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CPOTE2020 logo
6th International Conference on
Contemporary Problems of Thermal Engineering
Online | 21-24 September 2020

Abstract CPOTE2020-1027-A

Book of abstracts draft
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Natural gas liquefaction coupled with pressure reduction in the natural gas transmission system

Krzysztof PAJĄCZEK, Silesian University of Technology, Poland
Wojciech KOSTOWSKI, Silesian University of Technology, Poland

This article concerns the natural gas liquefaction installation coupled with natural gas pressure reduction. The intent is to reduce power consumption (kWh/kg) of the natural gas liquefaction process by partial recovery of high-pressure exergy. Natural gas pressure reduction is carried out at reduction stations, which are located on the outskirts of cities or in gas compressor stations, eg fuel gas for facilities of the compressor station. The article focuses on the gas letdown station where it was possible to build a natural gas liquefaction unit coupled with the fuel gas pipeline. The reduction of natural gas pressure using the expander allows for a significant reduction of the gas temperature, which greatly facilitates the liquefaction of natural gas. In this case, there is no additional heat to pre-heat the gas before entering the turboexpander. Moreover, the temperature drop of outlet gas was used as a stage of pre-cooling. Natural gas flows through the reduction stage retrofitted with heat exchanger and expander. A part of the feed gas flows through the heat exchanger to pre-cool inlet gas and to raise its temperature. The part of the gas, which is meant to be liquefied, is directed to the natural gas liquefaction plant and then partially liquefied. This document analyses power consumption, exergy recovery, and exergy efficiency for Nitrogen, SMR, and C3MR liquefaction units analysed in six different capacities. Finally the most suitable configuration in terms of exergy and energy efficiency will be proposed. Calculations of liquefied natural gas quantity and composition were carried out using computer software ProMax with a built-in environment of Peng-Robinson equations.

Keywords: Natural gas, Energy management, Liquefied natural gas (LNG), Natural gas transmission network, Expander technologies