Method for anaerobic digestion of carbonaceous materials

Abstract

A method of treating a carbonaceous material (e.g., wastewater sludge or organic waste) comprises: heat treating the carbonaceous material, thereby providing a heat treated carbonaceous material; cooling the heat-treated carbonaceous substance, thereby providing a cooled carbonaceous substance, the cooling being performed using a vacuum cooling process; and carrying out post-treatment on the cooled carbon-containing substance, and carrying out at least one time of carbon-containing substance degassing.

Description

TECHNICAL FIELD

[0001] The present invention relates to the treatment of carbonaceous materials including a thermal pretreatment step. More specifically, the present invention relates to the treatment of sludge or organic waste including at least one biological treatment step (such as anaerobic digestion). BACKGROUND ART

[0002] Anaerobic digestion is a key process for recovering the energy initially present in carbonaceous materials (such as wastewater and organic waste) in the form of biogas. Improving digestion efficiency leads to increased energy production, which helps to achieve energy self-sufficient WWTPs (wastewater treatment plants) and waste treatment facilities. However, anaerobic digestion exhibits certain limitations in the first hydrolysis step, resulting in slow degradation of organic matter and long residence times in the digester. To improve the kinetics of anaerobic biodegradation, many pretreatment techniques have been developed with the aim of accelerating the hydrolysis rate-limiting step and increasing biogas productivity, as well as improving the characteristics of the digested carbonaceous material (or sludge).

[0003] In Figure 1 different examples of improved digestion processes in the prior art are shown, which have a hydrolysis pretreatment step implemented upstream of the mesophilic digester. The hydrolysis pretreatment step (PT) can be thermal hydrolysis (TH) or biological hydrolysis (BH) carried out in a tank (H). The pretreatment step can also include a pre-dewatering step (which is carried out in the pre-dewatering unit DU) and storing the carbonaceous material in a storage unit (SS), where the carbonaceous material is pretreated before entering the heat treatment reactor (H).

[0004] Thermal hydrolysis (TH or THP) is the most widely used pretreatment technique for improving anaerobic digestion (AD) of sludge in WWTPs. The aim of thermal hydrolysis is to improve the digestion performance and dewaterability of biological or mixed sludge by breaking down the bacterial cell walls; thus, the cell contents become readily anaerobically degradable.

[0005] Another method for improving the rate-limiting hydrolysis step is based on biological hydrolysis (BH), which is also known as temperature-phased anaerobic digestion (TPAD or 2PAD). TPAD typically combines a short (1 - 3 days) thermophilic pretreatment stage (usually 50 to 70 °C or 75 °C) applied before conventional mesophilic anaerobic digestion (usually 35 °C to 38 °C, 10 - 20 days). TPAD is typically fed carbonaceous material exhibiting a dry solids (DS) content of 3 to 8% DS. It combines a short thermophilic pretreatment stage applied before conventional mesophilic anaerobic digestion. Compared to single-stage mesophilic digestion, thermophilic-mesophilic TPAD or 2PAD has been shown to be an effective treatment for improving methane production and volatile solids (VS) destruction.

[0006] Compared with thermohydrolysis, biohydrolysis shows poorer performance in terms of sludge dewaterability and digestion performance (biogas production, and the biogas produced is stored in the biogas storage BS). However, biohydrolysis is a meaningful alternative because it requires lower capital expenditure, which is particularly meaningful in emerging countries.

[0007] TPAD allows the production of US EPAB-class biosolids, while 2PAD allows the production of Class A biosolids.

[0008] In the United States (US), the beneficial reuse of biosolids through land application is regulated by the Environmental Protection Agency (EPA), more specifically by the EPA's Title 40 of the Code of Federal Regulations (CFR) Part 503 regarding biosolids regulations. Within the regulations of Part 503, the quality of biosolids is defined, and two common terms are clarified: Class A biosolids; and Class B biosolids. Although the regulations of Part 503 also define the quality regarding matters such as heavy metals, the focus of the AD process and digestion improvement is concentrated on meeting the relevant requirements for reducing pathogens and controlling vector attraction.

[0009] In the TPAD / 2PAD system, the sludge must be cooled between the (thermophilic) biohydrolysis reactor (about 55 °C) H and the mesophilic digester D, usually cooled at 37 °C. Currently, downstream of the hydrolysis step of TPAD, as Figure 2 shown, the sludge is cooled by a heat exchanger (recovery heat exchanger or water / sludge, further referred to as HEx).

[0010] The water used in the HEx is usually the process water of the wastewater treatment plant.

[0011] The size of the heat exchanger can become very large because it depends on the temperature of the process water. In fact, the size design of the HEx depends on the temperature difference between the cold side (cooling water) and the hot side (hydrolyzed sludge) in the heat exchanger. The smaller the temperature difference, the larger the HEx.

[0012] Multiple limitations of the current configuration are related to the current HEx.

[0013] Depending on the type of sludge and from one location to another, the viscosity varies significantly, which may seriously affect the size of the heat exchanger (heat transfer coefficient variability) and cause significant energy costs for pumping (large head losses). This may make the heat recovery HEx uneconomical or even infeasible. This also limits the scalability of the process from one location to another.

[0014] Many emerging countries are located in tropical or warm climate regions where the process water temperature (for cooling) may be too hot to effectively cool the sludge (the process water temperature is typically higher than 20 °C). This significantly increases the size of the HEx where the resulting head loss requires the use of large pumping capacity and size, and thus makes the solution energy-intensive and / or uneconomical. This is incompatible with the requirement to reduce energy consumption in countries with high energy costs.

[0015] This is why very few players on the market offer TPAD / 2PAD on large industrial facilities where the HEx sizing problem becomes difficult to solve.

[0016] Finally, deposits that occur in the heat exchanger also reduce the exchange quality because they reduce the heat transfer coefficient.

[0017] To overcome the above limitations, the heat exchanger design includes many safety margins to ensure correct operation. Therefore, the cooling heat exchanger can be very long. The longer the heat exchanger, the greater the head loss and the greater the electrical consumption of the pump.

[0018] In addition, the heat exchanger should be maintained and kept free of fouling (grease, solids, and mineral deposits may occur). The latter, in addition to increasing the head loss of the pump, also continuously reduces the global heat exchange to below the desired value.

[0019] And since the TPAD may operate in batches (in which case it is called 2PAD), the heat exchanger may only be used during a small part of the day with no flow passing through it. During these batch phases, significant deposits may occur and permanently adhere to the walls of the Hex, which further accelerates future deposition.

[0020] Another difficulty with the existing TPAD / 2PAD process lies in the sludge preheating step before supplying the sludge to the biohydrolysis reactor.

[0021] In the TPAD / 2PAD system, preheating is required because the first stage (BH) operates under thermophilic conditions. To reduce the heat demand of this first stage, hot hydrolyzed sludge can be used to heat the cold raw sludge supplied to the system. This heat recovery is typically carried out in a double heat exchanger hot sludge / water / cold sludge. Water is the energy transfer medium that carries energy from the hot sludge to the cold sludge.

[0022] This results in the need to construct another heat exchanger to recover energy. Another possibility lies in setting up a hot sludge / cold sludge heat exchanger. In this case, the heat transfer coefficient is very limited, and in terms of total mass, the mass of this sludge / sludge HEx is equivalent to that of the sludge / water / sludge HEx, so their costs are also in the same range.

[0023] In an anaerobic digestion process including a TH pretreatment step upstream of anaerobic digestion, or when carbonaceous materials must be pasteurized before being digested, the same drawbacks are found.

[0024] Finally, since non-condensable gases are generated in this process, the vacuum pump required to process carbonaceous materials must be more powerful and more energy-consuming than necessary. SUMMARY OF THE INVENTION

[0025] Aspects of the present invention almost eliminate the above-mentioned drawbacks of the intermediate HEx. The drawbacks and additional costs of the preheating step can also be significantly reduced.

[0026] Specifically, one aspect of the present invention relates to a method for temperature-phased anaerobic digestion of wastewater sludge, organic waste, or any type of carbonaceous material, which is continuous (TPAD) or batch (2PAD). In this method, a vacuum cooling step is used for sludge cooling downstream of the biological hydrolysis step, and at least one carbonaceous material degassing step is carried out.

[0027] In a first aspect, the present invention relates to a method for treating carbonaceous materials (such as wastewater sludge or organic waste), including the following steps:

[0028] (1) Heat-treat the carbonaceous material to provide a heat-treated carbonaceous material;

[0029] (2) Cool the heat-treated carbonaceous material to provide a cooled carbonaceous material, and this cooling is carried out using a vacuum cooling step;

[0030] (3) Post-treat the cooled carbonaceous material and carry out at least one carbonaceous material degassing step.

[0031] Advantageously, the degassing step operates at a vacuum level higher than the corresponding boiling point of the hot fresh carbonaceous material (sludge or organic waste).

[0032] As used herein, " Carbonaceous material " should be understood as a mixture of organic and inorganic substances, such as biomass. In the present disclosure, it can also be referred to as "organic matter". The carbonaceous material is usually wet. Its dry solid content is advantageously 3% to 25%. Examples of carbonaceous materials are organic waste and / or sludge, more particularly sludge from organic waste or drinking water or wastewater treatment plants. Generally, in the present disclosure, the carbonaceous material is sludge, such as wastewater treatment sludge. Examples of sludge are municipal sludge, biological sludge, and fresh or raw sludge.

[0033] As used herein, " Vacuum cooling”It should be understood as evaporation under vacuum, i.e., at a pressure below atmospheric pressure. Generally, it refers to a rapid cooling technique for evaporating water from any suspension containing organic matter (such as sludge or organic waste), and the evaporation is carried out under vacuum. In some cases, it is called “ Flash cooling ” or “ Vacuum flash cooling ” because the evaporation is almost “instantaneous”. Vacuum cooling is usually operated at an absolute pressure of 0.055 to 0.480 bar (i.e., 5500 to 48000 Pa), such as 0.055 to 0.170 bar (i.e., 5500 to 17000 Pa), or 0.15 to 0.48 bar (i.e., 15000 to 48000 Pa).

[0034] In the vacuum cooling step, a part of the water content of the sludge is evaporated, generating steam at a temperature determined by the absolute pressure in the vacuum cooling vessel, which is referred to as “ Recycled steam ” in this article. Hereinafter, it can also be called “flash steam” or simply “steam” for short. The recovered steam is different from “ Exhaust gas ” or “non-condensable gas”. “Exhaust gas” or “non-condensable gas” should be understood in this article as the gas generated downstream of the cooling unit, which does not condense in, for example, a subsequent heat recovery step (usually at a temperature of 50 °C to 80 °C and at a pressure equal to or close to the pressure in the vacuum cooling unit / step, i.e., at an absolute pressure of 0.055 to 0.48 bar (i.e., 5500 to 48000 Pa)). The exhaust gas usually contains N2 (nitrogen), H2S (hydrogen sulfide), CO2 (carbon dioxide), light hydrocarbons (saturated, straight-chain or branched C1-C4 hydrocarbon chains, especially methane), and / or NH3 (ammonia), or consists essentially of them.

[0035] Advantageously, the heat-treated carbonaceous material (especially sludge) is then cooled (e.g., cooled to a temperature of about 37 °C), and then temporarily stored (usually kept in an intermediate storage tank) and / or subjected to post-treatment.

[0036] As used herein, the “ Heat treatment ” in step 1) should be understood to include heating the carbonaceous material to 50 °C or higher, usually at a temperature between 50 °C and 90 °C. Examples of heat treatment include low-temperature hydrolysis (TH), biological hydrolysis (BH, corresponding to the first step of staged anaerobic digestion by temperature), thermophilic anaerobic digestion, or pasteurization.

[0037] “ Pasteurization ” is well known in the art. It is generally understood to be a process of treating liquid products with mild heat, usually at a temperature below 100 °C, advantageously between 70 °C and 75 °C, to eliminate pathogens.

[0038] Anaerobic digestionIt is a process involving microorganisms that decompose carbonaceous substances in the absence of oxygen. This process produces digestate and a gaseous fraction that contains methane and is typically composed essentially of methane and CO2 (which is also known as biogas). Anaerobic digestion is generally carried out under pH conditions of 7.0 to 7.5 (7.0 to 7.2 in one embodiment).

[0039] “ Thermophilic anaerobic digestion ” is well-known in the art. It is anaerobic digestion that is generally carried out at a temperature of 50°C to 60°C.

[0040] “ Low temperature hydrolysis ”, abbreviated as “TH”, is well-known in the art. As used herein, it should be understood as a process intended to improve the digestion performance and dewaterability of carbonaceous substances (usually biological or mixed sludge) by breaking down the cell walls of bacteria; the cell contents thus become readily anaerobically degradable.

[0041] Figure 1 A typical prior art TH process is depicted in. In this process, the carbonaceous substance (usually sludge, e.g., with a dry solids (DS) content of 12 - 22%) is heated to a temperature of 140 to 165°C, usually for 30 minutes. The hydrolyzed sludge is then cooled in a flash tank and then supplied to a digester D, where anaerobic digestion takes place. After hydrolysis, the sludge is usually diluted to a dry matter content of about 10% before being injected into the digester: although the concentration is high, mixing is effective because the hot hydrolysis reduces the sludge viscosity. The biogas produced is recovered into a tank T.

[0042] The following publications further disclose the TH process:

[0043] · Barber, W.P.F. "Thermal hydrolysis for sewage treatment: a

[0044] critical review." Water Research 104 (2016): 53 - 71. (Barber, W.P.F., Thermal hydrolysis for sewage treatment: a critical review, Water Research, 104 (2016): 53 - 71.)

[0046] · Sandino, Julian, et al. "Thermal Hydrolysis and Incineration of Sludge: Evaluating Their Role in Optimizing Energy Profiles

[0047] at Advanced BNR Facilities."Proceedings of the Water

[0048] Environment Federation 2018.18(2018):372-386.(Sandino,Julian et al., Hydrothermal hydrolysis and incineration of sludge: evaluating its role in optimizing the energy configuration of advanced

[0049] BNR facilities, Proceedings of the Water Environment Federation, 2018.18(2018):372-386.)

[0051] ·Gonzalez,A.,et al."Pre-treatments to enhance the

[0052] biodegradability of waste activated sludge:elucidating the rate-limiting step."Biotechnology advances 36.5(2018):1434-1469.(Gonzalez, A. et al., Pretreatments to enhance the biodegradability of waste activated sludge: elucidating the rate-limiting step, Biotechnology advances, 36.5

[0054] (2018):1434-1469.)

[0055] “ Biological hydrolysis ”(BH) is well known in the art. As used herein, it is Temperature-phased anaerobic digestion (TPAD) or 2PAD the first step. Generally, BH is a thermophilic digestion step, which advantageously operates at a temperature of 50 °C to 75 °C (whereas the second step of TPAD / 2PAD is usually a mesophilic digestion that operates at a temperature of 30 to 40 °C, advantageously 35 °C to 38 °C). The prior art TPAD / 2PAD including the BH step is described, for example, in ES2430739, DK3008193, and KR100588166B1.

[0056] Descriptions of the prior art TPAD / 2PAD process can also be found in the following publications:

[0057] ·https: / / www.epa.gov / biosolids / examples-equivalent-

[0058] processes-pfrp-and-psrp (retrieving 2PAD)

[0059] · Huyard, A., B. Ferran, and J-M. Audic. "The two-phase

[0060] anaerobic digestion process: sludge stabilization and

[0061] pathogens reduction." Water Science and Technology 42.9

[0062] (2000): 41-47. (Huyard, A., B. Ferran and J-M. Audic, Two-phase anaerobic digestion process: Sludge stabilization and pathogen reduction, Water Science and Technology, 42.9(2000): 41-47.)

[0063] · Willis, John, and Perry Schafer. "Advances in thermophilic

[0064] anaerobic digestion." Proceedings of the Water Environment

[0065] Federation 2006.7(2006): 5378-5392. (Willis, John and Perry Schafer, Advances in thermophilic anaerobic digestion, Proceedings of the Water Environment Federation, 2006.7(2006): 5378-5392.)

[0067] · Ge, Huoqing, Paul D. Jensen, and Damien J. Batstone. "Temperature phased anaerobic digestion increases apparent hydrolysis rate for waste activated sludge." Water Research 45.4(2011): 1597-1606. (Ge, Huoqing, Paul D. Jensen and Damien J. Batstone, Temperature phased anaerobic digestion increases apparent hydrolysis rate for waste activated sludge, Water Research, 45.4(2011): 1597-1606.)

[0068] · Ge, Huoqing, Paul D. Jensen, and Damien J. Batstone. "Increased temperature in the thermophilic stage in temperature phased anaerobic digestion (TPAD) improves degradability of waste activated sludge." Journal of Hazardous Materials 187.1-3 (2011): 355-361. (Ge, Huoqing, Paul D. Jensen and Damien J. Batstone, "Increased temperature in the thermophilic stage in temperature phased anaerobic digestion (TPAD) improves degradability of waste activated sludge." Journal of Hazardous Materials 187.1-3 (2011): 355-361.)

[0069] · Ge, Huoqing, Paul D. Jensen, and Damien J. Batstone. "Pre-treatment mechanisms during thermophilic–mesophilic temperature phased anaerobic digestion of primary sludge." Water research 44.1 (2010): 123-130. (Ge, Huoqing, Paul D. Jensen and Damien J. Batstone, "Pre-treatment mechanisms during thermophilic–mesophilic temperature phased anaerobic digestion of primary sludge." Water research 44.1 (2010): 123-130.)

[0070] · Watts, S., G. Hamilton, and J. Keller. "Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge from a biological nutrient removal plant." Water science and technology 53.8 (2006): 149-157. (Watts, S., G. Hamilton and J. Keller, "Two-stage thermophilic-mesophilic anaerobic digestion of waste activated sludge from a biological nutrient removal plant." Water science and technology 53.8 (2006): 149-157.)

[0071] Akgul, D., M. A. Cella, and C. Eskicioglu. "Temperature phased anaerobic digestion of municipal sewage sludge: a Bardenpho treatment plant study." Water Practice and Technology 11.3(2016):569-573.

[0072] As used herein, the term "step 3)" Post-treatment "This may include either mechanical and / or biological treatment." Mechanical treatment An example of " is a dehydration step. As used herein, " Biological treatment ” should be understood as thermophilic acidogenesis, aerobic digestion, anaerobic digestion or fermentation.

[0073] “ Fermentation " is a process well known in the art and can be defined as a biological anaerobic process in which energy is extracted from carbohydrates to produce small molecules (organic substrates), especially RBCs, in the absence of oxygen, especially by the action of enzymes. CH4 is not produced or is produced in trace amounts. There are five main types of fermentation:

[0074] Alcoholic fermentation, which primarily produces ethanol;

[0075] Lactic acid fermentation, which produces lactate;

[0076] Propionic acid fermentation, which produces propionate;

[0077] Butyrate / butanol fermentation, which produces butyrate and butanol;

[0078] Mixed acid fermentation, which produces VFA (primarily acetate, but also propionate

[0079] salt, lactate, butyrate).

[0080] The fermentation process can be controlled by the residence time of the sludge in the anaerobic tank, the temperature and pH value in the anaerobic tank, and the specific microbial population involved in the fermentation process (ie, the choice of microbial strain in the anaerobic tank).

[0081] In one embodiment, the method further comprises the step of preheating the carbonaceous material using the recovered steam in step 2).

[0082] In one embodiment, the carbonaceous material (e.g., raw sludge) entering the heat treatment step (1) is preheated by direct contact of the recovered steam generated in the vacuum cooling step (2) with the carbonaceous material. Alternatively, this preheating can be carried out by directly injecting the recovered steam generated in the flash cooling step (2) into the carbonaceous material (e.g., raw sludge).

[0083] In another embodiment, the recovered steam from step (2) is in direct contact with the carbonaceous material (raw sludge) upstream of the heat treatment step (1). Accordingly, the carbonaceous material (raw sludge) is first guided to a heat recovery vessel where the sludge comes into contact with the recovered steam generated in the vacuum cooling step. Then, the sludge enters the reactor of the first unit where the sludge undergoes thermophilic biological treatment or mechanical treatment.

[0084] In another embodiment, the method includes a step of capturing CO2 upstream of the cooling in step (2). This step of capturing CO2 can be carried out on the excess steam in the heat recovery vessel (4), for example, after the step of condensing (HEx) the excess steam but before the vacuum pump (VP).

[0085] In a specific embodiment, the method according to the present invention comprises the following steps:

[0086] (1) A first heat treatment of the wastewater sludge or organic matter or any carbonaceous material at a temperature T1 between 50 °C and 90 °C, for example between 50 °C and 75 °C, thereby producing a heat-treated carbonaceous material;

[0087]

[0088] (2) A cooling unit (flash cooler) operating under vacuum (usually operating at 0.055 to 0.170 bar (absolute pressure, i.e., 5500 to 17000 Pa))

[0089] in which the heat-treated carbonaceous material obtained downstream of step (1) is cooled to

[0090] a temperature T2 of 34 to 75 °C (T2 is lower than T1), thereby producing a cooled carbonaceous material;

[0091] (3) Post-treating the cooled carbonaceous material, and

[0092] (4) At least one degassing step of the carbonaceous material.

[0093] The heat treatment in step (1) can be pasteurization, thermophilic biological treatment, and / or low-temperature hydrolysis.

[0094] The post-treatment of step (3) can be any suitable treatment. The post-treatment can be a mechanical treatment, such as a dehydration process, temporary storage. It can also be an anaerobic treatment, such as fermentation or anaerobic digestion. The anaerobic digestion can be two-stage digestion or mesophilic digestion.

[0095] In a specific embodiment, the heat treatment of step (1) is pasteurization or low-temperature hydrolysis, preferably pasteurization. In this case, the post-treatment advantageously comprises or is an anaerobic treatment, such as fermentation or anaerobic digestion. The anaerobic digestion can be two-stage digestion or mesophilic digestion.

[0096] Step (2) can be carried out in one step or multiple sub-steps. In other words, the vacuum cooling step can include multiple cooling stages.

[0097] In this variant, the method of the invention generally comprises:

[0098] (1) subjecting the carbonaceous material to a first heat treatment at a temperature T1 of from 50 °C to 90 °C, such as from 50 °C to 75 °C, so as to provide a heat-treated carbonaceous material;

[0099] (2) a) operating a cooling unit (flash cooler) under vacuum (generally operating at from 0.15 to 0.48 bar (absolute pressure, i.e. 15000 to 48000 Pa))

[0100] in which the heat-treated carbonaceous material obtained downstream of step (1) is cooled to an intermediate temperature T of from 50 °C to 80 °C 2a (T 2a being lower than T1), so as to produce an intermediate cooled carbonaceous material;

[0101] (2) b) operating a cooling unit (flash cooler) under vacuum (generally operating at from 0.05 to 0.1 bar (absolute pressure), i.e. 5000 to 10000 Pa, such as at from 0.055 to 0.17 bar (absolute pressure), i.e. 5500 to 17000 Pa))

[0102] in which the intermediate cooled carbonaceous material downstream of step 2a) is cooled to

[0103] a final temperature T of from 34 °C to 47 °C 2b (T 2b being lower than T 2a ), so as to produce a cooled carbonaceous material;

[0104] (3) subjecting the cooled carbonaceous material to a post-treatment.

[0105] In one embodiment, the cooling temperature T of step (2a) 2aIt is about 50 °C when step (1) is carried out at 55 to 60 °C, about 65 °C when step (1) is carried out at 70 to 75 °C, and about 80 °C when step (1) is carried out at 85 °C to 90 °C.

[0106] In this variant, in one embodiment, step (1) is a pasteurization step. In this case, in one embodiment, the post-treatment is anaerobic treatment, such as fermentation or anaerobic digestion. The anaerobic digestion can be two-stage digestion or mesophilic digestion.

[0107] In a specific embodiment, the method according to the invention comprises the following steps:

[0108] (1) Perform a first thermophilic biological treatment on wastewater sludge or organic matter or any carbonaceous material at a temperature of 50 °C to 75 °C;

[0109] (2) In a flash cooler operating under vacuum (usually at 0.05 to 0.1 bar (absolute pressure, i.e.,

[0110] 5000 to 10000 Pa), for example operating at 0.055 to 0.17 bar), cool the hydrolyzed sludge or organic matter or carbonaceous material obtained downstream of the first stage from 50 to 75 °C to 35 to 42 °C, thereby producing cooled sludge;

[0111] (3) Perform post-treatment on the cooled sludge.

[0112] When the post-treatment of the obtained hydrolyzed and cooled carbonaceous material (such as sludge) (i.e., the carbonaceous material produced in step (2)) is a mesophilic digestion step, it is advantageously carried out at 35 to 42 °C in a second reactor.

[0113] The recovered steam generated in step (2) can be condensed in other unit operations at low pressure and low temperature.

[0114] In a second aspect, the invention relates to a facility for implementing the method, and a flash cooling unit designed to implement the method.

[0115] The new facility is constructed and arranged such that:

[0116] · The viscosity of the carbonaceous material (especially sludge) does not affect the system design;

[0117] · Grit sedimentation does not affect the system design;

[0118] · The temperature of the original carbonaceous material (especially sludge) does not affect the system design;

[0119] · The head loss generated is negligible compared to a heat exchanger;

[0120] · Maintenance is significantly reduced.

[0121] Accordingly, one aspect of the present invention relates to a facility comprising:

[0122] · At least one heat treatment unit (1) for heat-treating carbonaceous material;

[0123] · At least one vacuum cooling unit (2) located downstream of the heat treatment unit

[0124] for cooling the carbonaceous material; and

[0125] · At least one post-treatment unit located downstream of the vacuum cooling unit (2) for post-treating the cooled carbonaceous material; and

[0126] · At least one degassing tank (DT) installed upstream of the vacuum cooling unit (2).

[0128] Advantageously, the facility comprises at least one carbon dioxide scrubbing unit (CO2S) located upstream of the vacuum cooling unit (2).

[0129] In one embodiment, the facility according to the present invention comprises:

[0130] · A first unit having one or more reactors in which the sludge / organic matter is heat-treated, such as thermophilic biotreatment, at 50 to 90 °C, for example 50 to 75 °C. This unit can be divided into a plurality of sub-units in series or operate as a single tank.

[0131] · A vacuum cooling unit located downstream of the one or more first heat treatment units;

[0132] · One or more second units for post-treatment located downstream of the vacuum cooling unit.

[0133] Thus, the facility can comprise:

[0134] · A heat treatment unit for heat-treating carbonaceous material at a temperature of 50 to 90 °C, for example 50 to 75 °C, the heat treatment unit having a first inlet I1 and a first outlet O1, the heat treatment unit being arranged to be supplied with carbonaceous material at the first inlet I1 and to produce heat-treated carbonaceous material which is recovered at the first outlet O1;

[0135] · A vacuum cooling unit having a first inlet I2 and a first outlet O2, and optionally a second outlet O 2’, the first inlet I2 is fluidly connected to the first outlet O1 of the heat treatment unit. The vacuum cooling unit is configured to be supplied with the heat-treated carbonaceous material at the first inlet I2 and produce a cooled carbonaceous material, and optionally recover steam. The cooled carbonaceous material is recovered at the first outlet O2, and the recovered steam is recovered at the second outlet O 2’ where;

[0136] · A post-treatment unit having a first inlet I3 and a first outlet O3. The first inlet I3 is fluidly connected to the first outlet O2 of the vacuum cooling unit. The post-treatment unit is configured to be supplied with the cooled carbonaceous material at the first inlet I3 and produce a post-treated carbonaceous material, which is recovered at the first outlet O3.

[0137] As used herein, " Heat treatment unit " shall be understood as a unit suitable for heat-treating carbonaceous materials at a temperature of 50 to 90 °C, such as 50 to 75 °C. The heat treatment unit can be a TH unit, a BH unit, a thermophilic anaerobic digester or a pasteurization unit.

[0138] As used herein, " Vacuum cooling unit " shall be understood as a unit suitable for evaporation under vacuum, i.e., at a pressure below atmospheric pressure, which typically operates at an absolute pressure of 0.055 to 0.480 bar (i.e., 5500 to 48000 Pa), such as 0.055 to 0.170 bar (i.e., 5500 to 17000 Pa), or 0.15 to 0.48 bar (i.e., 15000 to 48000 Pa).

[0139] As used herein, " Unit for post-treatment " or " Post-treatment unit " shall be understood as a unit suitable for further biological treatment or mechanical treatment. In one embodiment, the post-treatment step includes further biological treatment, particularly a mesophilic digestion step.

[0140] Advantageously, the facility further includes a heat recovery vessel located downstream of the vacuum cooling unit.

[0141] In other words, the facility advantageously further includes:

[0142] · A heat recovery vessel having a first inlet I4, a first outlet O4, and a second outlet O 4’ , the first inlet I4 is connected to the second outlet O of the vacuum cooling unit 2’Fluid connection. The heat recovery vessel is arranged to be supplied with recovered steam at a first inlet I4. The recovered steam then contacts the carbonaceous material (or fresh organic material) entering the vessel to produce preheated carbonaceous material and further recovered steam. The preheated carbonaceous material is recovered at a first outlet O4, and the further recovered steam is recovered at a second outlet. Advantageously, the outlet O4 of the heat recovery vessel is fluidly connected to the inlet. Alternatively, the heat treatment unit includes a second inlet I 1’ , and the outlet O4 of the heat recovery vessel is fluidly connected to the inlet I 1’ , and the heat treatment unit is arranged to be supplied with preheated carbonaceous material.

[0143] Advantageously, the facility further includes a heat recovery vessel located upstream of the heat treatment unit for contacting the carbonaceous material with recovered steam.

[0144] Advantageously, the facility further includes a condenser having a first inlet I Hex , a first outlet O Hex , and a second outlet O Hex’ (not shown). The first inlet I Hex is fluidly connected to the second outlet O 4’ of the heat recovery vessel. The condenser is arranged to be supplied with recovered steam at the first inlet I Hex and to produce exhaust gas recovered at the first outlet O Hex , and condensed liquid (usually process water) recovered at the second outlet O Hex’ . In one embodiment, the condenser is a direct or indirect heat exchanger.

[0145] Advantageously, the facility further includes at least one carbon dioxide scrubbing unit (CO2S) connected to the heat recovery vessel (4, 4b).

[0146] Advantageously, a degassing tank (DT) is installed upstream of the vessel (4) and / or between the heat treatment unit (1) and the vacuum cooling unit (2).

[0147] Advantageously, the vacuum cooling unit (2) includes a boosted centrifugal fan and a vacuum pump.

[0148] Advantageously, each pipeline of the facility includes an independent vacuum pump.

[0149] In a variant, the facility further includes a second heat recovery vessel located downstream of the first heat recovery vessel and upstream of the heat treatment unit.

[0150] In a specific embodiment, the first unit or the heat treatment unit is a reactor suitable for thermophilic digestion. In this variant, the second unit or the post-treatment unit is a reactor suitable for mesophilic digestion.

[0151] In a specific embodiment, the vacuum cooling unit includes two vacuum cooling units installed in series. In other words, the vacuum cooling unit is a two-stage vacuum cooling unit. In this embodiment, the treated carbonaceous material is guided from the heat treatment unit to the first cooling unit, and then in the second cooling unit, the cooled carbonaceous material from the first cooling unit is further cooled and guided to the post-treatment unit.

[0152] Thus, in this embodiment, the facility includes:

[0153] · A heat treatment unit for heat-treating carbonaceous material at a temperature of 50 to 90 °C, for example 50 to 75 °C. The heat treatment unit has a first inlet I1 and a first outlet O1. The heat treatment unit is arranged to be supplied with carbonaceous material at the first inlet I1 and to produce heat-treated carbonaceous material, which is recovered at the first outlet O1;

[0154] · A first vacuum cooling unit having a first inlet I 2a and a first outlet O 2a , and optionally a second outlet O 2a’ . The first inlet I 2a is in fluid connection with the first outlet O1 of the heat treatment unit. The first vacuum cooling unit is arranged to be supplied with heat-treated carbonaceous material at the first inlet I 2a and to produce intermediate-cooled carbonaceous material, and optionally to recover steam. The intermediate-cooled carbonaceous material is recovered at the first outlet O 2a , and the recovered steam is recovered at the second outlet O 2a’ ;

[0155] · A second vacuum cooling unit having a first inlet I 2b and a first outlet O 2b , and optionally a second outlet O 2b’ . The first inlet I 2b is in fluid connection with the first outlet O 2a of the first vacuum cooling unit. The second vacuum cooling unit is arranged to be supplied with intermediate-cooled carbonaceous material at the first inlet I 2b and to produce cooled carbonaceous material recovered at the first outlet O 2b , and optionally, recovered steam at the second outlet O 2b’ ; and

[0156] · A post-treatment unit having a first inlet I3 and a first outlet O3. The first inlet I pt is in fluid connection with the first outlet O 2bFluid connection, the post-treatment unit is arranged to be supplied with cooled carbonaceous material at the first inlet I3 and to produce post-treated carbonaceous material recovered at the first outlet O3.

[0159] In this embodiment, the recovered steam generated in the first and second cooling units is condensed in one or more condensers. The condenser can be a direct or indirect heat exchanger Hex (more specifically, a water / steam heat exchanger Hex).

[0160] "Heat exchanger" is known in the art: it is a system for transferring heat between two or more fluids (at least one cold fluid and one hot fluid) and can be used for cooling and heating processes. The fluids can be separated by a solid wall to prevent mixing (indirect heat exchanger) or can be in direct contact (direct heat exchanger). In various aspects of the present invention, the heat exchanger is used to cool the recovered steam. The cold fluid is typically process water, while the hot fluid is steam.

[0161] The steam generated in the second cooling unit can be recovered and directed to a second heat recovery vessel, where the steam contacts the carbonaceous material (desirably, fresh organic material), thereby producing a first pre-heated carbonaceous material, which is then sent to a second heat recovery unit, where the first pre-heated carbonaceous material contacts the recovered steam from the first cooling unit.

[0162] Advantageously, the steam generated in the first cooling unit is recovered and sent to a heat recovery vessel, where the steam contacts the carbonaceous material (desirably, fresh organic material).

[0163] In a specific embodiment, the facility according to the present invention includes:

[0164] · A first unit having one or more sub-units (reactors), in which the sludge / organic material is heat-treated, such as thermophilic biological treatment, at 50 to 90 °C, for example 50 to 75 °C. This unit can be divided into a plurality of sub-units (a plurality of reactors) in series or operate as a single tank (reactor);

[0166] · A vacuum cooling unit located downstream of the first heat unit;

[0167] · A second unit divided into one or more sub-units for post-treatment, located downstream of the vacuum cooling unit.

[0168] The facility according to one aspect of the present invention may further include:

[0169] · A storage tank located before the first reactor, which stores fresh primary sedimentation, mixed or biological sludge / organic matter, or any carbonaceous matter to be treated. As an alternative, easily degradable organic matter (carbonaceous matter) can be directly sent to the post-treatment unit, while the sludge is first treated in the first reactor.

[0170] · A heat exchanger located on both the first unit and the second unit (or only on the first heat treatment unit), which is used to maintain the temperature of the carbonaceous matter at the required set point. Description of the Drawings

[0171] The present invention is described in more detail in the following drawings, where:

[0172] Figure 1 It shows a hydrolysis pretreatment implemented upstream of an existing wastewater sludge mesophilic digester;

[0173] Figure 2 It shows an existing wastewater sludge temperature-phased anaerobic digestion (TPAD) process;

[0174] Figure 3 It shows a facility for performing a wastewater sludge temperature-phased anaerobic digestion (TPAD) process according to an embodiment of the present invention;

[0175] Figure 4 It shows a facility for implementing a wastewater sludge treatment method according to an embodiment of the present invention;

[0176] Figure 5 It shows a facility for implementing a wastewater sludge treatment method according to an embodiment of the present invention;

[0177] Figure 6 It shows a facility for implementing a wastewater sludge treatment method according to an embodiment of the present invention;

[0178] Figure 7 It shows a facility for implementing a wastewater sludge treatment method according to an embodiment of the present invention;

[0179] Figure 8 It shows a facility for implementing a wastewater sludge treatment method according to an embodiment of the present invention; and

[0180] Figure 9 It shows a facility for implementing a wastewater sludge treatment method according to an embodiment of the present invention. Detailed Description of the Invention

[0181] According to one or more aspects of the present invention, the method is implemented in a facility including a first reactor 1 in which a heat treatment is carried out to treat municipal sludge, organic matter, or any carbonaceous material from a storage tank 1a. The hot organic matter is then cooled in a vacuum cooling unit 2 downstream of the heat reactor 1, and the organic matter then enters a second reactor 3 in which the cooled organic matter can be treated by post-treatment such as anaerobic digestion.

[0182] In other words, Figure 3 the facility includes:

[0183] · At least one heat treatment unit (1) for heat-treating carbonaceous material at a temperature between 50 and 90 °C, for example between 50 and 75 °C;

[0184] · At least one vacuum cooling unit (2) located downstream of the heat treatment unit for cooling the carbonaceous material; and

[0185] · At least one post-treatment unit (3) located downstream of the vacuum cooling unit (2)

[0186] for post-treating the cooled carbonaceous material.

[0187] More specifically, Figure 3 the facility includes:

[0188] · A heat treatment unit (1) for heat-treating carbonaceous material at a temperature between 50 and 90 °C, for example between 50 and

[0189] 75 °C, which has a first inlet I1 and a first outlet O1, and the heat treatment unit is arranged to be supplied with carbonaceous material at the first inlet I1 and to produce heat-treated carbonaceous material (TL2) which is recovered at the first outlet O1;

[0190] · A vacuum cooling unit (2) which has a first inlet I2 and a first outlet O2, and an optional second outlet O 2′ , the first inlet I2 is in fluid connection with the first outlet O1 of the heat treatment unit, and the vacuum cooling unit (2) is arranged to be supplied with heat-treated carbonaceous material (TL2) at the first inlet I2 and to produce cooled carbonaceous material (TL3) and optionally recovery steam 2’ at the second outlet O

[0191] (SL1), and the cooled carbonaceous material is recovered at the first outlet O2;

[0192] · A post - treatment unit (3) having a first inlet I3 and a first outlet O3, the first inlet I3 being fluidly connected to the first outlet O2 of the vacuum cooling unit (2). The post - treatment unit (3) is arranged to be supplied with cooled carbonaceous material (TL3) at the first inlet I3 and to produce post - treated carbonaceous material, which is recovered at the first outlet O3.

[0193] In a variant of the first embodiment, the steam generated during the cooling step is brought into contact via a flow line SL1 with raw sludge in a reactor 4 arranged upstream of the reactor 1 of the first unit (see Figure 3 ). This contact can be carried out using a counter - current direct contact column or any other device to limit the heat loss of the steam while maintaining maximum contact between the raw sludge and the steam to maximize condensation. As an alternative, the steam generated in the vacuum cooling step (2) in unit 2 can be sent back (SL2) to the reactor 1 for pre - heating it (injecting directly into the reactor 1).

[0194] The biogas generated in the reactors 1, 3 of the first and second units can be conveyed via biogas pipelines BL3, BL4 respectively to a biogas recovery unit 5, which is typically a CHP (combined heat and power) unit. Heat can be recovered from the biogas recovery unit 5 and sent via a heat pipeline HL to the reactor 1.

[0195] As another alternative, a heat exchanger HEx can be used for the generated steam to heat the raw (primary, mixed or biological) sludge (less preferred).

[0196] If it is uneconomical to inject the steam at full flow rate into the reactor 1 or the holding tank 1a or the heat exchanger of the first unit, a part of the steam can be condensed in a condenser while the remaining steam is sent for pre - heating the incoming sludge (see Figure 4 ).

[0197] Figure 4 The facility further comprises:

[0198] · A heat recovery vessel (4) having a first inlet I4 and a second outlet O4, the first inlet I4 being fluidly connected to the second outlet O of the vacuum cooling unit (2), the heat recovery vessel (4) being arranged to be supplied with recovered steam 2’ at the first inlet I4. The recovered steam (SL1) then comes into contact with the carbonaceous material (or fresh organic matter) (TL1) entering the vessel (4) to produce pre - heated carbonaceous material (TL1’) and recovered steam SL3, the pre - heated carbonaceous material being recovered at the first outlet O4 and the recovered steam being returned at the second outlet O

[0199] 4’ at.​

[0200] Receiving. Advantageously, the outlet O4 of the heat recovery vessel (4) is in fluid connection with the inlet I1. Alternatively, the heat treatment unit (1) includes a second inlet I 1’ , the outlet O4 of the heat recovery vessel (4) is in fluid connection with the inlet I 1’ and the heat treatment unit

[0201] (1) is arranged to be supplied with preheated carbonaceous material (TL1’).

[0202] Advantageously, Figure 4 the installation also includes a condenser Hex, which has a first inlet I Hex , a first outlet O Hex and a second outlet O Hex′ (not shown), the first inlet I Hex is in fluid connection with the second outlet O 4’ of the heat recovery vessel (4). The condenser Hex is arranged to be supplied with the recovered steam SL3 at the first inlet I Hex and to produce waste gas and condensed liquid, the waste gas being recovered at the first outlet O Hex , and the condensed liquid (usually process water) being recovered at the second outlet O Hex’ . In one embodiment, the condenser is a direct or indirect heat exchanger.

[0203] This reinjection of the low-pressure and low-temperature recovered steam enables the carbonaceous material (depending on step 1, which may be primary sedimentation, mixed or biological sludge) to be heated from a temperature of 10 to 20 °C to a temperature of 20 to 45 °C (usually 30 °C to 40 °C, for example 30 °C to 35 °C), thereby achieving overall energy savings in the process. The pressure of the recovered steam from step (2) is 0.055 to 0.480 bar (absolute pressure, i.e., 5500 to 48000 Pa). By means of a vacuum pump (i.e., a diaphragm vacuum pump) arranged downstream of the cooling unit (flash cooler), the recovered flash steam can be brought into contact with the carbonaceous material (which may be primary sedimentation / mixed / biological sludge). Due to the low solids content of the sludge (3 mass% to 25 mass%, especially 3 mass% to 8 mass%), this contact can be carried out without any additional intermediate device.

[0204] As Figure 4 shown, in a variant of this embodiment, the method includes the following steps:

[0205] (1a) bringing the wastewater sludge or organic matter or any carbonaceous material from the storage tank 1a into contact in the heat recovery vessel 4 with the recovered steam SL1 from the cooling step (2) downstream of the reactor 1 of the first unit, where heat treatment is carried out in the reactor 1 of this first unit, either at 50 °C to

[0206] Thermophilic biological treatment of sludge / organic matter / carbonaceous matter carried out at 90 °C, for example between 50 °C and 75 °C, which is either mechanical treatment of sludge / organic matter (carbonaceous matter);

[0207] (1) Subjecting the sludge / organic matter / carbonaceous matter preheated in the previous step to heat treatment in reactor 1 of the first unit, for example thermophilic biological treatment at 50 °C to 90 °C;

[0208] (2) Cooling the resulting sludge or organic matter or carbonaceous matter downstream of the first unit in a vacuum cooling unit 2 operating under vacuum (vacuum pump VP) (usually between 0.05 and 0.1 bar (absolute pressure), i.e. between 5000 and 10000 Pa), for example between 0.055 and 0.17 bar, from 50 to 90 °C to 35 to 42 °C, thereby producing cooled carbonaceous matter;

[0209]

[0210] (3) Post-treating the cooled sludge / organic matter / carbonaceous matter in reactor 3 of the second unit.(3) Post-treating the cooled sludge / organic matter / carbonaceous matter in reactor 3 of the second unit.

[0211] Sending the recovered steam (SL1) from the cooling unit 2 to the heat recovery vessel 4. Thus, the recovered steam (SL1) is at least partially condensed in the vessel 4. Sending the exhaust gas (SL2) to the vacuum pump for discharge from the facility or further treatment.

[0212] This embodiment is shown in Figure 4 and Figure 5 .

[0213] If the contact between the carbonaceous matter (more specifically, fresh sludge) and the recovered steam in the heat recovery vessel 4 is direct contact, a foam elimination step can be carried out, for example mechanical foam elimination (such as recycling the sludge in the vessel) or chemical foam elimination (such as injecting an anti-foaming product).

[0214] In another embodiment (not shown), advantageously a first part of the recovered steam SL1 is sent back to reactor 1 of the heat treatment unit for preheating it (injected directly into reactor 1), and a second part (SL2) is sent to the heat recovery vessel 4 to heat the fresh sludge (see Figure 4 ).

[0215] In Figure 5 is shown a vacuum cooling step with a minimum number of subunits / components. Such a facility can then have a minimum size with a minimum number of preheating steps. The cooling step is carried out in one step, so the steam temperature will be equal to the sludge temperature in the vacuum cooler, which is the lowest temperature achievable by the system.

[0216] The carbonaceous material is directed in treatment line TL1 to the heat recovery vessel 4 for contact with steam. The preheated carbonaceous material is then optionally held in the holding tank 1b. The carbonaceous material is directed via treatment line TL1” to the reactor 1 of the first unit for heat treatment or mechanical treatment. The non-condensable products can be treated in additional (one or more) treatment steps, such as an odor treatment unit.

[0217] The hot carbonaceous material is directed from the reactor 1 of the first unit via TL2 to the vacuum cooling unit 2. The cooled material is then sent via TL3 to the reactor 3 of the second unit, which can be the anaerobic digester 3. The steam recovered from the cooling unit 2 is directed by SL1 to the heat recovery unit vessel 4 for preheating of the raw carbonaceous material.

[0218] The excess steam in the vessel 4 can be directed via SL3 to the condenser HEx, and the non-condensable products can be conveyed via the non-condensable line to biogas recovery or further treatment steps. The condenser Hex can be a direct condenser or an indirect condenser, such as a contactor.

[0219] In Figure 6 the facility shown presents a vacuum cooling unit with two sub-steps for maximum heat recovery in the case of limited availability of the cooling fluid, such as process water.

[0220] Thus, the facility provides two cooling units 2a, 2b installed in series.

[0221] The organic material treated in the first reactor 1 is cooled in the first cooling unit 2a and then in the second cooling unit 2b. The steam generated in the second cooling unit 2b is recovered and sent to (S11b) the heat recovery vessel 4b, where the steam comes into contact with fresh organic material. The preheated organic material is then sent via TL1' to the second heat recovery unit 4a, where the first preheated organic material comes into contact with the recovered steam (SL1a) from the first cooling unit 2a. Thereby, the organic material is first preheated by the coldest recovered steam and then by the hottest recovered steam. These two steps of preheating the organic material allow for improvement of the rheological properties of the organic material, as the organic material is diluted and preheated prior to the second preheating step.

[0222] This avoids the need for cooling water to condense the steam generated in the second sub-step of vacuum cooling, where the steam condenses in the organic material. The condenser can be optional, as the steam can all be consumed in the preheating step, thus avoiding the need for water and a condenser.

[0223] In this example of the facility, the recovery steam (SL3a, SL3b) generated by two vacuum cooling units can be condensed in the condenser HEx. Two condensers HEx are shown in the drawings, but the condensation can be carried out in one condenser. The condenser Hex can be a direct or indirect condenser, such as a contactor. All non-condensable substances can then be processed in subsequent processing steps (such as an odor treatment pipeline), or discharged to the atmosphere, or combined with the generated biogas in post-treatment.

[0224] Figure 6 The facility includes:

[0225] · A heat treatment unit for heat-treating carbonaceous material at a temperature of 50 to 90 °C, for example 50 to 75 °C. The heat treatment unit has a first inlet I1 and a first outlet O1. The heat treatment unit is arranged to be supplied with carbonaceous material at the first inlet I1 and to produce heat-treated carbonaceous material (TL2), which is recovered at the first outlet O1;

[0226] · A first vacuum cooling unit (2a) having a first inlet I 2a and a first outlet

[0227] O 2a and optionally a second outlet O 2a’ The first inlet I 2a is fluidly connected to the first outlet O of the heat treatment unit tt The first vacuum cooling unit (2a) is arranged to be supplied with heat-treated carbonaceous material (TL2) at the first inlet I 2a and to produce intermediate-cooled carbonaceous material (TL2’) and optionally recovery steam

[0228] (SL1a). The intermediate-cooled carbonaceous material is recovered at the first outlet O 2a and the recovery steam is recovered at the second outlet O 2a’ ;

[0229] · A second vacuum cooling unit (2b) having a first inlet I 2b and a first outlet

[0230] O 2b and optionally a second outlet O 2b’ The first inlet I 2b is fluidly connected to the first outlet O of the first vacuum cooling unit 2a The second vacuum cooling unit (2b)

[0231] is arranged to be supplied with intermediate-cooled carbonaceous material 2b at the first inlet I

[0232] (TL2’), and produces a cooled carbonaceous material (TL3) and an optional recycled steam (SL3b), the cooled carbonaceous material being recovered at a first outlet O 2b and the recycled steam being recovered at a second outlet O 2b’ ; and

[0233] · A post-treatment unit (3), which has a first inlet I3 and a first outlet O3, the first inlet I3 being fluidly connected to the first outlet O 2b of the second vacuum cooling unit, the post-treatment unit (3) being arranged to be supplied with the cooled carbonaceous material at the first inlet I3 and to produce a post-treated carbonaceous material, the post-treated carbonaceous material being recovered at the first outlet O3.

[0234] In this embodiment, the recycled steam (SL3a and SL3b) produced in the first cooling unit and the second cooling unit is condensed in one or more condensers. The condenser can be a direct or indirect heat exchanger Hex (more specifically, a water / steam heat exchanger Hex).

[0235] The steam produced in the second cooling unit (2b) can be recovered and directed to a heat recovery vessel (4b), where the steam contacts a carbonaceous material (desirably, fresh organic material), thereby producing a first preheated carbonaceous material, which is then sent to a second heat recovery unit (4a), where the first preheated carbonaceous material contacts the recycled steam (SL1a) from the first cooling unit (2a).

[0236] Advantageously, the steam produced in the first cooling unit (2a) is recovered and sent to a heat recovery vessel (4), where the steam contacts a carbonaceous material (such as fresh organic material).

[0237] The method enables maximum energy recovery and is applicable to very viscous dry organic material streams with a very high dry matter concentration and / or facilities with limited availability of cooling water.

[0238] In Figure 7 , the facility shown provides a balance between optimizing heat recovery and minimizing the number of sub-units / components of the facility. This facility can be considered when cooling water is available and the organic material stream is easily preheated.

[0239] Thus, the facility also provides two vacuum cooling units 2a, 2b installed in series, but the treated organic material from the reactor 1 is cooled by the first cooling unit 2a, and the recycled steam (SL1a) from this unit 2a is used in the heat recovery vessel 4 to preheat the organic material before the reactor 1.

[0240] The cooled organic matter is then cooled a second time in the cooling unit 2b and then directed (TL3) towards the second reactor 3 for post-treatment.

[0241] The excess steam generated in the first and second cooling units is condensed (SL3a and SL3b) in a condenser (such as a water / steam heat exchanger HEx), which can be a direct or indirect heat exchanger. The condenser Hex can be a direct or indirect condenser, such as a contactor. Even if cooling water is required, the facility provides the best balance of cost / energy savings.

[0242] Figure 8 Example of

[0243] The production of non-condensable gases varies between 50 and 1000 NL / m 3 between the sludges, usually varying between 100 L and 500 NL / m 3 between the sludges, which depends in particular on the type of sludge, its rheological properties, its concentration and the heat treatment applied (step 1).

[0244] Therefore, the vacuum pump required to treat the carbonaceous material should be powerful enough to achieve a vacuum level capable of pumping the non-condensable gases (m 3 / h instead of Nm 3 / h). Due to these gases, the pump should therefore have a greater power than required and be more energy-consuming.

[0245] To overcome this problem, in an optimized embodiment, the method for treating carbonaceous material described above further includes at least one degassing step of the carbonaceous material (such as sludge).

[0246] The (one or more) degassing steps operate at a vacuum level above the corresponding boiling point of the fresh sludge heated (from the heat treatment).

[0247] The (one or more) degassing steps are capable of removing non-condensable gases from the fresh sludge heated (from the heat treatment) without generating steam and therefore without cooling the hot sludge.

[0248] In this embodiment, the facility for implementing the method according to the invention includes at least one degassing tank (DT), which:

[0249] · is installed (in series) upstream of the cooler 1 (2a); and / or

[0250] · is installed upstream of the condenser 2 (4b).

[0251] The degassing tank(s) operate(s) at a vacuum level above the respective boiling points of the fresh sludge that is hot (from heat treatment). The degassing tank(s) is / are capable of removing non-condensable gases from the hot (from heat treatment) fresh sludge without generating steam and thus without cooling the hot sludge. These degassing tanks can be connected to their own dedicated vacuum pump(s), share the same vacuum pump, or be connected to the vacuum pump of the rest of the heat recovery unit. In the latter case, the vacuum level is regulated using a valve located between the headspace of the degassing tank(s) and the rest of the facility.

[0252] This reduces the vacuum pump flow rate (considering a heat recovery unit operating at 66 mbar).

[0253] When a degassing tank operating at 500 mbar is installed, the vacuum pump must move Q2 = Q1 / (500 + 66)*66 = Q1 / 8.6. This significantly reduces the size of the pump. Typically, the degassing tank will operate between 200 and 800 mbar, which allows the size of the vacuum pump to be reduced to 1 / 4 to 1 / 13 of its original size.

[0254] The degassing tank on the cooler 1 (2a) has the most impact. In fact, the sludge entering the cooler 1 accounts for approximately 70% (by volume) of the non-condensable gases released in the system.

[0255] According to one embodiment ( Figure 8 ), the degassing tank is located upstream of the container 4 (heat recovery container in which the carbonaceous material is in contact with the recovered steam generated by the vacuum cooling step).

[0256] According to one embodiment ( Figure 8 ), the degassing tank is located between the heat treatment unit (1) and the vacuum cooling unit (2).

[0257] According to an embodiment ( Figure 8 ), the first degassing tank is located upstream of the container 4, and the second degassing tank is located between the heat treatment unit (1) and the vacuum cooling unit (2).

[0258] First optimization embodiment( Figure 9 )

[0259] According to one embodiment, the method for treating the carbonaceous material includes a step of capturing CO2 upstream of the step of cooling the heat-treated carbonaceous material.

[0260] In fact, since the proportion of CO2 in the non-condensable gas fraction can be as high as 75%, removing CO2 upstream of the vacuum pump reduces the load on the vacuum pump itself.

[0261] According to one embodiment, this step is implemented to capture CO2 into the excess steam in the container 4 (heat recovery container, in which the carbonaceous material comes into contact with the recovered steam generated by the vacuum cooling step), for example, after the condensation step (HEx) but before the vacuum pump (VP).

[0262] In this optimized embodiment, the facility for implementing the method according to the invention includes at least one CO2 scrubbing unit (CO2S), which is located upstream of the vacuum cooling unit (2). A carbon dioxide scrubber is a device that absorbs carbon dioxide (CO2).

[0263] In one embodiment, the carbon dioxide scrubber is connected to the heat recovery container (4), or to each recovery container (4, 4b).

[0264] In one embodiment, the carbon dioxide scrubber is located between the heat exchanger (HEx) and the vacuum pump (VP) (see Figure 9 ).

[0265] According to one embodiment, a chemical carbon dioxide scrubber can be used.

[0266] In Figure 9 is shown the vacuum cooling step with the minimum number of subunits / elements as Figure 5 shown. Figure 9 The facility of

[0267] Second optimized embodiment (not shown)

[0268] According to one embodiment, the facility includes a first cooling unit and a second cooling unit (SL3a and SL3b), as in the facility shown in Figure 6 and Figure 7 shown. The recovered steam generated in the first cooling unit and the second cooling unit (SL3a and SL3b) is condensed in the first condenser and the second condenser respectively. The condenser can be a direct or indirect heat exchanger Hex (more specifically, a water / steam heat exchanger Hex).

[0269] However, in this embodiment, the first condenser and the second condenser are connected to the same vacuum pump (VP).

[0270] According to this embodiment, the vacuum cooling unit (2) includes a combination of a booster centrifugal fan and a vacuum pump smaller than the vacuum pump in the previous embodiment. The booster can increase the absolute pressure by about 100 mbar. Accordingly, the flow rate of the vapor moved by the vacuum pump will be reduced accordingly.

[0271] Consider an example of the flow rate Q1 at 66 mbar: When a booster fan is installed, the vacuum pump must move Q2 = Q1 / (100 + 66)*66 = Q1 / 2.5. This significantly reduces the size of the pump.

[0272] Third optimized embodiment (not shown)

[0273] According to one embodiment, each pipeline of the facility operates independently with a vacuum pump.

[0274] Thus, in this embodiment, each pipeline of the facility includes an independent vacuum pump. According to an example, the facility includes:

[0275] · A first vacuum pump for the cooler 1, condenser 1, and final condenser 1 pipelines;

[0276] · A second vacuum pump for the cooler 2, condenser 2, and final condenser 2 pipelines.

[0277] Advantages of the present invention

[0278] Compared with a conventional heat exchanger operated with process water, cooling using a vacuum cooling system has many beneficial effects:

[0279] · The cooling efficiency does not depend on the process water temperature but on the vacuum pressure, which is much easier to control. The cooling is almost instantaneous and does not require a significant HRT (hydraulic retention time) as in a HEx.

[0280] · The change in sludge viscosity is no longer a problem.

[0281] · Without a HEx, there is no need to maintain sludge transfer pumps and pipelines.

[0282] The TPAD / 2PAD method according to an embodiment of the present invention can be implemented on a large industrial facility where the HEx size problem would be insoluble for prior art methods.

[0283] When operating in a batch configuration (2PAD), flash cooling can significantly reduce the sequence of removing sludge from the thermophilic reactor. Thus, this increases the batch time, which reduces the size of the thermophilic reactor heating HEx and / or the feed pump (the feed can be for a longer time).

[0284] Compared with the conventional heat exchanger-based pretreatment in known TPAD / 2PAD, the raw sludge preheating based on directly injecting the exhaust gas direct steam generated by flashing under vacuum pressure into the raw sludge has the following benefits.

[0285] Heat recovery is independent of sludge viscosity.

[0286] The exhaust gas generated by the vacuum cooling system may be problematic (odor problems due to the presence of H2S and NH3). Usually, this problem is addressed by injecting the gas into the digester as soon as it condenses. Without condensation, the exhaust gas is reused for preheating the raw sludge and allowed to be treated by the plant odor treatment unit 6 according to the standard process. In this application, compared with the conventional flash system, the low-temperature steam reduces the amount of odor and pollutants (evaporated organic materials).

[0287] In the absence of HEx, there is no need to maintain the sludge transfer pumps and pipelines.

[0288] In the field of sludge anaerobic digestion, vacuum cooling is usually associated with cooling high-temperature sludge (about 165 °C) treated with THP or other heat treatments to a temperature of about 100 °C. After this flash evaporation, the pressure remains above atmospheric pressure (ΔP of flash evaporation > atmospheric pressure) in the sludge treatment field.

[0289] Secondary vacuum cooling can be used to cool the sludge from a temperature of 100 to 110 °C to a temperature of about 60 °C (the term "about" covers variations of + / - 10%). The secondary flash evaporation can be operated under vacuum.

[0290] To cool the sludge to a temperature suitable for anaerobic digestion (mesophilic step) of 37 to 38 °C, the final cooling step is carried out by diluting the sludge with process water or mixing it with the raw primary settled sludge produced by the primary sedimentation tank.

[0291] The use of vacuum cooling to reduce the temperature of sludge below the 60 °C threshold has never been described in the field of municipal sludge treatment.

[0292] In the prior art methods, the non-condensable gas generated during one or more flash cooling steps after steam cooling and condensation to 37 °C to 38 °C is fed into the mesophilic reactor.

[0293] Finally, for the use of:

[0294] · At least one carbonaceous material degassing step (using at least one degassing tank (DT) installed upstream of the vacuum cooling unit); and / or

[0295] · At least one step of removing CO2 upstream of the vacuum pump (using at least one carbon dioxide scrubbing unit (CO2S)); and / or

[0296] · The combination of at least one booster centrifugal fan; and / or

[0297] · Vacuum pumps operating independently for each pipeline of the facility;

[0298] It is possible to reduce the load on the vacuum pump itself, thereby enabling the reduction of the size and power consumption of the vacuum pump.

[0299] It should be understood that the above-described respective embodiments can be combined according to any technically permissible combination.

[0300] The articles "a" and "an" may be used in connection with various elements, components, methods, or structures described herein. This is merely for convenience and to provide a general sense of the described method or structure. Such descriptions include "one or at least one" of the described element or component. Further, as used herein, the singular article also includes the description of a plurality of elements or components, unless the plural is clearly excluded from the specific context.

Claims

1. A method for treating carbonaceous material, comprising: Thermally treating the carbonaceous material to provide thermally treated carbonaceous material; Cooling the thermally treated carbonaceous material to provide cooled carbonaceous material, the cooling being carried out using a vacuum cooling step; and Post-treating the cooled carbonaceous material and carrying out at least one carbonaceous material degassing step.

2. The method according to claim 1, wherein Operating the carbonaceous material degassing at a vacuum level above the corresponding boiling point of the hot fresh carbonaceous material.

3. The method according to claim 1, the method comprising a step of capturing CO2 upstream of the cooling.

4. The method according to claim 1, the method comprising a step of preheating the carbonaceous material before thermally treating the carbonaceous material, the preheating step being carried out by direct steam contact between the recovered steam generated by the vacuum cooling step and the carbonaceous material.

5. The method according to claim 4, wherein, First, the carbonaceous material is guided to a heat recovery vessel in which the carbonaceous material is brought into contact with the recovered steam generated by the vacuum cooling step.

6. The method according to claim 4, further comprising a step of capturing CO2 on the excess steam in the heat recovery vessel.

7. The method according to claim 1, wherein: Carrying out the thermal treatment includes carrying out a first thermal treatment of the carbonaceous material at a temperature T1 of 50 °C to 90 °C to produce thermally treated carbonaceous material; And Cooling the thermally treated carbonaceous material includes cooling the thermally treated carbonaceous material downstream of the first thermal treatment to a temperature T2 below T1 and between 34 and 75 °C in a cooling unit operating under vacuum to produce cooled carbonaceous material.

8. The method according to claim 1, wherein The cooling is carried out in one or more sub-steps.

9. The method according to claim 8, wherein, The cooling includes: Cooling the thermally treated carbonaceous material obtained downstream of the thermal treatment to an intermediate temperature T2a below T1 and between 50 °C and 80 °C in a cooling unit operating under vacuum to produce intermediate cooled carbonaceous material; and Cooling the intermediate cooled carbonaceous material downstream of the cooled thermally treated carbonaceous material obtained by the cooling to a final temperature T2b below T2a and between 34 °C and 47 °C in a cooling unit operating under vacuum to produce cooled carbonaceous material, wherein the obtained thermally treated carbonaceous material is downstream of the thermal treatment.

10. The method according to claim 1, wherein, The thermal treatment is pasteurization, thermophilic biological treatment, or low-temperature hydrolysis.

11. The method according to claim 1, wherein, The post-treatment is: A mechanical treatment step, or a temporary storage step; or An anaerobic treatment step, anaerobic digestion, or a mesophilic digestion step.

12. The method according to claim 1, wherein, The carbonaceous material is organic waste and / or sludge.

13. A facility for implementing the method of claim 1, comprising: A thermal treatment unit for thermally treating carbonaceous material; A vacuum cooling unit located downstream of the thermal treatment unit for cooling the carbonaceous material; And A post-treatment unit located downstream of the vacuum cooling unit for post-treating the cooled carbonaceous material; and A degassing tank installed upstream of the vacuum cooling unit.

14. The facility according to claim 13, comprising a carbon dioxide scrubbing unit located upstream of the vacuum cooling unit.

15. The facility according to claim 13, comprising a first heat recovery vessel located upstream of the thermal treatment unit for bringing the carbonaceous material into contact with the recovered steam.

16. The facility as claimed in claim 15, comprising a carbon dioxide scrubbing unit connected to the first heat recovery vessel.

17. The facility according to claim 15, wherein, The degassing tank is installed upstream of the first heat recovery vessel and / or between the heat treatment unit and the vacuum cooling unit.

18. The facility according to claim 13, wherein, The vacuum cooling unit comprises a booster centrifugal fan and a vacuum pump.

19. The facility according to claim 13, wherein Each pipeline of the facility comprises an independent vacuum pump.

20. The facility as claimed in claim 15, further comprising a second heat recovery vessel, which is located downstream of the first heat recovery vessel but upstream of the heat treatment unit.

21. The facility according to claim 13, wherein, The vacuum cooling unit comprises two vacuum cooling units installed in series. In the first cooling unit of the two vacuum cooling units, the treated carbonaceous material from the heat treatment unit through the treatment pipeline is cooled, and then in the second cooling unit of the two vacuum cooling units, the cooled carbonaceous material is cooled again and guided through the treatment pipeline to the post-treatment unit for post-treatment.

22. The facility according to claim 21, wherein, The recovered steam generated in the first cooling unit and the second cooling unit is condensed in one or more condensers.

23. The facility according to claim 22, wherein, It is possible to recover the recovered steam generated in the second cooling unit and guide it to the heat recovery vessel, where the steam contacts the carbonaceous material, thereby generating a first preheated carbonaceous material, and then the first preheated carbonaceous material is sent to another heat recovery unit, where the first preheated carbonaceous material contacts the recovered steam from the first cooling unit (2a).

24. The facility according to claim 21, wherein, Recover the recovered steam generated in the first cooling unit and send it to the heat recovery vessel, where the steam contacts the carbonaceous material.

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