sitting bull :good day to......buy., page-4

Wind

Briefly ...

1)the coal is combusted within a "bubble" created within a fully saturated coal seam ie under water.

2-4) The process is controlled by ensuring the operating pressure within the "bubble" never exceeds a safe proportion of the hydrostatic pressure within the saturated coal seam (because of confining effects, the groundwater could have a head equivalent to many 10's of metres above the roof of the coal seam).

5) No more and more likely less than occurs with conventional underground long wall mining ... likely less because ucg can access deeper seams than can conventional mining ... surface expression of underground void collapse diminshes as the depth to the void increases ... its fair to view ucg as "virtual" long wall mining.

6)I think not ... refer 1) above.

7)Yes, syngas should be extracted via steel casing cemented (sealed) into the drilled borehole.

8) Refer 7) above.

Cheers
Dex