Computer Simulation of Heat Transfer in a Rotary Lime Kiln

2018 ◽  
Vol 10 (3) ◽  
Author(s):  
Ashish Agrawal ◽  
P. S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Rotary Kiln ◽  
Wall Temperature ◽  
Gas Temperature ◽  
Gas Radiation ◽  
Temperature Distributions ◽  
Refractory Wall ◽  
Radiation Heat Exchange ◽  
Shrinking Core ◽  
Energy Balances

In the present work, a steady-state, finite difference-based computer model of heat transfer during production of lime in a rotary kiln has been developed. The model simulates calcination reaction in the solid bed region of the rotary kiln along with turbulent convection of gas, radiation heat exchange among hot gas, refractory wall and the solid surface, and conduction in the refractory wall. The solids flow countercurrent to the gas. The kiln is divided into axial segments of equal length. The mass and energy balances of the solid and gas in an axial segment are used to obtain solids and gas temperature at the exit of that segment. Thus, a marching type of solution proceeding from the solids inlet to solids outlet arises. To model the calcination of limestone, shrinking core model with surface reaction rate control has been used. The output data consist of the refractory wall temperature distributions, axial solids and gas temperature distributions, axial percent calcination profile, and kiln length. The kiln length predicted by the present model is 5.74 m as compared to 5.5 m of the pilot kiln used in the experimental study of Watkinson and Brimacombe (1982, Watkinson, A.P. and Brimacombe, J. K., “Limestone Calcination in a Rotary Kiln,” Metallurgical Transactions B, Vol. 13B, pp. 369–378). The other outputs have been also satisfactorily validated with the aforementioned experimental results. A detailed parametric study lent a good physical insight into the lime making process and the kiln wall temperature distributions.

Computer Simulation of Drying of Food Products With Superheated Steam in a Rotary Kiln

2010 ◽  
Author(s):  
Koustubh Sinhal ◽  
P. S. Ghoshdastidar ◽  
Bhaskar Dasgupta
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Flow Rate ◽  
Rotary Kiln ◽  
Rotational Speed ◽  
Gas Flow ◽  
Superheated Steam ◽  
Gas Temperature ◽  
Gas Flow Rate ◽  
Refractory Wall

The present work reports a computer simulation study of heat transfer in a rotary kiln used for drying and preheating food products such as fruits and vegetables with superheated steam at 1 bar. The heat transfer model includes radiation exchange among the superheated steam, refractory wall and the solid surface, conduction in the refractory wall, and the mass and energy balances of the steam and solids. Finite-difference techniques are used, and the steady state thermal conditions are assumed. The false transient approach is used to solve the wall conduction equation. The solution is initiated at the inlet of the kiln, and proceeds to the exit. The output data consist of distributions of the refractory wall temperature, solid temperature, steam temperature, and the total kiln length. The inlet of the kiln is the outlet of the gas (superheated steam), since the gas flow is countercurrent to the solid. Thus, for a fixed solid and gas temperature at the kiln inlet, the program predicts the inlet temperature of the gas (i.e. at the kiln exit) in order to achieve the specified exit temperature. In the absence of experimental results for food drying in a rotary kiln, the present model has been satisfactorily validated against numerical results of Sass [1] for drying of wet iron ore in a rotary kiln. The results are presented for drying of apple and carrot pieces. A detailed parametric study indicates that the influence of controlling parameters such as percent water content (with respect to dry solids), solids flow rate, gas flow rate, kiln inclination angle and the rotational speed of the kiln on the axial solids and gas temperature profiles and the total predicted kiln length is appreciable. The study reveals that a good design of a rotary kiln requires medium gas flow rate, small angle of inclination and low rotational speed of the kiln.

Simulation and Optimization of Drying of Wood Chips With Superheated Steam in a Rotary Kiln

2009 ◽  
Vol 1 (2) ◽  
Author(s):  
P. S. Ghoshdastidar ◽  
Ankit Agarwal
Keyword(s):  
Heat Transfer ◽  
Rotary Kiln ◽  
Superheated Steam ◽  
Wood Chips ◽  
Transfer Model ◽  
Gas Temperature ◽  
Simulation And Optimization ◽  
Hot Gas ◽  
Refractory Wall ◽  
Optimization Study

The present work reports a computer simulation and optimization study of heat transfer in a rotary kiln used for drying and preheating wood chips with superheated steam at 1 bar. A rotary kiln employed for drying and preheating wet solids consists of a refractory lined cylindrical shell mounted at a slight incline from the horizontal plane. The kiln is slowly rotated about its longitudinal axis. Wet solids are fed into the upper end of the cylinder, and during the process, they are dried and heated by the counter-current flow of the hot gas. Finally, it is transferred to the lower end, where it reaches the desired temperature and is discharged. The heat transfer model includes radiation exchange among hot gas, refractory wall and the solid surface, transient conduction in the refractory wall, and mass and energy balances of the hot gas and solids. A finite-difference based computational heat transfer approach is used. A univariate search method has been used to obtain the minimum kiln length with respect to various kiln operating parameters subject to a constraint on the inlet gas temperature. The parametric study lent a good insight into the physics of the drying process in a rotary kiln. The optimization study reveals that for the same predicted kiln length, lower inlet steam temperature can be used, which will result in saving of energy cost.

Computer Simulation of Drying of Food Products With Superheated Steam in a Rotary Kiln

2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Koustubh Sinhal ◽  
P. S. Ghoshdastidar ◽  
Bhaskar Dasgupta
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Flow Rate ◽  
Rotary Kiln ◽  
Gas Flow ◽  
Superheated Steam ◽  
Food Products ◽  
Gas Temperature ◽  
Refractory Wall ◽  
Solid Temperature

The present work reports a computer simulation study of heat transfer in a rotary kiln used for drying and preheating food products such as fruits and vegetables with superheated steam at 1 bar. The heat transfer model includes radiation exchange among the superheated steam, refractory wall and the solid surface, conduction in the refractory wall, and the mass and energy balances of the steam and solids. The gas convection is also considered. Finite-difference techniques are used, and the steady state thermal conditions are assumed. The false transient approach is used to solve the wall conduction equation. The solution is initiated at the inlet of the kiln and proceeds to the exit. The output data consist of distributions of the refractory wall temperature, solid temperature, steam temperature, and the total kiln length. The inlet of the kiln is the outlet of the gas (superheated steam), since the gas flow is countercurrent to the solid. Thus, for a fixed solid and gas temperature at the kiln inlet, the program predicts the inlet temperature of the gas (i.e., at the kiln exit) in order to achieve the specified exit temperature of the gas. In the absence of experimental results for food drying in a rotary kiln, the present model has been satisfactorily validated against numerical results of Sass (1967, “Simulation of the Heat-Transfer Phenomena in a Rotary Kiln,” Ind. Eng. Chem. Process Des. Dev., 6(4), pp. 532–535) and limited measured gas temperature as reported by Sass (1967, “Simulation of the Heat-Transfer Phenomena in a Rotary Kiln,” Ind. Eng. Chem. Process Des. Dev., 6(4), pp. 532–535) for drying of wet iron ore in a rotary kiln. The results are presented for drying of apple and carrot pieces. A detailed parametric study indicates that the influence of controlling parameters such as percent water content (with respect to dry solids), solids flow rate, gas flow rate, kiln inclination angle, and the rotational speed of the kiln on the axial solids and gas temperature profiles and the total predicted kiln length is appreciable. The effects of inlet solid temperature and exit gas temperature on the predicted kiln length for carrot drying are also shown in this paper.

Computer Simulation of Heat Transfer in Alumina and Cement Rotary Kilns

2021 ◽  
pp. 1-57
Author(s):  
Atinder Pal Singh ◽  
P.S. Ghoshdastidar
Keyword(s):  
Heat Transfer ◽  
Computer Simulation ◽  
Rotary Kiln ◽  
Cement Kiln ◽  
Gas Temperature ◽  
Contact Heat ◽  
Dry Process ◽  
Radiation Exchange ◽  
Covered Wall ◽  
Rotary Kilns

Abstract The paper presents computer simulation of heat transfer in alumina and cement rotary kilns. The model incorporates radiation exchange among solids, wall and gas, convective heat transfer from the gas to the wall and the solids, contact heat transfer between the covered wall and the solids, and heat loss to the surroundings as well as chemical reactions. The mass and energy balances of gas and solids have been performed in each axial segment of the kilns. The energy equation for the wall is solved numerically by the finite-difference method. The dust entrainment in the gas is also accounted for. The solution marches from the solids inlet to the solids outlet. The kiln length predicted by the present model of the alumina kiln is 77.5 m as compared to 80 m of the actual kiln of Manitius et al. (1974, Manitius, A., Kurcyusz, E., and Kawecki, W., “Mathematical Model of an Aluminium Oxide Rotary Kiln,” Ind. Eng. Chem. Process Des. Dev., 13 (2), pp. 132-142). In the second part, heat transfer in a dry process cement rotary kiln is modelled. The melting of the solids and coating formation on the inner wall of the kiln are also taken into account. A detailed parametric study lent a good physical insight into axial solids and gas temperature distributions, and axial variation of chemical composition of the products in both the kilns. The effect of kiln rotational speed on the cement kiln wall temperature distribution is also reported.

Heat Transfer in the Non-reacting Zone of a Cement Rotary Kiln

1996 ◽  
Vol 118 (1) ◽  
pp. 169-172 ◽  
Author(s):  
P. S. Ghoshdastidar ◽  
V. K. Anandan Unni
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Rotary Kiln ◽  
Gas Flow ◽  
Transfer Model ◽  
Temperature Profiles ◽  
Gas Temperature ◽  
Gas Flow Rate ◽  
Steady State Heat ◽  
Steady State Heat Transfer

This paper presents a steady-state heat transfer model for a rotary kiln used for drying and preheating of wet solids with application to the non-reacting zone of a cement rotary kiln. A detailed parametric study indicates that the influence of the controlling parameters such as percent water content (with respect to dry solids), solids flow rate, gas flow rate, kiln inclination angle and the rotational speed of the kiln on the axial solids and gas temperature profiles and the total predicted kiln length is appreciable.

Paradoxes of Heat Transfer on a Permeable Wall

2010 ◽  
Author(s):  
A. I. Leontiev ◽  
V. G. Lushchik ◽  
A. E. Yakubenko
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Numerical Modeling ◽  
Turbulent Boundary Layer ◽  
Prandtl Number ◽  
Wall Temperature ◽  
Gas Injection ◽  
Gas Mixtures ◽  
Permeable Wall ◽  
Gas Temperature

Numerical modeling of a turbulent boundary layer on a permeable wall with gas injection is performed. New effects are discovered. It is shown in particular that the wall temperature in the region of the gas film may be lower than the injected gas temperature. This effect is especially essential for gas mixtures with low values of the Prandtl number.

A Novel Liquid Crystal Image Processing Technique Using Multiple Gas Temperature Steps to Determine Heat Transfer Coefficient Distribution and Adiabatic Wall Temperature

2004 ◽  
Vol 126 (4) ◽  
pp. 587-596 ◽  
Author(s):  
Abd Rahim Abu Talib ◽  
Andrew J. Neely ◽  
Peter T. Ireland ◽  
Andrew J. Mullender
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Crystal ◽  
Transfer Coefficient ◽  
Wall Temperature ◽  
Image Processing Technique ◽  
Transient Heat Transfer ◽  
Surface Measurement ◽  
Gas Temperature ◽  
Adiabatic Wall

This paper presents a novel experimental technique, which combines thermochromic liquid crystals with multiple steps in gas temperature, to determine heat transfer coefficient and adiabatic wall temperature distributions. The transient heat transfer experiments have been conducted on a flat plate using the low-temperature analogue of an ISO standard propane-air burner commonly used in aero-engine fire certification. The technique involves the measurement of the surface temperature response of an insulating model to a change in gas temperature. A coating comprising more than one thermochromic liquid crystal material is used to increase the range of the surface measurement and this is combined with multiple step changes in gas temperature. These measures induce several peaks in liquid crystal intensity throughout the transient experiment and these are shown to improve the accuracy. The current technique employs useful data from both the heating and cooling phases in the heat transfer test. To the authors’ knowledge, this has not been investigated before and it is likely to be very useful for other applications of the liquid crystal transient heat transfer experiment. The uncertainties in all measurements have been quantified and are presented in this paper.

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