Method for continuous extraction of lignocellulosic material
Patent Information
- Application Number
- JP2024506219
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2021-08-02
- Filing Date
- 2022-08-01
- Publication Date
- 2025-08-07
AI Technical Summary
Existing methods for extracting lignocellulosic materials are inefficient, costly, and lack flexibility in removing useful substances and impurities, necessitating a more effective and cost-effective approach.
A continuous extraction method involving the formation of a lignocellulosic material and solvent suspension, followed by squeezing and separation in a press device, with controlled flow rates and solvent recycling, allowing for high mass transport and efficient extraction in a one-step or multi-step process, preferably countercurrent.
The method achieves high extraction yields with reduced solvent use and fewer steps, utilizing convective transport instead of diffusion, resulting in efficient and flexible extraction of useful substances from lignocellulosic materials.
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to a method for continuous extraction of lignocellulosic material.
[0002] In view of the depletion of fossil fuel reserves and the need for more sustainable raw material extraction, the use of renewable resources, especially biological feedstocks such as lignocellulosic biomass, is becoming increasingly important. The term "biorefinery" is often used for processes and systems of biological material utilization for the production of biofuels and a wide range of other chemicals, for example to replace oil-based products with bio-based products.
[0003] Methods for the extraction of lignocellulosic materials are known from the prior art (see, for example, WO 2012 / 110231 (A1), WO 2018 / 114905 (A1), U.S. Pat. No. 8,822,657 (A), U.S. Pat. No. 8,772,427 (A), U.S. Pat. No. 9,624,449 (A), EP 2,862,890 (A1), EP 2,520,608 (A1), A. Patel and AR Shah, Integrated lignocellulosic biorefinery: Gateway for production of second-generation ethanol and value-added products, Journal of Bioresources and Bioproducts, doi:10.1016 / j.jobab.2021.02.001). However, there remains a need for efficient, cost-effective and flexible methods for extracting useful substances or impurities from lignocellulosic materials, and it is therefore an object of the present invention to provide such methods.
[0004] In one aspect, the present invention provides a method for continuous extraction of lignocellulosic material, comprising the steps of: a) conveying lignocellulosic material to an extractor; b) forming a suspension of lignocellulosic material and a solvent in an extractor; c) extracting the lignocellulosic material in the extractor with a solvent; d) Remove a portion of the suspension from the extractor and measure the flow rate.
[0005]
number
[0006]
number
[0007]
number
[0008]
number
[0009]
number
[0010]
number
[0011] The present invention provides an efficient, cost-effective and flexible method for extracting lignocellulosic material. The method of the present invention can be designed as a single-stage or multi-stage process, the latter being preferred. In embodiments where the method of the present invention is a multi-stage process, the process is preferably configured as a continuous countercurrent process.
[0012] In the method of the invention, the lignocellulosic material is conveyed to the extractor, for example by conveyor or gravity. A solvent, such as water, may be added to the lignocellulosic material on the way to the extractor, for example by spraying the solvent onto the lignocellulosic material on the conveyor. Alternatively or additionally, for example, the solvent may be added directly to the extractor. The amount of solvent added continuously is set to offset, on a net basis, any difference in the mass flow rate of any liquid phase removed from the process, for example as extract, i.e., of the process stages or, in particular in a multi-stage process, of the liquid phase entering or leaving the entire process or system. The added solvent may be fresh solvent, especially in the case of a one-stage process. In a multi-stage process, the solvent may be pressate produced in a subsequent stage, or fresh solvent, the latter being preferably used in the final stage. In the extractor, where a sufficient amount of solvent is preferably present, a suspension of lignocellulosic material and solvent is formed. The extractor may, for example, be equipped with an agitator to facilitate the formation of a suspension and the extraction of substances from the lignocellulosic material, especially from water absorbed by wet lignocellulosic material. In the extractor, the lignocellulosic material is extracted with a solvent.
[0013] A portion of the suspension of lignocellulosic material and solvent is continuously removed from the extractor and conveyed, for example, by a suitable pump (e.g., a rotary pump, a lobe pump or a progressive cavity pump) to a press device. The press device is preferably a screw separator. In the press device, the solvent is separated from the lignocellulosic material by squeezing the solvent from the lignocellulosic material. The pressed solvent (pressate) is conveyed, for example, by a suitable pump (e.g., a piston pump, a centrifugal pump) to a pressate tank. The pressed lignocellulosic material is removed from the press device. A first portion of the pressate is returned to the extractor and a second portion of the pressate is removed from the pressate tank as extract and can either be removed from the process for further processing or returned to the process, for example, by adding it to the lignocellulosic material as it is fed to the extractor or by adding it directly to the extractor containing the suspension of lignocellulosic material and solvent. The first portion of the pressate returned to the extractor may be returned by gravity, i.e. by locating the pressate tank higher than the extractor, and / or by using one or more pumps.
[0014] The term "lignocellulosic material" refers to biological material, e.g., plant material, that contains lignocellulose. Lignocellulosic material contains lignocellulose, which is composed of carbohydrate polymers of cellulose and hemicellulose, and lignin, which is an aromatic polymer. This term includes, for example, plant materials such as straw, e.g., rice and rice straw, sugarcane bagasse, corn stover, etc. The terms "lignocellulose-containing material", "lignocellulosic biomass" or "lignocellulose" may be used synonymously with the term "lignocellulosic material". The term "lignocellulosic material" as used herein includes, for example, fresh lignocellulosic material, i.e., lignocellulosic material that has not yet been extracted, at least not yet extracted by the method of the present invention, and pressed lignocellulosic material. The term "pressed lignocellulosic material" relates to lignocellulosic material from which the liquid phase has been squeezed out, e.g., by a screw press. This term should not be interpreted to mean that the lignocellulosic material must be in a compressed state or be completely free of any liquid phase bound by the lignocellulosic material after the pressing process.
[0015] The term "hydrothermally pretreated lignocellulosic material" refers to hydrothermally treated lignocellulosic material. Hydrothermal pretreatment refers to the application of hot water or steam at a temperature of more than 100°C, for example 150-300°C, to the lignocellulosic material (see, for example, Ahmed B, Aboudi K, Tyagi VK, Alvarez-Gallego CJ, Fernandez-Guelfo LA, Romero-Garcia LI, Kazmi AA, Improvement of Anaerobic Digestion of Lignocellulosic Biomass by Hydrothermal Pretreatment, Applied Sciences. 2019; 9(18): 3853, doi: 10.3390 / app9183853). The preferred temperature range for hydrothermal pretreatment is 150-250°C or 150-230°C. The term includes dilute acid pretreatment (DAP) with, for example, dilute sulfuric acid, nitric acid, phosphoric acid or hydrochloric acid, and alkaline pretreatment, i.e., the use of alkaline solutions such as solutions of NaOH, KOH, Ca(OH)2 or ammonia. Furthermore, the term includes the term "autohydrolysis" which refers to hydrothermal treatment with water only. The term "autohydrolysis pretreated lignocellulosic material" refers to lignocellulosic material that has been treated by autohydrolysis. "Hydrothermal pretreated lignocellulosic material" is sometimes also called "Steam Pretreated Biomass" (SPB). The term "hydrothermal pretreatment" should not be interpreted to include any subsequent enzymatic hydrolysis.
[0016] The term "extraction" as used herein refers to solid-liquid extraction and includes the term "leaching", where the solutes extracted from the lignocellulosic material are components of interest, e.g., useful substances, and the term "washing", where the solutes extracted from the lignocellulosic material are foreign substances, impurities or contaminants, i.e., unwanted components that are removed from the lignocellulosic material. Examples of useful substances extracted from the lignocellulosic material are xylan oligomers, xylose, arabinose, acetic acid, furfural, and HydroxyMethylFurfural (HMF). Examples of undesirable components washed from the lignocellulosic material are mineral components ("ash"), fine particles (minerals, lignin-rich particles, microorganisms), dust, or manure. In this application, any undesirable solutes may be collectively referred to as "contaminants".
[0017] The term "solvent" as used herein relates to the liquid phase used to extract material from lignocellulosic material and includes the terms "pressate" and "extract", and relates both to fresh solvent, i.e. solvent not yet containing substances extracted from lignocellulosic material, and to solvent containing or concentrated with substances extracted from lignocellulosic material. The term "pressate" relates to solvent that is pressed from a suspension composed of lignocellulosic material and solvent, thus containing substances extracted from the lignocellulosic material. The term "extract" as used as a noun in the context of the present invention refers to the amount of solvent that is expressed from the liquid phase used to extract material from lignocellulosic material.
[0018]
number
[0019] The term "raffinate" refers to the liquid phase still bound to the pressed lignocellulosic material, i.e., the moisture content of the pressed lignocellulosic material exiting the pressing apparatus. Unless otherwise stated or implied from the context, the term "extracted lignocellulosic material" or "extracted biomass" relates to lignocellulosic material that has been subjected to an extraction process according to the invention. The term "pressed lignocellulosic material" (see above) is used herein in reference to lignocellulosic material including the solid phase and the raffinate.
[0020] For example, the term "conveyed" with respect to lignocellulosic material, solvent, or press liquid relates to any transport of material from one location to another, such as via a pump, conveyor belt, screw conveyor, by gravity, or by other means.
[0021] For example, as used herein, terms such as "removing x from y," where "x" refers to a portion of the suspension, pressed lignocellulosic material, or pressate, means that x is removed or separated from y, e.g., a portion of the suspension is removed from the extractor (separated from the suspension in a separator).
[0022] The term "countercurrent flow" with respect to the methods of the present invention refers to the counterflow of the lignocellulosic material to be extracted or the suspension of lignocellulosic material and solvent, and the solvent used to extract the lignocellulosic material.
[0023] The term "multi-stage process" relates to a process which comprises at least two stages, such as 2, 3, 4, 5, 6 or more stages.
[0024] The term "screw separator" (also called "screw press separator", "screw compactor" or "screw press") refers to an apparatus for solid-liquid separation that includes a rotating auger that conveys and presses the suspension towards a solid outlet and a screen that can separate the liquid phase from the solid phase. The solid outlet may be equipped with a hydraulic piston to control the pressure.
[0025] The term "extractor" refers to a device used to extract substances from a material, i.e. to remove useful substances or contaminants from a material, e.g., lignocellulosic material, and transfer them to a solvent. An example of an extractor is a vessel equipped with a means for agitating the material suspended in the solvent.
[0026] Unless otherwise stated, flow rates are mass flow rates rather than volume flow rates.
[0027]
number
[0028] The method according to the invention combines (preferably repeated) suspension extraction and pressing. The former results in high mass transport rates, while the latter has the advantage that the raffinate flow is very low relative to the solids flow, i.e. the flow of the starting lignocellulosic material. As a result, fewer steps and fewer solvents are required, despite a high extraction yield, i.e. a high yield of solutes in the final extract. The advantage of the method of the invention is that the mass transport of useful substances or pollutants in the lignocellulosic material to the bulk phase of the solvent does not result exclusively from diffusion and mass transfer, as in conventional extractors. Rather, a very fast convective mass transport occurs when the solvent is squeezed from the lignocellulosic material in suspension by the pressing device. The lignocellulosic material is compressed and the solvent, together with the useful substances or pollutants, is actively squeezed out of the lignocellulosic material as a pressate. This mass transport is convective, since it is brought about by an externally applied force, and is faster than the diffusion of useful substances from the interior of the lignocellulosic material. When the lignocellulosic material is mixed with the solvent, further convective material transport may occur depending on the lignocellulosic material used, especially if the cellular structure of the lignocellulosic material used is largely maintained, in which case the solvent will diffuse into the lignocellulosic material and begin to swell.
[0029] In a preferred embodiment of the method of the present invention, the flow rate at which the suspension is conveyed to the pressing device in step d is
[0030]
number
[0031]
number
[0032]
number
[0033]
number
[0034] Flow rate of added solvent
[0035]
number
[0036]
number
[0037]
number
[0038] In a preferred embodiment of the method of the present invention, the flow rate of the added solvent
[0039]
number
[0040]
number
[0041] The lignocellulosic material may be conveyed to the extractor in step a by any suitable means. For example, the lignocellulosic material may be conveyed to the extractor by gravity, for example using a chute or funnel. This embodiment is advantageous in that it obviates the need for auxiliary energy, i.e. active mechanical assistance, to actively feed the lignocellulosic material to the extractor, and may be particularly useful for smaller plants.
[0042] In another preferred embodiment of the method according to the invention, the lignocellulosic material is conveyed to the extractor by a conveyor in step a. This facilitates the application of the solvent to the lignocellulosic material before it enters the extractor. The conveyor may be, for example, a conveyor belt or a screw conveyor. In a preferred embodiment of the method according to the invention, the solvent is added to the lignocellulosic material in step a as it is conveyed to the extractor. Additionally or alternatively, the solvent can be added in another suitable process step. The solvent can be added directly to the extractor, for example, in either step b or c. The addition of a solvent, especially fresh solvent, to the lignocellulosic material before it is fed to the extractor can be particularly useful for quickly obtaining a concentration equilibrium between the solutes in the liquid phase bound within the lignocellulosic material and the bulk phase of the solvent, thereby aiding in a rapid and uniform distribution of the solutes in the bulk phase of the solvent in the extractor.
[0043] In a further preferred embodiment of the method of the present invention, more of the pressate that is removed as extract is returned to the extractor. Thus, the flow rate of the pressate returned to the extractor
[0044]
number
[0045]
number
[0046] The pressing device may be any device capable of separating, preferably continuously, the lignocellulosic material from the solvent, such as a twin roll press, a belt filter press or a screw separator, the latter being preferred.
[0047] The extractor is preferably a stirred vessel such that the suspension can be suitably agitated, e.g., stirred, in the extractor. This facilitates mass transport of the solute from the lignocellulosic material to the solvent, especially in suspensions with a relatively low solids content. In conventional processes such as displacement washing (pulp washing) or percolation, mass transport from the lignocellulosic material surface to the bulk phase of the extract is only relatively slow, because the fluid phase flows slowly through the lignocellulosic material by free convection or small pressure differences, as well as due to particle-particle contacts, dead zones and stagnation points where the relative velocity between particles and fluid is zero and material transport is limited by diffusion. The solids content of the suspension is preferably less than 40 wt.%, more preferably 35 wt.% or less, 30 wt.% or less, 25 wt.% or less, 20 wt.% or less, 15 wt.% or less, or 10 wt.% or less, for example in the range of 0.5-15 wt.%, 1-12 wt.% or 2-8 wt.%, based on the total weight of the suspension.
[0048] In a preferred embodiment, the solvent is water. The temperature of the water is preferably between 20 and 95°C. For leaching purposes, it is particularly preferred to use hot water at a temperature of about 40-95°C, preferably 55-80°C, for example 60, 65 or 70°C. For washing purposes, the solvent is preferably water at a temperature of about 20-95°C. The solvent here may for example be process water, i.e. water in which the substance is already dissolved.
[0049] In a further preferred embodiment of the method of the invention, the lignocellulosic material is in particulate form, such as straw particles. The lignocellulosic material can be reduced in size by mechanical means, for example by crushing, cutting or grinding the particles using suitable means. The particle size can vary, but is preferably configured to be within a range that facilitates the transport and suspension of the lignocellulosic material and increases the surface area in contact with the solvent. The particle size may depend on the lignocellulosic material used, and is preferably less than 20 cm, preferably in the range of 0.5-10 cm, more preferably 0.5-5 cm or 0.5-3 cm, and particularly preferably 0.5-2 cm.
[0050] The lignocellulosic material may be any lignocellulosic material or may be lignocellulosic material pretreated with any pretreatment process suitable for lignocellulosic materials. In a particularly preferred embodiment of the method of the present invention, the lignocellulosic material is hydrothermally pretreated lignocellulosic material, i.e. pretreated with hot water or steam. It is particularly preferred that the lignocellulosic material is autohydrolysis pretreated. Hot water pretreatment leads to the decomposition of the lignocellulosic biomass and solubilization of the components, facilitating the extraction of useful substances from the lignocellulosic material. Furthermore, due to its spongy structure, the hydrothermally pretreated lignocellulosic material, which has been precompressed, for example by pressing, swells when in contact with the solvent and can also be compressed to a much smaller size. When mixed with the solvent, the prepressed pretreated lignocellulosic material swells and more solvent flows into the material, resulting in convective transport of substances into the solvent.
[0051] Hydrothermal pretreatment is described in the literature (Conrad, M., Haring, H. & Smirnova, I. Design of an industrial autohydrolysis pretreatment plant for annual lignocellulose, Biomass Conv.Bioref.(2019),doi:10.1007 / s13399-019-00479-1;Ruiz, HA, Conrad, M., Sun, S., Sanchez, A., R ocha, G., Romani, A., Castro, E., Torres, A., Rodriguez-Jasso, RM, Andrade, LP, Smirnova, I., Sun, R., & Meyer, A. (2019), Engineering aspects of hydrothermal pretreatment:From batch to continuous operation,scale-up and pilot reactor under biorefinery concept,Bioresource technology, 122685, doi:10.1016 / j.biortech.2019.122685; Conrad, M. and Smirnova, I. (2020), Two-Step Autohydrolysis Pretreatment: Towards High Selective Full Fractionation of Wheat Straw, Chemie Ingenieur Technik, 92:1723-1732, doi:10.1002 / cite.202000056. The two-stage autohydrolysis pretreatment may include the use of a screw conveyor reactor (SCR, see Ruiz et al., 2019, supra). A screw conveyor reactor (SCR) is an enclosed pressure-resistant device that includes at least one reactor vessel, e.g., a horizontal cylindrical vessel, with a rotating auger (screw) that transports solid material, such as lignocellulosic material or other moist biomass, in which the material may be exposed to hot water or steam under pressure.The screw conveyor reactor (SCR) preferably also includes a high-pressure screw feeder (HP screw) capable of providing powerful drainage of the lignocellulosic material (see Ruiz et al., 2019, supra).
[0052] In a further preferred embodiment of the method of the invention, the extraction of the lignocellulosic material is inserted between the two steps of a two-stage hydrothermal pretreatment, e.g. an autohydrolysis pretreatment. In this embodiment, the lignocellulosic material is hydrothermally pretreated before step a), i.e. before the lignocellulosic material is conveyed to the extractor and after it has been removed from the press device. The method of the invention may furthermore be carried out before the first hydrothermal treatment step and / or after the second hydrothermal treatment step. The hydrothermal pretreatment may serve, inter alia, to enrich the liquid phase (raffinate) of the lignocellulosic material with solutes.
[0053] In the method according to the invention, any upstream or downstream flow of fluids, suspensions (slurries) or solids is preferably arranged so that mass flow occurs by gravity, where possible and reasonable, however, it is also possible to use pumps or other means.
[0054] The process of the present invention can be designed as a cocurrent process, for example as a one-stage process. However, in a particularly preferred embodiment of the process of the present invention, the process is a multistage process, particularly preferably a countercurrent multistage process, comprising at least two stages, a final stage and a stage upstream of the final stage. The final stage comprises steps a to i described above. At least one upstream stage comprises a flow rate in any one or more of steps a to h and steps a, b, c, d, e or g described above.
[0055]
number
[0056]
number
[0057] In a multi-stage process according to the invention comprising more than two stages, in any of the upstream stages, i.e., a stage upstream of the final stage, including the first stage, it is preferred that the solvent added to the lignocellulosic material in any one or more of steps a, b, c, d, e or g of the stage comprises the second portion of pressate from the pressate tank of the stage immediately downstream of the stage.
[0058] In a further preferred embodiment of the method of the present invention, the method comprises at least three stages, namely a first stage, a final stage and one or more intermediate stages between the first stage and the final stage, and in any of the intermediate stages, a flow rate is adjusted in any one or more of steps a, b, c, d, e or g.
[0059]
number
[0060] In this embodiment, in a first stage, the lignocellulosic material, preferably fresh, i.e. not yet extracted, more preferably hydrothermally pretreated lignocellulosic material, particularly preferably in the form of particles such as rice straw particles, is conveyed, for example by a conveyor, such as a belt conveyor or a screw conveyor, to an extractor, such as an agitated stirred vessel. A solvent may be added to the lignocellulosic material on its way to the extractor on the conveyor, for example by spraying the solvent on the lignocellulosic material, and / or may be added directly to the extractor. In this embodiment, the solvent added is not fresh solvent, but pressate taken from the pressate tank of the next, i.e. second stage of the process. In the extractor, a suspension of lignocellulosic material and solvent is formed. It should be noted that the liquid phase in the extractor may comprise the solvent already provided in the extractor and the added solvent. The lignocellulosic material is extracted with the solvent in the extractor. In this step, the suspension is preferably agitated in a suitable manner, such as by stirring, to facilitate the extraction of useful substances, e.g. useful substances dissolved in the water that are bound in the lignocellulosic material, or to wash away contaminants. A portion of the suspension is continuously removed from the extractor and is then pumped at a flow rate, e.g. by a suitable pump.
[0061]
number
[0062]
number
[0063]
number
[0064]
number
[0065]
number
[0066]
number
[0067]
number
[0068]
number
[0069] In this embodiment, the pressed lignocellulosic material removed from the press in the first stage of the method of the invention is treated in the second stage in the same manner as described for the first stage. The above steps are performed again with the lignocellulosic material removed from the press in the first stage. The main difference is that the second part of the pressate removed from the press tank in the second stage is not removed from the process but reused in the first stage, i.e., added to the starting lignocellulosic material in the first stage. The solvent added to the lignocellulosic material in the second stage consists of the pressate removed from the next (final) stage. In the case of two or more intermediate stages (e.g., a four-stage, five-stage or six-stage process), the pressate from any intermediate stage is removed for addition to the lignocellulosic material treated as starting material in the previous stage, and the pressed lignocellulosic material removed from the press enters the subsequent stage as starting material for the next extraction.
[0070] In the final stage of this embodiment of the multi-stage process of the invention, a second portion of the pressate is also removed to be added to the lignocellulosic material in any one or more of steps a, b, c, d, e or g of the previous (upstream) stage, while fresh solvent is added in any one or more of steps a, b, c, d, e or g of the final stage, for example in step a of the final stage to the lignocellulosic material entering from the previous stage, or in steps b or c directly to the extractor used in the final stage. The finally extracted lignocellulosic material leaves the final stage and may or may not be further processed. Thus, the lignocellulosic material and solvent are used in a countercurrent fashion, i.e. fresh lignocellulosic material preferably enters the process in the first stage and is further extracted in each of the subsequent stages until finally extracted in the final stage, and fresh solvent preferably enters the process in the final stage, with the extracted components further concentrated from stage to stage in the reverse direction until finally removed as extract from the first stage. Thus, the lignocellulosic material is gradually depleted of extractable components from the first to the final stage, while the solvent is gradually enriched in extractable components in the opposite direction, i.e., from the final stage to the first stage. Considering only the liquid phase, it can be said that the raffinate, i.e. the liquid phase (comprising the solid and liquid phases) of the treated lignocellulosic material, is gradually depleted of solutes from stage to stage in the downstream direction, while the solvent is gradually enriched in solutes from the raffinate from stage to stage in the upstream direction.
[0071] In the multi-stage process according to the invention, it is preferred that the lignocellulosic material conveyed to the extractor in step a of the first stage consists of hydrothermally pretreated, preferably autohydrolysis pretreated, lignocellulosic material, and that the solvent added to the lignocellulosic material in the final stage in any one or more of steps a, b, c, d, e or g consists of fresh solvent. In the intermediate and final stages, the lignocellulosic material being treated is pressed lignocellulosic material from the respective previous (upstream) stage, and in the intermediate and first stages, the solvent added to the lignocellulosic material in any one or more of steps a, b, c, d, e or g is pressed liquor from the respective next (downstream) stage.
[0072] In a preferred embodiment of the two-stage or multi-stage embodiment of the method of the present invention, the flow rate at which the suspension is conveyed to the pressing device in each stage is
[0073]
number
[0074]
number
[0075]
number
[0076]
number
[0077] In a preferred embodiment of the multi-stage process of the present invention, the flow rate of solvent added at each intermediate stage and resulting from the next (downstream) intermediate stage or the final stage
[0078]
number
[0079]
number
[0080]
number
[0081]
number
[0082]
number
[0083]
number
[0084]
number
[0085]
number
[0086]
number
[0087]
number
[0088]
number
[0089]
number
[0090]
number
[0091]
number
[0092]
number
[0093] In a further preferred embodiment of the multi-stage process of the invention, all extraction stages, i.e. from the first to the final stage, are inserted between the two stages of a two-stage hydrothermal pretreatment, preferably a two-stage autohydrolysis pretreatment. In this embodiment, the lignocellulosic material is hydrothermally pretreated before the first extraction stage and after the final extraction stage. Furthermore, it is also possible to arrange the method according to the invention in the form of a one-stage, two-stage or multi-stage process before the first hydrothermal pretreatment stage and / or after the second hydrothermal pretreatment stage, for example in the following sequence: method according to the invention - first hydrothermal pretreatment stage - method according to the invention - second hydrothermal pretreatment stage - method according to the invention.
[0094] The present invention also relates to an apparatus for continuous extraction of lignocellulosic material according to the method of the present invention as described above. The apparatus may also be referred to as a "plant" or a "system". The apparatus of the present invention comprises at least one equipment module, which comprises a conveyor, an extractor, a pressurized liquid tank and a pressing device, each of which is constructed, arranged and interconnected in such a way that the method of the present invention can be carried out. A "conveyor" is any means capable of transporting lignocellulosic material to the extractor, for example a belt or screw conveyor.
[0095] The apparatus for continuous extraction of lignocellulosic material according to the method of the present invention comprises at least one module including a conveyor, an extractor, a pressate tank and a press device, in the direction of flow of the lignocellulosic material, the extractor is disposed downstream of the conveyor, the press device is disposed downstream of the extractor, and the pressate tank is disposed downstream of the press device, the pressate tank and the extractor being in fluid communication with each other directly or indirectly via a pump so that the pressate can be transported from the pressate tank to the extractor.
[0096] In a preferred embodiment of the device of the invention, the pressate tank is arranged higher relative to the extractor to allow a first portion of the pressate to be returned from the pressate tank to the extractor by gravity. In a further preferred embodiment, the pressing device is additionally or alternatively arranged higher relative to the extractor to allow a portion of the suspension to be returned from the pressing device to the extractor by gravity.
[0097] In a preferred embodiment of the device of the present invention, the extractor is a stirred vessel and the pressing device is a screw separator.
[0098] In a particularly preferred embodiment of the device of the invention, the device is configured to perform a multi-stage process according to the invention, preferably a countercurrent process as described above. In this embodiment, the device comprises two or more of the above-mentioned modules connected in series. Each module comprises a conveyor, an extractor, a pressate tank and a press device, in the direction of flow of the lignocellulosic material, the extractor is arranged downstream of the conveyor, the press device is arranged downstream of the extractor, and the pressate tank is arranged downstream of the press device, the pressate tank and the extractor being in fluid communication with each other directly or indirectly via a pump so that the pressate can be conveyed from the pressate tank to the extractor. Preferably, the modules are interconnected such that a countercurrent flow of the lignocellulosic material and the solvent can be achieved, as described above.
[0099] The modules are arranged and interconnected such that, for example, a first module performs a first step of the method of the invention, one or more modules each perform an intermediate step of the method of the invention, and a final module performs a final step of the method of the invention, as described above.
[0100] In a further preferred embodiment of a "multi-module" apparatus of the invention, i.e. an apparatus of the invention comprising two or more modules, the press apparatus of each module is positioned higher than the conveyor of the next module so that the pressed lignocellulosic material can be transported by gravity from the press apparatus to the conveyor of the next module.
[0101] The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]
[0102] [Figure 1] FIG. 1 is a schematic flow diagram of one embodiment of the method of the present invention. [Diagram 2] FIG. 2 is a schematic flow diagram of a further embodiment of the method of the present invention. [Diagram 3] FIG. 1 is a schematic flow diagram of a preferred embodiment of the method of the present invention. [Figure 4] 1 is a simplified system scheme of an embodiment of an apparatus for carrying out an embodiment of a multi-step process of the present invention. [Diagram 5] Experimental data for the suspension extraction of wheat straw (chopped straw and crushed straw) pretreated with steam (180°C, 35 min) in water in a stirred tank. Dimensionless concentration of total pentoses is shown. [Figure 6] FIG. 1 is a process window for a continuous suspension extraction process configured as a countercurrent percolation process. N=number of stages, L / S=solvent usage (liquid-to-solid ratio). [Figure 7] FIG. 1 is a process window for a continuous suspension extraction process configured as a countercurrent washing process. N=number of stages, L / S=solvent usage (liquid-to-solid ratio).
[0103] Figure 1 shows a flow diagram of a basic embodiment of the process of the invention, configured as a one-stage process. The relevant mass flows are indicated by arrows and the mass flow rate is represented by the symbol
[0104]
number
[0105]
number
[0106]
number
[0107]
number
[0108]
number
[0109]
number
[0110]
number
[0111]
number
[0112]
number
[0113] In a preferred embodiment, the mass flow rate from the extractor 2 to the pressing device 3
[0114]
number
[0115]
number
[0116]
number
[0117]
number
[0118]
number
[0119]
number
[0120] It should be noted here that in the case of a multi-stage process, FIG. 1 is also applicable to the last stage of the multi-stage process, except that the reference number 21 in the left-hand part of the figure must be replaced by the reference number 23, which indicates the pressed lignocellulosic material 21 that is extracted at least once by the method diagrammatically shown in FIG. 1.
[0121] Or, in the case of a multi-step process, it is fed back into the system, i.e. to a previous (upstream) step (see, for example, Figure 2 below).
[0122] FIG. 2 shows a schematic representation of part of an embodiment of a multi-stage process according to the invention, one of the stages being the final stage. Here, by way of example, two stages 50 connected in series are shown. The stages 50 are enclosed in dashed rectangles for clarity. Here, the mass flow
[0123]
number
[0124]
number
[0125]
number
[0126] Figure 3 shows a flow chart of a preferred embodiment of the method of the present invention. The process shown here in a schematic manner is a multi-stage process with three stages 50, namely a first stage (left), an intermediate stage 50 (centre) and a final stage 50 (right). Lignocellulosic material 21, preferably particulate hydrothermally pretreated biomass, e.g. hydrothermally pretreated straw particles, is continuously fed to the extractor 2 of the first stage 50 of the method. The lignocellulosic material 21, 23 is treated in each stage 50 as described above. Pressed (extracted) lignocellulosic material 23 from the first stage 50 enters the second (intermediate) stage 50, where it serves as starting material, is then treated in the intermediate stage 50 as described, and leaves the intermediate stage 50 in a further extracted state as pressed lignocellulosic material 23 to serve as starting material for the final stage 50, again treated in the steps described above. It is therefore transported from stage 50 to stage 50 (from left to right in FIG. 3) and finally leaves the final stage 50 as extracted lignocellulosic material 23. In contrast, the solvent 22 for the extraction of the lignocellulosic material 21, 23 enters the process in the final stage 50 and is transported in the opposite direction, i.e. from the final stage 50 to the first stage 50 (from right to left in FIG. 3), compared to the lignocellulosic material 21, 23, and is removed from the process as the extractant 20 produced in the first stage 50. The solvent is therefore gradually enriched with substances extractable from the lignocellulosic material 21, 23 from stage 50 to stage 50. This countercurrent process allows efficient extraction of the lignocellulosic material 21, 23, since the concentration difference of the extractant in the solvent is maintained at a preferred level. The already largely depleted lignocellulosic material 23 is extracted with fresh solvent to allow further extraction of biomass, and the fresh lignocellulosic material 21 is extracted with a solvent that is already enriched in extractable substances but is still capable of extracting substances from the fresh material.
[0127] In this embodiment, the method of the invention is combined with a two-step hydrothermal treatment (Ruiz, H.A., Conrad, M., Sun, S., Sanchez, A., Rocha, G., Romani, A., Castro, E., Torres, A., Rodriguez-Jasso, R.M., Andrade, L.P., Smirnova, I., Sun, R., & Meyer, A. (2019), Engineering aspects of hydrothermal pretreatment: From batch to continuous operation, scale-up and pilot reactor under biorefinery concept, Bioresource technology, 122685, doi:10.1016 / j.biortech.2019.122685; Conrad, M. and Smirnova, I. (2020), Two-Step Autohydrolysis Pretreatment: Towards High Selective Full Fractionation of Wheat Straw, Chemie Ingenieur Technik, 92:1723-1732, doi:10.1002 / cite.202000056). The above-mentioned three-stage extraction process is inserted between the first and second steps of a two-stage hydrothermal treatment. For this purpose, a first screw conveyor reactor (SCR) 30 is used to hydrothermally pretreat the lignocellulosic material 21, for example a granular biomass such as rice straw. The pretreated lignocellulosic material 21 is thus a moist sponge-like material highly suitable for subsequent extraction. After extraction, the extracted lignocellulosic material 23 leaving the final stage, whether a single-stage or a multi-stage process according to the invention, is treated in a second hydrothermal treatment step. In the embodiment shown, a high pressure screw feeder (HP screw) 31 that is part of a second screw conveyor reactor (SCR) 32 is used to discharge the lignocellulosic material 23 exiting the final stage 50 of the extraction process and feed the lignocellulosic material 23 to the reaction vessel of the second SCR 32.A high pressure screw feeder (HP screw) compresses and mechanically discharges the wet biomass (e.g. to a moisture content of about 40-55%) into a steam-tight plug. The liquid squeezed out in this process can be returned to the final stage 50 of the upstream extraction stage 50, as shown in Figure 3. The combination of the extraction process with two autohydrolysis steps improves the overall balance of the extraction, since more solutes are transferred to the liquid phase of the lignocellulosic material (raffinate) and the solids are finally in a drier state, and the useful substances in the moisture are transferred to the extract without loss.
[0128] Figure 4 shows a simplified system scheme of an inventive apparatus 200 configured to carry out the multi-stage process described in Figure 3. Components for the hydrothermal pretreatment of the lignocellulosic material 21, 23 are not shown here. The illustrated apparatus 200 comprises three modules 100 connected in series, each module 100 configured to carry out a single stage 50 of the process. Each module comprises a conveyor 1, an extractor 2, a press device 3 and a pressate tank 4. In the illustrated embodiment of the inventive apparatus 200, the extractor 2 and the pressate tank 4 of each module 100 are configured as stirred tanks. The press device 3 is configured as a screw separator. The suspension of fresh lignocellulosic material 21 or pressed lignocellulosic material 23 and solvent 22 is conveyed to the press 3 by a suitable pump 5 and the pressate is conveyed by pumps 6, 7, the latter conveying the pressate back to the extractor 2 of the same module 100 and the former conveying the pressate to the conveyor 1 of the previous module 100 or removing the pressate from the device 200. Of course it is also possible to use only a single pump for both pressate streams with suitable control valves. The press 3 is positioned higher than the pressate tank 4 and the extractor 2 so that the pressate and excess suspension can be returned by gravity to the pressate tank 4 and the extractor 2, respectively. EXAMPLES
[0129] According to the method of the present invention, suspension extraction was carried out on large and small particles (1-2 cm and 1-2 mm long, respectively) of straw pretreated at 180 ° C for 35 min, but not crushed or pressed. The large and small particles were cut, chopped and crushed, respectively. A large gradient was set up with respect to the concentration of useful substances in the straw and in the solvent, so more useful substances need to be transported until equilibrium is reached. Material transport here includes transport of liquid into the particles, mixing of the moisture present with the useful substances in the particles, diffusion of the useful substances through the sponge-like structure to the particle surface (longer transport path for large particles) and transport from the particle surface to the bulk phase.
[0130] For this purpose, 3000 mL of water at 70 °C was placed in a stirred 10 L tank and the pretreated straw was added at time t = 0. The solid loading in the suspension was 2%. The mixture was sampled at various test times and separated into solid and liquid phases with a syringe filter. The concentration of the liquid samples was tested for the composition of carbohydrates in monomeric and oligomeric forms. To compensate for the minor effects of different feed moisture and concentrations, the total pentose sugar concentration was reported as normalized in the range of 0% to a stable final concentration of 100% in at least three measurements before the addition of the pretreated straw. The normalized concentration course of total pentose sugars in the extract over time is shown in Figure 5.
[0131] The experimental and reported data are set forth in Tables 1, 2 and 3 below.
[0132] [Table 1]
[0133] [Table 2]
[0134] [Table 3]
[0135] For the larger cut particles, it can be seen that after 10 minutes the concentration of total pentose sugars is constant, thus completing the transport of material. The pentose sugars shown are 90% in oligomeric form. Therefore, faster transport is expected for smaller molecules. For the smaller cut and ground particles, it can be seen that after 1 minute it exceeds 80% of the equilibrium concentration. After 5 minutes, the equilibrium concentration is reached. It is expected that for molecules smaller than the oligomers of the invention, shorter equilibrium times are likely.
[0136] In conclusion, small particles of pretreated straw, as expected after continuous autohydrolysis pretreatment, show equilibration times short enough for the continuous suspension extraction method of the present invention. For larger straw particles, equilibration times are expected to be shorter in the washing process, and the contaminants are either smaller molecules than oligomeric pentoses or are found on the particle surface rather than internally, such as dust or manure.
[0137] The characteristics of the washing and leaching process of the invention were calculated for a specific substrate (straw) as an example. The aim of the calculation is to calculate a process window that indicates the number of stages (N) and solvent usage (L / S) for a given feed, desired extract concentration, and useful substance recovery. In this example, the feed from steam digestion (autohydrolysis) with wheat straw is taken with the following mass percentages: 25.8% dry biomass, 66.7% water, 7.5% dissolved useful substances for the leaching process, and 86.4% dry biomass, 9.1% water, 4.5% dissolved useful substances for the washing process. It was assumed that an equilibrium is established between the intragranular and extragranular concentrations of useful substances at each stage as follows: The press screw dewaters the solids to 33% dry matter. The last screw (high pressure feeder) dewaters the solids to 50% dry matter. The results were calculated for 2 to 5 stages and a solvent usage of 1.0 to 4.0 kg water per kg dry biomass. Figures 6 and 7 show the resulting process windows, clearly demonstrating that high extraction yields and high extract concentrations can be simultaneously achieved by the method of the present invention using very small amounts of solvent for both investigated applications. The choice of design parameters (number of stages, solvent consumption) allows the process performance to be flexibly tailored to the needs of the biorefinery.
Claims
1. 1. A method for continuous extraction of lignocellulosic material, comprising: a) conveying lignocellulosic material to an extractor; b) forming a suspension of the lignocellulosic material and a solvent in the extractor; c) extracting the lignocellulosic material in the extractor with the solvent; d) removing a portion of the suspension from the extractor and measuring the flow rate [Equation 1] and transporting the material to a press device. e) squeezing the solvent from the lignocellulosic material in the press device, and dissolving the squeezed solvent as a squeezed liquid. [Equation 2] separating the solvent from the lignocellulosic material by conveying the solvent to a pressate tank; f) removing the pressed lignocellulosic material from the press; [Equation 3] And take it out with g) dissolving the first portion of the expressed liquid in a flow rate [Equation 4] returning the pressate from the pressurized tank to the extractor; h) separating a second portion of the pressate as an extract from a flow rate of [Equation 5] and removing the squeezed liquid from the squeezed liquid tank. i) In any one or more of steps a, b, c, d, e or g, the flow rate [Equation 6] and adding a solvent to the lignocellulosic material.
2. In step d, the flow rate at which the suspension is conveyed to the press device [Equation 7] is the flow rate at which the squeezed liquid is transported to the squeezed liquid tank [Equation 8] and a flow rate at which the pressed lignocellulosic material is removed from the press. [Equation 9] and a portion of the suspension conveyed from the extractor to the press device is greater than the sum of [Equation 10] 2. The method of claim 1, wherein the mixture is returned from the press to the extractor at a temperature of 1000.degree.
3. 3. The method of claim 2, wherein a portion of the suspension is returned by gravity from the press to the extractor and / or the first portion of the pressate is returned by gravity from the pressate tank to the extractor.
4. The method of claim 1 , wherein in step a, the lignocellulosic material is transported into the extractor by a conveyor.
5. The flow rate of the pressurized liquid returned to the extractor [0011] is the flow rate of the squeezed liquid taken out as extract [0012] The method of claim 1 , wherein
6. 2. The method of claim 1, wherein the solvent is added to the lignocellulosic material in step a as it is conveyed to the extractor and / or added directly to the extractor in either step b or c.
7. The method of claim 1 , wherein the pressing device is a screw separator.
8. 10. The method of claim 1, wherein the extractor is a stirred vessel.
9. The method of claim 1 , wherein the solvent is water.
10. The method of claim 1 , wherein the lignocellulosic material is in particulate form.
11. The method according to claim 1 , wherein the lignocellulosic material is a hydrothermally pretreated lignocellulosic material, particularly preferably an autohydrolysis pretreated lignocellulosic material.
12. The method is a multi-stage process comprising at least two stages, the final stage comprising steps a to i above, and at least one upstream stage comprising a solvent flow rate controlling any one or more of steps a to h and a, b, c, d, e or g above. [0013] i) adding a solvent to the lignocellulosic material in the final stage to form a solvent mixture containing fresh solvent; and ii) adding a solvent mixture to the lignocellulosic material in the upstream stage to form a solvent mixture containing fresh solvent.
13. The method of claim 12, wherein the method is a countercurrent multistage process.
14. 13. The method of claim 12, comprising a first stage, a final stage, and one or more intermediate stages between the first stage and the final stage, wherein in any of the intermediate stages, the solvent added to the lignocellulosic material comprises or consists of the second portion of the pressate removed from the press tank in step h of the next stage, and the lignocellulosic material conveyed to the extractor consists of the pressed lignocellulosic material removed from the press device in step f of the previous stage.
15. 15. The method of claim 14, wherein the lignocellulosic material conveyed to the extractor in step a of the first stage consists of hydrothermally pretreated lignocellulosic material, preferably in particulate form, and the solvent added to the lignocellulosic material in the final stage consists of fresh solvent.
16. Flow rate of added solvent [0014] is the flow rate of the squeezed liquid taken out as an extract in each of the stages other than the first stage or the first stage and the final stage. [Equation 15] The method of claim 12, wherein the
17. 2. The method of claim 1, wherein the pressed lignocellulosic material removed from the pressing device is subjected to a subsequent hydrothermal treatment, preferably an autohydrolysis treatment, in the case of a multi-stage process, preferably after the final stage.
18. The method described in claim 1, wherein the method is a multi-stage process, and a stage of the method is inserted between two stages of a two-stage hydrothermal treatment, the hydrothermal treatment meaning the application of hot water or steam at a temperature above 100°C.
19. The method described in claim 18, wherein the lignocellulosic material is hydrothermally treated before the first stage and after the final stage, and / or extraction of the lignocellulosic material is further carried out before the first hydrothermal treatment stage or after the second hydrothermal treatment stage.
20. 20. An apparatus (200) for continuous extraction of lignocellulosic material according to the method of any one of claims 1 to 19, comprising at least one module (100) including a conveyor (1), an extractor (2), a pressate tank (4) and a press device (3), wherein in the direction of flow of the lignocellulosic material, the extractor (2) is arranged downstream of the conveyor (1), the press device (3) is arranged downstream of the extractor (2), and the pressate tank (4) is arranged downstream of the press device (3), the pressate tank (4) and the extractor (2) are in fluid communication with each other directly or indirectly via a pump so that pressate can be transported from the pressate tank (4) to the extractor (2).
21. 21. The apparatus (200) according to claim 20, wherein the press tank (4) is arranged higher relative to the extractor (2) and / or the pressing device (3) is arranged higher relative to the extractor (2).
22. the device (200) comprises two or more of the modules (100) connected in series; and / or 21. The apparatus (200) according to claim 20, wherein the extractor (2) is a stirred vessel and the pressing device (3) is a screw separator.