Study on improving gas storage capacity of fixed bed filled with wet activated carbon

Abstract

Gas hydrate technology is a new gas storage method developed in recent years and has great application potential. Due to the slow formation kinetics of hydrate and the low actual gas storage density, it is a promising method to prepare the fixed bed filled with wet porous materials to inducing adsorption-hydration coupling effect, so as to improve the gas storage efficiency. In this study, various additives including THF, TBAB and diesel oil were added to the water-bearing activated carbon fixed bed to improve its gas storage capacity. Our experimental results show that the addition of THF or TBAB can significantly promote the gas storage performance of the bed. At the optimum concentration of THF (7.5 wt%), the gas storage density of bed (Sb) and gas storage capacity of hydrate (Sw) were 128.66 V/Vb and 194.26 V/Vw, which are 2.89 times and 3.07 times higher than those of wet activated carbon fixed bed without additives, respectively. When 5 wt% TBAB was added, the Sb and Sw were increased by 1.86 times and 1.87 times, respectively. Moreover, using diesel to establish gas channels in the fixed bed to improve the gas mass transfer between the bulk gas phase and the fixed bed can also significantly improve the gas storage performance of the bed. When the oil-carbon ratio (Ro) is 0.5, the Sb and Sw are 97.97 V/Vb and 172.77 V/Vw, respectively. However, further increasing the amount of diesel oil will not significantly improve the gas storage density of the bed due to the volume increase of the bed caused by the addition of diesel. When both diesel oil and THF are added to the water-containing fixed bed, the effect will be not significantly better than that of the bed with diesel oil or THF alone because the two accelerators compete with each other. Finally, the gas release and decomposition speed of the water-bearing fixed bed with / without 7.5 wt%THF are investigated. The results show that the final gas recovery of the bed with 7.5 wt% THF could reach 95.01 %, indicating a good application prospect.