Separation of Natural Gas by Gas Hydrate Crystallization Technology: Calculation of Gas Hydrate Distribution Coefficients

The possibility of separating natural gas from the Orenburg field by the technology of gas hydrate crystallization in order to purify methane from impurities is discussed. The effect of the composition of the mixture and the temperature and pressure on the separation efficiency of the CH₄–C₂H₆–C₃H₈–i-C₄H₁₀–n-C₄H₁₀–C₅H₁₂–N₂–H₂S–CO₂ mixture was modeled mathematically. The efficiency was assessed on the basis of the gas hydrate distribution coefficients. It is shown that the gas hydrate distribution coefficient for methane changed little with the duration of operation of the field and amounted to less than 1. It was established that the CH₄, n-C₄H₁₀, n-C₅H₁₂, N₂, and CO₂ are concentrated predominantly in the gas phase and C₃H₈, i-C₄H₁₀, and H₂S in the gas hydrate. In the investigated ranges of temperature and pressure values the maximum gas hydrate distribution coefficient at 268.15 K and 8 MPa for C₃H₈, i-C₄H₁₀, and H₂S was established as 32.32, 44.66, and 31.61 respectively.