A multi-stage deep cooling and multi-adsorption methylene chloride recovery method and recovery system

Abstract

The application discloses a kind of multistage cryogenic and multiple adsorption methylene chloride recovery method and recovery system.The recovery method includes the following steps: tail gas is introduced into tail gas distribution equipment, tail gas distribution equipment measures tail gas concentration c, air volume Q' and dew point temperature Dp;Compare air volume Q', tail gas concentration c and preset value;Calculate the tail gas concentration c that input tail gas is cooled to-40~-70 ℃ refrigeration temperature point;Calculate the energy and consumable loss of tail gas input carbon fiber equipment, granular carbon equipment and rotary equipment for adsorption, and the tail gas concentration c of discharge;Statistics step passed by tail gas treatment, convert energy and consumable loss into carbon dioxide emission to sort scheme, form tail gas treatment scheme.The application uses multistage cryogenic as front-end processing equipment, uses adsorption equipment as downstream methylene chloride recovery system, ensures standard discharge, and selects the scheme with the lowest carbon emission for recovery treatment.

Description

Technical Field

[0001] This invention relates to a multi-stage cryogenic and multiple adsorption method for recovering dichloromethane, and also to a corresponding dichloromethane recovery system, belonging to the field of condensation recovery technology. Background Technology

[0002] Dichloromethane, a commonly used organic solvent, is widely used in pharmaceuticals, film, industrial refrigeration, and industrial extraction. Conventional technologies for recovering dichloromethane-containing tail gas mainly include condensation, adsorption, and solvent absorption.

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

[0004] The adsorption method utilizes adsorbents such as activated carbon or macroporous resins with microporous structures to adsorb dichloromethane molecules in exhaust gases. The dichloromethane is then desorbed and recovered using steam or hot air, while the adsorbent is regenerated and reused. The adsorption method is generally suitable for the recovery and environmental treatment of low-concentration organic exhaust gases with an organic matter content of less than 1%. High-concentration exhaust gases easily lead to adsorbent deactivation.

[0005] Chinese patent application No. 201810018769.4 discloses a method and system for recovering and reusing high-concentration dichloromethane tail gas. This technical solution collects dichloromethane tail gas through a gas collection pipe and a fan, then sends it to a compressor for compression and condensation recovery. The condensed tail gas is returned to the tail gas generation system. Once the amount recovered through compression and condensation decreases to a certain value, the gas collection pipe is switched to a high-efficiency pressure swing adsorption (PSA) device to treat the remaining dichloromethane in the system before discharge. The recovered dichloromethane can then be reused directly or after further treatment in production.

[0006] However, cryogenic processes consume a large amount of electricity, and the energy efficiency ratio varies greatly depending on the cooling temperature, while adsorption-desorption processes consume a large amount of steam and consumables. When the process parameters of the upstream feed are unstable, existing dichloromethane recovery systems 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 this invention is to provide a method for recovering dichloromethane through multi-stage cryogenics and multiple adsorption processes.

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

[0009] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0010] According to a first aspect of the present invention, a method for recovering dichloromethane using multi-stage cryogenic and multiple adsorption processes is provided, comprising the following steps:

[0011] Step S1: The exhaust gas is introduced into the exhaust gas distribution device, which measures the exhaust gas concentration c and the air volume Q', and then proceeds to step S3.

[0012] Step S2: Compare the air volume Q' with the preset air volume Q. If Q' > Q, discharge the air volume through the emergency exhaust system to make Q' = Q, and proceed to step S3. If Q' ≤ Q, calculate the air volume Q' and exhaust gas concentration c after increasing the air volume by the corresponding step size, and proceed to step S3.

[0013] Step S3: Compare the exhaust gas concentration c with the preset value. When c ≤ 120 mg / m³, proceed to step S10; when c ≥ 90 g / m³, proceed to steps S2 and S4; when 120 mg / m³ < concentration c < 90 g / m³, proceed to step S5.

[0014] Step S4: Calculate the exhaust gas concentration c when the input exhaust gas is cooled to the cooling temperature point of -40 to -70℃; obtain the required energy and material consumption, and jump to step S3;

[0015] Step S5: The exhaust gas distribution device measures the dew point temperature Dp of the exhaust gas, then proceeds to steps S2 and S6.

[0016] Step S6: Compare the exhaust gas concentration c with the preset value. If 70g / m³ < concentration c < 90g / m³, proceed to step S7; if 20g / m³ < concentration c ≤ 70g / m³, proceed to steps S7 and S8; if 1g / m³ < concentration c ≤ 20g / m³, proceed to step S8; if 120mg / m³ < concentration c ≤ 1g / m³, proceed to step S9.

[0017] Step S7: Calculate the energy and material loss of the exhaust gas input into the carbon fiber equipment for adsorption, as well as the concentration c of the exhaust gas, and then proceed to step S3.

[0018] Step S8: Calculate the energy and material losses of the exhaust gas input to the particulate carbon device for adsorption, as well as the concentration c of the removed exhaust gas, and then proceed to step S3.

[0019] Step S9: Calculate the energy and material losses of the exhaust gas input rotary device for adsorption, as well as the exhaust gas concentration c, and then proceed to step S3;

[0020] Step S10: Calculate the steps involved in exhaust gas treatment and the energy and material consumption required to form an exhaust gas treatment plan; convert the energy and material consumption into carbon dioxide emissions.

[0021] Step S11: Sort the exhaust gas treatment schemes from low to high carbon dioxide emissions, output the scheme with the lowest carbon dioxide emissions as the optimal exhaust gas treatment scheme, and output the second lowest number of schemes required by the design as alternative exhaust gas treatment schemes.

[0022] Preferably, step S4 further includes the following sub-steps:

[0023] Step S41: Compare the temperature T of the input exhaust gas. If the temperature T > -40℃, proceed to step S42; if the temperature -40℃ ≥ T > -70℃, proceed to step S43; if the temperature T ≤ -70℃, proceed to step S3.

[0024] Step S42: Based on the temperature T of the input exhaust gas, calculate the exhaust gas concentration c to cool the exhaust gas to -40℃, obtain the energy and material consumption required to cool to -40℃, and jump to step S3.

[0025] Step S43: Based on the temperature T of the input exhaust gas, 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 material consumption required for cooling, and jump to step S3.

[0026] Preferably, step S7 further includes the following sub-steps:

[0027] Step S71: Compare the dew point temperature Dp of the input exhaust gas of the carbon fiber equipment with the preset value. If Dp > 18°C, proceed to step S72; if Dp ≤ 18°C, proceed to step S73.

[0028] Step S72: Reduce the exhaust gas temperature T to 18°C, obtain the energy and material losses required to cool to 18°C, and proceed to step S74.

[0029] Step S73: Compare the temperature T of the input exhaust gas of the carbon fiber equipment with the preset value. If the temperature T ≤ 25℃, proceed to step S74; if the temperature T > 25℃, proceed to step S75.

[0030] Step S74: Increase the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to raise the temperature to 25°C, and proceed to step S76.

[0031] Step S75: Cool the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to cool to 25°C, and proceed to step S76.

[0032] Step S76: Calculate the energy and material losses of the exhaust gas input into the carbon fiber device for adsorption, as well as the concentration c of the exhaust gas, and then proceed to step S3.

[0033] Preferably, step S8 further includes the following sub-steps:

[0034] Step S81: Compare the dew point temperature Dp of the input exhaust gas of the particulate carbon device with the preset value. If Dp > 18°C, proceed to step S82; if Dp ≤ 18°C, proceed to step S83.

[0035] Step S82: Reduce the exhaust gas temperature T to 18°C, obtain the energy and material losses required to cool to 18°C, and proceed to step S84.

[0036] Step S83: Compare the temperature T of the input exhaust gas of the particulate carbon device with the preset value. If the temperature T ≤ 25℃, proceed to step S84; if the temperature T > 25℃, proceed to step S85.

[0037] Step S84: Increase the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to raise the temperature to 25°C, and proceed to step S86.

[0038] Step S85: Cool the exhaust gas temperature T to 25°C, obtain the energy and material losses required to cool to 25°C, and proceed to step S86.

[0039] Step S86: Calculate the energy and material losses of the exhaust gas input to the particulate carbon device for adsorption, as well as the concentration c of the removed exhaust gas, and then proceed to step S3.

[0040] Preferably, step S9 further includes the following sub-steps:

[0041] Step S91: Compare the dew point temperature Dp of the input exhaust gas of the rotary device with the preset value. If Dp > 28°C, proceed to step S92; if Dp ≤ 28°C, proceed to step S93.

[0042] Step S92: Reduce the exhaust gas temperature T to 28°C, obtain the energy and material losses required to cool to 28°C, and proceed to step S94.

[0043] Step S93: Compare the temperature T of the input exhaust gas of the rotary device with the preset value. If the temperature T ≤ 39℃, proceed to step S94; if the temperature T > 39℃, proceed to step S95.

[0044] Step S94: Increase the exhaust gas temperature T to 39°C, obtain the energy and material consumption required to raise the temperature to 39°C, and proceed to step S96.

[0045] Step S95: Cool the exhaust gas temperature T to 39°C, obtain the energy and material consumption required to cool to 39°C, and proceed to step S96.

[0046] Step S96: Calculate the energy and material losses of the exhaust gas input rotary device for adsorption, as well as the exhaust gas concentration c, and then proceed to step S3.

[0047] According to a second aspect of the present invention, a dichloromethane recovery system for implementing the above-described dichloromethane recovery method is provided, comprising a tail gas distribution device, a makeup air device, a multi-stage cryogenic device, a carbon fiber device, a granular carbon device, and a rotary device; wherein,

[0048] The input end of the exhaust gas distribution device is connected to the exhaust gas source, the output end of the make-up air 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 rotary wheel device;

[0049] The output end of the exhaust 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 rotary wheel device;

[0050] The input end of the make-up air device is connected to outside air and the exhaust gas source.

[0051] Preferably, the exhaust gas distribution device has the functions of measuring exhaust gas concentration, dew point temperature and air volume parameters, as well as the functions of calculating emission schemes based on parameters, calculating energy consumption and material consumption in emission schemes, and converting the corresponding energy consumption and material consumption into a unified carbon emission amount.

[0052] Carbon fiber equipment, granular carbon equipment, and rotary equipment all have built-in coolers and heaters for dehumidifying and temperature-controlling exhaust gases.

[0053] Preferably, the dichloromethane recovery system further includes emergency emission equipment and ventilation equipment; wherein...

[0054] The exhaust gas distribution device includes a first exhaust gas distribution unit and a second exhaust gas distribution unit;

[0055] The input end of the first exhaust gas distribution unit is connected to the exhaust gas source and the output end of the make-up air 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 rotary device;

[0056] 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 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 rotary wheel device;

[0057] The input end of the emergency emission device is connected to the exhaust gas source, and the output end is connected to the input end of the exhaust device.

[0058] 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 emission device, and the output end is connected to the atmosphere;

[0059] The input end of the make-up air device is connected to the exhaust gas source and outside air, and the output end is connected to the input end of the first exhaust gas distribution unit.

[0060] Compared with existing technologies, this invention achieves efficient and energy-saving recovery and treatment of dichloromethane tail gas while ensuring that the exhaust gas meets emission standards. This method uses a tail gas distribution device to monitor parameters such as tail gas concentration, airflow, and dew point temperature in real time, and intelligently selects the optimal recovery process based on these parameters. For high-concentration tail gas, multi-stage cryogenic equipment is used for condensation recovery; for medium- and low-concentration tail gas, multiple adsorption treatments are performed using 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 operating conditions, and the scheme with the lowest carbon emissions is selected as the optimal treatment scheme, while alternative schemes are provided to meet different needs. Through this intelligent treatment method, this invention not only improves the recovery efficiency of dichloromethane and 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. It is particularly suitable for operating conditions where the concentration of dichloromethane tail gas fluctuates greatly or the process parameters are unstable, and has significant economic and social benefits. Attached Figure Description

[0061] Figure 1(a) is a schematic diagram of the steps of a multi-stage cryogenic and multiple adsorption method for recovering dichloromethane in the first embodiment of the present invention;

[0062] Figure 1(b) is a schematic diagram of the sub-steps of step S4 in Figure 1;

[0063] Figure 1(c) is a schematic diagram of the sub-steps of step S7 in Figure 1;

[0064] Figure 1(d) is a schematic diagram of the sub-steps of step S8 in Figure 1;

[0065] Figure 1(e) is a schematic diagram of the sub-steps of step S9 in Figure 1;

[0066] Figure 2 Temperature-saturation content curves for multi-stage cryogenic equipment;

[0067] Figure 3 Temperature-power consumption curves for multi-stage cryogenic equipment;

[0068] Figure 4 Temperature-water consumption curves for multi-stage cryogenic equipment;

[0069] Figure 5 This is a schematic diagram of a dichloromethane recovery system according to the second embodiment of the present invention. Detailed Implementation

[0070] The technical content of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0071] The technical concept in this invention is as follows: based on the operating conditions of the exhaust gas (concentration, temperature, dew point, and air volume, etc.), the carbon emissions of different recovery schemes are calculated under the premise of ensuring emission compliance. The dichloromethane recovery system is then intelligently controlled to treat the exhaust gas according to the optimal recovery scheme. Specifically, the dichloromethane recovery system and control method use multi-stage cryogenic equipment 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 emission compliance.

[0072] First Embodiment

[0073] As shown in Figures 1(a) to 1(e), this embodiment of the invention provides a method for recovering dichloromethane using multi-stage cryogenic and multiple adsorption processes, comprising the following steps.

[0074] Step S1: The exhaust gas is introduced into the exhaust gas distribution device, which measures the exhaust gas concentration c and the air volume Q', and then proceeds to step S3.

[0075] In this embodiment of the invention, concentration c is the concentration of dichloromethane in the exhaust gas, and air volume Q' is the exhaust gas air volume.

[0076] Step S2: Compare the air volume Q' with the preset air volume Q (preset value). If Q' > Q, discharge the air volume through the emergency exhaust system to make Q' = Q, and jump to step S3. If Q' ≤ Q, calculate the air volume Q' and exhaust gas concentration c after increasing the air volume by the corresponding step size, and jump to step S3.

[0077] In this embodiment, the preset air volume Q is taken as an example based on the maximum operating air volume of the dichloromethane recovery system, and the air volume Q' after increasing the corresponding step air volume is ≤ Q. In the prior art, the air volume step size is selected as 1000~10000m³ / h. In this embodiment of the invention, a minimum operating air volume step size of 5000m³ / h is used as an example, and the preset air volume Q is taken as 25000m³ / h.

[0078] The energy consumption and material usage required for the operation of a dichloromethane recovery system vary depending on the airflow rate of the same concentration of exhaust gas.

[0079] As shown in Table 1, the case of carbon fiber equipment adsorbing exhaust gas with a concentration of 60 g / m³ is taken as an example.

[0080] Table 1. Energy consumption required for carbon fiber equipment to adsorb 60g / m³ of tail gas.

[0081]

[0082] It should be noted that the carbon fiber in the embodiments of this invention is also called fibrous activated carbon. It is produced by carbonizing and activating a fibrous precursor through a certain procedure. It has a faster adsorption and desorption rate and a larger adsorption capacity, making it a highly efficient activated adsorption material and environmental engineering material with performance superior to activated carbon.

[0083] As shown in Table 2, the adsorption of exhaust gas with a concentration of 40 g / m³ by a particulate carbon device is taken as an example.

[0084] Table 2 Energy consumption required for adsorbing 40g / m³ of tail gas using particulate carbon equipment

[0085]

[0086] As shown in Table 3, the case of a rotary device adsorbing exhaust gas with a concentration of 400 mg / m³ is taken as an example.

[0087] Table 3. Energy consumption required for rotary turbine equipment to adsorb 400 mg / m³ tail gas.

[0088]

[0089] Step S3: Compare the exhaust gas concentration c with the preset value. If c ≤ 120 mg / m³, proceed to step S10; if c ≥ 90 g / m³, proceed to steps S2 and S4; if 120 mg / m³ < concentration c < 90 g / m³, proceed to step S5.

[0090] The 120 mg / m³ is the emission concentration that meets the standards, set in accordance with relevant national laws and regulations, and may be adjusted more strictly according to local standards.

[0091] The 90g / m³ concentration is the optimal energy-consuming exhaust gas concentration for multi-stage cryogenic equipment and adsorption equipment. This means that exhaust gas with a concentration of 90g / m³ or higher is treated by the multi-stage cryogenic equipment. Furthermore, exhaust gas with a concentration exceeding 90g / m³ exceeds the optimal energy-consuming treatment concentration for carbon fiber and granular carbon equipment, requiring supplementary air to reduce the concentration before it can be adsorbed and recovered by the adsorption equipment. The carbon fiber equipment, granular carbon equipment, and rotary equipment are collectively referred to as adsorption equipment.

[0092] The optimal energy efficiency treatment concentration for carbon fiber equipment is 20–90 g / m³, while that for granular carbon equipment is 1–70 g / m³. The optimal energy efficiency treatment concentration for rotary equipment is 10–1000 mg / m³. Furthermore, exhaust gas with a concentration below 1 g / m³, after adsorption treatment by the rotary equipment, will inevitably have an emission concentration less than or equal to 120 mg / m³, thus meeting emission standards.

[0093] The multi-stage cryogenic equipment condenses and releases dichloromethane gas contained in the exhaust gas through refrigeration. The multi-stage cryogenic equipment can achieve a refrigeration range of 40 to -70°C. Based on the energy efficiency of the multi-stage cryogenic equipment, this embodiment of the invention selects its operating refrigeration range as -40 to -70°C.

[0094] In this step, the process of skipping to steps S2 and S4 for exhaust gas with a concentration c ≥ 90 g / m³ is to simultaneously form a multi-stage cryogenic scheme and a multi-adsorption scheme after exhaust gas makeup air dilution, for comparison.

[0095] Step S4: Calculate the exhaust gas concentration c when the input exhaust gas is cooled to the cooling temperature point of -40 to -70℃; obtain the required energy and material consumption, and jump to step S3.

[0096] Step S41: Compare the temperature T of the input exhaust gas of the multi-stage cryogenic equipment. If the temperature T > -40℃, proceed to step S42; if the temperature -40℃ ≥ T > -70℃, proceed to step S43; if the temperature T ≤ -70℃, proceed to step S3.

[0097] Step S42: Based on the temperature T of the input exhaust gas, calculate the exhaust gas concentration c to cool the exhaust gas to -40℃, obtain the energy and material consumption required to cool to -40℃, and jump to step S3.

[0098] Step S43: Based on the temperature T of the input exhaust gas, 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 material consumption required for cooling, and jump to step S3.

[0099] The purpose of this step is to compare the energy and material consumption of different cryogenic temperature schemes. For example, the preset temperature step size for the exhaust gas cooling temperature of a multi-stage cryogenic equipment is -1 to -10℃, that is, to calculate the exhaust gas concentration c at each preset cooling temperature point from -40 to -70℃.

[0100] The temperature-exhaust gas concentration curves corresponding to multi-stage cryogenic equipment are as follows: Figure 2 As shown.

[0101] The temperature-power consumption curves for multi-stage cryogenic equipment are as follows: Figure 3 As shown.

[0102] The temperature-water consumption curves corresponding to multi-stage cryogenic equipment are as follows: Figure 4 As shown.

[0103] Step S5: The exhaust gas distribution device obtains the dew point temperature Dp of the exhaust gas, and then proceeds to steps S2 and S6.

[0104] The method for obtaining the dew point temperature Dp of the exhaust gas is a well-known technique. For example, it can be measured using a dew point meter, or by measuring the exhaust gas temperature T and the exhaust gas relative humidity RH, and then calculating the dew point temperature Dp.

[0105] Makeup air is applied to exhaust gas with a concentration c ranging from 120 mg / m³ to 90 g / m³ in order to dilute the exhaust gas concentration and calculate the energy consumption and material consumption of different adsorption schemes.

[0106] Step S6: Compare the exhaust gas concentration c with the preset value. If 70g / m³ < concentration c < 90g / m³, proceed to step S7; if 20g / m³ < concentration c ≤ 70g / m³, proceed to steps S7 and S8; if 1g / m³ < concentration c ≤ 20g / m³, proceed to step S8; if 120mg / m³ < concentration c ≤ 1g / m³, proceed to step S9.

[0107] Since the optimal energy efficiency treatment concentrations of carbon fiber equipment and granular carbon equipment overlap between 20 and 70 g / m³, it is necessary to calculate the energy consumption and carbon emissions of carbon fiber equipment and granular carbon equipment respectively at this overlapping concentration in order to select a better treatment scheme.

[0108] As shown in Table 4, the energy consumption required to cool exhaust gas with a flow rate of 10,000 m³ / h to 18℃, 25℃, 28℃, and 39℃ respectively is as follows.

[0109] Table 4 Energy consumption required for exhaust gas cooling of 10000 m³ / h

[0110]

[0111] As shown in Table 5, the energy consumption required to cool exhaust gas with different air volumes and an initial temperature of 80℃ to 18℃, 25℃, 28℃, and 39℃ respectively is as follows.

[0112] Table 5 Energy consumption required for exhaust gas cooling at 80℃

[0113]

[0114] As shown in Table 6, the energy consumption required to raise the exhaust gas with an air volume of 10000 m³ / h to 25℃ and 39℃ respectively is as follows.

[0115] Table 6. Energy consumption required for exhaust gas heating at a capacity of 10000 m³ / h

[0116]

[0117] As shown in Table 7, the energy consumption required to raise the exhaust gas from an initial temperature of 20°C to 25°C and 39°C with different air volumes is as follows.

[0118] Table 7 Energy Consumption Required for Exhaust Gas Heating to 20℃

[0119]

[0120] Step S7: Calculate the energy and material losses of the exhaust gas input into the carbon fiber equipment for adsorption, as well as the concentration c of the exhaust gas, and then proceed to step S3.

[0121] Step S71: Compare the dew point temperature Dp of the input exhaust gas of the carbon fiber equipment with the preset value. If Dp > 18°C, proceed to step S72; if Dp ≤ 18°C, proceed to step S73.

[0122] Step S72: Reduce the exhaust gas temperature T to 18°C, obtain the energy and material losses required to cool to 18°C, and proceed to step S74.

[0123] Step S73: Compare the temperature T of the input exhaust gas of the carbon fiber equipment with the preset value. If the temperature T ≤ 25℃, proceed to step S74; if the temperature T > 25℃, proceed to step S75.

[0124] Step S74: Increase the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to raise the temperature to 25°C, and proceed to step S76.

[0125] Step S75: Cool the exhaust gas temperature T to 25°C, obtain the energy and material losses required to cool to 25°C, and proceed to step S76.

[0126] Step S76: Calculate the energy and material losses of the exhaust gas input into the carbon fiber device for adsorption, as well as the concentration c of the exhaust gas, and then proceed to step S3.

[0127] As shown in Table 8, the example is the carbon fiber equipment adsorbing exhaust gas with a volume of 10,000 m³ / h.

[0128] Table 8 Energy consumption required for carbon fiber equipment to adsorb 10000 m³ / h of tail gas

[0129]

[0130] Step S8: Calculate the energy and material losses of the exhaust gas input to the particulate carbon device for adsorption, as well as the concentration c of the removed exhaust gas, and then proceed to step S3.

[0131] Step S81: Compare the dew point temperature Dp of the input exhaust gas of the particulate carbon device with the preset value. If Dp > 18°C, proceed to step S82; if Dp ≤ 18°C, proceed to step S83.

[0132] Step S82: Reduce the exhaust gas temperature T to 18°C, obtain the energy and material losses required to cool to 18°C, and proceed to step S84.

[0133] Step S83: Compare the temperature T of the input exhaust gas of the particulate carbon device with the preset value. If the temperature T ≤ 25℃, proceed to step S84; if the temperature T > 25℃, proceed to step S85.

[0134] Step S84: Increase the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to raise the temperature to 25°C, and proceed to step S86.

[0135] Step S85: Cool the exhaust gas temperature T to 25°C, obtain the energy and material losses required to cool to 25°C, and proceed to step S86.

[0136] Step S86: Calculate the energy and material losses of the exhaust gas input to the particulate carbon device for adsorption, as well as the concentration c of the removed exhaust gas, and then proceed to step S3.

[0137] As shown in Table 9, the case of a particulate carbon device adsorbing exhaust gas with an air volume of 10,000 m³ / h is taken as an example.

[0138] Table 9 Energy Consumption Required for Granular Carbon Equipment to Adsorb 10000 m³ / h of Tail Gas

[0139]

[0140] Step S9: Calculate the energy and material losses of the exhaust gas input rotary device for adsorption, as well as the concentration c of the extracted exhaust gas, and then proceed to step S3.

[0141] Step S91: Compare the dew point temperature Dp of the input exhaust gas of the rotary device with the preset value. If Dp > 28°C, proceed to step S92; if Dp ≤ 28°C, proceed to step S93.

[0142] Step S92: Reduce the exhaust gas temperature T to 28°C, obtain the energy and material losses required to cool to 28°C, and proceed to step S94.

[0143] Step S93: Compare the temperature T of the input exhaust gas of the rotary device with the preset value. If the temperature T ≤ 39℃, proceed to step S94; if the temperature T > 39℃, proceed to step S95.

[0144] Step S94: Increase the exhaust gas temperature T to 39°C, obtain the energy and material consumption required to raise the temperature to 39°C, and proceed to step S96.

[0145] Step S95: Cool the exhaust gas temperature T to 39°C, obtain the energy and material losses required to cool to 39°C, and proceed to step S96.

[0146] Step S96: Calculate the energy and material losses of the exhaust gas input rotary device for adsorption, as well as the exhaust gas concentration c, and then proceed to step S3.

[0147] As shown in Table 10, the exhaust gas with a flow rate of 10,000 m³ / h is adsorbed by a rotary device as an example.

[0148] Table 10 Energy Consumption Required for Rotary Equipment to Adsorb 10000 m³ / h of Tail Gas

[0149]

[0150] Step S10: Calculate the steps involved in exhaust gas treatment and the energy and material consumption required to form an exhaust gas treatment plan; convert the energy and material consumption into carbon dioxide emissions.

[0151] The energy and materials consumed are all 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.

[0152] As shown in Table 11, taking 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, with an annual calculation of 7,200 hours.

[0153] Table 11 Material Consumption Required for Adsorption Equipment to Adsorb 10000 m³ / h of Tail Gas

[0154]

[0155] Step S11: Sort the exhaust gas treatment schemes from low to high carbon dioxide emissions, output the scheme with the lowest carbon dioxide emissions as the optimal exhaust gas treatment scheme, and output the second lowest number of schemes required by the design as alternative exhaust gas treatment schemes.

[0156] It is worth noting that the methods for obtaining exhaust gas parameters in the above steps include actual measurement and simulation calculation. For example, the exhaust gas distribution equipment can simulate and calculate the exhaust gas parameters after each make-up air volume based on the parameters of the input exhaust gas, or the exhaust gas distribution equipment can actually measure each parameter during the operation of the dichloromethane recovery system.

[0157] Second Embodiment

[0158] This invention provides a dichloromethane recovery system, including a tail gas distribution device, a makeup air device, a multi-stage cryogenic device, a carbon fiber device, a granular carbon device, a rotary device, an emergency emission device, and an exhaust device.

[0159] The exhaust gas distribution equipment has the function of measuring parameters such as exhaust gas concentration, temperature, relative humidity, dew point temperature, and air volume. It also calculates emission schemes based on these parameters, calculates energy and material consumption within the emission schemes, and converts the corresponding energy and material consumption into a unified carbon emission figure. Based on the aforementioned dichloromethane recovery method, the exhaust gas distribution equipment can output the lowest carbon emission exhaust gas treatment scheme (optimal treatment scheme) and the required number of second-lowest schemes. The exhaust gas distribution equipment can control the operation of the dichloromethane recovery system according to the aforementioned exhaust gas treatment scheme.

[0160] Carbon fiber equipment, granular carbon equipment, and rotary adsorption equipment are collectively referred to as adsorption equipment, which removes dichloromethane from exhaust gases through adsorption. Furthermore, carbon fiber equipment, granular carbon equipment, and rotary adsorption equipment all have built-in coolers and heaters for dehumidifying and temperature-controlling the exhaust gas. For example, the exhaust gas to be adsorbed is first cooled and then heated to reduce its humidity.

[0161] The input of the exhaust gas distribution equipment connects to the exhaust gas source, the output of the make-up air equipment, the output of the multi-stage cryogenic equipment, the output of the carbon fiber equipment, the output of the granular carbon equipment, and the output of the rotary drum equipment. The output of the exhaust gas distribution equipment connects to the input of the exhaust ventilation equipment, the input of the multi-stage cryogenic equipment, the input of the carbon fiber equipment, the input of the granular carbon equipment, and the input of the rotary drum equipment. The input of the make-up air equipment connects to both the outside air and the exhaust gas source. The input of the emergency emission equipment connects to the exhaust gas source, and the output of the emergency emission equipment connects to the input of the exhaust ventilation equipment.

[0162] like Figure 5 As shown, preferably, the exhaust gas distribution device includes a first exhaust gas distribution unit and a second exhaust gas distribution unit.

[0163] The input end of the first exhaust gas distribution unit is connected to the exhaust gas source and the output end of the make-up air device. The output end of the first exhaust 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 rotary wheel device.

[0164] 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. The output end of the second exhaust gas distribution unit 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 rotary wheel equipment.

[0165] The input end of the emergency emission device is connected to the exhaust gas source, and the output end of the emergency emission device is connected to the input end of the exhaust ventilation device.

[0166] The input end of the exhaust equipment is connected to 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 emergency exhaust equipment. The output end of the exhaust equipment is connected to the atmosphere.

[0167] The input end of the make-up air device is connected to the exhaust gas source and outside air, and the output end is connected to the input end of the first exhaust gas distribution unit. The connections between the devices are controlled by valves.

[0168] The exhaust gas distribution equipment can control the operating conditions of emergency emission equipment, make-up air equipment, rotary equipment, granular carbon equipment, carbon fiber equipment and multi-stage cryogenic equipment according to the parameters of the exhaust gas, call different treatment equipment to recover dichloromethane, and calculate the equipment combination treatment method with the lowest energy consumption and highest efficiency while ensuring that emissions meet the standards.

[0169] For example, exhaust gas with a concentration ≤1000mg / m³ can meet emission standards after entering the rotor by matching different rotor models. Carbon fiber and granular carbon equipment have an adsorption rate of 90% for dichloromethane exhaust gas. The dew point of the exhaust gas before entering the adsorption equipment must be at the optimal state required by the equipment to ensure adsorption efficiency and extend equipment life. Specifically, the optimal adsorption temperature for fiber and granular carbon equipment is 25℃, and the dew point temperature is ≤18℃; the optimal operating temperature for rotor equipment is 39℃, and the dew point temperature is ≤28℃.

[0170] The dichloromethane recovery system provided in this embodiment of the invention can maximize the advantages of each device, thereby achieving maximum efficiency.

[0171] In summary, the present invention provides a multi-stage cryogenic and multiple adsorption method and system for recovering dichloromethane. When the exhaust gas enters the equipment inlet, the 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 data and formulas from a comparative database, and then gradually provides detailed parameters such as energy consumption and consumables for each combination, allowing operators to make manual selections or the equipment to make automatic selections. The combinations are sorted according to carbon emission analysis, and the combination with the lowest carbon emission is used by default.

[0172] It should be noted that the above embodiments are merely illustrative examples. The technical solutions of each embodiment can be combined, and all are within the protection scope of this invention.

[0173] It should be noted that the order of steps in this invention can be changed according to actual needs, the order between steps can be changed, and serial processing can be changed to parallel processing. It is not limited to the order of steps listed in the embodiments.

[0174] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0175] The foregoing provides a detailed description of the multi-stage cryogenic and multiple adsorption method and system for recovering dichloromethane provided by this invention. Any obvious modifications made by those skilled in the art without departing from the essence of this invention will constitute an infringement of the patent rights of this invention and will incur corresponding legal liability.

Claims

1. A method for recovering dichloromethane using multi-stage cryogenic and multiple adsorption processes, characterized in that... Includes the following steps: Step S1: The exhaust gas is introduced into the exhaust gas distribution equipment, which measures the exhaust gas concentration c and the air volume Q'. Proceed to step S3; Step S2: Compare the air volume Q' with the preset air volume Q. If Q' > Q, discharge the air volume through the emergency exhaust system to make Q' = Q, and proceed to step S3. If Q' ≤ Q, calculate the air volume Q' and exhaust gas concentration c after increasing the air volume by the corresponding step size, and proceed to step S3. Step S3: Compare the exhaust gas concentration c with the preset value. When c ≤ 120 mg / m³, proceed to step S10; when c ≥ 90 g / m³, proceed to steps S2 and S4; when 120 mg / m³ < concentration c < 90 g / m³, proceed to step S5. Step S4: Calculate the exhaust gas concentration c when the input exhaust gas is cooled to a refrigeration temperature point of -40 to -70℃; Obtain the required energy and material consumption data, then proceed to step S3; Step S5: The exhaust gas distribution device obtains the dew point temperature Dp of the exhaust gas, and then proceeds to steps S2 and S6. Step S6: Compare the exhaust gas concentration c with the preset value. If 70g / m³ < concentration c < 90g / m³, proceed to step S7; if 20g / m³ < concentration c ≤ 70g / m³, proceed to steps S7 and S8; if 1g / m³ < concentration c ≤ 20g / m³, proceed to step S8; if 120mg / m³ < concentration c ≤ 1g / m³, proceed to step S9. Step S7: Calculate the energy and material loss of the exhaust gas input into the carbon fiber equipment for adsorption, as well as the concentration c of the exhaust gas, and then proceed to step S3. Step S8: Calculate the energy and material losses of the exhaust gas input to the particulate carbon device for adsorption, as well as the concentration c of the removed exhaust gas, and then proceed to step S3. Step S9: Calculate the energy and material losses of the exhaust gas input rotary device for adsorption, as well as the exhaust gas concentration c, and then proceed to step S3; Step S10: Calculate the steps involved in the exhaust gas treatment and the energy and material consumption required to form an exhaust gas treatment plan; convert the energy and material consumption into carbon dioxide emissions. Step S11: Sort the exhaust gas treatment schemes from low to high carbon dioxide emissions, output the scheme with the lowest carbon dioxide emissions as the optimal exhaust gas treatment scheme, and output the second lowest number of schemes required by the design as alternative exhaust gas treatment schemes.

2. The dichloromethane recovery method as described in claim 1, characterized in that... Step S4 further includes the following sub-steps: Step S41: Compare the temperature T of the input exhaust gas of the multi-stage cryogenic equipment. If the temperature T > -40℃, proceed to step S42. If the temperature is -40℃ ≥ T > -70℃, proceed to step S43; if the temperature is T ≤ -70℃, proceed to step S3. Step S42: Based on the temperature T of the input exhaust gas, calculate the exhaust gas concentration c to cool the exhaust gas to -40℃, obtain the energy and material consumption required to cool to -40℃, and jump to step S3. Step S43: Based on the temperature T of the input exhaust gas, 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 material consumption required for cooling, and jump to step S3.

3. The method for recovering dichloromethane as described in claim 1, characterized in that... Step S7 further includes the following sub-steps: Step S71: Compare the dew point temperature Dp of the input exhaust gas of the carbon fiber equipment with the preset value. If Dp > 18°C, proceed to step S72; if Dp ≤ 18°C, proceed to step S73. Step S72: Reduce the exhaust gas temperature T to 18°C, obtain the energy and material losses required to cool to 18°C, and proceed to step S74. Step S73: Compare the temperature T of the input exhaust gas of the carbon fiber equipment with the preset value. If the temperature T ≤ 25℃, proceed to step S74; if the temperature T > 25℃, proceed to step S75. Step S74: Increase the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to raise the temperature to 25°C, and proceed to step S76. Step S75: Cool the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to cool to 25°C, and proceed to step S76. Step S76: Calculate the energy and material losses of the exhaust gas input into the carbon fiber device for adsorption, as well as the concentration c of the exhaust gas, and then proceed to step S3.

4. The dichloromethane recovery method according to claim 1, characterized in that... Step S8 further includes the following sub-steps: Step S81: Compare the dew point temperature Dp of the input exhaust gas of the particulate carbon device with the preset value. If Dp > 18°C, proceed to step S82; if Dp ≤ 18°C, proceed to step S83. Step S82: Reduce the exhaust gas temperature T to 18°C, obtain the energy and material losses required to cool to 18°C, and proceed to step S84. Step S83: Compare the temperature T of the input exhaust gas of the particulate carbon device with the preset value. If the temperature T ≤ 25℃, proceed to step S84; if the temperature T > 25℃, proceed to step S85. Step S84: Increase the exhaust gas temperature T to 25°C, obtain the energy and material consumption required to raise the temperature to 25°C, and proceed to step S86. Step S85: Cool the exhaust gas temperature T to 25°C, obtain the energy and material losses required to cool to 25°C, and proceed to step S86. Step S86: Calculate the energy and material losses of the exhaust gas input to the particulate carbon device for adsorption, as well as the concentration c of the removed exhaust gas, and then proceed to step S3.

5. The method for recovering dichloromethane as described in claim 1, characterized in that... Step S9 further includes the following sub-steps: Step S91: Compare the dew point temperature Dp of the input exhaust gas of the rotary device with the preset value. If Dp > 28°C, proceed to step S92; if Dp ≤ 28°C, proceed to step S93. Step S92: Reduce the exhaust gas temperature T to 28°C, obtain the energy and material losses required to cool to 28°C, and proceed to step S94. Step S93: Compare the temperature T of the input exhaust gas of the rotary device with the preset value. If the temperature T ≤ 39℃, proceed to step S94; if the temperature T > 39℃, proceed to step S95. Step S94: Increase the exhaust gas temperature T to 39°C, obtain the energy and material consumption required to raise the temperature to 39°C, and proceed to step S96. Step S95: Cool the exhaust gas temperature T to 39°C, obtain the energy and material consumption required to cool to 39°C, and proceed to step S96. Step S96: Calculate the energy and material losses of the exhaust gas input rotary device for adsorption, as well as the exhaust gas concentration c, and then proceed 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... This includes exhaust gas distribution equipment, make-up air equipment, multi-stage cryogenic equipment, carbon fiber equipment, granular carbon equipment, and rotary wheel equipment; among which, The input end of the exhaust gas distribution device is connected to the exhaust gas source, the output end of the make-up air 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 rotary wheel device; The output end of the exhaust 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 rotary wheel device; The input end of the make-up air device is connected to outside air and the exhaust gas source.

7. The dichloromethane recovery system as described in claim 6, characterized in that: The exhaust gas distribution equipment has the functions of measuring exhaust gas concentration, dew point temperature and air volume parameters, as well as calculating emission schemes based on parameters, calculating energy consumption and material consumption in emission schemes, and converting the corresponding energy consumption and material consumption into a unified carbon emission amount. Carbon fiber equipment, granular carbon equipment, and rotary equipment all have built-in coolers and heaters for dehumidifying and temperature-controlling exhaust gases.

8. The dichloromethane recovery system as described in claim 7, characterized in that: The exhaust gas distribution device includes a first exhaust gas distribution unit and a second exhaust gas distribution unit; The input end of the first exhaust gas distribution unit is connected to the exhaust gas source and the output end of the make-up air 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 rotary device; 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 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 rotary wheel device.

9. The dichloromethane recovery system as described in claim 8, characterized in that... It also includes emergency exhaust equipment and ventilation equipment; among which, The input end of the emergency emission 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 emission device, and the output end is connected to the atmosphere.

10. The dichloromethane recovery system as described in claim 9, characterized in that: The input end of the make-up air device is connected to the exhaust gas source and outside air, and the output end is connected to the input end of the first exhaust gas distribution unit.

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