An integrated approach of the potential of hydrogen combustion for the decarbonization of tiles and bricks industry
Résumé
All high-temperature manufacturing industrial sectors face the challenge of decarbonisation. Among them, the Tiles and Bricks industry is an energy-intensive processing sector where most of the CO2 emissions (on average around 75%) come from the use of natural gas as a fuel, partly for drying and mainly for firing the products. To significantly reduce CO2 emissions in this industry, natural gas must be replaced by another sustainable low-carbon energy source such as hydrogen, but a little is known about its impact on firing features and product quality. Moreover, the specificity of combustion properties of hydrogen compared to traditional fuel such as natural gas requires fundamental and applied studies to expect its implementation. In this context, the HyDéTOP project aims to investigate the potential of hydrogen fuel in Tiles and Bricks manufacturing combustion process, by dealing on the effects of the progressive transition of gaseous fuel from natural gas to hydrogen on all main aspects: flame characteristics, heating features in the kiln, process monitoring and products quality. A first series of tests of several (H2-NG) blend compositions on different burners configurations demonstrate their versatility to operate in all blend proportion from natural gas to pure hydrogen in large thermal power and excess air ratio ranges. Complementary, a detailed experimental study of flame features is performed on a Top-Jet burner configuration. OH*chemiluminescence imaging shows significant evolution of flame structures and lengths from a hydrogen volumetric proportion of = 75%. Time-resolved coupled PIV and OH PLIF show the occurrence of two separated reaction zones at the exit of the burner for both methane and hydrogen turbulent flames. In a second part of the project, (H2-NG) burners are implemented in a pilot facility allowing to reproduce the complete heating cycle of bricks and tiles in a tunnel kiln. These tests show the feasibility to control this heating process whatever hydrogen proportion (α = 0, 6, 20, 50, 75 and 100 %). However, a change of heat release location in the kiln is observed for high H2 proportion because of the lower jet momentum of hydrogen flame. An increase of NOx emissions is also measured that can be mitigated by an adaptation of burner configuration. Last part of the project is focused on the potential impact of hydrogen on products quality. For this purpose, several series of bricks and tiles are fired in the pilot facility with the different H2-NG blend compositions. Then, a parametric characterisation of mechanical properties, thermal resistance and colorimetric aspects of these series of roof tiles and brick slips are performed. No specific change of products features is observed as far as the firing cycle is controlled. In conclusion, this integrated project covering all main aspects of the impact of hydrogen on heavy clay firing process demonstrates the potential of hydrogen for the decarbonisation of this industrial sector.