A phosphate rock slurry flue gas desulfurization system and process

Abstract

This invention discloses a flue gas desulfurization system and process using phosphate rock slurry, relating to the field of industrial flue gas purification technology. The system includes a flue gas purification unit, a slurry circulation and oxidation unit, a washing and demisting unit, and a slurry treatment and recovery unit connected in sequence. The core technology utilizes the Fe content in the phosphate rock slurry... 3+ / Fe 2+ The system utilizes catalytic oxidation to simultaneously absorb, oxidize, neutralize, and separate SO2 products. The process steps include phosphate rock slurry preparation, primary desulfurization absorption, slurry circulation and catalytic oxidation, secondary washing and demisting, slurry treatment and resource recycling, and system control. This invention directly utilizes phosphate rock slurry produced by the phosphate chemical enterprise as a desulfurizing agent, eliminating the need to purchase desulfurization chemicals. The desulfurization products can be returned to the main production system to achieve resource recycling. The desulfurization efficiency can reach over 99%, and the system is anti-clogging, stable in operation, and compact in size. It achieves low-cost, pollution-free industrial flue gas desulfurization, combining economic and environmental benefits.

Description

Technical Field

[0001] This invention relates to the field of industrial flue gas purification technology, specifically to a desulfurization system and process for treating sulfur dioxide (SO2) tail gas from industries such as sulfuric acid, metallurgy, and thermal power. In particular, it relates to a resource-based treatment system and method that utilizes phosphate rock slurry as a desulfurizing agent and achieves efficient desulfurization based on the catalytic oxidation of iron ions therein. Background Technology

[0002] Currently, commonly used flue gas desulfurization technologies in industry include the ammonia method, calcium method, sodium alkali method, dual alkali method, and magnesium oxide method. While these methods can achieve desulfurization, they generally suffer from high operating costs requiring continuous external purchases of desulfurizing agents, the generation of secondary solid waste (such as gypsum) or wastewater (such as saline wastewater), and low-value or difficult-to-treat byproducts. For phosphate chemical enterprises, there are usually associated sulfuric acid plants. The sulfuric acid production process generates large amounts of SO2-containing tail gas, such as sulfuric acid or pyrite-based acid production tail gas, and also produces large quantities of phosphate rock slurry raw materials. Traditional desulfurization technologies fail to integrate with the enterprise's own materials, resulting in resource waste and cost pressure.

[0003] While existing technologies have explored the use of slurry desulfurization, they generally suffer from problems such as unstable desulfurization efficiency, system clogging, low utilization of effective components in the slurry (e.g., CaO), and difficulty in recycling subsequent products. In particular, effectively activating and utilizing the inherent catalytic oxidation capacity of transition metal ions (e.g., Fe ions) in phosphate rock slurry to efficiently oxidize and fix SO2 under mild conditions, and achieving in-plant resource recycling of desulfurization products, remains a significant technical challenge that existing technologies have not adequately addressed.

[0004] To address these issues, we propose a phosphate rock slurry flue gas desulfurization system. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a phosphate rock slurry flue gas desulfurization system and process, which solves the problems mentioned in the background.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A flue gas desulfurization system using phosphate rock slurry includes a flue gas purification unit, a slurry circulation and oxidation unit, a washing and demisting unit, and a slurry treatment and recovery unit connected in sequence. It also includes a phosphate rock slurry conditioning system and an online automatic real-time monitoring system for the chimney and SO2 tail gas.

[0008] The flue gas purification unit mainly includes a desulfurization tower. The top of the desulfurization tower is equipped with a sulfur-containing flue gas inlet and a phosphate rock slurry spray layer, and the bottom is equipped with a purified gas outlet and a slurry outlet. The phosphate rock slurry spray layer is connected to a spray pipeline.

[0009] The slurry circulation and oxidation unit includes a first circulation tank, a first circulation pump, and an oxidation device. The first circulation tank is connected to the slurry outlet of the desulfurization tower, the inlet of the first circulation pump, and the phosphate rock slurry supply system through pipelines. The outlet of the first circulation pump is connected to the phosphate rock slurry spray layer of the desulfurization tower through a spray pipeline.

[0010] The washing and demisting unit includes a washing tower, a second circulation tank, and a second circulation pump. The lower part of the washing tower is provided with an air inlet and a washing liquid spray layer, and the upper part is provided with a demister and a clean air outlet. The clean air outlet is connected to the air inlet of the chimney.

[0011] The slurry treatment and recovery unit includes a filter press and a return water tank. The feed inlet of the filter press is connected to the first circulation tank through a mother liquor pump, its filter cake outlet is connected to the extraction tank of the main production system, and its filtrate outlet is connected to the return water tank.

[0012] As a further technical solution of the present invention, the first circulation tank is connected to an auxiliary agent tank, the auxiliary agent tank is provided with desulfurization auxiliary agent, and the lower end of the auxiliary agent tank is connected to the first circulation tank through an auxiliary agent supply pipe, and a flow control valve is also installed on the auxiliary agent supply pipe.

[0013] As a further technical solution of the present invention, the desulfurization tower adopts an empty tower spray structure, the gas and liquid inside the tower are in a co-current contact manner, the bottom of the tower is designed as an inclined plate structure, and no slurry is retained. The gas pipeline coming out of the lower part of the desulfurization tower is provided with a vertical rising section, and the vertical rising section is provided with a return water spray washing structure.

[0014] The washing tower is a combined tower, with an empty tower spray washing section at the bottom and a structured packing or cyclone plate demister built into the upper part, and equipped with a rinsing device.

[0015] As a further technical solution of the present invention, the oxidation device is disposed in the first circulation tank for forcibly mixing the slurry with air or oxygen. The oxidation device includes at least one oxygenation pump and a plurality of self-priming devices connected thereto. The self-priming devices are immersed in the slurry in the first circulation tank. The oxidation device also includes a mixing jet, which is installed above the first circulation tank and connected to the output end of the oxygenation pump through a pipe.

[0016] As a further technical solution of the present invention, the air inlet of the washing tower is connected to the purified gas outlet of the desulfurization tower through a pipeline, the second circulation tank is connected to the washing liquid outlet of the washing tower, the inlet of the second circulation pump and the water source pipeline through pipelines respectively, and the outlet of the second circulation pump is connected to the washing liquid spray layer of the washing tower.

[0017] As a further technical solution of the present invention, the lower part of the chimney is provided with an enlarged section to form a gas-water separator, and the liquid accumulated at the bottom is introduced into the return water tank through a liquid seal tank.

[0018] The return water tank is equipped with a pH adjustment device, and its outlet is connected to the first circulation tank, the second circulation tank and the phosphate rock slurry conditioning system through a return water pump. The return water tank is also equipped with an alkali addition tank.

[0019] As a further technical solution of the present invention, the phosphate slurry conditioning system includes a conditioning tank, the outlet of which is connected to a slurry conveying pump, the output end of which is connected to a slurry conveying pipe, and the other end of which is connected to a first circulation tank.

[0020] As a further technical solution of the present invention, a stirrer is provided in the slurry tank, the first circulation tank, the second circulation tank and the return water tank, and a pH sensor and a level gauge are provided in the first circulation tank and the second circulation tank.

[0021] A phosphate rock slurry flue gas desulfurization process includes the following steps:

[0022] S1. Phosphate rock slurry preparation: Phosphate rock slurry from the phosphoric acid production system is transported to the slurry preparation tank and its solid content is adjusted to 35%-40% for later use.

[0023] S2, Primary Desulfurization Absorption: SO2-containing flue gas is introduced from the top of the desulfurization tower. At the same time, the phosphate rock slurry after conditioning and the circulating slurry from the first circulation tank are sprayed into the desulfurization tower in the form of atomization through the phosphate rock slurry spray layer. The flue gas and slurry are fully contacted as they flow down in the tower. The SO2 in the flue gas is absorbed by the slurry and sulfurous acid is generated.

[0024] S3. Slurry Circulation and Catalytic Oxidation: The slurry that has absorbed SO2 flows into the first circulation tank. Under the action of air / oxygen blown in by the stirring and oxidation devices, the Fe in the slurry... 3+ Ion catalysis rapidly oxidizes sulfurous acid to sulfuric acid. At the same time, sulfuric acid reacts with components such as calcium carbonate in the phosphate rock slurry to produce phosphoric acid and calcium sulfate. Most of the slurry after the oxidation reaction is sent back to the desulfurization tower for circulating spraying via the first circulation pump, and a small portion is discharged as mother liquor.

[0025] S4, Secondary Scrubbing and Demisting: The purified gas discharged from the desulfurization tower enters the tower through the air inlet at the bottom of the scrubbing tower and comes into countercurrent contact with the scrubbing water sprayed from the second circulation tank in the scrubbing liquid spray layer, further removing residual SO2, acid mist and entrained solid particles. After the scrubbing gas passes through the demister at the top of the tower to remove liquid mist, it is discharged through the chimney in compliance with standards.

[0026] S5. Slurry treatment and resource recycling: The mother liquor discharged from the first circulation tank is separated into solid and liquid by a filter press. The resulting filter cake is returned to the extraction process of the phosphoric acid production system. The filtrate enters the return water tank, and after adding alkaline substances to neutralize it to near neutral, it is sent by the return water pump to the slurry conditioning tank, the first circulation tank and the second circulation tank respectively as supplementary water for recycling.

[0027] S6. System Control: By monitoring the pH value of the slurry in the first circulation tank, the discharge of mother liquor and the replenishment of new phosphate rock slurry are controlled to maintain desulfurization efficiency. By monitoring the pH and level of the washing water, the replenishment of process water is controlled.

[0028] As a further technical solution of the present invention, in step S2, the vertical rising section of the gas pipeline at the bottom of the desulfurization tower is washed with return water spray. The washed slurry and washing water return to the bottom of the desulfurization tower and automatically flow into the first circulation tank.

[0029] This invention provides a phosphate rock slurry flue gas desulfurization system and process, which has the following advantages compared with the prior art:

[0030] 1. The flue gas desulfurization system and process designed in this paper utilizes the phosphate rock slurry produced by the phosphate chemical enterprise as the desulfurizing agent, eliminating the need to purchase desulfurization chemicals (such as ammonia, limestone, sodium hydroxide, etc.), which significantly reduces the procurement cost of desulfurizing agents. Moreover, the desulfurization product (filter cake containing phosphoric acid and phosphogypsum) can be returned to the phosphoric acid production system as raw material, and the filtrate can be recycled after treatment, realizing the recovery of sulfur and water resources and zero wastewater discharge, further reducing operating costs.

[0031] 2. This design presents a phosphate rock slurry flue gas desulfurization system and process. It utilizes the catalytic oxidation effect of naturally occurring iron ions in the phosphate rock slurry, combined with the activation effect of desulfurization additives and the forced oxidation of the oxidation device, to rapidly convert the absorbed SO2 into sulfuric acid and react with the slurry. The desulfurization efficiency can reach over 99%. The subsequent washing tower and high-efficiency demister can effectively control the emission of acid mist and particulate matter, ensuring that the flue gas meets emission standards.

[0032] 3. This design presents a phosphate rock slurry flue gas desulfurization system and process. The desulfurization tower adopts an empty tower with co-current spray design, and the bottom of the tower has an inclined plate structure to prevent liquid accumulation. At the same time, a return water spray washing structure is set in the gas pipeline at the bottom of the desulfurization tower, which effectively avoids the problems of slurry deposition and scaling blockage in the tower and outlet pipeline. Moreover, the washing tower adopts an anti-clogging demister and is equipped with a flushing device, which further ensures the stability and reliability of the system operation and enables long-term continuous operation. The combination of the desulfurization tower, washing and demister tower and multiple circulation tanks provides high operational flexibility and adapts to fluctuations in flue gas load and SO2 concentration. Furthermore, the entire system organically integrates absorption, oxidation, washing, solid-liquid separation and water circulation processes, with a smooth process and reasonable equipment layout.

[0033] 4. This design includes a phosphate rock slurry flue gas desulfurization system and process. Attached Figure Description

[0034] Figure 1 This is a system block diagram of the present invention;

[0035] Figure 2 This is a schematic diagram of material consumption in the system of the present invention. The horizontal axis represents the percentage of CaO that has completed the reaction, and the vertical axis represents the amount of mineral powder consumed at the corresponding percentage of CaO that has completed the reaction.

[0036] Figure 3 This is a graph showing the amount of phosphate rock powder required for different calcium oxidation rates in the embodiments of the present invention. The horizontal axis represents the percentage of CaO that has completed the reaction, and the vertical axis represents the amount of phosphate rock powder consumed for the corresponding percentage of CaO that has completed the reaction.

[0037] In the diagram: 1. Desulfurization tower; 11. Sulfur-containing flue gas inlet; 12. Phosphate slurry spray layer; 13. Purified gas outlet; 14. Slurry outlet; 15. Spray pipeline; 2. First circulation tank; 21. First circulation pump; 23. Oxygen pump; 24. Mixing injector; 25. Auxiliary agent tank; 26. Auxiliary agent supply pipe; 27. Flow control valve; 3. Scrubber; 31. Air inlet; 32. Scrubber spray layer; 33. Demister; 34. Clean gas outlet; 35. Scrubber outlet; 4. Second circulation tank; 41. Second circulation pump; 5. Return water tank; 51. pH adjustment device; 52. Return water pump; 6. Filter press; 61. Mother liquor pump; 7. Slurry mixing tank; 71. Slurry conveying pump; 72. Slurry conveying pipe; 8. Chimney; 81. Liquid seal tank. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] Please see Figure 1-3This invention provides a phosphate rock slurry flue gas desulfurization system and process technology: 1. A phosphate rock slurry flue gas desulfurization system, comprising a flue gas purification unit, a slurry circulation and oxidation unit, a washing and demisting unit, and a slurry treatment and recovery unit connected in sequence, and further comprising a phosphate rock slurry conditioning system, a chimney, and an online automatic real-time monitoring system for SO2 tail gas. It should be noted that the online automatic real-time monitoring system for chimney and SO2 tail gas adopts an industrial flue gas SO2 continuous online monitoring device (i.e., a CEMS system) adapted to this phosphate rock slurry flue gas desulfurization system. Its core function is to monitor the SO2 content of the tail gas before and after desulfurization in real time and automatically calculate the desulfurization efficiency, providing a basis for system operation and control. To provide data support, and referencing the structure of conventional industrial CEMS systems, the main components include a sampling subsystem (a sampling probe inserted into the flue gas duct with electric heating and heat tracing function), a pretreatment subsystem (purifying, dehumidifying, and removing dust from the collected flue gas), a gaseous pollutant monitoring subsystem (using ultraviolet / infrared spectroscopy to accurately detect SO2 concentration, unaffected by moisture in the flue gas), a data acquisition and control subsystem (collecting and storing data, displaying it in real time, and supporting parameter adjustment), as well as auxiliary power supply and lightning protection systems to ensure continuous and stable operation. This system can be linked in real time with the pH monitoring of the first circulation tank 2 and the phosphate rock slurry adjustment, providing quantitative data for the long-term stable operation of the system and the compliance of exhaust gas emissions.

[0040] The flue gas purification unit mainly includes a desulfurization tower 1, with a sulfur-containing flue gas inlet 11 and a phosphate rock slurry spray layer 12 at the top and a purified gas outlet 13 and a slurry outlet 14 at the bottom; the phosphate rock slurry spray layer 12 is connected to a spray pipeline 15.

[0041] The slurry circulation and oxidation unit includes a first circulation tank 2, a first circulation pump 21, and an oxidation device. The first circulation tank 2 is equipped with a 75kW agitator and an oxidation device (i.e., an oxygenation pump 23 with two self-primers and a mixing injector 24). The slurry residence time is about 14 minutes to ensure that sulfurous acid is fully oxidized to sulfuric acid and reacts with the phosphate rock slurry. The first circulation tank 2 is connected to the slurry outlet 14 of the desulfurization tower 1, the inlet of the first circulation pump 21, and the phosphate rock slurry supply system through pipelines. The outlet of the first circulation pump 21 is connected to the phosphate rock slurry spray layer 12 of the desulfurization tower 1 through a spray pipe 15.

[0042] The washing and demisting unit includes a washing tower 3, a second circulation tank 4, and a second circulation pump 41. The lower part of the washing tower 3 is provided with an air inlet 31 and a washing liquid spray layer 32, and the upper part is provided with a demister 33 and a clean gas outlet 34. The clean gas outlet 34 is connected to the air inlet of the chimney 8. The air inlet 31 of the washing tower 3 is connected to the purified gas outlet 13 of the desulfurization tower 1 through a pipeline. The second circulation tank 4 is connected to the washing liquid outlet 35 of the washing tower 3, the inlet of the second circulation pump 41, and the process water source through pipelines. The outlet of the second circulation pump 41 is connected to the washing liquid spray layer 32 of the washing tower 3.

[0043] The slurry treatment and recovery unit includes a filter press 6 and a return water tank 5. The feed inlet of the filter press 6 is connected to the first circulation tank 2 via a mother liquor pump 61. Its filter cake outlet is connected to the extraction tank of the main production system, and its filtrate outlet is connected to the return water tank 5. The return water tank 5 is equipped with a pH adjustment device 51, and its outlet is connected to the first circulation tank 2, the second circulation tank 4, and the phosphate rock slurry conditioning system via a return water pump 52.

[0044] The first circulation tank 2 is connected to an auxiliary agent tank 25. The auxiliary agent tank 25 contains desulfurization auxiliary agent, and the lower end of the auxiliary agent tank 25 is connected to the first circulation tank 2 through an auxiliary agent supply pipe 26. This is used to add desulfurization auxiliary agent to the first circulation tank 2, activate metal ions such as Fe ions in the phosphate rock slurry, extend the activity time of the phosphate rock slurry, and make the desulfurization efficiency reach more than 99%, or even 100%. A flow control valve 27 is also installed on the auxiliary agent supply pipe 26 to precisely control the amount of auxiliary agent supplied.

[0045] Furthermore, the desulfurization tower 1 has a diameter of 7.5m and a height of 24m. It adopts an empty tower spray structure with an empty tower gas velocity of about 2m / s. The gas and liquid inside the tower are in a co-current contact manner. The bottom of the tower is designed with an inclined plate structure to prevent slurry from being retained, effectively avoiding slurry deposition and scaling inside the tower. In addition, the tower is equipped with three layers of phosphate rock slurry spray layer 12, which adopts anti-clogging atomizing nozzles, and the flue gas and slurry are in co-current contact.

[0046] Furthermore, the oxidation device is installed in the first circulation tank 2, and the slurry is forcibly mixed with air or oxygen in the spray mixing oxidation zone to improve the oxidation efficiency of sulfite. The oxidation device includes at least one oxygen pump 23 and multiple self-primers connected to it. The self-primers are immersed in the slurry in the first circulation tank 2. The oxidation device also includes a mixing jet 24, which is installed above the first circulation tank 2 and connected to the output end of the oxygen pump 23 through a pipe to enhance the mixing effect of slurry with air / oxygen and improve oxidation efficiency.

[0047] Furthermore, the scrubbing tower 3 has a diameter of 8m and a height of 20m. It is a combined tower with an empty tower spray scrubbing section at the bottom and a structured packing or cyclone plate demister built into the upper part. It is also equipped with a flushing device, which can effectively remove residual SO2, acid mist and solid particles from the gas, while preventing the demister from clogging.

[0048] Furthermore, the system also includes a chimney 8, the lower part of which is provided with an enlarged section to form a gas-water separator. The liquid accumulated at the bottom of the chimney is introduced into the return water tank 5 through the liquid seal tank 81 to realize the recycling of water resources.

[0049] Furthermore, the phosphate rock slurry conditioning system includes a conditioning tank 7, which is used to adjust the phosphate rock slurry (containing about 50% solids) from the grinding process to a solids content of 30% by adding water. It is equipped with a stirrer to ensure uniform mixing and to provide qualified phosphate rock slurry for the desulfurization reaction. The outlet of the conditioning tank 7 is connected to a slurry delivery pump 71, and the output end of the slurry delivery pump 71 is connected to a slurry delivery pipe 72. The other end of the slurry delivery pipe 72 is connected to the first circulation tank 2 to continuously provide qualified phosphate rock slurry for the desulfurization reaction.

[0050] Agitators are installed in the slurry mixing tank 7, the first circulation tank 2, the second circulation tank 4, and the return water tank 5 to ensure uniform mixing of materials in the tanks, avoid solid-liquid separation, and ensure stable reaction. pH sensors and level gauges are installed on the first circulation tank 2 and the second circulation tank 4 to monitor the pH value and level of the slurry in the tanks in real time, which facilitates system control. An alkali addition tank is also installed on the return water tank 5 to add alkaline substances to the return water tank 5 and adjust the pH value of the filtrate to near neutral.

[0051] Furthermore, the system is also equipped with an online automatic real-time monitoring system for SO2-containing exhaust gas, which can automatically monitor the SO2 content of the inlet exhaust gas and the SO2 content of the desulfurized exhaust gas, and automatically calculate the desulfurization efficiency, thereby realizing real-time monitoring of the system's operating status.

[0052] Furthermore, the released SO2 is absorbed by the slurry to form sulfurous acid, Fe... 3+ Ion catalysis rapidly oxidizes sulfurous acid to sulfuric acid, which then reacts with phosphate rock slurry to extract phosphoric acid. Depending on the size of the supporting equipment and the SO2 content in the tail gas, sulfuric acid can be produced as a byproduct, generating significant economic benefits.

[0053] A phosphate rock slurry flue gas desulfurization process based on the above system includes the following steps:

[0054] S1. Phosphate rock slurry preparation: The phosphate rock slurry from the phosphoric acid production system is transported to the slurry preparation tank 7, its solid content is adjusted to 35%-40%, and it is stirred evenly before use.

[0055] S2, Primary Desulfurization Absorption: SO2-containing flue gas is introduced from the sulfur-containing flue gas inlet 11 at the top of the desulfurization tower 1. At the same time, the phosphate rock slurry after slurry preparation and the circulating slurry from the first circulation tank 2 are sprayed into the desulfurization tower 1 in the form of atomization through the phosphate rock slurry spray layer 12. The flue gas and slurry are fully contacted as they flow down in the tower. The SO2 in the flue gas is absorbed by the slurry and sulfurous acid is generated.

[0056] S3. Slurry Circulation and Catalytic Oxidation: The slurry that has absorbed SO2 flows from the slurry outlet 14 at the bottom of the desulfurization tower 1 into the first circulation tank 2. Under the stirring action of the agitator and the action of air / oxygen blown in by the oxidation device, the Fe in the slurry... 3+Ion catalysis rapidly oxidizes sulfurous acid to sulfuric acid. At the same time, the sulfuric acid reacts with components such as calcium carbonate in the phosphate rock slurry to produce phosphoric acid and calcium sulfate. Most of the slurry after the oxidation reaction is sent back to the desulfurization tower 1 for circulating spraying via the first circulating pump 21, and a small portion is discharged as mother liquor to maintain the stability of the circulation system.

[0057] S4, Secondary Scrubbing and Demisting: The purified gas discharged from the purified gas outlet 13 at the bottom of the desulfurization tower 1 enters the tower through the air inlet 31 at the bottom of the scrubbing tower 3, and comes into countercurrent contact with the scrubbing water sprayed from the second circulation tank 4 by the scrubbing liquid spray layer 32, further removing residual SO2, acid mist and entrained solid particles; after the scrubbing gas passes through the demister 33 at the top of the tower to remove liquid mist, it enters the chimney 8 through the clean gas outlet 34 and is discharged in compliance with standards.

[0058] S5. Slurry treatment and resource recycling: The mother liquor discharged from the first circulation tank 2 is transported to the filter press 6 by the mother liquor pump 61 for solid-liquid separation. The resulting filter cake (mainly unreacted phosphate rock powder and calcium sulfate generated by the reaction) is returned to the extraction process of the phosphoric acid production system to realize resource recycling. The filtrate enters the return water tank 5, and after being neutralized to near neutral by adding alkaline substances through the pH adjustment device 51, it is sent by the return water pump 52 to the slurry preparation tank 7, the first circulation tank 2 and the second circulation tank 4 as supplementary water for recycling, realizing zero wastewater discharge.

[0059] S6. System Control: The pH value of the slurry is monitored by the pH sensor on the first circulation tank 2, and the discharge of mother liquor and the replenishment of new phosphate rock slurry are controlled accordingly to maintain stable desulfurization efficiency; the pH value and liquid level of the washing water in the second circulation tank 4 are monitored to control the replenishment of process water and ensure the washing and demisting effect.

[0060] S7. Anti-clogging auxiliary treatment: The gas pipeline coming out of the lower part of the desulfurization tower 1 is equipped with a vertical rising section. The return water is used to spray and wash the pipeline in this section to prevent the gas from carrying mineral slurry and causing pipeline blockage. The washed mineral slurry and washing water return to the bottom of the desulfurization tower 1 and automatically flow into the first circulation tank 2 to realize material recovery.

[0061] The above description is merely a preferred embodiment of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention. Structures, devices, and operating methods not specifically described or explained in this invention are implemented according to conventional methods in the art unless otherwise specified or limited.

Claims

1. A phosphate rock slurry flue gas desulfurization system, characterized in that, It includes a flue gas purification unit, a slurry circulation and oxidation unit, a washing and demisting unit and a slurry treatment and recovery unit connected in sequence, as well as a phosphate rock slurry conditioning system, a chimney (8) and an online automatic real-time monitoring system for SO2 tail gas; The flue gas purification unit mainly includes a desulfurization tower (1), the top of which is provided with a sulfur-containing flue gas inlet (11) and a phosphate rock slurry spray layer (12), and the bottom is provided with a purified gas outlet (13) and a slurry outlet (14). The phosphate rock slurry spray layer (12) is connected to a spray pipeline (15). The slurry circulation and oxidation unit includes a first circulation tank (2), a first circulation pump (21) and an oxidation device. The first circulation tank (2) is connected to the slurry outlet (14) of the desulfurization tower (1), the inlet of the first circulation pump (21) and the phosphate rock slurry supply system through pipelines. The outlet of the first circulation pump (21) is connected to the phosphate rock slurry spray layer (12) of the desulfurization tower (1) through a spray pipeline (15). The washing and demisting unit includes a washing tower (3), a second circulation tank (4), and a second circulation pump (41). The washing tower (3) is provided with an air inlet (31) and a washing liquid spray layer (32) at the bottom, and a demister (33) and a clean air outlet (34) at the top. The clean air outlet (34) is connected to the air inlet of the chimney (8). The slurry treatment and recovery unit includes a filter press (6) and a return water tank (5). The feed inlet of the filter press (6) is connected to the first circulation tank (2) through a mother liquor pump (61), its filter cake outlet is connected to the extraction tank of the main production system, and its filtrate outlet is connected to the return water tank (5).

2. The phosphate rock slurry flue gas desulfurization system according to claim 1, characterized in that, The first circulation tank (2) is connected to an auxiliary agent tank (25). The auxiliary agent tank (25) contains desulfurization auxiliary agent, and the lower end of the auxiliary agent tank (25) is connected to the first circulation tank (2) through an auxiliary agent supply pipe (26). A flow control valve (27) is also installed on the auxiliary agent supply pipe (26).

3. The phosphate rock slurry flue gas desulfurization system according to claim 1, characterized in that, The desulfurization tower (1) adopts an empty tower spray structure, and the gas and liquid in the tower are in a co-current contact manner. The bottom of the tower is designed as an inclined plate structure, and no slurry is retained. The gas pipeline coming out of the lower part of the desulfurization tower (1) is provided with a vertical rising section, and the vertical rising section is provided with a return water spray washing structure. The washing tower (3) is a combined tower with an empty tower spray washing section at the bottom and a structured packing or cyclone plate demister built into the upper part, and is equipped with a flushing device.

4. The phosphate rock slurry flue gas desulfurization system according to claim 1, characterized in that, The oxidation device is located in the first circulation tank (2) and is used to forcibly mix the slurry with air or oxygen. The oxidation device includes at least one oxygen pump (23) and a plurality of self-primers connected thereto. The self-primers are immersed in the slurry in the first circulation tank (2). The oxidation device also includes a mixing jet (24), which is installed above the first circulation tank (2) and is connected to the output end of the oxygen pump (23) through a pipe.

5. A phosphate rock slurry flue gas desulfurization system according to claim 1, characterized in that, The air inlet (31) of the washing tower (3) is connected to the purified gas outlet (13) of the desulfurization tower (1) through a pipeline. The second circulation tank (4) is connected to the washing liquid outlet (35) of the washing tower (3), the inlet of the second circulation pump (41) and the water source pipeline through pipelines respectively. The outlet of the second circulation pump (41) is connected to the washing liquid spray layer (32) of the washing tower (3).

6. The phosphate rock slurry flue gas desulfurization system according to claim 1, characterized in that, The lower part of the chimney (8) is provided with an enlarged section to form a gas-water separator, and the liquid accumulated at the bottom is introduced into the return water tank (5) through the liquid seal tank (81). The return water tank (5) is equipped with a pH adjustment device (51), and its outlet is connected to the first circulation tank (2), the second circulation tank (4) and the phosphate rock slurry conditioning system respectively through the return water pump (52). The return water tank (5) is also equipped with an alkali addition tank.

7. A phosphate rock slurry flue gas desulfurization system according to claim 1, characterized in that, The phosphate rock slurry conditioning system includes a conditioning tank (7), the outlet of which is connected to a slurry conveying pump (71), the output end of which is connected to a slurry conveying pipe (72), and the other end of which is connected to a first circulation tank (2).

8. A phosphate rock slurry flue gas desulfurization system according to claim 1, characterized in that, Agitators are installed in the slurry preparation tank (7), the first circulation tank (2), the second circulation tank (4) and the return water tank (5). A pH sensor and a level gauge are installed on the first circulation tank (2) and the second circulation tank (4).

9. A phosphate rock slurry flue gas desulfurization process based on the system described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Phosphate rock slurry preparation: Phosphate rock slurry from the phosphoric acid production system is transported to the slurry preparation tank (7) and its solid content is adjusted to 35%-40% for later use. S2, Primary desulfurization absorption: SO2-containing flue gas is introduced from the top of the desulfurization tower (1), and at the same time, the phosphate rock slurry after slurry preparation and the circulating slurry from the first circulation tank (2) are sprayed into the desulfurization tower (1) in the form of atomization through the phosphate rock slurry spray layer (12). The flue gas and the slurry are fully contacted in the tower as they flow down. The SO2 in the flue gas is absorbed by the slurry and sulfurous acid is generated. S3, Slurry Circulation and Catalytic Oxidation: The slurry that has absorbed SO2 flows into the first circulation tank (2). Under the action of air / oxygen blown in by the stirring and oxidation device, the Fe in the slurry... 3+ Ion catalysis rapidly oxidizes sulfurous acid to sulfuric acid. At the same time, sulfuric acid reacts with components such as calcium carbonate in the phosphate rock slurry to generate phosphoric acid and calcium sulfate. Most of the slurry after the oxidation reaction is sent back to the desulfurization tower (1) for circulating spraying via the first circulating pump (21), and a small portion is discharged as mother liquor. S4, Secondary scrubbing and demisting: The purified gas discharged from the desulfurization tower (1) enters the tower through the air inlet (31) at the bottom of the scrubbing tower (3), and comes into countercurrent contact with the scrubbing water sprayed from the second circulation tank (4) by the scrubbing liquid spray layer (32) to further remove residual SO2, acid mist and entrained solid particles. After the scrubbing gas passes through the demister (33) at the top of the tower to remove liquid mist, it is discharged through the chimney (8) in compliance with standards. S5. Slurry treatment and resource recycling: The mother liquor discharged from the first circulation tank (2) is separated into solid and liquid by the filter press (6). The resulting filter cake is returned to the extraction process of the phosphoric acid production system. The filtrate enters the return water tank (5), and after adding alkaline substances to neutralize it to near neutral, it is sent by the return water pump (52) to the slurry conditioning tank (7), the first circulation tank (2) and the second circulation tank (4) respectively as supplementary water for recycling. S6. System control: By monitoring the pH value of the slurry in the first circulation tank (2), the discharge of mother liquor and the replenishment of new phosphate rock slurry are controlled to maintain desulfurization efficiency. By monitoring the pH and level of the washing water, the replenishment of process water is controlled.

10. The phosphate rock slurry flue gas desulfurization process according to claim 9, characterized in that, In step S2, the vertical rising section of the lower gas pipeline of the desulfurization tower (1) is washed with return water spray. The washed slurry and washing water return to the bottom of the desulfurization tower (1) and automatically flow into the first circulation tank (2).

Images