What is the Difference Between Pyrolysis Carbonization and Torrefaction

The key difference between pyrolysis carbonization and torrefaction is that pyrolysis is the breakdown of the biomass in the absence of oxygen, and carbonization is the process of conversion of organic matter into carbon, whereas torrefaction is a mild form of pyrolysis.

1. Overview and Key Difference
2. What is Pyrolysis
3. What is Carbonization
4. What is Torrefaction
5. Pyrolysis vs Carbonization vs Torrefaction in Tabular Form
6. Summary

What is Pyrolysis?

Pyrolysis is a type of decomposition reaction in which organic materials break down in the absence of oxygen. In this process, heat is applied for this reaction to progress. Therefore, we can easily increase the rate of reaction by increasing the amount of heat provided. Generally, pyrolysis takes place at or above 430^oC. However, most of the time, 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 solid, it is typically charcoal or biochar.

Pyrolysis often 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. The destruction process breaks down the contaminants into small compounds, while the 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 Carbonization?

Carbonization is an industrial process where organic matter is converted into carbon. The organic matter we consider here includes plants and dead animal matter. The process occurs through destructive distillation. It is a pyrolytic reaction which is considered a complex process in which we can observe many chemical reactions occurring concurrently; for example, dehydrogenation, condensation, hydrogen transfer and isomerization.

The carbonization process is different from the coalification process because carbonization is a faster process due to its reaction rate being faster by many orders of magnitude. Generally, the amount of heat applied can control the degree of carbonization and the residual content of foreign elements. For instance, at 1200 K temperature, the carbon content of the residue is about 90% by weight, while at about 1600 K temperature, it is about 99% by weight.

Typically, carbonization is an exothermic reaction, and we can make it self-sustaining; we can use it as a source of energy that does not form any carbon dioxide gas trace. However, if the biomaterial is exposed to a sudden change in the heat, for example, in a nuclear explosion, the biomatter gets carbonized as soon as possible, and it turns into solid carbon.

What is Torrefaction?

Torrefaction is a mild form of pyrolysis that occurs at temperatures between 200 and 320 Celsius degrees. This process occurs with biomass such as wood and grain. The process of torrefaction can change the biomass properties in order to provide a better fuel quality for combustion and gasification applications. Moreover, this process can produce a relatively dry product that can eventually undergo reduction or elimination of its potential for organic decomposition.

When torrefaction and densification are combined with each other, it can create an energy-dense duel carrier of about 20 GJ/ton lower heating value (LHV). Further, this process can make the material undergo a Maillard reaction.

Typically, torrefaction is a thermochemical treatment of biomass that is carried out under atmospheric pressure and in the absence of oxygen. During this process, water in the biomass and the superfluous volatiles are released, allowing the biopolymers to partly decompose while forming different types of volatiles. Therefore, the final product of this process is the remaining solid, a dry material known as torrefied biomass (or biocoal).

Difference Between Pyrolysis Carbonization and Torrefaction

Pyrolysis is a decomposition reaction in chemistry where organic materials break down in the absence of oxygen. Carbonization is an industrial process where organic matter is converted into carbon. Torrefaction is a mild form of pyrolysis that occurs at temperatures between 200 and 320 Celsius degrees. The key difference between pyrolysis carbonization and torrefaction is that pyrolysis is the breakdown of the biomass in the absence of oxygen and carbonization is the conversion of organic matter into carbon, whereas torrefaction is the mild form of pyrolysis.

The below infographic lists the differences between pyrolysis carbonization and torrefaction in tabular form.

Summary – Pyrolysis vs Carbonization vs Torrefaction

Pyrolysis is a decomposition reaction in chemistry where organic materials break down in the absence of oxygen. Carbonization is an industrial process where organic matter is converted into carbon while torrefaction is a mild form of pyrolysis that occurs at temperatures between 200 and 320 Celsius degrees. The key difference between pyrolysis carbonization and torrefaction is that pyrolysis is the break down of the biomass in the absence of oxygen and carbonization is the process of conversion of organic matter into carbon whereas torrefaction is the mild form of pyrolysis.

Reference:

1.“Carbonization.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Carbonization Link Map – 1” By IUPAC – http://goldbook.iupac.org/C00840.html (Public Domain) via Commons Wikimedia
2. “Pyrolysis” By Mintrick at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia