Pilot Plant Work

Basic physical and thermodynamic property data are essential for the design and selection of equipment. Further, the state-of-the-art design of many kinds of equipment may require more or less extensive laboratory or pilot plant studies. Equipment manufacturers who are asked to provide performance guarantees require such information. As indicated in Appendix C, typical equipment suppliers questionnaires may require the potential purchaser to have performed such tests. 

Some of the more obvious areas definitely requiring test work are filtration, sedimentation, spray, or fluidized bed or any other kind of solids drying, extrusion pelleting, pneumatic and slurry conveying, adsorption, and others. Even in such thoroughly researched areas as vapor-liquid and liquid-liquid separations, rates, equilibria, and efficiencies may need to be tested, particularly of complex mixtures. A great deal can be found out, for instance, by a batch distillation of a complex mixture. 

In some areas, suppliers may make available small-scale equipment, such as leaf filters, that can be used to determine suitable operating conditions, or they may do the work themselves at suppliers facilities (e.g., use of drying equipment). 

Pilot plant experimentation is expensive and can be time consuming, delaying the introduction of the product in the marketplace. There have been trends and reports of recent successes whereby extensive pilot plant research has been bypassed. One such study involved the manufacture of bisphenol A in which laboratory work bypassed the pilot plant stage and a full-scale production unit was designed and operated successfully. This is not recommended, but using some laboratory research and simulation, may make it possible to reduce or eliminate expensive pilot plant work. However, confidence must be developed in using simulation to replace pilot plant work and this is obtained only through experience. 

105 Raw Material Feed (Typical of the analyses required for a liquid) Assay, wt per cent min  

The need for knowledge of basic physical properties as a factor in equipment selection or design requires no stressing. Beyond this, the state-of-the-art of design of many kinds of equipment and 

For a solid material chemical assay, level of impurities and its physical characteristics, such as specific density, bulk density, particle size distribution and the like are included. This physical shape information is required to assure that adequate processing and material handling operations will be provided. 

Here again specifications would be similar to that of the raw materia in equivalent or sometimes greater detail as often trace impurities affect the marketability of the final product. 

For solid products, type of container or method of shipment and loading facilities should be outlined.  

IOS Raw Material Feed (Typical of the analyses required for a liquid) Anay. wt per cent min -------------------------------------------------------------------------------------- 

Impurities, wt per cent max -Characteristic specifications Specific gravity---------------- 

Reaction rate with established reagent. Acid number --------------------------------------- 

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Both American Enka (87) and Courtaulds set up pilot-plant work in the eady 1980s with the objectives of developing fiber spinning and solvent... 

Historically, the annual consumption of nickel fluoride was on the order of a few metric tons. Usage is droppiag because nickel fluoride is Hsted ia the EPA and TSCA s toxic substance iaventory. Nickel fluoride tetrahydrate is packaged ia 200—500-lb (90.7—227-kg) dmms and the 1993 price was 22/kg. Small quantities for research and pilot-plant work are available from Advance Research Chemicals, Aldrich Chemicals, Johnson/Matthey, Pfalt2 and Bauer, PCR, and Strem Chemicals of the United States, Fluorochem of the United Kingdom, and Morita of Japan. 

Scheduling. A significant concern ia all pilot-plant work is minimizing the time iavolved between project iaception and meaningfiil data... 

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. 

The yield in a chemical reaction determines the quantities of materials in the material balance. Assumed yields are used to obtain approximate exploratoiy estimates. In this case, possible ranges should be given. Firmer estimates require yields based on laboratoiy or, preferably, pilot-plant work. 

Selection of Equipment If a new product is being considered, the preliminaiy study must be highly detailed. Laboratory or pilot-plant work must be done to establish the controhing factors. The problem is then to select and instaU equipment which 1 operate for quantity production at minimum overall cost. Most equipment vendors have pilot equipment available on a rental basis or can conduct test runs in their own customer-demonstration facilities. 

Few mechanisms of liquid/liquid reactions have been established, although some related work such as on droplet sizes and power input has been done. Small contents of surface-ac tive and other impurities in reactants of commercial quality can distort a reac tor s predicted performance. Diffusivities in liquids are comparatively low, a factor of 10 less than in gases, so it is probable in most industrial examples that they are diffusion controllech One consequence is that L/L reactions may not be as temperature sensitive as ordinary chemical reactions, although the effec t of temperature rise on viscosity and droplet size can result in substantial rate increases. L/L reac tions will exhibit behavior of homogeneous reactions only when they are very slow, nonionic reactions being the most likely ones. On the whole, in the present state of the art, the design of L/L reactors must depend on scale-up from laboratoiy or pilot plant work. 

Laboratory investigations may possibly establish reaction mechanisms, but quantitative data for design purposes require pilot plant work with equipment of the type expected to be used in the plant. 

Rough correlations have been made of minimum fluidization velocity, minimum bubbling velocity, bed expansion, bed level fluctuation, and disengaging height. Experts recommend, however, that any real design be based on pilot plant work. 

Identify the predominant rate-controlling mechanism kinetic, mass or heat transfer. Choose a suitable reactor type, based on experience with similar reactions, or from the laboratory and pilot plant work. 

As noted in Chapter 1, the priorities in batch processes are often quite different from those in large-scale continuous processes. Particularly when manufacturing specialty chemicals, the shortest time possible to get a new product to market is often the biggest priority (accepting that the product must meet the specifications and regulations demanded and the process must meet the required safety and environmental standards). This is particularly true if the product is protected by patent. The period over which the product is protected by patent must be exploited to its full. This means that product development, testing, pilot plant work, process design and construction should be fast tracked and carried out as much as possible in parallel. 

Bucky Badger has been investigating the residence time characteristics of a reactor that he plans to use for pilot plant work. He suggests... 

Another plant using dilute sulfuric acid for hydrolysis was built at Fullerton, Louisiana, in 1916 to produce daily 5,000 gallons of 188-proof alcohol. The Forest Products Laboratory, Madison, Wisconsin, assisted in the development and pilot plant work of both the Georgetown, and the Fullerton plants. The results of the work at these plants and in a Forest Products Laboratory pilot plant have been described by F. W. Kressman in U. S. Department of Agriculture Bulletin No. 983 (1922). This bulletin describes pilot plant investigations on the following variables ... 

Recycling of Acid Wood Sugar Solutions. The procedure used in this pilot plant work has involved the use of one hydrolyzer. A number of other procedures are possible. 

Part of the general increase in technology arose from improved techniques in pilot plant operation and interpretation. Studies with small quantities of material provided reliable data for the design of large scale units which could be counted upon to operate successfully. This pilot plant work was greatly facilitated by the parallel development of modern instruments and automatic controls. 

Materia] Balance of a Chlorination Process with Recycle A plant for the chlorination has the flowsheet shown. From pilot plant work, with a chlorine/benzene charge weight ratio of 0.82, the composition of the reactor effluent is... 

Some basic design features are the avoidance of sharp bends, a minimum of line fittings, provision for cleanout, and possibly electrical grounding. In many cases equipment suppliers may wish to do pilot plant work before making final recommendations. Figure... 

Batch fluidized bed dryers are made in quite small sizes, of the order of 100 lb/hr of feed as the data of Table 9.14(a) show, and are suitable for pilot plant work. 

Pilot plant work is essential as a basis for full scale design. It may be directed to finding suitable velocities, temperatures and drying times, or it may employ more basic approaches. The data provided for Example 9.8, for instance, are of particle size distribution, partial pressure of water in the solution, and heat and mass transfer coefficients. These data are sufficient for the... 

The main variables in the operation of atomizers are feed pressure, orifice diameter, flow rate and motive pressure for nozzles and geometry and rotation speed of wheels. Enough is known about these factors to enable prediction of size distribution and throw of droplets in specific equipment. Effects of some atomizer characteristics and other operating variables on spray dryer performance are summarized in Table 9.18. A detailed survey of theory, design and performance of atomizers is made by Masters (1976), but the conclusion is that experience and pilot plant work still are essential guides to selection of atomizers. A clear choice between nozzles and spray wheels is rarely possible and may be arbitrary. Milk dryers in the United States, for example, are equipped with nozzles, but those in Europe usually with spray wheels. Pneumatic nozzles may be favored for polymeric solutions, although data for PVC emulsions in Table 9.16(a) show that spray wheels and pressure nozzles also are used. Both pressure nozzles and spray wheels are shown to be in use for several of the applications of Table 9.16(a). 

The other mixing operations of the list require individual kinds of equipment whose design in some cases is less quantified and is based largely on experience and pilot plant work. Typical equipment for such purposes will be illustrated later in this chapter. Phase mixing equipment which accomplishes primarily mass transfer between phases, such as distillation and extraction towers, also are covered elsewhere. Stirred reactors are discussed in Chapter 17. 

Safety factors for scale up from laboratory leaf tests are difficult to generalize. On the basis of pilot plant work, adjustments of 11-21% are made to plate-and-frame filter areas or rates, and 14-20% to continuous rotary filters, according to Table 1.4. 

A detailed design of an ARD extractor based on pilot plant work is presented by Misek and Marek (in Lo et al., 1983, pp. 407-417). The design and operating parameters of the ARD extractor are related to the vessel diameter D (mm) thus ... 

The components of a commercial process employing chromatographic separation are represented on the flowsketch of Figure 15.28. The process is intermittent with very short cycles. The cost breakdown of a plant for the separation of a- and j8-pinenes is given in Table 15.7, which is based on pilot plant work in a 4 in. dia column. That company is no longer in that business thus the test... 

Other information deduced from pilot plant work is ... 

Ail answers to process design questions cannot be put into a book. Even at this late date in the development of the chemical industry, it is common to hear authorities on most kinds of equipment say that their equipment can be properly fitted to a particular task only on the basis of some direct laboratory and pilot plant work. Nevertheless, much guidance and reassurance are obtainable from general experience and specific examples of successful applications, which this book attempts to provide. Much of the information is supplied in numerous tables and figures, which often deserve careful study quite apart from the text. 

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