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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Computer Simulation of Heat Transfer During Dry Process Cement Production in a Rotary Kiln

Get access (open in a dialog) DOI: 10.1615/IHTC12.3520
6 pages

摘要

The present paper reports computer simulation results for the dry process cement production in a rotary kiln. The raw materials for cement production contain calcium carbonate, silica, shale and iron ore. Theses ingredients are ground to a very fine powder and mixed in a dry condition. Upon heating by hot gases various reactions occur leading to the production of cement compound. Except the final cement making reaction, all other reactions are endothermic. Heat is exchanged among the hot gas, the inner wall of the kiln and the solid surface primarily by radiation. The net radiative heat transfer is calculated using the theory of Hottel(1954) for a gray enclosure containing a gas that emits, absorbs and transmits radiation. Since the wall elements of the kiln are alternately heated and cooled during each revolution by the hot gas and solid respectively, quasi-steady heat conduction is present. False transient method is used to solve the wall conduction equation. Finite-difference techniques are used and steady state thermal conditions are assumed. The solution is initiated at the inlet and proceeds to the exit of the kiln. The direction of the hot gas flow is opposite to that of the solid charge flow. The kiln is divided into axial segments of equal length. The mass balance of each species in the solid charge, mass and energy balances of the solid and gas are used in each segment. The rates of reaction are assumed to be governed by Arrhenius equation. The present model predicts the length of the kiln to be 61.75 m as compared to 66 m of the actual kiln of 4 m inner diameter and 0.2 m thickness located in BASTAS cement plant in Ankara, Turkey reported in Guruz and Bac(1981). The cement production rate computed by the present program is 45133.2 kg/hr as compared to the actual value of 42400 kg/hr. The paper also presents axial solid and gas temperature profiles and axial solid compositions as well as circumferential and radial wall temperatures. A detailed parametric study lends good insight into the dry process cement making process.