(537c) Upgrading Producer Gas from Biomass Gasification to Produce High Purity Hydrogen
AIChE Annual Meeting
2006
2006 Annual Meeting
Sustainable Biorefineries
Catalytic Conversion of Renewable Resources to Synthesis Gases and Pyrolysis Oils
Thursday, November 16, 2006 - 1:10pm to 1:30pm
In the biorefinery concept, hydrogen is one commodity chemical that is very valuable for use either as an energy carrier for power generation or as a feedstock for producing other important chemicals such as ammonia. It is likely that the most efficient pathway to produce hydrogen from biomass is the thermo-chemical process path via biomass gasification followed by catalytic treatment of the cleaned producer gas to increase the hydrogen content followed by hydrogen purification/separation.
The traditional way to increase hydrogen content of the producer gas is by first passing the gas stream to a steam reformer at 800oC followed by a two-step water gas shift reactions (HT and LT shifts at 400 and 250C, respectively). CO2 is separated from hydrogen either by extraction or pressure swing absorption. The multistep process makes the process inefficient and costly.
At Iowa State University, research efforts have been made on improving the efficiency of producing hydrogen from biorenewable materials. Discussed will be results from tests conducted at the Biomass Energy Conversion Facility (BECON) in Nevada, Iowa which is operated by the Iowa Energy Center. A pilot scale fluidized bed reactor is used to produce the producer gas. The system is rated (2.8 MMBTU/h) thermal input, which corresponds to an average throughput of 180kg/h (400 lb/h) of solid biomass fuel. The cleaned producer gas from this gasifier is upgraded for its hydrogen content by using core-in-shell catalyst/sorbent technology that has been developed at Iowa State University in the past three years. This technology utilizes a unique material called core-in-shell combined catalyst/sorbent pellets in which a CaO core is surrounded by a porous shell that supports a nickel catalyst. By using the pellets, the production of pure H2 is reduced to a single step because simultaneous reaction rate improvement to produce hydrogen from the catalyst function and separation of H2 and CO2 via selective absorption of CO2 by CaO can be achieved. Effects of operating conditions on the product stream compositions will be addressed.