Decarbonisation
Assessing new raw materials for carbon-lean batches With decarbonisation at the forefront of the glass industry, Corinne Claireaux1, Mathi Rongen2, Luuk Thielen3 and Johan van der Dennen4 discuss how using alternative raw materials in batches could reduce direct CO2 emissions.
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ike every other energy-intensive industry, decarbonisation is the major challenge facing glass. It’s everywhere - on the news and on the desks of many technical, marketing, legal, and financial teams. Consequently, great initiatives all are pulling the industry towards the use of less carbonised energy sources and raw materials, such as GlassTrend projects, Glass Futures, furnace for the future and the Dutch-funded TKI project for hydrogen combustion piloting. Using hydrogen combustion and melters with a higher share of electrical energy is no longer a distant dream. Fossil fuel combustion is the first source of direct (Scope 1) CO2 emission, followed by the decarbonisation of the batch. Additionally, the CO2 footprint of the raw materials constituting the batch contributes to indirect (Scope 3) emissions. A step-by-step approach is proposed to help the glass industry progress towards a carbon-lean batch and glass production.
Batch-to-melt kinetics Finding undissolved particles in a final product is rather seldom. This high quality is achieved by careful optimisation of the residence time and the temperatures in the melter. Increasing the residence time or the temperature of the melt would degrade the overall energy performance of the melter, which is an absolute no-go. Therefore, any new raw material should not worsen the melting kinetics of the batch. Lab-scale evaluations consist in interrupting the melting of the batch at different times before completion of the conversion. The residual crystalline part of the batch is quantified by X-ray powder diffraction (XRD). This experiment allows the melting rate comparison and the identification of the nature of the residual defects. The effect of raw materials’ nature, particle size, cullet size and quality can be assessed in view of melting rate.
Fining and foaming Raw materials must not generate excessive
foaming, as this will have a negative impact on the process efficiency or alter the fining of the melt - leading to seeds, bubbles and other quality issues. In the High-Temperature Melting Observation System (HTMOS), coupled to the Evolved Gas Analysis (EGA) set-up, the entire melting process is filmed and gases arising from the gas-forming reactions are analysed. The atmosphere above the batch in the set-up is tuned to match the combustion atmosphere in the furnace. Undesired phenomena such as foaming, delayed or incomplete fining are directly observed while the gas analysis enables monitoring of the fining process and quantification of the batch emissions. This information is crucial to ensure that raw materials contribute to the attainment of a homogeneous, bubblefree melt.
Energy demand The purpose of a glass furnace is to provide the energy required to convert
22 0 Glass International February 2022
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