The excess air in the hearth of industrial steam boilers will affect the combustion in the hearth. Therefore, how to effectively control the excess air factor is one of the prerequisites to ensure the reasonable operation of the boiler. Today, we will take the excess air in the furnace of a gas boiler as an example to explain:
Furnace air excess coefficient is one of the important indicators for controlling the combustion process of the gas boiler hearth. For stratified burners, the excess air coefficient at the exit of the furnace is generally between 1.3-1.5. According to the leakage air volume of the flue gas flow through each flue section, the excess air coefficient at the smoke exhaust area should be 1.8-2.0.
There are three influencing factors that determine the heat loss of exhaust smoke: exhaust temperature, air excess coefficient, and cold air temperature. Among them, the gas boiler air excess coefficient is the main influencing factor. Excessive air excess is a huge waste. A large amount of cold air enters the furnace. First, the furnace temperature of the industrial steam boiler is lowered, the combustion conditions tend to be unstable, the volume of flue gas is increased, and the exhaust heat loss is increased. Calculations show that when the excess air coefficient is increased from 2.0 to 3.0, the heat loss from exhaust smoke increases to 4.5%. At the same time, the burden of the induced draft fan is increased, which increases its power consumption. In order to improve the thermal efficiency of gas-fired boilers, it is necessary to pay attention to and raise awareness of the serious hazards caused by excessive air excess coefficients, and strictly control the air excess coefficients in the combustion regulation, which is an area often overlooked in the current heating industry.
The key to avoiding excess air in the furnace lies in reasonable air distribution and monitoring and control methods suitable for it. Monitoring methods include CO2 or O2 content measurement methods. Gas boilers are usually tested for oxygen content. This is because gas boilers have a slightly positive pressure combustion and the sealing problem is easily solved. The measurement of oxygen content accurately reflects the excess air coefficient value. At present, the oxygen content measurement technology generally adopts a zirconia constant temperature oxygen analyzer, which continuously measures the oxygen content of flue gas on-line. According to the oxygen content of the flue gas as a reference, the air-fuel ratio is correctly adjusted for low-oxygen combustion.
At present, the better technology is to automatically adjust the PLD for low-oxygen combustion in the combustion process, select a burner with better performance, and require timely and regular maintenance to keep the burner in good condition for a long time, followed by careful adjustment " "Two doors" are throttle and damper to ensure normal combustion and no black smoke. The excess air coefficient should be as small as possible. Usually, the above two points are achieved. The excess air coefficient is very close to the critical value.
The above is the method that I share for you to deal with the excess air in the hearth of industrial steam boilers. I hope it will be helpful to everyone.
