Adsorption Behavior of CO₂in Coal and Coal Char

Abstract

Recent interest in sequestration of carbon dioxide (CO 2 ) in gasified coal seam (i.e., post-underground coal gasification sites) has created a need to understand the coal properties, specifically, the adsorption behavior of CO 2 on gasified coal. In the present study, the CO 2 excess adsorption isotherms were determined for four coal samples of different characteristics based on the volumetric method. Further, coal chars from a coking coal and a non-coking coal (within the studied samples) were investigated for their CO 2 adsorption capacity. The coal samples of size 22−32 mm were pyrolyzed in a drop-tube furnace at 800 and 1000 °C with a heating rate of approximately 2.5 °C s −1 under an inert atmosphere. Measurements were performed up to a pressure of 65 bar for all of the studied samples. Experiments were carried out at an isothermal temperature of 45.5 °C. The influence of coal properties on adsorption was also studied and compared to the literature data. Behavior of adsorption capacities was analyzed as a function of coal properties, such as vitrinite content, coal rank, volatile matter, ash content, and surface area. Results indicated that the adsorption capacity of coal char is much higher in comparison to the virgin coal samples. It was understood from the surface area analysis that there is a significant increase in surface area when coal is pyrolyzed. In addition, for coal samples, the trend of adsorption isotherms was in good agreement with the literature data.

Remediation with Semicoke-Preparation, Characterization, and Adsorption Application

“…SC micropores have a greater influence on high processes within the SC structures than macropores formations [ 53 ]. Pore structural formation further influences SC surface area activities [ 54 ]. In their study, [ 42 ] confirmed that SC surfaces can be finer than general porous carbon (PCs) as SC is compact and exhibits a non-porous structure unlike PCs with a large amount of pores spaces that may favor adsorbate diffusion.…”

Modelling Underground Coal Gasification—A Review

“…The accessibility of carbon dioxide to the pores of unworked deep coal seams is limited by the porosity and permeability of coals that tend to decrease with increasing overburden pressure [115]. However, the void created due to gasification and the amount of coal chars left behind after the UCG process triggers the possibility of storing carbon dioxide in that depleted space known as UCG-CCS [116].…”

“…At low pressure, the carbon dioxide storage potential in coal seams is mainly a function of its adsorption capacity; however, at high pressure, it is a strong function of the accessibility to CO 2 with respect to pore space for free gas [115][116][117]. Although the volume of pores in coal is much smaller than in other reservoir rocks, the storage potential of CO 2 in coal significantly differs from other rocks and exceeds its open pore volume by an order of magnitude predominantly due to the surface adsorption of micropores [117].…”

Influence of coal properties on the CO2 adsorption capacity of coal gasification residues

“…There have been a few techno‐economic studies reported; however, the capture capacities used in these studies consider mainly CO 2 storage in the void volume of the post‐UCG site. In addition to the storage capability of the void, CO 2 storage also occurs through adsorption in the left‐over seam and the gasification residues . Therefore, to improve the CO 2 storage capacity estimates, it is essential to gain a fundamental insight and accurate CO 2 storage capacities of the various strata as a function of coal properties and the gasification conditions [].…”