Natural gas storage properties of adsorbents synthesised from three different coal waste in South Africa

• Published in: Fuel (Guildford) Vol. 267; p. 117157
• Main Authors: Abdulsalam, Jibril, Mulopo, Jean, Bada, Samson, Oboirien, Bilainu
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.05.2020; Elsevier BV
• Subjects: Activated carbon; Adsorbents; Adsorption; Coal; Coal mines; Coal waste; Flotation; Isotherms; Low pressure; Methane; Mine wastes; Natural gas; Porous materials; Slurries; Storage; Synthesis; Technology; Thermal management; South Africa; Methane; Adsorption; Coal waste; Activated carbon
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2020.117157

[Display omitted] •Activated carbon was synthesised from three different South African coal waste.•The natural gas storage properties of the synthesised activated carbons were evaluated.•Activated carbon derived from run of mine fines (ACR) gave the highest volume of adsorbed methane at 37 bar.•The higher the surface area of the synthesised activated carbon, the higher the volume of methane adsorbed.•Activated carbons from South Africa coal waste have the potential as a suitable adsorbent for ANG storage system. Adsorbed natural gas (ANG) storage has been identified as the most promising low-pressure alternative to storing natural gas. However, in addition to the thermal management of the system, successful implementation of this technology is largely constrained by the cost of adsorbents. The usefulness and cost of suitable adsorbent such as activated carbon are essential to ANG technology's productivity. In this study, activated carbons were prepared from three South Africa coal waste samples (run-of-mine fines, discard and flotation slurry) by KOH activation. The adsorption isotherm of methane on the synthesized activated carbons revealed that the activated carbon synthesized from run of mine fines (ACR) has the highest adsorbed amount compared to activated carbons synthesized from coal discard (ACD) and slurry (ACS). The maximum adsorbed amount of methane was attained at an average pressure of 37 bar with ACR having the largest volume of methane adsorbed at 162.71 cm3/g followed by ACD (157.58 cm3/g) and ACS (106.69 cm3/g) respectively. This sequence is consistent with the BET surface areas of the activated carbons; ACR (1925.34 m2/g) > ACD (1826.41 m2/g) > ACS (1484.96 m2/g). The methane adsorption data were validated with Langmuir, Toth, and D-A isotherm models for the three activated carbons. It was found that, for all three activated carbons, the D-A model was the best fit. Based on the requirements of suitable porous materials for ANG application, the study indicated that the produced activated carbons from South Africa coal wastes could well be used for natural gas storage.