CN109182394B - Method for producing ethanol by using grains as raw materials - Google Patents
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- CN109182394B CN109182394B CN201811051019.3A CN201811051019A CN109182394B CN 109182394 B CN109182394 B CN 109182394B CN 201811051019 A CN201811051019 A CN 201811051019A CN 109182394 B CN109182394 B CN 109182394B
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- C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
- C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
- C12P7/00—Preparation of oxygen-containing organic compounds
- C12P7/02—Preparation of oxygen-containing organic compounds containing a hydroxy group
- C12P7/04—Preparation of oxygen-containing organic compounds containing a hydroxy group acyclic
- C12P7/06—Ethanol, i.e. non-beverage
- C12P7/08—Ethanol, i.e. non-beverage produced as by-product or from waste or cellulosic material substrate
Abstract
The invention discloses a method for producing ethanol by using grains as raw materials, and belongs to the technical field of wastewater treatment and ethanol fermentation industry. Mixing the membrane filtrate after membrane filtration of anaerobic digestion effluent, refined tower residual liquid, part of sterilized distiller's grain clear liquid and other material mixing water with crushed grain raw materials, and then carrying out liquefaction, saccharification, fermentation, distillation and other processes to obtain ethanol, wherein the membrane filtrate accounts for 40-90% of the total mass of the ingredient water, the refined tower residual liquid accounts for 1-15% of the total mass of the ingredient water, the distiller's grain clear liquid accounts for 1-30% of the total mass of the ingredient water, and the rest is the material mixing water, and controlling the volatile acid concentration of the ingredient water to be 1200mg/L by adjusting the proportion of the membrane filtrate, the refined tower residual liquid, the distiller's grain clear liquid and the other material mixing water or adding acetic acid. The method greatly reduces the wastewater discharge in ethanol production, saves water resources, effectively avoids the problem of acid generation by ethanol fermentation, obviously improves the yield of alcohol, improves the utilization rate of raw materials by 1 to 5 percent, and reduces the energy consumption and the cost of ethanol production.
Description
Technical Field
The invention relates to a method for producing ethanol by using grains as raw materials, belonging to the technical field of wastewater treatment and ethanol fermentation industry.
Background
Ethanol is an important industrial raw material, is widely applied to the industrial fields of food, medicine, chemical industry and the like, is also an important renewable biomass energy source (fuel ethanol), and is highly valued by governments of various countries in the world.
Ethanol is one of the most important bulk fermentation products in the fermentation industry of China. In 2017, more than 131 ethanol production enterprises in the whole country have the total yield of 830 ten thousand tons, and the total yield is the third world. Fifteen committees such as national development reform committee, energy agency, finance department and the like jointly printed implementation schemes about expanding the production of biofuel ethanol and popularizing and using ethanol gasoline for vehicles in 9 months of 2017. The proposal is provided, and the ethanol gasoline for vehicles can be popularized and used nationwide by 2020, so that the full coverage is basically realized. At that time, the demand of fuel ethanol in China will reach 1300 ten thousand tons/year, and the current fuel ethanol yield in China is 260 ten thousand tons/year, so that the newly increased fuel ethanol yield is estimated to reach 1000 ten thousand tons/year at that time, and the total ethanol yield in China will reach nearly 2000 ten thousand tons.
The ethanol industry is rapidly developing, and simultaneously, the ethanol industry faces very outstanding practical problems. Namely, the production process consumes a large amount of starchy raw materials and water resources and generates a large amount of high-concentration organic wastewater (vinasse). According to statistics, more than 60% of ethanol production raw materials in China at present are corn, wheat, aged rice and brown rice, about 3 tons of raw materials and 15-20 tons of process water are consumed for producing one ton of ethanol, and meanwhile, a considerable amount of wastewater is generated. These problems place a significant economic burden on the enterprise. Therefore, how to reduce the wastewater discharge of unit product, reduce water resource consumption, reduce wastewater treatment cost, and improve raw material utilization rate becomes a prominent problem which needs to be solved urgently by the ethanol industry at present.
When corn, wheat, rice and brown rice are used as raw materials to produce ethanol, the conventional process comprises the steps of crushing the raw materials, mixing, liquefying, saccharifying, fermenting, distilling and the like to obtain ethanol, and carrying out solid-liquid separation treatment on the residual distillation waste liquid (whole vinasse) to obtain vinasse clear liquid and wet vinasse residues. The pH value of the liquefaction process is between 5 and 6, the temperature is between 85 and 105 ℃, the liquefaction time is between 80 and 200 minutes, and the addition amount of the liquefying enzyme is between 8 and 20U/g of raw material; the pH value of the saccharification procedure is between 4.2 and 5.6, the temperature is between 58 and 62 ℃, the saccharification time is between 5 and 60 minutes, and the addition amount of the saccharifying enzyme is 120 and 200U/g of raw material; the fermentation adopts natural pH value, the temperature is 28-34 ℃, and the yeast inoculation amount is 10-30% (v/v); the distillation mainly comprises two steps of rough distillation and rectification, equipment such as an aldehyde removing tower, a methanol removing tower and the like can be added according to the quality requirement of the ethanol, and differential pressure distillation or atmospheric distillation can be adopted according to different operating pressures. The clear liquid of the vinasse is evaporated and concentrated to obtain concentrated solution (syrup) and evaporation condensed water, wherein the syrup and wet vinasse slag are mixed and dried to prepare vinasse protein feed (DDGS), the evaporation condensed water is mixed with the raffinate of a rectifying tower and other wastewater in the production process and then enters anaerobic digestion, and the effluent of the anaerobic digestion is further treated by aerobic biochemical treatment, Fenton oxidation and other procedures and then enters a three-level sewage pipe network or is discharged after reaching the standard.
The wastewater in the production process of grain raw material ethanol mainly comprises the following steps: (1) distillation waste liquid: the waste liquid is discharged from a crude distillation tower in the ethanol distillation process, and has the characteristics of high solid content, high COD (chemical oxygen demand) and low pH value; (2) and (3) refining tower raffinate: the waste liquid is discharged from a rectifying tower in the ethanol distillation process, and has the characteristics of limpidity, transparency, low COD, high temperature and no mixed bacteria; (3) evaporating condensed water: the secondary steam condensate water generated by evaporation and concentration of the clear liquid of the vinasse in the DDGS production process is clear and transparent, has low COD and has no mixed bacteria; (4) and (3) other wastewater: is waste water formed by cleaning equipment and the ground in the ethanol production process, and also comprises auxiliary waste water such as water vapor condensate water, water for cooling a pump and the like.
In order to reduce the waste water discharge and the waste water treatment cost, part of the clear liquid of the vinasse is directly reused in the ethanol batching process in the production, but researches show that the reuse proportion of the clear liquid of the vinasse is not more than 30 percent generally, otherwise, substances such as solid matters, acetic acid, lactic acid, sodium salt and the like in the clear liquid of the vinasse can be accumulated to poison ethanol fermentation yeast, so that the utilization rate of raw materials is low. Direct recycling of the vinasse clear solution for blending also has two disadvantages: firstly, the lees clear solution contains miscellaneous fungus, and the retrieval and utilization batching leads to ethanol fermentation to produce acid easily, reduces the material utilization ratio, and secondly, the whitewash pH is low behind the lees clear solution batching, needs to add alkali or ammonia water adjustment pH value to the most suitable pH scope of liquefying enzyme, has increased operation and cost.
The COD of the evaporated condensate is generally lower, about 1500mg/L, and the evaporated condensate does not contain mixed bacteria, and theoretically, the evaporated condensate is recycled without risk of bacteria contamination, but the evaporated condensate contains volatile impurities such as alcohol, aldehyde, acid, ester and the like. Although there are a large number of reports of recycling ingredients of evaporated condensate, practice has proved that even 10% of the ingredients of evaporated condensate in tap water can inhibit the proliferation and fermentation of yeast, reduce the yield of ethanol, and increase the raw material consumption per unit product.
The rectification tower raffinate is waste liquid discharged from a rectification tower in the ethanol distillation process, and the waste liquid is clear and transparent, but contains a certain amount of volatile acid, and the concentration of the volatile acid depends on ethanol fermentation. The volatile acid in the raffinate of the rectifying tower is 800mg/L (calculated by acetic acid) when the ethanol fermentation is normal, and the volatile acid in the raffinate of the rectifying tower can reach 3000mg/L when the ethanol fermentation is abnormal. As the temperature of the raffinate of the fine tower is about 90 ℃, the production is usually used for disinfecting production equipment such as a fermentation tank and the like, and the cleaned raffinate is discharged into an anaerobic digestion system for treatment.
In the existing technical scheme for recycling the clear liquid of the vinasse or the evaporated condensate, the aim of reducing the discharge amount of the wastewater is achieved only by partial recycling from the environmental protection perspective, and the slight influence of the recycling of the clear liquid of the vinasse and the evaporated condensate on the fermentation of the ethanol is ignored. Taking the conventional ethanol fermentation with material mixing concentration as an example, the ethanol concentration of mature fermented mash after the fermentation is finished is about 11-13% (v/v), if the absolute concentration of ethanol is reduced by 0.1-0.2% (v/v) due to the recycling of vinasse clear liquid and evaporation condensed water, the absolute concentration of ethanol is difficult to be perceived in production, but for ethanol production enterprises producing 10 ten thousand tons of ethanol annually, the economic loss caused by the slight influence can reach about 500 million RMB.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, improve the ethanol yield and reduce the raw material consumption while realizing emission reduction and water saving, and achieve the win-win effect of environmental protection and economic benefit.
The invention provides a method for producing ethanol by using grains as raw materials, which comprises the following steps: in the production process of the ethanol, membrane filtrate, fine tower residual liquid and distiller's grain clear liquid which are obtained by membrane filtration of anaerobic digestion effluent are used as ingredient water, wherein the membrane filtrate accounts for 40-90% of the mass of the total ingredient water, the fine tower residual liquid accounts for 1-15% of the mass of the total ingredient water, and the distiller's grain clear liquid accounts for 1-30% of the mass of the total ingredient water; the rectification tower residual liquid is waste liquid discharged from the bottom of a rectification tower in a distillation section, and the distiller's grain clear liquid is obtained by performing solid-liquid separation on the distillation waste liquid in the ethanol production; the anaerobic digestion effluent is obtained by anaerobic digestion of evaporation condensate in ethanol production or evaporation condensate in ethanol production and other wastewater in the production process.
In one embodiment of the invention, the clear stillage solution is sterilized or disinfected before entering the blending process.
In one embodiment of the present invention, the sterilization treatment is performed by keeping the temperature at 60 to 95 ℃ for 15 minutes or more.
In one embodiment of the invention, the evaporation condensed water is obtained by performing solid-liquid separation and evaporation concentration on distillation waste liquid in ethanol production; and in the production process, other waste water is equipment washing water, ground washing water, machine pump cooling water, domestic sewage, distiller's grain clear liquid, fine tower residual liquid or other process waste water.
In one embodiment of the invention, the ingredient water further comprises other ingredient water.
In one embodiment of the invention, the other material mixing water is one or more of tap water, surface cleaning water, tank washing water and cooling water.
In one embodiment of the invention, the method controls the concentration of the volatile acid of the ingredient water to be 100-1200mg/L by adjusting the proportion of the membrane filtrate, the refined tower raffinate, the distiller's grain clear liquid and other ingredient water.
In one embodiment of the invention, acetic acid is added to adjust the concentration of volatile acid when the concentration of volatile acid in the dosing water is less than 100 mg/L.
In one embodiment of the invention, preferably, the membrane filtrate accounts for 65-90% of the total ingredient water by mass, the refined tower raffinate accounts for 5-15% of the total ingredient water by mass, and the distiller's grains clear liquid accounts for 5-20% of the total ingredient water by mass.
In one embodiment of the present invention, preferably, the volatile acid concentration of the stirring water is 300-600 mg/L.
In one embodiment of the invention, part of anaerobic digestion effluent is filtered by a membrane and then recycled for batching, and the rest anaerobic digestion effluent enters an aerobic biochemical system.
In one embodiment of the invention, the solid-liquid separation operation is plate and frame filter pressing or centrifugal separation.
In one embodiment of the present invention, the method specifically comprises the following steps:
(1) mixing 40-90% by mass, 1-15% by mass, 1-30% by mass and 0-58% by mass of membrane filtrate, refined tower residual liquid, distiller's grain clear liquid and other material mixing water obtained by filtering anaerobic digestion effluent with crushed cereal raw materials;
(2) obtaining ethanol, distillation waste liquid and fine tower residual liquid through the processes of liquefaction, saccharification, fermentation and distillation;
(3) the distilled waste liquid is subjected to solid-liquid separation to obtain a clear liquid of the distiller's grains, and 1-30% of the clear liquid of the distiller's grains is subjected to high-temperature sterilization treatment and can be directly recycled as material mixing water; evaporating and concentrating the residual distiller's grain clear liquid to obtain evaporated condensate, and allowing the evaporated condensate and other wastewater in the production process to enter an anaerobic digestion process together to obtain anaerobic digestion effluent;
(4) part of anaerobic digestion effluent is filtered by a membrane to obtain membrane filtrate, and the rest anaerobic digestion effluent enters an aerobic biochemical system; (ii) a
(5) Mixing the refined tower residual liquid obtained in the step (2), the sterilized distiller's grain clear liquid obtained in the step (3) and the membrane filtrate obtained in the step (4) as ingredient water with crushed cereal raw materials for ingredient, and supplementing or adjusting with other ingredient mixing water when the ingredient water is insufficient or the volatile acid concentration of the ingredient water is more than 1200 mg/L;
and (4) sequentially circulating according to the steps (1) to (5), and in the circulating process, adjusting the proportion of the membrane filtrate, the clear liquid of the vinasse, the raffinate of the rectifying tower and other material mixing water according to the concentration of the volatile acid in the material mixing water, or adding acetic acid to ensure that the concentration of the volatile acid in the material mixing water is 100-1200mg/L (calculated by acetic acid).
In one embodiment of the invention, the feed-water ratio g/mL of the grain raw material to the feed water in the feed is 1 to (2-3.5).
In one embodiment of the present invention, the cereal raw material refers to one or more of corn, wheat, rice and brown rice.
In one embodiment of the invention, the membrane filtration is one or more of microfiltration, ultrafiltration or nanofiltration.
In one embodiment of the present invention, the volatile acid is a volatile organic acid such as acetic acid, propionic acid, butyric acid, etc., and is measured by a distillation method, and is calculated as an acetic acid concentration.
In one embodiment of the invention, the pulverization, the blending, the liquefaction, the saccharification, the fermentation, the distillation, the solid-liquid separation, the evaporation concentration and the anaerobic digestion are all conventional technologies in the ethanol production industry.
In one embodiment of the invention, the pH value of the liquefaction process is 5-6, the temperature is 85-105 ℃, the liquefaction time is 80-200 minutes, and the addition amount of the liquefying enzyme is 8-20U/g raw material; the pH value of the saccharification procedure is 4.2-5.6, the temperature is 58-62 ℃, the saccharification time is 5-60 minutes, and the addition amount of the saccharifying enzyme is 100-; the fermentation temperature is 28-38 ℃, and the yeast inoculation amount is 10-30% (v/v); the distillation includes rough distillation and rectification.
In one embodiment of the invention, the DDGS is obtained by drying syrup obtained by evaporating and concentrating wet distiller's grains residue and distiller's grains clear liquid obtained by solid-liquid separation of distillation waste liquid.
The invention has the following advantages:
(1) the membrane filtrate is used as the material mixing water, so that the wastewater reuse proportion can be greatly improved, the wastewater discharge amount is reduced by 6-8 tons per ton of ethanol, and equal water resources are saved: compared with directly recycling the clear liquid of the vinasse and the evaporated condensed water, most of organic matters in the wastewater which are toxic to the ethanol yeast are decomposed by anaerobic methane flora after anaerobic digestion treatment, thereby being beneficial to ethanol production.
(2) The membrane filtrate is used as the material mixing water, so that the problem of acid generation by ethanol fermentation can be avoided to the greatest extent: after membrane separation treatment, organic matters in the anaerobic digestion effluent, which are toxic to the yeast for ethanol fermentation, are further reduced, meanwhile, mixed bacteria in the anaerobic digestion effluent are filtered, and the problem of acid generation in ethanol fermentation can be effectively avoided.
(3) The residual liquid of the fine tower is supplemented as the material mixing water on the basis of the membrane filtrate, the alcohol yield can be obviously improved, the raw material utilization rate is improved by 1-5%, and for an annual 10 ten thousand ton ethanol production enterprise, the ethanol yield can be increased by more than 1000 tons on the premise of the same raw and auxiliary material consumption total amount: the membrane filtrate usually contains no more than 100mg/L of volatile acid, and the concentration of the volatile acid in the material mixing water can be adjusted to be reasonable by supplementing part of the refining tower residual liquid in the membrane filtrate, so that the fermentation performance of the ethanol is improved.
(4) The residual liquid of the fine tower is supplemented on the basis of the membrane filtrate to be used as material mixing water, so that the heat of the residual liquid of the fine tower can be recovered, and the temperature of the slurry after the material mixing is improved, thereby reducing the steam consumption of the liquefaction process; meanwhile, the residual liquid of the fine tower does not contain mixed bacteria, so that the process sanitation of the ethanol fermentation is improved, and the risk of producing acid by the ethanol fermentation is reduced.
(5) Evaporating condensate and other waste water pollutants (COD) during productionLower, the anaerobic digestion effluent after anaerobic digestion has low alkalinity (less than or equal to 1000 mgCaCO)3The concentration of ammonia nitrogen is less than or equal to 100mgL, so that the pH value of the powder slurry is not required to be adjusted by adding sulfuric acid during proportioning, and the cost is lowest.
(6) The membrane filtrate and the raffinate in the fine tower do not contain infectious microbes, the liquefaction process can adopt a low-temperature (86-88 ℃) cooking process, compared with the conventional high-temperature cooking process with the temperature of more than 95 ℃, the energy consumption for ethanol production can be reduced, and the steam consumption of the ethanol liquefaction process per ton can be reduced by more than 10 kg.
Drawings
FIG. 1 is a process flow diagram of the present invention.
Detailed Description
The invention will be further described in connection with fig. 1 and the examples.
The method for measuring the ethanol concentration comprises the following steps: accurately measuring 100mL of fermented mash by using a 100mL volumetric flask, injecting the fermented mash into a 500mL distillation flask, washing the volumetric flask by using 100mL of water, injecting the volumetric flask into the distillation flask, heating and distilling, collecting distillate into the 100mL volumetric flask, taking down the volumetric flask with the distillate when the distillate approaches to a scale, adding water to the scale, and shaking uniformly. Pouring into 100mL clean and dry measuring cylinder, measuring alcohol content and temperature with alcohol meter and thermometer, and making up conversion table according to the measured alcohol concentration and temperature, and converting into 20 deg.C alcohol concentration (%, v/v).
The total volatile acid determination method comprises the following steps: acidifying the waste water with phosphoric acid, evaporating volatile fatty acid, and titrating the distillate with NaOH solution by using phenolphthalein as an indicator. The ammonia nitrogen in the wastewater may interfere with the assay and should therefore be first evaporated under alkaline conditions.
Reagent:
1.10% NaOH solution;
NaOH standard solution, 0.1000 mol/L;
3.10% phosphoric acid solution, 70mL of phosphoric acid with a density of 1.7g/cm3 was diluted to 1L with water;
4. phenolphthalein indicator.
The determination step comprises:
1. 50-200mL of wastewater to be detected is put into a distillation flask, and the content of volatile acid is not more than 30 mmol. If the volume of the water sample is less than 100mL, the water sample can be diluted to 100mL by using distilled water. Adding a few drops of phenolphthalein indicator;
2. adding 10% NaOH solution to make the solution alkaline and make the NaOH slightly excessive;
3. starting distillation until the residual liquid in the distillation flask is 50-60 mL;
4. the remaining liquid in the flask was diluted to the original volume with distilled water, acidified with 10mL of 10% phosphoric acid, and 10mL of distilled water was put into the receiving flask and the receiving flask was connected to a condenser tube on the flask, and the pouring tube was immersed below the liquid level in the receiving flask. Distilling until the liquid in the bottle is 15-20 mL. After the distillation flask is cooled, adding 50mL of distilled water for distillation until 10-20 mL of liquid remains;
5. 10 drops of phenolphthalein were added to the distillate and titrated with NaOH standard solution until a pale pink color did not disappear.
And (3) calculating:
in the formula:
VNaOHtitration of the volume of NaOH standard solution consumed, mL;
c, titrating the accurate concentration of the consumed NaOH standard solution, mol/L;
Vsvolume of wastewater sample to be measured, mL.
The method for measuring the acidity of the mash and the fermented mash comprises the following steps: according to the acid-base neutralization principle, 10mL of crude filtrate is used, phenolphthalein is used as an indicator, 0.1mol/L NaOH standard solution is used for titration, and 1mL of 0.1mol/L NaOH standard solution is consumed, namely 1 degree.
Sucking 1mL of mash or fermentation liquor filtrate, placing in a 250mL triangular flask, adding 50mL of water, adding 2 drops of phenolphthalein indicator, titrating with 0.1mol/LNaOH standard solution, and titrating until the solution is reddish and does not fade within 30 s.
In the formula:
c-concentration of NaOH standard solution, mol/L;
v1-the volume of the sample, mL;
v-volume of NaOH standard solution consumed at titration, mL.
Example 1
The invention relates to a method for producing ethanol by using grains as raw materials, which comprises the following process steps:
mixing the membrane filtrate, the refined tower residual liquid and the clear liquid of the distiller's grains according to the proportion of 90: 5, wherein the concentration of the volatile acid is 100 mg/L; adding 100Kg of pulverized corn flour into 310L of mixed liquid, adding high temperature resistant alpha-amylase (8U/g starch), stirring, heating to 86 deg.C, and maintaining for 200 min; cooling to 60 deg.C, adding diastase (180U/g starch), stirring, and saccharifying for 30 min. After saccharification is finished, the temperature is reduced to 30 ℃, and 10% (v/v) yeast seed liquid is inoculated to start fermentation. After fermentation, ethanol, distillation waste liquid and refined tower residual liquid are obtained through distillation. Filtering the distillation waste liquid by using 60-mesh filter cloth to obtain wet distiller's grains residue and distiller's grains clear liquid, reserving a part of distiller's grains clear liquid, preserving the heat of the distiller's grains clear liquid at the temperature of 60 ℃ for 30 minutes, recycling ingredients, evaporating and concentrating the rest distiller's grains clear liquid to obtain syrup and evaporation condensate, mixing and drying the wet distiller's grains residue and the syrup to obtain DDGS, and allowing the evaporation condensate and other waste water to enter an anaerobic digestion section for treatment. And (3) filtering anaerobic digestion effluent by using an ultrafiltration membrane with the molecular weight cutoff of 10 ten thousand, and mixing membrane filtrate and refined tower residual liquid obtained in a distillation working section in proportion and then recycling the mixture for the next batch of ethanol fermentation. In this way, 10 batches are continuously circulated, the ratio of membrane filtrate to refined tower raffinate is adjusted according to the concentration of acetic acid when different batches are proportioned, and the concentration of volatile acid in the water of the proportioned material is controlled to be about 600 mg/L. The fermentation period of 10 batches of ethanol fermentation is 48h averagely, the average ethanol concentration is 11.2% (v/v), and the average acidity of the fermented mash is 3.2, while the fermentation period of the ethanol fermentation of the tap water mixture of the control group is 56h, the average ethanol concentration is 11.15% (v/v), and the average acidity of the fermented mash is 3.5.
In the embodiment, the natural pH value of the starch slurry after the membrane filtrate, the refined tower residual liquid, the vinasse clear liquid and the corn flour are mixed and blended is between 5.3 and 5.7, so that the pH value is not required to be adjusted by adding sulfuric acid in the liquefaction process. Meanwhile, the average acidity of the fermented mash is reduced by 0.3, the concentration of ethanol is improved by 0.05% (v/v), which is equivalent to the improvement of the utilization rate of raw materials by 0.4%.
Example 2
The invention relates to a method for producing ethanol by using grains as raw materials, which comprises the following process steps:
mixing the membrane filtrate, the refined tower residual liquid and the clear liquid of the distiller's grains according to the proportion of 65: 15: 20, wherein the concentration of the volatile acid is 300 mg/L; adding 100Kg of pulverized brown rice powder into 260L of mixed solution, adding high temperature resistant alpha-amylase (12U/g starch), stirring, heating to 90 deg.C, and maintaining for 160 min; cooling to 60 deg.C, adding saccharifying enzyme (150U/g starch), stirring, and saccharifying for 15 min. After saccharification is finished, the temperature is reduced to 30 ℃, and 15% (v/v) yeast seed liquid is inoculated to start fermentation. After fermentation, ethanol, distillation waste liquid and refined tower residual liquid are obtained through distillation. Filtering the distillation waste liquid by using 60-mesh filter cloth to obtain wet distiller's grains residue and distiller's grains clear liquid, preserving the temperature of the remained distiller's grains clear liquid at 75 ℃ for 15 minutes, recycling ingredients, evaporating and concentrating the remained distiller's grains clear liquid to obtain syrup and evaporation condensate, mixing and drying the wet distiller's grains residue and the syrup to obtain DDGS, and treating the evaporation condensate and other waste water in an anaerobic digestion section. And (3) filtering anaerobic digestion effluent by using an ultrafiltration membrane with the molecular weight cutoff of 30 ten thousand, and mixing membrane filtrate and refined tower residual liquid obtained in a distillation working section in proportion and then recycling the mixture for the next batch of ethanol fermentation. In this way, 10 batches are continuously circulated, the ratio of membrane filtrate to refined tower raffinate is adjusted according to the concentration of acetic acid when different batches are mixed, and the concentration of volatile acid in mixed water is controlled to be about 300 mg/L. The fermentation period of 10 batches of ethanol fermentation is 48h averagely, the average ethanol concentration is 12.15% (v/v), and the average acidity of the fermented mash is 3.2, while the fermentation period of the ethanol fermentation of the tap water mixture of the control group is 56h, the average ethanol concentration is 12.03% (v/v), and the average acidity of the fermented mash is 3.5.
In the embodiment, the natural pH value of the starch slurry after the membrane filtrate, the refined tower residual liquid, the vinasse clear liquid and the corn flour are mixed and blended is between 5.5 and 5.8, so that the pH value is not required to be adjusted by adding sulfuric acid in the liquefaction process. Meanwhile, the average acidity of the fermented mash is reduced by 0.3, the concentration of ethanol is improved by 0.12% (v/v), which is equivalent to the improvement of 1.0% of the utilization rate of raw materials.
Example 3
The invention relates to a method for producing ethanol by using grains as raw materials, which comprises the following process steps:
mixing the membrane filtrate, the refined tower residual liquid and the clear liquid of the distiller's grains according to the proportion of 40: 10: 30, wherein the concentration of the volatile acid is 500 mg/L; adding 2600L mixed solution into 1000Kg of pulverized brown rice powder, adding high temperature resistant alpha-amylase (10U/g starch), stirring, heating to 95 deg.C, and maintaining for 100 min; cooling to 58 deg.C, adding saccharifying enzyme (180U/g starch), stirring, and saccharifying for 30 min. After saccharification is finished, the temperature is reduced to 30 ℃, and 20% (v/v) yeast seed liquid is inoculated to start fermentation. After fermentation, ethanol, distillation waste liquid and refined tower residual liquid are obtained through distillation. Filtering the distillation waste liquid with 60-mesh filter cloth to obtain wet distiller's grains residue and distiller's grains clear liquid, keeping the temperature of part of distiller's grains clear liquid at 60 deg.C for 15min, recycling the ingredients, and evaporating and concentrating the rest distiller's grains clear liquid to obtain syrup and evaporated condensate. Mixing and drying the wet distillers' grains and syrup to obtain DDGS, and treating the evaporated condensed water and other waste water in an anaerobic digestion section. The effluent of anaerobic digestion is filtered by an ultrafiltration membrane with molecular weight cutoff of 80 ten thousand, and the membrane filtrate and the refined tower residual liquid obtained in the distillation section are mixed in proportion and then are reused for the next batch of ethanol fermentation. In this way, 10 batches of ethanol fermentation were continuously circulated, the fermentation period of 10 batches of ethanol fermentation was 48h on average, the average ethanol concentration was 12.16% (v/v), and the average acidity of the fermented mash was 3.2, while the fermentation period of ethanol fermentation of the tap water ingredient of the control group was 56h, the average ethanol concentration was 12.03% (v/v), and the average acidity of the fermented mash was 3.5.
In the embodiment, the natural pH value of the starch slurry after the membrane filtrate, the refined tower raffinate, the vinasse clear liquid and the corn flour are mixed and blended is between 5.5 and 5.9, so that the pH value is not required to be adjusted by adding sulfuric acid in the liquefaction process. Meanwhile, the average acidity of the fermented mash is reduced by 0.3, the concentration of ethanol is improved by 0.13% (v/v), which is equivalent to the improvement of 1.1% of the utilization rate of raw materials.
Example 4
The invention relates to a method for producing ethanol by using grains as raw materials, which comprises the following process steps:
mixing the membrane filtrate, the refined tower residual liquid, the distiller's grain clear liquid and tap water according to the proportion of 40: 10: 40, and adding acetic acid to ensure that the concentration of the volatile acid in the ingredient water reaches 1200 mg/L; adding 1000Kg of pulverized brown rice powder into 2600L of the mixed solution, adding high temperature resistant alpha-amylase (16U/g starch), stirring, heating to 90 deg.C, and maintaining for 120 min; cooling to 60 deg.C, adding diastase (180U/g starch), stirring, and saccharifying for 30 min. After saccharification is finished, the temperature is reduced to 30 ℃, and 30% (v/v) yeast seed liquid is inoculated to start fermentation. After fermentation, ethanol, distillation waste liquid and refined tower residual liquid are obtained through distillation. Filtering the distillation waste liquid with 60-mesh filter cloth to obtain wet distiller's grains residue and distiller's grains clear liquid, keeping the temperature of part of distiller's grains clear liquid at 80 deg.C for 15min, recycling the ingredients, and evaporating and concentrating the rest distiller's grains clear liquid to obtain syrup and evaporated condensate. Mixing and drying the wet distillers' grains and syrup to obtain DDGS, and treating the evaporated condensed water and other waste water in an anaerobic digestion section. And (3) filtering anaerobic digestion effluent by using an ultrafiltration membrane with the molecular weight cutoff of 30 ten thousand, and mixing membrane filtrate and refined tower residual liquid obtained in a distillation working section in proportion and then recycling the mixture for the next batch of ethanol fermentation. In this way, 10 batches of ethanol fermentation were continuously circulated, the fermentation period of the 10 batches of ethanol fermentation was 52h on average, the average ethanol concentration was 12.03% (v/v), and the average acidity of the fermented mash was 3.2, while the fermentation period of the ethanol fermentation of the tap water mixture of the control group was 56h, the average ethanol concentration was 12.03% (v/v)), and the average acidity of the fermented mash was 3.5.
In the embodiment, the natural pH value of the starch slurry after the membrane filtrate, the refined tower raffinate, the distiller's grain clear liquid, the tap water and the corn flour are mixed and blended is between 5.2 and 5.7, so the pH value is not required to be adjusted by adding sulfuric acid in the liquefaction process. Meanwhile, the average acidity of the fermented mash is reduced by 0.3, and the concentration of ethanol is equivalent to that of tap water.
Example 5
The invention relates to a method for producing ethanol by using grains as raw materials, which comprises the following process steps:
continuously mixing the membrane filtrate, the refined tower raffinate and the clear liquid of the distiller's grains at a ratio of 70: 15 in a material mixing water tank, and continuously feeding the mixed liquid into a material mixing tank by a pump while mixing, wherein the flow rate of the mixed liquid is 105m3The concentration of the volatile acid of the mixed solution fluctuates between 300 and 800 mg/L; continuously adding pulverized corn flour in a mixing tank at the same time, wherein the mass flow rate of the corn flour is 37.5t/h, and the raw material is 16U/gContinuously adding high-temperature resistant alpha-amylase in concentration unit; continuously heating the mixed powder slurry to 88 ℃ through a heater for liquefaction, continuously feeding and continuously discharging the liquefied mash in a liquefaction tank, and keeping the liquefied mash in the liquefaction tank for 120 min; continuously cooling the liquefied mash to 60 ℃ through a heat exchanger after liquefaction, feeding the liquefied mash into a saccharifying tank, continuously adding saccharifying enzyme into the saccharifying tank according to the concentration unit of 160U/g raw material, continuously feeding and discharging the material in the saccharifying tank, and keeping the saccharified mash in the saccharifying tank for 30 min; continuously pumping the mash into a heat exchanger by a pump, cooling to 30 deg.C, feeding into a fermentation tank, inoculating 25% (v/v) yeast seed solution, and allowing the fermentation tank to have a total volume of 1200m31000m of charge3After the fermentation tank is filled, the mash is fed into another fermentation tank through a switching valve, the operation is repeated, the temperature is controlled at 30-36 ℃ by a heat exchanger in the fermentation process, and the fermentation time of a single fermentation tank is 50-62 hours. After the fermentation is finished, performing differential pressure distillation on the two towers to obtain ethanol, distillation waste liquid and refining tower residual liquid; leave 15.75m3And continuously refluxing the residual liquid of the fine tower to a material mixing water tank, and allowing the residual liquid of the fine tower to pass through an anaerobic digestion tank. Filtering the distillation waste liquid with 60 mesh filter cloth plate frame to obtain wet distiller's grains residue and distiller's grains clear liquid, and reserving 15.75m3And h, preserving the temperature of the clear liquid of the vinasse at 65 ℃ for 40 minutes for sterilization, continuously refluxing to the material mixing water tank, and carrying out triple-effect evaporation and concentration on the clear liquid of the remaining vinasse to obtain syrup and evaporation condensate. Mixing and drying the wet distillers' grains and syrup to obtain DDGS, and treating the evaporated condensed water and other waste water in an anaerobic digestion section. The effluent of the anaerobic digestion is filtered by an ultrafiltration membrane with the molecular weight cutoff of 80 ten thousand, and the flow rate is 73.5m3And/h, continuously refluxing the membrane filtrate to a material mixing water tank, and mixing the membrane filtrate with the refined tower residual liquid and the distiller's grain clear liquid in proportion for the next batch of ethanol fermentation. In this way, 10 batches are continuously circulated, the ratio of membrane filtrate to refined tower raffinate is adjusted according to the concentration of acetic acid when different batches are mixed, and the concentration of volatile acid in mixed water is controlled to be about 300 mg/L. The fermentation period of 10 batches of ethanol fermentation is 48h averagely, the average ethanol concentration is 11.46% (v/v), and the average acidity of the fermented mash is 3.2, while the fermentation period of the ethanol fermentation of the tap water mixture of the control group is 56h, the average ethanol concentration is 11.34% (v/v), and the average acidity of the fermented mash is 3.5.
In the embodiment, the natural pH value of the slurry after the membrane filtrate, the refined tower raffinate and the corn flour are mixed and blended is between 5.5 and 5.9, so that the pH value is not required to be adjusted by adding sulfuric acid in the liquefaction process. Meanwhile, the average acidity of the fermented mash is reduced by 0.3, the concentration of ethanol is improved by 0.12% (v/v), which is equivalent to the improvement of 1.0% of the utilization rate of raw materials.
Example 6: effect of Water of batch containing different concentrations of acetic acid on ethanol fermentation
As shown in Table 1, the ethanol fermentation was carried out by adjusting the concentration of the volatile acid in the feed water by adding acetic acid, and as compared with tap water, the ethanol concentration was significantly increased when the concentration of the volatile acid in the feed water was not more than 1000mg/L, while the ethanol yeast growth was suppressed and the ethanol concentration was decreased when the concentration of the volatile acid was more than 1200 mg/L.
TABLE 1 comparison table of fermentation of ingredient water and tap water with different acetic acid concentrations
| Volatile acid mg/L | 0 (tap water) | 100 | 300 | 500 | 800 | 1000 | 1200 | 1400 |
| Ethanol% (v/v) | 12.03 | 12.08 | 12.15 | 12.16 | 12.11 | 12.05 | 12.03 | 11.32 |
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (4)
1. A method for producing ethanol by using grains as raw materials is characterized by comprising the following steps: in the production process of the ethanol, membrane filtrate, fine tower residual liquid and distiller's grain clear liquid which are obtained by membrane filtration of anaerobic digestion effluent are used as ingredient water, wherein the membrane filtrate accounts for 40-90% of the mass of the total ingredient water, the fine tower residual liquid accounts for 1-15% of the mass of the total ingredient water, and the distiller's grain clear liquid accounts for 1-30% of the mass of the total ingredient water; the rectification tower residual liquid is waste liquid discharged from the bottom of a rectification tower in a distillation section, and the distiller's grain clear liquid is obtained by performing solid-liquid separation on the distillation waste liquid in the ethanol production; the anaerobic digestion effluent is obtained by anaerobic digestion of evaporation condensate in ethanol production or evaporation condensate in ethanol production and other wastewater in the production process;
wherein the distillation waste liquid refers to waste liquid discharged from the bottom of a crude distillation tower in a distillation section; the evaporation condensed water is obtained by carrying out solid-liquid separation and evaporation concentration on the distillation waste liquid in the ethanol production; the other waste water in the production process is one or more of equipment washing water, ground washing water, machine pump cooling water, domestic sewage, fine tower residual liquid or other process waste water; before the clear liquid of the vinasse enters the batching procedure, the clear liquid of the vinasse needs to be sterilized or degerming; the method controls the concentration of volatile acid of the ingredient water to be 100-1000mg/L by adjusting the proportion of membrane filtrate, refined tower raffinate, distiller's grain clear liquid and other material mixing water;
the method specifically comprises the following steps:
(1) mixing 40-90% by mass, 1-15% by mass, 1-30% by mass and 0-58% by mass of membrane filtrate, refined tower residual liquid, distiller's grain clear liquid and other material mixing water obtained by filtering anaerobic digestion effluent with crushed cereal raw materials;
(2) obtaining ethanol, distillation waste liquid and fine tower residual liquid through the processes of liquefaction, saccharification, fermentation and distillation;
(3) the distilled waste liquid is subjected to solid-liquid separation to obtain a clear liquid of the distiller's grains, and 1-30% of the clear liquid of the distiller's grains is subjected to high-temperature sterilization treatment and can be directly recycled as material mixing water; evaporating and concentrating the residual distiller's grain clear liquid to obtain evaporated condensate, and allowing the evaporated condensate and other wastewater in the production process to enter an anaerobic digestion process together to obtain anaerobic digestion effluent;
(4) part of anaerobic digestion effluent is filtered by a membrane to obtain membrane filtrate, and the rest anaerobic digestion effluent enters an aerobic biochemical system;
(5) mixing the refined tower residual liquid obtained in the step (2), the sterilized distiller's grain clear liquid obtained in the step (3) and the membrane filtrate obtained in the step (4) as ingredient water with crushed cereal raw materials for ingredient, and supplementing or adjusting with other ingredient mixing water when the ingredient water is insufficient or the volatile acid concentration of the ingredient water is more than 1000 mg/L;
and (5) circulating in sequence according to the steps (1) to (5), and in the circulating process, adjusting the proportion of the membrane filtrate, the clear liquid of the vinasse, the raffinate of the rectifying tower and other material mixing water according to the concentration of the volatile acid in the material mixing water, or adding acetic acid to ensure that the concentration of the volatile acid in the material mixing water is 1000 mg/L-100.
2. The method for producing ethanol by using grains as raw materials according to claim 1, wherein the other material mixing water is one or more of tap water, clean surface water, tank washing water and cooling water.
3. The method for producing ethanol from grain as raw material according to claim 1, wherein the grain raw material is one or more of corn, wheat, rice and brown rice.
4. The method for producing ethanol from grains as claimed in claim 1 or 3, wherein the liquefaction process is carried out at a pH of 5-6, a temperature of 85-105 ℃, a liquefaction time of 80-200 minutes, and an amount of the added liquefaction enzyme is 8-20U/g of the raw material; the pH value of the saccharification procedure is 4.2-5.6, the temperature is 58-62 ℃, the saccharification time is 5-60 minutes, and the addition amount of the saccharifying enzyme is 100-; the fermentation temperature is 28-38 ℃, and the yeast inoculation amount is 10-30% (v/v); the distillation includes rough distillation and rectification.
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