Feed blends

Feed blends are automatically created blends for particular asset groups, distillation units or processing units represented by Base + Delta models. The blends can be optimized to make the best use of the material available to those assets. As a feed blend is created to represent a period of time to feed the asset group, the blend makes best use of the material available up to and during this time period.

When you create a feed blend, the configuration of the corresponding asset (distillation or process unit) ‑is used to create an independent configuration for the blend. Further changes to the asset configuration do not affect the blend configuration.

You can view and edit all the feed blends related to a particular asset from the Feed Blends pane in the Display page. On that same pane you can also create new blends and delete existing blends for that asset. You can also use this pane to reset blend configurations to the underlying asset configuration.

Feed blend optimization is only possible when the storage tanks are directly joined to the unit processing the feed. For example, feed blend optimization for CDU products is only possible when the crude storage tanks are directly connected to the CDU. This means that if there are some buffer (charge) tanks between the crude storage and CDU, it is not possible to use feed blend optimization.

Choose the blend optimization mode from the top-left corner of the Inspector:

• Min/Max: creates a blend with flows and properties between limit values and with a single parameter minimized or maximized.

• Targets: creates a blend whose flows and properties are as close to a set of target values as possible.

Min/Max mode

Use Min/Max mode to minimize or maximize one parameter of the feed blend. Other parameters can be constrained, so that they must be greater or less than a value, but only a single parameter can be minimized or maximized.

Example: It may be required to generate a feed blend which maximizes the time between switching feed blends, that is, to maximize the time that the feed blend runs for (to maximize the unit run-down). This time duration for the run-down is set as the maximization parameter.
However, this maximization should be within the bounds of keeping sensible operating conditions on the crude unit and downstream process units. That is, the flows and properties of the unit output should also be constrained to ensure stability in the unit operation. These can be set as minimum or maximum constraints for the problem.

Targets mode

Use Targets mode to generate a feed blend within some operational constraints; that is, no particular property or flow is targeted but it is attempted to create a blend which meets a set of constraints on flows and qualities from the assets. The precision to which the blend meets particular blend requirements such as flow rates or properties can be adjusted by setting scales for individual constraints which controls the constraints relative importance.

Along with targeting simple distillation and processing units, it is possible to work with assets as groups. A group is a collection of assets that can be worked with together, and are defined as group sets. When assets are added to a group set in the Target dialog, they can be reviewed and worked with to ensure collective scheduling of the assets as a whole.

Target scales

When using Target mode it is possible to set scales on each value to be targeted. This allows you to control the precision to which the value is targeted. Target mode will attempt to create a blend where the difference between the blend values and their targets is minimized. This occurs by minimizing an objective function in which all of the target values appear (technically, all of the absolute differences between the final blend value and the target value).

However, some of these target values may be more important to match closely. For example, you may choose to target both density and sulfur of a crude blend, but it may be more important to match the density closely and allow the sulfur to be different. In this case, setting the scale of the density target scale to a higher value would increase the weight of this parameter in the objective function, so during optimization this difference would be minimized more (at the expense of the sulfur value).

In another situation it may be desirable to target % residue yield and sulfur, but with equal importance. The residue yield may be around 40% and sulfur around 2%. As the residue yield is an order of magnitude greater than the sulfur, it is by default more significant than the sulfur (as a 10% difference in residue yield is numerically greater than a 10% difference in sulfur). Therefore, to ensure these are both targeted with equal weighting, the scale could be used to ensure they both had a similar magnitude weighting (for example by using a scale of 1 for residue yield, and 20 for sulfur).

Simulate a feed blend

Blend simulation is controlled by the Automatic Blend Simulation optional feature:

• If the feature is enabled, any edit to the blend triggers a simulation, as long as the portion of scheduling case needed to update the blend values has been simulated. You can still work on the blend while the simulation is running. Further edits stop the simulation and trigger a new one.

  Under these conditions, blends are simulated automatically even if the simulation for the full scheduling case is set to Manual.

• If the feature is disabled, you must simulate the blend manually by clicking the icon in the toolbar of the Single Blend Inspector.

When a blend needs simulating, values that may no longer be up to date turn red, and warning messages appear in the affected panes. Warnings also appear in the tooltips displayed when hovering your mouse pointer on affected cells.

Customize columns

The information available in the Single Blend Inspector is organized into several tables. You can fully configure each table to suit your workflow by moving, resizing, showing and hiding columns.

Note: The column configuration (widths, positions, visibility of columns) of a Blend Inspector is preserved after you close and reopen the Inspector, or Schedule. You do not need to save your case explicitly.
The internal layout of a Blend Inspector is not linked to a Display, but is common to all Blend Inspectors for the same type of blend. When you make a layout change in a Blend Inspector window, this is immediately reflected in any new Blend Inspector window for the same blend type.
These changes are local to your Schedule profile on your computer and are not shared with other users, even if you share your model. Similarly, if another user updates the Display and you get the updates via the Synchronize pane, the visibility, width and position of columns within the Inspectors are not affected.

Hide and show columns

Follow these steps to hide or show columns:

1. Right click on a column header and choose Manage Columns from the context menu. The Manage Columns dialog box appears.

2. If necessary, type in the Filter text box at the top of the window to show only the columns with names containing the text you entered.

3. Clear the check box in the Show column next to each column you want to hide. Similarly, select the check box near to each column you want to show. Changes are made to the table in real time.

4. Click Close once you have finished configuring columns.

Rearrange columns

You can rearrange columns in all tables of the Single Blend Inspector by right clicking on a column (not just the column header) and choosing either Move Column Left or Move Column Right from the context menu.

Alternatively, use the Alt + Left Arrow and Alt + Right Arrow keyboard shortcuts. This is especially useful if you need to move a column by several places.

To restore the default positions of the columns, choose Reset Column Order from the context menu.

The table in the Constraints tab works differently:

• To move a column, click and drag the column header.

• To show and hide columns, right click on a column header and choose Column Chooser from the context menu. Then drag column headers to and from the Customization window to hide and restore columns.

Manage source assets

In the Source Assets area of the General tab, you can manage the flow of material from each source asset into your blend. Select the check box in the Active column to use the corresponding asset as a blend source.

For each active asset, you can either set the Desired Ratio of material transfer relative to the other active assets, or the absolute Desired Flow Rate of transfer. Click the option button in the corresponding cell to enable either option.

Another quantity you can edit is the cost of the material in each source asset, in the Tank Price column. Any change is immediately reflected in the Transfer Cost column, which shows the cost of the material transferred during the blend.

Tip: A row at the bottom of the table shows the totals for various quantities over all active blend sources. Ratios, target and transfer rates and amounts are among the quantities for which a total is calculated.
This is especially useful for monitoring ratios. Suppose that you want the sum of your ratios to be 100. As you change ratios to experiment with different blend recipes, you can always make sure that their sum is correct, without having to do the calculation by hand.

Material override

Transfers can have material overrides. For a particular transfer stream choose an existing feedstock to use instead of the simulated transfer properties. The bulk set of properties defined for the feedstock will be used during optimization and for subsequent simulation, rather than the currently simulated set of qualities.

The material override feedstocks must be defined in the schedule's parent case.

Manage outputs

Output columns

When optimizing the feed blend it may be required to limit the property values for certain output streams. The constraining values can be added to relevant streams by adding the required properties as columns to the Outputs grid. To add columns:

• Right-click the Outputs grid and choose Manage Columns.

• Filter the list for the relevant property.

• Add the property and the Min/Max value for that property.

Manage unit configuration

The Configuration tab allows you to set the operational configuration of the destination unit during the feed blend activity:

• Cut points and swing cut ranges for distillation units.

• Operational parameters for other process units.

View and edit feed blends

Add the Feed Blends pane to a Display to view and bulk edit all the feed blends related to a given asset. This pane also allows the creation and deletion of feed blends. To open the Feed Blends pane, click Feed Blends in the Panes group of the Home ribbon tab.

From this pane you can do the following:

• Create a new feed blend entry for this asset by clicking Create and then entering the new information.

• Edit one or more blends by selecting the blends and clicking Edit. The feed blend inspector opens with the corresponding blends in the inspector.

• Delete one or more blends by selecting the blends and clicking Delete.

• Restore the configuration of one or more blends to match the configuration of the underlying assets. Select the desired blends and click Restore Configurations.

• Move the selected blends up or down in the list by clicking the arrow icons in the toolbar. Each selected blend moves by one position in the list. The blends are swapped in the schedule according to the new ordering, while keeping their original durations. Moving a blend is not possible in two cases:

  • The selected blend or the adjacent blend is linked to other blends.

  • The selected blend or the adjacent blend partially or fully overlaps with other blends.

Configuration for blend feed manifolds

Make sure the Blend feed manifold support optional feature is enabled to let blends manage the configuration of the manifolds feeding them.

The feature is enabled by default.

When this feature is enabled, a blend applies an effective configuration to the feed manifold, overriding its default configuration for the duration of the blend. This has several advantages:

• When creating a blend, the underlying manifold configuration remains unchanged. The manifold configuration no longer splits.

• Moving a blend to a different time does not require changes to the manifold configuration, since the effective configuration now moves with the blend.

• Multiple overlapping blends no longer interfere with each other. There is no risk of data loss from one blend overwriting the manifold configuration.