The Phillips Process

The Atlantic complex utilises the ConocoPhillips Cascade Process developed by ConocoPhillips Petroleum. Feed gas enters the plant and undergoes a standard pre-treatment process to remove carbon dioxide, water and mercury. The Phillips Process then utilises three refrigeration circuits – propane, ethylene and methane to cool the gas step by step to -161 degrees Celsius.

The first stage of propane chilling occurs ahead of dehydration. The treated gas then goes through additional stages of propane refrigerant chilling, each at a lower pressure and temperature. The gas from the last stage of propane cooling, along with a recycle stream from the open cycle methane refrigeration, undergoes further cooling and condensation in an ethylene refrigeration circuit. The condensed product from the ethylene chillers then enters an open loop refrigeration cycle which produces the LNG product. This is then piped to storage tanks. Boil off from the tanks is compressed back into the recycle stream for recovery by the process.

The main process utilises the ’2–train–in–one’ reliability concept employed successfully by the Kenai, Alaska plant for more than 30 years. Kenai was an earlier version of the ConocoPhillips Cascade Process. This approach allowed for the construction of a world scale plant using one train of liquefaction exchanges served by two parallel compressors on each refrigerant. The result is that downtime of a compressor or gas turbine does not mean a total loss of production capacity. With at least one compressor operating in each refrigeration loop, more than half of the train capacity remains available.