Today, the industrial implementation of WGS takes place
usually in a series of adiabatic converters where the effluent is
converted in two steps with the second one at a significant
lower temperature in order to shift the equilibrium towards
the hydrogen product. Conventional WGS reactors are used
for large scale application and operate at high pressure and
thus they are not suitable to be coupled with atmospheric
pressure gasification (suitable for small scale applications).
During the UNIfHY project [38], a WGS reactor operating at
atmospheric pressure has been assembled with catalysts
impregnated and supported on ceramic foams, to keep the
efficiency of the gasesolid (i.e. the catalytic surface area)
contact and reduce the pressure drop. The hydrogen rich gas
at the outlet of WGS reactor (WGSR) is cooled down and then
compressed to feed a PSA unit, which operates at relatively
low pressure, to separate H2 from residual gases producing
hydrogen PEFC (Proton Exchange membrane Fuel Cell or
PEMFC) grade. The WGSR (as described above), the compressor
and PSA are all part of the Portable Purification System (PPS)
realized by the partner Hygear in the ambit of the UNIfHY
project (HYGEAR B.V. “Engineering for sustainable growth”).
Following the plant and the gasifier model description, this
work shows the results of the system simulations carried out
to analyse the influence on the hydrogen conversion efficiency
of the variation of the main gasifier parameters (steam
to biomass ratio and gasification temperature).