Control system for reducing nitrogen oxides in flue gas

Abstract

The utility model relates to a control system for reducing nitrogen oxides in flue gas. The control system comprises a heating furnace, an induced draft fan, an air preheater, a chimney and an air blower, the top of the heating furnace is connected with the inlet end of the induced draft fan through a pipeline, the outlet end of the induced draft fan is connected to the air preheater through a pipeline, and the bottom of the air preheater leads out the pipeline to be connected to the chimney. A crossover line is led out of the pipeline between the air preheater and the chimney and connected to an inlet pipeline of an air blower, and an outlet pipeline of the air blower is connected to the air preheater and connected to the bottom of the heating furnace from the top of the air preheater. The outer side of the chimney is connected with a nitrogen oxide measuring point through a pipeline; the nitrogen oxide content can be reduced from 80mg / m < 3 > to 60mg / m < 3 > under the condition that the conditions of a heating furnace are not changed by small investment, a burner nozzle is not changed, the nitrogen oxide content can be reduced from 80mg / m < 3 > after implementation, and small-amplitude furnace temperature fluctuation can be dealt with while the nitrogen oxide content in the flue gas does not exceed the standard; meanwhile, heat efficiency of the heating furnace is improved, and fuel gas consumption is reduced.

Description

Technical Field

[0001] The utility model relates to emission control of nitrogen oxides when a heating furnace exhausts smoke, in particular to a control system for reducing nitrogen oxides in smoke, and belongs to the technical field of energy conservation, environmental protection and consumption reduction. Background Art

[0002] In recent years, domestic environmental protection has become increasingly strict, and heating furnace exhaust control of nitrogen oxides, sulfur dioxide, and particulate matter has been strengthened. At present, our company's emission standards are not higher than: sulfur dioxide 50mg / m3, nitrogen oxides 100mg / m3, and particulate matter 2050mg / m3. Our actual emission values ​​are: sulfur dioxide 0.07mg / m3, nitrogen oxides 80mg / m3, and particulate matter 220mg / m3.

[0003] The nitrogen oxide value emitted by our company is close to the emission target. When the heating furnace fluctuates slightly, it may cause the nitrogen oxide to exceed the standard. To solve this problem, the existing method is that the burner processing plant has introduced a low-nitrogen oxide burner. The principle is that when the fuel gas is burning, the air distribution volume is reduced through this burner. The same flow of fuel gas consumes less air and reduces the nitrogen oxides in the oxygen.

[0004] The disadvantage of this existing technology is that it is expensive. Our company only has 48 four-in-one furnace burners. If all are replaced, it will cost 400,000 yuan. The construction cost is also high. Because the burner is designed with low air, when the furnace load is high, incomplete combustion will occur, and the thermal efficiency is low. Utility Model Content

[0005] In view of the above-mentioned prior art methods, which require replacement of the heating furnace nozzle form and are costly and unstable during high-load operation, the purpose of the utility model is to provide a control system for reducing nitrogen oxides in flue gas, which reduces the nitrogen oxide content by changing the blast gas composition; at the same time, increases the thermal efficiency of the heating furnace and reduces the amount of fuel gas used.

[0006] In order to achieve the above-mentioned purpose, the technical scheme adopted by the utility model is: a control system for reducing nitrogen oxides in flue gas, comprising: a heating furnace, an induced draft fan, an air preheater, a chimney and a blower; the top of the heating furnace is connected to the inlet end of the induced draft fan through a pipeline, the outlet end of the induced draft fan is connected to the air preheater through a pipeline, and the pipeline from the bottom of the air preheater is connected to the chimney; a crossover line is led out from the pipeline between the air preheater and the chimney, the crossover line is connected to the inlet pipeline of the blower, the outlet pipeline of the blower is connected to the air preheater and connected from the top of the air preheater to the bottom of the heating furnace; the outside of the chimney is connected to a nitrogen oxide measuring point through a pipeline;

[0007] Furthermore, a control valve is provided on the pipeline between the top of the heating furnace and the inlet end of the induced draft fan near the induced draft fan, and the control valve is an automatic valve, model XV2304;

[0008] Furthermore, a bypass pipeline connected to the chimney is branched at the inlet end of the induced draft fan, and an air pre-bypass valve model XV2303 is provided on the bypass pipeline;

[0009] Furthermore, the pipeline leading out from the bottom of the air preheater is connected to the chimney through a bypass pipeline, and a control valve model XV2305 is provided on the pipeline leading out from the bottom of the air preheater;

[0010] Furthermore, a control butterfly valve is provided on the crossover line connected to the blower inlet pipeline, and a remote flow meter is provided at the lower part of the control butterfly valve for controlling the flow of the crossover line;

[0011] Furthermore, the flow rate of the cross-line accounts for 1 / 5 of the outlet flow rate of the induced draft fan.

[0012] Furthermore, a bypass pipeline is provided at the position where the blower outlet pipeline is connected to the air preheater, and an air preheater bypass valve of model TIC2321 is provided on the bypass pipeline;

[0013] Furthermore, the blower outlet pipeline is connected to the bottom of the heating furnace and is provided with a furnace air door main valve, model HIC2322.

[0014] In the above structure, remote thermometers are provided at the induced draft fan inlet, the air preheater outlet, and the blower outlet to control the temperature at their respective locations.

[0015] With the above structure, after combustion in the heating furnace, the flue gas enters the induced draft fan, and the outlet temperature of the induced draft fan is about 100 degrees after air preheating and is discharged to the chimney; it enters the blower from the cross-line, comes out of the blower to the air preheater and then returns to the heating furnace; the blower inhales air from the external air intake, and the blower inlet is the ambient temperature. Through the introduction of the cross-line, the blower inlet temperature can be increased by 20-30 degrees. When the blower supplies air to the heating furnace, the thermal efficiency of the furnace will increase due to the increase in temperature. At the same reaction temperature, more fuel gas can be saved; at the same time, the air blown by the blower has a lower oxygen content than that in the air. When combustion occurs in the furnace, the nitrogen oxides produced will be further reduced, which can achieve the effect of reducing nitrogen oxides in the flue gas.

[0016] The beneficial effects of the utility model are:

[0017] It can reduce the nitrogen oxide content by changing the blast gas composition with a small investment and without changing the burner. After implementation, the nitrogen oxide content can be reduced from 80mg / m3 to 60mg / m3 under the condition of unchanged heating furnace conditions. It can cope with small fluctuations in furnace temperature without exceeding the nitrogen oxide content in the flue gas standard. At the same time, it increases the thermal efficiency of the heating furnace and reduces the amount of fuel gas used. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural diagram of the utility model.

[0019] In the figure, 1, heating furnace, 2, induced draft fan, 3, air preheater, 4, chimney, 5, blower, 6, cross-line, 7, nitrogen oxide measuring point, 8, bypass pipeline, 9, air preheater bypass valve, 10, control butterfly valve, 11, remote flow meter, 12, furnace air door main valve, 13, remote thermometer. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned purposes, features and advantages of the utility model more obvious and easy to understand, the specific implementation methods of the utility model are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the utility model. However, the utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the utility model, so the utility model is not limited by the specific embodiments disclosed below.

[0021] like Figure 1 A control system for reducing nitrogen oxides in flue gas shown in the figure comprises: a heating furnace 1, an induced draft fan 2, an air preheater 3, a chimney 4 and a blower 5; the top of the heating furnace 1 is connected to the inlet end of the induced draft fan 2 through a pipeline, the outlet end of the induced draft fan 2 is connected to the air preheater 3 through a pipeline, and the pipeline leading out of the bottom of the air preheater 3 is connected to the chimney 4; a jumper 6 is led out from the pipeline between the air preheater 3 and the chimney 4, the jumper 6 is connected to the inlet pipeline of the blower 5, the outlet pipeline of the blower 5 is connected to the air preheater 3 and connected from the top of the air preheater 3 to the bottom of the heating furnace 1; the outside of the chimney 4 is connected to a nitrogen oxide measuring point 7 through a pipeline;

[0022] The pipeline between the top of the heating furnace 1 and the inlet end of the induced draft fan 2 is provided with a control valve near the induced draft fan 2. The control valve is an automatic valve with a model of XV2304.

[0023] A bypass pipeline 8 connected to the chimney 4 is branched at the inlet end of the induced draft fan 2, and an air pre-bypass valve 9 of model XV2303 is arranged on the bypass pipeline 8;

[0024] The pipeline leading out from the bottom of the air preheater 3 is connected to the chimney 4 through the bypass pipeline 8. The pipeline leading out from the bottom of the air preheater 3 is provided with a control valve, model XV2305;

[0025] The crossover line 6 connected to the inlet pipeline of the blower 5 is provided with a control butterfly valve 10, and a remote flow meter 11 is provided at the lower part of the control butterfly valve 10. A bypass pipeline is also provided at the position where the outlet pipeline of the blower 5 is connected to the air preheater 3, and an air preheater bypass valve is provided on the bypass pipeline, and the model is TIC2321;

[0026] The outlet pipeline of the blower 5 is connected to the bottom of the heating furnace 1, and a furnace air door main valve 12 is provided, and the model is HIC2322.

[0027] In the above structure, remote thermometers are provided at the inlet of the induced draft fan 2, the outlet of the air preheater 3, and the outlet of the blower 5 to control the temperature at their respective locations.

[0028] With the above structure, after combustion in the heating furnace 1, the flue gas enters the induced draft fan 2, and the outlet temperature of the induced draft fan 2 is about 100 degrees after air preheating and is discharged to the chimney 4; it enters the blower 5 from the crossover line 6, comes out of the blower 5 to reach the air preheater 3 and then returns to the heating furnace 1; the blower 5 inhales air from the external air intake, and the inlet of the blower 5 is the ambient temperature. Through the introduction of the crossover line 6, the inlet temperature of the blower 5 can be increased by 20-30 degrees. When the blower 5 distributes air to the heating furnace 1, the thermal efficiency of the furnace will be increased due to the increase in temperature. At the same reaction temperature, more fuel gas can be saved; at the same time, the air blown by the blower 5 has a lower oxygen content than that in the air. When combustion occurs in the furnace, the nitrogen oxides produced will be further reduced, which can achieve the effect of reducing nitrogen oxides in the flue gas.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present utility model, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0031] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the present utility model, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0033] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

Claims

1. A control system for reducing nitrogen oxides in flue gas, characterized in that: include: Heating furnace, induced draft fan, air preheater, chimney and blower; The top of the heating furnace is connected to the inlet end of the induced draft fan through a pipeline, the outlet end of the induced draft fan is connected to the air preheater through a pipeline, and the pipeline leading out from the bottom of the air preheater is connected to the chimney; a jumper is led out from the pipeline between the air preheater and the chimney, and the jumper is connected to the inlet pipeline of the blower, and the outlet pipeline of the blower is connected to the air preheater and connected from the top of the air preheater to the bottom of the heating furnace; the outside of the chimney is connected to a nitrogen oxide measuring point through a pipeline.

2. A control system for reducing nitrogen oxides in flue gas according to claim 1, characterized in that: A control valve is provided on the pipeline between the top of the heating furnace and the inlet end of the induced draft fan near the position of the induced draft fan. The control valve is an automatic valve with a model of XV2304.

3. A control system for reducing nitrogen oxides in flue gas according to claim 1, characterized in that: A bypass pipeline connected to the chimney is branched at the inlet end of the induced draft fan, and an air pre-bypass valve model XV2303 is installed on the bypass pipeline.

4. A control system for reducing nitrogen oxides in flue gas according to claim 3, characterized in that: The pipeline leading out from the bottom of the air preheater is connected to the chimney through a bypass pipeline. A control valve model XV2305 is arranged on the pipeline leading out from the bottom of the air preheater.

5. A control system for reducing nitrogen oxides in flue gas according to claim 1, characterized in that: A control butterfly valve is arranged on the crossover line connected to the blower inlet pipeline, and a remote flow meter is arranged at the lower part of the control butterfly valve.

6. A control system for reducing nitrogen oxides in flue gas according to claim 1, characterized in that: The flow rate of the cross-line accounts for 1 / 5 of the outlet flow rate of the induced draft fan.

7. A control system for reducing nitrogen oxides in flue gas according to claim 1, characterized in that: The blower outlet pipeline is connected to the bottom of the heating furnace, where a furnace air door main valve, model HIC2322, is provided.

8. A control system for reducing nitrogen oxides in flue gas according to claim 1, characterized in that: Remote thermometers are installed at the induced draft fan inlet, air preheater outlet and blower outlet.

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