Here are a couple of interesting segments from a recent Sunday...

Here are a couple of interesting segments from a recent
Sunday times focus on UCG.

Controlling Emissions.

There is now a readily-accessible body of published
information on the basic UCG process and its variants
for different applications.Broadly,sulphur and nitrogen
in the coal will report to the surface with the gas,
while ash [and most heavy metals] will remain in the
cavity.

Conventional sour gas cleaning technologies will remove
the sulphur compounds.The UCG cavity is controlled to a
pressure just below the hydrostatic pressure surrounding
the seam.At 500m,for example,this would be around 50 bar
and the product gas would reach the surface for processing
at upwards of 40 bar.

Under these conditions,the process and product gas ana-
logous to those of a coal gasifer,such as the Shell design
[selected for the Hatfield IGCC in the UK],or GE[formerly
Texaco],or Lurgi [further developed by Sasol],except that
the product gas has a somewhat lower CV.

The technology for removal of CO2 from such a gas is rel-
atively common.Physical solvents,with simple regeneration
by pressure reduction,can be used. [this contrasts with
post-combustion capture from flue gas at atmospheric
pressure.Even if that is perfected,the basic rule of
physics,chemistry and economics will leave it a poor
second to pre combustion capture in terms of cost eff-
ectiveness.]

For UCG in the UK,seams deeper than 800m are,the likely
targets,which will produce gas at correspondingly higher
pressures than 40 bar,making the penalty for CO2 removal
even less.For the typical gas referred to above,removal
of the CO2 from the raw gas will increase the CV to above
50% of that of natural gas.This will still leave the
methane and carbon monoxide to be burnt with the gas,
if it is to be used as a fuel for power generation,but
the carbon dioxide emissions per unit of output will be
slightly less than a CCGT.

However,if the reward for carbon capture is sufficiently
high,the CO2 capture can be readily increased,first by
shift reaction with steam to convert the CO to H2 +CO2,
and second,at greater cost, by reforming the methane to
H2+CO2.The energy content of the gas will then be hydrogen
basically carbon free,if all the CO2 is captured.This gas
could be a potential feed stock for fuel cells [the subject
of a recent MOU between Thornton New Energy and Waste2-
Tricity],but for bulk power generation,the main application must
be seen as gas turbines.


UCG as Gas Turbine Fuel.

A decade ago,the manufacture of large gas turbines running
on natural gas was well established,and such turbines had
successfully equipped the first generation of CCGT'S in
Britain however,gas containing a significant amount of
hydrogen [such as in an IGCC] was seen to present problems
for turbines of the time.Since then the problem has been
addressed.

In a paper presented recently to the UK coal research
forum in Leeds,Grant Budge of powerfuel,described the
plans for starting up and operating the power generating
capacity of the Hatfield IGCC project.The station will
first be built and operated on a natural gas fed CCGT.
The coal gasifer will be commissioned possibly a couple
of years later.The gas turbine is warranted to operate
on either natural gas or SYNGAS from the gasifer and
this flexibility is part of the business plan,where,
depending on the relative prices for coal,carbon dioxide
and gas,the adjacent mine output will either be sold or
gasified.

If operating experience at Hatfield bears out this cap-
ability for a new turbine to run on either fuel,it has
significant implications for using UCG gas as a substitute
for natural gas in CCGT'S.It will demonstrate that gas
turbine technology is becoming flexible enough to operate
a unit over a wide range of conditions.

In his recent budget,the UK Chancellor placed obligations
on new -coal-fired stations that will require the partial
implementation of carbon capture.Compared to coal,natural
gas produces about a third of CO2 per unit of output,so
an efficient CCGT should still be just capable of making
carbon limits for fossil-fueled stations-which will be
inevitable as Britain predictably fails to meet its re-
newable targets-will require CCGT'S also to reduce carbon
emissions.

This can only be done either by steam reforming some or
all of the methane in the fuel gas,with pre-combustion
carbon capture,or by post- combustion carbon capture.

Because of the ease of removing the Carbon in UCG gas,
to whatever extent is required,as explained above, the
eventuality of having to equip a combined cycle plant
with carbon capture,will offer another opportunity to
substitute UCG gas for fuel.....

Finally,the copy "back to the future" is a feature
length article on UCG,appeared as a "lead cover story"
for the Sunday Times Magazine.The article highlighted
the looming energy shortfall and investigated what
options are available.It emphasized the need for Gov-
ernments to look at the clean coal options especially
UCG.

[Russia has just signed a JV with Grant Budge]


HM.