3 replies to this topic

[Mainak Sarkar]

HI to every body, Can any one guide me detail about the Crude distillation unit's control mechanism, over flash and if possible a P&ID. I wand to know detail about the side cut drawing mechanism, wheather it is TC or LC or FC.

[Padmakar Katre]

Dear,
First of all let me make you clear that the CDU is not a small unit to describe you in details here unless you don't come up the specific requirement or doubt. Second thing is that the P&ID is the properietory document which nobody will share. So better you come up with the specific question we will have nice discussion.

[Zauberberg]

To control what in CDU? I hope you don't expect from us to elaborate all control loops in Crude distillation unit, or in the main tower only. The subject is huge.

Overflash can be controlled directly (FIC) or indirectly (the heaviest side-cut 95% point or some other quality parameter), which depends on stream routing - whether it goes for further treating and final product blending, or it is feeding a downstream unit. There are many, many options.

Side-cuts are usually drawn through ordinary FIC, since it is very hard to couple draw-off temperature with desired product quality for various crudes or blends being processed. Advanced control systems (MPC) are one step forward in this matter, but I believe there aren't many units operating in such way worldwide. In addition, side-cut yields can be dictated by overall heat balance of main CDU tower.

Google CDU, get books from Jones, Nelson, Mayers etc. You'll find a quite good starting point there.

[ARAZA]

To control what in CDU? I hope you don't expect from us to elaborate all control loops in Crude distillation unit, or in the main tower only. The subject is huge.

Overflash can be controlled directly (FIC) or indirectly (the heaviest side-cut 95% point or some other quality parameter), which depends on stream routing - whether it goes for further treating and final product blending, or it is feeding a downstream unit. There are many, many options.

Side-cuts are usually drawn through ordinary FIC, since it is very hard to couple draw-off temperature with desired product quality for various crudes or blends being processed. Advanced control systems (MPC) are one step forward in this matter, but I believe there aren't many units operating in such way worldwide. In addition, side-cut yields can be dictated by overall heat balance of main CDU tower.

Google CDU, get books from Jones, Nelson, Mayers etc. You'll find a quite good starting point there.

Dear,

I agree with Zauberberg, read through any process instrumentation and controls textbook and familiarize yourself with different control techniques for a distillation columns and come up with specific questions so that we can provide our input.

One book which I have in my mind is "Process Heat Transfer" by Donald Kern which describes controls around a distillation column in detail, for your purpose.

Araza