Continuous fermentation method of ethanol

Abstract

The present invention relates to the field of ethanol fermentation, and discloses a continuous fermentation method of ethanol, which comprises: sequentially crushing, slurrying and liquefying a starchy raw material to obtain a liquefied mash; performing a first heat exchange on the liquefied mash to obtain a material after the first heat exchange; adding a first saccharifying enzyme to the material after the first heat exchange, and then performing a second heat exchange to obtain a material after the second heat exchange; adding a second saccharifying enzyme to the material after the second heat exchange to obtain a fermented material, and then performing continuous fermentation to obtain ethanol; wherein the temperature of the material after the first heat exchange is 35-60°C; and the temperature of the material after the second heat exchange is 27-35°C. The technical solution of the present invention can effectively improve the ethanol concentration in the mature mash obtained by the continuous fermentation process (up to 15.5% v / v), improve production capacity, and save water consumption and steam consumption.

Description

Technical Field

[0001] The invention relates to the technical field of fuel ethanol, and in particular to a continuous fermentation method of ethanol. Background Art

[0002] The fuel ethanol production process can be divided into intermittent fermentation process and continuous (including semi-continuous or fully continuous, the same below) fermentation process according to the different fermentation methods. In 2020, my country's total fuel ethanol production capacity was about 6 million tons, of which about 3 million tons were produced by continuous fermentation process, accounting for about 50% of the total production capacity. Most of the domestic devices using intermittent fermentation technology have achieved concentrated mash fermentation, and the ethanol concentration of mature fermented mash is above 15% (v / v). However, in the continuous fermentation process, due to the use of separate saccharification and continuous fermentation processes, it is difficult to achieve low residual sugar and high alcohol fermentation. The ethanol concentration of mature fermented mash is generally 13.0%-13.5% (v / v), and some factories can achieve 14% (v / v) alcohol fermentation. Summary of the invention

[0003] The purpose of the present invention is to provide a new continuous fermentation method of ethanol without changing the continuous fermentation process, aiming at the problem of low ethanol concentration in mature mash in the existing alcohol continuous fermentation process. The method adopts dispersed addition of saccharifying enzyme combined with synchronous saccharification and fermentation process, which can effectively improve the ethanol concentration of mature mash, increase production capacity, and save water and steam consumption.

[0004] In order to achieve the above object, the present invention provides a continuous fermentation method of ethanol, which comprises: sequentially crushing, slurry conditioning and liquefying a starchy raw material to obtain a liquefied mash;

[0005] Performing a first heat exchange on the liquefied mash to obtain a material after the first heat exchange;

[0006] adding a first saccharifying enzyme to the material after the first heat exchange, and then performing a second heat exchange to obtain a material after the second heat exchange;

[0007] adding a second saccharifying enzyme to the material after the second heat exchange to obtain a material to be fermented, and then fermenting it to obtain ethanol;

[0008] The temperature of the material after the first heat exchange is 35-60°C; the temperature of the material after the second heat exchange is 27-35°C.

[0009] Preferably, the temperature of the material after the first heat exchange is 40-50°C.

[0010] The technical solution of the present invention can effectively improve the ethanol concentration in the mature mash obtained by the continuous fermentation process (up to 15.5% v / v), increase production capacity, and save water and steam consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a flow chart of the continuous fermentation of ethanol described in Example 1 of the present invention;

[0012] Figure 2 This is a flow chart of the continuous fermentation of ethanol described in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0013] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0014] The present invention provides a continuous fermentation method of ethanol, which comprises: sequentially crushing, slurry conditioning and liquefying a starchy raw material to obtain liquefied mash;

[0015] Performing a first heat exchange on the liquefied mash to obtain a material after the first heat exchange;

[0016] adding a first saccharifying enzyme to the material after the first heat exchange, and then performing a second heat exchange to obtain a material after the second heat exchange;

[0017] adding a second saccharifying enzyme to the material after the second heat exchange to obtain a material to be fermented, and then fermenting it to obtain ethanol;

[0018] The temperature of the material after the first heat exchange is 35-60°C; the temperature of the material after the second heat exchange is 27-35°C.

[0019] The starchy raw material may be a conventional starchy raw material in the art, and is preferably selected from at least one of brown rice, rice, corn and wheat.

[0020] In the present invention, when the starchy raw material contains at least two raw materials, the usage ratio of each raw material is not particularly limited, and those skilled in the art can select it according to needs.

[0021] One of the characteristics of rice is that it is not easy to preserve. It is very easy to age and mold. Under normal storage conditions, 0.5-1 year of storage will inevitably lead to aging of grains. Aged grains are not accepted by consumers because of their poor color, aroma and taste due to the deterioration of quality, especially edible quality. Eventually, they are unsalable and stored in warehouses, or auctioned at a low price or treated as feed grain, which greatly reduces the utilization rate of stored rice resources and causes huge economic losses. Other grain reserves also have the same problem that needs to be solved urgently.

[0022] In order to solve this problem, the brown rice, rice, corn and wheat are preferably aged brown rice, aged rice, aged corn and aged wheat, respectively and independently.

[0023] In the present invention, the pulverization may be performed by a conventional method in the art, and the pulverization method includes: pulverizing the starchy raw material to obtain a pulverized product. The pulverization may be performed in a pulverizer.

[0024] In the present invention, the pulverization conditions are not particularly limited. Preferably, the pulverization conditions are such that 70-95% by weight of the pulverized material can pass through a 20-mesh sieve.

[0025] In the present invention, the slurry preparation method may not be particularly limited. Preferably, the slurry preparation method includes: slurrying the pulverized material to obtain a slurry preparation liquid.

[0026] In the present invention, the slurry adjustment conditions may not be particularly limited. Preferably, the slurry adjustment conditions are such that the obtained slurry adjustment liquid has a dry matter concentration of 28-34% by weight.

[0027] In the present invention, the slurry adjustment temperature may be 35-95°C, preferably 60-70°C or 80-90°C.

[0028] The slurry adjustment process may further include a step of adjusting pH, and the adjusted pH is 3-8, preferably 4-6.5.

[0029] The pH can be adjusted by adding a pH adjuster, which can be an acid or base commonly used in the art, such as at least one of hydrochloric acid, sulfuric acid, nitric acid, potassium hydroxide, sodium hydroxide, calcium hydroxide, ammonia water and sodium carbonate, preferably ammonia water.

[0030] In the present invention, the liquefaction method comprises: liquefying the slurry obtained by slurry conditioning in the presence of amylase to obtain liquefied mash.

[0031] It should be understood that the amylase can be added during the slurry conditioning process or before liquefaction.

[0032] The amount of amylase added can be selected within a wide range. Preferably, the amount of amylase added is 10-40 U / g starchy raw material.

[0033] Preferably, the liquefaction temperature is 75-120°C, more preferably 80-105°C; the liquefaction time is 0.5-6h, more preferably 1.5-5h.

[0034] Preferably, the pH of the liquefied mash is 3.5-5.5.

[0035] The pH can be adjusted by adding a pH adjuster, which can be an acid or base commonly used in the art, such as at least one of hydrochloric acid, sulfuric acid, nitric acid, potassium hydroxide, sodium hydroxide, calcium hydroxide, ammonia water and sodium carbonate, preferably ammonia water.

[0036] Preferably, when the starchy raw material comprises wheat, the liquefaction method further comprises: adding xylanase to the slurry.

[0037] Preferably, the added amount of the xylanase is 1-10 U / g wheat.

[0038] The liquefaction method may be a conventional liquefaction method in the art, such as a jet liquefaction method or a cooking method.

[0039] Preferably, the conditions of the spray liquefaction method include: the spray temperature is 90-105°C.

[0040] Specifically, the jet liquefaction method may include, for example, heating the slurry to 90-105° C. by steam through an ejector, cooling the slurry to 84-94° C. through a pressure tank and a flash tank, and entering a liquefaction tank for liquefaction for 2.5-4 hours.

[0041] Preferably, the method further comprises: before the spraying liquefaction, controlling the temperature of the slurry to be within the range of 40-70°C or 80-90°C.

[0042] Specifically, the cooking method may include, for example, cooking the slurry at 84-94° C. for 15-60 minutes and then liquefying it for 2.5-4 hours.

[0043] In the present invention, the liquefied mash is subjected to a first heat exchange to obtain a material after the first heat exchange, a first saccharifying enzyme is added to the material after the first heat exchange, and then a second heat exchange is performed to obtain a material after the second heat exchange; a second saccharifying enzyme is added to the material after the second heat exchange to obtain a material to be fermented. After the first saccharifying enzyme is added to the material after the first heat exchange, pre-saccharification, i.e., partial saccharification, is performed.

[0044] Preferably, the temperature of the material after the first heat exchange is 40-50°C.

[0045] Preferably, the temperature of the material after the second heat exchange is 28-32°C.

[0046] The first heat exchange and the second heat exchange can be performed in a conventional heat exchanger in the art, as long as the material after heat exchange can reach the corresponding temperature. The first heat exchange and the second heat exchange can be performed once in one heat exchanger to the target temperature, or can be performed in at least two heat exchangers to the target temperature.

[0047] The first saccharifying enzyme and the second saccharifying enzyme may be the same or different, for example, they may be saccharifying enzymes purchased from Shandong Longkote Co., Ltd. (150,000 U / mL or 290,000 U / mL).

[0048] Preferably, the total amount of saccharifying enzyme added is 100-250 U / g starch raw material. The total amount of saccharifying enzyme added is the sum of the amount of the first saccharifying enzyme added and the amount of the second saccharifying enzyme added.

[0049] Preferably, the amount of the first saccharifying enzyme added is 30-70% of the total amount added, more preferably 30-45%. That is, the amount of the second saccharifying enzyme added is 30-70% of the total amount added, more preferably 55-70%. It should be understood that the amount added here is based on enzyme activity units. If the first saccharifying enzyme and the second saccharifying enzyme are of the same type, they can also be based on weight.

[0050] Preferably, the fermentation method comprises: adding yeast mash to the material to be fermented, and fermenting to obtain ethanol.

[0051] Preferably, the fermentation is fully continuous fermentation or semi-continuous fermentation. Fully continuous fermentation means that several fermentation tanks are connected in series to complete the entire fermentation process, and the materials flow into each level of fermentation tank in turn, and the fermented materials are discharged from the last fermentation tank; semi-continuous fermentation means that several continuous tanks at the front end are connected in series for continuous fermentation, and several tanks at the back end are independent intermittent tanks. After the materials are discharged from the continuous tanks, they can enter any intermittent tank for subsequent fermentation to ensure complete fermentation.

[0052] The fermentation can be carried out in a conventional fermentation system in the art. For example, when the fermentation is a semi-continuous fermentation, the fermentation system can include at least two pipelines including at least two continuous fermentation tanks connected in series, and at least four intermittent fermentation tanks connected in parallel. The continuous fermentation tank is upstream of the intermittent fermentation tank. Those skilled in the art can select the number of suitable fermentation tanks and their connection mode as needed.

[0053] In the present invention, yeast mash refers to the culture solution obtained by culturing brewing yeast, which is used as the seed solution for fermentation to produce ethanol. The yeast can be conventional yeast in the art, such as super brewing high-activity dry yeast purchased from Angel Yeast and Falquet brewing high-activity dry yeast from Lesaffre.

[0054] In the present invention, the brewer's yeast can be directly inoculated into the yeast culture medium in the form of dry powder for fermentation, or it can be activated before inoculation and then cultured.

[0055] The number of viable bacteria in the yeast dry powder can be selected in a wide range, preferably 2×10 10 Pieces / g or more.

[0056] The activation method may be a conventional method in the art, such as connecting the strain to an activation tank, mixing with water for activation, and obtaining an activation solution. Carbon sources, such as liquefied mash or fermented materials, may also be added to the activation tank as needed to activate the strain. The activation pH may be 4-7, preferably 3-6; the activation temperature may be 30-40°C, preferably 32-37°C; and the activation time may be 0.5-2h.

[0057] The yeast mash can be produced by continuous fermentation or intermittent fermentation. Preferably, the production method of the yeast mash includes: inoculating yeast into a yeast culture medium, culturing for 8-16 hours, using part of the obtained yeast mash for fermentation, and continuously culturing the remaining part, and ending the culturing after 36-72 hours.

[0058] If the yeast mash is produced by intermittent fermentation, the culture can be ended after 8-16 hours of culture.

[0059] The pH value during the yeast culture process can be 2-6, preferably 3-5; the culture temperature can be 25-35°C, preferably 28-32°C.

[0060] In the present invention, the inoculation amount of the yeast starter can be selected in a wide range. For example, the inoculation amount of the yeast starter is such that the number of yeasts in the fermentation medium is 1×10 8 pcs / mL or more, preferably 1-9×10 8 Pieces / mL.

[0061] Preferably, the yeast culture medium comprises the second heat-exchanged material and / or the material to be fermented, a nitrogen source and an acidic protease, and more preferably, the yeast culture medium comprises the second heat-exchanged material, a nitrogen source and an acidic protease. In the preferred case, the fermentation effect can be further improved.

[0062] Among them, the addition of nitrogen source and acidic protease is not only used for the cultivation of yeast but also for subsequent fermentation.

[0063] In the present invention, the nitrogen source may be a nitrogen source conventionally used in the art, preferably urea.

[0064] In the present invention, the acidic protease may be an acidic protease commonly used in the art, preferably, the enzyme activity of the acidic protease is 50,000-200,000 U / g. The acidic protease may be commercially available.

[0065] Preferably, in the yeast culture medium, the dosage of the acidic protease is 5-20U / g starch raw material.

[0066] Preferably, in the yeast culture medium, the amount of nitrogen source used is 1-2.4 mg / g starch raw material.

[0067] The starchy raw materials here refer to the total starchy raw materials, including the starchy raw materials corresponding to the yeast culture medium and the fermentation medium.

[0068] The fermentation is carried out in a fermentation tank, and the fermentation starter mash obtained by the culture can be inoculated into a fermentation tank containing materials to be fermented as needed, and the inoculation amount can be selected within a wide range. Generally speaking, when the fermentation is intermittent fermentation, the inoculation amount of the fermentation starter can be relatively small, such as 5-15% by volume; but the inoculation amount during continuous fermentation is higher, such as 35-60% by volume. The inoculation amount is the percentage of the fermentation starter mash in the total volume of the fermentation liquid.

[0069] In the present invention, the fermentation conditions can be selected within a wide range. Preferably, the fermentation conditions include: temperature of 25-38° C., pH of 2-6, and time of 45-78 h.

[0070] In the present invention, the product obtained by fermentation can also be subjected to crude distillation and rectification to obtain fuel ethanol. Those skilled in the art can perform the operation as needed, which will not be described in detail here.

[0071] In the present invention, the water used in the yeast culture and fermentation process is conventional water in the art, such as at least one of fresh water, process water and reclaimed water. Those skilled in the art can select the amount of each type of water according to actual conditions.

[0072] In the present invention, each step is carried out in conventional equipment, and those skilled in the art can select according to needs.

[0073] In the present invention, the ethanol content can be measured by a distillation method.

[0074] The present invention will be described in detail below through examples.

[0075] In the following examples, the yeast was super brewing high-activity dry yeast purchased from Angel Yeast Co., Ltd.

[0076] The amylase was a thermostable α-amylase purchased from DuPont, with an enzyme activity of 140,000 U / g;

[0077] Xylanase was purchased from Shandong Longkote Co., Ltd. (super heat-resistant), with an enzyme activity of 30,000 U / mL;

[0078] The saccharifying enzyme was purchased from Shandong Longkote Enzyme Preparation Co., Ltd., with an enzyme activity of 290,000 U / g;

[0079] Acidic protease was purchased from Shandong Longkote Enzyme Preparation Co., Ltd., with an enzyme activity of 100,000 U / g.

[0080] The water used contained 10 wt % of fresh water, 30 wt % of process water and 60 wt % of reclaimed water.

[0081] The brown rice is hulled brown rice from old rice stored for 2 years, with a hulling rate of 25% and a water content of 12% by weight;

[0082] The wheat was old wheat stored for 2 years, with a moisture content of 12% by weight;

[0083] The corn was purchased by the factory in the current season and had a moisture content of 12% by weight.

[0084] Unless otherwise specified, the reagents and raw materials involved in the following examples are all commercially available.

[0085] Example 1

[0086] This example is used to illustrate the continuous fermentation method of ethanol according to the present invention.

[0087] refer to Figure 1 The specific operation method is as follows:

[0088] (1) Crushing, slurry mixing and liquefaction

[0089] The brown rice raw material is crushed, mixed with water and d-amylase at 85°C and stirred evenly to obtain a slurry with a dry matter content of 30% by weight, the slurry is heated to 102°C by steam through an ejector, then cooled to 90°C through a pressure tank and a flash tank, and enters a liquefaction tank for liquefaction for 3 hours to obtain a liquefied mash. The dosage of α-amylase is 25U / g starch raw material.

[0090] (2) Saccharification and fermentation

[0091] After the first heat exchange, the liquefied mash is cooled from 90°C to 45°C to obtain the material after the first heat exchange. The first saccharifying enzyme is added after the heat exchanger, and the amount added is 45% of the total amount of saccharifying enzyme. After the liquefied mash with saccharifying enzyme is added, it is cooled to 30°C by the second heat exchange. Part of the cooled saccharifying mash is pumped to the first fermentation tank, and part is pumped to the yeast tank. The second saccharifying enzyme is added to the pipeline to the first tank, and the amount added is 55% of the total amount of saccharifying enzyme. Among them, the total amount of saccharifying enzyme added is 210U / g starch raw material.

[0092] The starter tank is cultured in the starter medium for 12 hours until mature and then pumped to the fermentation tank for continuous inoculation. The starter is continuously inoculated for 48 hours and the tank is cleaned. Urea and acid protease are also added to the starter medium, wherein the content of urea in the starter medium is 2 mg / g starch raw material, and the addition amount of acid protease is 15 U / g starch raw material.

[0093] The cultured yeast mash is fermented in the fermentation section. The fermentation section adopts a semi-continuous fermentation process, with 3×3 continuous fermentation tanks (three lines A, B, and C, 3 in each line) and 6 intermittent fermentation tanks. Each continuous tank is equipped with a circulation pump, a plate heat exchanger and a discharge pump, and the intermittent tank is equipped with an intermittent tank pump and a plate heat exchanger.

[0094] Specifically, the yeast mash enters the primary continuous tank A1, B1, and C1, and flows into the saccharification mash at the same time, with an inoculation volume of 50% by volume, a controlled temperature of 31°C, a pH of 4.0, and the primary continuous tank is full for about 12 hours. The primary continuous tank A1, B1, and C1 are pumped into the secondary continuous tank A2, B2, and C2 respectively, and the temperature is controlled at 32°C. After the secondary continuous tank is full, the secondary continuous tank A2, B2, and C2 are pumped into the tertiary continuous tank A3, B3, and C3 respectively, and the tertiary tank is controlled at 32°C. After 12 hours, they are merged into a line and pumped into the intermittent fermentation tank (can be pumped into any intermittent tank) with a temperature control of 31°C. The intermittent tank is cultured for 30 hours, and the total fermentation time is 66 hours. After the fermentation is completed, it is pumped into the mature mash tank for temporary storage.

[0095] After fermentation, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the total plant steam consumption and the primary water consumption of ingredients for each ton of ethanol produced (based on 99.5 volume %) were calculated. The results are shown in Table 1.

[0096] Example 2

[0097] This example is used to illustrate the continuous fermentation method of ethanol according to the present invention.

[0098] (1) Crushing, slurry mixing and liquefaction

[0099] The brown rice raw material and the wheat raw material are crushed, mixed and stirred evenly with water, xylanase and α-amylase at 65° C., and the pH is adjusted to 5.8 with ammonia water to obtain a slurry with a dry matter content of 30.6%. The slurry is heated to 92° C. by steam through an ejector, and then cooled to 90° C. through a pressure tank and a flash tank, and enters a liquefaction tank for liquefaction for 3 hours to obtain a liquefied mash. Among them, the amount of α-amylase is 25U / g starchy raw material (the starchy raw material is the sum of the brown rice raw material and the wheat raw material), and the amount of xylanase is 6U / g wheat.

[0100] (2) Saccharification and fermentation

[0101] After the first heat exchange, the liquefied mash is cooled from 90°C to 45°C to obtain the material after the first heat exchange. The first saccharifying enzyme is added after the heat exchanger, and the amount added is 30% of the total amount of saccharifying enzyme. After the liquefied mash with saccharifying enzyme is added, it is cooled to 30°C again after the second heat exchange. Part of the cooled saccharifying mash is pumped to the first fermentation tank, and part is pumped to the yeast tank. The second saccharifying enzyme is added to the pipeline to the first tank, and the amount added is 70% of the total amount of saccharifying enzyme. Among them, the total amount of saccharifying enzyme added is 210U / g starch raw material.

[0102] The starter tank is cultured in the starter medium for 12 hours until mature and then pumped to the fermentation tank for continuous inoculation. The starter is continuously inoculated for 48 hours and the tank is cleaned. Urea and acid protease are also added to the starter medium, wherein the content of urea in the starter medium is 2 mg / g starch raw material, and the addition amount of acid protease is 15 U / g starch raw material.

[0103] The fermentation process was the same as in Example 1. After the fermentation was completed, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the steam consumption of the whole plant and the water consumption of the ingredients were calculated for each 1t of ethanol produced (based on 99.5 volume %). The results are shown in Table 1.

[0104] Example 3

[0105] This example is used to illustrate the continuous fermentation method of ethanol according to the present invention.

[0106] (1) Crushing, slurry mixing and liquefaction

[0107] The corn raw material is crushed, mixed with water and d-amylase at 65°C and stirred evenly, and the pH is adjusted to 5.8 with ammonia water to obtain a slurry with a dry matter content of 31.5%. The slurry is heated to 92°C by steam through an ejector, and then cooled to 90°C through a pressure tank and a flash tank, and enters a liquefaction tank for liquefaction for 3 hours to obtain a liquefied mash. Among them, the dosage of α-amylase is 25U / g starch raw material.

[0108] (2) Saccharification and fermentation

[0109] After the first heat exchange, the liquefied mash is cooled from 90°C to 45°C to obtain the material after the first heat exchange. The first saccharifying enzyme is added after the heat exchanger, and the amount added is 55% of the total amount of saccharifying enzyme. After the saccharifying enzyme is added, the liquefied mash is cooled to 30°C after the second heat exchange. Part of the cooled saccharifying mash is pumped to the first fermentation tank, and part is pumped to the yeast tank. The second saccharifying enzyme is added to the pipeline to the first tank, and the amount added is 45% of the total amount of saccharifying enzyme. Among them, the total amount of saccharifying enzyme added is 210U / g starch raw material.

[0110] The starter tank is cultured in the starter medium for 12 hours until mature and then pumped to the fermentation tank for continuous inoculation. The starter is continuously inoculated for 48 hours and the tank is cleaned. Urea and acid protease are also added to the starter medium, wherein the content of urea in the starter medium is 1.5 mg / g starch raw material, and the addition amount of acid protease is 15 U / g starch raw material.

[0111] The fermentation process was the same as in Example 1. After the fermentation was completed, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the steam consumption of the whole plant and the water consumption of the ingredients per 1t of ethanol produced (based on 99.5 volume %) were calculated. The results are shown in Table 1.

[0112] Example 4

[0113] This example is used to illustrate the continuous fermentation method of ethanol according to the present invention.

[0114] (1) Crushing, slurry mixing and liquefaction

[0115] The corn raw material was crushed, mixed with water and α-amylase at 87°C, and the pH was adjusted to 5.8 with ammonia water to obtain a slurry with a dry matter content of 31.5%. The slurry was kept warm for 1 hour and then put into a liquefaction tank for liquefaction for 2.5 hours to obtain a liquefied mash. The dosage of α-amylase was 25U / g starch raw material.

[0116] (2) Saccharification and fermentation

[0117] After the first heat exchange, the liquefied mash is cooled from 90°C to 45°C to obtain the material after the first heat exchange. The first saccharifying enzyme is added after the heat exchanger, and the amount added is 70% of the total amount of saccharifying enzyme. After the saccharifying enzyme is added, the liquefied mash is cooled to 30°C after the second heat exchange. Part of the cooled saccharifying mash is pumped to the first fermentation tank, and part is pumped to the yeast tank. The second saccharifying enzyme is added to the pipeline to the first tank, and the amount added is 30% of the total amount of saccharifying enzyme. Among them, the total amount of saccharifying enzyme added is 210U / g starch raw material.

[0118] The starter tank is cultured in the starter medium for 12 hours until mature and then pumped to the fermentation tank for continuous inoculation. The starter is continuously inoculated for 48 hours and the tank is cleaned. Urea and acid protease are also added to the starter medium, wherein the content of urea in the starter medium is 1.5 mg / g starch raw material, and the addition amount of acid protease is 15 U / g starch raw material.

[0119] The fermentation process was the same as in Example 1. After the fermentation was completed, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the steam consumption of the whole plant and the water consumption of the ingredients were calculated for each 1t of ethanol produced (based on 99.5 volume %). The results are shown in Table 1.

[0120] Example 5

[0121] This example is used to illustrate the continuous fermentation method of ethanol according to the present invention.

[0122] (1) Crushing, slurry mixing and liquefaction

[0123] The corn raw material is crushed, mixed with water and α-amylase at 65°C and stirred evenly, and the pH is adjusted to 5.8 with ammonia water to obtain a slurry with a dry matter content of 31.5%. The slurry is heated to 92°C by steam through an ejector, and then cooled to 90°C through a pressure tank and a flash tank, and enters a liquefaction tank for liquefaction for 3 hours to obtain a liquefied mash. Among them, the dosage of α-amylase is 25U / g starch raw material.

[0124] (2) Saccharification and fermentation

[0125] After the first heat exchange, the liquefied mash is cooled from 90°C to 45°C to obtain the material after the first heat exchange. The first saccharifying enzyme is added after the heat exchanger, and the amount added is 50% of the total amount of saccharifying enzyme. After the saccharifying enzyme is added, the liquefied mash is cooled to 30°C after the second heat exchange. Part of the cooled saccharifying mash is pumped to the first fermentation tank, and part is pumped to the yeast tank. The second saccharifying enzyme is added to the pipeline to the first tank, and the amount added is 50% of the total amount of saccharifying enzyme. Among them, the total amount of saccharifying enzyme added is 210U / g starch raw material.

[0126] The starter tank is cultured in the starter medium for 12 hours until mature and then pumped to the fermentation tank for continuous inoculation. The starter is continuously inoculated for 48 hours and the tank is cleaned. Urea and acid protease are also added to the starter medium, wherein the content of urea in the starter medium is 1.5 mg / g starch raw material, and the addition amount of acid protease is 15 U / g starch raw material.

[0127] The fermentation process is full continuous fermentation. There are 2×8 continuous fermentation tanks (two lines A and B, 8 in each line), and each continuous tank is equipped with a circulation pump, a plate heat exchanger and a discharge pump. The cultured yeast enters the first-level continuous tank A1 and B1, and flows into the saccharification mash at the same time. The inoculation amount is 50% by volume, and the temperature is controlled at 31°C and pH 4.0. After the first-level fermentation tank is full for about 9.5 hours, the first-level continuous tank A1 and B1 are pumped into the second-level continuous tank A2 and B2 respectively, and the temperature is controlled at 32°C. After the second-level continuous tank is full, the second-level continuous tank A2 and B2 are pumped into the third-level continuous tank A3 and B3 respectively, and the temperature of the third-level tank is controlled at 32°C. After the third-level continuous tank is full, it flows into the fourth to seventh-level continuous tanks with the same process, and the temperature of the fourth to seventh-level continuous tanks is controlled at 31°C. The total fermentation time is 66.5 hours. After the fermentation is completed, it is pumped into the mature mash tank for temporary storage.

[0128] After fermentation, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the total plant steam consumption and the primary water consumption of ingredients for each ton of ethanol produced (based on 99.5 volume %) were calculated. The results are shown in Table 1.

[0129] Example 6

[0130] This example is used to illustrate the continuous fermentation method of ethanol according to the present invention.

[0131] The operation was carried out according to the method described in Example 1, except that the saccharification process was different. Specifically, the temperature of the material after the first heat exchange was 60°C.

[0132] After fermentation, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the total plant steam consumption and the primary water consumption of ingredients for each ton of ethanol produced (based on 99.5 volume %) were calculated. The results are shown in Table 1.

[0133] Comparative Example 1

[0134] This comparative example is used to illustrate the continuous fermentation method of ethanol for reference.

[0135] Reference Figure 2 The flow chart shown is operated according to the method described in Example 1, except that the saccharification process is different. Specifically, the saccharification method includes: the liquefied mash is subjected to a first heat exchange, and the temperature is reduced from 90°C to 60°C to obtain a material after the first heat exchange, and all saccharifying enzymes are added to the material after the first heat exchange after the heat exchanger, and then the material enters the saccharification tank for saccharification for 30 minutes, and the obtained saccharified mash is subjected to a second heat exchange and reduced from 60°C to 30°C. A part of the cooled saccharified mash is pumped to the first fermentation tank, and a part is pumped to the yeast tank, and no saccharifying enzyme is added to the pipeline to the first tank.

[0136] After fermentation, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the total plant steam consumption and the primary water consumption of ingredients for each ton of ethanol produced (based on 99.5 volume %) were calculated. The results are shown in Table 1.

[0137] Comparative Example 2

[0138] This comparative example is used to illustrate the continuous fermentation method of ethanol for reference.

[0139] The operation was carried out according to the method described in Example 2, except that the saccharification process was the saccharification process shown in Comparative Example 1.

[0140] After fermentation, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the total plant steam consumption and the primary water consumption of ingredients for each ton of ethanol produced (based on 99.5 volume %) were calculated. The results are shown in Table 1.

[0141] Comparative Example 3

[0142] This comparative example is used to illustrate the continuous fermentation method of ethanol for reference.

[0143] The operation was carried out according to the method described in Example 3, except that the saccharification process was the saccharification process shown in Comparative Example 1.

[0144] After fermentation, the alcohol content, residual total sugar, residual reducing sugar, residual filtered total sugar, residual dextrin and residual starch content of the mature mash were determined, and the total plant steam consumption and the primary water consumption of ingredients for each ton of ethanol produced (based on 99.5 volume %) were calculated. The results are shown in Table 1.

[0145] Table 1

[0146] parameter Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Dry matter% 30 30.6 31.5 31.5 31.5 30 30 30.6 31.5 Mixing temperature ℃ 85 65 65 87 65 85 85 65 65 Injection temperature ℃ 102 92 92 - 92 102 102 92 92 Alcohol content %v / v 15.50 15.02 15.10 14.95 14.99 15.43 14.91 14.76 14.89 Steam consumption of the whole plant t / t ethanol 3.59 3.61 3.61 3.64 3.65 3.6 3.75 3.78 3.75 Water consumption for batching t / t ethanol 0.6 0.6 0.6 0.6 0.6 0.62 2.6 2.61 2.55 Residual total sugar g / 100mL 1.23 1.66 2.13 2.18 2.14 1.32 2 2.60 2.37 Residual reducing sugar g / 100mL 0.21 0.3 0.27 0.31 0.28 0.23 0.38 0.45 0.32 Residual filtered total sugar g / 100mL 0.84 1.15 0.82 0.86 0.82 0.86 1.48 1.67 0.91 Residual dextrin g / 100mL 0.57 0.76 0.50 0.50 0.49 0.57 0.99 1.1 0.53 Residual starch g / 100mL 0.35 0.46 1.18 1.19 1.19 0.41 0.47 0.84 1.31

[0147] It can be seen from the results in Table 1 that the scheme described in the present invention can effectively increase the ethanol concentration in the mature mash obtained by the continuous fermentation process (up to 15.5% v / v), reduce residual sugar, increase production capacity, and save water and steam consumption.

[0148] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A continuous fermentation method for ethanol, characterized in that: The method comprises: sequentially pulverizing, slurry conditioning and liquefying starchy raw materials to obtain liquefied mash; Performing a first heat exchange on the liquefied mash to obtain a material after the first heat exchange; adding a first saccharifying enzyme to the material after the first heat exchange, and then performing a second heat exchange to obtain a material after the second heat exchange; adding a second saccharifying enzyme to the material after the second heat exchange to obtain a material to be fermented, and then continuously fermenting to obtain ethanol; The temperature of the material after the first heat exchange is 35-60°C; the temperature of the material after the second heat exchange is 27-35°C; the total amount of saccharifying enzyme added is 100-250U / g starch raw material; the amount of the first saccharifying enzyme added is 30-70% of the total amount added.

2. The method according to claim 1, wherein: The temperature of the material after the first heat exchange is 40-50°C; and / or The temperature of the material after the second heat exchange is 28-32°C.

3. The method according to claim 1, wherein: The starchy raw material is selected from at least one of brown rice, rice, corn and wheat; and / or The pulverizing conditions are such that 70-95% by weight of the pulverized material can pass through a 20-mesh sieve; and / or The slurry conditioning conditions are such that the obtained slurry conditioning liquid has a dry matter concentration of 28-34% by weight.

4. The method according to any one of claims 1 to 3, wherein: The liquefaction method comprises: liquefying the slurry obtained by slurry adjustment in the presence of amylase to obtain liquefied mash, wherein the pH of the liquefied mash is 3.5-5.

5.

5. The method according to any one of claims 1 to 3, wherein: The liquefaction conditions include: a temperature of 75-120° C.; and / or The time is 0.5-6h.

6. The method according to claim 4, wherein: The added amount of the amylase is 10-40 U / g starchy raw material.

7. The method according to claim 3, wherein: When the starchy raw material comprises wheat, the liquefaction method further comprises: adding xylanase to the slurry, wherein the amount of xylanase added is 1-10 U / g wheat.

8. The method according to any one of claims 1 to 3, wherein: The liquefaction method is a jet liquefaction method or a cooking method.

9. The method according to claim 8, wherein: The conditions of the spray liquefaction method include: the spray temperature is 90-105°C.

10. The method according to claim 8, wherein: The method further comprises: before the spraying liquefaction, controlling the temperature of the slurry to be within the range of 40-70°C or 80-90°C.

11. The method according to claim 8, wherein: The cooking method comprises cooking the slurry at 84-94° C. for 15-60 minutes and then liquefying it for 2.5-4 hours.

12. The method according to any one of claims 1 to 3, wherein: The fermentation method comprises: adding yeast mash to the material to be fermented, and fermenting to obtain ethanol.

13. The method according to any one of claims 1 to 3, wherein: The fermentation is fully continuous fermentation or semi-continuous fermentation.

14. The method according to claim 12, wherein: The production method of the yeast mash includes: inoculating yeast into a yeast culture medium, culturing for 8-16 hours, using part of the obtained yeast mash for fermentation, and continuously culturing the remaining part, and ending the culturing after 36-72 hours.

15. The method according to claim 14, wherein: The yeast culture medium comprises the second heat exchanged material and / or the material to be fermented, a nitrogen source and an acidic protease, wherein the amount of the acidic protease is 5-20 U / g starchy raw material, and the amount of the nitrogen source is 1-2.4 mg / g starchy raw material.

16. The method according to any one of claims 1 to 3, wherein: The fermentation conditions include: temperature of 25-38°C, pH of 2-6, and fermentation time of 45-78h.

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