Methods by which new or used boilers or furnaces ranging from small industrial to the largest utility units that are designed for coal or oil or natural gas or shredded waste or shredded biomass firing can substantially improve their technical operation and sharply reduce their capital and operating costs by implementing component modifications and process steps that (a) minimize the adverse impacts of coal ash and slag on boiler surfaces and particulate emissions thereby also facilitating the use of oil or gas designed boilers for coal firing, (b) drastically reduce the loss of water used to transport coal in slurry form to power plants, (c) essentially eliminate the combined total nitrogen oxides (NO.sub.x), sulfur dioxide (SO.sub.2), mercury (Hg), trace metals, and carbon dioxide (CO.sub.2) emissions, (d) separate and permanently sequester carbon dioxide released during combustion and (e) improve the coal and solid fuel combustion efficiency.