Pure N2O and N2O-CO2 mixture gas hydrates stability and kinetic characteristics

Abstract

In this research, the surface effect of different soil minerals on pure N2O and N2O-CO2 mixture-gas hydrate formation kinetics have been studied experimentally and equilibrium properties have been identified computationally. There have been no significant efforts for technical development to reduce N2O gas. We have applied the hydrate formation technology to the mitigation of N2O and CO2 simultaneously. The hydrate formation experiments were performed with pure deionized-water (DIW) and soil mineral-rich suspensions under static condition (273.3K and 30 bar) by using high-pressurized reactor. All mineral-rich suspensions showed faster hydrate formation kinetic than the pure DIW system. The fastest hydrate induction times have been found in slightly ionic concentrated (9.60E-04 - 6.00E-03) systems under near-neutral pH conditions (~pH 7-8). Illite and Nontronite were detected as efficient accelerators on N2O hydrate formation process by observing fastest kinetic rate (254 ± 186 min). N2O hydrate formation kinetic was considerably influenced by the geochemical behavior of the suspension and interaction of gas and water molecules on the mineral surface. Temperature and pressure changes were not significant on hydrate formation kinetic; however, induction time can be significantly affected by various chemical species formed under the different suspension pHs. Water activity, ionic strength and dominant chemical species in each suspension were estimated by geochemical equilibrium model, PHREEQC, to understand the factors affecting N2O hydrate formation process. The stability of N2O hydrates was in 0.718-0.774 of water activity value, while the natural gas hydrate and pure DIW are stable at >0.8 and 1.0, respectively. The mixed gas hydrate formation kinetic of 50% CO2 + 50% N2O was approximately two times faster than that of pure N2O hydrate in general. The fastest induction time for the mixed gas hydrate has been observed in Illite and Sphalerite suspensions (193 ±...