3 replies to this topic

[Alaaeldin55]

Hello,

 

I have a simple question...
If a reaction between two reactants one reactant is a gas while the other reactant is liquid. From the stoichiometric equation I can calculate the amounts and volumes of reactants required to give specific amount of products. I know the residence time during which the two reactants should be in contact so the reaction is complete.

The question is how to find the volume of reactor required to carry out this reaction. The reactor is a simple bubble column, wherein the gaseous reactant is bubbled through the liquid reactant.

 

Thanks in advance.

[Art Montemayor]

Alaaeldin55:

 

I believe you are interpreting a homework problem given to you but you are not interpreting it correctly and completely.  Just ask yourself: I am being ask to specify the correct dimensions of a required circular cross-section reactor; so what are the recommended diameter and height of the subject vessel?  Show the calculations.

 

I presume you are taking or have already taken the required ChE Unit Operations course where you are taught the Unit Operation of distillation.  If so, you should be familiar with the Brown-Soudars equation for the diameter of a distillation column.  If not, research it.  You are given residence time required for a complete reaction so the Kinetics has already been done.  All you need to know besides the above is the number of perforated plates , the space between them and the total height of your reactor.  You should draw and furnish a sketch and show all that is needed in the vessel to carry out the operation - which should include instrumentation locations, all nozzles and manways required for operation, instruments, safety relief valves, startup, shutdown, fill, drain, inspection and maintenance.

 

You should know how and why the Brown-Souders equation is derived in order to know how and why you can apply it.  This equation should give you the diameter.  The total height is the sum of all the required parts - including a sump height and a top vapor disengagement space height for the gaseous product that exits in the overheads (and probably is saturated and requires an overheads total condenser with produced condensate returned back to the top of the reactor).  All these details are normal, necessary requirements determined, calculated, and specified by a process engineer.  In this academic case, I presume that would be YOU.

 

Your question is simple; the answer requires work.  This is a typical Chemical Engineering challenge in industry.

[Alaaeldin55]

Art Montemayor,

Thank you very much. I know about Brown-Soudars equation but I'm not designing a vapor/liquid separator in this problem. It is a bubble column gas/liquid reactor. The liquid reactant flows as a continous phase in tubes while the gaseous reactant is bubbled through it. I' have done some research and found something related to gas holdup volume, and bubble diameter but I still can't get it.

 

Thanks again

[Art Montemayor]

You didn't get the message.  That's the reason I stressed that "You should know how and why the Brown-Souders equation is derived in order to know how and why you can apply it."

 

The way you ensure no liquid entrainment while you bubble gas through the liquid contents is by applying Brown-Souders.  It is exactly the same technique used in bubble cap distillation columns.  You stated you propose " a simple bubble column, wherein the gaseous reactant is bubbled through the liquid reactant."   What do you propose as a means to determine the diameter of the column?