A very good point about the very hot capability of anthracite coal. Sorry to be boring about this - my (Cockney) grandfather was a fireman in South Wales for a local colliery company which had a steam raising plant , burning the local product , - anthracite - for power generation. They used "Lancashire Boilers" - which I think had low PSI capabilty , and relied on a very thin bed , frequently fired on sparingly. The job must have been a nightmare as he spend the entire shift working his way down the stokehold , no doubt firing little and often - so despite my "good idea" - probably a non starter for main line operation. I only know what my father told me , and he was a very young man when he observed his Dad as fireman - there is , no doubt good evidence on why anthracite (best used for slow burning) is a non starter. Wonder if the "new" planned coking coal from Cumbria if that mine comes off , (it has planning permission) , might be an option.