Boiler Operation Skills| Gas-Fired Boilers Incomplete Combustion Cause Analysis and Improvement Measures

January 10, 2023

In recent years, with the rapid growth of the economy, the problem of environmental pollution has become increasingly serious.


The issue of energy saving and emission reduction has aroused the great attention of relevant departments. As a clean energy source, natural gas has gradually replaced kerosene as boiler fuel and is widely used in industrial production.


However, in the operation of the boiler, the problem of incomplete combustion of gas exists objectively, which is not conducive to energy saving and environmental protection. It will also affect the safe operation of the boiler to a large extent.


Causes of Incomplete Combustion of Gas-Fired Boilers


Incomplete combustion of gas boiler will not only affect its thermal efficiency, but also bring many hazards.


The reasons for the incomplete combustion of gas boilers are as follows:


a. Gas volume and air volume do not match.


During the operation of the gas-fired boiler, the blower pressurizes the air and sends it into the furnace to mix with the gas, heat up and burn. If the combustion adjustment of the boiler is not normal, the gas volume and air volume will not match properly. It will cause incomplete combustion of gas, thereby reducing the economy of boiler operation.


b. The flame temperature decreases.


In order to ensure that the gas can continue to burn stably and form a complete flame, it should be ensured that the flame is maintained at a standard temperature. Incomplete combustion occurs when the flame comes into contact with a cold object causing its temperature to drop.


c. Insufficient smoke extraction.


The flue gas generated by the operation of the gas boiler must be discharged in time and smoothly to ensure the combustion efficiency. If the flue gas discharge is not well controlled, part of the flue gas will stay in the furnace. Thus, the air supply required for combustion is insufficient, and incomplete combustion will also occur.


d. The ineffective mixing of gas and air in the furnace can also easily lead to incomplete combustion.


Hazards of Incomplete Combustion of Gas-Fired Boilers


a. reduce thermal efficiency.


Due to the existence of incomplete combustion, a reducing environment is formed in the furnace of the boiler. In addition, the high-C molecular components in the gas begin to carbonize and accumulate in the high-temperature environment, and stay on the inner wall of the smoke pipe or the outside of the water pipe. More soot will be formed for a long time, resulting in The thermal resistance of the heating surface of the boiler increases, the heat transfer rate decreases, the exhaust gas temperature gradually increases, and the heat loss in the exhaust process is too large, which affects the operating efficiency of the gas-fired boiler.


b. A large amount of C0 is generated.


Incomplete combustion of gas will produce a large amount of CO. If there is leakage, it will pose a great threat to the health and even life of the fireman, and will increase the risk of boiler explosion accidents. security risks.


c. Gas consumption is high.


Due to incomplete combustion, some gas in the furnace has not really participated in the combustion, resulting in an increase in gas consumption. Seriously affect the thermal efficiency and economy of the boiler.


d. Carbon black is produced.


When the gas boiler is in operation, the gas and oxidant on both sides of the flame zone are heated. During the thermal decomposition process of the gas, the dehydrogenation of the original compound and the gradual accumulation of carbon atoms produce heavy hydrocarbons, and even smaller carbon particles. It takes a certain amount of time to burn carbon particles, because the incomplete combustion of gas causes carbon particles to be taken away by the combustion products before being burned, and finally produces soot, which brings great pollution to the ecological environment.


Technical improvement measures for incomplete combustion of gas-fired boilers


Incomplete combustion of gas-fired boilers is likely to bring about serious consequences.

The following improvement measures should also be made according to the actual situation:


a. Improved air volume control.


The main goal of improving the air supply volume control is to ensure that the air supply volume and gas volume are maintained in a stable state, and to promote the improvement of the thermal efficiency of the gas boiler operation. Operators can make reasonable adjustments to the moving blades of the blower, and the air supply volume needs to be calculated according to the combustion rate demand and the proportional relationship between the gas volume. 

If the gas volume changes, the air supply volume should also be adjusted in time. Since the actual data measurement of the oxygen content in the furnace often has a certain lag, it can be controlled by an intelligent adjustment system. The air supply regulator and the damper can be set as a quick response system, and the oxygen content regulator is used for correction to ensure that the inside of the furnace The oxygen content is at a stable value, which allows the operator to reasonably determine the air supply volume.


b. Improved air volume control.


The improvement of the induced air volume control can ensure that the negative pressure of the boiler furnace is stable within the set allowable fluctuation range. If the negative pressure of the furnace is too low, it is easy to cause the flame and smoke to overflow.

It poses a great threat to the safety of boiler equipment and operators: if the negative pressure of the furnace is too high, cold air will enter, which will cause the induced draft fan to run too fast, and safety accidents will easily occur. In this regard, the operator needs to ensure that the negative pressure of the furnace is stable at about -200 Pa, and adjust the induced air volume. Usually, a single loop adjustment method can be selected, relying on the feedback before setting to achieve effective control.


c. Improved oxygen control in flue gas.


In the combustion control system, a closed-loop control circuit of the oxygen content of the flue gas is added to reasonably adjust the oxygen content in the flue gas in different production operations to ensure the complete combustion of the fuel. When the boiler is in normal operation, the oxygen content of the flue gas should be controlled at 2% to 4%. By monitoring the color of the furnace flame and the change of the value of the boiler oxygen meter, the ratio of boiler gas and air is adjusted in time to reduce the heat loss caused by incomplete combustion of the boiler.


d. Increase the boiler hot air temperature.


Reasonable air distribution to increase the air temperature at the entrance of the furnace is not only conducive to the rapid combustion of fuel but will not cause fluctuations in the temperature of the furnace. The specific operation method is to appropriately increase the air temperature at the suction port of the blower by adjusting the opening of the hot air recirculation valve; adjust the air distribution according to the combustion situation, and minimize the air distribution of the burners that do not participate in the combustion to ensure stable combustion and improve the furnace temperature. .


e. Strengthen energy conservation management.


Strengthen energy-saving management awareness, do a good job in daily maintenance of equipment, improve various boiler energy-saving management systems with the energy-saving post responsibility system of responsible personnel at all levels as the core; strengthen energy-saving knowledge training for managers and operators at all levels. Improve energy-saving awareness and operation level; carry out data management through monitoring, measurement, statistics, recording and analysis of energy consumption; regularly conduct combustion tests and combustion adjustments on boilers. Ensure that the boiler is operating in a reasonable working condition.




The soot and carbon black produced by incomplete combustion of gas-fired boilers will not only reduce the thermal efficiency of the boiler but also cause serious pollution to the environment. Incomplete combustion will also cause a large amount of gas consumption, affecting the energy saving of the boiler: the CO produced is even more detrimental to the safe and stable operation of the gas boiler. 

Combining the reasons for the incomplete combustion of the boiler, EPCB boiler puts forward effective technical improvement measures, which realizes the full combustion of the boiler gas, and improves the energy saving, environmental protection, safety and economy of the boiler operation.

Further Reading:

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