Two stage combustion

A process for combusting sulfur and nitrogen containing carbonaceous materials in a two stage combustion process comprising:

• introducing sulfur and nitrogen containing carbonaceous combustible materials selected from the group consisting of coal, oil shale, petroleum coke, peat, lignite, solid waste, refuse derived fuel, refiner and sewage plate sludges, liquid wastes, solid biomass materials, and mixtures thereof and sulfur fixation agent particulates selected from the group consisting of limestone, dolomite, siderite, iron oxide, zinc oxide, and mixtures thereof into a first combustion stage single fluidized bed supported upon and maintained fluidized by fluidizing gas introduced through a perforated sloping bed support grid within a single combustor having a density/size selective solids withdrawal conduit at a base portion of said bed with upflowing withdrawal gas, the superficial velocity in said fluidized bed is about 4 to about 15 feet per second;
• combusting said carbonaceous materials in said fluidized bed under substoichiometric oxygen conditions wherein the total amount of said oxygen of said fluidizing gas and said withdrawal gas is about 40 to about 70 percent of the stoichiometric oxygen necessary for complete combustion of said carbonaceous materials in said fluidized bed and at temperatures of about 1600.degree. to 2000.degree. F. producing ash and reducing gases forming a reducing region in a major portion of said single fluidized bed, said reducing gases comprising gaseous sulfur compounds;
• reacting said gaseous sulfur compounds with oxides of said sulfur fixation agent in said reducing region of said single fluidized bed to form an intermediate solid metallic sulfur compound;
• converting said nitrogen contained in said carbonaceous materials into molecular nitrogen in said reducing region of said single fluidized bed;
• reacting said intermediate solid metallic sulfur compound in an oxidizing region maintained at a base portion of said fluidized bed and the upper portion of said selective solids withdrawal conduit by said upflowing withdrawal gas to form a stable, solid, environmentally acceptable sulfur-containing compound;
• agglomerating said ash in said oxidizing region to form easy transportable, non-leachable, environmentally acceptable ash;
• withdrawing said agglomerated ash and said stable, solid, environmentally acceptable sulfur-containing compound from said single fluidized bed through said selective solids withdrawal conduit;
• passing said reducing gases, fine particulates of uncombusted said carbonaceous material, fine particulates of said sulfur fixation agent from said fluidized bed and tangentially introducing said reducing gases and said particulates into a second combustion stage cyclonic combustor wherein the velocity is about 30 to about 275 feet per second;
• burning said reducing gases and said uncombusted carbonaceous materials in said second stage cyclonic combustor under excess stoichiometric oxygen conditions achieved by tangentially introducing oxygen containing gas to provide said oxygen in an amount about 5 to about 10 percent excess of the stoichiometric oxygen necessary for complete combustion in said cyclonic combustor at temperatures of about 1800.degree. to 2200.degree. F.;
• reacting said fine particulates of said sulfur fixation agent with sulfur oxides formed during said burning in said second stage cyclonic combustor to form a stable, solid, environmentally acceptable sulfur-containing compound;
• separating solid fines separated in said second combustion stage cyclonic combustor and recycling said fines to said first combustion stage fluidized bed;
• and
• removing from said second stage combustor flue gases comprising environmentally acceptable amount of CO, NO.sub.x, SO.sub.x, and TCH content.