Physico-Chemical Studies on Dusts of Small Particle Size

Jaap, William J (1959) Physico-Chemical Studies on Dusts of Small Particle Size. PhD thesis, University of Glasgow.

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A brief description is given of the respiratory system and the way in which it deals with inhaled dusts; of the methods employed for sampling and analysing airborne dusts; of the methods employed in mines to suppress the fine dust particles; and of the mechanism of atomisation of aqueous media applied in dust suppression. An apparatus has been developed for the examination of the settling characteristics of fine dust clouds. This consists of a chamber fitted with a pair of photoelectric cells and connected to a recording instrument for the continuous measurement of the dust concentration. Dust present in the chamber intercepts some of the light reaching one of the cells and produces a differential current which is measured by the recorder. A thermal precipitator is incorporated in the apparatus for the calibration of the photoelectric cell system and also to enable samples of the dust clouds to be withdrawn for microscopic examination. Sedimentation studies have been carried out using various dusts. The results show that the dusts sediment rapidly over the first few hours, after which the rate of disappearance is less rapid until only the very small particles remain, when sedimentation is very slow. A compressed-air spray has been developed and calibrated, and the effects of alterations to the variables studied. The results indicate that the nozzle dimensions have no effect on atomisation, hut atomisation increases as the air rate and the velocity differential between air and water are increased. Atomisation decreases slightly as the sampling distance from the nozzle is increased. The effects of the air blast used for atomisation on the sedimenting dust cloud, have been studied and two theories have been put forward to account for them. The results show that more dust is removed than is predicted by theory. The effect of the water spray on the sedimenting dust cloud has been studied. The results indicate that a proportion of the dust cloud is removed. The amount of dust removed is increased as the atomisation, droplet velocity and duration of spraying are increased. The effect of the compressed-air spray on the size distribution of the dust in the suspended cloud has been investigated. The results show that the air blasts have little effect on the size distribution of the dust cloud, but the water sprays remove a proportion of all sizes of particles. A greater percentage of the >0.83mu particles is removed as the droplet diameter is decreased. The percentage of <0.83mu particles removed decreases as the droplet diameter is decreased. The results also show that as the duration of spraying is increased, the percentage of >0.83mu particles removed is increased whereas the percentage of <0.83mu particles removed is decreased. An instrument has been designed and made (the H-J sampler) which enables fairly large samples of airborne mine dusts to be collected from the atmosphere of the pit. Trials carried out underground have given good results. A comparison has been made with another manufactured sampler (the Hexhlet, designed by Wright) and it has been found that the H-J sampler gives larger samples and that this outweighs the advantage of the elutriater on the Hexhlet.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Analytical chemistry
Date of Award: 1959
Depositing User: Enlighten Team
Unique ID: glathesis:1959-79334
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 10:42
Last Modified: 05 Mar 2020 10:42

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