Process-Design Considerations

Compared to distillation, the process-design methodology for adsoiption is neither as Advanced theoretically nor as a l-e compassing in ita details. This is because of the inherently more complex nature of adsorption processes, caused by the presence of the adsorbent, and the fact that substantially less design information is available in the literature. Nevertheless, there is a growing body of design criteria, techniques, and practices which one can profitably nse, and these are discussed in the following sections. 

The type 3 of adsorbent is selected based on considerations of the selectivity, the equilibrium capacity, the dynamic adsorption rate, case of regeneration, compatibility with the stream, coadsorption effects, type of process cycle and economics. Many of these have been discussed at some length above. 

Solid adsorbents are usually offered in particle sizes4 5 that range from a 100 x 200 mesh screen analysis to in. (0.64 cm) nominal size. The smaller-size particles are usually in an irregular granular form while the larger sizes are produced in regular shapes such ns spheres and cylinders. Shape ns a parameter will be discussed in more detail below. 

There ase two major considerations to be made when selecting the pcrticle size of the adsorbent. They are the effects of size on the mass transfer characteristics and on the pressure drop. Pressure drop through 

Statement Number Gas- or Vapur-Phess Procaines Liquid-Phase Processes  

The mass transfer rate for adsorption is also inversely proportional to the particle size to a power not less than unity. High mass transfier rales are desirable, since less adsorbent is required for the same separation. Therefore, the size of the packed bed can be reduced by selecting the smaller particle size. Since these two criteria are not compatible, trade fls must be made in the design. 

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Raw material usages per ton of carbon disulfide are approximately 310 m of methane, or equivalent volume of other hydrocarbon gas, and 0.86—0.92 ton of sulfur (87,88), which includes typical Claus sulfur recovery efficiency. Fuel usage, as natural gas, is about 180 m /ton carbon disulfide excluding the fuel gas assist for the incinerator or flare. The process is a net generator of steam the amount depends on process design considerations. 

Maintaining the chloride-containing liquid in contact with the stainless steel at <70°C. Process design considerations limit this approach. 

Examples of Reactors for Illustration of Process Design Considerations 283... 

EXAMPLES OF REACTORS FOR ILLUSTRATION OF PROCESS DESIGN CONSIDERATIONS... 

The first example involves flammability issues that are not specifically covered in this Guidelines book. However, the discussion here is highly important for safe process design considerations and represents a good example of the problems of scale-up from test data. Runaway reactions may indeed result in the production of flammable gases so an understanding of the scale-up problems is critical. 

Column process design specifies the separation, and sets column pressure, reflux, stages, and feed point. These in turn yield internal flows and reboiler and condenser duties. This chapter addresses the main column process design considerations. The column is optimized during the process design, and many times later during operation. Computer control continuously optimizes the column on-line. Both design and on-line optimization are also addressed in this chapter. 

Wisniewski, R., Boschetti, E., and Jungbauer, A. (1996). Process design considerations for large scale chromatography of biomolecules Biotechnol. Biopharma. Manuf. Process. Preserv. 2, 61-181. 

Process Design Considerations for Extractive Distillation Separation of Propylene-Propane... 

Ball, B. R. and M. D. Edwards (1992). Air stripping VOCs from groundwater. Process design considerations. Environmental Prog. 11,1, 39-48. 

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