SCR (Selective Catalytic Reduction) denitration ammonia spraying device

Abstract

The utility model provides an SCR denitration ammonia spraying device. The SCR denitration ammonia spraying device comprises a flue, and an ammonia spraying grid, a catalytic bed layer and an air pre-heater are sequentially arranged in the flue from top to bottom; a first gas detector and a second gas detector are respectively arranged on two opposite sides above the ammonia spraying grid; a third gas detector and a fourth gas detector are respectively arranged on two opposite sides below the catalytic bed layer; ammonia gas inlets in the two opposite sides of the ammonia spraying grid are connected with an ammonia gas supply device, the ammonia gas inlet in one side of the ammonia spraying grid is connected with a first standby valve through a first main valve, and the ammonia gas inlet in the other side of the ammonia spraying grid is connected with a second standby valve through a second main valve. According to the device disclosed by the invention, the accurate and real-time regulation and control of the ammonia spraying amount are realized through the matched use of the equipment, and the defect that the denitration effect is poor or ammonia escapes due to the fact that the ammonia spraying amount is difficult to adjust accurately in time when flue gas components fluctuate in a traditional ammonia spraying mode is overcome.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of flue gas treatment, in particular to an ammonia injection device for SCR denitration. BACKGROUND

[0002] In order to meet the increasingly stringent emission limit value requirements of nitrogen oxides, more efficient flue gas denitration technology needs to be adopted. Selective catalytic reduction (SCR) denitration technology is widely used in the emission control of nitrogen oxides of fossil fuel power stations because it has the characteristics of high denitration efficiency (usually more than 90%), simple system operation and control, no secondary pollution, mature and reliable technology, etc. and is currently recognized as the most effective flue gas denitration technology at home and abroad. The SCR system sprays ammonia or other suitable reducing agents into the flue gas upstream of the catalyst, and uses the catalyst to convert NOx in the flue gas into nitrogen and water. In the usual design, liquid anhydrous ammonia or aqueous ammonia solution is used. First, the ammonia is evaporated, then mixed with dilution air or flue gas, and finally sprayed into the flue gas upstream of the SCR reactor through a distribution grid. In the SCR reactor, NO is converted to nitrogen by reacting with ammonia under the catalytic action of the catalyst, thereby achieving denitration. In order to improve the deteriorating ecological environment, the Ministry of Environmental Protection and other three ministries and commissions issued the "Work Plan for the Comprehensive Implementation of Ultra-Low Emission and Energy Saving Reform of Coal-Fired Power Plants", which clearly requires that ultra-low emission should be achieved, and the NOx emission standard should not be higher than 50 mg / m 3 .

[0003] Due to the objective reasons such as the inability to use the design coal type in the ultra-low emission reform of thermal power units, the content of nitrogen oxides at the inlet of the boiler SCR fluctuates sharply, and the NOx emission is high during the deep peak regulation of the thermal power unit. The ammonia injection device is difficult to accurately control the ammonia injection amount in time, and in order to meet the environmental protection examination requirements, an excessive amount of reducing agent is sprayed to solve the problem of high NOx emission. It can be seen that this method cannot accurately adjust the ammonia injection amount in time, which will cause the problems of poor denitration effect or ammonia escape. CONTENT OF THE UTILITY MODEL

[0004] The application provides an ammonia injection device for SCR denitration, which is used to solve the problem of poor denitration effect or ammonia escape caused by the difficulty in accurately adjusting the ammonia injection amount in time when the composition of flue gas fluctuates in the SCR denitration process.

[0005] The application provides an ammonia injection device for SCR denitration, which comprises a flue, and a ammonia injection grid, a catalytic bed and an air preheater are sequentially arranged in the flue from top to bottom.

[0006] The gas output end of the air preheater is connected with an ammonia gas supply device.

[0007] First and second gas detectors are respectively arranged on the opposite sides above the ammonia injection grid.

[0008] The third gas detector and the fourth gas detector are respectively arranged on opposite sides below the catalytic bed;

[0009] The first gas detector and the second gas detector correspond to the third gas detector and the fourth gas detector in the vertical direction;

[0010] The ammonia gas inlets on opposite sides of the ammonia injection grid are respectively connected with the ammonia gas supply device, the ammonia gas inlets on one side of the ammonia injection grid are respectively connected through the first main valve and the first standby valve, and the ammonia gas inlets on the other side of the ammonia injection grid are respectively connected through the second main valve and the second standby valve.

[0011] Optionally, the first gas detector, the second gas detector, the third gas detector, the fourth gas detector, the first main valve, the first standby valve, the second main valve and the second standby valve are electrically connected with the controller.

[0012] Optionally, a spoiler is arranged between the ammonia injection grid and the catalytic bed.

[0013] Optionally, the spoiler comprises a spoiler body, a plurality of first leaf fans are uniformly arranged in the spoiler body, and the rotation axis of the first leaf fan is parallel to the flue gas flow direction.

[0014] A plurality of second leaf fans are arranged between adjacent first leaf fans, the rotation axis of the second leaf fan is perpendicular to the flue gas flow direction, and the second leaf fan is a straight-leaf type leaf fan.

[0015] Optionally, the ammonia gas supply device comprises a urea solution storage tank, a liquid transfer pump, a urea decomposition tank and a mixer which are connected in sequence.

[0016] The steam input end of the urea decomposition tank is connected with a steam pipeline, and the material input end of the urea decomposition tank is connected with the liquid transfer pump and a catalyst storage tank.

[0017] The mixer is connected with the gas output end of the air preheater.

[0018] Optionally, a heat exchanger is arranged between the liquid transfer pump and the urea decomposition tank.

[0019] The heat exchange medium input end of the heat exchanger is connected with the hydrophobic output end of the urea decomposition tank.

[0020] Optionally, the urea decomposition tank comprises a shell.

[0021] The top of the shell is provided with a decomposition gas outlet and a material liquid inlet.

[0022] A plurality of heat exchange pipes are arranged in the lower part of the shell, one end of the heat exchange pipe penetrates into the shell, is bent into a U shape and then penetrates out of the shell, one end of the heat exchange pipe is connected with the steam pipeline, and the other end is connected with the heat exchange medium input end of the heat exchanger.

[0023] The SCR denitration ammonia injection device provided by the application can effectively ensure the stability of ammonia injection by arranging ammonia injection input ends on both sides of the ammonia injection grid; meanwhile, gas detectors are arranged above the ammonia injection grid and below the catalytic bed to analyze the gas components in the flue gas, and the operator can adjust the opening of the valve in real time according to the gas detector to ensure the accuracy of the ammonia injection amount; meanwhile, a standby valve is arranged in parallel with each main valve, and the standby valve can be put into use when the main valve fails, so that the adverse consequences of the failure of the main valve and the inability to inject ammonia for denitration on the side can be avoided, and the stability of the equipment operation can be ensured; in addition, the main valves on both sides are arranged in parallel, and the components of the flue gas fluctuate within a certain value, so that when a valve on one side fails, the opening of the standby valve on the side can be adjusted in real time according to the opening of the valve on the other side and the data detected by the gas detector, so that the adjustment is convenient; the device adjusts the ammonia injection amount in the SCR denitration process by the cooperation of the above-mentioned equipment, can effectively control the ammonia injection amount more accurately according to the components of the flue gas, and overcomes the disadvantages of poor denitration effect or ammonia escape caused by the difficulty in timely adjusting the ammonia injection amount when the components of the flue gas fluctuate in the traditional ammonia injection mode. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0025] Figure 1 The schematic diagram of the SCR denitration ammonia injection device provided by an embodiment of the application;

[0026] Figure 2 The schematic diagram of the SCR denitration ammonia injection device provided by another embodiment of the application;

[0027] Figure 3 The structural schematic diagram of the spoiler provided by an embodiment of the application;

[0028] Figure 4 The schematic diagram of the SCR denitration ammonia injection device provided by still another embodiment of the application;

[0029] Figure 5 The schematic diagram of the SCR denitration ammonia injection device provided by still another embodiment of the application;

[0030] Figure 6 The structural schematic diagram of the urea decomposition tank provided by an embodiment of the application.

[0031] EXPLANATION OF REFERENCE NUMERALS

[0032] 1, flue; 2, ammonia supply device; 3, controller; 4, steam pipeline; 10, first gas detector; 11, ammonia injection grid; 12, catalytic bed; 13, air preheater; 14, spoiler; 20, second gas detector; 21, urea solution storage tank; 22, circulating pump; 23, urea decomposition tank; 24, mixer; 25, catalyst storage tank; 26, heat exchanger; 30, third gas detector; 40, fourth gas detector; 100, first main valve; 140, spoiler body; 141, first vane; 142, second vane; 200, first standby valve; 201, decomposition gas outlet; 202, feed liquid inlet; 231, shell; 232, heat exchange pipe; 300, second main valve; 400, second standby valve. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application is described clearly and completely below. Obviously, the described embodiments are some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor also belong to the scope of protection of the present application.

[0034] As shown in Figure 1 , the present application provides an SCR denitration ammonia injection device, which comprises a flue 1, wherein the flue 1 is sequentially provided with an ammonia injection grid 11, a catalytic bed 12 and an air preheater 13 from top to bottom;

[0035] The gas output end of the air preheater 13 is connected with an ammonia supply device 2;

[0036] The opposite sides above the ammonia injection grid 11 are respectively provided with a first gas detector 10 and a second gas detector 20;

[0037] The opposite sides below the catalytic bed 12 are respectively provided with a third gas detector 30 and a fourth gas detector 40;

[0038] The first gas detector 10 and the second gas detector 20 correspond to the third gas detector 30 and the fourth gas detector 40 in the vertical direction;

[0039] The ammonia gas inlets on the opposite sides of the ammonia injection grid 11 are respectively connected with the ammonia supply device 2, the ammonia gas inlets on one side of the ammonia injection grid 11 are respectively connected through a first main valve 100 and a first standby valve 200, and the ammonia gas inlets on the other side of the ammonia injection grid 11 are respectively connected through a second main valve 300 and a second standby valve 400.

[0040] The device of the present application, in use, ammonia supplied by the ammonia supply device 2 passes through the first main valve 100 and the second main valve 300 into the ammonia injection grid 11 (the first standby valve 200 and the second standby valve 400 are in the closed state in normal operation), and is injected into the flue 1 from the ammonia gas input end on both sides of the ammonia injection grid 11.

[0041] At the same time, the flue gas discharged from the boiler enters the area where the ammonia injection device is located after heat exchange treatment by the previous equipment (such as an economizer, etc.) in the flue. When the flue gas passes through the first gas detector 10 and the second gas detector 20 in the flue, the detectors detect the content of nitrogen oxides in the flue gas and feed the data back to the corresponding analysis equipment. The operator adjusts the opening size of the first main valve 100 and the second main valve 300 in real time according to the data detected by the flue gas detectors on both sides, so as to avoid excessive ammonia injection causing ammonia escape or too little ammonia injection causing nitrogen oxides emission exceeding the standard. The ammonia gas injected from the ammonia injection grid 11 mixes with the flue gas and then enters the catalytic bed 12. Under the catalytic action of the catalyst (iron, vanadium, etc.) on the catalytic bed 12, the ammonia gas and the nitrogen oxides in the flue gas undergo oxidation-reduction reaction, and the nitrogen oxides are reacted to generate nitrogen gas, thereby achieving the purpose of ammonia removal. The flue gas after denitrification by the catalytic bed 12 continues to be discharged and passes through the third gas detector 30 and the fourth gas detector 40. The gas detectors detect the content of nitrogen oxides and ammonia in the flue gas in real time and feed the data back to the corresponding analysis equipment. The operator adjusts the opening of the valve according to the data fed back by the first gas detector 1, the second gas detector 20, the third gas detector 30 and the fourth gas detector 40, and further finely adjusts the ammonia injection amount after comprehensive judgment.

[0042] The discharged flue gas continues to move and exchanges heat with the air preheater 13 when passing through the air preheater 13, thereby heating the air in the air preheater 13. A part of the heated air is separated from the air preheater 13 and used in the ammonia supply device 2.

[0043] When the main valve on one side of the ammonia injection grid 11 needs to be repaired due to failure, the present application takes the repair of the first main valve 100 as an example. At this time, the first standby valve 200 is opened, and the first gas detector 10 and the second gas detector 20 detect the content of nitrogen oxides in the flue gas on both sides. When the content of nitrogen oxides detected by the gas detectors on both sides deviates by less than 100 mg / Nm 3 , the first standby valve 200 adjusts the ammonia injection amount according to the opening of the second main valve 300. When the content of nitrogen oxides at the inlet on both sides deviates by more than 100 mg / Nm 3 , the ammonia injection amount of the valve on this side (i.e. the first standby valve 200) is increased by 2% for each 100 mg / Nm 3 , until the adjustment and tracking are completed or the content of nitrogen oxides at the inlet on both sides is less than 100 mg / Nm3 That is, when the first main valve 100 fails and needs to be isolated for maintenance, the first standby valve 200 on the side mirrors the main road adjustment mode to control the ammonia injection amount and control the NOx content at the outlet on the side.

[0044] The SCR denitration ammonia injection device provided by the application can effectively ensure the stability of ammonia injection by arranging ammonia injection input ends on both sides of the ammonia injection grid 11, and can also ensure the accuracy of the ammonia injection amount by arranging gas detectors above the ammonia injection grid 11 and below the catalytic bed 12 to analyze the gas components in the flue gas, and by allowing the operator to adjust the opening of the valve in real time according to the data detected by the gas detector. In addition, the standby valve is arranged in parallel with each main valve, so that when the main valve fails, the standby valve can be put into use to avoid the adverse consequences of the side being unable to inject ammonia for denitration due to the failure of the main valve, thereby ensuring the stability of the equipment operation. Furthermore, since the main valves on both sides are arranged in parallel and the components of the flue gas fluctuate within a certain value, when a valve on one side fails, the opening of the standby valve on the side can be adjusted in a timely manner according to the opening of the valve on the other side and the data detected by the gas detector, thereby having the convenience of adjustment. The device of the application adjusts the ammonia injection amount in the SCR denitration process by the cooperation of the above-mentioned equipment, which can effectively control the ammonia injection amount more accurately according to the components of the flue gas, and overcomes the disadvantages of poor denitration effect or ammonia escape caused by the difficulty in timely and accurate adjustment of the ammonia injection amount when the components of the flue gas fluctuate in the traditional ammonia injection mode.

[0045] As shown in Figure 1 Optionally, the first gas detector 10, the second gas detector 20, the third gas detector 30, the fourth gas detector 40, the first main valve 100, the first standby valve 200, the second main valve 300, and the second standby valve 400 are electrically connected with the controller 3.

[0046] In the application, the controller 3 is arranged and the above-mentioned equipment is electrically connected with the controller 3. The first gas detector 10, the second gas detector 20, the third gas detector 30, and the fourth gas detector 40 feed the content data of nitrogen oxides in the flue gas to the controller 3, and the controller 3 adjusts the opening of the valve in the working state in real time according to the data fed back by the gas detector, thereby adjusting the ammonia injection amount.

[0047] As shown in Figure 2 Optionally, a spoiler 14 is arranged between the ammonia injection grid 11 and the catalytic bed 12.

[0048] In the application, the spoiler 14 is arranged to further promote the mixing of ammonia and flue gas.

[0049] As shown in Figure 3As shown, the spoiler 14 comprises a spoiler body 140, and a plurality of first leaflets 141 are evenly distributed in the spoiler body 140, and the rotation axis of the first leaflets 141 is parallel to the flue gas flow direction.

[0050] A plurality of second leaflets 142 are arranged between the adjacent first leaflets 141, the rotation axis of the second leaflets 142 is perpendicular to the flue gas flow direction, and the second leaflets 142 are straight leaflets.

[0051] In the present application, the first leaflets 141 are turbine leaflets, and when the mixed gas flow of the flue gas and the ammonia gas flows through the first leaflets 141, the first leaflets 141 are driven to rotate, and the flue gas and the ammonia gas are disturbed under the rotation of the first leaflets 141 so as to be mixed. Similarly, the second leaflets 142 are straight leaflets, and when the gas flow passes through, the second leaflets 142 are driven to rotate, and the flue gas and the ammonia gas are disturbed and mixed, and the flue gas and the ammonia gas are further fully mixed through the disturbance of the first leaflets 141 and the second leaflets 142 in the horizontal direction and the vertical direction respectively.

[0052] As shown, the ammonia gas supply device 2 comprises a urea solution storage tank 21, a liquid transfer pump 22, a urea decomposition tank 23 and a mixer 24 connected in sequence. Figure 4 The steam input end of the urea decomposition tank 23 is connected with the steam pipeline 4, and the material input end of the urea decomposition tank 23 is connected with the liquid transfer pump 22 and the catalyst storage tank 25 respectively.

[0053] The mixer 24 is connected with the gas output end of the air preheater 13.

[0054] In use, the urea solution (the concentration is 40-50wt%) stored in the urea solution storage tank 21 is pumped into the urea decomposition tank 23 through the liquid transfer pump 22, and the catalyst (such as phosphoric acid and ammonium phosphate aqueous solution) in the catalyst storage tank 25 is transferred into the urea decomposition tank 23, the urea is further heated (130-140℃) through heat exchange with the steam (the temperature is 165-170℃) input from the steam pipeline 4, and is decomposed into the mixed gas of the ammonia gas and the carbon dioxide under the catalysis of the catalyst. After the mixed gas is mixed with a part of the hot air (the temperature is 140-160℃) separated from the air preheater 13 in the mixer 24, the mixed gas is input into the ammonia injection grid 11 through the first main valve 100 and the second main valve 300 (the first standby valve 200 and the second standby valve 400 are in the closed state in normal operation), and is injected into the flue 1 from both sides of the ammonia injection grid 11.

[0055] As shown, the liquid transfer pump 22 and the urea decomposition tank 23 are provided with a heat exchanger 26.

[0056] Figure 5

[0057] ​​The heat exchange medium input end of the heat exchanger 26 is connected with the hydrophobic output end of the urea decomposition tank 23.

[0058] In the present application, the heat exchanger 26 is arranged to utilize the heat of the water and the exhaust steam generated by the steam after the urea solution is decomposed by the urea decomposition tank 23 to preheat the urea solution, so as to realize the secondary utilization of the heat and avoid the waste of energy.

[0059] As shown in Figure 6 Optionally, the urea decomposition tank 23 comprises a shell 231;

[0060] The top of the shell 231 is provided with a decomposition gas outlet 201 and a feed liquid inlet 202;

[0061] The lower part of the shell 231 is provided with a plurality of heat exchange pipes 232, one end of the heat exchange pipe 232 penetrates into the shell 231, is bent into a U shape and then penetrates out of the shell 231, one end of the heat exchange pipe 232 is connected with the steam pipeline 4, and the other end is connected with the heat exchange medium input end of the heat exchanger 26.

[0062] In the present application, when the urea is decomposed in the urea decomposition tank 23, the steam (temperature: 165-170℃) input by the steam pipeline 4 enters the heat exchange pipe 232 from one end of the heat exchange pipe 232, and the urea solution near the heat exchange pipe 232 is heated to the decomposition temperature (130-140℃). Due to the presence of the catalyst, at this temperature, the urea will be quickly decomposed into carbon dioxide and ammonia gas and overflow from the urea solution, and the hydrophobic and exhaust steam condensed after heat exchange are discharged from the other end of the heat exchange pipe 232 and input into the heat exchanger 26 to exchange heat with the urea solution (temperature: 50-60℃) to heat it. These exhaust steam will be condensed into water after heat exchange in the heat exchange pipe 232.

[0063] In the present application, as shown in Figure 6 The open ends of the plurality of heat exchange pipes 232 are connected with the head, the head is provided with a partition plate to separate the input end and the output end of the heat exchange pipe 232, and corresponding openings are arranged for medium input and output.

[0064] An SCR denitration ammonia injection device, and the working process is as follows:

[0065] In use, the urea solution (concentration 40-50wt%) stored in the urea solution storage tank 21 is pumped into the heat exchanger 26 by the liquid transfer pump 22, heated by the heat exchange with the steam output from the urea decomposition tank 23, and then enters the urea decomposition tank 23. At the same time, the catalyst (such as phosphoric acid, ammonium phosphate aqueous solution) in the catalyst storage tank 25 is transferred into the urea decomposition tank 23. The urea is further heated (130-140°C) by heat exchange with the steam (temperature 165-170°C) input from the steam pipeline 4, and decomposed into a mixed gas of ammonia and carbon dioxide under the catalytic action of the catalyst. In the urea decomposition tank 23, the steam (temperature 165-170°C) input from the steam pipeline 4 enters the heat exchange tube 232 from one end of the heat exchange tube 232, and the urea solution near the heat exchange tube 232 is heated to the decomposition temperature (130-140°C). Due to the presence of the catalyst, at this temperature, the urea will quickly decompose into carbon dioxide and ammonia and overflow from the urea solution. The steam condenses to form the water and exhaust steam after heat exchange in the heat exchange tube 232, which is discharged from the other end of the heat exchange tube 232 and input into the heat exchanger 26 to exchange heat with the urea solution (temperature 50-60°C), and the exhaust steam condenses into water after heat exchange in the heat exchange tube 232 and is output.

[0066] The mixed gas output from the urea decomposition tank 23 and a part of the hot air (temperature 140-160°C) separated from the air preheater 13, i.e. hot wind, are mixed in the mixer 24, and then input into the ammonia injection grid 11 through the first main valve 100 and the second main valve 300 (the first standby valve 200 and the second standby valve 400 are in the closed state in normal operation), and sprayed into the flue 1 from the ammonia gas input ends on both sides of the ammonia injection grid 11.

[0067] Meanwhile, the flue gas discharged from the boiler enters the area where the ammonia injection device is located after heat exchange treatment by the pre-sequenced equipment (such as the coal economizer, etc.) in the flue. When the flue gas passes through the first gas detector 10 and the second gas detector 20, the detectors detect the content of nitrogen oxides in the flue gas and feed back the data to the controller 3. The controller 3 adjusts the opening size of the first main valve 100 and the second main valve 300 in real time according to the data detected by the flue gas detectors on both sides, so as to avoid excessive ammonia injection amount causing ammonia escape or too small ammonia injection amount causing nitrogen oxides emission exceeding the standard. The ammonia gas injected from the ammonia injection grid 11 mixes with the flue gas, and under the disturbance mixing effect of the spoiler 14, the mixed gas enters the catalytic bed 12. Under the catalytic effect of the catalyst (iron, vanadium, etc.) on the catalytic bed 12, the ammonia gas and the nitrogen oxides in the flue gas undergo oxidation-reduction reaction, and the nitrogen oxides are reacted to generate nitrogen gas, so as to achieve the purpose of ammonia removal. The flue gas after denitrification by the catalytic bed 12 continues to be discharged and passes through the third gas detector 30 and the fourth gas detector 40. The gas detectors detect the content of nitrogen oxides and ammonia gas in the flue gas in real time and feed back the data to the controller 3. The controller 3 adjusts the opening of the valve according to the data fed back by the first gas detector 10, the second gas detector 20, the third gas detector 30 and the fourth gas detector 40, so as to adjust the ammonia injection amount.

[0068] The discharged flue gas continues to move and passes through the air preheater 13, and heat exchange occurs between the flue gas and the air preheater 13, so that the air in the air preheater 13 is heated. A part of the heated air is separated from the air preheater 13 and enters the mixer 24, and mixes with the ammonia gas and carbon dioxide generated after the decomposition of urea, which is used for ammonia injection denitrification.

[0069] When the main valve on one side of the ammonia injection grid 11 fails and needs to be repaired, the first main valve 100 is taken as an example for illustration. At this time, the controller 3 controls the first standby valve 200 to open, and the first gas detector 10 and the second gas detector 20 detect the content of nitrogen oxides in the gas on both sides. When the content of nitrogen oxides detected by the gas detectors on both sides deviates by less than 100 mg / Nm 3 , the first standby valve 200 adjusts the ammonia injection amount according to the opening of the second main valve 300. When the content of nitrogen oxides at the inlet on both sides deviates by more than 100 mg / Nm 3 , the ammonia injection amount of the valve on this side (i.e. the first standby valve 200) is increased by 2% for each 100 mg / Nm 3 , until the adjustment and tracking are completed or the content of nitrogen oxides at the inlet on both sides is less than 100 mg / Nm 3 .

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand; it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An SCR denitration ammonia injection device, characterized in that, The flue (1) is provided with an ammonia injection grid (11), a catalytic bed (12) and an air preheater (13) from top to bottom in sequence; The gas output end of the air preheater (13) is connected with an ammonia supply device (2); The first gas detector (10) and the second gas detector (20) are respectively arranged on the opposite sides above the ammonia injection grid (11); The third gas detector (30) and the fourth gas detector (40) are respectively arranged on the opposite sides below the catalytic bed (12); The first gas detector (10) and the second gas detector (20) correspond to the third gas detector (30) and the fourth gas detector (40) in the vertical direction; The ammonia inlets on the opposite sides of the ammonia injection grid (11) are respectively connected with the ammonia supply device (2), the ammonia inlet on one side of the ammonia injection grid (11) is connected through the first main valve (100) and the first standby valve (200), and the ammonia inlet on the other side of the ammonia injection grid (11) is connected through the second main valve (300) and the second standby valve (400).

2. The SCR de-NOx ammonia injection device according to claim 1, characterized in that, The first gas detector (10), the second gas detector (20), the third gas detector (30), the fourth gas detector (40), the first main valve (100), the first standby valve (200), the second main valve (300) and the second standby valve (400) are electrically connected with a controller (3).

3. The SCR de-NOx ammonia injection device of claim 1, wherein, A spoiler (14) is arranged between the ammonia injection grid (11) and the catalytic bed (12).

4. The SCR de-NOx ammonia injection device according to claim 3, characterized in that, The spoiler (14) comprises a spoiler body (140) provided with a plurality of uniformly distributed first vanes (141), and the rotation axis of the first vane (141) is parallel to the direction of flue gas flow; A plurality of second vanes (142) are arranged between adjacent first vanes (141), the rotation axis of the second vane (142) is perpendicular to the direction of flue gas flow, and the second vane (142) is a straight vane.

5. The ammonia injection device for SCR De-NOx according to any one of claims 1 to 4, characterized in that, The ammonia supply device (2) comprises a urea solution storage tank (21), a liquid transfer pump (22), a urea decomposition tank (23) and a mixer (24) connected in sequence; The steam input end of the urea decomposition tank (23) is connected with a steam pipeline (4), and the material input end of the urea decomposition tank (23) is connected with the liquid transfer pump (22) and a catalyst storage tank (25) respectively; The mixer (24) is connected with the gas output end of the air preheater (13).

6. The SCR de-NOx ammonia injection device of claim 5, wherein, A heat exchanger (26) is arranged between the liquid transfer pump (22) and the urea decomposition tank (23); The heat exchange medium input end of the heat exchanger (26) is connected with the hydrophobic output end of the urea decomposition tank (23).

7. The SCR de-NOx ammonia injection device of claim 6, wherein, The urea decomposition tank (23) comprises a shell (231); The shell (231) is provided with a decomposition gas outlet (201) and a liquid inlet (202) at the top; The lower part of the shell (231) is provided with a plurality of heat exchange pipes (232), one end of the heat exchange pipes (232) penetrates into the shell (231) and is bent into a U shape and then penetrates out of the shell (231), one end of the heat exchange pipes (232) is connected with the steam pipeline (4), and the other end is connected with the heat exchange medium input end of the heat exchanger (26).

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