Application of air cooling in the cooling process of material after steam explosion in the production of ethanol from biomass raw material

Abstract

The application relates to the field of biomass raw material production of ethanol, and discloses application of air cooling in a material cooling process after steam explosion in biomass raw material production of ethanol. The application comprises at least one of the following aspects: 1) improving the flowability of the material after steam explosion, improving heat exchange efficiency, and avoiding material caking; 2) in the process of enzymatic hydrolysis of cellulose, reducing the enzyme addition amount and / or shortening the enzymatic hydrolysis time; 3) improving the alcohol degree of the fermentation product, and reducing rectification steam consumption. Through air cooling, the cooling step of the steam exploded material can be simplified, the loss of C5 components in the material after steam explosion can be reduced, the alcohol degree can reach 6.5-7% v / v, and water consumption can be reduced.

Description

Technical Field

[0001] This invention relates to the field of ethanol production from biomass feedstocks, specifically to the application of air cooling in the material cooling process after vapor explosion in ethanol production from biomass feedstocks, a method for cooling materials after vapor explosion during ethanol production from biomass feedstocks, and a system for preparing ethanol from biomass feedstocks. Background Technology

[0002] In my country, according to statistics, the total theoretical straw resource volume reached 1.02 billion tons in 2017, an increase of nearly 400 million tons compared to the early 1990s. Of this, corn, rice, and wheat straw accounted for 430 million, 240 million, and 180 million tons respectively, representing 83.3% of the total. Corn straw, as the most produced crop straw in my country, has a total fiber content exceeding 70% (dry weight), including 35% cellulose and 23% hemicellulose. Besides some use in cattle and sheep feed, hundreds of millions of tons remain to be rationally utilized. Although the comprehensive utilization rate of straw in my country reached 85.45% in 2019, the vast majority is mainly used for general purposes such as fertilizer (crushing and returning to the field), feed, and fuel (straw pellets), failing to achieve efficient utilization of straw to produce high-value-added products.

[0003] Research on the production of ethanol using cellulose-containing raw materials (also known as biomass raw materials) has attracted much attention both at home and abroad, but large-scale industrial production has not yet been achieved in the world. This is mainly due to a series of problems such as high raw material consumption, high cost, high energy consumption, and low fermentation alcohol content (generally 4-4.5% v / v).

[0004] The core of the cellulose process is the steam explosion unit. The material following the steam explosion is a high-temperature material (typically 100-105℃, with a solid content of 30-50% by weight). This material needs to undergo enzymatic hydrolysis before fermentation. The enzymatic hydrolysis process requires a temperature of around 50℃ and a solid content of 20-25% by weight. Because the material after steam explosion is solid, its cooling is an engineering challenge; currently, water cooling is commonly used.

[0005] Foreign technologies employ a process where steam-exploded materials are diluted with process water until the enzymatic hydrolysis temperature reaches 50°C, resulting in a solid content of 10-15% by weight. This is followed by plate and frame filtration, and enzymatic hydrolysis is performed on the wet mash until the solid content reaches 20-25% by weight, followed by fermentation to produce ethanol. Similar processes are commonly used domestically. However, during plate and frame filtration, water-soluble sugars such as C5 are lost in the filtrate, requiring some of the filtrate to be returned for reuse before enzymatic hydrolysis. Because not all of the filtrate can be reused, the loss of soluble sugars results in relatively low alcohol content, around 4-4.5% v / v. Even with cooling via a chilled water system (a significant investment) to ensure the diluted material meets the requirements for enzymatic hydrolysis, the alcohol content of the mature fermented mash will not exceed 5% v / v. Furthermore, water cooling presents challenges such as difficulty in mixing materials, caking, and poor heat exchange. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of easy material caking, difficulty in mixing, poor heat exchange effect, and low fermentation alcohol content in the water-cooled cooling process of steam-exploded materials in the prior art. It proposes the application of air cooling in the cooling process of materials after steam explosion in the production of ethanol from biomass raw materials, a cooling method for materials after steam explosion in the process of producing ethanol from biomass raw materials, and a system for preparing ethanol from biomass raw materials. Air cooling overcomes the problems of easy material caking, difficulty in mixing, poor heat exchange effect, and low fermentation alcohol content in the water-cooled cooling process of steam-exploded materials.

[0007] To achieve the above objectives, the first aspect of the present invention provides the application of air cooling in the material cooling process after vapor explosion in the production of ethanol from biomass feedstocks, wherein the application includes at least one of the following aspects:

[0008] 1) Improve the flowability of materials after steam explosion, improve heat exchange efficiency, and prevent material agglomeration;

[0009] 2) During the enzymatic hydrolysis of cellulose, reduce the amount of enzyme added and / or shorten the hydrolysis time;

[0010] 3) Increase the alcohol content of fermentation products and reduce the consumption of distillation steam.

[0011] The second aspect of the present invention provides a method for cooling materials after vapor explosion during the production of ethanol from biomass feedstock. The method includes: air cooling the materials after vapor explosion to obtain cooled materials and a first gas phase.

[0012] Optionally, the first gas phase is separated to obtain a solid material and a second gas phase;

[0013] The cooled material and the solid material are the materials to be enzymatically hydrolyzed.

[0014] Preferably, the conditions for steam explosion are such that the temperature of the material after steam explosion is 100-105℃, the solid content is 30-50% by weight, and the particle size is less than 200μm.

[0015] The conditions for the air-cooling process ensure that the temperature of the cooled material is above 50°C.

[0016] Preferably, the air-cooling process is carried out in an air-cooling device.

[0017] More preferably, the air-cooled device includes a housing, a conveying assembly located inside the housing, a feed inlet and an air outlet located above the housing, and a discharge outlet and an air inlet located below the housing;

[0018] Along the material flow direction, the feed inlet is located above the starting section of the conveying assembly, and the discharge outlet is located below the ending section of the conveying assembly.

[0019] Preferably, a screen is also provided below the feed inlet.

[0020] Preferably, in the air-cooling process, the thickness of the material after the steam explosion on the conveying assembly is 9-18 cm.

[0021] A third aspect of the present invention provides a system for preparing ethanol from biomass feedstock, the system comprising:

[0022] A pulverizing unit is used to pulverize the biomass raw material to obtain pulverized biomass raw material;

[0023] The hydrolysis unit is used to steam-explode the pulverized biomass raw material to obtain the steam-exploded material.

[0024] A cooling unit is used to cool the material after the steam explosion to obtain the material to be enzymatically hydrolyzed;

[0025] An enzymatic hydrolysis unit is used to enzymatically hydrolyze the material to be hydrolyzed to obtain an enzymatic hydrolysate;

[0026] A fermentation unit is used to ferment the enzymatic hydrolysate to obtain mature mash;

[0027] A distillation unit is used to distill the mature mash to obtain ethanol;

[0028] The cooling unit includes:

[0029] Air-cooling equipment is used to air-cool materials after steam explosion to obtain cooled materials and the first gas phase;

[0030] Optional separation equipment is used to separate the first gas phase to obtain a solid material and a second gas phase.

[0031] Although both water cooling and air cooling are methods of material cooling, air cooling has not yet been found to be used in the cooling process of steam-exploded materials in the field of ethanol production from biomass feedstocks. During their research, the inventors of this invention discovered that using air cooling to cool steam-exploded materials not only overcomes the problems of material caking, difficulty in mixing, poor heat exchange, and low fermentation alcohol content caused by water cooling, but also improves the efficiency of enzymatic hydrolysis and reduces the amount of cellulase required. Compared to water cooling, air cooling can reduce the loss of C5 components in the steam-exploded material, increase the alcohol content of the fermentation product (6.5-7% v / v), and reduce the amount of steam used in the distillation process.

[0032] Air cooling can improve the fluidity of materials after steam explosion, allowing the materials to remain in a fluidized state during the cooling process, preventing them from caking, improving heat exchange efficiency, and reducing energy consumption.

[0033] Air cooling simplifies the cooling process for explosive materials and reduces water consumption.

[0034] Air cooling can reduce the content of substances that are not conducive to enzymatic hydrolysis (such as aldehydes and acids) in the material after steam explosion, thereby increasing the hydrolysis rate and reducing the amount of enzyme. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the cooling unit described in Embodiment 1 of the present invention.

[0036] Figure 2 This is a particle size distribution diagram of the material after steam explosion in Embodiment 1 of the present invention.

[0037] Explanation of reference numerals in the attached figures

[0038] E1, Air-cooled equipment; E2, Cyclone separator; E3, Scrubber tower; E4, Blower; E5, Exhaust fan;

[0039] E11, housing; E12, conveying assembly; E13, feed inlet; E14, discharge outlet; E15, air inlet; E16, air outlet; E17, temperature control device. Detailed Implementation

[0040] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0041] The first aspect of this invention provides the application of air cooling in a material cooling process after vapor explosion in the production of ethanol from biomass feedstocks, wherein the application includes at least one of the following aspects:

[0042] 1) Improve the flowability of materials after steam explosion, increase heat exchange efficiency, and reduce energy consumption;

[0043] 2) During the enzymatic hydrolysis of cellulose, reduce the amount of enzyme added and / or shorten the hydrolysis time;

[0044] 3) Increase the alcohol content of fermentation products and reduce the consumption of distillation steam.

[0045] The conditions and equipment required for the air-cooling process will be described in detail in the following two sections, and will not be repeated here.

[0046] The second aspect of the present invention provides a method for cooling materials after vapor explosion during the production of ethanol from biomass feedstock. The method includes: air cooling the materials after vapor explosion to obtain cooled materials and a first gas phase.

[0047] Optionally, the first gas phase is separated to obtain a solid material and a second gas phase;

[0048] The cooled material and the solid material are the materials to be enzymatically hydrolyzed.

[0049] In this invention, the method for preparing ethanol from biomass raw materials can be a conventional method in the art. This method may include: sequentially crushing, hydrolyzing, cooling, enzymatically hydrolyzing, fermenting, and distilling the biomass raw materials to obtain ethanol. It should be understood that, for this invention, the hydrolysis is achieved through a steam explosion process, and the cooling is achieved through at least an air-cooling process (e.g., water-cooling may also be included). That is, the method for producing ethanol from biomass raw materials includes: sequentially crushing, steam explosion, air cooling, enzymatically hydrolyzing, fermenting, and distilling the biomass raw materials to obtain ethanol.

[0050] In this invention, the biomass raw materials are those already existing in the art, as long as they contain biomass. These biomass raw materials include, but are not limited to, at least one of the following: corn stalks, corn husks, corn cobs, wheat straw, rice straw, sugarcane bagasse, bean stalks, cotton stalks, banana stalks, coconut shells, bamboo, switchgrass, reed, branches, wood chips, and sawdust. It is understood that the stalks include the stems and leaves of plants, and optionally, the roots.

[0051] In this invention, the pulverization method can be a conventional means used in the art, such as using a pulverizer to pulverize the biomass raw material. Preferably, the biomass raw material is first pulverized into coarse pulverized material with an average length of 5-10 cm through a first pulverization, then impurity removal is performed, followed by a second pulverization to obtain fine pulverized material with an average length of 0.5-3 cm, preferably fine pulverized material with an average length of 1-2 cm.

[0052] The impurity removal method can be any conventional technique in the art, as long as it can remove impurities from the biomass raw material. For example, a dust collector can be used to remove dust impurities from the coarsely crushed material, an impurity remover can be used to remove sand and gravel impurities from the coarsely crushed material, and magnetic adsorption can be used to remove iron impurities. Those skilled in the art can combine the aforementioned methods to perform impurity removal operations as needed.

[0053] In this invention, the steam explosion method can be a conventional steam explosion method in the art, preferably including at least one of neutral steam explosion, acidic steam explosion and alkaline steam explosion, and preferably neutral steam explosion.

[0054] The preferred method for the steam explosion includes mixing the pulverized product with water or a dilute acid or alkaline substance, and then maintaining the mixture at 150-210℃ (e.g., any range of 150, 160, 170, 180, 190, 200, 210℃ or any two of these values) and 0.5-1.8MPa (e.g., any range of 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1.0MPa, 1.1MPa, 1.2MPa, 1.3MPa, 1.4MPa, 1.5MPa, 1.6MPa, 1.7MPa, 1.8MPa or any two of these values) for 1-90 minutes (e.g., 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 minutes or any two of these values), followed by instantaneous decompression and release. It should be understood that when the pulverized product is mixed with water, it results in a neutral vapor explosion; when mixed with dilute acid, it results in an acidic vapor explosion; and when mixed with alkaline substances, it results in an alkaline vapor explosion.

[0055] In this invention, preferably, the amount of water, dilute acid, or alkali used is such that the content of the pulverized product in the mixture of the pulverized product and the water, dilute acid, or alkali is 30-60% by weight (for example, it can be 30, 35, 40, 45, 50, 55, 60% by weight, or any range between any two values).

[0056] In this invention, the content of the pulverized product is calculated based on the dry matter of the biomass raw material.

[0057] In this invention, the water can be water conventionally used in the art, such as tap water and industrial water, etc.

[0058] In this invention, the dilute acid is a dilute acid commonly used in the art, such as an acid solution with a concentration of 0.1-3% by weight (e.g., 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.5, 3% by weight and any range between any two values), and the acid includes, but is not limited to, phosphoric acid and sulfuric acid.

[0059] In this invention, the alkaline substance is an alkaline substance conventionally used in the art, such as an alkaline solution with a concentration of 1-20% by weight (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20% by weight and any range between any two values). The alkaline substance includes, but is not limited to, sodium hydroxide, potassium hydroxide, sodium sulfite, potassium sulfite, ammonium sulfite and ammonia.

[0060] In this invention, the steam explosion can be an intermittent steam explosion or a continuous steam explosion, preferably an intermittent steam explosion.

[0061] Preferably, the conditions for steam explosion are such that the temperature of the material after steam explosion is 100-105°C and the solid content is 30-50% by weight.

[0062] Preferably, the conditions for steam explosion result in the particle size of the material after steam explosion being less than 200 μm. More preferably, the conditions for steam explosion result in more than 60% by weight of the particles in the material after steam explosion having a particle size in the range of 2-100 μm. Even more preferably, the conditions for steam explosion result in more than 80% by weight of the particles in the material after steam explosion having a particle size in the range of 2-100 μm. It should be understood that a small number of particles with excessively large particle sizes may exist, but since they are present in small quantities, they are negligible.

[0063] In order to use the material after steam explosion for enzymatic hydrolysis, the material after steam explosion also needs to be cooled. In this invention, air cooling is used to cool the material after steam explosion.

[0064] Since the solid content of the cooled material is higher than that required for enzymatic hydrolysis, it needs to be diluted. If the temperature of the cooled material is higher than the temperature required for enzymatic hydrolysis (generally around 50°C), process water with a temperature lower than the enzymatic hydrolysis temperature is used for dilution; if the temperature of the cooled material is lower than the temperature required for enzymatic hydrolysis, process water with a temperature higher than the enzymatic hydrolysis temperature is used for dilution. To save energy, the temperature of the cooled material is generally kept higher than the temperature required for enzymatic hydrolysis; that is, preferably, the air-cooling conditions ensure that the temperature of the cooled material is above 50°C, more preferably 50-70°C. The proportion of solid material is relatively low, and its influence on temperature is negligible.

[0065] Preferably, the air-cooling process is performed in an air-cooling device. The air-cooling device can be any device in the art capable of achieving an air-cooling effect.

[0066] In a preferred embodiment of the present invention, the air-cooled device includes a housing, a conveying assembly located inside the housing, a feed inlet and an air outlet located above the housing, and a discharge outlet and an air inlet located below the housing; wherein, along the material flow direction, the feed inlet is located above the starting section of the conveying assembly, and the discharge outlet is located below the ending section of the conveying assembly.

[0067] It should be understood that there is at least one air inlet and one air outlet.

[0068] It should be understood that, for the final air-cooling effect, at least one stage of air-cooling equipment can be used for air-cooling treatment. That is, at least one stage of air-cooling equipment can be used to air-cool the explosive material until the cooled material reaches the expected temperature. When the air-cooling equipment has two or more stages, the air-cooling equipment can be connected in series and / or in parallel.

[0069] The conveying component can be a component that already exists in the art and can perform conveying functions, such as a conveyor belt.

[0070] In order to make the material distribution more uniform during the conveying process, the conveying assembly may also be equipped with a material layer adjustment plate to adjust the thickness of the material.

[0071] Preferably, in the air-cooling process, the thickness of the material after the steam explosion on the conveying assembly is 9-18 cm (for example, it can be 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 cm, or any range between any two values), more preferably 13-17 cm. In the preferred embodiment, the material flowability can be further improved, the heat transfer efficiency can be improved, and the material caking can be prevented.

[0072] On the conveying assembly, the material after the steam explosion exists in a fluidized state. That is, during the conveying process, there is relative movement between the particles in the material, which has good fluidity and thus avoids caking.

[0073] Preferably, the air-cooled equipment is equipped with a temperature control device for detecting the temperature of the material after the vapor explosion at the end of the conveying component, and adjusting the airflow and / or material conveying speed of the air-cooled equipment to control the temperature of the material after the vapor explosion at the end of the conveying component within a predetermined range. The temperature control device may include a temperature transmitter (which may be located at the tail of the conveying component of the air-cooled equipment) and a control system.

[0074] To improve the uniformity of material distribution, preferably, a screen is also provided below the feed inlet.

[0075] Preferably, the mesh size of the sieve is 12-20 mesh.

[0076] Preferably, the mesh size of the screen is at least one of cat's eye shape, round, square, rhomboid, and triangular, and more preferably cat's eye shape. In this preferred case, the uniformity of material distribution can be further improved, and screen clogging can be avoided to a greater extent.

[0077] In this invention, the air-cooled equipment may also be equipped with an air supply device for supplying air. The air supply device may be any device capable of supplying air in the art, such as a blower.

[0078] The air source can be air. The temperature of the air can change with the temperature of the external environment. In order to achieve the desired air cooling effect, those skilled in the art can adjust the conveying speed of the conveying components and the air supply volume of the air supply device.

[0079] In this invention, air cooling allows the heat from the material after the steam explosion to be expelled with the air, while also carrying away a small amount of small particles and volatile substances (such as small molecule aldehydes and small molecule acids). By separating the first gas phase, the resulting solid phase mainly consists of the carried-out small particles, while the second gas phase contains volatile substances.

[0080] The separation process can be carried out in conventional separation equipment, such as a cyclone separator. The number of separation devices can be the same as or different from the number of air-cooling devices, and those skilled in the art can adjust it as needed.

[0081] The solid material can be combined with the cooled material for subsequent enzymatic hydrolysis. Since the solid content of both the solid material and the cooled material is higher than the solid content required for the enzymatic hydrolysis process, they need to be diluted, i.e., mixed with water. This mixing can be carried out in equipment commonly used in the art, such as a mixing auger.

[0082] Those skilled in the art can select appropriate mixing augers and mixing conditions based on actual conditions, which will not be elaborated here.

[0083] Since the second gas phase contains volatile substances and cannot be directly discharged, the method preferably further includes: washing the second gas phase with water to obtain a washing waste liquid and a discharge gas.

[0084] The water washing process can be carried out using water washing equipment commonly used in the field, such as a washing tower.

[0085] The scrubbing tower may be equipped with a fixed spray device and a rotating spray device for thoroughly cleaning the second gas phase.

[0086] The washing waste liquid can be recycled. When the impurity content is higher than or equal to 5%-10%, it can be discharged from the system for wastewater treatment according to process requirements.

[0087] A demister, such as a wire mesh demister, can be installed below the air outlet at the top of the scrubbing tower to remove dust-containing droplets from the exhaust gas, ensuring that the exhaust gas meets environmental protection requirements.

[0088] In this invention, in the air-cooling process, in addition to the air-cooling equipment, there are also separation equipment and water washing equipment. In order to enable the equipment to operate better, an exhaust fan connected to the water washing equipment can also be configured to make the gas in the entire process flow in a specific way (from the air-cooling equipment to the separation equipment to the water washing equipment to the discharge).

[0089] The operating conditions of the exhaust fan can be selected within a wide range. Those skilled in the art can select a suitable exhaust fan and adjust its operating conditions according to the actual situation.

[0090] In this invention, preferably, the air-cooled material is mixed with the solid material and water to obtain a material to be enzymatically hydrolyzed that meets the requirements for enzymatic hydrolysis. The material to be enzymatically hydrolyzed is then subjected to enzymatic hydrolysis to obtain an enzymatic hydrolysate suitable for fermentation.

[0091] To achieve better enzymatic hydrolysis results, the material to be hydrolyzed can be subjected to pre-hydrolysis and main hydrolysis sequentially. The operating conditions for pre-hydrolysis and main hydrolysis can be the same or different, and are the conditions for conventional enzymatic hydrolysis in this field.

[0092] In this invention, the enzymatic hydrolysis temperature can be the optimal operating temperature of cellulase, generally 45-55℃, more preferably 48-52℃.

[0093] In this invention, the pH value for enzymatic hydrolysis can be any optimal pH for cellulase, generally 3-7, more preferably 4.5-5.5. Since the pH fluctuation during enzymatic hydrolysis is small, the pH value can be adjusted before adding the enzyme using methods commonly used in the art. For example, the pH of the material can be adjusted to 3-7, more preferably 4.5-5.5, using sulfuric acid solution or sodium hydroxide.

[0094] The longer the enzymatic hydrolysis time is theoretically, the better. Considering the equipment utilization rate, the preferred pre-enzymatic hydrolysis time is 1-10 hours; the main enzymatic hydrolysis time is 25-72 hours.

[0095] In this invention, the end point of enzymatic hydrolysis can be defined as when the cellulose conversion rate reaches 80%. The method for determining the cellulose conversion rate is as follows: measure the cellulose content in the biomass raw material, multiply by 1.11 to obtain the theoretical value of complete conversion to glucose, and then divide the actual measured glucose content by the theoretical value of glucose to obtain the cellulose conversion rate.

[0096] In this invention, the cellulase may be added during the pre-hydrolysis and / or main hydrolysis stages, or it may be omitted. Those skilled in the art can adjust this as needed.

[0097] In this invention, the amount of cellulase can be selected within a wide range. Preferably, the amount of cellulase is 1-10 enzyme activity units per gram of dry weight of biomass raw material, and more preferably 2-8 enzyme activity units.

[0098] In this invention, the cellulase can be an enzyme commonly used in the art, such as one that is commercially available.

[0099] In this invention, the enzymatic hydrolysate can be fermented to obtain a mature mash containing ethanol. The fermentation method preferably includes: inoculating the enzymatic hydrolysate with a bacterial strain for fermentation to obtain a mature mash.

[0100] It should be understood that the strain undergoes co-fermentation of glucose and xylose in the enzymatic hydrolysate. Because the strain utilizes glucose at a much higher rate than it utilizes xylose, in the early stages of fermentation, the strain primarily utilizes glucose from the hydrolysate, with a small amount of xylose also being used. Once the glucose is depleted, the strain begins fermentation with xylose as the primary carbon source. In the early stages of fermentation, glucose is rapidly consumed, generating a large amount of heat, requiring stirring and heat exchange to maintain the fermenter temperature and prevent excessive heat from damaging the cells. Once the cells enter the xylose fermentation stage, the fermentation rate is slower than that of glucose, and the heat production is smaller, but a small amount of aeration is needed to provide oxygen and promote xylose metabolism to produce ethanol.

[0101] In this invention, preferably, the fermentation conditions include: a pH value of 2-7, more preferably 3-6; a temperature of 30-36°C, more preferably 32-35°C; and a time of 32-64 hours, more preferably 32-48 hours.

[0102] In this invention, the microbial strain can be a yeast strain conventionally used in the art for ethanol fermentation, preferably *Pichia pastoris* and / or *Saccharomyces cerevisiae*. The inoculum size of the yeast used for fermentation can be 10 per gram of enzymatic hydrolysate. 3 -10 8 CFU. The yeast used in the fermentation of this invention can be a solid yeast preparation or a yeast strain, such as Angel Super Brewing High-Activity Dry Yeast produced by Hubei Angel Yeast Co., Ltd.

[0103] The colony-forming units of the bacterial strains described in this invention can be determined by methods known in the art, such as the methylene blue staining viable cell count method.

[0104] In this invention, the bacterial strain can be activated before inoculation. The activation method can be any conventional means used in the art, such as inoculating the strain into an activation tank, mixing it with water, and activating it to obtain a seed culture. Alternatively, a carbon source, such as corn saccharification mash, can be added to the activation tank as needed to activate the strain. The activation pH can be 2-7, preferably 3-6; the activation temperature can be 25-40℃, preferably 30-35℃; and the activation time can be 6-16 hours.

[0105] In this invention, the bacterial strain may undergo at least one stage of expansion before inoculation, which can be carried out in shake flasks and / or expansion tanks. Preferably, the bacterial strain undergoes at least three stages of expansion. It should be understood that the size of the expansion tanks increases progressively with each stage.

[0106] In this invention, the inoculum size for each stage of expansion can be selected within a wide range. Preferably, the inoculum size for each stage of expansion is 5-10 volumes.

[0107] The pH value in each stage of expansion culture can be 2-7, preferably 3-6; the temperature in each stage of expansion culture can be 26-34℃, preferably 28-32℃.

[0108] The time for each stage of expansion can be determined based on the set reducing sugar concentration and / or viable cell count, for example, 10-18 hours respectively.

[0109] The culture medium used for expansion can be any culture medium commonly used in the field, such as an enzyme hydrolysate.

[0110] The propagation method can be intermittent or continuous, and those skilled in the art can choose according to their needs.

[0111] During the propagation process, antibacterial agents can also be added. Those skilled in the art can select appropriate antibacterial agents and adjust their dosage as needed.

[0112] In this invention, the mature mash refers to the mash obtained after the fermentation liquid is separated from the bacteria after the fermentation is completed.

[0113] In this invention, the purpose of the distillation is to extract ethanol from the mature mash, and the distillation preferably includes crude distillation and rectification distillation; wherein, the crude distillation is preferably carried out in a crude distillation column, and the crude distillation column is preferably equipped with a crude distillation column reboiler.

[0114] The crude distillation method can be a method conventionally used in the art. Preferably, the mature mash is crudely distilled in a crude distillation tower at 70-90°C to obtain waste mash and crude distillate.

[0115] In this invention, the distillation method can be a method conventionally used in the art, and the distillation is preferably carried out in a distillation column equipped with a distillation column reboiler. The distillation can be carried out in at least one distillation column equipped with a distillation column reboiler, for example, in two distillation columns equipped with distillation column reboilers.

[0116] In a preferred embodiment of the invention, the distillation is carried out in a distillation column equipped with a distillation column reboiler.

[0117] Preferably, the crude distillate is subjected to a first rectification at 100-140°C in a first rectification column, and the resulting first rectification fraction is then subjected to a second rectification at 140-160°C in a second rectification column to obtain a second rectification fraction.

[0118] In this invention, the distillate obtained from the distillation can also be dehydrated to obtain ethanol. The second dehydration method can be a method conventionally used in the art, such as using a molecular sieve and / or membrane separation to obtain ethanol. The operating conditions of the molecular sieve can be an adsorption temperature of 120-140℃, an adsorption pressure of 0.02-0.06 MPa, and regeneration conditions of -0.02 to -0.06 MPa.

[0119] Unless otherwise specified, all pressures mentioned in this invention are gauge pressures.

[0120] A third aspect of the present invention provides a system for preparing ethanol from biomass feedstock, the system comprising:

[0121] A pulverizing unit is used to pulverize the biomass raw material to obtain pulverized biomass raw material;

[0122] The hydrolysis unit is used to steam-explode the pulverized biomass raw material to obtain the steam-exploded material.

[0123] A cooling unit is used to cool the material after the steam explosion to obtain the material to be enzymatically hydrolyzed;

[0124] An enzymatic hydrolysis unit is used to enzymatically hydrolyze the material to be hydrolyzed to obtain an enzymatic hydrolysate;

[0125] A fermentation unit is used to ferment the enzymatic hydrolysate to obtain mature mash;

[0126] A distillation unit is used to distill the mature mash to obtain ethanol;

[0127] The cooling unit includes:

[0128] Air-cooling equipment is used to air-cool materials after steam explosion to obtain cooled materials and the first gas phase;

[0129] Optional separation equipment is used to separate the first gas phase to obtain a solid material and a second gas phase.

[0130] Preferably, the air-cooled device includes a housing, a conveying assembly located inside the housing, a feed inlet and an air outlet located above the housing, and a discharge outlet and an air inlet located below the housing; wherein, along the material flow direction, the feed inlet is located above the starting section of the conveying assembly, and the discharge outlet is located below the ending section of the conveying assembly.

[0131] Preferably, the air-cooled equipment is equipped with a temperature control device for detecting the temperature of the material after the vapor explosion at the end of the conveying component, and adjusting the airflow and / or material conveying speed of the air-cooled equipment to control the temperature of the material after the vapor explosion at the end of the conveying component within a predetermined range. The temperature control device may include a temperature transmitter (which may be located at the tail of the conveying component of the air-cooled equipment) and a control system.

[0132] In this invention, the cooling unit preferably includes a water washing device, which has been described in detail in the second aspect and will not be repeated here.

[0133] The operating conditions of the cooling unit of the system have been described in detail in the second aspect and will not be repeated here.

[0134] Unless otherwise specified, the other units of this system can be operated in accordance with conventional operating conditions in the art.

[0135] The present invention will be described in detail below through embodiments.

[0136] The cellulase used was CTEC3 cellulase purchased from Novozymes.

[0137] The yeast strain is Angel Super Brewing High-Activity Dry Yeast from Hubei Angel Yeast Co., Ltd.

[0138] In the following embodiments, unless otherwise specified, the equipment and corresponding parameters used are conventional in the art.

[0139] Unless otherwise specified, all reagents and materials used were obtained commercially.

[0140] In the following embodiments, taking the crushing and hydrolysis units located indoors (15-30℃) and other units outdoors (ambient temperature 5-25℃) as an example, the fuel ethanol production scale is 30,000 tons / year, and the average flow rate of the material after vapor explosion is 50 m³ / h. 3 / h. The water temperature used is around 25℃.

[0141] The cellulose conversion rate is taken as the endpoint of enzymatic hydrolysis when it reaches 80%. The method for determining the cellulose conversion rate is as follows: measure the cellulose content in the biomass raw material, multiply it by 1.11 to obtain the theoretical value of complete conversion to glucose, and then divide the actual measured glucose content by the theoretical value of glucose to obtain the cellulose conversion rate.

[0142] Unless otherwise specified, the point values ​​mentioned below fluctuate within the range expected in this field.

[0143] Example 1

[0144] This embodiment illustrates a method for producing ethanol (to mature mash) from biomass feedstock through fermentation.

[0145] The production of ethanol using corn stalks as a biomass feedstock is carried out in the following system, which includes:

[0146] A pulverizing unit is used to pulverize the biomass raw material to obtain pulverized biomass raw material;

[0147] The hydrolysis unit is used to steam-explode the pulverized biomass raw material to obtain the steam-exploded material.

[0148] A cooling unit is used to cool the material after the steam explosion to obtain the material to be enzymatically hydrolyzed;

[0149] An enzymatic hydrolysis unit is used to enzymatically hydrolyze the material to be hydrolyzed to obtain an enzymatic hydrolysate;

[0150] A fermentation unit is used to ferment the enzymatic hydrolysate to obtain a fermentation broth.

[0151] The specific operating method is as follows:

[0152] (1) Crushing unit

[0153] The corn stalks are first crushed into pieces approximately 7cm in length using a primary crusher, and then fed into a dust collector to remove impurities. The dust collector is located above the dust collector. The crushed material is then further crushed into fragments approximately 1.5cm in length, yielding corn stalk powder. This powder is then conveyed to a buffer silo to provide raw material for the hydrolysis unit.

[0154] (2) Hydrolysis unit

[0155] The corn stalk powder was mixed with water and then subjected to neutral steam explosion treatment to obtain the steam-exploded material. The content of corn stalk powder in the mixture was 50% by weight, and the steam explosion conditions included: temperature of 180℃, pressure of 1.0MPa, and time of 20min. The temperature of the steam-exploded material was 100-105℃, the solid content was 35% by weight, and more than 80% by weight of the particles had a particle size in the range of 2-50μm (e.g., ...). Figure 2 (As shown).

[0156] (3) Cooling unit

[0157] like Figure 1 As shown, the cooling unit includes a blower E4, an air-cooling device E1, a cyclone separator E2, a scrubbing tower E3, and an induced draft fan E5 connected in series. The air-cooling device E1 includes a housing E11, a conveying assembly E12 (equipped with a material layer adjustment plate) located inside the housing E11, a feed inlet E13 located above the housing E11, a discharge outlet E14 located below the housing E11, multiple air inlets E15 located below the housing E11, multiple air outlets E16 located above the housing E11, and a temperature control device E17 (including a temperature transmitter and control system located at the tail of the air-cooling device). A 100-mesh cat's-eye shaped screen is installed below the feed inlet E13.

[0158] In the cooling unit, the material after the steam explosion is conveyed through the feed inlet E13 and a screen to the conveying assembly E12. Air is supplied by the blower E4 and enters the air-cooling device E1 through the air inlet E15, where it exchanges heat with the material on the conveying assembly E12. The heat-exchanged gas (first gas phase) is discharged through the air outlet E16. As the material is conveyed along the conveying assembly E12, its temperature gradually decreases. A temperature transmitter monitors the temperature of the conveyed material and adjusts the conveying speed and airflow of the conveying assembly accordingly. After reaching the predetermined cooling temperature, the material is discharged from the discharge outlet E14 and conveyed to the mixing auger for preparing the material to be enzymatically hydrolyzed.

[0159] Under the action of the induced draft fan E5, the first gas phase is conveyed from the outlet E16 to the cyclone separator E2 for separation, resulting in a solid material and a second gas phase. The solid material is discharged from the bottom of the cyclone separator E2 and sent to the mixing auger for preparing the material to be enzymatically hydrolyzed.

[0160] Under the action of the induced draft fan E5, the second gas phase is conveyed from the cyclone separator E2 to the washing tower E3. After washing, the wastewater and exhaust gas are obtained. The exhaust gas is discharged after meeting environmental protection requirements. The wastewater is discharged into the sewage treatment system after the impurity content reaches 10% by weight.

[0161] During the air-cooling process, the material is in a dense fluidized state, preventing caking and resulting in good heat exchange.

[0162] The thickness of the material on the control conveying component E12 is 15cm. The temperature of the cooled material is set to 55℃, the material conveying speed is 0.07m / s, and the air volume of the blower is 76000m³ / s. 3 / h, wind speed is 12m / s, wind pressure (total pressure) is 605Pa; the air volume of the induced draft fan is 80000m³ / h. 3 / h, air pressure (total pressure) is 2300Pa. During production, the parameters are adjusted as needed.

[0163] (4) Enzymatic hydrolysis unit

[0164] The cooled material and solid phase material were thoroughly mixed with water and cellulase in a mixing auger and pre-enzymatically hydrolyzed. The pre-enzymatically hydrolyzed material (solid content of 22% by weight) was transferred to two enzymatic hydrolysis tanks connected in series for 4 hours of pre-enzymatic hydrolysis, followed by main enzymatic hydrolysis in six enzymatic hydrolysis tanks connected in series for 60 hours to obtain the enzymatic hydrolysate. The amount of cellulase used was 4 enzyme activity units per gram of dry weight of biomass raw material. The conditions for pre-enzymatic hydrolysis and main enzymatic hydrolysis included a temperature of 50°C and a pH of 5.

[0165] (3) Fermentation unit

[0166] Saccharomyces cerevisiae was activated in shake flasks for 10 hours, and then the yeast was progressively amplified using a three-stage amplification method to obtain a seed culture. The culture media used for activation and amplification were both enzymatic hydrolysates, with an inoculum size of 5%, a temperature of 30℃, and a pH of 5. The first and second stages of amplification were intermittent, each lasting 12 hours. The first stage of the third amplification was 16 hours, followed by subsequent stages lasting 10-12 hours (determined based on the activity of the strain).

[0167] The enzymatic hydrolysate and seed culture are transferred to a fermenter for fermentation, wherein the inoculum size of the yeast is 10 relative to 1 gram of the enzymatic hydrolysate. 8 CFU. After inoculation, the mash was cultured under stirring conditions. The fermentation conditions were: fermentation temperature of 35℃, pH of 4.25, and fermentation time of 45 hours. After fermentation, the mash was filtered to obtain a mature mash with an alcohol content of 6.5% v / v.

[0168] For every 1 ton of ethanol produced (at 99.5% v / v), 1 ton of water is consumed and 2.3 tons of distillation steam is consumed.

[0169] Example 2

[0170] This embodiment illustrates a method for producing ethanol (to mature mash) from biomass feedstock through fermentation.

[0171] The operation is performed according to the method described in Example 1, with the following differences:

[0172] In the hydrolysis unit, the corn stalk powder is mixed with water and then subjected to neutral steam explosion treatment to obtain the steam-exploded material. The corn stalk powder content in the mixture is 45% by weight, and the steam explosion conditions include: temperature of 160℃, pressure of 0.8MPa, and time of 5min. The temperature of the steam-exploded material is 100-105℃, the solid content is 30% by weight, and more than 60% by weight of the particles have a particle size in the range of 80μm.

[0173] In the cooling unit, the thickness of the material on the control conveying assembly E12 is set to 13cm. The temperature of the cooled material is set to 55℃, the material conveying speed is 0.05m / s, and the air volume of the blower is 80000m³ / s. 3 / h, wind speed is 16m / s, wind pressure (total pressure) is 620Pa; the air volume of the induced draft fan is 6000m³ / h. 3 The airflow rate is 20 m / s, and the air pressure (total pressure) is 2400 Pa. During production, these parameters are adjusted as needed. During air cooling, the material is in a dense fluidized state, preventing caking and resulting in good heat exchange.

[0174] In the enzymatic hydrolysis unit, the pre-enzymatically hydrolyzed material (solid content of 20% by weight) is first pre-enzymatically hydrolyzed for 9 hours, and then mainly enzymatically hydrolyzed for 56 hours. The amount of cellulase used is 5 enzyme activity units per gram of dry weight of biomass raw material.

[0175] The fermentation time was 56 hours, and the alcohol content of the mature mash obtained after filtration after fermentation was 5.2% v / v.

[0176] For every 1 ton of ethanol produced (at 99.5% v / v), 1.3 tons of water and 2.5 tons of distillation steam are consumed.

[0177] Comparative Example 1

[0178] This comparative example illustrates the method for producing ethanol (to mature mash) from biomass feedstock through fermentation.

[0179] The operation is carried out according to the method described in Example 1, except that water cooling is used instead of air cooling. Specifically:

[0180] In the cooling unit, the material after steam explosion is diluted and cooled with process water (25°C) until the material temperature reaches 50°C and the solid content is 15% by weight. The diluted material is then filtered through a plate and frame filter press to obtain wet residue (solid content 22% by weight) and clear liquid. The wet residue is subjected to pre-enzymatic hydrolysis and main enzymatic hydrolysis in sequence. Part of the clear liquid is returned to the pre-enzymatic hydrolysis stage and used as process water.

[0181] During the enzymatic hydrolysis process, the amount of cellulase used is 7.5 enzyme activity units per gram of dry weight of biomass raw material. The pre-hydrolysis time is 10 hours, and the main hydrolysis time is 80 hours.

[0182] During the water cooling process, the heat exchange efficiency is low and not thorough due to the difficulty in mixing the materials, resulting in material clumping. At the same time, since the clear liquid cannot be fully returned for reuse, pentose sugars are lost, and the alcohol content of the resulting mature mash is relatively low. After 64 hours of fermentation, the alcohol content of the filtered mature mash is 4.1% v / v.

[0183] For every 1 ton of ethanol produced (at 99.5% v / v), 6.3 tons of water and 2.9 tons of distillation steam are consumed.

[0184] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. The use of air cooling in the process of cooling the material after steam explosion in the production of ethanol from biomass raw materials, wherein, The application comprises at least one of the following aspects: 1) improving the flowability of the material after steam explosion, improving the heat exchange efficiency, and avoiding material caking; 2) reducing the enzyme addition amount and / or shortening the enzyme hydrolysis time in the process of enzymatic hydrolysis of cellulose; 3) increasing the alcohol degree of the fermentation product and reducing the rectification steam consumption; The biomass raw material comprises at least one of corn straw, corn husk, corn cob, wheat straw, rice straw, sugarcane residue, bean pole, cotton pole, banana pole, coconut shell, bamboo, switchgrass, giant reed, tree branch, wood chip and sawdust. The application comprises: air-cooling the material after steam explosion to obtain the cooled material and the first gas phase. The air-cooling treatment is carried out in an air-cooling device. The air-cooling device comprises a shell, a conveying assembly located in the shell, a feeding port and an air outlet located above the shell, and a discharging port and an air inlet located below the shell. The feeding port is located above the starting section of the conveying assembly, and the discharging port is located below the ending section of the conveying assembly. The thickness of the material after steam explosion on the conveying assembly is 9-18 cm. The method comprises: air-cooling the material after steam explosion to obtain the cooled material and the first gas phase.

2. A method of cooling material after steam explosion in an ethanol production process from a biomass feedstock, characterized in that, Optionally, the first gas phase is separated to obtain the solid-phase material and the second gas phase. The cooled material and the solid-phase material are the material to be enzymatically hydrolyzed. The biomass raw material comprises at least one of corn straw, corn husk, corn cob, wheat straw, rice straw, sugarcane residue, bean pole, cotton pole, banana pole, coconut shell, bamboo, switchgrass, giant reed, tree branch, wood chip and sawdust. The air-cooling treatment is carried out in an air-cooling device. The air-cooling device comprises a shell, a conveying assembly located in the shell, a feeding port and an air outlet located above the shell, and a discharging port and an air inlet located below the shell. The feeding port is located above the starting section of the conveying assembly, and the discharging port is located below the ending section of the conveying assembly. The thickness of the material after steam explosion on the conveying assembly is 9-18 cm. The method for producing ethanol from the biomass raw material comprises: sequentially crushing, steam-explosively treating, air-cooling, enzymatically hydrolyzing, fermenting and distilling the biomass raw material to obtain ethanol. The steam-explosively treating mode is at least one of neutral steam explosion, acid steam explosion and alkaline steam explosion.

3. The method of claim 2, wherein, The steam-explosively treating mode is neutral steam explosion.

4. The method of claim 3, wherein, The steam-explosively treating conditions are such that the temperature of the material after steam explosion is 100-105°C, the solid content is 30-50% by weight, and the particle size is less than 200 μm.

5. The method of claim 4, wherein, The steam-explosively treating conditions are such that the particle size of more than 60% by weight of the particles in the material after steam explosion is in the range of 2-100 μm.

6. The method of any of claims 2-5, wherein, The air-cooling treatment is carried out in an air-cooling device.

7. The method of claim 6, wherein, The air-cooling device comprises a shell, a conveying assembly located in the shell, a feeding port and an air outlet located above the shell, and a discharging port and an air inlet located below the shell.

8. The method of any one of claims 2-5, wherein, The feeding port is located above the starting section of the conveying assembly, and the discharging port is located below the ending section of the conveying assembly. The thickness of the material after steam explosion on the conveying assembly is 9-18 cm. The air-cooling treatment is carried out in an air-cooling device. The air-cooling device comprises a shell, a conveying assembly located in the shell, a feeding port and an air outlet located above the shell, and a discharging port and an air inlet located below the shell. The feeding port is located above the starting section of the conveying assembly, and the discharging port is located below the ending section of the conveying assembly. The thickness of the material after steam explosion on the conveying assembly is 9-18 cm.

9. The method of claim 2, wherein, The air cooling device is provided with a temperature control device for detecting the temperature of the material at the end section of the conveying assembly and adjusting the air supply amount of the air cooling device and / or the material conveying speed to control the temperature of the material at the end section of the conveying assembly within a predetermined range.

10. The method of claim 9, wherein, The feeding port is further provided with a screen below.

11. The method of claim 10, wherein, The screen has a mesh size of 12-20 mesh. The screen has at least one of cat-eye shape, circular shape, square shape, diamond shape, and triangular shape.

12. The method of claim 11, wherein, The screen has a cat-eye shape.

13. The method of claim 2, wherein, In the air cooling process, the thickness of the material after steam explosion on the conveying assembly is 13-17 cm.

14. The method of claim 2, wherein, The method further comprises: performing water washing treatment on the second gas phase to obtain a water washing waste liquid and a discharged gas.

15. A system for the production of ethanol from a biomass feedstock, characterized by, The system comprises: a crushing unit for crushing the biomass raw material to obtain biomass raw material crushing products; a hydrolysis unit for steam explosion of the biomass raw material crushing products to obtain material after steam explosion; a cooling unit for cooling the material after steam explosion to obtain material to be enzymatically hydrolyzed; an enzymatic hydrolysis unit for enzymatically hydrolyzing the material to be enzymatically hydrolyzed to obtain enzymatic hydrolysis liquid; a fermentation unit for fermenting the enzymatic hydrolysis liquid to obtain mature mash; a distillation unit for distilling the mature mash to obtain ethanol; The cooling unit comprises: an air cooling device for air cooling treatment of the material after steam explosion to obtain cooled material and a first gas phase; The biomass raw material is a cellulose-containing raw material. The system is used for the cooling method of the material after steam explosion in the biomass raw material ethanol production process according to any one of claims 2-14.

16. The system of claim 15, wherein, The cooling unit further comprises a separation device for separation treatment of the first gas phase to obtain solid-phase material and a second gas phase. The air cooling device comprises a shell, a conveying assembly inside the shell, a feeding port and a gas outlet above the shell, and a discharging port and an air inlet below the shell. The feeding port is above the starting section of the conveying assembly along the material direction, and the discharging port is below the end section of the conveying assembly.

17. The system of claim 15, wherein, The air cooling device is provided with a temperature control device for detecting the temperature of the material at the end section of the conveying assembly and adjusting the air supply amount of the air cooling device and / or the material conveying speed to control the temperature of the material at the end section of the conveying assembly within a predetermined range.

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