Process of producing magnesia with sulfuric acid recycle

Claim 1

Process for producing magnesia from magnesium-containing carbonate ores which comprises: (a) leaching said ore with sulfuric acid; (b) neutralizing the solution from (a) with magnesia and separating undissolved impurities; (c) crystallizing magnesium sulfate from the solution from (b) under superatmospheric pressure and at temperatures above 150° C; (d) separating and cooling the magnesium sulfate crystals so that they contain 1.5-4 mols of water of crystallization and thereby have a crystal fineness suitable for decomposition in the fluidized bed reaction zone of step (f); (e) dehydrating and/or heating the crystals from (d) in a suspension-type heat-exchanger with exhaust gases from the fluidized-bed reaction zone of step (f); (f) feeding the crystals from (e) after separation to a fluidized bed reaction zone where they are decomposed to form magnesia and sulfur dioxide, the heat required for the decomposition reaction being generated by approximately a stoichiometric combustion of fuel charged into the fluidized bed reaction zone; (g) removing magnesia from the fluidized bed reaction zone and feeding same to a multi-stage fluidized-bed cooler operated with air as a fluidized gas; (h) feeding fluidized air from the fluidized bed cooler to the fluidized bed reaction zone of step (f); (i) converting the sulfur dioxide produced in step (f) into sulfuric acid and recycling same to leaching step (a).