Patent ID: 7856848

Claim:
A flexible hydrocarbon gas separation process that could dehydrate a water-saturated hydrocarbon gas (“raw gas” hereafter) and recover thereof the higher hydrocarbon liquid (“NGL” hereafter) with controllable ethane recovery rate ranging from >95% to <2% while keeping high recovery rate of all other heavier hydrocarbon components comprises the following steps: (a) Pre-cooling and pre-dehydrating the raw gas by directly contacting a counter-flowing liquid coolant comprising an aqueous solution of a gas hydrate inhibitor to get a pre-cooled pre-dehydrated gas and a partial NGL condensate; (b) Deep-cooling and deep-dehydrating the pre-cooled pre-dehydrated gas with a refrigerant from an external refrigerator to get a deep-cooled deep-dehydrated gas and a deep-cooled NGL condensate; (c) Flowing the NGL condensate into a condensate pre-demethanizer and a flexible condensate deethanizer in tandem to remove all the methane content therein and simultaneously reduce the ethane content therein to any desirable level to get a deep-cooled purified NGL condensate; (d) Flowing the deep-cooled deep-dehydrated gas into a flexible absorber and contacting the gas with a counter-flowing liquid absorbent (“lean oil” hereafter) to get a cold residue gas and a cold rich absorbent (“rich oil” hereafter) with a desirable level of ethane content; (e) Flowing the cold rich oil into a rich oil pre-demethanizer and a flexible rich oil deethanizer in tandem to remove all the methane content therein and simultaneously reduce the ethane content therein to any desirable level to get a purified rich oil; (f) Depressurizing the purified rich oil and distilling the purified rich oil in a rich oil fractionator to get an NGL vapor and a regenerated lean oil; (g) Cooling the NGL vapor with a heat transport medium to transport the heat energy from the NGL vapor to the deep-cooled rich oil in the flexible rich oil deethanizer; (h) Compressing the NGL vapor and mixing the compressed NGL vapor with the deep-cooled purified NGL condensate to get a low-temperature NGL vapor-liquid mixture; and (i) Liquefying the low-temperature NGL vapor-liquid mixture to get a final NGL product.