Calcium sulfate process for the coproduction of Portland cement clinker and concentrated sulfur dioxide adequate to manufacture sulfuric acid

摘要

This invention isolates in separate furnaces the three thermochemical processes required in manufacturing Portland cement and sulphur dioxide from a calcium sulfate source so as to yield improved pyrometallurgical treatment for each individual process. Separating these processes facilitates selection of the most kinetically suitable reactions by enabling the maintenance of optimum conditions for each process without compromising the thermal or kinetic efficiencies of the other processes. PPOnly one fourth of the calcium sulfate is reduced to calcium sulfide in a separate ad hoc reduction furnace specifically designed for achieving enhanced reduction parameters which results in minimized reduction equipment size. Treating most of the calcium sulfate elsewhere works to avoid side reactions and allows Portland cement raw mix components to have an enhanced synergistic catalytic effect on reduction kinetics. Compounds deleterious to both Portland cement and sulfuric acid, such as alkalies and fluorides, are removed with the reduction furnace gases while high concentrations of sulphur dioxide are achieved in the gases reporting to the sulfuric acid plant.P PThree fourths of the calcium sulfate is made to react separately and simultaneously in a flash calciner with the calcium sulfide to produce sulphur dioxide and calcium oxide. At the flash calciner heat of radiation from exothermic combustion reactions is applied directly to the highly endothermic desulfurization of calcium sulfate under an oxidizing atmosphere. The calcium oxide and other Portland cement components are then discharged onto a short rotary kiln where only clinkering reactions take place at high thermal efficiencies for enhanced throughput, minimized furnace size, and lower burning zone temperatures.