Material handling systems, plant design

However, unlike project work, studies are usually commenced without a definite plant design concept and construction plan these are subject to change, and the essential requirement is to find the most suitable concepts and plans which will become the basis for the detailed project designs, budgets, and schedules. Inevitably the plant design is developed in a series of iterations. Initially, relatively broad concepts are explored, and possible innovations are introduced. Some concepts, for example materials handling system, layout, or site location, may be quickly rejected, while others may need more detailed comparison to arrive at the best choice. The phases of initial conceptual development, and of more detailed design and evaluation, are often formally split into... 

Often, chemical plant design is informed by laboratory and pilot-scale experimentation. While the initial chapters in this book will inform the reader of the most important design parameters that need to be measured and determined from such experiments, how to then ensure that these parameters perform in the same way in a large-scale plant is the subject of Chapter 6. Although it is desirable to conduct the experimental work in the system for which the results are required, this is not always easy. The system of interest may be hazardous or expensive to build and run, while the fluids involved may be corrosive or toxic. In this case scale models are used, which overcome the above problems and allow extensive experimentation. In the majority of cases the model will be smaller in size than the actual, desired plant, but sometimes, due to the nature of the materials to be handled, the fluids involved may also be different. Scale-up is only possible if the model and plant are physically similar and, hence, the procedure is based on dimensionless groups. How to develop and use these groups is described in Chapter 6. 

Design of the raw material and fabricated product handling system has a major impact on the plant s manufacturing costs and housekeeping. It is based on the different materials used, annual volume of each material, number of different colors, production run lengths, etc. A properly designed pneumatic system generates plastic velocities of at least 5000 ft/min (1500 m/min). 

Therefore, an essential requirement in plant design is the stringent application of dust control techniques. Specifically designed enclosures enabling materials to be handled in closed systems and extraction and plenum air systems of sufficient capacity to maintain normal working areas free from contamination are essential. Special plant finishes to facilitate good housekeeping are an added requirement. 

The hazards associated with operations that involve more than one group can be reduced by the use of a permit system. O Driscoll has described the permit systems used in chemical operations many of these (hot work tank entry line breaking disposal operations excavations operation of material handling equipment and vehicles sprinkler-valve closing permit) are of interest in low-temperature plants. They are designed to permit the safe conduct of maintenance and repair functions. The use of written permits with copies to all groups concerned tends to increase the safety of potentially hazardous operations. Also, with use of written instructions, there is less chance for a misunderstanding. 

Modern central control and management systems are changing this situation, however. These systems have been called supervisory control, distributed control, CAD/CAM/CAE, and—the latest—CIM (computer integrated manufacturing Fig. 2-16). All these designations refer to a system that can monitor all operating parameters for every machine, every piece of materials handling equipment, and all other equipment in the plant. The system receives inputs on all parameters and can issue instructions to each machine to ensure efficient and profitable operation. 

One of the most vexing aspects of pilot-plant work can be feed and product handling as a pilot plant is neither designed nor operated as a closed-loop system like a commercial plant. Indeed, the problems involved in handling and storing feed and product materials can sometimes seem to rival the pilot-plant process problems in difficulty. 

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