Page 71 - Industrial Plants 2014

are represented by the fact that SNG can be
transported and distributed using existing natural
gas infrastructure and it can be combusted in any
conventional gas turbine to produce low carbon
energy.
The catalytic synthesis of methane from carbon
monoxide and hydrogen is described by the following
reaction:

CO + 3H ? CH + H O (1)
2
4
2
Carbon dioxide can also be converted to methane
according to

CO + 4H ? CH + 2H O (2)
2 2 4 2
Both these methanation reactions are strongly
exothermic (even if CO methanation is less
2
exothermic than CO methanation), therefore high
methane yields require or are favoured by low
temperatures and high pressures.
Methanation processes are characterized by a large
amount of heat released during methanation, and so
the main issue to be faced during the design of a
methanation process is the control of the reactors’
temperature by means of an efficient heat transfer
system [1]. The optimal heat recovery of the reaction
heat from the methanation reaction is also a critical
aspect [2].
Generally methanation catalysts Methanation processes
have to work in a reaction are characterized by
temperature range between 250- a large amount of
600 °C, while properly stabilized heat released during
catalysts can tolerate temperatures methanation, and so
up to a maximum of 700 °C. the main issue to be
To moderate the exothermic faced during the design
methanation reaction temperature of a methanation
several techniques can be process is the control
envisaged: the recycling of of the reactors’
products, the dilution with inert or temperature by means
steam, otherwise the installation of of an effcient heat
isothermal reactors. The main transfer system
he need to satisfy natural gas drawback of CH recycle is the
4
demand, by exploiting the coal need for recycle compressor which represents a
resources, which in many areas of significant part of the investment cost and of the
the world are more evenly distributed overall power consumption, and complicates the
and more abundant than gas, has scheme of the system.
T given a great boost to the A typical conceptual scheme of the standard
development of so-called alternative fuels derived methanation process is reported in figure 1.
from coal gasification: CTL (Coal to Liquids) and
SNG (Substitute Natural Gas). In particular, SNG
production from coal, that is, for example, still the The VESTA process

primary energy source in China, could diversify In this field, Foster Wheeler has developed a simple
energy options and reduce the dependency on fossil methanation process, called VESTA, using catalyst
fuels with their fluctuating prices. provided by Clariant, Foster Wheeler’s partner in
Further advantages of converting coal to natural gas SNG technology.

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