Coal gasification
With current state of technology and worldwide coal reserves,
coal is an economical and technically practical option to
produce hydrogen in large scale plants. Compared to the
existing methods (i.e. electrolysis), gasification is more suitable
for converting coal to hydrogen. In gasification, coal is
partially oxidized with steam and O2 in a high-temperature
and high-pressure reactor and the products are mainly H2,
CO, mixed with steam and CO2 (syngas). This syngas goes
through a shift reaction in order to increase the hydrogen
yield. The gas product can be processed and cleaned in cases
where there is a need to recover elemental sulfur or sulfuric
acid. Some of the syngas can further be processed and used in
gas turbines to generate electricity. Despite some advantages
of coal gasification, due to high carbon content of coal, this
method causes higher CO2 emissions compared to other
available hydrogen production technologies. Carbon capture
and storage technologies are currently developed in order to
address this issue. At present, hydrogen production cost of
coal gasification is slightly higher than that of natural gas
steam reforming. However, coal gasification techniques are
less well-defined than those used in the steam reforming of
natural gas. In terms of economics, making hydrogen from
coal differs from other fossil fuels: the unit raw material costs
are lower while the unit capital costs are higher for the coal
gasification plants