×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

semi-batch

semi-batch

semi-batch

(OP)
A semi- batch process. Reactant A is dosed by a metering pump to the reactor. Reactant B is dissolved in the solvent in the reactor and heated to 9 barg.
Dosing nozzle has no dip-pipe of J-pipe. So, it is splash loading.

Will there be any problems with splash? Reactor does have agitator and reaction is temperature controlled.


With dosing, liquid level in the reactor will be increased. Because product has lower vapor pressure than reactant B, in my opinion as long as the temperature is controlled, there should be no issue with over pressure.

Thanks.

RE: semi-batch

Rika,

It depends on the chemicals being used. Can you be more specific? Splash entry can cause foaming issues, depending on the contents of the vessel. If the material that is being fed via splash entry is flammable, you might want to reconsider the entry arrangement. Additionally, some applications can be feed-point sensitive, especially if reaction rate is fairly quick or particle size/ molecular weight distribution in important (in polymeric systems, for example).

RE: semi-batch

(OP)
Thanks TiCL,

This is a hydrolysis reaction. reaction is not very quick. single phase. reactant A's boiling point is 180ºC, flash point is also high. reactant B is just water. the solvent is Acetonitrile. exothermic reaction but very mild. The hydrolyzed product dissolves in acetonitrile. ACN and water are miscible. I assume the feed point doesn't impact a lot.

I am wondering the physical process. When the pump pushes cold A into hot vapor phase, what will happen? I think pressure will drop dramatically.

Reactor is 18 m3. Reactant B and ACN are 8m3, total A will be 6 m3. Reactor will be filled 80% full at end of the reaction. Will there be over pressure issue?

RE: semi-batch

Rika,

Okay, so you will have to figure out the energy balance yourself - compare the heat of hydrolysis to the incoming A enthalpy. You say that the reactor is “heated to 9 barg”. What does that mean? Heating is typically done to a temperature setpoint, not a pressure setpoint.

If you have a heated reactor, then you typically don’t have to worry too much about keeping temperature up - the heating jacket/coils/whatever should be more than sufficient to maintain bulk temperature. Still, you should perform the overall energy balance to ensure that is the case, as it really does depend on jacket heat transfer, heat of reaction, and feed enthalpy.

Dropping a cold feed through the vapor space won’t really have any discernible impact on pressure. As long as the process is maintained isothermal (meaning your temperature control loop is maintained at the same temp), your pressure will actually increase as the process continues. A bottled-up reactor that runs semi-batch is essentially an isothermal compression. You can calculate final pressure fairly easily from an isothermal compression of the acetonitrile/water mix. You’ll need to accept the higher pressure in the reactor or bleed the pressure as the batch continues if pressure starts approaching the MAWP.

This does bring to mind a question though - why is this semi-batch? Oftentimes a process is converted to semi-batch from full batch because of the difficulties in controlling exothermic batch reactions.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close