Particle-specific characterisation of non-hazardous, coarse-shredded mixed waste for real-time quality assurance

Abstract

The development of a pre-treatment plant for non-hazardous, solid mixed waste into a smart waste factory for future involves the introduction of real-time characterisation of waste streams by applying sensor technology. First, research has been conducted on the application of near-infrared spectroscopy for quality assurance of solid recovered fuels (SRF) produced by the pre-treatment plant. The method is based on statistical analyses, thereby requiring a comprehensive database of detailed waste data. To ensure high-precision measurements, data must be gathered at the level of individual particles and must cover a broad spectrum of different particle types. In a previous study, the fine-shredded SRF (<30 mm) was investigated. The scope of this study includes coarse-shredded SRF (30–80 mm) and mixed commercial waste (pre-shredded to a maximum of 500 mm), which is used as input for the waste pre-treatment plant. For a total of 2346 particles, the projected particle area, particle mass, and particle height were measured with average values of 11.5 cm2, 1.2 g and 10.4 mm, respectively, for the coarse-shredded SRF. Data results regarding pre-shredded waste input were 115 cm2 area, 16.7 g mass and 33.9 mm height. Combined with previous results, the dataset covers a range of particle areas from 15.7 mm2 to 16.7 dm2 and a range of particle mass from 1.6 mg to 882.5 g. Additionally, selected fuel parameters (heating value, chlorine content, and ash content) were measured using laboratory analysis of composite samples from coarse-shredded SRF and mixed commercial waste. The physico-chemical results of the present study confirmed previous results; however, the variance of values increased, and more outliers were identified. Despite the provision of particle data, the major goal of this study was to determine the correlation between the projected area and particle mass, which was calculated using the Spearman's correlation coefficient (SCC). The calculations resulted in an SCC of 0.58 for coarse-shredded SRF and an SCC of 0.22 for pre-shredded waste input. Although the SCC of SRF was sufficient for establishing a quality assurance system, the SCC of input waste must be substantially improved.