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Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: Woopy on September 22, 2013, 11:24:41 PM

Title: CSTR with recycle
Post by: Woopy on September 22, 2013, 11:24:41 PM
Hello,

Why does having a single CSTR with partial recycle not increase the conversion of a species reacting in the tank?
Title: Re: CSTR with recycle
Post by: curiouscat on September 23, 2013, 01:06:29 AM
Quote from: Woopy on September 22, 2013, 11:24:41 PM
Hello,

Why does having a single CSTR with partial recycle not increase the conversion of a species reacting in the tank?

Which conversion? Per pass or total?
Title: Re: CSTR with recycle
Post by: Woopy on September 23, 2013, 02:07:46 AM
Total conversion
Title: Re: CSTR with recycle
Post by: curiouscat on September 23, 2013, 03:02:11 AM
x fresh went in
y is recycled

x+y goes in reactor
Say 90% per pass conversion

Ok, now answer: How much came out of reactor?
Title: Re: CSTR with recycle
Post by: Woopy on September 23, 2013, 01:19:56 PM
0.10(x+y) comes out and is not recycled
Title: Re: CSTR with recycle
Post by: curiouscat on September 23, 2013, 01:50:21 PM
Quote from: Woopy on September 23, 2013, 01:19:56 PM
0.10(x+y) comes out and is not recycled

Good.

So I'm getting overall conversion as 0.9 (1+y/x)

That seems necessarily higher than 0.9 the per pass conversion.

So conversion does increase. Right?
Title: Re: CSTR with recycle
Post by: Woopy on September 23, 2013, 05:43:11 PM
I suppose, the reason I ask is because I was doing a practice exam and looked at the solution key, and it said that the recycle does not increase the conversion, which is why I asked why.

Is it ok to post chemical engineering homework problems on this specific forum? Or is this to discuss chemical engineering as a profession/academic discipline etc..
Title: Re: CSTR with recycle
Post by: curiouscat on September 24, 2013, 12:05:46 AM
Quote from: Woopy on September 23, 2013, 05:43:11 PM
I suppose, the reason I ask is because I was doing a practice exam and looked at the solution key, and it said that the recycle does not increase the conversion, which is why I asked why.

There's the chance I am wrong.

Quote
Is it ok to post chemical engineering homework problems on this specific forum? Or is this to discuss chemical engineering as a profession/academic discipline etc..

I think it is ok but I'm not a Moderator.
Title: Re: CSTR with recycle
Post by: thelastone on June 09, 2014, 08:44:14 AM
Well, maybe you have a zero-order reaction (independent of the concentration of the reactive) ... Could you please post some more data of the problem?