difference between Calcination and Roasting
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Answer:
Roasting vs Calcination
Roasting-One is heated in the presence of excess of oxygen or air.
Calcination- one is heated in the absence or limited supply of oxygen or air.
Roasting- This method is employed for sulphide ores.
Calcination- This method is employed for carbonate ores.
Roasting- Sulphur dioxide is produced along with metal oxide.
Calcination- Carbon dioxide is produced along with metal oxide.
Roasting - Example: For the ores ZnS (sphalerite) and Cu2S (chalcocite), balanced equations for the roasting are:
2ZnS+3O2-->2 Zno+ 2SO2
2 Cu2S + 3O2 → 2 Cu2O + 2 SO2
Calcination- Example: ZnCO3--> ZnO+ C02
CALCINATION IS THE PROCESS OF HEATING CONCENTRATED ORE IN THE ABSENCE OF AIR AT A TEMPERATURE BELOW ITS MELTING POINT.CARBONATES AND HYDROXIDES OF METALS DECOMPOSE TO FORM OXIDES.
ROASTING IS THE PROCESS OF HEATING CONCENTRATED ORE IN A CURRENT OF AIR AT A TEMPERATURE BELOW ITS MELTING POINT.WHEN THE CONCENTRATED ORE IS SUBJECTED TO ROASTING ,THE MOISTURE PRESENT IN IT IS REMOVED AS VAPOUR.