Calculator - Examples
The calculator module can be used in a number of stream and unit operation modules, particularly to determine the input conditions. There are nearly unlimited uses for the calculator module, in providing user calculated results for other flowsheet modules. Its usage is limited only by your imagination. Some of the typical applications which use this module are:
1. Calculation of special properties
To compute special stream properties, not available in the general property list, for use by a controller, MVC, or optimizer unit operation. For example, a generalized correlation might be used to compute the cetane number for a diesel fuel to be used as a specification for a controller module, in which a unit operating condition is adjusted to achieve a desired value for the stream property.
2. Simulation of process units
Calculators are often used to simulate special unit operations, such as reactors. The feed streams may be retrieved from the flowsheet, the calculations performed and the resultant product stream information transferred back to the flowsheet. Since the calculator is an "in-line" calculation, no system modifications are necessary to incorporate the reactor calculation.
3. Equipment sizing and costing
Equipment size and cost can be determined based on calculated unit parameters, for printout or optimization. Profit functions typically for flowsheet optimization can be calculated using the calculator. Raw material and operating costs may be subtracted from the product values to determine the net profit.
4. Purge/ Makeup calculations
The calculator module can be used to enhance convergence for flowsheets having recycles and purge or makeup streams. The purge or makeup rate needed to balance the flowsheet can be calculated and transferred to an unit operation, for example a splitter, in which the purge or makeup stream is a product.