Analysis of low-tonnage LNG production technologies with nitrogen circulation cycle

DOI: 10.17586/1606-4313-2023-22-1-55-65
UDC 621.59

Analysis of low-tonnage LNG production technologies with nitrogen circulation cycle

Sanavbarov Romin I. , Andrei V. Zaitsev, Shermatova Firuza M.

For citation: Sanavbarov R.I., Zaitsev A.V., Shermatova F.M. Analysis of low-tonnage LNG production technologies with nitrogen circulation cycle. Journal of International Academy of Refrigeration. 2023. No 1. p. 55-65. DOI: 10.17586/1606-4313-2023-22-1-55-65

LNG production is a very energy-intensive process and any efforts to reduce energy costs are of great interest. LNG production with a circulating nitrogen cycle is considered as the most suitable option for low-tonnage LNG production. In LNG production systems with a circulating nitrogen cycle, the maximum gas liquefaction coefficient can reach up to 100%. These systems require relatively small investments since it is possible to use a small refrigerating machine and an appropriate system for pretreatment of gas. The technological scheme of the systems under consideration is characterized by relative simplicity, reliability, rapid commissioning, compactness and minimal safety requirements. The main disadvantage of the technology is high energy consumption. The article provides an energy analysis of technologies with nitrogen cycle and the ways to reduce their energy costs. Various modifications of such technologies are considered. The use of a refrigerating machine with various working substances and their impact on the overall efficiency of the technology is also considered. The results of the analysis show that when the pre-cooling cycle is included in the scheme, the energy efficiency of the technology increases significantly. When the refrigerating machine with the working substance R410 is switched on, the specific energy consumption of the process is reduced by 22.7%, and when propane is used as a refrigerant in the refrigerating machine − by 20%. The analysis also considers cycles using CO2 and СН4‒СО2 pair. Their results show a reduction in energy costs by 7% and 12%, respectively.

Keywords: liquefied natural gas, gas expansion in the expander, liquefaction process, pre-cooling, energy analysis, nitrogen circulation cycle, refrigerating machine, working substance.

Read the full article