Phase equilibria of methane/TBAC mixed hydrates in the presence of produced water

Produced water (PW) is a by-product and one of the major pollutants from the oil and gas industry. PW contains various pollutants and must be treated as per environmental regulations before its disposal or reuse. Thus, it presents a substantial economic and ecological problem in the oil and gas industry. Currently, there is ongoing research on various methods to treat PW efficiently. Hydrate-based water desalination is one of the promising technologies. There is a continuing effort to identify a suitable hydrate former that can enhance the commercial feasibility of the process. This study investigates tetra-n-butyl ammonium chloride (TBAC) + methane as a potential clathrate former. The hydrate equilibrium temperatures of the mixed hydrates (TBAC + methane) are significantly higher at a given pressure than methane hydrates, suggesting the suitability of mixed hydrates for process development. There was a significant increase in the phase equilibrium temperature at 5 wt.% TBAC in the presence of PW compared to deionized water (DI), but the effect faded away as TBAC concentration increased in the solution. This can be attributed to a higher amount of chloride ions as the TBAC concentration is increased. These results elucidate the necessity to optimize the TBAC concentrations to develop an efficient hydrate desalination process for higher saline concentrations.

Automated summary

Produced water (PW) is a major pollutant from the oil and gas industry and requires treatment before disposal or reuse. This study investigates the use of tetra-n-butyl ammonium chloride (TBAC) + methane as a potential clathrate former in hydrate-based water desalination. The results show that mixed hydrates (TBAC + methane) have higher equilibrium temperatures than methane hydrates, indicating their suitability for process development. It is also found that the TBAC concentration needs to be optimized for efficient desalination of high saline concentrations in PW.