Throughput warnings

Throughput warnings may be generated if overall capacity is reduced due to process unit constraints

It is possible to set maximum unprocessed feed constraints on particular process units. When this is set for a unit, if a particular crude results in the unit exceeding its capacity and unprocessed feed constraint, then the amount of crude feed is reduced until the condition is met. However, reducing the crude feed means reducing the throughput of the refinery, and so a Product Realisation category in the Netback summary is highlighted to show a warning condition.

For example, imagine a refinery has a crude unit with a capacity of 100,000 bbl/day and a vacuum tower with a capacity of 40,000 bbl/day. A maximum unprocessed feed of 0 bbl/day could be set for the vacuum tower. In this case the vacuum tower must always be running at or below capacity. If a crude was processed which resulted in 35% (by vol) atmospheric residue, then in one day the vacuum tower would receive 35,000 bbl of feed, which does not violate our condition. However, if a crude was processed which resulted in 45% (by vol) atmospheric residue, then if the crude tower is run at capacity we would produce 45,000 bbl of atmospheric residue. However the vacuum tower can only process 40,000 bbl/day and there can be no unprocessed feed to the vacuum tower. The only choice we have is to reduce the amount of crude being fed to the crude unit until we are only producing the allowed 40,000 bbl/day of atmospheric residue. But this results in the overall refinery throughput being reduced and is a potential loss of margin. Therefore a throughput warning message shows when this is the case.

Timewise Graph

The Timewise Graph shows the variation in Netback margin for each crude in the case over a period of time

The Timewise Graph can be used to review the variation in Netback margin over time for the Netback Case and its crudes. To display the Timewise Graph, select the option from the Netback Tree and define the date range over which to calculate values using the Start Date and End Date calendars.

• Click Generate () to calculate the Product Realisation, Crude Cost and Margin over time.

Where an automated price feed is used the price for a crude or product will be for the same contract on the historical date. For example if my Netback Case uses Arab Light and the price is for delivery in two months time, then to calculate the Timewise Graph the price for Arab Light with delivery in two months on each separate day in the range will be used. Where a price is not available for that day the last updated price for that contract will be used until a new updated price becomes available.

When a custom price is used for a crude or product the price used will be the last valid entered custom price for that crude or product until a revised custom price becomes available.

BlendExplorer Graphs

When running Netback in Incremental Blend mode an extra page appears in the Preview branch for BlendExplorer Graphs. The graphs indicate the change in Netback value over the range of different blends. The total Netback value for the blend is shown, along with the value of each different product.

Product Yields

The Product Yields shows the products from each analysed crude and their relative values

For each crude in the Netback case, the Product Yields page shows the percentage of the input feed which is pooled into a final product.

By default, different grades for a product are listed separately in the table. To display only the overall results for each product, choose Product from the Group by dropdown menu.

By default any products which have no yield are hidden in the view. To view all products, clear the

Hide products with zero yield check box.

To change how data is displayed, choose one of the following options from the Yields by menu:

• Economic ($/bbl) - the value of the product per barrel

• Economic ($) - the value of the product per day

• Weight - the mass of product per day

Weight % on total products - the percentage mass the product contributes to a day's production relative to the total mass of products

• Weight % on crude - the percentage mass the product contributes to a day's production relative to the total mass of crude input

• Volume - the volume of product per day

• Volume % on total products - the percentage volume the product contributes to a day's production relative to the total volume of products (this will be greater than 100% because of volume expansion)

• Volume % on crude - the percentage volume the product contributes to a day's production relative to the total volume of crude input

Normally all manufactured product grades are listed with the respective yield of each. To group product grades into similar types select Product from the Group by: menu. For example, this would cause the several different gasoline grades to be presented as a single gasoline product whose total yield was the sum of the component yields.

When process units are running at capacity, excess feed to them is diverted to off-spec stream which will undergo no further processing. This off-spec stream will often have zero value, and so producing it reduces the refinery margin. Where these off-spec streams are produced in a model, the Product Yields grid will highlight them to show that stream has no value.

For example, imagine a hydrotreater has a capacity of 20,000 bbl/day. If the hydrotreater receives 25,000 bbl/day of feed, then 5,000 bbl/day remains unprocessed. This stream will not meet product specifications and so be unsuitable for blending into final products. Therefore it will remain as an unneeded stream with no value and be highlighted in the product yields grid.

Product Blending

For a particular crude the Product Blending page shows the amount of each stream which is pooled into a particular product. The streams present in the refinery are shown as rows in the grid of results, while the final products for the refinery are shown as columns in the grid.

The row headers show the total daily amount of each refinery stream, either as the total mass or volume, or as a percentage of the daily production.

The column headers show the total daily amount of the refinery products manufactured, either as a the total mass or volume, or as a percentage of the refinery's total production.

Results are shown for a single crude. The crude for which results are currently shown can be changed using the Crude menu.

The way in which results are shown can be changed using the View menu. Several views are available:

• Weight flowrate - the mass of each stream which is pooled in the particular product

• Volume flowrate - the volume of each stream which is pooled in the particular product

• % by grade - the percentage of the product which is due to a particular stream (so for example if the LPG column shows 90 in the propane row it means that 90% of the LPG is from the propane stream)

• % by stream - the percentage of the total stream which is in a particular product (so for example if the naphtha off-spec column shows 35 for straight-run light naphtha it means that 35% of the total light naphtha mass is in the off-spec naphtha, the remaining 65% in a different product)

Product Qualities

The Product Qualities show the final properties of each of the blended refinery products

For each crude in the Netback case the Product Qualities page shows the final property values for the pooled products. Where a product has an applied property constraint the cell has a red triangle in the top right corner . If a product has an applied constraint which is at its limit the cell is also shaded pink .

To change the crude for which results are displayed select the required crude name from the Crude menu.

When constraints are applied for product streams the mouse tooltip shows the applied value.

The mouse tooltip can be used to show the applied property constraints by hovering over the cells with constrained values . If a particular product is at the limit of its property value then excess stream which would normally be pooled in the stream is diverted to another lower value stream with lower specifications. For example some kerosene may be pooled into a diesel product (assuming diesel is worth more than jet) until the lower bound of the diesel density specification is met. The extra kerosene is then diverted to the lower value jet stream.

Stream Qualities

The Stream Qualities show the final properties of each of the refinery streams

For each stream in the Netback case the Stream Qualities page shows the properties of the stream. The properties represent the feed quality of the virgin input to the process units as well as the properties of the processed stream used for product pooling.

To change the crude for which results are displayed select the required crude name from the Crude menu.

Refinery Simulation

The Refinery Simulation provides a summary of the products from each process unit and the key properties

The Refinery Simulation page shows capacity and utilisation results for each process unit included in the refinery schematic on a crude-by-crude basis. For a particular crude the process capacity and final utilisation is shown. Also included is the amount of fuel used by the process unit in its operations, and the total fuel consumption as a relative amount of crude.

To change the crude for which results are displayed use the Crude menu.

Process Unit Simulation

For each process unit in the Netback case the Process Unit Simulation shows the properties of the feed and output streams. Also shown is the utilisation of the unit (the percentage of the unit's capacity used) and the processing amount (the percentage of potential feed which is actually processed).

To change the crude for which results are shown use the Crude drop-down menu. To change the process unit for which results are being displayed use the Unit drop-down menu.

The Process Unit Simulation page shows results for each unit assuming the unit is running at full capacity. That is, the property values calculated by the simulator are only for the actual input feed which is processed by the unit. Extra input feed above the unit capacity is not included in the calculation. For example, the kerosene hydrotreater simulation shows the expected properties of products from hydrotreatment of the input kerosene stream. If the unit capacity is exceeded, the excess kerosene is sent to a different unit for processing and pooling, and the properties of this are not included in the results for the hydrotreater.