Thermodynamics-guided design for lightweight aggregate production from waste glass and incinerated sewage sludge ash

Abstract

Recycling waste glass (WG) and incinerated sewage sludge ash (ISSA) in lightweight aggregate is a prospective approach for large-scale utilization of these municipal wastes. However, this application has been hindered by the poor process stability and performance control caused by the complex characteristics of WG and ISSA. To address this, this paper develops a thermodynamics-based framework for sintering process design of lightweight aggregate (LWA). Thermodynamic models are used to quantitatively analyse the impact of foaming agent dosage, ISSA content, and temperature variations on several key aspects during the sintering process, including (i) foaming potential, (ii) solid-liquid phase transition, (iii) liquid-solid phase characteristics, (iv) sintering capacity, and (v) heavy metal solidification. Besides, structure-thermodynamics-informed artificial neural networks (STIANN) trained on extensive data are utilized to calculate the fluidity and interfacial property of the liquid-solid phase. This framework allows the chemical components and sintering process of ISSA-WG based LWA to be designed and optimized, considering different target performances, such as liquid phase content, crystals precipitation, viscosity, surface tension, and oxide activity. Additionally, the ISSA-WG based LWA can achieve excellent environmentally friendly properties in the broad sintering temperature range of 800–1600 °C because the heavy metals (mainly As, Cr, Cu, and Ni) can be immobilized within LWA in stable forms.