Determining the chlorine content in the blast-furnace system

Abstract

The production of ferrous metals and the extraction and processing of raw materials are environmentally hazardous. Besides atmospheric and water pollution, many solid wastes are formed. Chlorine plays a special role in blast-furnace processes. The chlorine compounds present in the blast-furnace gas lead to the corrosion of pipelines, air heaters, and tuyeres in the furnace. The behavior of chlorine in the blast furnace determines the sinter properties during the reduction process. If the content of mineral chlorine (chlorine bound with metals) in residues at filters and dust traps is monitored, the toxicity of the wastes may be assessed, and the production processes may be evaluated. The chlorine content is determined by various physical methods: atomic-emission spectrometry, mass spectrometry with inductively bound plasma, and neutron-activated analysis. However, chemical methods have been widely adopted: titrimetric, photometric, electrochemical, and ion-chromatographic methods. It is important to develop fast and inexpensive methods of determining chlorine for the analysis of materials encountered in technological systems, including metallurgical systems. In the present work, attention focuses on samples of blast-furnace slag from PAO Tulachermet and dusty wastes from PAO Kosogorskii Metallurgicheskii Zavod. X-ray fluorescent methods are used for preliminary analysis of the sample composition. The interfering influence of other components is considered. Ionometric determination of chlorine by means of a crystalline chloride-selective electrode is proposed. The samples are decomposed by high-temperature sintering in a mixture with Na2CO3 and ZnO and subsequent leaching with water. The details of this method are described. The results of the analysis are confirmed by variation in the sample weight (n = 10; t tab = 2.26, P = 0.95) and also by comparison with X-ray fluorescent data. The precision of ionometric determination of chlorine in the blast-furnace system is assessed. The working range of the chlorine concentrations observed is 0.037–1.340 wt %.