Analysis of gypsum ore conversion with aid of gamma-ray transmission and CCRD

Abstract

Nowadays, except for very few imported furnaces, the monitoring of the conversion of the produced plaster at the Pole Plaster of Araripe is not done with aid of online techniques. This research work shows a simulation of operational conditions with an online meter of chemically combined water in plaster, by means of Central Composite Rotatable Designs (CCRD) and nuclear technique of gamma-ray transmission. In the family of central composite rotatable designs, the CCRD is more efficient than the others, regarding uniformity of variances of the points at the same distance from the center of the design. This process is a simulation of operational conditions with an online meter of the chemically combined water in plaster, by means of gamma radiation transmission technique. Such determination can be achieved by the effect caused by the variation of the mass attenuation coefficient of the partially dehydrated material. An Americium-241 gamma source (60 keV) was simulated in the implementation of the Beer–Lambert equation. The nuclear data required for simulation were obtained from XMuDat software, available from the site of the International Atomic Energy Agency. A program in Matlab programming language has demonstrated the possibility of monitoring at all stages of the dehydration process, with measurements of the specific mass of the sample having an estimated error of the order of 1%. To verify the operating conditions suitable for the process, experiments were simulated using a CCRD. The independent variables were the sample thickness and the amount of chemically combined water in plaster. Optimal conditions of the process were determined, which allowed the derivation of a model represented by response surface of the gypsum conversion.