CFD Modelling of Regenerative Pre-heating Systems for Recycled Glass Raw Material

The glass production industry has one of the highest energy consumption rates and environmental emission impact with respect to the existing industrial sectors. Moreover, the glass production sector is important in Italy (with production plants spread all over the country from North to South) from both production rates and engineering design and development competencies point of view. The glass furnaces are nowadays conceived with regenerative or recuperative systems to take advantage of the residual heat from the combustion exhausts in order to increase the thermal efficiency of the system. The exhaust gases are also used in innovative systems to reduce the NOx emissions in specifically designed gas recirculation systems tailored to the glass furnace. A remaining portion of the heat content in the exhaust gases could be used to pre-heat the raw material from recycled glass that, in some applications, forms a significant percentage of the glass recipe. In order to develop pre-heating systems for recycled glass as compact as possible, a detailed analysis of the heat transfer from the gases to the glass need to be developed. In the paper different CFD models for the heating process of recycled glass are presented. A numerical model for the recycled glass loose particles has been developed and used in the CFD models for both direct (the exhaust gases flow through the recycled glass matrix) and indirect (the recycled glass is heated through heat diffusion from the hot gases that flow into pipes) systems.