When students ask questions in the student section, the responses may be in more detail and focused on the academic problem. Real world applications often require different considerations. I will consider this a student question. A drawing of the system you are describing would be helpful.
Temperatures and vapor fractions along the crude preheat train depend upon composition and the heat exchanger network. Because of the tendency of the heavier components of crude oil to crack at high temperatures, the temperature of the feed furnace is controlled to be no higher than 700 F. Because this furnace duty is a huge operating expense, optimizing the exchanger preheat train has a large potential for energy savings. The temperature of the furnace feed is made as high as possible and the furnace firing is used to heat the feed the rest of the way. The system pressure is calculated around 'anchor points'. For a crude column the pressure at the top of the column is the 'anchor' and the upstream pressures are calculated according to their necessary pressure drops. Your question about the effect of a pre-flash drum in your system should be one of the goals of your project and cannot be answered without doing the work.
First of all, thanks for your reply.
I'm a final year student and I perform this project to graduate in next year. I looked for many topics and scientific papers that related to pre-flash drum. But it might be complex and several theories that I can not understand. However, after reading all references and I tend to carry out this project following this stages:
- I will collect all required data consisting of Crude Assay, Specification Products, Operating Conditions (1)
- I will choose the vapor fraction after releasing from the Pre-Flash Drum and the conditioning temperature ( V/F = 0.03 (the composition of light ends in crude assay accounts for 2.86% so that I choose 3% and T = 200 ) (2)
- I will do a simulation on Aspen Hysys and I will check the Specification Products (3)
- I get all data that are relevant to pre-heat train network, for example: the residue will be used to exchange heat with crude oil (4)
- I will use pinch technology to design a HEN (5)
- Conclusion, I will make a comparison to the initial configuration (does not pre-flash) (6), which is described below:
+ comparing to Specification Products
+ the energy consumption
+ CO2 emissions
+ operating costs
I assume that if I implement a pre-flash, the hydraulics in the main column (CDU) does not have any problems (flooding and weeping) and the ID (internal diameter) is constant.
Now I am doing at the fourth-stage and I continue to the next stage, but I am not sure that the above mentioned operating conditions of pre-flash drum are right so I do not know how to check the operating conditions. I think that I will calculate and design the size of the pre-flash drum which is able to prevent the entrainment "foaming" in pre-flash, but I do know which size is suitable for preventing this entrainment. I refer to a paper that discusses the undersized pre-flash may entrain foaming into the main column, but they do not mention which size is considered as undersized pre-flash ( a concrete number about height or diameter).
Besides that, I want to design a new HEN, I do not tend to retrofit or revamp the existing refinery because it is too complex with me.
That's all I want to share with you. Hope you reply me and help me to solve this. If there are any mistakes or failures in my steps, please tell me and I will fix it. Thank you so much, sir!
Edited by Leonard2511, 07 October 2021 - 05:39 AM.