| الملخص | In this study, the optimum conditions obtained by the previous laboratory study were examined at an upper scale and the courageous results were confirmed and even improved, where the same approaches (Leaching-Precipitation-Pyrohydrolysis) have been followed.
Leaching was performed by mixing Dolomite of (-2mm) particle size with 22% HCl at a solid percent of 25% and room temperature for 15 minutes with gradual increment. More than 99% of CaO and MgO contents were leached out and recovered into the leachant.
Successfully CaO and MgO were separated from each other, and the separation was achieved over two steps. The first step was hydration, in which Dolomite calcined at 1000 oC for 60 minutes (Dolime) added to the leachant in a ratio of 52.5% (Dolime/Dolomite) at 70 oC for 60 minutes. The second was carbonation at which single fold diluted slurry was injected with CO2 gas at a pressure of 2 bars and at room temperature for 100 minutes. The recovery for the whole stage of separation was 99.69% for CaO as precipitated calcium carbonate 1st stage (PCC, Calcite) with a purity of 92.50%, while 96.5% of MgO recovered as MgCl2 in the solution. The evaporation of the MgCl2 solution produced 2nd stage (PCC, Aragonite) with a higher purity of about 99.1% and the salt Bischofite with a purity of 97.28% and a total mass recovery of MgO of about 95.15% based on the total MgO found in the feeds (Dolomite and Dolime).
Pyrohydrolysis stage was performed using pyrohydrolysis furnace equipped with HCl regeneration unit. The process was conducted at 650 oC for 60 minutes and a high purity MgO ≥ 98 % was produced. The recovery of MgO for the whole three stages 95.15% and HCl solution with a concentration of ≥22%. | |
