6 replies to this topic

[yeek]

Hi,

Recently my company has embarked on a hydrocracker revamp project. Now that the flow rates and the temperatures of the process lines have changed, we have to study and rate the existing heat exchangers to study what is the %overdesign and so on.

Since the heat exchangers are already in place, the physical dimensions, TEMA type, nozzle locations, etc. are all available. What has changed however is the Tin, Tout, Pin, Pout and so on.

All this can be input easily into HTRI. But I'm having problems getting the physical properties of the two fluids. At the moment, I am trying to get them from HYSYS/ProII and enter them into HTRI but is there an easier way?

Also based on the PFD, the molar composition of C6+ is grouped together, so any component heavier than C6 is lumped together. As of now, I have split this into C6 to C10 and divided the total flow rate of C6+ equally. Is there a better approach?

Essentially what I want to ask is what is the best way to get the physical properties of the stream data into HTRI.

Regards,
yeek

[Dacs]

I'll just comment on the lumping problem.

What I normally do when C6+ is lumped, I just distribute the fraction from C6 to C10 (or beyond) such that the fractions will yield the same molecular weight compared to the original composition.

[smalawi]

Hi

you can import the process data directly from Hysys or Pro/II into HTRI using the provided simulation interface. check out the help section in HTRI, just search Hysys .

another approach is to import the exchanger all together, file => import => select file type as Hysys/Pro/II

on the C6+ what stream are you referring to ? if the recycle gas then it does not matter as long as you have all as vapour, C6+ should be very small. if its a mixed two phase flow with VGO/gasoil then it's not, you need full TBP to accurately predict the enthalpies

make sure the thermo package is suitable for this pressure, e.g. EOS based

also, make sure you check the material selection in case you have clads in the exchanger shell. these are designed for a specific temperature

cheers,

sm

[yeek]

Hi thanks for all the replies so far.

The C6+ is in the hydrocracker effluent. Its quite high and I think it is two phase flow.

I am still not sure how to model it accurately. The simulation files given by the client have different compositions and flow rates. I intend to start the rating from scratch with a new simulation.

The problem here is that we already have the heat exchanger (its a revamp study project). We are going to rate it to study the %overdesign, duty, etc.

[jcazenave]

Hi

I don't know if you have access to it, but you could use the Aspen Shell & Tube Exchanger model from within HYSYS to do a rigorous rating of the HX.

This allows you to use the same properties than HYSYS but do a HX calculation as rigorous than HTRI.

Kind Regards

[abhi_agrawa]

Yeek,

From your posts it looks like that you are trying to check the adequacy of some of the exchangers in the High Pressure loop of Hydrocracker. Please confirm my understanding.

If this is the case, then I'd suggest that you try to get the properties of the streams from your process licensor. I have been involved in the design of several hydrocrackers and I can tell you in the high pressure loop several physical properties are not predicted well by any of the process simulators. In these designs we used a lot of data collected over a several years to correct the physical property data predicted by the simulator.

For C6+ if you have a simulation from the licensor, to begin with you can try to match the same composition. Since you are trying to evaluate the operations of a existing plant, you can also try to get the stream in question sampled and get the composition from a laboratory analysis.

Hope this helps,
Abhishek

[yeek]

Abhishek:

Your understanding is correct.

Thanks for this piece of information. It is indeed very helpful. I have with me some simulation files but I am not certain of their accuracy. I will bring up this issue.