Hydrogen purification using compact pressure swing adsorption system for fuel cell

Abstract

Adsorption of CO and CO2 in mixtures of H2/CO/CO2 was achieved using compact pressure swing adsorption (CPSA) system to produce purified hydrogen for use in fuel cell. A CPSA system was designed by combining four adsorption beds that simultaneously operate at different processes in the pressure swing adsorption (PSA) process cycle. The overall diameter of the cylindrical shell of the CPSA is 35 cm and its height is 40 cm. Several suitable adsorbent materials for CO and CO2 adsorption in a hydrogen stream were identified and their adsorption properties were tested. Activated carbon from Sigma–Aldrich was the adsorbent chosen. It has a surface area of 695.07 m2/g. CO adsorption capacity (STP) of 0.55 mmol/g and CO2 at 2.05 mmol/g were obtained. The CPSA system has a rapid process cycle that can supply hydrogen continuously without disruption by the regeneration process of the adsorbent. The process cycle in each column of the CPSA consists of pressurization, adsorption, blowdown and purging processes. CPSA is capable of reducing the CO concentration in a H2/CO/CO2 mixture from 4000 ppm to 1.4 ppm and the CO2 concentration from 5% to 7.0 ppm CO2 in 60 cycles and 3600 s. Based on the mixture used in the experimental work, the H2 purity obtained was 99.999%, product throughput of 0.04 kg H2/kg adsorbent with purge/feed ratio was 0.001 and vent loss/feed ratio was 0.02. It is therefore concluded that the CPSA system met the required specifications of hydrogen purity for fuel cell applications.