Separation of Hydrogen Mixtures by a Two-Bed Pressure Swing Adsorption Process Using Zeolite 5A

Abstract

A study on a two-bed six-step pressure swing adsorption (PSA) process using zeolite 5A was performed experimentally and theoretically for bulk separation of H2/CO and H2/CH4 systems (70/30 vol %) as major components in coke oven gas. When the pressure is cycled between 1 and 11 atm at ambient temperatures, 70% H2 in the feed could be concentrated to 99.99% in the product with a recovery of 75.87% in the H2/CO mixture and 80.38% in the H2/CH4 mixture. The effects of adsorption pressure, P/F ratio, adsorption/purge step time, and pressure equalization step time were investigated experimentally. If the product end of an adsorption bed was not contaminated during the adsorption and depressurizing pressure equalization steps, elongation of both the adsorption and purge steps gave good adsorbent productivity and recovery without any decrease in purity. Certain elongations of step time in the pressure equalization step resulted in a better performance of a PSA process. When the H2 mole fraction of effluent stream during the pressure equalization step was not high, the initial H2 purity of the adsorption step was not good because of the contamination of the product end section. These results were analyzed by a mathematical model incorporating heat and momentum balances.

Adsorption dynamics of a layered bed PSA for H2recovery from coke oven gas

“…The isotherm data from previous work (Yang et al, 1997) were compared with other experimental data and these data agreed well with each other (Verelst and Baron, 1985;Ritter and Yang, 1987;Valenzuela and Myers, 1989;Chen et al, 1990).…”

“…The advantage of this assumption is that the previously established model for a single-adsorbent bed (Kim et al, 1995;Yang et al, 1995Yang et al, , 1997 can be applied to a layered bed with a minor modification, and this approach can also be easily extended to the adsorption bed packed with more than two adsorbents. Using an axially dispersed plug flow and an ideal-gas law, the material balance for the bulk phase in the adsorption column is given by and the overall mass balance can be represented as follows:…”

“…To imitate bed connectivities during a pressure-equalization step, temporal data of an effluent stream from the adsorption bed undergoing a depressurizing pressure equalization step were retained and later used for the pressurizing pressure-equalization step (Kumar, 1994;Yang et al, 1997). Figure 4 shows the two-bed PSA unit used in the present study.…”

Hydrogen permeation of BaCe_0.80Y_0.20O_{3&minus;&delta;}&ndash;Gd_0.1Ce_0.9O<i>_x</i> dual-phase membranes

“…Pt electrodes were formed on the both sides of the pellets using Pt paste (Tanaka, TR-7907) and attached with Pt mesh (100 mesh) as a current collector. The Pt electrode attached with the Pt mesh was co-sintered at 1000°C for 1 h. The area of both sides of the Pt electrodes was 0.28 cm 2 . The testing setup for hydrogen permeation is shown in Fig.…”

Synthesis and modification of zeolite NaA adsorbents for separation of hydrogen and methane

“…For the separation of CH 4 and H 2 , zeolite 5A has been studied [31] taking advantage of the equilibrium selectivity to CH 4 . It is still necessary to increase the adsorption capacity of the adsorbent.…”