Sciencemadness Discussion Board

Need help /ideas for reaction vessel safety...

JohnBee - 5-10-2015 at 03:39

As some of you may(or may not remember), I've been working on a project involving the transfer of fluids in excess of 100c through a cooling system. However, unfortunately, I had to suspend my experiments for several months during the summer months.
And so in light of this, I've resumed my work and have been readying for another round of experiments.

That said, I've recently discovered a lab procedure involving a reactor vessel that can solve two standing issues that I've been contending with:

1. The need to raise the boiling point of water above 100c
2. The need to move said super heated solution (mostly Di) through the system

That said, in spite of the vessel being rated as "explosion proof" and capable of withstanding pressures up-to 1000psi. I am both paranoid and somewhat terrified of putting either myself or my family at risk in going down this path. And so I wanted to ask if anyone had any tips or advice that I could use to keep the experiment safe. ie, such as a safety valve /mechanism or PSI gauge that might be compatible with glass, as the solution cannot come in contact with any metals or air during processing.

As always, I appreciate any help I could get with this and look forward to hearing from you.

JB

PS. The fluid will move through a capillary under the pressure created in the vessel once ready for cooling. Many years ago, I recall seeing in a book about the use of a heavy gauge rubber bulb attached to an open port in a system as a means from which to create a pressure buffer in cases where pressures need not exceed more than a few psi. Which in turn, would cause the bulb to balloon out instead of reaching critical pressures.

The issue here however, is where I'd like to reach 135c during processing and will relieve pressure for fluid transfer to cooling apparatus afterward.

[Edited on 5-10-2015 by JohnBee]

Praxichys - 5-10-2015 at 04:50

Look at some steam pressure tables.

http://www.phs.d211.org/science/smithcw/AP%20Chemistry/Poste...

According to this, your vessel would reach its rated pressure when the water inside reached 284C. Typically, pressure vessels are rated 3-5 times less than their burst pressure. To keep water from boiling at 135C requires only 45PSI, less if there is stuff dissolved in it.

You mention that the solution cannot come into contact with metals or air. Perhaps a threaded PTFE burst disk assembly made from teflon tape and a PTFE compression fitting? You could easily test this with an air compressor and calibrate to blow at like 100 PSI or something. I feel your "no-metal" requirement is excessively stringent. There are many alloys designed to resist attack in even the most corrosive environments. If your working fluid is just water, hundreds of years of steam engine use proves that metallic boilers work fine...

What is the application?

Bert - 5-10-2015 at 05:18
Quote:

What is the application?


What he said...

If you do not know the basics of boiler operation & engineering of steam systems and are a self taught chemist, you might best start out asking advice about your actual reaction before designing the process equipment.



JohnBee - 5-10-2015 at 09:29

Quote: Originally posted by Praxichys  
Look at some steam pressure tables.

http://www.phs.d211.org/science/smithcw/AP%20Chemistry/Poste...

According to this, your vessel would reach its rated pressure when the water inside reached 284C. Typically, pressure vessels are rated 3-5 times less than their burst pressure. To keep water from boiling at 135C requires only 45PSI, less if there is stuff dissolved in it.

You mention that the solution cannot come into contact with metals or air. Perhaps a threaded PTFE burst disk assembly made from teflon tape and a PTFE compression fitting? You could easily test this with an air compressor and calibrate to blow at like 100 PSI or something. I feel your "no-metal" requirement is excessively stringent. There are many alloys designed to resist attack in even the most corrosive environments. If your working fluid is just water, hundreds of years of steam engine use proves that metallic boilers work fine...

What is the application?


Thanks for the ideas. The idea of a burst disk as an added layer of protection certainly sounds like a viable option. Though I'm hoping I can add some form of working pressure control measure during processing. Such as a means from which to bleed off pressure to control the boiling point rather than to leave things run their own course(so to speak)

As for the pressure table and boiling point, I was aware of the psi prerequisites required to reach the desired boiling temperature and so I'm feeling quite confident about that particular part of the experiment. Though the idea of working with a superheated solution under pressure does have me on edge, as there will be a number of joints and fittings factor into the assessment as well.

As for the no metal contact, this nature of the solution makes this an unconditional condition I'm afraid. As for the application; I'd rather not disclose this until I've concluded the research as this would undermine the value of the work being done I'm afraid. Though I can however, assure you that the no metal or air contact with the solution is unconditional.

Praxichys - 5-10-2015 at 10:23

I hate to jump on the soapbox but it's kind of piss-poor ethically to supplement your research with a free online forum. Hypothetically you get paid for this research, or there is some kind of monetary reward; ergo we are helping you do your job for free.

Not that we'd enjoy credit - it's just that many of us also work in the field. Helping you with a commercial project is legally a conflict of interest with my current employment. I know I'm not the only one here whose intellectual property is wholly owned by his/her employer.

While I'm sure it is appreciated that someone of your experience is participant to this forum, being secretive also limits the extent to which we can actually help. Generic questions get generic answers: garbage in, garbage out. If you need help for commercial purposes, hire a consultant. Otherwise, either be open and specific, or do your own work!

aga - 5-10-2015 at 11:42

Tricky one is that.

Someone doing commercial work gets stuck, we go all schtum and annoyed.

Someone doing basic stuff, we all chip in to help.

Kind of limits what gets discussed, although the notion that the OP is getting Paid and we aren't is definitely galling.

Not sure that circle can ever be squared.

Certainly it seems that Modern commercial chemistry relies on Modern resources, and SM is a Modern resource, like it or not.

There are Pollutants like me here, so beware OP. Beware of the Answers !

Bert - 5-10-2015 at 11:43

No. You should not feel confident. You do NOT understand the behavior of a superheated water/steam system.

When the burst diaphragm goes, or the excess pressure is otherwise vented- Much of the remaining superheated water can then TURN TO STEAM NEARLY INSTANTLY. AND IT THEN OCCUPIES 1700 X THE VOLUME.

The usual result is what we in the boiler operator's trade call "an explosion".

As far as the question of helping you develop a commercial process, along with the mysterious nature of said "process"- No.

Bert - 6-10-2015 at 18:10

Does ANYONE besides the OP want this re-opened. U2U me if so.