3 replies to this topic

[BeigeSponge]

I am currently designing a high temperature water gas shift reactor. I am struggling to find a suitable rate equation which covers the large amount of variables which can affect the rate, primarily pressure. 

 

The paper by Singh and Saraf (1977) "Simulation of High-Temperature Water Gas Shift Reactors" presents a rate equation which would be perfect, however the units of the rate equation is cm^3 / h g of catalyst. 

 

I'm not sure whether cm3 is in terms of volumetric flow of CO or of the total gas feed. Does anyone know this? Additionally, how would I convert to mol / h g of catalyst?

 

Thanks

[Art Montemayor]

Beigesponge:

 

You raise a logical and concerned question that merits a warning.

 

If the authors of the paper that contains the equation you are basing your calculations on do not specifically cite the basis or identity of the units used in the presented equation, then – unfortunately – you are at the mercy of some sloppy engineering writers or editors.  This type of problem, unfortunately, is something that invades engineering communications and writing much too often nowadays.  The unidentified units make the equation worthless.

 

If you have no direct or quick access to the authors – as is the usual case – then you can direct your dilemma to your professor, who should be also concerned that in spite of doing serious research in finding the needed relationship, you can’t simply rely on guess work or “trust” in using the published equation.  He/she should be able to guide you or advise you how to handle this problem.

 

All engineering students should be made aware that there is a lot of literature and papers that have been published that contain not only badly written information – but also ERRATA.  A lot of the mistakes or errata are caused by editors that are either sloppy, lazy, or simply don’t know what they are checking.  My personal copy of Donald Kern’s famous classic book, “Process Heat Transfer” has a lot of my red ink identifying errors in the text of this famous publication.  Finding typos or erroneous information doesn’t alarm me anymore after 62 years.  You’ve done the right thing in challenging the need to identify clearly and explicitly the correct identity of the units in the expressed equation.  All engineering students should follow suit when they are in a similar situation.

[SilverShaded]

Beigesponge:

 

 

Have a look at this one, https://www.research...action_Kinetics

There are various kientics presented with the right sort of units.

The only effect of pressure on water gas shift reaction is residence time, however at higher pressures equilibrium in th reforming reacrtions can start to shift towards methane (hence reformer pressures and therefore HTS and LTS pressures are typically moderate ~ 30bar).

[BeigeSponge]

SilverShaded:

 

I had used that to find Singh and Saraf, I managed to find another equation from one of the referenced papers in that summary. Thanks!