Performance modeling of radiant heat recovery exchangers for rotary kilns

• Published in: Applied thermal engineering 2011-10, Vol.31 (14), p.2578-2589
• Main Authors: Caputo, Antonio C., Pelagagge, Pacifico M., Salini, Paolo
• Format: Article
• Language: English
• Subjects: Applied sciences; Cement kiln; Devices using thermal energy; Energy; Energy. Thermal use of fuels; Engineering Sciences; Equipment costs; Exact sciences and technology; Heat exchangers; Heat exchangers (included heat transformers, condensers, cooling towers); Heat recovery exchanger; Heat transfer; Kilns; Mathematical model; Mathematical models; Mechanics; Physics; Recovering; Rotary kiln; Rotary kilns; Rotating; Shells; Theoretical studies. Data and constants. Metering; Thermics
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2011.04.024

Heat loss from rotating kilns may represent a significant percentage of the total energy input especially in highly energy intensive industrial sectors such as cement production. As an alternative to traditional energy recovery methods, the possibility of recovering radiant heat lost through the kiln surface has been proposed in the literature. This may be accomplished by surrounding the kiln with a secondary external shell acting as a heat exchanger for a transfer fluid. In this work a mathematical model for sizing and performance estimation of a heat exchanger recovering waste heat from the external surface of rotating kilns is developed. The equipment has been configured as an array of pressurized water carrying tubes arranged in a longitudinal pattern on the surface of a cylindrical outer shell coaxial with the rotary kiln. An example of model application is utilized to discuss the involved heat transfer process and its impact on equipment design. An economic model has also been developed to determine the optimal size of the equipment. ► The problem of recovering heat lost from external surface of rotary kilns is discussed. ► A mathematical model of heat recovery exchangers for rotary kilns is developed. ► Heat exchange mechanisms and heat recovery performances bounds are discussed. ► A cost model and criteria for determining optimal equipment size are developed.