Verfahren zur Erzeugung eines wasserstoffreichen Produktgases aus Biomasse in einem Wirbelschichtvergaser (PDF)

The discussion about the future energy supply for mankind is based on the fact
that fossil energy resources are limited. It is also based on the fact, that the
emissions from the use of these fossil fuels has caused an increase in the
concentration of CO2 in the atmosphere over the last number of years.
There are several ways to reduce CO2 emissions. One is to increase the
efficiency of power plants to reduce their fuel needs. Another way – particularly
for fossil fuel - is to capture CO2 from the flue gases. A third way is to use
biomasses as fuel. As a first approach, one can say that biomass takes that
much CO2 out of the atmosphere during growth as it will emit during combustion.
This thesis is about a process which produces a hydrogen-rich gas from
biomass. This gas can further be used both as a base for further synthesis and
for electricity production.
In the process described, biomass is gasified under steam atmosphere at a
temperature between 450°C and 750°C. The reactor is a circulating fluidised
bed. Instead of inert bed material, which is normally used, lime is used. At this
temperature window lime reacts with the CO2 to produce limestone. CO2 is
taken from the gas phase to solid phase and is not present in product gas any
more. Additionally the equilibrium of watergas-shift-reaction (CO and H2O react
to H2 and CO2) is pushed to the H2 side due to the lack of CO2 in the product
gas. The absorption of the CO2 by the lime enhances the hydrogen production;
this process is called Absorption Enhanced Reforming (AER).