CN113357541A - Liquid storage tank tail gas treatment system and method - Google Patents
Liquid storage tank tail gas treatment system and method Download PDFInfo
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- CN113357541A CN113357541A CN202010138241.8A CN202010138241A CN113357541A CN 113357541 A CN113357541 A CN 113357541A CN 202010138241 A CN202010138241 A CN 202010138241A CN 113357541 A CN113357541 A CN 113357541A
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/08—Pipe-line systems for liquids or viscous products
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D1/00—Pipe-line systems
- F17D1/02—Pipe-line systems for gases or vapours
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D3/00—Arrangements for supervising or controlling working operations
- F17D3/01—Arrangements for supervising or controlling working operations for controlling, signalling, or supervising the conveyance of a product
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D5/00—Protection or supervision of installations
- F17D5/005—Protection or supervision of installations of gas pipelines, e.g. alarm
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23G—CREMATION FURNACES; CONSUMING WASTE PRODUCTS BY COMBUSTION
- F23G7/00—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals
- F23G7/06—Incinerators or other apparatus for consuming industrial waste, e.g. chemicals of waste gases or noxious gases, e.g. exhaust gases
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Abstract
The invention relates to the field of gas treatment, in particular to a liquid storage tank tail gas treatment system and a method thereof, and discloses a liquid storage tank tail gas treatment system which comprises a purification unit, a pressure regulating unit, a tail gas treatment unit and a control unit, wherein the purification unit is communicated with the top of a liquid storage tank, the pressure regulating unit comprises an air extraction device and an air supplement device, the air extraction device is communicated with the purification unit, the air supplement device is communicated with the top of the liquid storage tank, the tail gas treatment unit comprises a tail gas recovery device and a tail gas incineration device which are arranged in parallel, and the control unit comprises a first controller and a second controller. The system realizes the whole-process closed recovery of the tank top tail gas of the sulfur-containing sewage in the petrochemical plant, the safety control of the liquid storage tank and the recovery of high-value light hydrocarbon, has obvious effect, and can be popularized and applied in similar devices in petrochemical industry, coal chemical industry and the like.
Description
Technical Field
The invention relates to the field of gas treatment, in particular to a liquid storage tank tail gas treatment system and a method thereof.
Background
The sulfur-containing sewage raw material tank of the refinery sewage stripping device is generally a vault storage tank, and the storage tank forms tank top tail gas due to the fact that large breathing gas generated by liquid feeding, small breathing gas generated by rising of air temperature, evaporation gas generated by the fact that feeding temperature is higher than material temperature in the tank and dissolved gas released by high-pressure feeding during operation.
According to the related technical data, the tail gas at the top of the sulfur-containing sewage tank has the characteristics of complex gas composition, large pollutant concentration fluctuation, unstable discharged gas quantity and the like. If a certain device adopts an alkali washing absorption tail gas treatment process, the concentration of VOCs in the treated exhaust gas reaches 67600mg/m3And the emission concentration of VOCs is high, so that the requirements of new environmental protection standard 'emission standard of pollutants for petroleum refining industry' GB31570-2015 can not be met.
At present, the technologies for treating the tail gas of the sulfur-containing sewage tank in a refinery mainly comprise a combustion method, an adsorption method, a chemical absorption method and a combination method. From industrial application, the tail gas treatment technology cannot completely eliminate the pollution of the tail gas on the top of the tank to the environment. The combustion method is suitable for treating low-concentration organic waste gas. For the malodorous gas on the tank top which has high hydrocarbon content and high sulfide concentration and is in a flammable and explosive area, explosion-proof measures and economy are considered. The adsorption method is a traditional and still developing deodorization technique. Because the adsorption capacity of the adsorption method is low, the saturated adsorbent generates secondary pollution no matter the saturated adsorbent is buried or regenerated, and the replacement of the adsorbent is troublesome. The chemical absorption method can be classified into an alkali absorption method, an acid absorption method, a chemical oxidation method, and airCatalytic oxidation method, metal ion catalytic oxidation method, etc. have wide application, but the effect of removing organic sulfide and non-methane total hydrocarbon is not good. Part of factories send tail gas after chemical absorption to a sulfur incinerator for treatment, which causes energy waste and easily causes sulfur flue gas SO2The emission exceeds the standard.
According to the published data, the complete technology of 'low-temperature diesel oil absorption-desulfurization homogenization-catalytic oxidation (Tg-CO)' and 'low-temperature diesel oil absorption-homogenization-RTO (Tg-RTO)' developed by the compliant research institute can effectively remove organic sulfides and non-methane total hydrocarbons. However, the technical process is relatively complex, the investment is high, and the application condition in the oil refining industry is not ideal. Meanwhile, the sewage tank is provided with the breather valve, ammonia and hydrogen sulfide in tail gas easily generate ammonium bisulfide crystals on the sealing surface of the breather valve, the sealing surface of the breather valve is damaged, gas leakage at the breather valve is caused, and VOCs are discharged in an unorganized mode.
According to published data in journal of 8 months in 2018 of China and foreign energy, the tank top exhaust gas recovery automatic control integration technology of a sulfur-containing sewage tank of Guangzhou petrochemical refinery utilizes a steam jet compressor to pump tank top tail gas to a low-pressure gas system, and when the content of oxygen before the steam jet compressor is detected to be lower than a set value, the tail gas is pumped to the low-pressure gas system through a steam ejector to realize the totally-closed recovery of the tail gas. However, after the technology is practically applied, the problems of high energy consumption, high operation noise of a steam jet compressor, unstable pressure control of a sulfur-containing sewage tank and the like exist, and when the oxygen content is higher than a set value, a gate valve entering a low-tile system cannot be cut off in time, so that the technology is not beneficial to safe production.
Disclosure of Invention
The invention aims to solve the problems of environmental pollution caused by unorganized discharge of VOCs in the top of a liquid storage tank, unstable pressure at the top of the liquid storage tank and potential safety hazards caused by overhigh oxygen content in the process of recovering light hydrocarbon in the prior art, and provides a liquid storage tank tail gas treatment system and a method thereof.
In order to achieve the above object, a first aspect of the present invention provides a liquid storage tank tail gas treatment system, which comprises a purification unit, a pressure regulating unit, a tail gas treatment unit and a control unit, the purification unit is communicated with the top of the liquid storage tank, the pressure regulating unit comprises an air extracting device and an air supplementing device, the air extractor is communicated with the purification unit, the air supply device is communicated with the top of the liquid storage tank, the tail gas treatment unit comprises a tail gas recovery device and a tail gas incineration device which are arranged in parallel, the control unit comprises a first controller and a second controller, the first controller controls the air extraction device to be communicated with a tail gas recovery device or a tail gas incineration device of the tail gas treatment unit according to the oxygen content of the outlet gas of the air extraction device, and the second controller controls the operation of the air exhaust device and the air supplement device according to the pressure at the top of the liquid storage tank.
Preferably, the system further comprises a liquid seal tank, a gas inlet of the liquid seal tank is communicated with the top of the liquid storage tank, and a gas outlet of the liquid seal tank is communicated with the atmosphere.
The invention provides a liquid storage tank tail gas treatment method, which comprises the steps of purifying the tail gas at the top of a liquid storage tank, pressurizing the purified tail gas, and recovering light hydrocarbon from the pressurized tail gas when the oxygen content in the pressurized tail gas is lower than 2 volume percent; when the oxygen content in the pressurized tail gas is not lower than 2 volume percent, burning the pressurized tail gas;
when the pressure at the top of the liquid storage tank is lower than the set pressure of the liquid storage tank, gradually reducing the instantaneous amount of the tail gas to be purified, and when the instantaneous amount of the tail gas to be purified is reduced to the minimum value and the pressure is still lower than the set pressure of the liquid storage tank, supplementing inert gas to the top of the liquid storage tank and gradually increasing the instantaneous ventilation amount of the inert gas; when the pressure at the top of the liquid storage tank is higher than the set pressure, the instantaneous ventilation of the inert gas supplemented to the top of the liquid storage tank is gradually reduced until the instantaneous ventilation is zero, and when the instantaneous ventilation of the inert gas supplemented to the top of the liquid storage tank is zero and the pressure is still higher than the set pressure of the liquid storage tank, the instantaneous quantity of the tail gas to be purified is gradually increased until the instantaneous quantity is maximum.
Preferably, the liquid in the liquid storage tank is sulfur-containing sewage, the tail gas contains at least one gas selected from hydrogen sulfide, ammonia gas, mercaptan, thioether and aromatic compounds, and the purification mode comprises an alkali liquor absorption method, an alkali adsorption method or an activated carbon adsorption method.
Preferably, the light hydrocarbon recovery mode comprises that the pressurized tail gas is sent into a low-pressure gas system and then is compressed and sent into a high-pressure gas system, and then light hydrocarbon components in the tail gas are recovered.
Through the technical scheme, the system and the method for treating the tail gas of the liquid storage tank can realize that:
1. the tail gas of the tank top of the sulfur-containing sewage is deodorized and then is delivered to a low-pressure gas system through a pressurizing facility, so that the closed recovery of the tail gas of the tank top is realized, the possibility of the leakage of the tail gas of the tank top is eliminated by the arrangement of a liquid seal tank, the problem of the unorganized discharge of VOCs (volatile organic compounds) in the tail gas of the tank top of the sulfur-containing sewage is solved, the peripheral working environment is improved, and the clean production of the device is realized.
2. The air supply device for the inert gas of the sulfur-containing sewage tank, the frequency conversion control of the tail gas supercharger and the non-low point arrangement of pipelines realize the stable pressure of the sulfur-containing sewage tank. The positive and negative pressure water seal of the sulfur-containing sewage tank greatly reduces the overpressure of the sewage tank and the possibility of oxygen entering, thereby realizing the safety control of the sewage tank.
3. And the tail gas at the top of the sulfur-containing sewage tank is desulfurized and then is sent to a low-pressure gas system, and is then merged into a high-pressure gas system after subsequent treatment, so that high-value light hydrocarbon recovery is realized.
4. The pressure regulating unit realizes the automatic control of the pressure of the sulfur-containing sewage tank, and reduces the workload of external operation.
The results prove that the system and the method for treating the tail gas of the liquid storage tank can stably control the pressure of the sulfur-containing sewage tank to be 0.1-1.0 kPa; the oxygen content of the tank top tail gas meets the requirement of being lower than 2 percent, the tank top tail gas is completely pressurized and sent to a low-pressure gas system for recycling, the fuel gas recovery amount is about 50kg/h, and the high-value light hydrocarbon recovery effect is obvious. The invention has simple operation and low operation cost, realizes the closed discharge of the tank top tail gas, and can be popularized and applied in petrochemical industry, coal chemical industry and other similar devices.
Drawings
FIG. 1 is a flow chart of the present invention for treating the tail gas of a liquid storage tank.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
Unless otherwise stated, all references to pressure in the present invention are to gauge pressure.
In the invention, the liquid storage tank comprises an acid water tank in the petrochemical fields of oil refining and petrochemical industry, coal chemical industry and the like, and for example, the liquid storage tank can be a sulfur-containing sewage tank.
In a first aspect of the present invention, there is provided a liquid storage tank tail gas treatment system, as shown in fig. 1, the system includes a purification unit 1, a pressure regulating unit 2, a tail gas treatment unit 3 and a control unit 4, the purification unit 1 is communicated with the top of the liquid storage tank 5, the pressure regulating unit 2 comprises an air extracting device 21 and an air supplementing device 22, the air extracting device 21 is communicated with the purifying unit 1, the air supplementing device 22 is communicated with the top of the liquid storage tank 5, the tail gas treatment unit 3 comprises a tail gas recovery device 31 and a tail gas incineration device 32 which are arranged in parallel, the control unit 4 comprises a first controller 41 and a second controller 42, the first controller 41 controls the air extractor 21 to be communicated with the tail gas recovery device 31 or the tail gas incineration device 32 of the tail gas treatment unit 3 according to the oxygen content of the outlet gas of the air extractor 21, the second controller 42 controls the operation of the air extracting device 21 and the air supplementing device 22 according to the pressure at the top of the liquid storage tank 5.
According to a preferred embodiment of the invention, the system further comprises a liquid seal tank 6, a gas inlet of the liquid seal tank 6 is communicated with the top of the liquid storage tank 5, and a gas outlet of the liquid seal tank 6 is communicated with the atmosphere. The liquid in the liquid seal tank 6 is selected from a wide range, such as water or saline compound solution, and is preferably water from the viewpoint of reducing the cost of subsequent sewage treatment.
The form of the tank body of the liquid seal tank 6 is widely selected in the invention, and can be selected conventionally in the field as long as the purpose of the invention can be achieved.
Further preferably, the invention adopts a double water seal design water seal tank, the water in the water seal tank is long running water, and the invention has no special limitation on the embodiment of the long running water as long as the water in the water seal tank can achieve continuous supplement and continuous discharge, and the water flow rate of the continuous supplement or continuous discharge is preferably 0-0.3 t/h. Under the above embodiment, the generated sewage directly enters the liquid storage tank 5, so that the sewage is timely and nearby treated, and the positive and negative pressure water seals greatly reduce the overpressure of the liquid storage tank 5 and the possibility of oxygen entering, so that the safety control of the sewage tank 5 is realized. In the preferred embodiment, the liquid storage tank 6 eliminates the problem of unorganized emission of tail gas VOCs, and is more beneficial to keeping the surrounding environment of the liquid storage tank clean for a long time.
In the invention, by combining the first controller 41 and the second controller 42, the whole process of closed recovery of the tail gas is realized, the possibility of tail gas leakage at the top of the tank is eliminated, the problem of unorganized tail gas emission is solved, and the working environment around the liquid storage tank is improved; secondly, the pressure at the top of the liquid storage tank is stable, the possibility of air entering the liquid storage tank is eliminated, and the liquid storage tank realizes safety control; and thirdly, the oxygen content in the tail gas to be recycled is accurately controlled, so that the safe operation of the equipment during the recycling of the light hydrocarbon is guaranteed.
According to the present invention, preferably, the storage tank 5 is a sulfur-containing sewage storage tank, and the sulfur-containing sewage tank referred to in the present invention refers to a storage tank for receiving sulfur-containing sewage discharged from each equipment inside a refinery, the equipment includes, but is not limited to, equipment of each unit such as atmospheric pressure, catalytic cracking, coking, hydrofining, hydrocracking, and the like, and the equipment includes, but is not limited to, various vessels such as an atmospheric pressure distillation tower, a vacuum distillation tower, a stripping pressure distillation tower, a pump, a heat exchanger, a filter, a raw material buffer tank, and a low pressure separator. The tank body of the sulfur-containing sewage tank is not particularly limited, and is generally a vault liquid storage tank in an oil refining chemical plant, as shown in figure 1.
When the storage tank 5 is a sulfur-containing wastewater storage tank according to the present invention, the purification unit 1 preferably includes a desulfurization device, and the present invention is applied to the sulfur-containing wastewater storage tankThe selection range of the desulfurization device is wide, and the tail gas at the top of the liquid storage tank is purified to reduce the content of sulfur-containing and nitrogen-containing organic waste gas in the tail gas, wherein the organic waste gas is at least one of hydrogen sulfide, ammonia, mercaptan, thioether and aromatic compounds. Preferably, the method for reducing the organic waste gas by the desulfurization device may be a physical method and/or a chemical method. The physical method is not particularly limited in the present invention as long as the reduction of the content of the organic off-gas in the exhaust gas can be achieved, and for example, the physical method includes an activated carbon adsorption method, a membrane separation method, and the like. The chemical method is not particularly limited in the present invention, and may be a method known to those skilled in the art as long as the reduction of the content of the oil gas exhaust gas in the exhaust gas can be achieved, and for example, the chemical method includes an alkaline absorption method, an oxidation method, and a combustion method. The material for realizing alkalinity in the alkaline absorption method includes, but is not limited to, calcium hydroxide, sodium hydroxide, potassium hydroxide and ammonia water, and the device for realizing alkaline absorption method includes, but is not limited to, an alkaline absorption tower, which can be a conventional choice in the art, such as a packed tower or a plate tower. In the present invention, the oxidation method and the combustion method are not particularly limited, and the oxidation method may be selected so long as the content of the organic waste gas in the off-gas can be reduced by the oxidation reaction, and the combustion method may be selected so long as the content of the organic waste gas in the off-gas can be reduced by the combustion. In the invention, the content of the hydrogen sulfide in the tail gas is reduced to 10mg/m through the purification of the desulphurization device3The conditions for enabling entry into the low pressure gas system are thus achieved.
According to a preferred embodiment of the present invention, the storage tanks 5 are one or more in parallel, and preferably fire arresters 7 are arranged between each storage tank 5 and the purification unit 1, as shown in fig. 1. The flame arrester has a wide selection range, and only the safety protection function of the flame arrester can be realized. By adopting the preferred embodiment, the tail gas in the sulfur-containing sewage tank is converged and enters the main pipe before entering the desulfurization device, which is more beneficial to realizing the centralized treatment of the tail gas; fire arrestors are arranged on each branch line, so that the safe operation of the parallel connection of a plurality of tanks is realized, the safe operation of the whole plant is more facilitated, and the potential safety hazard is eliminated.
According to a preferred embodiment of the present invention, the gas extraction device 21 is selected from a wide range of gas extraction devices, which can be selected conventionally in the art, and comprises at least one of a variable frequency water ring vacuum pump, a variable frequency gas compressor and a steam ejector, preferably a variable frequency water ring vacuum pump. By adopting the preferred embodiment, the exhaust gas from the purification unit can be pumped, compressed and exhausted, the vacuum operation is more favorably realized, the whole process of the exhaust gas is closed without leakage, and the variable frequency adjustment of the instantaneous throughput of the gas is realized.
According to the present invention, preferably, said tail gas recovery device 31 comprises a low pressure gas system. The low pressure gas system of the present invention is a gas collection system well known to those skilled in the art. Further preferably, the pressure of the low pressure gas system is 5 to 10kPa, the system contains a gas component selected from at least one of methane, hydrogen, nitrogen, ethane and propane, and the methane content is 50 to 60 vol%.
The exhaust gas incinerator 32 is not particularly limited in the present invention, as long as all combustible components of the exhaust gas can be burned. In the embodiment of the invention, in order to fully utilize the existing equipment, the tail gas incineration device is selected to be a sulfur incinerator nearby.
The gas supplementing device is not particularly limited, can be selected conventionally in the field, and can be an inert gas tank, and the volume of the inert gas tank is not particularly limited as long as the purpose of continuously supplementing the inert gas to the tank top of the liquid storage tank can be achieved. The pressure in the inert gas tank is not particularly limited, and may be higher than the pressure in the liquid storage tank to which the inert gas tank is connected, so that the inert gas can be continuously supplied to the top of the liquid storage tank. According to the present invention, the inert gas is preferably a gas that does not participate in the reaction, and is preferably at least one of nitrogen, neon, and argon, and further preferably nitrogen in order to reduce costs.
The operation of the first controller and the second controller is realized through a logic control program, and the device for implementing the logic control program is not particularly limited and can be selected conventionally in the field. In the present invention, the first controller 41 and the second controller 42 may be controlled by the same logic control program, or may be independently controlled by different logic control programs, for example, DCS or SIS interlocking system, and those skilled in the art know how to implement the logic control function, and the selected devices may be as long as the purpose of the present invention can be achieved.
According to a preferred embodiment of the present invention, the first controller 41 is configured to control: when the oxygen content in the gas at the outlet of the air extractor 21 is lower than 2 vol%, the air extractor 21 is communicated with a tail gas recovery device 31 of the tail gas treatment unit, and the tail gas is pumped to a low-pressure gas system, then is compressed at downstream and then is sent to a high-pressure gas system, so that high-value light hydrocarbon components are recycled; when the oxygen content in the gas at the outlet of the air extractor 21 is not lower than 2 vol%, the air extractor 21 is communicated with the tail gas incineration device 32, the tail gas is automatically switched to the sulfur incinerator through a logic control program, and the emission concentration of VOCs in the flue gas after high-temperature incineration of the sulfur incinerator is 10mg/m3And the environment-friendly emission standard is met. Under this preferred embodiment, realized accurate detection air exhaust device 21 export in the tail gas oxygen content, more be favorable to the safe operation of low pressure gas system.
The method for detecting the oxygen content is not particularly limited, and those skilled in the art can select the method according to actual needs as long as the method can detect the oxygen content in the tail gas at the outlet of the air extractor 21. In the embodiment of the present invention, an oxygen content analyzer is selected as an exemplary illustration for detecting the oxygen content, as shown in fig. 1.
According to a preferred embodiment of the present invention, the second controller 42 is configured to control: when the pressure at the top of the liquid storage tank 5 is lower than the set pressure of the liquid storage tank 5, gradually reducing the operation frequency of the air extractor 21, and when the operation frequency of the air extractor 21 is reduced to the minimum value and the pressure is still lower than the set pressure of the liquid storage tank 5, communicating the top of the liquid storage tank 5 with the air compensator 22, and gradually increasing the instantaneous ventilation between the top of the liquid storage tank 5 and the air compensator 22; when the pressure at the top of the liquid storage tank 5 is higher than the set pressure, the instantaneous ventilation between the top of the liquid storage tank 5 and the air supplementing device 22 is gradually reduced until the communication between the top of the liquid storage tank 5 and the air supplementing device 55 is cut off, and when the instantaneous ventilation between the top of the liquid storage tank 5 and the air supplementing device 22 is zero and the pressure is still higher than the set pressure of the liquid storage tank 5, the operation frequency of the air extracting device 21 is gradually increased. Under the preferred embodiment, the pressure on the top of the liquid storage tank is more stable, so that the safety control of the liquid storage tank is ensured.
The invention adopts the way of matching the air extractor and the air compensator to control the pressure of the liquid storage tank. In the embodiment of the invention, the air pumping device adopts a water ring vacuum pump as an exemplary illustration; the air make-up device is exemplified by a nitrogen pressure control system. The nitrogen pressure control system adopts a mode of combining self-operated valve control and pressure control, and performs frequency conversion range division control on the top pressure of the liquid storage tank with the frequency conversion water ring vacuum pump, so as to realize stable control on the top pressure of the liquid storage tank. The invention has no special limitation on the self-operated valve and the pressure control valve, and is equipment well known by the technical personnel in the field, and the self-operated valve and the pressure control valve are combined to realize the automatic control of the pressure of the liquid storage tank, thereby reducing the workload of external operation.
The invention provides a liquid storage tank tail gas treatment method, which comprises the steps of purifying the tail gas at the top of a liquid storage tank, pressurizing the purified tail gas, and recovering light hydrocarbon from the pressurized tail gas when the oxygen content in the pressurized tail gas is lower than 2 volume percent; when the oxygen content in the pressurized tail gas is not lower than 2 volume percent, burning the pressurized tail gas;
when the pressure at the top of the liquid storage tank is lower than the set pressure of the liquid storage tank, gradually reducing the instantaneous amount of the tail gas to be purified, and when the instantaneous amount of the tail gas to be purified is reduced to the minimum value and the pressure is still lower than the set pressure of the liquid storage tank, supplementing inert gas to the top of the liquid storage tank and gradually increasing the instantaneous ventilation amount of the inert gas; when the pressure at the top of the liquid storage tank is higher than the set pressure, the instantaneous ventilation of the inert gas supplemented to the top of the liquid storage tank is gradually reduced until the instantaneous ventilation is zero, and when the instantaneous ventilation of the inert gas supplemented to the top of the liquid storage tank is zero and the pressure is still higher than the set pressure of the liquid storage tank, the instantaneous quantity of the tail gas to be purified is gradually increased until the instantaneous quantity is maximum.
According to a preferred embodiment of the present invention, said stepwise decreasing of the instantaneous amount of the tail gas subjected to purification is such that the instantaneous amount of the tail gas subjected to purification is decreased to a minimum value within 1-2 minutes; the step-by-step increase of the instantaneous amount of the tail gas to be purified is carried out such that the instantaneous amount of the tail gas to be purified is increased to a maximum value within 1-2 minutes, wherein the maximum value can be 600-3H is used as the reference value. Under the preferred embodiment, the stability of the top pressure of the liquid storage tank is more favorably and rapidly realized, and the safety control of the liquid storage tank is ensured.
In the invention, when the air extracting device is a frequency conversion device, the minimum value is a flow value when the running frequency of the frequency conversion device is 0. In order to avoid the plant stopping, it is common to keep the plant running continuously, preferably with a minimum operating frequency of said frequency conversion means such that the exhaust gas passes through a flow rate of 7-10% of the flow rate at the maximum operating frequency, for example 50-60m3H is used as the reference value. The maximum value is the flow value when the operation frequency of the frequency conversion device is full frequency (i.e. the maximum value of the set operation frequency, the maximum working frequency), and is preferably 600-650m3/h。
According to a preferred embodiment of the present invention, the instant ventilation of the inert gas is gradually increased to make the pressure at the top of the liquid storage tank reach the set pressure of the liquid storage tank within 5-10 minutes, and the instant ventilation of the inert gas is gradually decreased to make the instant ventilation of the supplementary inert gas at the top of the liquid storage tank be zero within 1-2 minutes. Under the preferred embodiment, the stability of the top pressure of the liquid storage tank is more favorably and rapidly realized, and the safety control of the liquid storage tank is ensured.
In the invention, the set pressure of the liquid storage tank depends on the liquid seal pressure of the liquid seal tank. According to the present invention, the set pressure of the liquid storage tank is preferably 0 to 1.5kPa, and more preferably 0.1 to 1 kPa.
According to the invention, the liquid in the liquid storage tank is sulfur-containing sewage, the tail gas contains at least one gas selected from hydrogen sulfide, ammonia, mercaptan, thioether and aromatic compounds, and the purification mode comprises a lye absorption method, an alkaline adsorption method or a membrane separation method.
According to the invention, preferably, the pressure increase increases the pressure of the cleaned exhaust gas to 20-40 kPa.
According to the invention, preferably, the light hydrocarbon recovery mode comprises the steps of sending the pressurized tail gas into a low-pressure gas system, then compressing the tail gas and sending the tail gas into a high-pressure gas system, and further recovering light hydrocarbon components in the tail gas. In the present invention, the high pressure gas system is a gas collecting system known to those skilled in the art, preferably, the pressure of the high pressure gas system is 0.5-0.6MPa, and the gas composition of the high pressure gas system is the low pressure gas system as described above, which is not described again.
In accordance with a preferred embodiment of the present invention the inert gas is delivered into the liquid reservoir from a location above the liquid level at the top of the liquid reservoir. The adoption of the implementation mode is more beneficial to keeping the pressure at the top of the liquid storage tank stable.
According to the liquid storage tank tail gas treatment system provided by the invention, the tank top of the sulfur-containing sewage is optimized and modified, and the tail gas variable-frequency supercharging equipment is added, so that the tank top tail gas is pressurized and conveyed to the low-pressure gas system or the sulfur burning system, the stable jacking pressure of the sulfur-containing sewage tank is realized, and meanwhile, the safe recovery of light hydrocarbon is realized by arranging the oxygen content analysis and detection equipment. The liquid storage tank tail gas treatment system is implemented and applied in four sets of acid water stripping devices for sea-fighting refining, and the pressure of a sewage tank is stably controlled to be 0.1-1.0 kPa; the oxygen content of the tank top tail gas meets the requirement that the oxygen content is lower than 2%, and the tank top tail gas is completely pressurized and conveyed to a low-pressure gas system for recycling. The method realizes the closed recovery of the tail gas at the top of the sulfur-containing sewage tank, improves the working environment, recovers the fuel gas by about 50kg/h, and has obvious high-value light hydrocarbon recovery effect. The discharge concentration of VOCs in the flue gas after high-temperature incineration in the sulfur incinerator is 10mg/m3And about, the discharge of VOCs is greatly eliminated, and the environmental protection discharge standard is reached. The method provided by the invention is simple and convenient to operate, has low operation cost, and can be used for petroleumThe device is popularized and applied in chemical industry, coal chemical industry and other similar devices.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications may be made to the technical solution of the invention, and in order to avoid unnecessary repetition, various possible combinations of the invention will not be described further. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.
Claims (16)
1. The utility model provides a liquid storage pot tail gas processing system, this system is including purifying unit, pressure regulating unit, tail gas processing unit and the control unit, purifying unit and the top intercommunication of liquid storage pot, the pressure regulating unit includes air exhaust device and air supplement unit, air exhaust device and purifying unit intercommunication, air supplement unit and liquid storage pot top intercommunication, tail gas processing unit burns the device including parallelly connected tail gas recovery unit and the tail gas that sets up, the control unit includes first controller and second controller, first controller is according to the gaseous oxygen content control of air exhaust device's export air exhaust device with tail gas recovery unit or the tail gas of tail gas processing unit burn the device intercommunication, the second controller is according to the pressure control air exhaust device at liquid storage pot top and the operation of air supplement unit.
2. The exhaust treatment system of claim 1, further comprising a liquid seal tank, wherein a gas inlet of the liquid seal tank is in communication with a top of the liquid storage tank, and a gas outlet of the liquid seal tank is in communication with the atmosphere.
3. The tail gas treatment system of claim 1, wherein the liquid storage tank is a sulfur-containing sewage storage tank, and the purification unit comprises a desulfurization device, and the desulfurization device is an alkaline absorption tower.
4. The exhaust gas treatment system according to any one of claims 1 to 3, wherein the storage tank is one or more than one storage tank arranged in parallel, preferably a flame arrester is arranged between each storage tank and the purification unit.
5. The exhaust treatment system of claim 1, wherein the gas extraction device comprises at least one of a variable frequency water ring vacuum pump, a variable frequency gas compressor, and a steam ejector.
6. The exhaust treatment system of claim 1, wherein the exhaust recovery device includes a low pressure gas system for recovering light hydrocarbon components from the exhaust.
7. The exhaust treatment system of claim 1, wherein the gas make-up device comprises an inert gas tank.
8. The exhaust gas treatment system according to any one of claims 1-7, wherein the first controller is configured to control: when the oxygen content in the gas at the outlet of the air extractor is lower than 2% by volume, the air extractor is communicated with a tail gas recovery device of the tail gas treatment unit; and when the oxygen content in the gas at the outlet of the air extractor is not lower than 2 vol%, the air extractor is communicated with the tail gas incineration device.
9. The exhaust gas treatment system according to any one of claims 1-8, wherein the second controller is configured to control: when the pressure at the top of the liquid storage tank is lower than the set pressure of the liquid storage tank, gradually reducing the operating frequency of the air extraction device, and when the operating frequency of the air extraction device is reduced to the minimum value and the pressure is still lower than the set pressure of the liquid storage tank, communicating the top of the liquid storage tank with the air supplement device, and gradually increasing the instantaneous ventilation between the top of the liquid storage tank and the air supplement device; when the pressure of the top of the liquid storage tank is greater than the set pressure, the instantaneous ventilation between the top of the liquid storage tank and the air supplementing device is gradually reduced until the communication between the top of the liquid storage tank and the air supplementing device is cut off, and when the instantaneous ventilation between the top of the liquid storage tank and the air supplementing device is zero and the pressure is still higher than the set pressure of the liquid storage tank, the operating frequency of the air extracting device is gradually increased.
10. A liquid storage tank tail gas treatment method comprises the steps of purifying tail gas at the top of a liquid storage tank, pressurizing the purified tail gas, and recovering light hydrocarbon from the pressurized tail gas when the oxygen content in the pressurized tail gas is lower than 2 volume percent; when the oxygen content in the pressurized tail gas is not lower than 2 volume percent, burning the pressurized tail gas;
when the pressure at the top of the liquid storage tank is lower than the set pressure of the liquid storage tank, gradually reducing the instantaneous amount of the tail gas to be purified, and when the instantaneous amount of the tail gas to be purified is reduced to the minimum value and the pressure is still lower than the set pressure of the liquid storage tank, supplementing inert gas to the top of the liquid storage tank and gradually increasing the instantaneous ventilation amount of the inert gas; when the pressure at the top of the liquid storage tank is higher than the set pressure, the instantaneous ventilation of the inert gas supplemented to the top of the liquid storage tank is gradually reduced until the instantaneous ventilation is zero, and when the instantaneous ventilation of the inert gas supplemented to the top of the liquid storage tank is zero and the pressure is still higher than the set pressure of the liquid storage tank, the instantaneous quantity of the tail gas to be purified is gradually increased until the instantaneous quantity is maximum.
11. The method for treating tail gas according to claim 10, wherein the liquid in the storage tank is sulfur-containing sewage, the tail gas contains at least one gas selected from hydrogen sulfide, ammonia gas, mercaptan, thioether and aromatic compounds, and the purification method comprises a lye absorption method, an activated carbon adsorption method or a membrane separation method.
12. The exhaust gas treatment method according to claim 10, wherein the pressure increase is performed by using an inverter water ring vacuum pump so that the pressure of the purified exhaust gas is increased to 20 to 40KPa, the minimum value of the instantaneous amount of the purified exhaust gas is a value when the frequency of the inverter water ring vacuum pump is 0, and the maximum value of the instantaneous amount of the purified exhaust gas is a value when the frequency of the inverter water ring vacuum pump is full.
13. The tail gas treatment method of any one of claims 10 to 12, wherein the light hydrocarbon recovery mode comprises feeding the pressurized tail gas into a low-pressure gas system, and then compressing the pressurized tail gas into a high-pressure gas system, so as to recover light hydrocarbon components in the tail gas.
14. The tail gas treatment method according to claim 10, wherein the set pressure of the liquid storage tank is 0-1.5kPa, preferably 0.1-1 kPa.
15. The exhaust gas treatment method according to any one of claims 10 to 14, wherein the instantaneous amount of the tail gas subjected to purification is gradually reduced in such a manner that the instantaneous amount of the tail gas subjected to purification is reduced to a minimum value within 1 to 2 minutes; the instantaneous quantity of the tail gas subjected to purification is gradually increased, so that the instantaneous quantity of the tail gas subjected to purification is increased to the maximum value within 1-2 minutes;
the instantaneous ventilation of the inert gas is gradually increased to enable the pressure at the top of the liquid storage tank to reach the set pressure of the liquid storage tank within 5-10 minutes, and the instantaneous ventilation of the inert gas is gradually decreased to enable the instantaneous ventilation of the inert gas supplemented at the top of the liquid storage tank to be zero within 1-2 minutes.
16. The exhaust gas treatment process according to any one of claims 10 to 15, wherein the inert gas is fed into the liquid storage tank from a position above the liquid level at the top of the liquid storage tank.
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