Why we can’t get 100% conversion in chemical processes?

A general understanding of chemical reaction is, reactant converted to product. We use conversion for the understanding of process efficiency on the quantitative basis. A data analysis of conversion with operating parameters gives us an idea of smooth process operability.

But why can’t we get 100 % conversion?

Well, this is the not in the case for all.

But mostly in all processes, lab (or pilot) scale model has 100% conversion or it does not matter on this small scale. But when it scales up to the industrial operations, problems are also scaled and become a challenging job to addressing it.

In this article, we try to look at the few resistances that restrict the process to approach 100% conversion.

Let’s take a tour of what, how & why of this topic.

What ?

Percentage of reactant converted to the product is the conversion.


Why ?

Using engineering controls, chemical processes are designed to maximizing rate of product formation with minimizing waste material.

When designing the process, first objective to get the maximum conversion that can obtain.

How ?

For an understanding of conversion, we need to know how reactant gets converted.

Without deeply understanding of Collision or State transition theory, just understand it with basic principles

A + B → C

A & B molecule will get some external energy for the reaction (Activation energy) & convert into product C.

We are not reacting one molecule of A with one molecule of B, but reacting some quantity of reactant A with some quantity of reactant B.

Here are some resistances or losses in the reaction of A with B.

Proper mixing of reactant

For the 100 % each of A should contact with each of B. That can’t be possible with real but can be achieved with increasing residence time in the reactor or premixing of reactants before reaction.

Energy loss in the process

The energy we are providing to the reactant in forms of Temperature & pressure based on theoretical & practical observations. It’s ideally impossible to transfer energy to each & every molecule in the mixture of A & B without any loss of energy. A constant monitoring of supply of energy vs. conversion can lead to address this issue to some extent.

Real vs. theoretical

A theoretical approach for understanding processes deviates from real processes to some extent. An experience or trial & error approach could be the possible way for better process operability.

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