Determination of chlorine in dusty waste in ferronickel production: Analysis and estimation of uncertainty

Abstract

A key stage in ferronickel production is sulfate-chlorination roasting, after which and at subsequent stages (up to the final product) exhaust gases are formed in the system accompanied by dust and metal chloride vapors outlet in roasting furnace. Enrichment of wastes during their removal with condensed chlorides indicates a decrease in the efficiency of sulfate-chlorination roasting. Therefore, the control of mineral chlorine in filter sediments is important both from the standpoint of environmental monitoring and evaluation of the technological process efficiency. In order to determine mineral chlorine in dusty waste during the ferronickel production, a quantitative chemical analysis procedure based on the ionometric method was developed in the testing laboratory of the South Ural Nickel Plant. This paper proposes a procedure for estimating the results uncertainty in determining chlorine in the sample. It consists of the following steps: compiling a mathematical model to determine the chloride-ion mass fraction, estimating the input quantities in the mathematical model and their uncertainties, estimating the output quantities in the mathematical model and their uncertainties, budgeting for uncertainty, determining the expanded uncertainty and presenting the results. The paper considers the results of calculating the total expanded uncertainty in determining the chloride-ion mass fraction – U(XCl – ) = ±9.4 % (kp = 2, P = 95 %) – for the samples with chlorine mass fraction from 0.4 to 0.8 %. Application of the proposed methodology in calculating uncertainty ensures reliable results in determining chlorine in dusty wastes of ferronickel production, which has a positive effect on the technological process and environmental monitoring efficiency.