sewage sludge and organic waste to make it safe for further handling. Typically, the process involves heating the material to temperatures ranging from 70°C to 100°C for a set period, often several hours, depending on the specific goals of the process and the nature of the material being treated. Pasteurization is widely used to kill harmful microorganisms without significantly changing the properties of a product. There are several pasteurization methods, each with its typical temperature and time combination. High-Temperature Short Time (HTST): Commonly 72°C for 15-20 seconds. Extended Shelf Life (ESL): Around 85°C for a few seconds. Ultra-High Temperature (UHT): Typically 135°C for 2- 5 seconds. Each process is designed to target specific pathogens and spoilage organisms, with the chosen temperatures and times balancing microbial safety with product quality. Pasteurization in the context of wastewater treatment typically involves similar temperatures to those used in the food industry, but the goals and standards might differ. The process is designed to significantly reduce the presence of pathogens. Temperatures are often around 65°C to 75°C and time intervals of 15 to 30 minutes are common, though the exact time can vary depending on regulatory requirements and the specific goals of the treatment.

[0175] Evaporative Cooler

[0176] From the thermal treatment system, the thermally treated biological / organic material may be transferred to an evaporative cooler. The transfer can be by pump or by differential pressure or gravity. In an evaporative cooler, the cooling is performed at atmospheric pressure or above, i.e. such as from 1 to 5 bar. Typical pressures in the evaporative cooler are in the range of 1 bar to 2 bar. If the evaporative cooler is in the form of a THP flash tank operated at 1-2 bar, the temperature is typically 100-120°C. The steam generated by the evaporative cooling is utilized in the “Downstream” ammonia removal systems where it can be utilized in different ways. The cooled material is transferred for further processing, typically in the anaerobic digester. The material from the evaporative cooler can also be transferred to the downstream system for further cooling. Dilution water can be added to the cooled material if required. Evaporative / Vacuum Cooler

[0177] From the thermal treatment system, the thermally treated biological / organic material may be transferred to an evaporative / vacuum Cooler. The transfer can be by pump or by differential pressure or gravity. In an evaporative / vacuum cooler, the cooling by evaporative cooling is performed below atmospheric pressure. Typical pressures and temperatures in the evaporative / vacuum cooler are in the range of 55 mbar to 700 mbar and 35 ° C to 90 ° C. The steam generated by the evaporative cooling is utilized in the “Downstream” ammonia removal systems where it can be utilized in different ways. The cooled material is transferred for further processing, typically in the anaerobic digester. The material from the evaporative / vacuum cooler can also be transferred to the downstream system for further cooling. Dilution water can be added to the cooled material if required.

[0178] Upstream product recovery from vapor

[0179] Product recovery on vapor from evaporative or evaporative / vacuum cooler. The thermally treated material entering the evaporative or evaporative / vacuum cooler can contain components that partly will enter the vapor phase and therefore leave the evaporative or evaporative / vacuum cooler with the vapor. The components can be recovered from the vapor in a scrubber / distillation / recovery process. As an example, part of the ammonia may enter the vapor in the evaporative or evaporative / vacuum cooler and can be recovered in an acid scrubber.

[0180] Pre-cooling

[0181] In one example of the invention, the thermally treated material is subject to further precooling by an indirect heat exchanger before biological or downstream processes. This can be in front of the evaporative or evaporative / vacuum cooler or between the evaporative or evaporative / vacuum cooler and the anaerobic digester. The pre-cooler will recover heat that can be used in the downstream processes or for other heating purposes, such as heating for the stripping process, a distillation process. Likewise, this could be used for purposes like preheating substrate, dilution water for substrate, polymer dilution water to enhance dewatering properties or boiler feed water to reduce fuel consumption for steam or heat production. Implementation will depend mainly on the operating conditions / temperature of the evaporative or evaporative / vacuum cooler. Additional heat sources

[0182] Additional sources of waste energy can be utilized to increase the product recovery in the down steam processes. As an example, the process gases out of a TH P pulper will contain some vapor. This vapor is today condensed in the process gas cooler. This vapor can be directed to the de-gasser / preheater of the downstream system.

[0183] Downstream system

[0184] Indirect pre-heating

[0185] The flow from the digester to the downstream system and / or between units in the downstream system can be heated indirectly by available heat sources. This heat can as example be from the pre-cooling in the upstream processes or it can be waste heat from CHP or biogas upgrade system. The pre-heating will increase the temperature of the media entering the downstream systems. The higher temperature will facilitate the de-gassing and / or stripping process. The indirect heating will typically be in a tube in tube heat exchanger.

[0186] De-gasser

[0187] A large cost, both CAPEX and OPEX, of the evaporative / vacuum cooler and ammonia stripping system is the system to remove the NCG from the system to maintain it below atmospheric pressure. Most methods to generate below atmospheric pressure in a system operate based on volume displacement. Therefore, 1 Nm3 removed at atmospheric pressure requires the removal of 10 m3 at 100 mbar(a) (assuming it is an ideal gas). One function of the de-gasser is to remove parts of the NCG in the media from the anaerobic digestion and from the vapor / NCG from the upstream systems.

[0188] This is done at a higher pressure compared to the pressure in the stripper and thereby reduces the overall size of the system to generate vacuum.

[0189] The de-gasser is a vessel that is operated below atmospheric pressure but normally above the pressure corresponding to the boiling point of the media entering the degasser. The de-gasser can operate in the range of 990 mbar(a) to 55 mbar(a) (35 ° C boiling point). Typically, the de-gasser will operate in the range of 70-300 mbar(a). The media from the anaerobic digester will typically contain both dissolved gases and gas bubbles in suspension. The reduced pressure in the de-gasser will cause parts of the gases (both bubbles and dissolved) to enter the gas phase of the de-gasser. The gases will be removed by means of a vacuum pump or other devices to generate a pressure below atmospheric pressure. The transfer from the anaerobic digester to the de-gasser can be done by a pump, however a preferred alternative is to transfer the media using the differential pressure between the anaerobic digester and the degasser vessel. The de-gasser is typically operated continuously or semi-continuously, but it can also be operated as batch.

[0190] Example A: the vacuum system of an evaporative / vacuum cooler and ammonia stripping system must in total remove 100 Nm3 / h of gas. The temperature of the media is 52 ° C and the stripper is operated at 46 ° C or 100 mbar(a). Without the degasser the total volume removed by the vacuum system is 1000 m3 / h. Assuming the de-gasser operates at 333 mbar(a) and can remove 75% of the total gas (or 75 Nm3 / h) then the de-gasser will remove 225 m3 / h and the rest 25Nm3 / h is removed in the stripper at 100 mbar(a) giving 250 m3 / h. In total, 475 m3 / h must be removed by the system or a reduction of 52,5% compared to removing all the NC gas at 100 mbar(a). The numbers given in the example are for illustration only. Actual numbers and optimum operation conditions will depend on site specific conditions.

[0191] Example B: Energy consumption savings using the de-gasser. The calculation is based on the pump curves for Busch Dolphin LX 0330 C liquid ring vacuum pump. Similar values are seen for different size of the Dolphin pump and for water ring pumps from other suppliers. In a system the stripper is operated at 42 ° C and 82 mbar. The specific energy consumption from the vacuum pump is 109 kJ / m3 or 1327 kJ / Nm3. The de-gasser is operated at 58 ° C and 180 mbar. The specific energy consumption for the vacuum pump on the de-gasser is 95 kJ / m3 or 524 kJ / Nm3. For a plant with 31 TS / hour of the THP pre-treatment and a recirculation ration of 100% of THP flow from the digester to the downstream system, the total flow of NC gas is estimated to 80,3 Nm3 / h with 1,5 Nm3 / m3 media from the digester. Around 91% of the NC gas is removed in the de-gasser under these conditions. The total energy consumption for the vacuum pump with the de-gasser is 13 kW. Total energy consumption for the vacuum pump without the de-gasser is 30 kW. The total energy savings for the vacuum pump with de-gasser are 55%.

[0192] In one example of the invention, the media extracted from the anaerobic digester to the de-gasser can be extracted from the bottom or close to the bottom of the anaerobic digester. At the bottom, more gases will be in the media, both as dissolved gas and as gas bubbles, due to the elevated pressure compared to media extracted closer to the top of the anaerobic digester. This configuration is preferred if the process inside the anaerobic digester will benefit from having gases removed from the media. In another example of the invention, the media can be extracted close to the top of the anaerobic digester or in the overflow system from the digester. In this region, parts of the gases are released from the media to the headspace of the anaerobic digester and therefore the gases sent to the de-gasser will be reduced. The reduced gases to the de-gasser will reduce the size of the system used to remove the gases from the de-gasser and thereby also the cost and the energy consumption.

[0193] Dissolved gas and gas bubbles enclosed in the cooling media to a direct condenser must also be removed by the vacuum system. Therefore, a de-gasser can with advantage also be used on some cooling media for direct condenser before the cooling media is sent to the direct condenser. This can be the case if the media for the condenser is material coming from another biological treatment step, like an anaerobic digester, and therefore contains gas bubbles and dissolved gases. In one example of the invention, the de-gasser in front of the stripper and the de-gasser for the cooling liquid for the direct condenser are connected to the same gas extraction system. This will reduce the number of gas extraction systems and thus the total cost of the system.

[0194] In one example of the system, the de-gasser is connected to the head space of the pulper of the THP plant. The excess vapor from the THP process can then be used to preheat the organic material in the de-gasser by direct condensation. This will both increase the temperature of the media in the de-gasser for enhanced de-gassing and subsequent stripping, and at the same time the process gas cooler on the THP plant can be eliminated. This will however increase the flow of NC gas to the vacuum pump.

[0195] In one example of the invention the steam from the steam stripper is used to preheat the sludge directly in the de-gasser. This is done after removing part of the ammonia from the steam from the steam stripper in a separate dedicated scrubber / distillation unit. Any excess steam after the de-gasser is condensed in a condenser.

[0196] Direct preheating and steam stripper

[0197] In one example of the invention, the vapor from the upstream system like the evaporative or evaporative / vacuum cooler can be transferred directly to the direct preheater and stream stripper. The direct preheater and steam stripper are placed between the anaerobic digester and any flash stripper, or between de-gasser and flash stripper if a de-gasser is included in the system. Due to the temperature difference between the media entering the direct preheater and the vapor from the evaporative or evaporative / vacuum cooler, part of the vapor will condense on the media and thereby heat the media. The fraction of free ammonia will increase with increasing temperature. The heating will also facilitate further de-gassing. The direct preheater will be designed to facilitate good contact between vapor and media.

[0198] In the direct preheater and steam stripper, vapor from the upstream processes is in direct contact with the media from the de-gasser. This will heat the media to a temperature at or just below the boiling point of water at the specific pressure setpoint of the direct preheater. This is given that the energy content in the vapor is equal to or larger than the energy required to raise the temperature of the media. The temperature is also dependent on the heat transfer between the vapor and media. To improve the heat transfer, media can be recirculated from the bottom to the top of the direct preheater and steam stripper.

[0199] Any excess vapor not condensed in the direct preheater and stream stripper will, along with the NCG, be transferred to the ammonia scrubber / distillation and / or final condenser.

[0200] In one example of the invention, the direct preheater and steam stripper are combined with the de-gasser in one system. In this example, the media is coming directly from the digester.

[0201] The transfer of the media from the direct preheater to any flash stripper can either be by a pump or by differential pressure / gravity. The media will typically be transferred continuously or semi-continuously.

[0202] The steam stripper and any flash stripper can be the same unit. This is the case if the pressure (and temperature) in the steam stripper and direct preheater is at a level where no further cooling of the media is required before further treatment. In this event, the media is pumped from the steam / flash stripper back to the anaerobic digester and / or to dewatering or other processing.

[0203] In one example of the invention the steam from the steam stripper is transferred to a dedicated scrubber / distillation for the recovery of ammonia at a higher temperature. This will allow for reuse of the steam in the de-gasser after removal of the ammonia. Indirect Preheating

[0204] In one example of the invention, the energy of vapor from the upstream system is partly transferred to the downstream system indirectly. This can be in different types of heat exchangers, e.g., shell and tube or tube in tube. Preferably, the energy is transferred in an evaporator type of system that simultaneously facilitates preheating of the media and evaporation of some of the water in the media. As an example, a falling film evaporator type can be used. The advantages of partly transferring the energy from the upstream part of the system by indirect preheating is that the amount of vapor from the upstream system, which is in direct contact with the media in the down steam system can be controlled.

[0205] In one example of the invention, the indirect preheating is driven by steam from a steam boiler or other steam sources. In this configuration, the steam condensate will remain clean and can be returned to the boiler system. In another example of the invention, two or more indirect systems are included where one of them is using clean steam.

[0206] Flash stripper

[0207] The media from the pre-heating may be transferred to a flash stripper by differential pressure or by pump. The transfer can be in batch but is preferably continues or semicontinuous. The media is preferably added to the head space of any flash stripper. In a flash stripper, part of the energy added to the media in the preheater is removed as vapor. A flash stripper is maintained at the desired operation temperature by adjusting the pressure to the boiling point of water at the operation temperature using the condenser and vacuum pump system. The vapor is continuously removed from the stripper to subsequent processes by differential pressure. NC gases not removed in the de-gasser are removed with the vapor in a flash stripper. A fraction of the ammonia will also be entrapped in this vapor.

[0208] Due to the low pressure in a flash stripper, instant boiling will take place inside a flash stripper. To avoid carryover from the flash tank to the subsequent process steps, a flash stripper is designed to ensure good separation of the vapor and media.

[0209] In one example of the invention, the media will enter the flash tank below medial level inside the tank. This will cause the flash to take place below the liquid level and can facilitate the stripping of ammonia. In one example of this invention, heat is applied to the media in a flash stripper. By adding heat, the amount of flash vapor increases. The heat can be added indirectly in a recirculation loop on a flash stripper. The heat can also be added indirectly using a heating jacket on a flash stripper or using a falling film shell and tube design heat exchanger like falling film evaporator design. Using indirect heating with at least part of the flash steam from an evaporative or evaporative / vacuum cooler enables collection of condensate from the evaporative or evaporative / vacuum cooler in a separate stream. Other means of heating the media can also be used; applying super-heated steam can facilitate the stripping of ammonia.

[0210] The media out of a flash stripper can flow by gravity if the flash tank is placed sufficiently high to overcome the operation vacuum in the flash tank by the liquid height in the outlet pipe. However, the media is commonly removed by means of a pump.

[0211] In one example of the invention, the flash stripper contains baffle plates or trays to increase the surface and thus facilitate the stripping. Furthermore, the stripping can be facilitated by recirculating the media from the bottom to the top of the flash tank through a spray nozzle.

[0212] A flash stripper is not required for the overall system to operate. If the pressure and temperature in the upstream preheater / strippers are as desired for the further downstream processes, then a flash stripper is not required.

[0213] In one example of the invention, part of the media is sent to further processing after a flash stripper. It will be an advantage to extract the media for dewatering on an anaerobic digester of biomass / organic material in the form of municipal sludge. Using the processed media for the dewatering will reduce undesirable methane emissions from the dewatering.

[0214] Media from the evaporative or evaporative / vacuum cooler can be added to a flash stripper. This will further cool the media from the evaporative or evaporative / vacuum cooler before downstream biological processes. At the same time, adding the media to a flash stripper will increase the flash vapor facilitating the stripping of ammonia.

[0215] In one example of the invention, a flash stripper is designed to avoid mixing of the media coming from the evaporative or evaporative / vacuum cooler and the steam stripper / preheater. This will make it possible to extract a fraction of the flow from the steam stripper directly to dewatering / further processing without having part of the media from the evaporative or evaporative / vacuum cooler in the flow. The media from the evaporative or evaporative / vacuum cooler requires further biological treatment before being sent to final dewatering.

[0216] Scrubber / recovery unit

[0217] The scrubber / recovery unit can be applied on the vapor from the evaporative or evaporative / vacuum cooler, from the steam stripper, and from a flash stripper. Part of the ammonia in the media will be in the flash vapor. The ammonia can be recovered from the vapor in a scrubber / recovery unit, like a distillation column. It is advantageous to apply a scrubber on the vapor as the components are already in the vapor phase. No regulation of the flow of vapor and gas through the scrubber is made and therefore the scrubber will be operated at the same pressure as the flash tank (except for a minor pressure drop through the scrubber).

[0218] As an example: to recover ammonia, a sulfuric acid scrubber can be used to recover ammonium sulfate. When using a sulfuric acid scrubber, a two-stage scrubbing system will commonly be used. In this setup, a high concentration stager is used first for extraction of the concentrated product, and a polishing stager is used where the final part of the ammonia is recovered in surplus of acid.

[0219] The ammonia can also be recovered in the condensate. By securing a sufficiently low temperature in the condenser, most of the components in the condensate will be recovered.

[0220] In one example of the invention, a distillation tower is added to the vapor to generate a concentrated media and a relative clean condensate without adding chemicals. A reflux distillation column can be used to concentrate the ammonia in the vapor out of the steam / flash stripper. Typical concentrations of ammonia in the vapor will be in the range of 1500 to 15000 mg / l. In the reflux evaporator, the concentration will be increased in the range of 10000 to 25000 mg / l in the final condensed ammonia hydroxide. The advantages of using reflux evaporator in combination with this invention compared to traditional air stripping systems is that the dilute ammonia solutions are already in the vapor phase, and therefore the energy consumption for the reboiler can be significantly reduced or eliminated. The de-gasser secures that the content of NC gases in the vapor is low, and it will therefore be a close correlation with operation pressure and boiling point.

[0221] Condenser

[0222] The vapor must be condensed to drive the vacuum in the system. The condensation can be either direct or indirect condensation. For both direct and indirect condensation, heat recovery can be an integrated part where the cooling media is a media where the energy from the condensation is utilized for the heating. In this way evaporative or evaporative / vacuum cooling can facilitate heat recovery.

[0223] In one example of the invention, there are two flash tanks and two condensers operating in series. Here, the first flash tank and the first condenser are operated at higher temperatures than the 2ndflash tank and 2ndcondenser. In this way, it is possible to optimize heat recovery from the flash vapor.

[0224] For the direct condenser, the cooling media can be removed from the condenser by gravity if the condenser is placed sufficiently high for the water height in the discharge pipe to overcome the vacuum inside the condenser. Alternatively, the cooling media can be removed by means of a pump.

[0225] Condensation of the steam will drive the vacuum in the system, but small amounts of NC gases must be removed continuously after the condensation of the steam. This is typically done by means of a vacuum pump but can also be done by an ejector.

[0226] One joined condenser and vacuum system can be used for both the de- gasser / preheater system and a flash stripper. This will typically be an advantage for smaller systems or systems where the amount of NC gas is low. For larger systems or systems with high amounts of NC gas, there can be a dedicated vacuum pump for the de-gassing and a dedicated condenser and vacuum system for the steam and flash stripper system. The 1stis operated at a higher pressure compared to the 2ndvacuum system.

[0227] In one example of the invention, the NC gases after the condensation of vapor (after a flash stripper, low pressure vacuum system) are transferred to the de-gasser and high- pressure vacuum system by means of a Roots pump. The advantages of the Roots pump or vacuum booster pump are the relatively low energy requirements per volume of gas transferred. The roots pump can typically operate with a limited differential pressure below 100 mbar. Therefore, it will be a limited pressure difference between the de-gasser and a flash stripper when using the booster pump. In one example, a flash stripper is operated at 40 ° C (73 mbar) and the de-gasser at 156 mbar, corresponding to a boiling temperature of 55 ° C giving a differential pressure of 83 mbar for the booster pump to overcome.

[0228] Specific embodiments of the invention

[0229] In one example of the invention, chemicals are added to the media.

[0230] Chemicals that enhance / accelerate / facilitate physical and / or chemical reactions in the evaporative or evaporative / vacuum cooler, de-gasser, and / or in the direct preheating and steam stripper can be added to the media. This can be added to facilitate the transfer of specific components to the vapor phase for subsequent recovery in the scrubber or condensate, or it can be added to facilitate specific chemical reactions. The chemicals can be added to the inlet media or to the recirculation media if recirculation is used.

[0231] In one example of the invention, chemicals, e.g. MgCI2, is added to the media in the de-gasser and / or preheater and / or flash stripper. The addition of these chemicals will facilitate the formation of phosphorus compounds, such as struvite and / or vivianite. In this way, scaling of down steam pumps and pipes can be reduced, and dewatering can be improved. The chemicals, e.g. MgCI2, can preferably be added in the degasser or preheater tank or to the inlet of the flash stripper to have more controlled precipitation of struvite and / or vivianite. Chemicals, e.g. MgCI2, can also be added directly to the digester.

[0232] In one example, the pH of the media is increased. Increasing the pH will facilitate ammonia transfer to the vapor phase due to an increasing fraction of free ammonia at increasing pH. Increasing the pH will preferably be done after the de-gasser, where part of the CO2 has been removed and thereby reducing the buffering capacity of the media. Example 1 Simple evaporative / vacuum cooler and ammonia extraction system The embodiment of figure 2 comprises a thermal treatment unit T 1 connected to an evaporative / vacuum cooler tank T2 via line L1. The material is transferred from T1 to T2 by differential pressure. The temperature in T1 is typically in the range of 102-120 ° C and pressure in the range of 1089 mbar and 1987 mbar, but temperature may be as low as 80 ° C. In practice the pressure will be slightly above the saturation pressure of water due to the presence of small amounts of NCG. This applies to not only T 1 but also to T2, T3, T4, T5, T6 and T7. The temperature in T2 is typically in the range of 38 ° C to 90 ° C and pressure in the range of 66 mbar to 702 mbar. The pressure in T2 is just above the pressure in T3. The only difference is the pressure drop from the pipe between T2 and T3 and the pressure drop in T3. Flash vapor from T2 is transferred to the lower part of a flash stripper tank T3 vial line L2 by differential pressure. At the lower part of T2, the media is transferred by pump P1 to digester T6 via line L3.

[0233] From the anaerobic digester T6, the media is transferred to the upper part of T3 by differential pressure via line L4. The flow in L4 is typically in the range of 100% to 300% of the flow in L1. T6 is typically operated slightly above ambient pressure. T3 is typically operated at a pressure between 66 mbar and 158 mbar. T3 is operated at a pressure given a boiling temperature of water desired for the further processing of the media in T6 considering heat loss and potential cooling / heating from adding dilution water. The media from T6 and the vapor from T2 moves counter current inside T3. T3 is equipped with baffle plates or packing material to secure good contact between the media and vapor. If the temperature of the media is below the boiling point of water at the operating pressure of T3, part of the vapor from T2 will condense and increase the temperature of the media. If the temperature of the media is above the boiling point of water at the operating pressure of T3, part of the water in the media will evaporate. Ammonia in the media will approach equilibrium with the vapor phase inside T3. Any excess vapor from T2 and / or flash vapor from media from T6 will leave T3. The vapor is extracted in the top of T3 and sent via line L5 to scrubber T4. The transfer is done by differential pressure. The vapor will also contain NC gases released from the media entering T3 and contained in the vapor from the evaporative / vacuum cooler. The media in T3 is pumped by P2. Part of the media is transferred to T6 via L10, and part of the media is transferred to downstream processes like dewatering via line L9.

[0234] In scrubber T4, components like ammonia are recovered from the vapor from T3. In this example, a sulfate scrubber is used but any scrubber / distillation system can be used. T4 is operated at a pressure just below the pressure in T3, defined by the combined pressure drop in L5 and T4. The vapor and NC gas are transferred to the condenser T5 via L6 by the pressure difference.

[0235] In this example, T5 is an indirect heat exchanger. The vapor from T4 is condensed using cooling water. The condensate is removed by pump P3 via line L8. The pressure in T5 is just below the pressure in T4, defined by the combined pressure drop in L6 and T5. The pressure in T5 is regulated by the vacuum pump P4, removing the NC gases in the vapor from T4.

[0236] Example 1. 1 Digesters in series

[0237] Digestion in series with 2 or more digesters and partly recirculation of digester material from last anaerobic digester to first anaerobic digester is common configuration and is shown in figure 3. The volatile solid reduction (VSR) increases through the serial digesters. Therefore, ammonia recovery is not done in the 1stdigester, where concentration is somewhat lower. The recovery of ammonia can with advantage be done on the final digester or between the 2ndlast and final digester. The ammonia recovery in this type of digester configuration will make it possible to increase recirculation (Line L12) from the last to the first digester with reduced risk of ammonia inhibition.

[0238] Example 1.2 Partly removal of suspended solid before ammonia stripping

[0239] In one example of the invention a liquid / solid separation step T7 is introduced before the ammonia stripping T3. This will generate a solid fraction removed by L12 or L13and a liquid fraction reaction with reduced suspended solids, which is sent to T3 via line L11 for further treatment. Removing a large fraction of the suspended solid from the liquid fraction before the ammonia stripping will make it possible to use a wider range of packing material types. This will significantly improve the applicable surface area and further enhance the stripping of ammonia. The solid fraction from T7 can be sent to further processing via L12 or recycled back to the anaerobic digester via L13 or a mix of the two routes. Further processing can as an option be back to the upstream thermal pre-treatment. This embodiment is shown I figure 3A.

[0240] Example 1.3 Evaporative cooling at or above atmospheric pressure

[0241] In one example of the invention the evaporative cooling T2 connected to the upstream thermal pretreatment T 1 via line L1 is operated at or above atmospheric pressure. The vapor from T2 is send to the downstream ammonia stripping system T3. The down stream treatment can be as described in the other examples. This configuration can be relevant in some thermal pre-treatment methods where only part of or none of the vapor from the evaporative cooling is recovered internally in the pretreatment. An example of such a thermal pre-treatment system is described in WO2016066752. This embodiment is shown I figure 3B

[0242] Example 1.4 Evaporative / vacuum cooler and ammonia extraction system with 2-stage heat recovery

[0243] The embodiment shown in figure 3C comprises a thermal pretreatment unit T1 connected to an evaporative / vacuum cooler tank T2 via line L1. The material is transferred from T1 to T2 by differential pressure. The temperature in T1 is typically in the range of 102-120 ° C and the pressure is in the range of 1089 mbar and 1987 mbar. The temperature in T2 is typically in the range of 38 ° C to 90 ° C and the pressure is in the range of 66 mbar to 702 mbar. The pressure in T2 is just above the pressure in T3. The only difference is the pressure drop from the pipe between T2 and T3 and the pressure drop in T3. Flash vapor from T2 is transferred to the lower part of a steam stripper tank T3 vial line L2 by differential pressure. At the lower part of T2, the media is transferred by pump P1 to digester T6 via line L3.

[0244] T3 is typically operated at a pressure between 66 mbar and 702 mbar and a temperature in the range of 38 °C to 90 °C. The maximum temperature of T3 is determined by the available flash steam from T2. The media from T6 and the vapor from T2 moves counter current inside T3. T3 is equipped with baffle plates, trays or packing material to secure good contact between the media and vapor. If the temperature of the media from T8 entering T3 is below the boiling point of water at the operating pressure of T3, part of the vapor from T2 will condense and increase the temperature of the media. Ammonia in the media will approach equilibrium with the vapor phase inside T3. Any excess vapor from T2 and / or flash vapor from media from T6 will leave T3. The vapor is extracted in the top of T3 and sent via line L5 to scrubber T4. The transfer is done by differential pressure. This vapor will also contain NC gases contained in the vapor from T2. The media in T3 is pumped by P2. Part of the media is transferred to T6 via L10, and part of the media is transferred to downstream processes like dewatering via line L9. In scrubber T4, components like ammonia are recovered from the vapor from T3. In this example, a sulfate scrubber is used but any scrubber / distillation system can be used. T4 is operated at a pressure just below the pressure in T3, defined by the combined pressure drop in L5 and T4. After removing part of the ammonia in the steam in T4, the steam is sent to T8 via line L11 by differential pressure. The pressure in T8 is just below the pressure in T4. From the anaerobic digester T6, the media is transferred to the upper part of de-gasser T8 by differential pressure via line L4 or by pump (not shown). Part of the steam from T4 will condense in the media from T8 and heat the media. The heating and low pressure in T8 will remove CO2 from the media. Any steam not condensed in T8 and NC gas are transferred to the condenser T5 via L13 by the pressure difference.

[0245] In this example, T5 is an indirect heat exchanger. The vapor from T8 is condensed using cooling water. The condensate is removed by pump P3 via line L8. The pressure in T5 is just below the pressure in T8, defined by the combined pressure drop in L6 and T5. The pressure in T5 is regulated by the vacuum pump P4, removing the NC gases in the vapor from T8.

[0246] Example 2 Advanced evaporative / vacuum cooling and ammonia extraction system The embodiment shown in figure 4 comprises a thermal treatment unit T 1 connected to a evaporative / vacuum cooler tank T2 via line L1. The material is transferred from T 1 to T2 by differential pressure. The temperature in T1 is typical in the range of 102-120 ° C and the pressure is close to or just above the saturation pressure of water at the given temperature of 1089 mbar and 1987 mbar, but temperature may be as low as 80 ° C. In practice the pressure will be slightly above the saturation pressure of water due to the presence of small amounts of NCG. This applies to not only T 1 but also to T2- T9. The temperature in T2 is typically in the range of 38 ° C to 90 ° C and the pressure is close to saturation of 66 mbar to 702 mbar. The pressure in T2 is just above the pressure in T4. The only difference is the pressure drop over the pipe L2. The pressure reduction from T1 to T2 will cause some of the water in the media to evaporate, creating vapor. Part of the energy in the media from T1 to T2 can be recovered by heat exchanger H3 if the energy has higher value for other applications than ammonia stripping. Flash vapor from T2 is transferred to the steam stripper / preheater tank T4 via line L2 by the differential pressure. At the lower part of the evaporative / vacuum cooler, the media is transferred by pump P1 to a flash stripper via line L3.

[0247] From the anaerobic digester T8, media is transferred to de-gasser T3 by the differential pressure via line L4. The media is heated indirectly in heat exchanger H1 by low temperature waste heat. The flow in L4 is typically in the range of 100% to 300% of the flow in L1. The temperature increase in H1 is typically in the range of 2-15 ° C. T8 is typically operated slightly above ambient pressure. T3 is typically operated at a pressure between 75 mbar and 900 mbar. The pressure in T3 is above boiling point pressure of the media entering T3. The pressure in T3 is regulated by means of vacuum pump P3, connected to the head space of T3 via line L5. Antifoam is dosage by pump P8 via line L17 to L4 if any of the tanks T3, T4 or T5 have problems with foam. The step vice reduction in pressure will for most media eliminate the need of antifoaming agents.

[0248] Excess vapor and NC gas from the pulper headspace T9 are transferred to T3 below liquid level via line L16. In T3, the vapor is condensed and used to preheat the media from T8. The NC gas from T9 is removed along with the gases from the media from T8 by the vacuum pump.

[0249] P3 is of the water ring vacuum pump type. The NC gases and small amounts of vapor coming from T3 will contain some ammonia that to some extent will be dissolved / condensed in the recirculation water in the vacuum pump. This is due to low temperature and atmospheric pressure, causing part of the CO2 to dissolve in the water and thus reduces the pH. Both low pH and low temperature facilitate the ammonia to dissolve in the water. In one example, acid is added to the recirculation liquid to further facilitate the capture of ammonia. The condensate / dilution water from P3, containing parts of the ammonia, will be sent to T6 by differential pressure via line L20.

[0250] The media is transferred from the de-gasser via line L6 to the steam stripper / preheater tank T4 by gravity / differential pressure. T4 is designed to ensure good contact between the media and the vapor transferred from T2 to T4 via L2. Line L2 enters T4 at the lower part of the tank. To further facilitate the media-vapor contact, pump P2 recirculates media from the lower part of T4 to the upper part of T4. The contact between vapor and media in T4 will cause the energy to be transferred from the vapor to the media by condensing part of the vapor. This condensation will increase the temperature of the media to a temperature just below or equal to the condensation temperature of water at the given pressure in T4. That is, if the contact between the media and the vapor is sufficient and there is enough energy from condensing the vapor. If there is excess energy in the vapor or the heat transfer to the media is not sufficient, then excess vapor and any remaining NC gases will be extracted from the upper part of T4. The vapor will contain parts of the ammonia in the media from T3. To further facilitate the stripping of ammonia, base is added to L7. The base is dosed by pump P9 via line L18. The vapor is sent to scrubber T6 via line L9. T6 is operated at a pressure below T4 and the flow through L9 is regulated by a valve. The flow is regulated to maintain the desired pressure in T4. Heat exchanger H2 on L7 is used to add additional heat to the media and thereby increase the excess vapor that will be removed via line L9 to the scrubber. The media in T4 is transferred to a flash stripper T5 via line L8, taken at the high-pressure side of P2.

[0251] Magnesium chloride MgCh is dosed by pump P10 via line L19 into line L8. MgCh will facilitate struvite precipitation in T5. T5 is operated at a pressure given a boiling temperature of water desired for the further processing of the media in T8 considering heat loss and potential cooling / heating from adding dilution water. The temperature in T5 is typically in the range of 38-60° C and the pressure in the range of 66 mbar and 199 mbar. The temperature is below the temperature in T4 and part of the water in the media will therefore evaporate. The flash vapor is extracted in the top of T5 and sent via line L10 to T6 by differential pressure. Inside T5, a vertical plate is installed to separate the media coming from T2 (via L3) and the media from T4. In this way, it is possible to send part of the media from T4 by pump P6 vial line L11 to further processing like dewatering and all the media coming from T2 to T8. The rest of the media from T4 will mix with media from T2 and be pumped to T8 by P7 via L12. In this way, only one flash stripper is required and the flash vapor from media from T2 can support the stripping of media from T4.

[0252] In scrubber T6, components, ammonia, are recovered from the vapor from T4 and T5. In this example, a sulfate scrubber is used, but it can be any scrubber system. T6 is operated at a pressure just below the pressure in T5, defined by the combined pressure drop in L10 and T6. The vapor is transferred to condenser T7 via L13 by differential pressure. T6 can have chemical dosing systems, recirculation pumps and can also be two tanks in series with a high concentration and a polishing step. All this is known to the skilled person and is not shown.

[0253] T7 is in this example an indirect heat exchanger. The vapor from T6 is condensed using cooling water. The condensate is removed by pump P5 via line L14. The pressure in T7 is just below the pressure in T6, defined by the combined pressure drop in L13 and T7. The pressure in T7 is regulated by removing the small amounts of NC gases in the vapor from T4 and T5 by vacuum pump P4. T7 can also be a direct condenser. Example 2. 1 Similar to system 2, but with chemical free ammonium hydroxide recovery by reflux distillation

[0254] The scrubber in example 2 can as shown in figure 5 be exchanged with a reflux distillation. This will eliminate the consumption of chemicals for the scrubber and produce ammonium hydroxide instead of ammonium salt. Ammonium hydroxide will likely be easier to sell as a product. Cost and safety issues when handling chemicals will be an advantage to avoid at the WWTP.

[0255] The specific advantages of using reflux distillation in combination with this invention that the ammonium is already in vapor phase when it enters the distillation column. Therefore, the energy consumption for the distillation is reduced and potentially the reboiler can be avoided.

[0256] Example 2.2 Similar to system 2, but steam from steam stripper is used to preheat sludge in de-gasser after removal of ammonia in a dedicated ammonia recovery unit. In the embodiment, shown in Figure 5A, the vapor from steam stripper T4 is directed to a dedicated unit T11 for ammonia removal (scrubber or distillation). The vapor with reduced ammonia concentration is then directed to the de-gasser T3. In T3, the steam from T11 is partly condensed and the media from digester T8 is preheated. Steam from T11 that is not condensed in T3 will leave T3 via line L5 and be condensed in condenser T10. On line L5 to T10, a unit for recovery of ammonia can be installed (not shown). The non-condensable gases will be removed by vacuum pump P8. The flow of non-condensable gases and steam from T2 to T4 to T11 to T3 to T10 to P8 is driven by differential pressure and, hence, the pressure will be lower in each tank going from T2 to P8. Flow of media from T3 to T4 can be by gravity if T3 is placed higher than T4, or by a pump (not shown). Flash stripper T5 in this example connected to dedicated ammonia recovery T6, condenser T7 and vacuum pump P4. A skilled person will easily realise that line L5 from the de-gasser can be connected directly to stripper T6 or condenser T7 with a suitable device for regulating the flow of steam and NC gas to maintain desired pressure in T3. This will eliminate the need for TIO and P8, and at the same time increase the load on T7 and P4.

[0257] The specific advantage of this configuration is that without increasing the energy consumption it is possible to increase the temperature in the de-gasser and steam stripper. The increased temperature facilitates de-gassing and the ammonia stripping. The increased temperature in condenser T10 will give the option of recovering heat at a higher temperature out of the condenser, alternative to using a condenser with reduced size due to the increased delta T.

[0258] Example 3 Indirect heat recovery and steam stripping

[0259] This example, shown in figure 6, uses an indirect heat exchanger T3 to transfer at least part of the heat from the evaporative / vacuum cooler T2 flash vapor via line L2 to the media from T6. This can be an advantage if the flash vapor from the evaporative / vacuum cooler contains components there is desirable not to have mixed with the process media from the T6. This configuration is also an advantage if it is desired reduced the total flow to the T6 and subsequent to final disposal L9 by removing a condensate stream via pump P5.

[0260] Example 4 No direct heat recovery from upstream process

[0261] In this example of an alternative solution, shown in figure 7, the energy from the thermal process T1 is transferred directly to the anaerobic digester T5 and through T5 further to the downstream processes in a flash stripper T2. The excess energy in T5 is removed by operating a flash stripper T2 at a pressure and therefore temperature below that required in T5. Most of the variation from example 2 can be implemented in this concept also (not shown), especially the de-gasser will be highly relevant. Energy from thermal process (THP, HTC, partial Wet Oxidation, and / or thermophile fermentation etc.) is still used for any flash stripping, but in a simpler setup. This configuration is especially relevant when the anaerobic digester T5 is operated at thermophilic conditions because a larger fraction of total ammonium is already as free ammonium due to the elevated temperature.

[0262] Further specific embodiments of the invention

[0263] The present invention may be further characterized by the following additional specific embodiments.

[0264] A1. A method for treatment of biomass / organic material having a dry matter content of at least 3% comprising the steps of: subjecting said biomass / organic material to a thermal pre-treatment, comprising one or more of THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, thereby obtaining a thermally pre-treated biomass / organic material subjecting said thermally pre-treated biomass / organic material to cooling by use of vacuum / evaporative cooling thereby generating: o a first vapor phase comprising at least 90% W / W steam, and o a cooled pre-treated biomass / organic material the average temperature of which is at least 10 °C lower than the average temperature of said thermally pre-treated biomass / organic material, subjecting a biomass / organic material, optionally said cooled thermally pretreated biomass / organic material, to a processing step in the form of an anaerobic digestion process, thereby obtaining a processed biomass / organic material, subjecting at least part of said processed biomass / organic material to a steam stripping step by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed biomass / organic material stripped of at least part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said method being characterized in that: said second vapor phase comprising steam used for said steam stripping of said at least part of said processed biomass / organic material comprises at least part of said first vapor phase comprising steam generated by said vacuum / evaporative cooling of said thermally pre-treated biomass / organic material, and said at least part of said processed biomass / organic material is stripped of at least 10% of its ammonia content in said steam stripping step.

[0265] A2. A method according to A1, further characterized in that said biomass / organic material processed in said anaerobic digestion comprises at least part of said thermally pre-treated biomass / organic material. A3. A method according to A1 or A2, further characterized in that at least part of said ammonia comprised in said third vapor phase is recovered from said third vapor phase, e.g., by scrubbing or distillation.

[0266] A4. A method according to A1 or A2, further characterized in that at least part of said first vapor phase comprising steam generated by said vacuum / evaporative cooling is continuously or semi-continuously transferred from said vacuum / evaporative cooling to said steam stripping step.

[0267] A5. A method according to A3, further characterized in that the part of said first vapor phase generated by use of said vacuum / evaporative cooling, which is comprised by said second vapor phase, which is used for said steam stripping step, and said third vapor phase generated in said steam stripping step are continuously transferred by differential pressure to said subsequent processes for recovery of said ammonia.

[0268] A6. A method according to A1 or A2, further characterized in that part of said pretreated biomass / organic material, e.g. in the form of VOC’s, CO2, NH3, CH4, C2H6, C3H8, C4HIO, C2H4, C3H6, C2H2, C6H6and / or H2S contained therein, enters said first vapor phase, when said pre-treated biomass / organic material is subjected to cooling by use of vacuum / evaporative cooling, and is recovered by a scrubber / distillation process before being used in said steam stripping step as part of said second vapor phase.

[0269] A7. A method according to A6, further characterized that at least part of said pretreated biomass / organic material, e.g. in the form of VOC’s, CO2, NH3, CH4, C2H6, C3H8, C4HIO, C2H4, C3H6, C2H2, C6H6and / or H2S contained therein, which enters said first vapor phase, is part of, said part of, said first vapor phase, which is comprised by said second vapor phase, which is used for said steam stripping step and is recovered by a scrubber / distillation performed on said third vapor phase generated in said steam stripping step.

[0270] A8. A method according to A1 or A2, further characterized in that said vacuum / evaporative cooling is performed at below atmospheric pressure, such as from 55 mbar to 700 mbar and at a temperature from 35 ° C to 90 ° C. A9. A method according to A1 or A2, further characterized in that said at least part of said processed biomass / organic material, which is subjected to said steam stripping step, is the liquid part of at least part of said processed biomass / organic material having been subjected to a liquid / solid separation step.

[0271] A10. A method according to A1 or A2, further characterized in that said pre-treated biomass / organic material is pre-cooled before being subjected to vacuum / evaporative cooling.

[0272] A11. A method according to A1 or A2, further characterized in that said cooled pretreated biomass / organic material is subjected to further cooling and / or processing, e.g. by the addition of dilution water.

[0273] A12. A method according to A1, A2 or A9, further characterized in that at least part of said steam stripped processed biomass / organic material and / or at least part of any solid part of said at least part of said processed biomass / organic material is returned to either said thermal pre-treatment or said anaerobic digestion process, thereby contributing to reducing the average concentration of ammonia in the material being subjected to said thermal pre-treatment or said anaerobic digestion process.

[0274] A13. A method according to A3, further characterized in that said recovery of said ammonia is achieved by:

[0275] - scrubbing of said third vapor phase by use of acid and said ammonia is recovered in the form of an ammonium salt, or

[0276] - distillation of said third vapor phase and said ammonia is recovered in the form of ammonia water.

[0277] A14. A method according to A1 or A2, further characterized in that CO2, whether dissolved whether or in the form of bubbles, in said pre-treated biomass / organic material enters the vapor phase and becomes part of said first vapor phase when said thermally pre-treated biomass / organic material is subjected to said cooling by use of vacuum / evaporative cooling, which contributes to an increase in the pH of said cooled pre-treated biomass / organic material compared to the pH of said thermally pre-treated biomass / organic material. A15. A method according to A1 or A2, further characterized in that at least part of any CO2 , whether dissolved or in the form of bubbles, in said processed biomass / organic material enters the vapor phase and becomes part of said third vapor phase when said processed biomass / organic material is subjected to said stream stripping, which contributes to an increase in the pH of said steam stripped processed biomass / organic material compared to said processed biomass / organic material.

[0278] A16. A method according to A1 or A2, further characterized in that at least part of any CO2, whether dissolved or in the form of bubbles, in said processed biomass / organic material is removed in a separate de-gassing step before said processed biomass / organic material is subjected to said steam stripping.

[0279] A17. A method according to A16 further characterized in that said de-gassing step is performed by use of a dedicated vacuum generating system.

[0280] A18 A method according to A16 further characterized in that at least part of said ammonia comprised in said third vapor phase is recovered from said third vapor phase, e.g., by scrubbing or distillation, and in that said third vapor phase, after removal of part of said ammonia, is used to directly or indirectly heat said processed biomass / organic material in said de-gasser

[0281] A19. A method according to A1 or A2, further characterized in that it includes adding chemical additives to said biomass / organic material, said pre-treated biomass / organic material, said cooled pre-treated biomass / organic material and / or said processed biomass / organic material to increase the pH of said processed biomass / organic material being subjected to or having been subjected to said steam stripping step.

[0282] A20. A method according to A1 or A2, further characterized in that it includes adding chemical additives to said biomass / organic material, said pre-treated biomass / organic material, said cooled pre-treated biomass / organic material and / or said processed biomass / organic material to facilitate phosphorus precipitation from said processed biomass / organic material being subjected to or having been subjected to said steam stripping step.

[0283] A21. A method according to A1 or A2, further characterized in that said stream stripping is followed by a flash stripping characterized in that the flash stripping is operated at a pressure, which is below the pressure in said steam stripping and gives rise to a boiling point of said biomass / organic material in the flash stripper, which is below the temperature of the biomass / organic material entering the flash stripper.

[0284] A22. A method for treatment of biomass / organic material having a dry matter content of at least 3% comprising the steps of: subjecting said biomass / organic material to a thermal pre-treatment step, comprising one or more of THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, thereby obtaining a thermally pre-treated biomass / organic material, subjecting at least part of said thermally pre-treated biomass / organic material to processing in the form of an anaerobic digestion process, thereby obtaining a processed biomass / organic material, subjecting at least part of said processed biomass / organic material to concomitant cooling and steam stripping by use of vacuum / evaporative cooling thereby generating: o a steam stripped and cooled processed biomass / organic material stripped of at least part of the ammonia content, and o a vapor phase comprising steam and ammonia, said method being characterized in that: at least part of said thermally pre-treated biomass / organic material is transferred directly from said thermal pre-treatment step to said processing step in the form of an anaerobic digestion process, without an interposed cooling step, said concomitant cooling and steam stripping by use of vacuum / evaporative cooling of at least part of said processed biomass / organic material is achieved by flash stripping, and said at least part of said processed biomass / organic material is stripped of at least 20% of its ammonia content in said steam stripping step.

[0285] A23. A method for treatment of biomass / organic material having a dry matter content of at least 3% comprising the steps of: subjecting said biomass / organic material to a thermal pre-treatment, comprising one or more of THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, thereby obtaining a thermally pre-treated biomass / organic material subjecting said thermally pre-treated biomass / organic material to cooling by use of evaporative cooling thereby generating: o a first vapor phase comprising at least 90% W / W steam, and o a cooled pre-treated biomass / organic material the average temperature of which is at least 10 °C lower than the average temperature of said thermally pre-treated biomass / organic material, subjecting a biomass / organic material, optionally said cooled thermally pretreated biomass / organic material, to a processing step in the form of an anaerobic digestion process, thereby obtaining a processed biomass / organic material, subjecting at least part of said processed biomass / organic material to a steam stripping step by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed biomass / organic material stripped of at least part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said method being characterized in that: said second vapor phase comprising steam used for said steam stripping of said at least part of said processed biomass / organic material comprises at least part of said first vapor phase comprising steam generated by said evaporative cooling of said thermally pre-treated biomass / organic material, and said at least part of said processed biomass / organic material is stripped of at least 10% of its ammonia content in said steam stripping step.

[0286] B24. A system for treatment of biomass / organic material comprising: one or more thermal pre-treatment units, such as units for THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, for producing a thermally pre-treated biomass / organic material a vacuum / evaporative cooling unit for subjecting said thermally pre-treated biomass / organic material to cooling thereby generating: o a first vapor phase comprising steam, and o a cooled pre-treated biomass / organic material, a processing unit in the form of an anaerobic digestion unit, for subjecting a biomass / organic material, optionally said cooled thermally pre-treated biomass / organic material, to a biological process in the form of an anaerobic digestion to obtain a processed anaerobically digested biomass / organic material, a steam stripping unit for subjecting at least part of said processed anaerobically digested biomass / organic material to steam stripping by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed anaerobically digested biomass / organic material stripped of part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said system being characterized in that: it comprises tubing and equipment, which tubing and equipment allows for at least part of said first vapor phase, comprising steam, generated in said vacuum / evaporative cooling unit, to be transferred to be part of said second vapor phase, comprising steam, used in said steam stripping unit.

[0287] B25. A system according to B24 further characterized in that it comprises tubing and equipment, which tubing and equipment allows for at least part of said thermally pretreated biomass / organic material to be transferred to said anaerobic digestion unit.

[0288] B26. A system according to B24 or B25, further characterized in that it comprises tubing and equipment, which tubing and equipment allows for at least part of said processed biomass / organic material to be subjected to a liquid / solid separation step, and for the liquid part of at least part of said processed biomass / organic material, having been subjected to said liquid / solid separation step, to be the part of said at least part of said processed biomass / organic material, which is subjected to said steam stripping step.

[0289] B27. A system according to any of B24-26, further characterized in that it comprises an ammonia scrubbing or distillation unit, which is connected to said steam stripping unit by tubing and equipment, which tubing and equipment allows for transfer of at least part of said third vapor phase from said steam stripping unit to said ammonia scrubbing or distillation unit.

[0290] B28. A system according to any of B24-26, further characterized in that it comprises tubing and equipment, which tubing and equipment allows for the continuous or semi- continuous transfer of at least part of said first vapor phase, comprising steam, generated by said vacuum / evaporative cooling unit, to said steam stripping unit.

[0291] B29. A system according to any of B24-26, further characterized in that it comprises tubing and equipment, which tubing and equipment allows for continuous transfer of at least part of said first vapor phase generated by use of said vacuum / evaporative cooling unit and at least part of said third vapor phase generated in said steam stripping unit by differential pressure to one or more scrubbing or distillation units, including said ammonia scrubbing or distillation unit.

[0292] B30. A system according to any of B24-26, further characterized in that it comprises a pre-cooling unit and tubing and equipment, which tubing and equipment allows for transfer of said pre-treated biomass / organic material from said pretreatment unit to said pre-cooling unit and transfer of material from said pre-cooling unit to said vacuum / evaporative cooling unit.

[0293] B31. A system according to any of B24-26, further characterized in that it comprises tubing and equipment, which tubing and equipment allows for further cooling and / or processing of said cooled pre-treated biomass / organic material, e.g. by the addition of dilution water.

[0294] B32. A system according to any of B24-26, further characterized in that it comprises tubing and equipment, which tubing and equipment allows for the return of at least part of said processed biomass / organic material, possibly in the form of part of said processed biomass / organic material having been subjected to a solid / liquid separation step, stripped of ammonia from said steam stripping unit, to said anaerobic digestion unit.

[0295] B33. A system according to any of B24-26 further characterized in that it comprises a de-gasser vessel placed downstream of said anaerobic digestion unit and upstream of said steam stripping unit and tubing and equipment, which tubing and equipment allows for transfer of material from said anaerobic digestion unit to said de-gasser vessel and from said de-gasser vessel to said steam stripping unit.

[0296] B34. A system according to any of B24-26, further characterized in that said de-gasser vessel is connected by tubing and equipment to a dedicated vacuum generating system.

[0297] B35. A system according to any of B24-26, further characterized in that it comprises tubing and equipment, which tubing and equipment allows for the return of at least part of said processed biomass / organic material, possibly in the form of part of said processed biomass / organic material having been subjected to a solid / liquid separation step, stripped of ammonia from said steam stripping unit, to upstream of either said anaerobic digestion unit or upstream of said thermal pre-treatment units.

[0298] B36. A system for treatment of biomass / organic material comprising: one or more thermal pre-treatment units, such as units for THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, for producing a thermally pre-treated biomass / organic material, a processing unit in the form of an anaerobic digestion unit, for subjecting said thermally pre-treated biomass / organic material to processing in the form of an anaerobic digestion process, to obtain a processed biomass / organic material, a flash stripping unit for subjecting at least part of said processed biomass / organic material to concomitant cooling and steam stripping by use of vacuum / evaporative cooling thereby generating: o a steam stripped and cooled processed biomass / organic material stripped of at least part of the ammonia content, and o a vapor phase comprising steam and ammonia, said system being characterized in that: it comprises tubing and equipment, which tubing and equipment allows for at least part of said thermally pre-treated biomass / organic material to be transferred directly from said thermal pre-treatment units to said processing unit in the form of an anaerobic digestion unit, without an interposed cooling unit, it comprises tubing and equipment, which tubing and equipment allows for at least part of said steam stripped and cooled processed biomass / organic material, stripped of at least part of the ammonia content, generated in said flash stripping unit to be returned to said a processing unit in the form of an anaerobic digestion unit.

[0299] B37. A system for treatment of biomass / organic material comprising: one or more thermal pre-treatment units, such as units for THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, for producing a thermally pre-treated biomass / organic material a evaporative cooling unit for subjecting said thermally pre-treated biomass / organic material to cooling thereby generating: o a first vapor phase comprising steam, and o a cooled pre-treated biomass / organic material, a processing unit in the form of an anaerobic digestion unit, for subjecting a biomass / organic material, optionally said cooled thermally pre-treated biomass / organic material, to a biological process in the form of an anaerobic digestion to obtain a processed anaerobically digested biomass / organic material, a steam stripping unit for subjecting at least part of said processed anaerobically digested biomass / organic material to steam stripping by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed anaerobically digested biomass / organic material stripped of part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said system being characterized in that: it comprises tubing and equipment, which tubing and equipment allows for at least part of said first vapor phase, comprising steam, generated in said evaporative cooling unit, to be transferred to be part of said second vapor phase, comprising steam, used in said steam stripping unit.

[0300] C38. A method of refurbishing an existing Water Resource Recovery Facility (WRRF), Waste Water Treatment Plant (WWTP) or anaerobic digestion plant for farm or industrial waste to ensure that said WRRF, WWTP or anaerobic digestion plant for farm or industrial waste comprises the units of a system according to any of B24-37.

Claims

Claims1. A method for treatment of biomass / organic material having a dry matter content of at least 3% comprising the steps of: subjecting said biomass / organic material to a thermal pre-treatment, comprising one or more of THP, HTC, partial Wet Oxidation, thermophilic digestion, thermophile acid fermentation and / or pasteurization, thereby obtaining a thermally pre-treated biomass / organic material subjecting said thermally pre-treated biomass / organic material to cooling by use of vacuum / evaporative cooling thereby generating: o a first vapor phase comprising at least 90% W / W steam, and o a cooled pre-treated biomass / organic material the average temperature of which is at least 10 °C lower than the average temperature of said thermally pre-treated biomass / organic material, subjecting a biomass / organic material, optionally said cooled thermally pretreated biomass / organic material, to a processing step in the form of an anaerobic digestion process, thereby obtaining a processed biomass / organic material, subjecting at least part of said processed biomass / organic material to a steam stripping step by use of a second vapor phase comprising steam thereby generating: o a steam stripped processed biomass / organic material stripped of at least part of the ammonia content, and o a third vapor phase comprising steam and ammonia, said method being characterized in that: said second vapor phase comprising steam used for said steam stripping of said at least part of said processed biomass / organic material comprises atleast part of said first vapor phase comprising steam generated by said vacuum / evaporative cooling of said thermally pre-treated biomass / organic material, and said at least part of said processed biomass / organic material is stripped of at least 10% of its ammonia content in said steam stripping step.

2. A method according to claim 1, further characterized in that said biomass / organic material processed in said anaerobic digestion comprises at least part of said thermally pre-treated biomass / organic material.

3. A method according to claim 1 or 2, further characterized in that at least part of said ammonia comprised in said third vapor phase is recovered from said third vapor phase, e.g., by scrubbing or distillation.

4. A method according to claim 1 or 2, further characterized in that at least part of said first vapor phase comprising steam generated by said vacuum / evaporative cooling is continuously or semi-continuously transferred from said vacuum / evaporative cooling to said steam stripping step.

5. A method according to claim 3, further characterized in that the part of said first vapor phase generated by use of said vacuum / evaporative cooling, which is comprised by said second vapor phase, which is used for said steam stripping step, and said third vapor phase generated in said steam stripping step are continuously transferred by differential pressure to said subsequent processes for recovery of said ammonia.

6. A method according to claim 1 or 2, further characterized in that part of said pretreated biomass / organic material, e.g. in the form of VOC’s, CO2, NH3, CH4, C2H6, C3H8, C4HIO, C2H4, C3H6, C2H2, C6H6and / or H2S contained therein, enters said first vapor phase, when said pre-treated biomass / organic material is subjected to cooling by use of vacuum / evaporative cooling, and is recovered by a scrubber / distillation process before being used in said steam stripping step as part of said second vapor phase.

7. A method according to claim 6, further characterized that at least part of said pretreated biomass / organic material, e.g. in the form of VOC’s, CO2, NH3, CH4, C2H6, C3H8, C4HIO, C2H4, C3H6, C2H2, C6H6and / or H2S contained therein, which enters said first vapor phase, is part of, said part of, said first vapor phase, which is comprised by said second vapor phase, which is used for said steam stripping step and is recovered by a scrubber / distillation performed on said third vapor phase generated in said steam stripping step.

8. A method according to claim 1 or 2, further characterized in that said vacuum / evaporative cooling is performed at below atmospheric pressure, such as from 55 mbar to 700 mbar and at a temperature from 35 ° C to 90 ° C.

9. A method according to claim 1 or 2, further characterized in that said at least part of said processed biomass / organic material, which is subjected to said steam stripping step, is the liquid part of at least part of said processed biomass / organic material having been subjected to a liquid / solid separation step.

10. A method according to claim 1 or 2, further characterized in that said pre-treated biomass / organic material is pre-cooled before being subjected to vacuum / evaporative cooling.

11. A method according to claim 1 or 2, further characterized in that said cooled pretreated biomass / organic material is subjected to further cooling and / or processing, e.g. by the addition of dilution water.

12. A method according to claim 1 , 2 or 9, further characterized in that at least part of said steam stripped processed biomass / organic material and / or at least part of any solid part of said at least part of said processed biomass / organic material is returned to either said thermal pre-treatment or said anaerobic digestion process, thereby contributing to reducing the average concentration of ammonia in the material being subjected to said thermal pre-treatment or said anaerobic digestion process.

13. A method according to claim 3, further characterized in that said recovery of said ammonia is achieved by:- scrubbing of said third vapor phase by use of acid and said ammonia is recovered in the form of an ammonium salt, or- distillation of said third vapor phase and said ammonia is recovered in the form of ammonia water.

14. A method according to claim 1 or 2, further characterized in that CO2, whether dissolved whether or in the form of bubbles, in said pre-treated biomass / organic material enters the vapor phase and becomes part of said first vapor phase when said thermally pre-treated biomass / organic material is subjected to said cooling by use of vacuum / evaporative cooling, which contributes to an increase in the pH of said cooled pre-treated biomass / organic material compared to the pH of said thermally pre-treated biomass / organic material.

15. A method according to claim 1 or 2, further characterized in that at least part of any CO2 , whether dissolved or in the form of bubbles, in said processed biomass / organic material enters the vapor phase and becomes part of said third vapor phase when said processed biomass / organic material is subjected to said stream stripping, which contributes to an increase in the pH of said steam stripped processed biomass / organic material compared to said processed biomass / organic material.

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