Cold energy recovery in LNG plants

During the production phase, natural gas (NG) is compressed and chilled to a liquid state (liquefied natural gas, LNG) to reduce volume and thereby streamline transportation. To be liquefied, natural gas must be cooled to approximately -160°C at 1 atm. After transport, LNG is pumped and regasified, exploiting the heat input provided by a thermal source prior to injection in the national grid.

Common technologies used for LNG regasification mainly comprise open-rack vaporizers (using seawater as a thermal source) and submerged combustion vaporizers (with NG as a thermal source). Alternatives include intermediate fluid vaporizers and ambient air vaporizers.

Cold Energy recovery LNG

COLD ENERGY UTILIZATION ACCOUNTS FOR LESS THAN 1% OF ITS POTENTIAL

ORC cold energy recovery power plant
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None of the regasification technologies exploit the cold energy available in LNG, which is approximately 740 kJ/kg of LNG (-160°C to 0°C at 80 bara). 

ORC cold energy plants are an efficient way to recover energy from the regasification of liquefied natural gas and decarbonize the Oil & Gas sector.

The Exergy Cold Energy Plant (CEP) is an efficient patented system based on ORC technology which regasifies liquefied natural gas and converts the heat absorbed from sea water into electricity by recovering the valuable exergy content of LNG. The CEP system designed by Exergy achieves high efficiency thanks to use of the Exergy Radial Outflow Turbine (ROT), combined with the patented multilevel condensation cycle. 

How an ORC cold energy plant works

The evaporator exchanges heat between sea water and the ORC working fluid. Working fluid vapor expands in the turbine, producing power in the generator. 

A multilevel condenser regasifies the LNG by releasing the waste heat from the CEP cycle.
The pump provides the pressure needed for the cycle

The advantages of a multilevel condensation cycle coupled with the Exergy ROT are:

The CEP is a low-maintenance and cost-effective solution that can be efficiently applied in the LNG industry to:

The CEP system designed by Exergy achieves high efficiency thanks to use of the proprietary Exergy Radial Outflow Turbine or “ROT”, combined with the patented multilevel condensation cycle. 

The ROT configuration naturally allows spillages between stage-enabling multi-level condensation.

Radial Outflow Turbine LNG application

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