5 replies to this topic

[Sophia]

Hi,

I am trying to simulate a distillation column and I really don't have a clue how to do it. This is the first time I am doing this and I am not exactly sure what I am doing.

This is what I know: Feed flow rate, The composition of the feed, feed pressure
also that the feed state is at bubble point. I don't know how to find the bubble point of the feed (considering that it is a multicomponent feed) and how to incorporate that into the simulation.

i know that i need the purpose is to have 96% benzene recovery.

Could anyone please provide me some guidelines or tips? Or if you know of any useful websites? Any help would be greatly appreciated

[Art Montemayor]

Sophia:

My guidelines and tips are:

You ask in the Student Forum (a post I have deleted since you are not allowed to make multiple posts of the same topic), “if you are told that the feed state is bubble point, what exactly does that mean an how do you put that into the simulation?? The answer is that if you don’t know about such basic and fundamental terms as “bubble point” and “dew point”, then you have no business getting involved with simulation. You should already have finished your second year course in Unit Operations – distillation, particularly, and you should have alread resolved binary distillation problems by hand using the McCabe Method and the Ponchon-Savarit Method before trying to set up a distillation simulation. The fact that you haven’t shows that you are not ready to take on a distillation simulation problem. You lack the very basics of what s going on and would have no idea of what you produce in your simulation rersults.

Before trying to drive a car, you have to know where you are going and how to get there. The car is a stupid machine and can’t make those basic decisions for you. You have to know how to – and when to – apply the brakes. You have to learn how to park it as well. The computer and its simulation program are no different; the computer is very stupid and awaits your instructions and guidance. The simulation program is pre-programmed to do some of the very basic instructions to the computer – such as what numbers to crunch out and what equations to apply. But it can’t make hard, logical, and engineering decisions and commands about the problem in front of it. That’s what you are supposed to do. And you have to know exactly what and how to decide with regards to a distillation problem. You do this with all the knowledge about how a distillation columns works and WHY. You have to know all the details.

How did you come to get involved in this problem?
What course of study are you taking in university and what year of study are you in?
What is the name of your university?

[Sophia]

My question was not 'What is the meaning of bubble point'.I don't think I phrased my question very well in my first post. My feed has a lot of components and I wasn't sure if the same rules applied to multi component feed as they did with binary feed. Although at this point, I do not think that I need to know the actual bubble point for simulation sake.

[Zauberberg]

Enthalpy condition of the feed is important for column simulation and design, as it will define the optimum feed location and affect both reboiler and condenser duty. Some of this information you can obtain by using the equations suggested by Art, or you can use the Shortcut Column operation in Hysys.

For setting the feed at the bubble point in Hysys, you need to specify the composition, pressure, and the vapor fraction must be set to zero. By definition, if you specify the pressure and if the vapor fraction is zero, Hysys assumes the bubble point condition. This equally applies for binary and multicomponent mixtures.

[math]

Hi, i read your question... will u please tell me which tool are u using. there are stimulation tools like Chem Cad , Aspen.