Melting behaviour of raw materials and recycled stone wool waste

Abstract

Stone wool is a widely used material for building insulation, to provide thermal comfort along with fire stability and acoustic comfort for all types of buildings. Stone wool waste generated either during production or during renovation or demolition of buildings can be recycled back into the stone wool melt production. This study investigates and compares the thermal response and melting behaviour of a conventional stone wool charge and stone wool waste. The study combines differential scanning calorimetry (DSC), hot stage microscopy (HSM) and X-ray diffraction (XRD). DSC reveals that the conventional charge and stone wool waste have fundamentally different thermal responses, where the charge experiences gas release, phase transition and melting of the individual raw materials. The stone wool waste experiences glass transition, crystallization and finally melting. Both DSC and HSM measurements indicates that the wool waste initiates melting at a lower temperature than the conventional charge. Also DSC measurements show that the wool waste requires less energy for heating and melting than the conventional charge, making stone wool waste recycling desirable both for environmental and for process purposes.

Waste Mineral Wool and Its Opportunities—A Review

“…This method is an effective way to lower the raw material cost by replacing coke usage. Moreover, a recent study compared the melting behavior of virgin raw materials and waste rock wool and concluded that re-melting the waste rock wool is 23% more energy-efficient on differential scanning calorimetry (DSC) [ 31 ].…”

“…Each rock wool factory uses different raw materials based on their preference and intended use. Nevertheless, the raw material is typically from the rock crystalline group and may include anorthosite, dolomite, diabase, olivine sand, or even slag [ 31 ]. Table 2 shows the compositions of chemicals of ordinary waste rock wool from different research studies.…”

“…Another common contaminant is mycological substances, for example, fungi, present in a humid environment [ 58 ]. Fortunately, recent research shows that resin or other organic matter can be burnt off by heating the waste to a specific temperature [ 31 ]. This finding also infers that if the resin is the only contaminant present, the chance to recycle the waste rock wool as raw material is high.…”

“…Several studies have been published to overcome the conundrums on the reclamation of waste rock wool into the rock wool production process [ 31 , 32 ]. It encompasses introducing waste rock wool as recycled fillers into different materials, including pozzolanic material [ 33 ], geopolymer concrete [ 34 ], alkali-activated material [ 35 ], polymer composites [ 36 ], and wood-fiber composites [ 37 ] as well as reutilizing the waste as a pollutant sorbent to remove split oil [ 38 ] and hexavalent chromium Cr(VI) [ 39 ] from water and filter hydrogen sulfide (H 2 S) gas.…”

Experimental methods in chemical engineering: Differential scanning calorimetry—DSC

“…DSC has a wide spectrum of applications ranging from simple heat of fusion evaluation() to advanced material microstructural evolution analyses and complex chemical reaction process identification . The versatility of the DSC is vast and researchers apply it to assess: coal,() cjceass,() waste,() catalysts,() minerals,() cement,() ceramics,() alloys,() and polymers. () Applications include: gasification,() pyrolysis,() combustion,() adsorption,() desorption,() calcination,() dehydration,() thermal stability,() phase transitions,() phase diagrams,() polymer crystallization,() glass transition, curing time, and reaction kinetics …”