Efficient methods and compositions for recovering products from organic acid pretreatment of plant materials

Abstract

Compositions and processes are provided for efficient downstream processing of products derived from organic acid pretreatment of plant materials.

Description

[0001] This application is a divisional application of the invention application with application number "201880093860.0" and invention name "Effective method and composition for recovering products from organic acid pretreatment of plant materials". Technical Field

[0002] The present invention relates to compositions and processes for: (i) recovering organic acids from a cellulose pulp derived from an organic acid pretreatment of a plant material, (ii) treating cellulose recovered from a cellulose pulp derived from an organic acid pretreatment of a plant material before conversion to glucose, (iii) separating and cleaning lignin from a lignin suspension derived from an organic acid pretreatment of a plant material, (iv) recovering organic acids from an aqueous phase derived from an organic acid pretreatment of a plant material, (v) recovering residual organic acids from a hemicellulose-containing fraction derived from an organic acid pretreatment of a plant material, and (vi) producing organic fertilizers from cellulose and hemicellulose juices derived from an organic acid pretreatment of a plant material. Background Art

[0003] In a first aspect, the present invention relates to a method for recovering organic acid from cellulose pulp using a combined dryer and desolventizer. This aspect of the invention improves the efficiency of existing organic acid pretreatment processes by allowing the recovery and reuse of the organic acid used to dissolve hemicellulose and lignin contained in lignocellulosic plant material. Following the solubilization step of the organic acid pretreatment of the plant material, a mixture of a soluble fraction and an insoluble fraction is obtained. After separating the mixture into the soluble and insoluble fractions, a cellulose pulp and an extract are obtained. The cellulose pulp is approximately 62% soluble fraction composed primarily of organic acid and water and 38% insoluble fraction composed primarily of undissolved cellulose.

[0004] Organic acid pretreatment processes suitable for use in the present invention are described in International Patent Publication Nos. WO 2011 / 154293 and WO 2010 / 006840, the contents of which are incorporated herein by reference in their entirety. The present invention also relates to recovering organic acid from an organic acid pretreatment process step that involves partial elimination of lignin to achieve a total residual lignin level of 0.3% to 4%. Such a step is described in International Patent Publication No. WO 2012 / 049054, the contents of which are incorporated herein by reference in their entirety.

[0005] In such processes, not only do the lost organic acids represent a significant portion of the unit operating costs, but the unrecovered organic acids also have an impact on environmental considerations. Therefore, efficient recovery of organic acids from cellulose pulp produced by organic acid pretreatment of plant material offers economic and environmental advantages over existing methods.

[0006] In another aspect, the present invention further relates to a process for treating cellulose by a combination of neutralization and alkalization, wherein the cellulose is derived from an existing process for producing bioethanol or other products, including organic acid pretreatment of plant material. Such an existing process is described in U.S. Patent Publication No. 2013-0183733, the contents of which are incorporated herein by reference in their entirety.

[0007] Bioethanol is produced by a process comprising an organic acid pretreatment step, involving an initial step of disrupting the structure of lignocellulosic plant material by subjecting it to a mixture of formic acid, acetic acid, and water. The next step involves separating the cellulose from other materials. In order to achieve the best possible yield from enzymatic hydrolysis of the separated cellulose, it is disclosed that lignin is partially eliminated prior to the enzymatic hydrolysis step. The cellulose is treated to eliminate lignin by treating it with sodium hydroxide, followed by a washing step designed to eliminate residual sodium hydroxide prior to enzymatic hydrolysis. The treatment is performed to achieve a preferred lignin level, wherein the overall level of residual lignin is approximately 1.65%.

[0008] Typically, organic acid-pretreated cellulose derived from plant material is treated by adding sodium hydroxide directly to the cellulose to adjust the pH to between pH 10 and pH 12, followed by a separation step to separate the mixture into treated cellulose and a filtrate (primarily containing sodium hydroxide and other soluble fractions). Cellulose produced by existing organic acid pretreatment processes contains residual organic acids from the pretreatment process, ranging from 0.5% to 5% by weight of the dry cellulose. Neutralization of these residual acids consumes large amounts of sodium hydroxide, which directly increases the cost of bioethanol production and indirectly increases the cost of filtrate treatment. Therefore, methods that minimize the amount of sodium hydroxide required to reach the operating pH range before subsequent cellulose processing represent a particularly important advantage over existing methods.

[0009] In another aspect, the present invention relates to a process for separating and cleaning lignin from an organic acid pretreated lignin suspension derived from plant material by using centrifugation.

[0010] The organic acid pretreatment process uses an organic acid solution as a reagent to dissolve the hemicellulose and lignin contained in the plant material. After separation, the extract is separated from the mixture. The extract, which primarily consists of cellulose, dissolved hemicellulose, lignin, minerals, organic acid, and water, is concentrated using an evaporation system to remove some of the organic acid and water, to a dry matter content of 55%-65% based on the total weight of the concentrated extract. This prior art process is described in International Patent Publications WO2000 / 068494, WO2009 / 092749, WO2011 / 154293, and WO2015 / 185639, the contents of each of which are incorporated herein by reference in their entirety.

[0011] In such processes, a lignin suspension is typically obtained by dispersing lignin in a mixture of concentrated extract and water. The lignin and sugars present in the lignin suspension are then separated using a filter press. After separation of the lignin, a filter cake containing a liquid containing lignin and sugars is obtained. The pressed lignin cake is then washed with water or a combination of air and water to obtain a final washed lignin and a washing liquid.

[0012] However, the filter press cannot be operated continuously throughout the entire process, and therefore, due to the structural limitations of the device, using a filter press to wash the cake does not produce a uniform product. The lignin filter cake is rectangular, making the washing path through the lignin cake variable and often inconsistent. The present disclosure provides a method for centrifugal recovery of lignin, thereby reducing water usage and, therefore, energy consumption, while improving the recovery of lignin from a lignin suspension.

[0013] In another aspect, the present invention relates to a process for producing hemicellulose juice from a hemicellulose mixture produced by organic acid pretreatment of plant material, the hemicellulose mixture primarily comprising dissolved hemicellulose, an organic acid, and water, by a combination of evaporation and steam stripping. The organic acid pretreatment process uses an organic acid solution as a reagent to dissolve the hemicellulose and lignin contained in the lignocellulosic feedstock at a relatively low temperature and atmospheric pressure, and even in the subsequent extract treatment process, which is carried out at a relatively low temperature and atmospheric pressure or vacuum pressure to prevent the production of furfural.

[0014] Typically, an extract consisting of dissolved hemicellulose, lignin, organic acid, and water is concentrated by a multiple-effect evaporation system to remove some of the organic acid and water, to a dry matter content of 55% to 65% based on the total weight of the concentrate. The lignin contained in the concentrate is separated by an existing process for separating lignin and sugars from the extract. In this process, before separating the lignin and sugars, the concentrate and water are mixed in equal parts by weight. The separated lignin must be washed with water to remove residual sugars and organic acids, and all soluble materials and water are collected together to form a hemicellulose mixture of dissolved hemicellulose, organic acid, and water produced in the process. Such a process is described in International Patent Publication Nos. WO2011 / 154293 and WO2010 / 006840, the contents of each of which are incorporated herein by reference in their entirety.

[0015] The dissolved hemicellulose in the hemicellulose mixture mainly comprises xylose and arabinose, which can be used to produce ethanol and other industrial products. However, the organic acids present in the hemicellulose mixture will inhibit the conversion of xylose and arabinose to ethanol and other industrial products. Therefore, for maximizing the yield of ethanol from the available sugars in the hemicellulose juice, it is particularly important to effectively remove organic acids from the hemicellulose mixture to produce hemicellulose juice.

[0016] On the other hand, the present invention relates to reclaiming organic acid from the high water content organic acid solution produced by the organic acid pretreatment process of plant material.Usually, the content of organic acid is higher than 83% of the total weight of the solution in such a process.Organic acid is used as a reagent to dissolve hemicellulose and lignin contained in the lignocellulosic raw material at relatively low temperature and atmospheric pressure to avoid producing furfural during the pretreatment process.After separation, the liquid contains dissolved hemicellulose, lignin, organic acid, water and other components.The water consisting of the water in the organic acid solution and the water in the raw material is concentrated by an evaporation system to remove the organic acid with water in part, which forms a first stream of high water content organic acid solution.

[0017] In this process, lignin contained in the concentrate is separated using an existing process for separating lignin and sugars from an extract. Prior to separating the lignin from the concentrate, the concentrate is mixed with water in an amount equal to the weight of the concentrate to precipitate the lignin in the concentrate. Subsequently, the separated lignin is washed with water to remove residual sugars, organic acids, and other water-soluble components.

[0018] All soluble materials are collected together with water, water remaining in the concentrate, water mixed with the concentrate used to precipitate lignin, and water used as wash water to form a mixture consisting primarily of dissolved hemicellulose, organic acids, water (remaining and added during the process), and other minor components. Such a process is described in International Patent Applications WO 2011 / 154293 and WO 2010 / 006840, the contents of each of which are incorporated herein by reference in their entirety.

[0019] To efficiently remove organic acid from a high-water-content organic acid solution, regardless of its source, a combined evaporation and stripping process is disclosed. The disclosed process includes a first pass through a multiple-effect evaporator to partially evaporate the organic acid from the mixture using water, with the evaporator condensate, which primarily contains organic acid and water, forming a second stream of the high-water-content organic acid solution.

[0020] The concentrated organic acid mixture from the evaporator is fed to a stripping column where the organic acid is further removed to a content of less than 2%, and the condensate from the stripping column forms a third stream of organic acid solution with a high water content.

[0021] The fourth stream of high-water content organic acid is derived from the recovery of organic acid from a cellulose pulp containing approximately 62% of a soluble fraction (which consists primarily of organic acid and water) and approximately 38% of an insoluble fraction (which consists primarily of cellulose) using a desolventizer adapted to utilize steam to remove residual organic acid from the dried cellulose pulp. In this aspect of the invention, the condensate from the desolventizer forms the fourth stream of high-water content organic acid solution.

[0022] In order to recycle the organic acid and water to the organic acid pretreatment process, additional water needs to be removed from the four streams of high water content organic acid solution to meet the water content requirements of the extraction and delignification steps.

[0023] In another aspect, the present invention relates to a method for producing organic fertilizer by utilizing stillage from cellulosic and hemicellulosic juices.

[0024] The present invention is based on organic acid pretreatment of plant material, wherein the plant material, particularly cereal straw, is used as the raw material. The separation of lignocellulosic feedstock into cellulose, hemicellulose juice, and lignin by organic acid pretreatment, the hydrolysis and fermentation of the cellulose and hemicellulose juice, and the conversion of a substantial portion of the cellulose and hemicellulose juice into ethanol are described in International Patent Application WO 2015 / 185639, the contents of which are incorporated herein by reference in their entirety.

[0025] Typically, in the process of producing fuel ethanol after fermentation, the mixture of fermented cellulose and hemicellulose juice is fed to the mash column of the distillation system, where ethanol is extracted to produce fuel ethanol. In such a process, residue is released from the bottom of the mash column. One result of the organic acid pretreatment process is that most of the nutrients (protein, potassium, phosphate, etc.) of the lignocellulosic raw material are separated into hemicellulose juice and mixed with fermentation materials (yeast, glycerol, etc.) as stillage. Using this stillage becomes a key issue. If there is no productive use, the stillage will be treated as waste, and the treatment of such waste is expensive. In the existing process, no good method is proposed. This aspect of the present invention provides a process for decanting and evaporating stillage solids to form a valuable organic fertilizer base, while the vapor derived from the stillage liquid acts as a thermocouple to help the stillage solids evaporation system, thereby producing a thermodynamically efficient method for recovering and processing stillage that is otherwise unproductive. Summary of the Invention

[0026] In a first aspect, the present invention discloses a method and composition for efficiently, thoroughly, and economically recovering organic acids from cellulose pulp using a combination of a dryer and a desolventizer. The method includes a first step using a dryer to reduce the organic acid content to 5% to 12% by weight, based on the total weight of the dried cellulose pulp. At this level, further removal of the organic acid by continued drying is difficult. To overcome this limitation, the present invention includes a second step using a desolventizer using live steam as the desolventizing medium to further remove the organic acid, reducing the organic acid content to less than 2% by weight, based on the total weight of the desolventized cellulose pulp.

[0027] Another aspect of the present invention provides a process and composition for treating cellulose by a combination of neutralization and alkalization, which uses the minimum amount of sodium hydroxide possible to prepare cellulose for enzymatic digestion, and a means of recycling the sodium hydroxide solution from the alkalization step to the neutralization step, using the minimum amount of sodium hydroxide to reduce the cost of bioethanol production and disposal of associated waste.

[0028] Another aspect of the present invention provides a lignin separation and cleaning process and composition using centrifugation, which further comprises recycling a specific portion of the centrifuge liquid and washing it online to obtain pure lignin, so as to reduce the overall water consumption and obtain high quality lignin.

[0029] Another aspect of the present invention is a process for efficiently and economically removing organic acids from a hemicellulose mixture of dissolved hemicellulose, organic acids, and water by combining evaporation with steam stripping to produce a hemicellulose juice composition. The process comprises, in a first step, a multiple-effect evaporation system to partially evaporate the organic acids using water to a dry matter content of 40% to 70% based on the total weight of the concentrated hemicellulose juice. The process further comprises a second step in which the concentrated hemicellulose juice is fed to a steam stripping column, wherein the organic acids are further removed to a content of less than 2% based on the total weight of the hemicellulose juice.

[0030] Another aspect of the present invention is a process for efficiently and economically removing water from a high-water-content organic acid solution by a process comprising multi-tower distillation to produce a composition suitable for subsequent recycling within an organic acid pretreatment process. The process is characterized by: a) employing a 2-5-tower distillation system to recover the organic acid; b) feeding only fresh steam to the first tower of the multi-tower distillation system; c) sequentially providing steam released from the previous tower to subsequent towers as heat energy; d) feeding one or more streams of the high-water-content organic acid solution to different towers within the multi-tower system to balance the energy requirements of the towers comprising the distillation system; e) adjusting the organic acid content in the condensate of the first tower to minimize fresh steam consumption; and f) recycling the total organic acid and total water discharged from the multi-tower distillation system to the overall process comprising the organic acid pretreatment of plant material, which minimizes energy, i.e., steam consumption, for recovering the organic acid while allowing the total organic acid and water to be recycled to the pretreatment process.

[0031] Another aspect of the present invention is a method for efficiently and economically producing an organic fertilizer composition using stillage from fermentation of cellulose and hemicellulose juice. Stillage is rich in organic matter and nutrients, which meet the needs of organic fertilizers. Organic fertilizers can improve soil quality and provide nutrients to plants (such as grains). In contrast, chemical fertilizers can damage the soil even while providing nutrients to plants. Organic fertilizers are an important emerging direction in agriculture. This aspect of the present invention is characterized in that stillage (fermentation byproducts) is used to produce valuable organic fertilizers in an effective and economical way. The method includes separating stillage by decantation to obtain a solid fraction of stillage and a thin stillage containing a more dilute fraction of stillage. The method further includes concentrating the thin stillage by a multiple-effect evaporation system to obtain concentrated stillage, mixing the solid fraction with the concentrated stillage to obtain a mixture, drying the mixture by a dryer to obtain organic fertilizer, using the steam released from the dryer as heat energy for the multiple-effect evaporation system, and feeding fresh steam to the multiple-effect evaporation system as supplementary heat energy. The present invention discloses the following technical solutions:

[0032] Scheme 1. A method for producing a lignin composition, the method comprising the following steps:

[0033] a) separating lignin by centrifugation from a lignin suspension produced by organic acid pretreatment of plant material, and

[0034] b) cleaning the lignin in the centrifuge by applying a wash solution to the lignin multiple times during centrifugation to form multiple centrates, and

[0035] c) recovering the first centrifuge liquid and the second centrifuge liquid for hemicellulose juice concentration, and

[0036] d) recycling the third centrifuge liquid used to separate the lignin from the concentrated extract in the separation step of the method, and

[0037] e) discharging the lignin from the centrifuge.

[0038] Option 2. The method according to Option 1, wherein the centrifuge is a scraper centrifuge.

[0039] Option 3. The method according to Option 1, wherein the centrifuge is equipped with a spray device for delivering the washing solution.

[0040] Option 4. A method according to Option 1, wherein the centrifuge rotates continuously throughout the method.

[0041] Option 5. The method according to Option 1, wherein the washing solution comprises formic acid, acetic acid and water.

[0042] Option 6. The method according to Option 1, wherein the washing solution consists only of water.

[0043] Option 7. A method according to Option 1, wherein the multiple applications of washing solution include: a first application of a washing solution comprising washing water with a high organic acid content, a second application of a washing solution comprising washing water with a low organic acid content, and a final application of a washing solution comprising fresh water.

[0044] Option 8. The method according to Option 5, wherein the formic acid content of the washing solution is 0% to 30% by weight.

[0045] Option 9. The method according to Option 5, wherein the acetic acid content of the washing solution is 0% to 20% by weight.

[0046] Option 10. The method of Option 1, wherein the first centrifuge liquid comprises liquid separated from the lignin suspension applied to the centrifuge.

[0047] Option 11. The method of Option 1, wherein the second centrifuge comprises a first wash solution of lignin applied to the centrifuge.

[0048] Option 12. The method according to Option 1, wherein the first centrifuge liquid and the second centrifuge liquid are collected and used for hemicellulose juice production.

[0049] Embodiment 13. The method of embodiment 1, wherein the third centrate comprises the second wash solution and any subsequent wash solutions applied to the lignin in the centrifuge.

[0050] Option 14. The method according to Option 1, wherein the third centrifuge liquid is recycled to the lignin precipitation step.

[0051] Option 15. The method of Option 1, wherein the first centrate constitutes 10% to 60% of the total centrate.

[0052] Option 16. The method of Option 1, wherein the second centrate constitutes 10% to 30% of the total centrate.

[0053] Option 17. The method of Option 1, wherein the third centrate constitutes 10% to 50% of the total centrate.

[0054] Embodiment 18. The method according to embodiment 1, wherein the purity of the lignin is 90% to 99% based on the total weight of the cleaned lignin.

[0055] Scheme 19. A lignin composition obtained by the method according to any one of Schemes 1 to 18.

[0056] Item 20. The lignin composition according to Item 19, wherein the purity of the lignin is 90% to 99% based on the total weight of the cleaned lignin. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1The present invention is a process diagram illustrating how to recover organic acids from cellulose pulp by a combination of a dryer and a desolventizer unit. Cellulose pulp (21) is introduced into a dryer unit (101) to obtain dried cellulose pulp (22) and steam (23). Steam (23) is used to provide heat energy to the extract concentration system and other operating units within the entire system. The dried cellulose pulp (22) is fed to the desolventizer (103) to further remove organic acids by using direct steam (23) as a desolventizing medium to obtain desolventized cellulose pulp (24). Steam (25) from the desolventizer unit is fed to condenser I (104). Uncondensed steam (26) from condenser I (104) is fed to condenser II (105). The condensed vapor solution (27) from condenser I and the condensed vapor solution (28) from condenser II (105) can be combined to form an organic acid solution (13).

[0058] Figure 2 Schematic diagram illustrating the structure of the desolventizer (103). Dried cellulose pulp (22) is fed to the top of the desolventizer (103) through the feed inlet (106). Direct steam (23) is ejected from the holes of the plate (109) and then discharged through the layer of dried cellulose pulp. At the same time, the direct steam carries out the residual organic acid contained in the dried cellulose pulp to form organic acid vapor, which is released from the vapor outlet (107) of the desolventizer (103). The released organic acid vapor is fed to condenser I (104), and the uncondensed vapor in condenser I (104) is fed to condenser II (105). The condensate of condenser I (104) and condenser II (105) forms an organic acid solution (13). After desolventization, the desolventized cellulose pulp (24) is discharged by a rotary discharger (108).

[0059] Figure 3 Schematic diagram illustrating the treatment of cellulose by a combination of neutralization and alkalization, wherein cellulose (21) is fed to a neutralization tank (101) where sodium hydroxide (23) and recycled sodium hydroxide solution (22) are added to form a neutralized cellulose mixture (24). The neutralized cellulose mixture (24) is fed to a press I (102) to obtain a filtrate (25) and neutralized cellulose (26). The filtrate (25) is discharged to a wastewater treatment system (103), while the neutralized cellulose (26) is fed to an alkalization reactor (104). Within the alkalization reactor (104), sodium hydroxide (27) is added to obtain an alkalized cellulose mixture (28). The alkalized cellulose mixture (28) is fed to a press II (105) to obtain a sodium hydroxide solution (22) that is recycled to the neutralization tank and a final alkalized cellulose (29) product.

[0060] Figure 4 is a process diagram illustrating a process for producing pure lignin. In the process, the third centrifuge (21) is mixed with the concentrated extract (22) to form a mixture, which is emulsified in a suspension tank (102) using a continuous or intermittent emulsifier (101) to form a stable lignin suspension (23). The lignin suspension (23) is then fed into a centrifuge (103) where the lignin suspension is separated into a lignin layer and a first centrifuge (25). The first centrifuge (25) is delivered to a multiple-effect evaporation system (104) for hemicellulose juice production. A first wash water (27) is introduced to wash the lignin layer to produce a second centrifuge (26). The first wash water may be from Figure 10-13 The high acid content water of the condenser 1 of the acid distillation unit (5) is also sent to the second centrifuge (26) for hemicellulose juice production. The second wash water (28) is introduced into the lignin layer to produce at least a third centrifuge (21). The second wash water may contain Figure 10-13 The lignin is suspended in the suspension tank (102) by combining the third centrifuge with any subsequent centrifuges. The washed lignin is discharged from the centrifuge as pure lignin (24).

[0061] Figure 5 The sequence of steps involved in producing hemicellulose juice is described. The raw hemicellulose juice (21), separated from the extract by lignin precipitation, filtration, and washing, is fed to a multiple-effect evaporation system (101). Concentrated hemicellulose juice (22) and condensed organic acids (23) are produced by the multiple-effect evaporator system. Fresh steam (26) and the concentrated hemicellulose juice (22) are introduced into a stripping column (102) to further remove organic acids, thereby obtaining a stripped hemicellulose juice (24) having an organic acid content of less than 2% of the total weight of the stripped hemicellulose juice and freshly condensed acids (25).

[0062] Figure 6 A 2-effect evaporation and stripping system is graphically detailed. Internal markings are described in Example 4.

[0063] Figure 7 A three-effect evaporation and stripping system is graphically detailed. Internal markings are described in Example 4.

[0064] Figure 8 A four-effect evaporation and stripping system is graphically detailed. Internal markings are described in Example 4.

[0065] Figure 9Flowchart of a process for recovering organic acids from a high water content organic acid solution by multi-tower distillation. A lignocellulosic plant material (11) is fed to an extraction step (101). In the extraction step (101), an organic acid (12) is added to the plant material to dissolve hemicellulose and lignin from the plant material (11) to obtain an extraction mixture (13). An extract (14) is produced by separating (102) soluble and suspended particles from the extraction mixture, wherein the insoluble and unsuspended residue contains cellulose pulp (15). The cellulose pulp (15) is dried in a dryer (109) to produce a dried cellulose pulp (27), and the condensate from the dryer, including the organic acid, can be recycled in the extraction step (101). In the process, the extract (14) is fed to an evaporation system (103) to partially remove residual organic acid and water to form a first stream (1) of a high water content organic acid solution and obtain a concentrate (16). The concentrate (16) is fed to the lignin separation (104) step, in which water (17) is added to precipitate the lignin, allowing the lignin to be separated from the concentrate (16) to obtain separated lignin (18) and a soluble material with water (19). The lignin needs to be washed with various wash waters (20) in a series of lignin washing steps (22) to remove residual sugars, organic acids and other water-soluble components. The water from the lignin washing step (105) and the soluble material with wash water (19) are collected to form a mixture (23) of hemicellulose, organic acids, water and other water-soluble components. In order to remove organic acids from this mixture (23) and reduce the water content, the mixture (23) is subjected to multiple-effect evaporation (106). The condensate of the multiple-effect evaporator forms a second stream (2) of a high-water content organic acid solution. After the multiple-effect evaporation (106), the concentrated mixture (24) is fed to a stripping tower (107) where the organic acid is further removed to a content of less than 2%, and the condensate from the stripping tower forms a third stream (3) of a high-water organic acid solution and hemicellulose juice (25). In order to remove the organic acid from the dried cellulose pulp (15), a desolventizer (108) is adapted to use live steam (26) to remove the residual organic acid. The condensate from the desolventizer forms a fourth stream (4) of a high-water organic acid solution and a desolventized cellulose pulp (28). The four streams of high-water organic acid solution are fed to a multi-tower distillation system (110) to reduce the water content. In the condensate discharged from the top of the first tower, an aqueous acid solution (5) with an acid content of 0.5-10% is obtained. The subsequent tower produces a condensate (7) discharge with an acid content of 0.2%-1%. The aqueous acid solution (6) with an acid content of 5% to 15% constitutes the bottom output of the first column. All acid percentages are calculated by weight.

[0066] Figure 10The details of the 2-column distillation system are described. The internal markings are described in Example 5.

[0067] Figure 11 The details of the 3-column distillation system are described. The internal markings are described in Example 5.

[0068] Figure 12 The details of the 4-column distillation system are described. The internal markings are described in Example 5.

[0069] Figure 13 The details of the 5-column distillation system are described. The internal markings are described in Example 5.

[0070] Figure 14 The present invention is a process diagram illustrating the production of organic fertilizer from fermentation stillage (21) at the bottom of a mash column (100) of an ethanol distillation system. The stillage (21) is fed into a decanter (101) to obtain a solid fraction (22) and a thin stillage (23). The thin stillage (23) is fed into a multiple-effect evaporation system (102) to produce a concentrated stillage (24). The solid fraction (22) and the concentrated stillage (24) are fed into a mixer (103), where the two fractions are mixed to obtain a mixture (25). The mixture (25) is fed into a dryer (104) to obtain a dried mixture (26), and the dried mixture (26) represents a high-quality organic fertilizer. The steam (27) released from the dryer (104) can be fed into the multiple-effect evaporator (102) to provide heat energy for the evaporation process, and fresh steam (28) can be fed into the multiple-effect evaporation system (102) as supplementary heat energy. DETAILED DESCRIPTION

[0071] Recovery of organic acids from cellulose pulp

[0072] A first aspect of the present invention discloses a method and composition for efficiently, completely, and economically recovering organic acids from cellulose pulp by a combination of a dryer and a desolventizer. The organic acid and desolventized cellulose pulp are produced by a process comprising the following steps:

[0073] a) drying the cellulose pulp produced by organic acid pretreatment of plant material in a dryer to remove organic acids to a content of 3% to 18%, calculated on the total weight of the dried cellulose pulp, and

[0074] b) capturing the vapor released from the dryer and using it as a heat source in the extract concentration system and other organic acid pretreatment operating systems, and

[0075] c) condensing vapors in the extract concentration system and other organic acid pretreatment operating systems to form the first phase of the organic acid solution of the organic acid pretreatment process, and

[0076] d) using live steam in a desolventizer to further remove organic acids from the cellulose pulp to a content of less than 2%, and

[0077] e) condensing the organic acid vapor released from the desolventizer to obtain a second phase of the organic acid solution of the organic acid pretreatment process.

[0078] This aspect of the invention relates to a method for recovering organic acid from cellulose pulp derived from an organic acid pretreatment process of plant material using a combination of a dryer and a desolventizer. The organic acid pretreatment process uses an organic acid as a reagent to dissolve hemicellulose and lignin contained in lignocellulosic plant material. After separating the cellulose pulp from a mixture of a soluble fraction and an insoluble fraction, the residue, including the insoluble fraction, is the cellulose pulp.

[0079] Existing organic acid pretreatment processes may include a step of partially eliminating lignin to achieve an overall residual lignin level of 0.3% to 4% of the total dry weight of the cellulose pulp. The organic acid content of the cellulose pulp may be 35% to 65% based on the total weight of the cellulose pulp. The cellulose content of the cellulose pulp may be 30% to 50% based on the total weight of the cellulose pulp.

[0080] like Figure 1 As shown, cellulose pulp from an organic acid pretreatment process is fed to a dryer. The dryer reduces the organic acid to a content of 3% to 18% based on the total weight of the dried cellulose pulp. Once the organic acid content is below 3%, the dryer cannot effectively remove further organic acid. If the organic acid content is above 18%, direct steam consumption in the desolventizer is inefficient.

[0081] The cellulose pulp is dried using a variety of dryers, including tubular dryers, pneumatic dryers, spray dryers, rotary disk dryers, and other dryer technologies known to those skilled in the art; tubular dryers are particularly preferred. The drying step can be performed at a temperature of 90°C to 150°C. After drying, the dried cellulose pulp discharged from the dryer is fed to a desolventizer.

[0082] The vapor released from the dryer can be used in the extract concentration system and to provide heat energy for other systems. The condensate of the vapor from the dryer condensed in the extract concentration system and other systems forms the first phase of the organic acid solution and can be reused in the organic acid pretreatment process.

[0083] exist Figure 2In the desolventizer shown, organic acids are further removed from the dried cellulose pulp to a content of less than 2% based on the total weight of the desolventized cellulose pulp. The desolventizer can utilize live steam as the desolventizing medium to further remove organic acids from the dried cellulose pulp. The desolventizer can further remove organic acids by using live steam as the desolventizing medium in step d) conducted at a temperature of 90° C. to 150° C.

[0084] After the desolventization step, the desolventized cellulose pulp can be used to produce ethanol and other products.

[0085] The organic acid vapor also contains water released from the desolventizer and is recovered by the condensation system of the organic acid distillation system, wherein the recovered organic acid is used in the organic acid pretreatment process. The condensation system is carried out by 1-3 condensers, preferably by 2 condensers.

[0086] Production of alkalized cellulose

[0087] This aspect of the invention relates to a process for treating cellulose by a combination of neutralization and alkalization to produce alkalized cellulose, comprising the steps of:

[0088] a) neutralizing the organic acids contained in the cellulose produced by the organic acid pretreatment of the plant material with the sodium hydroxide solution recycled from step d) of the process to form a neutralized cellulose mixture, and

[0089] b) separating the neutralized cellulose from the neutralized cellulose mixture with a press and releasing the filtrate directly to a wastewater treatment system, and

[0090] c) alkalizing the neutralized cellulose by adding a sodium hydroxide solution into a reactor to form an alkalized cellulose mixture, and

[0091] d) separating the alkalized cellulose from the alkalized cellulose mixture using a press, wherein the sodium hydroxide solution (filtrate of the alkalized cellulose mixture) contains sodium hydroxide for reuse in step a) of the process.

[0092] In this aspect of the invention, cellulose produced from a cellulose pulp derived from an organic acid pretreatment process and stripped of residual organic acids by the drying and desolventizing steps described above may still contain residual organic acid levels of 0.5% to 5% by weight of the total cellulose. In this aspect of the invention, such cellulose pulp is further treated to form alkalized cellulose by a process including neutralization and subsequent alkalization.

[0093] like Figure 3As described in [ 1 ], in step a) of the process, residual organic acids contained in the cellulose are neutralized by adding sodium hydroxide solution recycled from the alkalized cellulose separated from the alkalized cellulose mixture in step d). The pH of the sodium hydroxide solution is between pH 10 and pH 12. After the sodium hydroxide solution is added to the cellulose, the pH of the cellulose mixture is adjusted to a range of 5-8 by adding more sodium hydroxide as needed. Compared to current treatment processes, the use of sodium hydroxide solution recycled from the final step of the process for producing alkalized cellulose can reduce the total sodium hydroxide consumption from 30% by weight to 65% by weight.

[0094] In step b), the neutralized cellulose is separated from the neutralized cellulose mixture using a press. The press can be a screw press or other types of presses known to those skilled in the art. In this separation step, the neutralized cellulose mixture formed in step a) is separated into two streams, one containing the neutralized cellulose and the other containing the filtrate. The neutralized cellulose has a dry solids content of 30% to 45%. The filtrate is released directly into a wastewater treatment system at a pH of 5 to 8, eliminating the need for pH adjustment by titration as in existing treatment processes.

[0095] In step c), the neutralized cellulose is alkalized by adding a sodium hydroxide solution to the neutralized cellulose in the reactor at a temperature of 50° C. to 100° C. to a pH of 10 to 12. Under these conditions, the content of lignin contained in the cellulose can be reduced to a level of 1% to 2.5% based on the total weight of the cellulose.

[0096] In step d), the alkalized cellulose mixture is separated by using a press. In this separation step, the alkalized cellulose mixture is separated into two streams, one stream comprising the alkalized cellulose and the other stream comprising the sodium hydroxide solution.

[0097] The alkalized cellulose has a dry solid content of 30% to 45% based on the total weight of the alkalized cellulose.After the washing step, the alkalized cellulose can be hydrolyzed by cellulase with a high conversion rate of cellulose to glucose.

[0098] The sodium hydroxide solution can be recycled for neutralization of the organic acid in step a).

[0099] Production of pure lignin

[0100] This aspect of the invention relates to a process for separating and cleaning lignin from a lignin suspension by sedimentation and centrifugation, comprising the following steps:

[0101] a) separating lignin from a lignin suspension produced by organic acid pretreatment of plant material by batch or continuous centrifugation, and

[0102] b) cleaning the precipitated lignin in the centrifuge by applying a wash solution to the lignin layer multiple times during centrifugation to form multiple centrates, and

[0103] c) recovering the first centrifuge liquid and the second centrifuge liquid for hemicellulose juice concentration, and

[0104] d) recycling the third centrifuge liquid used to precipitate the lignin in the concentrated extract into the lignin suspension in the organic acid pretreatment process, and

[0105] e) discharging the lignin from the centrifuge.

[0106] The extract of this aspect of the present invention is obtained from an existing organic acid pretreatment process, wherein hemicellulose and lignin contained in the plant material are dissolved in an organic acid solution, and the extract is derived from the organic acid solution. The extract is separated from the mixture, and the extract, which comprises cellulose, dissolved hemicellulose, lignin, minerals, organic acid, water, and other minor components, is concentrated by an evaporation system to remove a portion of the organic acid and water, to a dry matter content of 55% to 65%, calculated based on the total weight of the concentrated extract.

[0107] According to the present invention, the separation device is a centrifuge, preferably a scraper centrifuge, which can be operated in a continuous or batch mode. The centrifuge is equipped with a spray device, which can spray washing water evenly onto the lignin layer to obtain pure lignin.

[0108] As in Figure 4 As described in [ 15 ], the third centrifuge liquid from step d) is mixed with the concentrated extract to form a mixture, which is then fed to a suspension tank. In the suspension tank, the mixture is emulsified using a continuous or batch emulsifier to form a stable lignin suspension. The lignin suspension is then continuously fed to a centrifuge, which then separates the lignin suspension to obtain a first centrifuge liquid and a lignin layer. 10% to 60% of the first centrifuge liquid, representing 10% to 60% of the total centrifuge liquid volume, is recovered for subsequent processing in the hemicellulose juice production unit.

[0109] The spray device delivers washing water, which may include a mixture of formic acid, acetic acid and water, to provide online washing of the lignin layer. In a preferred embodiment, the centrifuge rotates continuously. Under continuous rotation, the washing water can be evenly sprayed on the lignin layer to provide uniform cleaning of the lignin. During the spraying period, impurities are washed away with the washing water, and the recovered washing water and impurities form a second centrifuge, which accounts for 10%-30% of the total volume of the centrifuge. The centrifuge continues to operate while applying subsequent washing to produce a third centrifuge and possibly more centrifuges. The third centrifuge and subsequent centrifuges can account for 10%-50% of the total volume of the centrifuge. Once the final centrifuge is removed, the lignin layer is discharged from the centrifuge to obtain pure lignin containing 90% by weight to 99% by weight lignin.

[0110] Washing water can comprise water, or a mixture of formic acid, acetic acid and water, wherein the formic acid content of the mixture is 0%-30% based on the gross weight of the mixture, and the acetic acid content of the mixture is 0%-20% based on the gross weight of the mixture. The mixture of formic acid, acetic acid and water can be derived from the organic acid recovered from the high water content organic acid solution by the acid distillation unit. In a preferred embodiment, the initial washing water introduced into the centrifuge is derived from the high organic acid content washing water. In some embodiments, the second washing water introduced into the centrifuge is derived from the low organic acid content washing water. In some embodiments, the fresh water comprises the washing water for the third washing procedure and any subsequent washing procedure for cleaning the lignin layer to obtain pure lignin.

[0111] The first and second centrates may be recovered and delivered to a subsequent hemicellulose juice production unit, while the third centrate and any subsequent centrates may be recycled to the lignin suspension step to reduce water consumption for the initial lignin precipitation step, which consequently reduces energy consumption for the hemicellulose juice production and organic acid recovery units.

[0112] Production of hemicellulose juice

[0113] This aspect of the invention relates to a process for producing hemicellulose juice by a combination of evaporation and steam stripping, comprising the following steps:

[0114] a) introducing a hemicellulose mixture comprising dissolved hemicellulose, organic acid, water and other substances produced by organic acid pretreatment of plant material into a multiple effect evaporation system, and

[0115] b) evaporating the hemicellulose mixture in a multiple-effect evaporator to form a concentrated hemicellulose juice having a dry matter content of 40% to 70% (w / w), and

[0116] c) removing organic acids from the concentrated hemicellulose juice in a stripping column to form hemicellulose juice, wherein the hemicellulose juice comprises less than 2% (w / w) organic acids.

[0117] The present invention is based on existing organic acid pretreatment processes for plant materials, wherein a mixture of formic acid and acetic acid or only formic acid is used to solubilize hemicellulose and lignin from lignocellulosic plant raw materials, and after an initial separation step, an extract comprising the dissolved hemicellulose, lignin, organic acid, water and other minor components is separated from the remaining insoluble material (mainly comprising cellulose).

[0118] After the lignin precipitation, filtration and washing steps, the lignin is removed from the extract and the remainder, called hemicellulose juice, contains dissolved hemicellulose, organic acids, water and other minor water-soluble components.

[0119] The dissolved hemicellulose in the hemicellulose juice mainly contains xylose and arabinose, which can be used to produce ethanol and other industrial products. The remaining organic acids in the hemicellulose juice can inhibit the conversion of xylose and arabinose to ethanol and other industrial products. In addition, such organic acids represent the loss of expensive reagents in the entire organic acid pretreatment process. This aspect of the present invention is specifically related to producing hemicellulose suitable for optimal conversion to ethanol with minimal residual organic acids through a process that can simultaneously recycle such organic acids present in the hemicellulose juice for use in the organic acid pretreatment process.

[0120] The hemicellulose juice contains 2% to 20% dissolved hemicellulose, calculated based on the total weight of the hemicellulose mixture. The hemicellulose juice contains 10% to 30% organic acid, calculated based on the total weight of the hemicellulose mixture. Step a) of the present invention is characterized in that the organic acid is partially evaporated using water in a multiple-effect evaporation system to a dry matter content of 40% to 70%, calculated based on the total weight of the concentrated hemicellulose juice.

[0121] Multiple-effect evaporation can reduce steam / energy consumption for removing organic acids and concentrating hemicellulose juice. In some embodiments, multiple-effect evaporation is characterized by using a 2-4 effect evaporation system, such as Figure 6-8 In a preferred embodiment, the process uses a 3-effect evaporation system.

[0122] In some embodiments, the multi-effect evaporation of the organic acid with water is performed in a first-effect evaporator at a temperature of 60° C. to 160° C. In some embodiments, the multi-effect evaporation of the organic acid with water is performed in a final-effect evaporator at a temperature of 25° C. to 60° C.

[0123] The first evaporator of the multiple-effect evaporation system can use the steam output from the top of the stripping tower as all or part of the heat energy source. In each step of the multiple-effect evaporation system, the steam output from the top of the previous evaporator can be used as heat energy to drive the next tower, thereby reducing the total energy required for the multiple-effect evaporation system.

[0124] like Figure 6-8 As shown, the hemicellulose mixture is sequentially fed into and discharged from the first evaporator.

[0125] After the hemicellulose juice is concentrated by the multi-effect evaporation system, the dry matter content of the concentrated hemicellulose juice discharged from the first evaporator is 40%-70% of the total weight of the concentrated hemicellulose juice, and the viscosity of the concentrated hemicellulose juice is 200 mPas to 1000 mPas. If the viscosity is higher than this range, it is too difficult to further remove organic acids from the concentrated hemicellulose juice by evaporation.

[0126] The present invention is also characterized by combining a multiple-effect evaporation system with a stripping column. The concentrated hemicellulose juice discharged from the multiple-effect evaporation system is fed to the top plate of the stripping column. The stripping column utilizes live steam as the stripping medium to further remove organic acids to a content of less than 2% of the total weight of the stripped hemicellulose juice.

[0127] The steam output from the top of the stripping tower can be used as heat energy for the first evaporator of the multiple-effect evaporation system.

[0128] The stripped hemicellulose juice discharged from the bottom of the stripping column is used as the final product, ie, hemicellulose juice, which can be used to produce ethanol and other industrial products.

[0129] Removal of water from high water content organic acid solutions

[0130] This aspect of the invention relates to a process for recovering organic acid from a high water content organic acid solution by multi-tower distillation, comprising:

[0131] a) using a 2-5 column distillation system to recover the organic acid, and

[0132] b) feeding fresh steam only to the first column of a multi-column distillation system, with the remaining columns successively utilizing the vapor released from the previous column as heat energy, and

[0133] c) directing the vapor released from the previous column to the subsequent column as heat energy, so that the vapor released from the first column will be fed into the second column, and the vapor released from the second column will be fed into the third column, and so on through each column of the distillation system, and

[0134] d) feeding one or more streams of the high water content organic acid solution to different columns within a multi-column system to balance the energy requirements of the columns comprising the distillation system, and

[0135] e) adjusting the organic acid content in the condensate of the first column to minimize fresh steam consumption, and

[0136] f) recycling the total organic acid and the total water discharged from the multi-tower distillation system.

[0137] In this aspect of the present invention, the high water content organic acid solution is derived from the organic acid pretreatment process of plant material. Typically, the content of organic acid constitutes greater than 83% of the total weight of the solution. Typically, during the organic acid pretreatment process, and due to the downstream steps of cellulose pulp processing and lignin and hemicellulose sugar production at relatively low temperatures and atmospheric pressures, this results in no furfural being produced during the entire pretreatment process, and four streams of high water content organic acid solution being produced. In order to recycle the organic acid in the high water content organic acid stream into the organic acid pretreatment process, the water content must be reduced.

[0138] Recovery of organic acids from high-water organic acid solutions by distillation requires very high energy input. Therefore, reducing the energy required to recover and recycle organic acids is essential for the commercialization of organic acid pretreatment processes.

[0139] In one embodiment, the present invention is characterized in that the organic acid is recovered from the high water content organic acid solution by using a 2-5 column distillation system to maximize energy efficiency. The preferred embodiment uses a 4 column distillation system.

[0140] The greater the number of columns, the less steam / energy the distillation system consumes. However, the number of columns that can constitute a distillation system is limited by the temperature difference between the columns of the distillation system. Surprisingly, we have found empirically that if the system includes more than five columns, the temperature difference between the columns is too small to use the vapor released by the previous column as steam / energy for the next column in the series.

[0141] After scientific analysis, a 2-5 column distillation system may be suitable for recovering organic acid from high water content organic acid solution in this process, and a 4-column distillation is the most suitable from the viewpoints of efficiency and economy.

[0142] Typically, the organic acid pretreatment process produces four streams of high-water content organic acid solution as described above. The term "high-water content organic acid solution" refers to a water content higher than the water content required in the organic acid solution for dissolving plant material in the organic acid pretreatment process. Therefore, in order to recycle organic acid from the four high-water content organic acid streams, it is necessary to remove the other water added throughout the various process steps. In order to minimize the amount of steam / energy required for reclaiming organic acid from high-water content organic acid solution by multi-tower distillation, the steam / energy used for each tower must be controlled so that it is suitable for the organic acid level in the single tower in the series.

[0143] The present invention accomplishes this in two ways. First, by feeding the highest water content organic solution to the final column of the distillation system and the lowest water content organic acid solution to the first column of the distillation system, the energy input to the entire system is appropriately directed. Second, by adjusting the amount of steam / energy introduced to the first column, the organic acid content of the condensate discharged from the top of the first column is controlled to be between 0.5% and 10% by weight of the total condensate, allowing for balanced steam / energy consumption throughout the distillation system. The condensate from the first column, with an organic acid content of 0.5%-10%, can be diverted for use in the lignin precipitation step of the lignin production process.

[0144] In the system described herein, the other columns in series typically produce condensates having an organic acid content of 0.2% to 1% by weight of the total condensate input. These condensates can be recycled to the pretreatment process for washing lignin and other steps in the lignin production process.

[0145] In order to maintain an optimal temperature difference between the columns, the first column is operated at a temperature of 120°C to 175°C and the last column is operated at a temperature of 50°C to 95°C.

[0146] The water content of the organic acid solution discharged from the bottom of the first tower is 5%-15% based on the total weight of the organic acid solution, and the organic acid solution can be directly reused in the organic acid pretreatment process in the initial step of dissolving the plant raw materials.

[0147] organic fertilizer

[0148] exist Figure 14 This aspect of the invention described in

[0015] relates to a method for producing organic fertilizer from stillage produced from cellulosic and hemicellulosic juices, comprising the steps of:

[0149] a) separating stillage from the cellulosic and hemicellulose juice produced by organic acid pretreatment of plant material using a decanter to obtain a solid fraction of stillage and thin stillage, and

[0150] b) concentrating the thin stillage using a multiple-effect evaporation system to obtain concentrated stillage, wherein steam for the multiple-effect evaporation system is supplied by steam released from the dryer in process step d) optionally supplemented with fresh steam, and

[0151] c) mixing the solid fraction and the concentrated stillage to obtain a mixture, and

[0152] d) drying the mixture to obtain the organic fertilizer, wherein the steam released from the dryer is fed to the multiple-effect evaporation system as heat energy of the multiple-effect evaporation system for the process.

[0153] The present invention is based on existing organic acid pretreatment process. In the pretreatment process, organic acid solution is used as extraction agent to dissolve most of lignin, hemicellulose, salt (mainly potassium salt and phosphate), protein and other components of lignocellulosic plant material. The pretreatment mixture is separated into insoluble cellulose pulp and a mixture of hemicellulose juice and lignin. The cellulose pulp is dried to obtain cellulose. The hemicellulose juice and lignin mixture is separated into hemicellulose juice (containing hemicellulose, salt, protein and other soluble components) and lignin. After cellulose and hemicellulose juice are hydrolyzed and fermented, most of the cellulose and hemicellulose included in the hemicellulose juice are converted into ethanol. After ethanol is extracted from the fermented cellulose and hemicellulose juice by distillation, the residue of the fermented cellulose and hemicellulose juice is discharged from the bottom of the mash tower of the distillation system. The residue is stillage (a by-product of the process).

[0154] Stillage contains many nutrients (protein, potassium, phosphorus, calcium, magnesium, sodium, aluminum, etc.) and other nutrients from lignocellulosic raw materials. Other nutrients include yeast, secondary metabolites produced by the growth of yeast during fermentation, and residual yeast growth medium, which includes a large amount of nitrogen, potassium, phosphorus, and organic matter. Such materials represent all the needs of organic fertilizers. Organic fertilizers are fertilizers derived from animal matter, animal excrement (manure), human excrement, and plant matter (e.g., compost and crop residues). On the contrary, most fertilizers used in commercial agriculture are chemical fertilizers extracted from minerals (e.g., phosphate rock) or industrially produced (e.g., ammonia). As an agricultural system, organic agriculture allows the use of certain fertilizers and conditioners, but does not allow the use of other fertilizers and conditioners. Both organic fertilizers and chemical fertilizers can significantly increase plant yields, but organic fertilizers have a more complete mineral distribution and cannot cause the kind of soil damage that can be given by chemical fertilizers. Organic fertilizers are an important development direction for agriculture.

[0155] In one embodiment, the process disclosed herein uses agricultural residues as feedstock, and stillage is produced in part by hydrolysis of cellulose and hemicellulose recovered from the agricultural residues and fermentation of sugars released from the hydrolysis of cellulose and hemicellulose by yeast to produce organic fertilizer.

[0156] The method is characterized in that stillage is obtained from the bottom of a mash column of an ethanol distillation system. The stillage has a dry matter content of 2% to 20%, calculated based on the total weight of the stillage. In one embodiment, the stillage is separated into a solid fraction and a thin stillage fraction using a centrifuge. In a preferred embodiment, the centrifuge is a decanter centrifuge.

[0157] After separation, the solid fraction has a dry matter content of 20% to 45% based on the total weight of the solid portion of the stillage. The thin stillage fraction has a dry matter content of 1% to 15% based on the total weight of the thin stillage.

[0158] Thin stillage can be concentrated using a multiple-effect evaporation system. A multiple-effect evaporation system can include a 4- to 6-effect evaporation system. In a preferred embodiment, the multiple-effect evaporation system is a 5-effect evaporation system. In a multiple-effect evaporation system, vapor released from the top of the previous evaporator is used as heat energy for the next evaporator, minimizing the total energy consumption of the multiple-effect evaporation system. Thin stillage is fed to the final evaporator of the multiple-effect evaporation system and discharged from the first evaporator of the multiple-effect evaporation system. The multiple-effect evaporation system operates at a temperature of 30°C to 150°C.

[0159] After concentration, the concentrated stillage has a dry matter content of 28% to 45% based on the total weight of the concentrated stillage.

[0160] The condensate of the vapor separated in the multiple-effect evaporation system obtained in step b) can be reused as process water.

[0161] The solid portion and the concentrated stillage are fed to a mixer, where the two portions are mixed to obtain a mixture of a solid fraction and concentrated stillage. The mixture of the solid portion and the concentrated stillage is dried in a dryer (preferably a tubular dryer) to obtain an organic fertilizer. The dryer is operated at a temperature of 80° C. to 160° C. The dry solids content of the organic fertilizer is 50% to 80% based on the total weight of the organic fertilizer. The steam released from the dryer can be fed to a stillage multiple-effect evaporation system to provide heat energy to the multiple-effect evaporation system. After drying, the mixture of the solid portion and the concentrated stillage is dried, and the dried mixture can be used as an organic fertilizer.

[0162] Organic fertilizers contain organic matter, protein, potassium salts, phosphates, minerals, and more. Based on the total dry matter content of the organic fertilizer, the organic matter content is 30%-65%. Based on the total dry matter content of the organic fertilizer, the total nutrient content (calculated based on the formula: nutrients = nitrogen + phosphorus pentoxide + potassium oxide) is 5%-30%. The pH value of the organic fertilizer is 5.5-8.5. Based on the total weight of the organic fertilizer, the water content of the organic fertilizer is 20%-50%.

[0163] Example

[0164] Example 1

[0165] Recovery of organic acids from cellulose pulp

[0166] Corn stover was used as the lignocellulosic raw material. Cellulose pulp was obtained using an organic acid pretreatment process. The organic acid composition was 26% formic acid, 59% acetic acid, and 15% water. The temperature was 103°C, and the solvation time was 240 minutes. After separation, the cellulose pulp was separated from the liquid fraction.

[0167] About 5 kg of cellulose pulp was recovered, which, based on the total weight of the cellulose pulp, had a dry matter content of 38.0%, an organic acid content of 49.5%, and a water content of 12.5%. The cellulose pulp was fed to a dryer to obtain dried cellulose pulp at a drying temperature of 120° C. After drying, the dried cellulose pulp had an organic acid content of 5.5%.

[0168] The dried cellulose pulp was introduced into the desolventizer at a feed flow rate of 200 g / min, direct steam was introduced into the bottom of the desolventizer, the steam temperature was 120° C., and the direct steam feed flow rate into the desolventizer was 14.1 g / min. The desolventized cellulose pulp was discharged from the desolventizer.

[0169] The organic acid content of the desolvated cellulose pulp was 1.8%, calculated based on the total weight of the desolvated cellulose pulp.

[0170] A second cellulose pulp derived from corn stover was prepared under similar conditions to those described above. However, in this experiment, the dryer temperature was slightly lower (110° C.) and the steam flow rate in the desolventizer was increased to 26.3 g / min. The desolventized cellulose pulp produced under these conditions had an organic acid content of 1.95%.

[0171] In the third study, wheat straw was used as lignocellulosic feedstock, and cellulose pulp was obtained according to the above-mentioned organic acid pretreatment process.

[0172] About 5 kg of cellulose pulp was recovered, which, calculated based on the total weight of the cellulose pulp, had a dry matter content of 37.5%, an organic acid content of 50.2%, and a water content of 12.3%. The cellulose pulp was fed to a dryer to obtain dried cellulose pulp at a drying temperature of 115° C. After drying, the organic acid content of the obtained dried cellulose pulp was 6.7%.

[0173] The dried cellulose pulp was introduced into the desolventizer at a feed flow rate of 200 g / min, direct steam was introduced into the bottom of the desolventizer, the steam temperature was 120° C., and the direct steam feed flow rate into the desolventizer was 16.8 g / min. The desolventized cellulose pulp was discharged from the desolventizer.

[0174] The organic acid content of the desolventized cellulose pulp produced under these conditions was 1.91%.

[0175] Table 1 summarizes these data.

[0176] Table 1. Organic acid content of cellulose pulp

[0177]

[0178] Example 2

[0179] Neutralization and alkalization of cellulose.

[0180] Sample 1

[0181] Method A:

[0182] At the beginning, 0.4 kg of cellulose (lignin content of 4.1% and organic acid content of 1.56%) was fed into the reactor, the stirrer was started, and the pH was adjusted to 12 with sodium hydroxide solution, to which 3.34 L of additional water was added. The temperature of the reactor was maintained at 80° C. and the reaction was continued for 60 minutes.

[0183] When the reaction was finished, 9.16 g of sodium hydroxide was consumed, and the lignin content of the treated cellulose was 1.89%.

[0184] Method B:

[0185] In the initial neutralization step of the first process run, 0.4 kg of cellulose (lignin content of 4.1% and organic acid content of 1.56%) was fed into the reactor, the stirrer was started, and the pH was adjusted to pH 6.5 with sodium hydroxide solution. 3.34 L of additional water was added. The temperature of the reactor was maintained at 80° C., and the reaction was continued for 30 minutes. After the reaction, the cellulose mixture was filtered and pressed.

[0186] In the alkalization step, the neutralized cellulose is added to the alkalization reactor, the stirrer is started, and the pH is adjusted to pH 12 with sodium hydroxide solution, and 3.34 L of additional water are added. The temperature of the reactor is maintained at 80°C, and the reaction is continued for 30 minutes. Sodium hydroxide is added as needed to maintain the pH at pH 12. After 30 minutes, the alkalized cellulose mixture is filtered and pressed to obtain a sodium hydroxide solution and alkalized cellulose. The sodium hydroxide solution can be reused in the neutralization step in the second (subsequent) processing operation.

[0187] In the second process run, 0.4 kg of cellulose (with a lignin content of 4.1% and an organic acid content of 1.56%) was fed into the neutralization reactor, the stirrer was started, and the pH was adjusted to pH 6.8 using sodium hydroxide solution recovered from the alkalization step of the first process run, the temperature of the reactor was maintained at 80° C., and the reaction was continued for 30 minutes. After the reaction, the cellulose mixture was filtered and pressed.

[0188] The alkalization step of the second (and subsequent) processing runs included the same steps as described in the first run. Importantly, the sodium hydroxide solution recovered after filtering and pressing the alkalized cellulose can be reused in the neutralization step of the next processing operation. In the second processing run using the sodium hydroxide recovered from the first run, the total sodium hydroxide consumed was 4.58 g, and the lignin content of the treated cellulose was 1.85%.

[0189] Sample 2

[0190] Method A:

[0191] At the beginning, 0.4 kg of cellulose (lignin content of 3.6% and organic acid content of 2.68%) was fed into the reactor, the stirrer was started, the pH was adjusted to 12 with sodium hydroxide solution, and 3.34 L of additional water was added. The temperature of the reactor was maintained at 80° C. and the reaction was continued for 60 minutes.

[0192] When the reaction was finished, 12.4 g of sodium hydroxide was consumed, and the lignin content of the treated cellulose was 1.56%.

[0193] Method B:

[0194] In the initial neutralization step of the first process run, 0.4 kg of cellulose (lignin content of 3.6% and organic acid content of 2.68%) was fed into the reactor, the stirrer was started, and the pH was adjusted to pH 6.5 with sodium hydroxide solution. 3.34 L of additional water was added. The temperature of the reactor was maintained at 80° C., and the reaction was continued for 30 minutes. After the reaction, the cellulose mixture was filtered and pressed.

[0195] In the alkalization step, the neutralized cellulose is added to the alkalization reactor, the agitator is started, and the pH is adjusted to pH 12 with sodium hydroxide solution. 3.34 L of additional water is added. The reactor temperature is maintained at 80°C, and the reaction is continued for 30 minutes. Sodium hydroxide is added as needed to maintain the pH at pH 12. After 30 minutes, the alkalized cellulose mixture is filtered and pressed to obtain a sodium hydroxide solution and alkalized cellulose. The sodium hydroxide solution can be reused in the neutralization step in subsequent processing operations.

[0196] In the second process run, 0.4 kg of cellulose (with a lignin content of 3.6% and an organic acid content of 2.68%) was fed into the neutralization reactor, the stirrer was started, and the pH was adjusted to pH 6.8 using sodium hydroxide solution recovered from the alkalization step of the first process run, the temperature of the reactor was maintained at 80° C., and the reaction was continued for 30 minutes. After the reaction, the cellulose mixture was filtered and pressed.

[0197] The alkalization step of the second (and subsequent) processing runs included the same steps as described in the first run. Importantly, the sodium hydroxide solution recovered after filtering and pressing the alkalized cellulose can be reused in the neutralization step of the next processing operation. In the second processing run using the sodium hydroxide recovered from the first run, the total sodium hydroxide consumed was 7.87 g, and the lignin content of the treated cellulose was 1.58%.

[0198] Sample 3

[0199] Method A:

[0200] At the beginning, 0.4 kg of cellulose (lignin content of 3.8% and organic acid content of 4.52%) was fed into the reactor, the stirrer was started, and the pH was adjusted to pH 12 with sodium hydroxide solution, and 3.34 L of additional water was added. The temperature of the reactor was maintained at 80° C. and the reaction was continued for 60 minutes.

[0201] When the reaction was finished, 17.9 g of sodium hydroxide was consumed, and the lignin content of the treated cellulose was 1.66%.

[0202] Method B:

[0203] In the initial neutralization step of the first process run, 0.4 kg of cellulose (lignin content of 3.8% and organic acid content of 4.52%) was fed into the reactor, the stirrer was started, and the pH was adjusted to 6.5 with sodium hydroxide solution. 3.34 L of additional water was added. The temperature of the reactor was maintained at 80° C., and the reaction was continued for 30 minutes. After the reaction, the cellulose mixture was filtered and pressed.

[0204] In the alkalization step, the neutralized cellulose is added to the alkalization reactor, the agitator is started, and the pH is adjusted to pH 12 with sodium hydroxide solution. 3.34 L of additional water is added. The temperature of the reactor is maintained at 80°C, and the reaction is continued for 30 minutes. Sodium hydroxide is added as needed to maintain the pH at pH 12. After 30 minutes, the alkalized cellulose mixture is filtered and pressed to obtain a sodium hydroxide solution and alkalized cellulose. The sodium hydroxide solution can be reused in the neutralization step in subsequent processing operations.

[0205] In the second (subsequent) process run, 0.4 kg of cellulose (with a lignin content of 3.8% and an organic acid content of 4.52%) was fed into the neutralization reactor, the stirrer was started, and the pH was adjusted to pH 7.1 using sodium hydroxide solution recovered from the alkalization step of the first process run, the temperature of the reactor was maintained at 80° C., and the reaction was continued for 30 minutes. After the reaction, the cellulose mixture was filtered and pressed.

[0206] The alkalization step of the second (and subsequent) processing runs included the same steps as described in the first run. Importantly, the sodium hydroxide solution recovered after filtering and pressing the alkalized cellulose can be reused in the neutralization step of the next processing operation. In the second processing run using sodium hydroxide recovered from the first run, the total sodium hydroxide consumed was 13.3 g, and the lignin content of the treated cellulose was 1.63%.

[0207] Table 2 summarizes these sample data.

[0208] Table 2. Sodium hydroxide consumption for cellulose treatment

[0209]

[0210] Example 3

[0211] Lignin production

[0212] An extract was obtained from an organic acid pretreatment process, wherein the organic acid composition during the pretreatment included 26% formic acid, 59% acetic acid, and 15% water. The pretreatment temperature was 103°C, and the pretreatment extraction duration was 240 minutes. After separation, the extract was separated from the solid fraction and concentrated by evaporation to obtain a concentrated extract. The concentrated extract had a dry matter content of 60.1% and a lignin content of 29.5%. (Other components of the concentrated extract are listed in Table 3.)

[0213] 1.40 kg of the concentrated extract was combined with an equal weight of fresh water (1.40 kg) and an emulsifier (SHW300R laboratory emulsifier, Shanghai Shenghaiwei Electric Instruments Co., Ltd.) was used at 7500 rpm for about 30 minutes to produce a lignin suspension. The lignin suspension was introduced into a centrifuge and centrifuged for 5 minutes to obtain a first centrifuge (2.05 kg of liquid) and a solid lignin layer. The first centrifuge was removed from the centrifuge.

[0214] 1.94 kg of wash water was fed into the spray device to wash the lignin layer in the centrifuge. The wash water in this procedure included water and a mixture of formic acid, acetic acid, and water. When feeding the wash water to the centrifuge, an initial charge of 0.54 kg of high organic acid content wash water with an organic acid content of 5.92% was used, a second wash included 1.00 kg of low organic acid content wash water with an organic acid content of 0.8%, and a final wash including 0.40 kg of fresh water was found to be sufficient to wash the lignin layer to obtain pure lignin.

[0215] After the initial centrifugation and discharge of the initial centrate, the centrifuge was operated for a further 5 minutes, during which a first wash was performed with water high in organic acid, and a second centrate (0.54 kg) was obtained. The centrifuge was operated for an additional 5 minutes, during which a second wash was performed with water low in organic acid, and 1.40 kg of a third centrate was obtained. After a subsequent third wash with fresh water, a 0.75 kg lignin layer was obtained. The first and second centrates were recovered and can be incorporated into subsequent hemicellulose juice production unit operations. The dried lignin was discharged from the centrifuge and determined to have a purity of 98.1% (the composition of the lignin at each stage of the operation is shown in Table 3).

[0216] Table 3. Composition of concentrated extract, washing water and lignin (I)

[0217]

[0218]

[0219] Note: Impurities include cellulose, xylan, trace minerals, acetic acid, and formic acid.

[0220] The third centrifuge (1.40 kg) was recycled as a diluent for the concentrated extract using the SHW300R laboratory emulsifier as described above to produce a lignin suspension. The obtained lignin suspension was introduced into a centrifuge and the centrifuge was operated as described above to produce a lignin layer of about 0.75 kg.

[0221] In this operation, the first wash included 0.54 kg of high organic acid content wash water having an organic acid content of approximately 10%. The second wash included 1.00 kg of low organic acid content wash water having an organic acid content of approximately 2%, and the final wash included 0.40 kg of fresh water. All centrifugation operations and conditions were performed as described above. As previously described, the first and second centrifuges can be recycled for use in subsequent hemicellulose juice production unit operations. At the end of the operation, lignin was discharged from the centrifuge. In this case, the purity of the lignin was 97.2% (the composition of the lignin at each stage of the operation is shown in Table 4).

[0222] Table 4. Composition of concentrated extract, washing water and lignin (II)

[0223]

[0224] Note: Impurities include cellulose, xylan, trace minerals, acetic acid, and formic acid. H-water indicates high organic acid content wash water, while L-water indicates low organic acid content wash water.

[0225] Once again, the third centrifuge liquid (1.40 kg) from the above operation was recycled to dilute the concentrated extract, which was treated with a SHW300R laboratory emulsifier to produce a lignin suspension. The obtained lignin suspension was introduced into a centrifuge, and the centrifuge was operated as described above to produce a lignin layer.

[0226] In this operation, the first wash included 0.54 kg of high organic acid content wash water having an organic acid content of 5.92%. The second wash included 1.00 kg of low organic acid content wash water having an organic acid content of 0.8%, and the final wash included 0.79 kg of fresh water. All centrifugation operations and conditions were performed as described above. As previously described, the first and second centrifuges can be recycled for use in subsequent hemicellulose juice production unit operations. At the end of the operation, lignin was discharged from the centrifuge. In this case, the purity of the lignin was 98.8% (the composition of the lignin at each stage of the operation is shown in Table 5).

[0227] Table 5. Composition of concentrated extract, washing water and lignin (III)

[0228]

[0229] Note: Impurities include cellulose, xylan, trace minerals, acetic acid, and formic acid. H-water indicates high organic acid content wash water, while L-water indicates low organic acid content wash water.

[0230] Example 4

[0231] Hemicellulose juice processing

[0232] A concentrated hemicellulose mixture was obtained from an initial hemicellulose mixture comprising dissolved hemicellulose, organic acids, water and other soluble components (16.4% dry matter content, 6.0% formic acid, 14.4% acetic acid and 63.2% water) by using an evaporator (100 mm in diameter, 2 m in height) using indirect steam heating to evaporate organic acids and water from the hemicellulose mixture.

[0233] The hemicellulose mixture entered the evaporator at a flow rate of 10.0 kg / h, with an indirect steam flow rate of 6.2 kg / h and an evaporation temperature of 90°C, resulting in a flow rate of 2.96 kg / h of concentrated hemicellulose mixture. The concentrated hemicellulose mixture produced under these conditions had a dry matter content of 55.6%. The concentrated hemicellulose mixture had an acid content of 16.5%.

[0234] The resulting concentrated hemicellulose mixture is fed to the top of a stripping tower (100 mm in diameter and 2.5 m in height), and direct steam is fed to the bottom of the stripping tower for partially stripping the organic acids present in the concentrated hemicellulose into the direct steam. This produces a stripped hemicellulose mixture. The stripping specifications are adjusted to a direct steam flow rate of 1.51 kg / h and a direct steam temperature of 105 ° C, producing a flow rate of 2.46 kg / h of stripped hemicellulose mixture. The dry matter content of the stripped hemicellulose mixture is 60.4%. The acid content of the stripped hemicellulose mixture is 1.64%.

[0235] The evaporation and stripping processes were modeled using AspenPlus software (Aspen Technology, Inc., Massachusetts, USA), allowing exploration of many different operating parameters based on regression of vapor-liquid equilibrium with the experimental data described above.

[0236] Using the above model parameters, the conditions and performance of 2-, 3-, and 4-effect evaporation and stripping systems were simulated for the concentration of a hemicellulose mixture containing dissolved hemicellulose, organic acids, and water, among other components.

[0237] The flow charts of 2-, 3- and 4-effect evaporation and stripping systems constructed by Aspen Plus software are provided for use, which are shown in Figure 6-8 In these models, a hemicellulose mixture (21) containing dissolved hemicellulose, organic acid, water and other components is evaporated by evaporator II and evaporator I, and concentrated hemicellulose juice (22) is obtained. The concentrated hemicellulose juice (22) is fed to the top of a stripping tower (102), fresh steam (26) is fed to the bottom of the stripping tower (102), and stripped hemicellulose juice (24) is obtained. The steam discharged from the top of the stripping tower and the additional fresh steam (27) are used as a heat source for evaporator I, and the steam discharged from the top of the stripping tower and the additional fresh steam (27) condensed in evaporator I are recovered as condensed acid II (25). The steam from evaporator I is used as a heat source for evaporator II, and the steam from evaporator I condensed in evaporator II is used as condensed acid I (23). The same scenario involving the use of vapor initially recovered from the stripping column into evaporator I and the vapor recovered from evaporator I as a heat source for evaporator II is extended to a system including additional multiple-effect evaporator units, such as in a three-effect evaporator system. Figure 7 Neutralization 4-effect evaporator system Figure 8 As described in the 3-effect evaporator system Figure 7 No live steam is required in the process, and more steam (28) from the stripping column is used for other systems than the steam required for the 4-effect evaporator system discharged from the top of the stripping column.

[0238] The following table presents a number of observed and predicted parameters for each of the multiple-effect evaporator systems described herein.

[0239] Table 6. Observed inputs to the evaporation system model

[0240]

[0241] Table 7. Observed specifications of stripped hemicellulose juice

[0242] Evaporation effect Flow rate (t / h) Dry matter content (%) Total acid content (%) Water content (%) 2 3.27 60.2％ 0.53％ 39.27％ 3 3.25 60.5％ 1.65％ 37.85％ 4 3.27 60.1％ 0.93％ 38.97％

[0243] Table 8. Predicted steam consumption for evaporation and stripping systems

[0244] 2-effect 3 effects 4 effects Steam consumption for stripping (t / h) 3.85 2.75 3.23 Steam consumption for evaporation (t / h) 3.85 2.63 2.01 Residual steam (t / h) 0 0.12 1.22

[0245] Table 9. Predicted heat exchange surface area for evaporation system

[0246] 2-effect 3 effects 4 effects <![CDATA[Total heat exchange surface (m 2 )]]> 887 1377 2269

[0247] Example 5

[0248] Recovery of organic acids from high water content organic acid solutions

[0249] A high-water content organic acid solution (27.6% formic acid, 51.5% acetic acid, and 20.9% water) was fed at a flow rate of 4.0 kg / h to a distillation column (90 mm diameter, 3 m height, packed column) operated at a heat load of 12.6 MJ / h, a reflux ratio of 13.0, and a pressure of 1 atmosphere. Under these conditions, a condensate of vapor released from the top of the column was produced at a flow rate of 0.41 kg / h, containing 0.27% formic acid, 4.07% acetic acid, and 95.66% water. A distilled organic acid solution was obtained at a flow rate of 3.59 kg / h, containing 30.7% formic acid, 56.9% acetic acid, and 12.4% water, discharged from the bottom of the column.

[0250] The process was modeled using the above parameters using Aspen Plus software, allowing simulation of distillation systems containing 2, 3, 4, and 5 columns for separating water from high-water-content organic acid solutions. The flow charts generated by the modeling software for the 2-column, 3-column, 4-column, and 5-column distillation systems are shown in Figure 1. Figure 10-13 middle.

[0251] The organic acid compositions of various input streams of high water content organic acid solution from the organic acid pretreatment process are listed in Table 10.

[0252] Table 10. Organic acid composition of the input to the multi-column distillation system

[0253] flow Flow rate (kg / h) Formic acid content (%) Acetic acid content (%) Water content (%) 1 471.3 27.6％ 49.1％ 23.3％ 2 270.7 5.8％ 15.2％ 79.0％ 3 80.6 7.6％ 17.4％ 75.0％ 4 12.8 9.9％ 18.9％ 71.2％

[0254] Note: The stream symbol name is the same as in Figure 10 and those described below.

[0255] The basic distillation process of the 2-tower distillation system is Figure 10 1 . Three of the four input streams are fed to the first distillation column (201). These streams originate from the hemicellulose juice evaporation step (2), the hemicellulose juice stripping step (3), and the high water organic acid solution from the desolventizer step (4) of the cellulose pulp processing. The condensate of the vapor (7) discharged from the top of the first column (201) can be recovered for use in other unit operations. The concentrated mixture (301) is discharged from the bottom of the first column (201) and fed to column 2 (202). The remaining input stream (1) originating from the extract evaporation step of lignin production is also fed to column 2 (202). The condensate of the vapor (5) discharged from the top of the second column (202) can be recovered for use in other unit operations. The distilled organic acid solution (6) is discharged from the bottom of the second column (202). The organic acid content of the various output streams of the 2-column distillation system is presented in Table 11.

[0256] Table 11.2 Composition of organic acids in the output of the column distillation system

[0257] flow Flow rate (kg / h) Formic acid content (%) Acetic acid content (%) Water content (%) 5 129.8 0.0％ 0.8％ 99.2％ 6 477.8 32.0％ 60.0％ 8.0％ 7 227.8 0.0％ 0.8％ 99.2％

[0258] Note: The stream symbol name is the same as in Figure 10 and those described above.

[0259] exist Figure 11 A similar process is described in , which represents the process flow within a 3-column distillation system. In this case, the operation is similar with respect to the input and output streams of the 2-column system described above. However, in this case, the vapor condensates from the first two columns are combined to form a single output stream ( Figure 11 7), and the distilled organic acid solution (302) discharged from column 2 is fed to the third column (203), where the vapor condensate (5) is recovered, and the further distilled organic acid solution (6) is discharged from the bottom of the third column (203). The organic acid content of various output streams of the two-column distillation system is presented in Table 12.

[0260] Table 12.3 Composition of organic acids in the output of the column distillation system

[0261] flow Flow rate (kg / h) Formic acid content (%) Acetic acid content (%) Water content (%) 5 78.4 0.0％ 0.8％ 99.2％ 6 477.8 32.0％ 60.0％ 8.0％ 7 279.3 0.0％ 0.8％ 99.2％

[0262] Note: The stream symbol name is the same as in Figure 11 and those described above.

[0263] Similarly, in Figure 12 A process representative of the process flow within the 4-column distillation system is described in Table 13. The organic acid content of various output streams of the 2-column distillation system is presented in Table 13.

[0264] Table 13.4 Organic acid composition of the output of the column distillation system

[0265] flow Flow rate (kg / h) Formic acid content (%) Acetic acid content (%) Water content (%) 5 49.8 0.0％ 0.8％ 99.2％ 6 477.8 32.0％ 60.0％ 8.0％ 7 307.8 0.0％ 0.8％ 99.2％

[0266] Note: The stream symbol name is the same as in Figure 12 matches those described in .

[0267] exist Figure 13 A process representative of the process flow within the 5-column distillation system is described in Table 14. The organic acid content of the various output streams of the 5-column distillation system is presented in Table 14.

[0268] Table 14.5 Composition of organic acids in the output of the column distillation system

[0269] flow Flow rate (kg / h) Formic acid content (%) Acetic acid content (%) Water content (%) 5 37.5 0.0％ 0.8％ 99.2％ 6 477.8 32.0％ 60.0％ 8.0％ 7 320.2 0.0％ 0.8％ 99.2％

[0270] Note: The stream symbol name is the same as in Figure 12 matches those described in .

[0271] According to the simulation flowsheet, steam consumption can be significantly reduced by the number of distillation columns present in the system. Data supporting this observation are presented in Table 15.

[0272] Table 15. Steam consumption distribution of 2-column, 3-column and 4-column distillation systems

[0273]

[0274] The reduction in heat demand for the 2-tower system relative to the 3-tower system is shown to be 27.6%, while the reduction in heat demand for the 4-tower system is an additional 20% reduction over the 3-tower system, with the overall reduction in heat demand required for the 4-tower system being 42% of the heat demand of the two-tower system.

[0275] Interestingly, the additional tower provides minimal energy improvement. See Table 16.

[0276] Table 16. Steam consumption distribution of 4-column and 5-column distillation systems

[0277]

[0278] Example 6

[0279] organic fertilizer

[0280] In initial experiments, corn stover was used as a source of lignocellulosic plant material for organic acid treatment with formic and acetic acid to extract hemicellulose and lignin. The hemicellulose and lignin mixture was separated to obtain a cellulose pulp fraction and an extract. The cellulose pulp was treated to partially eliminate lignin and washed with water to obtain cellulose. The extract was concentrated to separate the lignin. After separation of the lignin, the residue was concentrated and stripped to obtain hemicellulose juice. The cellulose and hemicellulose juice mixture was hydrolyzed and fermented to produce ethanol by adding cellulase and yeast, respectively. Ethanol was separated from the fermentate by distillation, and the residual material from the distillation constituted stillage.

[0281] The stillage (2113 g, containing 9.23% dry matter content) was fed to a decanter, and after decantation, 61.4 g of a solid fraction (containing 38.0% dry matter content) and 2051.6 g of a thin stillage (containing 8.37% dry matter content) were produced. The thin stillage was evaporated (in an evaporator operated at 110° C.) to obtain 451.6 g of concentrated stillage (containing 38.0% dry matter content). The solid fraction and the concentrated stillage were combined to obtain a mixture (513.0 g). The mixture was dried in a dryer operated at a temperature of 120° C. to obtain 335.1 g of a final organic fertilizer; wherein the organic fertilizer had a dry matter content of 58.2% and a pH of 6.1. The organic fertilizer has a dry matter content of 58.2%, an organic matter content of 47.8%, and a total nutrient content of 5.86% (calculated based on the formula, where nutrients = nitrogen + phosphorus pentoxide + potassium oxide), calculated based on the total dry matter.

[0282] In a second experiment to produce organic fertilizer from stillage using corn stover as the initial input to the organic acid treatment process, stillage (2113 g, containing 9.23% dry matter) was fed to a decanter. After decantation, 67.1 g of a solid fraction (35.5% dry matter content) and 2046 g of thin stillage (8.37% dry matter content) were obtained. The thin stillage was evaporated (in an evaporator operated at 105° C.) to produce 456.7 g of concentrated stillage with a dry matter content of 37.5%. The solid fraction and the concentrated stillage were combined to produce 523.8 g of a mixture. The mixture was dried in a dryer operated at 130° C. to produce 297.7 g of a final organic fertilizer with a dry matter content of 65.5% and a pH of 6.0. The organic fertilizer contained 47.3% organic matter, with a total nutrient content of 5.81% calculated based on the total dry matter.

[0283] In the third experiment of producing organic fertilizer from stillage, wheat straw was used as the initial input of the organic acid treatment process, and stillage (1940 g, containing 9.38% dry matter) was fed into a decanter. After decantation, 59.5 g of a solid fraction (37.0% dry matter content) and 1880.5 g of a thin stillage (8.51% dry matter content) were obtained. The thin stillage was evaporated (in an evaporator operated at 115° C.) to produce 438.3 g of concentrated stillage with a dry matter content of 36.5%. The solid fraction and the concentrated stillage were combined to produce 497.8 g of a mixture. The mixture was dried in a dryer operated at 140° C. to produce 244.3 g of a final organic fertilizer with a dry matter content of 74.5% and a pH of 6.2. The organic fertilizer contained 48.5% organic matter, with a total nutrient content of 6.12%, calculated based on the total dry matter.

Claims

1. A method for recovering lignin from a lignin suspension produced from a concentrated extract of an organic acid pretreatment of a plant material, the method comprising the following steps: a) separating lignin from the lignin suspension by centrifugation to form separated lignin and a first centrifuge liquid, and b) cleaning the separated lignin in the centrifuge by applying a washing solution to the separated lignin multiple times during centrifugation to form at least a second and a third centrate, wherein the multiple applications of the washing solution include: a first application of a washing solution having an organic acid content of 0.5 wt % to 10 wt %, a second application of a washing solution having an organic acid content of 0.2 wt % to 1 wt %, and a final application of a washing solution comprising fresh water, wherein the organic acid content of the washing solution of the first application is greater than the organic acid content of the washing solution of the second application, and c) recovering the first centrifuge liquid and the second centrifuge liquid for hemicellulose juice concentration, and d) recycling the third centrifuge liquid used for separating lignin from the concentrated extract in the separation step of the method, and e) discharging the separated lignin from the centrifuge.

2. The method according to claim 1, wherein the centrifuge is a scraper centrifuge.

3. The method of claim 1, wherein the centrifuge is equipped with a spray device for delivering the washing solution.

4. The method of claim 1, wherein the centrifuge rotates continuously throughout the method.

5. The method of claim 1, wherein the first and second applied wash solutions comprise formic acid, acetic acid, and water.

6. The method of claim 1, wherein the second centrate comprises the first wash solution included in multiple applications of wash solutions applied to the separated lignin in the centrifuge.

7. The method of claim 1, wherein the third centrate comprises the second wash solution and any subsequent wash solutions included in multiple applications of wash solutions applied to the separated lignin in the centrifuge.

8. The method of claim 1, wherein the third centrifuge liquid is recycled to the lignin precipitation step.

9. The method of claim 1, wherein the first centrate constitutes 10% to 60% by volume of the total centrate.

10. The method of claim 1, wherein the second centrate constitutes 10% to 30% by volume of the total centrate.

11. The method of claim 1, wherein the third centrate constitutes 10% to 50% by volume of the total centrate.

12. The method of claim 1, wherein the purity of the separated lignin from step e) is 90% to 99% based on the total weight of the separated lignin from step e).

13. A lignin composition obtained by the process according to any one of claims 1 to 12.

14. The lignin composition according to claim 13, wherein the purity of the separated lignin is 90% to 99% based on the total weight of the cleaned lignin.

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