Overview

This unit shows how the concepts and methods described in Units 1-12 can be applied to control of batch processes. The economic aspects of batch process control are compared and contrasted with those of continuous process control.

Learning Objectives When you have completed this unit, you should:

1. Understand the differences between control of batch and continuous processes.

2. Know which benefits are most likely to be realized by improved control of a batch process.

3. Be able to estimate economic performance improvement from improved control of a batch process.

13-1 Batch Process Characteristics

The batch processes discussed in this unit may be described as discrete fluid processing. They can be considered to be a halfway house between continuous processing and discrete part manufacture. Most unit processes can be set up to run either in batch or in continuous mode.

Among the processes that are frequently run in batch mode are mixing, heat treating, reaction and separation. Perhaps the most often described unit is the batch reactor, usually visualized as shown in Fig. 13-1. Batch reactors come in many sizes, shapes and operating conditions, ranging from a benchtop 2 liter fermentor operating at 40 C to the 300 ton Basic Oxygen Furnace (BOF) shown in Fig. 13-2, which reaches 1600 C.

Figure 13-1: Typical Batch Reactor

Figure 13-2: A Basic-Oxygen Furnace (BOF) Tilts Forward to be Charged with Molten Iron from the Blast Furnace (Courtesy of Bethlehem Steel, Hogan Steel Archives, Fordham University Library, Bronx, NY)

The products from batch processing tend to...