A farm boiler flue gas purification system and process thereof

Abstract

The present application relates to the technical field of farm boiler flue gas purification system, and discloses a farm boiler flue gas purification system and process thereof, which comprises a spray desulfurization tower, a demisting device, a tube bundle dust removal device and a water curtain dust removal device are installed in the spray desulfurization tower from top to bottom, a flue is formed at the left lower end of the spray desulfurization tower, the demisting device is connected to a process water pool through a flushing pump, the tube bundle dust removal device, the water curtain dust removal device and the spray desulfurization tower are connected to a multi-stage sedimentation tank through a first circulating pump, a second circulating pump and a third circulating pump, a connecting port is arranged at the right lower end of the spray desulfurization tower, a sewage filtration and compression device is connected to the right of the connecting port, and one end of the sewage filtration and compression device is connected to the sedimentation tank; the farm boiler flue gas purification system and process thereof have high dust removal efficiency; ceramic multi-tube cyclone dust collectors are used for pre-dust removal, 80%-92% of particulate matters can be removed, the load of subsequent bag-type dust collectors is reduced, and the service life of filter bags is prolonged.

Description

Technical Field

[0001] This invention relates to the technical field of farm boiler flue gas purification systems, specifically a farm boiler flue gas purification system and its process. Background Technology

[0002] Coal-fired boilers, chain grate furnaces, and industrial kilns generate large amounts of flue gas containing soot and sulfur dioxide (SO2) during combustion. Soot causes particulate matter pollution, while sulfur dioxide is a significant precursor to acid rain and fine particulate matter, posing a considerable threat to the ecological environment and human health. Therefore, all types of industrial boilers require highly efficient flue gas dust removal and desulfurization devices to meet national environmental emission standards.

[0003] Currently, boiler flue gas dust removal typically employs processes such as cyclone dust collectors, bag filters, and electrostatic precipitators. Among these, cyclone dust collectors have a simple structure and low operating costs, but they are difficult to meet ultra-low emission requirements; bag filters have high dust removal efficiency, but if they are used to directly handle high-concentration dust flue gas, they can easily lead to severe wear of the filter bags, increased resistance, and shortened service life.

[0004] In desulfurization, commonly used processes include limestone-gypsum method, sodium alkali method, ammonia method, and dual alkali method. Among them, limestone-gypsum method has high equipment investment and complex system; sodium alkali method has high reagent cost; while dual alkali method combines the advantages of fast sodium alkali absorption and low lime cost, and has the advantages of stable operation, lower investment, and convenient maintenance, so it is widely used.

[0005] Therefore, there is a need for a flue gas purification system that can simultaneously achieve high-efficiency dust removal, high-efficiency desulfurization, stable operation, convenient maintenance, and low operating costs to meet the needs of industrial boiler flue gas treatment. Summary of the Invention

[0006] The purpose of this invention is to provide a farm boiler flue gas purification system and process to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A farm boiler flue gas purification system includes a spray desulfurization tower. Inside the spray desulfurization tower, from top to bottom, are installed a demister, a tube bundle dust collector, and a water curtain dust collector. A flue is located on the lower left side of the spray desulfurization tower. The demister is connected to a process water tank via a flushing pump. The tube bundle dust collector, the water curtain dust collector, and the spray desulfurization tower are connected to a multi-stage sedimentation tank via a first circulation pump, a second circulation pump, and a third circulation pump. A connection port is located on the lower right side of the spray desulfurization tower, and a wastewater filtration and compression device is connected to the wastewater filtration and compression device. One end of the wastewater filtration and compression device is connected to the sedimentation tank. A sedimentation tank is located on the right side of the sedimentation tank. A sodium alkali tank is installed on the upper right side of the multi-stage sedimentation tank, and both the sodium alkali tank and the sedimentation tank are equipped with agitators. The farm's boiler flue gas purification system also includes a dust collector, which consists of an upper housing, an ash hopper, and an ash discharge valve. The upper right side of the upper housing has a flue gas outlet and a flue gas inlet, and the lower right side of the upper housing has a connecting flange. The lower end of the upper housing has an ash hopper, and the ash discharge valve is installed below the ash hopper. The lower end of the dust collector is equipped with a support and a base plate.

[0008] A flue gas purification process for farm boilers, applicable to farm boiler flue gas purification systems, includes the following steps: Step 1: Flue gas pretreatment. The dust-laden flue gas from the boiler first enters the multi-tube cyclone dust collector for primary dry dust removal. The inlet dust concentration is controlled to be ≤5g / Nm³ and the flue gas temperature is ≤180℃. After dust removal, the outlet dust concentration is reduced to ≤500mg / Nm³. Step 2: Fine dust removal using bag filters. The flue gas treated in Step 1 is introduced into a bag filter and subjected to secondary filtration using PTFE base fabric + PTFE membrane PPS filter bags to control the outlet dust emission concentration to ≤30mg / Nm³. Step 3: Sodium-calcium dual alkali desulfurization. The flue gas purified in Step 2 is introduced into the desulfurization tower and sprayed with sodium alkali solution (NaCO3 / NaOH) as absorbent. SO2 in the flue gas reacts with sodium alkali to generate sodium sulfite / sodium bisulfite. The absorbent falls to the bottom of the tower and flows into the circulation pool. Step 4: Desulfurization liquid regeneration. The absorbed liquid produced in Step 3 is introduced into the regeneration tank, and lime slurry Ca(OH)2 is added to carry out the regeneration reaction, generating sodium hydroxide and calcium sulfite precipitates. The precipitates are separated in the sedimentation tank, and the supernatant overflows back into the circulation tank to replenish sodium alkali before being recycled. Step 5: Byproduct treatment. The calcium sulfite precipitate produced in Step 4 is dried or dehydrated and then transported off-site. The regenerated sodium alkali solution is reused in the desulfurization tower spray system.

[0009] Preferably, the principle of the desulfurization dual-alkali method can be divided into two parts: the desulfurization process and the regeneration process.

[0010] Preferably, the desulfurization process involves SO2 absorption within the tower; Na2CO3+SO2=Na2SO3+CO2 (1); Na2SO3+SO2+H2O=2NaHSO3 (2); 2NaOH+SO2=Na2SO3+H2O (3); Equations (1) and (2) are the reaction equations for the absorption of SO2 by the soda ash solution in the start-up stage, (2) is the main reaction equation when the pH of the regenerated liquid is high, and (3) is the reaction equation when the pH value is high.

[0011] Preferably, the regeneration process involves using lime water outside the tower to regenerate sodium alkali solution: Ca(OH)2+Na2SO3+1 / 2H2O=2NaOH+CaSO3·1 / 2H2O↓; Ca(OH)2+2NaHSO3=2NaOH+CaSO3·1 / 2H2O↓+3 / 2 H2O; In lime slurry (where the lime reaches saturation), NaHSO3 quickly reacts with Ca(OH)2, releasing [Na+]. ＋ SO3 2- ], [Ca 2＋ ]OH - In the reaction, CaSO3 precipitates as a hemihydrate compound, thereby causing [Na] to precipitate. ＋ [It can be regenerated.]

[0012] Preferably, Na2SO3 is a starting alkali; the actual alkali consumed during operation is lime, not soda ash. The regenerated NaOH and Na + The desulfurizing agent solution is recycled, and no wastewater is discharged.

[0013] Preferably, if a high-quality byproduct gypsum CaSO4·2H2O is required, it needs to be oxidized first, then regenerated, dried, and washed with clean water.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. High dust removal efficiency: Pre-dust removal is performed using a ceramic multi-tube cyclone dust collector, which can remove 80% to 92% of particulate matter, reducing the load on the subsequent bag filter and extending the service life of the filter bags.

[0015] 2. Stable and compliant emissions: By combining a ceramic multi-tube dust collector with a PTFE-coated PPS filter bag dust collector, the concentration of flue dust emissions can be stably controlled below 30 mg / Nm³.

[0016] 3. High desulfurization efficiency: The dual-alkali method uses sodium-based absorbent to rapidly absorb SO2 and then uses lime for regeneration, resulting in high desulfurization efficiency and meeting the environmental protection requirement of SO2 emission concentration ≤200mg / Nm³.

[0017] 4. Low operating cost: The system mainly consumes lime during operation, and only a small amount of soda ash needs to be added to maintain circulation. The reagent utilization rate is high, and the overall operating cost is significantly lower than that of the single alkali method.

[0018] 5. The equipment is less prone to scaling and clogging. The regeneration reaction and precipitation process are completed outside the tower, avoiding scaling and clogging inside the desulfurization tower and circulation pipelines, thus improving the long-term stable operation capability of the system.

[0019] 6. Excellent high temperature and corrosion resistance: The filter bag is made of PTFE base cloth + PTFE membrane PPS filter material, which has excellent resistance to acid and alkali corrosion, oxidation and high temperature, and can be used for flue gas conditions of about 180℃ for a long time.

[0020] 7. The system has a high degree of automation and can automatically replenish alkali solution according to the pH value of the circulating liquid, thereby automatically adjusting the concentration of the absorbent, reducing manual operation and improving operational stability.

[0021] 8. No wastewater discharge, absorption liquid is recycled, and only a small amount of desulfurization by-products are generated, achieving almost zero wastewater discharge and good environmental performance. Attached Figure Description

[0022] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the overall structure of the farm boiler flue gas purification system of the present invention; Figure 2 This is a process diagram of the farm boiler flue gas purification system of the present invention; Figure 3 This is a structural diagram of the dust collector in the farm boiler flue gas purification system of the present invention; In the diagram: 1-Demisting device, 2-Tube bundle dust removal device, 3-Water curtain dust removal device, 4-Spray desulfurization tower, 5-Flue duct, 6-Flushing pump, 7-First circulation pump, 8-Second circulation pump, 9-Third circulation pump, 10-Sewage filtration and compression device, 11-Sedimentation tank, 12-Regeneration tank, 13-Multi-stage sedimentation tank, 14-Sodium alkali tank, 15-Agitator, 16-Flue gas outlet, 17-Flue gas inlet, 18-Upper box, 19-Connecting flange, 20-Ash hopper, 21-Ash discharge valve, 22-Support, 23-Base plate. Detailed Implementation

[0023] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. In the embodiments of the present invention, the different types of cross-sectional lines are not labeled according to national standards, nor do they specify material requirements for the components; they are used to distinguish the cross-sectional views of the components.

[0024] Please see Figure 1-3 A farm boiler flue gas purification system includes a spray desulfurization tower 4. Inside the spray desulfurization tower 4, from top to bottom, are installed a demister 1, a tube bundle dust collector 2, and a water curtain dust collector 3. A flue duct 5 is located on the lower left side of the spray desulfurization tower 4. The demister 1 is connected to a process water tank via a flushing pump 6. The tube bundle dust collector 2, the water curtain dust collector 3, and the spray desulfurization tower 4 are connected to a multi-stage sedimentation tank 13 via a first circulation pump 7, a second circulation pump 8, and a third circulation pump 9. A connection port is located on the lower right side of the spray desulfurization tower 4, and the right side of this connection port is connected to a wastewater filtration and compression device 10. One end of the wastewater filtration and compression device 10 is connected to a sedimentation tank 11. A sedimentation tank 12 is located on the right side of the sedimentation tank 11. A sodium alkali tank 14 is installed on the upper right side of the multi-stage sedimentation tank 13, and both the sodium alkali tank 14 and the sedimentation tank 12 are equipped with a stirrer 15. The farm's boiler flue gas purification system also includes a dust collector, which consists of an upper housing 18, an ash hopper 20, and an ash discharge valve 21. The upper right side of the upper housing 18 has a flue gas outlet 16 and a flue gas inlet 17, and the lower right side of the upper housing 18 has a connecting flange 19. The lower end of the upper housing 18 has an ash hopper 20, and the ash discharge valve 21 is installed below the ash hopper 20. The lower end of the dust collector is equipped with a support 22 and a base plate 23.

[0025] A flue gas purification process for farm boilers, applicable to farm boiler flue gas purification systems, includes the following steps: Step 1: Flue gas pretreatment. The dust-laden flue gas from the boiler first enters the multi-tube cyclone dust collector for primary dry dust removal. The inlet dust concentration is controlled to be ≤5g / Nm³ and the flue gas temperature is ≤180℃. After dust removal, the outlet dust concentration is reduced to ≤500mg / Nm³. Step 2: Fine dust removal using bag filters. The flue gas treated in Step 1 is introduced into a bag filter and subjected to secondary filtration using PTFE base fabric + PTFE membrane PPS filter bags to control the outlet dust emission concentration to ≤30mg / Nm³. Step 3: Sodium-calcium dual alkali desulfurization. The flue gas purified in Step 2 is introduced into the desulfurization tower and sprayed with sodium alkali solution (NaCO3 / NaOH) as absorbent. SO2 in the flue gas reacts with sodium alkali to generate sodium sulfite / sodium bisulfite. The absorbent falls to the bottom of the tower and flows into the circulation pool. Step 4: Desulfurization liquid regeneration. The absorbed liquid produced in Step 3 is introduced into the regeneration tank, and lime slurry Ca(OH)2 is added to carry out the regeneration reaction, generating sodium hydroxide and calcium sulfite precipitates. The precipitates are separated in the sedimentation tank, and the supernatant overflows back into the circulation tank to replenish sodium alkali before being recycled. Step 5: Byproduct treatment. The calcium sulfite precipitate produced in Step 4 is dried or dehydrated and then transported off-site. The regenerated sodium alkali solution is reused in the desulfurization tower spray system.

[0026] The principle of the desulfurization dual-alkali method can be divided into two parts: the desulfurization process and the regeneration process.

[0027] The desulfurization process involves the absorption of SO2 within the tower. Na2CO3+SO2=Na2SO3+CO2 (1); Na2SO3+SO2+H2O=2NaHSO3 (2); 2NaOH+SO2=Na2SO3+H2O (3); Equations (1) and (2) are the reaction equations for the absorption of SO2 by the soda ash solution in the start-up stage, (2) is the main reaction equation when the pH of the regenerated liquid is high, and (3) is the reaction equation when the pH value is high.

[0028] The regeneration process involves using lime water outside the tower to regenerate sodium alkali solution. Ca(OH)2+Na2SO3+1 / 2H2O=2NaOH+CaSO3·1 / 2H2O↓; Ca(OH)2+2NaHSO3=2NaOH+CaSO3·1 / 2H2O↓+3 / 2 H2O; In lime slurry (where the lime reaches saturation), NaHSO3 quickly reacts with Ca(OH)2, releasing [Na+]. ＋ SO3 2- ], [Ca 2＋ ]OH - In the reaction, CaSO3 precipitates as a hemihydrate compound, thereby causing [Na] to precipitate. ＋ [It can be regenerated.]

[0029] Na₂SO₃ is a starting alkali; the actual alkali consumed during operation is lime, not soda ash. The regenerated NaOH and Na + The desulfurizing agent solution is recycled, and no wastewater is discharged.

[0030] To obtain high-quality byproduct gypsum (CaSO4·2H2O), it is necessary to first oxidize, then regenerate, dry, and wash with clean water.

[0031] It should be noted that the farm boiler flue gas purification system provided by the present invention adopts a flue gas purification process of **"multi-tube cyclone pre-dust removal - bag fine dust removal - sodium-calcium dual alkali desulfurization - desulfurization liquid regeneration and circulation"**, to achieve synergistic purification of particulate matter and sulfur dioxide in boiler flue gas.

[0032] The dust-laden flue gas generated by the boiler first enters the dust collector through flue gas inlet 17. The flue gas first enters the multi-tube cyclone dust collector for primary dry dust removal. Under the action of centrifugal force, large dust particles are separated from the flue gas and fall into the ash hopper 20, and are periodically discharged through the ash discharge valve 21, realizing flue gas pretreatment. After primary dust removal, the flue gas continues to enter the bag filter area in the upper box 18. The flue gas passes through PTFE base cloth + PTFE membrane PPS filter bags, and fine dust particles are trapped on the surface of the filter bags, realizing secondary fine dust removal. The purified flue gas enters the spray desulfurization tower 4 through the connecting flange 19.

[0033] After entering the spray desulfurization tower 4 through flue 5, the flue gas flows from bottom to top. The first circulation pump 7, the second circulation pump 8, and the third circulation pump 9 respectively transport the circulating absorbent liquid in the multi-stage sedimentation tank 13 to the water curtain dust collector 3, the tube bundle dust collector 2, and the spray desulfurization tower 4. After being sprayed, the absorbent liquid forms uniform droplets, which come into full contact with the flue gas, causing the sulfur dioxide in the flue gas to react with the sodium alkali absorbent liquid to generate sodium sulfite and sodium bisulfite, thus achieving desulfurization and purification. The flue gas continues to pass through the water curtain dust collector 3 and the tube bundle dust collector 2 for further dust removal and demisting, and finally passes through the demisting device 1 to remove entrained droplets before being discharged.

[0034] The absorbent liquid after absorbing sulfur dioxide flows into the multi-stage sedimentation tank 13, where it is mixed with the alkaline solution replenished by the sodium alkali tank 14 under the action of the stirrer 15. Simultaneously, the absorbent liquid is sent to the regeneration tank for regeneration. During the regeneration process, lime slurry is added, causing sodium sulfite and sodium bisulfite to react with calcium hydroxide, generating calcium sulfite precipitate and releasing sodium hydroxide, thus regenerating the sodium-based absorbent. The regenerated slurry sequentially enters sedimentation tanks 11 and 12 for solid-liquid separation. The precipitate is dewatered by the wastewater filtration and compression device 10 and then transported off-site. The supernatant is returned to the multi-stage sedimentation tank 13 and then pumped back to the spray desulfurization tower 4 for reuse.

[0035] When gypsum byproducts need to be prepared, calcium sulfite can be oxidized to convert it into gypsum (CaSO4·2H2O), which is then dehydrated, dried, and washed to obtain the gypsum product. The entire system forms a continuous operation process of pre-dust removal, fine dust removal, spray desulfurization, absorbent regeneration, solid-liquid separation, and recycling. While achieving boiler flue gas emission standards, it improves the utilization rate of desulfurizing agent, reduces operating costs, and reduces wastewater discharge.

[0036] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0037] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A farm boiler flue gas purification system, comprising a spray desulfurization tower (4), characterized in that: The spray desulfurization tower (4) is equipped with a demisting device (1), a tube bundle dust removal device (2), and a water curtain dust removal device (3) from top to bottom. A flue (5) is provided on the lower left side of the spray desulfurization tower (4). The demisting device (1) is connected to the process water tank through a flushing pump (6). The tube bundle dust removal device (2), the water curtain dust removal device (3), and the spray desulfurization tower (4) are connected to the multi-stage sedimentation tank (13) through a first circulation pump (7), a second circulation pump (8), and a third circulation pump (9). A connection port is provided on the lower right side of the spray desulfurization tower (4). The right side of the connection port is connected to a sewage filtration and compression device (10), and one end of the sewage filtration and compression device (10) is connected to a sedimentation tank (11). A sedimentation tank (12) is provided on the right side of the sedimentation tank (11). A sodium alkali tank (14) is installed on the upper right side of the multi-stage sedimentation tank (13), and a stirrer (15) is installed on both the sodium alkali tank (14) and the sedimentation tank (12). The farm boiler flue gas purification system also includes a dust collector, which consists of an upper box (18), an ash hopper (20), and an ash discharge valve (21). The upper right side of the upper box (18) is provided with a flue gas outlet (16) and a flue gas inlet (17), and the lower right side of the upper box (18) is provided with a connecting flange (19). The lower end of the upper box (18) is provided with an ash hopper (20), and the lower part of the ash hopper (20) is provided with an ash discharge valve (21). The lower end of the dust collector is provided with a bracket (22) and a base plate (23).

2. A flue gas purification process for farm boilers, applicable to farm boiler flue gas purification systems, characterized in that: The farm's boiler flue gas purification process includes the following steps: Step 1: Flue gas pretreatment. The dust-laden flue gas from the boiler first enters the multi-tube cyclone dust collector for primary dry dust removal. The inlet dust concentration is controlled to be ≤5g / Nm³ and the flue gas temperature is ≤180℃. After dust removal, the outlet dust concentration is reduced to ≤500mg / Nm³. Step 2: Fine dust removal using bag filters. The flue gas treated in Step 1 is introduced into a bag filter and subjected to secondary filtration using PTFE base fabric + PTFE membrane PPS filter bags to control the outlet dust emission concentration to ≤30mg / Nm³. Step 3: Sodium-calcium dual alkali desulfurization. The flue gas purified in Step 2 is introduced into the desulfurization tower and sprayed with sodium alkali solution (NaCO3 / NaOH) as absorbent. SO2 in the flue gas reacts with sodium alkali to generate sodium sulfite / sodium bisulfite. The absorbent falls to the bottom of the tower and flows into the circulation pool. Step 4: Desulfurization liquid regeneration. The absorbed liquid produced in Step 3 is introduced into the regeneration tank, and lime slurry Ca(OH)2 is added to carry out the regeneration reaction, generating sodium hydroxide and calcium sulfite precipitates. The precipitates are separated in the sedimentation tank, and the supernatant overflows back into the circulation tank to replenish sodium alkali before being recycled. Step 5: Byproduct treatment. The calcium sulfite precipitate produced in Step 4 is dried or dehydrated and then transported off-site. The regenerated sodium alkali solution is reused in the desulfurization tower spray system.

3. The farm boiler flue gas purification process according to claim 2, characterized in that: The principle of the desulfurization dual-alkali method can be divided into two parts: the desulfurization process and the regeneration process.

4. The farm boiler flue gas purification process according to claim 3, characterized in that: The desulfurization process involves the absorption of SO2 within the tower; Na2CO3+SO2=Na2SO3+CO2 (1); Na2SO3+SO2+H2O=2NaHSO3 (2); 2NaOH+SO2=Na2SO3+H2O (3); Equations (1) and (2) are the reaction equations for the absorption of SO2 by the soda ash solution in the start-up stage, (2) is the main reaction equation when the pH of the regenerated liquid is high, and (3) is the reaction equation when the pH value is high.

5. The farm boiler flue gas purification process according to claim 3, characterized in that: The regeneration process involves using lime water outside the tower to regenerate sodium alkali solution. Ca(OH)2+Na2SO3+1 / 2H2O=2NaOH+CaSO3·1 / 2H2O↓; Ca(OH)2+2NaHSO3=2NaOH+CaSO3·1 / 2H2O↓+3 / 2 H2O; In lime slurry (where the lime reaches saturation), NaHSO3 quickly reacts with Ca(OH)2, releasing [Na+]. ＋ SO3 2- ], [Ca 2＋ ]OH - In the reaction, CaSO3 precipitates as a hemihydrate compound, thereby causing [Na] to precipitate. ＋ [It can be regenerated.] 6. The farm boiler flue gas purification process according to claim 5, characterized in that: Na₂SO₃ is a starting alkali; the actual process consumes lime, not soda ash. The regenerated NaOH and Na₂SO₃ are used as the starting alkali. + The desulfurizing agent solution is recycled, and no wastewater is discharged.

7. The farm boiler flue gas purification process according to claim 5, characterized in that: To obtain high-quality byproduct gypsum (CaSO4·2H2O), it is necessary to first oxidize, then regenerate, dry, and wash with clean water.

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