Flue gas denitration system

Abstract

The utility model discloses a flue gas denitration system, ammonia gas generation and injection unit and ammonia adsorption-desorption-reuse system, ammonia gas generation and injection unit is connected to the high temperature section of boiler, ammonia adsorption-desorption-reuse system is connected between desulfurization tower and chimney. The ammonia gas generation and injection system injects excessive ammonia gas into high-temperature flue gas, nitrogen oxide is reduced into nitrogen and water, the ultralow emission requirement is met, unreacted ammonia gas is adsorbed and purified through the escaping ammonia adsorption-desorption-recovery system at the tail end and recovered to the ammonia gas injection system for reuse, and it is guaranteed that chimney emission is safe and environmentally friendly. Based on the SNCR system, ultralow emission of nitrogen oxide and closed-loop operation of a reducing agent are realized, one-time investment and operation cost is low, the problem of conventional ammonia escape pollution is solved, and the system is economical and environment-friendly.

Description

Technical Field

[0001] The utility model belongs to the technical field of industrial flue gas purification, and particularly relates to a flue gas denitrification system. Background Art

[0002] With the deepening of air pollution control in my country, ultra-low emission transformation of industrial flue gas has been gradually extended from the power industry to non-power industries such as steel and cement. x ) As one of the main pollutants in industrial flue gas, its ultra-low emission control faces challenges such as complex technology, wide scope of transformation, and high cost pressure.

[0003] The current mainstream flue gas denitrification technologies include:

[0004] SCR (Selective Catalytic Reduction): High denitrification efficiency (>90%), but high investment and operating costs, and strict requirements on the catalyst activity temperature window (300~400℃).

[0005] SNCR (Selective Non-Catalytic Reduction): The equipment is simple and the cost is low, but the denitrification efficiency is low (30%~70%). If the efficiency is forcibly increased, excessive ammonia injection is required, resulting in excessive ammonia escape and waste of reducing agent.

[0006] Other technologies (ozone oxidation, wet absorption, activated carbon method, etc.): There are problems such as difficult by-product treatment, high energy consumption or limited applicable scenarios, making it difficult to promote on a large scale.

[0007] To meet NO x To meet ultra-low emission requirements (≤50 mg / m³), the industry currently generally adopts SCR or SNCR+SCR combined technology, but the following problems still exist: the cost of SCR catalyst replacement and ammonia consumption is high, which is difficult for small and medium-sized enterprises to afford; SNCR efficiency improvement relies on excessive ammonia injection, which causes ammonia escape and secondary pollution; insufficient adaptability: the flue gas composition of non-power industries is complex (such as high dust and sulfur), the temperature fluctuates greatly, and the traditional technology has poor stability. Utility Model Content

[0008] The utility model aims to provide a flue gas denitrification system, which can achieve ultra-low emissions of nitrogen oxides based on SNCR and can control the emission of escaped ammonia to meet the emission standards.

[0009] The technical solution adopted by the present invention is that the flue gas denitrification system includes an ammonia generation and injection unit and an ammonia adsorption-desorption-recycling system. The ammonia generation and injection unit is connected to the high-temperature section of the boiler, and the ammonia adsorption-desorption-recycling system is connected between the desulfurization tower and the chimney.

[0010] The utility model is also characterized in that:

[0011] The ammonia adsorption-desorption-recycling system includes a escaping ammonia adsorption tower and a desorption regeneration tower;

[0012] A silo pump is installed at the bottom of the escaped ammonia adsorption tower, which is connected to the top of the desorption regeneration tower through a pipeline, and the bottom of the desorption regeneration tower is connected to the top of the escaped ammonia adsorption tower through a pipeline.

[0013] An ammonia outlet is provided at the top of the desorption regeneration tower, and the ammonia outlet is connected to an ammonia generation and injection unit.

[0014] The desorption regeneration tower is equipped with a microwave generator.

[0015] The escape ammonia adsorption tower is filled with ammonia adsorbent.

[0016] The ammonia adsorbent is Cu-Fe modified zeolite, Y-type molecular sieve or copper Prussian blue particles.

[0017] The temperature in the high temperature section is 900-1050℃.

[0018] A flue gas online monitoring system CEMS is installed on the chimney. The flue gas online monitoring system CEMS is associated with the control system of the ammonia generation and injection unit and is used to control the ammonia injection amount.

[0019] The beneficial effects of the utility model are:

[0020] The utility model realizes ultra-low emission of nitrogen oxides based on SNCR, and the excess ammonia injected is adsorbed and purified by the escape ammonia adsorption recovery system at the end and recovered to the injection system for reuse, thereby ensuring the safety and environmental protection of chimney emissions, and at the same time realizing the closed-loop use of ammonia, saving costs, and solving the system problems that the current ultra-low emission transformation must adopt SCR flue gas denitrification technology, resulting in high investment and operating costs, which are difficult for enterprises to bear, and secondary pollution of waste catalysts, and also solves the technical difficulties of economical and efficient adsorption-desorption and reuse of escape ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a process flow chart of the utility model;

[0022] In the figure: 1. Ammonia generation and injection unit, 2. Boiler, 3. Dust collector, 4. Desulfurization tower, 5. Escape ammonia adsorption tower, 6. Ammonia adsorbent, 7. Desorption and regeneration tower, 8. Microwave generator, 9. Silo pump, 10. Fan, 11. Chimney, 12. Flue gas online monitoring system CEMS. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0024] Example 1

[0025] A flue gas denitrification system, such as Figure 1 As shown, the system includes an ammonia generation and injection unit 1 and an ammonia adsorption-desorption-recycling system. The ammonia generation and injection unit 1 is connected to the high-temperature section of a boiler 2. The outlet of the boiler 2 is connected to a dust collector 3, a desulfurization tower 4, and a chimney 11 via pipelines. The ammonia adsorption-desorption-recycling system is connected between the desulfurization tower 4 and the chimney 11. This system uses the SNCR process to achieve ultra-low nitrogen oxide emissions.

[0026] Urea, ammonia water or ammonia gas is used as a reducing agent in the ammonia generation and injection unit 1, and the reducing agent is evenly sprayed into the boiler 2 to mix and react with the flue gas, thereby reducing nitrogen oxides (NO x ) is reduced to nitrogen and water to meet ultra-low emission requirements. During use, the urea raw material is diluted with water to form a urea solution, which is then pumped into a compressed air atomizer via a metering pump for atomization. The atomized urea solution is then evenly sprayed into the high-temperature flue gas area of ​​900-1050°C within boiler 2. Alternatively, 20%-25% ammonia water can be diluted to an appropriate concentration, metered, and then atomized and sprayed. Alternatively, liquid ammonia can be directly evaporated, diluted with air, and metered before evenly spraying.

[0027] The flue gas after the denitrification reaction is sequentially passed through the dust collector 3 for dust removal and the desulfurization tower 4 for sulfur oxide purification before entering the ammonia adsorption-desorption-recycling system to recover the excess ammonia gas and discharge it.

[0028] Example 2

[0029] A flue gas denitrification system, such as Figure 1 As shown, the system includes an ammonia generation and injection unit 1 and an ammonia adsorption-desorption-recycling system. The ammonia generation and injection unit 1 is connected to the high-temperature section of a boiler 2. The outlet of the boiler 2 is connected to a dust collector 3, a desulfurization tower 4, and a chimney 11 via pipelines. The ammonia adsorption-desorption-recycling system is connected between the desulfurization tower 4 and the chimney 11. This system uses the SNCR process to achieve ultra-low nitrogen oxide emissions.

[0030] Urea, ammonia water or ammonia gas is used as a reducing agent in the ammonia generation and injection unit 1, and the reducing agent is evenly sprayed into the boiler 2 to mix and react with the flue gas, thereby reducing nitrogen oxides (NO x ) is reduced to nitrogen and water to meet ultra-low emission requirements. During use, the urea raw material is diluted with water to form a urea solution, which is then pumped into a compressed air atomizer via a metering pump for atomization. The atomized urea solution is then evenly sprayed into the high-temperature flue gas area of ​​900-1050°C within boiler 2. Alternatively, 20%-25% ammonia water can be diluted to an appropriate concentration, metered, and then atomized and sprayed. Alternatively, liquid ammonia can be directly evaporated, diluted with air, and metered before evenly spraying.

[0031] The flue gas after the denitrification reaction is sequentially passed through the dust collector 3 for dust removal and the desulfurization tower 4 for sulfur oxide purification before entering the ammonia adsorption-desorption-recycling system to recover the excess ammonia gas and discharge it.

[0032] The ammonia adsorption-desorption-recycling system includes a fugitive ammonia adsorption tower 5 and a desorption regeneration tower 7. The fugitive ammonia adsorption tower 5 is connected between the desulfurization tower 4 and the chimney 11. The desorption regeneration tower 7 is connected to the fugitive ammonia adsorption tower 5 through a pipeline. The fugitive ammonia adsorption tower 5 is filled with ammonia adsorbent 6 and operates at a space velocity of 1000-3000h -1 The flue gas purified by the desulfurization tower 4 enters the escaped ammonia adsorption tower 5. Excess escaped ammonia in the flue gas is adsorbed and purified by the ammonia adsorbent 6 and then sent to the chimney 11 by the fan 10 for discharge. The desorption regeneration tower 7 is used to desorb the ammonia adsorbed in the ammonia adsorbent 6.

[0033] Example 3

[0034] A flue gas denitrification system, such as Figure 1 As shown, the system includes an ammonia generation and injection unit 1 and an ammonia adsorption-desorption-recycling system. The ammonia generation and injection unit 1 is connected to the high-temperature section of a boiler 2. The outlet of the boiler 2 is connected to a dust collector 3, a desulfurization tower 4, and a chimney 11 via pipelines. The ammonia adsorption-desorption-recycling system is connected between the desulfurization tower 4 and the chimney 11. This system uses the SNCR process to achieve ultra-low nitrogen oxide emissions.

[0035] Urea, ammonia water or ammonia gas is used as a reducing agent in the ammonia generation and injection unit 1, and the reducing agent is evenly sprayed into the boiler 2 to mix and react with the flue gas, thereby reducing nitrogen oxides (NO x ) is reduced to nitrogen and water to meet ultra-low emission requirements. During use, the urea raw material is diluted with water to form a urea solution, which is then pumped into a compressed air atomizer via a metering pump for atomization. The atomized urea solution is then evenly sprayed into the high-temperature flue gas area of ​​900-1050°C within boiler 2. Alternatively, 20%-25% ammonia water can be diluted to an appropriate concentration, metered, and then atomized and sprayed. Alternatively, liquid ammonia can be directly evaporated, diluted with air, and metered before evenly spraying.

[0036] The flue gas after the denitrification reaction is sequentially passed through the dust collector 3 for dust removal and the desulfurization tower 4 for sulfur oxide purification before entering the ammonia adsorption-desorption-recycling system to recover the excess ammonia gas and discharge it.

[0037] The ammonia adsorption-desorption-recycling system includes a fugitive ammonia adsorption tower 5 and a desorption regeneration tower 7. The fugitive ammonia adsorption tower 5 is connected between the desulfurization tower 4 and the chimney 11. The fugitive ammonia adsorption tower 5 is filled with an ammonia adsorbent 6 and operates at a space velocity of 1000-3000h -1The flue gas purified by the desulfurization tower 4 enters the escaped ammonia adsorption tower 5. The excess escaped ammonia in the flue gas is adsorbed and purified by the ammonia adsorbent 6 and then sent to the chimney 11 by the fan 10 for emptying. A silo pump 9 is installed at the bottom of the desorption and regeneration tower 7. The silo pump 9 is connected to the top of the desorption and regeneration tower 7. The bottom of the desorption and regeneration tower 7 is connected to the top of the escaped ammonia adsorption tower 5. When the ammonia adsorbent 6 in the escaped ammonia adsorption tower 5 gradually approaches adsorption saturation, the silo pump 9 is turned on to gradually transfer the ammonia adsorbent 6 from the bottom of the escaped ammonia adsorption tower 5 to the top of the desorption and regeneration tower 7. At the same time, the ammonia adsorbent 6 in the desorption and regeneration tower 7 that has completed desorption and regeneration is transferred from the bottom to the top of the escaped ammonia adsorption tower 5 for replacement use.

[0038] Both the escape ammonia adsorption tower 5 and the desorption regeneration tower 7 adopt a moving bed structure.

[0039] Example 4

[0040] A flue gas denitrification system, such as Figure 1 As shown, the system includes an ammonia generation and injection unit 1 and an ammonia adsorption-desorption-recycling system. The ammonia generation and injection unit 1 is connected to the high-temperature section of a boiler 2. The outlet of the boiler 2 is connected to a dust collector 3, a desulfurization tower 4, and a chimney 11 via pipelines. The ammonia adsorption-desorption-recycling system is connected between the desulfurization tower 4 and the chimney 11. This system uses the SNCR process to achieve ultra-low nitrogen oxide emissions.

[0041] Urea, ammonia water or ammonia gas is used as a reducing agent in the ammonia generation and injection unit 1, and the reducing agent is evenly sprayed into the boiler 2 to mix and react with the flue gas, thereby reducing nitrogen oxides (NO x ) is reduced to nitrogen and water to meet ultra-low emission requirements. During use, the urea raw material is diluted with water to form a urea solution, which is then pumped into a compressed air atomizer via a metering pump for atomization. The atomized urea solution is then evenly sprayed into the high-temperature flue gas area of ​​900-1050°C within boiler 2. Alternatively, 20%-25% ammonia water can be diluted to an appropriate concentration, metered, and then atomized and sprayed. Alternatively, liquid ammonia can be directly evaporated, diluted with air, and metered before evenly spraying.

[0042] The flue gas after the denitrification reaction is sequentially passed through the dust collector 3 for dust removal and the desulfurization tower 4 for sulfur oxide purification before entering the ammonia adsorption-desorption-recycling system to recover the excess ammonia gas and discharge it.

[0043] The ammonia adsorption-desorption-recycling system includes a fugitive ammonia adsorption tower 5 and a desorption regeneration tower 7. The fugitive ammonia adsorption tower 5 is connected between the desulfurization tower 4 and the chimney 11. The fugitive ammonia adsorption tower 5 is filled with an ammonia adsorbent 6 and operates at a space velocity of 1000-3000h -1The flue gas purified by the desulfurization tower 4 enters the escaped ammonia adsorption tower 5. The excess escaped ammonia in the flue gas is adsorbed and purified by the ammonia adsorbent 6 and then sent to the chimney 11 by the fan 10 for emptying. A silo pump 9 is installed at the bottom of the desorption and regeneration tower 7. The silo pump 9 is connected to the top of the desorption and regeneration tower 7. The bottom of the desorption and regeneration tower 7 is connected to the top of the escaped ammonia adsorption tower 5. When the ammonia adsorbent 6 in the escaped ammonia adsorption tower 5 gradually approaches adsorption saturation, the silo pump 9 is turned on to gradually transfer the ammonia adsorbent 6 from the bottom of the escaped ammonia adsorption tower 5 to the top of the desorption and regeneration tower 7. At the same time, the ammonia adsorbent 6 in the desorption and regeneration tower 7 that has completed desorption and regeneration is transferred from the bottom to the top of the escaped ammonia adsorption tower 5 for replacement use. A microwave generator 8 is installed in the desorption and regeneration tower 7. After the ammonia adsorbent 6 is transported into the desorption and regeneration tower 7, the microwave generator 8 generates microwaves for desorption and regeneration. The desorption temperature is 240-380°C. The desorbed ammonia gas is transported from the top of the desorption and regeneration tower 7 through a pipeline to the ammonia generation and injection unit 1 for recovery and reuse.

[0044] Example 5

[0045] On the basis of Example 4, the ammonia adsorbent 6 in this example is Y-type molecular sieve, Cu-Fe modified zeolite or copper Prussian blue particles.

[0046] The preparation method of Cu-Fe modified zeolite is as follows: when the solid-liquid ratio is 1:5, natural zeolite is mixed with CuCl2 and FeCl2 solutions with a mass concentration of 15%, stirred and immersed at 25°C for 24 hours, washed with clean water for 5 minutes, and dried at 105°C for 12 hours.

[0047] Example 6

[0048] On the basis of Example 5, in this embodiment, a flue gas online monitoring system CEMS12 is installed at the chimney 11 outlet. The flue gas online monitoring system CEMS12 is associated with the control system in the ammonia generation and injection unit 1 and is used to control the ammonia injection amount. The flue gas online monitoring system CEMS12 detects the NO in the chimney 11 in real time. x The emission concentration is fed back to the ammonia generation and injection unit 1 to regulate the amount of reducing agent injection to ensure NO x Ultra-low emissions.

[0049] The working process of the utility model system is as follows: the ammonia generation and injection unit 1 injects excess reducing agent ammonia into the high temperature flue gas section (900-1050℃) in the boiler 2, and the ammonia reacts with NO in the flue gas. x The reaction generates nitrogen and water to reach NO xTo meet the ultra-low emission requirements, unreacted ammonia is removed along with the flue gas through the dust collector 3 and the desulfurization tower 4, and then enters the escaped ammonia adsorption tower 5, where it is adsorbed and removed by the ammonia adsorbent 6 filled inside. The purified flue gas is sent to the chimney 11 for discharge through the fan 10. The saturated ammonia adsorbent 6 is transported to the desorption and regeneration tower 7, where microwaves are injected through the microwave generator 8. The adsorbed and fixed ammonia is desorbed and recovered and sent to the ammonia generation and injection unit 1 for reuse. While the saturated ammonia adsorbent 6 is being transported to the desorption and regeneration tower 7, the fresh ammonia adsorbent 6 that has completed desorption and regeneration in the desorption and regeneration tower 7 is transported to the escaped ammonia adsorption tower 5 for escaped ammonia adsorption. The ammonia adsorbent 6 is continuously moved between the escaped ammonia adsorption tower 5 and the desorption and regeneration tower 7 via the silo pump 9.

[0050] Example 7

[0051] The system of Example 6 was used to test the flue gas generated by boiler 2 at a temperature of 20×10 4 m 3 / h, flue gas temperature 142℃, NO concentration in flue gas 240mg / m 3 The ammonia generation and injection unit 1 evenly sprays the reducing agent ammonia into the 950-1000℃ flue gas temperature range of the boiler 2 until the flue gas online monitoring system CEMS measures NO x The concentration is 42 mg / m 3 , meeting the ultra-low emission requirements of nitrogen oxides, at this time, the escape ammonia adsorption tower 5 is filled with modified zeolite ammonia adsorbent 6, and the operating space velocity is 1400h -1 The flue gas online monitoring system CEMS measured the chimney escape ammonia concentration to be 0.8ppm.

[0052] Example 8

[0053] The system of Example 6 was used to test the flue gas generated by boiler 2 at a temperature of 16×10 4 m 3 / h, flue gas temperature 120℃, NO concentration in flue gas 430mg / m 3 The ammonia generation and injection unit 1 evenly sprays the reducing agent ammonia into the 950-1000℃ flue gas temperature range of the boiler 2 until the flue gas online monitoring system CEMS measures NO x Concentration is 45mg / m 3 , meeting the ultra-low emission requirements of nitrogen oxides, at this time, the escape ammonia adsorption tower 5 is filled with modified zeolite ammonia adsorbent 6, and the operating space velocity is 1200h -1 The flue gas online monitoring system CEMS measured the chimney escape ammonia concentration to be 0.6ppm.

[0054] Example 9

[0055] The system of Example 6 was used to test the flue gas generated by boiler 2 at a rate of 10×104 m 3 / h, flue gas temperature 165℃, NO concentration in flue gas 360mg / m 3 The ammonia generation and injection unit 1 evenly sprays the reducing agent ammonia into the flue gas temperature range of 1000-1050℃ in the boiler 2 until the flue gas online monitoring system CEMS measures NO x The concentration is 38 mg / m 3 , meeting the ultra-low emission requirements of nitrogen oxides, at this time, the escape ammonia adsorption tower 5 is filled with resin ammonia adsorbent 6, and the operating space velocity is 1000h -1 The flue gas online monitoring system CEMS measured the chimney escape ammonia concentration to be 0.5ppm.

[0056] The utility model reduces nitrogen oxides in the flue gas into nitrogen and water by injecting excess ammonia into high-temperature flue gas, thereby achieving ultra-low emission requirements. The unreacted ammonia is adsorbed and purified by the escaped ammonia adsorption recovery system at the end and recovered to the injection system for reuse, ensuring chimney emissions are safe and environmentally friendly. At the same time, closed-loop use of ammonia is achieved, saving costs. This solves the system problems that the current ultra-low emission transformation must adopt SCR flue gas denitrification technology, resulting in high investment and operating costs, which are difficult for enterprises to bear, and secondary pollution of exhaust gas catalysts. At the same time, it also solves the technical difficulties of economical and efficient adsorption-desorption and reuse of escaped ammonia.

[0057] The utility model is based on the SNCR denitrification method. Excessive reducing agent ammonia is sprayed into the high temperature flue gas section (900-1050℃). The ammonia reacts with NO in the flue gas. x The reaction generates nitrogen and water to reach NO x Ultra-low emission requirements. When the unreacted ammonia enters the escape ammonia adsorption tower installed after the desulfurization tower, it is adsorbed and removed by the ammonia adsorbent filled inside it, ensuring that the escape ammonia concentration in the exhaust gas meets the standard. The amount of ammonia injected is detected by the flue gas online monitoring system CEMS system installed in the chimney. x Concentration feedback control; escaped ammonia is subjected to adsorption-desorption-reuse closed-loop control. After the ammonia adsorbent in the ammonia escape adsorption tower is saturated, it is transferred to the desorption regeneration tower for microwave desorption. The desorbed ammonia is sent back to the front-end ammonia generation and injection unit for reuse, and the regenerated adsorbent is returned to the escaped ammonia adsorption tower for recycling.

Claims

1. Flue gas denitrification system, characterized in that: The invention comprises an ammonia generation and injection unit (1) and an ammonia adsorption-desorption-recycling system, wherein the ammonia generation and injection unit (1) is connected to the high-temperature section of the boiler (2), and the ammonia adsorption-desorption-recycling system is connected between the desulfurization tower (4) and the chimney (11); The ammonia adsorption-desorption-recycling system includes an escaped ammonia adsorption tower (5) and a desorption regeneration tower (7); A silo pump (9) is installed at the bottom of the escaped ammonia adsorption tower (5), and the silo pump (9) is connected to the top of the desorption regeneration tower (7) through a pipeline, and the bottom of the desorption regeneration tower (7) is connected to the top of the escaped ammonia adsorption tower (5) through a pipeline; The desorption regeneration tower (7) is provided with an ammonia outlet at the top, and the ammonia outlet is connected to the ammonia generation and injection unit (1); A microwave generator (8) is installed in the desorption regeneration tower (7).

2. The flue gas denitrification system according to claim 1, characterized in that: The escaped ammonia adsorption tower (5) is filled with an ammonia adsorbent (6).

3. The flue gas denitrification system according to claim 2, characterized in that: The ammonia adsorbent (6) is made of Cu-Fe modified zeolite, Y-type molecular sieve or copper Prussian blue particles.

4. The flue gas denitrification system according to claim 1, characterized in that: The temperature of the high temperature section is 900-1050°C.

5. The flue gas denitrification system according to claim 1, characterized in that: A flue gas online monitoring system CEMS (12) is installed on the chimney (11), and the flue gas online monitoring system CEMS (12) is associated with the control system of the ammonia generation and injection unit (1).

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