Views: 15 Author: Site Editor Publish Time: 2025-07-01 Origin: Site
The air preheater is a heat exchange equipment in the thermal system that utilizes the heat of the high-temperature flue gas discharged from the boiler to heat the cold air entering the boiler. The core logic of its heat recovery is as follows:
Energy recycling: The waste heat in the flue gas that would otherwise be emitted to the atmosphere (usually flue gas temperature of 120-250°C) is transferred to the air used for combustion to raise the temperature of the air from ambient (20-30°C) to 100-300°C. The air is then preheated to a temperature of 100-300°C. The air is then heated to a temperature of 100-300°C.
Enhancement of combustion efficiency: After the preheated air enters the furnace chamber, it can accelerate the combustion speed of fuels (e.g., coal), reduce incomplete combustion losses, and at the same time reduce fuel consumption (energy saving rate of about 5%-15%).
Environmental benefits: reduce the flue gas emission temperature, reduce thermal pollution, and at the same time with the desulfurization, denitrification system, can optimize the reaction conditions (such as low-temperature denitrification efficiency enhancement).
consists of metal plates forming a channel through which flue gas and air flow alternately and heat is transferred through the plates.
It is suitable for application in scenarios that require high space compactness, such as industrial boilers.
Key technology flow and design points of heat recovery system
System flow:
High temperature flue gas is led out from the boiler tail and enters into the flue gas side of the air preheater, releasing heat and then discharged through the dust collector and desulphurization tower;
Cold air is sent into the air side of the air preheater by the air blower, and after absorbing the heat, it becomes hot air, which is then used to fuel the combustion in the burner.
Design core considerations:
Heat transfer area optimization: Calculate the heat transfer area according to the flue gas volume, temperature and air heating demand, to avoid the “big horse-drawn cart” or insufficient heat recovery;
Anti-corrosion and ash buildup:
The low-temperature area of the flue gas side is susceptible to ammonium hydrogensulphate (NH4HSO4) corrosion (at a temperature of <150℃), corrosion-resistant materials need to be used (e.g., ND steel or increase the wall temperature). ND steel) or improve the wall temperature (such as heater heating);
accumulation of ash will reduce the efficiency of heat transfer, need to configure acoustic soot blowing, steam soot blowing and other soot removal devices;
air leakage control: rotary preheater need to be through the sealing structure (such as radial, axial sealing) will be the air leakage rate of less than 5%, to avoid the loss of heat on the air side.
