Distribution processes concepts

In this case, the co-solvent dosage rate is programmed in order to control the transient level of supersaturation in an effort to improve on the product crystal size distribution from simply dumping in all the solvent at the start of the batch. An experimental crystallizer within which a programmed microcomputer determines the set point of a variable speed-dosing pump is shown in Figure 7.7. Controlled co-solvent dosing improves the product crystal size, with a consequent increase in the filterability of the product. These process concepts are developed further in Chapter 9. 

NACD is an association of chemical distributor companies that purchase and take title of chemical products from manufacturers.62 Member companies process, formulate, blend, repackage, warehouse, transport, and market chemical products to industrial customers. NACD has developed the Responsible Distribution Process (RDP), which is similar in concept to the ACC Responsible Care code. 

The miniplant concept was proposed first by Ponton at the University of Edinburgh (UK) in 1993 [1,58-60], The potential benefits of distributed processing, as outlined above and reported elsewhere [2, 4], were identified, in particular focusing on an increase in process safety. However, the critical evaluation of the miniplant concept also revealed a number of potential drawbacks. For instance, the specific production costs of a small production units not only depend on reactor miniaturization, but are also determined by control instruments and other peripheral equipment. 

Mortimer86 has also recommended the two-dimensional method, using ethyl acetate-acetic acid-water and ethyl acetate-formamide-pyridine as developers. Methyl Cellosolve-ethyl methyl ketone-ammonium hydroxide may also be used. Since high content of water and the presence of an alcohol in the solvent mixture gave rise to diffuse spots, formamide was substituted for water. RF values relative to the movement of orthophosphate were determined and found to vary with the distance the solvent moved. Also, in complex mixtures, the presence of some esters resulted in elongation of other ester spots. This effect and the RF variation observed-do not conform to the concept of a liquid-liquid distribution process. 

The total number of columns and their distribution over the different sections is not fixed to eight with two columns per zone (2/2/2/2) as shown in Fig. 5.18. Another quite common set-up is 1/2/2/1 with only one column in sections I and IV. Naturally, this reduction in total number of columns can reduce investment costs. Conversely, the costs for fresh solvent will increase since regeneration of the solid phase has to take place in a shorter time and, therefore, requires a higher flow rate in section I. For a further decrease of column number, other continuous process concepts like VariCol or ISMB should be implemented (Section 5.3.5). 

Figure 9.4 Risk assessment for an aquatic environment based on a probabilistic procedure into which the concept of varying sensitivity in multispecies communities is incorporated (Nendza, Volmer and Klein, 1990). Exposure and effects are determined separately from experimental or, if not available, QSAR data. Physico-chemical data and information on bioaccumulation and biotransformation are the input for computer simulations of transport and distribution processes that estimate the concentrations of a potential contaminant in a selected river scenario, using, for example, the EXAMS model (Bums, Cline and Lassiter, 1982). For the effects assessment, the log-normal sensitivity distribution is calculated from ecotoxicological data and the effective concentrations for the most sensitive species are determined. The exposure concentrations and toxicity data are then compared by analysis of variance to give a measure of risk for the environment. Modified from Nendza, Volmer and Klein (1990) with kind permission from Kluwer Academic Publishers, Dordrecht.

From the above considerations, it is apparent that the non-stationary random process concept is being addressed, since it mostly applies to the natural circulation, where the t-h parameters are e q)ected to evolve over time of operation together with the relative distributions. Firstly, as first approach the failure criterion... 

The Borstar PP process concept combined with a special nucleation technology broadens the product flexibility in terms of MFI, molecular weight distribution, comonomer distribution, softness and rigidity. Due to the high operating temperature, the catalyst activity is typically 60 - 80 kg PP/g catalyst. 

The processes used commercially for the manufacture of film and sheeting materials are generaUy similar in basic concept, but variations in equipment or process conditions are used to optimize output for each type of film or sheeting material. The nature of the polymer to be used, its formulation with plasticizers (qv), fillers (qv), flow modifiers, stabilizers, and other modifiers, as weU as its molecular weight and distribution are aU critical to the... 

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