Page 73 - Industrial Plants 2014

possible. The plant designed by Foster Wheeler has Gas composition % mol Table 1 – Reference
a very simple process scheme that facilitates H 0.10 conditions and
2
excellent performance both in terms of SNG product CO 0.00 composition of the
and steam exported. The plant performances were CO 0.10 SNG produced by
the VESTA process
modelled with commercially available process 2
simulators, with the reactor performances regressed H O 0.00
2
on the basis of reserved laboratory data measured CH 4 99.30
by Clariant. N 2 0.30
Conceptual scheme of the Foster Wheeler process Ar 0.20
is represented in figure 2. H S + COS 0.00
2
After sulphur impurities removal in the acid gas
removal (AGR) unit, syngas is sent to the methanation High
section, in a once-through operation with no gas Parameters Low pressure steam pressure
recycle: the system consists of a shift reactor steam
followed by three methanators in series. After being
cooled, the raw SNG coming from the third Temperature (°C) sat. sat.
methanator is routed to the CO removal section, to Pressure (barg) 3.5 90
2
improve the SNG quality and to make it suitable for Mass flow rate (ton/h) 150 294
natural gas grid specification. If required, the SNG
composition can be refined adding a further VESTA SNG technology. According to this Table 2 - Typical
methanation reactor. agreement Wison Engineering is providing exported steam
engineering and construction services, Foster production
A fexible process Wheeler has licensed the technology, and Clariant
The plant shown allows the production of 2 billion will supply the proprietary catalyst. The cooperation
Nm /year of SNG (composition shown in table 1). agreement also sets out a framework for long-term
3
Notably the plant is not only thermally self-sufficient cooperation to deliver and build methanation plants
but also allows export of high and low pressure based on this technology in China.
steam as quantified in table 2. Although the process has not yet achieved
The most important feature of the VESTA process is commercial references, nevertheless the technology
its great flexibility: it can handle syngas of a variety is based only on well-proven equipment (fixed bed
of compositions coming from different sources such reactors, shell and tube exchangers etc.) and the
as coal, biomass, petroleum coke and solid waste. catalyst, a nickel-based catalyst, has already been
In particular, the use of biomass feedstock, a extensively tested by Clariant. Clariant has significant
carbon-neutral fuel, is an opportunity to reduce experience with the production of many commercial
greenhouse gas emissions; several technologies are nickel-based catalysts and is the lead supplier for
available and sufficiently mature for commercial this many of these applications. The methanation
application [4, 5, 6]. catalyst used in the process is a newly developed
This technology is also a possible solution for catalyst and exclusively available for the Foster
refineries where coke disposal is a problem or for Wheeler/Clariant VESTA cooperation and its
refineries that do not use delayed coking units customers. The chemistry of this catalyst has been
because they are concerned about coke disposal. optimized to meet the high quality standards
The petcoke [7] can be gasified to produce SNG, demanded by the new application.
which can finally be used for internal refinery
consumption or distributed outside the refinery Conclusion
fence. Foster Wheeler is able to produce up to 2 billion Nm /
3
To demonstrate this VESTA SNG production year of SNG with a single train, without the presence of
technology, Foster Wheeler and Clariant are erecting a recycle compressor.
a pilot plant in Nanjing, China, which is expected to With reference to the electrical energy consumption,
be in operation at the end of May 2014. The pilot the VESTA process does not need a recycle compressor
plant was designed for a capacity of 100 Nm /h of (that, in standard process schemes, typically recycles
3
SNG produced and includes all reactors in order not about 90% of the first reactor effluent), this delivers
only to verify the chemical reactions but also to significantly lower electrical power consumption within
completely simulate a real plant. Foster Wheeler has the SNG section. With reference to the steam
signed a cooperation agreement with Clariant production, the process is able to recover about 90%
International AG and Wison Engineering Ltd to build of the heat released by the reactions, producing high
the pilot plant to demonstrate the Foster Wheeler pressure superheated steam.

IndustrIal Plants - May 2014
69