The key difference between pyrolysis and gasification is that pyrolysis is done in the absence of air while gasification is done in the presence of air.
Pyrolysis and gasification are two important processes that are used to decompose materials. Both these processes are different from combustion because the combustion is carried out in the presence of an excessive amount of oxygen.
CONTENTS
1. Overview and Key Difference
2. What is Pyrolysis
3. What is Gasification
4. Side by Side Comparison – Pyrolysis vs Gasification in Tabular Form
5. Summary
What is Pyrolysis?
Pyrolysis is the process of thermal conversion of organic matter using a catalyst in the absence of oxygen. Therefore, it is the decomposition of material in an inert atmosphere. It is a chemical reaction that includes alteration of the chemical composition of the material. Moreover, it is a reversible process.
Figure 01: In Food Manufacturing, Caramelizaiton is an Important Pyrolytic Process
In pyrolysis, what we do is heating a material to a temperature above its decomposition temperature. It breaks down the chemical bonds of the material. Therefore, this process usually forms small molecules from large fragments. But, these small molecules can combine, forming large molecular masses as well. For example, pyrolysis of triglycerides form alkanes, alkenes, alkadienes, aromatics and carboxylic acids.
What is Gasification?
Gasification is a thermo-chemical process that converts biomass into a combustible gas called producer gas (syngas). Here, the materials decompose in an environment where a little amount of oxygen present. However, this amount of oxygen is not enough for combustion. The products of gasification are heat and combustible gas.
Figure 02 A Gasification Plant
Moreover, the process proceeds at temperatures ranging from 800°C – 1200°C. The principle components in the combustible gas that forms during this process include carbon monoxide and hydrogen gas. In addition, there are some other components such as water vapour, carbon dioxide, tar vapour, ash, etc.
What is the Difference Between Pyrolysis and Gasification?
Pyrolysis is the process of thermal conversion of organic matter using a catalyst in the absence of oxygen. Gasification is a thermo-chemical process that converts biomass into a combustible gas called producer gas (syngas). The key difference between pyrolysis and gasification is that pyrolysis is done in the absence of air while gasification is done in the presence of air. Besides, the products of pyrolysis are heat and combustible liquid and combustible gas while the products of gasification include heat and combustible gas. So, this is also a difference between pyrolysis and gasification.
Moreover, pyrolysis is useful for applications in food manufacturing, i.e. caramelization, production of fuel from biomass, production of ethylene, to treat plastic waste, etc. while gasification is useful for heat production, production of electricity, etc.
Summary – Pyrolysis vs Gasification
Pyrolysis is the process of thermal conversion of organic matter using a catalyst in the absence of oxygen. Gasification, on the other hand, is a thermo-chemical process that converts biomass into a combustible gas. The key difference between pyrolysis and gasification is that pyrolysis is done in the absence of air while gasification is done in the presence of air.
Reference:
1. “Introduction.” Olive Processing Waste Management – Literature Review and Patent Survey Waste Management Series, 2006, pp. 3–22., doi:10.1016/s0713-2743(06)80003-6.
Image Courtesy:
1. “Caramelisation of carrots” (CC BY-SA 2.0) via Commons Wikimedia
2. “Holzvergaser Güssing” By Gerfriedc – Own work (CC BY 2.5) via Commons Wikimedia