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USE OF SINGLE IMPACT TO UNDERSTAND ATTRITION OF ALUMINA PARTICLES
thesisposted on 2017-12-06, 00:00 authored by M Rashid
In the alumina industry, the quality of alumina is commonly assessed on the basis of an important parameter called attrition index. Attrition is a mechanical property of brittle material (such as alumina, coal, salt, stone, sand, etc.) defining chipping characteristics of those materials while these are impacted on a hard surface. The attrition index attempts to quantify the tendency of the alumina to break down during handling and produce fines. An alumina is considered to be a strong alumina if it’s attrition index is less than 15%. Alumina particles with a poor attrition index produce more dust, leading to loss of product and environmental pollution during handling. Alumina strength is currently measured using the Forsythe technique which involves producing a fluidised column of alumina in a standardised arrangement and measuring the relative percentage decrease in the mass of particles of sizes <45 µm. The method of measuring the attrition index takes a long time, as well as, it requires a large amount of samples for the experiment is required. This research deals with experimental and hypothetical analysis of determination of attrition levels of alumina using recently developed a powder breakage rig that uses Ghadiri’s single impact principle and a Malvern Mastersizer. A systematic experimental procedure that uses the above mentioned equipment with single impact technique has been worked out. A large number of samples of alumina produced in Australia have been tested for attrition by single impact method using a range of air-stream (impacting/falling) velocity following the developed procedure. Analysis of experimental results reveals that particle breakage has a direct relationship with the air-stream velocity and higher impact velocity creates more fines. Analysis of test suggests that the tests were able to demonstrate a good discrimination between original and the attrited alumina. It has been revealed that breakage rate of alumina depends upon its initial particle size and also upon the strength of particles. It has also been proven that the methodology and the technique worked well, used small amounts of samples and the methodology is much faster. The research has revealed valuable scientific data on effect of variable speed of impact and the attrition index for the provided alumina samples. II The output of the research works would be helpful particularly for alumina refineries/industries as well as food industries, pharmaceuticals (powder technology). These industries will be highly benefited using the expected experimental model for assessing the attrition of alumina, and other bulk materials. The environmental agencies may be benefited understanding more accurately the pollution levels caused by the refineries and process industries.