Boiler thermal efficiency refers to the percentage of the heat input from the fuel that is effectively utilized.
The thermal efficiency of coal-fired boilers typically ranges from 70% to 85%, while that of oil-fired, gas-fired, and electric boilers ranges from 90% to 99%.
The higher the thermal efficiency, the better the boiler's performance.
Improving boiler thermal efficiency entails increasing the effective utilization of heat and minimizing various heat losses within the boiler; the primary focus here is on reducing heat loss via flue gas discharge and mechanical heat loss due to incomplete combustion.
(1) Reducing Heat Loss via Flue Gas Discharge:
1) Reduce the air leakage rate in air preheaters, particularly in rotary-type air preheaters.
2) Strictly control the water quality parameters of the boiler water; when the scale accumulation inside the water-cooled wall tubes reaches 400 mg/m³, acid cleaning should be performed promptly.
3) Whenever possible, burn high-quality coal with a low sulfur content. While modern large-capacity power generation boilers are equipped with air preheaters—designed to prevent condensation on the cold-end heating surfaces (which leads to low-temperature corrosion)—one method used to extend the service life of the air preheater is to increase the temperature of the air entering the preheater, thereby raising the boiler's flue gas exit temperature (though this results in increased heat loss via flue gas).
(2) Reducing Mechanical Heat Loss Due to Incomplete Combustion:
1) Adjust combustion conditions based on the boiler load and operating time; optimize air distribution, and—to the greatest extent possible—lower the position of the flame center within the furnace to ensure the coal undergoes complete combustion.
2) Adjust the coal feed rate based on the volatile matter content of the raw coal and the operating time, maintaining the coal supply at an optimal level.
(3) Reducing Heat Dissipation Losses from the Boiler: This is primarily achieved by strengthening the maintenance and inspection of the insulation layers covering the boiler piping and the main boiler body.
Calculation of Boiler Thermal Efficiency
Taking a 1-ton boiler as an example: the boiler's heat output is 600,000 kcal/hour, and the calorific value of the natural gas fuel is 8,600 kcal/m³. (1) 600,000 kcal/h ÷ 8,600 kcal/Sm³ ÷ 100% = 69.76 Sm³
This means that, assuming a boiler energy conversion efficiency of 100%, the burner consumes 69.76 standard cubic meters of natural gas to generate 600,000 kcal/h of heat—sufficient to meet the operational requirements of a 1-ton boiler.
(2) 600,000 kcal/h ÷ 8,600 kcal/Sm³ ÷ 92% = 75.83 Sm³
This means that, assuming a boiler energy conversion efficiency of 92%, the burner consumes 75.83 standard cubic meters of natural gas to generate 600,000 kcal/h of heat—sufficient to meet the operational requirements of a 1-ton boiler.
(3) 600,000 kcal/h ÷ 8,600 kcal/Sm³ ÷ 96% = 72.67 Sm³
This means that, assuming a boiler energy conversion efficiency of 96%, the burner consumes 72.67 standard cubic meters of natural gas to generate 600,000 kcal/h of heat—sufficient to meet the operational requirements of a 1-ton boiler.
The higher the boiler's thermal efficiency, the lower the natural gas consumption.
Boiler thermal efficiency refers to the percentage of the heat input from the fuel that is effectively utilized.
The thermal efficiency of coal-fired boilers typically ranges from 70% to 85%, while that of oil-fired, gas-fired, and electric boilers ranges from 90% to 99%.
The higher the thermal efficiency, the better the boiler's performance.
Improving boiler thermal efficiency entails increasing the effective utilization of heat and minimizing various heat losses within the boiler; the primary focus here is on reducing heat loss via flue gas discharge and mechanical heat loss due to incomplete combustion.
(1) Reducing Heat Loss via Flue Gas Discharge:
1) Reduce the air leakage rate in air preheaters, particularly in rotary-type air preheaters.
2) Strictly control the water quality parameters of the boiler water; when the scale accumulation inside the water-cooled wall tubes reaches 400 mg/m³, acid cleaning should be performed promptly.
3) Whenever possible, burn high-quality coal with a low sulfur content. While modern large-capacity power generation boilers are equipped with air preheaters—designed to prevent condensation on the cold-end heating surfaces (which leads to low-temperature corrosion)—one method used to extend the service life of the air preheater is to increase the temperature of the air entering the preheater, thereby raising the boiler's flue gas exit temperature (though this results in increased heat loss via flue gas).
(2) Reducing Mechanical Heat Loss Due to Incomplete Combustion:
1) Adjust combustion conditions based on the boiler load and operating time; optimize air distribution, and—to the greatest extent possible—lower the position of the flame center within the furnace to ensure the coal undergoes complete combustion.
2) Adjust the coal feed rate based on the volatile matter content of the raw coal and the operating time, maintaining the coal supply at an optimal level.
(3) Reducing Heat Dissipation Losses from the Boiler: This is primarily achieved by strengthening the maintenance and inspection of the insulation layers covering the boiler piping and the main boiler body.
Calculation of Boiler Thermal Efficiency
Taking a 1-ton boiler as an example: the boiler's heat output is 600,000 kcal/hour, and the calorific value of the natural gas fuel is 8,600 kcal/m³. (1) 600,000 kcal/h ÷ 8,600 kcal/Sm³ ÷ 100% = 69.76 Sm³
This means that, assuming a boiler energy conversion efficiency of 100%, the burner consumes 69.76 standard cubic meters of natural gas to generate 600,000 kcal/h of heat—sufficient to meet the operational requirements of a 1-ton boiler.
(2) 600,000 kcal/h ÷ 8,600 kcal/Sm³ ÷ 92% = 75.83 Sm³
This means that, assuming a boiler energy conversion efficiency of 92%, the burner consumes 75.83 standard cubic meters of natural gas to generate 600,000 kcal/h of heat—sufficient to meet the operational requirements of a 1-ton boiler.
(3) 600,000 kcal/h ÷ 8,600 kcal/Sm³ ÷ 96% = 72.67 Sm³
This means that, assuming a boiler energy conversion efficiency of 96%, the burner consumes 72.67 standard cubic meters of natural gas to generate 600,000 kcal/h of heat—sufficient to meet the operational requirements of a 1-ton boiler.
The higher the boiler's thermal efficiency, the lower the natural gas consumption.