THERMAL EFFECTS ON THE BREAKTHROUGH CURVE OF A HYDROGEN TERNARY SYSTEM AT A FIXED BED

Abstract

The thermal effect on the breakthrough curve of a hydrogen ternary mixture (H2/CH4/CO; 60:30:10 vol%) was investigated experimentally and theoretically at a fixed bed in the range of 4 to 16 kgf/cm2 adsorption pressure and 4.5–9.1 LSTP/min feed flow rate. To understand the adsorption dynamics and the thermal effect by the heat of adsorption, a non-isothermal dynamic model incorporating mass, energy, and momentum balances was used and was compared with isothermal and adiabatic models. The adsorption thermal effects on adsorption dynamics were compared between an activated carbon bed and a zeolite 5A bed. In the activated carbon bed, the roll-up of CO by CH4 and the separation of mass transfer zones between CO and CH4 occurred and the H2 breakthrough curve showed a stepwise decrease and tailing. However, a small roll-up of CH4 and a wide breakthrough of CO in the experimental range was shown in the zeolite bed without the separation of two temperature wave fronts. The breakthrough time was elongated by an increase in adsorption pressure and by a decrease in feed flow rate in each adsorbent bed, but the extent of elongation was different due to the difference between the affinities of CO and CH4 to each adsorbent. Also, in the activated carbon bed, the extent of roll-up became wider with a decrease in feed flow rate and became steeper with an increase in adsorption pressure. Depending on the thermal condition in each bed, concentration and temperature profiles showed different behavior.