Steam Heat Transfer Stainless Steel Superheater Coil ASME Standard

Superheater tube wall metal in the boiler pressure parts under the highest temperature, so must use high quality low carbon steel and various chromium molybdenum alloy steel, in the highest temperature part sometimes also use austenitic chromium nickel stainless steel. In boiler operation, if the temperature of the pipeline exceeds the allowable temperature limit of the material's durable strength, fatigue strength or surface oxidation, the pipeline burst will occur.

Superheater is the part of boiler that heats steam from saturation temperature to superheating temperature, also known as steam superheater. Superheater can be divided into convection type, radiant type and semi-radiant type according to heat transfer mode. According to the structural characteristics can be divided into serpentine tube type, screen type, wall type and wrapped wall type. They all consist of a number of parallel pipes and inlet and outlet containers.

The outer diameter of the pipe is generally 30 ~ 60 mm.The most common type of superheater is the serpentine tube.It has a relatively dense tube set, arranged in the flue gas temperature of 450 ~ 1000℃, by the transverse and longitudinal erosion of flue gas.The flue gas mainly transfers heat to the pipe by convection, and some radiation absorbs heat.Screen type superheater consists of a plurality of tube screen, arranged in the upper part of the furnace or the outlet, belongs to the radiation or semi-radiation superheater.The former absorbs the radiant heat of the furnace flame, while the latter absorbs part of the convective heat.In the power station boiler above 10 mpa, generally both screen type and serpentine tube type superheater are used to increase heat absorption.The wall superheater applied to the inner wall of the furnace is the radiant superheater, which is seldom used.Wall type superheater is used in large capacity power station boiler to form the wall of the furnace roof and convection flue, and the insulation material is applied outside to form the light furnace wall.

Differences

Principle

• Principle of superheater is similar to steam generating tubes of boiler.

• The hot gases at high temperature sweep over superheater tubes and raise the temperature of steam which magnitude depends upon exit gas temperature leaving the superheater and gas velocity.

Application

Use for heating saturated steam, steam temperature could be up to 900 degree C.

Superheater Capacity Upgrades to Increase Power Generation

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