[ExI] Coal and PV

[Keith Henson]

It takes right at 3 MWh of heat energy to vaporize a ton of coal in
steam.  A considerable amount of coal is turned into syngas using
oxygen to burn part of the coal and provide heat.  I don't know for
sure how exact this is, but considering coal combustion at 6.7 kWh/kg
3 MWh will require burning 448 kg of coal.  This is done with oxygen
so there is a cost for the oxygen at 7 to 10 cents per kg, 1194 kg of
O2 costing $84 to $119.  What this means is that close to half a ton
of coal must be burned to vaporize a ton of coal.  There is also more
CO2 in the gas stream which increases the size of the absorber section
and the amount of CO2 vented or sequestered.

So the cost per ton vaporized would be 1.448 x the cost per ton of
coal plus the oxygen.  For coal at $20/ton, the cost to make syngas
would be about $130/ton of coal, most of it from the oxygen.

Compare: to a submerged arc.  For dedicated PV at 1.35 cents per kWh,
($13.50/MWh) the electrical cost would be $40.50.  Grid electricity
gets down to zero at times.  But to use this power would require a
syngas storage of considerable size.  An empty gas field would be
ideal.

Keith

PS, there is an ammonia plant that makes syngas from petroleum coke.
It is essentially a rocket engine followed by gas cleanup and
conditioning.  https://en.wikipedia.org/wiki/Coffeyville_Resources

Another related plant is here:

https://en.wikipedia.org/wiki/Dakota_Gasification_Company

The plant currently makes methane but is being converted to making hydrogen.