Pressure Reducing Valve or Orifice

[plantprowler]

I am planning a pilot scale reaction that is carried out in a large excess of H2O at 150 C in a single CSTR. Obviously, that CSTR operates under substantial autogenous pressure. A limpet coil provides the heat.

The part that confuses me is the mechanical design on the outlet side. Obviously, I must cool down below 100 C else the H2O will flash into steam on dropping P to 1 bara. So could I cool a pressured stream in a S&T HEX (say vs CW) & then reduce pressure to 0 barg?

What sort of device do I take the final pressure reduction over? A valve in a pipe? An orifice in a pipe? Something else?

Absolutely accurate pressure is *NOT* a concern. For testing purposes, can I use some sort of manual valve to do this?

 

[georgeverghese]

Typically should be operated on level control. If you have fluctuating feed flows, or you want to allow for some pressure fluctuations in the CSTR pressure, would be better to operate on constant flow control cascaded or reset by deadband level control from the CSTR.

 

[SNORGY]

Jordan Hribar,

I was specifically thinking about estimating the *restriction orifice* noise, not the control valve noise.

In the original post, I was uncertain whether or not the effects of flashing or cavitation, if any, existed; otherwise, at 10 ft/s liquid velocity, it might indeed be reasonable to assume that noise would not be expected to be a limiting issue.

Some research has been done in the field:

http://www.witpress.com/elibrary/wit-transactions-on-engineering-sciences/29/3845

While, for liquids, there is no tried-and-true methodology, my points were, simply:

(1) If the application could potentially give rise to noise, then it's easier to address that issue with control valve trim selection than it is to address it when all you've got is an orifice plate.
(2) It's worth at least attempting to make a calculated noise prediction, rather than just throwing in an orifice plate and waiting to see how that works out.