No description available.

No description available.

No description available.

The thesis is concerned with the development and testing of a mathematical model of a distillation process in which the components react chemically. The formaldehyde-methanol-water system was selected and only the reversible reactions between formaldehyde and water giving methylene glycol and between formaldehyde and methanol producing hemiformal were assumed to occur under the distillation conditions. Accordingly the system has been treated as a five component system. The vapour-liquid equilibrium calculations were performed by solving iteratively the thermodynamic relationships expressing the phase equilibria with the stoichiometric equations expressing the chemical equilibria. Using optimisation techniques, the Wilson single parameters and Henry's constants were calculated for binary systems containing formaldehyde which was assumed to be a supercritical component whilst Wilson binary parameters were calculated for the remaining binary systems. Thus the phase equilibria for the formaldehyde system could be calculated using these parameters and good accuracy was obtained when calculated values were compared with experimental values. The distillation process was modelled using the mass and energy balance equations together with the phase equilibria calculations. The plate efficiencies were obtained from a modified A.I.Ch.E. Bubble Tray method. The resulting equations were solved by an iterative plate to plate calculation based on the Newton Raphson method. Experiments were carried out in a 76mm I.D., eight sieve plate distillation column and the results were compared with the mathematical model calculations. Overall, good agreement was obtained but some discrepancies were observed in the concentration profiles and these may have been caused by the effect of limited physical property data and a limited understanding of the reactions mechanism. The model equations were solved in the form of modular computer programs. Although they were written to describe the steady state distillation with simultaneous chemical reaction of the formaldehyde system, the approach used may be of wider application.

No description available.

No description available.

A fluidized bed process development unit of 0.8 m internal diameter was designed on basis of results obtained from a bench scale laboratory unit. For the scaling up empirical models from the literature were used. The process development unit and peripheral equipment were constructed, assembled and commissioned, and instruments were provided for data acquisition. The fluidization characteristics of the reactor were determined and were compared to the design data. An experimental programme was then carried out and mass and energy balances were made for all the runs. The results showed that the most important independent experimental parameter was the air factor, with an optimum at 0.3. The optimum higher heating value of the gas produced was 6.5 MJ/Nm3, while the thermal efficiency was 70%. Reasonably good agreement was found between the experimental results, theoretical results from a thermodynamic model and data from the literature. It was found that the attainment of steady state was very sensitive to a continuous and constant feedstock flowrate, since the slightest variation in feed flow resulted in fluctuations of the gas quality. On the basis of the results a set of empirical relationships was developed, which constitutes an empirical model for the prediction of the performance of fluidized bed gasifiers. This empirical model was supplemented by a design procedure by which fluidized bed gasifiers can be designed and constructed. The design procedure was then extended to cover feedstock feeding and gas cleaning in a conceptual design of a fluidized bed gasification facility. The conceptual design was finally used to perform an economic evaluation of a proposed gasification facility. The economics of this plant (retrofit application) were favourable.

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No description available.

From an examination of the literature relating to the catalytic steam reforming of hydrocarbons, it is concluded that the kinetics of high pressure reforming, particularly steam-methane reforming, has received relatively little attention. Therefore because of the increasing availability of natural gas in the U.K., this system was considered worthy of investigation. An examination of the thermodynamics relating to the equilibria of steam-hydrocarbon reforming is described. The reactions most likely to have influence over the process are established and from these a computer program was written to calculate equilibrium compositions. A means of presenting such data in a graphica1 form for ranges of the operating variables is given, and also an operating chart which may be used to quickly check feed ratios employed on a working naphtha reforming plant is presented. For the experimental kinetic study of the steam-methane system, cylindrical pellets of ICI 46-1 nickel catalyst were used in the form of a rod catalyst. The reactor was of the integral type and a description is given with the operating procedures and analytical method used. The experimental work was divided into two parts, qualitative and quantitative. In the qualitative study the various reaction steps are examined in order to establish which one is rate controlling. It is concluded that the effects of film diffusion resistance within the conditions employed are negligible. In the quantitative study it was found that at 250 psig and 6500C the steam-methane reaction is much slower than the CO shift reaction and is rate controlling. Two rate mechanisms and accompanying kinetic rate equations are derived, both of which represent 'chemical' steps in the reaction and are considered of equal merit. However the possibility of a dual control involving 'chemical' and pore diffusion resistances is also expressed.