In certain situations, recovering Ethane from Natural gas stream is commercially attractive, it becomes possible by reducing the temperature of natural gas low enough to liquefy Ethane. This process ensures total recovery of Propane and near complete recovery of Ethane.
Pyramid E&C offers compact modular Cryogenic extraction units capable of recovering complete Propane and 98%+ Ethane in single train size ranging from 30 to 300 MMSCFD. These key advantages are:
- Flexibility to operate in Ethane recovery or rejection mode
- Modular construction helps easy transportation and quicker installation.
- Higher liquids recovery
- Lower power requirement
- Rapid installation and re-deployment of plant mitigates long term project risks.
The process comprises of following steps:
Feed gas Conditioning: Feed gas will first pass through a coalescing filter/separator designed to remove solid particles and liquid droplets carried over from upstream processes. If the gas is sour, it is treated in gas sweetening unit for removal of acid compounds in an absorption process. Then the feed gas is compressed, unless it is already at required pressure.
Dehydration: Gas is dried to avoid ice and hydrate formation in the cryogenic section of the process, the water content of the gas is reduced to an acceptable level through adsorption in molecular sieve desiccant beds. Downstream of the adsorption beds, the gas passes through a dust filter to remove any particulate carryover before subsequent processing. The regeneration of molecular sieve beds is achieved by heated gas.
Feed Cooling & Separation: Dehydrated gas flows into the cold section of the plant, where cooling of inlet gas takes place by exchanging heat with the cold residue gas in a brazed aluminum plate-fin heat exchanger. Condensed liquid is separated from gas in cold separator. The liquid from cold separator is sent to lower section of demethanizer column. Gas from the cold separator is partially sent to turbo expander and remaining gas flows through reflux exchanger. The expansion of gas cools it further and results in additional condensation. The cold gas from expander is sent to the de-methanizer column. Cooled gas from reflux exchanger is expanded via J-T valve and send to reflux separator. Liquid from the bottom of reflux separator is sent to de-methanizer column. All cooled gas and liquid streams are fed to de-methanizer column. The cold streams are fed to column at different sections depending on temperatures. The expansion turbine used in the process is also configured to recompress the gaseous methane effluent, to lower energy consumption. The plant produces condensate rich in C2, C3, C4 and higher hydrocarbons from bottom, and residual gas from the top of demethanizer column. Condensate (NGL) is fractionated into Ethane, Propane, Butane and C5+ as per market requirement.
