Determination of Fluorine, Chlorine, and Sulfur in Iron Ore Concentrates by High-Temperature Combustion Ion Chromatography (CIC)

Abstract

This application note specifies a fully automated analytical procedure for the simultaneous determination of fluorine, chlorine, and sulfur in iron ore concentrates, utilizing the SDXNS200 High-Temperature Combustion Ion Chromatography Analyzer. Following high-temperature hydrolytic combustion, target elements in the sample are converted into gaseous oxides, trapped by an absorption solution, and quantitatively determined by ion chromatography. Validation using certified reference materials (CRMs) of iron ore concentrate confirmed high accuracy and satisfactory precision, thereby meeting the requirements for quality control of iron ore concentrates and process monitoring in metallurgical operations.

Application note No.: SD-XNS-001-01001

Introduction

Iron ore concentrate serves as the principal raw material in blast furnace ironmaking. Its chemical composition directly governs smelting efficiency, equipment service life, and the ultimate quality of steel products. Although impurity elements such as fluorine, chlorine, and sulfur are present at low concentrations, their cumulative effects throughout the entire processes of mineral processing, sintering, and ironmaking have a systemic impact. Under high-temperature or moist conditions, fluorine and chlorine readily form highly corrosive gases such as HF and HCl, accelerating the corrosion of furnace linings, flues, and dust removal equipment. Furthermore, chlorides may deposit on internal piping surfaces, causing blockages and reducing thermal efficiency. Sulfur, when transferred into molten iron, increases the risk of hot shortness in steel and imposes a greater burden on desulfurization processes and environmental controls. With the steel industry’s increasing emphasis on refined raw material management and compliance with ultra-low emission standards, the accurate simultaneous determination of fluorine, chlorine, and sulfur in iron ore concentrates has evolved from an auxiliary metric to a critical component of quality control and process optimization.

Conventional analytical methods largely follow traditional ore analysis systems, where fluorine, chlorine, and sulfur are determined separately using alkali fusion coupled with ion-selective electrode (ISE), acid dissolution coupled with potentiometric titration, and the Eschka gravimetric method, respectively. These approaches involve disparate sample preparation and analytical procedures, characterized by lengthy workflows and substantial reagent consumption, rendering them inadequate for high-throughput analysis. This application protocol employs high-temperature combustion hydrolysis coupled with ion chromatography (IC). It enables the simultaneous separation and quantification of fluorine, chlorine, and sulfur from a single iron ore concentrate sample. While ensuring analytical accuracy, this method significantly streamlines the operational workflow, providing the metallurgical industry with an efficient and reliable analytical solution.

Test Principle

The iron ore concentrate sample undergoes hydrolytic combustion under high-temperature and oxygen-rich conditions. Halides are converted into gaseous hydrogen halides, while sulfur compounds are transformed into sulfur oxides. Under the impetus of a carrier gas stream, these gaseous species pass through a condensation tube, are trapped by an absorption unit, and are subsequently collected in a fixed volume. After homogenization, the solution is introduced into the ion chromatography system for quantitative determination of fluorine, chlorine, bromine, sulfur, and other relevant elements. The underlying principle and the instrumental workflow are illustrated in Figure 1 and Figure 2, respectively.

Figure 1: Schematic diagram of the test principle

Fig. 2 Schematic diagram of the instrumental test workflow

Test Conditions

Results and Discussion

The SDXNS200 High-Temperature Combustion Ion Chromatography Analyzer was employed to analyze a certified reference material of iron ore concentrate. The results are summarized in Table 1 (with six replicate measurements for each element). The findings indicate:

The mean determined values were 997.7 mg/kg for fluorine, 261.8 mg/kg for chlorine, and 1246.0 mg/kg for sulfur. These results demonstrate close agreement with the certified values, with relative deviations falling within the specified uncertainty ranges of the standards.

Recoveries for all elements ranged from 94.74 % to 107.93 %, residing within the acceptable interval of 90 %–110 %.

Regarding precision, the Relative Standard Deviations (RSDs) for fluorine, chlorine, and sulfur were 4.36 %, 3.03 %, and 3.78 %, respectively. All RSDs were below 5 %, indicating satisfactory repeatability that meets routine testing requirements.

Table 1: Test Results for Iron Ore Concentrate Certified Reference Material

References

ASTM D7359 Standard Test Method for Total Fluorine, Chlorine and Sulfur in Aromatics and Other Volatile Organic Compounds by Oxidative Combustion followed by Ion Chromatography Detection

GB/T 30729 Solid biomass fuels—Determination of chlorine content

GB/T 3558 Coal—Determination of chlorine content

GB/T 4633 Coal—Determination of fluorine content