Combustion control adjusting system capable of operating at low load and guaranteeing parameters and low nitrogen emission at same time

Abstract

The invention discloses a combustion control and regulation system capable of operating at low load and simultaneously guaranteeing parameters and low nitrogen emission, which comprises a hearth of a boiler provided with a plurality of combustors and a tail flue, and an air inlet pipe of each combustor is communicated with the tail flue through a recirculation flue gas pipeline; each recirculation flue gas pipeline communicated with the burner air inlet pipe is provided with an independent recirculation adjusting air door, each burner air inlet pipe is communicated with the combustion-supporting air pipeline through a pipeline, and each pipeline communicated with the combustion-supporting air pipeline is provided with an independent adjusting air door. By means of the method and device, designers can reasonably arrange the amount of combustion-supporting air entering the combustor and the amount of recycled smoke, and therefore combustion can be accurately adjusted. Under the low load, it is guaranteed that the normal excess of the running oxygen amount of each combustor is 3%-4%, the smoke circulation amount is controlled to be at the optimal level of 15%-20%, stable and sufficient combustion is guaranteed, meanwhile, NOX emission is kept at 30 mg / Nm < 3 >, and the emission standard is met.

Description

Technical Field

[0001] The present invention relates to the technical field of gas boilers, and in particular to a combustion control and regulation system capable of low-load operation while maintaining parameters and low nitrogen emissions, and is applied to natural gas combustion. Background Art

[0002] Gas boilers have the advantages of high operating efficiency and low pollution, and are developing rapidly. X To meet emission requirements, gas boilers generally use flue gas recirculation to achieve low nitrogen combustion and control NO X However, for boilers with multiple burners, if several of the burners are turned off during the start-up process and long-term low-load operation, excess oxygen will intensify the oxidation of nitrogen in the combustion air, increasing thermal NO X The amount of production, resulting in exhaust NO X Emissions do not meet standards. If the combustion air and recirculated flue gas volume are directly reduced, the combustion stability will be affected, which will have an adverse effect on the continuous operation of the boiler. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention designs a combustion control and regulation system that can operate at low load while maintaining parameters and low nitrogen emissions. It can ensure reasonable air volume distribution under low load, ensure stable combustion and reduce NO X The content meets the emission standards and is suitable for various types of gas boilers, with broad market application prospects.

[0004] The present invention adopts the following technical solutions: A combustion control and adjustment system for low-load operation while maintaining parameters and low nitrogen emissions includes a furnace and a tail flue of a boiler equipped with multiple burners, wherein the air inlet pipe of each burner is connected to the tail flue through a recirculating flue gas pipe, and each recirculating flue gas pipe connected to the burner air inlet pipe is respectively provided with an independent recirculation regulating damper, and each burner air inlet pipe is respectively connected to a combustion-supporting air pipeline through a pipe, and each pipe connected to the combustion-supporting air pipeline is respectively provided with an independent regulating damper.

[0005] Preferably, a recirculation fan is provided on the recirculation flue gas duct.

[0006] Preferably, a blower is provided on the combustion air pipeline.

[0007] Preferably, a flow monitor is provided in each of the recirculating flue gas ducts connected to the burner air inlet pipe and in the tail flue.

[0008] Preferably, an oxygen content detector is provided in the furnace.

[0009] During the period of low-load operation of the boiler, only a few of the burners are started. During this period, open the regulating damper corresponding to the running burner, and slightly open the regulating damper corresponding to the stopped burner to ensure that most of the combustion air enters the running burner to achieve sufficient combustion and maintain the normal operating oxygen content of the burner, that is, 3~4% excess oxygen. When the flue gas recirculation is put into operation, open the running burner and the corresponding recirculating flue gas regulating damper, and close the recirculating flue gas regulating damper of the stopped burner to ensure the amount of flue gas participating in the tail convection heat exchange and achieve parameter-maintaining operation. At the same time, ensure that the flue gas circulation volume entering the burner is balanced, that is, each burner has a flue gas circulation volume of 10~30%. This flue gas circulation volume can ensure the stability of the flame and reduce the combustion of nitrogen oxides NO. X The content meets the emission requirements.

[0010] The present invention can be effectively applied to various types of gas boilers. After adopting the above technical solution, compared with general gas boilers, the main differences are as follows: First, under low-load conditions, the amount of flue gas participating in the tail heat exchange is guaranteed, and parameter-guaranteed operation of low-nitrogen combustion is achieved. Second, unlike directly using a fan for adjustment, an air damper and a recirculating flue gas air damper are set in front of the burner to adjust the air volume and oxygen content ratio entering the burner, so that the combustion is sufficient while reducing NO. X Third, independent air duct dampers and flue gas circulation adjustment dampers are set for each burner to adjust the air volume for each burner separately, so that under low load conditions, the combustion air can enter the running burner as much as possible to ensure stable combustion and achieve low NO X emission.

[0011] The beneficial effects of the present invention are: (1) The present invention can achieve parameter-maintaining operation under low load. For boilers with multiple burners, only a few of the burners are turned on under low load, and at the same time, the amount of fuel and flue gas is reduced, which leads to insufficient convective heat exchange at the tail. By adopting the present invention, the amount of flue gas entering the tail is guaranteed by opening the recirculation regulating damper, thereby ensuring heat exchange and achieving parameter-maintaining operation under low load; (2) The present invention sets an regulating damper and a flue gas circulation regulating baffle in front of the burner to adjust the air volume entering the burner. Compared with general gas boilers that are directly controlled by the fan, the response is faster and the adjustment is more precise. By accurately controlling the air volume and oxygen content, full combustion is achieved while effectively suppressing thermal NO X The production of NO X (3) The present invention sets up independent air duct baffles and flue gas circulation regulating baffles for each burner, which avoids the situation where a large amount of combustion air enters the stopped burner under low load conditions, making the burner fuel configuration more uniform and the air volume distribution more reasonable. While ensuring the stability of the combustion flame, low NOX emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of a system structure of the present invention; In the figure: 1. Furnace, 2. Tail flue, 3. Recirculation flue gas duct, 4. Recirculation fan, 5. Combustion air pipeline, 6. Blower, 7. Recirculation damper 1, 8. Recirculation damper 2, 9. Adjustment damper 1, 10. Adjustment damper 2, 11. Burner 1, 12. Burner 2. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example: Figure 1 As shown, a combustion control and regulation system for low-load operation while maintaining parameters and low nitrogen emissions includes a boiler furnace 1, a tail flue 2, burners 11 and 12. The air inlet pipes of burners 11 and 12 are connected to the tail flue through recirculation flue gas ducts 3, each equipped with a recirculation fan 4. The recirculation flue gas ducts connecting the air inlets of burners 1 and 2 are respectively equipped with recirculation dampers 1 and 8. The air inlets of burners 11 and 12 are respectively connected to the combustion air pipeline 5 through pipes, and the pipes connecting the air inlets of burners 1 and 2 to the combustion air pipeline are respectively equipped with dampers 1 and 10.

[0014] A blower is installed on the combustion air line. A flow monitor is installed in each recirculating flue gas duct connected to the burner air inlet pipe and in the tail flue. An oxygen content detector is installed in the furnace.

[0015] During normal boiler operation, the combustion air, driven by the blower, passes through dampers 1 and 2, respectively, and enters burners 1 and 2. Recirculated flue gas, driven by the recirculation fan, passes through recirculation dampers 1 and 2, respectively, from the rear heating surface of the tail flue, where it mixes with the combustion air and enters burners 1 and 2. Burners 1 and 2 inject fuel, combustion air, and recirculated flue gas into the furnace for combustion. The combustion products enter the tail flue, and a portion of the tail flue gas is withdrawn by the recirculation fan for flue gas recirculation.

[0016] In this example, when the boiler is running at a low load, that is, at 20% load, only Burner 1 is turned on and Burner 2 is turned off. At this time, open damper 1 and recirculation damper 1, slightly open recirculation damper 2 and close damper 2. Burner 1 sprays fuel, combustion air and recirculated flue gas into the furnace for combustion, and the combustion products enter the tail flue, and part of the tail flue gas is drawn back by the recirculation fan for flue gas recirculation. Only opening damper 1 corresponding to burner 1 can ensure that all combustion air enters the running burner, which is convenient for accurately controlling the amount of combustion air required by the running burner, and is conducive to stable combustion and control of NO X Slightly open the recirculation damper 2 to ensure the flue gas volume and superheater inlet parameters, and to protect the equipment by using a small amount of combustion air to cool the stopped burner.

[0017] By adopting this invention, designers can reasonably arrange the amount of combustion air entering the burner and the amount of recirculated flue gas, so as to accurately adjust the combustion. Under low load, it is ensured that each burner maintains a normal excess oxygen of 3%-4% and the flue gas circulation volume is controlled at an optimal level of 15%-20%, ensuring stable and sufficient combustion while making NO X Emissions are maintained at 30mg / Nm 3 , meeting emission standards.

[0018] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A combustion control and regulation system for low-load operation while maintaining parameters and low nitrogen emissions, comprising a furnace and a tail flue of a boiler equipped with multiple burners, characterized in that: The air inlet pipe of each burner is connected to the tail flue through a recirculating flue gas pipe, and each recirculating flue gas pipe connected to the burner air inlet pipe is respectively provided with an independent recirculation regulating damper. The air inlet pipe of each burner is respectively connected to the combustion-supporting air pipeline through a pipe, and each pipe connected to the combustion-supporting air pipeline is respectively provided with an independent regulating damper.

2. A combustion control and adjustment system for low-load operation while maintaining parameters and low nitrogen emissions according to claim 1, characterized in that: The recirculating flue gas duct is provided with a recirculating fan.

3. The combustion control and adjustment system for low-load operation while maintaining parameters and low nitrogen emissions according to claim 1 is characterized in that: A blower is provided on the combustion-supporting air pipeline.

4. The combustion control and adjustment system for low-load operation while maintaining parameters and low nitrogen emissions according to claim 1 is characterized in that: A flow monitor is provided in each of the recirculating flue gas ducts connected to the burner air inlet pipe and in the tail flue.

5. The combustion control and adjustment system for low-load operation while maintaining parameters and low nitrogen emissions according to claim 1 is characterized in that: An oxygen content detector is provided in the furnace.

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