A boiler pre-denitration device

Abstract

The application discloses a boiler front denitration device, and particularly relates to a denitration technology applied to various power station boilers, waste incineration boilers, petrochemical cracking furnaces and metallurgical heating furnaces. The denitration device is characterized in that denitration spray guns are arranged on the bed and under the bed of the boiler, and the flue gas is mixed at the same time, the oxygen content of the combustion-supporting air is reduced, good denitration reaction conditions are realized, and early denitration is achieved.

Description

Technical Field

[0001] This invention relates to a boiler denitrification device, particularly a pre-denitrification device for boilers widely used in power plant boilers (pulverized coal boilers, circulating fluidized bed boilers, waste incinerators), petrochemical cracking furnaces, and industrial metallurgical heating furnaces during cold ignition and low-load operation, where the exhaust gas temperature is too low to reach the denitrification reaction temperature, resulting in serious problems of excessive nitrogen oxide emissions and ammonia escape. Background Technology

[0002] Currently, in power plant boilers (mainly coal-fired pulverized coal boilers, coal-fired circulating fluidized bed boilers, and waste incinerators), petrochemical cracking furnaces, and industrial metallurgical heating furnaces, the input heat is relatively small during cold ignition and low-load operation, and the tail exhaust temperature is too low to reach the denitrification reaction temperature, resulting in excessive nitrogen oxide emissions and serious ammonia escape problems.

[0003] Nitrogen oxide removal, also known as denitrification, is currently achieved by installing several urea spray guns (SNCR) or catalyst carrier denitrification (SCR) in the flue gas duct at the tail end of the boiler. Urea solution (or ammonia water) is directly sprayed into the high-temperature exhaust gas to achieve the reduction reaction of nitrogen oxides, generating nitrogen and water, thus achieving compliant emissions.

[0004] In the currently used denitrification processes, SNCR requires a flue gas reaction temperature of no less than 850℃, while SCR requires a flue gas temperature of no more than 350℃, and both require an oxygen-deficient environment.

[0005] With the further tightening of environmental protection standards, it is required that flue gas emissions be monitored during the boiler ignition and startup process. Summary of the Invention

[0006] The purpose of this invention is to provide a boiler pre-denitrification device for all operating times of various boilers.

[0007] To achieve the above objectives, the technical means employed in this invention are as follows:

[0008] The present invention provides a boiler pre-denitrification device, the technical means of which is to send denitrification agent into each combustion air passage of the boiler during the cold start and load-bearing stages of the boiler, and to use flue gas recirculation technology to achieve an oxygen-deficient combustion atmosphere.

[0009] Compared with existing technologies, the aforementioned boiler pre-denitrification device introduces the denitrification agent into the furnace in advance, solving the problem of insufficient denitrification reaction when the furnace temperature is low and the load is low, and significantly reducing ammonia escape. At the same time, it adopts flue gas recirculation technology to achieve a denitrification reaction environment under and inside the bed.

[0010] Other features and advantages of the present invention will become clearer from the detailed description of an exemplary embodiment of a boiler pre-denitrification device with reference to the accompanying drawings. Attached Figure Description

[0011] The accompanying drawings, which form part of this specification, illustrate embodiments of the invention and, together with the specification, serve to explain the principles of the invention.

[0012] in:

[0013] Appendix Figure 1 This is a main schematic diagram of an implementation scheme for a boiler pre-denitrification device.

[0014] Figure reference numerals: 1 Furnace; 2 Air chamber; 3 Air distribution plate; 4 Flue gas recirculation pipe; 5 Fluidizing fan; 6 Supersonic Laval type denitrification spray gun; 7 Denitrification agent; 8 Atomizing agent; 9 Secondary air duct; 10 Mixing fluidizing air duct. Detailed Implementation

[0015] The following is a reference to the appendix. Figure 1 Various exemplary embodiments of the present invention will be further described in detail. It should be noted that, unless otherwise specifically stated, the relative positions, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0016] At the same time, it should be understood that, for ease of description, the dimensions of the various components shown in the accompanying drawings are not drawn to actual scale.

[0017] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0018] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0019] In all embodiments shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations; therefore, other examples of exemplary embodiments may have different values.

[0020] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0022] The structure of this invention is described as follows:

[0023] As a preferred option, an implementation case study is conducted using a circulating fluidized bed boiler as an example (note: pulverized coal boilers are relatively simpler). Refer to the appendix for technical analysis. Figure 1 As shown, a boiler pre-denitrification device is provided, and the components are labeled in the following order: 1 furnace; 2 air chamber; 3 air distribution plate; 4 flue gas recirculation pipe; 5 fluidizing fan; 6 supersonic Laval type denitrification spray gun; 7 denitrification agent; 8 atomizing agent; 9 secondary air duct; 10 mixing fluidizing air duct.

[0024] The functions and connections of each component are explained below:

[0025] The furnace chamber is located at the top of the boiler.

[0026] The two air chambers mentioned above are located at the bottom of the boiler and are only found in circulating fluidized bed boilers.

[0027] The aforementioned three air distribution plates separate the furnace chamber and the air chamber, a feature unique to circulating fluidized bed boilers.

[0028] The 4 flue gas recirculation pipe takes out the waste flue gas emitted from the boiler and supplies it to the 5 fluidizing blower.

[0029] The five fluidizing blowers deliver ignition and combustion air to the underside of the circulating fluidized bed boiler, and the air pressure is relatively high.

[0030] The aforementioned 6 supersonic Laval-type denitrification spray guns are installed in the 9 secondary air duct and spray denitrification agent into the 1 furnace and 2 air chamber.

[0031] The aforementioned denitrifying agent can be ammonia or urea solution.

[0032] The atomizing agent can be compressed air or steam. Preferably, steam is selected. When a steam atomizing agent is selected, it also becomes a denitrification agent.

[0033] The 9 secondary air ducts supply secondary combustion air into the 1 furnace.

[0034] The 10 mixing fluidized air duct mixes the fresh combustion air drawn in by the 5 fluidized air blower with some flue gas and sends it into the 2 air chamber to dilute the oxygen content in the fluidized air.

[0035] The aforementioned 6 supersonic Laval-type denitrification spray guns are arranged inside the 9 secondary air ducts (i.e., the bed).

[0036] The six supersonic Laval-type denitrification spray guns are arranged in the 10 mixed fluidized air ducts (i.e., under the bed).

[0037] 7. Denitrifying agent and 8. Atomizing agent are introduced into the tail of the supersonic Laval type denitrification spray gun.

[0038] See attached document Figure 1 As shown, the working process and advantages of the boiler pre-denitrification device are as follows:

[0039] The general technical principle is: during both the boiler start-up and ignition stages and the load-bearing stage, the 4 flue gas recirculation pipeline is opened to introduce part of the waste flue gas after boiler combustion into the 5 fluidizing blower. The direct effect of this is to reduce the oxygen content of the fluidizing air under the bed.

[0040] 1. Under-bed denitrification process during boiler start-up and ignition: When the boiler is cold-ignited, the furnace temperature is extremely low, resulting in extremely low flue gas temperature. No matter what kind of denitrification device is used at the tail end, it will not be effective. However, the aforementioned boiler pre-denitrification device (taking a circulating fluidized bed boiler as an example) arranges the aforementioned 6 supersonic Laval type denitrification spray guns in the boiler under-bed ignition air duct (i.e., mixing fluidized air duct) and the secondary combustion air duct on the bed. When the oil gun in the under-bed air duct is started and ignited, the aforementioned 6 supersonic Laval type denitrification spray guns located in the mixing fluidized air duct are immediately put into operation, and the aforementioned 4 flue gas recirculation pipe is opened. The aforementioned 5 fluidized blower simultaneously draws in fresh air and waste flue gas, directly generating combustion air with extremely low oxygen content, making the air entering the aforementioned 3 air distribution plate oxygen-deficient air. Since the flue gas temperature generated by the oil gun combustion is relatively high, it can meet the reaction window temperature of the denitrification agent, and can directly remove nitrogen oxides generated by fuel oil in the aforementioned 2 air chamber, realizing under-bed pre-denitrification.

[0041] 2. Denitrification process during stable ignition stage: After the bed temperature reaches the standard, coal is added one after another. After the coal is burning stably, the ignition oil guns are gradually disconnected and the supersonic Laval type denitrification spray guns located in the secondary air duct 9 are put into operation in a timely manner. Since the nozzle of the secondary air duct is far from the outlet of the furnace 1, the denitrification process is realized in the early stage of the oxygen-deficient combustion zone (i.e., the burnout zone) in the upper part of the furnace 1, which is the bed pre-denitrification.

[0042] 4. The intervention of pre-denitrification prolongs the reaction time of the two-phase materials (denitrification agent and nitrogen oxides), reduces the amount of denitrification agent used, and reduces tail ammonia escape (especially when the boiler load is low, causing serious tail ammonia escape), thus extending the service life of the tail denitrification catalyst with SCR carrier.

[0043] 5. The aforementioned 6-speed supersonic Laval-type denitrification spray gun is not an ordinary spray gun. It uses high-pressure atomizing medium for atomization and has super jet rigidity, which can deliver the denitrification agent mixture to the required location.

[0044] 6. One of the technical features of the aforementioned boiler pre-denitrification device is the addition of denitrification agent in the air chamber (i.e., under the bed) and secondary air duct (i.e., on the bed) of the circulating fluidized bed boiler, thereby achieving early denitrification of the fluidized bed boiler.

[0045] 7. In the fluidized bed ignition duct of the circulating fluidized bed boiler, flue gas recirculation is introduced to change the coal-fired combustion air at the bottom into oxygen-deficient combustion air. After the boiler starts up and enters the load stage, the four flue gas recirculation pipes are continuously opened to realize the staged low-NOx combustion of coal in the fluidized bed boiler. This is also the second technical feature of the boiler pre-denitrification device.

[0046] 8. When the 5 fluidizing blower is replaced by the primary air blower of the pulverized coal boiler, the oxygen-deficient supply of primary air (including pulverized coal) can be realized, and the oxygen-deficient and fuel-rich combustion of the staged low-NOx burner of the pulverized coal boiler can be enhanced. At this time, the 6 supersonic Laval type denitrification spray gun located in the 9 secondary air duct is usually installed in the upper area of ​​SOFA air.

[0047] The present invention has now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions disclosed herein based on the above description.

[0048] Although some specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0049] Those skilled in the art will understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

[0050] As a preferred option Figure 1 The embodiments provided are merely one implementation of the boiler pre-denitrification device. Any similar technical modifications inspired by the essence of this technology fall within the protection scope of this invention.

Claims

1. A boiler pre-treatment denitrification device, comprising a furnace, an air chamber, an air distribution plate, a flue gas recirculation pipe, a fluidizing blower, a supersonic Laval-type denitrification spray gun, a denitrification agent, an atomizing agent, a secondary air duct, and a mixing fluidizing air duct, characterized in that, The supersonic Laval-type denitrification spray gun installed in the mixing fluidized air duct injects denitrification agent into the mixing fluidized air duct under the boiler bed. The supersonic Laval-type denitrification spray gun installed in the secondary air duct on the boiler bed injects denitrification agent into the upper combustion zone of the furnace. At the same time, the fluidizing fan introduces boiler waste flue gas through the flue gas recirculation pipe and mixes it with fresh air to form oxygen-deficient combustion air, which is then sent into the ignition air duct and air chamber under the boiler bed in sequence.

2. A boiler pre-denitrification device according to claim 1, characterized in that, The fluidizing blower is specifically designed for circulating fluidized bed boilers. When applied to pulverized coal boilers, it serves as the primary air blower for the boiler.

3. A boiler pre-denitrification device according to claim 1, characterized in that, The supersonic Laval type denitrification spray gun mentioned above includes, but is not limited to, the supersonic Laval type denitrification spray gun.

4. A boiler pre-denitrification device according to claim 1, characterized in that, The atomizing agent includes, but is not limited to, high-parameter vapor.

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