Usually, metals are obtained from oxide ores after going through the reduction or electrolysis process. While oxide ores are easy to reduce it is not the same with sulphides and carbonates. These ores can be turned into metals only after converting carbonates and sulphides to an oxide ore. The conversion is mostly done through the processes of calcination or roasting. So, here in this page we will learn about calcination and roasting and try to understand the various topics related to them.
Table of Contents
- What is Calcination
- What is Roasting
- Important differences
What is Calcination?
Calcination is defined as the process of converting ore into an oxide by heating it strongly. The ore is heated below its melting point either in absence of air or in limited supply. This method is commonly used for converting carbonates and hydroxides to their respective oxides. During calcination, moisture and volatile impurities are also removed. Calcination can also be described as a thermal process that is used to convert ores and other solid materials by bringing about a thermal decomposition. In calcination, the reaction most of the time occurs at or above the thermal decomposition temperature.
Calcination is derived from the Latin word calciner which translates as “to burn lime”. So, calcination is mostly used in the decomposition of limestone (calcium carbonate) to lime (calcium oxide) and carbon dioxide.
CaCO3 —> CaO + CO2
Meanwhile, the products that are derived from calcination are known as calcining, and it is regardless of actual compounds undergoing thermal treatment.
What is Roasting?
Roasting is a process of metallurgy where ore is converted into its oxide by heating it below its melting point in the presence of excess air. While calcination is mostly used in the oxidation of carbonates, roasting is a method that is used for converting sulphide ores. During roasting, moisture and non-metallic impurities are released in the form of volatile gases. The process of roasting consists of solid-gas thermal reaction which includes oxidation, reduction, sulfation, chlorination and pyro hydrolysis.
However, roasting which involves sulphides is a major source of air pollution and the main drawback of this process is that it releases a large amount of metallic as well as toxic and acidic compounds which cause harm to the environment.
An example of roasting is when Zinc sulphide is converted into zinc oxide.
2ZnS+3O2 —> 2ZnO + 2SO2
Important Differences Between Calcination and Roasting
Here are some of the major differences between calcination and roasting.
| Calcination | Roasting |
| Calcination is a process in which ore is heated in the absence of air or air might be supplied in a limited quantity | Roasting involves the heating of ore lower than its melting point in the presence of air or oxygen. |
| Calcination involves the thermal decomposition of carbonate ores. | Roasting is carried out mostly for sulfide minerals. |
| During calcination, moisture is driven out from an ore. | Roasting does not involve dehydrating an ore. |
| Carbon dioxide is given out during calcination | During roasting, large amounts of toxic, metallic and acidic compounds are released. |
For detailed discussion on this topic and other chemistry concepts, you can keep visiting BYJU’s for an interesting learning experience.
FAQs
Calcination is a process where the air might be supplied in limited quantities, 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.
What is calcination and roasting? ›
Calcination is a process in which ore is heated in the absence of air or air might be supplied in a limited quantity. Roasting involves the heating of ore lower than its melting point in the presence of air or oxygen. Calcination involves the thermal decomposition of carbonate ores.
What do you mean by roasting? ›
Roasting is a process in metallurgy in which a sulphide ore is heated in air. The process may convert a metal sulphide to a metal oxide or to a free metal. Example: Roasting ZnS may yield ZnO; roasting HgS may yield free Hg metal.
What is an example of calcination? ›
Calcination, therefore, is sometimes considered a process of purification. A typical example is the manufacture of lime from limestone. In this process the limestone is brought to a temperature high enough to expel the carbon dioxide, producing the lime in a highly friable or easily powdered condition.
What is the difference between calcination and roasting how these processes are used in extraction of zinc? ›
Process in which ore is heated in the absence of air or supplied in small quantities is known as calcination. Roasting is the process where ore is converted into its oxide. This process is done in the presence of excess air by heating it above its melting point. During calcination moisture is pumped out from an ore.
What calcination means? ›
Calcination is a process in which the ore is heated to a high temperature blow its melting point in the absence of air or in a limited supply of air. During calcination, the organic matter, moisture, volatile impurities like carbon dioxide and sulphur dioxide are expelled from the ore.
What is roasting in cooking? ›
Roasting, like baking, is a method of cooking that uses hot, dry air to cook food in the oven, but at higher temperatures. Roasting is typically used for foods with a solid structure such as vegetables and meats. Roasting uses the bake setting at 400ºF (204ºC) or higher to brown the surface and develop flavor.
What is the calcination process? ›
Calcination is a process in which a material is heated to a temperature below its melting point to affect a thermal decomposition or a phase transition other than melting (McGraw-Hill, 2003).
What does it's roasting mean? ›
: to criticize someone harshly : to yell at or criticize someone in an angry and severe way.
What is the process known as roasting? ›
Roasting is a process in which sulfide is heated in presence of air and it is converted to an oxide and sulfur is released as sulfur dioxide. Heating of ore occurs.
Alchemists distinguished two kinds of calcination, actual and potential. Actual calcination is that brought about by actual fire, from wood, coals, or other fuel, raised to a certain temperature.
Why is it called calcination? ›
Calcination is derived from the Latin word calculate which means to burn lime. For the calcination process, usually, the decomposition occurs near or above thermal decomposition temperature. The products derived from the calcination process are called calcining.
Is calcination done in air? ›
Calcination is a process in which ore is heated in the absence of air.
What is roasting and calcination with example? ›
The calcination is carried out in a limited supply of air or absence of air. The example for calcination is the decomposition of calcium carbonate into calcium oxide and carbon dioxide. The roasting is the process of converting the sulphide ores into oxide ore by heating strongly above the melting point.
Which furnace is suitable for calcination and roasting? ›
Calcination and roasting take place only in reverberatory furnace.
Where are calcination and roasting carried in? ›
Reverbratory furnace is used for roasting and calcination.
The process of calcination and roasting is carried out in reverberatory furnace.
What is the process of calcination? ›
Calcination is a technique comprising heating the solids at a higher temperature to remove volatile substances or oxidizing a specific amount of mass.
What is oven for calcination? ›
Overview. Calcining Ovens create phase change or remove moisture. The function of a Calcining Oven is to heat solid materials or ores to induce phase transition, or for removal of a volatile fraction or crystalline water as water vapor.
What is the difference between drying and calcination? ›
Drying is to remove surface water, and calcination is to remove crystal water.
