System and method for improving capacity of activated carbon for adsorbing organic waste gas VOCs (Volatile Organic Compounds)

Abstract

The invention provides a system and method for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas, and the system comprises: a heat exchanger for introducing steam heat of the medium and low temperature VOCs waste gas to perform waste heat recovery to generate high temperature circulating water; the refrigerating system is used for receiving the high-temperature circulating water through a pipeline and recovering heat of the high-temperature circulating water to enable the refrigerating system to generate a refrigerant, and the refrigerant enters the heat exchanger to exchange heat with the medium-low-temperature VOCs waste gas; the activated carbon fixed bed adsorption device is used for receiving the medium and low temperature VOCs waste gas after heat exchange and adsorbing organic gas in the waste gas; the steam thermal desorption device is used for introducing steam into the activated carbon fixed bed adsorption device for desorption after the activated carbon fixed bed adsorption device is saturated in adsorption, and the steam takes away the organic gas adsorbed by the activated carbon fixed bed adsorption device and enters a downstream phase change heat exchanger; and the phase change heat exchanger is used for recycling steam heat after analysis by using circulating water to generate high-temperature circulating water, and after heat is recycled, waste gas is condensed, so that organic gas is dissolved in water to form an organic solvent to be recycled.

Description

Technical Field

[0001] The present invention relates to the field of environmental protection, and particularly to a system and method for improving the ability of activated carbon to adsorb organic waste gas VOCs. Background Art

[0002] In the process of treating air pollution, the treatment of organic waste gas VOCs is an important part.

[0003] The technology of activated carbon adsorbing organic waste gas VOCs has been widely adopted in recent years. It has attracted a lot of attention and application due to its large adsorption capacity, low cost, and wide and easy availability of sources. Generally speaking, during the use of activated carbon, as the temperature of the adsorbed gas rises, the adsorption capacity of activated carbon decreases significantly, which in turn leads to a decrease in adsorption efficiency, an increase in the emission of organic waste gas, an increase in the replacement frequency of activated carbon, and an increase in the regeneration cost. When activated carbon adsorbs organic waste gas, the best adsorption temperature is 10 - 20°C. Cooling the temperature of medium and low temperature VOCs waste gas to the above temperature can not only increase the adsorption capacity of activated carbon, but also significantly reduce the steam desorption cost.

[0004] In the existing activated carbon adsorption organic waste gas treatment system, a large amount of circulating water is basically used to cool the organic solvent mixture after steam desorption. The waste heat generated by the steam desorption of activated carbon is not effectively recovered, resulting in a certain degree of energy waste. At the same time, due to the insufficiently low adsorption temperature, the adsorption performance of activated carbon also decreases accordingly. Therefore, activated carbon needs to be replaced frequently, increasing the treatment cost. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to provide a system and method for improving the ability of activated carbon to adsorb organic waste gas VOCs, so as to solve the problem of waste heat after steam desorption. The waste heat in the steam desorption device is used to generate a cold source through a refrigeration system to cool the VOCs waste gas, so as to reach the best adsorption temperature of activated carbon, increase the adsorption amount of VOCs waste gas, and reduce the amount of desorbed steam.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas, comprising:

[0008] A heat exchanger for recovering the waste heat of the steam heat of the introduced medium and low temperature VOCs waste gas as an energy source to heat the water source in the heat exchanger to generate high-temperature circulating water;

[0009] A refrigeration system for receiving the high-temperature circulating water through a pipeline and recovering its heat as an energy source to make the refrigeration system generate refrigerant. The refrigerant enters the heat exchanger to exchange heat with the medium and low temperature VOCs waste gas, and the exchanged refrigerant is re-introduced into the refrigeration system;

[0010] An activated carbon fixed bed adsorption device, which is connected to the heat exchanger to receive the medium and low temperature VOCs waste gas after heat exchange and adsorb the organic gas in the waste gas;

[0011] A steam thermal desorption device, which is used to introduce steam into the activated carbon fixed bed adsorption device for desorption when the activated carbon fixed bed adsorption device is saturated with adsorption. The steam takes away the organic gas adsorbed by the activated carbon fixed bed adsorption device and enters the downstream phase change heat exchanger;

[0012] A phase change heat exchanger, which uses circulating water to recover the heat of the desorbed steam to generate high-temperature circulating water. The high-temperature circulating water enters the refrigeration system through a pipeline. After the heat is recovered, the waste gas is condensed so that the organic gas is dissolved in water to form an organic solvent for recycling.

[0013] In one embodiment, the refrigeration system is a refrigerating machine.

[0014] In one embodiment, the activated carbon fixed bed adsorption device is a box body with a containing cavity. The box body includes a baffle plate, a W-shaped activated carbon adsorption device and a plurality of steam nozzles. The box body is provided with a baffle plate at the upper waste gas inlet. After the waste gas enters the box body, it enters the shunt area through the holes on both sides of the air inlet. The perforated plate is arranged at the bottom of the shunt area. The W-shaped activated carbon adsorption device is arranged below the perforated plate. The gas is adsorbed at the W-shaped activated carbon adsorption device after passing through the perforated plate. The inside of the W-shaped activated carbon adsorption device is filled with granular activated carbon. The bottom of the box body is provided with a gas outlet to discharge the purified gas. The bottom of the containing cavity is provided with a plurality of steam nozzles. Each steam nozzle is provided with a plurality of small-diameter nozzles along the cross-section of the box body at the upper end. The small-diameter nozzles are evenly distributed on the same circumference. After the steam enters the steam nozzle, it sprays upward to perform thermal desorption regeneration on the activated carbon layer.

[0015] In one embodiment, circulating water is used to recover the waste heat generated by the steam thermal desorption device in the phase change heat exchanger, and the temperature of the circulating water after heating is 60-80°C.

[0016] In one embodiment, the refrigeration system is used to convert the heat energy of the high-temperature circulating water into a refrigerant for cooling the medium and low temperature VOCs waste gas, and the temperature of the waste gas drops by 20-80°C.

[0017] In one embodiment, there are at least two sets of the activated carbon fixed bed adsorption devices and they are connected in parallel.

[0018] The present invention also provides a method for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas. The method includes:

[0019] S1: The VOCs waste gas is cooled by a heat exchanger and then enters the activated carbon fixed bed adsorption device for physical adsorption, and the purified waste gas is discharged. After adsorption saturation, the activated carbon fixed bed adsorption device is switched to another activated carbon fixed bed adsorption device;

[0020] S2: The activated carbon fixed bed adsorption device after adsorption saturation is subjected to thermal steam desorption. After thermal desorption, the steam carries the organic solvent into the phase change heat exchanger;

[0021] S3: In the phase change heat exchanger, the heat of the desorbed steam is recovered by circulating water to generate high-temperature circulating hot water, and the high-temperature circulating hot water enters the downstream refrigeration system;

[0022] S4: The high-temperature circulating hot water enters the refrigeration system as a heat source, and the refrigeration system generates refrigerant for downstream cooling;

[0023] S5: The refrigerant generated by the refrigeration system exchanges heat with the medium and low-temperature VOCs waste gas in the heat exchanger, thereby reducing the temperature of the waste gas, increasing the adsorption capacity of the activated carbon fixed bed, and reducing the desorption steam consumption.

[0024] Due to the adoption of the above technical solution, the beneficial effects of the present invention include: recovering the heat in the waste gas or after thermal desorption of the steam, generating a cold source through the refrigeration system to cool the VOCs waste gas in the heat exchanger, thereby achieving the optimal adsorption temperature of the activated carbon, increasing the adsorption capacity of the VOCs waste gas, and reducing the desorption steam consumption. Description of the Drawings

[0025] Figure 1 It is a schematic structural diagram of the adsorption system according to an embodiment of the present invention.

[0026] Figure 2 It is a schematic structural diagram of the activated carbon fixed bed adsorption device according to an embodiment of the present invention.

[0027] Description of the Reference Numerals in the Drawings

[0028] 1. First cold water pipeline; 2. Hot water pipeline;

[0029] 3. Refrigeration system; 4. Second cold water pipeline;

[0030] 5. Steam condensation inlet; 6. VOCs waste gas;

[0031] 7. Fixed bed activated carbon adsorption device; 8. Purified waste gas;

[0032] 9. Desorption steam; 10. Phase change heat exchanger;

[0033] 11. Heat exchanger; 12. Perforated plate;

[0034] 13. Baffle plate; 14. Activated carbon fixed bed adsorption device;

[0035] 15. Steam nozzle. Detailed implementation mode

[0036] In order to make the objectives, technical solutions and beneficial effects of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] For convenience of description, when needed, spatial relative terms such as "below", "beneath", "under", "above", "on" etc. will be used to describe the relationship of one element or feature shown in the drawings relative to another element or feature. The spatial relative terms are intended to include different orientations of the device in use or operation other than the orientation shown in the drawings. For example, if the device in the drawings is flipped, an element described as "below" or "beneath" other elements or features will be oriented "above" other elements or features.

[0038] Unless otherwise defined, the terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs, and the terms should be understood to have a meaning consistent with the meaning in the context of the related art, and should not be understood in an idealized or overly formalized manner, except in the case where the present invention is clearly defined.

[0039] As Figure 1 shown, for example, a system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas includes: an activated carbon fixed bed adsorption device, a steam thermal desorption device, a phase change heat exchanger device, a refrigeration system, and a heat exchanger;

[0040] The heat exchanger is used to recover the waste heat of the steam heat introduced into the medium and low temperature VOCs waste gas as energy to heat the water source in the heat exchanger, generating high-temperature circulating water;

[0041] The refrigeration system is used to receive the high-temperature circulating water through a pipeline and recover its heat as energy to enable the refrigeration system to generate refrigerant. The refrigerant enters the heat exchanger to exchange heat with the medium and low temperature VOCs waste gas, and the exchanged refrigerant is re-introduced into the refrigeration system;

[0042] The activated carbon fixed bed adsorption device is communicated with the heat exchanger to receive the heat-exchanged medium and low temperature VOCs waste gas and adsorb the organic gas in the waste gas;

[0043] The steam thermal desorption device is used to introduce steam into the activated carbon fixed bed adsorption device for desorption when the activated carbon fixed bed adsorption device is saturated with adsorption. The steam takes away the organic gas adsorbed by the activated carbon fixed bed adsorption device and enters the downstream phase change heat exchanger;

[0044] The phase change heat exchanger recovers the heat of the steam after analysis with circulating water to generate high-temperature circulating water. The high-temperature circulating water enters the refrigeration system through a pipeline. After the heat is recovered, the waste gas is condensed to dissolve the organic gas in water to form an organic solvent for recycling.

[0045] The steam thermal analysis device is used to remove the organic waste gas adsorbed in the activated carbon. The operating temperature of the thermal analysis is low-pressure saturated steam. After ensuring sufficient analysis time, the adsorption capacity of the activated carbon can be restored to the initial state.

[0046] The refrigeration system generates a cold source after the high-temperature circulating water passes through it, and then cools the VOCs waste gas after heat exchange through a heat exchanger, thereby increasing the adsorption capacity of the activated carbon adsorbent for the organic waste gas.

[0047] In one embodiment, the activated carbon fixed bed adsorption device is a box body with a containing cavity. The box body includes a baffle plate, a W-shaped activated carbon adsorption device, and a plurality of steam nozzles. The box body is provided with a baffle plate at the upper waste gas inlet. After the waste gas enters the box body, it enters the diversion area through the holes on both sides of the air inlet. The perforated plate is arranged at the bottom of the diversion area. The W-shaped activated carbon adsorption device is arranged below the perforated plate. The gas is adsorbed at the W-shaped activated carbon adsorption device after passing through the perforated plate. The inside of the W-shaped activated carbon adsorption device is filled with granular activated carbon. The bottom of the box body is provided with a gas outlet to discharge the purified gas. The bottom of the containing cavity is provided with a plurality of steam nozzles. Each steam nozzle is provided with a plurality of small-diameter nozzles along the cross-section of the box body at the upper end. The small-diameter nozzles are evenly distributed on the same circumference. After the steam enters the steam nozzle, it sprays upward to perform thermal analysis and regeneration on the activated carbon layer.

[0048] The activated carbon fixed bed adsorption device is used to remove the organic waste gas in the waste gas, and the adsorbent used is granular activated carbon. After the waste gas enters the adsorption device from the upper pipeline, it first passes through the baffle plate to reduce the air flow pressure, make the air flow velocity uniform, and be distributed to the perforated plates on both sides, so that the air flow enters the activated carbon fixed bed adsorption device evenly. The activated carbon fixed bed adsorption device adopts a W-shaped activated carbon structure, which has a large filling space and a small floor area. The middle is filled with activated carbon, which is beneficial to saving space and improving the purification efficiency. The steam enters from the left nozzle and sprays upward through a plurality of small-diameter nozzles for thermal analysis to make the analysis more thorough and uniform.

[0049] In one embodiment, the phase change heat exchanger is used to recover the waste heat of the steam after analysis, and generate high-temperature circulating water to provide heat source for the refrigeration system; the temperature of the circulating water heated by the phase change heat exchanger is 60 - 80 °C.

[0050] In one embodiment, the refrigeration system is used to convert the heat energy of the high-temperature circulating water into a refrigerant to cool the medium and low-temperature VOCs waste gas, and the temperature of the waste gas drops by 20 - 80 °C.

[0051] In one embodiment, at least two activated carbon fixed bed adsorption devices are provided and are connected in parallel.

[0052] The present invention also provides a method for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas, including:

[0053] S1: The VOCs waste gas is cooled by a heat exchanger and then enters the activated carbon fixed bed adsorption device for physical adsorption, and the purified waste gas is discharged; after adsorption saturation, the fixed bed is switched to another activated carbon fixed bed adsorption device to be used.

[0054] S2: For the activated carbon fixed bed adsorption device after adsorption saturation, thermal steam desorption is carried out. After a certain period of thermal desorption, the steam carries organic solvents and enters the downstream phase change heat exchanger.

[0055] S3: In the phase change heat exchanger, the heat of the steam is recovered by circulating water to generate high-temperature circulating hot water, and the high-temperature circulating hot water enters the downstream refrigeration system.

[0056] S4: The high-temperature circulating hot water enters the refrigeration system as a heat source, and a refrigerant is generated through the refrigeration system for cooling downstream.

[0057] S5: The refrigerant generated by the refrigeration system exchanges heat with the medium and low temperature VOCs waste gas in the heat exchanger, thereby reducing the temperature of the waste gas, increasing the adsorption capacity of the activated carbon fixed bed adsorption device, and reducing the desorption steam consumption.

[0058] Compared with the prior art inventions, the beneficial effects of the present invention are as follows:

[0059] 1. The present invention realizes the cooling of the medium and low temperature VOCs waste gas temperature by 20 - 80 °C through waste heat recovery, increases the adsorption capacity of activated carbon for VOCs, and reduces steam consumption.

[0060] 2. The present invention makes full use of the phase change heat exchanger to recover the waste heat after the thermal steam desorption of activated carbon, generating high-temperature circulating hot water at 60 - 80 °C, thereby greatly saving the system energy consumption.

[0061] 3. The present invention uses the refrigeration system to use the recovered thermal energy for the refrigerator to produce a refrigerant for reducing the temperature of the medium and low temperature VOCs waste gas, thereby greatly increasing the adsorption capacity of activated carbon.

[0062] 4. The present invention uses a W-shaped activated carbon adsorption device. The flow rate of the gas flow is made uniform through the baffle plate and the perforated plate. By using the W-shaped device to fill more activated carbon, not only the internal space of the device is saved, but also the adsorption efficiency of the device can be improved; by using multiple small-diameter steam nozzles, the steam is ejected evenly and densely, which is beneficial to more thorough and uniform desorption.

[0063] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas, characterized in that: include: A heat exchanger is used to recover the waste heat of the steam introduced into the medium- and low-temperature VOCs waste gas and use it as energy to heat the water source in the heat exchanger to generate high-temperature circulating water; A refrigeration system is used to receive the high-temperature circulating water through a pipeline and recover its heat as energy to generate refrigerant in the refrigeration system. The refrigerant enters a heat exchanger to exchange heat with medium- and low-temperature VOCs waste gas, and the refrigerant after heat exchange is re-introduced into the refrigeration system; An activated carbon fixed bed adsorption device is connected to the heat exchanger to receive the medium and low temperature VOCs waste gas after heat exchange and adsorb the organic gas in the waste gas; A steam thermal analysis device, used for passing steam into the activated carbon fixed bed adsorption device for analysis when the activated carbon fixed bed adsorption device is saturated with adsorption, and the steam takes away the organic gas adsorbed by the activated carbon fixed bed adsorption device and enters the downstream phase change heat exchanger; The phase change heat exchanger uses circulating water to recover the heat of the analyzed steam to produce high-temperature circulating water. The high-temperature circulating water enters the refrigeration system through a pipeline. After the heat is recovered, the exhaust gas is condensed to dissolve the organic gas in water to form an organic solvent for recycling.

2. The system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas according to claim 1, characterized in that: The refrigeration system is a refrigerator.

3. The system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas according to claim 1, characterized in that: The activated carbon fixed bed adsorption device is a box with a accommodating chamber, the box includes a baffle, a W-shaped activated carbon adsorption device and a plurality of steam nozzles. The box is provided with a baffle at the upper exhaust gas inlet. After the exhaust gas enters the box, it enters the diversion area through the holes on both sides of the air inlet. The porous plate is arranged at the bottom of the diversion area. The W-shaped activated carbon adsorption device is arranged below the porous plate. After the gas passes through the porous plate, it is adsorbed at the W-shaped activated carbon adsorption device. The W-shaped activated carbon adsorption device is filled with granular activated carbon. A gas outlet is provided at the bottom of the box to purify the gas and discharge it. A plurality of steam nozzles are provided at the bottom of the accommodating chamber. A plurality of small-diameter nozzles are opened at the upper end of each steam nozzle along the cross section of the box, and the small-diameter nozzles are evenly distributed on the same circumference. After the steam enters the steam nozzle, it is sprayed upward to perform thermal analysis and regeneration on the activated carbon layer.

4. The system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas according to claim 1, characterized in that: The waste heat generated by the steam thermal analysis device is recovered by circulating water in the phase change heat exchanger. The temperature of the circulating water after heating is 60-80℃.

5. The system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas according to claim 1, characterized in that: The refrigeration system converts the heat energy of high-temperature circulating water into refrigerant for cooling medium and low-temperature VOCs waste gas, and the waste gas temperature drops by 20-80℃.

6. The system for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas according to claim 1, characterized in that: The activated carbon fixed bed adsorption device comprises at least two sets connected in parallel.

7. A method for improving the ability of activated carbon to adsorb medium and low temperature VOCs waste gas, characterized in that: The method comprises: S1: After being cooled by the heat exchanger, the VOCs waste gas enters the activated carbon fixed bed adsorption device for physical adsorption and discharges the clean waste gas; after the adsorption is saturated, the activated carbon fixed bed adsorption device is switched to another activated carbon fixed bed adsorption device; S2: After adsorption saturation, the activated carbon fixed bed adsorption device is subjected to thermal steam analysis. After thermal analysis, the steam and the organic solvent enter the phase change heat exchanger; S3: Recover the heat of the analyzed steam with circulating water in the phase change heat exchanger to generate high-temperature circulating hot water, which enters the downstream refrigeration system; S4: High-temperature circulating water enters the refrigeration system as a heat source, and generates refrigerant through the refrigeration system for downstream cooling; S5: The refrigerant generated by the refrigeration system exchanges heat with the medium and low temperature VOCs waste gas in the heat exchanger, thereby reducing the temperature of the waste gas, increasing the adsorption capacity of the activated carbon fixed bed, and reducing the amount of analytical steam used.

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