Cullet – another step towards glass sustainability

Cullet is an important raw material that will help the glass industry achieve sustainability. This chapter focuses on the benefits and risks of increasing the use of recycled glass in manufacturing. There are three sources of cullet available to most manufacturers, the plant’s internal cullet, cullet from a downstream processing plant and post-consumer recycled cullet. The chemistry and redox of external cullet will match that of the glass being produced and therefore adjustments to the batch recipe are required. The addition of cullet to the batch mix introduces changes to the physical properties that influence the size and thermal behavior of the batch piles in the furnace. The chapter looks at the two key properties: density and thermal conductivity. To investigate and quantify the effect of batch to cullet ratios, a computational fluid dynamics model study was undertaken. The results of the study confirmed the trends predicted from the theoretical analysis. © 2021 The American Ceramic Society, all rights reserved.