Multi-stage cryogenic and multi-adsorption dichloromethane recovery method and recovery system

Abstract

The invention discloses a dichloromethane recovery method and a dichloromethane recovery system based on multi-stage cryogenic and multi-adsorption. The recovery method comprises the following steps that tail gas is introduced into tail gas distribution equipment, and the tail gas distribution equipment measures the tail gas concentration c, the air volume Q'and the dew point temperature Dp; comparing the air volume Q ', the tail gas concentration c and a preset value; calculating the tail gas concentration c when the input tail gas is cooled to a refrigeration temperature point of-40 DEG C to-70 DEG C; calculating the energy and consumable loss of the tail gas input into the carbon fiber equipment, the granular carbon equipment and the runner equipment for adsorption and the concentration c of the removed tail gas; the steps of tail gas treatment are counted, energy and consumable loss is converted into carbon dioxide emission, scheme sequencing is conducted, and a tail gas treatment scheme is formed. According to the invention, multi-stage cryogenic treatment is used as front-end treatment equipment, and adsorption equipment is used as a downstream dichloromethane recovery system, so that standard emission is ensured, and meanwhile, a scheme of lowest carbon emission is selected for recovery treatment.

Description

Technical Field

[0001] The invention relates to a multi-stage deep cooling and multi-adsorption dichloromethane recovery method and also relates to a corresponding dichloromethane recovery system, belonging to the technical field of condensation recovery. Background Art

[0002] As a commonly used organic solvent, dichloromethane is widely used in the fields of medicine, film, industrial refrigeration, industrial extraction, etc. Conventional dichloromethane tail gas recovery technologies mainly include condensation method, adsorption method and solvent absorption method.

[0003] The condensation method is simple and easy to operate, but because the atmospheric boiling point of dichloromethane is only 39.8°C, even when the temperature reaches 0°C, the gas saturation partial pressure of dichloromethane is still about 19.3kPa, and the volume concentration is still about 20%. In order to further reduce the concentration of dichloromethane in the gas and increase the recovery rate, some manufacturers use cryogenic equipment at -15°C or even -35°C for freezing treatment.

[0004] The adsorption method uses adsorbents such as activated carbon or macroporous resin with microporous structure to adsorb dichloromethane molecules in the tail gas, and then uses water vapor or hot air to desorb and recover dichloromethane, while the adsorbent is regenerated and reused. The adsorption method is mostly suitable for the recovery and environmental protection of low-concentration organic tail gas with an organic content of less than 1%. High-concentration tail gas can easily lead to the deactivation of the adsorbent.

[0005] In the Chinese patent application with application number 201810018769.4, a method and system for recycling and reusing high-concentration dichloromethane tail gas is disclosed. The technical solution collects dichloromethane tail gas through a gas collecting pipe and a fan, and sends it to a compressor for compression and condensation recovery, and the condensed tail gas is returned to the tail gas generation system. After the compressed condensation recovery amount becomes small to a certain value, the pipeline of the gas collecting pipe is switched to a high-efficiency pressure swing adsorption analysis equipment, and the remaining dichloromethane in the system is discharged after pressure swing adsorption treatment. The dichloromethane recovered by condensation can be directly or after treatment and returned to production.

[0006] However, the cryogenic process consumes a lot of electricity, the energy efficiency ratios of different cooling temperatures vary greatly, and the adsorption and desorption process consumes a lot of steam and consumables. When the process parameters of the upstream incoming materials are unstable, the methylene chloride recovery system in the existing technology cannot automatically select a process flow with better energy-saving and carbon-reducing effects. Summary of the invention

[0007] The primary technical problem to be solved by the present invention is to provide a dichloromethane recovery method with multi-stage deep cooling and multiple adsorption.

[0008] Another technical problem to be solved by the present invention is to provide a dichloromethane recovery system for realizing the above-mentioned dichloromethane recovery method.

[0009] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: According to a first aspect of an embodiment of the present invention, a multi-stage cryogenic and multi-adsorption dichloromethane recovery method is provided, comprising the following steps: Step S1: exhaust gas is passed into the exhaust gas distribution device, the exhaust gas distribution device measures the exhaust gas concentration c and the air volume Q', and jumps to step S3; Step S2: Compare the air volume Q' with the preset air volume Q. When Q'>Q, discharge the air volume through the emergency discharge system to make Q'=Q, and jump to step S3; when Q'≤Q, calculate the air volume Q' and exhaust gas concentration c after increasing the corresponding step air volume, and jump to step S3; Step S3: Compare the exhaust gas concentration c with the preset value. When c≤120mg / m³, jump to step S10; when c≥90g / m³, jump to step S2 and step S4; when 120mg / m³<concentration c<90g / m³, jump to step S5; Step S4: Calculate the exhaust concentration c when the input exhaust gas is cooled to a refrigeration temperature point of -40 to -70°C; obtain the required energy and consumables loss, and jump to step S3; Step S5: the exhaust gas distribution device measures the dew point temperature Dp of the exhaust gas, and jumps to step S2 and step S6; Step S6: Compare the exhaust gas concentration c with the preset value. When 70g / m³<concentration c<90g / m³, jump to step S7; when 20g / m³<concentration c≤70g / m³, jump to steps S7 and S8; when 1g / m³<concentration c≤20g / m³, jump to step S8; when 120mg / m³<concentration c≤1g / m³, jump to step S9; Step S7: Calculate the energy and consumables loss of the tail gas input into the carbon fiber device for adsorption, as well as the concentration c of the tail gas removed, and jump to step S3; Step S8: Calculate the energy and consumables loss of the exhaust gas input into the granular carbon device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3; Step S9: Calculate the energy and consumables loss of the exhaust gas input to the rotor device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3; Step S10: Counting the steps of tail gas treatment and the energy and consumables loss required to form a tail gas treatment plan; converting the energy and consumables loss into carbon dioxide emissions; Step S11: Sort the exhaust gas treatment schemes from low to high according to the carbon dioxide emissions, output the scheme with the lowest carbon dioxide emissions as the optimal exhaust gas treatment scheme, and output the number of second lowest schemes required by the design as alternative exhaust gas treatment schemes.

[0010] Preferably, step S4 further includes the following sub-steps: Step S41: compare the temperature T of the input exhaust gas, when the temperature T>-40℃, jump to step S42; when the temperature -40℃≥T>-70℃, jump to step S43; when the temperature T≤-70℃, jump to step S3; Step S42: based on the temperature T of the input exhaust gas, calculate the exhaust gas concentration c required to cool the exhaust gas to -40°C, obtain the energy and consumables loss required to cool to -40°C, and jump to step S3; Step S43: Based on the input exhaust gas temperature T, subtract the preset temperature step value, calculate the exhaust gas concentration c at the temperature after subtracting the preset temperature step value, obtain the energy and consumables loss required for cooling, and jump to step S3.

[0011] Preferably, the step S7 further comprises the following sub-steps: Step S71: Compare the dew point temperature Dp of the input exhaust gas of the carbon fiber device with the preset value. When Dp>18℃, jump to step S72; when Dp≤18℃, jump to step S73; Step S72: lower the exhaust gas temperature T to 18°C, obtain the energy and consumables loss required for cooling to 18°C, and jump to step S74; Step S73: compare the temperature T of the input exhaust gas of the carbon fiber device with the preset value, and when the temperature T≤25°C, jump to step S74; when the temperature T>25°C, jump to step S75; Step S74: Raise the exhaust gas temperature T to 25° C., obtain the energy and consumables loss required to raise the temperature to 25° C., and jump to step S76; Step S75: Cooling the exhaust gas temperature T to 25°C, obtaining the energy and consumables loss required for cooling to 25°C, and jumping to step S76; Step S76: Calculate the energy and consumables loss of the exhaust gas input into the carbon fiber equipment for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

[0012] Preferably, step S8 further includes the following sub-steps: Step S81: compare the dew point temperature Dp of the input exhaust gas of the granular carbon device with the preset value, when Dp>18℃, jump to step S82; when Dp≤18℃, jump to step S83; Step S82: lower the exhaust temperature T to 18°C, obtain the energy and consumables loss required for cooling to 18°C, and jump to step S84; Step S83: compare the temperature T of the exhaust gas input to the granular carbon device with a preset value, and when the temperature T≤25°C, jump to step S84; when the temperature T>25°C, jump to step S85; Step S84: Raise the exhaust gas temperature T to 25°C, obtain the energy and consumables loss required to raise the temperature to 25°C, and jump to step S86; Step S85: Cooling the exhaust gas temperature T to 25°C, obtaining the energy and consumables loss required for cooling to 25°C, and jumping to step S86; Step S86: Calculate the energy and consumables loss of the exhaust gas input into the granular carbon equipment for adsorption, as well as the exhaust gas concentration c, and jump to step S3.

[0013] Preferably, the step S9 further includes the following sub-steps: Step S91: compare the dew point temperature Dp of the input exhaust gas of the runner device with the preset value, when Dp>28℃, jump to step S92; when Dp≤28℃, jump to step S93; Step S92: lower the exhaust temperature T to 28°C, obtain the energy and consumables loss required for cooling to 28°C, and jump to step S94; Step S93: compare the temperature T of the exhaust gas input to the runner device with a preset value. When the temperature T is less than or equal to 39°C, jump to step S94; when the temperature T is greater than or equal to 39°C, jump to step S95; Step S94: Raise the exhaust gas temperature T to 39° C., obtain the energy and consumables loss required to raise the temperature to 39° C., and jump to step S96; Step S95: Cooling the exhaust gas temperature T to 39° C., obtaining the energy and consumables loss required for cooling to 39° C., and jumping to step S96; Step S96: Calculate the energy and consumables loss of the exhaust gas input to the rotor device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

[0014] According to a second aspect of an embodiment of the present invention, a dichloromethane recovery system for implementing the above-mentioned dichloromethane recovery method is provided, comprising an exhaust gas distribution device, an air supply device, a multi-stage cryogenic device, a carbon fiber device, a granular carbon device and a rotor device; wherein, The input end of the exhaust gas distribution device is connected to the exhaust gas source, the output end of the air supply device, the output end of the multi-stage cryogenic device, the output end of the carbon fiber device, the output end of the granular carbon device and the output end of the rotor device; The output end of the tail gas distribution device is connected to the input end of the multi-stage cryogenic device, the input end of the carbon fiber device, the input end of the granular carbon device and the input end of the wheel device; The input end of the air supply device is connected to the external air and the exhaust gas source.

[0015] Preferably, the exhaust gas distribution equipment has the function of measuring exhaust gas concentration, dew point temperature and air volume parameters, as well as the function of calculating the emission scheme according to the parameters, counting the energy consumption and consumables consumption in the emission scheme, and converting the corresponding energy consumption and consumables consumption into a unified carbon emission amount; The carbon fiber equipment, granular carbon equipment and rotary wheel equipment are all equipped with built-in coolers and heaters for dehumidifying and controlling the temperature of the exhaust gas.

[0016] Preferably, the dichloromethane recovery system also includes emergency discharge equipment and exhaust equipment; wherein, The tail gas distribution device comprises a first tail gas distribution unit and a second tail gas distribution unit; The input end of the first tail gas distribution unit is connected to the tail gas source and the output end of the air supply device, and the output end is connected to the input end of the multi-stage cryogenic device, the input end of the carbon fiber device, the input end of the granular carbon device and the input end of the wheel device; The input end of the second tail gas distribution unit is connected to the output end of the multi-stage cryogenic device, the output end of the carbon fiber device and the output end of the granular carbon device, and the output end is connected to the input end of the carbon fiber device, the input end of the granular carbon device and the input end of the wheel device; The input end of the emergency discharge device is connected to the exhaust gas source, and the output end is connected to the input end of the exhaust device; The input end of the exhaust device is connected to the output end of the multi-stage cryogenic device, the output end of the carbon fiber device, the output end of the granular carbon device and the output end of the emergency exhaust device, and the output end is connected to the atmosphere; The input end of the air supply device is connected to the exhaust gas source and external air, and the output end is connected to the input end of the first exhaust gas distribution unit.

[0017] Compared with the prior art, the present invention realizes efficient and energy-saving recovery and treatment of dichloromethane tail gas under the premise of ensuring that the tail gas meets the emission standards. The method monitors the concentration, air volume and dew point temperature of the tail gas in real time through the tail gas distribution equipment, and intelligently selects the optimal recovery process according to these parameters. For high-concentration tail gas, multi-stage deep cooling equipment is used for condensation recovery; for medium and low-concentration tail gas, multiple adsorption treatments are carried out through carbon fiber equipment, granular carbon equipment and rotary equipment. The energy consumption and carbon emissions of each treatment scheme are automatically calculated according to different working conditions, and the scheme with the lowest carbon emissions is selected as the optimal treatment scheme, and alternative schemes are provided to meet different needs. Through this intelligent treatment method, the present invention not only improves the recovery efficiency of dichloromethane, reduces energy consumption and carbon emissions, but also extends the service life of the adsorption equipment, providing enterprises with an economical, environmentally friendly and efficient tail gas treatment solution, which is particularly suitable for working conditions where the concentration of dichloromethane tail gas fluctuates greatly or the process parameters are unstable, and has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 (a) is a schematic diagram of the steps of a multi-stage cryogenic and multi-adsorption dichloromethane recovery method in the first embodiment of the present invention; FIG1( b ) is a schematic diagram of sub-steps of step S4 in FIG1 ; FIG1( c ) is a schematic diagram of sub-steps of step S7 in FIG1 ; FIG1( d ) is a schematic diagram of sub-steps of step S8 in FIG1 ; FIG1( e ) is a schematic diagram of sub-steps of step S9 in FIG1 ; Figure 2 It is a temperature-saturation content curve diagram of a multi-stage cryogenic equipment; Figure 3 It is a temperature-power consumption curve diagram of a multi-stage cryogenic equipment; Figure 4 It is the temperature-water consumption curve of multi-stage cryogenic equipment; Figure 5 This is a structural schematic diagram of a dichloromethane recovery system in the second embodiment of the present invention. DETAILED DESCRIPTION

[0019] The technical content of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The technical concept in the embodiment of the present invention is: based on the working conditions of the tail gas (concentration, temperature, dew point and air volume and other parameters), the carbon emissions of different recovery schemes are calculated under the premise of ensuring that the emission meets the standard, and the dichloromethane recovery system is intelligently controlled to treat the tail gas according to the better recovery scheme. Specifically, the dichloromethane recovery system and control method use multi-stage cryogenics as the front-end equipment, combined with downstream carbon fiber equipment, granular carbon adsorption equipment and rotary adsorption equipment as the back-end equipment to ensure that the emission meets the standard.

[0021] First embodiment As shown in FIG. 1 ( a ) to FIG. 1 ( e ), an embodiment of the present invention provides a multi-stage cryogenic and multi-adsorption dichloromethane recovery method, comprising the following steps.

[0022] Step S1: exhaust gas is introduced into the exhaust gas distribution device, the exhaust gas distribution device measures the exhaust gas concentration c and the air volume Q', and then jumps to step S3.

[0023] In the embodiment of the present invention, the concentration c is the concentration of dichloromethane in the tail gas, and the air volume Q' is the tail gas air volume.

[0024] Step S2: Compare the air volume Q' and the preset air volume Q (preset value). When Q'>Q, discharge the air volume through the emergency discharge system to make Q'=Q, and jump to step S3; when Q'≤Q, calculate the air volume Q' and exhaust gas concentration c after increasing the corresponding step air volume, and jump to step S3.

[0025] The preset air volume Q is exemplified by the maximum operating air volume of a dichloromethane recovery system, and the air volume Q'≤Q after the corresponding step air volume is increased. In the prior art, the air volume step value is 1000-10000 m³ / h. The embodiment of the present invention is exemplified by the minimum operating air volume step of 5000 m³ / h, and the preset air volume Q is exemplified by 25000 m³ / h.

[0026] When the exhaust gas of the same concentration has different air volumes, the energy consumption and consumables required for the operation of the dichloromethane recovery system are different.

[0027] As shown in Table 1, take the carbon fiber equipment adsorbing 60g / m³ exhaust gas as an example.

[0028] Table 1 Energy consumption of carbon fiber equipment for adsorbing 60g / m³ tail gas It should be noted that the carbon fiber in the embodiment of the present invention is also called fibrous activated carbon. It is made of fibrous precursors, which are activated by carbonization in a certain process. It has a faster adsorption and desorption rate and a larger adsorption capacity. It is a highly efficient active adsorption material and environmental engineering material with better performance than activated carbon.

[0029] As shown in Table 2, take the granular carbon equipment adsorbing exhaust gas with a concentration of 40g / m³ as an example.

[0030] Table 2 Energy consumption of granular carbon equipment for adsorbing 40g / m³ tail gas As shown in Table 3, take the rotary device adsorbing exhaust gas with a concentration of 400 mg / m³ as an example.

[0031] Table 3 Energy consumption required for the rotary equipment to adsorb 400mg / m³ tail gas Step S3: Compare the exhaust gas concentration c with the preset value. When c≤120mg / m³, jump to step S10; when c≥90g / m³, jump to step S2 and step S4; when 120mg / m³<concentration c<90g / m³, jump to step S5.

[0032] Among them, 120mg / m³ is the standard emission concentration, which is set in accordance with relevant national laws and regulations and can be adjusted more strictly according to local standards.

[0033] 90g / m³ is the multi-stage cryogenic concentration, which is set according to the optimal energy consumption treatment tail gas concentration of the multi-stage cryogenic equipment and the adsorption equipment. That is, tail gas with a concentration of 90g / m³ and above is recycled and treated by the multi-stage cryogenic equipment. In addition, tail gas with a concentration of more than 90g / m³ exceeds the optimal energy consumption treatment concentration of carbon fiber and granular carbon equipment, and needs to be supplemented with air to reduce the concentration before it can be adsorbed and recovered by the adsorption equipment. Among them, carbon fiber equipment, granular carbon equipment and rotary equipment are collectively referred to as adsorption equipment.

[0034] The best energy efficiency treatment concentration for carbon fiber equipment is 20-90g / m³, and the best energy efficiency treatment concentration for granular carbon equipment is 1-70g / m³. The best energy efficiency treatment concentration for rotary equipment is 10-1000mg / m³, and the exhaust gas concentration below 1g / m³ must be less than or equal to 120mg / m³ after adsorption treatment by the rotary equipment, which meets the emission requirements.

[0035] The multi-stage cryogenic device condenses and precipitates the dichloromethane gas contained in the tail gas through refrigeration. The refrigeration range that the multi-stage cryogenic device can reach is 40 to -70°C. According to the energy efficiency of the multi-stage cryogenic device, the embodiment of the present invention selects the refrigeration range of its operation to be -40 to -70°C.

[0036] In this step, the tail gas with a concentration of c ≥ 90 g / m³ is jumped to step S2 and step S4 in order to simultaneously form a multi-stage deep cooling scheme and a multiple adsorption scheme after tail gas supplementary air dilution for comparison.

[0037] Step S4: Calculate the exhaust concentration c when the input exhaust gas is cooled to a refrigeration temperature point of -40 to -70°C; obtain the required energy and consumables loss, and jump to step S3.

[0038] Step S41: Compare the temperature T of the input exhaust gas of the multi-stage cryogenic equipment. When the temperature T>-40℃, jump to step S42; when the temperature -40℃≥T>-70℃, jump to step S43; when the temperature T≤-70℃, jump to step S3.

[0039] Step S42: Based on the temperature T of the input exhaust gas, calculate the exhaust gas concentration c required to cool the exhaust gas to -40°C, obtain the energy and consumables loss required for cooling to -40°C, and jump to step S3.

[0040] Step S43: Based on the input exhaust gas temperature T, subtract the preset temperature step value, calculate the exhaust gas concentration c at the temperature after subtracting the preset temperature step value, obtain the energy and consumables loss required for cooling, and jump to step S3.

[0041] The purpose of this step is to compare the energy and consumables loss of each cryogenic temperature point solution. For example, the preset temperature step of the exhaust gas cooling temperature of the multi-stage cryogenic equipment is -1 to -10°C, that is, the exhaust gas concentration c is calculated at each preset refrigeration temperature point of -40 to -70°C.

[0042] The temperature-exhaust concentration curve corresponding to the multi-stage cryogenic equipment is as follows: Figure 2 shown.

[0043] The temperature-power consumption curve corresponding to the multi-stage cryogenic equipment is as follows Figure 3 shown.

[0044] The temperature-water consumption curve corresponding to the multi-stage cryogenic equipment is as follows Figure 4 shown.

[0045] Step S5: The exhaust gas distribution device obtains the dew point temperature Dp of the exhaust gas, and jumps to step S2 and step S6.

[0046] The method for obtaining the dew point temperature Dp of the exhaust gas is a well-known technology, for example, by measuring with a dew point meter, or measuring the exhaust gas temperature T and the exhaust gas relative humidity RH, and calculating the dew point temperature Dp.

[0047] The purpose of supplementary air for tail gas with concentration c between 120mg / m³ and 90g / m³ is to dilute the tail gas concentration with supplementary air and calculate the energy consumption and consumable loss of different adsorption schemes.

[0048] Step S6: Compare the exhaust gas concentration c with the preset value. When 70g / m³<concentration c<90g / m³, jump to step S7; when 20g / m³<concentration c≤70g / m³, jump to steps S7 and S8; when 1g / m³<concentration c≤20g / m³, jump to step S8; when 120mg / m³<concentration c≤1g / m³, jump to step S9.

[0049] Since the optimal energy efficiency treatment concentrations of carbon fiber equipment and granular carbon equipment overlap at 20-70g / m³, it is necessary to calculate the energy consumption and carbon emissions of the carbon fiber equipment and granular carbon equipment respectively at the overlapping concentration in order to select a better treatment plan.

[0050] As shown in Table 4, taking the exhaust gas with an air volume of 10,000 m³ / h being cooled to 18°C, 25°C, 28°C, and 39°C respectively as an example, the required energy consumption is as follows.

[0051] Table 4 Energy consumption required for cooling 10000m³ / h exhaust gas As shown in Table 5, taking the exhaust gas with different air volumes and an initial temperature of 80°C being cooled to 18°C, 25°C, 28°C, and 39°C as an example, the required energy consumption is as follows.

[0052] Table 5 Energy consumption required for cooling exhaust gas at 80℃ As shown in Table 6, taking the exhaust gas with an air volume of 10,000 m³ / h as an example, when the temperature is raised to 25°C and 39°C respectively, the required energy consumption is as follows.

[0053] Table 6 Energy consumption required for heating 10000m³ / h exhaust gas As shown in Table 7, taking the exhaust gas with different air volumes and an initial temperature of 20°C being heated to 25°C and 39°C respectively as an example, the required energy consumption is as follows.

[0054] Table 7 Energy consumption required for heating exhaust gas to 20℃ Step S7: Calculate the energy and consumables loss of the exhaust gas input into the carbon fiber equipment for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

[0055] Step S71: Compare the dew point temperature Dp of the input exhaust gas of the carbon fiber device with the preset value. When Dp>18°C, jump to step S72; when Dp≤18°C, jump to step S73.

[0056] Step S72: reduce the exhaust gas temperature T to 18°C, obtain the energy and consumables loss required for cooling to 18°C, and jump to step S74.

[0057] Step S73: Compare the temperature T of the input exhaust gas of the carbon fiber device with the preset value. When the temperature T≤25°C, jump to step S74; when the temperature T>25°C, jump to step S75.

[0058] Step S74: Raise the exhaust gas temperature T to 25°C, obtain the energy and consumables loss required to raise the temperature to 25°C, and jump to step S76.

[0059] Step S75: Cool down the exhaust gas temperature T to 25°C, obtain the energy and consumables loss required for cooling to 25°C, and jump to step S76.

[0060] Step S76: Calculate the energy and consumables loss of the exhaust gas input into the carbon fiber equipment for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

[0061] As shown in Table 8, take the carbon fiber equipment adsorbing exhaust gas with an air volume of 10,000 m³ / h as an example.

[0062] Table 8 Energy consumption required for carbon fiber equipment to adsorb 10000m³ / h tail gas Step S8: Calculate the energy and consumables loss of the exhaust gas input into the granular carbon equipment for adsorption, as well as the exhaust gas concentration c, and jump to step S3.

[0063] Step S81: Compare the dew point temperature Dp of the input exhaust gas of the granular carbon device with the preset value. When Dp>18°C, jump to step S82; when Dp≤18°C, jump to step S83.

[0064] Step S82: reduce the exhaust gas temperature T to 18°C, obtain the energy and consumables loss required for cooling to 18°C, and jump to step S84.

[0065] Step S83: Compare the temperature T of the input exhaust gas of the granular carbon device with the preset value. When the temperature T≤25°C, jump to step S84; when the temperature T>25°C, jump to step S85.

[0066] Step S84: Raise the exhaust gas temperature T to 25°C, obtain the energy and consumables loss required to raise the temperature to 25°C, and jump to step S86.

[0067] Step S85: Cool down the exhaust gas temperature T to 25°C, obtain the energy and consumables loss required for cooling to 25°C, and jump to step S86.

[0068] Step S86: Calculate the energy and consumables loss of the exhaust gas input into the granular carbon equipment for adsorption, as well as the exhaust gas concentration c, and jump to step S3.

[0069] As shown in Table 9, take the exhaust gas adsorbed by the granular carbon equipment with an air volume of 10,000 m³ / h as an example.

[0070] Table 9 Energy consumption required for granular carbon equipment to adsorb 10000m³ / h tail gas Step S9: Calculate the energy and consumables loss of the exhaust gas input into the rotor device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

[0071] Step S91: Compare the dew point temperature Dp of the input exhaust gas of the rotor device with the preset value. When Dp>28℃, jump to step S92; when Dp≤28℃, jump to step S93.

[0072] Step S92: reduce the exhaust gas temperature T to 28°C, obtain the energy and consumables loss required for cooling to 28°C, and jump to step S94.

[0073] Step S93: Compare the temperature T of the input exhaust gas of the rotor device with the preset value. When the temperature T≤39°C, jump to step S94; when the temperature T>39°C, jump to step S95.

[0074] Step S94: Raise the exhaust gas temperature T to 39°C, obtain the energy and consumables loss required to raise the temperature to 39°C, and jump to step S96.

[0075] Step S95: Cool down the exhaust gas temperature T to 39°C, obtain the energy and consumables loss required for cooling to 39°C, and jump to step S96.

[0076] Step S96: Calculate the energy and consumables loss of the exhaust gas input to the rotor device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

[0077] As shown in Table 10, take the exhaust gas adsorbed by the rotary equipment with an air volume of 10,000 m³ / h as an example.

[0078] Table 10 Energy consumption required for the rotary equipment to adsorb 10000m³ / h tail gas Step S10: Count the steps of tail gas treatment and the energy and consumables loss required to form a tail gas treatment plan; convert the energy and consumables loss into carbon dioxide emissions.

[0079] The energy and consumables consumed are converted into carbon emissions. For example, the amount of carbon emitted in the production of consumables is used as the carbon emissions of the consumables.

[0080] As shown in Table 11, taking the exhaust gas with an air volume of 10,000 m³ / h as an example, the consumables required to adsorb exhaust gas of different concentrations are as follows, where 7,200 hours are calculated per year.

[0081] Table 11 Material consumption required for adsorption equipment to adsorb 10000m³ / h tail gas Step S11: Sort the exhaust gas treatment schemes from low to high according to the carbon dioxide emissions, output the scheme with the lowest carbon dioxide emissions as the optimal exhaust gas treatment scheme, and output the number of second lowest schemes required by the design as alternative exhaust gas treatment schemes.

[0082] It is worth noting that the method for obtaining the exhaust gas parameters in the above steps includes actual measurement and simulation calculation. For example, the exhaust gas distribution device can simulate and calculate the exhaust gas parameters after each air supply volume according to the input exhaust gas parameters, or the exhaust gas distribution device can actually measure the parameters during the operation of the dichloromethane recovery system.

[0083] Second embodiment The embodiment of the present invention provides a dichloromethane recovery system, including tail gas distribution equipment, air supply equipment, multi-stage cryogenic equipment, carbon fiber equipment, granular carbon equipment, wheel equipment, emergency discharge equipment and exhaust equipment.

[0084] The tail gas distribution equipment has the function of measuring parameters such as tail gas concentration, temperature, relative humidity, dew point temperature and air volume, as well as calculating the emission plan based on the parameters, statistically analyzing the energy consumption and consumables consumption in the emission plan, and converting the corresponding energy consumption and consumables consumption into a unified carbon emission. The tail gas distribution equipment can output the tail gas treatment plan with the lowest carbon emission (optimal treatment plan) and the required number of the second lowest plan based on the above-mentioned dichloromethane recovery method. The tail gas distribution equipment can control the operation of the dichloromethane recovery system based on the above-mentioned tail gas treatment plan.

[0085] Carbon fiber equipment, granular carbon equipment and rotary equipment are collectively referred to as adsorption equipment, which are equipment for removing dichloromethane from exhaust gas by adsorption. In addition, carbon fiber equipment, granular carbon equipment and rotary equipment all have built-in coolers and heaters for dehumidifying and controlling the temperature of exhaust gas. For example, the exhaust gas to be adsorbed is first cooled and then heated to reduce the humidity of the exhaust gas.

[0086] The input end of the exhaust gas distribution equipment is connected to the exhaust gas source, the output end of the air supply equipment, the output end of the multi-stage cryogenic equipment, the output end of the carbon fiber equipment, the output end of the granular carbon equipment and the output end of the rotary equipment, and the output end of the exhaust gas distribution equipment is connected to the exhaust equipment, the input end of the multi-stage cryogenic equipment, the input end of the carbon fiber equipment, the input end of the granular carbon equipment and the input end of the rotary equipment. The input end of the air supply equipment is connected to the external air and the exhaust gas source. The input end of the emergency discharge equipment is connected to the exhaust gas source, and the output end of the emergency discharge equipment is connected to the input end of the exhaust equipment.

[0087] like Figure 5As shown, preferably, the exhaust gas distribution device includes a first exhaust gas distribution unit and a second exhaust gas distribution unit.

[0088] The input end of the first tail gas distribution unit is connected to the tail gas source and the output end of the air supply device, and the output end of the first tail gas distribution unit is connected to the input end of the multi-stage cryogenic device, the input end of the carbon fiber device, the input end of the granular carbon device and the input end of the wheel device.

[0089] The input end of the second exhaust gas distribution unit is connected to the output end of the multi-stage cryogenic device, the output end of the carbon fiber device and the output end of the granular carbon device, and the output end of the second exhaust gas distribution unit is connected to the input end of the carbon fiber device, the input end of the granular carbon device and the input end of the wheel device.

[0090] The input end of the emergency discharge device is connected to the exhaust gas source, and the output end of the emergency discharge device is connected to the input end of the exhaust device.

[0091] The input end of the exhaust device is connected to the output end of the multi-stage cryogenic device, the output end of the carbon fiber device, the output end of the granular carbon device and the output end of the emergency discharge device, and the output end of the exhaust device is connected to the atmosphere.

[0092] The input end of the air supply device is connected to the exhaust gas source and the external air, and the output end is connected to the input end of the first exhaust gas distribution unit. The connection between the devices is controlled by a valve.

[0093] The exhaust gas distribution equipment can control the operating conditions of the emergency emission equipment, air supply equipment, rotary equipment, granular carbon equipment, carbon fiber equipment and multi-stage cryogenic equipment according to the exhaust gas parameters, call different processing equipment to recover dichloromethane, and calculate the equipment combination processing method with the lowest energy consumption and the highest efficiency while ensuring that the emission meets the standards.

[0094] For example, after the exhaust gas with a concentration of ≤1000mg / m³ enters the rotor, it can meet the emission standards by matching different types of rotors. The adsorption rate of dichloromethane exhaust gas by carbon fiber equipment and granular carbon equipment is 90%. The dew point of the exhaust gas before entering the adsorption equipment must be in the optimal state required by the equipment to ensure the adsorption efficiency and extend the life of the equipment. Among them, the optimal adsorption temperature of the fiber equipment and granular carbon equipment is 25℃, and the dew point temperature is ≤18℃; the optimal operating temperature of the rotor equipment is 39℃, and the dew point temperature is ≤28℃.

[0095] The dichloromethane recovery system provided in the embodiment of the present invention can make the best use of the advantages of each device, thereby maximizing the benefits.

[0096] In summary, the embodiment of the present invention provides a multi-stage deep cooling and multiple adsorption dichloromethane recovery method and recovery system. When the exhaust gas enters the equipment inlet, its flow rate and concentration are detected by a flow meter and a concentration meter and the detection results are uploaded to the exhaust gas distribution equipment. The exhaust gas distribution equipment intelligently analyzes several suitable equipment processing combinations based on the information and formulas in the comparison database, and then gradually gives detailed parameters such as energy consumption and consumables of each combination for manual selection by operators and automatic selection by equipment. Several combinations are sorted according to carbon emission analysis, and the combination with the lowest carbon emission is used by default.

[0097] It should be noted that the above embodiments are only examples, and the technical solutions of the various embodiments can be combined, all within the protection scope of the present invention.

[0098] It should be noted that the order of steps of the present invention can be changed according to actual needs, the order of the steps can be changed, and serial processing can be changed to parallel processing, which is not limited to the order of steps listed in the embodiments.

[0099] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0100] The above is a detailed description of a multi-stage deep cooling and multi-adsorption dichloromethane recovery method and recovery system provided by the present invention. For a person skilled in the art, any obvious changes made to it without departing from the essence of the present invention will constitute an infringement of the patent right of the present invention and will bear the corresponding legal liability.

Claims

1. A multi-stage deep cooling and multiple adsorption dichloromethane recovery method, characterized in that The following steps are involved: Step S1: exhaust gas is introduced into the exhaust gas distribution device, and the exhaust gas distribution device measures the exhaust gas concentration c and air volume Q'; Jump to step S3; Step S2: Compare the air volume Q' with the preset air volume Q. When Q'>Q, discharge the air volume through the emergency discharge system to make Q'=Q, and jump to step S3; when Q'≤Q, calculate the air volume Q' and exhaust gas concentration c after increasing the corresponding step air volume, and jump to step S3; Step S3: Compare the exhaust gas concentration c with the preset value. When c≤120mg / m³, jump to step S10; when c≥90g / m³, jump to step S2 and step S4; when 120mg / m³<concentration c<90g / m³, jump to step S5; Step S4: Calculate the exhaust concentration c when the input exhaust gas is cooled to a refrigeration temperature point of -40 to -70°C; Obtain the required energy and consumables consumption, and jump to step S3; Step S5: the exhaust gas distribution device obtains the dew point temperature Dp of the exhaust gas, and jumps to step S2 and step S6; Step S6: Compare the exhaust gas concentration c with the preset value. When 70g / m³<concentration c<90g / m³, jump to step S7; when 20g / m³<concentration c≤70g / m³, jump to steps S7 and S8; when 1g / m³<concentration c≤20g / m³, jump to step S8; when 120mg / m³<concentration c≤1g / m³, jump to step S9; Step S7: Calculate the energy and consumables loss of the tail gas input into the carbon fiber device for adsorption, as well as the concentration c of the tail gas removed, and jump to step S3; Step S8: Calculate the energy and consumables loss of the exhaust gas input into the granular carbon device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3; Step S9: Calculate the energy and consumables loss of the exhaust gas input to the rotor device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3; Step S10: Counting the steps of tail gas treatment and the energy and consumables loss required to form a tail gas treatment plan; converting the energy and consumables loss into carbon dioxide emissions; Step S11: Sort the exhaust gas treatment schemes from low to high according to the carbon dioxide emissions, output the scheme with the lowest carbon dioxide emissions as the optimal exhaust gas treatment scheme, and output the number of second lowest schemes required by the design as alternative exhaust gas treatment schemes.

2. The method for recovering dichloromethane as claimed in claim 1, characterized in that The step S4 further comprises the following sub-steps: Step S41: compare the temperature T of the input exhaust gas of the multi-stage cryogenic device, and when the temperature T>-40°C, jump to step S42; When the temperature is -40°C ≥ T>-70°C, jump to step S43; when the temperature T≤-70°C, jump to step S3; Step S42: based on the temperature T of the input exhaust gas, calculate the exhaust gas concentration c required to cool the exhaust gas to -40°C, obtain the energy and consumables loss required to cool to -40°C, and jump to step S3; Step S43: Based on the input exhaust gas temperature T, subtract the preset temperature step value, calculate the exhaust gas concentration c at the temperature after subtracting the preset temperature step value, obtain the energy and consumables loss required for cooling, and jump to step S3.

3. The method for recovering dichloromethane as claimed in claim 1, characterized in that The step S7 further comprises the following sub-steps: Step S71: compare the dew point temperature Dp of the input exhaust gas of the carbon fiber device with the preset value, when Dp>18℃, jump to step S72; when Dp≤18℃, jump to step S73; Step S72: lower the exhaust gas temperature T to 18°C, obtain the energy and consumables loss required for cooling to 18°C, and jump to step S74; Step S73: compare the temperature T of the input exhaust gas of the carbon fiber device with the preset value, and when the temperature T≤25°C, jump to step S74; when the temperature T>25°C, jump to step S75; Step S74: Raise the exhaust gas temperature T to 25°C, obtain the energy and consumables loss required to raise the temperature to 25°C, and jump to step S76; Step S75: Cooling the exhaust gas temperature T to 25°C, obtaining the energy and consumables loss required for cooling to 25°C, and jumping to step S76; Step S76: Calculate the energy and consumables loss of the exhaust gas input into the carbon fiber equipment for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

4. The method for recovering dichloromethane as claimed in claim 1, characterized in that The step S8 also includes the following sub-steps: Step S81: compare the dew point temperature Dp of the input exhaust gas of the granular carbon device with the preset value, when Dp>18℃, jump to step S82; when Dp≤18℃, jump to step S83; Step S82: lower the exhaust temperature T to 18°C, obtain the energy and consumables loss required for cooling to 18°C, and jump to step S84; Step S83: compare the temperature T of the exhaust gas input to the granular carbon device with a preset value, and when the temperature T≤25°C, jump to step S84; when the temperature T>25°C, jump to step S85; Step S84: Raise the exhaust gas temperature T to 25°C, obtain the energy and consumables loss required to raise the temperature to 25°C, and jump to step S86; Step S85: Cooling the exhaust gas temperature T to 25°C, obtaining the energy and consumables loss required for cooling to 25°C, and jumping to step S86; Step S86: Calculate the energy and consumables loss of the exhaust gas input into the granular carbon equipment for adsorption, as well as the exhaust gas concentration c, and jump to step S3.

5. The method for recovering dichloromethane as claimed in claim 1, characterized in that The step S9 also includes the following sub-steps: Step S91: compare the dew point temperature Dp of the input exhaust gas of the runner device with the preset value, when Dp>28℃, jump to step S92; when Dp≤28℃, jump to step S93; Step S92: lower the exhaust temperature T to 28°C, obtain the energy and consumables loss required for cooling to 28°C, and jump to step S94; Step S93: compare the temperature T of the exhaust gas input to the runner device with a preset value. When the temperature T is less than or equal to 39°C, jump to step S94; when the temperature T is greater than or equal to 39°C, jump to step S95; Step S94: Raise the exhaust gas temperature T to 39° C., obtain the energy and consumables loss required to raise the temperature to 39° C., and jump to step S96; Step S95: Cooling the exhaust gas temperature T to 39° C., obtaining the energy and consumables loss required for cooling to 39° C., and jumping to step S96; Step S96: Calculate the energy and consumables loss of the exhaust gas input to the rotor device for adsorption, as well as the concentration c of the exhaust gas removed, and jump to step S3.

6. A dichloromethane recovery system for implementing the dichloromethane recovery method according to any one of claims 1 to 5, characterized in that Including tail gas distribution equipment, air supply equipment, multi-stage cryogenic equipment, carbon fiber equipment, granular carbon equipment and rotor equipment; among them, The input end of the exhaust gas distribution device is connected to the exhaust gas source, the output end of the air supply device, the output end of the multi-stage cryogenic device, the output end of the carbon fiber device, the output end of the granular carbon device and the output end of the rotor device; The output end of the tail gas distribution device is connected to the input end of the multi-stage cryogenic device, the input end of the carbon fiber device, the input end of the granular carbon device and the input end of the wheel device; The input end of the air supply device is connected to the external air and the exhaust gas source.

7. The dichloromethane recovery system according to claim 6, characterized in that: The exhaust gas distribution equipment has the function of measuring exhaust gas concentration, dew point temperature and air volume parameters, as well as calculating the emission scheme according to the parameters, counting the energy consumption and consumables consumption in the emission scheme, and converting the corresponding energy consumption and consumables consumption into a unified carbon emission amount; The carbon fiber equipment, granular carbon equipment and rotary wheel equipment are all equipped with built-in coolers and heaters for dehumidifying and controlling the temperature of the exhaust gas.

8. The dichloromethane recovery system as claimed in claim 7, characterized in that: The tail gas distribution device comprises a first tail gas distribution unit and a second tail gas distribution unit; The input end of the first tail gas distribution unit is connected to the tail gas source and the output end of the air supply device, and the output end is connected to the input end of the multi-stage cryogenic device, the input end of the carbon fiber device, the input end of the granular carbon device and the input end of the wheel device; The input end of the second exhaust gas distribution unit is connected to the output end of the multi-stage cryogenic equipment, the output end of the carbon fiber equipment and the output end of the granular carbon equipment, and the output end is connected to the input end of the carbon fiber equipment, the input end of the granular carbon equipment and the input end of the wheel equipment.

9. The dichloromethane recovery system as claimed in claim 8, characterized in that It also includes emergency discharge equipment and exhaust equipment; among which, The input end of the emergency discharge device is connected to the exhaust gas source, and the output end is connected to the input end of the exhaust device; The input end of the exhaust device is connected to the output end of the multi-stage cryogenic device, the output end of the carbon fiber device, the output end of the granular carbon device and the output end of the emergency exhaust device, and the output end is connected to the atmosphere.

10. The dichloromethane recovery system according to claim 9, characterized in that: The input end of the air supply device is connected to the exhaust gas source and external air, and the output end is connected to the input end of the first exhaust gas distribution unit.

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