How Air Preheater in Thermal Power Plant Boosts Combustion and Reduces Fuel Consumption

A boiler releases useful heat energy together with hot flue gases. An air preheater in thermal power plant helps retrieve this residual heat before gas is discharged through the stack. Instead of giving up this heat into the atmosphere, the equipment transfers it to the incoming combustion air.

This simple heat recovery operation impacts combustion quality, fuel consumption, and heat balance of a boiler. Whether it would be beneficial is a matter of how well the air preheater suits the boiler, fuel, air flow, and flue-gas properties.

Heat Recovery Mechanism

Flue gas, after burning, goes through the boiler and carries the remaining sensible heat toward the exhaust system. A air preheater in thermal power plant utilizes this energy to warm the air which is going to be burned in the furnace.

A air preheater for flue-gas heat recovery helps reduce fuel quantity necessary to preheat combustion air. A air preheater for flue-gas heat recovery can help the energy so recovered go a long way in the boiler heat balance.

Why Combustion May Benefit from Hotter Air

Combustion relies on the correct proportions of fuel, oxygen, temperature, and mixing. The lower temperature of air would reduce the level of heat available for the ignition. Moreover the ignition of coal may require very stable combustion conditions.

An air preheater in thermal power plant heats incoming air before delivering it to the burners. This could facilitate more reliable ignition and maintain furnace heat at desired level.

The effects depend on the type of fuel and design of the boiler. The air preheater for improving boiler efficiency produces a better output if it operates within the designed outlet-air temperature range for the combustion system.

It is better that an air preheater for improving boiler efficiency is set at the point of operation of the boiler.

Fuel Consumption Saving Factors

The principle is simple: The boiler needs energy to heat up the combustion air, i.e., the fuel. When a portion of the air is already heated, the fuel can do more with that energy.

A air preheater in thermal power plant can thus minimize heat losses from the stack and increase the overall efficiency of the boiler.

Flue-gas heat recovery in a air preheater for flue gas heat recovery must be assessed on an hourly or daily operation basis rather than a generic efficiency figure.

If designed rightly, the air preheater for improving boiler efficiency not only enhances efficiency but reduces fuel consumption as well.

Final Results Are Dependent on More Than the Heat Transfer

The most common pitfall is measuring the performance of the air preheater in thermal power plant through heat-transfer area. Yet in reality, pressure loss, air leakage, fouling and maintenance also contribute to the overall picture.

High resistance on the air side will drive fan power consumption up in an attempt to maintain the desired air flow levels. The result of air leakage is the combustion air may go through the flue-gas route without getting involved in combustion.

One of the challenges is the accumulation of fouling. Deposits of ash and other residues on the heat-transfer surfaces reduce the heat flow across the tubes while at the same time increasing the resistance. This underlines the importance of cleanability and selection of materials for the air preheater for flue gas heat recovery.

The very same reasoning is also valid for air preheater for improving boiler efficiency: even top-notch performance in heat transfer will be a non- issue when the boiler conditions make it impractical for the plant.

Buyer Checkpoints

All air preheaters, especially an air preheater for flue gas heat recovery, that get selected in boiler installation should undergo an evaluation of the following aspects:

·Flue-gas outlet and inlet temperatures

·Combustion-air outlet temperature

·Air and gas flow rates

·Permissible pressure drop

·Fuel type and the properties of ashes

·Fouling conditions

·Material and corrosion requirements

·Air leakage control

Combining these pieces together will give you a fair idea if this air preheater for flue gas heat recovery will be able to deliver that much desired amount of heat without causing an increase in your operating costs.

Efficient Boiler System Depends on Full Utilization of Heat Transfer

The function of the air preheater for improving boiler efficiency is not only to recover heat but also to influence combustion, losses of heat from the stack, the amount of energy spent on fans, and maintenance work simultaneously.

This is why the complete boiler heat balance must be considered for air preheater for improving boiler efficiency design. A goal is not only to raise the highest possible temperature of air. Excessively high heat recovery might be accompanied by the risk of corrosion, fouling, or undesired modifications to the combustion conditions that could affect other system parameters, too.

An efficient air preheater for flue heat recovery achieves a compromise that allows heat loss prevention, pressure drop, and maintenance activities without compromising reliability.

Conclusion

It is a known fact that an air preheater in thermal power plane increases boiler efficiency through recovering the sensible heat of flue gas which is transferred to the air that is to be burnt. An air preheater for flue gas heat recovery is central to this process. With this air, the heat for fuel can be reduced in such a way that the process remains stable throughout.

It is the best results that come off if you treat it as an integral part of the boiler system. An air preheater for improving boiler efficiency will have to be able to do the heat recovery without creating any problems related to airflow, leakage, fouling, or maintenance.

Only when these aspects are considered together, is it possible for an air preheater for flue gas heat recovery to take an amount of the energy that would normally be released through the stack and use it again, which is very beneficial to a power plant in terms of lower fuel consumption and more efficient ‌operation.