3difference between calcination and roasting•dont spàm
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Calcination and Roasting
Chemistry
Calcination and Roasting
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What is Calcination and Roasting?
Metals are usually obtained from oxide ores after going through the electrolysis or reduction process. While oxide ores are easy to reduce, it is not the same with carbonates and sulphides. These ores are turned to metals only after converting sulphides and carbonates to an oxide ore. So how is it done? Well, mostly, the conversion is done through the processes of roasting or calcination. So, here, we will learn about roasting and calcination and try to understand various topics related to them.
Define Calcination and Roasting?
What is Calcination?
As per the traditional definition, calcination can be defined as the process of converting ore into an oxide by heating it strongly. The ore is heated below the melting point either in limited supply or absence of air. We use this method in common for converting hydroxides and carbonates to their respective oxides. During calcination, the volatile and moisture impurities are also removed. We can also describe calcination as a thermal process that can be used to convert ores and other solid materials by bringing about a thermal decomposition. In calcination, most of the time, the reaction occurs at the thermal decomposition tempurature or above it.
Calcination is derived from the Latin word "calculate," which translates "to burn lime." Thus, calcination is mostly used in the decomposition of limestone (calcium carbonate) to carbon dioxide and lime (calcium oxide).
CaCO3 --> CaO + CO2
Whereas, the products derived from calcination are referred to as calcining, and it is regardless of the actual compounds undergoing thermal treatment.
What is Roasting?
When we discuss roasting, basically, it is a process of metallurgy where the ore is converted into its oxide by heating it in the presence of excess air above its melting point. While calcination is the process mostly used in the oxidation of carbonates, roasting is a method that can be used for converting the sulphide ores.
Whereas, during roasting, the non-metallic and moisture impurities in the form of volatile gas are released. The roasting process contains the solid-gas thermal reaction that includes reduction, oxidation, chlorination, sulfation, and also pyro hydrolysis.
However, roasting that involves the sulphides is a major source of air pollution, and the major drawback of this process is, it releases a large amount of metallic, toxic, and acidic compounds as well, which causes harm to the environment.
An example of roasting can be given as when Zinc sulphide is converted into zinc oxide.
2ZnS+3O2 --> 2ZnO + CO2
Differentiate between Roasting and Calcination
A few of the major differences between calcination and roasting are tabulated below..
Calcination
Roasting
Calcination is a process where the air might be supplied in limited quantity, or the ore is heated in the absence of air.
Roasting includes heating of ore lower than its melting point in the presence of oxygen or air.
Calcination involves the thermal decomposition of carbonate ores.
Roasting is mostly carried out for sulfide minerlas.
Moisture is driven out from ore during calcination.
Roasting does not involve dehydration of ore.
Answer:
Calcination:
Calcination is a process where the air might be supplied in limited quantity, or the ore is heated in the absence of air.
Calcination involves the thermal decomposition of carbonate ores.
Moisture is driven out from ore during calcination.
Roasting:
Roasting does not involve dehydration of ore.
Roasting includes heating of ore lower than its melting point in the presence of oxygen or air.
Roasting is mostly carried out for sulfide minerals.
Roasting does not involve dehydration of ore.