Ethane recovery from residue gas by adsorption processes: A feasibility study

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NOVA Chemicals Corporation (NCC) is one of the largest producers of ethylene in Canada. Ethylene is the building block for polyethylene and is one of the most important petrochemicals in terms of global production. Ethylene is produced from ethane which is extracted from natural gas through the gas sub-cooled process (GSP). In this process, natural gas is cooled and separated into two fractions using a cryogenic. The lighter fraction which is termed as the residue gas, contains 96-98 mol% methane and 1-3 mol% ethane. The residue gas is compressed and sent to the pipeline where the unrecovered ethane is burnt as a fuel along with methane, instead of being converted to value added products. Owing to the limitations of the current process, it becomes uneconomical to increase the recovery of the high-value ethane beyond 80%. An additional 50 thousand barrels per day could be added to the Canadian production if the recovery is improved to 95%. NCC is studying alternate separation processes to improve ethane recovery. The current Engage plus proposal is a continuation of an ongoing Engage project with the University of Alberta (UofA). The Engage project showed that adsorption (a separation technology that exploits the ability of certain solids to selectively retain one component from a gas mixture) can produce high purity ethane and has the potential to be incorporated into the production process. While the Engage grant focused on a stand-alone adsorption process, the current Engage plus proposal will explore the methods to integrate the process into the existing natural gas extraction plant operated by NCC. It will specifically study the impact on energy consumption and provide data for NCC to estimate the cost of such an integration. Success of the project could result in avoiding ca. 50 thousand barrels per day of ethane being burnt as a fuel and diverting them as feedstocks for the ethylene manufacturers. NCC being the primary consumer of most ethane produced in Canada will be in a position to convince NGL-extraction plant operators to consider this technology.