"Commercially available coal feeding methods for gasification consist of injection of coal-water slurry, or dry feed lock-hoppers. Coal-water slurry can be injected at very high pressure to efficient, high-pressure gasifiers; however, the debit of additional water required for slurry feeding tends to limit the types of coal used in these slurry-fed gasifiers to higher-rank, drier, and more expensive coals (primarily bituminous coal). In other words, if low-rank coals were to be slurried, their inherent high moisture levels combined with addition of slurry water results in excessive water content, causing inefficiencies in gasification. Dry feed lock-hoppers can handle dry coal feeds, but cannot be utilized except at lower operating pressures, at which gasifier operation is less efficient."
So in effect slurry feeds are more efficient as the gasifier can run at higher temp, limited to higher rank coals as additional water to lignite would make water content too great. CHTD over comes this by forming a upgraded slurry with lower water content at low cost.
http://www.netl.doe.gov/research/coal/energy-systems/gasification/feed-systems
CHTD cost is around $12/t with around 25-30%wc
Coldry cost is around $35/t with around 12-15%wc
So CHTD is better than Coldry for gasification, and if new feeding tech becomes available with increases dry feed efficiency the cost factor will still make CTHD preferable.
The only drawback of CHTD is the high capital cost for setup, which I believe was the reason for the ALDP knock back. Coldry was knocked back was because after 20 odd years of development the best partner they could offer was a mobile phone number with an answering machine and they had no solution to transport to port.
