Process of producing magnesia with sulfuric acid recycle
AssigneeMetallgesellschaft Aktiengesellschaft
InventorsHarry Edward Cross, Wolfgang Krieger, Eberhard Anschutz, Lothar Reh, Martin Hirsch
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Abstract
This invention relates to a process of producing magnesia from magnesium-containing carbonate ores, which comprises leaching with sulfuric acid, subsequently neutralizing the solution with magnesia, separating the undissolved impurities, crystallizing magnesium sulfate under pressure and above 150.degree. C so the crystals have from 1.5 to 4 moles of water per magnesium sulfate molecule and thermally decomposing the latter to form magnesia and SO.sub.2, recovering sulfuric acid from the sulfur dioxide produced in the decomposing steps and recycling the sulfuric acid to the leaching stage.
Claims5
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.degree. 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).
Dependencies are inferred from the claim text.