Piping design for LNG liquefaction systems

Abstract

Liquefied Natural gas is the future of the energy sector, as it is a source of clean energy. The liquefaction of natural gas is achieved at 111.67 K temperature, 1 atm; which is a cryogenic temperature. The cryogenic flow needs special attention because fluid, as well as material of the pipe, behave differently at cryogenic temperature. Two-phase flow is another critical point in the liquefaction of natural gas. The objective of this thesis work is to select the material of the pipe, calculate frictional losses in the pipe, and pressure drop in the pipe through which the cryogenic fluid flows. The frictional loss in the pipe mostly depends on Reynolds number, Roughness factor, and phase of flow. As the Reynolds number increases, the friction factor increases in a greater value. As the time lapses, corrosion and erosion factor plays a key role in frictional pressure drop. As there is an increment in pipe diameter, the pressure drop due to friction or frictional losses decrease but by virtue of that the weight of the piping system increases which is an unfavourable condition from an economic point of view. The flow in pipe encounters different forms of fluid in the liquefaction cycle of natural gas i.e. liquid phase flow, Gas phase flow and mix flow of liquid and gas. The Liquid flow and gas flow in a pipe are mainly deal with the Colebrook equation. Two-phase flow is a critical phenomenon in the liquefaction cycle. The pipe sizes mentioned in the result can be used for experimental setup. It is found that the corrosion factor is 0.3 and 3 mm respectively for a period of 30 years. Also, it is found that, there exists two phase flow after the joule Thomson expansion device. While selecting the pipe size, it has been observed that the thickness of the pipe greatly depend on internal pressure of the flowing fluid.