3 replies to this topic

[stelu85]

Dears,

 

I'm seeking for ideas on how to recover Acetone from blanketing of vessel and reactors, routed to flare.

At the moment we have an industrial chiller circuit, very hold, with R422a.

 

Instead of just thinking to replace it with a brand new one with different refrigeration gas, I was wondering to find any better solution or even more compact.

 

we talk about 350 kg/h acetone lost to flare if this equipment doesn't work. It is required for me in reactions.

 

Any idea or any other application you use?

 

regards

 

[Technical Bard]

I worked on one system where we recovered acetone/isopropanol from a wet air vent hood system through the same process you describe.  Ran the duct through a chiller to drop the temperature to a point where the organics would condense.  You may get a lot of water condensing as well, depending if your stream is wet or not.

[Whit123]

I think using your existing chiller is the best option, you may think of replacing the chilling fluid though.

[Art Montemayor]

Stelu85:

 

Your English writing is not very clear and may have spelling errors.  Please clear up our doubts or confirm your following script:

• “we have an industrial chiller circuit, very hold, with R422a”  - Do you mean “very old”?

• What do you mean by “even more compact”?
• What do you mean by “It is required for me in reactions”?  Do you mean to say that you are required to recover the 350 kg/h of acetone normally going to flare because of the obvious waste and production cost?

If you are required to recover the normally flared acetone vapors, then this should be a very simple process of condensing the acetone vapors using a refrigerant - or a series of refrigerants.  I don’t know if you are a chemist or chemical engineer, so I’ll take the extra time to explain in the following:

 

I have to assume that you are generating the acetone in some chemical reaction taking place upstream in a reactor.  Is that correct?  If so, then the acetone is being generated as a vapor - and not as a liquid.  Is this also correct?  If so, then the acetone is possibly in a mixture of other gaseous products also formed in the same reaction(s).  Is this also true?

 

If you have a hot product vapor being produced that has several chemical components in it, then you should identify the composition of the product vapor.  This is important in order to confirm that you can selectively condense the desired acetone without also condensing the other constituents.  If there is a mixture of other vapors, then you will condense out a related liquid mixture as well.  The acetone will not selectively condense out by itself when the gaseous mixture is cooled below the boiling point of acetone (56 °C at 1.0 atmA).

 

Because of its relatively high boiling point, you should first condense the vapors from the reactor(s) using a conventional water-cooled shell and tube heat exchanger.  I am assuming that your reactor(s) and the produced vapors are at essentially atmospheric pressure.  (You failed to tell us the pressure, temperature, and compositions of the vapor stream)  Using a water-cooled condenser should condense out the majority of the acetone content in the vapor stream.  The remaining vapors can subsequently be put through another condenser cooled by the R-422A refrigerant - or another refrigerant.

 

If acetone is the only component that you wish to condense from the vapor stream, you have an easy job.  Acetone’s relatively high boiling point makes it easy, so you don’t have to use a so-called “deep” refrigerant like R-422A that normally is used down to -56 °F (-49 °C).  You could easily use a much lower cost and more efficient refrigerant such as ammonia.

 

If you want to use your existing R-422A compressor (and related evaporator) you certainly can do that.  However, as I state, that will be an “over-kill” for what I understand are your intentions or scope of work.  From what you give us as information, I would try to use a water-cooled condenser prior to applying a refrigerant compression unit.  Depending on the amount of recovery obtained by the refrigerant compression unit, that would be the measuring stick as to its justification.

 

Since you haven’t furnished all of the Basic Data for what you propose, I (and others) can’t give you any specific information on what you can or should do.  For example, an economic analysis should be done on what you intend to spend in capital and operating costs in order to recover the 350 kg/h of acetone currently wasted.  We don’t know the flow rates, pressures, temperatures, compositions, etc., etc.   We don't even know if the acetone flaring rate is a continuous one (which I doubt).   What is the acetone flare quantity per day, per week?