Flue gas treatment apparatus and method

Abstract

The present application relates to the technical field of flue gas treatment, and discloses a flue gas treatment device and method, wherein the flue gas treatment part of the flue gas treatment device comprises a flue extending spirally along the height direction, and a plurality of dispersion feeding pieces are arranged at intervals along the spiral direction of the flue, and the dispersion feeding pieces are used for feeding treatment agents to purify the flue gas. The present application has the advantages of improving the treatment effect, reducing the scale of the device and the energy consumption of the device.

Description

Technical Field

[0001] This invention relates to the field of flue gas treatment technology, and more specifically to a flue gas treatment device and method. Background Technology

[0002] As refineries pursue economic efficiency, many have begun blending residual oil into their FCC (Fuel Controlled Crush) units to improve profitability. However, the high impurity content in residual oil leads to a sharp increase in SO3 content in FCC regeneration flue gas. When flue gas containing gaseous SO3 passes through a wet flue gas desulfurization (FGD) system, the rapid cooling below the acid dew point causes SO3 to quickly form difficult-to-capture submicron-sized H2SO4 aerosols through homogeneous nucleation and heterogeneous nucleation using particulate matter as condensation nuclei. While larger droplets in the flue gas can generally be removed by absorption towers, they are ineffective against submicron-sized H2SO4 aerosols. These submicron-sized H2SO4 aerosols are then released into the atmosphere through the chimney, creating the "blue smoke" phenomenon at the chimney outlet. Furthermore, when manually sampling particulate matter in flue gas according to the requirements of the current "Determination of Low Concentration Particulate Matter in Exhaust Gas from Stationary Sources by Gravimetric Method" (HJ 836-2017), such aerosols can cause a large positive deviation in the final sampling results.

[0003] CN201620978839.7 proposes a system for the synergistic removal of fine particulate matter through phase change agglomeration in wet flue gas desulfurization (FGD) devices. Utilizing the high humidity of the flue gas in wet FGD devices, the system uses circulating cooling water in the phase change agglomeration unit to induce fine particulate matter to approach the cold wall under the thermophoretic force generated by the temperature gradient, enhancing collisions between fine particles and between fine particles and droplets / liquid films. Furthermore, the cooling water causes water vapor to grow using the fine particles as condensation nuclei, achieving the agglomeration and removal of fine particulate matter.

[0004] CN201620257231.5 integrates deep purification charged electrostatic precipitator technology with phase change coagulation technology, combining the coagulation of fine particles and the charge removal of large particles to improve the system's particle removal efficiency.

[0005] CN201510587296.6 provides a method that utilizes the principle of composite phase change condensation to condense supersaturated water vapor on the surface of fine particulate matter, promoting collision and coalescence of dust-laden droplets, thereby increasing the particle size of fine particulate matter in flue gas and improving the collection efficiency of the desulfurization tower. By arranging a vortex phase changer in the flue gas inlet pipe, the flue gas is cooled, undergoing a phase change and generating swirling flow, achieving the purpose of phase change condensation and coalescence removal.

[0006] However, existing technologies have problems such as low SO3 removal rate, high energy consumption, and long-term operation of waste heat boilers in FCC units. Summary of the Invention

[0007] The purpose of this invention is to provide a flue gas treatment device and method that has the advantages of improving treatment efficiency and reducing device size and energy consumption.

[0008] To achieve the above objectives, the present invention provides a flue gas treatment device. The flue gas treatment section of the flue gas treatment device includes a flue extending spirally along the height direction. A plurality of dispersive feeders are spaced apart in the flue along its own spiral direction. The dispersive feeders are used to feed a treatment agent to purify the flue gas.

[0009] In some embodiments of the present invention, the flue is configured as a purification section and a dust removal section from the feed end to the discharge end.

[0010] In some embodiments of the present invention, the flue is configured from the feed end to the discharge end as a purification section, a dust removal section and a removal section, wherein the removal section is used to remove the purifying agent from the purification section;

[0011] In some embodiments of the present invention, the purification section is used to contact the purification agent with the flue gas to desulfurize, decarbonize or denitrify the flue gas.

[0012] In some embodiments of the present invention, the dispersing feeder located in the purification section is connected to the purification agent feed line, the dispersing feeder located in the dust removal section is connected to the dust removal agent feed line, and the dispersing feeder located in the removal section is connected to the removal agent feed line.

[0013] In some embodiments of the present invention, the dispersing feeder is configured as a nozzle.

[0014] In some embodiments of the present invention, the flue gas treatment unit includes an inner cylinder and an outer cylinder nested together, and a swirl plate extending axially along the inner cylinder is provided between the inner cylinder and the outer cylinder to form the flue.

[0015] In some embodiments of the present invention, the bottom end of the flue extends outward and penetrates the outer cylinder to form an inlet flow channel, and a plurality of liquid passage holes are provided on the bottom wall of the inlet flow channel located inside the outer cylinder.

[0016] In some embodiments of the present invention, the inlet channel is connected to the flue gas outlet of the FCC device.

[0017] In some embodiments of the present invention, the bottom of the outer cylinder is connected to a skirt housing, which surrounds a space for receiving slurry falling from the flue gas treatment section.

[0018] In some embodiments of the present invention, the skirt housing is connected to the feed end of part or all of the dispersive feeder of the dust removal section via a slurry circulation pipeline.

[0019] In some embodiments of the present invention, the flue gas treatment device is provided with a filter, the inlet of which is connected to the space formed around the skirt housing for filtering the slurry.

[0020] In some embodiments of the present invention, the outlet of the filter is connected to the inlet of part or all of the dispersing feeder of the dust removal section via a filtrate circulation pipeline.

[0021] In some embodiments of the present invention, the filter is disposed in the skirt housing.

[0022] In some embodiments of the invention, the filter is located outside the skirt housing.

[0023] In some embodiments of the present invention, the filter includes multiple annular filter layers nested inside and outside, with the inner cylinder extending into the innermost annular filter layer, and the pore size of the annular filter layer gradually increasing from the outside to the inside.

[0024] In some embodiments of the present invention, the ratio of the pore size of the outer layer to the inner layer in two adjacent annular filter layers is 0.5 to 0.9.

[0025] In some embodiments of the present invention, the pore size of the outermost annular filter layer is 10-50 micrometers, and the pore size of the innermost annular filter layer is 50-1000 micrometers.

[0026] In some embodiments of the present invention, the top of the outer cylinder is connected to a chimney via an upwardly tapering variable diameter section, and a cyclone demister is sealed to the inner wall of the variable diameter section for demisting the flue gas from the flue gas treatment unit.

[0027] A second aspect of the present invention provides a flue gas treatment method, the flue gas treatment method comprising: causing the flue gas to flow in a spiral shape, and feeding a treatment agent in segments along the flue gas flow direction and feeding it into contact with the flue gas through a dispersing feeder.

[0028] In some embodiments of the present invention, the treatment agent includes a purifying agent and a dust removal agent that are sequentially dispersed and fed along the flue gas flow direction.

[0029] In some embodiments of the present invention, the treatment agent includes a purifying agent, a dust removal agent, and a removing agent that are sequentially dispersed and fed along the flue gas flow direction through a dispersing feeder, wherein the removing agent is used to remove the purifying agent.

[0030] In some embodiments of the present invention, the purifying agent includes at least one of a desulfurizing agent, a decarbonizing agent, or a denitrifying agent.

[0031] In some embodiments of the present invention, the desulfurizing agent includes a solid alkali agent.

[0032] In some embodiments of the present invention, the particle size of the solid alkali agent is preferably 80-1200 mesh.

[0033] In some embodiments of the present invention, 500 mesh to 1200 mesh is preferred.

[0034] In some embodiments of the present invention, the solid alkali agent is selected from sodium-containing alkali agents;

[0035] In some embodiments of the present invention, the sodium-containing alkali agent is calculated as sodium, the sulfur oxides in the flue gas are calculated as sulfur, and the sodium / sulfur molar ratio is 1-1.5:1.

[0036] In some embodiments of the present invention, the sodium-containing alkali agent is selected from sodium bicarbonate powder.

[0037] In some embodiments of the present invention, the treatment agent includes a liquid phase, and after the treatment agent treats the flue gas, it forms a slurry. The pH value of the slurry is adjusted and then used as a dust removal agent.

[0038] In some embodiments of the present invention, the slurry is adjusted to pH value and then filtered to obtain filtrate, which is then used as a dust removal agent.

[0039] In some embodiments of the present invention, the pH value of the slurry is controlled between 6.5 and 7.2.

[0040] In some embodiments of the present invention, the slurry is subjected to multi-layer filtration, and the pore size of the filter layer gradually increases along the slurry flow direction.

[0041] In some embodiments of the present invention, the ratio of the pore size of the outer layer to that of the inner layer in two adjacent filter layers is 0.5 to 0.9.

[0042] In some embodiments of the present invention, the pore size of the outermost filter layer is 10-50 micrometers, and the pore size of the innermost filter layer is 50-1000 micrometers.

[0043] In some embodiments of the present invention, the filter is backwashed every 3600s-10800s.

[0044] In some embodiments of the present invention, the flue gas to be treated contains SO2 and SO3.

[0045] In some embodiments of the present invention, the flue gas to be treated comes from an FCC device.

[0046] In some embodiments of the present invention, the flue gas treatment method of the present invention employs the flue gas treatment device described in the present invention.

[0047] Through the above technical solution, the spirally extended flue of the present invention can prolong the contact time between flue gas and treatment agent, and the dispersed feeders arranged at intervals along the extension direction of the flue can enhance the collision contact between flue gas and treatment agent, thereby improving absorption efficiency while effectively reducing the size of the device and energy consumption.

[0048] Furthermore, when used to treat FCC flue gas, it can efficiently and with low energy consumption remove SO3 from the flue gas, reduce the impact on the normal operation of the FCC unit, eliminate the blue smoke trailing phenomenon of FCC flue gas, and at the same time ensure that the particulate matter sampling at the outlet meets the standards. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the structure of a flue gas treatment device according to one embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the flue gas treatment device according to another embodiment of the present invention;

[0051] Figure 3 yes Figure 1 Structural diagram of the components in the inner and outer cylinders;

[0052] Figure 4 This is a schematic diagram of the flue gas treatment device according to another embodiment of the present invention;

[0053] Figure 5 This is a schematic diagram of the flue gas treatment device according to another embodiment of the present invention;

[0054] Figure 6 This is a schematic diagram of the flue gas treatment device according to another embodiment of the present invention;

[0055] Figure 7 This is a schematic diagram of the flue gas treatment device according to another embodiment of the present invention;

[0056] Figure 8 This is a schematic diagram of the flue gas treatment device according to another embodiment of the present invention;

[0057] Figure 9 This is a schematic diagram of an existing sodium-based wet desulfurization unit.

[0058] Explanation of reference numerals in the attached figures

[0059] 1.1 Cyclone demister; 1.2 Slurry drain pipe; 1.3 Slurry overflow pipe; 1.4 Filter backwash pipe; 1.5 Bottom filtrate drain pipe; 1.6 Inlet flue; 1.7 Skirt housing; 1.8 Filter; 1.9 Variable diameter section; 1.10 Chimney; 2 Inner cylinder; 2.1 Outer cylinder; 2.2 Cyclone plate; 2.3 Liquid passage hole; 2.4 Purification section; 2.5 Dust removal section; 2.6 De-dust removal section. Detailed Implementation

[0060] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0061] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0062] In this invention, unless otherwise stated, "inner" and "outer" refer to the inner and outer contours of each component itself, and "upper," "lower," "top," and "bottom" are generally used to describe the relative positional relationships of the components in relation to the directions shown in the accompanying drawings or in relation to the vertical, perpendicular, or gravitational directions.

[0063] This invention discloses a flue gas treatment device, see reference. Figures 1-8 As shown, the flue gas treatment unit of this flue gas treatment device includes a flue extending spirally along its height direction. Multiple dispersing feeders are spaced apart along the spiral direction of the flue, and these feeders disperse the feed treatment agent to purify the flue gas. This invention, through the spirally extending flue, extends the residence time of the flue gas during the purification process. Furthermore, the multiple dispersing feeders spaced apart along the spiral direction of the flue allow for better collision and contact between the spirally advancing flue gas and the dispersed treatment agent, thereby improving absorption efficiency.

[0064] In this invention, the flue is configured with a purification section 2.4 and a dust removal section 2.5 from the feed end to the discharge end, each used to purify and remove dust from the flue gas in sequence.

[0065] like Figure 1 , Figure 5 As shown, in this invention, the flue is configured from the feed end to the discharge end as a purification section 2.4, a dust removal section 2.5, and a removal section 2.6, wherein the removal section 2.6 is used to remove the purifying agent from the purification section 2.4.

[0066] The flue gas treatment device of the present invention has a wide range of applications and can be used for the removal of pollutants with a washing process. According to actual needs, a suitable purifying agent is selected in the purification section to contact the flue gas for desulfurization, decarbonization or denitrification.

[0067] Specifically, in this invention, the dispersing feeder located in the purification section 2.4 is connected to the purifying agent feed pipeline, the dispersing feeder located in the dust removal section 2.5 is connected to the dust removal agent feed pipeline, and the dispersing feeder located in the removal section 2.6 is connected to the removal agent feed pipeline, so as to realize the sequential purification, dust removal and purifying agent removal of flue gas.

[0068] like Figure 1 , Figure 5 As shown, the flue gas treatment unit of the present invention can be configured to include an inner cylinder 2 and an outer cylinder 2.1 nested together. A swirl plate 2.2 extending axially along the inner cylinder 2 is sealed between the inner cylinder 2 and the outer cylinder 2.1. Thus, the inner cylinder 2, the outer cylinder 2.1 and the swirl plate 2.2 together form the spiral upward flue of the present invention.

[0069] like Figure 1 , Figure 3 , Figure 5 , Figure 7 As shown, in this invention, the discharge end of the dispersing feeder is obliquely downward toward the inner cylinder 2, spraying the treatment agent downward and colliding with the spirally rising flue gas. The dispersing feeder can be configured as a nozzle, with multiple nozzles spaced apart along the spiral direction of the swirl plate 2.2 on the lower surface of the swirl plate 2.2. This ensures the spraying effect as much as possible and prevents the flue gas from bypassing the nozzles. Those skilled in the art will understand that this invention is not limited to the aforementioned nozzles, and other structural forms capable of achieving dispersing feed should also fall within the scope of protection of this application.

[0070] The bottom end of the flue extends outward and penetrates the outer cylinder 2.1 to form the inlet flow channel 1.6. The inventors discovered that with the aforementioned spirally upward-extending flue, the treatment agent would backflow along the flue into the inlet flow channel 1.6 and even into the flue gas source device. To address this, the present invention provides multiple liquid passage holes 2.3 on the bottom wall of the inlet flow channel 1.6 located inside the outer cylinder 2.1. The slurry obtained after treating the flue gas falls through the liquid passage holes 2.3, thereby avoiding backflow. Furthermore, when the flue gas to be desulfurized and dust-removed enters the swirl plate 2.2, it will not come into contact with the slurry, thus not hindering the spiral upward movement of the flue gas, but will directly come into contact with the purifying agent, dust removal agent, and removal agent respectively.

[0071] Referring to the background technology, in the prior art, refineries add residual oil to the feedstock of FCC units to improve the efficiency of the FCC units, which leads to a sharp increase in the SO3 content in the FCC regeneration flue gas. When using existing wet flue gas desulfurization systems, a "blue smoke" phenomenon will form at the chimney outlet. The inlet channel 1.6 of the flue gas treatment device of the present invention is connected to the flue gas outlet of the FCC unit. Using the flue gas treatment device of the present invention, the flue gas from the FCC unit passes through solid alkali powder absorption, bottom filtrate absorption and demineralized water absorption in sequence, which can efficiently remove SO3 from the flue gas, reduce the impact on the normal operation of the FCC unit, eliminate the blue smoke tailing phenomenon of FCC flue gas, and at the same time ensure that the manual sampling of outlet particulate matter is qualified and meets the standards.

[0072] like Figures 1-8 As shown, the bottom of the outer cylinder 2.1 is connected to a skirt housing 1.7. The skirt housing 1.7 surrounds and forms a space to accommodate the slurry falling from the flue gas treatment section. Preferably, the skirt housing 1.7 is connected to the feed end of part or all of the dispersing feeder of the dust removal section 2.5 through a slurry circulation pipeline, so as to return the slurry to the dust removal section 2.5 as a dust removal agent for recycling.

[0073] Furthermore, the flue gas treatment device of the present invention is provided with a filter 1.8, the inlet of the filter 1.8 being connected to the space formed around the skirt housing 1.7 for filtering the slurry.

[0074] like Figure 4 As shown, the outlet 1.5 of the filter 1.8 is connected to the feed end of all the dispersing feed components of the dust removal section 2.5 through the filtrate circulation pipeline, so that the filtrate obtained after slurry filtration can be returned to the dust removal section 2.5 as a dust removal agent for recycling.

[0075] It should be noted that, as Figures 1-4 As shown, to save space, the filter 1.8 can be installed in the skirt housing 1.7; or it can be installed as shown in the diagram. Figure 8 As shown, the filter 1.8 is located outside the skirt housing 1.7 and is connected to the slurry drain pipe 1.2 located at the bottom of the skirt housing 1.7 and / or the slurry overflow pipe 1.3 located at the top of the skirt housing 1.7.

[0076] like Figure 8 As shown, the upper part of the dust removal section 2.5 is connected to the outlet 1.5 of the filter 1.8 through the filter liquid circulation pipeline, and the lower part of the dust removal section 2.5 is connected to the skirt housing 1.7 through the slurry circulation pipeline. In this way, the flue gas flow direction can first come into preliminary contact with the slurry and then come into contact with the filter liquid for enhanced treatment.

[0077] In this invention, the filter section of filter 1.8 is configured as a multi-layered annular filter layer with inner and outer nesting. The inner cylinder 2 extends into the innermost annular filter layer, and the pore size of the annular filter layer gradually increases from the outside to the inside. The inventors discovered that in this invention, the pore size of the annular filter layer decreases from large to small, causing large particles of contaminant to gradually penetrate deeper into the filter layer. Since the slurry contains a large amount of inorganic salts, some of these inorganic salts crystallize and grow on the surface of the contaminants deep within the filter layer, making them impossible to completely remove during backwashing. This results in a decrease in the filtration effect of the filter layer and an increase in resistance. On the other hand, using a filter layer with uniformly small pore sizes would increase the overall operating resistance. Therefore, this invention uses pores with increasing sizes to intercept most of the contaminants while preventing the overall filtration pressure from becoming too high.

[0078] In this invention, it is preferred that the ratio of the pore size of the outer layer to the inner layer in two adjacent annular filter layers is 0.5 to 0.9.

[0079] In this invention, the pore size of the outermost annular filter layer can be 10-50 micrometers, and the pore size of the innermost annular filter layer can be 50-1000 micrometers. For example, when the annular filter layer has a 10-layer structure, the pore diameter from the outside to the inside can be 10-20-30-40-50-100-200-400-800-1000 micrometers; when the annular filter layer has a 15-layer structure, the pore diameter from the outside to the inside can be 10-20-30-40-50-60-70-80-100-150-300-450-600-750-900 micrometers.

[0080] The present invention also includes a filter backwash pipe 1.4 that runs through the skirt housing 1.7 and communicates with the filter 1.8 to backwash the filter.

[0081] In this invention, the top of the outer cylinder 2.1 is connected to a chimney 1.10 via an upwardly tapering variable diameter section 1.9. A cyclone demister 1.1 is sealed to the inner wall of the variable diameter section 1.9. The feed end of the cyclone demister is connected to the flue, and the discharge end of the cyclone demister is connected to the chimney 1.10 to demist the flue gas from the flue gas treatment unit. In the prior art, wet electrostatic precipitators and phase change condensation technology are used. The former requires a large amount of electrical energy and causes great loss to the discharge tip under high load; the latter requires a large amount of cooling energy for deep cooling of the flue gas, resulting in high energy consumption. This invention, through the aforementioned structural design of the flue gas treatment unit combined with the cyclone demister 1.1, can desulfurize and remove dust from the flue gas by using solid alkali absorption and water washing, avoiding the problems of SO3 escape, corrosion, and high energy consumption caused by using wet desulfurization, electrostatic demisters, and other technologies. It should be noted that the structure of the cyclone demister that achieves cyclone demisting is well known to those skilled in the art and is not part of the core improvement of this application, so it will not be described in detail here.

[0082] Based on the foregoing disclosure, this invention discloses a flue gas treatment method, which includes: causing the flue gas to flow in a spiral shape, and feeding a treatment agent in segments along the flue gas flow direction and dispersing it through a dispersing feeder (such as the aforementioned nozzle) to contact the flue gas and achieve flue gas purification. In this invention, the spiral flow of the flue gas can prolong the contact time with the segmented and dispersed treatment agent, enabling the flue gas and the treatment agent to collide and contact better, thereby improving the absorption efficiency.

[0083] In this invention, the treatment agent includes a purifying agent and a dust removal agent that are sequentially dispersed and fed through a dispersing feeder along the flue gas flow direction. The purifying agent and the dust removal agent are used to purify and remove dust from the spirally flowing flue gas in sequence.

[0084] In this invention, the preferred treatment agent comprises a purifying agent, a dust removal agent, and a removing agent that are sequentially dispersed and fed along the flue gas flow direction, wherein the removing agent is used to remove the purifying agent.

[0085] In this invention, the purifying agent is selected according to actual needs. For example, the purifying agent may include at least one of desulfurizing agent, decarbonizing agent or denitrifying agent. In this invention, there are no special requirements for decarbonizing agent or denitrifying agent. Conventional decarbonizing agent or denitrifying agent in wet scrubbing technology in this field can be used. For example, denitrification can be achieved by using ferrous EDTA complexing agent, ferrous NTA complexing agent or ferrous TEA complexing agent, etc. This invention will not elaborate further on this.

[0086] The desulfurizing agent of the present invention includes a solid alkali agent. By combining solid alkali and water washing, the utilization rate of the alkali agent can be effectively improved, and the efficiency of desulfurization and dust removal can be further enhanced. More preferably, the particle size of the solid alkali agent is 80 mesh-1200 mesh, and even more preferably 500 mesh-1200 mesh.

[0087] In this invention, the solid alkali agent is selected from sodium-containing alkali agents; preferably, the sodium-containing alkali agent is calculated as sodium, the sulfur oxides in the flue gas are calculated as sulfur, and the sodium / sulfur molar ratio is 1-1.5:1.

[0088] In this invention, the sodium-containing alkali agent is selected from sodium bicarbonate powder.

[0089] In this invention, the treatment agent includes a liquid phase. After the flue gas is treated, the treatment agent is formed into a slurry. The pH value of the slurry after the flue gas is treated is adjusted and it is used as a dust removal agent. Alternatively, the pH value of the slurry after the flue gas is treated is adjusted and it is filtered to obtain a filtrate, which is then used as a dust removal agent.

[0090] In this invention, during the dust removal stage, the flue gas is first brought into contact with the slurry after pH adjustment along the flue gas flow direction, and then into contact with the filtrate.

[0091] In this invention, the pH value of the bottom filtrate can be adjusted by the amount of solid alkali injected and the amount of demineralized water replenished, and the pH value of the filtrate can be controlled between 6.5 and 7.2.

[0092] Preferably, the aforementioned slurry is filtered through multiple layers using a filter to obtain filtrate, with the pore size of the filter layer gradually increasing along the flow direction of the filtered material.

[0093] In this invention, the ratio of the pore size of the outer layer to the inner layer in two adjacent filter layers is 0.5 to 0.9.

[0094] In this invention, a two-layer filter is used for filtration. The pore size of the outer filter layer is 10-50 micrometers, and the pore size of the inner filter layer is 50-1000 micrometers. For example, when the annular filter layer has a 10-layer structure, the pore diameter from the outside to the inside can be 10-20-30-40-50-100-200-400-800-1000 micrometers; when the annular filter layer has a 15-layer structure, the pore diameter from the outside to the inside can be 10-20-30-40-50-60-70-80-100-150-300-450-600-750-900 micrometers.

[0095] In this invention, the filter is backwashed every 3600s-10800s.

[0096] In this invention, the flue gas contains SO2 and SO3.

[0097] The flue gas treatment method of the present invention is carried out using the flue gas treatment device of the present invention, wherein the flue gas to be treated is introduced from the bottom of the flue of the flue gas treatment unit, and the treatment agent is fed through the dispersing feeder.

[0098] In this process, along the flow direction of the flue gas in the flue, the purifying agent is fed through the nozzle of the purification section 2.4, the dust removal agent is fed through the nozzle of the dust removal section 2.5, and the removal agent is fed through the nozzle of the removal section 2.6.

[0099] The aforementioned purifying agent, dust remover, and descaling agent come into contact with the flue gas to form a slurry, which falls into the space enclosed by the skirt housing. After adjusting the pH value, the slurry is returned to the dust removal section through the slurry circulation pipeline and / or the slurry is filtered through filter 1.8 to obtain filtrate, which is then returned to the dust removal section through the filtrate circulation pipeline.

[0100] The treated flue gas is discharged through chimney 1.10.

[0101] In this invention, the flue gas originates from an FCC unit. Addressing the issues of low SO3 removal rate, high energy consumption, and long-term operation of the waste heat boiler in the FCC unit due to the deterioration of FCC raw materials, the flue gas treatment method of this invention is implemented in a flue gas treatment device, offering the following advantages: 1) This invention uses solid alkali powder and detergent technology to absorb sulfur oxides and particulate matter in the flue gas; simultaneously, it uses a scrubbing tower with an inner and outer cylindrical structure, causing the flue gas to spiral upwards; the spirally rising flue gas can collide and contact with the solid alkali powder, circulating filtrate, and demineralized water in stages, resulting in high absorption efficiency and the ability to recycle the filtrate; using a spiral flue increases the flue gas treatment capacity while effectively reducing the device size; 2) This invention uses solid alkali to absorb sulfur oxides in the flue gas while simultaneously using filtrate spraying... The removal of particulate matter and solid alkali powder from flue gas can efficiently remove SO2 and SO3 simultaneously, avoiding the deficiency of existing wet desulfurization technology in removing SO3. The use of a scrubbing tower with inner and outer cylindrical structures and a swirl plate between the inner and outer cylinders allows the flue gas to spiral upward, which not only prolongs the residence time of the flue gas in the desulfurization and dust removal process, but also allows the spiraling flue gas to better collide and contact with the spray liquid dispersed by the nozzles, thereby improving the absorption efficiency. Through the setting of the filter in the tower, the absorption liquid can be filtered during the desulfurization and dust removal process, which not only reduces waste, but also further improves the absorption efficiency. 3) Through the setting of the inlet flue and multiple liquid passage holes 2.3 on the bottom wall, the flue gas to be desulfurized and dust removed will not come into contact with the absorption liquid when it enters the swirl plate, and will not hinder the spiral upward operation trend of the flue gas.

[0102] When this invention desulfurizes flue gas, for example, when treating sulfur-containing flue gas from an FCC unit, the sulfur-containing flue gas first comes into contact with a solid alkali to remove SO3 and most of SO2. The remaining SO2 and particulate matter are then removed by an alkaline circulating slurry (initially, water circulation needs to be established first, and only when there is enough circulating water in the tower can it be used for flue gas purification). The pH value of the circulating slurry can be adjusted by the amount of solid alkali injected. The demineralized water at the top is used for end-of-pipe purification of the flue gas.

[0103] In this invention, when desulfurizing flue gas, the desulfurizing agent includes demineralized water. Sodium bicarbonate is used to remove SO3, and demineralized water is used to remove SO2 and dust. Sodium bicarbonate is used to maintain the pH of the circulating desulfurization solution at the center. Sodium hydroxide can also be added appropriately according to actual needs.

[0104] This invention provides purified flue gas emissions by demisting the flue gas after it has been purified, dusted, and depurified.

[0105] The advantages of the present invention are illustrated below through examples, but the present invention is not limited thereto. Unless otherwise specified, the experimental methods in the following examples are conventional methods in the art; unless otherwise defined, the raw materials, instruments, and equipment used can be obtained commercially or through existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations.

[0106] Example 1

[0107] This embodiment uses, as follows: Figures 1 to 4 The flue gas treatment device shown has an outer cylinder 2.1 and an inner cylinder 2 coaxially nested together, with an annular space between the inner and outer cylinders. A swirl plate 2.2 is positioned within this annular space and spirals upwards along the height direction. The space enclosed by the swirl plate 2.2 and the inner and outer cylinders serves as a flue. Dispersing feed components are nozzles, spaced at intervals along the lower surface of the swirl plate 2.2. The nozzles in the purification section 2.4 are connected to the purifying agent feed line, the nozzles in the dust removal section 2.5 are connected to the dust removal agent feed line, and the nozzles in the removal section 2.6 are connected to the removal agent feed line. These nozzles spray the purifying agent, dust removal agent, and removal agent downwards, creating an impact with the spirally rising flue gas. The filter 1.8 in the skirt housing filters the bottom slurry, forming a filtrate for circulating and washing the flue gas.

[0108] The bottom of the swirl plate 2.2 is equipped with an inlet flue 1.6, which has evenly spaced liquid passage holes 2.3 on the bottom wall of the outer cylinder. The filter 1.8 consists of 10 hollow cylindrical filter layers with a composite structure. Each filter layer uses filter cloth, with pore sizes ranging from 10 micrometers to 1000 micrometers. The outermost filter layer and the skirt housing 1.7 form a liquid-holding space for the concentrated liquid, while the innermost filter layer contains the filtrate. The filtrate is pumped through the filtrate discharge pipe 1.5 to the nozzles of the dust removal section 2.5 to remove dust from the flue gas. The top of the outer cylinder 2.1 is connected to the chimney 1.10 through an upwardly tapering variable diameter section 1.9. The inner wall of the variable diameter section 1.9 is sealed with a cyclone demister 1.1. The feed end of the cyclone demister is connected to the flue, and the discharge end of the cyclone demister is connected to the chimney 1.10.

[0109] In conjunction with the aforementioned device, the present invention also provides a flue gas treatment method, comprising the following steps:

[0110] Step S101: The flue gas to be purified is introduced into the flue gas inlet channel 1.6, so that the flue gas spirals upward along the swirl plate 2.2;

[0111] In step S102, the spiraling flue gas collides sequentially with the alkaline powder (purifying agent) from the first stage of purification, the bottom filtrate (dust remover) from the second stage of purification, and the demineralized water (removal agent) from the third stage of purification, thus completing the three-stage flue gas purification. After the three-stage purification, the flue gas is demisted and the liquid droplets are removed, and then it continues to rise and passes through the variable diameter section and the chimney before being discharged into the atmosphere.

[0112] In step S103, the demineralized water and filtrate after flue gas treatment flow through the cyclone plate 2.2 to the filter 1.8 and then filter the slurry through the filter cloth. The filtered filtrate is used as filtrate for secondary spray purification of flue gas.

[0113] In step S104, filter 1.8 is backwashed with demineralized water every 5400 cycles to ensure the filtration effect of the filter cloth at the bottom of the tower.

[0114] In this embodiment, the alkali powder is sodium bicarbonate powder, and the sodium / sulfur molar ratio of the alkali powder to the sulfur oxides in the flue gas is 1.2:1. The particle size of the sodium bicarbonate powder is 800 mesh, and the pH value of the slurry is controlled between 6.5 and 7.2. The flue gas to be purified comes from an FCC unit with degraded raw materials, and the dust content of the flue gas to be purified is 200 mg / Nm³. 3 SO2 800mg / Nm 3 SO3 80mg / Nm 3 .

[0115] Results: The dust concentration in the flue gas discharged into the atmosphere was 10 mg / Nm³. 3 SO2 10mg / Nm 3 SO3 5mg / Nm 3 .

[0116] Example 2

[0117] Unlike Example 1, the method used is as follows Figures 5 to 8 The flue gas treatment device shown in step S102 uses a four-stage, five-section purification process for the spirally rising flue gas. The first stage of purification consists of a solid alkali absorption stage, the second stage consists of a slurry spray stage, the third stage consists of two stages of circulating filtrate spray, and the fourth stage consists of a demineralized water spray stage.

[0118] Among them, such as Figure 8 As shown, in this embodiment, the filter 1.8 is externally mounted. Part of the slurry at the bottom of the tower is pumped to the nozzle of the lower half of the dust removal section through the slurry discharge pipe 1.2, and the rest either overflows through the slurry overflow pipe 1.3 or is pumped by the slurry discharge pipe 1.2 to the external filter for filtration.

[0119] The filtrate from the external filter is circulated to the nozzles in the upper part of the dust removal section of the tower, where it is used as the tertiary purification spray to purify the flue gas.

[0120] The flue gas to be purified contains dust with a concentration of 1000 mg / Nm³. 3 SO2 500mg / Nm 3 SO3 80mg / Nm 3 .

[0121] Result: The dust concentration in the flue gas discharged into the atmosphere was 15 mg / Nm³. 3 SO2 10mg / Nm 3 SO3 5mg / Nm 3 .

[0122] Example 3

[0123] Unlike Example 1, the sodium bicarbonate powder used has a particle size of 120 mesh.

[0124] Result: Dust concentration 50 mg / Nm 3 SO2 10mg / Nm 3 SO3 40mg / Nm 3 .

[0125] Comparative Example

[0126] Unlike Example 1, the following method is used. Figure 9 The process shown employs sodium-based wet desulfurization technology. After the flue gas enters the desulfurization tower, it undergoes three-stage scrubbing, with the pH value of the scrubbing liquid controlled at 7-8. The desulfurization mechanism of NaOH is similar to that of other desulfurizing agents; both involve an acid-base neutralization reaction between the alkaline substance and the sulfurous acid solution generated by sulfur dioxide dissolving in water. The pH value of the circulating liquid is adjusted by regulating the amount of sodium hydroxide added.

[0127] First, sulfur dioxide in the flue gas comes into contact with water to form sulfurous acid. Then, sulfurous acid reacts with NaOH to form Na₂SO₃, which further reacts with H₂SO₃ to form NaHSO₃. NaHSO₃ then reacts with NaOH to accelerate the formation of sodium sulfite. Part of the generated sodium sulfite is recycled as an absorbent, while the other part is sent to the wastewater treatment unit for solid-liquid separation and oxidation, and then discharged as a harmless sodium sulfate aqueous solution. There are also some side reactions, such as the reaction of sulfur trioxide, hydrochloric acid, and hydrofluoric acid with sodium hydroxide to form a mixture of sodium sulfate and sodium chloride.

[0128] Result: Dust concentration 28 mg / Nm 3 SO2 30mg / Nm 3 SO3 40mg / Nm 3 .

[0129] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A flue gas treatment device, characterized in that, The flue gas treatment unit of the flue gas treatment device includes a flue extending spirally along the height direction. Multiple dispersive feeders are spaced apart in the flue along its own spiral direction. The dispersive feeders are used to feed treatment agents to purify the flue gas.

2. The flue gas treatment device according to claim 1, characterized in that, The flue is configured as a purification section (2.4) and a dust removal section (2.5) from the feed end to the discharge end; Preferably, the flue is configured from the feed end to the discharge end as a purification section (2.4), a dust removal section (2.5), and a removal section (2.6), wherein the removal section (2.6) is used to remove the purifying agent from the purification section (2.4); More preferably, the purification section (2.4) is used to contact the purification agent with the flue gas to desulfurize, decarbonize or denitrify the flue gas.

3. The flue gas treatment device according to claim 1 or 2, characterized in that, The dispersing feeder located in the purification section (2.4) is connected to the purification agent feed line; the dispersing feeder located in the dust removal section (2.5) is connected to the dust removal agent feed line; and the dispersing feeder located in the removal section (2.6) is connected to the removal agent feed line; and / or The dispersing feeder is configured as a nozzle.

4. The flue gas treatment device according to claim 1, characterized in that, The flue gas treatment unit includes an inner cylinder (2) and an outer cylinder (2.1) nested together. A swirl plate (2.2) extending axially along the inner cylinder (2) is provided between the inner cylinder (2) and the outer cylinder (2.1) to form the flue.

5. The flue gas treatment device according to claim 4, characterized in that, The bottom end of the flue extends outward and penetrates the outer cylinder (2.1) to form an inlet channel (1.6). Multiple liquid passage holes (2.3) are provided on the bottom wall of the inlet channel (1.6) located within the outer cylinder (2.1). Preferably, the inlet channel (1.6) is connected to the flue gas outlet of the FCC device; and / or The bottom of the outer cylinder (2.1) is connected to a skirt housing (1.7), which surrounds and forms a space to accommodate the slurry falling from the flue gas treatment section. Preferably, the skirt housing (1.7) is connected to the feed end of part or all of the dispersive feeder of the dust removal section (2.5) through a slurry circulation pipeline.

6. The flue gas treatment apparatus according to claim 1 or 5, characterized in that, The flue gas treatment device is equipped with a filter (1.8), the inlet of which is connected to the space formed by the skirt housing (1.7) for filtering the slurry; and / or Preferably, the outlet (1.5) of the filter (1.8) is connected to the inlet of part or all of the dispersing feed component of the dust removal section (2.5) via a filtrate circulation pipeline; and / or Preferably, the filter (1.8) is disposed in the skirt housing (1.7); or Preferably, the filter (1.8) is located outside the skirt housing (1.7).

7. The flue gas treatment device according to claim 6, characterized in that, The filter (1.8) includes multiple annular filter layers nested inside and outside. The inner cylinder (2) extends into the innermost annular filter layer. From the outside to the inside, the filter pore size of the annular filter layer gradually increases. Preferably, in two adjacent annular filter layers, the ratio of the filter pore size of the outer layer to that of the inner layer is 0.5 to 0.9; and / or Preferably, the pore size of the outermost annular filter layer is 10-50 micrometers, and the pore size of the innermost annular filter layer is 50-1000 micrometers.

8. The flue gas treatment apparatus according to claim 4 or 5, characterized in that, The top of the outer cylinder (2.1) is connected to a chimney (1.10) via an upwardly tapering variable diameter section (1.9). The inner wall of the variable diameter section (1.9) is sealed with a cyclone demister (1.1) for demisting the flue gas from the flue gas treatment unit.

9. A method for treating flue gas, characterized in that, The flue gas treatment method includes: making the flue gas flow in a spiral shape, and feeding the treatment agent in segments along the flue gas flow direction and feeding it into contact with the flue gas through a dispersing feeder.

10. The flue gas treatment method according to claim 9, wherein, The treatment agent includes a purifying agent and a dust removal agent that are sequentially dispersed and fed along the flue gas flow direction; Preferably, the treatment agent comprises a purifying agent, a dust removal agent, and a removing agent that are sequentially dispersed and fed along the flue gas flow direction through a dispersing feeder, wherein the removing agent is used to remove the purifying agent.

11. The flue gas treatment method according to claim 10, wherein, The purifying agent includes at least one of desulfurizing agent, decarbonizing agent or denitrifying agent; Preferably, the desulfurizing agent comprises a solid alkali agent, more preferably the particle size of the solid alkali agent is 80 mesh-1200 mesh, and even more preferably 500 mesh-1200 mesh.

12. The flue gas treatment method according to claim 11, wherein, Solid alkali agents are selected from sodium-containing alkali agents; Preferably, the sodium-containing alkali agent, calculated as sodium, and the sulfur oxides in the flue gas, calculated as sulfur, have a sodium / sulfur molar ratio of 1-1.5:1; and / or The preferred sodium-containing alkali agent is sodium bicarbonate powder.

13. The flue gas treatment method according to claim 9, wherein, The treatment agent includes a liquid phase. After the treatment agent treats the flue gas, it forms a slurry. The pH value of the slurry is adjusted and then used as a dust removal agent. and / or The slurry was adjusted to pH and then filtered to obtain filtrate, which was then used as a dust removal agent. Preferably, the pH value of the slurry is controlled between 6.5 and 7.2; and / or Preferably, the slurry is filtered through multiple layers, with the pore size of the filter layer gradually increasing along the slurry flow direction.

14. The flue gas treatment method according to claim 13, wherein, In two adjacent filter layers, the ratio of the pore size of the outer layer to that of the inner layer is 0.5 to 0.9; and / or The outermost filter layer has a pore size of 10-50 micrometers, while the innermost filter layer has a pore size of 50-1000 micrometers.

15. The flue gas treatment method according to claim 9, wherein, Backwash the filter every 3600-10800 seconds; and / or The flue gas to be treated contains SO2 and SO3; and / or The flue gas to be treated comes from an FCC unit.

16. The flue gas treatment method according to any one of claims 9-15, wherein, The method employs the flue gas treatment apparatus described in any one of claims 1-8.

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