11 replies to this topic

[Celopsin.Khan]

As'salam o Alaikum,

 

I am facing a problem in Energy Balance of my plant design Final Year Project titled: Recovery of Naphtha from Crude Oil by fractional distillation.

 

Attached is the PFD of my project, data of which is taken from Attock Refinery Limited, Pakistan. 

https://www.dropbox....LAM 600 dpi.png

 

 

Using Fig 5.1 of Nelson Petroleum Engineering, I can calculate the Cp values at any temperature for a given API gravity. I know the API gravity values of

- Crude Oil 

- Naphtha

- LWK - Light Weight Kerosene

- LGO - Light Gas Oil

- HGO - Heavy Gas Oil

- FFO - Fuel Furnace Oil

 

which allows me to do energy balance on Heat Exchangers.

 

Now the problem I am facing is that, I dont know how to calculate the API gravity of LGO Pump-around and Naphtha Pump-around as they are impure than the finished product

 

 

Explanation
problem is that for energy balance 

around E-303 I need the API of Naphtha Pump around

around E-307 I need the API of LGO Pump around

which I dont have   nor do I knw how to calculate them. So how I may carry out the energy balance around these exchangers

[gegio1960]

you should act as an engineer.... not as a scientist ;-)

good luck!

[Celopsin.Khan]

please I m in real trouble ... Help me have my project presentation due on 6th Feb

[PingPong]

Now the problem I am facing is that, I dont know how to calculate the API gravity of LGO Pump-around and Naphtha Pump-around as they are impure than the finished product

Without a simulation you cannot calculate them, but only (gu)estimate them.

 

But you do not really need them. The duties of E-303 and E-307 can simply be calculated on the crude side.

[Celopsin.Khan]

@Ping Pong

 

You are right, I can calculate the duties on Tube Side. Can I use those Duties to estimate Cp on Shell Side of LGO PA and Naphtha PA? ..

Also how do I carry out energy balance on this multi-draw distillation column? The procedure in my mind is that I calculate heat contents of all the streams entering and leaving the column, but that would be a tiring task, also heat content graph is also based on API gravities (fig 5.3 Nelson Petroleum Refinery Engg)

[Celopsin.Khan]

GVillamizar:

 

You are right, but cant work on approximations as our teachers wont accept that

[Celopsin.Khan]

GVillamizar: 

 

this graph would tell u that how is this an approximation .... in real world the cp value is a function of temperature at constant API gravity (which is a characterization of crude oil)

Attached Files

•  E-301 Tube Crude .jpg   212.61KB   6 downloads

[PingPong]

I don't know what exactly you mean by an Energy Balance.

 

You are right, I can calculate the duties on Tube Side. Can I use those Duties to estimate Cp on Shell Side of LGO PA and Naphtha PA? ..

You can do that, and see whether that Cp makes sense in view of the following:

 

- The LGO of the PA will be the same as the LGO feed to the sidestripper, which is slightly lighter than the LGO product. My guess is that the LGO PA will have API gravity about 2 points higher than that of LGO product.

 

- Naphtha PA is more difficult to estimate, but I expect in the order of 50 - 60 ^oAPI.

[Celopsin.Khan]

PingPong: 

 

Actually, its part of our Final Year Project, In which we take an existing operation (process) and verify it,

1. Firstly by Material Balance, in which we verify Material In = Material Out for each Equipment;
2. Secondly Energy Balance, in which we calculate the H of stream In = streams out for each equipment, or the Duties of Shell and tube side are verified to be equal