Process for purifying and separating n-hexane waste gas in grain and oil production

Abstract

The invention discloses a process for purifying and separating n-hexane waste gas in grain and oil production, and belongs to the technical field of agricultural and sideline product waste gas treatment. The mixed adsorbent is introduced into a solvent absorption tower, the n-hexane waste gas is adsorbed by the solvent absorption tower to obtain a mixed absorption liquid, and the mixed absorption liquid is treated by a desorption tower to realize separation of n-hexane and the mixed adsorbent. The whole process does not involve catalytic reaction, separation and recovery of n-hexane are realized mainly by means of physical absorption and desorption processes, grain and oil production does not need to be suspended, grain and oil production and n-hexane tail gas separation are performed synchronously, and the grain and oil processing efficiency can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural and sideline product waste gas treatment, and particularly relates to a process for purifying and separating n-hexane waste gas in grain and oil production. Background Art

[0002] Grains and oils are essential basic commodities in daily life, widely used in various fields, including home cooking, food processing, and industrial production. These primarily include cereals, oilseed crops, and their processed forms and semi-finished products. They are a major component of the diet, providing the human body with essential nutrients such as energy, carbohydrates, and fat. With increasing awareness of food safety and nutritional health, quality requirements for grain and oil products are becoming increasingly stringent. Oilseed crops, among which grains and oils, are a crucial component of agricultural production. They are high in oil and fat. These oils, after processing, can be converted into edible oils such as soybean oil, peanut oil, and rapeseed oil. Extracting and processing oils from oilseeds is a core component of the grain and oil industry. Oils from oilseeds are primarily produced through physical or chemical extraction methods. Traditional oil extraction methods include pressing and solvent extraction. Pressing involves physically squeezing oilseed crops, allowing the oil to naturally flow out. This simple process, devoid of chemical reagents, effectively preserves the nutritional properties and original flavor of the oil, meeting food safety requirements and is suitable for oilseed crops with high oil content. However, this method is costly, produces low oil yields, and contains numerous impurities. It also requires complex chemical processes such as filtration, alkali refining, bleaching, and deodorization before it can be consumed. Furthermore, high temperatures, such as steaming, during the pre-processing of oilseed crops can denature nutrients such as protein, starch, and polyphenols.

[0003] Solvent extraction utilizes the principle of like dissolves like, using organic solvents to dissolve the oil from the oilseed. Post-processing then separates the organic solvent from the oil. This method is a relatively advanced oil extraction method, offering simple operation, high oil yields, and resistance to nutrient degradation. However, because the organic solvents used are toxic to the human body and can enter the body through multiple pathways, including the respiratory tract, digestive tract, and skin, causing poisoning, their removal during the production and processing of oilseed crops has become a key research goal in grain and oil production.

[0004] n-Hexane is a commonly used organic solvent in grain and oil production. Due to its volatility and low boiling point, n-hexane is released into the air during extraction and evaporation during grain and oil production and processing. Improper handling can cause serious harm. Most existing technologies rely on the physical adsorption of biochar to treat n-hexane waste gas. However, because biochar easily reaches adsorption saturation and its structure easily affects adsorption efficiency, actual production often requires replacement of the biochar. This replacement process can cause grain and oil production and processing to stagnate, further affecting production efficiency.

[0005] Therefore, studying a method for separating n-hexane that does not require frequent replacement of adsorption materials is of great significance to improving the efficiency of grain and oil processing. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention introduces a mixed adsorbent into a solvent absorption tower, where the n-hexane waste gas is adsorbed by the solvent absorption tower to obtain a mixed absorption liquid. The mixed absorption liquid is then processed in a desorption tower to separate the n-hexane from the mixed adsorbent, thereby solving the technical problems raised in the background art. Specifically, the technical solution of the present invention includes the following: A process for purifying and separating n-hexane waste gas in grain and oil production, the process comprising the following steps: The mixed adsorbent is pumped into the solvent absorption tower through the absorption liquid replenishment pump; The n-hexane waste gas is introduced into the solvent absorption tower through a centrifugal fan to be mixed with the mixed adsorbent to obtain a mixed absorption liquid. The remaining gas in the solvent absorption tower is discharged through the top of the solvent absorption tower. The mixed absorption liquid is pumped into the desorption tower for desorption treatment to obtain desorption tower bottom liquid and desorbed gas. The desorption tower bottom liquid is treated by a cooler and enters the solvent absorption tower from the bottom of the desorption tower. The desorbed gas is treated by a cooler and enters the solvent-water separation tank from the top of the desorption tower. The oil-water mixture in the solvent-water separation tank is recovered by a solvent transfer pump to obtain n-hexane liquid.

[0007] Furthermore, the mixed adsorbent is composed of 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil in a weight ratio of 0.7-0.8:1.

[0008] Furthermore, the mixed adsorbent is pumped into the solvent absorption tower via the absorption liquid replenishment pump at a flow rate of 250 kg / h.

[0009] Furthermore, the concentration of the n-hexane waste gas is 10000 mg / cm 3 .

[0010] Furthermore, the conditions for the n-hexane waste gas to be introduced into the solvent absorption tower through the centrifugal fan include an air volume of 1000m 3 / h and temperature 25°C.

[0011] Furthermore, the conditions for the mixed adsorption include an adsorption temperature of 25° C., a liquid-to-gas ratio of the mixed adsorbent to n-hexane waste gas of 0.25-0.3, and an adsorption time of 50-60 min.

[0012] Furthermore, the conditions for discharging the remaining gas in the solvent absorption tower through the top of the solvent absorption tower include an air volume of 1000 m³ / h and a temperature of 25°C.

[0013] Furthermore, the mixed absorption liquid is pumped into the desorption tower at a flow rate of 250 kg / h and a temperature of 35°C.

[0014] Furthermore, the desorption treatment conditions include a desorption temperature of 96° C. to 103° C., a theoretical plate number of 6 to 7, a reflux ratio of 0.4 to 0.5, and a desorption time of 30 min.

[0015] Furthermore, the conditions for the desorption tower bottom liquid to be treated by the cooler include a flow rate of 250 kg / h and a cooling temperature of 35°C.

[0016] Furthermore, the conditions for the desorbed gas to be processed through the cooler include a flow rate of 10 kg / h and a cooling temperature of 35°C.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses an ionic liquid 1-ethyl-3-methylimidazolium diethyl phosphate and paraffin oil to form a mixed adsorbent. The hydrophobic alkyl side chain on the cationic structure of 1-ethyl-3-methylimidazolium diethyl phosphate and the long hydrophobic carbon chain of paraffin oil synergistically enhance the selective adsorption of n-hexane. No chemical reaction occurs between 1-ethyl-3-methylimidazolium diethyl phosphate, paraffin oil and n-hexane, thereby avoiding the influence of side reactions during the separation process. In addition, the boiling point of this mixed adsorbent is significantly different from that of n-hexane, making it easy to separate n-hexane from the mixed adsorbent through subsequent high-temperature desorption. The mixed adsorbent is used as an absorption liquid for adsorbing n-hexane waste gas. The n-hexane waste gas is passed into a solvent absorption tower containing the mixed adsorbent. The solubility of n-hexane in the mixed adsorbent is much greater than its dispersion in air, so that it is absorbed. The absorbed n-hexane is mixed with the mixed adsorbent in a liquid state to form a mixed absorption liquid. The mixed absorption liquid is then passed into a desorption tower. After being heated in the desorption tower, a desorption gas containing n-hexane and a desorption tower bottom liquid containing the mixed adsorbent are obtained, thereby achieving separation of the mixed adsorbent and n-hexane. The separated desorption tower bottom liquid is re-passed into the solvent absorption tower for recycling. The adsorption separation process designed by the present invention improves the separation effect of n-hexane, so that n-hexane can be better adsorbed and captured. The entire process does not involve a catalytic reaction, and mainly relies on physical absorption and desorption processes to achieve the separation and recovery of n-hexane. There is no need to suspend grain and oil production, and the simultaneous progress of grain and oil production and n-hexane tail gas separation is achieved, which can effectively improve grain and oil processing efficiency.

[0018] (2) Through the process designed by the present invention, the concentration of n-hexane in the residual gas in the solvent absorption tower is reduced to 50 mg / m 3 The concentration of n-hexane in the desorbed gas is as high as 99.98%, indicating that the process of the present invention has a good treatment effect on n-hexane waste gas and is suitable for industrial application in grain and oil production and processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions of the present invention through the embodiments and drawings of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0021] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0022] Example 1: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into a mixed adsorbent storage tank at a weight ratio of 0.7:1 and mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through an absorption liquid replenishing pump at a flow rate of 250 kg / h. At the same time, a concentration of 10000 mg / cm 3 The n-hexane waste gas, with an air volume of 1000 3 / h centrifugal fan is introduced into the solvent absorption tower from the bottom of the solvent absorption tower. The temperature of the n-hexane waste gas is controlled at 25°C when it is introduced, so that the mixed adsorbent and n-hexane waste gas are fully mixed and contacted in the solvent absorption tower in a countercurrent manner. The temperature of the solvent adsorption tower is controlled at 25°C, and the liquid-gas ratio of the mixed adsorbent and n-hexane waste gas in the solvent adsorption tower is controlled at 0.25. Then the mixed adsorption treatment is carried out for 50 minutes. The mixed absorption liquid obtained after the mixed adsorption is then heated to 35°C and then pumped into the desorption tower through a centrifugal pump at a flow rate of 250kg / h. The desorption temperature in the desorption tower is controlled in the range of 96~103°C, the theoretical plate number of the desorption tower is controlled at 6, the reflux ratio is controlled at 0.4, and then the desorption treatment is started for 30 minutes. The remaining gas in the solvent adsorption tower is discharged through the top of the solvent absorption tower. The exhaust air volume is controlled at 1000m³ / h and the temperature is controlled at 25°C. The residual n-hexane concentration in the exhaust gas is then detected, and the concentration value is 41.62mg / m 3 The desorption tower bottom liquid and desorbed gas obtained after desorption treatment are pumped out from the bottom of the desorption tower, and cooled through the absorption liquid cooler. The flow rate pumped into the absorption liquid cooler is 250kg / h, and the cooling temperature is controlled at 35°C. The mixed adsorbent obtained after cooling re-enters the solvent absorption tower through the circulation pump. The desorbed gas is discharged from the top of the desorption tower, and the concentration of the desorbed gas is tested. The concentration of n-hexane is measured to be 99.98%. The desorbed gas is cooled through the absorption liquid cooler, and the flow rate discharged to the absorption liquid cooler is controlled at 10kg / h, and the cooling temperature is controlled at 35°C. The oil-water mixture obtained after cooling enters the solvent-water separation tank, and then is recovered by the solvent mobile pump to obtain n-hexane liquid. See the specific process flow chart. Figure 1 .

[0023] Example 2: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into a mixed adsorbent storage tank at a weight ratio of 0.75:1, mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through an absorption liquid replenishing pump at a flow rate of 250 kg / h. At the same time, a concentration of 10000 mg / cm 3 The n-hexane waste gas, with an air volume of 1000 3 / h centrifugal fan is introduced into the solvent absorption tower from the bottom of the solvent absorption tower. The temperature of the n-hexane waste gas is controlled at 25°C when it is introduced, so that the mixed adsorbent and n-hexane waste gas are fully mixed and contacted in the solvent absorption tower in a countercurrent manner. The temperature of the solvent adsorption tower is controlled at 25°C, and the liquid-gas ratio of the mixed adsorbent and n-hexane waste gas in the solvent adsorption tower is controlled at 0.27. Then the mixed adsorption treatment is carried out for 55 minutes. The mixed absorption liquid obtained after the mixed adsorption is then heated to 35°C and then pumped into the desorption tower through a centrifugal pump at a flow rate of 250kg / h. The desorption temperature in the desorption tower is controlled in the range of 96~103°C, the theoretical plate number of the desorption tower is controlled at 6, the reflux ratio is controlled at 0.4, and then the desorption treatment is started for 30 minutes. The remaining gas in the solvent adsorption tower is discharged through the top of the solvent absorption tower. The exhaust air volume is controlled at 1000m³ / h and the temperature is controlled at 25°C. The residual n-hexane concentration in the exhaust gas is then detected and the concentration value is 45.15mg / m 3 The desorption tower bottom liquid and desorbed gas obtained after desorption treatment are pumped out from the bottom of the desorption tower, and cooled through the absorption liquid cooler. The flow rate pumped into the absorption liquid cooler is 250kg / h, and the cooling temperature is controlled at 35°C. The mixed adsorbent obtained after cooling re-enters the solvent absorption tower through the circulation pump. The desorbed gas is discharged from the top of the desorption tower, and the concentration of the desorbed gas is tested. The concentration of n-hexane is measured to be 99.47%. The desorbed gas is cooled through the absorption liquid cooler, and the flow rate discharged to the absorption liquid cooler is controlled at 10kg / h, and the cooling temperature is controlled at 35°C. The oil-water mixture obtained after cooling enters the solvent-water separation tank, and then is recovered by the solvent mobile pump to obtain n-hexane liquid. See the specific process flow chart. Figure 1 .

[0024] Example 3:

[0025] A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into the mixed adsorbent storage tank at a weight ratio of 0.8:1 and mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through the absorption liquid replenishment pump at a flow rate of 250 kg / h. At the same time, a concentration of 10000 mg / cm 3 The n-hexane waste gas, with an air volume of 1000 3 / h centrifugal fan is passed from the bottom of the solvent absorption tower to the solvent absorption tower. The temperature of the n-hexane waste gas is controlled at 25°C when it is passed in, so that the mixed adsorbent and n-hexane waste gas are fully mixed and contacted in the solvent adsorption tower in a countercurrent manner. The temperature of the solvent adsorption tower is controlled at 25°C, and the liquid-gas ratio of the mixed adsorbent and n-hexane waste gas in the solvent adsorption tower is controlled to 0.3, followed by mixed adsorption treatment for 60 minutes. The mixed absorption liquid obtained after the mixed adsorption is then heated to 35°C and then pumped into the desorption tower through a centrifugal pump at a flow rate of 250kg / h. The desorption temperature in the desorption tower is controlled in the range of 96~103°C, the theoretical plate number of the desorption tower is controlled to 7, the reflux ratio is controlled to 0.5, and then the desorption treatment begins for 30 minutes. The remaining gas in the solvent adsorption tower is discharged through the top of the solvent absorption tower. The exhaust air volume is controlled to 1000m³ / h and the temperature is controlled to 25°C. The residual n-hexane concentration in the exhaust gas is then detected, and the concentration value is 47.48mg / m 3 The desorption tower bottom liquid and desorbed gas obtained after desorption treatment are pumped out from the bottom of the desorption tower, and cooled through the absorption liquid cooler. The flow rate pumped into the absorption liquid cooler is 250kg / h, and the cooling temperature is controlled at 35°C. The mixed adsorbent obtained after cooling re-enters the solvent absorption tower through the circulation pump. The desorbed gas is discharged from the top of the desorption tower, and the concentration of the desorbed gas is tested. The concentration of n-hexane is measured to be 99.06%. The desorbed gas is cooled through the absorption liquid cooler, and the flow rate discharged to the absorption liquid cooler is controlled at 10kg / h, and the cooling temperature is controlled at 35°C. The oil-water mixture obtained after cooling enters the solvent-water separation tank, and then is recovered by the solvent mobile pump to obtain n-hexane liquid. See the specific process flow chart. Figure 1 .

[0026] Through the test results of Examples 1 to 3, it can be found that the mixed adsorbent is composed of an ionic liquid 1-ethyl-3-methylimidazole diethyl phosphate salt and paraffin oil. The hydrophobic alkyl side chain on the cationic structure of 1-ethyl-3-methylimidazole diethyl phosphate salt and the long hydrophobic carbon chain of paraffin oil can synergistically enhance the selective adsorption of n-hexane. There is no chemical reaction between 1-ethyl-3-methylimidazole diethyl phosphate salt, paraffin oil and n-hexane, which avoids the influence of side reactions during the separation process. Moreover, the boiling point of this mixed adsorbent is far different from that of n-hexane, and it is easy to separate n-hexane from the mixed adsorbent by subsequent high-temperature desorption. The adsorption separation process designed by the present invention improves the separation effect of n-hexane, so that n-hexane can be better adsorbed and captured. The concentration of n-hexane in the desorbed gas can reach up to 99.98, indicating that the separation and treatment effect of n-hexane waste gas is good, and the n-hexane content in the residual gas in the solvent absorption tower is reduced to 50 mg / m 3 This significantly reduces environmental pollution from tail gas from the solvent absorption tower. The entire process involves no catalytic reaction and relies primarily on physical absorption and desorption to separate and recover n-hexane. This process eliminates the need to suspend grain and oil production, allowing for simultaneous production and n-hexane tail gas separation, effectively improving grain and oil processing efficiency.

[0027] Comparative Example 1: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into the mixed adsorbent storage tank at a weight ratio of 0.8:1 and mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through the absorption liquid replenishment pump at a flow rate of 250 kg / h. At the same time, a concentration of 10000 mg / cm 3 The n-hexane waste gas, with an air volume of 1000 3 / h centrifugal fan is introduced into the solvent absorption tower from the bottom of the solvent absorption tower. The temperature of the n-hexane waste gas is controlled at 25°C when it is introduced, so that the mixed adsorbent and the n-hexane waste gas are fully mixed and contacted in the solvent absorption tower in a countercurrent manner. The temperature of the solvent adsorption tower is controlled at 25°C, and the liquid-gas ratio of the mixed adsorbent and the n-hexane waste gas in the solvent adsorption tower is controlled to 0.2. Then the mixed adsorption treatment is carried out for 60 minutes. The mixed absorption liquid obtained after the mixed adsorption is then heated to 35°C and then pumped into the desorption tower through a centrifugal pump at a flow rate of 250kg / h. The desorption temperature in the desorption tower is controlled in the range of 96~103°C, the theoretical plate number of the desorption tower is controlled to 7, the reflux ratio is controlled to 0.5, and then the desorption treatment is started for 30 minutes. The remaining gas in the solvent adsorption tower is discharged through the top of the solvent absorption tower. The exhaust air volume is controlled to 1000m³ / h and the temperature is controlled to 25°C. The residual concentration of n-hexane in the exhaust gas is then detected, and the concentration value is 108.14mg / m 3 The desorption tower bottom liquid and desorbed gas obtained after desorption treatment are pumped out from the bottom of the desorption tower, and are cooled through the absorption liquid cooler. The flow rate pumped into the absorption liquid cooler is 250kg / h, and the cooling temperature is controlled at 35°C. The mixed adsorbent obtained after cooling re-enters the solvent absorption tower through the circulation pump. The desorbed gas is discharged from the top of the desorption tower, and the concentration of the desorbed gas is tested. The concentration of n-hexane is measured to be 98.68%. The desorbed gas is cooled through the absorption liquid cooler, and the flow rate discharged to the absorption liquid cooler is controlled at 10kg / h, and the cooling temperature is controlled at 35°C. The oil-water mixture obtained after cooling enters the solvent-water separation tank, and then is recovered by the solvent mobile pump to obtain n-hexane liquid. See the specific process flow chart. Figure 1 From Comparative Example 1, it can be seen that when the liquid-gas ratio is too low, the mixed adsorbent may not be able to effectively capture the target components in the n-hexane waste gas, and the mass transfer area is insufficient, resulting in poor adsorption driving force and reduced separation efficiency.

[0028] Comparative Example 2: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into the mixed adsorbent storage tank at a weight ratio of 0.8:1 and mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through the absorption liquid replenishment pump at a flow rate of 250 kg / h. At the same time, a concentration of 10000 mg / cm 3 The n-hexane waste gas, with an air volume of 1000 3 / h centrifugal fan is introduced into the solvent absorption tower from the bottom of the solvent absorption tower. The temperature of the n-hexane waste gas is controlled at 25℃ when it is introduced, so that the mixed adsorbent and n-hexane waste gas are fully mixed and contacted in the solvent adsorption tower in a countercurrent manner. The temperature of the solvent adsorption tower is controlled at 25℃, and the liquid-gas ratio of the mixed adsorbent and n-hexane waste gas in the solvent adsorption tower is controlled at 0.4. Then the mixed adsorption treatment is carried out for 60 minutes. The mixed adsorption liquid obtained after the mixed adsorption is then heated to 35℃ and then pumped into the desorption tower through a centrifugal pump at a flow rate of 250kg / h. The desorption temperature in the desorption tower is controlled in the range of 96~103℃, the theoretical plate number of the desorption tower is controlled at 7, the reflux ratio is controlled at 0.5, and then the desorption treatment is started for 30 minutes. The remaining gas in the solvent adsorption tower is discharged through the top of the solvent absorption tower. The exhaust air volume is controlled at 1000m³ / h and the temperature is controlled at 25℃. The residual n-hexane concentration in the exhaust gas is then detected, and the concentration value is 95.76mg / m 3 The desorption tower bottom liquid and desorbed gas obtained after desorption treatment are pumped out from the bottom of the desorption tower, and are cooled through the absorption liquid cooler. The flow rate pumped into the absorption liquid cooler is 250kg / h, and the cooling temperature is controlled at 35°C. The mixed adsorbent obtained after cooling re-enters the solvent absorption tower through the circulation pump. The desorbed gas is discharged from the top of the desorption tower, and the concentration of the desorbed gas is tested. The concentration of n-hexane is measured to be 98.91%. The desorbed gas is cooled through the absorption liquid cooler, and the flow rate discharged to the absorption liquid cooler is controlled at 10kg / h, and the cooling temperature is controlled at 35°C. The oil-water mixture obtained after cooling enters the solvent-water separation tank, and then is recovered by the solvent mobile pump to obtain n-hexane liquid. See the specific process flow chart. Figure 1 From Comparative Example 2, it can be seen that when the liquid-gas ratio is too high, the liquid flow rate is much greater than the gas flow rate, and the gas may not be able to fully contact the liquid, which reduces the mass transfer efficiency and the separation efficiency.

[0029] Comparative Example 3: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into the mixed adsorbent storage tank at a weight ratio of 0.8:1 and mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through the absorption liquid replenishment pump at a flow rate of 250 kg / h. At the same time, a concentration of 10000 mg / cm 3 The n-hexane waste gas, with an air volume of 1000 3 / h centrifugal fan is introduced into the solvent absorption tower from the bottom of the solvent absorption tower. The temperature of the n-hexane waste gas is controlled at 25°C when it is introduced, so that the mixed adsorbent and the n-hexane waste gas are fully mixed and contacted in the solvent absorption tower in a countercurrent manner. The temperature of the solvent adsorption tower is controlled at 25°C, and the liquid-gas ratio of the mixed adsorbent and the n-hexane waste gas in the solvent adsorption tower is controlled at 0.3. Then the mixed adsorption treatment is carried out for 60 minutes. The mixed absorption liquid obtained after the mixed adsorption is then heated to 35°C and then pumped into the desorption tower through a centrifugal pump at a flow rate of 250kg / h. The desorption temperature in the desorption tower is controlled in the range of 96~103°C, the theoretical plate number of the desorption tower is controlled at 8, the reflux ratio is controlled at 0.5, and then the desorption treatment is started for 30 minutes. The remaining gas in the solvent adsorption tower is discharged through the top of the solvent absorption tower. The exhaust air volume is controlled at 1000m³ / h and the temperature is controlled at 25°C. The residual n-hexane concentration in the exhaust gas is then detected, and the concentration value is 112.09mg / m 3 . The mixed adsorbent bottom liquid and desorption tower bottom liquid obtained after desorption treatment are pumped out from the bottom of the desorption tower, and cooled through the absorption liquid cooler. The flow rate pumped into the absorption liquid cooler is 250kg / h, and the cooling temperature is controlled at 35°C. The mixed adsorbent obtained after cooling re-enters the solvent absorption tower through the circulation pump. The desorbed gas is discharged from the top of the desorption tower, and the concentration of the desorbed gas is tested. The concentration of n-hexane is measured to be 99.21%. The desorbed gas is cooled through the absorption liquid cooler, and the flow rate discharged to the absorption liquid cooler is controlled at 10kg / h, and the cooling temperature is controlled at 35°C. The oil-water mixture obtained after cooling enters the solvent-water separation tank, and then recovered by the solvent mobile pump to obtain n-hexane liquid. See the specific process flow chart. Figure 1 From Comparative Example 3, it can be seen that when the number of theoretical plates is too large, the flow resistance of the gas-liquid two-phase may be increased, the gas and liquid cannot effectively contact each other, the mass transfer efficiency is reduced, and the separation efficiency decreases.

[0030] Comparative Example 4: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into the mixed adsorbent storage tank at a weight ratio of 0.8:1 and mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through the absorption liquid replenishment pump at a flow rate of 250 kg / h. At the same time, a concentration of 10000 mg / cm 3 The n-hexane waste gas, with an air volume of 1000 3 / h centrifugal fan is introduced into the solvent absorption tower from the bottom of the solvent absorption tower. The temperature of the n-hexane waste gas is controlled at 25°C when it is introduced, so that the mixed adsorbent and n-hexane waste gas are fully mixed and contacted in the solvent adsorption tower in a countercurrent manner. The temperature of the solvent adsorption tower is controlled at 25°C, and the liquid-gas ratio of the mixed adsorbent and n-hexane waste gas in the solvent adsorption tower is controlled at 0.3. Then the mixed adsorption treatment is carried out for 60 minutes. The mixed adsorption liquid obtained after the mixed adsorption is then heated to 35°C and then pumped into the desorption tower through a centrifugal pump at a flow rate of 250kg / h. The desorption temperature in the desorption tower is controlled in the range of 96~103°C, the theoretical plate number of the desorption tower is controlled at 5, the reflux ratio is controlled at 0.5, and then the desorption treatment is started for 30 minutes. The remaining gas in the solvent adsorption tower is discharged through the top of the solvent absorption tower. The exhaust air volume is controlled at 1000m³ / h and the temperature is controlled at 25°C. The residual concentration of n-hexane in the exhaust gas is then detected, and the concentration value is 87.85mg / m 3 . The desorption tower bottom liquid and desorbed gas obtained after desorption treatment are pumped out from the bottom of the desorption tower, and cooled through the absorption liquid cooler. The flow rate pumped into the absorption liquid cooler is 250kg / h, and the cooling temperature is controlled at 35°C. The mixed adsorbent obtained after cooling re-enters the solvent absorption tower through the circulation pump. The desorbed gas is discharged from the top of the desorption tower, and the concentration of the desorbed gas is tested. The concentration of n-hexane is measured to be 98.95%. The desorbed gas is cooled through the absorption liquid cooler, and the flow rate discharged to the absorption liquid cooler is controlled at 10kg / h, and the cooling temperature is controlled at 35°C. The oil-water mixture obtained after cooling enters the solvent-water separation tank, and then is recovered by the solvent mobile pump to obtain n-hexane liquid. See the specific process flow chart. Figure 1 From Comparative Example 4, it can be seen that when the number of theoretical plates is too small, the dynamic distribution of the gas-liquid phase may be destroyed, resulting in the inability to effectively adsorb n-hexane under the separation process of this system and a decrease in separation efficiency.

[0031] Comparative Example 5: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into a mixed adsorbent storage tank in a weight ratio of 0.9:1, mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through an absorption liquid replenishing pump at a flow rate of 250 kg / h. The rest of the process was consistent with Example 3. The residual concentration of n-hexane in the exhaust gas was measured to be 109.63 mg / m 3 , the concentration of n-hexane in the desorbed gas is 98.75%.

[0032] Comparative Example 6: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: By means of a centrifugal pump, 1-ethyl-3-methylimidazole diethyl phosphate and paraffin oil were pumped into a mixed adsorbent storage tank in a weight ratio of 0.6:1, mixed and stirred to obtain a mixed adsorbent. Then, the mixed adsorbent in the mixed adsorbent storage tank was pumped from the top of the solvent absorption tower into the solvent absorption tower through an absorption liquid replenishing pump at a flow rate of 250 kg / h. The rest of the process was consistent with Example 3. The measured residual concentration of n-hexane in the exhaust gas was 121.74 mg / m 3 , the concentration of n-hexane in the desorbed gas is 98.97%.

[0033] It can be found from Comparative Examples 5 and 6 that when the amount of ionic liquid used in the mixed adsorbent is too high or too low, it is not conducive to the adsorption of n-hexane.

[0034] Comparative Example 7: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: The mixed adsorbent in Example 3 was directly replaced with 1-ethyl-3-methylimidazole diethyl phosphate. The rest of the process was consistent with Example 3. The residual concentration of n-hexane in the exhaust gas was measured to be 147.03 mg / m 3 , the concentration of n-hexane in the desorbed gas is 98.54%.

[0035] Comparative Example 8: A process for purifying and separating n-hexane waste gas in grain and oil production specifically includes the following steps: The mixed adsorbent in Example 3 was directly replaced with paraffin oil, and the rest of the process was consistent with Example 3. The residual concentration of n-hexane in the exhaust gas was measured to be 131.28 mg / m 3 , the concentration of n-hexane in the desorbed gas is 98.71%.

[0036] It can be found from Comparative Examples 7 and 8 that the use of one adsorbent in the mixed adsorbent alone has a poorer adsorption effect on n-hexane than when the mixed adsorbents are used, which is not conducive to the adsorption treatment of n-hexane.

[0037] The following conclusions can be drawn from the test results of Comparative Examples 1 to 8: The separation process parameters of the present invention and the composition ratio of the mixed adsorbent used have an important influence on the treatment of n-hexane waste gas by the present invention.

[0038] The above embodiments and accompanying drawings provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A process for purifying and separating n-hexane waste gas in grain and oil production, characterized in that: The process The following steps are involved: The mixed adsorbent is pumped into the solvent absorption tower through the absorption liquid replenishment pump; The n-hexane waste gas is introduced into the solvent absorption tower through a centrifugal fan to be mixed with the mixed adsorbent to obtain a mixed absorption liquid. The remaining gas in the solvent absorption tower is discharged through the top of the solvent absorption tower. The mixed absorption liquid is pumped into the desorption tower for desorption treatment to obtain desorption tower bottom liquid and desorbed gas. The desorption tower bottom liquid is treated by a cooler and enters the solvent absorption tower from the bottom of the desorption tower. The desorbed gas is treated by a cooler and enters the solvent-water separation tank from the top of the desorption tower. The oil-water mixture in the solvent-water separation tank is recovered by a solvent transfer pump to obtain n-hexane liquid.

2. A process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The mixed adsorbent is prepared by mixing 1-ethyl-3-methylimidazole diethyl phosphate salt and paraffin oil in a weight ratio of 0.7-0.8:

1.

3. The process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The mixed adsorbent is pumped into the solvent absorption tower via the absorption liquid replenishment pump at a flow rate of 250 kg / h.

4. A process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The concentration of the n-hexane waste gas is 10000 mg / cm 3 .

5. A process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The conditions for the n-hexane waste gas to be introduced into the solvent absorption tower through the centrifugal fan include an air volume of 1000m 3 / h and temperature 25°C.

6. A process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The mixed adsorption conditions include an adsorption temperature of 25° C., a liquid-to-gas ratio of the mixed adsorbent to the n-hexane waste gas of 0.25-0.3, and an adsorption time of 50-60 min.

7. The process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The mixed absorption liquid is pumped into the desorption tower at a flow rate of 250 kg / h and a temperature of 35°C.

8. The process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The desorption treatment conditions include a desorption temperature of 96° C. to 103° C., a theoretical plate number of 6 to 7, a reflux ratio of 0.4 to 0.5, and a desorption time of 30 min.

9. The process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The conditions for the desorption tower bottom liquid to be treated by the cooler include a flow rate of 250 kg / h and a cooling temperature of 35°C.

10. The process for purifying and separating n-hexane waste gas in grain and oil production according to claim 1, characterized in that: The conditions for the desorbed gas to be treated through the cooler include a flow rate of 10 kg / h and a cooling temperature of 35°C.

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