Method and apparatus for treating biomass and organic waste

Abstract

The present invention provides a method for treating biomass materials by fermentation, the method comprising pretreating the biomass materials by hot hydrolysis and wet explosion to obtain an intermediate product with a dry matter concentration of more than 25% and a temperature of more than 90°C, which is introduced into fermentation, wherein a portion of the contents of the digester used for fermentation is recycled and mixed with a portion of the intermediate product from the pretreatment.

Description

Technical Field

[0001] This invention relates to methods, processes, and apparatus for treating materials that are primarily of organic origin, such as waste or biomass, wherein the sugar, etc., content of the treated material can be used for fermentation into one or more desired products. Background Technology

[0002] Sludge and waste from urban and industrial sources, as well as other waste sources, primarily organic, such as byproducts from horticulture, agriculture, forestry, the timber industry, and food processing, have been increasingly recognized as potential starting materials for the production of CO2-neutral fuels, such as bioethanol or biogas, over the years.

[0003] Many different pretreatment methods for biomass materials have been described in the literature, with contents such as sugars being more readily available. The most well-known are: strong acid and weak acid hydrolysis; wet explosion (steam explosion - STEX); wet oxidation (WO); alkaline cellulose explosion (ammonia cellulose explosion - AFEX); and hot water hydrolysis (liquid hot water - LHW).

[0004] Strong acid and weak acid hydrolysis are typically characterized by the hydrolysis and dissolution of hemicellulose, increasing the availability of cellulose for subsequent acid-based or enzymatic hydrolysis. When using these types of hydrolysis, after separating the insoluble and soluble fractions, these fractions can be further processed by fermentation. Lightner (US 6.258.175) describes strong acid hydrolysis, which also describes the possibility of reusing the acid after precipitation with ethanol. The primary objective of this process is to dissolve cellulose and hemicellulose for subsequent use, for example, in the production of ethanol via fermentation.

[0005] Acid hydrolysis of biomass involves several issues. First, the material needs to be broken down into very fine particles (<1 mm), which is extremely energy-intensive. Second, the treated material needs to be neutralized, typically by adding CaCO3 (limestone). This means that the process consumes a high amount of chemicals, and the neutralization process accumulates large amounts of hydrated calcium sulfate. Furthermore, compared to materials obtained through other treatment methods, materials from acid hydrolysis exhibit inhibitory effects on enzymatic hydrolysis and microbial fermentation (see below). Finally, pumps, reactors, and other components are susceptible to corrosion due to the acid-catalyzed process.

[0006] Descriptions of the STEX process date back to 1928, when Mason developed a process for manufacturing cardboard (US 1.824.221 and 2.759.856). The STEX process involves hot water hydrolysis under high pressure, followed by pressure release through a process known as “flash evaporation,” in which the rapid drop in pressure causes each fiber to explode, hence the name wet explosion (or steam explosion). This process was later further developed for the manufacture of, for example, ethanol or paper (e.g., WO 98 / 27269).

[0007] In STEX, partial dissolution of hemicellulose (>80%) typically occurs, and the cellulose can be used for subsequent hydrolysis. STEX functions similarly to acid hydrolysis—however, the STEX process makes process equipment less susceptible to wear and tear and is less demanding in terms of chemical use and waste accumulation. However, a considerable amount of material that inhibits potential subsequent fermentation processes is still formed in STEX (Palmqvist and Hahn-Hagerdal 2000), especially when the material is pre-liquefied with acid (SO2 or H2SO4 (Martin et al., 2002)).

[0008] Wet oxidation (WO) has been developed to oxidize organic waste fractions (US 2,690,425) and has been subsequently improved to obtain hemicellulose solutions from biomass and organic waste containing lignin cellulose (see, for example, WO 00 / 14120). Wet oxidation involves a thermal process with the addition of an oxidant (such as superpressure oxygen). In wet oxidation, the hemicellulose fraction dissolves, and a portion of the lignin present is oxidized, thereby increasing the availability of cellulose. Typically, WO does not require additional process steps to remove inhibitory substances.

[0009] Alkaline Fiber Explosion (AFEX) is a process that combines steam explosion with the addition of an alkaline catalyst. In conventional AFEX, biomass is liquefied in ammonia water at a moderate temperature (~50°C), followed by a sudden release of pressure (explosion). Through this process, cellulose and lignin are modified, making the cellulose more reactive (available) while releasing hemicellulose.

[0010] Hot water hydrolysis (LHW) is a process in which the high dissolution of hemicellulose and the partial dissolution of lignin occur simultaneously, and the availability of cellulose is improved (for enzymatic hydrolysis) (typically at 170°C–230°C). Sugarcane waste that has not been pre-separated and pretreated with LHW, after the addition of a moderate amount of enzyme, results in a theoretical ethanol yield of up to 90% after enzymatic hydrolysis and fermentation (Van Walsum et al., 1996). US Patent 4,461,648 describes a method for increasing the availability of materials containing cellulose and lignocellulose. This method involves adding steam under pressure, heat treatment, and wet explosion, further describing the impossibility of steam recycling.

[0011] Known methods for producing CO2 neutral fuels based on such organic waste or biomass typically involve a pretreatment step using some form of thermal hydrolysis (THP) process, followed by anaerobic digestion.

[0012] These processes are typically based on a thermal hydrolysis step using a combination of high temperature and high pressure in one or more reactors to break down the cellular structure of organic materials in waste or sludge and decompose high molecular weight organic compounds into smaller molecules.

[0013] The hydrothermal hydrolysis step may be followed by a steam explosion step in one or more pressure-relief tanks, where the contents of the tanks decompose due to the rapid release of pressure. This decomposition and fragmentation of biomass makes subsequent fermentation steps more efficient.

[0014] The products generated from the pretreatment step using a hot water hydrolysis (THP) process are typically at high temperatures (e.g., above 90°C) and characterized by relatively high dry matter content (e.g., above 25%), and in some cases, relatively low pH (e.g., below 5). Therefore, the processing of this product usually requires highly specialized equipment, and it must also typically be cooled, neutralized, and / or diluted (e.g., with water) before being introduced into subsequent anaerobic digestion-based processes, which are generally carried out at lower temperatures, lower dry matter content, and neutral pH.

[0015] WO2007 / 009463 discloses a method for converting cellulosic materials into ethanol and other products. The method involves hydrothermal pretreatment of the cellulosic material through at least one soaking operation, hydrothermal pretreatment in a pressure reactor, and subsequent pressing to produce a fibrous fraction and a liquid fraction. The hydrothermal pretreatment retains at least 80% of the lignin in the fibrous fraction. Because it involves processing materials with high dry matter content, the process described in WO2007 / 009463 typically requires highly specialized equipment.

[0016] WO03 / 013714 discloses a gate system through which products with high dry matter content can be dispensed and then transported through at least one gate chamber and two pressure plugs respectively, thereby allowing (e.g.) transfer from a low-pressure area to a high-pressure area.

[0017] Over the years, various improvements have been developed to the aforementioned biomass and organic waste treatment processes. Therefore, one way to achieve these improvements is through the use of recycling. In particular, the recycling of steam otherwise used in the process and its use for preheating biomass, as well as the recycling of water effluent from the process to reduce the consumption of process water otherwise used in the process, have been described in the prior art.

[0018] WO2011 / 006854 discloses a method and apparatus for hot hydrolysis and steam explosion of biomass. The method comprises the following steps: preheating the biomass; directing the preheated biomass into at least two reactors, where it is heated and pressurized by the addition of steam; and finally, gradually reducing the pressure using two pressure relief tanks. The preheating tanks are preheated by return steam from the first and second pressure relief tanks.

[0019] WO01 / 60752 discloses a continuous process involving wet oxidation or steam explosion for fermenting biomass materials into ethanol. The fermentation wastewater effluent, separated from the produced ethanol, then undergoes an anaerobic fermentation step to produce methane and wastewater effluent, wherein the amount of potentially inhibitory substances is at a sub-inhibitory level, allowing all or part of the effluent to be recycled back into the process to reduce process water consumption.

[0020] WO2014 / 039984 discloses a method for processing biomass to obtain monomeric sugars, wherein the pretreated biomass undergoes enzymatic hydrolysis, and at least a portion of the liquefied material from the enzymatic hydrolysis reactor is recycled as part of the coolant for the thermally pretreated biomass to a location upstream of the added enzyme.

[0021] US2009 / 0098616 discloses a method for treating plant material to release fermentable sugars. This method involves a two-stage enzymatic hydrolysis process, preferably preceded by an autohydrolysis step, wherein the material is preferably subjected to high temperature, steam, and pressure in the presence of acid. The low-viscosity effluent from the first hydrolysis stage is partially recycled back to the first enzymatic hydrolysis stage, some or all of it is fed directly into the reactor, or it may be mixed with fresh lignocellulosic feedstock before entering the reactor. Further disclosed is that the enzymatic process can be carried out under vacuum to remove volatile components, such as enzyme-inhibiting compounds (e.g., furfural).

[0022] Despite the many methods available for processing biomass materials, there remains a need for a method where biomass is pretreated and subsequently fermented without the excessive use of chemical additives or specialized equipment to process dense materials with high dry matter content, high temperatures, and relatively low pH. Additionally, a method is needed that minimizes water dilution while reducing energy costs. Summary of the Invention

[0023] In a first aspect, the present invention relates to a method for processing biomass materials, comprising at least the following steps:

[0024] - The pretreatment of this biomass material includes the following steps:

[0025] 1) Hydrolysis at temperatures above 140℃, followed by

[0026] 2) Wet explosion results in an intermediate product dry matter concentration exceeding 25% and a temperature exceeding 90℃.

[0027] The intermediate product was then fermented in a digester.

[0028] Furthermore, it is characterized in that the intermediate product is introduced into the digester by mixing it into a portion of the contents of the digester being transported in a recycling loop starting from the digester, wherein the mixing is performed before the mixture of the intermediate product and the portion of the contents of the digester enters the digester.

[0029] In a second aspect, the present invention relates to an apparatus for processing biomass materials, wherein the apparatus comprises:

[0030] -One or more reactors,

[0031] - One or more pressure relief tanks connected to the reactor for releasing pressure on the biomass, and

[0032] - One or more digestion tanks connected to the pressure relief tank for fermentation.

[0033] The digester is connected to the pressure relief tank for recycling a portion of the contents of the digester, which are mixed with a portion of the contents of the pressure relief tank.

[0034] The aforementioned improvements involving recycling do not overcome the need for highly specialized equipment to further process the products generated by conventional pretreatment steps using hot hydrolysis processes, which have high temperatures (e.g., above 90°C), relatively high dry matter content (e.g., above 25%), and relatively low pH (e.g., below 5).

[0035] In contrast, the method and apparatus of the present invention utilize the recycling of a portion of the material being fermented to overcome the aforementioned normal need for specialized equipment, cooling, neutralization, and / or dilution (e.g., with water). Attached Figure Description

[0036] Figure 1 An embodiment of the invention is shown (illustratively).

[0037] Figure 2 (Illustratively) illustrates a typical embodiment of a known prior art method, involving, for example, conveying materials with high dry matter content via a pipeline using a worm, spiral, or helical conveyor.

[0038] Figure 3 An embodiment of the invention is illustrated (illustratively) for pretreating biomass first by hot hydrolysis (d) and wet explosion (j), and then fermenting the intermediate products obtained therefrom in a digester (q), wherein a portion of the contents of the digester is conveyed in a recirculation loop (t) into a pressure relief tank (j). This embodiment includes the optional feature of flash steam being introduced into a condenser (g) and a circulation pump (k), and the option to guide the condensate to a downstream digester (q) or further processing to recover chemicals (p).

[0039] Figure 4 An embodiment of the invention is shown (illustratively) for pretreating biomass by first hot hydrolysis (d) and wet explosion (j), and then fermenting the intermediate product obtained therefrom in a digester (q), wherein a portion of the contents of the digester is transported in a recirculation loop (t) into a pressure relief tank (j).

[0040] Figure 5 An embodiment of the invention is shown (illustratively), wherein a portion of the contents of the digester (q) is dehydrated (ah) and returned as a so-called dehydrated cake with increased dry matter content to the feed line (a) for use in the hydrolysis reactor (d), thereby mixing it with biomass material fed into the process in other ways. Detailed Implementation

[0041] This invention relates to a method for processing biomass materials, comprising at least the following steps:

[0042] - The pretreatment of this biomass material includes the following steps:

[0043] 1) Hydrolysis at temperatures above 140℃, followed by

[0044] 2) Wet explosion results in an intermediate product dry matter concentration exceeding 25% and a temperature exceeding 90℃.

[0045] The intermediate product was then fermented in a digester.

[0046] Furthermore, it is characterized in that the intermediate product is introduced into the digester by mixing it into a portion of the contents of the digester being transported in a recycling loop starting from the digester, wherein the mixing is performed before the mixture of the intermediate product and the portion of the contents of the digester enters the digester.

[0047] Materials produced by processes similar to THP typically have extremely high dry matter content, sometimes exceeding 90%. When the dry matter content exceeds 25%, problems arise when using conventional equipment and apparatus because the intermediate product cannot be transported to the digester via standard piping and pumping equipment. Therefore, highly specialized equipment is required, such as piping with screw, spiral, or helical conveyors, and the use of any such equipment necessitates frequent maintenance and repair due to the relatively low pH, high temperature, and dry matter content of the material. Therefore, one advantage of the method of this invention is that materials with high dry matter content, which conventional methods require transport via specialized equipment, are now mixed with a recirculated stream from the downstream digester. Since the contents of the digester have a lower dry matter content and lower viscosity, the mixed stream has a relatively lower dry matter content and viscosity, and is therefore suitable for convenient transport via standard piping and pumping equipment.

[0048] Scaling, scaling, and sometimes blockages in containers, piping, and especially heat exchangers / coolers, are known problems during the heat treatment of certain materials, particularly organic materials rich in lignin, resins, etc. Reduced productivity and operational difficulties can be critical to the operation of such plants. Frequent use of in-situ cleaning systems may be required to maintain operability, and alkaline cleaning chemicals are typically used. Biodegradation occurring in downstream anaerobic digestion (fermentation) degrades organic acids and utilizes alkaline liquids to establish a relatively alkaline environment. An additional advantage of this invention is that containers, piping, valves, and coolers benefit from the recycling of the digested material, providing continuous alkaline cleaning without the need for additional chemicals during normal operation. For most feedstocks, this process requires no in-situ cleaning (CIP) chemicals. For the most challenging feedstocks, the consumption of additional cleaning chemicals will be significantly reduced.

[0049] The behavior of fibrous and cellulose materials is influenced by several factors. The inventors have discovered that one of the factors affecting the ability to maintain fiber suspension is pH. The low pH resulting from the thermal pretreatment of organic materials makes it difficult to maintain fiber suspension, thus clogging becomes a major problem. The main advantage of the recycling method of this invention is that the alkaline digest increases the pH, thereby altering the behavior of fibrous and cellulose materials, allowing them to remain in suspension, and enabling them to be pumped to downstream processes without the use of a conveyor system.

[0050] Specifically, the inventors have discovered that the pH obtained during fermentation in a digester, typically in the range of pH 7.3-8.3, is favorable for fiber wettability and transport properties. Completely or partially hydrolyzed biomass fibers, for example, obtained from wet blasting, tend to separate from remaining intermediates at low pH levels (e.g., below pH 6). Therefore, by recirculating a portion of the digester's contents and mixing it with products from wet blasting, the pH of other slightly acidic intermediates can be increased, while maintaining the dissolution of completely or partially hydrolyzed biomass fibers.

[0051] In a specific embodiment of the present invention, the pH of the feed to the digester obtained by mixing the intermediate product with the recycled fermentation product is higher than pH 6; in a preferred embodiment, the pH of the feed to the digester after mixing is higher than pH 6.5.

[0052] According to one embodiment of the present invention, the temperature of the above intermediate product is higher than 100°C.

[0053] In such cases, where intermediate products are involved at temperatures above 100°C, additional advantages can be gained because the steam that typically accompanies such intermediate products (when as a result of a process similar to THP) can then be used to heat or even pasteurize other process streams containing organically derived materials (e.g., liquid manure) that will be added to the pretreated material before digestion.

[0054] In another embodiment of the invention, the pH of the intermediate product is below 5.

[0055] Intermediates from hot hydrolysis pretreatment are typically acidic (e.g., pH 4-5). Therefore, in addition to the fact that such products usually must be neutralized separately (requiring chemicals) before being introduced into anaerobic digestion-based processes, the transport of acidic material from the pretreatment process to the digester may involve specialized equipment. However, in the method of the present invention, at least a portion of the intermediate product can be neutralized simultaneously with the recycling from the digester. This provides an additional advantage in reducing the need for chemical neutralization and / or other specialized equipment for transporting acidic material. In one embodiment of the invention, the intermediate product is neutralized by mixing it with recycled material from the digester. The method of the present invention can be tailored such that the higher the acidity of the intermediate product, the more digestate will be recycled to obtain an optimal pH range.

[0056] As another benefit, the process of the present invention can be carried out in a closed system. Therefore, the surrounding environment will benefit from being spared from volatile compounds that would otherwise evaporate from the material undergoing pretreatment and subsequent fermentation in the digester, and which could be potentially hazardous and smell very unpleasant.

[0057] Hydrothermal hydrolysis pretreatment can typically be performed in batches. A similar continuous process flow may be downstream of hydrothermal hydrolysis, thus allowing the relatively large amount of steam released from wet explosion (i.e., at material temperatures above 100°C) to be processed, captured, and utilized, which further leads to the minimization of external energy consumption for the entire process.

[0058] According to the present invention, the recirculation from the digester to the pressure release tank is preferably a continuous process. Due to the hot hydrolysis feed, the pressure release tank is preferably a batch process, in which case the hydrolysate content in the pressure release tank will vary. When the method of the present invention is applied in this manner, the pressure release tank is further used as a buffer storage tank, thereby obtaining a continuous process flow to the downstream digester and the fermentation process therein.

[0059] For large-scale facilities, it is advantageous to include more than one reactor for the hydrothermal pretreatment. In this way, several batches with delayed cycles can be operated, resulting in a time-varying output to the pressure relief tank, as the required steam input for heating the reactors is more evenly distributed. This benefits the size design of the steam production facility and its energy requirements. Semi-continuous flow to the pressure relief tank can be achieved in this manner. Another advantage of including more than one reactor for the hydrothermal step is the increased upstream advantage of continuous biomass feed from the biomass storage tank to the hydrothermal tank.

[0060] In one embodiment of the invention, return steam from the wet explosion step (carried out in one or more pressure relief tanks) can be used to preheat the biomass in the preheating tank before pumping it to the reactor. Steam is also supplied to the reactor during and after biomass filling to heat the biomass to the desired temperature. This reduces the need to add fresh steam to the reactor.

[0061] Intermediate products from the pretreatment of biomass materials (i.e., hydrothermal hydrolysis and wet explosion) typically have a dry matter concentration higher than 25% and a temperature higher than 90°C. Generally, the transport of intermediate products with high dry matter content is handled using highly specialized equipment. Furthermore, the temperature of the intermediate products is usually lowered using conventional cooling water. This invention is based on the recycling of at least a portion of the contents of the digester, thereby eliminating the disadvantages of other necessary treatments before the intermediate products can enter the digester. The pretreatment of biomass materials can be carried out in various ways as described below.

[0062] Many different pretreatment methods for biomass materials have been described in the literature, where contents such as sugars are more readily available; some of these methods are mentioned in the background section herein. The most well-known are: strong and weak acid hydrolysis, wet explosion, wet oxidation (WO), ammonia cellulose explosion (AFEX), hot water hydrolysis (liquid hot water - LHW), and combinations thereof. These treatments can be used individually or in any combination as part of the pretreatment of this invention. Depending on the choice of pretreatment, the method of this invention may further include a pretreatment step of wholly or partially milling the biomass.

[0063] Other details of the preprocessing steps are described below:

[0064] Hot water hydrolysis

[0065] Biomass and / or organic waste materials are introduced into the reactor, wherein the materials are mixed with direct or indirect steam and heated to a temperature above 140°C, typically in the range of 140-220°C, preferably in the range of 140-200°C, more preferably in the range of 150-190°C, even more preferably in the range of 160-180°C, and most preferably in the range of 170°C (at saturation pressure). When the desired temperature and pressure are reached, the materials can be maintained under these conditions for 5-30 min, preferably 10-25 min, more preferably 10-20 min, and most preferably 15-20 min.

[0066] In one specific embodiment of the invention, the hydrolysis is carried out at a temperature above 140°C and maintained for 5-30 minutes, followed by a wet explosion by reducing the pressure from 5-35 bar to atmospheric pressure.

[0067] wet oxidation

[0068] In one embodiment of the invention, the method further comprises wet oxidation, which is preferably carried out after the hydrothermal hydrolysis step but before the wet explosion. After the hydrothermal hydrolysis is terminated, a suitable oxidant, preferably oxygen, hydrogen peroxide, or air, can be added to the material in an amount that can depend on the lignin content and is typically equivalent to 2-20%, preferably 3-19%, more preferably 5-17% (e.g., preferably 7-16%), more preferably 8-15% (e.g., preferably 9-14%), more preferably 10-13% of the material's COD (chemical oxygen demand) content, and is determined by the pressure development of the reactor. Wet oxidation can typically be carried out in a temperature range of 170-220°C.

[0069] As wet oxidation proceeds, the pressure and temperature can be increased to 15-35 bar, preferably 20-35 bar, more preferably 25-35 bar, and most preferably 30-35 bar, and 170-210°C, preferably 180-200°C, and more preferably 190-200°C, respectively. In one embodiment, the oxidation pressure is higher than the saturation pressure in the hot hydrolysis of step 1). When the desired temperature and pressure are reached after the addition of the oxidant, the material can be maintained under these conditions for 1-30 min, preferably 5-25 min, more preferably 10-20 min, and most preferably 15-20 min. Optionally, after the wet oxidation reaction is terminated, the pressure of the material can be partially released to 5-10 bar. In this case, the pressure range for subsequent wet explosion is 5-35 bar. If partial pressure release is not performed, the pressure range is 1-35 bar.

[0070] In one specific embodiment of the invention, the method comprises oxidation at a pressure of 15-35 bar and a temperature of 170-220°C, which is maintained for 1-30 minutes. In a more specific embodiment of the invention, the method comprises oxidation at a pressure of 15-35 bar and a temperature of 170-210°C, which is maintained for 1-30 minutes, and this oxidation is carried out in another preferred embodiment after hot hydrolysis but before wet explosion.

[0071] wet explosion

[0072] After the hydrothermal hydrolysis step and optional wet oxidation step are terminated, the treated biomass material is then directed to one or more pressure relief tanks, during which the pressure is reduced from 5-35 bar; the pressure can typically be reduced to below 2 bar, preferably below 1.5 bar. Preferably, the pressure is reduced from 15-35 bar to about 1 bar, i.e., atmospheric pressure. During this wet explosion, most of the cellular structures are broken down. After the wet explosion, the temperature of the oxidized material is immediately, preferably, 95-110°C, to sterilize the material. As the heat-treated material is discharged from the hydrothermal hydrolysis reactor, the discharge to one or more pressure relief tanks is driven by the pressure difference between the reactor and the downstream pressure relief tanks. Due to the pressure drop, the condensed vapors will flash inside the pressure relief tanks. The wet explosion is carried out through one pressure relief tank, or sequentially in two or more pressure relief tanks. The terms "flash tank" and "pressure relief tank" are used interchangeably herein.

[0073] Fermentation

[0074] After cooling to the required temperature, the treated material can be further processed through fermentation into ethanol, hydrogen, lactic acid, methane, succinic acid, organic acids, or other desired products.

[0075] The overall process of the present invention may also cover treatment with enzymes (e.g., cellulase) to convert carbohydrates into monohydrates before fermentation into ethanol or other fermentation products.

[0076] After pretreatment, the slurry and / or its aqueous phase may be further subjected to enzymatic hydrolysis, resulting in at least partial hydrolysis of cellulose and hemicellulose, to obtain a slurry and / or aqueous phase containing a certain amount of microbial fermentable sugars.

[0077] The purpose of such enzymatic hydrolysis is to hydrolyze oligosaccharides and possibly polysaccharides produced during wet oxidation (if any) and / or steam explosions of cellulose and / or hemicellulose sources, to form fermentable sugars (e.g., glucose, xylose, and possibly other monosaccharides).

[0078] In one embodiment of the invention, the method further includes enzymatic hydrolysis of the intermediate product, which is performed prior to the fermentation step, but may be performed before or after the intermediate product is mixed with a portion of the contents of the digester. In a preferred embodiment, the method does not include any separate enzymatic hydrolysis step.

[0079] Enzymatic hydrolysis can be achieved in a known manner by treatment with one or more suitable carbohydrate hydrolases (glycosidases, EC 3.2). In preferred embodiments, the carbohydrate hydrolases are selected from the group consisting of: cellulase (EC 3.2.1.4) for hydrolyzing cellulose or cellulose fragments; xylanase (e.g., endo-1,4-3-xylanase, EC 3.2.1.8) for hydrolyzing xylose; 3-glucanase including dextran-1,3-β-glucosidase (exo-1,3-β-glucanase, EC 3.2.1.58) or endo-1,3(4)-β-glucanase, EC 3.2.1.6 for hydrolyzing soluble cellulose fragments into glucose; and pectinase (polygalacturonase, EC 3.2.1.15) for hydrolyzing pectin and other galacturonic acids. Related commercial enzyme products include Celluclast, available from Novo Nordisk A / S in Bagswald, Denmark. TM For example, as Celluclast TM 1.5L (liquid formulation). Celluclast exhibits cellulase activity (degrading cellulose into glucose, cellobiose, and higher glucose polymers) and some degree of xylanase activity.

[0080] Fermentable sugars, particularly monosaccharide products, obtained through hydrolysis can be further converted to produce other useful products (such as ethanol or xylitol). Therefore, glucose (derived from cellulose) and xylose (derived from xylan in hemicellulose) can be converted to ethanol using relevant fermenting microorganisms as described herein, and xylose can be converted to xylitol, for example, by established methods (e.g., by catalytic hydrogenation or by fermentation), depending on the circumstances.

[0081] In the method according to the invention, the intermediate product is fermented in one or more digesters. The fermentation step may employ one or more fermenting microorganisms capable of degrading oligosaccharides and / or monosaccharides present in the liquid phase to form ethanol.

[0082] Regarding the fermentation of glucose to produce ethanol, for example, any microorganism capable of converting glucose into ethanol can be used in the process of this invention. Suitable microorganisms include mesophilic microorganisms (i.e., microorganisms that grow optimally in the temperature range of 20-40°C), such as yeasts also known as "bread yeast" or brewer's yeast (Saccharomyces cerevisiae).

[0083] Regarding the production of ethanol from xylose (e.g.), any microorganism capable of converting xylose into ethanol can be used in the process of this invention. Useful microorganisms include, for example, certain types of thermophilic bacteria (i.e., organisms that grow optimally at high temperatures—typically above about 50°C) and genetically engineered microorganisms derived therefrom. In preferred embodiments, suitable organisms for ethanol fermentation are selected from the group consisting of: thermophilic bacillus species including *T. matrani*, fermentomonas species including *Z. mobilis*, and yeast species (e.g., *Pichia pastoris*). Examples of useful strains of *T. matrani* are described in Sonne-Hansen et al., 1993, or Ahring et al., 1996, where the strain is named strain A3M4.

[0084] It should be understood that useful ethanol fermentation organisms can be genetically modified organisms selected from one of the aforementioned useful organisms, which possess increased or improved ethanol fermentation activity relative to their source organisms. The term "genetically modified bacteria" as used herein is used in its conventional sense, referring to strains or spontaneously occurring mutants obtained by subjecting the organism to any conventionally used mutagenesis treatment (including treatment with chemical mutagens such as ethanesulfonate (EMS) or N-methyl-N'-nitro-N-nitroguanidine (NTG), UV light treatment), including classical mutagenesis. Furthermore, since genetically modified bacteria can be provided by random mutagenesis or by selecting spontaneously occurring mutants, i.e., without the use of recombinant DNA technology, it is conceivable that, once a specific DNA sequence is identified and isolated, mutants of the aforementioned organisms can be provided by such techniques, including site-directed mutagenesis and PCR, as well as other in vitro or in vivo modification techniques for such sequences.

[0085] Fermenting glucose and xylose to produce ethanol using microorganisms with different optimal growth temperature requirements may necessitate a two-stage fermentation process. In this process, the slurry and / or aqueous phase following the aforementioned steps is first contacted with one of the microorganisms under suitable conditions (e.g., *Saccharomyces cerevisiae* at approximately 30°C), and subsequently with the other microorganism under suitable conditions (e.g., *Thermosynthetium martensii* at approximately 70°C). In this invention, the recirculation of a portion of the digester's contents can be performed using the contents of one or both of the two stages. Where increased cooling capacity is required, recirculation may preferably be performed using the first, less warm stage. The two stages may suitably be carried out in separate fermentation reactors or sequentially within the same reactor.

[0086] Unlike enzymatic hydrolysis, which has a well-defined process and depends on factors such as temperature, pH, and enzyme dosage, fermentation is more critical from the perspective of the need for suitable growth conditions for the selected microorganisms. Furthermore, the growth medium (in this case, pretreated biomass material) needs to be balanced in terms of, for example, nutrients and toxic or inhibitory substances. Important balances include: C:N ratio, NPK balance, S content, and the content of key micronutrients. Some biomass materials may initially contain low amounts of components such as, but not limited to, selenium, molybdenum, and cobalt. Therefore, particularly unilateral biomass materials may initially contain low amounts of certain key components required for optimized fermentation. In such cases, balancing the original material with supplemental biomass material is beneficial, and thus the present invention also allows for processes based on mixed biomass materials. Where material balancing is not feasible, micronutrients may need to be added based on actual nutrient balance analysis during fermentation. If necessary, depending on the type of nutrient mixture deemed necessary based on micronutrient analysis of the fermentation material, nutrient solutions can be added via injection points placed on the circulation loop, or by adding nutrients directly to the material feed entering the fermentation vessel. Chemicals can also be added to bind certain components that would otherwise inhibit the process if present in high concentrations. An example of such a component is sulfur, which, if present in high concentrations in certain processes, can inhibit the intended fermentation process, but can be removed by adding FeCl solution to bind the sulfur into ferric sulfate.

[0087] Regarding this invention, it is particularly noteworthy that enzymatic hydrolysis typically produces a hydrolysate with a pH of 4 to 6. Fermentation of biomass material, first by hot hydrolysis and then by wet explosion pretreatment, on the other hand, yields a fermentation product with a pH typically in the range of 7-8.5, preferably in the range of 7-8.3, and more preferably in the range of 7.3-8.3. From these pH differences, it can be seen that, according to the invention, the advantages described herein—increased fiber wettability, solubility, and thus transport properties—are obtained only by recycling a portion of the digester contents to the product from the wet explosion, and not by any possible recycling from the enzymatic step. Due to the recycling loop starting from the digester, the method of the invention provides a digester feed with an increased pH. In specific embodiments of the invention, the digester feed obtained by mixing the intermediate product with the recycled fermentation product has a pH higher than pH 6; in preferred embodiments, the pH of the mixed digester feed is higher than pH 6.5.

[0088] Some process parameters affecting fermentation processes are solids residence time (SRT) and hydraulic residence time (HRT). The latter is a measure of the average length of time soluble compounds remain in the digester. SRT and HRT can vary significantly for fermentation processes by introducing a separation step in the circulation loop starting from the fermentation vessel, as shown in the accompanying figures. In the method of the present invention, fermentation is typically carried out as a continuous process, with an HRT of 10-40 days, preferably 15-30 days, and an SRT of 10-40 days, preferably 20-40 days, ensuring longer exposure of recalcitrant solids present in the biomass material and thus increasing its volatile solids reduction (VSR). In one embodiment of the invention, fermentation is a continuous process with an HRT between 2 and 20 days; preferably between 10 and 20 days; more preferably between 15 and 17 days. In another embodiment of the invention, fermentation is a continuous process with an SRT between 15 and 40 days; preferably between 20 and 40 days, and more preferably between 30 and 40 days. In essence, the efficiency of the aforementioned separation steps is crucial to the difference between the resulting HRT and SRT. On the other hand, high separation can also be energy-intensive, which may be detrimental to all applications. Hydrocyclones designed for this purpose are generally sufficient to effectively improve the difference between HRT and SRT with acceptable attempts, and can typically increase the solid residence time (SRT, compared to HRT) by 5-30%, depending on the specific substrate and process parameters.

[0089] In another embodiment of the invention, testing revealed the positive effects of hydrolysis in two stages. Therefore, in a preferred embodiment of the invention, a portion of the contents of the fermentation vessel can be dehydrated and returned to the feed line as a so-called dehydrated cake with increased dry solids (DS) content for the hydrolysis step, thereby mixing it with the biomass material otherwise fed into the process in a or x of the figures. Dehydration can take place at position ac or ah or, if appropriate, downstream. A portion of the material can then be reintroduced into the process at a suitable location to achieve two-stage hydrolysis of recalcitrant solids present in the biomass material. Such embodiments of the invention are shown in the figures... Figure 5 The diagram illustrates the process. Dehydration can be performed in centrifuges, belt thickeners, belt presses, filter presses, screw presses, or any other suitable dehydration machine. Combinations of different dehydration machines (e.g., gravity belt thickeners and screw presses) can significantly increase the potential for power consumption reduction compared to conventional centrifuges. Power consumption reductions may be in the range of 1 / 2 to 1 / 6 of that of a sedimentation centrifuge.

[0090] One or more fermentation steps of the type discussed can be carried out using any suitable, known type of fermentation vessel (digester / fermenter). For further details on suitable vessels, see, for example, JEBailey and DFOllis, 1986. Both batch and continuous fermentation are applicable here. The terms “fermentation vessel,” “digester,” and “digester tank” are used interchangeably herein.

[0091] After the ethanol fermentation step, ethanol is separated from the fermentation medium.

[0092] Recycle

[0093] As described earlier herein, the method of the present invention utilizes a recirculated stream from the contents of a digester, wherein a portion of the contents from the digester is recycled to the final step of pretreatment and thus mixed with intermediate products. The final step of pretreatment is wet explosion, or optionally any further pretreatment step performed on biomass material.

[0094] The flow rate of material from the digester is preferably significantly higher than that of pretreated material produced by the final pretreatment step (thermal hydrolysis, wet explosion, and optionally further pretreatment, such as wet oxidation), typically 3-30 times higher, preferably 5-25 times higher. In this way, the resulting mixed stream entering the digester will have pH, temperature, and dry matter content compatible with the normal operating process parameters of the digester. Furthermore, the dry matter content, and therefore viscosity, will be adjusted by balancing the recirculation with digestate recirculation 3-30 times. However, recirculation itself does not affect the average dry matter content of the feed from the thermal hydrolysis reaction. Instead, the dry matter content can be (e.g.) prior to thermal hydrolysis (ag). Figure 3, 4 The method described in 5 is adjusted by diluting with water or by entering the pressure relief tank (af) via a recirculation loop.

[0095] According to an embodiment of the present invention, a portion of the contents of the digester is mixed with a portion of the intermediate product, such that at least 10 parts (volume) of the contents of the digester are mixed with one part (volume) of the intermediate product, preferably at least 20 parts (volume) of the contents of the digester are mixed with one part (volume) of the intermediate product.

[0096] Mixing can be achieved by directing flows from individual pipes into a mixing tank or directly into a common conduit. Alternatively, mixing can be achieved using an additional mixing device.

[0097] Recirculation can be achieved, for example, by injecting the contents from the digester below the pressure relief tank level, thereby simultaneously achieving effective mixing. Alternatively, the recirculated flow from the digester can be directed, for example, through a nozzle to the top of the pressure relief tank, whereby the recirculated flow also serves as a quenching liquid for condensing flash vapors inside the pressure relief tank.

[0098] In a preferred embodiment of the invention, mixing is carried out in a pressure-relief tank; one of the main advantages of this recycling step is the enhanced wettability and transport properties of the fibers after wet blasting. Therefore, maximum benefit is obtained by mixing directly after wet blasting but before any transport of intermediate products. However, mixing at a later stage is also possible.

[0099] The mixing of 10 parts (volume) of digester contents with one part (volume) of intermediate product should be understood as mixing the two products at a volume ratio of 10:1; preferably, the volume ratio is in the range of 3:1 to 30:1, depending on the feed characteristics, and measured at the same pressure and temperature.

[0100] The term "digester contents" refers to liquid and / or aqueous slurry produced by fermentation but prior to the separation of fermentation products (such as ethanol).

[0101] The term "intermediate product" refers to liquid and / or aqueous slurry produced by pretreatment but prior to fermentation.

[0102] The term “partial contents” should be understood as a portion or all of the liquid and / or aqueous slurry.

[0103] In an embodiment of the invention, a portion (volume) of intermediate product is prepared at a rate of at least 5 m³. 3 / h, preferably at least 10m 3 A flow rate of / h is introduced for mixing. The flow rate of the contents or intermediate products from the digester is measured at 25°C and 1 bar and expressed as m³ / h. 3 / h.

[0104] Biomass materials can be selected from the group consisting of: straw, wood, fiber, feed, pulp, and waste streams; or from by-products of other processing industries (such as food processing), energy crops, leaves, branches, pulp, and household waste, or other similar materials suitable for the production of ethanol or other bioproducts. Preferably, the biomass material is selected from biomass rich in cellulose and / or hemicellulose. Straw, lignocellulose, and energy crops (e.g., corn) particularly achieve beneficial results. In a preferred embodiment of the invention, the biomass material is selected from the group consisting of: straw, lignocellulose, and energy crops (e.g., corn).

[0105] Typically, biomass introduced by the method of this invention can have a dry matter content of 50-80%. In one embodiment of the invention, the dry matter concentration of the biomass material introduced by the process is higher than 25% by weight, preferably higher than 50% by weight, and more preferably higher than 75% by weight. The percentage of dry matter content or concentration refers to weight percentage, i.e., % (w / w).

[0106] According to one embodiment of the invention, the dry matter concentration of the intermediate product is greater than 25% by weight, preferably greater than 30%, more preferably greater than 35%, and most preferably greater than 40%. The intermediate product herein refers to the pretreated product (thermal hydrolysis and wet explosion) after this pretreatment step and before any mixing with the recycled contents from the digester or before any further dilution with water.

[0107] Depending on the biomass material used, the method of the present invention may further include one or more dilution steps. Dilution of the biomass material or intermediate product can be performed at several points during the method. For example, dilution can be performed before thermal hydrolysis, for example by introducing water into the thermal hydrolysis reactor; or upstream of the thermal hydrolysis reactor, for example by introducing water into the recirculation loop into the pressure relief tank or directly into the pressure relief tank. The latter option allows the use of dilution water to at least partially quench the flash steam. Since the dry matter content in the digester is much lower, the dilution of the dry matter content can be further adjusted by the volume ratio of the recirculated material from the digester.

[0108] In a preferred embodiment of the invention, dilution is carried out via a recirculation loop or directly into a pressure relief tank.

[0109] Dilution (if necessary) helps control the dry matter content in the digester feed, and thus helps control the loading rate. The loading rate of the digester is typically between 2-10 kg VS / m³. 3 Within the range of / day (VS = volatile solids), and preferably within 3-6 kg VS / m³. 3Within a range of / day. Different feed materials can provide different viscosities, and the load rate can be adjusted accordingly. Traditionally, biomass viscosity has been one of the limiting factors for load rate; however, this invention significantly improves fiber wettability and conveying properties, thereby allowing for higher load rates.

[0110] The cryogenic stream from the digester can be further used to condense the gas phase from the pressure relief tank, providing an additional advantage: the ability to recover beneficial components (such as volatile acids) that would otherwise be lost from the gas phase back into the digester. Furthermore, undesirable components, such as furfural, can be extracted and separated from the gas phase in this manner to avoid inhibiting downstream digestion, or for subsequent external purification and use, or for oxidation for heat recovery.

[0111] By using a portion of the liquid and / or aqueous slurry produced by fermentation as a cooling medium, the gas phase from the pressure relief tank can be condensed (making the gas liquid).

[0112] According to one embodiment of the present invention, a portion of the gas phase from the pretreatment is condensed by using a portion of the contents of the digestion tank as a cooling medium.

[0113] The term "partial gas phase" refers to a portion or all of the gas phase in the pressure relief tank.

[0114] In one embodiment of the invention, furfural in the condensed gas phase is separated by extraction. Furfural is also known as furan-2-carbaldehyde. Other names are, for example, furan-2-carboxaldehyde, furfural, 2-furancarbaldehyde, and pyroxenaldehyde.

[0115] In embodiments of the invention, volatile acids in the gaseous phase from the pressure relief tank are condensed and then recycled back to the digester, where they can be used for fermentation. Volatile acids refer to low-boiling-point acids such as carbonic acid, acetic acid, and butyric acid.

[0116] The present invention also relates to apparatus for achieving the same advantages as the method described in the present invention.

[0117] In a second aspect, the present invention relates to an apparatus for processing biomass materials, wherein the apparatus comprises:

[0118] -One or more reactors,

[0119] - One or more pressure relief tanks connected to the reactor for releasing pressure on the biomass, and

[0120] - One or more digestion tanks connected to the pressure relief tank for fermentation.

[0121] The digester is connected to the pressure relief tank for recycling a portion of the contents of the digester, which is mixed with a portion of the contents of the pressure relief tank. The "reactor" mentioned in this article can also be called a "thermal hydrolysis reactor".

[0122] As those skilled in the art will appreciate, for most applications, the digester includes an outlet that can exit from the top surface, side, or bottom. However, for certain types of feed materials, different solids residence times (SRT) and hydraulic residence times (HRT) may be advantageous. This can be achieved by including one or more separators or concentrators in the apparatus of the present invention.

[0123] The method and apparatus of the present invention may further include one or more separators or thickeners, preferably one or more hydrocyclones, connected to a recirculation loop from the digester for separating solids. One outlet of the separator or thickener has an increased dry matter content, and another outlet has a lower dry matter content. The outlet with the increased dry matter content may be returned to the digester, or may preferably be connected to a pressure relief tank, and the outlet with the lower dry matter content may be the digester discharge outlet.

[0124] In this invention, any combination of digester outlet (i.e., exiting from the top surface, side, or bottom) and / or supplemented by the outlet of a separator with a lower dry matter content can be applied. However, to obtain the maximum difference between SRT and HRT, the outlet via the separator can be maximized, and the outlet directly from the digester can be minimized.

[0125] In one embodiment of the invention, the method and apparatus further include a separator connected to a recirculation loop originating from the digester for separating solids. One outlet of the separator has an increased dry matter content, and another outlet has a lower dry matter content. The outlet with the increased dry matter content is connected to a pressure relief tank, and the outlet with the lower dry matter content is the digester discharge outlet. In this embodiment, the separator is preferably a hydrocyclone.

[0126] In one embodiment of the invention, the method or apparatus further includes a separator for separating solids connected to the digester's discharge outlet; one outlet of the separator has an increased dry matter content and another outlet has a lower dry matter content, the outlet with the increased dry matter content being connected to the inlet of a hydrothermal hydrolysis reactor or to the biomass feed to the hydrothermal hydrolysis reactor; and the outlet with the lower dry matter content is the process discharge outlet. In this way, the separated portion with the increased dry matter content can be returned to the hydrothermal hydrolysis reactor for a second hydrothermal hydrolysis treatment. In this specific embodiment, the separator is preferably selected from centrifuges, belt thickeners, belt presses, filter presses, and screw presses. The apparatus or method may have only a discharge outlet via the separator, or it may have both a discharge outlet via the separator and a discharge outlet directly from the digester.

[0127] Separators can typically be cyclone separators (e.g., hydrocyclones), centrifuges, belt thickeners, belt presses, filter presses, screw presses, or any other suitable separation or dewatering machines.

[0128] In one embodiment of the invention, three reactors are provided in parallel. The number of reactors may vary. Using three reactors allows for continuous filling of the reactors.

[0129] The device of the present invention may include one or more pressure relief tanks. By using at least two pressure relief tanks in series, more energy can be recovered.

[0130] According to embodiments of the invention, the apparatus may further, but not necessarily, include a heat exchanger connected to the digester and the pressure relief tank, which uses a portion of the contents of the digester as a cooling medium to condense a portion of the gas phase from the pressure relief tank. In the case of a two-stage pressure relief tank solution, the second tank may be equipped with an internal cooling loop instead of a recirculating digester.

[0131] In one embodiment of the invention, the apparatus further includes an extraction component for separating furfural from the condensed gas phase.

[0132] In another embodiment of the invention, a heat exchanger is connected to a digester for recirculating volatile acids in the condensate phase.

[0133] The features and embodiments described herein with respect to the methods of the present invention are applicable to the apparatus of the present invention, with only necessary modifications; and vice versa.

[0134] Detailed description of the attached figures

[0135] Figure 1A method and apparatus for pretreating biomass and organic waste fractions followed by biodegradation (e.g., anaerobic digestion) are illustrated. Solid biomass and / or organic waste fractions typically received in a receiving / storage (a) bin are conveyed (b) to one or more high-pressure reactors (d) via a feeding device (c) (typically a feed valve or a steam-assisted feeding system). High-pressure steam (e) is introduced into the reactors, and sufficient pressure is achieved to enable beneficial hydrolysis of the received biomass by closing inlet and outlet valves (c and f). Once sufficient steam pressure is reached, the valves remain closed until a beneficial holding time has elapsed. Depending on the characteristics of the feedstock, removal of some gases during heating and holding may be beneficial. If these gases are not vented, they can be directed to a condenser system (g) via a release valve (h). After the holding time has elapsed, the pressure can be reduced via the release valve (h) before opening the discharge valve (f). When the discharge valve opens, the pretreated material is rapidly discharged into a flash tank (j) via a robustly supported discharge pipe (i). The discharge rate is driven by the pressure difference between the reactor and the downstream flash tank (j). Due to the pressure drop, the condensed steam will flash and separate from the material and water inside the flash tank (j). Excess flash steam released from inside the flash tank (j) is released from the top of the flash tank through a pipe. The flash steam is preferably directed to the condenser (g). The condenser, preferably consisting of a quench tower with a circulation pump (k) and a condensate cooler (I), liquefies the excess steam. The condenser may be operated with cold cooling water directly injected into the condenser (g), as appropriate. Non-condensate (m) is discharged from the condenser, which may require odor treatment. The condensate is discharged back to the flash tank (n), transported through a pipe (o) to downstream processes, or separated from further processing processes that may be used for chemical recovery (p). Biodegradable materials, such as digestate from the downstream anaerobic digester (q), are circulated back to the flash tank via the digester circulation pump (r). Mixing inside the flash tank is achieved by injecting the liquid into the flash tank below the liquid level (t). If condensation inside the flash tank is preferred, the recirculated flow is directed to the top of the flash tank through nozzles(s), thus the flash tank serves as a quencher for condensing the flash steam. Such condensation may not be beneficial due to the overall generation of inhibitors. In such cases, condensation should take place inside a separate condenser(g). The mixture of pretreated material, condensate, and recycled biodegradable material (e.g., digestate) is pumped to a downstream process, such as an anaerobic digester(q), via a feed pump(u). Cooling can then be carried out in a cooler (v or w), depending on the preferred temperature in the downstream process.

[0136] Liquid biomass (x) that benefits from thermal pretreatment can be added directly or via the feed system (a or b) to the reactor (d) for advantageous mixing prior to the reactor. Liquid biomass (y) that benefits less from thermal pretreatment can be directed directly to the flash tank or to the digester recirculation loop (z-1 or z-2). Appropriate pumps (aa and ab) must be selected for delivering the liquid biomass to the process.

[0137] Figure 3 Another example of a method and apparatus for first pretreating biomass (e.g., organic waste) and then biodegrading it via fermentation is shown. Figure 3 like Figure 1 The process is described, except that there is no condensate cooler (I) and no discharge of condensate (n) back to the flash tank (j). However, two possible connections for water dilution are shown: one via a recirculation loop to the flash tank (af), and the other connected to the inlet (c) of the hot hydrolysis reactor (d). A separator or concentrator (ac) connected to the recirculation loop between the digester (q) and the flash tank (j) is further shown, with the separator (ac) having an output (ad). The direct outlet from the digester (q) is shown as (ae).

[0138] Figure 4Another example of a method and apparatus is shown for pretreating biomass first by hot hydrolysis (d) and wet explosion (j), and then fermenting the intermediate products obtained therefrom in a digester (q), wherein a portion of the contents of the digester is conveyed in a recirculation loop (t) into a pressure relief tank (j). Solid biomass and / or organic waste portions typically received in the receiving / storage (a) bin are conveyed (b) via a feed device (c) (e.g., a feed valve or a steam-assisted feed system) to one or more high-pressure reactors (d). Liquid biomass (x) benefiting from hot hydrolysis can be added directly or via the feed system (a or b) to the reactor (d) for advantageous mixing prior to reactor. High-pressure steam (e) is added to the reactor (d), and sufficient pressure is achieved to realize the beneficial hydrolysis of the received biomass by closing the inlet and outlet valves (c and f). When sufficient steam pressure is reached, the valves remain closed until a beneficial holding time has elapsed. Depending on the characteristics of the feedstock, it may be beneficial to remove some gases via a release valve (h). Pressure can be reduced via a release valve (h). When the discharge valve (f) is open, the pretreated material is rapidly discharged into the pressure relief tank (j) via the discharge pipe (i). The discharge rate is driven by the pressure difference between the reactor and the downstream pressure relief tank (j). Due to the pressure drop, the condensed vapor will flash and can be released from the top of the pressure relief tank through the pipe. Fermentation material (e.g., digestate) from the downstream digester (q) is circulated to the pressure relief tank (j) via the digester circulation pump (r) and via a separator or concentrator (ac). The separator (ac) has an output (ad) and another direct outlet from the digester (q) is shown as (ae). Mixing inside the pressure relief tank is achieved by injecting below the liquid level (t). If condensation inside the pressure relief tank is preferred, the recirculated flow is directed to the top of the pressure relief tank (j) through the nozzle (s), whereby the pressure relief tank (j) acts as a quencher for condensing the flash vapor. The mixture of pretreated material and recirculated biodegradable material (e.g., digestate) is pumped to the downstream process, such as the digester (q), via the feed pump (u). Cooling can be carried out in a cooler (v or w) depending on the preferred temperature in the downstream process. Liquid biomass (y) that benefits less from thermal pretreatment can be directed directly to a pressure relief tank or to a circulation loop (z-1 or z-2) starting from the digester. Water dilution can be directed into the process via a recirculation loop (af) to a flash tank (j) or directly to the inlet (c) of the hydrolysis reactor (d). Appropriate pumps (aa and ab) must be selected to deliver the liquid biomass into the process. The direct outlet from the digester (q) is shown as (ae).

[0139] Figure 5Another embodiment of the invention is shown, wherein a portion of the contents of the digester (q) is dehydrated (ah) in a separator (ah) and returned as a so-called dehydrated cake with increased dry matter (dry solids) content to the feed line (a) for the hydrolysis step, thereby mixing it with biomass material fed into the process in other ways.

Claims

1. A method for processing biomass materials, comprising at least the following steps: The pretreatment of the biomass material includes the following steps: 1) Hydrolysis at temperatures above 140℃, followed by 2) Wet explosion produces intermediate products with a dry matter concentration higher than 25%, a temperature higher than 90℃, and a pH value lower than 6. The intermediate product was then fermented in a digester, and The method is further characterized in that the intermediate product is introduced into the digester by mixing it into a portion of the contents of the digester being transported in a recirculation loop originating from the digester. The mixing is carried out before the mixture of the intermediate product and the contents of the portion of the digester enters the digester; wherein the pH of the portion of the digester is in the range of 7-8.5, and the pH after the mixing and before the mixture enters the digester is higher than pH 6.

2. The method according to claim 1, wherein the temperature of the intermediate product is above 100°C.

3. The method according to any one of claims 1 to 2, wherein the pH value of the intermediate product is less than 5.

4. The method according to any one of claims 1 to 2, wherein the method further comprises wet oxidation, the wet oxidation being performed after the hot hydrolysis and before the wet explosion.

5. The method according to any one of claims 1 to 2, wherein the portion of the contents of the digester is mixed with the intermediate product in such a manner that, by volume, at least 10 portions of the contents of the digester are mixed with one portion of the intermediate product.

6. The method according to any one of claims 1 to 2, wherein a portion of the gas phase from the pretreatment is condensed by using a portion of the contents of the digester as a cooling medium.

7. The method according to claim 6, wherein the furfural in the condensed gas phase is separated by extraction.

8. The method of claim 6, wherein the volatile acid in the condensed gas phase is recycled back into the digester.

9. The method according to any one of claims 1 to 2, wherein the biomass material introduced into the method has a dry matter concentration of more than 50% by weight.

10. The method according to any one of claims 1 to 2, wherein the biomass material introduced into the method is selected from the group consisting of: straw, wood, fiber, feed, pulp and household waste.

11. The method of claim 10, wherein the biomass material introduced into the method is pulp.

12. The method according to any one of claims 1 to 2, wherein The hydrolysis is carried out at a temperature above 140°C and maintained for 5-30 minutes, followed by... Wet explosions are carried out by reducing the pressure from 5-35 bar to atmospheric pressure.

13. The method of claim 1, wherein the pH value is higher than pH 6.5 after the intermediate product is mixed with the recycled fermentation product from the digester and before the mixture enters the fermenter.

14. The method of claim 1, wherein the volume ratio of the contents of the digester mixed with the intermediate product is in the range of 3:1 to 30:

1.

15. The method according to any one of claims 1 to 2, wherein the portion of the contents of the digester is mixed with the intermediate product in such a manner that, by volume, at least 20 portions of the contents of the digester are mixed with one portion of the intermediate product.

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