Determination of existing relationship among grindability, chemical composition and particle size of raw material mix at Aruwakkalu Limestone.

Abstract

In the production process of the Siam City Cement (Lanka) Ltd, grindability can be mainly effected by the chemical composition of the raw materials, ball mill performance and moisture content. However, currently, in the production process ball mill performance is in its optimum stage and moisture content remains constant at 7%. On account of that the chemical composition and particle size of raw material are the main effecting factors to the lower grindability. This research study is expected to make a relationship between the grindability and the chemical constituents and particle size of limestone in the raw meal feed. Percentages of SiO2, Al2O3, Fe2O3, CaO, MgO, Cl-, SO3, Na2O and K2O in limestone are observed for this research. The suitable analysis method (time series and scatter plot analysis) was performed to correlate the chemical constituents with the grindability. The company has been already used a method to check the chemical composition and the grindability hourly of these samples. The XRF (X - ray Fluorescence) analysis is used to check the chemical composition and grindability is checked in the form of residue test of No 212 sieve residue. These chemical analysis and residue test results data of year 2016 were used in data analysis of the research study. The distribution curves of the variables were analyzed to examine the skewness of the distribution. The time series analysis was carried out to find the best fitting curve between grindability and the variables. Scatter plot analysis was finally performed and the results show the effect of chemical components such as SiO2, Al2O3, Fe2O3, CaO, MgO, SO3, Cl-, Na2O, K2O and particle size distribution of raw meal were found to be range correlated with the raw meal grindability. Standard normal distribution analysis of Percentages of SiO₂, Al₂O₃, Fe2O3, CaO and LSF, AR and SR follow the standard normal distribution perfectly. It means it gives unbiased estimation of statistical parameters of the population. Therefore the quality parameter such as LSF, AR and SR lie on the required quality target range upheld by the company. The mathematical relationship among the grindability and variables Silicon Oxide (SiO2), Aluminium Oxide (Al₂O₃), Ferric Oxide (Fe2O3) Calcium Oxide (CaO), LSF and SR cannot be given in the form of polynomial, exponential or logarithmic manner, since R2 values do not equal to the unity. The most suitable chemical constituents range for improved grindability of raw meal are given based on 68% , 95% and 99% confidence interval. The quality parameters such as Lime Saturation Factor (LSF), Alumina Ratio (AR) and Silica Ratio (SR) also evaluated based on certain error level