Semi-dry flue gas treatment system for denitration by using ammonium sulfite generated by urea desulfurization

Abstract

The utility model belongs to the technical field of flue gas purification, and particularly relates to a semi-dry flue gas treatment system for denitration by utilizing ammonium sulfite generated by urea desulfurization. The system at least comprises a mixer and a bag-type dust collector which are communicated in sequence, the gasifier is communicated with the mixer; and the urea desulfurization system is communicated with the gasifier. According to the semi-dry flue gas treatment device, the cloth bag is used as a reactor, and ammonium sulfite generated by urea desulfurization is subjected to denitration semi-dry flue gas treatment. Based on the flue gas desulfurization system, the dedusted original flue gas is discharged after being denitrated and desulfurized, and ammonium sulfite is generated through urea desulfurization reaction and is further used for denitration.

Description

Technical Field

[0001] This utility model belongs to the field of flue gas purification technology, specifically relating to a semi-dry flue gas treatment system that utilizes ammonium sulfide generated from urea desulfurization for denitrification. Background Technology

[0002] The flue gas generated in kilns in steel, cement, building materials, glass, metallurgy and other industries contains a large amount of pollutants such as sulfur dioxide, nitrogen oxides and soot, which cause great harm to human health and the ecological environment. Traditional treatment methods only set up a separate treatment device for a certain pollutant. To treat all pollutants, the process is long, the equipment is complex, and the investment and operating costs are high. Utility Model Content

[0003] To address the shortcomings of existing technologies, this invention provides a semi-dry flue gas treatment system and method utilizing ammonium sulfite generated from urea desulfurization for denitrification. This invention uses a bag filter as a reactor to treat the flue gas using ammonium sulfite generated from urea desulfurization for denitrification. Based on this invention, the original flue gas, after dust removal, is discharged after denitrification and desulfurization, and the ammonium sulfite generated from the urea desulfurization reaction is further used for denitrification.

[0004] The technical solution provided by this utility model is as follows:

[0005] A semi-dry flue gas treatment system utilizing ammonium sulfide generated from urea desulfurization for denitrification includes at least:

[0006] The mixer and the bag filter are connected in sequence;

[0007] A vaporizer connected to the mixer;

[0008] And a urea desulfurization system, which is connected to the gasifier.

[0009] Among the aforementioned technology providers:

[0010] Ammonium sulfide is vaporized in the vaporizer;

[0011] After gasification, ammonium sulfite enters the mixer and reacts fully with the original flue gas after dust removal to produce ammonium sulfate particles. These particles enter the filter bag along with the flue gas. Meanwhile, unreacted ammonium sulfite condenses into microparticles and continues to react with nitrogen oxides in the flue gas. The resulting ammonium sulfate particles adhere to the surface of the filter bag. When the pressure difference of the filter bag increases, the filter bag is back-blown to discharge the material.

[0012] The flue gas passing through the bag filter enters the desulfurization tower and is further desulfurized using urea.

[0013] The ammonium sulfide generated during desulfurization can then enter the gasifier and participate in the denitrification reaction.

[0014] The ammonium sulfate particles generated inside the bag enter the gasifier and then enter the crystallizer from the bottom of the gasifier to achieve solid-liquid separation.

[0015] The main reaction equation for denitrification between the mixer and the bag filter is as follows:

[0016] 2(NH4)2SO3+2NO=2(NH4)2SO4+N2

[0017] 4(NH4)2SO3+2NO2=4(NH4)2SO4+N2

[0018] Main reaction equations in the desulfurization absorption tower:

[0019] CO(NH)₂ + 2H₂O = (NH₄)₂CO₃

[0020] (NH4)2CO3 + SO2 = (NH4)2SO3 + CO2

[0021] (NH4)2SO3 + H2O + SO2 = 2NH4HSO3

[0022] 2NH4HSO3+(NH4)2CO3=2(NH4)2SO3+CO2+H2O

[0023] The vaporizer utilizes the property that ammonium sulfide can be vaporized and that it is soluble in water but insoluble in organic solvents. It uses high-temperature heat transfer oil as the heat medium to vaporize ammonium sulfide. Meanwhile, ammonium sulfate is also insoluble in heat transfer oil and will not decompose, but it will deposit in the heat transfer oil. The heat transfer oil can be used to separate ammonium sulfide and ammonium sulfate, thereby improving the utilization rate of ammonium sulfide and the purity of ammonium sulfate.

[0024] The vaporizer can utilize external heating. To reduce localized overheating and decomposition of the heat transfer oil, the heater can employ high-pressure steam heating. Simultaneously, a circulating pump is matched to the heater to heat the upper layer of heat transfer oil in the vaporizer to 120-160℃. The lower layer of heat transfer oil can remain unheated, utilizing heat conduction or the settling ammonium sulfate for heating, ensuring the lower layer's temperature is maintained at 80-90℃. An agitator with straight blades is installed inside the vaporizer to enhance radial flow of the heat transfer oil on the vaporizer surface. This ensures that the material entering the vaporizer falls evenly onto the heat transfer oil surface. The ammonium sulfate solid particles coated in the heat transfer oil then spirally descend along the vaporizer wall under centrifugal force to the bottom, entering the oil-water separation chamber.

[0025] The vaporizer features an inverted conical bottom to concentrate the settling ammonium sulfate before it enters the oil-water separation chamber. Utilizing the immiscibility of heat transfer oil and water, particulate ammonium sulfate in the separation chamber falls from the heat transfer oil side to the aqueous solution side and dissolves. The upper half of the chamber contains heat transfer oil, and the lower half contains aqueous solution. A glass viewing window clearly shows the oil-water interface. Two layers of screens are installed on the water side of the lower half. The screen with larger apertures (e.g., 5mm) near the oil side intercepts large ammonium sulfate particles encapsulated in the heat transfer oil. As the ammonium sulfate particles gradually dissolve, the oil droplets become smaller and float to the surface. The lower screen with smaller apertures (e.g., 0.2mm) collects small oil droplets mixed with ammonium sulfate in the aqueous solution. A device for cleaning oil droplets, such as a scraper with a brush, is installed on the screen. When a large number of oil droplets adhere to the screen, the scraper is activated to peel the small droplets off the screen surface, allowing them to float to the oil-water interface. The heat transfer oil used is a high-boiling-point, stable alkyl biphenyl type. The oil-water separation chamber of the vaporizer is connected to the crystallizer via a pipeline. Dissolved ammonium sulfate is sent to the crystallizer through the bottom of the separation chamber via a circulating solution. The vaporizer should be a closed system to prevent the leakage of vaporized ammonium sulfite and environmental pollution. The vaporizer and heater should be insulated, and the ammonium sulfite vaporization pipeline should be equipped with heat tracing to ensure that the ammonium sulfite vapor temperature is not lower than 100°C.

[0026] Baghouse dust collectors are used to collect ammonium sulfite and sulfuric acid solid particles from flue gas. Simultaneously, the ammonium sulfite solid particles adsorbed on the surface of the filter bags continue to react with remaining nitrogen oxides in the flue gas, generating ammonium sulfate particles. The mixer at the inlet of the baghouse dust collector is used to thoroughly mix the gasified ammonium sulfite with the flue gas; a combination of multi-point distribution and swirl flow can be used.

[0027] Specifically, the urea desulfurization system includes:

[0028] An induced draft fan is connected to the bag filter.

[0029] The desulfurization tower is connected to the induced draft fan;

[0030] A urea dissolving tank connected to the desulfurization tower, the desulfurization tower having a liquid outlet;

[0031] And a centrifugal separator, which is connected to the liquid outlet of the desulfurization tower and the gasifier, respectively.

[0032] The urea desulfurization system includes a desulfurization tower, a urea dissolving tank, a centrifugal separator, etc.

[0033] The desulfurization tower can be an absorption tower, which adopts countercurrent contact between gas and liquid. The flue gas flows from bottom to top, and the absorption solution flows from the top of the tower downwards, dispersed in the gas phase in droplets. In the absorption tower: the gas and liquid have sufficient contact time and area; the gas and liquid phases can be strongly disturbed; the operating range is wide; the operation is stable; the resistance is low; and it has sufficient mechanical strength and corrosion resistance.

[0034] The bottom of the desulfurization tower is connected to the circulating pump and the outlet pump. The tower employs a multi-layer spray system with pressure-type conical nozzles, providing a wide, uniform spray angle and reducing clogging. The absorbent is pumped into the nozzles via the circulating pump. A demister is located at the top of the tower and can be an integrated tubular dust and mist collector to reduce droplet carryover and lower sulfate content in the clean flue gas. The demister requires periodic flushing with process water. The flow rate is adjusted using a urea replenishment pump to control the pH of the desulfurization tower solution between 6 and 7.

[0035] A 30-40% urea solution is prepared in the urea dissolving tank.

[0036] As the desulfurization reaction continues, the concentration of ammonium sulfite in the desulfurization tower increases. When the ammonium sulfite in the desulfurization tower reaches supersaturation and the solid content is between 2-10%, the slurry can be further pumped into a hydrocyclone for preliminary separation, and then into a rotary drum centrifuge for liquid-solid separation. The filtrate is then returned to the desulfurization tower for recrystallization and growth.

[0037] Specifically:

[0038] The desulfurization tower has an absorbent spraying device;

[0039] The absorbent spraying device is connected to the urea dissolving tank.

[0040] Specifically, the desulfurization tower has an exhaust port, which is connected to the chimney.

[0041] Specifically:

[0042] The bag filter has a dust outlet at the bottom;

[0043] The dust outlet is connected to the gasifier.

[0044] Specifically:

[0045] The vaporizer is equipped with a stirrer;

[0046] The vaporizer has an inverted conical bottom.

[0047] Further:

[0048] The bottom of the vaporizer is connected to an oil-water separation chamber;

[0049] The upper part of the oil-water separation chamber has an oil-water separation zone;

[0050] A large oil droplet collection net is installed in the middle of the oil-water separation chamber;

[0051] The lower part of the oil-water separation chamber is equipped with a small oil droplet collection net.

[0052] Furthermore: the oil-water separation chamber is connected to a crystallizer via a circulation pipeline, and the crystallizer is connected to a centrifuge.

[0053] The crystallizer can be in the form of a guide tube, and the agitator uses an axial flow multi-stage blade design. The size of the crystal particles is controlled according to the agitator speed. The crystallizer is equipped with a steam heater and a circulating pump to ensure that the water side temperature in the oil-water separation chamber is 80-90℃, promoting the rapid dissolution of ammonium sulfate. When ammonium sulfate continuously enters the crystallizer and reaches supersaturation, crystallization begins. After the crystal particles grow by adjusting the agitator speed, they are sent to a hydrocyclone for preliminary separation by a discharge pump, and then enter a rotary drum centrifuge for liquid-solid separation. The filtrate is then returned to the crystallizer for further crystallization and growth.

[0054] Specifically:

[0055] The bag filter dust collector includes several dust collector units;

[0056] The inlet of each dust collector unit is connected to a flue gas inlet pipe;

[0057] The outlet of each dust collector unit is connected to a flue gas outlet pipe;

[0058] The back-blowing port of each of the dust collector units is connected to a back-blowing air fan;

[0059] Each pair of adjacent dust collector units is connected through a backflushing port.

[0060] In the aforementioned technical approach, the baghouse dust collector consists of several units. To minimize the impact of bag backflushing on the system's denitrification process, the number of units is preferably greater than 10. Each unit contains several filter bags, and the inlets of each unit are interconnected, while the outlets can be individually isolated for isolation from the operating filter bags during backflushing. Each filter bag unit has a large-angle hopper and a star valve below for material storage and discharge. The filter bags utilize a telescopic spring frame, which allows for large deformation, facilitating the removal of particles adhering to the bag surface. The baghouse dust collector is equipped with a large bypass, which is opened during system startup and closed when the system temperature rises.

[0061] The filter bags can be made of polyester or polypropylene fibers to prevent acid corrosion and withstand temperatures up to 150℃. They should also have low water absorption and high air permeability. Use filter bags with a diameter of 200-300mm and a length of 8-10m to reduce the volume of the bag filter dust collector while ensuring that the air velocity filtered by the filter bags is 0.5-1m / min.

[0062] Specifically, the mixer is connected to the original flue gas pipe after dust removal.

[0063] Furthermore, the mixer is connected to the bag filter via a flue, and sulfur dioxide and nitrogen oxide analyzers, as well as temperature, pressure, and air volume meters are installed at the inlet and outlet of the bag filter.

[0064] Furthermore, the mixer is connected to the gasifier outlet, and the gasifier discharge port is connected to the crystallizer via a circulation pipe.

[0065] Furthermore, the outlet of the bag filter is connected to the inlet of the induced draft fan via a pipe, with temperature and pressure gauges installed in between. The material discharge port of the bag filter is connected to the feed port of the gasifier.

[0066] Furthermore, the outlet of the induced draft fan is connected to the inlet pipe of the desulfurization tower via a flue, with temperature and pressure gauges installed in between. Sulfur dioxide and nitrogen oxide analyzers, as well as temperature, pressure, and airflow gauges, are installed at the outlet of the desulfurization tower.

[0067] Furthermore, the outlet of the desulfurization tower is connected to the flue via a flue.

[0068] Furthermore, the desulfurization tower is connected to a rotary drum centrifuge via a liquid outlet pipe, and the centrifuge's discharge pipe is connected to a gasifier.

[0069] Furthermore, the heaters of the gasifier and the crystallizer are connected to the steam pipeline via pipes, allowing the steam to heat the gasifier first and then the crystallizer, thereby improving steam utilization.

[0070] This utility model also discloses a semi-dry flue gas treatment method using ammonium sulfide generated from urea desulfurization for denitrification, comprising the following steps:

[0071] The gasified ammonium sulfide in the gasifier enters the mixer and reacts fully with the original flue gas after dust removal to generate ammonium sulfate particles. The ammonium sulfate particles enter the bag filter along with the flue gas.

[0072] Unreacted ammonium sulfite condenses into particles and reacts with nitrogen oxides in the original flue gas after dust removal, generating ammonium sulfate particles that adhere to the surface of the bag filter.

[0073] In the urea desulfurization system, urea is used to desulfurize the flue gas discharged from the bag filter, and the ammonium sulfide generated by desulfurization enters the gasifier.

[0074] Preferably, the upper heat transfer oil in the vaporizer is heated to 120-160°C.

[0075] Preferably, the lower layer of heat transfer oil is heated by heat conduction or by sinking ammonium sulfate to ensure that the temperature is 80-90°C.

[0076] The beneficial effects of this utility model are as follows:

[0077] Compared with traditional desulfurization and denitrification, this invention does not use a catalyst during denitrification, produces no wastewater, and is environmentally friendly and safe. The generated ammonium sulfate can be used in other industries. Compared with wet desulfurization, it has higher efficiency and the equipment is less prone to clogging. Attached Figure Description

[0078] Figure 1 This is a schematic diagram of the semi-dry flue gas treatment system for denitrification using ammonium sulfide generated from urea desulfurization, provided by this utility model.

[0079] Figure 2 This is a schematic diagram of an oil-water separation chamber.

[0080] Figure 3 This is a schematic diagram of a bag filter dust collector.

[0081] Appendix Figure 1 , 2 In section 3, the structures represented by each label are listed below:

[0082] 1. Gasifier; 2. Crystallizer; 3. Mixer; 4. Baghouse dust collector; 41. Dust collector unit; 42. Flue gas inlet pipe; 43. Flue gas outlet pipe; 44. Backflush air blower; 45. Backflush flow port; 5. Exhaust fan; 6. Centrifuge; 7. Desulfurization tower; 8. Urea dissolving tank; 9. Centrifuge; 10. Glass window. Detailed Implementation

[0083] The principles and features of this utility model are described below. The embodiments given are only used to explain this utility model and are not intended to limit the scope of this utility model.

[0084] Unless otherwise specified, the test methods used in the embodiments are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0085] Example 1

[0086] like Figure 1 As shown, the semi-dry flue gas treatment system utilizing ammonium sulfide generated from urea desulfurization for denitrification includes: a mixer 3, a bag filter 4, and a gasifier 1. The mixer 3 and the bag filter 4 are connected in sequence. The gasifier 1 is connected to the mixer 3. The urea desulfurization system is connected to the gasifier 1.

[0087] The heat transfer oil in the gasifier is kept at a certain level and heated to 120-160℃. After the ammonium sulfate and ammonium sulfide particles enter the gasifier, part of the ammonium sulfide is vaporized on the surface of the high-temperature heat transfer oil and the other part is decomposed into ammonia and sulfur dioxide, which enter the flue gas mixer together for denitrification reaction. The ammonium sulfate sinks into the oil-water separation chamber at the bottom of the gasifier and dissolves, thus achieving the separation of ammonium sulfate and ammonium sulfide.

[0088] After gasification, ammonium sulfite reacts with nitrogen oxides in the flue gas to produce ammonium sulfate solid particles and gasified ammonium sulfite crystalline particles. These particles enter the bag filter along with the flue gas. The ammonium sulfite solid particles are adsorbed on the surface of the filter bags and continue to react with nitrogen oxides in the flue gas passing through the bags to produce ammonium sulfate particles. When the pressure difference of the filter bags increases, the filter bags are backflushed for unloading.

[0089] In the urea desulfurization system, desulfurization is carried out by urea solution. When the generated ammonium sulfite solution reaches supersaturation and the solid content reaches 2-10%, it can be further sent to a centrifuge for liquid-solid separation. The generated ammonium sulfite can enter the gasifier for denitrification.

[0090] Example 2

[0091] Based on Example 1, such as Figure 1 , 3 As shown, the baghouse dust collector includes several dust collector units 41. The inlet of each dust collector unit 41 is connected to the flue gas inlet pipe 42. The outlet of each dust collector unit 41 is connected to the flue gas outlet pipe 43. The back-blowing port of each dust collector unit 41 is connected to the back-blowing fan 44. Each pair of adjacent dust collector units 41 are connected through a back-blowing flow port 45. The bottom of the baghouse dust collector 41 has a dust outlet. The dust outlet is connected to the gasifier 1. Based on this technical solution, inside the baghouse dust collector, ammonium sulfide solid particles are adsorbed on the surface of the filter bags and continue to react with nitrogen oxides in the flue gas passing through the filter bags. The resulting ammonium sulfate particles, when the pressure difference of the filter bags increases, cause back-blowing and unloading of the filter bags.

[0092] Example 3

[0093] Based on Example 1, such as Figure 1 As shown, the urea desulfurization system includes: an induced draft fan 5, a desulfurization tower 7, a urea dissolving tank 8, and a centrifugal separator 6. The induced draft fan 5 is connected to a bag filter 4. The desulfurization tower 7 has a liquid outlet, an absorbent spray device, and an exhaust outlet. The desulfurization tower 7 is connected to the induced draft fan 5. The absorbent spray device is connected to the urea dissolving tank 8. The exhaust outlet of the desulfurization tower 7 is connected to a chimney. The centrifugal separator 6 is connected to both the liquid outlet of the desulfurization tower 7 and the gasifier 1. Based on this technical solution, the ammonium sulfide generated by desulfurization through the urea solution can be fed into the gasifier for denitrification.

[0094] Example 4

[0095] Based on Example 1, such as Figure 1 As shown, a stirrer is installed inside the vaporizer 1, and it adopts an inverted conical bottom. An oil-water separation chamber is connected to the bottom of the vaporizer 1. The upper part of the oil-water separation chamber has an oil-water separation zone. A large oil droplet collecting net is installed in the middle of the oil-water separation chamber. A small oil droplet collecting net is installed in the lower part of the oil-water separation chamber. A glass viewing window 10 may be installed in the oil-water separation chamber. Figure 2As shown, an oil-water separation interface, a large oil droplet trapping layer, and a small oil droplet trapping layer are formed sequentially from top to bottom. Based on this technical solution, the oil-water separation chamber of the gasifier is connected to the crystallizer via a pipeline, and the dissolved ammonium sulfate can be sent to the crystallizer through the bottom of the separation chamber via a circulating solution.

[0096] Example 5

[0097] Based on Example 1, such as Figure 1 As shown, the oil-water separation chamber is connected to crystallizer 2 via a circulation pipeline, and crystallizer 2 is connected to centrifuge 9. Ammonium sulfate particles continuously enter the crystallizer from the vaporizer. When the ammonium sulfate solution reaches supersaturation, the ammonium sulfate particles in the slurry continuously grow in the crystallizer, and then liquid-solid separation can be performed.

[0098] Example 1

[0099] The semi-dry flue gas treatment method using ammonium sulfide generated from urea desulfurization for denitrification is implemented according to the following steps:

[0100] 1. After the system is ready, prepare a 30-40% urea solution in the urea dissolving tank, and send a certain level of urea solution into the desulfurization tower to ensure that the liquid level is sufficient for circulation. Then start the desulfurization circulation pump to start the absorption liquid circulation.

[0101] 2. Start the induced draft fan to draw in the flue gas for system heating, open the bypass valve of the bag filter, and simultaneously adjust the system air volume and pressure to ensure the bag filter inlet negative pressure is -0.5 to -2 kPa. When the bag filter outlet temperature reaches 90℃, close the bag bypass valve and the bag filter will continue to heat up.

[0102] 3. When the pH of the absorbent in the desulfurization tower is 6-7 and the temperature is 60-70℃, crystal particles will precipitate when the ammonium sulfite solution in the tower is supersaturated. When the solid content reaches 10%, the desulfurization tower outlet pump is started to send slurry to the hydrocyclone. The supernatant of the hydrocyclone is returned to the desulfurization tower, and the slurry with high solid content in the lower part enters the centrifuge. After separation, the solid is sent to the gasifier for denitrification, and the filtrate is returned to the desulfurization tower for recrystallization.

[0103] 4. Start the agitator and steam heater inside the gasifier to raise the temperature of the heat transfer oil to between 140-160℃. Adjust the mass of ammonium sulfide entering the gasifier and regulate the nitrogen oxides at the outlet of the bag filter. Generally, the sulfur dioxide content in flue gas is much higher than that of nitrogen oxides, so the desulfurization product, ammonium sulfide, is more abundant than that required for denitrification. Therefore, the ammonium sulfide produced during desulfurization is excessive. Because the ammonium sulfide from the centrifuge has a low content and high moisture content (generally around 80% effective component), adding a high-moisture ammonium sulfide to the gasifier requires more steam for moisture evaporation; therefore, the steam input needs to be increased.

[0104] 5. Simultaneously, based on the bag pressure differential, when the bag pressure differential is between 1.0 and 2.0 kPa, start the bag filter back-flushing system. Back-flush each dust collector unit sequentially. During back-flushing, close the outlet valve of the dust collector unit, open the back-flushing air inlet valve, and start the bag filter back-flushing fan. The back-flushing time for each dust collector unit is set at 20-40 seconds. After the back-flushing of a dust collector unit is completed, close the back-flushing air inlet valve and open the outlet valve. Proceed to the next unit for back-flushing. After all back-flushing is completed, stop the back-flushing fan. Simultaneously, start the hopper star valve for unloading.

[0105] 6. The material collected by the bag filter is fed into the gasifier. Because the material collected by the bag filter contains ammonium sulfide and ammonium sulfate, and has a low moisture content, less steam is required during gasification. The mixture of ammonium sulfate and ammonium sulfide fed into the gasifier is separated and reused. The ammonium sulfate enters the oil-water separation chamber through the bottom of the gasifier and dissolves on the water side. At the same time, the flow rate of ammonium sulfide from the centrifugal separator outlet to the gasifier is adjusted.

[0106] 7. Start the agitator, heater, and circulating pump of the crystallizer to send the dissolved ammonium sulfate from the water side of the oil-water separation chamber into the crystallizer. As ammonium sulfate is continuously sent from the gasifier to the crystallizer, the ammonium sulfate particles continue to grow in the recrystallizer. When the solid content of the slurry reaches 10%, start the discharge pump to send the slurry to the centrifuge for solid-liquid separation. The filtrate is then returned to the crystallizer. The collected ammonium sulfate can be dried, packaged, and transported.

[0107] The parameters are as follows:

[0108] A 35% urea solution is prepared in the urea dissolving tank.

[0109] The heat transfer oil is heated to approximately 140°C (generally 120-160°C).

[0110] The composition of the original flue gas after dust removal: Nitric oxide: 200 mg / m³; Sulfur dioxide: 3000 mg.

[0111] The exhaust gas from the chimney meets emission standards, with low concentrations of nitrogen monoxide and sulfur dioxide: each below 20 mg.

[0112] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A semi-dry flue gas treatment system for denitration using sulfamine generated by desulfurization with urea, characterized by, At least comprising: a mixer (3) and a bag filter (4) which are sequentially connected; a gasifier (1) connected to the mixer (3); and a urea desulfurization system connected to the gasifier (1).

2. The semi-dry flue gas treatment system for denitration by sulfocarbamide generated by desulfurization using urea according to claim 1, characterized by, The urea desulfurization system comprises: an induced draft fan (5) connected to the bag filter (4); a desulfurization tower (7) connected to the induced draft fan (5); a urea dissolving tank (8) connected to the desulfurization tower (7), the desulfurization tower (7) having a liquid outlet; and a centrifugal separator (6) connected to the liquid outlet of the desulfurization tower (7) and the gasifier (1) respectively.

3. The semi-dry flue gas treatment system for sulfamine denitration generated by urea desulfurization according to claim 2, characterized in that: the desulfurization tower (7) has an absorption liquid spraying device; the absorption liquid spraying device is connected to the urea dissolving tank (8).

4. The semi-dry flue gas treatment system for sulfamine denitration generated by urea desulfurization according to claim 2, characterized in that: the desulfurization tower (7) has an exhaust port; the exhaust port of the desulfurization tower (7) is connected to a chimney.

5. The semi-dry flue gas treatment system for sulfamine denitration generated by urea desulfurization according to claim 1, characterized in that: the bag filter (4) has a dust outlet at the bottom; the dust outlet is connected to the gasifier (1).

6. The semi-dry flue gas treatment system for sulfamine denitration generated by urea desulfurization according to claim 1, characterized in that: the gasifier (1) is provided with a stirrer; the gasifier (1) adopts an inverted conical bottom.

7. The semi-dry flue gas treatment system for sulfamine denitration generated by urea desulfurization according to claim 6, characterized in that: the bottom of the gasifier (1) is provided with an oil-water separation chamber; the upper part of the oil-water separation chamber has an oil-water separation area; the middle part of the oil-water separation chamber is provided with a large oil droplet trapping net; the lower part of the oil-water separation chamber is provided with a small oil droplet trapping net.

8. The semi-dry flue gas treatment system for desulphurization using urea and denitrification using sulphuretted ammonia according to claim 7, characterized in that: The oil-water separation chamber is connected to a crystallizer (2) through a circulation pipeline, and the crystallizer (2) is connected to a centrifugal separator (9).

9. The semi-dry flue gas treatment system for sulfamine denitration generated by urea desulfurization according to any one of claims 1 to 8, characterized in that: the bag filter (4) comprises a plurality of filter units (41); the inlet of each filter unit (41) is connected to a flue gas inlet pipe (42); the outlet of each filter unit (41) is connected to a flue gas outlet pipe (43); the blowback port of each filter unit (41) is connected to a blowback air fan (44); each two adjacent filter units (41) are connected through a blowback flow passage (45).

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