CN115738576A - Volatile organic compound-containing tail gas treatment system and tail gas treatment process - Google Patents
Volatile organic compound-containing tail gas treatment system and tail gas treatment process Download PDFInfo
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- CN115738576A CN115738576A CN202211466879.XA CN202211466879A CN115738576A CN 115738576 A CN115738576 A CN 115738576A CN 202211466879 A CN202211466879 A CN 202211466879A CN 115738576 A CN115738576 A CN 115738576A
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Abstract
The application discloses contain volatile organic compounds tail gas processing system and tail gas treatment process belongs to tail gas treatment technical field. Contain volatile organic compounds tail gas treatment system includes: the condensation module is a multi-stage condensation module and is used for carrying out fractional condensation treatment on tail gas entering the condensation module; the gas outlet of the condensation module is connected with the gas inlet of the absorption module; the absorption module is internally provided with an absorption liquid nozzle so that tail gas entering the absorption module is contacted with absorption liquid; the gas outlet of the absorption module is connected with the inlet of the absorption module; and the outlet of the adsorption module is connected with the inlet of the discharge module. The application provides a tail gas processing system can effectively retrieve most methyl alcohol in the methyl alcohol tail gas, ensures simultaneously that the exhaust gas satisfies national and local atmospheric pollutants emission index requirement, has good social and economic benefits.
Description
Technical Field
The application relates to the technical field of tail gas treatment, in particular to a tail gas treatment system containing volatile organic compounds and a tail gas treatment process.
Background
Methanol is the most basic raw material in the petrochemical industry, and in the loading and unloading process of methanol, a finished methanol storage tank conveys the methanol to a tank car through a pump, organic matters and methanol volatile matters in the tank car can be continuously discharged into the atmosphere along with the rise of the liquid level in the tank car, so that the loss of methanol products can be caused, environmental pollution can be caused, the ecological environment can be damaged, meanwhile, peculiar smell is discharged on site, the physical and mental health of site operators is influenced, and occupational diseases can be caused after long time.
Because the waste gas generally contains air, the concentration of organic matters in the waste gas is in an explosion limit range, and the waste gas can not directly enter an incineration system. At present, the property of infinite mutual solubility of methanol and water is generally adopted for the situation, the discharged methanol tail gas is collected firstly, and then is discharged after being washed by water. Other substances such as gasoline or diesel oil are possibly loaded in the tank truck before methanol is loaded, so that other water-insoluble Volatile Organic Compounds (VOCs) gas are also contained in the methanol loading process, and the water washing cannot completely remove the water-insoluble volatile organic compounds, so that the non-methane total hydrocarbons in the exhaust gas exceed the standard. Meanwhile, the methanol-containing waste liquid after washing is discharged as waste water, and the methanol component in the tail gas cannot be effectively recovered.
Disclosure of Invention
The application aims to provide a volatile organic compound-containing tail gas treatment system, which can effectively recover methanol and avoid the problem that the concentration of non-methane total hydrocarbons in exhaust gas exceeds the standard.
The application provides a contain volatile organic compounds tail gas treatment system includes:
the condensation module is a multi-stage condensation module and is used for carrying out fractional condensation treatment on tail gas entering the condensation module;
the gas outlet of the condensation module is connected with the gas inlet of the absorption module; the absorption module is internally provided with an absorption liquid nozzle so that tail gas entering the absorption module is contacted with absorption liquid;
the gas outlet of the absorption module is connected with the inlet of the absorption module;
and the outlet of the adsorption module is connected with the inlet of the discharge module.
Optionally, in some embodiments of the present application, a pressurization module is disposed between the absorption module and the adsorption module, and is configured to pressurize the tail gas entering the adsorption module.
Optionally, in some embodiments of the present application, a detection device is disposed between the adsorption module and the emission module, and the detection device is configured to detect a concentration of an organic substance in the tail gas before entering the emission module.
Optionally, in some embodiments of the present application, the outlet of the adsorption module is connected to the inlet of the adsorption module.
Optionally, in some embodiments of the present application, the apparatus further includes a rectifying tower, the rectifying tower is connected to the liquid outlet of the absorption module, and the waste liquid after the absorption liquid contacts with the tail gas enters the rectifying tower through the liquid outlet of the absorption module.
Optionally, in some embodiments of the present application, the condensing module further comprises a collecting tank connected to the liquid outlet of the condensing module; the collecting tank is used for collecting liquid obtained by condensation of the condensation module.
Optionally, in some embodiments of the present application, in the absorption module, the absorption liquid nozzle is located above the absorption module, and a flow direction of the absorption liquid at the absorption liquid nozzle is opposite to a flow direction of the gas.
Optionally, in some embodiments of the present application, the adsorption module further includes a nitrogen desorption device, and the nitrogen desorption device is connected to the adsorption module and is configured to deliver nitrogen into the adsorption module.
Optionally, in some embodiments of the present application, the adsorption module further comprises a combustion device, and the combustion device is connected with the adsorption module.
Optionally, in some embodiments of the present application, the system further comprises a control system, connected to at least one of the condensation module, the absorption module, the adsorption module, the pressurization module, the discharge module, and the detection device, for controlling the operation of the modules; and the control system controls communication or closing between the modules.
Correspondingly, the application also provides a tail gas treatment process, which adopts the tail gas treatment system, and comprises the following steps:
introducing the tail gas containing volatile organic compounds into a condensation module, and liquefying through fractional condensation treatment of the condensation module to obtain condensate; wherein the fractional condensation treatment comprises: performing primary refrigeration at the treatment temperature of 0-5 ℃ to obtain first condensate; performing secondary refrigeration at the treatment temperature of-35 to-40 ℃ to obtain second condensate; performing tertiary refrigeration at the treatment temperature of-70 to-75 ℃ to obtain third condensate;
the tail gas treated by the condensation module enters an absorption module, and absorption liquid in the absorption module absorbs part of organic matters in the tail gas;
the process tail gas after absorption module handles gets into the adsorption module, adsorbent in the adsorption module is arranged in the surplus organic matter of absorption tail gas, flows into the emission module after reaching emission standard through detection device detection exhaust gas.
Optionally, in some embodiments of the application, the tail gas treated by the absorption module is treated by the pressurization module and then enters the adsorption module; and the pressurization module performs frequency conversion adjustment according to the pressure value of the tail gas before entering the condensation module, so that the system pressure is kept stable.
The tail gas treated by the absorption module is treated by the demisting module and then enters the pressurizing module; the demisting module is used for separating a small amount of absorption liquid carried in the tail gas.
Optionally, in some embodiments of the present application, a concentration of the organic matters in the tail gas after being treated by the condensation module is 5000mg/Nm 3 The following.
And after the adsorbent adsorbs residual organic matters in the tail gas, introducing nitrogen to desorb the organic matters in the adsorbent, and then introducing the adsorbent into a combustion device to perform combustion treatment so as to remove the organic matters.
The beneficial effect of this application lies in:
the application provides a tail gas processing system can effectively retrieve most methyl alcohol in the methyl alcohol tail gas, reduces non-methane total hydrocarbon concentration in the exhaust gas simultaneously, ensures that the exhaust gas satisfies national and local atmospheric pollutants emission index requirement, has good social and economic benefits.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a tail gas treatment system containing volatile organic compounds according to an embodiment of the present disclosure;
fig. 2 is a flow chart of a tail gas treatment process provided in an embodiment of the present application.
Description of reference numerals: 1-a condensation module, 2-an absorption module, 3-a demisting module, 4-a pressurization module, 5-an absorption module, 51-a first absorption tank, 52-a second absorption tank, 7-an exhaust module, 8-a liquid enrichment pump, 9-a condensate pump, 10-a collection tank, 11-a nitrogen heater, 101-a methanol loading and unloading stack field, 102-an absorption liquid, 103-a low-pressure nitrogen, 104-a combustion device, 105-a rectification tower, 106-a crude methanol tank, 201-a pressure detection device, 202-a flow detection device, 203-a first liquid level detection device, 204-a second liquid level detection device, 205-a concentration detection device, 206-a first temperature detection device, 207-a second temperature detection device, 301-a first control valve, 302-a second control valve, 303-a third control valve, 304-a fourth control valve, 305-a fifth control valve, 306-a sixth control valve, 307-a seventh control valve, 308-an eighth control valve, 309-a ninth control valve, 310-a tenth control valve, and 401-a control system.
Detailed Description
The technical solutions in the embodiments of the present application will be described clearly and completely with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Furthermore, it should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are given by way of illustration and explanation only, and are not intended to limit the scope of the invention. In the present application, unless indicated to the contrary, the use of the directional terms "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, and more particularly to the orientation of the figures of the drawings; while "inner" and "outer" are with respect to the outline of the device.
The embodiment of the application provides a volatile organic compound-containing tail gas treatment system and a tail gas treatment process. The following are detailed descriptions. It should be noted that the following description of the embodiments is not intended to limit the preferred order of the embodiments.
The embodiment of this application provides a volatile organic compounds containing tail gas processing system, as shown in fig. 1, includes: a condensation module 1, an absorption module 2, an adsorption module 5 and a discharge module 7. Conceivably, in the tail gas treatment system of the embodiment of the present application, most of the organic matters in the tail gas are removed by the cooling effect of the condensation module 1; then the organic matters in the tail gas are removed through an absorption module 2; and then the part of organic matters in the tail gas are removed through the adsorption module 5, and the adsorption module 5 can be recycled until the content of the volatile organic matters in the tail gas reaches the emission standard and then enters the emission module 7.
Furthermore, the condensation module 1 is a multi-stage condensation module, and the tail gas entering the condensation module 1 is subjected to fractional condensation treatment, so that organic matters in the tail gas can be liquefied with lower energy consumption, and the liquefaction effect is more sufficient than that of a method for directly reducing the tail gas to the lowest condensation temperature. Further, the condensing module may be a three-stage condensing module, which is denoted as a first-stage refrigeration, a second-stage refrigeration, and a third-stage refrigeration, respectively. For example, the treatment temperature of the first stage refrigeration is 0-5 ℃, the treatment temperature of the second stage refrigeration is-35 to-40 ℃, the treatment temperature of the third stage refrigeration is-70 to-75 ℃, and under the condition of the three-stage condensation, other organic matters in the methanol can be effectively removed through the gradually-cooled refrigeration environment, and the methanol can be efficiently recovered. The condensation module of the system can also be four-stage condensation and the like, and is determined according to methanol and other components in the tail gas to be treated.
In some embodiments, as shown in fig. 1, the off-gas of the present application is derived from a methanol loading stack field 101, and the off-gas of the methanol loading stack field 101 containing methanol and other volatile organic compounds enters the condensation module 1 through a pipeline. And a pressure detection device 201 and a second control valve 302 are arranged between the methanol loading and unloading stack field 101 and the condensation module 1, and the second control valve 302 can control the pipeline communication or blocking between the methanol loading and unloading stack field 101 and the condensation module 1.
In some embodiments, the condensation module 1 is further connected to a collection tank 10 for collecting the liquid condensed in the condensation module 1. For example, the collection tank may include a methanol collection tank, and other collection tanks that may respectively collect liquids liquefied at different periods of time. It is conceivable that the inlet of the collection tank 10 is connected to the liquid outlet of the condensation module 1. Further, a second liquid level detection device 204 is connected to the collection tank 10, and the second liquid level detection device 204 detects the liquid level of the collection tank 10. When the liquid level reaches a certain level, the liquid can be transferred by the condensate pump 9 to another collection tank, such as the crude methanol tank 106.
Further, as shown in fig. 1, the gas outlet of the condensing module 1 is connected to the gas inlet of the absorbing module 2. That is, the tail gas treated by the condensing module 1 enters the absorbing module 2. Furthermore, the absorption module 2 is provided with an absorption liquid nozzle for spraying absorption liquid so that the tail gas entering the absorption module 2 contacts with the absorption liquid therein. Conceivably, in the absorption module 2, the absorption liquid nozzle is located above the gas inlet, so that the tail gas enters the absorption module through the gas inlet, the airflow direction is from bottom to top, the absorption liquid moves from top to bottom through the absorption liquid nozzle, the absorption liquid and the absorption liquid move in opposite directions in a countercurrent manner and contact with each other, the absorption liquid can take away organic matters in the tail gas, the absorption liquid is collected at the bottom of the absorption module 2, and the rest tail gas upwards enters other modules.
Further, as shown in fig. 1, the absorption module 2 is connected with an absorption liquid 102 through a pipeline for introducing the absorption liquid into the absorption module 2. The pipeline between the absorption module 2 and the absorption liquid 102 is further provided with a flow detection device 202, and the flow detection device 202 is used for detecting the flow of the absorption liquid. The pipeline between the absorption module 2 and the absorption liquid 102 is further provided with a first control valve 301, the first control valve 301 is used for controlling the connection or disconnection between the absorption liquid 102 and the absorption module 2, and in other words, the first control valve 301 controls whether the absorption liquid enters the absorption module 2.
In some embodiments, as shown in fig. 1, the bottom of the absorption module 2 may be additionally connected with a device for storing or post-treating the absorption liquid collected at the bottom of the absorption module 2. Further, as shown in fig. 1, the absorption module 2 is connected to the rectifying tower 105 through a pipeline, specifically, the rectifying tower 105 is connected to a liquid outlet of the absorption module 2, and a waste liquid after the absorption liquid contacts with the tail gas enters the rectifying tower 105 through the liquid outlet of the absorption module 2. Further, the absorption module 2 is connected to a first liquid level detection device 203 for detecting the liquid level of the absorption liquid collected at the bottom of the absorption module 2. Be connected with rich liquid pump 8 on the pipeline between rectifying column 105 and the absorption module 2, when the liquid level reachd a certain height, can utilize rich liquid pump 8 to shift the absorption liquid that the bottom of absorption module 2 was catched to rectifying column 105, avoid the bottom of absorption module 2 to collect too much liquid and influence the absorption effect to tail gas.
In some embodiments, as shown in fig. 1, the exhaust gas treatment system further includes a defogging module 3, where the defogging module 3 is located between the absorption module 2 and the adsorption module 5 to remove the absorption liquid remaining in the exhaust gas after contacting the absorption liquid in the absorption module 2. For example, the demister module 3 may be arranged above the absorption module, in other words, behind the absorption module, i.e. in the direction of gas flow; for example, the defogging module and the absorption module may be disposed together for ease of use.
Further, the gas outlet of the absorption module 2 is connected to the inlet of the adsorption module 5. As shown in fig. 1, the demister module 3 and the absorption module 2 are arranged in one device, and it can also be said that the gas outlet of the demister module 3 is connected to the inlet of the adsorption module 5.
Further, a pressurizing module 4 is arranged between the absorption module 2 and the adsorption module 5, and the tail gas entering the adsorption module 5 is pressurized. The adsorbent is loaded in the adsorption module 5, and organic matters in the tail gas can be adsorbed by the adsorbent, so that the tail gas is treated.
Furthermore, the outlet of the adsorption module 5 is connected with the inlet of the emission module 7, and the tail gas treated by the adsorption module 5 enters the emission module 7 for emission. Conceivably, the tail gas treated by the adsorption module 5 can reach the emission standard, and then enters the emission module. The height of the exhaust module 7 is not less than 15m. For example, the height of the exhaust module 7 may be 15m, 20m, 25m, 30m, or the like.
In some embodiments, as shown in fig. 1, a concentration detection device 205 is disposed between the adsorption module 5 and the exhaust module 7. The concentration detection device 205 is used to detect the concentration of organic matters in the exhaust gas before entering the exhaust module, so as to determine whether the exhaust gas reaches the emission standard. If the concentration detection device 205 detects that the emission standard is not met, the adsorption module continues to perform treatment.
Further, the outlet of the adsorption module 5 is connected with the inlet of the adsorption module 5, so that the tail gas can be circularly adsorbed in the adsorption module 5. Furthermore, a control valve is arranged between the outlet of the adsorption module 5 and the inlet of the adsorption module 5 to control the connection or disconnection of the channels.
In some embodiments, the adsorption module may include one adsorption tank. In some embodiments, referring to fig. 1, the adsorption module 5 may include two adsorption tanks arranged in parallel, i.e., a first adsorption tank 51 and a second adsorption tank 52. Only one of the first adsorption tank 51 and the second adsorption tank 52 may be operated, or both of them may be operated.
Furthermore, each adsorption tank is connected with a temperature detection device for detecting the temperature in the adsorption tank. For example, the first canister 51 is connected to a first temperature detection device 206, and the second canister 52 is connected to a second temperature detection device 207.
As shown in fig. 1, the pressurizing module 4 is connected to the first adsorption tank 51, and a third control valve 303 is provided between the bottom vent of the first adsorption tank 51 and the pressurizing module 4. A fifth control valve 305 is provided between the top vent of the first adsorption tank 51 and the discharge module 7. Similarly, a fourth control valve 304 is provided between the bottom vent of the second canister 52 and the pressurizing module 4. A sixth control valve 306 is provided between the top vent of the second canister 52 and the purge module 7. And a ninth control valve 309 and a tenth control valve 310 are provided between the bottom vent port of the first adsorption tank 51 and the bottom vent port of the second adsorption tank 52.
In this embodiment, the tail gas of the adsorption module 5 will not enter the emission module 7 until reaching the emission standard after being detected by the concentration detection device 205. Therefore, the control valves in the adsorption tanks can regulate the movement of the tail gas in the adsorption tanks through the opening and closing of the control valves.
Further, the exhaust gas treatment system further comprises a control system 401. The control system 401 may control the opening or closing of all valves according to the concentration information detected by the concentration detection device 205.
Further, the control system 401 is connected to the condensing module 1, the absorbing module 2, the adsorbing module 5, the pressurizing module 4, the discharging module 7, and all the detecting devices to control the operation of the modules. The control system 401 is capable of controlling all control valves in the exhaust treatment system, such that the control system 401 is capable of controlling communication or blocking between modules, and between devices.
In some embodiments, the tail gas treatment system comprises a nitrogen desorption device connected with the adsorption module for delivering nitrogen into the adsorption module. As shown in fig. 1, the nitrogen desorption device includes a low-pressure nitrogen gas 103 and a nitrogen gas heater 11, a seventh control valve 307 is further provided between the nitrogen desorption device and the first adsorption tank 51, and an eighth control valve 308 is further provided between the nitrogen desorption device and the second adsorption tank 52.
In some embodiments, the exhaust gas treatment system comprises a combustion device 104, and the combustion device 104 is connected to the adsorption module 5 for combusting the organic substances desorbed from the adsorption module 5. Specifically, the piping between the combustion apparatus 104 and the first canister 51 is controlled by a ninth control valve 309, and the piping between the combustion apparatus 104 and the second canister 52 is controlled by a tenth control valve 310.
In this application, methanol loading and unloading storehouse field come contain the methyl alcohol tail gas entering system after, through condensation module, absorption module, defogging module, pressure boost module, adsorption module, discharge through exhaust module after up to standard. And the methanol condensate discharged by the condensation module is collected by a methanol collection tank and discharged to a crude methanol tank through a condensate pump. The absorption liquid enters from the upper part of the absorption tower, the waste liquid is discharged from the bottom of the tower, and the waste liquid is pressurized by a pregnant solution pump and then sent to the rectifying tower. The low-pressure nitrogen enters the adsorption module after being heated by the nitrogen heater, the adsorption module is desorbed, and the desorbed waste gas enters the combustion device. Therefore, the modules and the equipment are connected by pipelines, and the whole system adopts automatic control and is realized by various detection devices and control valves.
The tail gas treatment system of this application embodiment can regard as the organic waste gas recovery clean system in methyl alcohol stack field.
The embodiment of the application also provides a tail gas treatment process, which adopts the tail gas treatment system. As shown in fig. 2, the tail gas treatment process includes the following steps:
s1, introducing tail gas containing volatile organic compounds into a condensation module, and liquefying through fractional condensation treatment of the condensation module to obtain condensate;
s2, enabling the tail gas treated by the condensation module to enter an absorption module, and absorbing part of organic matters in the tail gas by absorption liquid in the absorption module;
s3, the tail gas treated by the absorption module enters the adsorption module, and an adsorbent in the adsorption module is used for adsorbing residual organic matters in the tail gas until the waste gas detected by the detection device reaches the emission standard and then flows into the emission module.
Wherein, in S1, the fractional condensation treatment comprises: first stage refrigeration, second stage refrigeration, and third stage refrigeration, or even more staged processes.
In one embodiment, the first stage refrigeration: the treatment temperature is 0-5 ℃, and first condensate is obtained; the step is mainly used for treating water and heavy components of the tail gas, most of water is intercepted, the possibility of frosting of the water or the heavy components of the tail gas in the two-stage refrigeration at the back is reduced, and therefore the pressure of a tail gas pipeline cannot rise too fast. In the embodiment of the application, the tail gas can recover 75% of methanol through the first-stage refrigeration stage, so that the methanol is primarily recovered.
Further, the second stage of refrigeration: the treatment temperature is-35 to-40 ℃, and a second condensate is obtained; this step makes it possible to liquefy and recover part of the tail gas. The recovery rate of the methanol can reach more than 90 percent when the tail gas passes through the second stage refrigeration stage; meanwhile, part of alkanes with 4-10 carbon atoms, especially alkanes with 4 or 5 carbon atoms, in the tail gas are recovered through a second stage refrigeration stage.
Further, the third stage of refrigeration: the treatment temperature is-70 to-75 ℃, and a third condensate is obtained; and deeply liquefying and recovering part of oil gas. After three-stage condensation, the concentration of organic matters in the tail gas is 5000mg/Nm 3 The following. The recovery rate of the methanol can reach more than 99 percent when the tail gas passes through the third stage refrigeration stage; meanwhile, partial alkane with 4-10 carbon atoms in the tail gas can be recovered, and the alkane especially hasAn alkane of 4 or 5 carbon atoms.
In the embodiment of the application, the first-stage refrigeration is carried out at 0-5 ℃, then the second-stage refrigeration is carried out at-35-40 ℃, and then the third-stage refrigeration is carried out at-70-75 ℃, so that the cascade refrigeration process is more favorable for recovering methanol, and compared with a method of directly refrigerating without cascade refrigeration, the cascade refrigeration of the application can reduce energy consumption and further reduce cost.
In some embodiments, the tail gas treated by the absorption module is treated by the pressurization module and then enters the adsorption module. Furthermore, the pressure boost module carries out frequency conversion adjustment according to the pressure value of tail gas before entering the condensation module, makes system pressure keep stable. The pressurization module can maintain stable delivery of the tail gas. Specifically, the function of the pressurization module is to provide energy for the waste gas to overcome the resistance of a rear pipeline and equipment while ensuring that the pressure of the front-end operation side is within an allowable range, so as to realize stable transportation of the tail gas.
Further, the pressure at the front end of the pressurizing module is kept to be micro negative pressure; furthermore, the pressure before the pressurizing module is controlled in the range of-0.6 KPag to 0KPag, for example, -0.6KPag, -0.5KPag, -0.4KPag, -0.3KPag, -0.2KPag, -0.1KPag or 0KPag, to ensure that the high concentration waste gas does not leak into the environment. The rear end pressure of the pressurizing module is in a range of 3-300 KPag, for example, the tail gas is promoted to be subjected to subsequent adsorption treatment. The pressure in the embodiments of the present application can be measured by a conventional detection method.
In some embodiments, the tail gas treated by the absorption module is treated by the demisting module and then enters the pressurizing module. The demisting module is used for separating a small amount of absorption liquid carried in the tail gas.
In some embodiments, the concentration of organics in the tail gas after treatment by the condensation module is 5000mg/Nm 3 The following.
And after the adsorbent adsorbs the residual organic matters in the tail gas, introducing nitrogen to desorb the organic matters in the adsorbent, and then introducing the adsorbent into a combustion device to perform combustion treatment so as to remove the organic matters.
In one embodiment, in conjunction with fig. 1 and 2, the methanol in the methanol loading and unloading yard is treated using a tail gas treatment system, the tail gas treatment process is described in detail below.
The methanol-containing tail gas of the methanol loading and unloading stack field 101 enters a gas collection main pipe after being collected, a pressure detection device 201 is arranged on the gas collection main pipe, when the pressure on the gas collection main pipe is detected to reach a certain set value, a control system 401 sends an instruction, a control valve 302 is opened, a pressurization module 4 is opened, and the tail gas is introduced into a tail gas treatment system.
The tail gas firstly enters a condensation module 1, the temperature of the tail gas is reduced by the module through a continuous cooling method, the temperature of the tail gas is reduced to the dew point temperature corresponding to each component under the pressure of each component, and different components of the tail gas are condensed into liquid in a grading manner. The condensing module 1 can adopt a compressor for mechanical refrigeration and can also utilize liquid nitrogen as a cold source. After the tail gas passes through the module, about more than 95% of methanol and other organic matters are condensed and recovered, and then enter the methanol collection tank 10, and the rest tail gas enters the absorption module 2.
Absorption liquid in the absorption module 2 contacts with tail gas in a countercurrent mode, residual methanol in the tail gas is absorbed by the absorption liquid and enters a liquid phase, waste liquid enters a tower kettle of the absorption tower, and the tail gas enters the demisting module 3. The defogging module 3 may be provided separately or may be built in the absorption module 2. The demisting module 3 can separate a small amount of absorption liquid carried in the tail gas.
Tail gas after the defogging gets into pressure boost module 4, and pressure boost module 4 can carry out frequency conversion according to the detected value of pressure measurement 201 and adjust, guarantees that the pressure stability of gas collection house steward is in certain scope, avoids influencing the normal work of front end methyl alcohol loading and unloading stack field 101.
The tail gas enters the adsorption module 5 after being pressurized by the pressurization module 4, the module is provided with two first adsorption tanks 51 and two second adsorption tanks 52, each adsorption tank is loaded with an adsorbent, the tail gas firstly enters the first adsorption tank 51, at the moment, the third control valve 303 and the fifth control valve 305 are opened, the fourth control valve 304, the sixth control valve 306, the seventh control valve 307, the eighth control valve 308, the ninth control valve 309 and 310 are closed, organic matters which are not condensed and absorbed are adsorbed by the adsorbent, and are separated from air in the tail gas. For example, the types of adsorbents include, but are not limited to, activated carbon, silica gel, molecular sieves, porous resins. A concentration detection device 205 is arranged on a pipeline between the adsorption module 5 and the emission module 7, when the concentration of organic matters in the tail gas is detected to exceed the emission standard, a third control valve 303 and a fifth control valve 305 are closed, a fourth control valve 304 and a sixth control valve 306 are opened, the tail gas enters a second adsorption tank 52, a seventh control valve 307 and a ninth control valve 309 are opened, low-pressure nitrogen 103 is heated by a nitrogen heater 11 and then enters a first adsorption tank 51, a first temperature detection device 206 and a second temperature detection device 207 are respectively arranged on the first adsorption tank 51 and the second adsorption tank 52, and when the temperature measured by the first temperature detection device 206 reaches 120 ℃, the temperature is stabilized for a period of time, and the organic matters adsorbed in the adsorbent are desorbed by the nitrogen and enter a combustion device 104 for treatment. After the desorption is completed, the nitrogen heater 11 is closed, low-pressure nitrogen is continuously introduced to cool the first adsorption tank 51, and when the temperature measured by the first temperature detection device 206 is reduced to 30 ℃, the seventh control valve 307 and the ninth control valve 309 are closed, and the first adsorption tank 51 is in a standby state.
When the concentration of the organic matters in the tail gas is detected to exceed the emission standard, the fourth control valve 304 and the sixth control valve 306 are closed, the third control valve 303 and the fifth control valve 305 are opened, the tail gas enters the first adsorption tank 51, meanwhile, the eighth control valve 308 and the tenth control valve 310 are opened, the low-pressure nitrogen 103 is heated by the nitrogen heater 11 and then enters the second adsorption tank 52, when the temperature measured by the second temperature detection device 207 reaches 120 ℃, the temperature is stabilized for a period of time, and the organic matters adsorbed in the adsorbent are desorbed by the nitrogen and enter the combustion device 104 for treatment. After the desorption is completed, the nitrogen heater 11 is turned off, low-pressure nitrogen is continuously introduced to cool the first adsorption tank 51, when the temperature measured by the first temperature detection device 206 is reduced to 30 ℃, the eighth control valve 308 and the tenth control valve 310 are turned off, and the second adsorption tank 52 is in a standby state.
And the tail gas after being treated reaches the standard enters the emission module 7 and is emitted to the atmosphere through the emission module 7. In the embodiment of the application, the treatment is carried out through the adsorption module 5The content of non-methane total hydrocarbon in the tail gas entering the discharge module 7 is less than or equal to 120mg/m 3 . Therefore, the catalyst meets the national standard GB 31570-2015 discharge Standard for pollutants for the Petroleum refining industry or GB 31571-2015 discharge Standard for pollutants for the petrochemical industry, and the content of non-methane total hydrocarbons is less than or equal to 120mg/m 3 。
The methanol collection tank 10 is provided with a second liquid level detection device 204, when the second liquid level detection device 204 reaches a certain set value, the control system 401 sends an instruction to open the condensate pump 9 and convey methanol condensate to the crude methanol tank, and when the second liquid level detection device 204 falls to a certain set value, the control system 401 sends an instruction to close the condensate pump 9.
The flow rate detection device 202 and the first control valve 301 are arranged on the absorption liquid pipeline, and the flow rate of the absorption liquid is controlled at a set value through the control system 401 so as to control the amount of the absorption liquid in the absorption module 2. The flow rate of the absorption liquid needs to meet the minimum liquid holdup of the packing; further, liquid-to-gas ratio (m) 3 /m 3 ) The amount of the organic solvent is controlled to be 0.002 to 0.008, for example, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007 or 0.008. For example, the absorption liquid is selected from, but not limited to, desalinated water, fresh water, production water, preferably desalinated water.
The tower kettle of the absorption tower is provided with a first liquid level detection device 203, when the first liquid level detection device 203 reaches a certain set value, the control system 401 sends an instruction to open the collection tank 10 and convey waste liquid to the rectifying tower 105, and when the first liquid level detection device 203 falls to a certain set value, the control system 401 sends an instruction to close the collection tank 10.
To sum up, adopt the tail gas processing system of this application, can effectively retrieve most methyl alcohol in the methyl alcohol tail gas, wherein step refrigeration not only can effectively improve recovery efficiency, can also reduce the energy consumption. By adopting the tail gas treatment system, the concentration of non-methane total hydrocarbons in the exhaust gas can be reduced, the exhaust gas is ensured to meet the national and local atmospheric pollutant emission index requirements, and good social and economic benefits are achieved.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to the related descriptions of other embodiments.
The above detailed description is made on a volatile organic compound-containing tail gas treatment system and a tail gas treatment process provided in the embodiments of the present application, and specific examples are applied herein to explain the principle and the implementation manner of the present application, and the description of the above embodiments is only used to help understanding the method and the core concept of the present application; meanwhile, for those skilled in the art, according to the idea of the present application, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (12)
1. A volatile organic compound-containing tail gas treatment system is characterized by comprising:
the condensation module is a multi-stage condensation module and is used for carrying out fractional condensation treatment on tail gas entering the condensation module;
the gas outlet of the condensation module is connected with the gas inlet of the absorption module; the absorption module is internally provided with an absorption liquid nozzle, so that tail gas entering the absorption module is contacted with absorption liquid;
the gas outlet of the absorption module is connected with the inlet of the absorption module;
and the outlet of the adsorption module is connected with the inlet of the discharge module.
2. The voc-containing tail gas treatment system according to claim 1, wherein a pressurizing module is disposed between the absorption module and the adsorption module to pressurize the tail gas entering the adsorption module.
3. The system of claim 1, wherein a detection device is disposed between the adsorption module and the emission module, and the detection device is configured to detect the concentration of organic compounds in the exhaust gas before entering the emission module.
4. The voc-containing tail gas treatment system according to claim 1, wherein the outlet of the adsorption module is connected to the inlet of the adsorption module.
5. The volatile organic compound-containing tail gas treatment system according to claim 1, further comprising a rectifying tower, wherein the rectifying tower is connected with the liquid outlet of the absorption module, and waste liquid obtained after the absorption liquid is contacted with the tail gas enters the rectifying tower through the liquid outlet of the absorption module.
6. The voc-containing tail gas treatment system according to claim 1, further comprising a collection tank connected to the liquid outlet of the condensing module; the collecting tank is used for collecting liquid obtained by condensation of the condensation module.
7. The voc-contained tail gas treatment system according to claim 1, wherein the absorption liquid spray opening is located above the absorption module, and the flow direction of the absorption liquid at the absorption liquid spray opening is opposite to the flow direction of the gas.
8. The system of claim 1, further comprising a nitrogen desorption device connected to the adsorption module for delivering nitrogen to the adsorption module; and/or
Still include burner, burner with the adsorption module is connected.
9. The voc-containing tail gas treatment system according to claim 2, further comprising a control system coupled to at least one of the condensing module, the absorbing module, the adsorbing module, the pressurizing module, the discharging module, and the detecting device for controlling operation of the modules.
10. An exhaust gas treatment process, characterized in that the exhaust gas treatment system according to any one of claims 1 to 9 is used, comprising the steps of:
introducing the tail gas containing volatile organic compounds into a condensation module, and liquefying through fractional condensation treatment of the condensation module to obtain condensate; wherein the fractional condensation process comprises: performing primary refrigeration at the treatment temperature of 0-5 ℃ to obtain first condensate; performing secondary refrigeration at the treatment temperature of-35 to-40 ℃ to obtain second condensate; performing tertiary refrigeration at the treatment temperature of-70 to-75 ℃ to obtain third condensate;
the tail gas treated by the condensation module enters an absorption module, and absorption liquid in the absorption module absorbs part of organic matters in the tail gas;
the process tail gas after absorption module handles gets into adsorption module, adsorbent in the adsorption module is arranged in adsorbing the surplus organic matter in the tail gas, flows into emission module after reaching emission standard through detection device detection exhaust.
11. The tail gas treatment process according to claim 10, wherein the tail gas treated by the absorption module is treated by the pressurization module and then enters the adsorption module; the pressurization module carries out frequency conversion adjustment according to the pressure value of the tail gas before entering the condensation module, so that the system pressure is kept stable;
the tail gas treated by the absorption module is treated by the demisting module and then enters the pressurizing module; and the demisting module is used for separating absorption liquid carried in the tail gas.
12. The tail gas treatment process of claim 10, wherein the concentration of organic matter in the tail gas treated by the condensation module is 5000mg/Nm 3 The following;
and after adsorbing the residual organic matters in the tail gas, the adsorbent is introduced with nitrogen to desorb the organic matters in the adsorbent, and then introduced with a combustion device to be combusted so as to remove the organic matters.
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