Science of Industrial Processes – Laboratory Scale
November 30th, 2012
Preface
This covers work to elucidate the main non-scale dependent mechanisms at work in the various major processes, where these were not already in the open literature, and to render them in a mathematical form to be used in the FKT equations[1].
In the 1960s the industrially most important, previously unknown or sparsely known fields were free radical reaction mechanisms in hydrocarbon, hydroxycarbon and chlorohydrocarbon systems; catalytic and other surface mechanisms for the same systems, carbon and soot formation in these systems and also fuel combustion (oxidation processes); two-phase flows of organic liquids and polymers where the vapour component is not air or steam (as in the heavily researched steam boiler field), and the liquids not diesel (as in the heavily researched fuel systems – but see link to soot forming in diesel combustion).
Polymer morphology including crystalline and pre-crystalline oriented forms, chain conformation and cross-linking kinetics are fundamental to a detailed understanding of the solid state properties of polymers and therefore the performance of commercial products. This again continues to be a heavily researched topic, but from about the 1980s onwards the main focus of commercial interest has been on composite filled varieties (based primarily on glass fibres and talc) because these give strength and stiffness properties rivalling those of the softer metals, and mouldabilities rivalling those of metal casting in its variety of shape, but much cheaper and lighter with production rates up to a million times greater.
The papers and patents on Self Assembly of Fibre Reinforcement (SAFIRE) (1988-2000) will describe the basic phenomena involved in all the main commercial applications of this technology (link). Polymer morphology has not of course been ignored because (a) it is affected by the presence of relatively high concentrations of fibres, and (b) because in synthetic fibres in particular the rate of processing has profound effects (usually beneficial) on strength and stiffness. Moreover, the ability to dye (or pigment) post formed polymer products is perhaps the most sensitive indicator of their morphology available on a mass, commercially important scale.
Interpreting “reaction” to mean supra molecular as well as molecular reaction, then as stressed in the Preface to this section, reaction instability is of a critical importance to the over-riding goals of smooth running of a process and consistency of product.
Extreme versions of chemical reaction instability on the industrial scale are (a) sudden extinction and (b) explosion. Intermediate instabilities, not always noticed on individual streams of a large plant are oscillations including vibrations (e.g. of fibre thread-lines), pulsations (e.g. in extrusions and other pumping situations), as well as oscillations in the chemical reaction itself. A complete analysis and experimental verification of this latter phenomenon on both the laboratory and industrial scales has been given for the chlorination of hydrocarbons and extended to other systems (see Royal Society paper and American Society paper).
Non-uniformity is endemic in all confined flow processes because at the wall of a vessel or pipe or extruder, the fluid is stationary. Occasionally a fluid containing solid elements will slip, giving rise to non-uniformity in time. More generally hydrocarbons close to the walls of a vessel will react to unwanted by products, the most pernicious being carbon attached to the surface which gradually degrades it, or loose particulates in the form of soot, which contaminates the product stream (or the exhaust in the case of internal combustion). The papers in this category show how the combination of experiment and mathematical model leading to redesign can greatly mitigate this problem.
References
[1] Flow Kinetics Transfer equation (FKT) – the fundamental equation for Process Manufacture [see Mathematics & Computation].