A method for analysis of nuisance dust from integrated steel works: chemical and mineralogical characteristics of contributing sources

Abstract

Background: Integrated steelmaking is known to emit coarse airborne ‘nuisance’ dust (10–100 µm) to the production site and in the local environs. We present a method to quantitatively analyse the provenance, mineralogical and chemical attributes of the constituent particles in nuisance dust related to the integrated steelworks of Tata Steel, IJmuiden, the Netherlands. The dust is characterised per particle, using scanning electron microscopy with energy-dispersive spectrometry (SEM–EDS) microanalysis, and in bulk with quantitative X-ray diffraction (XRD) analysis. Based on mineralogical characteristics, particles in the dust are sorted into populations that can be related in detail to industrial processes and subsequent atmospheric weathering influence. The method is illustrated by application to a nuisance dust complaint sample from the neighbouring town Wijk aan Zee containing a large contribution of several dust sources from the integrated steelworks. Results: Besides a background contribution from urban and natural dust, diverse sources from the integrated steelworks are identified in the nuisance dust sample, derived from coke-making, iron-ore agglomeration processes and blast furnace ironmaking, steelmaking slag processing, process fluxes, as well as steelmaking refractory materials. The most voluminous of these in the sample are directly verified by comparison with a set of reference source materials. The abundances, mineralogical and chemical attributes of the various dust particle populations in the sample are quantitatively examined including, specifically, the occurrence of the potentially toxic elements Mn and V. These elements occur with highest concentrations in dust derived from steelmaking converter slag: V is housed in dilute form (solid solution) in the phases di-calcium silicate and brownmillerite, and Mn chiefly in Mg–Fe-oxide (Mg-wustite ((Mg,Mn,Fe)O) and its oxidation product ((Mg,Mn,Fe)(Fe,Mn)2O4)). Conclusions: By treating nuisance dust as a particulate, multi-phase, multi-source material, the outlined method provides crucial information for toxicological evaluation and for mitigation of emissions, which is not obtainable by bulk chemical analyses alone. It also helps address the lack of adequate monitoring options for deposits of nuisance dust from integrated steel production, necessary to evaluate the relationship between deposition and monitored emissions that are regulated by the European Industrial Emissions Directive and by local permits based on this legislation.