Method and system for treating liquefied gas desulfurization alcohol-alkali liquid regeneration tail gas

Abstract

The invention provides a treatment method and system for liquefied gas sweetening alcohol-alkali liquor regeneration tail gas, and the treatment method comprises the following steps: step 1, conveying the liquefied gas sweetening alcohol-alkali liquor regeneration tail gas and an alkali absorbent into a first-stage supergravity device, and carrying out gas-liquid contact to remove alkali liquor entrained in the liquefied gas sweetening alcohol-alkali liquor regeneration tail gas; step 2, carrying out gas-liquid separation on the gas-phase mixture obtained in the step 1 to remove the alkali absorbent entrained in the gas-phase mixture so as to obtain liquefied gas sweetening alkali liquor regeneration tail gas without alkali liquor; and step 3, conveying the liquefied gas sweetening alcohol lye regeneration tail gas without the lye obtained in the step 2 and diphenyl ether to a secondary supergravity device, and carrying out gas-liquid contact so as to remove disulphide in the liquefied gas sweetening alcohol lye regeneration tail gas. According to the invention, diphenyl ether is adopted as an absorbent of disulphide, so that the content of organic matters in the treated tail gas can be prevented from being too high, the solvent loss can be reduced, the removal rate of disulphide in the tail gas can be improved, and diphenyl ether can be recycled.

Description

Technical Field

[0001] The invention belongs to the field of liquefied gas processing, and in particular relates to a method for treating liquefied gas desulfurization alcohol alkali solution regeneration tail gas. Background Art

[0002] Liquefied petroleum gas comes from the primary and secondary processing of natural gas associated gas and crude oil. It contains a certain amount of sulfides, including hydrogen sulfide, carbonyl sulfide, mercaptans and sulfides, of which hydrogen sulfide generally accounts for more than 90% of the total sulfur mass fraction, and the rest is mainly mercaptans. Hydrogen sulfide is highly toxic, and mercaptans have a foul odor. Sulfides can corrode equipment and easily cause catalyst deactivation in downstream processes and unqualified total sulfur in products. During the combustion process of liquefied gas, if the sulfide content is too high, a large amount of SO x , which harms the ecological environment. Therefore, liquefied gas must be desulfurized and refined before it leaves the factory as a final product or is used as a raw material for downstream devices for further processing.

[0003] At present, the conventional refining process is amine washing to remove hydrogen sulfide and alkali washing to remove mercaptans. The general process of the alkali washing process is as follows: the liquefied gas after amine washing is pre-washed with alkali to remove residual hydrogen sulfide or directly enters the extraction unit, and the liquefied gas is contacted with lean alkali (sodium hydroxide solution after regeneration), and mercaptans react with sodium hydroxide solution to form sodium mercaptide, thereby removing mercaptans from the liquefied gas. After the mercaptans are removed, the liquefied gas is washed with water and de-alkalied, and then sent to the downstream device or product tank area. The rich alkali containing sodium mercaptide enters the alkali solution regeneration unit. Under the conditions of oxygen and catalyst, at a certain temperature and pressure, the sodium mercaptide is converted into sodium hydroxide and disulfide through the alkali solution regeneration reaction, and the disulfide is separated from the regenerated lean alkali, and the lean alkali is sent to the extraction unit for recycling. The disulfides generated during the alkali solution regeneration process include dimethyl disulfide, diethyl disulfide, and methyl ethyl disulfide. This type of organic sulfur belongs to the oil phase and has a high relative volatility. It enters the tail gas while the alkali solution is regenerated. In addition, there are a small amount of entrained alkali solution droplets in the tail gas. Improper treatment of this tail gas can cause environmental pollution, equipment corrosion, blockage, and safety hazards. The current conventional treatment methods and existing problems of this tail gas in industry are as follows:

[0004] (1) Direct emission: Direct emission does not comply with the "GB14554-93 Odor Pollutant Emission Standard" (the emission limit disulfide concentration is ≯0.03~0.71mg / m 3 );

[0005] (2) Emissions after incineration: After incineration, disulfide is converted into sulfur dioxide. If it is discharged directly without subsequent treatment, it will not comply with the "GB31570-2015 Petroleum Refining Industry Pollutant Emission Standard" (emission limit sulfur dioxide concentration ≯100mg / m 3, special emission limit sulfur dioxide concentration ≯50mg / m 3 ); In addition, since the tail gas contains trace amounts of alkali liquid droplets and untreated disulfide, the direct incineration method will cause the furnace tube to be scaled and blocked;

[0006] (3) Water washing and de-alkali + absorption method: The tail gas is first removed from the alkali solution by a water washing and de-alkali unit, and then sent to the solvent oil stripping unit to remove disulfides. The water washing unit uses a packing / plate tower as the de-alkali site. The solvent oil is generally naphtha or diesel. After being absorbed by the solvent oil, the tail gas contains hydrocarbons. Therefore, the purified gas must be diluted to below the lower explosion limit by an air blower before being discharged, but the VOCs emission concentration is difficult to meet the standard; in addition, the alkali solution carried by the tail gas during the absorption process will enter the oil phase and be sent to the distillate oil hydrogenation unit as a raw material along with the stripping oil. Sodium ions will cause poisoning and deactivation of the hydrogenation catalyst, and there is a great risk of long-term operation. The hydrogenation unit requires that the sodium ion content in the raw material is not more than 1 mg / kg. The index is very harsh, and traditional tower and other mass transfer equipment are difficult to achieve this effect.

[0007] CN104624019B provides a method for treating tail gas containing mercaptide alkali solution oxidation regeneration; the tail gas containing mercaptide alkali solution oxidation regeneration to be treated enters from the bottom of a water washing tank, passes through a gas distribution plate in the tank, exits the exhaust pipe on the top of the water washing tank, enters the bottom air inlet of a dehydration tank, is dried by a desiccant in the dehydration tank, enters an ultra-gravity separator, contacts with diesel entering from a liquid phase inlet of the ultra-gravity separator, and enters an exhaust gas diesel separation and recovery tank from a gas phase outlet of the ultra-gravity separator; the ultra-gravity separator ultra-gravity machine is a rotating packed bed operated in gas-liquid countercurrent, cocurrent or baffled form; the operating range of the ultra-gravity separator is: gas-liquid ratio 5 to 2000:1, operating gauge pressure 0 to 0.3 MPa, and operating temperature 10 to 60°C; the method achieves ultra-low sulfur emissions from liquefied gas alkali solution oxidation regeneration tail gas, and the absorbent diesel can be removed from a hydrogenation device for desulfurization treatment, effectively reducing the total sulfur emissions carried by the "three wastes" of the factory. However, the absorbent diesel contains sodium ions, which can easily poison and deactivate the hydrogenation catalyst in the hydrogenation unit; the exhaust gas will contain diesel components after diesel absorption, and the concentration is the ratio of the saturated vapor pressure at a specific temperature to the total pressure. Since it is a gas phase component, it is difficult to remove it completely through the oil-gas separation tank, so the final exhaust gas still contains a certain concentration of disulfides and VOCs.

[0008] CN104624033B provides a combined method for deep desulfurization of liquefied gas; liquefied gas is sent to an extraction tower, and countercurrently contacts with alkali solution, and the desulfurized liquefied gas and regenerated alkali solution enter a static mixer for mixing and second-stage extraction, and the mixed solution is separated in a liquefied gas alkali solution separation tank, and the liquefied gas is sent to water washing, and the alkali solution to be produced flowing out from the bottom of the extraction tower enters a flash tank, and the residual liquefied gas discharged from the top of the tank is sent to the gas system, and the reduced liquid to be produced obtained at the bottom of the tank enters a supergravity reactor after heating and reacts with non-purified wind, and the tail gas discharged from the supergravity reactor is sent back to the flash tank after removing the alkali solution through a coalescer, and the de-alkali liquid tail gas goes to a diesel absorption tower, and countercurrently contacts with diesel, and the purified tail gas discharged from the top of the tower returns to the supergravity reactor for recycling, and the rich diesel is discharged from the bottom of the tower and sent to a diesel hydrogenation unit, and the regenerated alkali solution is recycled. The method adopts a coalescence method that cannot completely remove the alkali solution entrained in the tail gas, and still causes poisoning of the catalyst of the downstream hydrogenation unit, and the method has a long process flow and high operating cost.

[0009] Therefore, further research is needed in this field on the treatment of liquefied gas sweetening alcohol alkali solution regeneration tail gas. Summary of the invention

[0010] The main purpose of the present invention is to provide a method and system for treating tail gas from liquefied gas sweetening and alkali liquor regeneration, so as to overcome the defects in the prior art that the tail gas from liquefied gas sweetening and alkali liquor regeneration still does not meet the discharge standards after treatment, or that the solvent oil is mixed with alkali after desulfurization, and is thus difficult to be used in a hydrogenation device.

[0011] In order to achieve the above object, the present invention provides a method for treating liquefied gas desulfurization alcohol alkali solution regeneration tail gas, comprising the following steps:

[0012] Step 1, transporting the liquefied gas sweetening alkali liquid regeneration tail gas and the alkali absorbent to a primary supergravity device for gas-liquid contact to remove the alkali liquid entrained in the liquefied gas sweetening alkali liquid regeneration tail gas to obtain a gas phase mixture;

[0013] Step 2, performing gas-liquid separation on the gas phase mixture obtained in step 1 to remove the alkali absorbent carried in the gas phase mixture, and obtaining the liquefied gas sweetening alkali liquid regeneration tail gas from which the alkali liquid is removed;

[0014] Step 3, transporting the liquefied gas sweetening alkali liquid regeneration tail gas and diphenyl ether obtained in step 2 to a secondary supergravity device for gas-liquid contact to remove disulfide in the liquefied gas sweetening alkali liquid regeneration tail gas.

[0015] The method for treating the tail gas from the desulfurization of liquefied gas by alkali solution regeneration of the present invention further comprises:

[0016] Step 4, transporting the liquefied gas sweetening alkali liquid regeneration tail gas from which disulfide is removed in step 3 to the catalyst regeneration unit of the catalytic cracking device to be burned as combustion-supporting air.

[0017] The method for treating the tail gas from the desulfurization of liquefied gas by alkali solution regeneration of the present invention further comprises:

[0018] Step 5, desulfurizing the flue gas after combustion in step 4, and then discharging it.

[0019] The method for treating liquefied gas desulfurization alkali solution regeneration tail gas of the present invention, wherein the alkali absorbent is water.

[0020] The method for treating liquefied gas sweetening alkali liquor regeneration tail gas of the present invention, wherein, in step 2, the gas-liquid separation method is: the gas phase mixture obtained in step 1 is contacted with a desiccant, and the desiccant is at least one of anhydrous calcium chloride, soda lime and quicklime.

[0021] The method for treating liquefied gas sweetening alkali liquid regeneration tail gas of the present invention comprises the following operating conditions: operating temperature of 20-40°C, operating pressure of 10-100 kPa, gas-liquid ratio of 50-500 v / v, and rotor speed of 100-1000 rpm.

[0022] The method for treating liquefied gas sweetening alkali liquid regeneration tail gas of the present invention comprises the following operating conditions: operating temperature of 50-80°C, operating pressure of 10-100 kPa, gas-liquid ratio of 50-500 v / v, and rotor speed of 100-1000 rp.

[0023] The method for treating liquefied gas desulfurization alkali solution regeneration tail gas of the present invention, wherein in step 4, the combustion temperature is 650-720°C.

[0024] The method for treating the tail gas of liquefied gas desulfurization alkali solution regeneration of the present invention, wherein the content of disulfide in the tail gas of liquefied gas desulfurization alkali solution regeneration of disulfide removal in step 3 is less than 10 mg / m 3 .

[0025] In order to achieve the above object, the present invention also provides a processing system for liquefied gas desulfurization alcohol alkali liquid regeneration tail gas, comprising:

[0026] A first-stage supergravity device, in which the liquefied gas sweetening alcohol alkali liquid regeneration tail gas and the alkali absorbent are in gas-liquid contact to remove the alkali liquid entrained in the liquefied gas sweetening alcohol alkali liquid regeneration tail gas;

[0027] A gas-liquid separation device is connected to the first-stage supergravity device, so that the gas phase mixture obtained by the first-stage supergravity device is subjected to gas-liquid separation in the gas-liquid separation device, and the alkali absorbent entrained in the gas phase mixture is removed to obtain the liquefied gas sweetening alkali liquid regeneration tail gas removed from the alkali liquid;

[0028] The secondary supergravity device is connected to the gas-liquid separation device so that the liquefied gas sweetening alkali liquid regeneration tail gas and diphenyl ether are in gas-liquid contact in the secondary supergravity device to remove disulfide from the liquefied gas sweetening alkali liquid regeneration tail gas.

[0029] Beneficial effects of the present invention:

[0030] The present invention adopts a supergravity device to remove alkali liquor and disulfide in the tail gas of liquefied gas sweetening alkali liquor regeneration, which can greatly improve the removal rate of alkali liquor and disulfide in the tail gas and reduce the corrosion degree of the tail gas to the downstream pipeline and equipment.

[0031] The present invention adopts diphenyl ether as the absorbent of disulfide, which can avoid excessive content of organic matter in the tail gas after treatment, reduce solvent loss, and improve the removal rate of disulfide in the tail gas, and the diphenyl ether can be recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic diagram of a system for treating tail gas from liquefied gas desulfurization with alkali solution in one embodiment of the present invention.

[0033] Wherein, the reference numerals are:

[0034] 1. LPG desulfurization alkali solution regeneration tail gas

[0035] 2. Level 1 Supergravity Device

[0036] 3 Alkali absorbent

[0037] 4 Liquid mixture

[0038] 5 Gas phase mixture

[0039] 6 Gas-liquid separation device

[0040] 7 Wastewater

[0041] 8 Combined wastewater

[0042] 9. Removal of alkali liquor from liquefied gas to sweeten alkali liquor to regenerate tail gas

[0043] 10 Secondary Supergravity Device

[0044] 11 Diphenyl ether

[0045] 12 Rich solvent

[0046] 13 Removal of disulfide from liquefied gas and regeneration of tail gas with sweetening alcohol and alkali solution

[0047] 14 Catalytic cracking regeneration unit

[0048] 15 Catalytic main wind

[0049] 16 Combustion smoke

[0050] 17 Catalytic cracking flue gas treatment equipment

[0051] 18 Flue gas purification DETAILED DESCRIPTION

[0052] The technical scheme of the present invention is described in detail below. The following implementation modes are implemented on the premise of the technical scheme of the present invention, and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following implementation modes. The structures or experimental methods of specific conditions are not specified in the following implementation modes, and generally conventional conditions are followed.

[0053] The present invention provides a method for treating liquefied gas desulfurization alkali liquid regeneration tail gas. The liquefied gas desulfurization alkali liquid regeneration tail gas is generated in the process of alkali washing and desulfurization of liquefied gas. Specifically, the liquefied gas is mixed with the alkali liquid, and the mercaptans in the liquefied gas react with the alkali to form mercaptide salts; the alkali liquid containing the mercaptide salts regenerates the mercaptide salts into hydroxides and disulfides. Therefore, the alkali liquid regeneration tail gas contains disulfides and a small amount of entrained alkali liquid droplets. The disulfides include dimethyl disulfide, diethyl disulfide, methyl ethyl disulfide, etc.

[0054] The present invention removes the entrained alkali solution from the liquefied gas desulfurization alkali solution regeneration tail gas by super gravity, and then uses diphenyl ether to absorb the disulfide in the tail gas. In one embodiment, the desulfurized tail gas is introduced into the regeneration unit in the catalytic cracking device as combustion-supporting air for incineration, and the generated flue gas is sequentially separated and heat-exchanged before entering the desulfurization unit in the catalytic cracking device for treatment, and the purified flue gas is discharged.

[0055] In one embodiment, the method for treating the tail gas from the desulfurization of liquefied gas by alkali solution regeneration of the present invention comprises the following steps:

[0056] Step 1, transporting the liquefied gas sweetening alkali liquid regeneration tail gas and the alkali absorbent to a primary supergravity device for gas-liquid contact to remove the alkali liquid entrained in the liquefied gas sweetening alkali liquid regeneration tail gas to obtain a gas phase mixture;

[0057] Step 2, performing gas-liquid separation on the gas phase mixture obtained in step 1 to remove the alkali absorbent carried in the gas phase mixture, and obtaining the liquefied gas sweetening alkali liquid regeneration tail gas from which the alkali liquid is removed;

[0058] Step 3, transporting the liquefied gas sweetening alkali liquid regeneration tail gas and diphenyl ether obtained in step 2 to a secondary supergravity device for gas-liquid contact to remove disulfide in the liquefied gas sweetening alkali liquid regeneration tail gas.

[0059] In another embodiment, the method for treating liquefied gas sweetening alkali liquor regeneration tail gas of the present invention further comprises: step 4, transporting the liquefied gas sweetening alkali liquor regeneration tail gas from which disulfide has been removed in step 3 to the catalyst regeneration unit of the catalytic cracking device and burning it as combustion-supporting air.

[0060] In another embodiment, the method for treating the tail gas from the desulfurization of liquefied gas with alkali solution regeneration of the present invention further comprises: step 5, desulfurizing the flue gas after combustion in step 4, and then discharging it.

[0061] The present invention does not specifically limit the primary supergravity device and the secondary supergravity device, and conventional supergravity devices in the art can be used. In one embodiment, the primary supergravity device and the secondary supergravity device are in the form of a rotating packed bed, and the internal rotor thereof can be a wire mesh filler, or a stator and rotor or other corresponding structures.

[0062] In one embodiment, the operating conditions of the first-stage supergravity device are: operating temperature of 20-40°C, operating pressure of 10-100 kPa (G), gas-liquid ratio of 50-500 v / v, and rotor speed of 100-1000 rpm. The liquefied gas sweetening alkali liquid regeneration tail gas and the alkali absorbent are in gas-liquid contact in the first-stage supergravity device. In another embodiment, the two are in countercurrent contact, the liquefied gas sweetening alkali liquid regeneration tail gas enters from the bottom of the first-stage supergravity device, and the alkali absorbent enters from the top of the first-stage supergravity device. In another embodiment, the alkali absorbent is water.

[0063] After the gas-liquid contact in step 1, a gas phase mixture and a liquid phase mixture are obtained. The liquid phase mixture can be sent to the wastewater stripping unit outside the process for treatment. The gas phase mixture is subjected to gas-liquid separation to remove the liquid entrained in the gas phase mixture, such as alkali absorbent, alkali solution, etc., to obtain the liquefied gas sweetening alkali solution regeneration tail gas removed from the alkali solution.

[0064] In one embodiment, gas-liquid separation is performed in a gas-liquid separator. The present invention does not specifically limit the gas-liquid separator, and any device that can achieve gas-liquid separation in the art can be used. In another embodiment, a filler is provided in the gas-liquid separator to aggregate the droplets entrained in the gas phase mixture, and the grown droplets are collected at the bottom of the separator and discharged. The filler is a wire mesh or microsphere particles, and its unit specific surface area is, for example, 100 to 50,000 m 2 / m 3 In another embodiment, a desiccant is arranged in the gas-liquid separator, and the desiccant may be at least one of anhydrous calcium chloride, soda lime and quicklime, and the gas phase mixture contacts the desiccant to adsorb the liquid droplets entrained in the gas phase mixture to obtain the liquefied gas sweetening and desulfurization alkali liquid regeneration tail gas from which the alkali liquid is removed.

[0065] Step 3 is: transporting the liquefied gas sweetening alkali liquid regeneration tail gas and diphenyl ether obtained in step 2 to a secondary supergravity device for gas-liquid contact to remove disulfide in the liquefied gas sweetening alkali liquid regeneration tail gas.

[0066] In one embodiment, the operating conditions of the secondary high gravity device are: operating temperature of 50-80°C, operating pressure of 10-100 kPa, gas-liquid ratio of 50-500 v / v, and rotor speed of 100-1000 rp. The liquefied gas sweetening alkali liquid regeneration tail gas removed from the alkali liquid and diphenyl ether are in gas-liquid contact in the secondary high gravity device. In another embodiment, the two are in countercurrent contact, the liquefied gas sweetening alkali liquid regeneration tail gas removed from the alkali liquid enters from the bottom of the secondary high gravity device, and diphenyl ether enters from the top of the secondary high gravity device, and the two are in countercurrent contact to complete the removal of most of the disulfides.

[0067] Among them, diphenyl ether has a boiling point of 258°C, is insoluble in water, has an extremely low vapor pressure, is not easy to decompose and is not easy to volatilize; using diphenyl ether instead of naphtha, diesel, etc. as a solvent can avoid the problem of high organic matter content in exhaust gas after treatment and difficulty in meeting emission standards, and can also greatly reduce solvent losses and save operating costs.

[0068] Since the solubility of disulfide in diphenyl ether is very high (≮45% at a specific temperature), and the content of disulfide in the tail gas of most such devices is ≯2kg / h, and the content of disulfide in the tail gas of some high-sulfur raw material devices is also ≯5kg / h, diphenyl ether can maintain long-term operation at a certain circulation volume without any treatment. When the solubility in diphenyl ether is close to saturation, according to the regular monitoring of the total sulfur concentration in the circulating absorbent, a small amount of part of the absorbent is replaced, and the discharged rich solvent is mixed with catalytic gasoline and sent to the gasoline hydrodesulfurization unit for treatment. Therefore, the use of diphenyl ether as a sulfur absorbent in the present invention can also avoid the problem that solvent oil is difficult to post-process. In one embodiment, after removing disulfide from the tail gas regenerated by liquefied gas sweetening alcohol alkali solution, the disulfide content in the tail gas is <30mg / m 3 , more preferably, <10 mg / m 3 .

[0069] In one embodiment, the liquefied gas sweetening alkali liquid regeneration tail gas from which disulfide is removed in step 3 is transported to the catalyst regeneration unit of the catalytic cracking unit and burned as combustion-supporting air. In another embodiment, the flue gas after combustion is desulfurized and then discharged.

[0070] In one embodiment, the regeneration unit in the catalytic cracking unit includes a coke burning tank and a regenerator, which is a catalyst regeneration site in the catalytic cracking unit. Its main function is to perform a coke burning reaction at a temperature of 650-720°C, burn off the coke on the coked catalyst to restore the activity of the catalyst, and regenerate the catalyst. During the process, the tail gas first participates in the coke burning reaction in the lower coke burning tank, and then enters the upper regenerator. In another embodiment, the oxygen volume content in the flue gas generated by the coke burning reaction is 2-9%.

[0071] The present invention does not particularly limit the catalyst regeneration method and desulfurization method of the catalytic cracking unit, and conventional methods in the art may be used.

[0072] The present invention adopts diphenyl ether as the absorbent of disulfide, which can avoid excessive content of organic matter in tail gas after treatment, reduce solvent loss, and improve the removal rate of disulfide in tail gas, and diphenyl ether can be recycled. The method of the present invention can realize harmless and odorless treatment of liquefied gas desulfurization alkali liquid regeneration tail gas, and the equipment is simple, reliable, low-cost, and the production process meets environmental protection requirements.

[0073] The present invention also provides a treatment system for liquefied gas desulfurization alcohol alkali liquid regeneration tail gas, see Figure 1 , including a first-level supergravity device 2, a gas-liquid separation device 6 and a second-level supergravity device 10.

[0074] The liquefied gas sweetening alkali liquid regeneration tail gas 1 and the alkali absorbent 3 are in gas-liquid contact in the primary supergravity device 2 to remove the alkali liquid entrained in the liquefied gas sweetening alkali liquid regeneration tail gas, and obtain a gas phase mixture 5 and a liquid phase mixture 4. The gas phase mixture 5 flows out from the gas phase outlet of the primary supergravity device 2, and the liquid phase mixture 4 flows out from the liquid phase outlet of the primary supergravity device 2.

[0075] The gas-liquid separation device 6 is connected to the primary supergravity device 2 to separate the gas phase mixture 5 obtained by the primary supergravity device 2 into gas and liquid, remove the liquid entrained in the gas phase mixture 5, such as alkali absorbent, alkali solution, etc., to obtain the liquefied gas sweetening alkali solution regeneration tail gas 9 and wastewater 7 from which the alkali solution is removed. The liquid phase mixture 4 can be mixed with the wastewater 7 to obtain the combined wastewater 8 and transported to the sewage treatment plant for treatment.

[0076] The secondary supergravity device 10 is connected to the gas-liquid separation device 6, so that the liquefied gas sweetening alkali liquid regeneration tail gas 9 and diphenyl ether 11 are in gas-liquid contact in the secondary supergravity device 10, and the disulfide in the liquefied gas sweetening alkali liquid regeneration tail gas is removed to obtain the liquefied gas sweetening alkali liquid regeneration tail gas 13 and the rich solvent 12. The rich solvent 12 can be recycled.

[0077] In one embodiment, the secondary supergravity device 10 is connected to the catalytic cracking regeneration unit 14, and the liquefied gas sweetening alkali liquid regeneration tail gas 13 with disulfide removed and the catalytic main wind 15 are transported to the catalytic cracking regeneration unit 14, and the liquefied gas sweetening alkali liquid regeneration tail gas 13 with disulfide removed is burned as combustion-supporting wind. The combustion flue gas 16 is output.

[0078] In another embodiment, the catalytic cracking flue gas treatment device 17 is connected to the catalytic cracking regeneration unit 14, and the combustion flue gas 16 is transported to the catalytic cracking flue gas treatment device 17 for desulfurization treatment and then discharged as purified flue gas 18. The catalytic cracking flue gas treatment device 17 is used to remove sulfur from the flue gas of the catalytic cracking unit, that is, sulfur derived from the catalytic cracking itself. The content of disulfide in the tail gas treated with the alkali absorbent and diphenyl ether of the present invention is ≯30mg / m 3 , far below the requirements of the gas emission standard "GB31570-2015 Petroleum Refining Industry Pollutant Emission Standard", and can directly meet the emission standards. In one embodiment, because disulfide has a bad smell, in order to directly ensure the on-site working environment of the device, in practice, sometimes catalytic cracking devices and flue gas desulfurization process flows are relied upon to completely achieve harmless and odorless tail gas treatment.

[0079] The system for treating tail gas from liquefied gas desulfurization with alkali solution regeneration of the present invention can be used in the above-mentioned method for treating tail gas from liquefied gas desulfurization with alkali solution regeneration.

[0080] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0081] Embodiment 1:

[0082] A petrochemical plant uses the present invention to treat the tail gas containing disulfide from the desulfurization of liquefied gas and the regeneration of alkali liquid. Main parameters: tail gas disulfide concentration 3000-3500mg / Nm 3 The first-stage high-gravity reactor has an operating temperature of 35°C, an operating pressure of 45kPa(G), a rotation speed of 300rpm, a gas-liquid ratio of 200v / v, and deionized water as the alkali absorbent; the gas-liquid separator is filled with regular packing, and a foam breaking net is set on the top; the second-stage high-gravity reactor has an operating temperature of 60°C, an operating pressure of 35kPa(G), a rotation speed of 250rpm, a gas-liquid ratio of 150, and diphenyl ether as the liquid phase. Effect: Deionized water is used as the alkali absorbent, and the alkali content in the sulfur-containing tail gas after enhanced absorption and gas-liquid separation in the first-stage high-gravity reactor is ≯1mg / m 3 ; Using diphenyl ether as the absorbent, the disulfide in the desulfurized tail gas after enhanced absorption in the secondary supergravity reactor is ≯30mg / m 3 , VOCs≯1mg / m 3, far below the requirements of the gas emission standard "GB31570-2015 Petroleum Refining Industry Pollutant Emission Standard". The amount of diphenyl ether replaced is ≯3 tons / year. This method achieves harmless and odorless treatment of tail gas, eliminates the solvent oil back extraction process, and saves operating costs of about 8 million yuan / year.

[0083] The tail gas from the desulfurization of liquefied gas is transported to the catalyst regeneration unit of the catalytic cracking unit and burned as combustion-supporting air. The flue gas after combustion is desulfurized and denitrified before being discharged.

[0084] Embodiment 2:

[0085] A petrochemical plant uses the present invention to treat the tail gas containing disulfide from the desulfurization of liquefied gas and the regeneration of alkali liquid. Main parameters: tail gas disulfide concentration 800-1500mg / Nm 3 The first-stage high-gravity reactor has an operating temperature of 30°C, an operating pressure of 50kPa (G), a rotation speed of 350rpm, a gas-liquid ratio of 150, and an alkali absorbent of deionized water; the gas-liquid separator is filled with regular packing, and a foam breaking net is set on the top; the second-stage high-gravity reactor has an operating temperature of 65°C, an operating pressure of 42kPa (G), a rotation speed of 200rpm, a gas-liquid ratio of 180, and a liquid phase of diphenyl ether; the desulfurized tail gas is sent to the carbon monoxide incinerator of the catalytic cracking unit for incineration. Effect: Deionized water is used as the alkali absorbent, and the alkali content in the sulfur-containing tail gas after enhanced absorption and gas-liquid separation in the first-stage high-gravity reactor is ≯1mg / m 3 ; Using diphenyl ether as the absorbent, the disulfide in the desulfurized tail gas after enhanced absorption in the secondary supergravity reactor is ≯20mg / m 3 , VOCs≯1mg / m 3 , far below the requirements of the gas emission standard "GB31570-2015 Petroleum Refining Industry Pollutant Emission Standard". The amount of diphenyl ether replaced is ≯2 tons / year. This method achieves harmless and odorless treatment of tail gas, eliminates the solvent oil back extraction process, and saves operating costs of about 6 million yuan / year.

[0086] Embodiment 3:

[0087] A petrochemical plant uses the present invention to treat the tail gas containing disulfide from the desulfurization of liquefied gas and the regeneration of alkali liquid. Main parameters: tail gas disulfide concentration 4500-5200mg / Nm 3The operating temperature of the first-stage supergravity reactor is 35°C, the operating pressure is 48kPa (G), the speed is 230rpm, the gas-liquid ratio is 180, and the alkali absorbent is deionized water; the gas-liquid separator is filled with anhydrous calcium chloride and quicklime as desiccants, and a foam breaking net is installed on the top; the operating temperature of the second-stage supergravity reactor is 63°C, the operating pressure is 40kPa (G), the speed is 200rpm, the gas-liquid ratio is 160, and the liquid phase is diphenyl ether. The desulfurized tail gas is sent to the carbon monoxide incinerator of the catalytic cracking unit for incineration. Effect: Deionized water is used as the alkali absorbent, and the alkali content in the sulfur-containing tail gas after enhanced absorption and gas-liquid separation in the first-stage supergravity reactor is ≯0.1mg / m 3 ; Using diphenyl ether as the absorbent, the disulfide in the desulfurized tail gas after enhanced absorption in the secondary supergravity reactor is ≯10mg / m 3 , VOCs≯1mg / m 3 , far below the requirements of the gas emission standard "GB31570-2015 Petroleum Refining Industry Pollutant Emission Standard". The amount of diphenyl ether replaced is ≯1 ton / year. This method achieves harmless and odorless treatment of tail gas, eliminates the solvent oil back extraction process, and saves operating costs of about 6 million yuan / year.

[0088] Comparative Example 1

[0089] The same liquefied gas sweetening alkali liquor regeneration tail gas as in Example 3 is directly sent to the sulfur recovery device. Due to the long pipeline, entrained and saturated precipitated water often freezes in the pipeline in winter, posing a great safety hazard.

[0090] Comparative Example 2

[0091] The same liquefied gas desulfurization alcohol alkali liquid regeneration tail gas as in Example 2 is not washed with water, and diesel is directly used to absorb disulfides in the tail gas. An absorption tower is used as the absorption equipment, and the tower is filled with regular packing. The tail gas enters from the bottom of the tower, and the absorbent diesel enters from the top of the tower. The two are countercurrently contacted to remove disulfides in the tail gas, and the gas-liquid ratio is 10-50. Desulfurized tail gas VOCs ≯200mg / m 3 , must be further processed, generally by sending it to an incinerator for incineration. Since this method does not completely remove sulfur, the combustion of sulfur-containing tail gas in the incinerator will cause serious corrosion and scaling of the furnace tubes; the sodium ion content in sulfur-containing diesel is 80-100 mg / kg. The use of this sulfur-containing diesel in the hydrogenation unit will cause the catalyst of the diesel hydrogenation unit to deactivate, and there will be multiple hot spots in the catalyst bed. The catalyst replacement was stopped 8 months earlier than the expected catalyst replacement time.

[0092] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for treating tail gas from liquefied gas desulfurization with alkali liquor regeneration, It is characterized in that The steps include: Step 1, transporting the liquefied gas sweetening alcohol alkali liquid regeneration tail gas and the alkali absorbent to a primary supergravity device for gas-liquid contact to remove the alkali liquid entrained in the liquefied gas sweetening alcohol alkali liquid regeneration tail gas to obtain a gas phase mixture; Step 2, performing gas-liquid separation on the gas phase mixture obtained in step 1 to remove the alkali absorbent carried in the gas phase mixture, and obtaining the liquefied gas sweetening alkali liquid regeneration tail gas from which the alkali liquid is removed; Step 3, transporting the liquefied gas sweetening alkali liquid regeneration tail gas and diphenyl ether obtained in step 2 to a secondary supergravity device for gas-liquid contact to remove disulfide in the liquefied gas sweetening alkali liquid regeneration tail gas.

2. The method for treating the tail gas from liquefied gas desulfurization by alkali liquor regeneration according to claim 1, It is characterized in that Also includes: Step 4, transporting the liquefied gas sweetening alkali liquid regeneration tail gas from which disulfide is removed in step 3 to the catalyst regeneration unit of the catalytic cracking device to be burned as combustion-supporting air.

3. The method for treating the tail gas from liquefied gas desulfurization by alkali liquid regeneration according to claim 2, It is characterized in that Also includes: Step 5, desulfurizing the flue gas after combustion in step 4, and then discharging it.

4. The method for treating the tail gas from liquefied gas desulfurization by alkali liquid regeneration according to claim 1, It is characterized in that The alkali absorbent is water.

5. The method for treating the tail gas from liquefied gas desulfurization by alkali liquid regeneration according to claim 1, It is characterized in that In step 2, the gas-liquid separation is carried out by contacting the gas phase mixture obtained in step 1 with a desiccant, wherein the desiccant is at least one of anhydrous calcium chloride, soda lime and quicklime.

6. The method for treating the tail gas from liquefied gas desulfurization by alkali liquid regeneration according to claim 1, It is characterized in that The operating conditions of the first-stage supergravity device are: operating temperature of 20-40°C, operating pressure of 10-100kPa, gas-liquid ratio of 50-500v / v, and rotor speed of 100-1000rpm.

7. The method for treating the tail gas from liquefied gas desulfurization by alkali liquid regeneration according to claim 1, It is characterized in that The operating conditions of the secondary supergravity device are: operating temperature of 50-80°C, operating pressure of 10-100kPa, gas-liquid ratio of 50-500v / v, and rotor speed of 100-1000rp.

8. The method for treating the tail gas from liquefied gas desulfurization by alkali liquid regeneration according to claim 2, It is characterized in that In step 4, the combustion temperature is 650-720°C.

9. The method for treating the tail gas from liquefied gas desulfurization by alkali liquid regeneration according to claim 1, It is characterized in that Step 3: Removal of disulfide: The disulfide content in the liquefied gas sweetening alcohol alkali solution regeneration tail gas is less than 10 mg / m 3 .

10. A system for treating tail gas from liquefied gas desulfurization and alkali liquor regeneration. It is characterized in that include: A first-stage supergravity device, in which the liquefied gas sweetening alcohol alkali liquid regeneration tail gas and the alkali absorbent are in gas-liquid contact to remove the alkali liquid entrained in the liquefied gas sweetening alcohol alkali liquid regeneration tail gas; A gas-liquid separation device is connected to the first-stage supergravity device, so that the gas phase mixture obtained by the first-stage supergravity device is subjected to gas-liquid separation in the gas-liquid separation device, and the alkali absorbent entrained in the gas phase mixture is removed to obtain the liquefied gas sweetening alkali liquid regeneration tail gas removed from the alkali liquid; The secondary supergravity device is connected to the gas-liquid separation device so that the liquefied gas sweetening alkali liquid regeneration tail gas and diphenyl ether are in gas-liquid contact in the secondary supergravity device to remove disulfide from the liquefied gas sweetening alkali liquid regeneration tail gas.

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