Research Of The Testing Measure Of S And Cl～- In Cement Industry

The cement is the essential basic construction material in the nation economy development. Since the day it was invented 170 years ago, it has made great contribution to the social and economical development. The contents of sulfur and chlorine are two important indexes in the process of production and quality control of cement. It is prescribed in the "cement industry mandatory regulations" that the SO3 content in Portland cement shouldn't overrun 3.5% and chloride content in raw material of not more than 0.06%.BaSO₄ gravimetric analysis, high-temperature combustion combined with neutralization, coulometer titration and the X-ray fluorescence analysis are the main methods of determination of total sulfur content in coal currently. BaSO₄ gravimetric analysis is the GB method, as it is an accurate, simple, reliable, and absolute method, and usually acting as the arbitral means for other methods. X-ray fluorescence measuring instrument is a new type of sulfur detector developed in recent years with a broad prospect for the features of simple operation and fast determination. However, the high cost of equipment and maintenance limit its application. According to survey, there is no real-time monitoring process of sulfur content in the raw, fuel materials in a large part of cement plants, especially small and medium-sized plants in China's cement industry, which is one of the main reasons that the neck of pipes are always clogged by crust in cement producing process. The present sulfur detectors can not widely applied in that they increase the manufacturing cost to some degree. Gravimetric analysis needn't specialized equipment, but requires a long time to finish the complex operation, so it is also not applicable. Therefore, this paper presents a new measurement of sulfur content: oxygen bomb combustion-BaCrO4 photometric method.Chlorine content in cement is measured by approach of mercury sulfate titration in GB, which is simple, fast, but limited by concentration of chlorine. When the chloride content is very low, the sensitivity dropped, in the end it is hard to determine. Traditional silver chloride turbidimetry attained relative stability by use of stabilizing agents, and the absorbance of suspension could remain a few minutes. However, stabilizing agents always affect the background of solution and the accuracy of method dropped correspondingly, especially in the case of lower chloride ion concentration. According to the augments that different concentrations of silver chloride suspension absorbance changes with time with a peak appeared and the one-to-one correspondence of peak value and chloride ion concentration, this paper proposes a new method to measure the chloride concentration in cement.The results show that, the two methods, oxygen bomb combustion-BaCrO₄ photometric analysis for S content and AgCl turbidimetry for Cl content, presented in this paper have high reliability and Beer's law is obeyed in both of them. The regression equation of the former is: A=0.02149C+0.01339, with correlation coefficient of 0.99601 in 4¹60mg·L^-1 and the regression equation of the latter is: A_max=0.0742C+0.00968, with correlation coefficient of 0.99973 in 0.5～8mg·L^-1. Recovery test showed high accuracy, and repetitive test proved good stability of the two methods. In addition, both of them needn't additional equipment. Therefore, these two methods are particularly suitable in China's cement enterprises.