Abstract
Hydrogen is an important energetic vector nowadays. The most common industrial method to produce ultrapure hydrogen is by steam methane reforming (SMR), where hydrogen is first produced as a mixture mainly composed of hydrogen, carbon monoxide, methane, and carbon dioxide. A purification step by pressure swing adsorption (PSA) is carried out usually using activated carbon and 5A zeolite as adsorbents. The design of this process requires fundamental information about the adsorption and diffusion of the components of SMR-off gas, which is only available in the literature for a limited number of adsorbents. In this work, adsorption Henrys law constants and reciprocal diffusion time constants have been measured for hydrogen, carbon monoxide, methane, and carbon dioxide on BPL 4X10 activated carbon and 13X zeolite pellets from pulse experiments. Adsorption isotherms of these gases in both adsorbents at temperatures between 298 and 338 K, up to pressures of 20 bar for hydrogen and 25 bar for the other gases, have also been measured volumetrically. A PSA cycle for hydrogen purification using BPL activated carbon and 13X zeolite has been designed introducing the measured adsorption and diffusion data in a simulation tool. The process can yield 99.99+% hydrogen with 90% recovery and 7.2 mol H-2 kg(1) h(1). If 13X zeolite is replaced by 5A zeolite with the same operating conditions, the hydrogen purity falls down to 99.81%.