UCG produces low quality combustible gases at atmospheric...

UCG produces low quality combustible gases at atmospheric pressure.

Current combined cycle plants require CH4(99% methane) and extremely high pressures to feed into the gas turbine.

The reason UCG is not being used at present in Australia is simple. It is not commercially viable because we can extract high quality coals extremely cheaply and for many years. The reason we never had solar on roof tops is that it was not viable. Of courrse a govt subsidy of 50c/kWh changed that and for good reason. We now have a renewable base. There is nothing renewable about UCG.

UCG gas must be firstly scrubbed and then if it is to be combusted in a gas turbine it must be compressed.Because of the shear volumes of the stuff (it contins CO2 and other non combustibles) it is treated much like blast furnace gas.

These types of custom made compressors can consume as much as 40% of the power output. You can google Boa Shan project which used ABB/Kawasaki 11N2 gas turbines modifed to burn this type of gas.

It was quadruple the capital cost of a normal combined cycle GT almost entirly because of the compressor. It had the largest external combustion chamber I have ever seen in order to allow the gas resident time to combust before passing through the turbine blades and was incredibly complex. Try and google how many were installed after Bao Shan which was more than 10 yrs ago.

I have nothing against UCG as I think it is facinating technology but it's time is not now. You wont see it in the next 30 yrs in anything other than subsidised demonstrations. Technology is facinating and I expect my grandchildrens grandchildren may well see it as the new technology on the block if we havnt all been killed off by some virus or nuclear war.

Good luck.