Abstract: A conventional pulverized coal-fired furnace is supplied fuel at two different levels. The raw coal is classified into a stream of relatively pure coal ground to conventional fineness for burners at the lower level, and a stream of very finely divided coal with a large, heavy mineral content for burners at the higher level.

Abstract: Sawdust is mixed with partially concentrated black liquor from pulp manufacture. The sawdust, coated with the solids of the black liquor, is dried by heated air. The sawdust, coated with organic and inorganic black liquor solids, is fed to the hearth of a chemical recovery boiler. Combustion of the char formed on the boiler hearth produces heat which causes additional organic material to pyrolize. The inorganic material combines to form molten smelt. The moisture-laden, heated air from the dryer is introduced into the boiler with the secondary air and the smelt is tapped off into an aqueous solution to form green liquor.

Abstract: The potassium compounds in heavy black liquor flowing in the recovery cycle are reduced by the introduction of magnesium nesosilicate to form magnesium potassium silicate which is voided from the system by filtration.

Abstract: Sawdust is mixed with partially concentrated black liquor from pulp manufacture. The sawdust, coated with the solids of the black liquor, is dried by heated air. The sawdust, coated with organic and inorganic black liquor solids, is fed to the hearth of a chemical recovery boiler. Combustion of the char formed on the boiler hearth produces heat which causes additional organic material to pyrolize. The inorganic material combines to form molten smelt. The moisture-laden, heated air from the dryer is introduced into the boiler with the secondary air and the smelt is tapped off into an aqueous solution to form green liquor.

Abstract: A Kraft pulping process by which spent pulping liquor is burned in a recovery furnace 12 to reduce inactive alkali sulfates therein to active alkali sulfides while producing molten smelt that when added to water forms green liquor and residual dregs bearing catalytic iron. The dregs are separated from the green liquor and divided into first and second portions. The first portion of the dregs is discarded while the second portion of dregs required to maintain a concentration of iron in the smelt at from 0.05% to 5% is recirculated back to the furnace to provide optimum catalytic reduction of alkali sulfates to alkali sulfides. A quantity of alkali metal compounds is added at 24 to the pulping liquor in line 10 to serve as a temperature depressor that, together with the co-addition of said dregs, lowers the temperature of the molten smelt in furnace 12 from approximately 800.degree. C. to a more favorable temperature of about 650.degree. C.

Abstract: Sulfur oxides in the flue gases from a glass furnace are converted to sodium sulfate particles by introducing sodium oxide fume into the hot flue gases immediately downstream of the furnace. The fume is generated by forming a bed of carbonaceous material and sodium carbonate that is caused to react under hot reducing conditions. Sodium gas is thereby produced that burns above the bed to produce sodium oxide fume.