boiler exhaust gas temperature, ZOZEN explain why the temperature of boiler exhaust gases should be maintained above minimum value

The lower the boiler exhaust gas temperature, the better the boiler operation. This is a misunderstanding. Today, ZOZEN will explain why the boiler exhaust gas temperature should be maintained above minimum value. The exhaust gas temperature is low, which indicates the good utilization of the boiler's waste heat. However, if the boiler exhaust gas temperature is too low, there will also be bad influence. Next, ZOZEN will explain why the temperature of boiler exhaust gases should be maintained above minimum value for you.

1. Abnormal phenomena of too low exhaust gas temperature - ZOZEN's first reason to explain why the temperature of boiler exhaust gases should be maintained above minimum value

1) Low boiler exhaust gas temperature measured due to cold air enters the measurement area

2) Too high excess air coefficient of the flue gas duct

3) Too low work load of the boiler

4) Insufficient combustion caused by the too low furnace temperature

5) Leakage of the superheater, reheater, economizer and air preheater at the boiler end

2. Series consequences of too low exhaust gas temperature - ZOZEN's second reason to explain why the temperature of boiler exhaust gases should be maintained above minimum value

The too low boiler exhaust gas temperature can cause the series problems of low-temperature sulfuric acid corrosion, ulceration and perforation of heating surface tube wall at the boiler end. Therefore, large and medium sized oil boilers and some coal boilers are equipped with the steam air heater at the boiler end to increase the exhaust gas temperature. ZOZEN senior engineer suggests that normal boiler exhaust gas temperature should be consistent with the rated values of the boiler.

ZOZEN gas-fired boiler system

After the above analysis, we believe you have understood ZOZEN's reasons to explain why the boiler exhaust gas temperature should be maintained above minimum value. Besides the reasons to explain why the temperature of boiler exhaust gases should be maintained above minimum value, ZOZEN is also willing to introduce the reasons why the boiler exhaust gas temperature rises. (Take the gas-fired boiler as an example.)

1) Scaling and ash deposition on the heating surface. The scaling and ash deposition on the water-cooled wall of the furnace and the ash deposition of the superheater, convention tube bundles, economizer and preheater can increase the thermal resistance of the flue gas, weaken the heat transfer, lessen the cooling effect of the flue gas and increase the boiler exhaust gas temperature.

2) Too high excess air coefficient. Under normal circumstances, as the furnace outlet excess air coefficient increases, the boiler exhaust gas temperature rises.

3) Too high air leakage coefficient. The air leakage refers to the air leakage in the furnace and flue gas duct, which is one of the main reasons why the boiler exhaust gas temperature rises. This factor is inevitable. Therefore, the allowable air leakage coefficient for a certain heating surface is specified. When the air leakage coefficient increases, the exhaust gas temperature of the gas-fired boiler rises.

4) High feed water temperature. The heat transfer temperature difference between the flue gas temperature and the water temperature is small, which correspondingly increases the exhaust gas temperature of the gas-fired boiler.

5) The increase of moisture in the fuel. It can increase the amount and specific heat of the flue gas, which increases the boiler exhaust gas temperature.

6) The increase of boiler's work load. The work load increases, and the flue gas amount, steam quantity, feed water quantity, air quantity also increase proportionally. However, due to the increase of furnace outlet flue gas temperature, the boiler exhaust gas temperature rises.

7) Poor fuel quality. When the low calorific value gas fuel is used, the furnace temperature decreases, the radiation heat transfer in the furnace reduces and the flue gas amount increases due to the non-combustible components in the low-calorific value fuel, which increases the boiler exhaust gas temperature.

8) The secondary combustion in the flue gas duct at the boiler end.

These are the reasons to explain why the boiler exhaust gas temperature should be maintained above minimum value and why the exhaust gas temperature of the gas-fired boiler increases. In general, boiler exhaust gas temperature design should comprehensively consider the safety and economy of the boiler. If you have more questions about ZOZEN’s reasons to explain why the temperature of boiler exhaust gases should be maintained above minimum value, welcome to consult the online customer service of ZOZEN Boiler.