Impact of NH3 combustion on the properties of carbonate-free Na/Ca silicate-based soda-lime silicate glass

Abstract

The traditional soda-lime silicate glass (SLS glass) melting process, utilizing fossil fuels and carbonate-containing raw materials, generates significant CO₂ emissions. Alternatively, NH₃ is gaining attention as a carbon-free fuel. Additionally, Na and Ca silicates possess the appropriate composition for SLS glass formation and do not emit CO₂ during melting. However, limited studies have reported SLS glass melting with NH₃ combustion owing to the difficulty faced during NH₃ combustion at high temperatures as 1450 °C. In this study, we used a model furnace with experimental glass melting conditions set at 1450 °C or higher, employing two-stage combustion on parallel independent jets to conduct melting experiments, where carbonate-free SLS glass raw materials are vitrified through NH₃ combustion. The resulting glass is subjected to material analysis using XRD, XRF, and gas chromatography to assess the occurrence of bubbles, inclusions, and color tone according to industry quality standards. The results demonstrate the feasibility of melting decarbonized SLS glass using NH₃ combustion and carbonate-free materials. However, NH₃ combustion influences the color tone, glass transition temperature, and clarity. Developing cost-effective methods for producing silicates without CO₂ emissions is crucial for alternative raw materials to remain competitive with conventional options. This method of preventing CO₂ generation from both raw materials and fuel in glass production indicates that combining decarbonized fuel combustion and silicate-based glass melting holds promise for reducing CO₂ emissions.