Experimental Studies of the Separation of C2 Compounds from CH4 + C2H4 + C2H6 + N2 Gas Mixtures by an Absorption-Hydration Hybrid Method

An absorption-hydration hybrid method was employed for separating C2 components (C2H4 + C2H6) from low-boiling gas mixtures such as refinery dry gas using water-in-diesel emulsions under hydrate formation conditions. Span 20 was used to disperse the water or hydrate in diesel to form the emulsion or hydrate slurry. To simulate a three-stage separation process, three (CH4 + C2H4 + C2H6 + N-2) feed gas mixture samples with different gas molar compositions were prepared. Separation experiments were performed under different conditions to investigate the influences of feed composition, temperature, pressure, initial water cut in the emulsion, and initial gas/liquid volume ratio on separation efficiency. The experimental results show that the absorption-hydration hybrid method is obviously superior to the single-absorption method. After three stages of separation at appropriate operating conditions, we found that C2 compounds can be enriched from similar to 15 to more than 50 mol % in the (hydrate + diesel) slurry phase and that the content of C2 compounds in the residual gas phase can be reduced to lower than 2 mol %. Low temperature, low initial gas/liquid volume ratio, high pressure, and high water cut were found to be favorable for the recovery of C2 compounds. However, when the temperature was lower than 270.2 K and the water cut was higher than 30 vol %, the formation of flowable hydrate slurry became difficult.