Feasibility study on CO2-rich industrial waste gas storage and replacement in carbonate gas reservoir based on adsorption characteristics

Abstract

The emission of CO2-rich industrial waste gas (CO2-rich IWG) poses a huge challenge to environmental protection. If the CO2-rich IWG could be used directly or after simple treatment for underground storage and replacement, then clean utilization of CO2-rich IWG will certainly be promoted. In this paper, the feasibility of CO2-rich IWG for underground storage and replacement in carbonate gas reservoirs was studied from the perspective of gas adsorption characteristics. Firstly, the reliability of the molecular model was verified by fitting Monte Carlo simulation data of four representative gases with isothermal adsorption experimental data. Then, molecular dynamics simulation was used to study the adsorption mechanism of various components on the calcite surface in CO2-rich IWG. Finally, the competitive adsorption mechanism between CO2-rich IWG and methane, and the multi-component competitive mechanism between dominant gases are studied. The results show that the adsorption capacity of each component on calcite surface is HF > CO2>SO2>H2S > NO2>CH4>CO. Hydrogen bond and electrostatic force are the main adsorption forces of HF. The electrostatic force between negatively charged atoms in the molecule and Ca2+ is the main adsorption force for CO2, SO2 and H2S. The weak van der Waals force is the main adsorption force for NO2, CH4 and CO. In the competitive systems, the absolute adsorption capacity of CO2-rich IWG is reduced by 25–50% compared with single component adsorption. However, in the competitive adsorption systems of HF/CH4, CO2/CH4, H2S/CH4 and SO2/CH4, the relative adsorption capacity of the four industrial waste gases to methane is increased by 9 times, 5.5 times, 4 times and 3.75 times as compared with the non-competitive ones. In the competitive adsorption systems of HF/CH4, CO2/CH4, H2S/CH4, and SO2/CH4 the negatively charged atoms are more likely to combine with Ca2+ to generate strong electrostatic attraction, while generating electrostatic repulsion to the negatively charged C atoms in CH4, leading to the weakening or even disappearance of CH4 adsorption. Therefore, CO2-rich IWG has a good application prospect in carbonate gas reservoirs, but the CO and NO2 should be removed before use.