Method for preparing fuel ethanol from straw biomass and fuel ethanol

Abstract

The present invention discloses a method for preparing fuel ethanol from straw biomass and the fuel ethanol, belonging to the technical field of fuel ethanol production. It includes: dissolving and hydrolyzing straw and concentrated sulfuric acid to obtain a saccharified solution, separating out a sugar-rich solution in a simulated moving bed chromatography system, and then mixing it with Saccharomyces cerevisiae SEB3 for fermentation, and generating fuel ethanol through distillation. The method for preparing fuel ethanol from straw biomass provided by the present invention can obtain fermentable sugars under normal pressure and low temperature conditions by using concentrated acid hydrolysis, and has the remarkable advantages of low energy consumption, low toxic by-products, and no need to input cellulase. And Saccharomyces cerevisiae SEB3 is used for fermentation. This strain has the ability of co-fermenting all sugars, can realize the fermentation of all sugars, synchronously convert all sugars into ethanol, the sugar consumption efficiency reaches more than 90%, and the ethanol recovery rate reaches more than 80%, and it is applicable to industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel ethanol production, and particularly relates to a method for preparing fuel ethanol from straw biomass and the fuel ethanol. Background Art

[0002] Using agricultural straw biomass as a raw material to produce biofuels, biobased chemicals, etc. can solve problems such as high carbon emissions and environmental pollution caused by the consumption of fossil resources. Cellulose fuel ethanol has received great attention as an ideal substitute for vehicle fuels. At present, the method of "pretreatment + enzymatic hydrolysis" is commonly used to produce fuel ethanol. However, the cost of cellulose enzymes is still relatively high at present, the energy consumption of the pretreatment process under high temperature and high pressure is high, and more toxic by-products that inhibit subsequent enzymatic hydrolysis and biological fermentation are generated, making the production cost of this process remain high, and there are great challenges in commercial application. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for preparing fuel ethanol from straw biomass and the fuel ethanol, which solves the problems of high cost and large energy consumption in producing fuel ethanol using straw biomass.

[0004] The present invention is achieved by the following technical solutions:

[0005] The present invention provides a method for preparing fuel ethanol from straw biomass, including:

[0006] Dissolving straw with sulfuric acid having a mass fraction of 70% - 80% according to an acid-to-material ratio of (1.1 - 1.3):1 at a temperature of 30°C - 60°C for 30 min - 60 min to obtain a dissolved product;

[0007] Adding water to the dissolved product to dilute it until the mass fraction of sulfuric acid in the dissolved product is 30% - 40%, heating to 80°C - 100°C, and performing a hydrolysis reaction for 80 min - 100 min to obtain a hydrolysis solution containing sugar and solid residues;

[0008] Performing pressure filtration on the hydrolysis solution to obtain a saccharified solution, and performing chromatographic separation in a simulated moving bed chromatography system to separate a rich acid solution and a rich sugar solution containing oligosaccharides and reducing sugars;

[0009] After converting the oligosaccharides in the rich sugar solution into monosaccharides, using the Saccharomyces cerevisiae SEB3 strain for fermentation to produce ethanol, and generating fuel ethanol through distillation.

[0010] Further, in the method for preparing fuel ethanol from straw biomass, the straw is pre-treated by crushing and drying in advance;

[0011] And / or, the diameter of the crushed straw is 5 mm - 10 mm;

[0012] And / or, drying until the moisture content of the straw is below 10%; or,

[0013] Performing pressure filtration on the hydrolysis solution to obtain a saccharified solution, including:

[0014] Performing pressure filtration on the hydrolysis solution containing sugar and solid residues at a pressure of 3 MPa to 5 MPa for 20 min to 40 min to obtain a saccharified solution and solid residues.

[0015] Further, in the method for preparing fuel ethanol from straw biomass, the simulated moving bed chromatography system includes 4 to 6 separation columns filled with zwitterionic exchange resin. A plurality of the separation columns are sequentially divided into region c, region d, region a, and region b. Region c is 1 to 3 separation columns, and regions d, a, and b are each 1 separation column;

[0016] Performing chromatography separation on the saccharified solution in the simulated moving bed chromatography system, including:

[0017] Feeding the saccharified solution into the chromatography separation system from the feeding point, and separating a first sugar-rich solution from the discharging point after passing through region a;

[0018] Feeding the eluent into the chromatography separation system from the feeding point, and separating an acid-rich solution from the discharging point after passing through region c;

[0019] Feeding the eluent into the chromatography separation system from the feeding point, and separating a second sugar-rich solution from the discharging point after sequentially passing through region c, region d, and region a;

[0020] Sequentially passing the liquid in the chromatography separation system through region c, region d, region a, and region b to complete the internal circulation;

[0021] Taking the above steps as one process, when proceeding to the next process, the positions of the feeding point and the discharging point both move backward by one separation column, and the regions change accordingly. Four to six processes of the separation method are taken as one cycle;

[0022] And / or, the feeding amount of the saccharified solution raw material is 35 - 70 mL / L-resin, and the feeding speed is 12 - 17 mL / L-resin / min;

[0023] And / or, the feeding amount of the eluent is 63 - 175 mL / L-resin, and the flow rate is 12 - 17 mL / L-resin / min;

[0024] And / or, the eluent is dechlorinated tap water;

[0025] And / or, the internal circulation flow rate of the liquid in the chromatography separation system is 84 - 168 mL / L-resin, and the flow rate is 12 - 17 mL / L-resin / min;

[0026] and / or, the raw material feeding rate, the feeding rate of the eluent and the internal circulation rate are the same;

[0027] and / or, the separation temperature is 35 - 50 °C.

[0028] Furthermore, in the method for preparing fuel ethanol from straw biomass, the preparation of the zwitterionic exchange resin includes:

[0029] Adding sodium styrene sulfonate solution to a chromatographic column filled with chloride-type strongly basic anion exchange resin for resin modification to obtain styrene sulfonic acid ion-type strongly basic anion exchange resin;

[0030] Transferring the obtained styrene sulfonic acid ion-type strongly basic anion exchange resin, adding an azo compound water-soluble free radical initiator, and after the initiator is dissolved, intermittently stirring at room temperature for more than 2 days;

[0031] Performing a heating polymerization reaction on the stirred resin solution to obtain the zwitterionic exchange resin;

[0032] and / or, the strongly basic anion exchange resin is a resin containing a quaternary ammonium group strongly basic group;

[0033] and / or, the azo compound water-soluble free radical initiator includes: 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide), azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-methyl-N-hydroxypropionamide) or 2,2'-azobis(N,N'-dimethyleneisobutyramidine) dihydrochloride;

[0034] and / or, the molar amounts of sodium styrene sulfonate and the azo compound water-soluble free radical initiator used per unit volume of the chloride-type strongly basic anion exchange resin are 3 - 8 moL and 0.1 - 0.5 moL respectively;

[0035] and / or, performing the heating polymerization reaction includes: heating at 70 °C - 75 °C for 1 h - 10 h and heating and polymerizing at 80 °C - 85 °C for 1 h - 10 h.

[0036] Furthermore, in the method for preparing fuel ethanol from straw biomass, the conversion of oligosaccharides in the sugar-rich solution into monosaccharides includes:

[0037] Adjusting the pH of the sugar-rich solution to 0.8 - 0.9 and heating at 120 °C - 130 °C for 50 min - 60 min.

[0038] Furthermore, in the method for preparing fuel ethanol from straw biomass, the fermentation treatment of Saccharomyces cerevisiae SEB3 includes:

[0039] Adjust the pH of the saccharified liquid to 3 - 5, and continuously ferment the non - sterilized saccharified liquid and the sterilized basic medium at a volume ratio of 9:1 using Saccharomyces cerevisiae SEB3 to synchronously convert monosaccharides into ethanol;

[0040] Among them, the basic medium includes: corn steep liquor 50 g / L, (NH4)2SO4 5 g / L, KH2PO4 5 g / L, MgSO4·7H2O 5 g / L, and CaCl2·2H2O 10 g / L.

[0041] Furthermore, in the method for preparing fuel ethanol from straw biomass, the method further includes: washing the solid residue by a counter - current washing process to recover the acid and sugar in the solid residue, and the counter - current washing process includes:

[0042] Use fresh water as the third - stage injection water to wash the solid residue for the first time;

[0043] The third - stage drainage separated by the first - time washing is divided into two paths. The first path is used as the second - stage injection water to wash the solid residue for the second time, and the second path is used as the dilution water in the hydrolysis reaction;

[0044] The second - stage drainage separated by the second - time washing is used to wash the solid residue for the third time;

[0045] The first - stage drainage separated by the third - time washing enters the filtrate;

[0046] And / or, the water consumption of fresh water is 1 - 2 times the volume of water added in the hydrolysis reaction process;

[0047] And / or, the water consumption of the second - stage injection water is 1 / 3 - 1 / 2 of the volume of the third - stage drainage.

[0048] Furthermore, in the method for preparing fuel ethanol from straw biomass, the method further includes: anaerobic digestion treatment of the distillation wastewater obtained from the distillation process, including:

[0049] Send the distillation wastewater into the acidification phase, and carry out acid - production reaction under the conditions of introducing a small amount of air and gas circulation in the acidification phase;

[0050] The pretreated wastewater after the acid - production reaction is precipitated and stratified;

[0051] Take the supernatant of the pretreated wastewater after precipitation and stratification, and send it into the methane - production phase to carry out methane - production reaction;

[0052] The lower - layer sludge after precipitation and stratification treatment is returned to the acidification phase.

[0053] Furthermore, in the method for preparing fuel ethanol from straw biomass, the anaerobic digestion reaction includes:

[0054] The seed sludge of the acidification phase adopts granular sludge for anaerobic treatment of organic wastewater;

[0055] And / or, the temperature for acidogenesis reaction is 35°C to 37°C, or 53°C to 55°C;

[0056] And / or, the flow rate of the air introduced is 5 mL / L / min to 15 mL / L / min;

[0057] And / or, the flow rate of gas circulation in the acidification phase is 0.5 L / L / min to 4 L / L / min; and / or, the stirring speed is 60 rpm to 100 rpm;

[0058] And / or, the liquid circulation volume is 50 L / L / d to 100 L / L / d;

[0059] And / or, the acidification treatment adopts a feeding and discharging method of daily input and daily output;

[0060] And / or, the hydraulic retention time is 1 day to 4 days;

[0061] And / or, the oxidation-reduction potential of the liquid in the acidification phase is -300 mV to -200 mV;

[0062] And / or, the pH value of the liquid in the acidification phase is 5 to 12;

[0063] And / or, the precipitation treatment includes: the precipitation time of the pretreated wastewater is 60 min to 120 min;

[0064] And / or, the seed sludge of the methanogenesis phase is granular sludge for anaerobic treatment of organic wastewater;

[0065] And / or, the liquid supply flow rate of the supernatant entering the methanogenesis phase is 0.05 L / L / d to 0.1 L / L / d.

[0066] The present invention also provides a fuel ethanol, which is prepared by the method for preparing fuel ethanol from straw biomass as described above.

[0067] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0068] The method for preparing fuel ethanol from straw biomass provided by the present invention can obtain fermentable sugars under normal pressure and low temperature conditions by using concentrated acid hydrolysis, and has the remarkable advantages of low energy consumption, low toxic by-products, and no need for cellulose enzyme input. And Saccharomyces cerevisiae SEB3 is used for fermentation, which can realize the fermentation of full sugar utilization, synchronously convert full sugar into ethanol, the sugar consumption efficiency reaches more than 90%, and the ethanol recovery rate reaches more than 80%, and it is applicable to industrial production.

[0069] The method for preparing fuel ethanol from straw biomass provided by the present invention has strong inclusiveness for the types of lignocellulosic raw materials. The total sugar recovery rate in the hydrolysis process, the recovery rates of acid and sugar in the acid-sugar separation process, etc. have all reached the industrial application level, and there is no wastewater and waste residue discharge throughout the process, resulting in little environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings:

[0071] Figure 1 It is the separation chromatogram of DIAION SA10A (modified) resin in Application Case 1 of the present invention;

[0072] Figure 2 It is the separation chromatogram of DIAION SA10A resin in Application Case 1 of the present invention;

[0073] Figure 3 It is the schematic diagram of the operation process of the simulated moving bed chromatography system in Example 2 of the present invention;

[0074] Figure 4 It is the separation curve of acid-sugar separation within one cycle in Application Case 2 of the present invention; wherein, the square represents glucose, the triangle represents xylose, and the diamond represents sulfuric acid;

[0075] Figure 5 It is the process flow chart of the method for preparing fuel ethanol from straw biomass provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0076] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in combination with the embodiments and the drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0077] A method for preparing fuel ethanol from straw biomass, comprising:

[0078] The straw raw material is pretreated by crushing it to less than 5 - 10 mm and drying to a moisture content of less than 10%.

[0079] 1) Step S1: Saccharification:

[0080] The saccharification method includes: dissolving straw with sulfuric acid having a mass fraction of 70% to 80% according to an acid-to-material ratio of (1.1 to 1.3):1 at a temperature of 30°C to 60°C for 30 min to 60 min to obtain a dissolved product;

[0081] Adding water at 80°C to 95°C to the dissolved product to dilute the mass fraction of sulfuric acid in the dissolved product to 30% to 40%, heating to 80°C to 100°C, and performing a hydrolysis reaction for 80 min to 100 min to obtain a hydrolysis solution containing sugar and solid residues.

[0082] The straw biomass mainly contains three major components: cellulose, hemicellulose, and lignin. Among them, the proportion of cellulose and hemicellulose is as high as 60% - 70%. After hydrolysis, monosaccharides such as glucose and xylose are generated. There are multiple hydroxyl groups in the molecular structures of hemicellulose and lignin, which are prone to chemical cross-linking to form a stable three-dimensional network structure. This network structure binds cellulose inside, resulting in the difficulty of straw hydrolysis and utilization.

[0083] Using high-concentration sulfuric acid to dissolve straw to break the formed three-dimensional network structure and release the bound cellulose, with sulfuric acid having a mass fraction of 70% to 80%. If the concentration of sulfuric acid is too high, the straw will be carbonized; if the concentration of sulfuric acid is too low, the three-dimensional network structure cannot be destroyed, making subsequent hydrolysis difficult. In addition, the acid-to-material ratio is also an important influencing factor. When the traditional acid-to-material ratio is greater than 2, the excessive acid can completely hydrolyze the straw, but it will also cause the sugar concentration to be lower than 50 g / L, resulting in an excess of acid solution and difficulties in the subsequent separation and recovery of acid and sugar.

[0084] Controlling the acid-to-material ratio between (1.1 - 1.3):1 can not only ensure sufficient contact between straw and sulfuric acid for dissolution and hydrolysis, but also prevent the excess of sulfuric acid. The sugar concentration in the obtained hydrolysis mixture is as high as 200 g / L, laying a foundation for the efficient and industrial separation of acid and sugar in the subsequent process. When the acid-to-material ratio is less than 1.1, the amount of acid solution is too small, and the straw cannot be effectively dissolved, resulting in partial agglomeration, which affects the dissolution reaction process of the straw and makes the subsequent hydrolysis reaction unable to proceed normally; when the acid-to-material ratio is greater than 1.3, the sugar concentration in the hydrolysis mixture is low due to the large amount of acid solution, lower than 180 g / L. The lower the sugar concentration in the hydrolysis mixture, the greater the energy consumption, water consumption, and recovery cost for acid-sugar separation.

[0085] During the straw hydrolysis process, it is very difficult to increase the sugar concentration. Firstly, the concentration of sulfuric acid, the acid-to-feed ratio, the hydrolysis temperature, and the dissolution time during the dissolution process, as well as the concentration of diluted sulfuric acid, the hydrolysis temperature, and the hydrolysis time during the hydrolysis process, these factors affect each other. Under the premise that the sulfuric acid concentration is limited to 70% - 80%, the method of the present invention controls the acid-to-feed ratio between 1.1 - 1.3:1, and reasonably controls other influencing factors to obtain a saccharified solution with a high sugar concentration greater than 200 g / L.

[0086] This saccharification step can achieve the hydrolysis of straw to obtain fermentable sugars at normal pressure and low temperature. This method has low energy consumption, few toxic by-products, and does not require the input of cellulase, and can achieve better industrial application.

[0087] 2.) Step S2: Solid-liquid separation

[0088] Press-filter the hydrolysis solution to obtain a saccharified solution, including: subjecting the hydrolysis solution containing sugar and solid residue to press-filtration at a pressure of 3 MPa - 5 MPa for 20 min - 40 min to obtain a saccharified solution and solid residue.

[0089] Specifically, subject the hydrolysis solution containing monosaccharides and straw residue to press-filtration at a pressure of 3 MPa - 5 MPa for 20 min - 40 min to obtain a saccharified solution and straw residue; the pressure can be 3 MPa, 3.2 MPa, 3.5 MPa, 3.8 MPa, 4 MPa, 4.2 MPa, 4.5 MPa, 4.8 MPa, 5 MPa, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0090] The press-filtration time can be 20 min, 25 min, 30 min, 35 min, 40 min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0091] 3) Step S3: Acid-sugar separation

[0092] The saccharified solution separated in the solid-liquid separation process is chromatographically separated in a simulated moving bed chromatography system to separate a rich acid solution and a rich sugar solution.

[0093] The simulated moving bed chromatography system includes 4 - 6 separation columns filled with zwitterionic exchange resin. The multiple separation columns are divided into region c, region d, region a, and region b. Region c is 1 - 3 separation columns, and regions d, a, and b are each 1 separation column;

[0094] The chromatographic separation of the saccharified solution in the simulated moving bed chromatography system includes:

[0095] Feed the saccharified solution into the simulated moving bed chromatography system from the feed point, and separate a first rich sugar solution from the discharge point after passing through region a;

[0096] Feed the eluent into the feed point of the chromatographic separation system, and separate the acid-rich liquid from the discharge point after passing through region c.

[0097] Feed the eluent into the feed point of the chromatographic separation system, and separate the second sugar-rich solution from the discharge point after successively passing through region c, region d, and region a.

[0098] Pass the liquid in the chromatographic separation system successively through region c, region d, region a, and region b to complete the internal circulation.

[0099] Taking the above steps as one process, when proceeding to the next process, the positions of the feed point and the discharge point both move backward by one separation column, and the regions change accordingly. Four to six processes of the separation method constitute one cycle.

[0100] Furthermore, the simulated moving bed chromatographic system separates a sugar-rich liquid containing sugars (oligosaccharides and monosaccharides).

[0101] Furthermore, the feeding amount of the saccharified liquid raw material is 35 - 70 mL / L-resin, which can be 35 mL / L-resin, 45 mL / L-resin, 55 mL / L-resin, 60 mL / L-resin, 70 mL / L-resin, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable. The feeding speed is 12 - 17 mL / L-resin / min, which can be 12 mL / L-resin / min, 14 mL / L-resin / min, 15 mL / L-resin / min, 16 mL / L-resin / min, 17 mL / L-resin / min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0102] And / or, the feeding amount of the eluent is 63 - 175 mL / L-resin, which can be 63 mL / L-resin, 75 mL / L-resin, 90 mL / L-resin, 110 mL / L-resin, 120 mL / L-resin, 125 mL / L-resin, 150 mL / L-resin, 175 mL / L-resin, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable. The flow rate is 12 - 17 mL / L-resin / min, which can be 12 mL / L-resin / min, 14 mL / L-resin / min, 15 mL / L-resin / min, 16 mL / L-resin / min, 17 mL / L-resin / min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0103] And / or, the eluent is dechlorinated tap water;

[0104] And / or, the internal circulation flow rate of the liquid in the chromatographic separation system is 84 - 168 mL / L-resin, which can be 84 mL / L-resin, 100 mL / L-resin, 120 mL / L-resin, 135 mL / L-resin, 150 mL / L-resin, 168 mL / L-resin, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable; the flow rate is 12 - 17 mL / L-resin / min, which can be 12 mL / L-resin / min, 13 mL / L-resin / min, 15 mL / L-resin / min, or 17 mL / L-resin / min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0105] And / or, the feeding rate of the saccharified liquid, the flow rate of the eluent, and the internal circulation rate are the same.

[0106] And / or, the separation temperature is 35 - 50 °C, which can be 35 °C, 38 °C, 41 °C, 44 °C, 47 °C, 50 °C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0107] Furthermore, the simulated moving bed chromatographic system includes 6 separation columns filled with zwitterionic exchange resin, and region c is 3 separation columns, and the separation method is carried out in six processes as one cycle.

[0108] Furthermore, the preparation of the zwitterionic exchange resin includes:

[0109] Adding sodium styrenesulfonate solution to the chromatographic column filled with chloride-type strongly basic anion exchange resin for resin modification to obtain styrenesulfonic acid ion-type strongly basic anion exchange resin;

[0110] Transfer the obtained styrenesulfonic acid ion-type strongly basic anion exchange resin, and add an azo compound water-soluble free radical initiator. After the initiator is dissolved, intermittently stir at room temperature for more than 2 days;

[0111] Carry out a heat polymerization reaction on the stirred resin solution to obtain a zwitterionic exchange resin suitable for separating high-concentration sulfuric acid and sugar.

[0112] Furthermore, the strongly basic anion exchange resin is a resin containing a quaternary ammonium group strongly basic group. In the present invention, in order to be more suitable for industrialization, the selected resin is an existing commercial resin, such as DIAION SA10A, and all strongly basic anion exchange resins containing a quaternary ammonium group strongly basic group on the market meet the requirements.

[0113] Furthermore, the chromatographic column filled with strongly basic anion exchange resin is balanced by alternately adding an electrolyte solution and ultrapure water.

[0114] Furthermore, electrolyte solution and ultrapure water are alternately added for resin equilibration, including:

[0115] They are alternately added in the order of adding electrolyte solution with a concentration of 0.5 mol / L to 2 mol / L and then ultrapure water until the electrolyte solution is completely washed out by the ultrapure water;

[0116] The electrolyte solutions added are NaCl solution, NaOH solution and HCl solution in sequence.

[0117] The concentrations of the NaCl solution, NaOH solution and HCl solution used can be 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, 1.5 mol / L, 1.75 mol / L or 2 mol / L, etc., but are not limited to the listed values, and other unlisted values within this range are equally applicable. Furthermore, the azo compound water-soluble radical initiator includes: 2,2'-Azobis(2-methylpropionamidine) dihydrochloride, 2,2'-Azobis(isobutyronitrile), 2,2'-Azobis(2-methyl-N-(2-hydroxyethyl)propionamide), 2,2'-Azobis(2-methyl-N-hydroxypropionamidine) dihydrate or 2,2'-Azobis(N,N'-dimethyleneisobutyramidine) dihydrochloride. Preferably, the azo compound water-soluble radical initiator used in the present invention is 2,2'-Azobis(2-methylpropionamidine) dihydrochloride.

[0118] Furthermore, heat polymerization reaction is carried out, including:

[0119] It is heated at 70 °C to 75 °C for 1 to 10 h. Specifically, the heating temperature can be 70 °C, 71 °C, 72 °C, 73 °C, 74 °C, 75 °C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable. The time can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0120] It is heated for polymerization reaction at 80 °C to 85 °C for 1 to 10 h. Specifically, the polymerization temperature can be 80 °C, 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable. The time can be 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0121] Further, after obtaining an amphoteric ion exchange resin suitable for separating high-concentration sulfuric acid and sugar and washing it with water, it is filled into a packed column and rinsed with an NaCl solution to replace the unreacted styrene sulfonic acid ions with chloride ions until no styrene sulfonic acid ions are detected. The NaCl solution used can have concentrations such as 0.5 mol / L, 0.75 mol / L, 1 mol / L, 1.25 mol / L, 1.5 mol / L, 1.75 mol / L, or 2 mol / L, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0122] Further, the molar amounts of sodium styrene sulfonate and an azo compound water-soluble free radical initiator used per unit volume (L) of the chloride-form strongly basic anion exchange resin are 3 - 8 moL and 0.1 - 0.5 moL respectively. They can be molar amounts such as 3 moL, 4 moL, 5 moL, 6 moL, 7 moL, 8 moL, etc. and 0.1 moL, 0.2 moL, 0.3 moL, 0.4 moL, 0.5 moL, etc., but are not limited to the listed values, and other unlisted values within this range are equally applicable.

[0123] 4. Step S4: Fermentation

[0124] After the oligosaccharides in the sugar-rich liquid separated in the acid-sugar separation process are converted into monosaccharides, they are mixed with Saccharomyces cerevisiae SEB3 for fermentation, and fuel ethanol is produced by distillation.

[0125] (1) Conversion: In the sugar-rich liquid after acid-sugar separation, there are relatively high concentrations of oligosaccharides that cannot be directly fermented and utilized. This part of the oligosaccharides needs to be converted into monosaccharides (glucose and xylose). The pH of the sugar-rich liquid is about 0.6. Add Ca(OH)2 to adjust the pH to 0.8 - 0.9, and keep it in a bent coiled tube at 120 - 130 °C for 50 - 60 min to convert the oligosaccharides into monosaccharides.

[0126] (2) Fermentation: The fermentation treatment of the Saccharomyces cerevisiae SEB3 (strain number: CGMCC11323). This strain has the ability to ferment all sugars and has flocculability, and it will settle by itself after fermentation, which is convenient for the separation and recovery of Saccharomyces cerevisiae SEB3 cells.

[0127] The fermentation treatment of the Saccharomyces cerevisiae SEB3 includes:

[0128] Adjust the pH of the saccharified liquid to 3 - 5, and continuously ferment the non-sterilized saccharified liquid and the sterilized basal medium at a volume ratio of 9:1 to synchronously convert the monosaccharides into ethanol;

[0129] Among them, the basal medium includes: 50 g / L of corn steep liquor, 5 g / L of (NH4)2SO4, 5 g / L of KH2PO4, 5 g / L of MgSO4·7H2O, and 10 g / L of CaCl2·2H2O.

[0130] 5). Step S5: Distillation

[0131] The fermentation broth from the fermentation process is subjected to distillation treatment to obtain fuel ethanol and distillation residues.

[0132] 6). Step S6: Biological treatment

[0133] The distillation residues generated from the distillation process are subjected to biological treatment:

[0134] (1) Anaerobic digestion: The sulfate content in the distillation wastewater is relatively high, reaching 1 - 3 g / L. The anaerobic acidification-methanogenesis combined treatment method is used for anaerobic digestion treatment. In the acidification phase, the residual organic matter is converted into volatile acids, avoiding the deterioration or failure caused by excessive rapid acidification in a single-phase fermentation reactor. No pre-desulfurization treatment such as chemical precipitation is required, which can reduce the inhibition of H2S and increase the COD removal in the distillation wastewater by more than 85 - 90%. The wastewater treatment effect is obvious.

[0135] The anaerobic digestion method includes:

[0136] Step S1: Feed the distillation wastewater in straw ethanol preparation into the acidification phase, and carry out acid production reaction under the conditions of introducing a small amount of air and gas circulation in the acidification phase;

[0137] Step S2: The pretreated wastewater after the acid production reaction is subjected to precipitation and stratification;

[0138] Step S3: Take the supernatant of the pretreated wastewater after precipitation and stratification and feed it into the methanogenesis phase for methanogenesis reaction;

[0139] Step S4: The lower sludge after precipitation and stratification treatment is returned to the acidification phase.

[0140] For the distillation wastewater in straw ethanol preparation with high COD, high sulfur content, and low COD / SO4 2- ratio, the anaerobic digestion method of the present invention directly uses the distillation wastewater in straw ethanol preparation as the raw material, adopts the anaerobic acidification-methanogenesis combined treatment method, does not require pre-desulfurization treatment such as chemical precipitation, can reduce the inhibition of H2S, and increase the COD removal in the distillation waste liquid by more than 85 - 90%. The wastewater treatment effect is obvious.

[0141] In the anaerobic acidification reaction of the present invention, acidification is coupled with micro-aeration (the air flow rate is 5 mL / L / min to 15 mL / L / min) and gas circulation to carry out in-situ desulfurization. H2S in the produced gas is oxidized into elemental sulfur and enters the sludge precipitation, which can avoid the inhibition of acidification-phase microorganisms by H2S and convert the organic matter in the wastewater into volatile fatty acids. At the same time, the sulfur-containing sludge in the acidification phase does not enter the subsequent methane production phase, so the H2S inhibition in the methane fermentation process can be reduced. It can be seen that the anaerobic acidification reaction of the present invention will reduce the inhibition of H2S and improve the wastewater treatment efficiency.

[0142] In the anaerobic digestion method of the present invention, the COD in the distillation waste liquid undergoes an acidogenesis reaction in the acidification phase and is converted into volatile fatty acids, providing a substrate that is easy to utilize for biogas production in the subsequent methane production phase, and avoiding the imbalance between acidogenesis and methane production caused by excessive acidification in the methane production phase, which may lead to the failure of the reaction.

[0143] In the anaerobic digestion method of the present invention, by controlling the redox potential of the liquid in the acidification phase to be -300 mV to -200 mV, based on this, the flow rate of the air supplied into the reactor can be automatically adjusted, more effectively reducing the inhibition of H2S on acidification and methane production, thereby promoting the methane fermentation efficiency.

[0144] Furthermore, the seed sludge of the acidification phase adopts granular sludge for anaerobic treatment of organic wastewater.

[0145] Furthermore, the temperature for the acidogenesis reaction is 35°C to 37°C, which can be 35°C, 35.3°C, 35.5°C, 35.7°C, 36°C, 36.3°C, 36.5°C, 36.7°C, 37°C, etc.; or 53°C to 55°C, which can be 53°C, 53.3°C, 53.5°C, 53.7°C, 54°C, 54.3°C, 54.5°C, 54.7°C, 55°C, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0146] Furthermore, the acidogenesis reaction includes:

[0147] The air flow rate is 5 mL / L / min to 15 mL / L / min, which can be 5 mL / L / min, 7 mL / L / min, 10 mL / L / min, 11 mL / L / min, 12 mL / L / min, 13 mL / L / min, 14 mL / L / min, 15 mL / L / min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0148] The flow rate of gas circulation in the acidification phase is 0.5 L / L / min to 4 L / L / min, which can be 0.5 L / L / min, 0.7 L / L / min, 1 L / L / min, 1.5 L / L / min, 2 L / L / min, 2.5 L / L / min, 3 L / L / min, 3.5 L / L / min, 4 L / L / min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable. And / or, the stirring speed is 60 rpm to 100 rpm, which can be 60 rpm, 65 rpm, 70 rpm, 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm, 100 rpm, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0149] And / or, the liquid circulation volume is 50 L / L / d to 100 L / L / d, which can be 50 L / L / d, 55 L / L / d, 60 L / L / d, 67 L / L / d, 75 L / L / d, 85 L / L / d, 95 L / L / d, 100 L / L / d, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0150] And / or, the acidification treatment adopts a feeding and discharging method of daily inflow and daily outflow;

[0151] And / or, the hydraulic retention time is 1 day to 4 days, which can be 1 day, 2 days, 3 days, 4 days, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0152] Furthermore, the acid production reaction also includes: the oxidation-reduction potential of the liquid in the acidification phase is -300 mv to -200 mv, which can be -300 mv, -290 mv, -280 mv, -270 mv, -260 mv, -250 mv, -240 mv, -230 mv, -220 mv, -210 mv, -200 mv, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0153] And / or, the pH value of the liquid in the acidification phase is 5 - 12.

[0154] Furthermore, in the anaerobic digestion method, the judgment for stopping the continuous supply of air is:

[0155] When the oxidation-reduction potential of the liquid in the acidification phase is greater than or equal to -200 mv;

[0156] And / or, when the oxygen content in the produced gas of the acidification phase is greater than or equal to 1%.

[0157] Further, the precipitation time of the pretreated wastewater is 60 min to 120 min, which can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0158] Further, the seed sludge in the methanogenic phase is granular sludge for anaerobic treatment of organic wastewater.

[0159] Further, the liquid supply flow rate of the supernatant entering the methanogenic phase is 0.05 L / L / d to 0.1 L / L / d, which can be 0.05 L / L / d, 0.06 L / L / d, 0.07 L / L / d, 0.08 L / L / d, 0.09 L / L / d, 0.1 L / L / d, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0160] (2) Advanced denitrification:

[0161] The anaerobic digestion treatment liquid adopts biological nitrification-denitrification to remove residual organic matters and NH4 + .

[0162] The wastewater 1 after the biological treatment process is sent to the leaching process to wash the residue and is used as dilution water for the concentrated acid hydrolysis process.

[0163] 7). Step S7: Leaching

[0164] The solid residue separated in the solid-liquid separation process is washed by the countercurrent washing process to recover the acid and sugar in the solid residue.

[0165] The countercurrent washing process includes:

[0166] Using fresh water as the tertiary injection water to wash the solid residue for the first time;

[0167] The tertiary drainage separated in the first washing is divided into two paths. The first path is used as the secondary injection water to wash the solid residue for the second time, and the second path is used as the dilution water in the hydrolysis reaction;

[0168] The secondary drainage separated in the second washing is used to wash the solid residue for the third time;

[0169] The primary drainage separated in the third washing enters the filtrate.

[0170] Further, the water consumption of fresh water is 1-2 times the volume of water added in the hydrolysis reaction process;

[0171] And / or, the water consumption of the secondary injection water is 1 / 3 to 1 / 2 of the volume of the tertiary drainage.

[0172] 8. Step S8: Combustion

[0173] The washed solid residue separated in the rinsing process is burned in a biomass boiler, the steam is supplied for ethanol distillation, and the ash fertilizer is used in farmland.

[0174] 9. Step S8: Concentration

[0175] The acid-rich liquid separated in the acid-sugar separation process is passed through a sulfuric acid concentration device to obtain 70-80% concentrated sulfuric acid and condensed water. The recovered concentrated sulfuric acid is reused in the saccharification process.

[0176] 9. Step S9: Acetic acid recovery

[0177] The condensed water recovered in the concentrated acid process is subjected to acetic acid recovery. The recovered sodium acetate is used as a denitrifying carbon source for sewage treatment, and the separated treated water 2 is reused for washing and dehydrating in the acid-sugar separation process.

[0178] To further illustrate the present invention, the following describes the method for preparing fuel ethanol from straw biomass provided by the present invention in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given. It is only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments.

[0179] The acid-to-feed ratio in the present invention is the mass ratio of sulfuric acid to straw.

[0180] The calculation formula for sugar recovery rate is:

[0181]

[0182] It should be noted that the unit: mL / L / min represents the fluid volume per minute in a unit volume (mL).

[0183] The unit: L / L / min represents the fluid volume per minute in a unit volume (L).

[0184] The unit: L / L / d represents the fluid volume per day in a unit volume (L). In the following embodiments of the present invention, the strongly basic anion exchange resin used is DIAION SA10A resin purchased from Mitsubishi Chemical Corporation of Japan. DIAION SA10A is a commercial resin of acrylate type, having excellent chemical stability, mechanical strength and adsorption capacity.

[0185] Example 1:

[0186] In the method for preparing fuel ethanol from straw biomass provided in this example, the zwitterionic exchange resin, and its preparation method includes the following steps:

[0187] Step S1, resin equilibration: An electrolyte solution and ultrapure water were successively added to a chromatographic column (500 ml) filled with chloride-form DIAION SA10A resin in the order of 1M NaCl, ultrapure water, 1M NaOH, ultrapure water, 1M HCl, and ultrapure water for resin equilibration. Each electrolyte solution was 5 L, and the amount of ultrapure water added was until the electrolyte solution was completely washed out.

[0188] Step S2, resin modification: 2.5 L of 1M sodium styrenesulfonate was added to a column (500 ml) filled with chloride-form DIAION SA10A resin to obtain styrenesulfonic acid ion-form DIAION SA10A resin. It was washed with ultrapure water until no styrenesulfonic acid ions were detected in the effluent.

[0189] Step S3, resin activation: The styrenesulfonic acid ion-form DIAION SA10A resin was transferred to a 2 L round-bottom reaction flask using 1 L of ultrapure water. A water-soluble radical initiator, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] N-hydrate, was added. After the initiator was dissolved, the reaction flask was intermittently stirred at room temperature for 2 days to allow the initiator to diffuse into the resin.

[0190] Among them, the molar amounts of sodium styrenesulfonate and azo compound water-soluble radical initiator used for unit volume (L) of chloride-form strongly basic anion exchange resin were 5 moL and 0.2 moL, respectively.

[0191] Step S4: Polymerization of styrenesulfonic acid: The resin mixture obtained in Step S3 was stirred and heated at 72.5 °C for 3 h, and then heated at 82.5 °C for 3 h to polymerize the styrenesulfonic acid in the resin, that is, an amphoteric ion exchange resin suitable for separating high-concentration sulfuric acid and sugar was obtained.

[0192] Step S5: Post-treatment: After cooling, the obtained amphoteric ion exchange resin suitable for separating high-concentration sulfuric acid and sugar was washed with water. Then, the resin was rinsed in a packed column with 1M NaCl solution to replace the unreacted styrenesulfonic acid ions with chloride ions. After supplying 5 L of 1M NaCl in total, no styrenesulfonic acid ions were detected.

[0193] The amphoteric ion exchange resin prepared in this example and suitable for separating high-concentration sulfuric acid and sugar was denoted as DIAION SA10A (modified).

[0194] Application Case 1

[0195] The DIAION SA10A (modified) resin and the DIAION SA10A resin prepared in Example 1 were respectively filled into a glass chromatography column (diameter 1.5 cm, length 30 cm, water circulation temperature control at 50 °C), and the filling volume was 50.9 - 53.4 ml.

[0196] The filled resins were first equilibrated with 30 wt% sulfuric acid and then washed with water until the pH was neutral. A total of 15 ml of the simulated saccharified solution (326 g / L sulfuric acid; 150 g / L glucose) was slowly added to the glass column through a peristaltic pump, and then ultra-pure water was pumped in for elution. The speed of the peristaltic pump was 2 BV (bed volumes) / hour, and the effluent was taken as one sample every 5 ml (0.1 BV) to measure the sulfuric acid and glucose concentrations. The chromatograms of the separation of the DIAION SA10A (modified) resin and the DIAION SA10A resin are shown in Figure 1 and Figure 2 as shown.

[0197] From Figure 1 and Figure 2 it can be seen that both of these two resins, the DIAION SA10A (modified) resin and the DIAION SA10A resin, exhibit good acid-sugar separation curves. Due to the adsorption and retardation effect of the resin on sulfuric acid, glucose flows out of the chromatography column first and sulfuric acid flows out later, showing an obvious separation trend between the two. The two resins show similar glucose distribution curves, however, the distribution curves of sulfuric acid are significantly different: in the Figure 1 effluent, the maximum concentration of sulfuric acid is as high as 252 g / L, and the acid-sugar separation effect is obvious; while in the Figure 2 effluent, the maximum sulfuric acid concentration is less than 200 g / L, lower than that of the DIAION SA10A (modified) resin, and the acid-sugar separation effect is poor. In addition, it can be clearly seen that the sulfuric acid tailing phenomenon disappears in Figure 1 , and Figure 2 shows the sulfuric acid tailing phenomenon.

[0198] Example 2:

[0199] Please refer to Figure 3 as shown. The saccharified solution provided in this example was chromatographically separated in a simulated moving bed chromatography system. From the Figure 1 operating principle of the simulated moving bed chromatography system (SMB) in it, it can be known that the SMB system includes a total of 6 chromatography columns (diameter 30 cm, length 50 cm). The SMB system is divided into four regions: region a, region b, region c, and region d, which are in sequence from left to right as region c, region d, region a, and region b. Among them, region c has 3 chromatography columns, and regions a, b, and d each have one chromatography column.

[0200] The feeding, discharging, and internal circulation of each chromatography column are respectively controlled by three pumps (raw material pump, eluent water pump, and circulation pump) to be completed, with consistent and controllable flow rates.

[0201] One cycle of the operation of the SMB system in this embodiment consists of 6 steps, and each step is further divided into 4 sub-steps (A, B, C, and D). The specific steps are as follows:

[0202] Step A: At the start of the operation, 85.2 ml of the saccharified liquid raw material F (at a rate of 29.5 ml / min) is pumped in at the position indicated by the arrow in the figure. After passing through zone a, the first rich sugar solution R1 is obtained.

[0203] Step B: The stripping water pump runs to pump in 168.2 ml of stripping water W1 (at a rate of 29.5 ml / min). After passing through zone c, the sulfate radicals adsorbed on the stationary phase resin are eluted to obtain the rich acid solution P.

[0204] Step C: Continue to pump in 15.7 ml of stripping water W1. After passing through zones a, b, and c, the subsequent second rich sugar solution R2 is obtained.

[0205] In step D, the internal liquid continuously flows through all the pipelines at a rate of 29.5 ml / min for a total of 6.88 min.

[0206] At the start of the next step, the positions of the feed point and the discharge point both move back one column and repeat from the second step until all 6 steps are completed. After one cycle ends, the next cycle still proceeds in the same manner.

[0207] Application Case 2

[0208] The zwitterionic exchange resin DIAION SA10A (modified) obtained in Example 1 is filled into the simulated moving bed system chromatographic column in Example 2. Each column is filled with approximately 402 ml, and there are a total of six columns, with a total filling volume of 402 * 6 = 2412 ml.

[0209] In accordance with Example 2, after the saccharified liquid is treated with activated carbon to remove colored compounds, SMB will continue to be used for sugar-acid separation. The simulated moving bed chromatographic separation system runs for 1 month. After three cycles, the chromatograph enters a stable state. Samples are taken at the 50th cycle, 70th cycle, and 90th cycle respectively, and separation curves are plotted. The results are shown in Figure 4 .

[0210] It can be seen from Figure 4 that the sugar is not adsorbed by the resin and is separated very early, reaching the peak quickly. The xylose and glucose in the saccharified liquid show similar separation trends; then, the adsorbed acid radicals are eluted from the resin by the stripping water, and then a peak appears.

[0211] Test the material balance of sugar-acid separation in a certain cycle during the operation of the SMB system, and calculate the recovery rates of acid and sugar according to the formula: recovery efficiency = rich sugar / acid liquid component concentration × rich sugar / acid liquid component volume / (hydrolysis liquid component concentration × hydrolysis liquid volume) × 100. The results are shown in Table 1.

[0212] Table 1 Sulfuric acid and sugar material balance table in a certain cycle

[0213]

[0214] As can be seen from the above table, by completing the steps of Example 2, the separation of acid and sugar can be achieved, and the recovery efficiencies reach 98.5 (acid) and 98% (sugar) respectively.

[0215] Example 3

[0216] Please refer to Figure 5 As shown, in the saccharification process of the method for preparing fuel ethanol from straw biomass provided in this example, the following steps are included:

[0217] Step 1, pretreatment: Crush the straw to a diameter of 5 mm, and then dry it until the moisture content of the straw is 5%;

[0218] Step 2, dissolution: Mix the straw with sulfuric acid with a mass fraction of 72% at an acid-to-material ratio of 1.1:1, and carry out a dissolution reaction at 30 °C for 30 min to obtain a dissolved substance;

[0219] Step 3, hydrolysis: Add water at 80 °C to the dissolved substance to dilute the sulfuric acid mass fraction in the dissolved substance to 30%, heat it to 80 °C, and carry out a hydrolysis reaction for 60 min to obtain a hydrolysis liquid containing sugar and straw residue.

[0220] Application Case 3

[0221] Carry out the saccharification process according to an acid-to-material ratio of 1.1:1, including the following steps:

[0222] Weigh 3.0 kg of dried corn straw (sugar content 60%, including 37% glucose and 23% xylose), first add 4.4 kg of 75 wt.% sulfuric acid according to an acid-to-material ratio of 1.1:1, and then add 1.0 kg of straw in three portions every 10 minutes (0 min, 10 min, 20 min). After adding the straw, measure the temperature and heat the material to 50 °C and maintain it for 30 min; Add 3.6 kg of hot water (85 °C) to dilute the sulfuric acid concentration to 30 wt.%, heat the material to 80 °C, and maintain it for 1 h. After the reaction ends, measure the sugar concentration in the mixture to be 83.55 g / kg.

[0223] In addition, the liquid of the mixture after solid-liquid separation (sugar concentration: 166.39 g / L) was taken, diluted 10 times, the pH was adjusted to 0.9, and it was maintained at 121 °C for 1 h. The measured sugar concentration was 211.32 g / L. The oligosaccharide concentration of the mixture was determined to be 46.34 g / kg (the oligosaccharide content was included in the sugar recovery), and the sugar recovery rate was calculated to be 80.60%.

[0224] The acid-to-material ratio was adjusted to 1.2:1, and the sugar concentration of the mixture was measured to be 80.72 g / kg; the oligosaccharide concentration of the mixture was determined to be 42.35 g / kg (the oligosaccharide content was included in the sugar recovery), and the sugar recovery rate was calculated to be 82.04%.

[0225] The acid-to-material ratio was adjusted to 1.3:1, and the sugar concentration of the mixture was measured to be 86.01 g / kg; the oligosaccharide concentration of the mixture was determined to be 30.35 g / kg (the oligosaccharide content was included in the sugar recovery), and the sugar recovery rate was calculated to be 84.04%.

[0226] The acid-to-material ratio was adjusted to 1:1, and the sugar concentration of the mixture was measured to be 70.2 g / kg; the oligosaccharide concentration of the mixture was determined to be 30.35 g / kg (the oligosaccharide content was included in the sugar recovery), and the sugar recovery rate was calculated to be 60.79%.

[0227] The acid-to-material ratio was adjusted to 1.4:1, and the sugar concentration of the mixture was measured to be 80.77 g / kg; the oligosaccharide concentration of the mixture was determined to be 25.22 g / kg (the oligosaccharide content was included in the sugar recovery), and the sugar recovery rate was calculated to be 82.43%.

[0228] Example 4

[0229] Please refer to Figure 5 As shown, in the solid-liquid separation process of the method for preparing fuel ethanol from straw biomass provided in this example, the following steps are included:

[0230] The hydrolysis solution containing monosaccharides and solid residues obtained in Example 3 was subjected to pressure filtration at a pressure of 3 MPa for 20 min to obtain a saccharified solution and solid residues.

[0231] Example 5

[0232] Please refer to Figure 5 As shown, in the acid-sugar separation process of the method for preparing fuel ethanol from straw biomass provided in this example, the following steps are included:

[0233] The saccharified solution obtained in Example 4 was subjected to chromatographic separation using the simulated moving bed chromatography system in Example 2 to separate the acid-rich solution and the sugar-rich solution.

[0234] Example 6

[0235] Please refer to Figure 5 As shown, in the fermentation process of the method for preparing fuel ethanol from straw biomass provided in this example, the following steps are included:

[0236] Add Ca(OH)2 to the sugar-rich solution obtained in Example 5 to adjust the pH to 0.8 - 0.9, heat it at 120 - 130 °C for 50 - 60 min in a bent coiled pipe, convert the oligosaccharides into monosaccharides, and then mix with Saccharomyces cerevisiae SEB3 for fermentation, and generate fuel ethanol through distillation.

[0237] The fermentation treatment of the Saccharomyces cerevisiae SEB3 includes:

[0238] Adjust the pH of the saccharified solution to 3.5, and perform continuous fermentation on the non-sterilized saccharified solution and the sterilized basal medium at a volume ratio of 9:1 to synchronously convert monosaccharides into ethanol;

[0239] Among them, the basal medium includes: 50 g / L of corn steep liquor, 5 g / L of (NH4)2SO4, 5 g / L of KH2PO4, 5 g / L of MgSO4·7H2O, and 10 g / L of CaCl2·2H2O.

[0240] Application Case 4

[0241] For a certain sugar-rich solution with a pH of about 0.56, add Ca(OH)2 to adjust the pH to 0.9, and heat it at 120 °C for 60 min (residence time) in a bent coiled pipe to convert oligosaccharides into monosaccharides: the sugar concentration before oligosaccharide decomposition: 107.2 g / L, the sugar concentration after oligosaccharide decomposition: 141.3 g / L.

[0242] Adopt a tower reactor for continuous ethanol fermentation, which is a tower reactor with a working volume of 0.45 L and a solid-liquid-gas separation device at the upper end. The filtered air continuously enters from the bottom of the reactor through a spherical aeration device, and the aeration rate is set at 0.03 vvm. There is a sandwich in the reactor, which is connected to a constant temperature water bath through a pipeline, and constant temperature circulating water is introduced into the sandwich to control the temperature in the reactor at 35 °C for fermentation experiments. Before the fermentation experiment starts, first sterilize the reactor with 0.2% NaClO solution, then rinse it with sterile water, and then add 0.45 L of pre-culture solution. The non-sterilized saccharified solution (pH 3.5) and the sterilized basal medium (50 g / l of corn steep liquor, 5 g / l of (NH4)2SO4, 5 g / l of KH2PO4, 5 g / l of MgSO4·7H2O, 10 g / l of CaCl2·2H2O) are respectively introduced from the bottom of the reactor at a volume ratio of 9:1 by using P-1 and P-2 peristaltic pumps, and the liquid in the reactor continuously circulates by using a roller pump P-3. The experimental dilution rate is fixed at 0.1 h -1The pH in the reactor was monitored in real time with a pH controller, and a 0.5N NaOH solution was pumped into the reactor by a peristaltic pump P-4 to keep the pH in the reactor constant. The fermented mash overflowed from the solid-liquid-gas separation device at the top of the reactor. The inlet concentrations of glucose and xylose in the tower reactor were 81.7 and 45.4 g / L, respectively. The concentrations of glucose, xylose, and ethanol in the reactor were monitored daily.

[0243] Fermentation results: Residual sugar concentration 10.4 g / L (glucose 0.9 g / L; xylose 9.5 g / L); ethanol concentration 53.1 g / L, sugar consumption efficiency 91.8%, ethanol yield 81.9% (based on total sugar), 89.2% (based on consumed sugar).

[0244] Example 7

[0245] Please refer to Figure 5 As shown, the distillation process in the method for preparing fuel ethanol from straw biomass provided in this example includes the following steps:

[0246] The fermentation broth obtained in Example 6 was subjected to distillation treatment to obtain fuel ethanol and distillation residue.

[0247] Example 8

[0248] Please refer to Figure 5 As shown, the biological treatment process in the method for preparing fuel ethanol from straw biomass provided in this example includes the following steps:

[0249] (1) Acidogenesis reaction: The distillation wastewater filtered from the distillation residue obtained in Example 7 was fed into the acidification phase, and the acidogenesis reaction was carried out under the conditions of introducing air and gas circulation in the acidification phase. Among them, the seed sludge in the acidification phase was granular sludge for anaerobic treatment of organic wastewater. The acidogenesis reaction included: the temperature for anaerobic digestion was 37 °C; the flow rate of introduced air was 10 mL / L / min; the flow rate of gas circulation in the acidification phase was 1 L / L / min; the stirring speed was 80 rpm; the liquid circulation volume was 90 L / L / d; the acidification treatment adopted a daily feeding and discharging method; the hydraulic retention time was 2 days; the redox potential of the liquid in the acidification phase was -250 mv; the pH value of the liquid in the acidification phase was 7.

[0250] The pretreated wastewater after the acidogenesis reaction was precipitated and stratified. Among them, the precipitation time of the pretreated wastewater was 80 min.

[0251] The supernatant of the pretreated wastewater after precipitation and stratification was taken and fed into the methanogenesis phase for methanogenesis reaction. Among them, the seed sludge in the methanogenesis phase was granular sludge for anaerobic treatment of organic wastewater, and the liquid supply flow rate of the supernatant entering the methanogenesis phase was 0.1 L / L / d.

[0252] (2) Deep denitrification

[0253] The biological nitrification-denitrification process removes residual organic matter and NH4 + , where the nitrified liquid is refluxed to the denitrification reactor to achieve internal circulation (the circulation speed is 2 times the feeding speed of the anaerobic treatment liquid raw material), including: a tower reactor, an activated sludge reactor, and a biological nitrification reactor connected in sequence.

[0254] Denitrification treatment: The tower reactor is 0.45L, the temperature is controlled at 37°C (controlled by circulating warm water in the reactor jacket), activated sludge is added to the reactor, and the anaerobic treatment liquid is fed from the lower part of the reactor.

[0255] Aerobic treatment: The activated sludge reactor is 1.3L (internally divided into a static area of 0.3L and an aeration area of 1.0L), the temperature is maintained at 30°C by a heating rod, the air supply rate is 1.3L / L / min, and the upper overflow liquid is fed to the nitrification reactor.

[0256] Biological nitrification: The total volume of the biological nitrification reactor is 2.6L (where the fixed bed area is 1.3L, and a hair curler is placed in the fixed bed area to achieve the attachment of nitrifying bacteria), the temperature is controlled at 30°C by a heating rod, the pH is controlled at about 7.5 by supplying 5% NaHCO3, and the aeration speed is 3L / L / min.

[0257] Experimental results: The TOC concentration of the anaerobic treatment liquid raw material is about 820mg / L; NH4 + 84mg / L. The organic load of the anaerobic treatment liquid is 2g / L / d. After treatment, the TOC concentration is reduced to 240mg / L; NH4 + is reduced to 4mg / L.

[0258] Application Case 5

[0259] (1) Wastewater composition

[0260] Wastewater 1: An artificial wastewater is prepared with glucose as the chemical oxygen demand (COD) source and Na2SO4 as the sulfate source, and the composition is: COD 2000mg / L, SO4 2- 300mg / L.

[0261] Wastewater 2: An artificial wastewater is prepared with glucose as the chemical oxygen demand (COD) source and Na2SO4 as the sulfate source, and the composition is: COD 2000mg / L, SO4 2- 1800mg / L.

[0262] NH4Cl and KH2PO4 were added to wastewater 1 and wastewater 2 as nitrogen source and phosphorus source respectively (the ratio of COD:N:P was 300:5:1), and 1 ml of trace element solution (mg / L) was added to each liter of wastewater: MgCl2·6H2O (100), CaCl2·2H2O (80), FeCl3·6H2O (60), CoCl2·6H2O (0.05), MnCl2·4H2O (0.05), ZnCl2 (0.05), AlCl3·6H2O (0.05), NiCl2·6H2O (0.05), H3BO3 (0.05), CuCl2·2H2O (0.05). The pH of wastewater 1 and wastewater 2 was maintained at 7.0 ± 0.1.

[0263] (2) Seed sludge

[0264] For both the acidification phase and the methanogenesis phase, anaerobic treatment granular sludge from an IC reactor for starch wastewater treatment was used as the seed sludge.

[0265] The seed sludge for both the acidification phase and the methanogenesis phase contained: 11.3 g / L of mixed liquor suspended solids (MLSS) and 9.1 g / L of mixed liquor volatile suspended solids (VSS).

[0266] (3) Experimental procedure

[0267] For the acidification phase reaction, a completely stirred (CSTR) reactor was used (with a total volume and an effective volume of 1.0 L and 0.8 L respectively). For the methanogenesis phase, an IC reactor or a UASB reactor was used (with a total volume and an effective volume of 1.0 L and 0.8 L respectively).

[0268] Using the completely stirred (CSTR) reactor adopted in the acidification phase, the IC reactor or the UASB reactor in the acidification phase as a two-phase reactor, and the completely stirred (CSTR) reactor adopted in the acidification phase as a single-phase reactor for anaerobic digestion reaction. In the completely stirred (CSTR) reactor, the gas from the acidification phase was pumped into the water storage bottle through a gas circulation pump (1.0 L / L / min), and the washed gas was returned to the reactor for the next cycle. While the gas was circulating, a small amount of air (10 ml / L / min) was supplied to the gas path. The reactor temperature was maintained at 37 °C, the stirring speed was 80 rpm, the hydraulic retention time was 2 days, the liquid circulation volume was 90 L / L / d, and the oxidation-reduction potential of the liquid was -250 mv.

[0269] The distilled wastewater treated by the completely stirred (CSTR) reactor was sedimented for 80 min, and the supernatant was fed into the IC reactor or the UASB reactor at a liquid supply rate of 0.1 L / L / d for methanogenesis reaction, which generally took 10 days.

[0270] The experiments of single-phase reactor and two-phase reactor were evenly divided into three stages. In the first stage, wastewater 1 was supplied; in the second stage, wastewater 2 was supplied; in the third stage, wastewater 2 was supplied, but there was no gas circulation and micro-aeration in the acidification phase. The reactor fed and discharged materials in a daily manner. The residence time of the acidification phase was 2 days, and the residence time of the methanogenic phase was 10 days. Each of the three stages was maintained for 30 days.

[0271] (4) Experimental results:

[0272] First stage: Wastewater 1 was respectively supplied into the single-phase reactor and the two-phase reactor. The COD removal rates of the single-phase and two-phase reactors were 93.7% and 93.5% respectively, and the methane yields were 311 ml / g-COD and 307 ml / g-COD respectively.

[0273] It can be seen that due to the low content of SO2 in the wastewater - The H2S reduced from it did not cause obvious inhibition to the single-phase or two-phase reactor. Both configurations showed good performance, and the COD removal rate and methane yield were close.

[0274] Second stage: As wastewater 2 replaced wastewater 1 and was supplied into the single-phase and two-phase reactors, the organic degradation of the single-phase was significantly inhibited. After 30 days of operation, the COD removal rate decreased to about 80%, and the methanogenic efficiency decreased to about 130 ml / g-COD; while the performance of the two-phase reactor was not significantly affected, its COD removal efficiency remained ≥90% (90 - 92%), and the methane production rate ≥300 ml / g-COD (300 - 315 ml / g-COD).

[0275] This is because during the anaerobic digestion process of the single-phase reactor, a high concentration of SO2 - was reduced to H2S, which was toxic to methanogens and even acidogens, resulting in a decrease in COD removal efficiency and methane production efficiency. In the two-phase reactor, since SO2 - was reduced to H2S in the acidification reactor, and H2S reacted with the supplied O2 to produce elemental S and some SO2 - , which settled in the acidification sludge or the upper cover of the reactor. Only the low-sulfur acidification liquid (SO2 - concentration about 438 mg / L) entered the methanogenic phase, and there was no inhibition of H2S on the anaerobic digestion process, especially on methanogens.

[0276] Third stage: Wastewater 2 continued to be supplied into the single-phase and two-phase reactors. The organic degradation of the single-phase reactor was significantly inhibited and continued to decline. After 30 days of operation, the COD removal rate decreased to 60%, and the methanogenic efficiency decreased to about 30 ml / g-COD. The reactor was on the verge of collapse; while the performance of the two-phase reactor also deteriorated. For example, its COD removal efficiency decreased to about 75%, and the methane production rate was about 210 ml / g-COD. This shows that SO2 in the acidification phase- H2S is generated by reduction. Excessive H2S causes severe inhibition of acidifying microorganisms, thus hindering the sulfate reduction process (compared with the second stage, the SO4 in the acidification phase treatment liquid 2- is relatively high, about 1200 mg / L). The sulfate-containing liquid enters the methanogenic phase and is further reduced to produce H2S, resulting in the inhibition of acidifying bacteria and methanogenic bacteria and a low methane production rate. However, because the two-phase system can reduce the inhibition of methanogenic bacteria by providing separate favorable environments compared to the single-phase system.

[0277] Taking a certain distillation wastewater as an example, the COD concentration in this wastewater is 6290 mg / L, and the SO4 2- concentration is 2300 mg / L. This wastewater is anaerobically digested using the two-phase configuration reactor (coupled with a micro-aeration + gas circulation system) in the test example. The reactor operates stably for 90 days, and the COD removal efficiency fluctuates in the range of about 90 - 92.7%, and the stable methane production rate is 301 ml / g-COD.

[0278] Example 9

[0279] Please refer to Figure 5 As shown, in the leaching process of the method for preparing fuel ethanol from straw biomass provided in this example, the following steps are included:

[0280] The solid residue obtained in Example 4 is washed using a countercurrent washing process to recover the acid and sugar in the solid residue. The countercurrent washing process includes:

[0281] Using fresh water as the tertiary injection water to wash the solid residue for the first time; the water consumption of the fresh water is 1 - 2 times the volume of water added in the hydrolysis reaction process;

[0282] The tertiary drainage separated from the first washing is divided into two paths. The first path is used as the secondary injection water to wash the solid residue for the second time, and the second path is used as the dilution water in the hydrolysis reaction; the water consumption of the secondary injection water is 1 / 3 - 1 / 2 of the volume of the tertiary drainage;

[0283] The secondary drainage separated from the second washing is used to wash the solid residue for the third time;

[0284] The primary drainage separated from the third washing enters the filtrate.

[0285] Application Example 6

[0286] In Example (3), the sugar recovery rate after sulfuric acid hydrolysis of corn straw was 80.60% (acid-to-material ratio 1.1.1). The hydrolyzate contained sugar, acid, water, and residues such as insoluble lignin. The hydrolyzate was subjected to solid-liquid separation by plate-and-frame filtration (3 MPa, 30 min) to obtain a saccharified solution and solid residues. The sugar content in the saccharified solution was 40.18%, and the sugar content in the solid residues was 40.42%. It can be seen that the loss of sugar remaining in the residues was relatively serious.

[0287] In order to recover sugar and acid from the solid residues, washing was carried out using a countercurrent washing process with three-stage water injection:

[0288] A total of 5.4 kg of fresh water was used for the three-stage water injection (1.5 times the hydrolysis dilution water);

[0289] The three-stage drainage of about 5.4 kg (1.5 times the hydrolysis dilution water) was divided into two paths. The first path was used as the secondary water injection of 1.8 kg (containing 1 / 3 water), and the second path was used as the dilution water for the hydrolysis section of 3.6 kg (containing 2 / 3 water = hydrolysis dilution water volume) for the concentrated acid hydrolysis process;

[0290] The secondary water injection used the first path of the three-stage drainage of 1.8 kg (containing 1 / 3 water), and the secondary drainage of 1.8 kg (containing 1 / 3 kg water) was used as the primary water injection of 1.8 kg (containing 1 / 3 water);

[0291] The primary drainage of 1.8 kg (containing 1 / 3 water) directly entered the filtrate.

[0292] Using this washing method, 38.43% of the sugar could be recovered from the solid residues (the loss was 1.98%, i.e., <2%), achieving an effective actual sugar recovery; and the sulfur content in the residues after washing was <1% (equivalent to the sulfur content in high-quality coal). The residues were incinerated to produce thermal steam for heat supply links such as ethanol distillation.

[0293] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing fuel ethanol from straw biomass, characterized in that: include: The straw is dissolved in sulfuric acid with a mass fraction of 70% to 80% at an acid-to-solid ratio of (1.1 to 1.3):1 at a temperature of 30°C to 60°C for 30min to 60min to obtain a dissolved product; Add water to the dissolved substance to dilute it until the mass fraction of sulfuric acid in the dissolved substance is 30% to 40%, raise the temperature to 80° C. to 100° C., and perform a hydrolysis reaction for 60 min to 100 min to obtain a hydrolyzate containing sugar and solid residue; The hydrolyzate is filtered to obtain a saccharified liquid, and chromatographic separation is performed in a simulated moving bed chromatography system to separate an acid-rich liquid and a sugar-rich liquid containing oligosaccharides and reducing sugars; After the oligosaccharides in the sugar-rich liquid are converted into monosaccharides, the ethanol is fermented using the SEB3 strain of Saccharomyces cerevisiae, and fuel ethanol is produced through distillation; The simulated moving bed chromatography system comprises 4 to 6 separation columns filled with amphoteric ion exchange resins; The preparation of the amphoteric ion exchange resin comprises: Adding a sodium styrene sulfonate solution to a chromatographic column filled with a chloride ion type strong basic anion exchange resin to modify the exchange resin, thereby obtaining a styrene sulfonic acid ion type strong basic anion exchange resin; The obtained styrene sulfonic acid ion-type strong basic anion exchange resin is transferred, and an azo compound water-soluble free radical initiator is added, and after the initiator is dissolved, intermittent stirring is performed at room temperature for more than 2 days; The stirred resin solution is subjected to a heating polymerization reaction to obtain the amphoteric ion exchange resin; The strong basic anion exchange resin is a resin containing a quaternary ammonium strong basic group.

2. The method for preparing fuel ethanol from straw biomass according to claim 1, characterized in that: The straw is pre-processed by crushing and drying in advance; and, the diameter of the crushed straw is 5mm to 10mm; and, drying until the moisture content of the straw is below 10%; and, The hydrolyzate is filtered to obtain a saccharified liquid, comprising: The hydrolyzate containing sugar and solid residue is subjected to filter pressing treatment at a pressure of 3MPa to 5MPa for 20min to 40min to obtain saccharified liquid and solid residue.

3. The method for preparing fuel ethanol from straw biomass according to claim 1, characterized in that: The plurality of separation columns are divided into region c, region d, region a and region b, region c has 1 to 3 separation columns, and region d, region a and region b each have 1 separation column; The saccharified liquid is subjected to chromatographic separation in a simulated moving bed chromatography system, comprising the following steps: The saccharified liquid is fed into the chromatographic separation system from a feed point, and a first sugar-rich solution is separated from a discharge point after passing through area a; The eluent is fed into the chromatographic separation system from a feed point, and after passing through region c, an acid-rich liquid is separated from a discharge point; The eluent is fed into the chromatographic separation system from a feed point, and after passing through regions c, d, and a in sequence, a second sugar-rich solution is separated from a discharge point; The liquid in the chromatographic separation system passes through area c, area d, area a, and area b in sequence to complete the internal circulation; The above steps are regarded as one process. When the next process is carried out, the positions of the feeding point and the discharging point are moved backward by one separation column, and the area changes accordingly. The separation method is carried out for four to six processes as one cycle. and, the feed amount of the saccharified liquid raw material is 35-70 mL / L-resin, and the feed speed is 12-17 mL / L-resin / min; and, the feed amount of the eluent is 63-175 mL / L-resin, and the flow rate is 12-17 mL / L-resin / min; and, the eluent is dechlorinated tap water; and, the liquid in the chromatographic separation system has an internal circulation flow rate of 84-168 mL / L-resin and a flow rate of 12-17 mL / L-resin / min; and, the feed rate of raw material, feed rate of eluent and internal circulation rate are the same; And, the separation temperature is 35~50℃.

4. The method for preparing fuel ethanol from straw biomass according to claim 3, characterized in that: The azo compound water-soluble free radical initiator includes: azobiscarboxyethyl-2-isobutylamidine hydrate, azobisisobutyronitrile, azobisisopropylimidazoline, azobisN-hydroxyisobutylamidine hydrate or azobisN,N'cyclobutylisobutylamidine hydrate; and, the molar amounts of sodium styrene sulfonate and azo compound water-soluble free radical initiator used per unit volume (L) of chloride ion type strong basic anion exchange resin are 3-8 mol and 0.1-0.5 mol, respectively; and conducting a heating polymerization reaction, including: heating at 70° C. to 75° C. for 1 h to 10 h, and heating the polymerization reaction at 80° C. to 85° C. for 1 h to 10 h.

5. The method for preparing fuel ethanol from straw biomass according to claim 1, characterized in that: The oligosaccharides in the sugar-rich solution are converted into monosaccharides, comprising: Adjust the pH of the sugar-rich solution to 0.8-0.9 and heat at 120°C-130°C for 50-60 minutes.

6. The method for preparing fuel ethanol from straw biomass according to claim 1, characterized in that: The fermentation process of the yeast SEB3 comprises: The pH of the saccharification liquid is adjusted to 3-5, and the unsterilized saccharification liquid and the sterilized basic medium are continuously fermented with Saccharomyces cerevisiae SEB3 at a volume ratio of 9:1 to simultaneously convert monosaccharides into ethanol; The basic culture medium includes: corn steep liquor 50 g / L, (NH4)2SO4 5 g / L, KH2PO4 5 g / L, MgSO4·7H2O 5 g / L and CaCl2·2H2O 10 g / L.

7. The method for preparing fuel ethanol from straw biomass according to claim 1, characterized in that: The method further comprises: the solid residue is washed by a wash process to recover the acid and sugar in the solid residue, the wash process comprising: using fresh water as tertiary injection water to wash the solid residue for the first time; The tertiary drainage separated from the first washing is divided into two paths, the first path is used as secondary injection water for the second washing of the solid residue, and the second path is used as dilution water in the hydrolysis reaction; The solid residue is washed for the third time using the secondary drainage separated from the second washing; The primary drainage separated by the third washing enters the filtrate; And, the amount of fresh water used is 1-2 times the volume of water added in the hydrolysis reaction process; And, the water consumption of secondary injection is 1 / 3 to 1 / 2 of the volume of tertiary drainage.

8. The method for preparing fuel ethanol from straw biomass according to claim 1, characterized in that: The method further comprises: performing anaerobic digestion treatment on the distillation wastewater obtained in the distillation process, comprising: The distilled wastewater is fed into the acidification phase, and an acid-generating reaction is carried out under the conditions of introducing a trace amount of air and circulating the gas in the acidification phase; The pre-treated wastewater after the acid-generating reaction is precipitated and layered; The upper clear liquid in the pre-treated wastewater after sedimentation and stratification is sent to the methanogenic phase for methanogenic reaction; The lower sludge after the sedimentation and stratification treatment is returned to the acidification phase.

9. The method for preparing fuel ethanol from straw biomass according to claim 8, characterized in that: Anaerobic digestion reactions include: The seed sludge of the acidification phase adopts organic wastewater anaerobic treatment granular sludge; and, the temperature for the acid-generating reaction is 35° C. to 37° C., or 53° C. to 55° C.; and, the flow rate of air is 5mL / L / min~15mL / L / min; and, the flow rate of gas circulation in the acidification phase is 0.5L / L / min to 4L / L / min; and, the stirring speed is 60 rpm to 100 rpm; and, the liquid circulation volume is 50L / L / d~100L / L / d; And, the acidification treatment adopts the method of daily inflow and daily outflow; and, hydraulic retention time 1 to 4 days; and, the redox potential of the liquid in the acidified phase is -300mv to -200mv; and, the pH value of the liquid in the acidified phase is 5 to 12; and, performing sedimentation treatment includes: the sedimentation time of the pretreated wastewater is 60min to 120min; and, the seed sludge of the methanogenic phase is granular sludge obtained from anaerobic treatment of organic wastewater; And, the liquid supply flow rate of the supernatant liquid entering the methanogenic phase is 0.05L / L / d to 0.1L / L / d.

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