T. R. Bott

Equilibrium and Rate Data for the Extraction of Lipids Using Compressed Carbon Dioxide

Abstract Equilibrium data are given for the solubilities in compressed C02 of the lipid components in freshly ground rape seed and of glycerol trioleate (a typical constituent of rape oil) at pressures up to 200 bar and temperatures 25 to 75C. Continuous flow tests in which a bed of ground rape seed was contacted with a stream of liquid CO2 at 25C and varied flow conditions are also reported. The results are collated in terms of an empirical mass transfer coefficient. A sharp change took place in the lipid concentration in the extractant stream leaving the bed when about 65% of the available oil had been extracted. This, and changes in the composition of the extract, are discussed, together with the use of this type of data for design purposes.

Problems Associated with the Development of Gas Extraction and Similar Processes

Abstract The potential scope and possible areas of application of gas extraction as a separation technique are outlined. Some problems to be overcome are discussed and the need for accurate physical data determinations and also operating experience at pilot plant level are stressed. Some work directed towards fulfilling these needs is described. Reliable economic, appraisal is essential before large scale design can be contemplated but is probably not practicable with sufficient accuracy until the above needs have been met.

The Use of Hydrocyclones for Small Particle Separation

Abstract Hydrocyclone operating characteristics have been studied by measuring the capacity for separating haematite, magnetite and silica particles suspended in water. The effects of viscosity (achieved by changing temperature) and throughput have been investigated and are satisfactorily correlated. The measurements demonstrate that under appropriate conditions of high pressure drop and low viscosity, particles below the usually accepted limit of 2 μm can be separated. Measured particle separation is expressed as a hydrocyclone efficiency, and its variation with particle size is shown. Anomalous results with magnetite and haematite suspensions are suggested to occur because these materials exist as agglomerates with effective density less than half that of the bulk material.

Some Liquid Thermal Diffusion Separations in a Continuous Thermogravitational Column

Abstract The separation of three binary mixtures on n-heptane-1,1,2,2-tetrachloroethylene, n-propanol-1,1,2,2-tetrachloroethylene, and n-heptane-methylcyclohexane was studied in a continuously operated thermogravitational column. The effects of feed rate, the ratio of top and bottom product rates, and temperature difference on separation were determined. The separations were found to be dependent on the feed rate with the maximum separation occurring at flow rates approaching zero. Over the range studied, the effect of top to bottom product flow rate ratio was found to be negligible. Temperature difference appeared to influence separation when finite flow rates were used.

Some Observations on Asymmetrical Separation in Thermal Diffusion Columns

Abstract Data have been obtained in steady-state batch operated thermogravitational separation columns using different binary mixtures to test the theory recently published by Morgado et al. The experimental results confirm that separations by thermal diffusion are asymmetrical except when the initial concentration is 0.5 and that the asymmetry is larger as the initial concentration deviates from 0.5 and as the separation potential increases.

Nonsymmetrical separations in thermal diffusion columns

Abstract The influence of the feed composition upon the actual degrees of separation attained at the top and bottom sections of a thermogravitational column is discussed using the classical phenomenological theory of Furry, Jones, and Onsager. It is shown that, except for a feed composition of C 0 = 0.5 (mass fraction), the separation profile is nonsymmetric, i.e., the separations in the top and bottom sections of the column are nonsymmetric with respect to the feed composition, the asymmetry increasing as the feed composition moves away from C 0 = 0.5. An equation for the determination of the optimum feed location as a function of the feed composition is derived.

Separation by Thermal Diffusion in a Rotary Column

Abstract A rotary thermal diffusion column with the inner cylinder rotating and the outer cylinder static was used to separate n-heptane-benzene mixtures at different speeds of rotation. The results show that the column efficiency depends on the speed of rotation. For the optimum speed the increase in efficiency relative to the static column was of the order of 8%. The role of the geometric irregularities in the annulus width on performance of the rotary column is also discussed.

A Method of Improving Liquid Thermal Diffusion Separations

Abstract By the use of a permeable, but immiscible, liquid layer in a liquid thermal diffusion column, it is possible to reduce remixing effects and hence improve separation. The technique is illustrated by using water as the permeable layer in the separation of benzene and carbon tetrachloride.