Evaluation of Membrane Separation Processes for Recovery and Purification of Hydrogen Derived from Dehydrogenation of Methylcyclohexane

摘要

hydrogen derived from dehydrogenation of methylcyclohexane for use in fuel cell vehicles (FCVs). Process conditions were assumed as follows: (a) Feed gas treated by the quenching process contains 98 % hydrogen and 2 % toluene; (b) Operating pressures of feed and permeate are 0.3 MPa and 0.1 MPa, respectively; (c) Target hydrogen recovery rate is 90 % with less than 0.3 ppm of residual toluene in purified hydrogen; (d) Purified hydrogen is stored at a pressure of 0.7 MPa; (e) Activity of the membrane stage follows the cross plug flow model. The single stage process required only specific power of 0.12 kWh Nm(-3)-H(2)for compressing hydrogen into the storage tank. This process required the least energy but needed an ultra-high ideal separation factor of 280,000 at least. The two stage cascade process with a moderate ideal separation factor of 1000 to 1500 attained the recovery target and required specific power of 0.19 kWh Nm(-3)-H-2 including recompression of the first stage permeate. The three stage process, which consists of the single stage followed by the two stage cascade, enabled membranes with an ideal separation factor of around 10,000 to achieve the target, and required specific power of less than 0.19 kWh Nm(-3)-H-2. Membrane separation processes are competitive with pressure swing adsorption (PSA) processes.