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he increasing demand for natural gas efficient heat transfer system [5] and the optimal
and the consequent high prices in the recovery of the reaction heat [6].
recent past has led both scientific and In conventional SNG processes, the risk of runaway of
industrial research to investigate the methanation reaction is very high, while in the
possible alternative pathways that VESTA process such risk is avoided due to the
T account for more abundant resources presence of CO and water, which act as temperature
2
to supply end users demand. In this field, many dampers. In contrast to other available technologies,
industries developed unconventional methods of CO removal in the VESTA process is performed
2
natural gas production [1]. The Substitute Natural Gas downstream of the methanation reactors rather before
(SNG) production coming from different sources with a the methanation section, and there is no need of
suitable methanation process is considered as one of product recycle compressors (that, in standard process
the most flexible approaches to decarbonise the schemes, typically recycles about 90% of the first
applications of residential heating (including cooking), reactor effluent).
cogeneration, and transportation systems by using This strategy of avoiding the recycle of reaction gases
compressed SNG [2, 3, 4]. reduces the high installation, operating, and
The potentialities of SNG are expected to play a key maintenance costs associated with the recycle
role in the energy sector due to the easy connection of compressor. Moreover, the CO recovered downstream
2
production plants to existing natural gas network and of the methanation section could have a higher purity
the availability of mature technologies for commercial than that recovered from the syngas upstream, can be
application. When based on biomass, this process can liquefied, and may be used for other industrial purposes.
help to reduce dependency on fossil fuels and help With reference to the optimal recovery of reaction heat,
meet environmental targets. Furthermore, the SNG in VESTA technology the heat recovered by the cooling
produced can be combusted in any conventional gas of the reaction is exploited for the production of steam
turbine to produce low carbon energy and it can be [7]. For the sake of clarity, figure 1 shows schematically
transported and distributed using the existing grids and the concept of the once through VESTA process.
infrastructure. SNG produced from renewable sources
like biomass or biogas is called Green-SNG or Bio-
SNG. Coal-to-SNG: the Pilot Plant
VESTA catalytic methanation to produce SNG can In many areas of the world, like China, in-house natural
provide an efficient, robust, and viable system, which gas resources are not present in sufficient quantity to
can play a significant role in this trend to reduce the meet domestic demand, while, on the contrary, plentiful
carbon impact in sectors that traditionally stand on and more distributed coal reserves are available. The
natural gas without losing the possibilities to achieve conversion of coal to SNG by coal gasification and
the sufficient offer to end user needs. subsequent methanation of the produced syngas
provides an alternative energy option in these countries.
To this end, in 2013 Foster Wheeler signed a cooperation
VESTA Methanation Process agreement with Clariant International, the catalyst
The methanation process occurs with the conversion of
the carbon oxides, mainly carbon monoxide, and
hydrogen into methane, in line with the following
equilibrium reaction:

CO + 3H ↔ CH + H O
2 4 2
Carbon dioxide can also be converted to methane
according to:

CO + 4H ↔ CH + 2H O
2 2 4 2
High methane yields are thermodynamically favoured
by low temperatures and high pressures. Both these
methanation reactions are strongly exothermic, hence
the methanation processes are characterised by a large Fig. 1 - The concept of VESTA process. The main sections can be adapted
amount of heat released, and so the main issues to be to Customers’ need. The main sections reported in this block flow diagram
faced during the design of a methanation process is the are in order: gasification, sulphur removal, methanation block, and CO
2
control of the reactors’ temperature by means of an removal. CO and water in syngas control the exothermic heat of reaction
2
with no need of product recycle
IndustrIal Plants - May 2018
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