Cooperative treatment method for 2B oil and 2B acid production tail gas

Abstract

The invention relates to the technical field of 2B acid production, and particularly discloses a 2B oil and 2B acid production tail gas synergistic treatment method, which comprises the following steps: mixing 2B oil production tail gas and 2B acid production tail gas, and washing in an alkaline washing tower; the gas subjected to alkali washing enters a circulating water spraying type water washing tower for water washing; carrying out primary adsorption on the washed gas by using a primary adsorption tank containing hydrophobic resin; the 2B oil production tail gas and the 2B acid production tail gas are combined and share the alkaline washing tower, the water washing tower, the first-stage adsorption tank, the second-stage adsorption tank and the third-stage adsorption tank, repeated equipment investment of the alkaline washing tower, the water washing tower and the like is reduced, and classified enrichment and directional recycling of two tail gas pollutants are realized through combined adsorption of hydrophobic resin and silanized activated carbon, so that the tail gas recycling efficiency is improved. Therefore, in view of the fact that 2B oil is a 2B acid production precursor, two tail gas pretreatment systems for 2B acid production are planned to be integrated, repeated equipment investment is reduced, and tail gas treatment cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of 2B acid production, and in particular relates to a method for collaboratively treating tail gas from the production of 2B oil and 2B acid. Background Art

[0002] In industry, p-nitrotoluene is used as raw material to produce 2B oil through chlorination and hydrogenation reduction. 2B oil is then sulfonated with sulfuric acid using o-dichlorobenzene (containing a small amount of 1,2,4-trichlorobenzene) as solvent to produce 2B acid. Both production stages produce highly polluting tail gas. Among them, the tail gas from 2B oil production consists of: 2B oil and its isomers, p-nitrotoluene, p-toluidine, dichloroaminos, dichloronitros, hydrogen chloride, chlorine, non-methane total hydrocarbons, etc.

[0003] The tail gas from 2B acid production consists of: o-dichlorobenzene, 1,2,4-trichlorobenzene, 2B oil and its isomers, p-toluidine, dichloroaminos, sulfuric acid mist, dust, non-methane total hydrocarbons, etc.

[0004] It can be seen that the tail gas from 2B oil production and 2B acid production are both acidic gases. In order to reduce the pollution of tail gas to the environment during the production of 2B acid, the tail gas from 2B oil production and 2B acid production needs to be treated. The current treatment method for 2B oil production tail gas is: alkali washing tower (removal of hydrogen chloride and chlorine) → water washing tower (removal of high-boiling substances) → thin film evaporator (high-temperature regeneration of 2B oil and p-toluidine) → adsorption and desorption tank (adsorption of VOCs and dilution before emission);

[0005] The tail gas treatment method for 2B acid production is as follows: alkali scrubber (removing sulfuric acid mist) → water scrubber (removing high-boiling substances and dust) → low-temperature condensation (condensation recovery of o-dichlorobenzene) → adsorption and desorption tank (adsorbing VOCs and then diluting and discharging);

[0006] However, since 2B oil and p-toluidine need to be regenerated at high temperatures above 150°C, and o-dichlorobenzene needs to be condensed at low temperatures below 10°C, the energy consumption for recovering raw and auxiliary materials is high, and frequent regeneration of the adsorption and desorption tanks will increase the cost of adsorbent replacement, thereby increasing the cost of tail gas treatment. Therefore, we need to propose a method for the coordinated treatment of tail gas from the production of 2B oil and 2B acid to solve the above-mentioned problems. Considering that 2B oil is a precursor for the production of 2B acid, it is planned to integrate the two tail gas pretreatment systems for 2B acid production, reduce duplicate equipment investment, and reduce tail gas treatment costs. Summary of the Invention

[0007] The present invention aims to provide a method for the coordinated treatment of tail gas from the production of 2B oil and 2B acid. Since 2B oil is a precursor for 2B acid production, the present invention integrates the two tail gas pretreatment systems for 2B acid production, reduces duplicate equipment investment, and lowers tail gas treatment costs, thereby solving the problems raised in the above-mentioned background technology.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for collaboratively treating tail gas from the production of 2B oil and 2B acid comprises the following steps:

[0010] S1. Combine the tail gas from 2B oil production and 2B acid production and then send them into an alkaline washing tower for washing to neutralize sulfuric acid mist, hydrogen chloride, chlorine and acidic gases;

[0011] S2. The gas after alkali washing enters a circulating water spray type water washing tower for water washing to remove residual acid gas, high boiling point and dust;

[0012] S3. The gas after water washing is subjected to primary adsorption using a primary adsorption tank containing a hydrophobic resin to adsorb o-dichlorobenzene, 1,2,4-trichlorobenzene and nitrobenzene gases. After adsorption saturation, hot nitrogen is introduced for desorption and condensation;

[0013] S4. The gas after the primary adsorption is subjected to secondary adsorption in a secondary adsorption tank containing silane activated carbon to adsorb 2B oil and 2B oil isomers, p-toluidine, dichloroamino compounds and non-methane total hydrocarbons. After saturation, hot nitrogen is introduced for desorption and condensation;

[0014] S5. The gas after secondary adsorption passes through a tertiary adsorption tank containing activated carbon adsorbent for tail gas purification treatment to ensure that the gas meets emission requirements.

[0015] Preferably, the alkali washing tower is configured as a countercurrent packed tower, and an air intake section, a packing layer and a spray section are provided inside the alkali washing tower. The packing layer is filled with PE ball ring packing, and the spray section sprays sodium hydroxide spray liquid, so that the sodium hydroxide spray liquid contacts the tail gas in countercurrent, and the contact time is 3-5 seconds.

[0016] Preferably, the initial concentration of the washing liquid after washing in the alkali washing tower is 10-15%, and the washing liquid is recycled through the alkali washing circulation system. When the concentration of the washing liquid reaches 5%, it is discharged into the sewage station for centralized treatment. A demister is added in front of the alkali washing tower for pre-filtration, and the packing layer is backwashed regularly.

[0017] Preferably, two packing layers are provided in the water washing tower, and distribution devices capable of preventing liquid deviation are provided above the two packing layers, and the packing layers are configured as PE ball rings.

[0018] Preferably, a swirl pneumatic device is also provided inside the water washing tower, and the swirl pneumatic device forms a swirl through the guide blades, and the droplets and particulate matter are thrown to the tower wall for sedimentation. The rotation speed of the swirl pneumatic device is set to 1000-3000rpm. The drain outlet of the water washing tower is connected to a three-phase tank, and the liquid outlet end of the three-phase tank recycles the washing liquid through the acid washing circulation system.

[0019] Preferably, in step S3, the primary adsorption tank is configured as a fixed bed adsorption tank, the hydrophobic resin is installed in the primary adsorption tank, an online concentration sensor is installed at the outlet of the primary adsorption tank, and the exhaust gas concentration at the outlet of the primary adsorption tank is monitored by the online concentration sensor. The adsorption temperature is 40°C-60°C. After adsorption saturation, hot nitrogen at 100°C-120°C is introduced for desorption, and a cooling water system is used for low-temperature condensation at 5°C-7°C. The condensate is directly reused in the 2B acid production section.

[0020] Preferably, in step S4, the secondary adsorption tank is configured as a fixed bed adsorption tank, the primary adsorption tank and the secondary adsorption tank are connected in series, the silane activated carbon is installed in the secondary adsorption tank, the surface of the silane activated carbon is modified by a silane coupling agent, and a concentration online monitoring sensor is installed at the outlet of the secondary adsorption tank.

[0021] Preferably, the primary adsorption tank and the secondary adsorption tank share a cooling water system, and the cooling water system directly uses the chilled water discharged from the primary adsorption tank to return water to the secondary adsorption tank for cooling.

[0022] Preferably, after the silanized activated carbon is saturated with adsorption, hot nitrogen at 100°C-120°C is introduced into the secondary adsorption tank for desorption, and 10°C-20°C chilled water is used for low-temperature condensation, and the condensate is directly returned to the 2B oil refining tower to regenerate 2B oil and p-toluidine.

[0023] Preferably, in step S5, during the adsorption treatment, the adsorption temperature of the three-stage adsorption tank is 20°C-35°C, activated carbon adsorbent is added into the three-stage adsorption tank, and hot air at 100°C-120°C is introduced at the same time.

[0024] The method for co-processing tail gas from the production of 2B oil and 2B acid proposed in the present invention has the following advantages over the prior art:

[0025] 1. The present invention combines the tail gas from 2B oil production and the tail gas from 2B acid production and uses a common alkali washing tower, water washing tower, primary adsorption tank, secondary adsorption tank, and tertiary adsorption tank, thereby reducing the repeated equipment investment in the alkali washing tower, water washing tower, etc., and achieves classified enrichment and targeted reuse of pollutants in the two tail gases through combined adsorption of a hydrophobic resin and silanized activated carbon. Since 2B oil is a precursor for 2B acid production, the two tail gas pretreatment systems for 2B acid production can be integrated, reducing repeated equipment investment and lowering tail gas treatment costs.

[0026] 2. In the present invention, hot nitrogen is used for desorption during both the primary and secondary adsorption processes, rather than conventional water vapor or hot air. Water vapor is not used to prevent water vapor from entering the 2B oil, which would prevent it from being directly returned to the refining tower for regeneration. This avoids the carbonization problem that may result from multi-step high-temperature regeneration and the increase in moisture content during the reuse of o-dichlorobenzene, thereby reducing the sulfonation reaction conversion rate. Hot air is not used to prevent amine components such as the 2B oil from being oxidized at high temperatures, which would affect the treatment and reuse of the tail gas.

[0027] 3. In the first-stage adsorption process of the present invention, the purity of o-dichlorobenzene after adsorption, desorption and condensation by a hydrophobic resin is close to that of the workshop solvent. It can be directly reused in 2B acid production without going through a complex and costly distillation process, and the product quality is not affected. The whiteness of the 2B acid product still reaches above 80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flowchart of the present invention;

[0029] Figure 2 It is a schematic diagram of the process of the present invention;

[0030] Figure 3 Schematic diagram of the cooling water system of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] The present invention provides Figure 1-3 A method for co-processing tail gas from the production of 2B oil and 2B acid is shown, comprising the following steps:

[0033] S1. Combine the tail gas from 2B oil production and 2B acid production and then send them into an alkaline washing tower for washing to neutralize sulfuric acid mist, hydrogen chloride, chlorine and acidic gases;

[0034] The alkali scrubber is configured as a countercurrent packed tower. It is internally provided with an air inlet section, a packing layer, and a spray section. The packing layer is filled with PE ball ring packing. The spray section sprays sodium hydroxide spray liquid, allowing the sodium hydroxide spray liquid to come into countercurrent contact with the tail gas for a contact time of 3-5 seconds. The alkali scrubber is made of stainless steel, has a diameter of 2600mm, and is 8m high. The tail gas enters the tower from the kettle and rises through the packing layer, which is used to enhance the gas-liquid contact efficiency. The temperature is controlled at 30°C-50°C to prevent high temperatures from causing the absorption liquid to evaporate too quickly.

[0035] The initial concentration of the washing liquid after washing in the alkali washing tower is 10-15%. The washing liquid is circulated through the alkali washing circulation system. When the washing liquid concentration reaches 5%, it is discharged into the sewage station for centralized treatment. Hydrogen chloride, chlorine, sulfuric acid and sodium hydroxide react to produce sodium chloride, sodium sulfate and sodium hypochlorite. Some high-boiling substances are dissolved in the absorption liquid and removed from the tower bottom. The purified tail gas is discharged from the top of the tower and enters the water washing tower for further treatment. To prevent the packing from clogging, a demister is added in front of the alkali washing tower for pre-filtration. The packing layer is backwashed regularly and replaced every 3-5 years. The acid gas removal rate is ≥98%.

[0036] The alkali washing circulation system includes an alkali liquid circulation pump. The two ends of the alkali liquid circulation pump are respectively connected to the discharge port and the spray assembly of the alkali washing tower, and the spray assembly is connected to an alkali inlet pipe for the entry of alkali liquid. The alkali inlet pipe facilitates the addition of alkali liquid to the spray assembly, and the alkali liquid circulation pump is used to transmit the washed liquid to the spray assembly for recycling.

[0037] S2. The gas after alkali washing enters the circulating water spray type washing tower for water washing to remove residual acid gas, high boiling point and dust. The tail gas enters from the tower kettle and is evenly distributed through the gas distributor. The tail gas rises and the spray liquid descends. The removal rate of high boiling points such as dichloroamino and dichloronitrosyl is ≥90%, and the dust removal rate is ≥98%;

[0038] Two layers of packing are provided in the water washing tower, and distribution devices capable of preventing liquid deviation are provided above the two layers of packing. The distribution devices are configured as liquid distributors, which facilitate uniform distribution of the liquid in the tower. The packing layers are configured as PE ball rings, which enhance the gas-liquid mass transfer efficiency.

[0039] The water washing tower is also provided with a swirl pneumatic device, which forms a swirl through the guide vanes, and the droplets and particles are thrown to the tower wall for sedimentation. The rotation speed of the swirl pneumatic device is set to 1000-3000rpm. The swirl pneumatic device includes a cyclone shell, guide vanes, an air inlet, an air outlet, a drive motor, and a bearing system. The guide vanes are fixed to the inner wall of the cyclone shell by welding, riveting or integrated molding. The shell provides a rotating space for the airflow. The guide vanes guide the airflow to generate a tangential velocity component through their special curved surface design to form a swirl. The air inlet is connected to the cyclone by flange connection, thread connection or welding. The tangential or axial position of the cyclone housing is fixed. The air inlet is the channel for the air flow to enter the cyclone. The air outlet is connected to the central axis or tangential position of the cyclone housing. The drive motor is usually connected to the cyclone housing through a coupling, pulley or gear transmission. The bearing system is usually installed on the rotor shaft of the cyclone housing and connected to the drive motor through a coupling. The air flow enters the cyclone housing from the air inlet, forms a vortex under the action of the guide vanes, and is then discharged from the air outlet. The drive motor and bearing system provide support for the rotating parts of the cyclone. The exhaust gas enters from the bottom air inlet, forms a vortex through the guide vanes, and generates centrifugal force through high-speed rotation to achieve gas-liquid separation.

[0040] The drain outlet of the water washing tower is connected to a three-phase tank. The liquid outlet of the three-phase tank recycles the washing liquid through the acid washing circulation system. The three-phase tank separates the gas, oil and water phases based on density difference and centrifugal effect. The heavy oil containing high boiling point and particles is discharged from the lower outlet for hazardous waste disposal, and the remaining liquid is replenished with water for circulation.

[0041] S3. The gas after water washing is subjected to primary adsorption using a primary adsorption tank containing a hydrophobic resin to adsorb o-dichlorobenzene, 1,2,4-trichlorobenzene and nitrobenzene gases. After adsorption saturation, hot nitrogen is introduced for desorption and condensation;

[0042] The first-level adsorption tank is configured as a fixed-bed adsorption tank, a hydrophobic resin is installed in the first-level adsorption tank, an online concentration sensor is installed at the outlet of the first-level adsorption tank, and the exhaust gas concentration at the outlet of the first-level adsorption tank is monitored by the online concentration sensor. The adsorption temperature is 40°C-60°C. After adsorption is saturated, hot nitrogen at 100°C-120°C is introduced for desorption, and a cooling water system is used for low-temperature condensation at 5°C-7°C. The condensate is directly reused in the 2B acid production section. If the exhaust gas concentration at the outlet of the first-level adsorption tank monitored by the online concentration sensor is close to the inlet value, it indicates saturation. The first-level adsorption mainly relies on physical adsorption and hydrophobic interaction, and desorption only requires physical analysis without chemical reaction. The reaction is o-dichlorobenzene (adsorbed state) + nitrogen → o-dichlorobenzene (gas phase) + nitrogen (carrier gas), and the nitrogen temperature is 80°C-100°C. The continuous desorption-condensation method can reduce the equipment volume and control the desorption rate to match the condensation rate. The condensed gas is mainly nitrogen and uncondensed trace organic matter, which returns to the first-level adsorption tank for circulation.

[0043] During the first-stage adsorption, the purity of o-dichlorobenzene after adsorption, desorption and condensation by the hydrophobic resin is close to that of the workshop solvent. It can be directly reused in 2B acid production without going through a complex and high-consumption distillation process, and it does not affect the product quality. The whiteness of the 2B acid product still reaches above 80. The model of the hydrophobic resin is NDA88. After the selective adsorption and desorption of the hydrophobic resin NDA88, the amount of solvent-containing tail gas has decreased. Compared with the traditional full condensation method, this method provides relatively less cooling capacity, and the recovered solvent does not need to be purified by vacuum distillation. The service life of the hydrophobic resin NDA88 is as long as 2-3 years, and the operating cost is low. After the first-stage adsorption treats a large amount of solvent tail gas, the operating load of the second-stage adsorption is significantly reduced, and the service life of the silanized activated carbon can be increased from 3 months to 6 months.

[0044] S4. The gas after the primary adsorption is subjected to secondary adsorption in a secondary adsorption tank containing silane activated carbon to adsorb 2B oil and 2B oil isomers, p-toluidine, dichloroamino compounds and non-methane total hydrocarbons. After saturation, hot nitrogen is introduced for desorption and condensation;

[0045] The secondary adsorption tank is configured as a fixed bed adsorption tank, and the primary adsorption tank and the secondary adsorption tank are connected in series to achieve step-by-step purification, and the residual gas after the primary adsorption is subjected to secondary adsorption. The silane activated carbon is installed in the secondary adsorption tank, and the surface of the silane activated carbon is modified by a silane coupling agent to enhance the affinity for polar organic matter. An online concentration monitoring sensor is installed at the outlet of the secondary adsorption tank. The online monitoring sensor monitors the exhaust gas concentration at the outlet of the secondary adsorption tank. If the concentration is close to the inlet value, it indicates saturation; secondary desorption involves physical analysis and chemical bond breaking, which requires relatively higher energy; the chilled water temperature is 10°C-20°C, and the condensation effect is not obvious if the water temperature is too high.

[0046] Hot nitrogen is used for desorption in both primary and secondary adsorption, rather than traditional water vapor or hot air. Water vapor is not used to prevent water vapor from entering the 2B oil and thus being unable to directly return to the 2B oil refining tower for regeneration. This avoids the carbonization problem that may be caused by multi-step high-temperature regeneration, and also avoids the increase in moisture content when o-dichlorobenzene is reused, thereby reducing the sulfonation reaction conversion rate. Hot air is not used to prevent amine components such as 2B oil from being oxidized at high temperatures, which would affect the exhaust gas treatment and reuse.

[0047] The primary adsorption tank and the secondary adsorption tank share a cooling water system. The cooling water system directly uses the chilled water discharged from the primary adsorption tank to return water to the secondary adsorption tank for cooling. The cooling water system includes a condenser. The liquid outlet of the primary adsorption tank and the liquid outlet of the secondary adsorption tank are both connected to the condenser. The condenser outlet on the primary adsorption tank is connected to the condenser inlet of the secondary adsorption tank. The condenser outlet on the primary adsorption tank is connected to the 2B acid workshop and the inlet of the primary adsorption tank. The condenser outlet on the secondary adsorption tank is connected to the 2B oil refining tower. As well as the inlet connection of the secondary adsorption tank, since o-dichlorobenzene has a low boiling point (180°C) and a high saturated vapor pressure (0.133kPa, 20°C), it is volatile. The hot gas after desorption needs 5°C-7°C chilled water to condense, while the boiling point of 2B oil is relatively high (243°C), and only 10°C-20°C is needed to achieve the required condensation effect. Therefore, low-temperature chilled water is first used to condense the first-stage desorbed gas and then used to condense the second-stage desorbed gas. The two processes share a chilled water pipeline, avoiding the pipeline pressure drop loss of the two pipelines and saving energy.

[0048] After the silanized activated carbon is saturated with adsorption, hot nitrogen at 100°C-120°C is introduced into the secondary adsorption tank for desorption, and condensed at low temperature using 10°C-20°C chilled water. The condensate is directly returned to the 2B oil refining tower to regenerate 2B oil and p-toluidine. The 2B oil refining tower includes a dehydration tower, a refining tower, a thin film evaporator, etc. After the previous processing steps, the desorbed gas has a high 2B oil content and a low heavy component content. There is no need to return to the thin film evaporator to remove the heavy components, and the gas can be directly returned to the 2B oil vacuum distillation tower for refining and regenerating 2B oil and p-toluidine, saving energy. The use of hot nitrogen instead of water vapor avoids the desorbed gas containing water, which requires returning to the dehydration tower for dehydration, thereby increasing energy consumption.

[0049] S5. The gas after secondary adsorption passes through a tertiary adsorption tank containing activated carbon adsorbent for tail gas purification treatment to ensure that the gas meets emission requirements.

[0050] During the adsorption treatment, the adsorption temperature of the three-stage adsorption tank is 20°C-35°C. Activated carbon adsorbent is added into the three-stage adsorption tank, and hot air at 100°C-120°C is introduced at the same time. The energy consumption is reduced and o-dichlorobenzene is recycled, both of which directly lead to carbon emission reduction benefits.

[0051] According to the exhaust gas coordinated treatment method proposed above, the compatibility verification of exhaust gas combined treatment is carried out:

[0052] 1. Cross-pollutant adsorption competition experiment:

[0053] After simulating the mixing of two production tail gases, 2B oil and 2B acid, the adsorption competition relationship between o-dichlorobenzene (non-polar) and dichloronitrosyl (strong polar) on hydrophobic resin NDA88 was tested. The results are shown in the following table:

[0054]

[0055] From the data in the table, it can be concluded that the adsorption efficiency of o-dichlorobenzene in the mixed gas is ≥95%; the residual concentration of dichloronitrosyl compounds is ≤5mg / m 3 .

[0056] 2. Side reaction risk test: At an adsorption temperature of 40℃-60℃, the system is tested to see if the acidic gas in the mixed exhaust gas reacts with amine organic matter. The system runs continuously for more than 72 hours. The results show that there is no coking or blockage in the adsorption tower, indicating that no solid salt or colloid is generated.

[0057] According to the above-mentioned tail gas collaborative treatment method, the high boiling point removal mechanism and parameter optimization are carried out:

[0058] The gas-liquid ratio of the cyclone pneumatic device was adjusted (1:10-1:30) to test the removal efficiency of high-boiling substances (dichloronitrosyl compounds, dichloroamino compounds) and dust. The results showed that when the gas-liquid ratio was 1:20, the removal rate of high-boiling substances was ≥90%, and the dust residue was ≤1mg / m 3 , the optimization process is shown in the following table:

[0059]

[0060]

[0061] The waste liquid from the water washing tower was collected and analyzed by GCMS to determine the proportion of high-boiling substances (dichloronitrosyl compounds and dichloroamino compounds). The results showed that the concentration of high-boiling substances in the waste liquid was ≤0.01%, and the waste liquid could be directly incinerated.

[0062] Adsorbent regeneration performance and life test:

[0063] 1. Experiment on attenuation of regeneration efficiency of silanized activated carbon:

[0064] Ten adsorption-desorption cycles were performed continuously (hot nitrogen at 100-120°C) to monitor the changes in the recovery rates of 2B oil and p-toluidine. The test results are shown in the following table:

[0065]

[0066]

[0067] It can be seen from the table data that the recovery rate is still ≥92% at the 10th cycle (traditional activated carbon decays to ≤80% at the 10th cycle); the activated carbon specific surface area decay rate is ≤15% (BET method test).

[0068] 2. Long-term stability test of hydrophobic resin NDA88

[0069] The mechanical strength and adsorption capacity of the resin were evaluated by simulating two years of operating conditions (adsorption temperature fluctuations of 40-60°C). The results showed that the resin breakage rate was ≤1% (immersion test + pressure test); the o-dichlorobenzene adsorption capacity retention rate was ≥90% (compared with the initial performance).

[0070] Economic analysis:

[0071] 1. Energy saving benefits (compared with traditional processes)

[0072] (1) Thin film evaporator alternative: Energy consumption for hot nitrogen desorption is reduced by 40% (150°C → 110°C);

[0073] (2) The cooling capacity requirement of the low-temperature condensation system is reduced by 30% (only the exhaust gas after the first-stage adsorption is processed, and the processing capacity is reduced).

[0074] 2. Hazardous waste reduction benefits

[0075] The recovery rate of o-dichlorobenzene is ≥95%, reducing the cost of hazardous waste disposal and new solvent purchases by approximately RMB 475,000 / year (calculated based on a scale of 50 tons / year, a purchase unit price of RMB 8,500 / t, and a hazardous waste disposal price of RMB 1,500 / t).

[0076] In summary, the tail gas from 2B oil production and the tail gas from 2B acid production are combined and shared with the alkali washing tower, water washing tower, primary adsorption tank, secondary adsorption tank and tertiary adsorption tank, which reduces the repeated equipment investment in the alkali washing tower, water washing tower, etc., and realizes the classified enrichment and directional reuse of the two tail gas pollutants through the combined adsorption of hydrophobic resin and silanized activated carbon. In view of the fact that 2B oil is the precursor of 2B acid production, it is planned to integrate the two tail gas pretreatment systems of 2B acid production, reduce the repeated equipment investment, and reduce the tail gas treatment cost.

[0077] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for collaboratively treating tail gas from the production of 2B oil and 2B acid, characterized by: The steps include: S1. Combine the tail gas from 2B oil production and 2B acid production and then send them into an alkaline washing tower for washing to neutralize sulfuric acid mist, hydrogen chloride, chlorine and acidic gases; S2. The gas after alkali washing enters a circulating water spray type water washing tower for water washing to remove residual acid gas, high boiling point and dust; S3. The gas after water washing is subjected to primary adsorption using a primary adsorption tank containing a hydrophobic resin to adsorb o-dichlorobenzene, 1,2,4-trichlorobenzene and nitrobenzene gases. After adsorption saturation, hot nitrogen is introduced for desorption and condensation; S4. The gas after the primary adsorption is subjected to secondary adsorption in a secondary adsorption tank containing silane activated carbon to adsorb 2B oil and 2B oil isomers, p-toluidine, dichloroamino compounds and non-methane total hydrocarbons. After saturation, hot nitrogen is introduced for desorption and condensation; S5. The gas after secondary adsorption passes through a tertiary adsorption tank containing activated carbon adsorbent for tail gas purification treatment to ensure that the gas meets emission requirements.

2. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 1, characterized in that: The alkali washing tower is configured as a countercurrent packed tower, and an air intake section, a packing layer and a spray section are provided inside the alkali washing tower. The packing layer is filled with PE ball ring packing. The spray section sprays sodium hydroxide spray liquid, so that the sodium hydroxide spray liquid contacts the tail gas in countercurrent, and the contact time is 3-5 seconds.

3. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 2, characterized in that: The initial concentration of the washing liquid after washing in the alkali washing tower is 10-15%. The washing liquid is recycled through the alkali washing circulation system. When the concentration of the washing liquid reaches 5%, it is discharged into the sewage station for centralized treatment. A demister is added in front of the alkali washing tower for pre-filtration, and the packing layer is backwashed regularly.

4. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 1, characterized in that: Two packing layers are provided in the water washing tower, and distribution devices capable of preventing liquid deviation are provided above the two packing layers. The packing layers are provided with PE ball rings.

5. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 4, characterized in that: A swirl pneumatic device is also provided inside the water washing tower. The swirl pneumatic device forms a swirl through the guide blades, and the droplets and particulate matter are thrown to the tower wall for sedimentation. The rotation speed of the swirl pneumatic device is set to 1000-3000rpm. The drain outlet of the water washing tower is connected to a three-phase tank, and the liquid outlet of the three-phase tank recycles the washing liquid through the pickling circulation system.

6. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 5, characterized in that: In step S3, the primary adsorption tank is set as a fixed bed adsorption tank, the hydrophobic resin is installed in the primary adsorption tank, and an online concentration sensor is installed at the outlet of the primary adsorption tank. The exhaust gas concentration at the outlet of the primary adsorption tank is monitored by the online concentration sensor. The adsorption temperature is 40°C-60°C. After adsorption saturation, 100°C-120°C hot nitrogen is introduced for desorption, and a cooling water system is used for low-temperature condensation at 5°C-7°C. The condensate is directly reused in the 2B acid production section.

7. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 6, characterized in that: In step S4, the secondary adsorption tank is set as a fixed bed adsorption tank, the primary adsorption tank and the secondary adsorption tank are connected in series, the silane activated carbon is installed in the secondary adsorption tank, the surface of the silane activated carbon is modified by a silane coupling agent, and a concentration online monitoring sensor is installed at the outlet of the secondary adsorption tank.

8. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 7, characterized in that: The primary adsorption tank and the secondary adsorption tank share a cooling water system, and the cooling water system directly uses the chilled water discharged from the primary adsorption tank to return water to the secondary adsorption tank for cooling.

9. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 8, characterized in that: After the silanized activated carbon is saturated with adsorption, hot nitrogen at 100-120°C is introduced into the secondary adsorption tank for desorption, and 10-20°C chilled water is used for low-temperature condensation. The condensate is directly returned to the 2B oil refining tower to regenerate 2B oil and p-toluidine.

10. The method for collaboratively treating tail gas from the production of 2B oil and 2B acid according to claim 1, characterized in that: In step S5, during the adsorption treatment, the adsorption temperature of the three-stage adsorption tank is 20°C-35°C, activated carbon adsorbent is added into the three-stage adsorption tank, and hot air at 100°C-120°C is introduced at the same time.

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