Process Design and Engineering

Process flowsheets for separations of numerous metals have been published.Synthesis and design of such processes for a given fned stream require consideration of the following factors  

A practical extractant omst also be subject to regeneration. The extraction must be reversible such thel snipping is possible with otinimal consumption of reagents. Stripping should yield a porified and concentrated foou of the metal product. 

FIGURE 8.6-1 Solvent extraction circuit of the Falconbridge Nikkelvert A/S matte leach plant for separation of iron, copper, and cobell. From Ref. 6, with permission. 

While efficiency is a factor in equipment selection, mechanical considerations often provide the determining criteria. One must always be sure to minimize solvent losses, and concern about entrainment and emulsion formation can dictate the mode of operation if not the choioe of contactor. For example, power input for mixing may be titrated or the less viscous phase chosen to be coiuinuons to ensure good phase disengagement. 

Many of these and other practical aspects of process design and operation, such as appropriate male rials of construction, prevention of cnid formation, effiuent treatment methods, and typical procase costs, are discussed by Riicey and Ashbrouk.5 

Choice of Diluent, Modifiers, and Extractant Concentration. The formulation and composition of the organic-phase solution play a major role in determining both the chemical and physical perfotituince characteristics of an extraction system. The use of modifiers and mixed extractants alters both equilibrium and kinetics properties and can have a strong infiuence on intetfocial phenomena. It b patticulariy important to formuiate a system that minimizes organic solubility in the aqueous phase, promotes phase disengagement, and prevents emulsion formation. Problems in any of these areas can quickly render a process uneconomic or infeasible. 

Choice of Process Configuration. The sequence of processing steps and flowsheet configuration must be selected concurrently with the choice of extraction chemistry. Some of the established heuristics of separation process synthesis may be helpful here. For example, in multimetal fractionation it is probably better to tiy selective stripping from a single organic stream than to do multiple selective-extraction oper- 

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Woods D.R (1995) Process Design and Engineering Practice, Prentice Hall, New Jersey. 

Development of solvent extraction processes in the petroleum industry and theoretical aspects of solvent extraction are reviewed. Six extraction processes which have received industrial acceptance are described and performance characteristics of furfural, phenol, and Duosol processes are compared. Data are presented to demonstrate the applicability of adsorption analyses for stock evaluation and prediction of commercial extraction yields. Correlations for predicting solvent requirements and layer compositions and process design and engineering considerations are included. The desirability of further fundamental work to facilitate design calculations from physical data is suggested. 

A Phase 0 Design is the starting point for a complete process design and engineering specification (Phase 1) and is also the basis for the preliminary cost estimate required to optimize a process and/or decide to continue or cancel it. 

The Case Study initiated with the initial Plan of Action in Section 5.3 has evolved into a Phase 0 Design Package and now a Preliminary Cost Estimate is required to confirm the viability of the project and, if required, request funds for the preparation of a Detailed Process Design and Engineering Specification (Phase 1) and an appropriation quality estimate. 

D.R. Woods, Data for Process Design and Engineering Practice, PTR Prentice Hall, Englewood Cliffs, NJ, 1995. 

For flow ratios of 1.5 to 3 in direct gas-liquid heat exchange, a packed tower is generally selected to effect the heat transfer and maintain a reasonable pressure drop. See Table 3-18 of D.R. Woods, Process Design and Engineering Practice., p. 3-73, Prentice Hall (1995). 

The chemical process industries represent one of the most technically complex sectors of our society. To fulfill the purposes outlined in Section 1.2, both chemical engineers and chemists at all degree levels are needed. These chemical professionals work in both fundamental and applied research in process and product development, in process design and engineering, in manufacturing, in sales and in administration, frequently at the highest level. A distribution of chemical professionals according to job function is presented in Table 1.3. 

Process Design and Engineering Practice qualitative rating on the corrosivity of pure components contacting carbon steel, copper, and 316 stainless steel. These can be used for an initial screen to sensitize engineers to the potential hazard (Woods, 1994). 

D. R. Woods, Data for Process Design and Engineering Practice. Englewood Cliffs, NJ Prentice Hall, 1994. Gives order of magnitude values of properties for more than 1200 compounds and a guide to sources for more accurate data. This includes the PDEP Corrosion Index referred to in Table 13.16. 

For details, see chapter on heat transfer. Reproduced from Rules of Thumb for Process Design and Engineering Practice with permission from Donald R. Woods, 2001. 

Custom (pan) pelletizing, full-scale testing, process design and engineering)... 

Another source is provided by the ratings of the National Fire Protection Association (NFPA), which are tabulated for many chemicals in Data for Process Design and Engineering Practice (Woods, 1995). The first of three categories is titled Hazard to Health and is rated from 0 to 4, with 0 meaning harmless and 4 meaning extremely hazardous. 

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