MadSci Network: Chemistry

Re: How does a pilot chemical reactor work?

Date: Tue Dec 5 10:47:55 2000
Posted By: Edward Peterson, Staff, Chemical Engineering, S&B Engineers and Constructors
Area of science: Chemistry
ID: 974525579.Ch

A pilot reactor is built for the purpose of exploring the chemical, 
mechanical and physical parameters that influence a reaction.  Pilot 
reactors are built on a small scale to minimize cost, minimize hazard, 
increase the flexibility of operation, and to make modifications to the 
reactors be as easy as possible in order to learn enough about the 
reaction to make it full scale.  You hope to learn the reaction kinetics 
and thermodynamics, understand the equilibria, know how temperature and 
pressure affect the reaction, study the amount and identity of the 
byproducts formed in the reaction, and even look at the influence of 
impure reactants since you oftne cannot control the reactant purity beyond 
some point. Once you know the optimum conditions for operating your 
reactor to make the best product at the best yield, you may want to 
understand the costs involved with purifying your product, handling the 
product, storing the product, and determing the cost per pound you would 
expect it to cost to make. If the idea is to make a product that is going 
to make you money, you need to know how much product you can make (volume) 
and how much it will cost you to build a plant, and whether you will make 
money from it in the long term or whether doing the project will actually 
COST you money.

You would expect to find all the required information you want in 
scientific journals and reports, but that is often not the case.  In your 
reaction going from ethylene chlorohydrin (2-chloro ethanol) to ethylene 
glycol (1,2 ethane diol), I suspect that you could find out all you need 
to know if you chose to form the glycol mixing the reactant with a base 
such as caustic (NaOH in water).  This is a simple recation that has been 
thoroughly studied.  You might not need a pilot reactor study in that 
case.  However, if you were contemplating a new reaction pathway where the 
reaction was going to be done in the vapor state with a new catalyst, then 
you want to study the effect of the reactant flow rate through the 
catalyst bed, look at the amount of bed fluidization (if a fluidized bed 
is used), as well as temperature and pressure and catalyst life.

Following a pilot reactor test, the process or design engineer takes the 
data and looks at designing a plant. The pilot reactor is only the first 
step in looking at whether a chemical process method is a good idea to 
take further toward full scale production.

If this has not answered your question, please let me know.  I might infer 
from your question that you wanted a design for a pilot reactor that would 
react 2-chloro ethanol and caustic to form ethylene glycol.  That is a 
very complex question requiring more input from you.  You might actually 
want to use ammonia instead of caustic, so that would change the design.  
There are many different ways to get from the reactant to the product in 
your case.  I know.  I do this for a living.


Edward Peterson, PhD, P.E.

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