Determination of Chlorine and Sulfur Contents in Coke by Sundy SDXNS200H High-Temperature Combustion Ion Chromatography (CIC)

Abstract

The determination of chlorine and sulfur contents in coke was performed using high-temperature combustion ion chromatography (C-IC), with 0.1% hydrogen peroxide as the absorption solution. The test results of three certified reference materials (CRMs) of coke were all within the certified value ranges. The limits of detection (LODs) for chlorine and sulfur were 0.24 mg/kg and 0.19 mg/kg, respectively, and the limits of quantification (LOQs) were 0.80 mg/kg and 0.63 mg/kg, respectively. The relative standard deviations (RSDs) of all test results were within 3%. Application Note: SD-XNS-001-006

Introduction

Coke is an indispensable raw material for blast furnace ironmaking in the steel industry, produced from bituminous coal through high-temperature carbonization. During the high-temperature smelting process, halogens (fluorine and chlorine) are released as HF and HCl, which not only corrode equipment but also cause atmospheric pollution. Sulfur directly affects the quality of hot metal, and its content is one of the key indicators for coke quality evaluation. The SO₂ generated from combustion is also subject to stringent environmental emission limits. Therefore, accurate determination of halogen and sulfur contents in coke is critical for coke quality assessment and clean production in the steel industry. [1] At present, elemental analysis of coke primarily employs sample preparation techniques such as the Eschka method, oxygen bomb combustion, and steam distillation / pyrolysis, with determination methods including the electrode method, coulometric method, titration, and ion chromatography. [2-4] However, conventional methods often require different sample preparation and analytical approaches for halogens and sulfur, respectively, resulting in prolonged analysis cycles and high costs. This application note establishes a simultaneous determination method for chlorine and sulfur in coke based on combustion ion chromatography (C-IC). The method employs a fully automated high-temperature combustion sampling system, combined with high-efficiency ion chromatographic separation and conductivity detection, using ultrapure water to absorb chlorine and hydrogen peroxide to absorb sulfur oxides. This approach significantly simplifies the sample preparation workflow. The precision and accuracy of the method meet practical testing requirements. The entire process requires no strong acid or alkali reagents, making it environmentally friendly and serving as a reliable technical tool for coke quality control and environmental monitoring.

1 Experimental

1.1 Instrument

SDXNS200 High-Temperature Combustion Ion Chromatography Analyzer

1.2 Reagents and Samples

1000 mg/L certified mixed anion standard solution. 100 mg/L anion standard intermediate solution: Transfer an appropriate volume of the standard solution (Section 1.2.1) to a 100 mL volumetric flask, dilute to volume, and mix thoroughly. Hydrogen peroxide. Absorption solution: Transfer 1 mL of hydrogen peroxide (Section 1.2.3) to a 1000-mL volumetric flask, dilute to volume with water, and mix thoroughly. 99.99% Oxygen. 99.99% Argon. Grade 1 water complying with the requirements of GB/T 6682. Commercially available national certified reference materials (CRMs) of coke.

1.3 Testing Procedures

1.3.1 Testing Procedure: Weigh 0.05-0.1 g of sample and place it into a crucible. Set the test method, sample mass, and injection sequence number on the instrument operating software, then start the experiment. 1.3.2 Calibration Curve: Transfer 0.5, 1, 2, 5, and 10 mL of the standard intermediate solution (Section 1.2.2) to 100 mL volumetric flasks, respectively, dilute to volume, and mix thoroughly. Inject into the ion chromatograph for analysis, to obtain corresponding concentrations of 0.5, 1, 2, 5, and 10 mg/L. Plot the calibration curve using concentration as the x-axis and peak area as the y-axis. 1.3.3 Combustion Furnace Operating Conditions

1.3.4 Ion Chromatography Operating Conditions

2 Results and Discussion

Under optimal conditions, the analytical performance of this method was validated. The linear range, limits of detection, and relative standard deviations are summarized in Table 1. The correlation coefficients for both chlorine and sulfur were 0.9999. The limits of detection (LOD) were calculated as three times the standard deviation of seven blank measurements, yielding 0.24 mg/kg for chlorine and 0.19 mg/kg for sulfur. The limits of quantification (LOQ) were calculated as ten times the standard deviation, yielding 0.80 mg/kg for chlorine and 0.63 mg/kg for sulfur, meeting the detection requirements for chlorine and sulfur in coke. Table 1 Analytical Performance of C-IC for the Determination of Chlorine and Sulfur in Coke

Table 2 Determination of Chlorine in Certified Reference Materials of Coke

Table 3 Determination of Sulfur in Certified Reference Materials of Coke

To verify the accuracy of the method for the determination of chlorine and sulfur in coke, three certified reference materials (CRMs) were analyzed and the recoveries were calculated. The certified values of the CRMs and the test results obtained by C-IC are listed in Tables 2 and 3, respectively. The measured values of all CRMs showed no significant deviation from the certified values. In addition, the RSDs (n = 3) for chlorine and sulfur ranged from 1.61% to 2.62% and from 0.95% to 1.53%, respectively, both below to 3%, indicating good method precision and demonstrating that C-IC exhibits excellent accuracy and repeatability.

3 Conclusion

The test results demonstrate that the determination of chlorine and sulfur contents in coke using C-IC yielded results all within the certified value ranges. The limits of detection (LOD) for chlorine and sulfur were 0.24 mg/kg and 0.19 mg/kg, respectively, and the limits of quantification (LOQ) were 0.80 mg/kg and 0.63 mg/kg, respectively, with all relative standard deviations (RSD) within 3%. This method is suitable for the determination of chlorine and sulfur contents in coke.

4 Innovations and Technical Advantages

(1) Simultaneous dual-element determination in a single injection; single-sample analysis in under 12 Minutes. C-IC enables the simultaneous determination of chlorine and sulfur in coke, acquiring two key parameters in a single run. The combustion time per sample is less than 12 minutes, and the system supports concurrent combustion of the next sample during chromatographic analysis, achieving a streamlined continuous operation workflow. (2) Sub-ppm level detection limits, meeting stringent testing requirements. The entire process requires no acid or alkali reagents, using only ultrapure water and a trace amount of hydrogen peroxide as the absorption solution, thereby eliminating the introduction of impurities at the source. The method detection limits are 0.24 mg/kg for chlorine and 0.19 mg/kg for sulfur, with RSDs below to 3%, demonstrating both excellent sensitivity and repeatability. (3) High-throughput fully automated analysis with 49-position batch processing. Equipped with an automated quartz boat drive system and a 49-position autosampler, the system can load up to 49 samples per batch and operate unattended around the clock, fully meeting the dual requirements of high throughput and stability for large-scale quality inspection. (4) Full-process traceability and data compliance. The fully automated workflow minimizes human intervention, eliminates operational errors, and ensures that analytical results are stable, reliable, and clearly traceable, providing robust support for quality system certification and data auditing. (5) Integrated information management with seamless LIMS connectivity. The system supports seamless integration with LIMS, enabling automated acquisition, uploading, and centralized management of testing data, facilitating the digital transformation and automation of laboratories. The application scope of the SDXNS200 High-Temperature Combustion Ion Chromatography Analyzer is not limited to coke. C-IC is recommended for quality control of raw materials, intermediates, and finished products, and can also be used for compliance monitoring with relevant environmental regulations and standards (e.g., ISO 20999, RoHS, WEEE). By adjusting the combustion temperature, oxidant gas ratio, and absorption solution composition, the method can be extended to the determination of halogens (F, Cl, Br, I) and sulfur (S) in various fuels, lubricants, additives, and other petroleum products, as well as polymers, flame retardants, textiles, specialty chemicals, catalysts, and various types of waste products, as well as polymers, flame retardants, textiles, specialty chemicals, catalysts, and various types of waste materials, demonstrating excellent matrix adaptability and method versatility.

References

Simultaneous determination of fluorine, chlorine, sulfur and nitrogen contents in imported petroleum coke by high-temperature hydrolysis-ion chromatography [J]. Physical Testing and Chemical Analysis (Part B: Chemical Analysis), 2018, 54 (5): 520-524. (Original: Zhang Aiping, Wang Hongwei, Shi Jinhui, et al. Gao wen shui jie – li zi se pu fa tong shi ce ding jin kou shi you jiao zhong fu, lv, liu he dan de han liang [J]. Li Hua Jian Yan (Hua Xue Fen Ce), 2018, 54 (5): 520-524.) Solid mineral fuels — Determination of total fluorine in coal, coke and fly ash: ISO 11724:2019 [S]. International Organization for Standardization, 2019. ASTM International. D2847-New Test Method for Total Fluorine and Chlorine in Coal, Coke, and their Residues by Oxidative Pyrohydrolytic Combustion followed by Ion Chromatography Detection (Combustion Ion Chromatography-CIC): ASTM RR:D05-1054 [R]. ASTM International, 2019. National Technical Committee 469 on Coal Chemical Industry of Standardization Administration of China, Subcommittee 3 on Coking Chemistry (SAC/TC 469/SC 3). Determination of total sulfur content in coke: GB/T 2286-2017 [S]. China Standards Press, 2017. (Original: Quan guo mei hua gong biao zhun hua ji shu wei yuan hui lian jiao hua xue fen ji shu wei yuan hui (SAC/TC 469/SC 3). Jiao tan quan liu han liang de ce ding fang fa: GB/T 2286-2017 [S]. Zhongguo Biao Zhun Chu Ban She, 2017.)

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