Re: some questions about dynamic simulation with Hysys

[st...@nospam.com]

Raheleh,

The reason that you would have reverse flow is due to either

(1) the pressure gradients within the system (generally, flow must occur
from streams of high pressure to streams of low pressure), or
(2) the specification of a flow boundary in the model that requires a
negative flow through the feed stream.

I would suggest you reconsider the boundaries you have set in the model, and
think about why (physically) your feed stream would be "pushed" back out of
the model.

Also, something that "one_speed" said rings true - namely the reverse flow
messing with your feed compositions. Check that you have set the "feed
block" (go to the dynamic tab, and hit the "Feed Block" button to see the
properties of the... er... let's call it the infinite feed tank that HYSYS
is drawing from to supply your column.) to the correct composition and
temperature. Once this is set, I think that reverse flow won't be able to
"reset" your feed conditions - so when you resolve the reverse flow, you
should be able to get your desired feed stream conditions again.

Perhaps you could try setting a flow specification/boundary on the stream
entering your column, and set pressure specs/boundaries on the tops and
bottoms of your column - that's how I would do a stand-alone model for the
"sake" of building a column model.

Good luck!

[anjuc...@gmail.com]

Sir,
I am doing my M.Tech in Chemical Process Control. As a part of my project,I work with Dynamic modeling of Syncgas production using HYSYS. May I know the correct specifications to be given as the input with reactors.Since I have multiple reactors ,now I am in a dilemma of how to link these unit operations.I have tried different ways to input these specifications,but the response from "HYSYS" is that the specifications are "overdefined".


Kindly reply