13 replies to this topic

[AAAIK]

1. The problem statement, all variables and given/known data
I am required to obtain the following 
1) Energy targets and pinch temperatures
2) Composite Curves
3) Grand Composite Curve with and without utilities?
4) What utilities are you going to use to fulfill the energy targets? Why have you selected these utilities?
5) Design a HEN that fulfills the energy targets
6) Design a HEN that fulfills the minimum total costs
7) What is the difference between the two HEN designed


2. Relevant equations
http://publications....text/142245.pdf
This link contains the process description.
3. The attempt at a solution
I am not expecting anyone to read 60 pages, but there is part of it which is of relevance to me in solving the problem that is the process description. I am not confident in my understanding of the process and how the streams get heated to their target temperatures from just looking at the process flow diagram.I am using ASPEN Energy analyzer software to design a Heat exchanger network drawing both composite curve and  Grand composite curve based on the stream data. In drawing the hot and cold composite curves we should not take into account the utility streams and from the data I cant figure out which is which?

Attached Files

•  Process Streams in the distillation area.png   84.46KB   5 downloads
•  Stream data for pinch analysis.png   63.64KB   4 downloads

Edited by AAAIK, 08 December 2018 - 09:21 AM.

[PingPong]

All streams except 13, 14 and 15 are process streams.

[AAAIK]

All streams except 13, 14 and 15 are process streams.

May I ask you why you chose streams 13, 14 and 15 as utility streams?

[Art Montemayor]

AAAIK:

 

What does the Gothenburg Refinery have to do with the topic at hand?

 

On your question regarding utility streams: are you aware of the meaning of feed water?  Are you aware of what a refinery uses feed water for?  Do you know where the feed water comes from?  I ask this because it is so elementary and also basic process knowledge that all feed water is a basic utility originating in off-limits to the main process.  That, I believe, is why PingPong picked it up immediately.  

[PingPong]

It is not clear what you expect from us.

 

If you have questions about the process description, or composite curves, or ..... (whatever) then you can post them here, but be specific and clear in formulating your questions.

[AAAIK]

The crude oil is heated by a number of heat exchangers before entering the first furnace. This results in a preheated crude oil stream which decreases the energy demand of the furnace. The stream continues to the atmospheric distillation column where four different fractions are extracted.

So stream 1A represents crude oil before entering the furnace and Steam 1B crude oil to the atmospheric distillation column, right?.

In the process flow diagram What does E-11 represent, a heat-exchanger?

[PingPong]

So stream 1A represents crude oil before entering the furnace and Stream 1B crude oil to the atmospheric distillation column, right?.

Yes.

Stream 1B is partly vaporized, hence the higher dH/dt which is there called Cp although it not really is.

In the process flow diagram What does E-11 represent, a heat-exchanger?

It is a heat exchanger consisting of one shell with two different tube bundles in it. See Figure 18 in 142245.pdf.

[AAAIK]

I constructed the composite curve and determined the ideal minimum cooling and heat requirements as 3811 KW and 3648 KW respectively and the pinch temperature at 252 degrees Celsius. I also Constructed a GCC but I don't know how from Energy Analyzer one can find the temperature interval where the GCC bends back on itself in order to figure out where to set utility targets. I also don't know on what basis should I select the utilities given in pastedImage (2).png, Should we choose the utilities with the least cost per energy in order to satisfy the cooling and heating requirements. Are streams 13, 14, and 15 we excluded cold utilities we should employ in my HEN design and GCC? 

Attached Files

•  Stream data.png   85KB   3 downloads
•  CC.png   67.35KB   1 downloads
•  GCC.png   59.35KB   1 downloads
•  pastedImage (2).png   283.37KB   1 downloads

Edited by AAAIK, 09 December 2018 - 06:37 PM.

[PingPong]

So stream 1A represents crude oil before entering the furnace and Stream 1B crude oil to the atmospheric distillation column, right?

Just to be more clear: Stream 1B starts at 185 ^oC, which is somewhere in the preheat train, and ends at the furnace outlet at 360 ^oC at which point it is partly vaporized.

 

the ideal minimum cooling and heat requirements as 3811 KW and 3648 KW respectively and the pinch temperature at 252 degrees Celsius.

Is that based on a pinch dT of 15 ^oC like they used in that thesis? If so your result is different from theirs.

 

I am not familiar with Aspen Energy Analyzer. That last table pastedImage (2).png is a mystery to me.

By the way: that is the only image that I can read. The other three are too small.

[AAAIK]

Yes I used Delta T min =15 degrees celsius. and obtained 252 ^oC as the pinch temperature for the hot stream and 237 ^oC as the pinch temperature for the cold stream. 

[PingPong]

Well, then you have to figure out why your result is different from that in the thesis.

 

Either you or they must have made a mistake.

[AAAIK]

No, the results I obtained are similar to the pinch temperatures in the thesis

[PingPong]

I constructed the composite curve and determined the ideal minimum cooling and heat requirements as 3811 KW and 3648 KW respectively

Your cold and hot utility demands are different than in the thesis: table 7 gives 3145 & 3718 kW.

[AAAIK]

 

I constructed the composite curve and determined the ideal minimum cooling and heat requirements as 3811 KW and 3648 KW respectively

Your cold and hot utility demands are different than in the thesis: table 7 gives 3145 & 3718 kW.

 

I revised my calculations and all calculations were correct. I revised the process data in the master thesis and I detected mistakes in calculating the heat loads.

Edited by AAAIK, 10 December 2018 - 07:21 AM.