Specifying pH Value in HYSYS

[EmmanuelTop]

1) Is it possible to specify pH value of a given stream within HYSYS flowsheet, in the same way that temperature, pressure, flow and composition are being specified?

2) When defining stream composition, input of 99% H2O and 1% H2SO4 does not come up with any pH value as the result. Why is that happening?

I am using Electrolyte fluid package, of course.




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[kenvlach]

Presuming units of 99% H2O and 1% H2SO4 are weight %,
then at ambient temperature (25 C) & 1 atm pressure,
I calculate the solution density as [ρ] = 1.010 g/mL,
mole fraction of sulfuric, x_H2SO4 = 0.00185,
molarity of sulfuric acid, [H2SO4] = wt/FW = 10.1/98 = 0.10306,
Since dilute sulfuric is completely dissociated,
[H+] = 2 x [H2SO4] = 0.2061,
pH = -log[H+] = 0.686

 

[EmmanuelTop]

Thanks Kenvlach for participating.

It wasn't a problem to calculate pH of 1% H2SO4 manually. I have also solved the problem I described at point no. 2, it was my mistake.

But I still wondering about possibility to specify pH value of any stream within flowsheet. I have problems in making a model of refinery wastewater equalisation basin, where all waste streams are routed to - I have pH values of all streams and I want to simulate steady state and dynamic behaviour of this system when individual or multiple changes are made in quality of the streams. But, it is impossible to enter (specify) pH value of a stream - it can be done only by manipulating concentrations of acid and base components, which is long long iteration process. So I was wondering if it is possible to specify pH and wait for HYSYS to back-calculate concentrations of acid and base components, and make the simulations much more faster.


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"Our Music is New Black Polished Chrome That Came Into Summer Like Liquid Light"

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[Amphoteric]

I think the best that you can do is get Hysys to do the iterations for you:

A) Put all of your inputs, plus an acid or base stream, through a mixer. Use an Adjuster block to alter the flowrate of the acid/base stream, so that your mixed stream has the pH you want.

B) If you look in the list of "Electrolytes Ops" you can add a "Neutralizer" unit, which looks like a stirred tank. It can accomplish the same thing, and lets you add an energy stream

For both of these methods you can play with your tolerences to get the accuracy/calculation speed you want. You may have to dilute the acid/base stream to make it easier on the solver. I've never tried this in dynamics.

 

[EmmanuelTop]

Thanks Amphoteric,

Is it possible to use multiple (double) adjuster for pH-trimming of the same stream? I am asking this because some streams are sometimes acidic, and sometimes are with pH above 7. So the perfect and complete option would be to have a possibility to adjust pH "online", based on actual analyses or on-line pH measuements.

Why only one reagent is allowed in "Neutralizer" operation? This option assumes that stream is either always acidic or always basic.

Thanks again,


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"Our Music is New Black Polished Chrome That Came Into Summer Like Liquid Light"

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[Amphoteric]

You want a single item that can move pH up or down? I've got no idea, but then I've hardly ever used electrolytes. Try aspentech support for help, if you can.