Review on Energy Efficiency Progresses, Technologies and Strategies in the Ceramic Sector Focusing on Waste Heat Recovery

Thermal processes represent a considerable part of the total energy consumption in manufacturing industry, in sectors such as steel, aluminium, cement, ceramic and glass, among others. It can even be the predominant type of energy consumption in some sectors. High thermal energy processes are mostly associated to high thermal losses, (commonly denominated as waste heat), reinforcing the need for waste heat recovery (WHR) strategies. WHR has therefore been identified as a relevant solution to increase energy efficiency in industrial thermal applications, namely in energy intensive consumers. The ceramic sector is a clear example within the manufacturing industry mainly due to the fuel consumption required for the following processes: firing, drying and spray drying. This paper reviews studies on energy efficiency improvement measures including WHR practices applied to the ceramic sector. This focuses on technologies and strategies which have significant potential to promote energy savings and carbon emissions reduction. The measures have been grouped into three main categories: (i) equipment level; (ii) plant level; and (iii) outer plant level. Some examples include: (i) high efficiency burners; (ii) hot air recycling from kilns to other processes and installation of heat exchangers; and (iii) installation of gas turbine for combined heat and power (CHP). It is observed that energy efficiency solutions allow savings up to 50–60% in the case of high efficiency burners; 15% energy savings for hot air recycling solutions and 30% in the when gas turbines are considered for CHP. Limitations to the implementation of some measures have been identified such as the high investment costs associated, for instance, with certain heat exchangers as well as the corrosive nature of certain available exhaust heat.