Steam boilers are integral in manufacturing industries for heating and drying purposes in process operations. Boilers generate steam by igniting fuels through combustion that requires an optimal amount of fuel, heat, and air. Although all three elements are vital for proper combustion, this article will discuss the role of air in detail.
Improper combustion leads to carbon monoxide poisoning that may cause more damage than the collective impact of pressure vessel failure and combustion explosion. Therefore, it is necessary to ensure proper maintenance, operation, and inspection of the combustion system. Various factors affect the combustion air supply, leading to the issue of carbon monoxide.
Carbon monoxide is caused by incomplete or improper combustion. It is colorless and odorless that cannot be detected with an instrument. In some cases, there are indicators for the production of carbon monoxide. During improper burning of natural gas, the formation of aldehydes along with carbon monoxide causes an unpleasant odor. Similarly, smoke or soot is released during the oil combustion, indicating unburned oil with its smell.
Carbon monoxide is occurred due to two primary reasons:
- Improper mixing of the air with the fuel used during the combustion
- Inadequate supply of combustion air to the fuel-burning equipment
The improper mixing of air and fuel in combustion usually occurs due to the adjustments of components consisting of the burner. It is also important to ensure that the burner is provided with an adequate air supply for proper and complete combustion. Since most of the steam boilers are inspected by boiler manufacturers and independent organizations, steam boiler design is less likely to be the cause of carbon monoxide.
Various factors should be considered for ensuring adequate air supply in combustion:
- The amount of air needed for the combustion process
- The amount of air needed for cooling and ventilation in the boiler room
- The impact of the venting system such as vent hoods, economizers, barometric dampers, and draft control systems
- Presence of exhaust fans that may be the source of providing the air or consuming the air from the boiler room
- Any other equipment that may draw the air needed for combustion
- Burner maintenance
- Boiler room maintenance
The amount of air required for the combustion process depends on the chemical composition of the fuel used. On the other hand, the amount of air needed for cooling and ventilation in the boiler room is determined by the heat loss from the boiler shell, boiler piping, or any other equipment that generates heat. Heat loss from the boiler shell usually ranges up to 4% of the boiler output, depending on the steam boiler size, pressure, temperature, boiler design, and insulation. In most cases, a large boiler faces less heat loss. To ensure the optimum amount of air in the burner; the boiler room temperature, at the burner fan inlet, should be maintained between 50°F and 100°F.
The venting system can impact the amount of air needed in the boiler room and the performance of the air fan in providing the required amount of airflow. For instance, draft hoods and barometric dampers consume the air from the boiler room that could have been used for combustion. The result of introducing an economizer must be considered before its installation. The flue gas economizer accelerates the pressure loss through the venting system. In case of substantial pressure loss, the overall combustion air fan performance is reduced.
Exhaust fans in the boiler room can be considered a severe challenge in the combustion air supply unless provided with adequate makeup air. Facilities that draw combustion air from the plant itself face more unbalance.
Regular maintenance of the burner and boiler room is essential to ensure adequate combustion air supply. A clean boiler room is vital for the proper combustion process. Dirt or impediments in the fan inlet screens or flan blades lead to soot formation and carbon monoxide. Timely boiler flue-gas analysis helps in detecting an insufficient supply of combustion air. Burner adjustments must be performed by a trained professional with a necessary instrument to assess the amount of oxygen or carbon dioxide and ppm of carbon monoxide.
It is paramount to ensure that the air supply is sufficient for the combustion process to prevent the possibility of mishaps such as furnace explosion in process plants.
Since our inception in 1983, Rakhoh Boilers have emerged as a globally leading industrial steam boiler manufacturer. With our beginning as a steam boiler manufacturer in Pune, we are presently one of the trusted names as boiler manufacturers and thermal solution providers in over 26 countries worldwide. We manufacture a range of efficient steam boilers, waste heat recovery boilers, thermic fluid heaters, and boiler accessories. We provide the best boiler services like energy audit, steam trap assessment, boiler automation, annual maintenance contract, turnkey solutions, etc.
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