11 replies to this topic

[daraj]

Many times, in literature we have GHSV(based on standard conditions or STP) given for a particular fixed bed reactor system. Using GHSV you cna arrive at reactor volume as follows:

 

Reactor volume = Volumetric flow rate at exit(at STP)/GHSV

 

Now I assume this reactor volume already includes voidage etc.  So if i know the catayust manufacturer given bulk density, then can  arrive at catalyst mass needed by multiplying above calculated Reactor volume X bulk density?

 

Please let know. Surprisingly this aspect is not being mentioned in a lot of references(whether the volume calculated using GHSV is apparent volume or true).

[breizh]

Hi,

Asking my good friend, I got this info:

 

Gas hourly space velocity (GHSV) = Volumetric flow rate of reactant or exhaust gas/External volume of catalyst monolith

 

Is this relevant?

Breizh

[daraj]

iam trying to find catalyst mass needed, using GHSV

[daraj]

and this is for packed bed not monolith

[daraj]

question is , using GHSV i cna first find reactor volume using the formula i stated earlier, and then using that volume and bulk density(which you get from manufacturer site ) you can ultimately calcxulate the catalyst mass that you need to buy, right? or not?

[breizh]

Hi,

You should ask yourself how people calculate the volume of catalyst needed at start up?  Most probably they submit the as built drawing of the reactor to vendors to get a quote based on vendors' calculation.

I don't see the difference in the methodology between monolith and Packed bed.

I will learn from others.

Note: Why do you post in the student forum?

Breizh 

[daraj]

pl move this to professionals forum if needed, I thought this was a fairly academic or basic doubt so I posted it here..

[daraj]

i just need it for model/preiminary design purposes..so not very rigorous..just need to know if my approach is right..I think GHSV is based on reactor volume(which includes voidage) and hence if you multiply this volume with apparent desinity or bulk density you should get catalyst mass needed.

[daraj]

silvershaded/Pingpong/Pilesar, pl share your inputs on this..this is for preliminary calculation sfor an industrial reactor like say a methanol or water gas shift reactor

[Pilesar]

If there is any doubt, tell the catalyst vendor that you will want to fill a specified volume with catalyst and ask how best to order. It may be prudent to purchase 110% of what you think you will use. 

[latexman]

You should give the vendor the dimensions of the volume, in case there is the potential to crush the catalyst at some height. In that case, they should recommend breaking it up in multiple sub-volumes.

[daraj]

Hi Pilesar and Latexman, thanks. Not in touch with any vendor or anything at this stage. Like I said this is just a conceptual design/study and a high level cost estimation exercise. So with that in mind can I multiply the reactor volume obtained from GHSV with bulk density(obtained from online references/catalyst vendor sites) and arrive at a rough estimate of the catalyst mass needed? I believe GHSV is based on reactor volume(which includes catalyst+voidage). So if you multiply this with bulk density this should give mass needed right?