6 replies to this topic

[SP500]

I am currently looking at a CSTR in which an homogeneous liquid phase reaction takes place and am trying to determine how to approach a mechanical design of such a liquid vessel.

 

I know how to carry out a mechanical design for a pressure vessel ( eg for a vessel occupied with gases at an elevated pressure).

 

What I would like to ask is:

 

1- Is a liquid vessel considered to be a pressure vessel? I thought that as liquid reactions are unaffected by pressure these reactions are always carried out at ambient pressure..?

2- When considering the design is the procedure the same as that of a pressure vessel? Before I go into the mechanical design what considerations do I have to make concerning the amount of pressure exerted on the vessel's wall besides the hydrostatic pressure?

 

[latexman]

What are the liquid reactants and products?  The operating temperature range?  Is it batch, semi-batch, continuous?

[SP500]

It is a CSTR (continuous operation). 

The temperature operating range is from 0 to 8 Celcius degrees. 

In the reactor hydrochloric acid reacts with aniline to form anilinium chloride and with sodium nitrite to form nitrous acid ( and sodium chloride).

The nitrous acid then reacts with anilinium chloride to form a diazonium chloride salt.

[Art Montemayor]

A pressure vessel is designed to contain both liquids and gases at a pressure above 15 psig.  At least that is what the ASME code specifies.

 

Why haven't you mentioned the operating and design pressure that you have set for this reactor?   All reactions are not necessarily designed for atmospheric or low pressures.

 

Before you can discuss a pressure vessel, you must specify the design pressure.  What you mean by "elevated" pressure is subjective.

[SP500]

Thank you for the clarification.

I haven't set the pressure as I am trying to determine it . After doing that I want to look into the mechanical design.

 

The design pressure , I am guessing, is the atmospheric pressure plus hydro-static pressure due to the liquid contents.

Edited by SP500, 28 January 2017 - 03:01 PM.

[latexman]

0-8 C.  Not much vapor pressure, huh?

 

Is it exothermic?  If so, how will the heat be removed?

[SP500]

The reaction is exothermic and I am using a jacketed vessel to assume isothermal operation.

Unless there is cooling failure, there will be slight vapour pressure rise due to some decomposition of the diazonium salt giving nitrogen but at the subject temperature it is practically negligible. However, to account for this i'll multiply the design pressure by a safety factor of 1.2 (20%). 

 

So the design pressure will be chosen how exactly? I'm rather confused. Ill add the sum of ( hydrostatic pressure + atmospheric pressure+ max vapour pressure rise) and all this multiplied by my safety factor? Is this thinking correct or am I in a totally wrong path?

Edited by SP500, 29 January 2017 - 09:37 AM.