Natural gas purification
The purification takes place within the following sections :
- carbon dioxide (CO2) removal through the absorption with the use of water solution of monoethanoloamine MEA (10-15%) ;
- moisture (H2O) removal through adsorption on molecular sieves 4A ;
- heavy hydrocarbons (C5+) removal through adsorption on activated charcoal.
Low temperature (cryogenic) natural gas distillation
The purified gas is precooled within the plate heat exchangers. Then, after passing expansion turbines and Joule-Thomson valves, it is further subcooled. Within distillation columns, as a result of different boiling temperatures, the stream separates into liquefied natural gas (>96% CH4), liquid nitrogen and crude helium gas. Next the liquefied natural gas is regasified within the low-temperature heat exchangers and then piped to the compressor station. A small part of the stream is retained in the liquefied form and stored as LNG.
High-methane gas compression
Our compressor station consists of Cooper-Bessemer and Waukesha-Ariel compressors. There we compress our final product - the high-methane gas, as well as the gas to be transmitted by the National Transmission Operator.
Crude helium gas (around 80%) is purified within three successive sections :
- hydrogen removal through it's burning, and next - moisture removal within separators and molecular sieves adsorbers ;
- nitrogen and oxygen removal as the result of condensation and low temperature adsorption on molecular sieves and activated charcoal ;
- neon removal - through adsorption on activated charcoal .
The purified helium stream is liquefied through the compression-expansion cycle and heat exchange within low-temperature plate heat exchangers. A deep vacuum, approaching the level 5x10-5torr, is essential in order to maintain the close to absolute zero temperature necessary for liquefaction.