The boiler body consists of two parts: a pot and a furnace. The "pot" is a container for steam and water, and its function is to absorb the heat released by the "furnace" to raise the temperature of water or turn it into steam with a certain pressure. "Boiler" is composed of various components that bear internal or external pressure and form a closed system, including boiler shell, boiler drum, downcomer, header, water wall, slag pipe, boiler tube bundle, steam-water separator, steam temperature regulator, steam superheater and economizer. "Furnace" is a fuel burning equipment, whose function is to provide fuel burning conditions and transfer the heat generated by fuel burning to "pot". The furnace is composed of various parts of the fuel burning place, including furnace wall, furnace arch, furnace (combustion chamber), coal hopper in front of the furnace, coal gate, grate, slag discharge plate, distribution air supply device and various burners.

Auxiliary equipment includes fuel supply system equipment, air supply equipment, steam-water system equipment, ash removal equipment, flue gas purification system equipment, instruments and automatic control system equipment.

Working principle and technology: it can be divided into furnace method and pot method at the same time. The former includes the combustion process of fuel and the heat transfer process in the furnace on the flue gas side outside the heating surface; The latter includes the heat transfer process between the heating surface metal and the service, the heating, evaporation and overheating process of the working medium, the flow process of the working medium and the thermochemical process of the working medium side (such as steam quality, salt precipitation, scaling and corrosion of the heating surface).

In-furnace process: coal is sent to the raw coal bunker of the boiler through the coal conveying device, and the coal in the raw coal bunker enters the front coal hopper and then falls on the chain grate moving slowly forward, and then enters the combustion chamber through the coal gate. The air required for fuel combustion is pressed into the air preheater by the blower, heated and then enters the sectional air supply bin below the grate, and then fully contacts and mixes with the coal above the grate for a strong combustion reaction. The generated high-temperature flue gas transfers heat to the mixture of water and steam water in the water wall around the combustion chamber in the form of radiation heat exchange. Then, the high-temperature flue gas passes through the flue window and washes the steam superheater transversely and longitudinally, then flows into the convection flue and washes the boiler tube bundle transversely along the refractory wall, and transfers heat to working fluids such as steam, water and steam-water mixture in the convection heating surface tube bundle through convection heat exchange; The flue gas with gradually decreasing temperature along the way enters the tail flue, which washes the economizer transversely, and transfers part of the heat to the working medium (water) in the tube through convection heat exchange, then the flue gas flows into the air preheating tube, and transfers the heat to the working medium (air) flowing out of the tube through convection heat exchange, and the heated air enters the furnace, thus enhancing the combustion in the furnace. At this time, the flue gas temperature has been reduced to the economical exhaust temperature, leaving the boiler body, being removed by the dust collector, and then discharged into the atmosphere through the induced draft fan, flue and chimney.

In-furnace process: the feed water that meets the boiler water quality requirements after being treated by the water treatment system is sent to the economizer by the feed pump through the pipeline, and the water absorbs the heat of the tail flue gas in the economizer, and then enters the upper drum after preheating. The flow process of working medium in the pot includes heating process, evaporation process and overheating process (small boilers generally have no process). Working fluid is divided into natural circulation and forced circulation according to the flow mode.