Complex designing

Natural gas liquefaction

For covering peak gas consumption loads, gas transportation, provision of gas supply to remote, rural and resort areas and for using gas as engine fuel, LENNIICHIMMASH Ltd designs both large-capacity plants for production of liquefied natural gas at outputs of 10-40 t/hour with a high (more than 90%) gas liquefaction ratio, and low-capacity plants with outputs up to 1 t/h. The liquefaction process comprises a single-flow cooling cycle using mixture of hydrocarbons and nitrogen. Such plant includes the following units:

• gas preparation (profound drying and, in case of a high content of harmful impurities, cleaning; filtration)
• coolant compression
• pre-cooling
• condensation and re-cooling
• storage of liquefied natural gas
• rectification (for production of coolant components)

For low-capacity gas liquefying plants, the following liquefaction methods are possible:

• the use of one-flow cooling cycle in processing of low flow rates of source gas (liquefaction ratio is 0.95)
• the use of expander cycle:
  • a) closed-circuit cycle with a liquefaction ratio of 0.7 – 0.8;
  • b) open-circuit cycle with a liquefaction ratio of 0.08 – 0.12.

The latter is recommended to be used at gas distribution stations where the reducing unit is replaced by a natural gas liquefaction plant providing gas expansion in an expansion unit and partial liquefaction. This method practically does not require any energy input. The plant output depends on the flow rate of gas arriving at gas distribution stations and on the station inlet/outlet pressure difference range.

The plant includes the following units:

• gas preparation
• cooling and separation
• expansion (with one or two expansion stages)
• storage of liquefied natural gas

For production of engine fuel, a wide range of plant capacities is possible in terms of both processed gas and produced liquefied gas,depending on the gas source and requirements (i.e., sales opportunities).