Composite denitration system of circulating fluidized bed boiler

Abstract

The utility model discloses a composite denitration system of circulating fluidized bed boiler, including boiler, cyclone separator, superheater, economizer, air pre-heater, SCR reactor and reductant spray gun, the outlet of superheater is connected with leading-out flue, the leading-out flue is communicated with the reactor inlet flue of SCR reactor, there are two groups of reductant spray gun, and the reductant spray gun is connected with the reactor inlet flue. And the two groups of reducing agent spray guns are respectively arranged in the separator inlet flue and the superheater inlet flue. The reducing agent spraying inlet is formed in the inlet of the cyclone separator, and the spraying inlet is formed in the top flue of the inlet of the superheater, so that the problem of low utilization rate of the reducing agent due to high ash concentration in the flue at the inlet of the cyclone separator can be avoided, and the denitration efficiency is improved. The SCR can be arranged at an outlet of a high-temperature economizer or an outlet of a low-temperature economizer, one path of smoke is led to an SCR inlet from an outlet of a superheater, and the situation that the reaction temperature of a catalyst cannot be met due to the low temperature of the SCR inlet during low load can be avoided.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas purification, in particular to the technical field of denitration systems. Background Art

[0002] In order to achieve ultra-low emissions of NOx, some fluidized bed denitrification technologies now usually use SNCR+SCR. The SNCR / SCR combined flue gas denitrification process has two reaction zones. Through the injection system arranged on the pre-decomposition kiln, the reductant is first sprayed into the first reaction zone, the inlet of the cyclone separator. At a high temperature of 800℃~1150℃, the reductant and NOx in the flue gas undergo a reduction reaction without catalytic participation to achieve denitrification. Then the unreacted reductant enters the second reaction zone of the mixed process, the SCR reactor, and further denitrifies with catalytic participation. The most important improvement of the SNCR / SCR combined flue gas denitrification process is that it greatly reduces the amount of catalyst used, reduces investment and operating costs, and enhances the flexibility of the system and the adaptability of environmental protection policies. In addition, if the boiler load fluctuates greatly and the reaction temperature of the SNCR zone is lower than 800℃, the SNCR reaction cannot be carried out, and the main denitrification reaction can be achieved in the SCR zone.

[0003] During operation, it was found that when using conventional SNCR+SCR composite denitrification technology, ammonia slip often exceeds the standard or the NOx emission concentration fails to meet the standard during low-load operation. This is mainly related to the following reasons:

[0004] The spray gun is set at the inlet flue of the cyclone separator. Since the ash concentration at the inlet of the cyclone separator is relatively high, it is easy to cause insufficient contact between the flue gas and the reducing agent, low efficiency, resulting in high ammonia escape later, and easy to generate ABS in the low temperature area, causing blockage of the air preheater.

[0005] The flue gas temperature at the SCR inlet is required to be at least 300℃. In many renovation projects, the economizers are not divided into high-temperature economizers and low-temperature economizers. If the SCR is to be set in a temperature range above 300℃, the economizer needs to be modified, which increases the investment cost and construction difficulty. In another case, at low load, the flue gas temperature at the SCR inlet cannot meet the catalyst reaction temperature range of 300℃. Utility Model Content

[0006] The purpose of the utility model is to solve the problems in the prior art and to propose a composite denitration system for a circulating fluidized bed boiler, which can achieve ultra-low emission of NOx under low load and avoid blockage of an air preheater.

[0007] To achieve the above-mentioned purpose, the utility model proposes a circulating fluidized bed boiler composite denitrification system, comprising a boiler, a cyclone separator, a superheater, an economizer, an air preheater, an SCR reactor and a reducing agent spray gun, the boiler is connected to the cyclone separator through a separator inlet flue, the cyclone separator is connected to the superheater through a superheater inlet flue, the superheater is connected to an economizer, the economizer is connected to an air preheater, the reactor inlet flue of the SCR reactor is connected to the outlet of the economizer, the reactor outlet flue of the SCR reactor is connected to the inlet of the air preheater, the outlet of the superheater is connected to an outlet flue, the outlet flue is connected to the reactor inlet flue of the SCR reactor, the outlet flue is connected to the outlet flue, the outlet flue is connected to the reactor inlet flue of the SCR reactor, the outlet flue is provided with an adjustable baffle door, and the reducing agent spray gun is provided with two groups, and the two groups of reducing agent spray guns are respectively arranged at the top of the separator inlet flue and the superheater inlet flue.

[0008] Preferably, the cyclone separators are provided with two on the left and right sides.

[0009] Preferably, the economizer includes a low-temperature economizer and a high-temperature economizer.

[0010] Preferably, the SCR reactor can be arranged at the outlet of the high-temperature economizer and the inlet of the low-temperature economizer, or at the outlet of the low-temperature economizer and the inlet of the air preheater.

[0011] Beneficial effects of the utility model:

[0012] 1. The utility model not only arranges a reducing agent injection port at the inlet of the cyclone separator, but also arranges an injection port at the top flue of the superheater inlet, which can avoid the problem of low reducing agent utilization rate due to high ash concentration in the flue of the cyclone separator inlet, improves the denitrification efficiency, and can also avoid the problem of excessive ammonia escape caused by uneven injection amount and insufficient reaction in the subsequent reaction.

[0013] 2. SCR can be set at the high-temperature economizer outlet or the low-temperature economizer outlet. Leading flue gas from the superheater outlet to the SCR inlet can avoid the low SCR inlet temperature from being unable to meet the catalyst reaction temperature at low load. Especially for the modification project, if the high-temperature economizer and the low-temperature economizer are not separated, there is no need to modify the economizer and set the SCR at the low-temperature economizer outlet, and the reaction temperature range required by the SCR catalyst can be achieved, which greatly reduces the difficulty and investment of the modification.

[0014] 3. The utility model can achieve ultra-low NOx emissions under low load and meet further environmental protection requirements.

[0015] The features and advantages of the present invention will be described in detail through embodiments in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a structural schematic diagram of the utility model.

[0017] In the figure: 1- boiler; 2- cyclone separator; 3- superheater; 4- economizer; 5- air preheater; 6- SCR reactor; 7- reducing agent spray gun; 21- separator inlet flue; 31- superheater inlet flue; 61- reactor inlet flue; 62- reactor outlet flue; 8- outlet flue. DETAILED DESCRIPTION

[0018] See also Figure 1 A circulating fluidized bed boiler composite denitrification system comprises a boiler 1, a cyclone separator 2, a superheater 3, an economizer 4, an air preheater 5, an SCR reactor 6 and a reducing agent spray gun 7, wherein the boiler 1 is connected to the cyclone separator 2 through a separator inlet flue 21, the cyclone separator 2 is connected to the superheater 3 through a superheater inlet flue 31, the superheater 3 is connected to the economizer 4, the economizer 4 is connected to the air preheater 5, the reactor inlet flue 61 of the SCR reactor 6 is connected to the outlet of the economizer 4, and the SCR reactor The reactor outlet flue 62 of the reactor 6 is connected to the inlet of the air preheater 5. The outlet of the superheater 3 is connected with an outlet flue 8, and the outlet flue 8 is communicated with the reactor inlet flue 61 of the SCR reactor 6. An adjustable baffle door is provided in the outlet flue 8. Two groups of reducing agent spray guns 7 are provided, and the two groups of reducing agent spray guns 7 are respectively arranged in the separator inlet flue 21 and the top 31 of the superheater inlet flue. The cyclone separator 2 is provided with two left and right ones. The reactor inlet flue 61 is connected to the outlet of the economizer.

[0019] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention falls within the protection scope of the present invention.

Claims

1. A circulating fluidized bed boiler composite denitrification system, characterized in that: The invention comprises a boiler (1), a cyclone separator (2), a superheater (3), an economizer (4), an air preheater (5), an SCR reactor (6) and a reducing agent spray gun (7), wherein the boiler (1) is connected to the cyclone separator (2) via a separator inlet flue (21), the cyclone separator (2) is connected to the superheater (3) via a superheater inlet flue (31), the superheater (3) is connected to the economizer (4), the economizer (4) is connected to the air preheater (5), the reactor inlet flue (61) of the SCR reactor (6) is connected to the economizer (4), and the reactor inlet flue (61) of the SCR reactor (6) is connected to the economizer (4). The outlet of the coal burner (4) is connected, the reactor outlet flue (62) of the SCR reactor (6) is connected to the inlet of the air preheater (5), the outlet of the superheater (3) is connected to an exhaust flue (8), the exhaust flue (8) is connected to the reactor inlet flue (61) of the SCR reactor (6), an adjustable baffle door is provided in the exhaust flue (8), and two groups of reducing agent spray guns (7) are provided, and the two groups of reducing agent spray guns (7) are respectively arranged at the top of the separator inlet flue (21) and the superheater inlet flue (31).

2. The composite denitration system for a circulating fluidized bed boiler according to claim 1, characterized in that: The cyclone separators (2) are provided with two.

3. The composite denitration system for a circulating fluidized bed boiler according to claim 1, characterized in that: The economizer (4) comprises a high-temperature economizer and a low-temperature economizer.

4. The composite denitration system for a circulating fluidized bed boiler according to claim 3, characterized in that: The SCR reactor (6) is arranged between the high-temperature economizer outlet and the low-temperature economizer inlet.

5. The composite denitration system for a circulating fluidized bed boiler according to claim 3, characterized in that: The SCR reactor (6) is arranged between the outlet of the low-temperature economizer and the inlet of the air preheater.

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