A desulfurization tower and a desulfurization method coupling a limestone-gypsum method and a seawater desulfurization method

Abstract

This invention belongs to the field of flue gas desulfurization, and relates to a desulfurization tower and method that couples limestone desulfurization and seawater desulfurization. The desulfurization tower has a flue gas inlet and outlet, and sequentially includes a limestone-gypsum desulfurization zone and a seawater desulfurization zone along the flue gas flow. The limestone-gypsum desulfurization zone includes a slurry spray assembly and a slurry pool; the seawater desulfurization zone includes a seawater spray assembly. An isolation and guiding assembly is provided between the two desulfurization zones, including a supporting base, multiple sets of guiding pipes, splash guards on the top of the guiding pipes, and a collection channel. The supporting base forms the boundary between the two desulfurization zones; the guiding pipes are vertically continuous pipes, and multiple sets of guiding pipes are located on the supporting base, constructing a flue gas passage between the two desulfurization zones; the splash guards are used to prevent seawater absorbent from the seawater desulfurization zone from entering the guiding pipes; the collection channel is used to collect the seawater absorbent blocked by the splash guards. The desulfurization tower of this invention achieves flue gas flow and liquid phase isolation between the two desulfurization zones, improving flue gas desulfurization efficiency and reducing operating costs.

Description

Technical Field

[0001] This invention belongs to the field of flue gas desulfurization, specifically relating to a desulfurization tower and desulfurization method that couples limestone-gypsum desulfurization and seawater desulfurization. Background Technology

[0002] As my country's air pollutant emission standards become increasingly stringent, the demand for in-depth treatment of SO2 in industrial flue gas continues to rise. Limestone-gypsum method and seawater desulfurization method are currently the two most widely used mainstream flue gas desulfurization technologies in the industrial field.

[0003] Among them, the limestone-gypsum method has been widely used in industries such as power and metallurgy due to its advantages such as high technical maturity, stable desulfurization efficiency, and the resource recovery of by-product gypsum. However, this technology has significant shortcomings in practical applications: First, when treating high-sulfur flue gas, the consumption of limestone raw materials is huge, and the cost of desulfurizing agent accounts for a high proportion of the system operating cost; second, in order to meet ultra-low emission requirements, the slurry circulation volume needs to be greatly increased, resulting in a significant increase in system circulation energy consumption; third, corrosive acidic impurities such as HCl and HF in the flue gas will continuously consume limestone desulfurizing agent, further aggravating raw material waste, and will also affect the oxidation and crystallization effect of gypsum in the slurry tank.

[0004] Seawater desulfurization is a technology that removes SO2 from flue gas using the natural alkalinity of seawater. It boasts significant advantages such as requiring no additional chemical desulfurizing agents, low operating costs, and a simple process, making it particularly suitable for industrial flue gas treatment in coastal areas. However, this technology also has significant limitations: First, desulfurization efficiency is greatly affected by the SO2 concentration at the flue gas inlet and the alkalinity of the seawater; under high-sulfur flue gas conditions, it is difficult to consistently achieve ultra-low emission requirements. Second, dust and acidic impurities carried in the flue gas ineffectively consume seawater alkalinity, further reducing desulfurization efficiency. Third, to ensure desulfurization effectiveness, the seawater spray volume needs to be significantly increased, which not only increases system energy consumption but also significantly increases the load on the subsequent seawater aeration treatment system.

[0005] In summary, neither of the existing desulfurization technologies, when applied individually, can simultaneously meet the core requirements of "high desulfurization efficiency" and "low operating costs." Furthermore, conventional two-stage desulfurization coupling schemes generally suffer from the technical defect of mutual mixing of the upper and lower desulfurization liquids. This not only leads to limestone slurry consuming seawater alkalinity and seawater diluting the limestone slurry, reducing reaction efficiency, but also causes frequent pH fluctuations in the slurry tank, severely affecting the quality of gypsum crystallization, thus failing to truly achieve the complementary advantages of the two desulfurization technologies. Therefore, developing a desulfurization device that can efficiently couple the two desulfurization technologies while avoiding mutual interference between the two desulfurization liquids, and significantly reduce system operating costs while stably meeting ultra-low emission requirements, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to overcome the above-mentioned defects of the prior art and provide a desulfurization tower and desulfurization method that couples limestone-gypsum desulfurization and seawater desulfurization, which can effectively reduce the raw material consumption and operating cost of the desulfurization system while ensuring stable deep desulfurization efficiency of flue gas.

[0007] Based on the above considerations, the first aspect of the present invention provides a desulfurization tower that couples limestone-gypsum desulfurization and seawater desulfurization, wherein the desulfurization tower has a flue gas inlet and a flue gas outlet, and a limestone-gypsum desulfurization zone and a seawater desulfurization zone are arranged sequentially along the flue gas flow path. The limestone-gypsum desulfurization zone includes a slurry spraying assembly and a slurry tank. The slurry spraying assembly is used to spray limestone slurry onto the flue gas to remove acidic pollutants. The slurry tank is located below the slurry spraying assembly (A2) and is used to receive the limestone slurry that has completed the absorption reaction. The seawater desulfurization zone includes a seawater spraying assembly, which is used to spray seawater absorbent onto the flue gas after preliminary desulfurization in the limestone-gypsum desulfurization zone to deeply remove acidic pollutants. The flue gas inlet is connected to the flue gas intake side of the limestone-gypsum desulfurization zone, and the flue gas outlet is connected to the exhaust side of the seawater desulfurization zone. An isolation and diversion assembly is provided between the limestone-gypsum desulfurization zone and the seawater desulfurization zone. The isolation and diversion assembly includes a support base, multiple sets of diversion pipes, splash guards that are installed on the top of the diversion pipes in a one-to-one correspondence with the diversion pipes, and a liquid collection channel. The supporting matrix is ​​fixed to the inner wall of the tower, forming a physical boundary between the limestone-gypsum desulfurization zone and the seawater desulfurization zone; The guide pipe is a vertically penetrating pipe, and multiple sets of guide pipes are evenly arranged on the supporting base to construct a flue gas flow channel from the limestone-gypsum desulfurization zone to the seawater desulfurization zone. The splash guard is fixed above the top opening of the corresponding guide pipe to prevent the seawater absorbent from falling into the guide pipe. The collection channel is an annular groove that is set in a closed loop along the inner wall of the tower body between the supporting base and the inner wall of the tower body, and is used to collect the seawater absorption liquid blocked by the splash guard.

[0008] A second aspect of the present invention provides a method for desulfurizing flue gas using the aforementioned desulfurization tower, wherein... The concentration of SO2 in the flue gas is 500~5000 mg / m³. 3 The flue gas temperature is 120~160℃; The limestone slurry has a solid content of 10% to 30%, and the particle size of the solids in the limestone slurry is 10 to 60 μm. Optionally, 0.05% to 0.2% by mass of an organic acid buffer is added to the limestone slurry. The organic acid buffer is adipic acid and / or citric acid. The pH value of the slurry and limestone slurry in the slurry tank is 4.0~6.0; The temperature of the seawater absorbent is 15~35℃, the salinity is 30~35‰, and the alkalinity (calculated as calcium carbonate) is 100~300mg / L. Preferably, the flow velocity of flue gas in the desulfurization tower is 2.5~4.5 m / s, and the residence time is ≥3.5s.

[0009] Preferably, when limestone slurry is supplied to the slurry spraying assembly through the recycling branch, the slurry circulation ratio is 15 to 30 times, and the outlet pressure of the circulation pump is 0.3 to 0.6 MPa. Preferably, the slurry tank is equipped with an oxidation aeration assembly with an aeration intensity of 1.5~3.0 m. 3 / (m 2 h) Preferably, the seawater desulfurization zone is equipped with a packing layer, and the spray density at the packing layer is 15~30 m³ / s. 3 / (m 2 h).

[0010] The beneficial effects of this invention are as follows: 1. This invention achieves efficient coupling of limestone-gypsum desulfurization and seawater desulfurization through the sequential arrangement of limestone-gypsum desulfurization zone, isolation and flow guiding component, and seawater desulfurization zone within the tower body. The isolation and flow guiding component, through the coordinated structure of support base, flow guiding pipe, splash guard, and liquid collection channel, simultaneously realizes flue gas conduction and liquid phase physical isolation between the two desulfurization zones, completely avoiding interference from the mixing of the two desulfurization liquids. While ensuring stable flue gas desulfurization efficiency, it significantly reduces system raw material consumption and operating costs.

[0011] 2. This invention, by setting a Venturi variable diameter flow channel and spiral guide vanes in the guide pipe, can rectify and equalize the flow of flue gas, avoiding the impact of flue gas deviation on the desulfurization effect. At the same time, it can enhance the turbulence of flue gas, improve the gas-liquid mass transfer efficiency in the seawater desulfurization zone, and achieve pre-demisting through swirling centrifugal force, reducing the processing load of subsequent demisting units. The local negative pressure formed by the Venturi flow channel can also achieve self-cleaning of the support substrate surface, avoid liquid accumulation and scaling, and extend the stable operation cycle of the equipment.

[0012] 3. By setting a packing layer and optimizing the spray density in the seawater desulfurization zone, and coordinating with the temperature and salinity control of the seawater absorbent, the present invention can form a uniform and continuous liquid film on the packing surface, which greatly increases the gas-liquid contact area and contact time, enhances the deep desulfurization effect, and significantly reduces the seawater spray volume and subsequent aeration treatment load, further reducing the system operating cost.

[0013] 4. By optimizing the particle size distribution, circulation ratio, and pH control range of the limestone slurry, and by precisely controlling the aeration intensity of the oxidation aeration components, this invention can significantly improve the atomization effect and gas-liquid reaction rate of the limestone slurry, ensure the high oxidation rate of calcium sulfite and the crystallization quality of gypsum, greatly improve the utilization rate of limestone desulfurizer, and further reduce raw material consumption. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a desulfurization tower for a coupled limestone-gypsum method and seawater desulfurization provided by the present invention.

[0015] Figure 2 This is a schematic diagram of the isolation and flow guiding component in the desulfurization tower.

[0016] exist Figure 1 and Figure 2 middle: A- Limestone-gypsum desulfurization zone, A1 Flue gas inlet, A2 Slurry spraying assembly, A3 Slurry tank, A4 Slurry outlet; B-Isolation and diversion assembly, B1-Supporting base, B2-Diffusion pipe, B3-Splash shield, B4-Collection channel, B5-Seawater outlet; C-Seawater desulfurization zone, C1-Seawater spray assembly, C2-Flue gas outlet, C3-Packing layer, C4-Demister. Detailed Implementation

[0017] The technical solution and its effects of the present invention will be further described below with reference to specific embodiments / examples. The following embodiments / examples are merely illustrative of the present invention and are not intended to limit it. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0018] The first aspect of the present invention provides a desulfurization tower for coupled limestone-gypsum desulfurization and seawater desulfurization, comprising a tower body with a flue gas inlet A1 and a flue gas outlet C2. Within the tower body between the flue gas inlet A1 and the flue gas outlet C2, functional units such as a limestone-gypsum desulfurization zone A, an isolation and guiding component B, and a seawater desulfurization zone C are sequentially arranged along the flue gas flow path. After the flue gas enters the tower body from the flue gas inlet A1, it flows sequentially through each functional unit along a preset flue gas treatment path, and after completing the staged desulfurization and gas-liquid separation treatment, it is discharged through the flue gas outlet C2.

[0019] In some embodiments, the tower body adopts a vertical structure, and the flue gas treatment passage is a counter-current passage from bottom to top. The limestone-gypsum desulfurization zone A, the isolation and guiding component B, and the seawater desulfurization zone C are arranged vertically in sequence within the tower body along the flue gas flow direction. The flue gas to be treated completes two-stage counter-current desulfurization from bottom to top and is then discharged in compliance with standards. This passage adopts a graded treatment of "coarse desulfurization pretreatment - deep desulfurization fine treatment", which takes into account the high-load desulfurization capacity of the limestone-gypsum method and the advantages of low-cost deep purification of the seawater method. While reducing limestone consumption, it steadily improves the overall desulfurization efficiency.

[0020] Limestone-gypsum desulfurization zone A In this invention, the limestone-gypsum desulfurization zone A is a primary coarse desulfurization and pretreatment unit for flue gas, which is located in the lower part of the desulfurization tower body and mainly includes a flue gas inlet A1, a slurry spraying assembly A2, a slurry pool A3, and a slurry outlet A4.

[0021] Wherein, the flue gas inlet A1 is the air inlet for the flue gas to be treated to enter the desulfurization tower; the slurry spraying assembly A2 is used to spray limestone slurry onto the flue gas flowing through the limestone-gypsum desulfurization zone A, and the absorption reaction occurs through gas-liquid countercurrent contact to remove acidic pollutants from the flue gas; the slurry tank A3 is used to receive and store the limestone slurry after the gas-liquid absorption reaction is completed; the slurry outlet A4 is opened on the bottom side wall of the slurry tank A3, and is equipped with slurry circulation and discharge pipelines to realize the recycling of slurry and / or the discharge of gypsum by-products.

[0022] In some embodiments, the flue gas inlet A1 is located on the lower side wall of the corresponding tower body in this area, with its opening positioned above the liquid surface of the slurry pool A3 and below the slurry spraying assembly A2, and fully connected to the flue gas inlet side of this area; after the flue gas to be treated enters the tower body horizontally through the flue gas inlet A1, it changes to a bottom-up flow direction and enters the spraying coverage area of ​​the slurry spraying assembly A2 evenly, ensuring sufficient countercurrent contact between the flue gas and the limestone slurry.

[0023] Preferably, each flue gas inlet A1 is equipped with a variable diameter guide flue, which can reduce the local resistance when the flue gas enters the tower and reduce the energy consumption of the fan during system operation.

[0024] In some embodiments, the limestone slurry uses calcium carbonate suspension as the core component, with a solid content controlled at 10% to 30%, and may selectively add 0.05% to 0.2% of organic acid buffer (such as adipic acid or citric acid) to stabilize the pH value of the slurry and improve the SO2 gas-liquid absorption efficiency.

[0025] Preferably, the pH value of the slurry in the slurry tank A3 is 4.0~6.0 (preferably 4.5~5.2). This range can match the reaction kinetics requirements of sulfite oxidation and calcium sulfate crystallization, providing a stable environment for forced oxidation of calcium sulfite and crystal growth of gypsum dihydrate, improving the oxidation rate and crystal purity of gypsum, and reducing the content of by-product impurities.

[0026] In some embodiments, the slurry spraying assembly A2 is mounted above the slurry tank A3 and above the flue gas inlet A1. After entering the area from the flue gas inlet A1, the flue gas passes through the sprayed coverage area from bottom to top, forming a counter-current gas-liquid contact with the limestone slurry sprayed from top to bottom. More than 80% of SO2, as well as corrosive acidic gases such as HCl and HF, and most dust particles in the flue gas are captured and removed by the slurry during this process. The synergistic effect of coarse desulfurization and pretreatment in this area not only completes the primary removal of flue gas and significantly reduces the treatment load of the subsequent seawater desulfurization zone C, but also removes corrosive impurities in advance, avoiding ineffective loss of seawater alkalinity and corrosion of the spraying system, and ensuring the long-term stable operation of the seawater desulfurization zone C.

[0027] Preferably, the slurry spraying assembly A2 adopts 1 to 4 sets of spray pipe networks arranged vertically along the flue gas flow direction, which is suitable for the characteristics of limestone slurry with high solid content and easy wear and blockage. Each set of spray pipe networks adopts a distributed structure of main pipe-branch pipe, and the branch pipe is equipped with several large-channel anti-clogging centrifugal atomizing spray nozzles. The nozzles are made of wear-resistant high-chromium cast iron or polyurethane-lined material, which can effectively avoid slurry wear and blockage. Moreover, each set of spray pipe networks is equipped with independent control valves, which can flexibly adjust the number of spray pipe networks opened, the flow rate and pressure of spray slurry according to the SO2 concentration, flue gas volume and emission requirements of the flue gas to be treated, so as to minimize the operating energy consumption of the circulating pump while ensuring desulfurization efficiency.

[0028] Preferably, the slurry tank A3 is also equipped with an oxidation aeration component and a stirring component.

[0029] The oxidation aeration component can be a perforated tube aerator or a swirl-mixing aerator. The air outlet of the aerator is submerged below the surface of the limestone slurry. Compressed air is blown into the slurry by an oxidation blower to force the calcium sulfite in the slurry to be oxidized into calcium sulfate, thereby improving the gypsum production efficiency and the purity of the by-products.

[0030] The stirring assembly can be a side-entry stirrer or a top-entry stirrer. The blades of the stirrer extend to the bottom of the slurry tank A3. By continuously stirring, the gypsum particles in the slurry are prevented from settling and accumulating, ensuring the solid-liquid uniformity of the slurry system, preventing material accumulation and blockage in the tower, and enhancing the reaction effect of oxidation aeration.

[0031] Preferably, the slurry outlet A4 is located on the lower side wall of the slurry tank A3, and is divided into two independent pipelines, corresponding to the slurry recycling and by-product discharge functions respectively. Both pipelines are equipped with independent control valves and power equipment, and the operating mode can be flexibly switched according to the slurry conditions. One of the pipelines is a circulation pipeline, which is connected to the spraying pipeline network of the slurry spraying component A2 via a slurry circulation pump. When the pH value of the slurry in the slurry tank A3 is stable at 4.0~6.0 and the gypsum solid content is less than 10%, the unreacted calcium carbonate in the slurry still has sufficient desulfurization capacity. At this time, the circulation pipeline is opened first to pressurize and transport the slurry to the slurry spraying component A2 for circulation spraying, which can improve the utilization rate of limestone desulfurizing agent.

[0032] The other route is an external discharge pipeline, equipped with a control valve connected to the gypsum dewatering system. When the gypsum solid content of the slurry in slurry tank A3 reaches 10%~20%, or when the pH value of the slurry remains below 4.0 and cannot be restored by adding fresh limestone slurry, the external discharge pipeline is opened to discharge the slurry to the gypsum dewatering system for solid-liquid separation to obtain gypsum by-products. At the same time, fresh limestone slurry is added to slurry tank A3 to maintain the stability of the pH value and solid content of the slurry system, ensuring the continuous and efficient desulfurization reaction.

[0033] In some implementations, when the desulfurization tower is running continuously and stably, the circulation pipeline is kept open with a large flow rate, while the discharge pipeline operates synchronously with a small flow rate for continuous discharge. This can maintain the stability of the solid content, pH value, and liquid level in the slurry tank A3, avoid fluctuations in system operating conditions, and adapt to long-term operation scenarios with stable unit loads.

[0034] Isolation and diversion component B In this invention, the isolation and diversion component B is the core functional unit for realizing the independent operation of the two desulfurization zones. It is fixed at the boundary of the flue gas passage between the limestone-gypsum desulfurization zone A and the seawater desulfurization zone C, and is correspondingly set in the middle area of ​​the desulfurization tower body. It has the dual functions of uniform flue gas diversion and liquid phase isolation. This component mainly includes a support base B1, a diversion pipe B2, a splash guard B3, and a liquid collection channel B4, and a seawater outlet B5 is set in the liquid collection channel B4.

[0035] The supporting base B1 serves as the overall foundation for the component, forming the physical boundary between the two desulfurization zones. The guide pipe B2 is used to construct the flue gas flow channel between the two desulfurization zones, while also rectifying and equalizing the flow of the flue gas. The splash guard B3 is used to prevent the absorbent liquid from the seawater desulfurization zone C from entering the guide pipe, achieving liquid phase isolation. The collection channel B4 is used to receive and collect the blocked seawater absorbent liquid. The seawater outlet B5 is located at the collection channel B4, used to realize the recycling and harmless discharge of the absorbent liquid.

[0036] In some implementations, for the bottom-up counter-current flue gas passage of the vertical tower, the isolation and guiding component B is located at the top of the limestone-gypsum desulfurization zone A and the bottom of the seawater desulfurization zone C, forming a physical boundary between the two desulfurization zones. The flue gas pretreated in the limestone-gypsum desulfurization zone A passes through the internal flow channel of the guiding pipe B2 from bottom to top, and enters the seawater desulfurization zone C evenly after rectification. The alkaline seawater sprayed down from the seawater desulfurization zone C is completely blocked by the splash-proof cap B3 at the top of the guiding pipe B2, and cannot fall into the limestone-gypsum desulfurization zone A below through the guiding pipe B2, thus simultaneously achieving the synergistic effect of flue gas conduction and liquid phase isolation.

[0037] Supporting substrate B1 In this invention, the supporting base B1 serves as the foundation for the isolation and diversion component B, and is fixed to the inner wall of the desulfurization tower. Its core function is to support and fix the diversion pipe B2, the splash guard B3, and the liquid collection channel B4. At the same time, it works in conjunction with the sealing structure to achieve the basic physical separation of the two desulfurization zones.

[0038] In some implementations, the structural form of the support base B1 can be flexibly selected according to the tower diameter, flue gas load, and installation and maintenance requirements. Commonly used forms in the art include integral sealed tower tray, grid-type support frame, or combined beam support structure.

[0039] Among them, the integral sealed tower tray is a circular rigid corrosion-resistant plate, whose outer edge is fixed to the inner wall of the tower body by welding or flange sealing, completely isolating the cross-section of the tower body; the grid-type support frame is formed by cross-welding of transverse and longitudinal steel beams to form a grid-like frame, and the surface of the frame is covered with an integral corrosion-resistant sealing plate; the combined beam frame support structure is formed by splicing main load-bearing beams and secondary beams to form a support skeleton, and the surface of the skeleton is covered with an integral corrosion-resistant sealing plate.

[0040] In some embodiments, the fixing points of the support base B1 to the inner wall of the tower and the joints of the sealing plates are all treated with corrosion-resistant sealing to prevent seawater absorbent from leaking into the limestone-gypsum desulfurization zone A through the gaps; the outer edge of the support base B1 is seamlessly sealed to the inner wall of the collection channel B4, providing a flow path for the liquid accumulated on the surface of the base.

[0041] Regardless of the support base structure used, the contact point between the guide pipe B2 and the support base B1 must be sealed and fixed. This is to block the only path for seawater to leak downwards through the installation gap between the guide pipe and the support base. For integral sealed trays, the sealing and fixing act directly on the contact surface between the tray and the pipe body; for grid-type and combined beam frame structures, the sealing and fixing act on the contact surface between the integral sealing plate laid on the surface and the pipe body, working in conjunction with the sealing performance of the sealing plate itself to form a complete physical barrier.

[0042] Preferably, the upper surface of the supporting substrate B1 is provided with a 3°~5° inclined flow guide slope towards the liquid collection channel B4, so as to use gravity to guide the liquid accumulated on the surface of the substrate to flow quickly towards the liquid collection channel B4, avoiding long-term stagnation and scaling of the liquid; at the same time, this slope can be combined with the negative pressure ejection effect of the venturi diversion tube described below to further improve the flow efficiency of the liquid and realize the self-cleaning of the substrate surface.

[0043] Guide tube B2 In this invention, the guide pipe B2 is the core of the flue gas guiding component B, which consists of multiple sets of vertically connected pipes evenly arranged along the cross-section of the tower body. It is vertically installed on the supporting base B1. The core is used to construct a stable flow channel for flue gas from limestone-gypsum desulfurization zone A to seawater desulfurization zone C. At the same time, it can rectify and equalize the flow of flue gas to prevent flue gas from deviating.

[0044] In some embodiments, the guide tube B2 can be installed in one of the following two ways.

[0045] The first type is a through-type installation: the guide pipe B2 runs vertically through the supporting base B1, with the upper and lower ends of the pipe protruding from the upper and lower planes of the supporting base B1, respectively. The contact between the tank and the supporting base is sealed and fixed by welding or sealant. The flue gas enters from the lower inlet of the guide pipe B2 and flows out from the upper outlet. This installation method can extend the flow stabilization path and is more conducive to working conditions with large fluctuations in the flue gas flow field and frequent load changes.

[0046] The second type is the top-mounted installation: the guide pipe B2 is located above the upper plane of the support base B1. The bottom of the pipe is aligned with and sealed to the pre-set through hole on the support base B1. The inner diameter of the through hole is the same as the inner diameter of the inlet of the guide pipe B2 to avoid step flow channels that may cause airflow disturbance. The flue gas enters the guide pipe B2 through the hole from below the support base B1, and flows out from the upper outlet after being rectified by the pipe. This installation method has a simple structure, is convenient for installation and maintenance, and is more suitable for normal scenarios with stable flue gas conditions.

[0047] In some embodiments, the internal flow channel of the guide tube B2 may employ one of the following two methods.

[0048] The first type is a cylindrical flow channel: the guide pipe B2 is a cylindrical channel with a uniform inner diameter and vertical penetration. It has a simple structure, low flow resistance, and is more suitable for treatment scenarios with conventional flue gas volume and medium sulfur content.

[0049] The second type is the Venturi variable diameter flow channel: the guide pipe B2 is a vertically continuous Venturi tubular structure. Along the flow direction of flue gas from bottom to top, the flow channel is continuously and seamlessly connected with the inlet narrowing section, the middle section, and the outlet widening section.

[0050] The inlet tapering section is the flue gas inlet section of the guide pipe B2, and the flow channel structure is a frustum-shaped channel with an inner diameter that narrows linearly from bottom to top; the cone angle of the inlet tapering section is 15°~30°, the axial length is 20%~30% of the total length of the guide pipe B2, and the inner diameter of the bottom inlet is consistent with the maximum inner diameter of the guide pipe B2.

[0051] The middle section is the core flow passage of the guide pipe B2, which is seamlessly connected between the inlet narrowing section and the outlet widening section. The flow channel structure is a cylindrical channel with a uniform inner diameter, which is the minimum inner diameter of the entire guide pipe B2 flow channel. The inner diameter of the middle section is 30% to 50% of the maximum inner diameter of the guide pipe B2, and the axial length is 1 to 3 times its own inner diameter.

[0052] The outlet gradually expanding section is the flue gas outlet section of the guide pipe B2, and the flow channel structure is a frustum-shaped channel with an inner diameter that increases linearly from bottom to top; the cone angle of the outlet gradually expanding section is 8°~15°, the axial length is 30%~40% of the total length of the guide pipe, and the inner diameter of the top outlet is consistent with the maximum inner diameter of the guide pipe B2.

[0053] In some implementations, the guide pipe B2 using the aforementioned Venturi variable diameter flow channel can achieve flue gas rectification and self-cleaning without power through its own structure. On the one hand, the inlet converging section can rectify and guide the flue gas entering the guide pipe, guiding the flue gas to converge smoothly into the middle section, avoiding the generation of additional resistance due to airflow turbulence; when the flue gas flows through the middle section, the flow velocity increases sharply due to the sudden narrowing of the flow channel cross section, and the static pressure drops significantly at the same time, forming a local negative pressure zone relative to the normal pressure environment inside the tower at the junction of the upper outlet of the middle section and the outlet expanding section; finally, after the flue gas is decelerated and stabilized by the outlet expanding section, it is evenly diffused to the entire cross section of the seawater desulfurization zone C, avoiding the desulfurization effect caused by flue gas deviation.

[0054] On the other hand, the local negative pressure zone formed in the middle section can generate continuous suction on the liquid accumulated on the upper surface of the support base B1, continuously drawing the liquid into the guide pipe B2. After the liquid flows out of the guide pipe with the rising flue gas, it is blocked by the splash cap B3 above and finally falls into the collection channel B4 for discharge. This reduces the accumulation of liquid and salt scale on the surface of the support base B1, achieves self-cleaning without power, and extends the stable operation cycle of the equipment.

[0055] In some embodiments, the guide pipe B2 can reduce uneven spraying of seawater absorbent caused by flue gas deviation by equalizing and rectifying the flue gas, reduce the amount of liquid accumulation on the surface of the support substrate B1, and reduce the collection load of the collection channel B4.

[0056] Preferably, the inner wall of the guide pipe B2 is provided with spiral guide blades, which extend continuously spirally along the inner wall of the guide pipe B2. When the flue gas passes through the guide pipe B2, it forms a rotating and rising airflow along the spiral trajectory of the blades. On the one hand, the radial centrifugal force generated by the rotating airflow will throw the tiny limestone slurry droplets, which are denser than gas, carried in the flue gas onto the inner wall of the guide pipe B2, and they will fall down along the inner wall to the limestone-gypsum desulfurization zone A, achieving pre-demisting and reducing the processing load of the subsequent demister. On the other hand, the rotating and rising airflow will form a uniform swirling field in the seawater desulfurization zone C, strengthening the turbulent contact between the flue gas and the seawater absorbent, and working together with the packing layer C3, it can significantly improve the gas-liquid mass transfer efficiency.

[0057] Preferably, the guide pipe B2 adopts a Venturi variable diameter flow channel structure, and its inner wall of the expansion section is provided with a flow straightening grid, which can form a uniform flow field before the flue gas enters the inlet narrowing section, and avoid the local mass transfer effect reduction caused by flue gas deflection.

[0058] Preferably, multiple sets of guide pipes B2 are evenly arranged in an equilateral triangular matrix or a square matrix, covering the entire effective flow cross section of the supporting base B1, ensuring that the flue gas is evenly distributed within the cross section of the tower body, without flow deviation or dead zones.

[0059] Splash cap B3 In this invention, the splash guard B3 is a liquid-blocking structure that is matched one-to-one with the single guide pipe B2. It is fixed above the top opening of the guide pipe B2 by a support rod. Its core function is to prevent the seawater sprayed from the seawater desulfurization zone C from directly entering the guide pipe B2, while guiding the seawater along its own structure to the surrounding liquid collection channel B4, thus achieving the dual function of liquid phase isolation and directional flow guidance.

[0060] In some embodiments, the outer edge of the splash guard B3 is vertically projected and falls completely within the opening of the collection channel B4. The seawater absorbent blocked by the splash guard B3 can fall directly and without splashing into the collection channel B4 below along the slope of the splash guard B3, and then be discharged outside the tower through the matching pipeline. This structure avoids leakage and mixing of absorbent, completely isolates the liquid phase, and solves the problem of liquid accumulation, splashing, and seepage that are easy to occur in conventional baffle structures.

[0061] Preferably, the splash guard B3 has a conical structure, and the vertical projection of its outer edge completely covers the top opening of the corresponding guide tube B2; the apex is fixed to the center of the top opening of the guide tube by a central support rod with the apex facing downward. Preferably, the splash guard B3 is provided with a slope of 3°~5° inclined to one side of the guide pipe B2, and the outer edge of the splash guard B3 is provided with a liquid-blocking edge that bends to one side of the guide pipe B2; the downward slope can use gravity to guide the seawater on the guard to flow quickly to the collection channel B4, and the downward bend of the liquid-blocking edge can prevent the seawater from forming a water film along the outer edge of the guard and splashing to the opening of the guide pipe B2, thus preventing liquid accumulation and scaling on the surface of the guard.

[0062] Collection channel B4 and seawater outlet B5 In this invention, the liquid collection channel B4 is an annular groove that is closed-loop between the support base B1 and the inner wall of the tower. It is the core structure for collecting and discharging the absorbent of the isolation and diversion component B, and is used to receive the seawater absorbent blocked by the splash guard.

[0063] In some embodiments, the liquid collection channel B4 is a closed annular trough that extends continuously along the circumference of the inner wall of the desulfurization tower and is connected end to end, with no flow interruption points, and completely covers the outer annular area of ​​the tower body cross-section; the outer wall of the liquid collection channel B4 is sealed and fixed to the inner wall of the tower body, and the inner wall is sealed and fixed to the outer edge of the supporting base B1.

[0064] In some embodiments, the bottom of the collection channel B4 is lower than the upper surface of the supporting base B1, while the upper edge of the channel opening is higher than the upper surface of the supporting base B1, and the entire structure is located below the splash guard B3. This structure utilizes the gravity difference to allow seawater on the surface of the supporting base B1 to automatically flow into the collection channel B4. At the same time, the slightly higher channel opening forms an annular weir to prevent accumulated liquid from overflowing into the connection gap between the channel and the tower wall and the supporting base, minimizing the amount of liquid retained on the surface of the supporting base.

[0065] In some embodiments, the vertical projection of the inlet of the collection channel B4 completely covers the outermost edge of all splash guards B3, ensuring that all seawater dripping and splashing from the outer edge of the splash guards B3 falls directly into the collection channel, preventing seawater from splashing into the central area of ​​the support base or the gaps in the tower wall. The core of the collection channel B4 is used to receive the seawater absorption liquid blocked by the splash guards B3 and guided by the support base B1. It is equipped with circulation and discharge pipelines to realize the cascade utilization and harmless discharge of seawater.

[0066] In this invention, the seawater outlet B5 is a fixed interface for the discharge of absorbent liquid, which is located at the bottom of the collection channel B4 and communicates with the inner cavity of the collection channel B4.

[0067] In some embodiments, the tank body of the liquid collection channel B4 can be integrally formed with the inner wall of the tower or a separate welded fixed structure, which can be flexibly selected according to the tower body processing technology; the tank body material is the same corrosion-resistant material as the supporting base B1, and at least one seawater outlet B5 is opened at the bottom of the tank body.

[0068] Preferably, the main pipeline of the seawater outlet B5 is divided into two independent branches via a tee joint, and each branch is equipped with an independent on / off control valve, flow regulating valve, and power equipment. One of the routes is a recycling branch, which connects the filter unit and the seawater circulation pump in series, and then connects to the inlet of the seawater spray assembly C1 in the seawater desulfurization zone C. When the pH value of the seawater in the collection channel is ≥6.0 and the alkalinity meets the desulfurization requirements, the suspended solids in the seawater are removed and then recycled to the spray system.

[0069] The other route is an external discharge treatment branch, which is connected to the downstream seawater aeration treatment system. When the pH value of the seawater in the collection channel is lower than 6.0 or the alkalinity is insufficient, it is discharged to the aeration system through seawater outlet B5 for harmless treatment, while fresh seawater is added to the system at the same time.

[0070] Preferably, the bottom of the collection channel B4 is provided with a unidirectional flow guide slope of 0.3% to 0.5% towards the seawater outlet B5. The slope is inclined towards the seawater outlet B5 along the circumference of the channel, which can guide the seawater to flow quickly into the seawater outlet and discharge, avoiding the accumulation and stagnation of liquid in the channel.

[0071] Preferably, the radial width of the annular groove of the liquid collection channel B4 is not less than 1.2 times the radial projected width of a single splash guard B3.

[0072] In some embodiments, the collection channel B4, the supporting base B1, the guide pipe B2, and the splash guard B3 form a complete collaborative chain, constructing a complete seawater absorption liquid barrier-collection-discharge pathway: most of the seawater sprayed from the seawater desulfurization zone C falls directly onto the upper surface of the supporting base B1, with a small amount falling onto the upper surface of the splash guard B3; the splash guard B3 prevents seawater from directly entering the guide pipe B2 and guides the seawater falling on it along its own slope to the outer edge area of ​​the supporting base B1; the upper surface of the supporting base B1 is provided with a guide slope of 3°~5° towards the collection channel B4, guiding all the seawater accumulated on the surface into the collection channel B4; finally, all the seawater flows into the collection channel B4 for unified treatment, and with the fully welded sealing structure of the tank body, tower wall, and supporting base, there is no path for any leakage to the limestone-gypsum desulfurization zone A below, achieving complete independence of the two desulfurization zones.

[0073] Seawater desulfurization zone C In this invention, the seawater desulfurization zone C is a secondary deep desulfurization unit for flue gas, which is located in the upper part of the desulfurization tower body. It is completely physically isolated from the limestone-gypsum desulfurization zone A below and operates independently through the isolation and flow guiding component B. This zone mainly includes a seawater spray component C1 and a flue gas outlet C2, and optionally includes a packing layer C3 and a demister.

[0074] The seawater spraying assembly C1 is used to spray seawater absorbent onto the flue gas after preliminary desulfurization in the limestone-gypsum desulfurization zone C, utilizing the natural alkalinity of seawater to remove residual acidic pollutants from the flue gas, thus achieving deep purification of the flue gas. The flue gas outlet C2 is the outlet port for the purified flue gas after desulfurization to exit the tower. The packing layer C3 is used to increase the contact area between seawater and flue gas, enhance gas-liquid mass transfer efficiency, and improve the desulfurization effect. The demister C4 is located at the front end of the flue gas outlet C2 and is used to perform gas-liquid separation on the purified flue gas after desulfurization, removing liquid droplets carried in the flue gas.

[0075] In some embodiments, the flue gas outlet C2 is located at the top center of the corresponding tower body in this area, with the opening located on the air outlet side of the demister C4 and fully connected to the flue gas outlet side of this area; the clean flue gas that has completed deep desulfurization and gas-liquid separation is discharged from the tower body through the flue gas outlet C2 and enters the subsequent flue and chimney for emission in compliance with standards.

[0076] Preferably, the flue gas outlet C2 is equipped with a variable diameter guide flue, which can reduce the local resistance when the clean flue gas is discharged from the tower body and reduce the energy consumption of the fan during system operation.

[0077] In some embodiments, the seawater absorbent is natural seawater with an alkalinity of 100-200 mg / L (calculated as calcium carbonate). It contains alkaline buffer components such as bicarbonate and carbonate. It can be selectively mixed with seawater desalination concentrate according to desulfurization requirements to increase the seawater alkalinity to 200-300 mg / L and enhance the seawater desulfurization effect.

[0078] In some embodiments, after being rectified and homogenized by the lower isolation and guiding component B, the flue gas enters this area and, along the flue gas path from bottom to top, sequentially passes through the packing layer C3, the spray coverage area of ​​the seawater spray component C1, and the demister C4, finally exiting through the flue gas outlet C2. During the flow, the flue gas forms a sufficient countercurrent contact with the seawater absorbent sprayed from top to bottom by the seawater spray component C1. The remaining SO2 in the flue gas undergoes a neutralization reaction with the alkaline components in the seawater and is completely removed, thus stably controlling the SO2 concentration at the flue gas outlet C2 at 35 mg / m³. 3 The acidic seawater, after completing the absorption reaction, falls under the influence of gravity and is collected and discharged outside the tower through the collection channel of the isolation and diversion component B. Throughout the process, it does not come into contact with the slurry in the limestone-gypsum desulfurization zone A below, ensuring the independent and stable operation of the two desulfurization zones.

[0079] Preferably, the packing layer C3 is mounted on the flue gas outlet side of the isolation and guiding component B and below the seawater spraying component C1 via a supporting grid. After the flue gas flows out of the isolation and guiding component B, it first passes through the packing layer C3 and then comes into contact with the seawater absorbent. The packing has a large specific surface area, which allows the seawater absorbent to form a uniform and continuous liquid film on the surface of the packing, greatly increasing the gas-liquid contact area, prolonging the contact time between the flue gas and the absorbent, improving the seawater desulfurization efficiency, and at the same time reducing the seawater spraying volume and the subsequent aeration treatment load.

[0080] More preferably, the packing layer C3 adopts structured corrugated packing or random packing; wherein the structured corrugated packing can be made of polypropylene or 6L stainless steel perforated plate corrugated packing, which has the advantages of low resistance, large throughput and uniform gas-liquid distribution, and is suitable for large flue gas volume treatment scenarios; the random packing can be made of Pall rings or stepped ring packing, which can be flexibly selected according to the flue gas treatment volume and desulfurization requirements.

[0081] Preferably, the seawater spray assembly C1 adopts 2 to 6 sets of spray pipe networks arranged along the flue gas flow direction, which is suitable for the characteristics of strong seawater corrosivity and high requirements for atomization uniformity. Each set of spray pipe networks adopts a distributed structure of main pipe-branch pipe made of 316L stainless steel or duplex steel, and the branch pipes are equipped with several corrosion-resistant conical atomizing nozzles. Among them, the nozzles on the side near the demister C4 are set to spray in one direction towards the flue gas flow direction to avoid seawater spraying onto the demister C4 and causing corrosion. The other sets of nozzles can adopt a bidirectional spraying setting to enhance gas-liquid disturbance and contact effect and improve seawater desulfurization efficiency. Each set of spray pipe networks is equipped with an independent control valve, which can flexibly adjust the number of spray pipe networks opened and the seawater spray volume according to the flue gas SO2 concentration and flue gas volume, thereby reducing operating energy consumption while ensuring seawater desulfurization efficiency.

[0082] Preferably, the demister C4 is installed in the flue gas passage between the seawater spray assembly and the flue gas outlet C2, and is used to perform gas-liquid separation on the desulfurized clean flue gas, remove the liquid droplets carried in the flue gas, avoid the liquid droplets being discharged with the flue gas and causing corrosion of the subsequent flue and chimney, and at the same time eliminate the visual pollution of "white smoke" emitted by the flue gas.

[0083] In some implementations, when the purified flue gas after deep desulfurization flows through the demister C4, the liquid droplets carried in the flue gas are captured and separated under the action of inertial collision and interception, which can control the liquid droplet content of the purified flue gas to below 50mg / m3, effectively protecting the subsequent emission system.

[0084] More preferably, the demister C4 is a folding plate demister or a wire mesh demister; the folding plate demister can adopt a two-stage herringbone folding plate structure, which is suitable for desulfurization flue gas treatment scenarios with large flue gas volume and high humidity; the wire mesh demister has a higher efficiency in capturing fine mist droplets and can be flexibly selected according to the flue gas conditions.

[0085] A second aspect of the present invention provides a method for desulfurizing flue gas using the aforementioned desulfurization tower.

[0086] In some embodiments, the method is applicable to the deep desulfurization treatment of industrial flue gas from coal-fired power plant boilers, steel sintering machines, non-ferrous metal smelting furnaces, and petrochemical heating furnaces in coastal areas; the main pollutants in the flue gas to be treated include SO2, dust, HCl, and HF, with an SO2 concentration at the flue gas inlet of 500~5000 mg / m³. 3 The flue gas temperature is 120~160℃.

[0087] In some embodiments, the desulfurization process involved in the method is as follows: the flue gas to be treated enters the tower through the flue gas inlet, and first enters the limestone-gypsum desulfurization zone to complete the first-stage coarse desulfurization along the bottom-up flow path. Then, after being rectified and evenly distributed by the isolation and guiding components, it enters the seawater desulfurization zone to complete the second-stage deep desulfurization. Finally, the clean flue gas after desulfurization is treated by the demister and then discharged through the flue gas outlet in compliance with standards. Throughout the process, the contact between the seawater absorbent and the limestone slurry is blocked by the isolation and guiding components, which is conducive to achieving independent and stable operation of the two desulfurization zones.

[0088] In some implementations, during the primary coarse desulfurization process in the limestone-gypsum desulfurization zone, the limestone slurry transported to the slurry spraying assembly in this zone can be a slurry with calcium carbonate suspension as the main component, and the solid content can be controlled at 10% to 30%, which is beneficial to ensuring the desulfurization reaction activity and flow stability of the slurry.

[0089] In some embodiments, the limestone slurry delivered to the slurry spraying assembly has a particle size that can be controlled between 10 and 100 μm, which is beneficial for improving the slurry atomization effect and gas-liquid reaction rate, and reducing limestone raw material consumption.

[0090] Preferably, 0.05~0.2 wt% of an organic acid buffer is optionally added to the limestone slurry. The buffer is selected from one or more of diacid and citric acid, which helps to stabilize the pH value of the slurry and reduce the gas-liquid mass transfer resistance.

[0091] In some implementations, the pH value of the slurry in the limestone-gypsum desulfurization zone can be controlled at 4.0~6.0, which is conducive to providing a stable reaction environment for calcium sulfite oxidation and gypsum crystallization.

[0092] In some implementations, when limestone slurry is supplied to the slurry spraying assembly through a circulation pipeline, the slurry circulation ratio can be controlled at 15 to 30 times, and the outlet pressure of the circulation pump can be maintained at 0.3 to 0.6 MPa. This is beneficial to improve the spraying coverage of the slurry in the cross-section of the tower and achieve sufficient countercurrent contact between the flue gas and the slurry.

[0093] In some implementations, the aeration intensity of the oxidation aeration components installed in the slurry tank can be controlled between 1.5 and 3.0 m. 3 / (m 2 h) helps to increase the oxidation rate of calcium sulfite in the slurry, ensuring the crystallization purity and quality of gypsum by-products.

[0094] In some implementations, during the operation of the isolation and diversion assembly, the replenishment seawater flow rate of the water seal layer in the collection channel of this area can be controlled at 0.5~1.2 m³. 3 / h, which helps to maintain the water seal liquid column height at a stable level of 120~180 mm, ensuring that the static pressure generated by the liquid column is always greater than the pressure difference of the flue gas inside the tower, thus achieving a stable liquid phase isolation effect.

[0095] In some implementations, during the secondary deep desulfurization process in the seawater desulfurization zone, the temperature of the seawater absorbent supplied to the seawater spray assembly in the zone can be controlled at 15~35 ℃, and the salinity can be maintained at 30~35‰. This helps to avoid excessively high temperatures that could lead to the decomposition of bicarbonate in the seawater and excessively rapid alkalinity decay, thus ensuring the long-term stability of the deep desulfurization effect.

[0096] In some embodiments, the seawater absorbent supplied to the seawater spraying assembly can be natural seawater, with its alkalinity controlled at 100-200 mg / L (calculated as calcium carbonate). This is beneficial for utilizing the natural alkalinity of seawater to remove residual acidic pollutants from the flue gas. Seawater desalination concentrate can be mixed in according to desulfurization requirements to increase the seawater alkalinity to 200-300 mg / L, which is beneficial for enhancing the deep desulfurization effect.

[0097] In some implementations, when a packing layer is installed in the seawater desulfurization zone, the spray density of the packing layer can be controlled at 15~30 m³. 3 / (m 2 h) This facilitates the formation of a continuous and uniform liquid film on the surface of the packing material by the seawater absorbent, significantly increasing the gas-liquid contact area, enhancing gas-liquid mass transfer efficiency, and reducing seawater consumption.

[0098] In some implementations, during the entire process of flue gas operation in the desulfurization tower, the empty tower flow velocity of the flue gas can be controlled at 2.5~4.5 m / s, and the total residence time of the flue gas in the tower is not less than 3.5s, which is conducive to the full contact and reaction between acidic pollutants and the corresponding absorbent liquid, thereby improving the overall desulfurization efficiency.

[0099] In some implementations, when the flue gas enters the demister for gas-liquid separation after two-stage desulfurization, the flushing water pressure of the demister can be controlled at 0.4~0.8 MPa, the flushing cycle can be set to 30~60 min, and the single flushing time can be controlled at 30~60 s. This is beneficial for timely removal of salt scale and dust on the surface of the demister element, preventing scale buildup and blockage of the element that could lead to increased system resistance, and ensuring long-term stability of the demister effect.

[0100] Example 1 This embodiment uses the desulfurization tower of the coupled limestone-gypsum method and seawater desulfurization described in this invention to desulfurize the flue gas of a coal-fired boiler. The tower body is arranged from bottom to top as follows: limestone-gypsum desulfurization zone A, isolation and diversion component B, seawater desulfurization zone C, and equipped with slurry spray component A2, slurry pool A3, oxidation aeration component, diversion pipe B2, splash guard B3, liquid collection channel B4, seawater spray component C1, packing layer C3, demister and other components.

[0101] The specific desulfurization operation process is as follows: 1. Primary Coarse Desulfurization: The flue gas to be treated enters the limestone-gypsum desulfurization zone A through the flue gas inlet, and comes into countercurrent contact with the limestone slurry sprayed by the slurry spraying component A2 to complete the primary absorption. Most of the SO2, dust, HCl, and HF in the flue gas are removed here. In this embodiment, the limestone slurry particle size is 30~80 μm, the slurry circulation ratio is set to 22 times, and the circulation pump outlet pressure is maintained at 0.45 MPa; the pH of the slurry in the slurry tank A3 is stabilized at 4.5~5.2, and the aeration intensity of the matching oxidation aeration component is set to 2.2 m. 3 / (m 2 h) Ensure that the calcium sulfite oxidation rate in the slurry is not less than 95%, providing a stable environment for gypsum oxidation and crystallization.

[0102] 2. Flue Gas Guiding and Liquid Phase Isolation: After the flue gas completes the first-stage absorption, it is rectified and evenly distributed through the guide pipe B2 of the isolation and guiding component B before entering the seawater desulfurization zone C. The seawater absorbent liquid falling from the seawater desulfurization zone C is completely blocked by the splash guard B3 and flows into the collection channel B4, preventing it from entering the limestone-gypsum desulfurization zone A. In this embodiment, the replenishment seawater flow rate of the water seal layer in the collection channel B4 is 0.9 m³ / s. 3 / h, maintaining the water seal liquid column height at a stable 150 mm, ensuring a stable and leak-free liquid phase isolation effect.

[0103] 3. Secondary Deep Desulfurization: In the seawater desulfurization zone C, the flue gas first passes through the packing layer C3 and then comes into countercurrent contact with the seawater absorbent sprayed by the seawater spray assembly C1, completing the secondary deep desulfurization. In this embodiment, the temperature of the seawater absorbent is set at 25°C, and the salinity is maintained at 30~35‰; the spray density of the packing layer C3 is controlled at 22 m³ / s. 3 / (m2 h), to ensure that a continuous and uniform liquid film is formed on the surface of the packing; the seawater after absorbing SO2 is led out of the tower through the seawater outlet of the collection channel B4 and sent to the subsequent aeration system for treatment.

[0104] 4. Demisting and Compliance Emission: After desulfurization, the clean flue gas passes through a demister to remove any carried liquid droplets before being discharged through the flue gas outlet in compliance with emission standards. In this embodiment, the empty flue gas velocity inside the desulfurization tower is set to 3.5 m / s, and the total residence time of the flue gas inside the tower is 4 seconds to ensure sufficient removal of acidic pollutants. The flushing water pressure of the demister is set to 0.6 MPa, the flushing cycle is 45 minutes, and the single flushing time is 45 seconds to prevent scaling and clogging of the demister elements.

[0105] In this embodiment, the two-stage system operates synchronously under normal conditions, which can stably control the SO2 concentration at the flue gas outlet at 35 mg / m³. 3 The following conditions are met to meet ultra-low emission requirements: When the unit is under low load and the sulfur content in the flue gas is low, the limestone slurry circulation pump or seawater transfer pump can be shut down and the single-stage desulfurization mode can be switched to reduce the system operating cost while ensuring desulfurization efficiency.

Claims

1. A desulfurization tower coupled with limestone-gypsum desulfurization and seawater desulfurization, wherein the desulfurization tower has a flue gas inlet (A1) and a flue gas outlet (C2), and a limestone-gypsum desulfurization zone (A) and a seawater desulfurization zone (C) are arranged sequentially along the flue gas flow path; The limestone-gypsum desulfurization zone (A) includes a slurry spraying assembly (A2) and a slurry tank (A3). The slurry spraying assembly (A2) is used to spray limestone slurry onto the flue gas to remove acidic pollutants. The slurry tank (A3) is located below the slurry spraying assembly (A2) and is used to receive the limestone slurry that has completed the absorption reaction. The seawater desulfurization zone (C) includes a seawater spray assembly (C1), which is used to spray seawater absorbent onto the flue gas after preliminary desulfurization in the limestone-gypsum desulfurization zone (A) to deeply remove acidic pollutants. The flue gas inlet (A1) is connected to the flue gas inlet side of the limestone-gypsum desulfurization zone (A), and the flue gas outlet (C2) is connected to the outlet side of the seawater desulfurization zone. Its features are, An isolation and diversion assembly (B) is provided between the limestone-gypsum desulfurization zone (A) and the seawater desulfurization zone (A). The isolation and diversion assembly (B) includes a support base (B1), multiple sets of diversion pipes (B2), splash guards (B3) that are installed on the top of the diversion pipes (B2) in a one-to-one correspondence, and a liquid collection channel (B4). The supporting substrate (B1) is fixed to the inner wall of the tower, forming a physical boundary between the limestone-gypsum desulfurization zone (A) and the seawater desulfurization zone (C); The guide pipe (B2) is a vertically penetrating pipe. Multiple sets of guide pipes are evenly arranged on the supporting base (B1) to construct the flue gas flow channel from the limestone-gypsum desulfurization zone (A) to the seawater desulfurization zone (C). The splash guard (B3) is fixed above the top opening of the corresponding guide pipe (B2) to prevent the seawater absorbent liquid falling from the seawater desulfurization zone (C) from entering the guide pipe (B2). The collection channel (B4) is an annular groove that is set in a closed loop along the inner wall of the tower between the support base (B1) and the inner wall of the tower, and is used to receive the seawater absorption liquid blocked by the splash guard.

2. The desulfurization tower according to claim 1, characterized in that, The internal flow channel of the guide tube (B2) is a cylindrical flow channel or a Venturi variable diameter flow channel; wherein The cylindrical flow channel is a vertically continuous cylindrical channel with a uniform inner diameter. The Venturi variable flow channel is a vertically continuous Venturi tubular structure, with an inlet narrowing section, a middle section, and an outlet widening section arranged sequentially along the flue gas flow direction from bottom to top. Preferably, the inner wall of the guide pipe (B2) is provided with spiral guide vanes to guide the flue gas to form a swirling upward airflow.

3. The desulfurization tower according to claim 2, characterized in that, The inlet tapering section is located at the flue gas inlet section of the guide pipe (B2), and the flow channel structure is a frustum-shaped channel with an inner diameter that narrows linearly from bottom to top; the cone angle of the inlet tapering section is 15°~30°, the axial length is 20%~30% of the total length of the guide pipe (B2), and the inner diameter of the bottom inlet is consistent with the maximum inner diameter of the guide pipe (B2); The intermediate section is seamlessly connected between the inlet narrowing section and the outlet widening section, and the flow channel structure is a cylindrical channel with equal inner diameter; the inner diameter of the intermediate section is 30% to 50% of the maximum inner diameter of the guide tube (B2), and the axial length is 1 to 3 times its own inner diameter. The outlet gradually expanding section is located at the flue gas outlet section of the guide pipe (B2), and the flow channel structure is a frustum-shaped channel with an inner diameter that increases linearly from bottom to top; the cone angle of the outlet gradually expanding section is 8°~15°, the axial length is 30%~40% of the total length of the guide pipe (B2), and the inner diameter of the top outlet is consistent with the maximum inner diameter of the guide pipe (B2). Preferably, the inner wall of the inlet tapering section is provided with a flow-rectifying grille.

4. The desulfurization tower according to claim 1, characterized in that, The guide pipe (B2) is installed on the support base (B1) in a through-type or top-mounted manner; wherein The through-type installation is as follows: the guide pipe (B2) runs vertically through the support base (B1), and the upper and lower ends of the pipe protrude from the upper and lower planes of the support base (B1) respectively, and the contact point between the pipe and the support base (B1) is sealed and fixed. The above-mounted installation is as follows: the guide pipe (B2) is located above the upper plane of the support base (B1), and the bottom of the pipe is aligned with the pre-set through hole on the support base (B1) and sealed and fixed. Preferably, the multiple sets of the guide tubes (B2) are evenly arranged in an equilateral triangular matrix or a square matrix, covering the entire gas flow cross section of the supporting substrate (B1).

5. The desulfurization tower according to any one of claims 1 to 4, characterized in that, The outer wall of the liquid collection channel (B4) is sealed and fixed to the inner wall of the tower body, and the inner wall is sealed and fixed to the outer edge of the support base (B1). The bottom of the liquid collection channel (B4) is lower than the upper surface of the support base, the upper edge of the channel opening is higher than the upper surface of the support base (B1), and the whole channel is located below the splash guard (B3). The vertical projection of the channel opening of the liquid collection channel (B4) completely covers the outermost edge of all splash guards (B3). Preferably, the bottom of the collection channel (B4) is provided with a seawater outlet (B5), and the main pipe of the seawater outlet (B5) is divided into two independent branches through a T-joint: one branch is a recycling branch, which connects the filter unit and the seawater circulation pump in series and is connected to the inlet of the seawater spray assembly (C1) in the seawater desulfurization zone (C); the other branch is an external discharge treatment branch, which is connected to the downstream seawater aeration treatment system. Preferably, the bottom of the collection channel (B4) is provided with a guide slope of 0.3% to 0.5% towards the seawater outlet (B5).

6. The desulfurization tower according to any one of claims 1 to 5, characterized in that, The upper surface of the support base (B1) is provided with a slope of 3°~5° towards the liquid collection channel (B4); And / or, the splash guard (B3) is provided with a slope of 3°~5° on one side of the guide tube (B2), and the outer edge of the splash guard (B3) is provided with a liquid-blocking edge that is bent on one side of the guide tube (B2); Preferably, the support base (B1) adopts an integral sealed tower tray, a grid-type support frame, or a combined beam support structure.

7. The desulfurization tower according to any one of claims 1 to 5, characterized in that, The slurry spraying assembly (A2) adopts 1 to 4 sets of spraying pipe networks arranged vertically along the flue gas flow direction, and each set of spraying pipe networks adopts a distributed structure of main pipe-branch pipe. And / or, the seawater spray assembly (C1) adopts 2 to 6 sets of spray pipe networks arranged vertically along the flue gas flow direction, and each set of spray pipe networks adopts a distributed structure of main pipe-branch pipe.

8. The desulfurization tower according to any one of claims 1 to 6, characterized in that, The slurry tank (A3) is equipped with an oxidation aeration assembly and a stirring assembly; wherein The oxidation aeration component adopts a perforated tube aerator or a swirl-mixing aerator. The air outlet of the aerator is submerged below the slurry surface in the slurry tank (A3) and is used to blow compressed air into the slurry to oxidize the calcium sulfite in the slurry tank (A3) into calcium sulfate. The mixing assembly adopts a side-entry mixer or a top-entry mixer, and the impeller of the mixer extends to the bottom of the slurry tank to stir the slurry and prevent gypsum particles from settling. Preferably, the lower side wall of the slurry tank (A3) is provided with a slurry outlet (A4), which is provided in two ways: one way is connected to the slurry spraying assembly (A2) through a circulation pump, and the other way is connected to the downstream gypsum dewatering device through an external discharge pipeline.

9. The desulfurization tower according to any one of claims 1 to 8, characterized in that, The seawater desulfurization zone (C) further includes a packing layer (C3) and / or a demister (C4), wherein, The packing layer (C3) is mounted on the flue gas outlet side of the isolation and diversion assembly (B) and below the seawater spray assembly (C1) via a supporting grid; the demister (C4) is located in the flue gas passage between the seawater spray assembly (C1) and the flue gas outlet (C2). Preferably, the packing layer (C3) is made of structured corrugated packing or random packing; the structured corrugated packing is made of polypropylene or 6L stainless steel perforated plate corrugated packing; the random packing is made of Pall ring packing or stepped ring packing. Preferably, the demister is a folding plate demister or a wire mesh demister.

10. A method for desulfurizing flue gas using the desulfurization tower according to any one of claims 1-9, characterized in that, The concentration of SO2 in the flue gas is 500~5000 mg / m³. 3 The flue gas temperature is 120~160℃; The limestone slurry has a solid content of 10% to 30%, and the particle size of the solids in the limestone slurry is 10 to 60 μm. Optionally, 0.05% to 0.2% by mass of an organic acid buffer is added to the limestone slurry. The organic acid buffer is adipic acid and / or citric acid. The pH value of the slurry and limestone slurry in the slurry tank (A3) is 4.0~6.0; The temperature of the seawater absorbent is 15~35℃, the salinity is 30~35‰, and the alkalinity (calculated as calcium carbonate) is 100~300mg / L. Preferably, the flow velocity of flue gas in the desulfurization tower is 2.5~4.5m / s, and the residence time is ≥3.5s. Preferably, when limestone slurry is supplied to the slurry spraying assembly (A2) through the recycling branch, the slurry circulation ratio is 15 to 30 times, and the outlet pressure of the circulation pump is 0.3 to 0.6 MPa. Preferably, the slurry tank (A3) is equipped with an oxidation aeration assembly with an aeration intensity of 1.5~3.0 m. 3 / (m 2 h); Preferably, the seawater desulfurization zone (C) is equipped with a packing layer (C3), and the spray density of the packing layer (C3) is 15~30 m³. 3 / (m 2 h).

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