Dual energy gamma-ray transmission techniques applied to on-line analysis in the coal and mineral industries

The use of dual energy γ-ray transmission techniques to determine the concentration of a higher atomic number (Z) component in a lower Z matrix is investigated. Examples discussed are the determination of lead in lead-zinc ore, iron in high-grade iron ore, uranium in solution, and ash in coal. These examples are considered in relation to the main application fields of on-stream analysis of mineral slurries and solutions, on-line analysis on conveyors, and scanning of borecores.

A method for reducing errors in analysis by compensating for variations in concentration of some of the wanted or matrix components is proposed. This method depends on choice of one γ-ray energy in the photoelectric absorption region and the other in the pair production region. Calculations show that this method reduces errors in the determination of ash in coal caused by variation in concentration of iron in the ash. However, sensitivity to ash is poor, so this application is suitable only when γ-ray path lengths in the coal are large.

Preliminary results are presented of the combination of dual energy γ-ray transmission and pair production techniques to give an estimate of iron concentration in coal. This can be used to give an approximate estimate of sulphur in pyrites in coal, assuming that iron is present only as pyrites.