Accurate denitration method for selective catalytic reduction of flue gas of coal-fired boiler

Abstract

The invention relates to a selective catalytic reduction accurate denitration method for flue gas of a coal-fired boiler. A boiler furnace flue gas infrared temperature measurement system, a boiler top convection heating area flue gas infrared temperature measurement system and a precise denitration controller are arranged on a boiler body, and a precise denitration sub-controller A, a precise denitration sub-controller B and a precise denitration sub-controller C are arranged on a denitration flue A, a denitration flue B and a denitration flue C respectively. The device comprises an electric baffle door A, an electric baffle door B, an electric baffle door C, an ammonia gas spray gun A, an ammonia gas spray gun B, an ammonia gas spray gun C and a denitration catalyst layer. According to the invention, the process design principle of real-time control and precise switching is adopted, so that the ammonia gas injection point and the denitration reaction are always in the optimal temperature interval, thereby ensuring the accuracy and effectiveness of selective catalytic reduction denitration, improving the long-term stability of the denitration efficiency, greatly saving the use cost of a denitration reducing agent and improving the economic benefit. And the service life of the denitration catalyst is greatly prolonged, the process adaptability is wide, and the dynamic adjustment accuracy is high.

Description

Technical Field

[0001] The present invention relates to a method for selective catalytic reduction and precise denitration of flue gas from a coal-fired boiler, and in particular to a method for selective catalytic reduction and precise denitration of flue gas from a coal-fired boiler, in which a boiler furnace flue gas infrared temperature measurement system, a boiler top convection heating zone flue gas infrared temperature measurement system and a precise denitration controller are respectively arranged on a boiler body, and precise denitration sub-controllers A, B, C, electric baffle doors A, B, C, ammonia spray guns A, B, C and a denitration catalyst layer are respectively arranged on denitration flues A, B, C. Background Art

[0002] In my country, the removal of flue gas nitrogen oxides from coal-fired power plants mostly adopts the selective catalytic reduction method. Due to its high denitrification efficiency, the proportion of selective catalytic reduction denitrification process application has reached more than 95%. However, with my country's increasing attention to the pollution control of atmospheric pollutants such as nitrogen oxides from coal-fired boilers, and the gradual increase in the operating requirements of the selective catalytic reduction denitrification method, selective catalytic reduction denitrification has also exposed some urgent problems to be solved. The catalysts for selective catalytic reduction denitrification mostly use high-temperature catalysts, and the reducing agent mostly uses ammonia. There is an optimal temperature range for the position of the ammonia injection point and the reaction of ammonia and nitrogen oxides under the action of high-temperature catalysts. The temperature range is generally 315℃~400℃. In the actual operation process, due to the complexity of the evolution of characteristic parameters such as the coal combustion process and the flue gas temperature, the ammonia injection point in the flue and the temperature range where the denitrification reaction occurs frequently change, which has a great impact on the effective removal of nitrogen oxides in the flue gas, and also causes a large increase in the use of denitrification reducing agents, and also has an extremely adverse effect on the service life of the denitrification catalyst. The accuracy of selective catalytic reduction denitrification has gradually become a frontier hotspot in basic research and technological development.

[0003] The present invention is based on long-term data collection, modeling and analysis and demonstration, combined with continuous optimization of engineering practice experience, and according to the characteristics and laws of the coal combustion process and flue gas temperature evolution, adopts the process design principle of real-time control and precise switching, so that the ammonia injection point and the denitrification reaction are always in the optimal temperature range, thereby ensuring the accuracy and effectiveness of selective catalytic reduction denitrification, improving the long-term stability of denitrification efficiency, greatly saving the cost of using denitrification reducing agents, and greatly extending the service life of denitrification catalysts. The process of the present invention has wide adaptability and strong accuracy of dynamic adjustment. Summary of the invention

[0004] The purpose of the present invention is to provide a method for selective catalytic reduction and precise denitration of flue gas from a coal-fired boiler, which adopts a method for selective catalytic reduction and precise denitration of flue gas from a coal-fired boiler, wherein a boiler furnace flue gas infrared temperature measurement system, a boiler top convection heating zone flue gas infrared temperature measurement system and a precise denitration controller are respectively arranged on the boiler body, and precise denitration sub-controller A, precise denitration sub-controller B and precise denitration sub-controller C, electric baffle doors A, electric baffle doors B and electric baffle doors C, ammonia spray guns A, ammonia spray guns B and ammonia spray guns C and a denitration catalyst layer are respectively arranged on the denitration flue A, denitration flue B and denitration flue C. The present invention adopts the process design principle of real-time control and precise switching, so that the ammonia injection point and the denitration reaction are always in the optimal temperature range, thereby ensuring the accuracy and effectiveness of selective catalytic reduction denitration, improving the long-term stability of denitration efficiency, greatly saving the use cost of denitration reducing agent, and greatly extending the service life of denitration catalyst. The process of the present invention has wide adaptability and strong accuracy of dynamic adjustment.

[0005] In order to achieve the above-mentioned purpose, the present invention respectively sets a boiler furnace flue gas infrared temperature measurement system, a boiler top convection heating zone flue gas infrared temperature measurement system and a precise denitrification controller on the boiler body. The boiler furnace flue gas infrared temperature measurement system is used to measure and dynamically obtain the flue gas temperature data and dynamic distribution on the BB' section of the boiler combustion zone in real time, and transmit the above data to the precise denitrification controller in real time. The boiler top convection heating zone flue gas infrared temperature measurement system is used to measure and dynamically obtain the flue gas temperature data and dynamic distribution on the AA' section of the boiler top convection heating zone in real time, and transmit the above data to the precise denitrification controller in real time.

[0006] To achieve the above-mentioned purpose, the precise denitrification controller of the present invention, after obtaining the real-time flue gas temperature data and dynamic distribution on the AA' section and the BB' section, combines the input and dynamically adjusted fuel, coal combustion characteristics of the boiler body, boiler and flue dimensions, water-cooled walls and heat exchange surfaces, system air leakage rate and other data, through real-time simulation calculation and dynamic optimization adjustment of mathematical models and control programs, and finally obtains the temperature range distribution data in the boiler rear high-temperature flue, providing a precise control basis for the precise setting of the denitrification flue on the boiler rear high-temperature flue.

[0007] In order to achieve the above object, the present invention sequentially arranges denitrification flue A, denitrification flue B and denitrification flue C on the high-temperature flue at the tail of the boiler. The vertical distance between the center line of the denitrification flue A and the AA' section of the convection heating zone at the top of the boiler is 6 meters, the vertical distance between the center line of the denitrification flue B and the AA' section of the convection heating zone at the top of the boiler is 13 meters, and the vertical distance between the center line of the denitrification flue C and the AA' section of the convection heating zone at the top of the boiler is 19.5 meters.

[0008] In order to achieve the above object, the present invention sets a precise denitration sub-controller A on the denitration flue A, sets a precise denitration sub-controller B on the denitration flue B, and sets a precise denitration sub-controller C on the denitration flue C. The precise denitration sub-controller A, the precise denitration sub-controller B and the precise denitration sub-controller C all work under the control of the precise denitration controller.

[0009] In order to achieve the above-mentioned object, the present invention respectively arranges electric damper door A, electric damper door B and electric damper door C at the inlet ends of denitrification flue A, denitrification flue B and denitrification flue C. When electric damper door A is opened and electric damper door B and electric damper door C are closed, flue gas enters denitrification flue A, and nitrogen oxides in the flue gas are removed in denitrification flue A. When electric damper door B is opened and electric damper door A and electric damper door C are closed, flue gas enters denitrification flue B, and nitrogen oxides in the flue gas are removed in denitrification flue B. When electric damper door C is opened and electric damper door A and electric damper door B are closed, flue gas enters denitrification flue C, and nitrogen oxides in the flue gas are removed in denitrification flue C.

[0010] To achieve the above object, the present invention arranges an ammonia spray gun A on the denitrification flue A to spray ammonia gas, a denitrification reducing agent, into the denitrification flue A. The ammonia spray gun A is connected to an ammonia-air mixer, and the ammonia-air mixer is connected to a liquid ammonia storage tank.

[0011] To achieve the above purpose, the present invention arranges an ammonia spray gun B on the denitrification flue B to spray ammonia gas, a denitrification reducing agent, into the denitrification flue B. The ammonia spray gun B is connected to an ammonia-air mixer, and the ammonia-air mixer is connected to a liquid ammonia storage tank.

[0012] To achieve the above purpose, the present invention arranges an ammonia spray gun C on the denitrification flue C to spray ammonia gas, a denitrification reducing agent, into the denitrification flue C. The ammonia spray gun C is connected to an ammonia-air mixer, and the ammonia-air mixer is connected to a liquid ammonia storage tank.

[0013] To achieve the above purpose, the ammonia-air mixer of the present invention is used to mix ammonia and air, and the volume ratio of ammonia to air in the mixed gas (ammonia-air mixing ratio) is controlled within 5%. The liquid ammonia storage tank is used to provide ammonia to the ammonia-air mixer.

[0014] In order to achieve the above-mentioned purpose, the present invention provides a denitration catalyst layer in the denitration flue A, the denitration flue B and the denitration flue C. The catalyst in the denitration catalyst layer adopts a high-temperature catalyst, and the type is honeycomb, plate or corrugated. The chemical composition of the catalyst is TiO 2 As carrier, the active ingredient is V 2 O 5 .

[0015] After automatic analysis and judgment by the precise denitrification controller of the present invention, when the center line of the denitrification flue A is at a temperature range of 355°C to 385°C, the precise denitrification controller sends control signals to the precise denitrification sub-controller A, the precise denitrification sub-controller B and the precise denitrification sub-controller C respectively; under the control of the precise denitrification sub-controller A, the electric baffle door A is opened and the ammonia spray gun A is put into use; under the control of the precise denitrification sub-controller B, the electric baffle door B is closed and the ammonia spray gun B is deactivated; under the control of the precise denitrification sub-controller C, the electric baffle door C is closed and the ammonia spray gun C is deactivated; at this time, the flue gas enters the denitrification flue A, and the nitrogen oxides in the flue gas are removed in the denitrification flue A.

[0016] After automatic analysis and judgment by the precise denitrification controller of the present invention, when the center line of the denitrification flue B is at a temperature range of 355°C to 385°C, the precise denitrification controller sends control signals to the precise denitrification sub-controller A, the precise denitrification sub-controller B and the precise denitrification sub-controller C respectively; under the control of the precise denitrification sub-controller B, the electric baffle door B is opened and the ammonia spray gun B is put into use; under the control of the precise denitrification sub-controller A, the electric baffle door A is closed and the ammonia spray gun A is deactivated; under the control of the precise denitrification sub-controller C, the electric baffle door C is closed and the ammonia spray gun C is deactivated; at this time, the flue gas enters the denitrification flue B, and the nitrogen oxides in the flue gas are removed in the denitrification flue B.

[0017] Through automatic analysis and judgment by the precise denitrification controller of the present invention, when the center line of the denitrification flue C is at a temperature range of 355°C to 385°C, the precise denitrification controller sends control signals to the precise denitrification sub-controller A, the precise denitrification sub-controller B and the precise denitrification sub-controller C respectively; under the control of the precise denitrification sub-controller C, the electric baffle door C is opened and the ammonia spray gun C is put into use; under the control of the precise denitrification sub-controller A, the electric baffle door A is closed and the ammonia spray gun A is deactivated; under the control of the precise denitrification sub-controller B, the electric baffle door B is closed and the ammonia spray gun B is deactivated; at this time, the flue gas enters the denitrification flue C, and the nitrogen oxides in the flue gas are removed in the denitrification flue C.

[0018] Compared with the prior art, the present invention has the following characteristics: (1) Based on long-term data collection, modeling and analysis and demonstration, combined with continuous optimization of engineering practice experience, the present invention adopts the process design principle of real-time control and precise switching according to the characteristics and laws of the coal combustion process and the evolution of flue gas temperature, so that the ammonia injection point and the denitrification reaction are always in the optimal temperature range, thereby ensuring the accuracy and effectiveness of selective catalytic reduction denitrification, improving the long-term stability of denitrification efficiency, and being suitable for the actual situation of my country's flue gas denitrification conditions with changeable conditions, with strong load adaptability and flexible condition adjustment.

[0019] (2) The present invention can greatly save the cost of using the denitration reducing agent and significantly extend the service life of the denitration catalyst.

[0020] (3) The process of the present invention has wide adaptability and high precision of dynamic adjustment.

[0021] (4) The patented invention has the characteristics of easy inspection and maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0023] Figure 1 It is a schematic diagram of the process flow of the patent of this invention.

[0024] In the figure: 1. Boiler body, 2. High-temperature flue at the rear of the boiler, 3-A. Denitrification flue A, 3-B. Denitrification flue B, 3-C. Denitrification flue C, 4. Vertical low-temperature flue, 5. Horizontal low-temperature flue, 6. Denitrification catalyst layer, 7. Boiler furnace flue gas infrared temperature measurement system, 8. Boiler top convection heating zone flue gas infrared temperature measurement system, 9. Precision denitrification controller, 10. Precision denitrification sub-controller A, 11. Precision denitrification sub-controller B, 12. Precision denitrification sub-controller C, 13. Electric damper door A, 14. Electric damper door B, 15. Electric damper door C, 16. Ammonia spray gun A, 17. Ammonia spray gun B, 18. Ammonia spray gun C, 19. Ammonia-air mixer, 20. Liquid ammonia storage tank. DETAILED DESCRIPTION

[0025] Figure 1 In the invention, a boiler furnace flue gas infrared temperature measurement system (7), a boiler top convection heating zone flue gas infrared temperature measurement system (8) and a precise denitration controller (9) are respectively arranged on the boiler body (1); a precise denitration sub-controller A (10), a precise denitration sub-controller B (11) and a precise denitration sub-controller C (12), an electric damper door A (13), an electric damper door B (14) and an electric damper door C (15), an ammonia spray gun A (16), an ammonia spray gun B (17) and an ammonia spray gun C (18) and a denitration catalyst layer (6) are respectively arranged on the denitration flue A (3-A), the denitration flue B (3-B) and the denitration flue C (3-C).

[0026] After automatic analysis and judgment by the precise denitration controller (9) of the present invention, when the center line of the denitration flue A (3-A) is located in the temperature range of 355°C to 385°C, the precise denitration controller (9) sends control signals to the precise denitration sub-controller A (10), the precise denitration sub-controller B (11) and the precise denitration sub-controller C (12) respectively. Under the control of the precise denitration sub-controller A (10), the electric damper door A (13) is opened and the ammonia spray gun A (16) is put into use. Under the control of the precise denitration sub-controller B (11), the electric damper door B (14) is closed and the ammonia spray gun B (17) is deactivated. Under the control of the precise denitration sub-controller C (12), the electric damper door C (15) is closed and the ammonia spray gun C (18) is deactivated. At this time, the flue gas enters the denitration flue A (3-A) and the nitrogen oxides in the flue gas are removed in the denitration flue A (3-A).

[0027] After automatic analysis and judgment by the precise denitration controller of the present invention, when the center line of the denitration flue B (3-B) is located in the temperature range of 355°C to 385°C, the precise denitration controller (9) sends control signals to the precise denitration sub-controller A (10), the precise denitration sub-controller B (11) and the precise denitration sub-controller C (12) respectively. Under the control of the precise denitration sub-controller B (11), the electric damper door B (14) is opened and the ammonia spray gun B (17) is put into use. Under the control of the precise denitration sub-controller A (10), the electric damper door A (13) is closed and the ammonia spray gun A (16) is deactivated. Under the control of the precise denitration sub-controller C (12), the electric damper door C (15) is closed and the ammonia spray gun C (18) is deactivated. At this time, the flue gas enters the denitration flue B (3-B) and the nitrogen oxides in the flue gas are removed in the denitration flue B (3-B).

[0028] After automatic analysis and judgment by the precise denitration controller of the present invention, when the center line of the denitration flue C (3-C) is located in the temperature range of 355°C to 385°C, the precise denitration controller (9) sends control signals to the precise denitration sub-controller A (10), the precise denitration sub-controller B (11) and the precise denitration sub-controller C (12) respectively. Under the control of the precise denitration sub-controller C (12), the electric damper door C (15) is opened and the ammonia spray gun C (18) is put into use. Under the control of the precise denitration sub-controller A (10), the electric damper door A (13) is closed and the ammonia spray gun A (16) is deactivated. Under the control of the precise denitration sub-controller B (11), the electric damper door B (14) is closed and the ammonia spray gun B (17) is deactivated. At this time, the flue gas enters the denitration flue C (3-C) and the nitrogen oxides in the flue gas are removed in the denitration flue C (3-C).

[0029] The ammonia-air mixer (19) of the present invention mixes ammonia and air, and the volume ratio of ammonia to air in the mixed gas (ammonia-air mixing ratio) is controlled within 5%. The liquid ammonia storage tank (20) is used to provide ammonia to the ammonia-air mixer.

[0030] The catalyst in the denitration catalyst layer (6) of the present invention adopts a high-temperature catalyst, which is in the form of a honeycomb, plate or corrugated type, and the chemical composition of the catalyst is TiO 2 As carrier, the active ingredient is V 2 O 5 .

[0031] The above is only a specific implementation of the present invention, and the technical features of the present invention are not limited thereto. Any changes or modifications made by technicians in the field of the present invention should be included in the patent scope of the present invention.

Claims

1. A method for selective catalytic reduction of precise denitrification of flue gas from a coal-fired boiler, wherein the method is implemented by a device for selective catalytic reduction of precise denitrification of flue gas from a coal-fired boiler, wherein the device for selective catalytic reduction of precise denitrification of flue gas from a coal-fired boiler comprises a boiler furnace flue gas infrared temperature measurement system, a boiler top convection heating zone flue gas infrared temperature measurement system, a precise denitrification controller, a denitrification flue A, a denitrification flue B, a denitrification flue C, a precise denitrification sub-controller A, a precise denitrification sub-controller B, a precise denitrification sub-controller C, an electric baffle door A, an electric baffle door B, an electric baffle door C, an ammonia spray gun A, an ammonia spray gun B, an ammonia spray gun C and a denitrification catalyst layer, characterized in that: The boiler body is respectively provided with a boiler furnace flue gas infrared temperature measurement system, a boiler top convection heating zone flue gas infrared temperature measurement system and a precise denitrification controller; the denitrification flue A, denitrification flue B and denitrification flue C are sequentially arranged on the high-temperature flue at the rear of the boiler; the denitrification flue A is provided with a precise denitrification sub-controller A, an electric damper door A, an ammonia spray gun A and a denitrification catalyst layer; the denitrification flue B is provided with a precise denitrification sub-controller B, an electric damper door B, an ammonia spray gun B and a denitrification catalyst layer; the denitrification flue C is provided with a precise denitrification sub-controller C, an electric damper door C, an ammonia spray gun C and a denitrification catalyst layer.

2. The method for selective catalytic reduction of flue gas from a coal-fired boiler according to claim 1, characterized in that: When the center line of the denitrification flue A is at a temperature range of 355℃ ~ 385℃, the precise denitrification controller sends control signals to the precise denitrification sub-controller A, the precise denitrification sub-controller B and the precise denitrification sub-controller C respectively. Under the control of the precise denitrification sub-controller A, the electric damper door A opens and the ammonia spray gun A is put into use. Under the control of the precise denitrification sub-controller B, the electric damper door B is closed and the ammonia spray gun B is deactivated. Under the control of the precise denitrification sub-controller C, the electric damper door C is closed and the ammonia spray gun C is deactivated. At this time, the flue gas enters the denitrification flue A and the nitrogen oxides in the flue gas are removed in the denitrification flue A.

3. The method for selective catalytic reduction of flue gas from a coal-fired boiler according to claim 1, characterized in that: When the center line of the denitrification flue B is at a temperature range of 355°C to 385°C, the precise denitrification controller sends control signals to the precise denitrification sub-controller A, the precise denitrification sub-controller B and the precise denitrification sub-controller C respectively. Under the control of the precise denitrification sub-controller B, the electric damper door B opens and the ammonia spray gun B is put into use. Under the control of the precise denitrification sub-controller A, the electric damper door A closes and the ammonia spray gun A is deactivated. Under the control of the precise denitrification sub-controller C, the electric damper door C closes and the ammonia spray gun C is deactivated. At this time, the flue gas enters the denitrification flue B and the nitrogen oxides in the flue gas are removed in the denitrification flue B.

4. The method for selective catalytic reduction of flue gas from a coal-fired boiler according to claim 1, characterized in that: When the center line of the denitrification flue C is at a temperature range of 355°C to 385°C, the precise denitrification controller sends control signals to the precise denitrification sub-controller A, the precise denitrification sub-controller B and the precise denitrification sub-controller C respectively. Under the control of the precise denitrification sub-controller C, the electric baffle door C opens and the ammonia spray gun C is put into use. Under the control of the precise denitrification sub-controller A, the electric baffle door A is closed and the ammonia spray gun A is deactivated. Under the control of the precise denitrification sub-controller B, the electric baffle door B is closed and the ammonia spray gun B is deactivated. At this time, the flue gas enters the denitrification flue C and the nitrogen oxides in the flue gas are removed in the denitrification flue C.

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