Convert natural gas to liquefied natural gas (LNG) form for transportation and/or storage using the PRICO mixed refrigerant process. Applications range from large base load LNG units to small peak-shaving units.
Product: LNG is produced at process pressure to be stored at –260°F and atmospheric pressure. Additional products, such as ethane, liquefied petroleum gas (LPG) and gasoline may be recovered in liquid form, when present in the feed gas.
The process is a very simple, efficient, reliable and cost-effective mixed-refrigerant cycle. A single mixed-refrigerant, composed of nitrogen and light hydrocarbons from methane through pentane, is circulated in a closed refrigeration loop. Proportions of individual refrigerant components are adjusted to match the processed gas. This loop contains a compressor (1), a partial condenser (2), an accumulator (3), a refrigerant heat exchanger (4), an expansion valve (5) and a refrigerant suction drum (6). Accumulator liquids are directed to the refrigerant heat exchanger with a low head centrifugal pump (7). A single case centrifugal or axial flow compressor can be used with or without intercooling.
The refrigerant heat exchanger (4) is composed of multiple plate-fin brazed aluminum cores arranged in parallel to provide desired production capacity and allow expansion easily.
Natural gas feed is pretreated for removal of carbon dioxide (CO2) to less than 50 ppmv and dried to less than 1 ppmv water by conventional methods. Natural gas liquids (NGL) from the natural gas feed are separated in (8). The NGLs may then be separated by subsequent fractionation into desired products. Nitrogen in the natural gas feed is dealt with according to the LNG product specification requirements by adjusting the liquefaction conditions. The process matches
well with gas turbine, steam turbine or electric motordriven compression systems.
Licensor: Black & Veatch Pritchard Inc.