Cycling and regeneration of adsorbed natural gas in microporous materials

Abstract

Adsorbed natural gas (ANG) technology is an energy-efficient method for storing natural gas at room temperature and low pressure. The search for high-storage-performance natural gas sorbents for gaseous fuels is currently pursued by numerous research groups worldwide. While research in this field is mainly devoted to optimizing the gravimetric and volumetric storage capacity of methane, this work investigates the long-term effect of large alkanes on natural gas storage. This article investigates the evolution of storage capacity and gas composition during adsorption/desorption cycles at room temperature (charge/discharge of an ANG tank) and at various elevated temperatures (regeneration of tank) on a commercial, high-surface-area activated carbon (Maxsorb MSC-30, Kansai Coke and Chemical Co. Ltd.). Cycling and regeneration study of sorbent for hundreds of cycles has been investigated. The evolution of storage capacity is measured after successive cycling using a custom-built Sievert apparatus. For natural gas, gravimetric excess adsorption drops to 33% in the first 100 cycles and continues to decrease slowly until it reaches 25% by the 1000th cycle. Volumetric storage capacity shows a deterioration of 50% after 100 cycles and remains approximately constant after that. The contaminant gas composition is measured as a function of successive cycling using gas chromatography. Finally, efficient regeneration techniques have been tested to allow a continuous operation for thousands of cycles.