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Hydrogen yield of conventional biomass gasification is limited by chemical equilibrium constraints. A novel technique that has the potential to enhance the hydrogen yield by integrating the gasification and absorption reactions has been suggested. The method involves gasification of biomass in presence of a CO2 sorbent. Ethanol was used as the model biomass compound and CaO was the representative sorbent. Equilibrium modeling was used to determine the product gas composition and hydrogen yield. The analysis was done using ASPEN PLUS software (version 12.1) and the Gibbs energy minimization approach was followed. The effects of temperature, pressure, steam/ethanol ratio, and CaO/ethanol ratio on product yield were investigated. Three case studies were conducted to understand the effect of sorbent addition on the hydrogen yield. Thermodynamic studies showed that the use of sorbents has the potential to enhance the equilibrium hydrogen yield of conventional gasification by ∼19% and reduce the equilibrium CO2 content of product gas by 50.2%. It was also found that the thermodynamic efficiency of sorbent-enhanced gasification (72.1%) was higher than conventional gasification (62.9%). Sorbent-enhanced gasification is a promising technology with a potential to improve the yield and lower the cost of hydrogen production.

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Two types of commercial activated carbons, Westvaco BAX 1100 and Chemviron LAC 30-57, were characterized by microporosity, equilibrium, and kinetic adsorption of propane and propylene. The porosity was determined by the measurement of the N2 adsorption isotherm at 77 K. Single component equilibrium adsorption of propane and propylene on the adsorbents was measured in the temperature range (273 to 343) K and the pressure range (0.0001 to 1) bar and correlated by several well-known isotherm models. The enthalpies of adsorption were estimated by the Clausius−Clapeyron equation and its dependence on adsorption coverage. Fractional uptake experiments performed to study the single component kinetics and apparent diffusivity were evaluated.

A vacuum pressure swing adsorption (VPSA) using zeolite 5A was studied experimentally and theoretically. An equimolar mixture of propylene/propane was used as a feed gas for an eightstep, four-bed VPSA process. Isotherm data of zeolite 5A at various temperatures and breakthrough curves of propylene and propane for both adsorption and regeneration steps were obtained to acquire the input parameters for the test runs with the pilot plant. Experimental measurements by the pilot plant have been obtained between a maximum pressure of P H ) 5.8-6.4 bar and a minimum pressure of P L ) 0.1-0.05 bar at a constant temperature of 70 °C. The effects of feed rate and dilution with H 2 , purge rate, and vacuum pressure on the product purity and recovery were also investigated via experimentation. Using a feed rate of 320 NL/h of a mixture of 50% propylene/propane at 70 °C, a purity of 92% propylene and a recovery of 29% were obtained. Comparison of the results from the experiments and the simulation gave a reasonable agreement.