A new highly stable methane hydrate from the synergic mixture of common promoters: Experimental and modeling surveys

One of the main issues in flow assurance in offshore operations, specially at high pressure conditions as in deep pipelines is the formation of hydrates in the corners of pipelines that causes notable problems like pipe blockage followed by an explosion. Hydrate or gas hydrate is a bright solution for gas storage and transportation. Tetrabutylphosphonium bromide (TBPB) and tetrabutylammonium bromide (TBAB) are salts capable of tackling the thermodynamic and kinetic limitations of hydrate formation/dissociation conditions. In the present work, the effect of TBAB, TBPB and TBAB + TBPB mixture on CH4 hydrate dissociation condition was studied. All experiments were performed by pursuing a constant-volume pressure search technique with the step heating approach to study the effects of additive mixtures with different compositions. A mass fraction of 5%, 10% TBAB/TBPB was used. The experiments were conducted at 280-290.05 K and 1-5.5 MPa. In all the conducted experiments, the mixture had a promoting effect. After generating the accurate data of TBAB-TBPB-CH4 hydrate in water system, a thermodynamic prediction model was developed to investigate efficient hydrate-based applications. The hydrate phase was predicted on the basis of Chen and Guo's approach. Soave-Redlich-Kwong equation of state was applied to predict the required methane properties in the gas phase. The TBAB-TBPB activity coefficient and water activity in the electrolyte phase were obtained through the Bromley equations. The results of the proposed thermodynamic model showed that there is a satisfactory accordance between the experimental phase equilibrium data and the predicted data with an acceptable AARD % of 0.95%.

Automated summary

The study found that TBAB, TBPB, and TBAB + TBPB mixture have a promoting effect on CH4 hydrate dissociation conditions, which can be used to improve the efficiency of hydrate systems.