One of the important elements of gas main lines is a cooling system of the transported gas, which helps to increase its reliability and reduce operating costs. As gas temperature decreases, the capacity of the main gas pipelines increases.
Cooling of gases is based on application of cooling systems (tubular heat exchangers) which decrease the temperature of hot dusty gases without supply of external air to into the cooled gas stream.
System operation is based on convection process - heat transfer from heated gases to refrigerant. Gas (in the majority of cases -atmospheric air) or liquid (most commonly water or oil) can serve as refrigerant. Heat exchange occurs on the walls of the heat exchanger’s tubes.
Application of this system also allows usage of the cooler as the first stage of dust elimination. Cooled gas containslarge dust fractions that are caught at this stage.
The dust that is contained in process gas tends to adhere to tubes surfaces. To prevent this, a chain cleaning system is used – it helps to avoid formation of dust layers on the surface of the cooling tubes.
The direction of the cooled gas flow is from top to bottom, the refrigerant moves perpendicular to it. Such a system contributes to the loss of dust in the collecting cone, separated in the chamber of the heat exchanger. For heat exchangers using cooling gas, the latter is injected into the heat exchanger tubes by means of axial or centrifugal fans. For heat exchangers using liquid, the pressure of the supply network is used.
Process gas cooling systems can be:
Heat exchanger tubes: carbon and stainless steel, aluminum, copper, titanium and their alloys.
Fins: carbon and stainless steel, aluminum, copper, titanium and their alloys.
Casing: carbon and stainless steel.
Tube sheet: carbon and stainless steel, copper, titanium and their alloys.
Advantages of this system:
|Pressure||up to 400 bar (tube side), up to 70 bar (shell side)|
|Temperature||up to 600 °C|
|Dimensions||with no particular limits|