Sedimentation equipment, selection

For most materials, the particle size hes somewhere between these two extremes, and the torques required in two properly designed thickeners of the same size but in distinct applications can differ greatly. Unfortunately, test methods to specify torque from small-scale tests are of questionable value, since it is difficult to duplicate actual conditions. Manufacturers of sedimentation equipment select torque ratings from experience with similar substances and will recommend a torque capability on this basis. Definitions of operating torque vary with the manufacturer, and the user should ask the supplier to specify the B-10 life for bearings and to reference appropriate mechanical... 

Along with the selection of JSltration machineiy, attempts have been made to provide a basis for the selection of sedimentation equipment [Wakeman, 1994]. Table 1.1 contains some of this information, in abridged form vhich points to the ptincpal fiictors influencing such selections. 

In this chapter practical methods of obtaining information for filtration, consolidation, cake washing, gas defiquoring and sedimentation are described. The aim is to illustrate how important data for equipment selection (see Chapter 5), scale-up and process simulafion (see Ch ters 6 and 7) can be measured in the laboratory using either weU established, manually operated apparatus or state-of-the-art, automated apparatus. In some cases details of step-by-step experimental procedures are presented to illustrate best practice. Methods of data analysis are also presented and their use is illustrated through worked examples. 

In the current context the results of a sedimentation test are used in equipment selection to eliminate unsuitable equipment from a sometimes lengthy list. The objective is to determine the initial (constant) rate of settling, clarity of the supernatant liquid and the final proportion of sludge. 

Although comprehensive descriptions of equipment selection are given in this chapter the specifics of data analysis and equipment simulation are presented elsewhere. Chapter 4 provides practical methodologies, theories and principles that underpin the analysis of filtration, jar sedimentation and expression tests. Chapters 6 and 7 respectively present extensive descriptions of batch and continuous filter simulations, however, an introduction to simulation is described here. 

The consistent analysis of filtration, expression and jar sedimentation tests to allow the accurate determination of the parameters required for process simulation and the basic information needed for equipment selection... 

If we consider a well trajectory from surface to total depth (TD) it is sensible to look at the shallow section and the intermediate and reservoir intervals separately. The shallow section, usually referred to as top hole consists of rather unconsolidated sediments, hence the formation strength is low and drilling parameters and equipment have to be selected accordingly. 

The types of sedimentation encountered in process technology will be greatly affected not only by the obvious factors—particle size, hquid viscosity, sohd and solution densities—but also by the characteristics of the particles within the shiny. These properties, as well as the process requirements, will help determine both the type of equipment which will achieve the desired ends most effectively and the testing methods to be used to select the equipment. 

The design, construction and application of thickeners, centrifuges and filters is a specialised subject, and firms who have expertise in these fields should be consulted when selecting and specifying equipment for new applications. Several specialist texts on the subject are available Svarovsky (2001), Ward (2000) and Wakeman and Tarleton (1998). The theory of sedimentation processes is covered in Volume 2, Chapter 5 and filtration in Chapter 7. 

We have considered the common non-solvent-based methods of separating postconsumer plastics. However, except for depolymerization, only selective dissolution is capable of purifying bonded, blended, and fill plastics effectively. Dissolution of the polymer releases the impurities which are then removed by filtration, adsorption, or flotation/sedimentation. This yields polymers of high purity for reuse in original applications. The major drawback of a solvent system is Ae increased expense due to the complexity of equipment and higher energy requirements. 

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