Second law assessment of a Hoffmann kiln for the red ceramics industry

Abstract

This study presents the results of a thermodynamic analysis carried out for a Hoffmann kiln installed in a red ceramics industry in Northeast Brazil. From the case study, it was evident that the red ceramics industry has not advanced significantly in the last decades or made any significant improvements in the manufacturing progresses. Exergy analysis revealed a high rate of exergy destruction; 99.46% of the firewood exergy was being destroyed through mixing of different chemical components and heat exchange among substances at different temperatures or due to heat transfer to the environment. A large amount of infiltrated air was revealed by the mass balance, which contributed to the low exergy efficiency. Negative effects on fuel consumption and lower temperatures of combustion air are also consequences of infiltration of cold air. Energy and exergy performance improvements are achievable through excess air elimination and exhaust preheating. On a monthly basis, elimination of infiltrated air could save approximately 27.6 m3 of firewood, while the use of chimney gases to preheat the bricks could save 28.9 m3 of firewood.