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 m 3 of firewood, while the use of chimney gases to preheat the bricks could save 28.9 m 3 of firewood. Keywords Hoffmann kiln • Red ceramics • Exergy analysis • Energy analysis List of symbols c Specific heat (kJ kg −1 K −1) ex Specific exergy (kJ kg −1) Ex Exergy rate (kW) h Specific enthalpy (kJ kg −1) I Irreversibility rate (kW) M Mass flow (kg s −1) P Pressure (kPa) Q Heat (kW) s Specific entropy (kJ kg −1 K −1) T Temperature (K) V Velocity (m s −1) Greek γ Activity coefficient φ Chemical exergy correction factor ƞ Efficiency

Energy, Exergy, Entropy Generation Minimization, and Exergoenvironmental Analyses of Energy Systems-A Mini-Review

“…There should be a balance of useful, dissipated, and remaining energy (maximum extractable work, frictional losses, and unutilized energy, respectively) (Yip and Elimelech, 2012). Energy assessments evaluate the energy content of final and intermediate products, losses and several shares of energy associated with mass flows at the inputs and outputs (Carvalho and da Silva, 2018), which can help establish energy efficiency and conservation strategies. Efficiencies are calculated as the ratios of energy quantities and are employed to evaluate and compare different systems (Terzi, 2018).…”

Exergoeconomic Assessment of a Compact Electricity-Cooling Cogeneration Unit

“…Exergy analysis is fundamental to characterize the utilization and destruction of exergy in the various steps of the process [28,29]. As the irreversibilities can be pinpointed and quantified, equipment that could benefit from energy improvements can be identified [30][31][32]. Therefore, exergy analysis is crucial to complement energy analysis and the evaluation of thermal efficiency indicators.…”