There was a small gasworks near where I live. The site is still there, and the old coking furnace and chimney are still in place, and form a 'feature' of the use that the building is now put to. The coke that was produced from the gas making process, went to a car engine casting plant nearby, and was also bagged and sold to the general public, so there must have been a demand for it for 'household' use. I seem to remember my parents buying both coal and coke, and I have a dim recollection of a fire being 'made' with coal, and then banked with coke, which burnt much more slowly, and gave off a more steady heat than a roaring fire up the chimmally ... I also seem to recall the fire being 'calmed' at night by banking it up with powdered and chipped coal that my old dad used to refer to as "nutty slack" I think it was ??
Arfa