carlherrnstein wrote:Coal bricks? are they held together by a binder? how much ash do you get out of them?
The big ones you see here are made of ground up, dehydrated sub-bit coal. They were invented in the 1880s as a low-budget surrogate for the higher ranking bituminous coal and anthracite. Those were needed for the industry, the railways and the Kaiser´s navy, so the government would indirectly influence the consumption by raising the price for high quality coals on the one hand and subsidising the production of coal bricks on the other hand... There were - and are to this day two kinds of briquettes available: the large ones made of sub-bit and small oval ones made of the anthracite and bitumious coal fines that would have gone to waste otherwise.
The large bricks need no binder, unlike the small oval briquettes made of anthracite and bituminous coal fines. The specs say:
energy: 19MJ/kg ~ 18.000BTUs
From what I´ve seen so far they keep their form, burn like hard wood for 1-1.5hrs, then turn to embers and stay like that for 2-2.5hrs and produce significant heat for 2.5-3hrs if I let them have enough combustion air to burn propperly.
Can get them to burn over night, too - it s a lengthy process, though! Can´t claim it s my invention either - followed grandmothers advice here: 4 bricks at a time, pack them closely together. Let volatiles burn off for 30mins, next layer of 4, let burn for 30mins, next layer of 4, let burn for 20mins. shut damper, reduce draft, place some glossy paper (our mailbox is full of advertising folders) on top of the coals. The glossy paper turns into a solid layer of ashes if you don´t disturbe it and insulates the coal underneath. 12hrs later: the room is comfortably warm, the stove is still hot to the touch and enough coals left to revive the fire.