Heat convection and radiation in flighted rotary kilns: A minimal model

Abstract

We propose a minimal model aiming to describe heat transfer between particles (i.e. grains) and gases in a model of flighted rotary kilns. It considers a channel in which a convective gas interacts with a granular suspension and a granular bed. Despite its simplicity it captures the main experimental findings in the case of dilute suspension of heavy grains typical of what can be observed in many industrial rotary kilns. Energy balance between each phase takes into account the main heat transfer mechanisms between the transverse granular motion and the convective gas. In the absence of radiation heat transfer, the model predicts exponential variations of the temperatures characterized by a length which depends on the granular and gas heat flow rates as well as on the exchange areas. When radiation is taken into account, the model can be solved numerically. For this case, the temperature variations can be fitted by stretched exponentials whose parameters are found to be independent of the studied phases. Finally, an efficiency criterion is proposed to optimize the length of the system

Energy efficiency of flights rotary kiln

“…The numerical model is able to compute a large range of size of drum, LD, to predict the optimal kiln size, = Λ for the desired asphalt materials temperature ( ). As expected, the ratio Λ ⁄ for counter-current is found herein lower that co-current technology [11] as shown in the left-hand of the figure 7.…”

Experimental research and numerical analysis on thermal dynamic characteristics of rotary kiln

“…The main factors affecting the thermal dynamic characteristics of the rotary kiln include the following: coating thickness; rotary kiln structure size; type of burner; pulverized coal concentration; coal fugitive constituent; excess air ratio; and oxygen content . In this numerical model, the structure size and burner type of the rotary kiln are fixed.…”

“…In the rotary kiln, in order to meet the needs of clinker generation, the combustion temperature is relatively high. Therefore, the radiation heat transfer process must be considered . The P1 model is used to simulate the heat transfer.…”

Rotary kiln process: An overview of physical mechanisms, models and applications

“…Gas-solid transfer The thermal transfer between the gas phase and the solid phase in rotary kilns has been the subject of several research studies. Some authors have formulated it in the form of heat flux, while others in the form of an exchange coefficient or stretched exponential function of the gas and solid temperature [101]. Mujumdar and Ranade [28] proposed the relation in (21) to assess the radiative heat flow between the gas and the solid.…”