Vertical Boiler Air Preheater Tubular for Thermal Power Plant Boilers

Introduction

Air preheater is a kind of equipment which can improve the heat exchange performance of the boiler and reduce the energy consumption. The function of the air preheater is to heat the flue gas discharged from the tail flue of the boiler and transmit it to the air before entering the boiler through the radiator, so as to preheat the air to a certain temperature.

The air preheater is generally used for coal-fired boilers in power station.It can be divided into tubular type and rotary type. The rotary type can be further divided into wind hood rotary type and heating surface rotary type.Power stations usually use the heating surface rotary air preheater. Generally, the application in boilers is two-compartment, three-compartment and four-compartment, among which the four-compartment is more commonly used in CFB boilers.

Working principle

Taking rotary air preheater as an example, the principle of air preheater is illustrated. The rotary air preheater rotates slowly when it works. The smoke will enter the smoke side of the air preheater and then be discharged. The heat carrried in the smoke will be absorbed by the radiator in the air preheater. After that, the air preheater rotates slowly, and the radiator moves to the air side, then the heat wil be transferred to the air before entering the boiler.

The air preheater applied in the boiler is mostly three-compartment type with fire alarm system, clearance adjustment system and frequency conversion control system. The air preheater is widely used in flue gas boiler system because of its convenient use, simple operation and safe operation, and can improve the heat exchange performance of the boiler system.

Functions

Improve and enforce combustion

The air through the heat exchanger enters the furnace, which accelerates the drying, ignition and combustion process of the fuel, ensures the stable combustion in the boiler and improves the combustion efficiency.

2, Enhance heat transfer

Because the combustion in the furnace has been improved and strengthened, and the temperature of hot air entering the furnace has been increased, the average temperature level in the furnace has also been raised, so the radiation heat in the furnace can be strengthened.

3,Reduce the loss of the furnace, lower the exhaust gas temperature and improve the thermal efficiency of the boiler

Because of the stable combustion in the furnace and the enhanced radiation heat exchange, the chemical incomplete combustion loss can be reduced. On the other hand, the air preheater uses the waster heat of flue gas to further reduce the loss of the exhaust gas, thus improving the thermal efficiency of the boiler. According to experience, when the air in the preheater rises by 1.5 degrees, the exhaust gas temperature can be reduced by 1 degree. After installation of the air preheater in the boiler, if the air temperature can be raised by 150-160 degrees by the waste heat, the exhaust gas temperature can be reduced by 110-120 degrees, and the thermal efficiency of the boiler can be increased by 7-7.5E%. Fuel can be saved by 11-12%.

4,Hot air can be used as fuel disiccant.

For layer boilers, if there is hot air, fuels with higher moisture and ash content can be used. For power station boilers, hot air is an important desiccant and pulverized coal conveying medium in grease powder system.

Tubular Air Preheater

The main heat transfer component of tubular air preheater is thin-walled steel tube. The tubular air preheaters are mostly cubic. The steel tubes are arranged vertically and staggered with each other. Both ends are welded on the upper and lower tube sheets.The tubular air preheater is equipped with an intermediate tube sheet in the tube box. The flue gas passes through the preheater up and down the pipe, while the air passes through the preheater horizontally to complete heat transfer.

Tubular air preheater is widely used in power station boilers and industrial boilers because of its advantages of good sealing, high heat transfer efficiency, easy manufacturing and processing. The shortcomings of tubular air preheater are large volume, easy ash plugging of steel tube content, difficult cleaning and easy wear and tear at flue gas inlet.

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