Biomass-Derived Hydrogen from a Thermally Ballasted Gasifier
The goal of this project is to develop an indirectly heated gasification system that converts switchgrass into hydrogen-rich gas suitable for powering fuel cells. The project includes investigations of the indirectly-heated gasifier, development of particulate removal equipment, evaluation of catalytic methods for upgrading producer gas, development of contaminant measurement and control techniques, modeling of the thermal performance of the ballasted gasifier, and estimation of the cost of hydrogen from the proposed gasification system. Specific technologies investigated include a thermally ballasted gasifier, a moving bed granular filter, and catalytic reactors for steam reforming and water-gas shift reaction. The approach to this project was to employ a pilot-scale (5 ton per day) gasifier to evaluate the thermally ballasted gasifier as a means for producing hydrogen from switchgrass. A slipstream from the gasifier was used to evaluate gas cleaning and upgrading options. Other tests were conducted with laboratory-scale equipment using simulated producer gas. The ballasted gasifier operated in conjunction with a steam reformer and two-stage water-gas shift reactor produced gas streams containing 54.5 vol-% H2. If purge gas to the feeder system could be substantially eliminated, hydrogen concentration would reach 61 vol-%, which closely approaches the theoretical maximum of 66 vol-%. Tests with a combined catalyst/sorbent system demonstrated that steam reforming and water-gas shift reaction could be substantially performed in a single reactor and achieve hydrogen concentrations exceeding 90 vol-%. Cold flow trials with a laboratory-scale moving bed granular filter achieved particle removal efficiencies exceeding 99%. Two metal-based sorbents were tested for their ability to remove H2S from biomass-derived producer gas. The ZnO sorbent, tested at 450° C, was effective in reducing H2S from 200 ppm to less than 2 ppm (>99% reduction) while tests with the MnO sorbent were inconclusive. A computer model was developed that successfully predicted the thermal performance of the ballasted gasifier. An economic comparison of an air-blown gasification plant and a ballasted gasifier plant found that operating costs for ballasted gasification plant are about 31% higher than for the air blown gasifier plant. Hydrogen from the ballasted gasification plant and air blown gasification plant are projected to be $2.43/kg and $1.85/kg, respectively. This is lower than U.S. DOE’s 2010 target price of $2.90/kg and comparable to U.S. DOE’s 2015 target price of $2.00/kg.
- Research Organization:
- Iowa State Univ., Ames, IA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- FC36-01GO11091
- OSTI ID:
- 901792
- Report Number(s):
- DOE/GO/11091-5; TRN: US200722%%308
- Country of Publication:
- United States
- Language:
- English
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