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How to best characterize your liquid hydrocarbons
Guest Blogger: Marimuthu Ananthavelu of CB&I
Characterizing your hydrocarbons is surely an art; the history begins with efforts taken to prepare API technical data book sometime when the energy industry started realizing the importance of hydrocarbon resources and its much needed infrastructure.
Experiments at the Pennsylvania State University, Department of chemical engineering make remarks in the field of Liquid hydrocarbons characterization involving different mathematical manipulations to match the experimental data all the time. (While I was graduating, I did not realize that mathematics was going to be such an important thing in the field of chemical engineering)
We see hundreds of research papers getting published in the field of characterization of Liquid hydrocarbons and mainly tried with heavy oils.
It is very beautiful to understand how best the liquid hydrocarbons can be characterized in PRO/II. The best we characterize, there are always best results guaranteed. This will mainly be important when we have the raw true boiling numbers found with volume % of vaporization in industrial laboratory when we don’t have updated assay database or when we have the change in feed blend.
Let’s see some important features to be considered;
1. Look clearly at the numbers;
Whether it is TBP (True Boiling Point) curve or % of sulfur content or specific gravity curve or Watson K factor; the entry of these numbers are most important. Time which you may neglect giving these inputs correctly, will fire back heavily.
Make Lighters possibly into your characterization. In case if you get to have many different types of crude, define all the lighter components individually with respective composition in each crude before you blend. When you blend, don’t expect that the blended product stream will have the same number of components as any one of the crude type which has maximum number of components. You may think this helps reducing the convergence time, but it would give you less usable outputs, for example in the column overhead off gases stream quantity or the stream goes to ejector.
Better use as many components as possible since it takes very little time.
2. Define your impurities level for each cut point
It is preferred to give the impurity range for each cut-point or with respect to % distilled. It produces the % of impurity getting landed in each product or in by-products and become the basis for downstream processing units design.
3. Look at the Characterization options;
There are many different combinations for characterization in PRO/II that serve various chemical engineering applications. Look mainly at the different methods whore the key inputs are generated mainly Normal Boiling point of the pseudo components, Molecular weight of the pseudo components, and specific gravity of the pseudo components. These are just most important parameters based upon which the individual pseudo components properties getting calculated which all make one stream. There are different ways to calculate the above properties.
5. Always have your eye on heavy oil
It is well understood by the industry, though many mathematical combinations have been successful in representing the experimental results, it is still a universal challenge for any process simulator to predict the properties of heavy oil with great accuracy. Refer data book, public crude assay data before you conclude in defining such hydrocarbons. (Editior’s note: SimSci-Esscor has done a lot of work on heavy oils – get more information here)
6. If you are in operating industry and having still doubt in selecting the right thermodynamic model, just try matching the basic engineering design data with your selected thermo model results and then fix your thermo model. Careful consideration is preferred before fixing the same.
7. Whenever possible use Crude assay database, it becomes an easy task when you integrate your Spiral crude assay database with PRO/II. (Editior’s note: direct integration between Spiral and PRO/II is coming soon)
How to best characterize your liquid hydrocarbons
Guest Blogger: Marimuthu Ananthavelu of CB&I
Characterizing your hydrocarbons is surely an art; the history begins with efforts taken to prepare API technical data book sometime when the energy industry started realizing the importance of hydrocarbon resources and its much needed infrastructure.
Experiments at the Pennsylvania State University, Department of chemical engineering make remarks in the field of Liquid hydrocarbons characterization involving different mathematical manipulations to match the experimental data all the time. (While I was graduating, I did not realize that mathematics was going to be such an important thing in the field of chemical engineering)
We see hundreds of research papers getting published in the field of characterization of Liquid hydrocarbons and mainly tried with heavy oils.
It is very beautiful to understand how best the liquid hydrocarbons can be characterized in PRO/II. The best we characterize, there are always best results guaranteed. This will mainly be important when we have the raw true boiling numbers found with volume % of vaporization in industrial laboratory when we don’t have updated assay database or when we have the change in feed blend.
Let’s see some important features to be considered;
1. Look clearly at the numbers;
Whether it is TBP (True Boiling Point) curve or % of sulfur content or specific gravity curve or Watson K factor; the entry of these numbers are most important. Time which you may neglect giving these inputs correctly, will fire back heavily.
Make Lighters possibly into your characterization. In case if you get to have many different types of crude, define all the lighter components individually with respective composition in each crude before you blend. When you blend, don’t expect that the blended product stream will have the same number of components as any one of the crude type which has maximum number of components. You may think this helps reducing the convergence time, but it would give you less usable outputs, for example in the column overhead off gases stream quantity or the stream goes to ejector.
Better use as many components as possible since it takes very little time.
2. Define your impurities level for each cut point
It is preferred to give the impurity range for each cut-point or with respect to % distilled. It produces the % of impurity getting landed in each product or in by-products and become the basis for downstream processing units design.
3. Look at the Characterization options;
There are many different combinations for characterization in PRO/II that serve various chemical engineering applications. Look mainly at the different methods whore the key inputs are generated mainly Normal Boiling point of the pseudo components, Molecular weight of the pseudo components, and specific gravity of the pseudo components. These are just most important parameters based upon which the individual pseudo components properties getting calculated which all make one stream. There are different ways to calculate the above properties.
4. Look at the Thermodynamic models used;
You should have plenty of literature to choose your thermodynamic model. Customize your thermo model to the specificapplication.
When you are in doubt, just regenerate the base properties which were used to define the whole components properties for example NBP (bubble point) and specific gravity. Then compare with the base properties originally used. This will give you a quick view whether the thermo model used is conveniently true or not.
You should have plenty of literature to choose your thermodynamic model. Customize your thermo model to the specificapplication.
When you are in doubt, just regenerate the base properties which were used to define the whole components properties for example NBP (bubble point) and specific gravity. Then compare with the base properties originally used. This will give you a quick view whether the thermo model used is conveniently true or not.
5. Always have your eye on heavy oil
It is well understood by the industry, though many mathematical combinations have been successful in representing the experimental results, it is still a universal challenge for any process simulator to predict the properties of heavy oil with great accuracy. Refer data book, public crude assay data before you conclude in defining such hydrocarbons. (Editior’s note: SimSci-Esscor has done a lot of work on heavy oils – get more information here)
6. If you are in operating industry and having still doubt in selecting the right thermodynamic model, just try matching the basic engineering design data with your selected thermo model results and then fix your thermo model. Careful consideration is preferred before fixing the same.
7. Whenever possible use Crude assay database, it becomes an easy task when you integrate your Spiral crude assay database with PRO/II. (Editior’s note: direct integration between Spiral and PRO/II is coming soon)
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