Entropy-statistical analysis of a natural gas liquefaction unit with a nitrogen cooling cycle
DOI: 10.17586/1606-4313-2025-24-4-35-44
UDC 621.59
Safonov Igor V., Зайцев А. В.
Keywords: entropy-statistical analysis, liquefied natural gas, nitrogen cycle, specific energy consumption, entropy production.
UDC 621.59
Entropy-statistical analysis of a natural gas liquefaction unit with a nitrogen cooling cycle
For citation: Safonov I.V., Zaitsev A.V. Entropy-statistical analysis of a natural gas liquefaction unit with a nitrogen cooling cycle. Journal of International Academy of Refrigeration. 2025. No 4. p. 35-44. DOI: 10.17586/1606-4313-2025-24-4-35-44 (in Russian)
Abstract
This article presents a detailed study of a natural gas liquefaction unit opertion using a nitrogen refrigeration cycle. Primary attention is paid to assessing the energy efficiency of the liquefaction process, as well as finding ways to increase the efficiency of such equipment operation. A specific low-tonnage unit with a capacity of 7 tons of LNG per hour produced by Cryogenmash OOO located in the Kaliningrad region is being considered as an object of research. This unit has been chosen due to its typical design and prevalence among Russian oil and gas sector enterprises. The main purpose of the analysis presented is to develop effective qualitative recommendations for improving energy performance. A complete diagram of a natural gas liquefaction unit with a description of the key elements and interactions between them is provided. Special attention is paid to energy performance in the operation of heat exchangers of various types, compressor units, and expander units. For each node, calculations showing the contribution of this device to the overall balance of thermal energy and the degree of dissipation of useful potential were performed. Based on the analysis conducted, it was revealed which elements of the unit carry the highest energy consumption and determine the efficiency of the entire technological cycle. Important conclusions and recommendations have been formulated, in particular: 1) maximum entropy production values are observed mainly in heat exchange devices; 2) compressor efficiency indicators significantly depend on ambient temperature conditions; 3) the state of the environment has a significant impact on the overall productivity of the unit. A priority area is to study the dependence of energy consumption on ambient temperature. The results show that when the air temperature noticeably decreases, the amount of necessary mechanical work for the gas liquefaction process is significantly reduced. Thus, the operation of such an unit in cold regions, such as the Arctic, allows achieving significant economic benefits by reducing electricity costs.
Abstract
This article presents a detailed study of a natural gas liquefaction unit opertion using a nitrogen refrigeration cycle. Primary attention is paid to assessing the energy efficiency of the liquefaction process, as well as finding ways to increase the efficiency of such equipment operation. A specific low-tonnage unit with a capacity of 7 tons of LNG per hour produced by Cryogenmash OOO located in the Kaliningrad region is being considered as an object of research. This unit has been chosen due to its typical design and prevalence among Russian oil and gas sector enterprises. The main purpose of the analysis presented is to develop effective qualitative recommendations for improving energy performance. A complete diagram of a natural gas liquefaction unit with a description of the key elements and interactions between them is provided. Special attention is paid to energy performance in the operation of heat exchangers of various types, compressor units, and expander units. For each node, calculations showing the contribution of this device to the overall balance of thermal energy and the degree of dissipation of useful potential were performed. Based on the analysis conducted, it was revealed which elements of the unit carry the highest energy consumption and determine the efficiency of the entire technological cycle. Important conclusions and recommendations have been formulated, in particular: 1) maximum entropy production values are observed mainly in heat exchange devices; 2) compressor efficiency indicators significantly depend on ambient temperature conditions; 3) the state of the environment has a significant impact on the overall productivity of the unit. A priority area is to study the dependence of energy consumption on ambient temperature. The results show that when the air temperature noticeably decreases, the amount of necessary mechanical work for the gas liquefaction process is significantly reduced. Thus, the operation of such an unit in cold regions, such as the Arctic, allows achieving significant economic benefits by reducing electricity costs.
Keywords: entropy-statistical analysis, liquefied natural gas, nitrogen cycle, specific energy consumption, entropy production.
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