DETERMINATION OF ASH CONTENT OF SOME NIGERIAN COALS USING GAMMA TRANSMISSION MEASUREMENTS BY

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Date
2007-12
Authors
OMEJE, CORNELIUS UCHENNA
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Abstract
An experimental facility which utilizes gamma transmission technique has been developed for routine determination of ash content of coal. It consists of 241Am and 137Cs radioisotope sources and NaI(Tl) detector coupled with single channel analyzer, characterized with relatively high sensitivity and with windows set at appropriate energy for determination of transmitted γ-counts from the sample. The facility is based on principles of Absorption and attenuation of low energy -rays which depend on the mean atomic number of elements and thus can be used to determine the ash content of coal since the mean atomic number of ash is greater than that of coal matter. The system was calibrated using simulated standard prepared by doping graphite powder with different concentrations of incombustible elements in their compound form. The calibration coefficients determined from measurements of simulated standards containing different amounts of ash in single and dual energy mode were used for the determination of ash content of various coal samples obtained from different areas in Nigeria namely; Okaba, Ogboyoga, Okpara, Ogwashi/Azagba, Owukpa, Lafia-obi and Inyi. The results compare reasonably well with results from chemical assay of the coal samples. The predicted ash for single energy also largely agrees with prediction based on dual energy transmission measurements. The accuracy of ash determinations however depends to some extent on variation in chemical composition of the ash and the coal matter. With proper control of sources of experimental error the facility shows great promise in accurate determination of raw and washed coal samples and favourably lends itself to adaptation to industrial on-line quality control of coal.
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A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL IN PARTIAL FULFILLMENT of the REQUIREMENTS FOR THE AWARD OF DEGREE OF MASTERS IN PHYSICS (NUCLEAR OPTION) DEPARTMENT OF PHYSICS FACULTY OF SCIENCES AHMADU BELLO UNIVERSITY ZARIA NIGERIA DECEMBER, 2007
Keywords
DETERMINATION, ASH CONTENT, NIGERIAN COALS, GAMMA TRANSMISSION, MEASUREMENTS
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