Complicatedly, the fuel extinguishes heat and is transferred to the water in the boiler. The effect of heat transfer is called thermal efficiency. The higher the thermal efficiency, the better the heat transfer function. The thermal efficiency of ordinary coal-fired boilers is 70 to 85%, and the thermal efficiency of oil, gas and electric heating boilers is 90 to 99%.
How is the boiler thermal efficiency calculated?
There are two ways to determine the boiler thermal efficiency. One is obtained indirectly from the definition of boiler thermal efficiency, which is the ratio of the boiler's ineffective applied heat to the boiler's input heat (positive equilibrium method):
The formula is: η = Q1 / Q2 × 100%
The other is the anti-equilibrium method commonly used in boiler design or thermal efficiency experiments, that is, after determining the various heat losses, use the following formula to obtain the thermal efficiency of the boiler:
The formula is: η = 100- (q2 + q3 + q4 + q5 + q6)%
The boiler positive equilibrium test method is complex and easy to use, and it is more accurate when used for industrial boilers with low thermal efficiency. The reverse equilibrium method is more complicated, but after measuring and analyzing various heat losses, we can find out the way to improve the boiler economy. The anti-equilibrium method is suitable for large-capacity and high-efficiency ancient chemical power station boilers, because at this time the fuel consumption cannot be accurately measured, and the evaporation error is also large. When one-sided identification of boilers, it is necessary to do both positive and negative equilibrium experiments.
How does the boiler thermal efficiency improve?
Boiler thermal efficiency is an important goal to clarify the economic function of the boiler. A high thermal efficiency indicates that the boiler is economical and wastes fuel to reduce the primary power consumption.
Improving the thermal efficiency of the boiler is to add ineffective application heat and increase the various heat losses of the boiler. The focus is to reduce the boiler exhaust heat loss and the loss of machinery not completely extinguished.
1. Reduce the heat loss of boiler exhaust gas (1) Reduce the air leakage rate of the air preheater, especially the air leakage rate of the rotary air preheater.
(2) Strictly control the water quality target of the boiler water. When the scale content in the water-cooled wall tube reaches 400mg / m, it should be pickled in time.
(3) Burn high-quality fuel with low sulfur content as much as possible, and reduce the air temperature at the inlet of the air preheater. The ancient large-capacity power generation boilers were equipped with air preheaters to avoid condensation on the heated front surface of the cold preheater. Incurred high temperature corrosion of the air preheater.
2. Reduce the heat loss due to the machine not being completely extinguished. (1) Adjust the extinguishing conditions according to the boiler load and time, and reasonably distribute the air so that the fuel is fully extinguished in the furnace.
(2) Adjust the feeding amount according to fuel volatile content and time to maintain the fuel value.