Comsumption properties

Yield outputs can be marked as a Consumption property. This means that the process unit actually consumes the stream, but in a proportion which is driven by the other parameters for a process unit. When the model is imported into Spiral Plan the consumption output will be transformed into an input pipe for the model, and the amount of this feed the model requires is then calculated for the model according to the Base Delta values for the stream.

For example, hydrotreaters have two inputs, their feed and hydrogen. However the hydrogen consumption is dependent upon the sulphur content of the feed stream and therefore varies depending upon the crude slate being used to produce the hydrotreater feed. As such for hydrotreaters hydrogen is added as an output and marked as a consumption yield. This means that the hydrogen is used in the unit in a proportion which depends upon the qualities of the feed, and the hydrogen pipe will appear as an input on the flowsheet in Spiral Plan.

Tip: Units which commonly have streams marked as consumption include:
- Hydrotreaters (hydrogen)
- Alkylation (isobutane)

Property x Yield

When adding a new property it is possible to add it as a Property x Yield property. When the process model is used in Spiral Plan the output value for that property will be the calculated property value multiplied by the stream yield. The calculated property value is taken in the units of measure specified in the Edit Property Output dialog. The yield is taken in the weight/volume basis and in the unit of measure specified next to the Property x Yield check box.

Example

If sulphur (in ppm) was marked as a property x yield prediction, and the result of the Base Delta calculation for a stream was a sulphur content of 3ppm and yield of 10%, the property value reported for the model would be 3 x 10 = 30ppm.