Towards energy-efficient hydrate-based desalination: A comprehensive study on binary hydrate formers with propane as a promoter

Hydrate-based desalination technology has garnered significant attention due to its energy efficiency and the ready availability of hydrate formers. This research investigated the kinetics of different binary hydrates (CO2 + C3H8, N2 + C3H8, and Ar + C3H8) using propane as a promoter, aiming to enhance the desalination efficiency and reduce the energy cost. Experiments were conducted at temperatures ranging from 275.15 K to 279.15 K and initial pressures from 2.5 to 4.0 MPa. The formation rate and water-to-hydrate conversion of binary hydrates in a 3.5 wt% brine system were evaluated across different propane ratios (10%, 15%, and 19%) and stirring rates (0–600 rpm). Results indicated that a temperature of 275.15 K and a pressure of 4.0 MPa fostered optimal hydrate kinetics. Additionally, increasing the propane ratio from 10% to 19% positively influenced N2 + C3H8 and Ar + C3H8 hydrate formation kinetics due to enhanced phase equilibrium. For CO2 + C3H8, while the final water conversion rate increased with added propane, the formation rate and amount of hydrates formed within one hour for the 81% CO2 + 19% C3H8 combination decreased. Stirring enhanced nucleation and growth for N2 + C3H8 but remained ineffective for CO2 + C3H8. Among hydrate formers of the same ratio, CO2 + C3H8, with its higher solubility, emerged as superior in terms of both lower formation pressure and faster formation kinetics, achieving greater water-to-hydrate conversion in minimal time. This study offers valuable insights for choosing optimal experimental conditions and binary hydrate formers to fast-track the kinetics of hydrate formation and energy-efficient in hydrate-based desalination technology. •Propane significantly boosts hydrate-based desalination efficiency.•Best hydrate formation achieved at 275.15 K and 4 MPa pressure.•Higher propane ratios enhance kinetics of hydrate formation.•The CO2 + C3H8 combination excels in terms of hydrate growth speed and water-to-hydrate conversion rate.