RECYCLING INCINERATION WASTES FOR PRODUCING SYNTHETIC AGGREGATES

摘要

This work involves the utilisation of a by-product from municipal solid waste incineration (MSWI) for producing lightweight aggregates to be further used in building construction. This residue that comprehends fly ashes from the heat recovery devices as well as the residues produced in the scrubber and bag filters, is referred as Air Pollution Control (APC) residues. At present this waste has limited applications, and is usually landfilled after stabilization/solidification with hydraulic binders. The residue is considered as hazardous mainly due to its high content of soluble salts and heavy metals. The industrial process of lightweight aggregates could be used to recycle the waste, which would replace a small percentage of the main raw material (expanded clay). The main goal of the present study is to measure the effect of the waste in the technological properties of the aggregates, mainly in what concerns the density. Other properties such as the compressive strength, water adsorption and bloating index were also determined. On the other hand, the assessment of the environmental impact is an important aspect to be considered, and thus the gaseous emissions during the firing process were also quantified. In fact, acid gases such as HCl may be produced due to the high chloride content present on the waste. The acid neutralization capacity (ANC) was also determined, in order to evaluate how sensitive the material is to the external pH variations. The results obtained show that synthetic lightweight aggregates may be considered as a valuable way for recycling these residues produced all over Europe and other developed countries.