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Video: FSC 432 Lesson 4 (2:23)
Hello. In Lesson 4, we will start talking about separation processes. This is the first part of the separation processes. Remember, we have talked about having four different types of processes in petroleum refinement. Separation is, of course, the first process.
Now the separation is very critical. The distillation process, which separates the crude oil with respect to the boiling point of the constituent compounds, is really the gateway to the refinery. There, we separate the crude oils into different fractions that are processed in downstream units until they end up as the desirable product that leave the refinery.
Now, in laboratories, we could have different distillation methods to characterize the crude oils. So we can inform the industrial or commercial distillation process. There are three different distillation methods. And we will go through them in this lesson, to see how different they are, and what specific applications would each of these different distillation methods-- laboratory methods-- have in terms of applying to the refinery processes.
Now, in this lesson, we will also define distillation terms. What do we mean by cut points? What do we mean by yield, and so forth. So that we can have a more educated discussion on the distillation process.
We will also introduce the vacuum distillation. And talk about why one would need vacuum for distillation of the residue from the atmospheric crude tower.
Distillation is perhaps the energy guzzler of the refinery. It consumes the largest fraction of energy in a given refinery. That's why the efficiency of distillation is very important for the overall efficiency of a refinery.
Overview
As introduced in Lesson 3, distillation is a key separation process that fractionates crude oil into a number of streams with specific boiling point ranges, or distillation cuts. Removing salt from crude oil usually precedes the distillation process to protect the downstream units from corrosion caused by Cl¯. Desalting process could also remove metals (e.g., Fe, Ni, V) and other inorganic solids and sediments that may deactivate catalysts used in conversion and finishing units. Depending on the specific gravity and the amount of salt present in a crude oil, refineries conduct from one up to three stages of desalting [1]. Heavy and crudes may require three stages of desalting, using processes such as gravity settling, electrostatic coalescence, and packed column separation [2]. Figure 4.1 shows a simple desalting process that uses gravity settling to separate brine (NaCl +H2O) from crude oil after diluting the crude with water and adding de-emulsifiers (chemical additives) to facilitate phase separation.
Learning Outcomes
By the end of this lesson, you should be able to:
- compare and evaluate different distillation methods;
- define boiling point ranges (TBP) of distillation fractions of crude oil;
- identify and exemplify distillation terminology, including cut points and product yields in distillation ranges;
- illustrate the crude fractionation in Atmospheric Distillation and calculate the extent of separation between the distillation fractions;
- illustrate Vacuum Distillation and assess the application of Watson Characterization Factor to select the temperature in Vacuum Distillation Tower.
What is due for Lesson 4?
This lesson will take us one week to complete. Please refer to the Course Syllabus for specific time frames and due dates. Specific directions for the assignment below can be found on the Assignments page within this lesson.
| Reading | J. H. Gary, G. E. Handwerk, Mark J. Kaiser, Chapter 4 (Crude Distillation) |
|---|---|
| Assignments | Exercise 3: Appraisal of the degree of separation between distillation fractions Quiz 2: Will cover the material in Lessons 3-4. |
Questions?
If you have any questions, please post them to our Help Discussion (not email), located in Canvas. I will check that discussion forum daily to respond. While you are there, feel free to post your own responses if you, too, are able to help out a classmate.