Page 163 - Advances in bioenergy the sustainability challenge

The typical catalyst for methanation is nickel and the main reaction is

Ni-based catalysts are also active in water-gas shift and hydration of higher hydrocarbons, like
olefins. Normally a H :CO ratio of 3 is necessary, which is obtained by a water-gas shift
2
reactor before methanation. In some types of reactors, e.g., fluidized beds, the water-gas shift
can be carried out also in parallel with the methanation, so no external adjustment of the
H :CO ratio is necessary.
2

Methanation can be done at atmospheric pressure, although according to the thermodynamics
higher pressure is preferred.
As Ni-based catalysts are sensitive to sulfur poisoning, gas treatment is quite important before

the methanation, and sulfur compounds have to be removed to below 0.1 ppm.

There is one main difference in the synthesis gas treatment compared with other synthesis.
Almost all gasifiers have some methane in the product gas, depending on the operation
temperature. As methane has not to be converted in the methanation, high methane content in the
synthesis gas is a big advantage for the production of BioSNG (if the overall efficiency is
higher, the higher the methane content in the product gas is). Thus especially indirect gasifiers
are advantageous for methanation, which have a syngas with a methane content of 10 vol% or
more.

EXAMPLES OF SYNTHESIS GAS UTILIZATION

In the following chapter some examples of gasification systems for production of synthesis gas
are described. They were selected, as there are some innovative aspects included, like:

Innovative consortium as here forest industry works together with a refinery (Neste Oil-
Stora Enso)

Concept of decentral biomass upgrading by pyrolysis to increase the energy density for
transport and central gasification in extremely large scale (Bioliq process)

Using coal gasification technology and adjusting the biomass properties by torrefaction
(BioTfueL)

Synthesis gas platform, where R&D on different synthesis is performed, taking slip streams
of synthesis gas from a commercial biomass CHP (biomass CHP Güssing)

Dual fluidized bed gasification optimized for SNG (ECN)

Sorption-enhanced reforming, to adjust the H :CO ratio direct inside the gasifier
2
Microchannel reactor technology (Oxford Catalysts, Velocys)

Decentral small scale methanation for production of BioSNG (Distributed SNG)

Large-scale FT synthesis (Choren)