Preparation of High Purity ( MgO) from Iraqi Dolomite (Bench – Scale Experiments) تحضير اوكسيد المغنيسيوم عالي النقاوه من الدولومايت العراقي (تجارب منضدية)

Abstract

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%) at room temperature for (15 min) 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˚C) for (60 min) (Dolime) added to the leachant in a ratio of (52.5%) (Dolime / Dolomite) at (70˚C) for (60 min). 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 (100min) . 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 min) 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%.