(487ao) Low-Cost Coal to Hydrogen for Electricity with CO2 Sequestration

The goal of our process is to produce hydrogen at low cost from clean coal for electric generation.

Currently, coal costs about $1.20 /MMBtu, considerably less than electricity or hydrogen. By contrast,

hydrogen costs more than $100/MMBtu, or considerably more than electricity. I would like to describe

experiments done on an innovative, membrane reactor approach that generates hydrogen from coal gas

while extracting that hydrogen at low cost. The hydrogen can be used to feed fuel cells or gas-turbine

electric generators. Further, the waste carbon-dioxide (CO2), produced in this process remains at high

pressure, about 800 psi. It is thus is more-easily sequestered than the low-pressure CO2 produced in the

cancelled FutureGen project.

The general scheme I propose is shown in the figure below. The first steps are coal gasification

and H2S removal. This is done by one of the several, attractive coal gasifier designs that are commercially

available. A particularly attractive one of these, the GE design, can produce clean coal gas at about 800

psi., with a hydrogen content approaching 40%.There is also a significant CO (carbon monoxide) content,

and the rest is largely CO2. For FutureGen, the CO was converted to H2 and CO2 through a series of

water-gas-shift (WGS) reactors. Hydrogen was then extracted by a pressure-swing scrubber that produced

low-pressure CO2. For sequestration, the CO2 had to be repressurized. By contrast, the approach I propose

could use a single water gas shift (WGS) membrane reactor with no heat-interchange because the

membrane reactor helps drive the reaction. The hydrogen would be delivered at lower pressure, but the

CO2 would remain at high pressure for easy sequestration. There are thus fewer heat exchangers and other

parts to the WGS system. REB Research & Consulting has been developing and selling membrane

reactors for the last 15 years, mostly for use generating hydrogen from methanol. We have good

experimental evidence on the efficacy of these reactors operating on coal gas, based on a reactor tests on a

1 ton ton/day coal gasifier at Western Research Institute, Laramie WY.

Because there are fewer components in this design, it should be possible to make hydrogen at a

much lower capital cost with the membrane reactor. Further since only the coal, water and a small

amount of oxygen are compressed for this process, while the CO2 is delivered at 800 psi, we save on the

capital cost of compressors for sequestration as well as requiring fewer parts and far less compression

energy. The science of membrane reactors will be discussed briefly along with our experiments on

hydrogen membrane fabrication and testing.

References:

1. R. E. Buxbaum and H. Lei, "Power

output and load following in a fuel cell

fueled by membrane reactor hydrogen," J.

Power Sources, 5467 (2003) 1-5.

2. R. E. Buxbaum, "Membrane Reactor

Advantages for Methanol Reforming and

Similar Reactions," Separation Science and

Technol., 34 (1999) 2113-2123.