Comparison of the cost of hydrogen from air‐blown and thermally ballasted gasifiers

Abstract

AbstractThe objective of this study was to compare the cost of producing hydrogen by two types of biomass gasifiers: a conventional air‐blown fluidized‐bed gasifier and a thermally ballasted fluidized‐bed gasifier developed at Iowa State University. The ballasted gasifier is an indirectly heated gasifier that uses a single reactor for both combustion and pyrolysis. Heat accumulated in high‐temperature phase‐change material during the combustion phase is released during the pyrolysis phase to generate producer gas. Experimental data from pilot‐scale air‐blown and ballasted gasification tests have been used as a basis for this study. Experimental data has been scaled up to calculate the cost and feasibility associated with 50 Mg of hydrogen per day production plants. Air‐blown gasification yields for total direct cost, total capital cost, and the annual operating cost were $19.20, $43.21 and $38.65 million, respectively. The cost estimate of a system producing 50 Mg/day of hydrogen via air‐blown gasification is projected to be $2.23/kgH2. The total direct cost, total capital cost and the annual operating cost for ballasted gasification were $30.17 $67.80, and $52.11 million, respectively. The hydrogen production cost for ballasted gasification showed $3.01/kgH2. This is 35% higher than that of air‐blown gasification. A sensitivity analysis was performed to help to assist economic feasibility which includes variables for labor, capital charges, biomass costs, and hydrogen yields. The cost of biomass was found to be the most influential contribution to hydrogen production costs. As a result, a detailed analysis based on a state‐by‐state model is used to demonstrate the effect of biomass cost on hydrogen production cost. This model also predicts the potential number of 50 Mg ofH2/day plants that might be built in each state based on potential switchgrass supply. © 2012 Society of Chemical Industry and John Wiley & Sons Ltd