Design of the equipment

An atomic absorption spectrophotometer consists of a source of light 

The flame can be replaced as an atomization device by flame-less atomizers (graphite rod, graphite tube cuvette), but special working 

In order to atomize in the flame an element to be determined, the sample is sprayed via a pneumatic sprayer into a mixing chamber where it is mixed 

The monochromator used in AAS does not require the high resolving power 

An important disturbing factor in AAS is chemical interference . This can 

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Enhancements to the process may be required due to sub-optimal initial design of the equipment, or to implement new technology, or because an idea for improving the production system has emerged. De-bottlenecking would be an example of an... 

Classifiers can be grouped into horizontal current and vertical current types, or into mechanical, nonmechanical, sedimentation, and hydrauHc or fluidized-bed types depending on the design of the equipment. The available equipment, their sizes, capacities, and their uses are given in Table 5. 

Correcting Particle Segregation. The main techniques to consider when segregation problems are present are to change the material, change the process, or change the design of the equipment. 

Process simulators stop generally at the process specifications for the equipment. For the detailed mechanical design of the equipment, such as heat exchangers and distillation columns, stand-alone programs are often used. They make process calculations, size the equipment, calculate thermal and mechanical stresses, design mechanical support of the parts of the equipment, design inlet and outlet nozzles, etc. 

These data may be evaluated by selecting different nominal overflow rates (equivalent to settling rates) for each of the detention-time values, and then plotting the suspended-solids concentrations for each nominal overflow rate (as a parameter) against the detention time. For a specified suspended-sohds concentration in the effluent, a cui ve of overflow rate versus detention time can be prepared from this plot and used for optimizing the design of the equipment. 

These matters are organized into three major divisions the types of equipment, the criteria employed in the selection of equipment, and the sizing and design of the equipment. 

Unless a manufacturer/fabricator is guaranteeing the performance of an exchanger in a specific process service, they cannot and most likely will not accept responsibility for the fouling effects on the heat transfer surface. Therefore, the owner must expect to specify a value to use in the thermal design of the equipment. This value must be determined... 

The diameter of sheaves for well-measuring wire should be as large as the design of the equipment will permit but not less than 100 times the diameter of the wire. 

The extent to which the flow-sheet can be drawn up before any work is done on the detailed design of the equipment will depend on the complexity of the process and the information available. If the design is largely a duplication of an existing process, though possibly for a different capacity, the equipment performance will be known and the stream flows and compositions can be readily calculated. For new processes, and for major modifications of existing processes, it will only be possible to calculate some of... 

In any equipment where an interface exists between two phases (e.g. liquid-vapour), some means of maintaining the interface at the required level must be provided. This may be incorporated in the design of the equipment, as is usually done for decanters, or by automatic control of the flow from the equipment. Figure 5.16 shows a typical arrangement for the level control at the base of a column. The control valve should be placed on the discharge line from the pump. 

When optimizing a superstructure for a multiphase reaction, the rate of mass transfer must be specified. This will, to a large extent, be determined by the design of the equipment. Yet, the objective of the superstructure... 

As the flowsheet becomes more firmly defined, the detailed process and mechanical design of the equipment can progress. The control scheme must be added and detailed hazard and operability studies carried out. All this is beyond the scope of the present text. However, all these considerations might require the flowsheet to be readdressed if problems are uncovered. 

Separations are an important phase in almost all chemical engineering processes. Separations are needed because the chemical species from a single source stream must be sent to multiple destinations with specified concentrations. The sources usually are raw material inputs and reactor effluents the destinations are reactor inputs and product and waste streams. To achieve a desired species allocation you must determine the best types and sequence of separators to be used, evaluate the physical or chemical property differences to be exploited at each separator, fix the phases at each separator, and prescribe operating conditions for the entire process. Optimization is involved both in the design of the equipment and in the determination of the optimal operating conditions for the equipment. 

Propose changes in the procedure and design of the equipment to decrease the percent error. 

For example, a high yield of an intermediate in a consecutive reaction depends sensitively on the instant in time when the reaction is quenched. For such applications, the fast response of the ATR method more than compensates for deficiencies related to sensitivity when the ATR technique is compared with other methods. The design of the equipment depends on the specific requirements of the application. 

Baffle pitch, or distance between baffles, normally is 0.2-1.0 times the inside diameter of the shell. Both the heat transfer coefficient and the pressure drop depend on the baffle pitch, so that its selection is part of the optimization of the heat exchanger. The window of segmental baffles commonly is about 25%, but it also is a parameter in the thermal-hydraulic design of the equipment. 

The design of the equipment used in our laboratory for the purification is shown in Figure 19.4. Spectrograde acetonitrile is successively distilled three times from P205 under vacuum at room temperature, with the final distillation... 

Frontal polymerization carried out as described above can be turned into a continuous process. In order to do this, it is necessary to move the newly formed polymer and the reactive mixture in the direction opposite to the direction of spreading of a thermal front at a velocity equal to the velocity of the front development to feed the reactor with a fresh reactive mass.254 Control of the process, choice of process parameters and proper design of the equipment require solving the system of equations modelling the main physical and chemical processes characteristic of frontal reactions. 

For the calculation of the heat transfer coefficient of the external film, some models are also available [2], describing the hydraulics of the flow in the jacket or in the half-welded coils. The results depend strongly on the technical design of the equipment. Thus, the direct experimental determination is mostly preferred. 

Good design practices to ensure that the mechanical design of the equipment is suited to normal operation, startup, shutdown, and emergency conditions (for example, ensuring that vessel wall thickness, design temperature and pressure, corrosion allowance, etc., adhere to industry or national codes and standards) ... 

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