Explain thermal reduction, gravity speration in extraction of metals?

Dear Student

Thermal reduction is the process in which a group of processes are carried out to bring about the extraction of metal compounds into corresponding metals through the involvement of some more active metals. Thus, the metals compounds can be oxides, halides, etc., and the active metals are magnesium, silicon, aluminium. The major step here is the evolution of heat which brings about the reduction of metal compounds into metal. Based on the reducing metal, this process of thermal reduction is classified into magnesiothermy, silicothermy, aluminothermy, etc. There, however, turn out to be more expensive as compared to reduction involving carbon. 
Kinds of Thermal Reduction -
1.) Out-of-Furnace Process-
Used in those cases where the amount of heat evolved is sufficiently large ranging from 1750 to 3000 degree C.
2.) Electric Furnace Process-
This method is employed in case where the heat evolved in inadequate and additional heat is supplied through electric heating.
3.) Vaccum Thermal Reduction -
Highly volatile metals, like magnesium, etc are reduced through this technique, under vaccum at a temperature of 800 to 1400 degree C, as well as it is also used to reduce those metals which have a very low gas content.

Gravity Separation can be defined as a process in which the two components are separated  through the use of either water or air, on the basis of the difference in their specific gravities.
Here, the two components can be either a suspension or dry granular mixture where these are separated based on their gravity, that is the components or the particles involved have different specific weight.
In this, the two immiscible phases (solid-solid, liquid-solid, or solid-gas, etc.) are allowed to separate under the influence of gravity, thus, the denser phase settled down. This process is employed on a large scale in ore dressing and has variety of applications in other industrial chemical processes. 


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