Working principle of pure steam generator:

The pure steam generator first uses a coal mill to grind coal into powder. Pulverized coal is carried by air and fed into the furnace for combustion through a burner installed on the furnace wall. The gas temperature at the center of the flame reaches 1500~1600 ℃. The evaporative heating surface of the boiler is installed on the inner wall of the furnace, forming a water-cooled wall that absorbs the radiation heat of high-temperature flames and flue gas in the furnace, reducing the flue gas temperature at the outlet of the furnace to 1000~1150 ℃. The upper part of the rear wall water-cooled wall (at the inlet of the horizontal flue) forms a sparse array of slag solidification pipes to prevent slag formation. To prevent the accumulation of ash or slag on the heating surface of the boiler, a soot blower is also used. The superheater is located in the horizontal flue, and its function is to heat the saturated steam coming out of the drum into superheated steam with a certain temperature, with the aim of improving the economic efficiency of the power plant. After passing through the superheater, the temperature of the flue gas decreases to 500-600 ℃, and then enters the tail flue. One of the heating surfaces in the tail flue is the economizer. It is composed of many parallel serpentine tubes, whose function is to preheat the feed water before entering the drum and reduce the exhaust temperature. The other rear heating surface is the air preheater. Its function is to heat the air to a certain temperature before entering the furnace, in order to improve combustion and further reduce the exhaust temperature, thereby improving boiler efficiency.

In terms of the water steam system of a pure steam generator, the feedwater is heated to a certain temperature in the heater, enters the economizer through the feedwater pipeline, further heated, and then sent to the drum. After mixing with the boiler water, it flows down the downcomer to the inlet header of the water-cooled wall. Water absorbs the radiation heat from the furnace inside the water-cooled wall tube to form a steam water mixture, which reaches the drum through the rising tube and is separated by a steam water separation device. The separated saturated steam flows from the upper part of the drum to the superheater, continues to absorb heat and become 450 ℃ superheated steam, which is then sent to the steam turbine.

In terms of combustion and smoke air systems, the pure steam generator uses a forced draft fan to send air into the air preheater and heat it to a certain temperature. Pulverized coal is ground into a certain fineness in the coal mill, and is carried by a portion of hot air from the air preheater and sprayed into the furnace through the burner. The mixture of coal powder and air sprayed by the burner is mixed and burned with other hot air in the furnace, releasing a large amount of heat. The hot flue gas after combustion flows through the furnace, slag bundle, superheater, economizer, and air preheater in sequence, and then passes through the dust removal device to remove the fly ash. It is then sent to the chimney by an induced draft fan for exhaust to the atmosphere.