Exhaust gas absorption system in cotton protein production workshop

Abstract

This utility model discloses a tail gas absorption system for a cotton protein dephenolization production workshop. The outlet of the workshop's mixed gas phase pipe is connected to the shell-side inlet of a mixed gas phase condenser. The shell-side outlet of the mixed gas phase condenser is connected to the shell-side inlet of a refrigeration condenser. The shell-side outlet of the refrigeration condenser is connected to the lower inlet of a hexane absorption tower. The top exhaust port of the hexane absorption tower is connected to the lower inlet of a methanol absorption tower. The bottom outlet of the methanol absorption tower is connected to the hot-side inlet of a water cooler via a water absorption circulation pump. The hot-side outlet of the water cooler is connected to the upper spray port of the methanol absorption tower. The top exhaust port of the methanol absorption tower is connected to a tail gas discharge pipe via a tail gas fan. This system can absorb mixed tail gas under conditions of two absorbents and lower temperatures, thereby reducing system solvent consumption, improving tail gas emission indicators, and increasing production economic efficiency.

Description

Technical Field

[0001] This utility model relates to an absorption system for oil and solvent exhaust gas, and more particularly to an exhaust gas absorption system for a cotton protein dephenolization production workshop, belonging to the field of resource recycling technology. Background Technology

[0002] my country is a major cotton-producing country in the world. Cottonseed can be processed into cottonseed oil and cottonseed meal. Cottonseed meal is a good protein feed resource, but it contains high levels of gossypol. If used directly as feed without processing, it can affect animal reproductive function and, through bioaccumulation, harm human health. This severely limits the application of cottonseed protein.

[0003] Currently, most cottonseed protein production using dephenolized cottonseed protein employs a two-step extraction method. Specifically, the pretreated cottonseed is first extracted with n-hexane in a defatting extractor to obtain a mixed oil and defatted cottonseed meal. The mixed oil undergoes hexane recovery and oil refining in a solvent evaporation and refining section to obtain crude extracted oil. The defatted cottonseed meal then enters a dephenolized extractor, where methanol quenches most of the free gossypol in the cottonseed meal, resulting in a free gossypol content of approximately 1000 ppm. The liquid phase obtained from the dephenolized extractor enters a phase separator to separate the methanol phase from the n-hexane phase. The cottonseed meal can either be sent to the methanol recovery system to recover methanol or returned directly to the dephenolizing extractor for reuse. The wet meal obtained from the dephenolizing extractor enters the desolventizing and drying system through the wet meal scraper, which further reduces the content of free gossypol in the cottonseed meal to below 400 ppm. Multiple vertical dryers and steam extractors are connected in series or in parallel to form the desolventizing and drying system. Hexane and methanol are steamed off from the wet meal under the action of indirect or direct steam. Hexane, methanol and water vapor and non-condensable air entering the desolventizing and drying system together form a mixed gas phase.

[0004] For the mixed gas phase generated by the phenol removal leaching unit and the evaporation system, the current mainstream recycling process involves the mixed gas phase and circulating cooling water first exchanging heat in a mixed gas phase condenser, during which approximately 90% of the condensable gases in the mixed gas phase are condensed. Then, the mixed gas phase exchanges heat with the even cooler circulating water in the final condenser, and the condensable gases are condensed again, leaving approximately 1% of the mixed gas phase uncondensed. Subsequently, the uncondensed mixed gas phase enters a methanol absorption tower for absorption, where the absorbent used is low-temperature circulating water. On the one hand, the polarity of water is similar to that of methanol, allowing water to absorb methanol; on the other hand, the low-temperature water causes some of the n-hexane to condense, reducing the n-hexane content in the tail gas. Finally, the mixed gas phase after passing through the methanol absorption tower is discharged into the atmosphere by the exhaust gas fan.

[0005] The shortcomings of existing technologies are as follows: the minimum temperature of the circulating cooling water entering the final condenser is related to the ambient temperature and the heat dissipation capacity of the cooling tower. The circulating cooling water is generally above 30°C, resulting in a small temperature difference with the mixed gas phase. The flow rate of the condensed tail gas remains high, placing a heavy load on the absorption tower. Simultaneously, the high tail gas temperature leads to ineffective absorption by subsequent absorption towers. While methanol and water have similar polarities, n-hexane differs significantly. Using a methanol absorption tower with water circulation only absorbs methanol, failing to absorb n-hexane in the mixed gas phase, thus resulting in a higher amount of n-hexane in the exhaust gas. Currently used circulating water cooling and single absorption towers result in high tail gas flow rates, incomplete tail gas absorption, and significant solvent emissions into the atmosphere, leading to excessive solvent loss and economic losses. Utility Model Content

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, and such simplifications or omissions should not be construed as limiting the scope of the present invention.

[0007] In view of the problems existing in the above and / or prior art, this utility model is proposed.

[0008] The purpose of this invention is to overcome the problems existing in the prior art and provide a tail gas absorption system for a cotton protein dephenolization production workshop. This system can absorb mixed tail gas under two absorbent liquids and at a lower temperature, thereby reducing system solvent consumption, improving tail gas emission indicators, and increasing production economic efficiency.

[0009] To solve the above technical problems, this utility model provides a tail gas absorption system for a cotton protein dephenolization production workshop, including a workshop mixed gas phase pipe. The outlet of the workshop mixed gas phase pipe is connected to the shell-side inlet of a mixed gas phase condenser. The shell-side outlet of the mixed gas phase condenser is connected to the shell-side inlet of a refrigeration condenser. The shell-side outlet of the refrigeration condenser is connected to the lower inlet of a hexane absorption tower. The top exhaust port of the hexane absorption tower is connected to the lower inlet of a methanol absorption tower. The bottom outlet of the methanol absorption tower is connected to the hot-side inlet of a water cooler via a water absorption circulation pump. The hot-side outlet of the water cooler is connected to the upper spray port of the methanol absorption tower. The top exhaust port of the methanol absorption tower is connected to a tail gas discharge pipe via a tail gas fan.

[0010] Furthermore, the bottom drain of the n-hexane absorption tower is connected to the cold-side inlet of the mineral oil heat exchanger via a cold mineral oil pump. The cold-side outlet of the mineral oil heat exchanger is connected to the tube-side inlet of the mineral oil heater. The tube-side outlet of the mineral oil heater is connected to the upper inlet of the n-hexane desorption tower. The bottom outlet of the n-hexane desorption tower is connected to the hot-side inlet of the mineral oil heat exchanger via a hot mineral oil pump. The hot-side outlet of the mineral oil heat exchanger is connected to the hot-side inlet of the mineral oil cooler. The hot-side outlet of the mineral oil cooler is connected to the upper inlet of the n-hexane absorption tower.

[0011] Furthermore, the liquid overflow port of the methanol absorption tower is connected to the methanol distillation system via an overflow pipe.

[0012] Furthermore, a drain outlet is provided at the lower part of the exhaust gas fan outlet duct, and the drain outlet is connected to the reflux port of the methanol absorption tower through a water trap.

[0013] Furthermore, the lower steam inlet of the n-hexane desorption tower is connected to a steam pipe, and the top exhaust port of the n-hexane desorption tower is connected to the shell-side inlet of the mixed gas phase condenser.

[0014] Furthermore, the shell-side steam inlet of the mineral oil heater is connected to a steam pipe via a steam regulating valve. The opening degree of the steam regulating valve is controlled by the tube-side outlet temperature of the mineral oil heater. The shell-side condensate outlet of the mineral oil heater is connected to a condensate outlet pipe.

[0015] Furthermore, the tube-side inlet of the mixed gas phase condenser is connected to the circulating water inlet pipe, and the tube-side outlet of the mixed gas phase condenser is connected to the circulating water outlet pipe; the shell-side condensate outlet of the mixed gas phase condenser is connected to the methanol-n-hexane phase separator through the condensate outlet pipe.

[0016] Furthermore, the tube-side inlet of the refrigeration condenser is connected to the refrigerant inlet pipe, and the tube-side outlet of the refrigeration condenser is connected to the cooling medium outlet pipe; the shell-side condensate outlet of the refrigeration condenser is connected to the methanol-n-hexane phase separator through the final condensate outlet pipe.

[0017] Compared to the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following: 1. Replace the circulating cooling water in the final condenser with a low-temperature refrigerant, which lowers the temperature of the final condenser, increases the amount of condensation of the mixed gas phase, and reduces the gas phase flow rate entering the absorption system. 2. A hexane absorption tower was added to absorb hexane in the mixed tail gas, which significantly reduced the amount of hexane in the exhaust gas and reduced the degree of air pollution. 3. Adding a matching stripping tower to the hexane absorption tower can desorb the hexane that has been absorbed by mineral oil, and then condense it in the condenser to realize the recovery and utilization of hexane, reduce the consumption of hexane, and save production costs. 4. Equipping the n-hexane absorption tower and n-hexane desorption tower with a mineral oil heat exchange system can achieve most of the heat recovery, significantly reduce the heat consumption during the mineral oil circulation process, save steam consumption, and improve economic efficiency; the mineral oil circulates between the desorption tower and the absorption tower without additional mineral oil consumption. The flow rate of mineral oil is regulated by the interlocking control of the level gauge and the variable frequency motor, ensuring stable circulation of mineral oil between the two towers. 5. Equip the methanol absorption tower with a water cooler, using a low-temperature freezing medium as the heat exchange medium, which reduces the temperature of the absorption water in the methanol absorption tower and improves the methanol absorption efficiency. 6. Each ton of cottonseed can reduce hexane consumption by 1.5 kg and save methanol consumption by 1.5 kg. Taking a factory with a daily processing capacity of 1000 tons as an example, with a hexane price of 8500 yuan / ton and a methanol price of 2500 yuan / ton, and 320 processing days per year, the annual processing cost savings can be at least 1000*1.5 / 1000*320*(8500+2500)=5.28 million yuan. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit this utility model. Wherein: Figure 1 This is a flowchart of the exhaust gas absorption system in the cotton protein dephenolization production workshop of this utility model; In the diagram: E1. Mixed vapor phase condenser; E2. Refrigeration condenser; E3. Mineral oil heater; E4. Mineral oil heat exchanger; E5. Mineral oil cooler; E6. Water cooler; F1. Exhaust fan; P1. Hot mineral oil pump; P2. Cold mineral oil pump; P3. Water absorption circulation pump; V1. Hexane desorption tower; V2. Hexane absorption tower; V3. Methanol absorption tower G1. Mixed gas phase pipe in workshop; G2. Circulating water inlet pipe; G3. Circulating water outlet pipe; G4. Condensate outlet pipe; G5. Standby non-condensable gas inlet pipe; G6. Refrigerant inlet pipe; G7. Cooling medium outlet pipe; G8. Final condensate outlet pipe; G9. Steam pipe; G10. Condensate outlet pipe; G11. Overflow pipe; G12. Make-up water pipe; G13. Exhaust gas emission pipe. Detailed Implementation

[0019] In the following description of this utility model, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not mean that the device must have a specific orientation.

[0020] To make the technical means, creative features, achieved objectives and effects of this utility model easier to understand, the present utility model will be further described below with reference to specific illustrations. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0022] like Figure 1 As shown, the exhaust gas absorption system of the cotton protein dephenolization production workshop of this utility model includes a mixed gas phase condenser E1, a refrigerated condenser E2, a mineral oil heater E3, a mineral oil heat exchanger E4, a mineral oil cooler E5, a water cooler E6, a hexane desorption tower V1, a hexane absorption tower V2, and a methanol absorption tower V3. The outlet of the workshop mixed gas phase pipe G1 is connected to the shell-side inlet of the mixed gas phase condenser E1, and the shell-side outlet of the mixed gas phase condenser E1 is connected to the shell-side inlet of the refrigerated condenser E2. The shell-side outlet of condenser E2 is connected to the lower inlet of n-hexane absorber V2. The top exhaust port of n-hexane absorber V2 is connected to the lower inlet of methanol absorber V3. The bottom outlet of methanol absorber V3 is connected to the inlet of water absorption circulation pump P3. The outlet of water absorption circulation pump P3 is connected to the hot side inlet of water cooler E6. The hot side outlet of water cooler E6 is connected to the upper spray port of methanol absorber V3. The liquid overflow port of methanol absorber V3 is connected to the methanol distillation system through overflow pipe G11.

[0023] The top exhaust port of methanol absorption tower V3 is connected to the inlet of tail gas fan F1, and the outlet of tail gas fan F1 is connected to tail gas discharge pipe G13. A drain outlet is provided at the bottom of the outlet duct of tail gas fan F1, and this drain outlet is connected to the return port of methanol absorption tower V3 through a water trap.

[0024] The bottom drain of the hexane absorber V2 is connected to the inlet of the cold mineral oil pump P2. The outlet of the cold mineral oil pump P2 is connected to the cold side inlet of the mineral oil heat exchanger E4. The cold side outlet of the mineral oil heat exchanger E4 is connected to the tube-side inlet of the mineral oil heater E3. The tube-side outlet of the mineral oil heater E3 is connected to the upper inlet of the hexane desorption tower V1. The bottom outlet of the hexane desorption tower V1 is connected to the inlet of the hot mineral oil pump P1. The outlet of the hot mineral oil pump P1 is connected to the hot side inlet of the mineral oil heat exchanger E4. The hot side outlet of the mineral oil heat exchanger E4 is connected to the hot side inlet of the mineral oil cooler E5. The hot side outlet of the mineral oil cooler E5 is connected to the upper inlet of the hexane absorber V2.

[0025] The top exhaust port of the n-hexane desorption tower V1 is connected to the shell-side inlet of the mixed gas phase condenser E1, and the lower steam inlet of the n-hexane desorption tower V1 is connected to the steam pipe G9.

[0026] The shell-side steam inlet of the mineral oil heater E3 is connected to the steam pipe G9 via a steam regulating valve. The opening degree of the steam regulating valve is controlled by the temperature of the tube-side outlet of the mineral oil heater E3. The shell-side condensate outlet of the mineral oil heater E3 is connected to the condensate outlet pipe G10.

[0027] The tube-side inlet of the mixed gas phase condenser E1 is connected to the circulating water inlet pipe G2, and the tube-side outlet of the mixed gas phase condenser E1 is connected to the circulating water outlet pipe G3. The shell-side condensate outlet of the mixed gas phase condenser E1 is connected to the methanol-n-hexane phase separator through the condensate outlet pipe G4.

[0028] The tube-side inlet of the refrigeration condenser E2 is connected to the refrigerant inlet pipe G6, the tube-side outlet of the refrigeration condenser E2 is connected to the cooling medium outlet pipe G7, the shell-side inlet of the refrigeration condenser E2 is also connected to the spare uncondensed gas inlet pipe G5, and the shell-side condensate outlet of the refrigeration condenser E2 is connected to the methanol-n-hexane phase separator through the final condensate outlet pipe G8.

[0029] Taking a production line that processes 1000 tons of cottonseed daily to produce cottonseed oil and dephenolized cottonseed protein as an example, this invention addresses the condensation and absorption of a mixed gas phase composed of hexane, methanol, water vapor, and non-condensable air entering the solvent removal and drying system. The mixed gas phase enters the shell side of the mixed gas phase condenser E1 through the workshop mixed gas phase pipe G1 for condensation. Additionally, the hexane gas phase desorbed from the hexane desorption tower V1 also enters the shell side of the mixed gas phase condenser E1. Circulating water enters the tube side of the mixed gas phase condenser E1 through the circulating water inlet pipe G2 and flows back to the cooling tower through the circulating water outlet pipe G3. After condensation by the circulating water, some of the hexane, methanol, and water vapor in the mixed gas phase are condensed and flow into the methanol-hexane separator through the condensate outlet pipe G4 for separation.

[0030] Uncondensed mixed gas phase in mixed gas phase condenser E1 enters the shell side of refrigeration condenser E2. In addition, uncondensed gas phase from other condensing equipment enters the shell side of refrigeration condenser E2 through spare uncondensed gas inlet pipe G5. Low-temperature refrigerant processed by the refrigeration unit enters the tube side of refrigeration condenser E2 through refrigerant inlet pipe G6. After heat exchange, it flows back to the refrigeration unit through cooling medium outlet pipe G7. The condensate generated in the shell side of refrigeration condenser E2 enters the methanol-n-hexane phase separator for phase separation through final condensate outlet pipe G8.

[0031] The uncondensed mixed gas phase in the refrigeration condenser E2 enters the hexane absorber V2. In the hexane absorber V2, mineral oil flows from top to bottom and the mixed gas phase flows from bottom to top, with the gas and liquid phases undergoing countercurrent contact for mass transfer. Due to the similar polarity of hexane to mineral oil, the hexane in the mixed gas phase is absorbed by the mineral oil during the countercurrent contact. The mineral oil containing a high concentration of hexane is drawn out by the cold mineral oil pump P2 and enters the cold side of the mineral oil heat exchanger E4 to indirectly exchange heat with the hot mineral oil on the hot side. It then flows into the tube side of the mineral oil heater E3, where it is indirectly heated by the steam in the shell side. The steam enters the shell side of the mineral oil heater E3 from the steam pipe G9, and the condensate formed after heat exchange flows out from the condensate outlet pipe G10. The steam flow rate entering the mineral oil heater E3 is controlled by a regulating valve, the opening of which is controlled by the temperature of the hot mineral oil at the outlet of the mineral oil heater E3.

[0032] The hot mineral oil, heated by the mineral oil heater E3, enters the top of the n-hexane desorption tower V1 for desorption. The steam enters the lower part of the n-hexane desorption tower V1 through the steam pipe G9 and flows from bottom to top, supplementing the heat of the mineral oil flowing from top to bottom. The hexane and some water vapor desorbed at high temperature are discharged from the top of the hexane desorption tower V1 and enter the condenser E1 for further condensation. The mineral oil that releases hexane is extracted by the hot mineral oil pump P1 and sent to the hot side of the mineral oil heat exchanger E4 to exchange heat with the cold mineral oil extracted by the cold mineral oil pump P2. Then the hot mineral oil enters the hot side of the mineral oil cooler E5 for cooling. The cooling of the mineral oil is achieved by heat exchange with the circulating water on the cold side. The circulating water flows into the cold side of the mineral oil cooler E5 through the circulating water inlet pipe G2 and flows out through the plate circulating water outlet pipe G3. The cooled mineral oil enters the top of the hexane absorption tower V2 to absorb hexane again. The circulation flow rate of the mineral oil between the hexane absorption tower and the mineral oil desorption tower is controlled by the variable frequency motor of the hot mineral oil pump P1. The frequency of the variable frequency motor is controlled by the liquid level of the mineral oil desorption tower.

[0033] After the mixed gas phase passes through the hexane absorber V2, most of the hexane is absorbed, and methanol constitutes the majority of the mixed gas phase. The mixed gas phase then enters the methanol absorber V3 to absorb the methanol. The absorbent in the methanol absorber V3 is low-temperature water, which flows from the top of the tower downwards and accumulates at the bottom. Under the suction of the water absorption circulation pump P3, the water at the bottom of the tower is drawn to the top, achieving water circulation within the methanol absorber V3. The circulating water in the methanol absorber V3 flows through the hot side of the water cooler E6 to exchange heat with the refrigerant. The refrigerant enters the water cooler E6 from the cooling medium outlet pipe G7 and exits from the water cooler E6 from the refrigerant outlet pipe G8, returning to the refrigeration system. During the absorption process, as the amount of absorbed methanol gradually increases, the methanol-water solution gradually becomes saturated, requiring the replenishment of fresh water to ensure the absorption effect. The water replenishment pipe G12 is connected to the outlet pipe of the water absorption circulation pump P3. A water replenishment regulating valve is installed on the water replenishment pipe, and its opening degree is controlled by the flow rate measured by the flow meter on the pipe. Excess water in the methanol absorption tower V3 flows out through the overflow pipe G11 and enters the methanol distillation system to recover methanol. Non-condensable gases and trace amounts of methanol and n-hexane in the methanol absorption tower V3 are extracted by the tail gas blower F1 and discharged through the tail gas discharge pipe G13. A condensate pipe connects the duct between the tail gas discharge pipe G13 and the outlet of the tail gas blower F1 to the methanol absorption tower V3.

[0034] The specific parameters for the operation of this system are as follows: after the mixed gas phase is condensed by the mixed gas phase condenser E1, the temperature is between 30-35℃ and the mass flow rate is about 155kg / h, of which n-hexane is 50kg / h, methanol is 40kg / h, water vapor is 5kg / h and air is 60kg / h.

[0035] The mixed gas phase temperature at the shell-side outlet of the E2 refrigeration condenser is between 10-12℃, with a mass flow rate of 94 kg / h, consisting of 18 kg / h of n-hexane, 14 kg / h of methanol, 2 kg / h of water vapor, and 60 kg / h of air. During this process, the refrigerant temperature rises from 4-6℃ to 12-14℃.

[0036] After passing through the hexane absorber V2, the temperature of the mixed gas phase is around 20℃, the methanol mass flow rate remains essentially unchanged, and the residual hexane in the tail gas is reduced to around 500 mg / m³. The mineral oil temperature after being cooled by the mineral oil cooler E5 is 40℃, and in the hexane absorber V2, the mineral oil temperature is reduced to around 35℃.

[0037] Cold mineral oil containing a high concentration of n-hexane flows through the cold side of mineral oil heat exchanger E4, where its temperature increases from 35°C to approximately 60°C. Meanwhile, the hot mineral oil on the hot side of heat exchanger E4 decreases from 100°C to approximately 75°C. The mineral oil then enters the cold side of mineral oil heater E3, where its temperature increases to approximately 103°C, before entering the n-hexane desorption tower V1 for desorption.

[0038] After absorption by methanol absorption tower V3, the residual methanol in the tail gas is reduced to about 800 mg / m³. The water at the bottom of the tower is sent by water absorption circulation pump P3 to the hot side of water cooler E6 to exchange heat with the refrigerant. The water temperature drops from about 15°C to about 10°C and then enters the top of methanol absorption tower V3.

[0039] After passing through this system, the concentrations of hexane and methanol in the exhaust gas are reduced to approximately 500 mg / m³ and 800 mg / m³, respectively. The system consumes 1.5 kg of methanol and 0.5 kg of hexane per ton of cottonseed to process. Compared with traditional single methanol absorption towers and ambient temperature circulating water heat exchangers, this system saves 1.5 kg of methanol and 1.5 kg of hexane solvent per ton of cottonseed, resulting in significant economic value.

[0040] The above description is merely a preferred embodiment of the present utility model, showing and describing the basic principles, main features, and advantages of the present utility model. It is not intended to limit the scope of patent protection of the present utility model. Those skilled in the art should understand that the present utility model is not limited to the above embodiments. In addition to the above embodiments, the present utility model may have other implementations without departing from the spirit and scope of the present utility model. Various changes and improvements to the present utility model are also possible. All technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present utility model. The scope of protection claimed by the present utility model is defined by the appended claims and their equivalents. Technical features not described in the present utility model can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A tail gas absorption system for a cotton protein dephenolization production workshop, comprising a workshop mixed gas phase pipe (G1), characterized in that: The outlet of the mixed gas phase pipe (G1) is connected to the shell-side inlet of the mixed gas phase condenser (E1). The shell-side outlet of the mixed gas phase condenser (E1) is connected to the shell-side inlet of the refrigeration condenser (E2). The shell-side outlet of the refrigeration condenser (E2) is connected to the lower inlet of the n-hexane absorption tower (V2). The top exhaust port of the n-hexane absorption tower (V2) is connected to the lower inlet of the methanol absorption tower (V3). The bottom outlet of the methanol absorption tower (V3) is connected to the hot-side inlet of the water cooler (E6) via the water absorption circulation pump (P3). The hot-side outlet of the water cooler (E6) is connected to the upper spray port of the methanol absorption tower (V3). The top exhaust port of the methanol absorption tower (V3) is connected to the exhaust pipe (G13) via the exhaust fan (F1).

2. The tail gas absorption system of a dephenolated cotton protein production plant according to claim 1, characterized in that: The bottom drain of the hexane absorber (V2) is connected to the cold-side inlet of the mineral oil heat exchanger (E4) via a cold mineral oil pump (P2). The cold-side outlet of the mineral oil heat exchanger (E4) is connected to the tube-side inlet of the mineral oil heater (E3). The tube-side outlet of the mineral oil heater (E3) is connected to the upper inlet of the hexane desorption tower (V1). The bottom outlet of the hexane desorption tower (V1) is connected to the hot-side inlet of the mineral oil heat exchanger (E4) via a hot mineral oil pump (P1). The hot-side outlet of the mineral oil heat exchanger (E4) is connected to the hot-side inlet of the mineral oil cooler (E5). The hot-side outlet of the mineral oil cooler (E5) is connected to the upper inlet of the hexane absorber (V2).

3. The tail gas absorption system of a dephenolated cotton protein production plant according to claim 1, characterized in that: The liquid phase overflow port of the methanol absorption tower (V3) is connected to the methanol distillation system through an overflow pipe (G11).

4. The dephenolated cotton protein production plant off-gas absorption system of claim 1, wherein: The exhaust fan (F1) outlet duct is provided with a drain outlet at its low point, which is connected to the reflux port of the methanol absorption tower (V3) via a water trap.

5. The off-gas absorption system of a dephenolized cotton protein production plant according to claim 2, characterized in that: The lower steam inlet of the hexane desorption tower (V1) is connected to the steam pipe (G9), and the top exhaust port of the hexane desorption tower (V1) is connected to the shell-side inlet of the mixed gas phase condenser (E1).

6. The off-gas absorption system of a dephenolized cotton protein production plant according to claim 2, characterized in that: The shell-side steam inlet of the mineral oil heater (E3) is connected to the steam pipe (G9) via a steam regulating valve. The opening degree of the steam regulating valve is controlled by the tube-side outlet temperature of the mineral oil heater (E3). The shell-side condensate outlet of the mineral oil heater (E3) is connected to the condensate outlet pipe (G10).

7. The dephenolated cotton protein production plant off-gas absorption system of claim 1, wherein: The tube-side inlet of the mixed gas phase condenser (E1) is connected to the circulating water inlet pipe (G2), and the tube-side outlet of the mixed gas phase condenser (E1) is connected to the circulating water outlet pipe (G3); the shell-side condensate outlet of the mixed gas phase condenser (E1) is connected to the methanol-n-hexane phase separator through the condensate outlet pipe (G4).

8. The dephenolated cotton protein production plant off-gas absorption system of claim 1, wherein: The tube-side inlet of the refrigeration condenser (E2) is connected to the refrigerant inlet pipe (G6), and the tube-side outlet of the refrigeration condenser (E2) is connected to the cooling medium outlet pipe (G7); the shell-side condensate outlet of the refrigeration condenser (E2) is connected to the methanol-n-hexane phase separator through the final condensate outlet pipe (G8).

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