Catalytic cracking flue gas dust removal and desulfurization integrated process method and device

Abstract

The invention provides a catalytic cracking flue gas dust removal and desulfurization integrated process method and a catalytic cracking flue gas dust removal and desulfurization integrated device. The method comprises the following steps: firstly, spraying sodium-based powder onto an inlet flue, and carrying out contact reaction on the sodium-based powder and flue gas to remove SO3; then, the flue gas is introduced into the integrated dust removal and desulfurization tower to rise and sequentially passes through a first-stage quenching section: a plurality of quenching spray heads spray slurry from the tower bottom, so that the flue gas is quenched and cooled, and SO2 is absorbed; in the second-stage absorption section, a plurality of layers of absorption section nozzles spray slurry from the bottom of the tower, the flue gas is washed and dedusted, and SO2 is absorbed; in the multi-tube array tube dust removal section, fine particles are condensed after flue gas passes through a plurality of venturi tubes, and dust is intercepted and removed under the action of spraying slurry; in the dust and fog drop removal section, the flue gas enters a cyclone cylinder assembly to be subjected to rotary centrifugal separation, and small particles are condensed, collide with the wall of a cyclone cylinder and are captured and absorbed by a liquid film to realize dust and fog drop removal and then discharged through a chimney. According to the invention, dust removal and desulfurization of the flue gas are integrated, SO2, SO3 and particulate matters with different particle sizes in the flue gas can be efficiently removed, and the device has the characteristics of short flow, small resistance drop and high efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic cracking flue gas treatment. Specifically, it relates to an integrated process method and device for dust removal and desulfurization of catalytic cracking flue gas. Background Art

[0002] The fluid catalytic cracking (FCC) unit is an important secondary processing unit in the oil refining process and an important means to increase the yield of light oils such as gasoline and diesel. The flue gas generated during the catalyst burning and regeneration process of FCC has the characteristics of high exhaust gas temperature, large fluctuation in dust content, and rich in fine and hard FCC catalyst particles, and is one of the main pollutant emission sources in the refinery.

[0003] Specifically, the concentration of NO X and SO X in the catalytic cracking flue gas usually fluctuates greatly. Generally, the SO X concentration is 700 - 4500 mg / m 3 , and the NO X concentration is 50 - 400 mg / m 3 ; the temperature of the regeneration flue gas is relatively high, the normal temperature is 180°C - 230°C, and the maximum temperature can reach 350°C - 500°C when the catalytic waste heat boiler or CO boiler fails; the concentration of particulate matter in the flue gas fluctuates greatly. Under normal operating conditions, after passing through three-stage and four-stage cyclone separators, the particulate matter concentration is 150 - 300 mg / m 3 , while when regularly blowing soot on the waste heat boiler or CO boiler, the maximum concentration can reach 3000 - 4000 mg / Nm 3 ; most of the particulate matter carried in the flue gas is fine powder of the catalytic cracking catalyst, with a small particle size distribution. The particle size of 0 - 5 μm accounts for more than 70%, and the hardness is relatively large. Due to the above characteristics of the catalytic cracking flue gas, the technical requirements for dust removal and desulfurization are relatively harsh.

[0004] According to the causes of SO X and dust generation, the measures for catalytic cracking flue gas treatment are mainly divided into two categories. One category is to reduce the sulfur content of the raw material, including using SO X transfer agent or FCC raw material hydrotreating; the other category is to build dust removal and desulfurization facilities for the discharged flue gas, that is, flue gas desulfurization technology. With the increasing maturity, simplicity and reliability of the wet desulfurization technology, the first category of technology has gradually been replaced by the integrated wet dust removal and desulfurization technology.

[0005] CN104971612A discloses a catalytic cracking flue gas dust removal and desulfurization collaborative treatment process, including the following steps: the catalytic cracking regenerated flue gas after waste heat utilization is cooled to 150-200 °C by a flue gas cooling device; the dust in the flue gas is removed by a bag filter, pressurized by a booster fan and then enters a heat exchanger, and after exchanging heat with the clean flue gas coming out of the top of the desulfurization tower, the temperature is reduced to 105-115 °C, and then enters the desulfurization tower for desulfurization; in the desulfurization tower, the desulfurization slurry forms a reverse direct contact with the upward regenerated flue gas through a slurry circulation pump and a spray layer to remove sulfur dioxide in the flue gas; after the fog droplets entrained in the flue gas are removed by a demister, the flue gas enters the chimney for emission through a heat exchanger from the outlet flue at the top of the absorption tower.

[0006] CN205084627U discloses a catalytic cracking flue gas dust removal and desulfurization device, which consists of a desulfurization absorption tower, a dust removal quench tower, a slurry circulation pump, and a slurry return pipeline. By installing an aeration oxidation device at the bottom of the dust removal quench tower, the sulfite and bisulfite in the circulating slurry can be oxidized to sulfate and bisulfate, improving the absorption capacity of the circulating slurry for sulfur dioxide in the flue gas and reducing the sulfur dioxide content in the discharged flue gas.

[0007] CN108636037A discloses a wet desulfurization, denitrification and dust removal process for catalytic cracking flue gas. The catalytic cracking flue gas enters a high-temperature resistant bag filter for dust removal and then enters a spray tower, where it makes efficient contact with the sprayed lime slurry for flue gas desulfurization; the desulfurized flue gas reacts with a denitrification oxidant before entering the wet desulfurization and denitrification tower to oxidize the nitrogen oxides in the flue gas to nitrogen; the flue gas containing lime and calcium sulfite enters the wet desulfurization and denitrification tower, where the desulfurization and denitrification tower, the circulation tank, and the oxidation fan jointly constitute a wet desulfurization and denitrification system, operating in a cycle to remove SO2 and oxidized N2O5 in the flue gas. The formed calcium sulfite and calcium nitrite and other substances are oxidized to form a mixed solution of calcium sulfate and calcium nitrate, which is discharged regularly for treatment, and the treated flue gas is discharged from the top of the tower.

[0008] However, in the current wet dust removal and desulfurization integrated technology, there are still some problems. For example, the removal of SO3 in catalytic cracking flue gas is insufficient. The SO3 in the flue gas will form sub-micron sulfuric acid aerosol with the rapid cooling of the flue gas at the inlet of wet dust removal and desulfurization. Conventional spray washing is difficult to effectively remove sulfuric acid mist. Finally, it condenses with particulate dust in the discharged flue gas and presents blue under the action of light scattering, making the discharged flue gas prone to blue smoke phenomenon. For SO2 and particulate matter in catalytic cracking flue gas, their removal efficiency needs to be further improved, especially when the imported flue gas conditions fluctuate greatly and for the removal of fine particles in particulate matter. At the same time, the removal of a large amount of droplets contained in the flue gas after desulfurization and dust removal also needs to be further improved. Therefore, it is of great significance to develop an integrated wet dust removal and desulfurization technology process for catalytic cracking flue gas that meets the current industry requirements. Summary of the Invention

[0009] The purpose of the present invention is to overcome the deficiencies in the prior art and provide an integrated process method and device for dust removal and desulfurization of catalytic cracking flue gas, which integrates dust removal and desulfurization of flue gas and efficiently removes SO2, SO3 and particulate matter with different particle sizes in the flue gas.

[0010] The technical solution provided by the present invention is as follows:

[0011] An integrated process method for dust removal and desulfurization of catalytic cracking flue gas includes the following steps:

[0012] (1) Inject sodium-based powder into the high-temperature flue at the inlet of the integrated dust removal and desulfurization tower, and contact and react with the high-temperature catalytic cracking flue gas in the flue to remove SO3 in the flue gas;

[0013] (2) The high-temperature catalytic cracking flue gas rises into the integrated dust removal and desulfurization tower through the flue gas inlet, and is sequentially treated by a primary quenching section, a secondary absorption section, a multi-tubular tube dust removal section, and a dust and droplet removal section, and then discharged through a chimney, where:

[0014] In the first-stage quenching section, a number of quenching nozzles spray the circulating absorption slurry from the oxidation section at the bottom of the tower to completely cover the cross-section of the flue gas inlet, rapidly cool the flue gas and absorb and remove SO2. In the second-stage absorption section, a number of layers of absorption section nozzles spray the circulating absorption slurry from the oxidation section at the bottom of the tower to completely cover the cross-section inside the tower, and the flue gas is washed, dust-removed and absorbs and removes SO2. In the multi-tube type tube dust-removal section, after the flue gas passes through a number of parallel Venturi tube structures, fine particles coagulate, and are intercepted and washed under the action of the sprayed slurry above to achieve dust removal. The sprayed slurry comes from the dust collector liquid sump in the multi-tube type tube dust-removal section. In the dust and mist droplet removal section, the flue gas enters the cyclone cylinder assembly for rotational centrifugal separation. Tiny particles coagulate into large droplets and collide with the cyclone cylinder wall whose surface is wetted by spraying, and are captured and absorbed by the liquid film to achieve dust and mist droplet removal. In the oxidation section at the bottom of the tower, the circulating absorption slurry undergoes primary oxidation under the action of the introduced oxidation air, oxidizing the sulfite in the slurry into sulfate and reducing the COD of the absorption slurry.

[0015] When the indicators of the circulating absorption slurry exceed the standard, a part of the absorption slurry needs to be discharged to ensure the desulfurization and dust removal efficiency. Then, the process method further includes step (3):

[0016] (3) A part of the circulating absorption slurry is subjected to sedimentation treatment in a sedimentation tank, then fed into an oxidation tank for secondary oxidation, and then cooled and discharged.

[0017] It should be noted that the above-mentioned integrated process method for dust removal and desulfurization of catalytic cracking flue gas is a continuous operation process, and the above steps do not limit the absolute time sequence.

[0018] The present invention is further arranged such that in step (1), it specifically includes the following steps:

[0019] Sodium-based powder, namely a mixture of Na2CO3 and NaHCO3 powder, is sprayed into the inlet high-temperature flue duct. The sodium-based powder is provided by a sodium-based powder silo, ground fine by a grinder, and then fed into the flue duct by the compressed air provided by an air compressor. After the sodium-based powder reacts with the high-temperature flue gas, it enters the integrated dust removal and desulfurization tower.

[0020] The present invention is further arranged such that in step (2), it specifically includes the following steps:

[0021] In the primary quenching section: The high-temperature flue gas after reacting with the sodium-based powder to remove SO3 enters the primary quenching section in the integrated dust removal and desulfurization tower horizontally through the flue gas inlet. A number of quenching nozzles in the primary quenching section spray the circulating absorption slurry sent by the first and second slurry circulation pumps to rapidly cool down the high-temperature flue gas to its saturation temperature. The quenching nozzles spray the slurry to form a number of flat conical curtain-shaped impinging water curtains, covering the entire cross-section of the flue gas inlet. The high-temperature flue gas passes through the number of flat conical curtain-shaped impinging water curtains to be rapidly cooled down, and SO2 and dust are removed through preliminary washing reaction. The sprayed liquid flows downward into the bottom liquid collecting tank of the tower bottom oxidation section.

[0022] In the secondary absorption section: The flue gas after rapid cooling then rises to the secondary absorption section. A number of layers of absorption section nozzles in the secondary absorption section spray the circulating absorption slurry sent by the first and second slurry circulation pumps to absorb and wash the flue gas. Each layer of absorption section nozzles sprays the slurry to form a flat conical curtain-shaped impinging water curtain, covering the entire cross-section of the tower. And the absorption section nozzles between layers are arranged with a certain angle offset, covering the cylinder body of the secondary absorption section. The rising flue gas quickly collides violently and comes into close contact with the droplets in the impinging water curtain, effectively removing the coarse particles in the flue gas, and quickly undergoing a chemical reaction to remove SO2. The pH value of the absorption slurry is maintained at about 7.0. The sprayed liquid flows downward along the tower wall into the bottom liquid collecting tank of the tower.

[0023] In the multi-tube type tube dust removal section: The flue gas after being washed, dust removed, and SO2 absorbed in the secondary absorption section rises to the multi-tube type tube dust removal section. The flue gas enters each venturi tube of the multi-tube type tube dust collector, rotates and rises after being guided by the guide vanes. Under the action of the venturi tube structure, intense collisions and aggregations occur between dust particles and droplets or between dust particles, aggregating into dust-containing droplets with a larger particle size. Spray nozzles corresponding one by one are provided above the venturi tubes, using the high-density spray slurry generated by the spray nozzles to intercept and filter the flue gas at the outlet of the venturi tubes, intercepting and washing the large-particle fine dust aggregated in the venturi tubes, thereby removing the fine water mist particles entrained in the flue gas, and at the same time, SO3 entrained in the droplets can be removed. The liquid sprayed by the spray nozzles is collected by the dust collector liquid collecting tank in the multi-tube type tube dust removal section and pumped out by the third slurry circulation pump and sent into the spray nozzles to form a slurry circulation.

[0024] In the dust and fog droplet removal section: The flue gas after multi-tube type tube dust removal rises to the dust and fog droplet removal section. The flue gas enters each cyclone cylinder assembly of the high-efficiency dust and fog droplet remover. Multiple cyclone cylinders are arranged in each cyclone cylinder assembly, and cyclone plates are additionally arranged in the cyclone cylinders, so that the flue gas rotates in the cyclone cylinders. Tiny particulate matters collide with each other, agglomerate and condense into large droplets, and move centrifugally outwards to collide with the cyclone cylinder wall. The flushing nozzles above the cyclone cylinder assembly spray fresh water to wet the cyclone cylinder wall, so that the large droplets colliding with the cyclone cylinder wall are captured and absorbed by the liquid film on the cyclone cylinder wall, realizing the high-efficiency dust and fog droplet removal of the flue gas. The liquid sprayed by the flushing nozzles flows downwards to the multi-tube type tube dust removal section and is collected by the liquid collection tank of the dust remover.

[0025] In the bottom tower oxidation section: An oxidation air distributor is arranged in the bottom tower oxidation section, and its oxidation air pipes are evenly distributed on the bottom cross-section of the tower. Oxidation air is introduced into the slurry through the oxidation air distributor to perform forced primary oxidation on the circulating absorption slurry at the bottom of the tower, oxidize the sulfite in the circulating absorption slurry into sulfate, and reduce the COD of the circulating absorption slurry. And the circulating absorption slurry at the bottom of the tower can overflow to the slurry collection pool through the overflow pipe, and after being stirred and mixed evenly in the slurry collection pool, it is recycled back to the bottom liquid collection tank of the bottom tower oxidation section.

[0026] The present invention is further arranged such that in step (3), it specifically includes the following steps:

[0027] During normal operation, the contents of dissolved salts, chlorides, and suspended catalyst solids in the circulating absorption slurry should be controlled. Specifically, the suspended solids SS ≤ 4 g / l, the chloride ions ≤ 750 mg / l, and the TDS content ≤ 5 wt%. When the above indicators exceed the standard, part of the circulating absorption slurry needs to be discharged to ensure the desulfurization and dust removal efficiency. Part of the circulating absorption slurry is sent to the settler through the outlet side lines of the first and second stage slurry circulation pumps, and a flocculant with a certain concentration is added to the inlet liquid pipe at the front end of the settler. In the supernatant of the slurry sedimentation in the settler, part of it is returned to the bottom liquid collection tank of the integrated dust removal and desulfurization tower for recycling, and part of it is introduced into the oxidation tank, and secondary oxidation is carried out by introducing compressed air; the slurry after COD is removed by oxidation flows from the oxidation tank to the drain tank by gravity, and then is sent to the slurry cooler by a drain pump. The temperature of the discharged wastewater is reduced to below 40 °C by using circulating cooling water and then discharged. The indicators of the discharged wastewater are SS ≤ 50 mg / L and COD ≤ 50 mg / L.

[0028] The present invention is further arranged such that the operating temperature of the integrated dust removal and desulfurization tower is 55 ± 10 °C, and the operating pressure is 4000 ± 100 Pa (G). When the flue gas load varies under the working conditions of 70% - 110%, the integrated dust removal and desulfurization tower can adapt to the load fluctuation and maintain normal operation.

[0029] The present invention is further configured such that the liquid collection tank at the bottom of the integrated dust removal and desulfurization tower stores the circulating absorption slurry, which is sent to the first-stage rapid cooling section and the second-stage absorption section through the first-stage and second-stage slurry circulation pumps for recycling; the liquid collection tank of the dust collector stores the circulating slurry of the multi-tube type tube dust removal section, and is sent into the spray nozzles of the multi-tube type tube dust removal section through the third-stage slurry circulation pump for recycling; the slurry in the liquid collection tank of the dust collector can overflow to the liquid collection tank at the bottom of the tower through the overflow pipe of the dust collector. During the slurry circulation process, the pH value of the liquid is monitored, and since there are fine catalyst particles in the circulating absorption slurry, in order to ensure the stable operation of the pump, the circulating pumps need to be switched alternately for operation.

[0030] The present invention is further configured such that a 10wt% - 30wt% NaOH solution, ammonia water or liquid ammonia is used as the absorbent, which is added to the liquid collection tank at the bottom of the tower and the liquid collection tank of the dust collector by an alkali liquid pump, and the amount of the added alkali liquid is regulated according to the pH value of the circulating slurry to maintain the pH of the circulating slurry at 6.0 - 7.5.

[0031] The present invention is further configured such that in order to supplement the water lost during the evaporation process and the slurry discharge process, fresh process water is supplemented to the liquid collection tank at the bottom of the tower and the liquid collection tank of the dust collector, and the liquid level at the bottom of the tower is monitored according to the liquid level gauge provided on the liquid collection tank at the bottom of the tower, and the amount of the supplemented fresh process water is regulated.

[0032] The present invention is further configured such that the first-stage rapid cooling section of the integrated dust removal and desulfurization tower is provided with a temperature alarm. When the flue gas temperature in the tower changes too much, or the temperature of the flue gas cooled by the rapid cooling nozzles in the first-stage rapid cooling section exceeds 85°C, or when the catalyst in the fluid catalytic cracking unit runs into the tower, the emergency rapid cooling water system is started to quickly supply a large amount of emergency rapid cooling water to the rapid cooling nozzles in the first-stage rapid cooling section. The rating of each control valve on the emergency rapid cooling water pipeline should be set at 50% of the required total flow rate. On the contrary, after the flue gas temperature in the tower is normal or the fault is eliminated, the integrated dust removal and desulfurization tower enters the normal operation state, and the flue gas after dust removal and desulfurization is discharged from the chimney above the integrated dust removal and desulfurization tower.

[0033] The present invention is further configured such that the suspended particulate matter in the settler aggregates at the bottom of the settler through flocculation sedimentation and is discharged to the filter box or the vacuum belt filter press in the form of thick slurry. The solid content in the thick slurry is 3wt% - 5wt%. After being filtered by the filter box or dried by the vacuum belt filter press, about 30wt% - 60wt% of solid matter is produced, which is regularly cleaned and transported out. The clear liquid after filtration and drying flows by gravity to the collection pond and is circulated back to the settler through the collection pond pump.

[0034] The present invention is further configured such that, after a portion of sodium bisulfite in the oxidation tank is oxidized to produce acid, in order to maintain an appropriate pH, an alkali solution is introduced into the oxidation tank, and the pH of the overflow liquid of the oxidation tank is monitored by an on-line pH meter. The regulating valve on the alkali solution pipeline is controlled through the pH meter interlock, so as to control the addition amount of the alkali solution and keep the pH of the effluent at about 7±0.5.

[0035] The second aspect of the present invention lies in providing a catalytic cracking flue gas dust removal and desulfurization integrated device. The integrated device includes an integrated dust removal and desulfurization tower, and a flue gas inlet system, a liquid supply and circulation system, and a slurry treatment system that are provided in a supporting manner. Among them:

[0036] The integrated dust removal and desulfurization tower sequentially includes a tower bottom oxidation section, a primary quench section, a secondary absorption section, a multi-tube type tube dust removal section, a dust and mist droplet removal section, and a chimney from bottom to top; the tower bottom oxidation section is provided with a tower bottom liquid collecting tank and an oxidation air distributor; the primary quench section is provided with a flue gas inlet and a number of quench spray nozzles; a number of layers of absorption section spray nozzles are arranged on the tower wall of the secondary absorption section; the multi-tube type tube dust removal section is provided with a multi-tube type tube dust collector, including a dust collector liquid collecting tank, a number of juxtaposed venturi tubes fixedly installed through the slot plate of the dust collector liquid collecting tank, and a spray pipe arranged above the venturi tubes and spray nozzles arranged on the spray pipe; the dust and mist droplet removal section is provided with a high-efficiency dust and mist droplet remover, including a number of juxtaposed cyclone tube assemblies and a flushing hose arranged above the cyclone tube assemblies and a flushing nozzle connected to the flushing hose.

[0037] The present invention is further configured such that the oxidation air pipes of the oxidation air distributor are evenly distributed on the tower bottom cross-section, and the inlet of the oxidation air distributor is connected to an oxidation air blower to provide oxidation air for the tower bottom oxidation section. The quench spray nozzles of the primary quench section are set to 1 to 4, and are used to spray the circulating absorption slurry from the tower bottom. The absorption section spray nozzles of the secondary absorption section are set to 2 to 5 layers at different heights from bottom to top, with 3 to 5 spray nozzles arranged in each layer, a total of 6 to 25 spray nozzles, and are used to spray the circulating absorption slurry from the tower bottom to wash the flue gas rising in the tower, and the layers of the spray nozzles in each layer are arranged in a staggered manner at a certain angle. The outer periphery of the slot plate of the dust collector liquid collecting tank of the multi-tube type tube dust collector is connected to the tower inner wall and is installed at a certain angle; a guide vane is arranged at the bottom inlet of the venturi tube, and the spray nozzles and the venturi tubes correspond one by one; a dust collector overflow pipe is fixedly arranged through the slot plate of the dust collector liquid collecting tank, and the bottom outlet of the dust collector overflow pipe is communicated with the tower bottom liquid collecting tank. A multi-stage combined cyclone tube is arranged in the cyclone tube assembly of the high-efficiency dust and mist droplet remover, and a cyclone plate is added in the cyclone tube to make the flue gas rotate and collide and coagulate.

[0038] The present invention is further configured such that the flue gas inlet system includes an inlet high-temperature flue connected to the flue gas inlet and a sodium-based powder spray gun provided on the inlet high-temperature flue. The inlet of the sodium-based powder spray gun is connected to an air compressor and a sodium-based powder bin; preferably, a grinder is provided between the inlet of the sodium-based powder spray gun and the sodium-based powder bin.

[0039] The present invention is further configured such that the liquid supply and circulation system includes a bottom tower circulation spraying system, a multi-tubular tube dust removal section circulation system, a bottom tower circulation system, a process water supply system, an absorbent supply system, and an emergency water supply system; wherein:

[0040] The bottom tower circulation spraying system includes first and second stage slurry circulation pumps connected to the bottom end of the bottom tower liquid collection tank. The outlets of the first and second stage slurry circulation pumps are connected to the quench nozzles and the absorption section nozzles to provide absorbent slurry for spraying in the first stage quench section and the second stage absorption section; the multi-tubular tube dust removal section circulation system includes a third stage slurry circulation pump connected to the bottom end of the dust collector liquid collection tank. The outlet of the third stage slurry circulation pump is connected to the spray pipe; the bottom tower circulation system includes an overflow pipe provided on the side wall of the bottom tower oxidation section. The overflow pipe is connected to a slurry collection pool, and the slurry collection pool is connected to the bottom tower liquid collection tank through a slurry collection pool pump.

[0041] The process water supply system includes a fresh water pressurizing pump. The outlet of the fresh water pressurizing pump is connected to the dust collector liquid collection tank and the bottom tower liquid collection tank to provide replenishing fresh water for the integrated dust removal and desulfurization tower; it is also connected to the flushing hose to provide fresh water for flushing and spraying in the dust removal and mist droplet removal section; the absorbent supply system includes an alkali liquid pump connected to an alkali liquid tank. The outlet of the alkali liquid pump is connected to the bottom tower liquid collection tank and the dust collector liquid collection tank to provide replenishing absorbent alkali liquid for the integrated dust removal and desulfurization tower; the emergency water supply system includes an emergency water replenishing pump connected to an emergency water tank. The outlet of the emergency water replenishing pump is connected to the quench nozzles to provide emergency quench water for the integrated dust removal and desulfurization tower during emergencies.

[0042] The present invention is further configured such that the slurry treatment system includes a settler, an oxidation tank, a drain tank, a drain pump, and a slurry cooler connected in sequence; wherein, the inlet of the settler is connected to the outlets of the first and second stage slurry circulation pumps. The thick slurry outlet of the settler is connected to a filter box or a vacuum belt filter. The clear liquid outlet of the filter box or the vacuum belt filter is connected to a collection pool. The collection pool is connected to the inlet of the settler through a collection pool pump to perform cyclic sedimentation and filtration treatment on the filtered clear liquid; the clear liquid outlet of the settler is connected to the oxidation tank and is also connected to the bottom tower liquid collection tank to return part of the sedimented clear liquid to the tower for reuse; the oxidation tank is provided with two or three in series to perform oxidation treatment on the sedimented clear liquid in sequence.

[0043] The present invention is further configured such that the oxidation tank is connected to an oxidation blower to oxidize the clarified liquid after sedimentation using compressed air; the inlet of the oxidation tank is further connected to the outlet of the lye pump to supplement lye to the oxidation tank, so that the pH value of the oxidized effluent is maintained at about 7±0.5.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) The present invention integrates dust removal and desulfurization, has a short process flow, a small pressure drop, and high efficiency.

[0046] (2) The present invention adopts a hierarchical treatment method. By setting a primary quenching section, a secondary absorption section, a multi-tube type tube dust removal section, and a dust and mist droplet removal section, the SO2 and particulate matter dust with different particle sizes in the flue gas are disposed hierarchically to ensure that the desulfurization efficiency and the particulate matter dust reach the standard stably in the long term.

[0047] (3) The integrated dust removal and desulfurization tower of the present invention adopts a special structural design, including the setting of structures such as a quenching nozzle in the main tower, an absorption section nozzle, a multi-tube type tube dust collector and its spray nozzle, a high-efficiency dust and mist droplet remover and its flushing nozzle, etc. And the NaOH solution, ammonia water or liquid ammonia is provided by the alkali dissolving tank as the absorbent to achieve the effects of rapid cooling and temperature reduction of the flue gas and high-efficiency desulfurization and dust removal in the integrated dust removal and desulfurization tower. Moreover, the present invention has strong impact load resistance. The quenching nozzle and the absorption section nozzle both adopt large-diameter non-atomizing nozzles, which wash the large-particle and high-concentration particulate matter while reducing the flue gas temperature to saturation. Even in the case of catalyst loss during the operation of the fluid catalytic cracking unit, the dust removal and desulfurization effects can be ensured.

[0048] (4) The present invention sets a spray gun on the inlet flue of the integrated dust removal and desulfurization tower, and uses compressed air to spray the sodium-based powder into the flue to react with the high-temperature flue gas, so as to remove SO3 in the flue gas before entering the dust removal and desulfurization tower, and the injection of the sodium-based powder on the inlet flue can reduce the amount of caustic alkali required in the subsequent integrated dust removal and desulfurization tower.

[0049] (5) The primary quenching section of the present invention adopts a quenching nozzle with a special structural design. 1 to 4 quenching nozzles are arranged at a special angle at the flue gas inlet, so that the jet water curtains in the shape of flat cones sprayed by each nozzle overlap at multiple angles to completely cover the cross-section of the flue gas inlet. The high-temperature flue gas is rapidly cooled and temperature-reduced, absorbs SO2, and removes large particles while passing through the jet water curtain.

[0050] Since the quenching nozzle is arranged on the tower wall or the flue gas inlet, the jet water curtain can continuously wash the tower wall, and the acidic and particle-containing liquid formed by the contact of the flue gas and the slurry on the tower wall is washed and falls into the bottom liquid collecting tank, effectively avoiding the corrosion and abrasion of the wet-dry interface in the inlet section of the integrated dust removal and desulfurization tower.

[0051] (6) The secondary absorption section of the present invention adopts a special structural design. The absorption section is provided with 2 to 5 layers of absorption section nozzles at different heights from bottom to top according to the amount of flue gas to be treated. The multiple annular nozzles in each layer spray slurry to form a flat cone-shaped torrent water curtain to fully cover the cross-section inside the tower. The nozzles between layers are staggered at a certain angle to fully cover the cylinder of the secondary absorption section. The special structural design enables the flue gas to quickly collide violently and closely contact with the droplets in the torrent water curtain, thereby effectively removing the coarse particles and rapidly causing chemical reaction desulfurization.

[0052] Since the annular nozzle of the secondary absorption section is set on the tower wall, a torrent of water curtain is formed to continuously flush the tower wall, and the acidic and particle-containing liquid formed on the tower wall by the contact between the flue gas and the slurry is flushed and falls into the slurry pool at the bottom of the tower, thereby effectively preventing corrosion and abrasion of the integrated dust removal and desulfurization tower wall.

[0053] (7) The multi-tube tube dust collector of the present invention adopts a special structural design. The trough plate of the dust collection tank in the multi-tube tube dust collector is welded on the main tower at a certain angle. Multiple Venturi tubes are arranged on the trough plate. A guide vane is set at the inlet of each Venturi tube to make the flue gas rotate and rise. The Venturi principle is then used to remove fine particles entrained in the flue gas, so that the fine particles are aggregated into large particles. A non-atomizing spray nozzle is set at a certain height above the Venturi tube. Each spray nozzle corresponds to a Venturi tube. The high-density conical water film sprayed by the nozzle is used to intercept and wash the fine dust aggregated into large particles in the Venturi tube. At the same time, SO3 entrained in the droplets can be removed, achieving the effect of efficient fine dust removal and desulfurization. The high-density conical water film sprayed by the spray nozzle has the advantages of stable shape, strong impact resistance, and the water curtain is not easy to scatter.

[0054] (8) The present invention adopts a highly efficient dust removal and mist removal facility to eliminate the phenomenon of raining in the chimney. The structure is composed of a plurality of cyclone cylinder assemblies, each of which is provided with a multi-stage cyclone cylinder, and a cyclone plate is provided in the cyclone cylinder to make the desulfurized clean flue gas rotate in the cyclone cylinder. Through centrifugal separation, a violent rotation and disturbance of the gas-liquid two phases are formed above the cyclone, so that the fine droplets, fine dust particles, aerosols and other tiny particles in the clean flue gas collide with each other, agglomerate and condense into large droplets, and then, under the action of the outward rotation structure of the cyclone plate, the dust-removed and desulfurized clean flue gas moves outward centrifugally, and the large droplets formed by aggregation collide with the cyclone cylinder wall and are captured and absorbed by the cyclone cylinder wall liquid film, thereby achieving highly efficient mist removal and dust removal.

[0055] (9) The oxidation air distributor is arranged in the bottom oxidation section of the present invention to perform primary oxidation on the circulating absorption slurry in the tower. Then, two or three oxidation tanks connected in series are arranged after the settler in the process to further oxidize the slurry. The present invention adopts the two-stage oxidation technology inside and outside the tower to ensure that the COD of the discharged wastewater meets the discharge standard. And the present invention uses an efficient settler to treat the discharged slurry. The settler adopts a special structural design and is suitable for the slurry with a relatively small particle size distribution of catalytic cracking flue gas dust (the particle size of 0-5μm accounts for more than 70%) and relatively large hardness. The precipitation effect is good, the supernatant is clean, which is beneficial to the stable operation of the subsequent process oxidation tank and slurry heat exchanger, and avoids the problems of blockage and scaling. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 It is a process flow block diagram of the integrated process method for dust removal and desulfurization of catalytic cracking flue gas of the present invention;

[0057] Figure 2 It is a process flow chart of the integrated process method for dust removal and desulfurization of catalytic cracking flue gas of the present invention;

[0058] Among them, 1. Inlet high-temperature flue; 2. Sodium-based powder spray gun; 3. Air compressor; 4. Sodium-based powder silo; 5. Grinder; 6. Emergency water tank; 7. Emergency water make-up pump; 8. Integrated dust removal and desulfurization tower; 9. Bottom liquid collection tank of the tower; 10. Oxidation air distributor; 12. Flue gas inlet; 13. Quench spray head; 14. Absorption section spray head; 15. Multi-tube tubular dust collector; 16. Dust collector liquid collection tank; 17. Spray nozzle; 18. Dust collector overflow pipe; 19. High-efficiency dust and mist eliminator; 20. Flushing nozzle; 21. Chimney; 22. First and second stage slurry circulation pumps; 23. Third stage slurry circulation pump; 24. Fresh water booster pump; 25. Alkali liquid tank; 26. Alkali liquid pump; 27. Slurry collection pool; 28. Slurry collection pool pump; 29. Oxidation fan; 30. Flocculant tank; 31. Settler; 32. Oxidation tank; 33. Drainage tank; 34. Drainage pump; 35. Slurry cooler; 36. Filter box; 37. Collection pool; 38. Collection pool pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] The technical solutions of the present invention will be clearly and completely described below with specific embodiments. It should be understood that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of the present invention. Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art.

[0060] Example 1

[0061] The present invention provides an integrated device for catalytic cracking flue gas dust removal and desulfurization, the integrated device comprises an integrated dust removal and desulfurization tower 8, and a flue gas introduction system, a liquid supply and circulation system, and a slurry treatment system arranged in conjunction with the integrated dust removal and desulfurization tower 8, wherein:

[0062] The integrated dust removal and desulfurization tower 8 includes, from bottom to top, a bottom oxidation section, a primary quenching section, a secondary absorption section, a multi-tube tube dust removal section, a dust removal and mist removal section, and a chimney 21; the bottom oxidation section is provided with a bottom liquid collecting tank 9 and an oxidation air distributor 10; a flue gas inlet 12 is provided on the wall of the primary quenching section, and a plurality of quenching nozzles 13 are provided on the wall of the primary quenching section or the wall of the flue gas inlet 12; a plurality of layers of absorption section nozzles 14 are provided on the wall of the secondary absorption section; the multi-tube tube dust removal section is provided with A multi-tube tube-in-tube dust collector 15, which includes a dust collector sump 16, a plurality of parallel venturi tubes (not shown in the figure) fixedly installed through the trough plate of the dust collector sump 16, and a spray pipe arranged above the venturi tube and a spray nozzle 17 arranged on the spray pipe; the dust removal and mist removal section is provided with a high-efficiency dust removal and mist removal device 19, which includes a plurality of parallel cyclone cylinder assemblies and a flushing hose arranged above the cyclone cylinder assembly and a flushing nozzle 20 connected to the flushing hose.

[0063] Furthermore, the oxidation air ducts of the oxidation air distributor 10 are evenly distributed in the cross section of the tower bottom, and the inlet of the oxidation air distributor 10 is connected to an oxidation fan 29 to provide oxidation air for the oxidation section at the bottom of the tower and to force oxidation of the circulating slurry at the bottom of the tower.

[0064] Furthermore, the quenching nozzles 13 of the first-stage quenching section are preferably arranged to be 1 to 4, which are used to spray the circulating absorption slurry from the bottom of the tower to form a plurality of flat cone-shaped rapid water curtains, which fully cover the entire cross-section of the flue gas inlet, and quench the flue gas entering the flue gas inlet to reach the saturation temperature.

[0065] Furthermore, the absorption section nozzles 14 of the secondary absorption section are preferably arranged in 2 to 5 layers at different heights from bottom to top, with 3 to 5 nozzles on each layer, for a total of 6 to 25 nozzles, for spraying circulating absorption slurry from the bottom of the tower to wash the flue gas rising in the tower; each layer of nozzles sprays slurry to form a flat cone-shaped torrent water curtain to fully cover the entire cross-section of the tower, and the layers of each layer of nozzles are staggered at a certain angle to fully cover the cylinder of the secondary absorption section.

[0066] Furthermore, the quenching nozzle 13 and the absorption section nozzle 14 can both be selected from a quenching nozzle disclosed in the prior art CN104138812A, and the slurry is sprayed to form a torrent water curtain in the shape of a flat cone curtain.

[0067] Further, the outer periphery of the trough plate of the dust collector liquid collecting tank 16 of the multi-tube tubular dust collector 15 is connected to the inner wall of the integrated dust removal and desulfurization tower 8, preferably welded to the inner wall of the integrated dust removal and desulfurization tower 8 at a certain inclination angle; a guide vane is arranged at the bottom inlet of the Venturi tube to make the rising flue gas rotate upward, and the structure of the Venturi tube is used to remove the fine particles entrained in the flue gas and aggregate them into large particles; the spray nozzles 17 correspond to the Venturi tubes one by one, and the number of Venturi tubes and spray nozzles 17 is set according to the amount of raw flue gas, and the high-density conical water film sprayed by the nozzles is used to intercept and wash the large particles of dust aggregated by the Venturi tubes.

[0068] Further, a dust collector overflow pipe 18 is fixedly arranged through the trough plate of the dust collector liquid collecting tank 16, and the bottom outlet of the dust collector overflow pipe 18 is communicated with the bottom liquid collecting tank 9, and is used to overflow the liquid accumulated in the dust collector liquid collecting tank 16 in the multi-tube tubular dust removal section into the bottom liquid collecting tank 9.

[0069] Further, a multi-stage combined cyclone tube is arranged in the cyclone tube assembly of the high-efficiency dust removal and mist droplet remover 19, that is, a plurality of cyclone tubes are arranged in series and superimposed vertically in the cyclone tube assembly, and a cyclone plate is additionally arranged in the cyclone tube, so that the desulfurized clean flue gas rising in the tower rotates in the cyclone tube, so that the tiny particulate matters collide with each other, agglomerate and condense into large droplets and move centrifugally outward, and are captured and absorbed by the liquid film on the cyclone tube wall, realizing high-efficiency mist droplet and dust removal.

[0070] The flue gas introduction system includes an inlet high-temperature flue 1 from the upstream and connected to the flue gas inlet 12 and a sodium-based powder spray gun 2 arranged on the inlet high-temperature flue 1. The inlet of the sodium-based powder spray gun 2 is connected to an air compressor 3 and a sodium-based powder silo 4. The compressed air provided by the air compressor 3 is used to send the sodium-based powder into the inlet high-temperature flue 1 and introduce it into the integrated dust removal and desulfurization tower 8; a grinding machine 5 is preferably arranged between the inlet of the sodium-based powder spray gun 2 and the sodium-based powder silo 4 to improve the reaction efficiency of the sodium-based powder.

[0071] The liquid supply and circulation system includes a bottom circulation spray system, a multi-tube tubular dust removal section circulation system, a bottom circulation system, a process water supply system, an absorbent supply system and an emergency water supply system; among them,

[0072] The bottom circulation spray system includes first and second stage slurry circulation pumps 22 communicated with the bottom end of the bottom liquid collecting tank 9. The outlets of the first and second stage slurry circulation pumps 22 are connected to the quench spray nozzles 13 and the absorption section spray nozzles 14 to provide absorbent slurry for the spraying of the first stage quench section and the second stage absorption section, forming a slurry circulation loop for the first stage quench section and the second stage absorption section; the first and second stage slurry circulation pumps 22 are preferably set to three units, two in operation and one in standby, and are rotated alternately to ensure the stable operation of the pumps.

[0073] The multi-tube tubular dust removal section circulation system includes a three-stage slurry circulation pump 23 connected to the bottom end of the liquid collection tank 16 of the dust collector. The outlet of the three-stage slurry circulation pump 23 is connected to the spray pipe, forming a circulation loop of the slurry in the multi-tube tubular dust removal section. Preferably, two three-stage slurry circulation pumps 23 are provided, one in operation and one in standby, and they are switched alternately to ensure the stable operation of the pumps.

[0074] The bottom tower circulation system includes an overflow pipe 11 provided on the side wall of the bottom tower oxidation section. The overflow pipe 11 is connected to a slurry collection tank 27, and the slurry collection tank 27 is connected to the bottom tower liquid collection tank 9 through a slurry collection tank pump 28.

[0075] The process water supply system includes a fresh water pressurizing pump 24 connected to upstream fresh water. The outlet of the fresh water pressurizing pump 24 is connected to the dust collector liquid collection tank 16 and the bottom tower liquid collection tank 9, providing make-up fresh water for the integrated dust removal and desulfurization tower 8 to supplement the water lost during evaporation and slurry discharge. The outlet of the fresh water pressurizing pump 24 is also connected to the flushing hose, providing fresh water for flushing and spraying in the dust removal and demisting section.

[0076] The absorbent supply system includes an alkali liquid pump 26 connected to an alkali liquid tank 25. The outlet of the alkali liquid pump 26 is connected to the bottom tower liquid collection tank 9 and the dust collector liquid collection tank 16, providing make-up absorbent alkali liquid for the integrated dust removal and desulfurization tower 8.

[0077] The emergency water supply system includes an emergency water make-up pump 7 connected to an emergency water tank 6. The outlet of the emergency water make-up pump 7 is connected to the quench spray head 13, providing emergency quench cold water for the integrated dust removal and desulfurization tower 8 during emergencies.

[0078] The slurry treatment system includes a settler 31, an oxidation tank 32, a drainage tank 33, a drainage pump 34, and a slurry cooler 35 connected in sequence. Among them, the inlet of the settler 31 is connected to the outlet of the first and second stage slurry circulation pumps 22 and is also connected to a flocculant tank 30. The thick slurry outlet of the settler 31 is connected to a filter box 36. The clear liquid outlet of the filter box 36 is connected to a collection pond 37. The collection pond 37 is connected to the inlet of the settler 31 through a collection pond pump 38 to circulate and filter the filtered clear liquid for sedimentation. The clear liquid outlet of the settler 31 is connected to the oxidation tank 32 and is also connected to the bottom tower liquid collection tank 9 (not shown in the figure), returning part of the settled clear liquid back into the tower for reuse. The oxidation tank 32 is connected to an oxidation blower 29 to further oxidize part of the settled clear liquid using compressed air.

[0079] Further, the inlet of the oxidation tank 32 is also connected to the outlet of the lye pump 26 to supplement lye to the oxidation tank 32, so that the pH value of the oxidized effluent is maintained at about 7.

[0080] Further, two filter boxes 36 are provided, one in use and one in standby, and they are switched for use with each other; two or three oxidation tanks 32 are provided in series to further oxidize the settled clear liquid in sequence.

[0081] Embodiment 2

[0082] The present invention also provides a catalytic cracking flue gas dust removal and desulfurization integrated process method using the integrated device, which includes the following steps:

[0083] (1) Sodium-based powder is sprayed into the inlet high-temperature flue 1 and reacts with the high-temperature catalytic cracking flue gas in the inlet high-temperature flue 1 to remove SO3 in the flue gas;

[0084] (2) The high-temperature catalytic cracking flue gas passes through the flue gas inlet 12 into the integrated dust removal and desulfurization tower 8 and rises. After being processed by the primary quenching section, secondary absorption section, multi-tube type tube dust removal section, and dust and mist droplet removal section in sequence, it is discharged through the chimney 21;

[0085] In the primary quenching section, several quenching nozzles 13 spray the circulating absorption slurry from the bottom oxidation section of the tower to completely cover the cross-section of the flue gas inlet 12, so that the flue gas is quickly cooled and SO2 is absorbed and removed;

[0086] In the secondary absorption section, several layers of absorption section nozzles 14 spray the circulating absorption slurry from the bottom oxidation section of the tower to completely cover the cross-section inside the tower. The flue gas is washed and dust-removed and SO2 is absorbed and removed;

[0087] In the multi-tube type tube dust removal section, the flue gas is condensed with fine particles after passing through several parallel venturi tube structures, and is intercepted and washed under the action of the sprayed slurry above to achieve dust removal. The sprayed slurry comes from the dust collector liquid collecting tank in the multi-tube type tube dust removal section;

[0088] In the dust and mist droplet removal section, the flue gas enters the multi-stage cyclone cylinder to rotate and centrifugally separate. The tiny particles are condensed into large droplets and collide with the cyclone cylinder wall whose surface is wetted by spraying, and are captured and absorbed by the liquid film to achieve dust and mist droplet removal;

[0089] In the bottom oxidation section of the tower, the circulating absorption slurry is subjected to primary oxidation under the action of the introduced oxidation air to oxidize sulfite to sulfate and reduce the COD of the absorption slurry;

[0090] When the indexes of the circulating absorption slurry exceed the standard and part of the absorption slurry needs to be discharged to ensure the desulfurization and dust removal efficiency, the process method further includes step (3):

[0091] (3) After part of the circulating absorption slurry is settled by the settler 31, it is introduced into the oxidation tank 32 for secondary oxidation, and then cooled and discharged.

[0092] In the step (1), the following steps are specifically included:

[0093] The high-temperature catalytic cracking flue gas is taken out from the outlet flue of the upstream waste heat boiler, and sodium-based powder c1, specifically a mixture of Na2CO3 and NaHCO3 powders, is sprayed into the inlet high-temperature flue 1 before entering the integrated dust removal and desulfurization tower 8. The sodium-based powder c1 is provided by the sodium-based powder bin 4, and after being ground by the grinder 5, it is sent into the flue by the compressed air a1 provided by the air compressor 3. After the sodium-based powder c1 reacts with the high-temperature flue gas g1, it enters the integrated dust removal and desulfurization tower 8 along with the flue gas g1. A number of sampling ports are respectively arranged before and after the SO3 removal reaction section of the inlet high-temperature flue 1, and the powder spraying amount is controlled according to the analysis. The pneumatic conveying system of the air compressor 3 can ensure the good conveying and feeding of the sodium-based powder to the flue, and prevent bridging and caking inside the sodium-based powder bin 4.

[0094] In the step (2), the following steps are specifically included:

[0095] In the primary quenching section: The high-temperature flue gas g2 after reacting with the sodium-based powder to remove SO3 enters the primary quenching section in the integrated dust removal and desulfurization tower 8 horizontally through the flue gas inlet 12. A number of quenching nozzles 13 in the primary quenching section spray the circulating absorption slurry L1 sent by the first and second slurry circulation pumps 22 to quench and cool the high-temperature flue gas g2 and make it reach the saturation temperature. The quenching nozzles 13 spray the slurry to form a number of flat conical curtain-shaped impinging water curtains, covering the entire cross-section of the flue gas inlet 12. The high-temperature flue gas g2 passes through a number of flat conical curtain-shaped impinging water curtains to be quenched and cooled, and SO2 and dust are removed through preliminary washing reaction. The sprayed liquid flows downward to the bottom liquid collecting tank 9 in the bottom oxidation section of the tower.

[0096] In the secondary absorption section: The quenched and cooled flue gas then rises to the secondary absorption section. A number of absorption section nozzles 14 in the secondary absorption section spray the circulating absorption slurry L2 sent by the first and second slurry circulation pumps 22 to absorb and wash the flue gas. Each layer of absorption section nozzles 14 sprays the slurry to form a flat conical curtain-shaped impinging water curtain, covering the entire cross-section of the tower, and the absorption section nozzles 14 between layers are arranged at a certain angle in a staggered manner to cover the entire cylinder of the secondary absorption section. The rising flue gas quickly collides violently and comes into close contact with the liquid droplets in the impinging water curtain, so as to effectively remove the coarse particles in the flue gas and quickly carry out a chemical reaction to remove SO2. The pH value of the absorption slurry is maintained at about 7.0, and the sprayed liquid flows downward along the tower wall to the bottom liquid collecting tank 9.

[0097] In the multi-tube tubular dust removal section: The flue gas after being washed and dedusted in the secondary absorption section and absorbing SO2 rises to the multi-tube tubular dust removal section. The flue gas enters each venturi tube of the multi-tube tubular dust collector 19, rotates and rises after being guided by the guide vanes. In its contraction tube and throat tube, the relative flow velocity between the gas and liquid phases is very large, the gas is saturated with water, the gas film attached to the surface of the dust particles is broken, and the dust particles are wetted by water. Therefore, intense collisions and aggregations occur between the dust particles and droplets or between the dust particles. In its diffuser tube, the decrease in the gas flow velocity and the rise in pressure make this aggregation effect with dust particles as the condensation nuclei occur faster, aggregating into dust-containing droplets with larger particle sizes. A spray layer is provided above the venturi tube, and the spray nozzles 17 correspond to the venturi tubes one by one. The high-density spray slurry generated by the spray nozzles 17 is used to intercept and filter the flue gas at the outlet of the venturi tube, intercept and wash the large-particle fine dust aggregated in the venturi tube, thereby removing the fine water mist particles entrained in the flue gas, and at the same time, SO3 entrained in the droplets can be removed. The liquid sprayed by the spray nozzles 17 is collected by the dust collector liquid collection tank 16 of the multi-tube tubular dust removal section, and is pumped out by the three-stage slurry circulation pump 23 and sent into the spray nozzles 17 to form a slurry circulation.

[0098] In the dust and mist droplet removal section: The flue gas after multi-tube tubular dust removal rises to the dust and mist droplet removal section. The flue gas enters each cyclone cylinder assembly of the high-efficiency dust and mist droplet remover 19. Under the action of the cyclone plates in the multi-stage cyclone cylinders, the flue gas rotates in the cyclone cylinders. Through the centrifugal separation method, a violent rotation and disturbance of the gas-liquid two-phase are formed above the cyclone cylinders, so that the fine liquid droplets, fine dust particles, aerosols and other fine particulate matters in the flue gas collide, agglomerate and aggregate into large liquid droplets. Then, under the action of the outer rotation structure of the cyclone plates, the flue gas moves centrifugally outwards, and the large liquid droplets formed by aggregation collide with the cyclone cylinder wall. The flushing nozzles 20 above the cyclone cylinder assembly spray fresh water to wet the cyclone cylinder wall, so that the large liquid droplets colliding with the cyclone cylinder wall are captured and absorbed by the liquid film on the cyclone cylinder wall, realizing the high-efficiency dust and mist droplet removal of the flue gas. The liquid after dust and mist droplet removal flows down to the multi-tube tubular dust removal section and is collected by the dust collector liquid collection tank 16.

[0099] In the bottom tower oxidation section: An oxidation air distributor 10 is provided in the bottom tower oxidation section, and its oxidation air pipes are evenly distributed on the bottom cross-section of the tower. Oxidation air is introduced into the slurry through the oxidation air distributor 10 to perform forced primary oxidation on the circulating absorption slurry at the bottom of the tower, oxidize the sulfite in the circulating absorption slurry into sulfate, and reduce the COD of the circulating absorption slurry. And the circulating absorption slurry L4 at the bottom of the tower can overflow to the slurry collection pool 27 through the overflow pipe 11, and after being stirred and mixed evenly in the slurry collection pool 27, it is recycled back to the bottom liquid collection tank 9.

[0100] Furthermore, the operating temperature of the integrated dust removal and desulfurization tower 8 is 55 ± 10 °C, and the operating pressure is 4000 ± 100 Pa (G). When the flue gas load varies under the working conditions of 70% - 110%, the integrated dust removal and desulfurization tower 8 can adapt to the load fluctuation and maintain normal operation.

[0101] Furthermore, the bottom liquid collection tank 9 of the integrated dust removal and desulfurization tower 8 stores the circulating absorption slurry L, which is sent to the primary quenching section and the secondary absorption section through the primary and secondary slurry circulation pumps 22 to complete the circulation, and is used as the quenching absorption slurry L1 and the washing absorption slurry L2. During the slurry circulation process, the pH value of the liquid is monitored. Since there will be fine catalyst particles in the circulating absorption slurry L, to ensure the stable operation of the pump, the primary and secondary slurry circulation pumps 22 need to be rotated and operated alternately, and it is recommended to rotate once a day.

[0102] Furthermore, the dust collector liquid collection tank 16 stores the circulating slurry L7 of the multi-tube type tube dust removal section, which is sent into the spray nozzles 17 of the multi-tube type tube dust removal section through the tertiary slurry circulation pump 23 for recycling. During the slurry circulation process, the pH value of the liquid is monitored. The slurry L6 in the dust collector liquid collection tank 16 can overflow to the bottom liquid collection tank 9 through the dust collector overflow pipe 18. Since there will be fine catalyst particles in the circulating slurry L7, to ensure the stable operation of the pump, the tertiary slurry circulation pump 23 needs to be rotated and operated alternately, and it is recommended to rotate once a day.

[0103] Furthermore, in order to avoid the influence of the uneven air flow distribution of the high-efficiency dust removal and mist droplet remover 19 in a large-size space on the dust removal and mist droplet removal effect, the cyclone cylinder assemblies are evenly arranged in the entire cross-section of the integrated dust removal and desulfurization tower 8, so that the air flow movement in each parallel cyclone cylinder assembly is uniform and there will be no phenomenon of uneven flow.

[0104] Furthermore, in order to ensure the dust removal and mist droplet removal effect, multi-stage combined cyclone cylinders are arranged in each cyclone cylinder assembly, so that the dust and tiny particle mist droplets in the flue gas are repeatedly aggregated and removed in the multi-stage cyclone cylinders, and the unnecessary excessive change of the flow pattern of the flue gas in the flow direction can be avoided, thereby increasing the resistance.

[0105] Furthermore, in order to ensure that the high-efficiency dust removal and mist droplet remover 19 can achieve the dust removal effect when the flue gas load is low, the full flow field of the flow channel in the tube type cyclone cylinder assembly is simulated and optimized. By adjusting the spacing between the inner swirl plates of each layer of the swirl and the spacing between the cyclone cylinder assemblies, it is ensured that the dust removal effect can be achieved within the range of 70% - 110% of the flue gas load.

[0106] Further, in order to supplement the water lost during the evaporation process and the slurry discharge process, process water w needs to be supplied to the integrated dust removal and desulfurization tower 8. Specifically, fresh process water w2 and w3 are supplemented to both the bottom liquid collecting tank 9 and the dust collector liquid collecting tank 16 of the integrated dust removal and desulfurization tower 8, and the amount of fresh process water entering the tower is adjusted and controlled according to the monitoring of the liquid level in the bottom liquid collecting tank 9 by the liquid level gauge. Under the action of gravity, the process water supplemented in the dust collector liquid collecting tank 16 can overflow to the bottom liquid collecting tank 9 through the dust collector overflow pipe 18, and the pollutants captured in the multi-tube type tube dust removal section and the dust and mist droplet removal section will be carried away by the supplemented process water during this process.

[0107] Further, 30wt% NaOH solution, ammonia water or liquid ammonia is used as the absorbent c3, and is added to the bottom liquid collecting tank 9 by the alkali liquid pump 26 to maintain the pH value of the circulating absorption slurry in the bottom liquid collecting tank 9 at 6.0 - 7.5. pH meters are installed on the circulation circuits of the first and second stage slurry circulation pumps 22, and the amount of alkali liquid added to the bottom liquid collecting tank 9 is adjusted and controlled through the pH value. The absorbent c3 is also added to the dust collector liquid collecting tank 16 by the alkali liquid pump 26 to maintain the pH value of the slurry in the dust collector liquid collecting tank 16 and prevent the materials of the downstream multi-tube type tube dust collector 15, high-efficiency dust and mist droplet remover 19 and chimney 21 from being corroded. A pH meter is installed on the circulation circuit of the third stage slurry circulation pump 23, and the amount of alkali liquid added to the dust collector liquid collecting tank 16 is adjusted and controlled through the pH value.

[0108] Further, a temperature alarm is provided in the first stage rapid cooling section of the integrated dust removal and desulfurization tower 8. When the flue gas temperature in the tower changes too much, or the temperature of the flue gas cooled by the rapid cooling nozzles 13 in the first stage rapid cooling section exceeds 85°C, or when the catalyst in the catalytic cracking unit runs away and enters the tower, the emergency rapid cooling water system is started to protect the equipment safety. Specifically, the emergency water make-up pump 7 and the emergency water switch valve are opened, and a large amount of emergency rapid cooling water is quickly provided from the emergency water tank 6 to the rapid cooling nozzles 13 in the first stage rapid cooling section. The rating of each control valve on the emergency rapid cooling water pipeline should be set at 50% of the required total flow rate. Conversely, after the flue gas temperature in the tower is normal or the fault is eliminated, the integrated dust removal and desulfurization tower 8 enters the normal operation state, and the flue gas after dust removal and desulfurization is discharged from the chimney 21 above the integrated dust removal and desulfurization tower 8.

[0109] Furthermore, when the catalyst operation is abnormal, such as when there is too much catalyst carried in the flue gas, the emergency rapid cooling water system should be started manually. After adding emergency rapid cooling water to the integrated dust removal and desulfurization tower 8, the excessive catalyst is diluted and discharged from the system. When the emergency rapid cooling water system is started manually, the system always needs to be controlled manually.

[0110] In the step (3), it specifically includes the following steps:

[0111] During normal operation, the contents of dissolved salts, chlorides, and suspended catalyst solids in the circulating absorption slurry should be controlled. Specifically, the suspended solids SS ≤ 4 g / l, chloride ions ≤ 750 mg / l, and the TDS content ≤ 5 wt%. If the above indicators are measured to exceed the standard, the tower bottom circulating spray system needs to discharge a part of the circulating absorption slurry L3 to ensure the efficiency of desulfurization and dust removal. The discharged circulating absorption slurry L3 is sent to the slurry treatment unit through the outlet side line of the first and second stage slurry circulating pumps 22. The discharge amount is set according to the process requirements and is controlled by a regulating valve. To optimize the process operation, the discharge amount and indicators need to be monitored and recorded daily.

[0112] The discharged circulating absorption slurry L3 is sent to the settler 31 through the outlet side line of the first and second stage slurry circulating pumps 22, and a flocculant f with a certain concentration is added to the inlet liquid pipe at the front end of the settler 31. In the upper clear liquid L8 after the slurry settles in the settler 31, a part is returned to the bottom liquid collecting tank 9 of the integrated dust removal and desulfurization tower 8 for recycling, and a part is introduced into the oxidation tank 32 for subsequent treatment. Through the oxidation pipe arranged in the oxidation tank 32, compressed air a2 is introduced to perform secondary oxidation on the upper clear liquid L8. To enhance the oxidation effect, a stirrer is provided in the oxidation tank 32, and the compressed air a2 is blown into the oxidation tank 32 from the bottom by the oxidation blower 29, so that the oxidation air and the upper clear liquid L8 are fully contacted to further reduce the COD therein.

[0113] The slurry after removing COD by oxidation flows from the oxidation tank 32 to the drain tank 33 by gravity, and then is sent to the slurry cooler 35 by the drain pump 34. The temperature of the discharged wastewater dw is reduced to below 40 °C by using circulating cooling water cw and then discharged. The indicators of the discharged wastewater dw are: SS ≤ 50 mg / L; COD ≤ 50 mg / L.

[0114] Furthermore, the suspended particulate matter in the settler 31 aggregates at the bottom of the settler after flocculation sedimentation and is discharged to the filter box 36 in the form of thick slurry sL. The solid content in the thick slurry sL is 3 wt% - 5 wt%. After being filtered and dried by the filter box 36, about 30 wt% - 60 wt% of solid matter s is generated, which is regularly cleaned and transported out. The clear liquid sL1 after filtration by the filter box flows to the sump 37 by gravity and is circulated back to the inlet of the settler 31 through the sump pump 38 for re-sedimentation and filtration. Two filter boxes 36 are provided, one in use and one in standby, and they are switched and used alternately.

[0115] Further, part of the sodium bisulfite in the oxidation tank 32 is oxidized to produce acid. To maintain an appropriate pH, caustic solution c4 is introduced into the oxidation tank 32, and the outlet pH of the overflow liquid in the oxidation tank 32 is monitored using an on-line pH meter. The regulating valve on the caustic solution pipeline is controlled through pH meter interlock, so as to control the addition amount of caustic solution c4 and keep the outlet pH at about 7.

[0116] In the process method of the present invention, the process principles of flue gas dust removal and desulfurization in each unit are as follows:

[0117] Regarding step (1), the process principle of injecting sodium-based powder to remove SO3 in the flue gas is as follows:

[0118] Injecting dry sodium-based powder into the high-temperature inlet flue can control the emission of SO3 / H2SO4 in the flue gas. The sodium-based powder is activated under the action of high-temperature flue gas and becomes carbonate and bicarbonate like "popcorn". This "popcorn effect" greatly increases the reaction surface area. The acidic high-temperature flue gas fully contacts with the activated sodium-based powder to carry out chemical reactions, generating sulfates. SO3 and other acidic media in the flue gas are absorbed and purified, and the sulfates are removed by the subsequent integrated dust removal and desulfurization tower. The sodium brought into the absorption slurry by the sodium-based powder injection method will reduce the amount of caustic alkali required for the subsequent integrated dust removal and desulfurization tower.

[0119] Generally, sodium bicarbonate and sodium carbonate are mainly applied to high-temperature working conditions (>160 °C), and their efficiency increases with the increase of temperature. In addition, the quality of the sodium bicarbonate reagent also has a very important impact on its use efficiency. For example, under the same material conditions, freshly ground sodium bicarbonate has the highest efficiency. Since the sodium-based powder reacts chemically with acidic gases (such as SO3, SO2) in the flue gas, the injection point of the sodium-based powder, the reaction time and the flue gas velocity in the flue are factors that must be considered to ensure the maximum efficiency of sodium-based powder deacidification.

[0120] The alkaline chemical reactions related to SO3 removal are as follows:

[0121] Na2CO3 + SO3 → Na2SO4 + CO2

[0122] Na2CO3 + H2O + 2SO3 → 2NaHSO4 + CO2

[0123] NaHCO3 + SO3 → NaHSO4 + CO2

[0124] Na2CO3 + SO2 → Na2SO3 + CO2

[0125] Na2CO3 + 1 / 2O2 + SO2 → Na2SO4 + CO2

[0126] In the step (2), the flue gas desulfurization is mainly carried out through a primary quenching section and a secondary absorption section, and the process principle of SO2 removal is as follows:

[0127] The high-temperature flue gas introduced into the integrated dust removal and desulfurization tower first passes through a plurality of jet water curtains in the shape of flat cones ejected by the quenching nozzles in the primary quenching section, is quenched and cooled to saturation, and SO2 is removed through preliminary washing reaction. Then the flue gas enters the multi-layer jet water curtains in the shape of flat cones ejected by the absorption section nozzles in the secondary absorption section for further absorption and washing to remove SO2.

[0128] The present invention can use a NaOH solution (30wt%) as the desulfurizing agent, that is, the absorbent, and carry out an acid-base neutralization reaction through the alkaline substance and the sulfurous acid solution formed by sulfur dioxide dissolved in water, and adjust the pH value of the circulating liquid by adjusting the addition amount of sodium hydroxide. The selection of the liquid-gas ratio and the number of nozzles required for absorbing sulfur dioxide is determined according to the inlet concentration of sulfur dioxide, the absorbent liquid, the discharge requirements, and the temperature of the saturated gas.

[0129] First, sulfur dioxide in the flue gas contacts with water to generate sulfurous acid:

[0130] SO2 + H2O → H2SO3

[0131] Then, H2SO3 reacts with NaOH to generate Na2SO3, Na2SO3 further reacts with H2SO3 to generate NaHSO3, and NaHSO3 reacts with NaOH to accelerate the generation of Na2SO3; a part of the generated sodium sulfite is recycled as the absorbent, and the other unused part is oxidized and sent to the subsequent wastewater system for further treatment as a harmless aqueous solution of sodium sulfate.

[0132] H2SO3 + 2NaOH → Na2SO3 + 2H2O

[0133] Na2SO3 + H2SO3 → 2NaHSO3

[0134] NaHSO3 + NaOH → Na2SO3 + H2O

[0135] Na2SO3 + 1 / 2O2 → Na2SO4

[0136] There are also some side reactions, such as the reaction of sulfur trioxide with sodium hydroxide to form sodium sulfate, etc.

[0137] 2NaOH + SO3 → Na2SO4 + H2O

[0138] The remaining unreacted SO3 is partially removed in the multi-tube type tubular dust collector.

[0139] In the said step (2), the flue gas dust removal is mainly carried out through the secondary absorption section and the multi-tube type tube dust removal section, and the technological principle of the dust removal is as follows:

[0140] Most of the fine particles contained in the flue gas are the catalyst powder carried by the flue gas in the heavy oil catalytic cracking unit. By utilizing the flat conical curtain-shaped impact water curtain formed by multiple layers of annular nozzles in the integrated dust removal and desulfurization tower, the coarse fine particles in the flue gas are removed in the secondary absorption section: for fine particles with a size larger than 2 - 3 μm, almost 100% can be captured; at the same time, a small part of finer fine particles can also be captured. The liquid inlet pipe of the nozzle in the absorption section is provided with a certain angle with the tower wall to improve the dust removal efficiency.

[0141] The remaining finer fine particles are removed by the multi-tube type tube dust removal section. The multi-tube type tube dust remover sets multiple parallel Venturi tubes according to the gas volume of the raw flue gas, uses the Venturi principle to remove fine particles, and a spray nozzle is correspondingly arranged at the outlet of each Venturi tube. The flue gas after quenching, desulfurization and dust removal contains fine particles and water vapor. Utilizing the Venturi principle, it ascends and enters the Venturi tube through the diversion. In its contraction tube and throat tube, the relative flow rate between the gas-liquid two phases is very large, the gas is saturated with water, the gas film attached to the surface of the dust particles is broken, so that the dust particles are wetted by water. Therefore, intense collisions and aggregations occur between the dust particles and the liquid droplets or between the dust particles; in its diffuser tube, the decrease in the gas flow velocity and the rise in pressure make this aggregation effect with the dust particles as the condensation nuclei occur faster, aggregating into larger-sized dust-containing liquid droplets; in the forked cross-section of the Venturi tube, due to the expansion of the saturated flue gas, the water thin film condenses on the fine particles, resulting in coalescence; and then it is captured by the spray liquid ejected from the upper nozzle.

[0142] In the said step (2), the flue gas mist droplet removal mainly utilizes the dust removal and mist droplet removal section, and the technological principle of the mist droplet removal is as follows:

[0143] The flue gas after dust removal and desulfurization contains a large amount of mist droplets, and the mist droplets are composed of slurry droplets, condensate droplets and fine dust particles.

[0144] When this part of the clean flue gas enters the high-efficiency dust removal and mist droplet remover, the cyclone plates added in the multi-stage cyclone cylinder make the clean flue gas after dust removal and desulfurization rotate in the cyclone cylinder, forming a violent rotation and disturbance of the gas-liquid two phases above the cyclone cylinder. As a result, the tiny particulate matters such as the fine droplets, fine dust particles and aerosols in the clean flue gas collide, agglomerate and aggregate with each other to form large droplets. Then, under the action of the outer rotation structure of the cyclone plate, the clean flue gas after dust removal and desulfurization moves centrifugally outwards, and the large droplets formed by aggregation collide with the cyclone cylinder wall and are captured and absorbed by the liquid film on the cyclone cylinder wall, realizing high-efficiency mist droplet removal and dust removal.

[0145] This application has been described in detail with the aim of enabling those skilled in the art to understand the content of this application and implement it. However, this should not limit the scope of protection of this application. Any equivalent changes or modifications made in accordance with the spirit and essence of this application should be covered within the scope of protection of this application.

Claims

1. An integrated process for dust removal and desulfurization of catalytic cracking flue gas, characterized in that, It includes the following steps: (1) Inject sodium-based powder into the high-temperature flue at the inlet of the integrated dust removal and desulfurization tower, contact and react with the high-temperature flue gas in the flue to remove SO3 in the flue gas; (2) The high-temperature flue gas rises into the integrated dust removal and desulfurization tower and is discharged through the chimney after being processed successively by the primary quenching section, secondary absorption section, multi-tube type tube dust removal section, and dust and mist droplet removal section. Among them: In the primary quenching section, several quenching nozzles spray the circulating absorption slurry from the bottom oxidation section of the tower to rapidly cool down the flue gas and absorb and remove SO2; In the secondary absorption section, several layers of absorption section nozzles spray the circulating absorption slurry from the bottom oxidation section of the tower, and the flue gas is washed and dust-removed and absorbs and removes SO2; In the multi-tube type tube dust removal section, the flue gas coagulates fine particles after passing through several parallel venturi tubes, and is intercepted and washed under the action of the sprayed slurry above to achieve dust removal. The sprayed slurry comes from the dust collector liquid collecting tank in the multi-tube type tube dust removal section; In the dust and mist droplet removal section, the flue gas enters the cyclone cylinder assembly for rotary centrifugal separation. The tiny particles coagulate into large droplets and collide with the cyclone cylinder wall whose surface is wetted by spraying, and are captured and absorbed by the liquid film to achieve dust and mist droplet removal; In the bottom oxidation section of the tower, the circulating absorption slurry is subjected to primary oxidation under the action of the introduced oxidation air to oxidize the sulfite in the slurry into sulfate and reduce the COD of the slurry.

2. The process method according to claim 1, characterized in that, In the step (1), the sodium-based powder is injected into the high-temperature flue at the inlet, that is, the mixed powder of Na2CO3 and NaHCO3. After being ground by a grinder, it is sent into the flue by the compressed air provided by an air compressor. After the sodium-based powder contacts and reacts with the high-temperature flue gas, it enters the integrated dust removal and desulfurization tower.

3. The process method according to claim 1, wherein In the step (2), in the primary quenching section, the high-temperature flue gas enters the primary quenching section in the integrated dust removal and desulfurization tower through the flue gas inlet. Several quenching nozzles in the primary quenching section spray the circulating absorption slurry sent by the primary and secondary slurry circulating pumps to rapidly cool down the high-temperature flue gas to reach the saturation temperature; the slurry sprayed by the quenching nozzles forms several flat cone-shaped impinging water curtains that completely cover the cross-section of the flue gas inlet. The high-temperature flue gas passes through several flat cone-shaped impinging water curtains to be rapidly cooled down, and SO2 and dust are removed through preliminary washing reaction. The sprayed liquid flows downward into the bottom liquid collecting tank of the bottom oxidation section of the tower.

4. The process method according to claim 1, characterized in that, In the step (2), in the secondary absorption section, several layers of absorption section nozzles spray the circulating absorption slurry sent by the primary and secondary slurry circulating pumps to absorb and wash the rising flue gas; the slurry sprayed by the absorption section nozzles on each layer forms a flat cone-shaped impinging water curtain that completely covers the entire cross-section of the tower, and the absorption section nozzles between layers are arranged with a certain angle offset to completely cover the cylinder body of the secondary absorption section. The rising flue gas collides and contacts with the droplets in the impinging water curtain to remove the coarse particles in the flue gas and react to remove SO2. The sprayed liquid flows downward along the tower wall to the bottom liquid collecting tank of the bottom oxidation section of the tower.

5. The process method according to claim 1, characterized in that, In step (2), in the multi-tubular tube dust removal section, the flue gas enters each venturi tube of the multi-tubular tube dust collector, rotates and rises after being guided by the guide vanes. Under the action of the venturi tube structure, dust particles collide and agglomerate with liquid droplets or among dust particles to form dust-containing liquid droplets with larger particle sizes; above the venturi tube, there is a spray nozzle corresponding to it one by one, and the spray slurry sprayed by the spray nozzle is used to intercept, filter and remove dust from the flue gas at the outlet of the venturi tube, and at the same time remove SO3 entrained in the liquid droplets; the liquid sprayed by the spray nozzle is collected by the liquid collection tank of the dust collector in the multi-tubular tube dust removal section, and is pumped out by a three-stage slurry circulation pump and sent into the spray nozzle to form a slurry circulation.

6. The process method according to claim 1, characterized in that, In step (2), in the dust and mist droplet removal section, the flue gas enters each cyclone tube assembly of the high-efficiency dust and mist droplet remover. A multi-stage cyclone tube is arranged in each cyclone tube assembly and a cyclone plate is added in the cyclone tube to make the flue gas rotate in the cyclone tube. Tiny particulate matters collide and agglomerate with each other to form large liquid droplets and move centrifugally outwards to collide with the cyclone tube wall. The flushing nozzle above the cyclone tube assembly sprays fresh water to wet the cyclone tube wall, so that the large liquid droplets colliding with the cyclone tube wall are captured and absorbed by the liquid film on the cyclone tube wall, realizing the dust and mist droplet removal of the flue gas; the liquid sprayed by the flushing nozzle flows downwards and is collected by the liquid collection tank of the dust collector in the multi-tubular tube dust removal section.

7. The process method according to claim 1, characterized in that, In step (2), an oxidation air distributor is arranged in the bottom oxidation section of the tower, and its oxidation air pipes are evenly distributed on the bottom cross-section of the tower. Oxidation air is introduced into the slurry through the oxidation air distributor to perform primary oxidation on the circulating absorption slurry at the bottom of the tower; And the circulating absorption slurry at the bottom of the tower overflows to the slurry collection pool through the overflow pipe, and after being stirred and mixed evenly in the slurry collection pool, it is recycled back to the bottom liquid collection tank in the bottom oxidation section of the tower.

8. The process method according to claim 1, characterized in that, In the process method, NaOH solution, ammonia water or liquid ammonia is used as an absorbent and is added to the bottom liquid collection tank and the dust collector liquid collection tank, and the amount of the added alkali solution is regulated according to the pH value of the circulating slurry to maintain the pH of the circulating slurry within the range of 6.0 - 7.5; In order to supplement the water lost during the evaporation process and the slurry discharge process, fresh process water is supplemented to the bottom liquid collection tank and the dust collector liquid collection tank, and the liquid level of the bottom of the tower is monitored according to the liquid level gauge arranged on the bottom liquid collection tank, and the amount of the supplemented fresh process water is regulated; The slurry in the dust collector liquid collection tank overflows to the bottom liquid collection tank through the dust collector overflow pipe.

9. The process method according to claim 1, characterized in that, The primary quenching section is equipped with a temperature alarm. When the temperature of the flue gas in the tower changes too much, or the temperature of the flue gas cooled by the quenching nozzles in the primary quenching section exceeds 85 °C, or when the catalyst stripping of the fluid catalytic cracking unit enters the tower, the emergency quenching water system is started to provide emergency quenching water to the quenching nozzles in the primary quenching section. The rating of each control valve on the emergency quenching water pipeline is set to 50% of the required total flow rate; when the temperature of the flue gas in the tower is normal or the fault is eliminated, the integrated dust removal and desulfurization tower enters the normal operation state.

10. The process method according to claim 1, characterized in that, When the index of the circulating absorption slurry exceeds the standard, the process method further includes step (3): (3) Part of the circulating absorption slurry is sent to the settler through the outlet side lines of the first and second stage slurry circulating pumps for flocculation sedimentation. In the supernatant liquid after sedimentation, a part is returned to the bottom liquid collecting tank of the integrated dust removal and desulfurization tower for recycling, and a part is introduced into the oxidation tank, and secondary oxidation is carried out by introducing compressed air; the slurry after oxidation flows from the oxidation tank to the drainage tank by gravity, and then is sent to the slurry cooler by the drainage pump, and is discharged externally after the temperature drops below 40°C; A stirrer is provided in the oxidation tank, and compressed air is blown into the oxidation tank from the bottom by an oxidation blower, so that the compressed air and the supernatant liquid are in full contact; an alkali solution is introduced into the oxidation tank, and the addition amount of the alkali solution is adjusted according to the pH of the overflow liquid of the oxidation tank to keep the pH of the effluent at about 7±0.

5.

11. The process method according to claim 10, characterized in that, The suspended particulate matter in the settler is aggregated at the bottom of the settler through flocculation sedimentation and discharged to the filter box or the vacuum belt filter press in the form of thick slurry. The solid content in the thick slurry is 3wt% - 5wt%. After being filtered by the filter box or dried by the vacuum belt filter press, 30wt% - 60wt% of solid matter is produced, which is regularly cleaned and transported out. The clear liquid after filtration and drying flows to the collection pool by gravity and is circulated back to the settler through the collection pool pump.

12. An integrated dust removal and desulfurization device for catalytic cracking flue gas using the process method described in any one of claims 1-11, characterized in that, The integrated device includes an integrated dust removal and desulfurization tower, and a flue gas inlet system, a liquid supply and circulation system, and a slurry treatment system configured therewith, wherein: The integrated dust removal and desulfurization tower sequentially includes a bottom oxidation section, a first stage quenching section, a second stage absorption section, a multi-tube type tube dust removal section, a dust and mist droplet removal section, and a chimney from bottom to top; the bottom oxidation section is provided with a bottom liquid collecting tank and an oxidation air distributor; the first stage quenching section is provided with a flue gas inlet and a plurality of quenching nozzles; a plurality of layers of absorption section nozzles are arranged on the tower wall of the second stage absorption section; the multi-tube type tube dust removal section is provided with a multi-tube type tube dust collector, including a dust collector liquid collecting tank, a plurality of parallel venturi tubes fixedly installed through the trough plate of the dust collector liquid collecting tank, and a spray pipe and spray nozzles arranged above the venturi tubes; the dust and mist droplet removal section is provided with a high-efficiency dust and mist droplet remover, including a plurality of parallel cyclone cylinder assemblies and a flushing hose and flushing nozzles arranged above the cyclone cylinder assemblies; The flue gas inlet system includes an inlet high-temperature flue connected to the flue gas inlet and a sodium-based powder spray gun arranged on the inlet high-temperature flue; The liquid supply and circulation system includes a bottom circulation spraying system, a multi-tube type tube dust removal section circulation system, a process water supply system, and an absorbent supply system; The slurry treatment system includes a settler, an oxidation tank, a drainage tank, a drainage pump, and a slurry cooler connected in sequence.

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