Considerations in design and operation

4 Considerations in design and operation (1) Wall losses and particle bouncing 

To minimize the particle bounce off effect, collection surfaces should also be selected carefully. Common types of impaction surfaces include membrane, fiberglass, silver membrane, Teflon and Nuclepore filter, and brass and stainless steel shim stock. Table 2.2 shows an example of the effect of selection of collection surface on the wall losses (Newton et al., 1990). In Table 2.2, the test aerosols are droplets of 1% CsCl plus 1% uranine. Three types of cascade impactors were used, including Mercer, Sierra Radial Slit Jet (SRSJ), and Lovelace Multi-Jet (LMJ). The occurrence of particle bouncing may be indicated by the presence of excess mass on the back-up filter. 

Particle bounce can be effectively controlled by coating an adhesives layer on the collection surface to keep collected particles from bouncing off the plates. Typical coating materials include Antifoam A, Hi-Vac silicone grease, Apiezon L, viscous oils, Vaseline, and glycerin. The typical thickness of the adhesive 

Cascade impactor Collection surface Total wall losses 

Sierra Radial Slit Jet Millipore membrane mixed esters of cellulose 19.0 

---

Particular features that require consideration in design and operation include ... 

Numerous factors must be taken into consideration in designing and operating an industrial water treatment facility. These include the following factors ... 

Research-Cottrell has demonstrated the commercial availability of limestone flue gas desulfurization on a 115 MW installation. Certain chemistry and process considerations were taken into account in designing and operating these systems. Methods have been developed to minimize the occurrence of potential problems. 

Evaporative light scattering detectors. Recently a new detector type has become commercially available, known as the evaporative light scattering detector (ELSD), but also referred to as the evaporative analyser or mass detector [40,41]. This detector is relatively simple in design and operation and is of considerable interest due to its apparent potential as a universal detector. 

A brief overview of selected evaporator designs including considerations for design and operation is given in Table 7-4. 

Depending on its severity, cavitation in pumps can result in loss of performance, severe erosion, vibration and noise. All these effects may be minimised by attention to design and operation, and by prudent use of erosion-resistant materials. Pumps vary considerably in design and function, and it is convenient to use the centrifugal pump to illustrate cavitation problems because of its common usage in fluid systems. 

This chapter covers safety considerations in design, installation, operation, and maintenance of selected process equipment and auxiliary systems. The first section (3.1) briefly discusses the impact of material selection on process equipment safety. Section 3.2 introduces the subject of corrosion and its control. The following more specific topics are then covered ... 

Commercial melt spinning processes involve substantial filament cooling, and control of the quench profile is one of the practical considerations for design and operation. Laboratory experiments are often designed to operate isothermally, however, typically by spinning in a temperature-controlled chamber with rapid solidification effected at a fixed position (by spinning into a water bath, for example) or by taking... 

The experience gained in design and operation of existing nuclear cogeneration plants was also taken into consideration when compiling the list of accidents. 

Examples of possible radiation sources in a research reactor to be taken into consideration in the programmes for radiation protection and radioactive waste management in design and operation are provided in Annex I. 

P13 l( Prepare a list of safety considerations for designing and operating chemical reactors. See the August ) 985 issue oJ Chemical Engineering Progress, P13-2b Review the example problems in this chapter and use u software package such as Polymath or MATLAB to carry out a parameter sensitivity analysis to answer the following What if..." questions. 

A major concern in reactor technology is associated with the products of the fission process. Fission products indude many radioactive isotopes that are important in a munber of ways. Their radioactivity can damage the fuel elements and thus limit file time fuel can be allowed to remain in the reactor. In addition, fission products are the sources of most of the radioactivity in irradiated fuel. Because of this latter consideration, reactor design and operation had to provide for control and containment of fission products under both normal and abnormal conditions. Adequate protection of the safety and health of the general population from the hazards of fission products became a requirement in power-reactor design. 

The selection of a particular type of reduction depends on technical feasibiUty and the economics of the process as well as on physicochemical considerations. In particular, the reducing agent should be inexpensive relative to the value of the metal to be reduced. The product of the reaction, RX, should be easily separated from the metal, easily contained, and safely recycled or disposed of. Furthermore, the physical conditions for the reaction should be such that a suitable reactor can be designed and operated economically. 

API, In Situ Air Sparging. Evaluation of Petroleum Industy Sites and Considerations for Applicability, Design, and Operation, Pubhcation No. 841-46090, American Petroleum Institute, Washington, D.C., 1995. 

Design and Operation ImpoiTant consideration in the design and operation of landfarming systems include (1) site selection, (2) site preparation, (3) waste charac tei istics, (4) method of waste application, (5) waste-application rate, (6) site management, and (7) monitoring. Important factors related to these design and operation considerations are reported in Table 25-75. 

Compressor surge is a phenomenon of considerable interest, yet it is not fully understood. It is a form of unstable operation and should be avoided in both design and operation. Surge has been traditionally defined as the lower limit of stable operation in a compressor and involves the reversal of flow. This reversal of flow occurs because of some kind of aerodynamic instability within the system. Usually a part of the compressor is the cause of the aerodynamic instability, although it is possible that the system arrangement could be capable of augmenting this instability. Figure 6-36 shows a typical... 

Other Considerations Moisture and eorrosives eontent are the major gas stream eharaeteristies requiring design eonsideration. Standard fabrie filters can be used in pressure or vaeuum serviee, but only within the range of about 640 millimeters of water eolumn (25 inehes of water eolumn). Well-designed and operated baghouses have been shown to be eapable of redueing overall partieulate emissions to less than 0.05 g/m (0.010 gr/fF), and in a number of eases, to as low as 0.002 to 0.011 g/m (0.001 to 0.0115 gr/fF). 

BS 2486 was first published in 1954, revised in 1978, and revised again in 1997. The 1978 revision contained two primary tables setting out water chemistry guidelines these were both quite broad in nature and covered FT (shell) boilers and WT boilers. This revision has now been withdrawn by BSI and replaced by the 1997 revision. The latest revision brings the technical content up to date, reflecting considerable additional experience gained in boiler design and operation by the subcommittee and 14 other bodies that provided contributions. 

In this chapter, consideration will be given to the basic principles underlying mass transfer both with and without chemical reaction, and to the models which have been proposed to enable the rates of transfer to be calculated. The applications of mass transfer to the design and operation of separation processes are discussed in Volume 2, and ihe design of reactors is dealt with in Volume 3. 

---