Critical Review of Cp Calculation Within the Fluidized Bed of Cement Rotary Kilns

One thermodynamic parameter that is crucial to heat transport within the fluidized bed inside the rotary kiln, during clinker production, is the specific heat capacity. The particular parameter is often considered constant in the open literature, while, in reality, it strongly depends on the fluidized bed’s temperature and composition, considering that the temperature inside the kiln ranges from approx. 800 K up to 2000 K. For the current study, a mixing rule reported in the literature was applied in order to calculate the Cp of the fluidized bed, utilizing temperature and composition profiles available in the literature. An in-house code was developed for the comparison of the literature-reported Cps and those resulting from the mixing rule. It was discovered that the Cp of the fluidized bed had a proportional increase with the increase in the temperature along the length of the kiln. The deviation between the two values (calculated and literature) is relatively small in some cases, whereas, in others, it is quite significant, ranging from 1.56% to 52.49%, thus making the adoption of the temperature-dependence of Cp necessary. Establishing a more accurate relation for the specific heat capacity leads to a better energy balance inside the kiln, which, along with other improvements, can lead to a decrease in the energy consumed and a significant reduction in greenhouse gas emissions.