The key difference between calcination and pyrolysis is that calcination is done in the presence of a limited amount of air or oxygen, whereas pyrolysis is done in the absence of air.
Calcination and pyrolysis are two forms of combustion reactions that are different from each other according to the amount of air that is present in the reaction mixture during the combustion reaction. Calcination is a chemical process in pyrometallurgy that involves the heating of metal ore in the presence of limited air or oxygen. Pyrolysis, on the other hand, is a decomposition reaction in chemistry where organic materials break down in the absence of oxygen.
CONTENTS
1. Overview and Key Difference
2. What is Calcination
3. What is Pyrolysis
4. Side by Side Comparison – Calcination and Pyrolysis in Tabular Form
5. Summary
What is Calcination
Calcination is a chemical process in pyrometallurgy that involves the heating of metal ore in the presence of limited air or oxygen. In the calcination process, we need to heat the ore to a temperature below its melting point. This is a very useful process. The name calcination comes from a Latin name due to its major application – the heating of calcium carbonate ores.
Figure 01: Calcination
We can do the calcination process in a reactor that has a cylindrical structure; we call it the calciner. Calcination occurs inside this calciner reactor under controlled conditions. Carbon dioxide is formed and released during calcination, and calcium carbonate converts into calcium oxide. This calcination process is important, mainly to remove volatile impurities. However, sometimes we need to use a furnace for calcination because it involves heating a substance to very high temperatures.
A good example of calcination is the production of lime from limestone. During this process, we need to heat limestone to a high temperature, i.e., a temperature high enough to form and release carbon dioxide gas. In this process, lime forms in an easily powdered condition.
What is Pyrolysis?
Pyrolysis is a decomposition reaction in chemistry where organic materials break down in the absence of oxygen. We need to apply heat for this reaction to progress. Therefore, we can increase the rate of reaction via increasing the amount of heat provided. Generally, pyrolysis takes place at or above 430oC. However, most of the times, we can perform these reactions in the near absence of oxygen because it is very difficult to obtain an atmosphere free of oxygen. The final product of this reaction is in the gas phase, liquid phase or solid phase. Mostly, this process produces gases. If it produces a liquid, we call this liquid “tar”. If it is a solid, typically, can be charcoal or biochar.
Figure 02: Pyrolysis
Most of the times, pyrolysis converts organic matter into their gaseous components, a solid residue of carbon and ash, and a liquid called pyrolytic oil. We use two major methods to remove any contaminants from a substance; destruction and removal. Destruction process breaks down the contaminants into small compounds while removal process separates the contaminants from the desired substance.
This reaction is used in various industries to produce charcoal, activated carbon, methanol, etc. Moreover, it can destroy semi-volatile organic compounds, fuels, etc. In addition, we can use this process to treat organic waste coming out from factories.
What is the Difference Between Calcination and Pyrolysis?
Calcination and pyrolysis are important chemical reactions. The key difference between calcination and pyrolysis is that calcination is done in the presence of a limited amount of air or oxygen, whereas pyrolysis is done in the absence of air. Calcination is used in the production of lime from limestone, while pyrolysis is used in the production of charcoal, activated carbon, methanol, etc.
Below infographic summarizes the differences between calcination and pyrolysis.
Summary – Calcination vs Pyrolysis
Calcination and pyrolysis are important chemical reactions. The key difference between calcination and pyrolysis is that calcination is done in the presence of a limited amount of air or oxygen, whereas pyrolysis is done in the absence of air.
Reference:
1. Helmenstine, Anne Marie. “Roasting Definition in Chemistry.” ThoughtCo, Feb. 11, 2020, Available here.
Image Courtesy:
1. “LDLimeShaftKilnBasic” By LinguisticDemographer – Originally from en.wikipedia. (Public Domain) via Commons Wikimedia
2. “Pyrolysis” By Mintrick at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia