Process problems

If the operational problem is one of cross-contamination, this is most likely due to a funnel flow pattern. If this is the case, changing to mass flow should correct it. It should be recognised that even with mass flow there will be a velocity distribution across the vessel, so achieving perfect first-in-flrst-out is seldom achievable. 

If there are problems with inventory control, this is usually a signal that the flow pattern needs to be changed from funnel flow to mass flow (Pittenger et al. 1999). Sometimes a weighing system is needed in order to provide proper inventory information. 

If the bin is being used as a processing vessel such as for drying, purging or conditioning of the bulk solid, non-uniform processing may occur. This is usually an indication that a funnel flow pattern needs to be changed to mass flow. Sometimes an insert is used in such applications, but this must be done with caution (Carson et al. 1995). 

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As mentioned in Chapter 2, the numerical solution of the systems of algebraic equations is based on the general categories of direct or iterative procedures. In the finite element modelling of polymer processing problems the most frequently used methods are the direet methods. 

As the particles grow, they require more soap to remain stable. If soap is not available the particles can destabilize, causing product and process problems. 

Microscopists in every technical field use the microscope to characterize, compare, and identify a wide variety of substances, eg, protozoa, bacteria, vimses, and plant and animal tissue, as well as minerals, building materials, ceramics, metals, abrasives, pigments, foods, dmgs, explosives, fibers, hairs, and even single atoms. In addition, microscopists help to solve production and process problems, control quaUty, and handle trouble-shooting problems and customer complaints. Microscopists also do basic research in instmmentation, new techniques, specimen preparation, and appHcations of microscopy. The areas of appHcation include forensic trace evidence, contamination analysis, art conservation and authentication, and asbestos control, among others. 

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. 

I onsucrose Components from Storage or Damag e of Beets. Some nonsucrose components are associated with the conditions under which the beets have been stored prior to processing, as respiration products or products of microbial attack In either case they direcdy and indirectly reduce sucrose yield and may cause other processing problems. Glucose and fmctose have already been discussed and can derive from either source. 

Producing the chlorobenzenes higher than mono- can pose significant process problems because production must match the market or the unwanted material must be destroyed. Use must be found for the HCl by-product and CI2 must be available at a reasonable price. 

The differences in composition between water-borne and solvent-bome air-drying paints necessitate change in driers and drier combinations. Since traditional driers are dissolved in mineral spirits, xylene, or other aUphatic/aromatic solvents, they are not readily dispersed in an aqueous system. If traditional driers are used, they must be dissolved in the vehicle before neutralization, which may result in a severe viscosity increase and processing problems. 

Wei, C.N., Diagnose Process Problems, Chemical Engineeiing Piogiess, September 1991, 70-74. (Parameter estimate monitoring for fault detection)... 

One processing problem is presented by the roasting of coffee. This releases smoke, odor, and particulate matter. The particulate matter, primarily dusty and chaff, can be removed with a cyclone. The smoke and... 

Because of processing problems 2-chloroethyl vinyl ether has now been replaced with other cure site monomers. These include vinyl and allyl chloracetates and allyl glycidyl ether. 

Processing problems associated with the shortlist materials. 

Use the material balance for each unit operation to pinpoint the problem areas associated with a process. The material-balance exercise may have brought to light the origin of wastes with high treatment costs, or may indicate which wastes are causing process problems in which operations. The material balance should be used to set priorities for long-term waste reduction. 

The models presented correctly predict blend time and reaction product distribution. The reaction model correctly predicts the effects of scale, impeller speed, and feed location. This shows that such models can provide valuable tools for designing chemical reactors. Process problems may be avoided by using CFM early in the design stage. When designing an industrial chemical reactor it is recommended that the values of the model constants are determined on a laboratory scale. The reaction model constants can then be used to optimize the product conversion on the production scale varying agitator speed and feed position. 

The most important objective of the pilot study is testing and improving the integration plan. Deficiencies may be uncovered in the design or installation process. Problems with the installation will usually be evident immediately, as will some design problems other design problems may not be evident for sometime. 

For the record let it be known that in the past (half century ago) about 80% of fabricating problems was due to inadequate drying of all types of plastics when a processing problem developed. Now it could be down to 50%. 

When water (a Newtonian liquid) is in an open-ended pipe, pressure can be applied to move it. Doubling the water pressure doubles the flow rate of the water. Water does not have a shear-thinning action. However, in a similar situation but using a plastic melt (a non-Newtonian liquid), if the pressure is doubled the melt flow may increase from 2 to 15 times, depending on the plastic used. As an example, linear low-density polyethylene (LLDPE), with a low shear-thinning action, experiences a low rate increase, which explains why it can cause more processing problems than other PEs. The higher-flow melts include polyvinyl chloride (PVC) and polystyrene (PS). 

Takaes, Lajos, Stochastic Processes, Problems and Solutions, Methuen s Monographs on Applied Probability and Statistics, John Wiley and Sons, Inc., New York, 1960. 

Continuous emulsion polymerization systems are studied to elucidate reaction mechanisms and to generate the knowledge necessary for the development of commercial continuous processes. Problems encountered with the development of continuous reactor systems and some of the ways of dealing with these problems will be discussed in this paper. Those interested in more detailed information on chemical mechanisms and theoretical models should consult the review papers by Ugelstad and Hansen (1), (kinetics and mechanisms) and by Poehlein and Dougherty (2, (continuous emulsion polymerization). 

Process problems include slag formation, ash removal, and process control because of the heterogeneous solid waste feed. These problems have been managed to some degree by "overdesigning" the plant, with the result that combustion of municipal solid waste is not economically competitive in areas where low-cost electricity or landfills for waste disposal are available. The future cost of electricity is difficult to predict. However, the steady decrease in the availability of landfills portends increasing use of this process to dispose of municipal wastes, particularly in large cities. 

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