When working on the design of batch processes, a major factor controlling success of the completed facility is process equipment scheduling. Inadequate attention to moving materials through the process can reduce production capacity and increase capital costs, limiting the margins available for a profitable facility.

In defining and solving control problems, it is imperative that timing relationships for process equipment be fully understood so that effective sequences and interlocks can be developed and implemented. Understanding these relationships is also necessary for recipe creation and developing rules for recipe sequencing in multi-product facilities.

Batch Design Simulator (BDS) from Bio-Pharm Technologies, a division of Day & Zimmermann International Inc. (Philadephia, Pa.), was developed to assist the control engineer in understanding the dynamics of batch processes. This software focuses on the needs of multi-product batch facilities for specialty chemical, biotech, and pharmaceutical production.

To help in understanding batch facility dynamics, BDS includes several tools, including:

• Resource utilization trends;
• Cycle time analysis;
• Work-in-progress (WIP) tracking; and
• Scheduling of product batches.

These analysis aids are used on a detailed model of the process that tracks material from raw material input to final product(s). The model starts with a process flow diagram (PFD) details to help develop the model. Using the PFD, detailed process graphics are created that show all equipment and process interconnections. A specification sheet associated with each item of equipment defines operational parameters.

Over this physical system model, the user then defines product recipes from raw materials, required equipment sequences, and processing times. To create a recipe, a user first forms the master control sequence then develops steps associated with each piece of equipment, which the master file uses to produce the product. For example, a reactor vessel may have multiple recipe sequences associated with it, but the master product recipe determines the active step.

Once the model is fully developed, the user can begin to perform "what-if" tests for product mix and process variations. The software's analysis tools are available to provide end-to-end determination of process capabilities and aid in process revisions. At this point, the process-configuration control system definition can be finalized, product recipes defined, and sequencing limitations determined.

BDS is a very detailed modeling package. It provides many tools for performing detailed batch processing analysis, but is not a "quick" analysis package because many levels of detail are needed to perform a system analysis.

This review is based upon the demonstration CD for Batch Design Simulator. This package operates under Microsoft Windows 95/98/NT and the UNIX operating systems. The current release the software is version 5.2. The demonstration CD uses Lotus ScreenCam to illustrate product functionality for four applications. It is also marketed as the BioPharmaceutical Design Simulator with the addition of several application extensions.

For more info on BDS, online at www.controleng.com/freeinfo.