Method for continuous desulphurization of regenerative flue gas sodium process and system for continuous desulphurization of regenerative flue gas sodium process

Abstract

This invention relates to the field of catalytic cracking regenerated flue gas purification, and discloses a method for continuous desulfurization of regenerated flue gas using the sodium alkali method and a system for continuous desulfurization of regenerated flue gas using the sodium alkali method. The method includes: (1) in the lower section of the absorber, using regenerated flue gas to concentrate a primary circulating liquid containing sodium sulfate to obtain a first flue gas and a concentrated circulating liquid; (2) in a high gravity reactor, the first flue gas and the circulating absorbent from the middle section of the absorber undergo a first counter-current contact desulfurization to obtain a second flue gas and a tertiary circulating liquid, wherein the tertiary circulating liquid is circulated back to the middle section of the absorber; wherein the SO2 content in the second flue gas is not higher than 35 mg / Nm³. 3 (3) In the upper section of the absorption tower, the second flue gas and the secondary circulating liquid are subjected to a second counter-current contact to obtain purified flue gas and a fourth circulating liquid. In the purified flue gas, the SO2 content is not higher than 20 mg / Nm³. 3 This method has the advantages of excellent desulfurization effect, low absorbent consumption, and low energy consumption.

Description

Technical Field

[0001] This invention relates to the field of catalytic cracking regenerated flue gas purification, specifically to a method for continuous desulfurization of regenerated flue gas using the sodium alkali method and a system for continuous desulfurization of regenerated flue gas using the sodium alkali method. Background Technology

[0002] The flue gas emitted from the regenerator of the catalytic cracking unit is the largest source of air pollution in refineries and a major emission source in the petroleum refining industry. The pollutants in this flue gas mainly include particulate matter, sulfur oxides, nitrogen oxides, and carbon monoxide. During the catalytic cracking and catalytic pyrolysis reactions in petroleum, carbon deposits form on the surface of the catalyst over a long period, reducing its activity and requiring regeneration to restore its performance. Air is used to combust and remove the carbon deposits from the catalyst in the regenerator. The resulting high-temperature flue gas is then separated from the entrained catalyst by a cyclone separator, and after energy recovery via a flue gas fan and waste heat boiler, it is discharged into the atmosphere. This process generates catalytic cracking regeneration flue gas.

[0003] Current technologies for treating catalytic cracking regeneration flue gas mainly employ sodium alkali desulfurization. This requires the regeneration flue gas to undergo extensive washing with a large amount of circulating absorbent to remove particulate matter and sulfides before being released into the atmosphere. However, this extensive washing with circulating absorbent inevitably leads to high system energy consumption and increased operating costs, while also generating large amounts of wastewater containing particulate matter and salinity, which is difficult to treat subsequently.

[0004] For example, CN201871320U discloses a method of using alkaline solution to absorb and neutralize sulfides in catalytic cracking regeneration flue gas, and using circulating water to wash away particulate matter in the catalytic cracking regeneration flue gas. In order to achieve the standard emission of pollutants, a large amount of circulating absorbent is set up for washing. At the same time, in order to maintain the balance of salt and particulate matter in the tower, a large amount of desulfurization wastewater containing particulate matter and COD is discharged. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a method and system for continuous desulfurization of regenerated flue gas using the sodium alkali method. This method has the advantages of excellent desulfurization effect, low absorbent consumption, and low energy consumption.

[0006] To achieve the above objectives, the present invention provides a method for continuous desulfurization of regenerated flue gas using the sodium alkali method, the method comprising the following steps:

[0007] (1) In the lower section of the absorption tower, the primary circulating liquid containing sodium sulfate is concentrated using regenerated flue gas to obtain the first flue gas and the concentrated circulating liquid;

[0008] (2) In a high-gravity reactor, the first flue gas is subjected to a first counter-current contact desulfurization process with the circulating absorbent from the middle section of the absorber tower to obtain a second flue gas and a third-stage circulating liquid, wherein the third-stage circulating liquid is recycled to the middle section of the absorber tower; wherein the SO2 content in the second flue gas is not higher than 35 mg / Nm³. 3 ;

[0009] (3) In the upper section of the absorption tower, the second flue gas and the secondary circulating liquid undergo a second counter-current contact to obtain purified flue gas and a fourth-stage circulating liquid. In the purified flue gas, the SO2 content is not higher than 20 mg / Nm³. 3 .

[0010] A second aspect of the present invention provides a system for continuous desulfurization of regenerated flue gas using the sodium alkali method, the system comprising an absorption tower and a supergravity reactor;

[0011] The lower section of the absorption tower is equipped with a first spray pipe, which is used to concentrate the primary circulating liquid containing sodium sulfate with regenerated flue gas to obtain the first flue gas and the concentrated circulating liquid.

[0012] The supergravity reactor is used to perform a first counter-current contact desulfurization between the first flue gas and the circulating absorbent from the middle section of the absorption tower to obtain the second flue gas and the third-stage circulating liquid.

[0013] The upper section of the absorption tower is equipped with a second spray pipe, which is used to make the second flue gas and the secondary circulating liquid in a second counter-current contact to obtain purified flue gas and quaternary circulating liquid.

[0014] A liquid collection funnel is provided in the middle section of the absorption tower for storing the absorption liquid;

[0015] The first liquid inlet of the liquid collecting funnel is connected to the liquid outlet of the supergravity reactor.

[0016] The beneficial effects of the present invention through the above technical solution include:

[0017] The sodium alkali method for continuous desulfurization of regenerated flue gas provided by this invention has excellent desulfurization effect, significantly reduces the amount of absorbent used, simplifies the process, and greatly reduces system energy consumption and equipment investment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the system provided by the present invention.

[0019] Explanation of reference numerals in the attached figures

[0020] 1. Dust collector; 2. Absorption tower; 3. First circulating liquid pump;

[0021] 4. High gravity reactor; 5. Second circulating liquid pump; 6. Third circulating liquid pump;

[0022] 21. First spray pipe; 22. Liquid collecting funnel; 23. Demister;

[0023] 24. Second spray pipe; 25. Demister; 26. Liquid receiving plate. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0025] In this invention, the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0026] In this invention, the terms "first," "second," and "third" do not limit the substances and operations, but are only used to distinguish the substances introduced in different steps and the operations performed in different stages.

[0027] The first aspect of this invention provides a continuous desulfurization method for regenerated flue gas using the sodium alkali method, the method comprising the following steps:

[0028] (1) In the lower section of the absorption tower, the primary circulating liquid containing sodium sulfate is concentrated using regenerated flue gas to obtain the first flue gas and the concentrated circulating liquid;

[0029] (2) In a high-gravity reactor, the first flue gas is subjected to a first counter-current contact desulfurization process with the circulating absorbent from the middle section of the absorber tower to obtain a second flue gas and a third-stage circulating liquid, wherein the third-stage circulating liquid is recycled to the middle section of the absorber tower; wherein the SO2 content in the second flue gas is not higher than 35 mg / Nm³. 3 ;

[0030] (3) In the upper section of the absorption tower, the second flue gas and the secondary circulating liquid undergo a second counter-current contact to obtain purified flue gas and a fourth-stage circulating liquid. In the purified flue gas, the SO2 content is not higher than 20 mg / Nm³. 3 .

[0031] In the method provided by this invention, step (1) uses the waste heat of regenerated flue gas to concentrate the primary circulating liquid (where water is vaporized and sodium sulfate components are concentrated), which improves the energy utilization efficiency of the system; effectively avoids the impact of excessive sodium sulfate content on the desulfurization process, reduces the energy consumption of downstream sodium sulfate product recovery; significantly reduces the amount of salt-containing (sodium sulfate) water discharged from desulfurization, and reduces the amount of water to be added to the system; and can also remove some sulfur dioxide from the flue gas.

[0032] According to a preferred embodiment of the present invention, the sodium sulfate content in the primary circulating liquid in step (1) is not higher than 20%, preferably 5-15%. This preferred embodiment helps control the sulfate content entrained in the flue gas, ensuring flue gas indicators, while also ensuring the smooth transport of the concentrated circulating liquid.

[0033] According to a preferred embodiment of the present invention, the temperature of the first flue gas is 50-65°C.

[0034] According to a preferred embodiment of the present invention, step (1) includes: atomizing the primary circulating liquid in the lower section of the absorber at a spray pressure of 0.2-0.6 MPaG, and then concentrating the atomized primary circulating liquid with regenerated flue gas to obtain first flue gas and concentrated circulating liquid. This preferred embodiment increases the contact intensity and area between the regenerated flue gas and the primary circulating liquid, improving the concentration efficiency; it also facilitates the removal of some sulfur dioxide.

[0035] According to a preferred embodiment of the present invention, at least a portion of the concentrated circulating liquid obtained in step (1) is returned to step (1) for recycling.

[0036] According to a preferred embodiment of the present invention, a portion of the concentrated circulating liquid obtained in step (1) is sent to a downstream ammonium sulfate crystallization unit for processing to ensure that the mass content of sodium sulfate in the primary circulating liquid of step (1) is always no higher than 20%; the remaining portion is returned to step (1) for use as the primary circulating liquid.

[0037] According to a more preferred embodiment of the present invention, the concentrated circulating liquid obtained in step (1) is oxidized in an oxidizing atmosphere, and a portion is sent to the downstream ammonium sulfate crystallization unit for processing to ensure that the mass content of sodium sulfate in the primary circulating liquid of step (1) is never higher than 20%; the remaining portion is returned to step (1) for use as the primary circulating liquid. In this preferred embodiment, sodium sulfite in the concentrated circulating liquid is oxidized in an oxidizing atmosphere to obtain sodium sulfate, facilitating the recovery of sodium sulfate.

[0038] The present invention has a wide range of choices for the type of oxidizing atmosphere. According to a preferred embodiment of the present invention, the oxidizing atmosphere is air or oxygen.

[0039] It should be noted that, in the above process, the flow rate of the concentrated circulating liquid sent to the downstream ammonium sulfate crystallization unit is controlled in order to maintain the sodium sulfate content in the primary circulating liquid in step (1) not higher than 20%.

[0040] In the method provided by the present invention, step (2) uses a supergravity reactor for desulfurization, which achieves a highly dispersed distribution of the circulating absorbent, greatly enhances the mass transfer in the absorption process, improves the desulfurization efficiency, and significantly reduces the amount of absorbent used, thereby greatly reducing system energy consumption and equipment investment.

[0041] The present invention does not particularly limit the specific conditions of the first reverse contact, as long as the sulfur dioxide content in the second flue gas meets the above conditions.

[0042] The amount of circulating absorbent used in this invention is determined based on the sulfur dioxide content in the regenerated flue gas. According to a preferred embodiment of this invention, the liquid-to-gas ratio of the circulating absorbent to the first flue gas is 2-5 L / Nm³. 3 .

[0043] According to a preferred embodiment of the present invention, the operating conditions of the supergravity reactor include: a temperature of 50-65°C and a centrifugal force of 10-1000g.

[0044] According to a preferred embodiment of the present invention, step (2) includes: in a centrifugal reactor, under a spray pressure of 0.2-0.8 MPaG, atomizing the circulating absorbent and performing a first counter-current contact desulfurization with the first flue gas to obtain a second flue gas and a third-stage circulating liquid. Using this preferred embodiment, the interphase mass transfer rate is significantly improved, increasing the contact intensity and area between sulfur dioxide and the alkaline absorbent, allowing more sulfur dioxide to be absorbed, improving desulfurization efficiency, accelerating the absorption rate of sulfur dioxide, and reducing equipment specifications.

[0045] According to a preferred embodiment of the present invention, the sodium sulfate content in the absorbent liquid in the middle section of the absorption tower is not higher than 8%, preferably 2-5%. This preferred embodiment facilitates the absorption of SO2 from the flue gas by the circulating absorbent liquid, while simultaneously reducing the sulfate content entrained in the flue gas and ensuring flue gas performance indicators.

[0046] According to a preferred embodiment of the present invention, the fresh absorbent and the tertiary circulating liquid obtained in step (2) are sent to the middle section of the absorption tower, and then drawn out and divided into two streams: part of it is sent to the lower section of the absorption tower as the primary circulating liquid to ensure that the mass content of sodium sulfate in the absorbent in the middle section of the absorption tower is not higher than 8%; the remaining part is sent to the supergravity reactor as the circulating absorbent.

[0047] It should be noted that during the above process, the flow rate sent to the lower section of the absorption tower is controlled to maintain the sodium sulfate content in the absorbent in the middle section of the absorption tower at no more than 8%.

[0048] The present invention does not impose any particular limitation on the type of absorbent liquid, and any conventional choice in the art can be made. According to a preferred embodiment of the present invention, the absorbent liquid is an aqueous solution of sodium hydroxide.

[0049] According to a preferred embodiment of the present invention, the concentration of the fresh absorption liquid is 15-40 wt%.

[0050] The present invention allows for a wide range of structural options for the supergravity reactor, as long as the above objectives can be achieved.

[0051] According to a preferred embodiment of the present invention, the supergravity reactor includes a motor and a rotor, the rotor being filled with packing material and driven to rotate by the motor; wherein the packing material is used to disperse the circulating absorbent liquid, and the rotor is used to drive the circulating absorbent liquid to rotate.

[0052] According to a preferred embodiment of the present invention, the supergravity reactor includes a shell, a rotor is provided inside the shell, the rotor is filled with packing material, and the rotor is driven to rotate by a motor.

[0053] According to a preferred embodiment of the present invention, the rotor is connected to a liquid phase tube and a gas phase tube, wherein the liquid phase tube is fitted inside the gas phase tube, the other end of the liquid phase tube is the liquid inlet, and the other end of the gas phase tube is the gas outlet.

[0054] According to a preferred embodiment of the present invention, a liquid outlet is provided at the bottom of the housing.

[0055] According to a specific embodiment of the present invention, the side wall of the supergravity reactor shell is provided with a gas inlet. The first flue gas enters the inner cavity of the shell tangentially through the gas inlet and enters the packing through the outer edge of the rotor. The circulating absorbent enters the rotor through the liquid inlet and is sprayed on the inner edge of the rotor. The circulating absorbent is dispersed by the packing therein, thereby improving the mass transfer and reaction process with the regenerated flue gas. The circulating absorbent that is thrown out flows out by gravity through the liquid outlet.

[0056] The present invention allows for a wide range of choices for the types of packing material used in the supergravity reactor, and can be any conventional choice in the art. For example, it can be at least one of stainless steel wire mesh packing, stainless steel porous corrugated plate, and foam ceramic packing.

[0057] The present invention does not impose any particular limitation on the amount of packing material in the supergravity reactor, but rather on the amount of flue gas to be treated and the pollutant index in the flue gas.

[0058] In the method provided by the present invention, step (3) uses a secondary circulating liquid to perform secondary washing on the second flue gas. A large amount of SO2 and entrained sodium sulfate in the second flue gas condense and precipitate out and are washed away by the secondary circulating liquid, thereby achieving effective control of pollutants in the regenerated flue gas.

[0059] The present invention does not particularly limit the specific conditions of the second reverse contact, as long as the sulfur dioxide content in the purified flue gas meets the above conditions.

[0060] According to a preferred embodiment of the present invention, step (3) includes: in the upper section of the absorption tower, under a spray pressure of 0.4-0.8 MPaG, the secondary circulating liquid is atomized and subjected to a second counter-current contact with the second flue gas to obtain purified flue gas and quaternary circulating liquid. This preferred embodiment can improve contact efficiency and effectively control sulfate entrainment in the flue gas.

[0061] According to a preferred embodiment of the present invention, at least a portion of the replenished water and the fourth-stage circulating fluid obtained in step (3) is returned to step (3) for use as a second-stage circulating fluid.

[0062] According to a more preferred embodiment of the present invention, the supplementary water and part of the fourth-stage circulating liquid obtained in step (3) are returned to the middle section of the absorption tower to ensure that the mass content of sodium sulfate in the absorbent in the middle section of the absorption tower is not higher than 8%; the remaining part is returned to the upper section of the absorption tower for use as a secondary circulating liquid.

[0063] According to a preferred embodiment of the present invention, the temperature of the supplemental water is 5-60°C and the pressure is 0.6-1 MPa.

[0064] It should be noted that during continuous operation, the mass content of sodium sulfate in the absorbent liquid in the middle section of the absorption tower is not higher than 8%, preferably 2-5%.

[0065] To ensure that the sodium sulfate content in the absorbent in the middle section of the absorption tower never exceeds 8%, the following two methods are mainly used:

[0066] Method 1 (reducing sodium sulfate concentration): send the fresh absorbent and the three-stage circulating liquid obtained in step (2) to the middle section of the absorption tower, and then send part of it to the lower section of the absorption tower for concentration as described in step (1);

[0067] Method 2 (Dilution): The supplemental water and part of the fourth-stage circulating liquid obtained in step (3) are returned to the middle section of the absorption tower.

[0068] According to a preferred embodiment of the present invention, the method further includes performing a defoaming operation before the second flue gas and the secondary circulating liquid undergo a second reverse contact. This preferred embodiment helps to remove sulfate components entrained in the mist from the second flue gas, thereby avoiding any impact on the subsequent second reverse contact.

[0069] According to a preferred embodiment of the present invention, the liquid separated by the defoaming operation flows by gravity to the middle section of the absorption tower.

[0070] According to a specific embodiment of the present invention, the fresh absorbent, the liquid separated by the defoaming operation, and the tertiary circulating liquid obtained in step (2) are sent to the middle section of the absorption tower and then divided into two parts: one part is sent to the lower section of the absorption tower as the primary circulating liquid to ensure that the mass content of sodium sulfate in the absorbent in the middle section of the absorption tower is not higher than 8%; the remaining part is sent to the supergravity reactor as the circulating absorbent.

[0071] According to a preferred embodiment of the present invention, the method further includes: first subjecting the second flue gas to a second counter-current contact with a secondary circulating liquid, and then performing a demisting operation to obtain purified flue gas. This preferred embodiment is beneficial for removing water droplets and sulfate entrainment, thereby improving droplet collection efficiency.

[0072] The present invention does not particularly limit the source of the regenerated flue gas, and it can be regenerated flue gas obtained by various means in the art. According to a preferred embodiment of the present invention, the regenerated flue gas is catalytic cracking regenerated flue gas.

[0073] In this invention, the catalytic cracking regenerated flue gas refers to the flue gas generated during catalytic cracking and catalytic pyrolysis reactions. Coke deposits form on the surface of the catalyst, requiring it to be regenerated in a regenerator to restore its activity. Air is used in the regenerator to burn off the coke deposits. The resulting flue gas is then separated from the entrained catalyst by a cyclone separator, and after energy recovery via a flue gas turbine and waste heat boiler, it is discharged into the atmosphere. This process generates catalytic cracking regenerated flue gas.

[0074] The present invention does not particularly limit the composition of the regenerated flue gas, and the method described in the present invention is suitable for processing regenerated flue gas with different compositions.

[0075] According to a preferred embodiment of the present invention, the temperature of the regenerated flue gas is 150-250°C and the pressure is 0.004-0.01 MPaG.

[0076] According to a preferred embodiment of the present invention, the SO2 content in the regenerated flue gas is 500-3000 mg / Nm³. 3 Particulate matter content is 100-1000 mg / Nm³ 3 .

[0077] According to a preferred embodiment of the present invention, the method further includes: removing particulate matter from the regenerated flue gas before concentrating the primary circulating liquid with regenerated flue gas, so that the particulate matter content in the regenerated flue gas is reduced to 1-20 mg / Nm³. 3 .

[0078] A second aspect of the present invention provides a system for continuous desulfurization of regenerated flue gas using the sodium alkali method, the system comprising an absorption tower 2 and a supergravity reactor 4;

[0079] The lower section of the absorption tower 2 is equipped with a first spray pipe 21, which is used to concentrate the primary circulating liquid containing sodium sulfate with regenerated flue gas to obtain the first flue gas and the concentrated circulating liquid.

[0080] The supergravity reactor 4 is used to perform a first counter-current contact desulfurization between the first flue gas and the circulating absorbent from the middle section of the absorption tower 2 to obtain the second flue gas and the third-stage circulating liquid.

[0081] The upper section of the absorption tower 2 is provided with a second spray pipe 24, which is used to make the second flue gas and the secondary circulating liquid in a second counter-current contact to obtain purified flue gas and quaternary circulating liquid.

[0082] The middle section of the absorption tower 2 is equipped with a liquid collection funnel 22 for storing the absorption liquid;

[0083] The first liquid inlet of the liquid collecting funnel 22 is connected to the liquid outlet of the supergravity reactor 4.

[0084] According to a preferred embodiment of the present invention, the top of the absorption tower 2 is further provided with a gas outlet for discharging purified flue gas.

[0085] According to a preferred embodiment of the present invention, the liquid collecting funnel 22 is provided with an absorbent replenishment inlet for introducing fresh absorbent (alkaline solution).

[0086] According to a preferred embodiment of the present invention, a demister 23 is further provided in the middle section of the absorption tower 2, arranged above the liquid collection funnel 22, for defoaming the second flue gas. In the present invention, the liquid separated by the demister 23 flows by gravity into the liquid collection funnel 22.

[0087] According to a preferred embodiment of the present invention, the absorption tower 2 is further provided with a liquid receiving plate 26 for receiving the fourth-stage circulating liquid.

[0088] According to a more preferred embodiment of the present invention, the liquid receiving plate 26 is used to receive the fourth-stage circulating liquid and the replenishment water from the boundary area.

[0089] According to a preferred embodiment of the present invention, the liquid receiving plate 26 is provided with a vertically arranged and vertically continuous gas riser for gas circulation.

[0090] According to a preferred embodiment of the present invention, the liquid receiving plate 26 separates the upper section of the absorption tower 2 from the middle section of the absorption tower 2.

[0091] According to a preferred embodiment of the present invention, the liquid receiving plate 26 is connected to the second spray pipe 24 in the upper section of the absorption tower 2. In this preferred embodiment, the makeup water from the boundary area, the fourth-stage circulating liquid, and the liquid separated by the demister 23 are collected on the liquid receiving plate 26, and then at least a portion is sent to the second spray pipe 24 in the upper section of the absorption tower 2 for use as a secondary circulating liquid.

[0092] According to a preferred embodiment of the present invention, the liquid receiving plate 26 is connected to the second liquid inlet of the liquid collecting funnel 22. This preferred embodiment ensures that the mass content of sodium sulfate in the absorbent in the middle section of the absorption tower 2 does not exceed 8%.

[0093] According to a preferred embodiment of the present invention, the upper section of the absorption tower 2 is further provided with a makeup water inlet, which is located between the second spray pipe 24 and the liquid receiving plate 26, for introducing makeup water from the boundary area into the upper section of the absorption tower 2.

[0094] According to a preferred embodiment of the present invention, the upper section of the absorption tower 2 is further provided with a demister 25, which is arranged above the second spray pipe 24 for demisting.

[0095] According to a preferred embodiment of the present invention, an oxidizing atmosphere inlet is provided on the lower section of the absorption tower 2 for introducing an oxidizing atmosphere.

[0096] According to a preferred embodiment of the present invention, the supergravity reactor 4 includes a motor and a rotor, the rotor being filled with packing material and driven to rotate by the motor; wherein the packing material is used to disperse the circulating absorbent liquid, and the rotor is used to drive the circulating absorbent liquid to rotate.

[0097] According to a preferred embodiment of the present invention, the supergravity reactor 4 includes a shell, a rotor is provided inside the shell, the rotor is filled with packing material, and the rotor is driven to rotate by a motor.

[0098] According to a preferred embodiment of the present invention, the rotor is connected to a liquid phase tube and a gas phase tube, wherein the liquid phase tube is fitted inside the gas phase tube, the other end of the liquid phase tube is the liquid inlet, and the other end of the gas phase tube is the gas outlet.

[0099] According to a preferred embodiment of the present invention, a liquid outlet is provided at the bottom of the housing.

[0100] According to a specific embodiment of the present invention, the side wall of the shell of the supergravity reactor 4 is provided with a gas inlet. The first flue gas enters the inner cavity of the shell tangentially through the gas inlet and enters the packing through the outer edge of the rotor. The circulating absorbent enters the rotor through the liquid inlet and is sprayed on the inner edge of the rotor. The circulating absorbent is dispersed by the packing therein, thereby improving the mass transfer and reaction process with the regenerated flue gas. The circulating absorbent that is thrown out flows out by gravity through the liquid outlet.

[0101] According to a preferred embodiment of the present invention, the liquid outlet of the lower section of the absorption tower 2 is connected to the first spray pipe 21 of the lower section of the absorption tower 2 and the downstream ammonium sulfate crystallization unit, respectively. In this preferred embodiment, a portion of the concentrated circulating liquid is sent to the downstream ammonium sulfate crystallization unit for processing to ensure that the mass content of sodium sulfate in the remaining concentrated circulating liquid returned to the first spray pipe 21 of the lower section of the absorption tower 2 does not exceed 20%; the remaining portion is returned to the first spray pipe 21 of the lower section of the absorption tower 2.

[0102] According to a preferred embodiment of the present invention, the system further includes a first circulating liquid pump 3 for pressurizing and atomizing the primary circulating liquid.

[0103] According to a preferred embodiment of the present invention, the system further includes a second circulating liquid pump 5 for pressurizing and atomizing the circulating absorbent liquid.

[0104] According to a preferred embodiment of the present invention, the system further includes a third circulating liquid pump 6 for pressurizing and atomizing the secondary circulating liquid.

[0105] According to a preferred embodiment of the present invention, the system further includes a dust collector 1 disposed before the absorption tower 2 for removing particulate matter from the regenerated flue gas.

[0106] According to a specific embodiment of the present invention, refer to Figure 1 The regenerated flue gas is sent to dust collector 1 to remove particulate matter, and then introduced into the lower section of absorption tower 2 to concentrate the primary circulating liquid, resulting in first flue gas and concentrated circulating liquid. The concentrated circulating liquid is oxidized in an oxidizing atmosphere and then drawn out and pressurized by the first circulating liquid pump 3 and divided into two parts. One part is sent to the downstream ammonium sulfate crystallization unit for further processing; the remaining part is sent to the first spray pipe 21 in the lower section of absorption tower 2 as primary circulating liquid.

[0107] The hypergravity reactor 4 is equipped with a motor, a rotor, and packing material. The packing material is used to disperse the circulating absorbent liquid. The motor and rotor are used to drive the circulating absorbent liquid to rotate. The first flue gas is sent into the hypergravity reactor 4 and undergoes a first counter-current contact desulfurization with the circulating absorbent liquid introduced from the liquid outlet of the collection funnel 22 to obtain the second flue gas and the third-stage circulating liquid. The third-stage circulating liquid flows by gravity from the liquid outlet of the hypergravity reactor 4 to the second liquid inlet of the collection funnel 22.

[0108] Fresh absorbent from the boundary area enters through the absorbent replenishment inlet of the collecting funnel 22. At the same time, the absorbent in the collecting funnel 22 is sent out and pressurized by the second circulating liquid pump 5 and divided into two parts: part is sent to the lower section of the absorption tower 2 as the primary circulating liquid; the remaining part is sent to the supergravity reactor 4 to wash and absorb SO2 in the first flue gas.

[0109] In the middle section of absorption tower 2, the second flue gas is defoamed by demister 23 and then sent to the upper section of absorption tower 2 via liquid receiving plate 26 (on which is equipped with vertically arranged and vertically connected air riser pipes). The liquid separated by demister 23 flows by gravity into liquid collection funnel 22. At the second spray pipe 24 in the upper section of absorption tower 2, the second flue gas has a second counter-current contact with the atomized secondary circulating liquid, and then is defoamed by demister 25 and discharged into the atmosphere through the gas outlet at the top of absorption tower 2.

[0110] The makeup water from the boundary area that enters from the upper section of the absorber tower 2 and the fourth-stage circulating liquid obtained by the counter-current contact of the second section of the upper section of the absorber tower 2 are collected on the receiving plate 26 and led out. Then, after being pressurized by the third circulating liquid pump 6, it is divided into two parts: part is sent to the second spray pipe 24 of the upper section of the absorber tower 2 as the secondary circulating liquid; the remaining part is sent to the liquid collection funnel 22 in the middle section of the absorber tower 2 to maintain the sodium sulfate content in the absorbent in the middle section of the absorber tower 2 not higher than 8%.

[0111] The present invention will be described in detail below through embodiments.

[0112] In the following embodiments, the sulfur content and particulate matter content parameters in the flue gas were measured by an online flue gas monitoring instrument.

[0113] Example 1

[0114] Continuous desulfurization process using sodium alkali method for catalytic cracking regenerated flue gas, such as Figure 1 As shown, the main steps include:

[0115] The regenerated flue gas from the catalytic cracking waste heat boiler has a temperature of 180℃, a pressure of 0.005 MPaG, and an SO2 content of 780 mg / Nm³. 3 Particulate matter content 230 mg / Nm 3 .

[0116] First, the regenerated flue gas is sent to dust collector 1 to remove particulate matter. The particulate matter content in the regenerated flue gas exiting dust collector 1 is reduced to 10 mg / Nm³. 3 It is sent to the lower section of absorption tower 2.

[0117] In the lower section of absorption tower 2, regenerated flue gas is used to concentrate the primary circulating liquid to obtain the first flue gas cooled to 56°C and the concentrated circulating liquid.

[0118] The concentrated circulating liquid sent from the lower section of the absorber tower 2 is pressurized to 0.3 MPaG by the first circulating liquid pump 3 and then divided into two streams: the first stream is sent to the first spray pipe 21 in the lower section of the absorber tower 2 as the primary circulating liquid; the second stream is sent to the downstream ammonium sulfate crystallization unit for further processing. The flow rate of the second concentrated circulating liquid sent to the downstream ammonium sulfate crystallization unit is controlled to maintain the sodium sulfate mass content in the first concentrated circulating liquid at 10%.

[0119] The supergravity reactor 4 includes a motor and a rotor. The rotor is filled with packing material and is driven to rotate by the motor. The packing material is used to disperse the circulating absorbent liquid, and the rotor is used to drive the circulating absorbent liquid to rotate.

[0120] The first flue gas, emitted from the lower section of absorber 2, is fed into the gas inlet of the hypergravity reactor 4. The circulating absorbent is introduced through the liquid inlet. Under hypergravity conditions of 56°C and 150g centrifugal force, the first flue gas undergoes a first counter-current contact with the first flue gas to remove SO2, resulting in a second flue gas and a tertiary circulating liquid at 56°C. The SO2 content in the second flue gas is 30 mg / Nm³. 3 The second flue gas discharged from the gas outlet of the supergravity reactor 4 returns to the middle section of the absorption tower 2; the tertiary circulating liquid flows by gravity from the liquid outlet of the supergravity reactor 4 to the liquid collection funnel 22 in the middle section of the absorption tower 2; the liquid-to-gas ratio of the circulating absorbent flow rate to the first flue gas flow rate in the supergravity reactor 4 is 3 L / Nm³. 3 .

[0121] A 20wt% sodium hydroxide aqueous solution from the boundary area enters the absorbent replenishment inlet of the collection funnel 22 in the middle section of the absorption tower 2. At the same time, the absorbent in the collection funnel 22 is pressurized to 0.4MPaG by the second circulation pump 5 and then divided into two streams: one stream is sent to the supergravity reactor 4 to wash and absorb SO2 in the first flue gas, and the other stream is sent to the lower section of the absorption tower 2 for concentration to maintain the sodium sulfate content in the absorbent in the middle section of the absorption tower 2 at 2wt%.

[0122] In the middle section of the absorption tower 2, the second flue gas is defoamed by the demister 23 and then sent to the upper section of the absorption tower 2 via the liquid receiving plate 26; the liquid separated by the demister 23 flows by gravity to the liquid collection funnel 22 in the middle section of the absorption tower 2.

[0123] At the second spray pipe 24 in the upper section of the absorption tower 2, the second flue gas and the atomized secondary circulating liquid make a second counter-current contact to remove residual SO2 and sodium sulfate components entrained in the mist from the flue gas. After being demisted by the demister 25, the purified flue gas is discharged into the atmosphere.

[0124] The makeup water (temperature 25℃, pressure 0.8MPa) from the boundary area that is added to the upper section of the absorption tower 2 comes into countercurrent contact with the second stage of the upper section of the absorption tower 2. The resulting 56℃ fourth-stage circulating liquid is collected on the receiving plate 26 and divided into two streams: one stream is pressurized to 0.8MPaG by the second circulating liquid pump 5 and sent to the second spray pipe 24 of the upper section of the absorption tower 2 as the secondary circulating liquid; the other stream is sent to the liquid collection funnel 22 in the middle section of the absorption tower 2.

[0125] The absorption liquid consumption, energy consumption, and desulfurization results during stable operation are shown in Table 1.

[0126] Comparative Example 1

[0127] Taking a 3 million tons / year catalytic cracking process as an example, its regenerated flue gas volume is approximately 448,000 Nm³. 3 / h, SO2 content is approximately 780 mg / Nm 3 The particulate matter content is approximately 230 mg / Nm³. 3 .

[0128] Desulfurization was carried out in accordance with the method of CN201871320U.

[0129] The absorption liquid consumption, energy consumption, and desulfurization results during stable operation are shown in Table 1.

[0130] Table 1

[0131]

[0132] As can be seen from the results in Table 1, compared with Comparative Example 1, Example 1 of the present invention has the advantages of better desulfurization effect, less circulating absorbent consumption and lower energy consumption.

[0133] This invention utilizes regenerated flue gas to further concentrate the primary circulating liquid (primary concentrate), thereby improving the system's energy utilization rate and reducing the amount of wastewater discharged and the amount of water to be added to the system.

[0134] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for continuous desulfurization of regenerated flue gas using sodium alkali, characterized in that, The method includes the following steps: (1) In the lower section of the absorption tower, the primary circulating liquid containing sodium sulfate is concentrated using regenerated flue gas to obtain the first flue gas and the concentrated circulating liquid; (2) in a high gravity reactor, the first flue gas is subjected to first reverse contact desulfurization with circulating absorption liquid from the middle section of the absorption tower, to obtain second flue gas and tertiary circulating liquid, and the tertiary circulating liquid is circulated to the middle section of the absorption tower; wherein the SO2 content in the second flue gas is not higher than 35 mg / Nm 3 ; (3) In the upper section of the absorption tower, the second flue gas and the secondary circulating liquid undergo a second counter-current contact to obtain purified flue gas and a fourth-stage circulating liquid. In the purified flue gas, the SO2 content is not higher than 20 mg / Nm³. 3 .

2. The method according to claim 1, wherein, In step (1), the mass content of sodium sulfate in the primary circulating liquid is not higher than 20%, preferably 5-15%; Preferably, the temperature of the first flue gas is 50-65°C; Preferably, step (1) includes: in the lower section of the absorber, the primary circulating liquid is atomized under a spray pressure of 0.2-0.6 MPaG, and then the atomized primary circulating liquid is concentrated using regenerated flue gas to obtain the first flue gas and the concentrated circulating liquid; Preferably, at least a portion of the concentrated circulating liquid obtained in step (1) is returned to step (1) for recycling.

3. The method according to claim 1 or 2, wherein, The flow rate of the circulating absorbent to the first flue gas has a liquid-to-gas ratio of 2-5 L / Nm³. 3 ; Preferably, the operating conditions of the centrifugal reactor include: a temperature of 50-65℃; and a centrifugal force of 10-1000g. Preferably, step (2) includes: in a supergravity reactor, under a spray pressure of 0.2-0.8 MPaG, the circulating absorbent is atomized and subjected to first reverse contact desulfurization with the first flue gas to obtain the second flue gas and the third-stage circulating liquid; Preferably, the sodium sulfate content in the absorbent in the middle section of the absorption tower is not higher than 8%, and more preferably 2-5%. Preferably, the fresh absorbent and the tertiary circulating liquid obtained in step (2) are sent to the middle section of the absorption tower, and then drawn out and divided into two streams: part of it is sent to the lower section of the absorption tower as the primary circulating liquid; the remaining part is sent to the supergravity reactor as the circulating absorbent. Preferably, the absorbent is an aqueous solution of sodium hydroxide.

4. The method according to any one of claims 1-3, wherein, The hypergravity reactor includes a motor and a rotor. The rotor is filled with packing material and is driven to rotate by the motor. The packing material is used to disperse the circulating absorbent liquid, and the rotor is used to drive the circulating absorbent liquid to rotate.

5. The method according to any one of claims 1-4, wherein, Step (3) includes: in the upper section of the absorption tower, under a spray pressure of 0.4-0.8 MPaG, the secondary circulating liquid is atomized and comes into a second counter-current contact with the second flue gas to obtain purified flue gas and quaternary circulating liquid; Preferably, at least a portion of the replenished water and the fourth-stage circulating fluid obtained in step (3) is returned to step (3) for use as a second-stage circulating fluid.

6. The method according to any one of claims 1-5, wherein, The temperature of the regenerated flue gas is 150-250℃, and the pressure is 0.004-0.01 MPaG; Preferably, the SO2 content in the regenerated flue gas is 500-3000 mg / Nm³. 3 Particulate matter content is 100-1000 mg / Nm³ 3 .

7. A system for continuous desulfurization of regenerated flue gas using sodium alkali method, the system comprising an absorption tower (2) and a supergravity reactor (4); The lower section of the absorption tower (2) is equipped with a first spray pipe (21) for using regenerated flue gas to concentrate the primary circulating liquid containing sodium sulfate, so as to obtain the first flue gas and the concentrated circulating liquid. The supergravity reactor (4) is used to perform a first counter-current contact desulfurization of the first flue gas and the circulating absorbent from the middle section of the absorption tower (2) to obtain the second flue gas and the third-stage circulating liquid. The upper section of the absorption tower (2) is provided with a second spray pipe (24) for making the second flue gas and the secondary circulating liquid in a second counter-current contact to obtain purified flue gas and quaternary circulating liquid; The absorption tower (2) is equipped with a liquid collection funnel (22) in the middle section for storing the absorption liquid; The first liquid inlet of the liquid collecting funnel (22) is connected to the liquid outlet of the supergravity reactor (4).

8. The system according to claim 7, wherein, The liquid collection funnel (22) is provided with an absorbent replenishment inlet for introducing fresh absorbent; Preferably, a demister (23) is also provided in the middle section of the absorption tower (2), arranged above the liquid collection funnel (22), for defoaming the second flue gas.

9. The system according to claim 7 or 8, wherein, The absorption tower (2) is also equipped with a liquid receiving plate (26) for receiving the fourth-stage circulating liquid; Preferably, the liquid receiving plate (26) is provided with a vertically arranged and vertically connected air riser pipe for gas circulation; Preferably, the upper section of the absorption tower (2) is separated from the middle section of the absorption tower (2); Preferably, the liquid receiving plate (26) is connected to the second liquid inlet of the liquid collecting funnel (22); Preferably, the liquid receiving plate (26) is connected to the second spray pipe (24) in the upper section of the absorption tower (2); Preferably, the upper section of the absorption tower (2) is also provided with a demister (25), which is arranged above the second spray pipe (24) for demisting.

10. The system according to any one of claims 7-9, wherein, The supergravity reactor (4) includes a motor and a rotor. The rotor is filled with packing material and is driven to rotate by the motor. The packing material is used to disperse the circulating absorbent liquid, and the rotor is used to drive the circulating absorbent liquid to rotate. Preferably, the liquid outlet of the lower section of the absorption tower (2) is connected to the first spray pipe (21) of the lower section of the absorption tower (2) and the downstream ammonium sulfate crystallization unit, respectively.

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