Assessment of the melting behavior of batches containing boron oxide carrier raw materials

• Charakterisierung des Schmelzverhaltens von Gemengen mit boroxidhaltigen Rohstoffen

Jatmiko, Widiya; Conradt, Reinhard (Thesis advisor)

Aachen (2014)
Dissertation / PhD Thesis

Zugl.: Aachen, Techn. Hochsch., Diss., 2014

Abstract

The kinetic aspects of batch melting related to grain size, primary melt formation, gas liberation, and quartz dissolution can only be characterized by performing laboratory experiments, whereas the thermodynamic aspects can be quantified theoretically. One approach to close the gap between laboratory and industrial practice is scaling up experiments from the milligram to the kilogram range. In the micro scale (less than 150 mg sample), physical and chemical reactions of one component, as well as binary and ternary systems, can be observed through the differential thermal analysis (DTA), coupled with the thermo-gravimetry instrument (TG). Experiments at the mesoscale are: thermal-optical observations (30 g batch), conductometry (200 g batch), modified batch-free time (50 g batch and 250 g cullet), and kilogram 10 kg tests in which 4 kg batch and 7 kg cullet are involved. The present study aims to investigate whether these methods could be applied to free alkali and B2O3 containing glass batches. The investigated system were the eutectic CaO-Al2O3-SiO2 (CAS) and CaO-MgO-Al2O3-SiO2 (CMAS) based E-glass combined with various B2O3 content. The onset of melting or primary melt formation in free alkali glass batches is generated by its eutectic melting, while in soda-lime-silica batch, the onset of melting corresponds to physical melting of soda ash. The last part of the present paper is feasibility study of alternative B2O3 carriers applied in boron containing glass batches. Conventional borax pentahydrate is one of the substance in the list of SVHC (Substance of Very High Concern) under EU REACH (Registration, Evaluation, Authorization of Chemical substances) regulation. For borosilicate batches, no significant impact is observed between the conventional and alternative B2O3 carrier. Ulexite as alternative B2O3 carrier shows kinetic advantages in E-glass and insulation wool glass in terms of early onset of melting and short foaming decay, respectively. However, these advantages could not be seen during industrial trial in insulation wool glass melter tank, due to insufficient ulexite data. Both borax pentahydrate and ulexite batches demonstrate similar behavior in respects to energy consumptions. Furthermore, since ulexite is beneficiated in finely ground powder, it contributes to higher emission level after filtration in an electrostatic precipitator equipment.

Institutions

• Division of Materials Science and Engineering [520000]
• Chair of Ceramics and Institute of Mineral Engineering [524110]