Gas Liquefaction

Liquefied natural gas (LNG) is a cryogenic liquid mixture of light hydrocarbons, primarily composed of methane. LNG is a non-toxic, colorless liquid with no odor. Its volume is 600 times smaller than that of natural gas, making it easier to store and transport over long distances.

LNG liquefaction plants are crucial components in the production and supply chain of LNG, where natural gas is prepared for long-distance transportation. The majority of LNG transportation is carried out by LNG tankers, hence these plants are often located on the coast or near rivers. The site selection takes into account the placement of large-scale equipment, technological lines, and large storage tanks for LNG. Maritime ports are often chosen as sites for LNG facilities.

Typically, LNG plants consist of the following units:

• Gas conditioning
• Gas cooling
• Gas liquefaction
• Fractionation
• LNG storage and dispensing systems
• Life support systems

The configuration of an LNG plant is influenced by the composition of natural gas and the specifications of the LNG product. The presence of different components in the raw gas in varying proportions can impact capital investments and operational costs.

The technology of natural gas cooling and liquefaction plays a crucial role in industrial processes. Over the course of the global LNG industry's existence, several technologies for industrial LNG liquefaction have been developed. Large-scale processes typically employ closed-loop cooling cycles using pure or mixed refrigerants. Small-scale liquefaction processes are based on open turboexpander cycles or single-stream refrigeration cycles.

Currently, several different technological processes are utilized, but they are all based on the same principle: cooling and condensing natural gas in a heat exchanger using one or more refrigerants. The refrigerants circulate in closed thermodynamic cycles, where compression, cooling by air or water, expansion, and heating by the cooled natural gas occur sequentially.

When selecting the cooling and liquefaction technology, the principle of minimizing heat losses in the cycle is followed. The cooling curves of natural gas and refrigerant should be as close as possible. The closer the cooling curves, the more efficient the cooling process, resulting in lower energy consumption per unit of produced LNG. This principle applies to all liquefaction processes.