Method and system for treating protein drying tail gas

Abstract

The invention relates to a protein drying tail gas treatment method and system, and belongs to the technical field of protein drying tail gas treatment. The method comprises the following steps: pretreating protein drying tail gas; under set conditions, carrying out first purification on the pre-treated protein drying tail gas by using a pervaporation method so as to separate fermentation metabolites and gas of the pre-treated protein drying tail gas to obtain first tail gas; the first tail gas is physically dried to remove fermentation metabolites of the first tail gas, and second tail gas is obtained; and the second tail gas is subjected to activated carbon adsorption, and clean air is obtained. According to the embodiment of the invention, the technical problems that the purification efficiency of the protein drying tail gas is low, odorous fermentation metabolites in part of the drying tail gas escape into the atmosphere, and the surrounding environment is influenced are solved.

Description

Technical Field

[0001] This application relates to the technical field of protein drying tail gas treatment, and particularly relates to a method and system for treating protein drying tail gas. Background Art

[0002] The waste bacteria from one-carbon biological fermentation to produce ethanol have a small diameter, high protein content, high material viscosity, and contain some metabolites such as alcohols and acids produced during the fermentation process. During the drying process, spray drying is generally used. The hot air and the atomized protein concentrate are in a co-current contact manner to separate the water and some metabolites in the protein concentrate from the hot air and the protein powder, obtaining the drying tail gas.

[0003] However, due to the presence of metabolites in the fermentation process, the drying tail gas has a certain smell, which has a certain impact on the surrounding environment; the operating flexibility of the drying tail gas is small. When there are fluctuations in the upstream fermentation, more odors will diffuse into the air, affecting the surrounding environment; the temperature of the drying tail gas is relatively high when it enters the alkali scrubbing tower, increasing the working load of the alkali scrubbing tower and affecting the purification efficiency of the odor during the alkali scrubbing process. Summary of the Invention

[0004] This application provides a method and system for treating protein drying tail gas to solve the following technical problem: how to improve the purification efficiency of protein drying tail gas.

[0005] In the first aspect, an embodiment of this application provides a method for treating protein drying tail gas, and the method includes:

[0006] Pre-treat the protein drying tail gas;

[0007] Under set conditions, use pervaporation to perform primary purification on the pre-treated protein drying tail gas to separate the fermentation metabolites and gas in the pre-treated protein drying tail gas, obtaining a first tail gas;

[0008] Physically dry the first tail gas to remove the fermentation metabolites in the first tail gas, obtaining a second tail gas;

[0009] Perform activated carbon adsorption on the second tail gas to obtain clean air.

[0010] Optionally, the set conditions include: the vacuum side pressure of the pervaporation membrane and the operating temperature of the pervaporation membrane; wherein,

[0011] The vacuum side pressure of the pervaporation membrane is -50 kPa to -90 kPa, and the operating temperature of the pervaporation membrane is 30°C to 150°C.

[0012] Optionally, the physical drying method includes one of the following: cold drying method, molecular sieve drying method.

[0013] Optionally, the temperature of the second tail gas is 5°C to 8°C.

[0014] Optionally, the activated carbon includes one of the following: coal-based activated carbon, wood-based activated carbon, fruit shell activated carbon, synthetic activated carbon.

[0015] Optionally, the pretreatment of the protein drying tail gas includes:

[0016] Cooling the protein drying tail gas;

[0017] Precisely filtering the cooled protein drying tail gas.

[0018] Optionally, the cooling of the protein drying tail gas includes:

[0019] Using air to exchange heat with the protein drying tail gas to cool the protein drying tail gas; wherein,

[0020] The temperature of the protein drying tail gas is 70°C to 90°C, and the temperature of the air is -20°C to 37°C.

[0021] Optionally, the filtration accuracy of the precise filtration is <0.02 μm.

[0022] In a second aspect, an embodiment of the present application provides a system for purifying protein drying tail gas for implementing the method described in any one of the first aspects. The system includes:

[0023] A pretreatment component 1;

[0024] A pervaporation membrane 2;

[0025] A dryer 3, connected to the pervaporation membrane 2;

[0026] An activated carbon box 4, connected to the dryer 3.

[0027] Optionally, the pretreatment component 1 includes:

[0028] A heat exchanger 11;

[0029] A precision filter 12, respectively connected to the heat exchanger 11 and the pervaporation membrane 2.

[0030] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0031] The method for treating the protein drying tail gas provided by the embodiment of the present application includes: pre-treating the protein drying tail gas; under set conditions, using pervaporation to perform first purification on the pre-treated protein drying tail gas to separate the fermentation metabolites and gas in the pre-treated protein drying tail gas, obtaining a first tail gas; physically drying the first tail gas to remove the fermentation metabolites in the first tail gas, obtaining a second tail gas; performing activated carbon adsorption on the second tail gas to obtain clean air. Under set conditions, using pervaporation to perform first purification on the pre-treated protein drying tail gas. During the pervaporation separation process, gas molecules of different components in the drying tail gas generate a concentration gradient due to their different solubilities, so that the air and fermentation metabolites in the protein drying tail gas can be separated; the first tail gas is physically dried, and the phase change caused by the temperature change is used to further remove the metabolites. The combination of pervaporation and physical drying can more effectively purify the tail gas; the second tail gas is subjected to activated carbon adsorption. The activated carbon has a high specific surface area and a developed pore structure, effectively adsorbing impurities and harmful substances in various gases and liquids, thereby obtaining clean air. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0033] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0034] Figure 1 It is a schematic flowchart of a method for treating protein drying tail gas provided by an embodiment of the present application;

[0035] Figure 2 It is a schematic structural diagram of a system for treating protein drying tail gas provided by an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts fall within the scope of protection of the present application.

[0037] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0038] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing direction in the drawings. Additionally, in the description of the present application specification, the terms "including", "comprising", etc. mean "including but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0039] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present application can be obtained through market purchases or can be prepared by existing methods.

[0040] In a first aspect, an embodiment of the present application provides a method for treating the tail gas of protein drying. Figure 1 is a schematic flow chart of a method for treating the tail gas of protein drying provided by an embodiment of the present application; please refer to Figure 1 , the method includes:

[0041] S1. Pre-treat the tail gas of protein drying;

[0042] This step is to preliminarily treat the original tail gas of protein drying to prepare for subsequent purification steps. The pre-treatment may include removing large particulate impurities in the tail gas, adjusting the temperature and pressure of the tail gas, etc., to ensure the smooth progress of subsequent steps.

[0043] In some embodiments, the pre-treating the tail gas of protein drying includes:

[0044] Cool the tail gas of protein drying;

[0045] Precisely filter the cooled tail gas of protein drying.

[0046] In some embodiments, the cooling the tail gas of protein drying includes:

[0047] Use air to exchange heat with the protein drying tail gas to cool the protein drying tail gas; wherein,

[0048] The temperature of the protein drying tail gas is 70°C to 90°C, and the temperature of the air is -20°C to 37°C.

[0049] In the embodiment of the present application, the protein drying tail gas is pretreated, including cooling and fine filtration, in order to better prepare for the subsequent pervaporation process. The cooling step can reduce the tail gas temperature and reduce the possible damage to subsequent equipment (such as the pervaporation membrane) caused by high temperature. At the same time, it also helps the preliminary separation of some easily condensable components. The fine filtration step is to remove solid impurities in the tail gas to prevent these impurities from entering the pervaporation membrane, blocking the membrane pores or affecting the normal operation of other components, thereby improving the stability and treatment effect of the entire tail gas treatment system.

[0050] The protein drying tail gas exchanges heat with air, heating the air while reducing the tail gas temperature, and reducing heat source consumption. The temperature of the protein drying tail gas can be 70°C to 90°C, and the temperature of the air can be -20°C to 37°C, which can fully recover the heat of the protein drying tail gas. Exemplarily, the temperature of the protein drying tail gas can be 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, etc.; the temperature of the air can be -20°C, -15°C, -10°C, -5°C, 0, 1°C, 2°C, 3°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 37°C, etc.

[0051] In some embodiments, the filtration accuracy of the fine filtration < 0.02μm.

[0052] In the embodiment of the present application, when the drying tail gas passes through the fiber material in the filter, these materials contain many small pores. The size of the pores can be adjusted as needed so that the filter can capture particles of different sizes. Larger particles are blocked on the surface of the filter, while smaller particles enter the interior through the pores. The fine filtration air filter can be provided with a multi-stage filtration device. The first-stage filtration device generates a coalescence effect through a cylindrical mesh filter core, and large particles are adsorbed on the filter material, and moisture condenses into larger water droplets. When entering the separation chamber, the air velocity slows down, causing the particles to agglomerate again, and the water mist condenses on the honeycomb-shaped water collector and then is discharged through the drainage device. The filtration accuracy of the fine filtration < 0.02μm. A filtration accuracy less than 0.02μm means that this fine filtration process can effectively intercept very small particles, fully protecting the pervaporation membrane from being contaminated by impurities and continuously having a high working efficiency. Exemplarily, the filtration accuracy of this fine filtration can be 0.019μm, 0.018μm, 0.017μm, 0.016μm, etc.

[0053] S2. Under set conditions, the pretreated protein drying tail gas is first purified using pervaporation to separate the fermentation metabolites and gas in the pretreated protein drying tail gas, obtaining a first tail gas.

[0054] Under set conditions, the pretreated tail gas is purified using pervaporation. Pervaporation is a separation technique based on the solubility differences of components, achieving the separation of different components by forming a concentration gradient.

[0055] In this process, the fermentation metabolites (such as organic substances, moisture, etc.) in the tail gas and air are separated due to different solubilities. The fermentation metabolites are enriched on one side of the pervaporation membrane, while air is discharged through the other side of the membrane, forming a first tail gas.

[0056] In some embodiments, the set conditions include: the pressure on the vacuum side of the pervaporation membrane and the operating temperature of the pervaporation membrane; wherein,

[0057] the pressure on the vacuum side of the pervaporation membrane is -50 kPa to -90 kPa, and the operating temperature of the pervaporation membrane is 30°C to 150°C.

[0058] In the embodiments of the present application, pervaporation is achieved through a pervaporation membrane. During the pervaporation membrane separation process, gas molecules of different components in the drying tail gas generate a concentration gradient due to their different solubilities. The gas molecules undergo an evaporation process on the membrane surface, enter the pores of the membrane material and diffuse inside, and finally are released from the other side of the membrane surface. Since the solubilities of different gas components in the solution are different, their diffusion rates in the membrane are also different, thus achieving separation.

[0059] The pressure on the vacuum side of the pervaporation membrane can be -50 kPa to -90 kPa, which is a negative pressure range. The negative pressure environment plays a key role in the pervaporation process, providing a powerful driving force for pervaporation. According to the mass transfer principle, a lower pressure on the vacuum side can significantly reduce the partial pressure of components on the downstream side (vacuum side) of the pervaporation membrane. When the pressure on the vacuum side decreases, the partial pressure of water or organic substances (depending on the selectivity of the membrane) on the downstream side of the membrane is much lower than that on the upstream side, making it easier for these components to diffuse through the pervaporation membrane from the upstream side to the downstream side, thereby improving the separation efficiency. Exemplarily, the pressure on the vacuum side of the pervaporation membrane can be -50 kPa, -55 kPa, -60 kPa, -65 kPa, -70 kPa, -75 kPa, -80 kPa, -85 kPa, -90 kPa, etc.

[0060] The operating temperature of the pervaporation membrane can be 30°C to 150°C. The increase in temperature is beneficial to the movement of molecules. Within this temperature range, the molecules in the mixture have sufficient energy to overcome the resistance of the membrane for diffusion. As the temperature rises, the thermal motion of molecules intensifies, and the collision frequency with the membrane surface increases, making it easier for molecules to penetrate the pervaporation membrane. Changes in membrane performance: Different pervaporation membrane materials have their suitable temperature ranges. Within the range of 30°C to 150°C, the performance of the membrane material can be better exerted. Exemplarily, the operating temperature of the pervaporation membrane can be 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.

[0061] In addition, the protein tail gas is dried to obtain the protein-dried tail gas. The hot air temperature of the drying tower for drying is 100°C to 250°C, and the pressure is 3 kPa to 50 kPa.

[0062] S3. Physically dry the first tail gas to remove the fermentation metabolites in the first tail gas and obtain the second tail gas;

[0063] Physically dry the first tail gas to remove the remaining fermentation metabolites therein. Physical drying mainly uses the phase change caused by temperature change (such as gas-liquid, gas-solid transformation) to further remove metabolites.

[0064] Through physical drying, the moisture and other volatile metabolites in the tail gas are removed to form the second tail gas.

[0065] In some embodiments, the physical drying method includes one of the following: cold drying method, molecular sieve drying method.

[0066] In some embodiments, the temperature of the second tail gas is 5°C to 8°C.

[0067] In the embodiments of the present application, the cold drying method mainly reduces the gas temperature through a refrigeration system so that the water vapor therein reaches below the dew point temperature, thereby undergoing a phase change, condensing from a gaseous state to a liquid state, and then removing the liquid water through a gas-liquid separation device. The molecular sieve drying method utilizes the adsorption characteristics of molecular sieves to achieve gas drying. In this process, when the dried tail gas containing metabolites enters the cold dryer, as the temperature drops, the saturated vapor pressure of the gas also decreases. According to the phase equilibrium principle, when the gas temperature is lower than the dew point temperature of the metabolites, the metabolites will change from a gaseous state to a liquid state, thereby achieving condensation. Molecular sieve is a material with a uniform microporous structure, and the micropore size is similar to the size of water molecules. When the gas passes through the molecular sieve bed layer, the water molecules will be adsorbed by the micropores of the molecular sieve, while other gas molecules can pass through smoothly, thereby achieving the purpose of drying the gas.

[0068] The second tail gas temperature can be 5°C to 8°C, which can ensure the removal efficiency of the fermentation metabolites in the first tail gas. A relatively low temperature is beneficial to the subsequent activated carbon adsorption process. Activated carbon adsorbs impurities by physical adsorption, which is an exothermic reaction. A low-temperature environment can promote the forward progress of the adsorption reaction. Exemplarily, the second tail gas temperature can be 5°C, 6°C, 7°C, 8°C, etc.

[0069] In addition, the fermentation metabolites are condensed, and the end temperature of the condenser is less than 30°C. When the actual partial pressure of the metabolites in the dry tail gas exceeds the saturated vapor pressure at this temperature, the metabolites will condense out to form liquid water.

[0070] S4. Perform activated carbon adsorption on the second tail gas to obtain clean air.

[0071] The second tail gas is adsorbed through activated carbon to remove residual impurities and harmful substances therein. Activated carbon has a strong adsorption capacity due to its high specific surface area and developed pore structure.

[0072] Through activated carbon adsorption, trace organic substances, inorganic substances, odor substances, etc. in the tail gas are effectively removed, and finally clean air is obtained.

[0073] In some embodiments, the activated carbon includes one of the following: coal-based activated carbon, wood-based activated carbon, fruit shell activated carbon, synthetic activated carbon.

[0074] In the embodiments of the present application, the activated carbon can be one of coal-based activated carbon, wood-based activated carbon, fruit shell activated carbon, and synthetic activated carbon. The activated carbon can be coconut shell activated carbon. Coconut shell activated carbon has excellent adsorption performance, mainly due to its high specific surface area and developed pore structure. These characteristics enable coconut shell activated carbon to effectively adsorb impurities and harmful substances in various gases and liquids, and at the same time, it also has the advantages of high wear resistance and long service life. After the second tail gas is subjected to activated carbon adsorption and the odor is further removed, clean air almost free of fermentation metabolites and odor is obtained.

[0075] A method for treating protein drying tail gas provided by the embodiments of the present application has the following advantages:

[0076] 1. Preliminary purification by pervaporation: Based on the solubility differences of different gas components, a concentration gradient is constructed to achieve the separation of air and fermentation metabolites. This is a physical separation method that does not require additional chemical reagents and conforms to the concept of green environmental protection. By utilizing the characteristics of molecules themselves, the initial purification step is cleverly driven to preliminarily purify the complex protein drying tail gas, screen out relatively purer first tail gas, and reduce the subsequent treatment burden;

[0077] 2. Physical drying for deep removal: Relying on the phase transition caused by temperature, the fermentation metabolites remaining after pervaporation are precisely attacked. When the temperature is properly controlled, the gaseous fermentation metabolites will condense into liquid or solid and leave the exhaust gas flow. This process relies only on simple physical changes to maintain the physical purification characteristics of the entire process and avoid the introduction of new pollutants. Just like cooling down to condense water vapor into water droplets, those stubborn fermentation metabolites are nowhere to be found;

[0078] Synergistic effect of pervaporation and physical drying: Following the pervaporation step, the fermentation metabolites that were not removed in the previous step are processed, complementing the advantages of pervaporation. The combination of the two greatly improves the purification efficiency, making the exhaust gas closer to the clean standard and preparing "cleaner" intake air for activated carbon adsorption;

[0079] 3. Fine purification by activated carbon adsorption: The high specific surface area and developed pore structure of activated carbon are like a powerful "molecular trap". When the gas flows through, impurities and harmful substances will be captured and adsorbed by the pores. No matter the trace fermentation metabolites missed in the first two steps, or other odors and harmful gases, they are all difficult to escape, and the exhaust gas is deeply purified. This process is also pure physical adsorption, which ensures the environmental protection and safety of the purification process. The exhaust gas pretreated by the first two processes is then finely polished by activated carbon adsorption to completely remove all kinds of impurities and purify the air.

[0080] In a second aspect, an embodiment of the present application provides a system for purifying protein drying tail gas, which is used to implement the method described in any one of the first aspects. Figure 2 This is a structural diagram of a system for treating protein drying tail gas provided in an embodiment of the present application; see Figure 2 , the system comprising:

[0081] Preprocessing component 1;

[0082] Pervaporation membrane 2;

[0083] A dryer 3 connected to the pervaporation membrane 2;

[0084] The activated carbon box 4 is connected to the dryer 3 .

[0085] In some embodiments, the pre-processing component 1 comprises:

[0086] Heat exchanger 11;

[0087] The precision filter 12 is connected to the heat exchanger 11 and the pervaporation membrane 2 respectively.

[0088] In the embodiment of the present application, the dryer 3 can be a refrigerated dryer or a molecular sieve drying unit. Working principle of the refrigerated dryer: The refrigerated tail gas dryer is based on the principle of refrigeration and dehumidification. Using a fully enclosed compression refrigeration system, the compressed gas discharged from the compressor is cooled down, so that a large amount of saturated water vapor and oil mist condensate droplets contained therein are condensed. After the gas-liquid separation, they are discharged by an automatic drainer. The saturated tail gas at a relatively high temperature enters the pre-cooler of the refrigerated dryer, where it exchanges heat with the dry and cold gas from the evaporator, and after the temperature is reduced, it enters the evaporator of the refrigeration system and exchanges heat with the refrigerant vapor for the second time, so that its own temperature drops to close to the evaporation temperature of the refrigerant. During the two cooling processes, the water vapor in the tail gas condenses into liquid water droplets and enters the gas-liquid separator along with the air flow. The separated liquid water is discharged outside the machine through the automatic drainer. The relatively low-temperature dry compressed gas enters the pre-cooler and exchanges heat with the newly entered wet saturated gas, so that its own temperature is increased, and thus dry compressed gas with a lower water content (i.e., a lower dew point) and a very low relative humidity is obtained at the exhaust port of the refrigerated dryer. Working principle of the molecular sieve drying unit: First, the dust particle size of the tail gas after treatment is ≤0.01 μm, and it is adsorbed by one tower to produce qualified dry finished gas, while the other tower is regenerated. When heating and regenerating, the regeneration gas is extracted from the preliminarily treated tail gas (after compression) by a circulation fan, heated to above 160 °C by a heater, and blown into the regeneration tower to take away the water adsorbed by the adsorbent, and then discharged to the tail gas recovery. When cold-blowing and regenerating, a part of the finished gas is used as the regeneration gas to cold-blow and regenerate the adsorbent, so as to achieve the purpose of regenerating the adsorbent and realize the cyclic operation and regeneration of the two towers.

[0089] The system further includes: a condenser 5 for discharging the fermented metabolite organic matter out of the system after cooling.

[0090] The protein drying tail gas is communicated with the hot side inlet of the air inlet heat exchanger 11, the hot side outlet of the air inlet heat exchanger 11 is communicated with the inlet of the precision filter 12, the outlet of the precision filter 12 is communicated with the inlet of the pervaporation membrane 2, the outlet of the pervaporation membrane 2 is communicated with the inlet of the condenser 5, the outlet of the condenser 5 obtains the fermented metabolite organic matter, the outlet of the pervaporation membrane 2 is communicated with the inlet of the dryer 3, the outlet of the dryer 3 is communicated with the inlet of the activated carbon box 4, and the outlet of the activated carbon box 4 is communicated with the atmosphere.

[0091] The system for purifying the protein drying tail gas is realized based on the above method for purifying the protein drying tail gas. The specific steps of the method for purifying the protein drying tail gas can refer to the above embodiment. Since the system for purifying the protein drying tail gas adopts some or all of the technical solutions of the above embodiment, it has at least all the beneficial effects brought by the technical solutions of the above embodiment, which will not be elaborated one by one here.

[0092] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. For the experimental methods without specific conditions noted in the following embodiments, they are generally determined in accordance with national standards. If there is no corresponding national standard, they are carried out in accordance with general international standards, conventional conditions or the conditions recommended by the manufacturer.

[0093] Example 1

[0094] The protein drying tail gas is pretreated, including: cooling the protein drying tail gas (using air to exchange heat with the protein drying tail gas to cool the protein drying tail gas); finely filtering the cooled protein drying tail gas; wherein, the temperature of the protein drying tail gas is 30°C, and the temperature of the air is; finely filtering the cooled protein drying tail gas; the filtration accuracy of the fine filtration is 0.2 μm;

[0095] Under set conditions, the pretreated protein drying tail gas is first purified by pervaporation to separate the fermentation metabolites and gas from the pretreated protein drying tail gas, obtaining a first tail gas; the pressure on the vacuum side of the pervaporation membrane is -80 kPa, and the operating temperature of the pervaporation membrane is 30°C;

[0096] The first tail gas is physically dried to remove the fermentation metabolites of the first tail gas, obtaining a second tail gas; the physical drying is the cold drying method, and the temperature of the second tail gas is 5°C;

[0097] The second tail gas is adsorbed by activated carbon to obtain clean air; the activated carbon is coconut shell activated carbon.

[0098] Example 2

[0099] The protein drying tail gas is pretreated, including: cooling the protein drying tail gas (using air to exchange heat with the protein drying tail gas to cool the protein drying tail gas); finely filtering the cooled protein drying tail gas; wherein, the temperature of the protein drying tail gas is 40°C, and the temperature of the air is; finely filtering the cooled protein drying tail gas; the filtration accuracy of the fine filtration is 0.1 μm;

[0100] Under set conditions, the pretreated protein drying tail gas is first purified by pervaporation to separate the fermentation metabolites and gas from the pretreated protein drying tail gas, obtaining a first tail gas; the pressure on the vacuum side of the pervaporation membrane is -90 kPa, and the operating temperature of the pervaporation membrane is 40°C;

[0101] The first tail gas is physically dried to remove the fermentation metabolites of the first tail gas, obtaining a second tail gas; the physical drying is the cold drying method, and the temperature of the second tail gas is 6°C;

[0102] The second tail gas is adsorbed by activated carbon to obtain clean air; the activated carbon is coconut shell activated carbon.

[0103] Example 3

[0104] . The protein drying tail gas is pre-treated, including: cooling the protein drying tail gas (using air to exchange heat with the protein drying

[0105] tail gas to cool the protein drying tail gas); finely filtering the cooled protein drying tail gas; wherein, the temperature of the protein drying tail gas is 35 °C, and the temperature of the air is; finely filtering the cooled protein drying tail gas; the filtering accuracy of the fine filtration is 0.15 μm;

[0106] Under set conditions, the pre-treated protein drying tail gas is first purified by pervaporation to separate the fermentation metabolites and gas of the pre-treated protein drying tail gas, obtaining the first tail gas; the pressure on the vacuum side of the pervaporation membrane is -60 kPa, and the operating temperature of the pervaporation membrane is 35 °C;

[0107] The first tail gas is physically dried to remove the fermentation metabolites of the first tail gas, obtaining the second tail gas; the physical drying is the cold drying method, and the temperature of the second tail gas is 8 °C;

[0108] The second tail gas is adsorbed by activated carbon to obtain clean air; the activated carbon is coconut shell activated carbon.

[0109] Comparative Example 1

[0110] The protein drying tail gas is pre-treated, including: finely filtering the protein drying tail gas; wherein, the temperature of the protein drying tail gas is 80 °C, and the filtering accuracy of the fine filtration is 0.15 μm;

[0111] Under set conditions, the pre-treated protein drying tail gas is first purified by pervaporation to separate the fermentation metabolites and gas of the pre-treated protein drying tail gas, obtaining the first tail gas; the pressure on the vacuum side of the pervaporation membrane is -60 kPa, and the operating temperature of the pervaporation membrane is 80 °C;

[0112] The first tail gas is physically dried to remove the fermentation metabolites of the first tail gas, obtaining the second tail gas; the physical drying is the cold drying method, and the temperature of the second tail gas is 5 °C;

[0113] The first tail gas is adsorbed by activated carbon to obtain non-clean air; the activated carbon is coconut shell activated carbon.

[0114] Comparative Example 2

[0115] Pretreat the protein drying tail gas, including: cooling the protein drying tail gas (using air to exchange heat with the protein drying tail gas to cool the protein drying tail gas); precisely filtering the cooled protein drying tail gas; wherein, the temperature of the protein drying tail gas is 40°C, and the temperature of the air is; precisely filtering the cooled protein drying tail gas; the filtering accuracy of the precise filtration is 0.15μm;

[0116] Under set conditions, use pervaporation to perform primary purification on the pretreated protein drying tail gas to separate the fermentation metabolites and gas of the pretreated protein drying tail gas, obtaining a first tail gas; the pressure on the vacuum side of the pervaporation membrane is -60 kPa, and the operating temperature of the pervaporation membrane is 40°C;

[0117] Physically dry the first tail gas to remove the fermentation metabolites of the first tail gas, obtaining a second tail gas; the physical drying is cold drying, and the temperature of the second tail gas is 20°C;

[0118] Adsorb the second tail gas with activated carbon to obtain non-clean air; the activated carbon is coconut shell activated carbon.

[0119] Test the indicators of the purified air finally obtained in Examples 1 to 3 and Comparative Examples 1 to 2. For the test results, please refer to Table 1.

[0120] Table 1 Purified air VOCs (mg / m 3 )

[0121] Serial number <![CDATA[Purified air VOCs (mg / m 3 )]]> Example 1 55 Example 2 65 Example 3 68 Comparative example 1 160 Comparative example 2 175

[0122] As can be seen from Table 1, a method for treating protein drying tail gas provided by an embodiment of the present application can achieve purified air VOCs lower than 70 mg / m 3 . In Comparative Example 1, since the cooling of the drying tail gas before entering the pervaporation membrane was not set, a part of the metabolites in the drying tail gas could not be effectively removed before the ceramic membrane, affecting the final exhaust gas quality and the service life of the pervaporation membrane; in Comparative Example 2, since the temperature of the second tail gas was too high, a part of the drying tail gas metabolites could not be completely condensed, affecting the final exhaust gas quality.

[0123] One or more technical solutions in the embodiments of the present application at least further have the following technical effects or advantages:

[0124] (1) The drying tail gas exchanges heat with the incoming air, further recovering the heat in the drying tail gas and reducing the consumption of heat sources during the drying process;

[0125] (2) Using a pervaporation membrane, the organic matter and water in the drying tail gas are completely separated to obtain clean air;

[0126] (3) The embodiment of the present application realizes the improvement of the purification efficiency of the drying tail gas, avoids the escape of the odorous fermentation metabolites in part of the drying tail gas into the atmosphere, and affects the surrounding environment.

[0127] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for treating the exhaust gas from protein drying, the method comprising: Pre-treating the exhaust gas from protein drying; Under set conditions, using pervaporation to perform primary purification on the pre-treated exhaust gas from protein drying so as to separate the fermentation metabolites and gas of the pre-treated exhaust gas from protein drying, obtaining a first exhaust gas; Physically drying the first exhaust gas to remove the fermentation metabolites of the first exhaust gas, obtaining a second exhaust gas; Performing activated carbon adsorption on the second exhaust gas to obtain clean air.

2. The method according to claim 1, characterized in that, The set conditions include: the pressure on the vacuum side of the pervaporation membrane and the operating temperature of the pervaporation membrane; wherein, The pressure on the vacuum side of the pervaporation membrane is -50 kPa to -90 kPa, and the operating temperature of the pervaporation membrane is 30°C to 150°C.

3. The method according to claim 1, wherein The physical drying method includes one of the following: cold drying method, molecular sieve drying method.

4. The method according to claim 1, characterized in that, The temperature of the second exhaust gas is 5°C to 8°C.

5. The method according to claim 1, characterized in that, The activated carbon includes one of the following: coal-based activated carbon, wood-based activated carbon, fruit shell activated carbon, synthetic activated carbon.

6. The method according to claim 1, characterized in that The pre-treating the exhaust gas from protein drying includes: Cooling the exhaust gas from protein drying; Precisely filtering the cooled exhaust gas from protein drying.

7. The method according to claim 6, wherein The cooling the exhaust gas from protein drying includes: Using air to exchange heat with the exhaust gas from protein drying so as to cool the exhaust gas from protein drying; wherein, The temperature of the exhaust gas from protein drying is 70°C to 90°C, and the temperature of the air is -20°C to 37°C.

8. The method according to claim 6, wherein The filtration accuracy of the precise filtration is <0.02 μm.

9. A system for purifying the exhaust gas from protein drying, for implementing the method according to any one of claims 1 to 8, the system comprising: A pre-treatment assembly (1); A pervaporation membrane (2); A dryer (3), connected to the pervaporation membrane (2); An activated carbon box (4), connected to the dryer (3).

10. The system according to claim 9, wherein The pre-treatment assembly (1) includes: A heat exchanger (11); A precision filter (12), respectively connected to the heat exchanger (11) and the pervaporation membrane (2).

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