Device for adjusting ammonia escape of flue gas of circulating fluidized bed boiler
By replacing the purified tail flue gas to the secondary air system of the circulating fluidized bed boiler, the problems of ammonia escape and thermal efficiency of the circulating fluidized bed boiler are solved, and the balance of nitrogen oxides and ammonia escape is reduced, which improves the improvement of the improvement of nitrogen oxides and ammonia escape. Thermal efficiency.
Patent Information
- Application Number
- CN202421108986.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-21
- Publication Date
- 2024-12-27
- Estimated Expiration
- Not applicable · inactive patent
AI Technical Summary
There are challenges in controlling ammonia escape and thermal efficiency in circulating fluidized bed boilers. It is difficult for the prior art to achieve the balance of nitrogen oxides and ammonia escape at the same time, and excessive use of denitrifying agents leads to a reduction in thermal efficiency.
Design a device to regulate the escape of flue gas ammonia in the circulating fluidized bed boiler. By replacing the purified tail flue gas to the secondary air system, the mixture of fuel nitrogen and oxygen is reduced, and the fuel NOx is reduced to be reduced by forming a combustion-rich area, and the fuel NOx is reduced by using Residual ammonia removes nitrogen oxides in the flue gas, reduces the amount of denitrifying agent added, and improves thermal efficiency.
It effectively reduces ammonia escape by 20%-40%, while ensuring qualified emissions of nitrogen oxides, improves the boiler thermal efficiency, reduces the amount of denitrifying agent, controls the oxygen content of chimney flue gas, and avoids adverse consequences.
Smart Images
Figure CN222256526U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of boiler flue gas ammonia escape control, and in particular to a device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler. Background Art
[0002] Circulating fluidized bed boilers use fluidized combustion, which has effectively solved the basic problems of thermodynamics, mechanics, materials science, and engineering problems such as expansion, wear, and overheating, and has become an advanced technology for energy utilization of difficult-to-burn solid fuels (such as coal gangue, oil shale, urban garbage, sludge, and other wastes). As various regions attach importance to the control of pollutants in boiler tail flue gas, most regions have set the emission limit of ammonia fugitive emissions from circulating fluidized bed boilers at 8mg / m 3 At present, it is still difficult to achieve stable ammonia escape standards, and there is no mature and effective technology to control ammonia escape.
[0003] As we all know, the denitrification technology route of circulating fluidized bed boilers is mainly SCR and SNCR, and the denitrification agents used are mainly ammonia water and urea. In use, there is often an overuse of denitrification agents and ammonia escape exceeds the standard. At present, there are two main technical routes for controlling ammonia escape. One is to improve the mixing efficiency of denitrification agents and flue gas by controlling the concentration of denitrification agents, the position and angle of denitrification agent injection devices, etc., so as to achieve the method of reducing nitrogen oxide emission data. This method requires careful design during the construction period, but it is often not ideal when it is put into operation, and it cannot achieve the balance of nitrogen oxides and ammonia escape. The second is to reduce the original emission concentration of thermal nitrogen oxides by adjusting the temperature of the boiler combustion chamber. This method will cause adverse effects such as reduced boiler output and reduced thermal efficiency.
[0004] Therefore, it is necessary to design a device for regulating ammonia slip in flue gas of a circulating fluidized bed boiler to solve the problem that the existing boiler flue gas control ammonia slip operation effect is not ideal and causes low boiler thermal efficiency. Utility Model Content
[0005] In view of the problems existing in the prior art, the purpose of the utility model is to provide a device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler, so as to effectively reduce the dosage of denitrification agent and reduce the ammonia escape emission concentration of flue gas at the tail of the circulating fluidized bed boiler.
[0006] The technical solution adopted by the utility model to solve its technical problems is: a device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler, comprising a furnace, a flue and a flue gas return fan, the furnace is connected to a return feeder, the smoke outlet of the return feeder is connected to the flue, an air preheater is installed on the flue, the flue is connected to the flue through a flue gas return pipeline, the outlet of the flue gas return fan is connected to a secondary fan inlet pipe and a return fan to a secondary fan crossover pipe, the secondary fan inlet pipe is connected to the secondary fan, the secondary fan is connected to the air preheater, and the air preheater is connected back to the furnace through the preheated secondary air pipeline.
[0007] Specifically, a smoke return line cut-off valve is installed on the smoke return line, the smoke return line is connected to the air distribution line, an air distribution line cut-off valve is installed on the air distribution line, and the air distribution line is located behind the smoke return line cut-off valve.
[0008] Specifically, a smoke return inlet secondary air shut-off valve is installed on the connecting pipe between the smoke return fan and the secondary fan inlet pipe, and a secondary fan outlet shut-off valve is installed at the rear of the secondary fan.
[0009] Specifically, a return fan to secondary fan crossover pipe cut-off valve is installed on the return fan to secondary fan crossover pipe.
[0010] Specifically, the preheated secondary air duct is provided with three branch ducts, all of which are connected to the furnace, and the three branch ducts are respectively installed with secondary air duct cut-off valve 1, secondary air duct cut-off valve 2, and secondary air duct cut-off valve 3.
[0011] Specifically, an ammonia spray gun is installed on the returner, the ammonia spray gun is connected to an ammonia pipeline and a compressed air pipeline, the ammonia pipeline is connected to an ammonia tank, an ammonia pump is installed on the ammonia pipeline, and a return fan is installed at the bottom of the returner.
[0012] Specifically, the flue is connected to a chimney, and an environmental protection online monitoring device is installed on the chimney.
[0013] Specifically, an economizer and a deoxidized catalyst container are installed in sequence on the flue of the return device smoke exhaust port, an air preheater is installed at the rear of the deoxidized catalyst container, a primary air preheater is installed at the rear of the air preheater, a dust collector is installed at the rear of the primary air preheater, and an induced draft fan is installed at the rear of the dust collector.
[0014] Specifically, a primary fan is installed on the primary air preheater.
[0015] The utility model has the following beneficial effects:
[0016] The utility model is a device for regulating the ammonia escape of flue gas from a circulating fluidized bed boiler. The tail flue gas after purification of the circulating fluidized bed boiler is returned to the secondary air system of the circulating fluidized bed boiler to reduce the mixing of fuel nitrogen and oxygen in the combustion air, and reduce the fuel NOx to N by forming a rich combustion area. 2 , in order to reduce "fuel" type NOx, and at the same time use the residual ammonia in the tail flue gas after purification to remove nitrogen oxides in the flue gas, reducing the dosage of denitrification agent by 20%-40%, while ensuring the qualified emission of nitrogen oxides and effectively reducing ammonia escape, effectively reducing the ammonia escape emission concentration in the tail flue gas of the circulating fluidized bed boiler, and reducing the dosage of denitrification agent.
[0017] The utility model is designed to adjust the ammonia escape of flue gas from a circulating fluidized bed boiler. Since the oxygen content of the secondary air changes from the original air to the purified return flue gas, the oxygen content therein is greatly reduced. When the circulating fluidized bed boiler is running at a low load, the oxygen content in the furnace of the circulating fluidized bed boiler is adjusted by the utility model, and the oxygen content of the chimney flue gas is controlled. When the data of the environmental protection online monitoring facility is converted, no adverse consequences are caused by the high oxygen content.
[0018] The utility model is a device for regulating ammonia escape of flue gas of a circulating fluidized bed boiler. Since the flue gas temperature after purification of the circulating fluidized bed boiler is about 100°C, which is higher than the room temperature of the original secondary fan inlet air, the flue gas heat recovery is realized and the overall thermal efficiency of the boiler is improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 It is a schematic diagram of the structure of a device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler.
[0020] In the figure: 1- flue; 2- flue gas return pipeline; 3- flue gas return pipeline cut-off valve; 4- air distribution pipeline cut-off valve; 5- air distribution pipeline; 6- flue gas return fan; 7- flue gas return secondary air cut-off valve; 8- return fan to secondary fan crossover pipe; 9- return fan to secondary fan crossover pipe cut-off valve; 10- secondary fan inlet pipe; 11- secondary fan; 12- secondary fan outlet cut-off valve; 13- air preheater; 14- secondary air pipeline after preheating; 15 -Secondary air duct shut-off valve one; 16-Secondary air duct shut-off valve two; 17-Secondary air duct shut-off valve three; 18-Ammonia tank; 19-Ammonia pump; 20-Compressed air pipeline; 21-Ammonia spray gun; 22-Furnace; 23-Returner; 24-Economizer; 25-DeNOx catalyst container; 26-Return fan; 27-Primary air preheater; 28-Dust collector; 29-Induced draft fan; 30-Chimney; 31-Primary fan; 32-Environmental protection online monitoring device. DETAILED DESCRIPTION
[0021] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely further describe the technical solutions in the embodiments of the utility model. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0022] Embodiment 1.
[0023] like Figure 1 As shown, a device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler comprises a furnace 22, a flue 1 and a flue gas return fan 6, the furnace 22 is connected to a return feeder 23, a smoke outlet of the return feeder 23 is connected to the flue 1, an ammonia spray gun 21 is installed on the return feeder 23, the ammonia spray gun 21 is connected to an ammonia pipeline and a compressed air pipeline 20, the ammonia pipeline is connected to an ammonia tank 18, an ammonia pump 19 is installed on the ammonia pipeline, and a return fan 26 is installed at the lower part of the return feeder 23.
[0024] The economizer 24 and the catalyst container 25 are sequentially installed on the flue 1 of the exhaust port of the return device 23, the air preheater 13 is installed at the rear of the catalyst container 25, the primary air preheater 27 is installed at the rear of the air preheater 13, and the primary fan 31 is installed on the primary air preheater 27. The dust collector 28 is installed at the rear of the primary air preheater 27, and the induced draft fan 29 is installed at the rear of the dust collector 28.
[0025] An air preheater 13 is installed on the flue 1. The flue 1 is connected to the flue gas return fan 6 through the flue gas return pipeline 2. The outlet of the flue gas return fan 6 is connected to the secondary fan inlet pipe 10 and the return fan to secondary fan crossover pipe 8. The return fan to secondary fan crossover pipe cut-off valve 9 is installed on the return fan to secondary fan crossover pipe 8. The secondary fan inlet pipe 10 is connected to the secondary fan 11, and the secondary fan 11 is connected to the air preheater 13. The air preheater 13 is connected back to the furnace 22 through the preheated secondary air pipeline 14.
[0026] A smoke return pipeline cut-off valve 3 is installed on the smoke return pipeline 2, the smoke return pipeline 2 is connected to the air distribution pipeline 5, the air distribution pipeline 5 is installed with an air distribution pipeline cut-off valve 4, and the air distribution pipeline 5 is located behind the smoke return pipeline cut-off valve 3.
[0027] A smoke return inlet secondary air shut-off valve 7 is installed on the connecting pipe between the smoke return fan 6 and the secondary fan inlet pipe 10 , and a secondary fan outlet shut-off valve 12 is installed at the rear of the secondary fan 11 .
[0028] After preheating, the secondary air duct 14 is provided with three branch ducts, all of which are connected to the furnace 22, and the three branch ducts are respectively installed with a secondary air duct cut-off valve 15, a secondary air duct cut-off valve 2 16, and a secondary air duct cut-off valve 3 17.
[0029] The flue 1 is connected to the chimney 30, and an environmental protection online monitoring device is installed on the chimney 30. The environmental protection online monitoring device adopts the existing PID principle VOCs online monitoring instrument and is connected to the configuration monitoring platform.
[0030] Embodiment 2, the working principle of the device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler adopts the structural form of embodiment 1.
[0031] A method for operating a device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler comprises the following steps:
[0032] 1. The flue gas return fan 6 adopts frequency conversion control, and the flue gas volume is designed to be 10%-40% of the air volume of the secondary fan 11. The flue gas return pipeline cut-off valve 3, the air distribution pipeline cut-off valve 4, the return fan to the secondary fan crossover pipe cut-off valve 9, and the secondary fan outlet cut-off valve 12 are remotely centrally controlled, or manually adjusted on-site by a manual valve. The application scenarios of the utility model can be divided into two types.
[0033] 2. The first usage scenario is that the power used by the secondary fan 11 is greater than the full load power of the flue gas return fan 6: the purified boiler flue gas passes through the flue 1 of the circulating fluidized bed boiler through the flue gas return pipeline 2, the flue gas return pipeline cut-off valve 3, the flue gas return fan 6, the flue gas return enters the secondary air cut-off valve 7, the secondary fan inlet pipe 10, the secondary fan 11, the secondary fan outlet cut-off valve 12, and the air preheater 13, and then passes through the secondary air pipeline 14, the secondary air pipeline cut-off valve one 15, the secondary air pipeline cut-off valve two 16, the secondary air pipeline cut-off valve three 17, and enters the furnace 22 to participate in combustion and denitrification reaction.
[0034] 3. The second usage scenario is that the power used by the secondary fan 11 is less than or equal to the full load power of the flue gas return fan 6: the purified boiler flue gas passes through the flue of the circulating fluidized bed boiler through the flue gas return pipeline 2, the flue gas return pipeline shut-off valve 3, the flue gas return fan 6, the return fan to the secondary fan crossover pipe 8, the return fan to the secondary fan crossover pipe shut-off valve 9, the air preheater 13, the secondary air pipeline 14 after preheating, the secondary air pipeline shut-off valve 1 15, the secondary air pipeline shut-off valve 2 16, the secondary air pipeline shut-off valve 3 17, and enters the furnace 22 to participate in the combustion and denitrification reaction; in this scenario, the flue gas returns to the secondary air shut-off valve 7, the secondary fan outlet shut-off valve 12 is closed, and the secondary fan 11 stops running. At this time, the oxygen content in the return flue gas is controlled by adjusting the opening of the air distribution pipeline shut-off valve 4 set on the air distribution pipeline 5.
[0035] The solution to high ammonia escape is:
[0036] The main reasons for high ammonia slip in circulating fluidized bed boilers are that the ammonia entering the boiler to participate in the denitrification reaction is not fully utilized and the original emission concentration of nitrogen oxides is high.
[0037] The main structure of the circulating fluidized bed boiler includes two parts: the combustion chamber and the circulating return material. The combustion chamber is mainly divided into the lower dense phase area and the upper dilute phase area. The combustion air required by the combustion chamber is mainly supplied by the primary fan and the secondary fan after being pressurized and preheated by the air preheater. The primary air enters the dense phase area of the combustion chamber from the bottom air distribution plate of the circulating fluidized bed boiler to maintain the fluidization of the bed layer in the dense phase area of the combustion chamber, and at the same time provides oxygen to the fuel in the dense phase area at the bottom of the furnace to ensure combustion. The secondary air enters from the lower middle part of the furnace 22 of the circulating fluidized bed boiler, mainly to supplement the oxygen required by the boiler combustion chamber, strengthen the mixing of materials, and adjust the distribution of the temperature field in the furnace.
[0038] The utility model returns the purified flue gas to the secondary air system and enters the furnace 22. Since the oxygen content of the secondary air is changed from the original air to the purified return flue gas, the oxygen content is greatly reduced. When the material blending is strengthened, the combustion of coal is suppressed, the burnout time of coal is prolonged, the generation of nitrogen oxides is reduced, the formation amount and existence time of coke can be increased, and the generated nitrogen oxides are reduced to nitrogen and water through the reduction reaction of coke and nitrogen oxides, thereby further reducing the original emission concentration of nitrogen oxides.
[0039] The surplus ammonia carried in the purified flue gas after the denitrification reaction, after returning to the secondary air system and entering the furnace 22, enters the dense phase area and the dilute phase area in the furnace combustion chamber through the secondary air, and is fully mixed with the fuel and the flue gas. Compared with the SNCR device at the furnace outlet and the SCR device near the economizer, they have the characteristics of uniform mixing and long residence time. Therefore, the ammonia therein can be fully utilized in the process of reacting with nitrogen oxides, thereby reducing the ammonia water consumption of the SNCR or SCR denitrification device and achieving the emission reduction goal of reducing the escape concentration of ammonia in the flue gas exhausted by the circulating fluidized bed boiler.
[0040] Through the analysis of the reasons for the excessive ammonia escape, it can be known that the fundamental reason is that the ammonia entering the boiler to participate in the denitrification reaction is not fully utilized. The utility model uses the tail flue gas after purification of the circulating fluidized bed boiler to be returned to the secondary air system of the circulating fluidized bed boiler, thereby reducing the mixing of fuel nitrogen and oxygen in the combustion air, and reducing the fuel NOx to N2 by forming a rich combustion area to reduce "fuel" type NOx. At the same time, the residual ammonia in the tail flue gas after purification is used to remove nitrogen oxides in the flue gas, which can reduce the dosage of the denitrifier by 20%-40%, and effectively reduce ammonia escape while ensuring the qualified emission of nitrogen oxides.
[0041] The present utility model is not limited to the above-mentioned implementation modes, and anyone should be aware of the structural changes made under the inspiration of the present utility model. Any technical solutions that are the same or similar to the present utility model fall within the protection scope of the present utility model.
[0042] The technology, shape and structure parts not described in detail in the present invention are all known technologies.
Claims
1. A device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler, characterized in that: It includes a furnace, a flue and a flue gas return fan, the furnace is connected to a return feeder, the smoke outlet of the return feeder is connected to the flue, an air preheater is installed on the flue, the flue is connected to the flue through a flue gas return pipeline, the outlet of the flue gas return fan is connected to a secondary fan inlet pipe and a return fan to a secondary fan crossing pipe, the secondary fan inlet pipe is connected to the secondary fan, the secondary fan is connected to the air preheater, and the air preheater is connected back to the furnace through a secondary air pipeline after preheating.
2. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 1, characterized in that: The smoke return pipeline is provided with a smoke return pipeline cut-off valve, the smoke return pipeline is connected to the air distribution pipeline, the air distribution pipeline is provided with an air distribution pipeline cut-off valve, and the air distribution pipeline is located at the rear of the smoke return pipeline cut-off valve.
3. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 1, characterized in that: A smoke return inlet secondary air shut-off valve is installed on the connecting pipe between the smoke return fan and the secondary fan inlet pipe, and a secondary fan outlet shut-off valve is installed at the rear of the secondary fan.
4. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 1, characterized in that: A return fan to secondary fan crossover pipe cut-off valve is installed on the return fan to secondary fan crossover pipe.
5. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 1, characterized in that: The post-preheating secondary air duct is provided with three branch ducts, all of which are connected to the furnace, and the three branch ducts are respectively installed with secondary air duct cut-off valve 1, secondary air duct cut-off valve 2, and secondary air duct cut-off valve 3.
6. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 1, characterized in that: An ammonia spray gun is installed on the returner, the ammonia spray gun is connected to an ammonia pipeline and a compressed air pipeline, the ammonia pipeline is connected to an ammonia tank, an ammonia pump is installed on the ammonia pipeline, and a return fan is installed at the bottom of the returner.
7. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 1, characterized in that: The flue is connected to a chimney, and an environmental protection online monitoring device is installed on the chimney.
8. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 1, characterized in that: An economizer and a deoxidized catalyst container are sequentially installed on the flue of the return device smoke outlet, an air preheater is installed at the rear of the deoxidized catalyst container, a primary air preheater is installed at the rear of the air preheater, a dust collector is installed at the rear of the primary air preheater, and an induced draft fan is installed at the rear of the dust collector.
9. The device for regulating ammonia escape from flue gas of a circulating fluidized bed boiler according to claim 8, characterized in that: A primary fan is installed on the primary air preheater.