HYSYS – Simulation of a distillation column with defined cutpoints for sidedraw

[bird23]

Dear all,
I am trying to find the best way to simulate and design a distillation column with a defined cuts for a sidedraw. The sidedraw will be the mainproduct in this operation.

Example:
Assay Boilingrange: 150°C to 350°C
Sidedraw with CUT: 200-300°C

Which type of Subflowsheet and respective specifications should be used for the simulation?


I solved the Simulation using: “distillation column subflowsheet” with the specs: "temperature on the draw tray" to 200°C @ vap frac 1 and 300°C @ vap frac 0.

But…this way seems to be too time consuming and I think there might be an easier way as defined cuts for sidedraws should be used often enough in refinery-engineering.

What's your poinion?

Regards
Andre

 

[georgeverghese]

On Pro II- Simsci, it is possible to set the side draw specification based on ASTM D86 IBP or EBP - you havent said what reference std is relevant to this 200-300degC side draw.

The same specification variable should be available on the simulator you are using ?

 

[bird23]

Thanks George,

I defined two Specs (in HYSYS called 'cutpoint') to receive a defined draw:

Spec1:
Stage 13
Type: D86
Temp: 200°C
Phase: Liq

Spec2:
Stage 13
Type: D86
Temp: 300°C
Phase: Vap

Let's say stage 13 ist my stage for the sidedraw.

For solving the simulation, I have to vary the drawstage and the cutpoint-specs manually - this way seems to be quite time-consuming.

Regards,
Andre

 

[georgeverghese]

The D86 spec seems to be incomplete : D86 at what % by volume does this temp refer to?

 

[TD2K]

Wny are you specifying both the vapor and liquid D86 points (and at what % as mentioned by George)?

How many specs do you have to provide and what are you providing in addition to these two?

 

[bird23]

@all:

see my specs in the attached pdf.

@TD2K:
Wny are you specifying both the vapor and liquid D86 points --> warong post by myself...see pdf attached


My question: is there an easier way to run the simulation than using these three specs?

Regards,
Andre

 

[TD2K]

I'm not seeing a PDF attached. Post a sketch of your system and some information on the feed and products you want.

In general terms, I prefer to initially set up a distillation just on flows, that gets the model converged usually fairly easily. I can then look at the streams and either start changing the flows to get properties to match what I want or change the spec then to a D86 or some other specification. Do one stream at a time, don't try to put D86 specs on all three streams and hit the "solve" button.

Initial estimates can really help. Spend some time with pen and a piece of paper so you have an idea of what the general splits should be. If you are setting up a crude tower, you should be able to look at the feed stream and get reasonable estimates for the naphtha, kero, diesel, etc streams from the feed assay.

 

[georgeverghese]

Usually the D86 95% v/v temp is used on the main column side draw to vary reboil, and the D86 5% v/v temp is specified on the side stripper to vary steam rate.