Simulation of coal pyrolysis by solid heat carrier in a moving-bed pyrolyzer Peng Liang a,b, * , Zhifeng Wang a , Jicheng Bi a a State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, PR China b College of Chemical and Environmental Engineering, Shandong University of Science and Technology, Qingdao 266510, PR China Received 28 November 2006; received in revised form 26 June 2007; accepted 26 June 2007 Available online 26 July 2007 Abstract A one-dimensional, steady state, numerical model for coal pyrolysis by solid heat carrier in moving-bed has been developed. The mul- tiple-reaction model of coal pyrolysis and the gas–solid–solid three phases heat transfer theory in packed bed have been applied to account for the pyrolysis process. The results show that the axial temperature distribution of the coal particles increase with a heating rate more than 600 K/min. Coal particle size has significant influence on the heating rate, while blending ratio is the determinant factor of pyrolysis temperature. Given the main operating parameters, product distributions (H 2 , CO, CH 4 , tar, etc) are calculated by the model. The modeling results are found to agree the experimental data using a moving-bed pyrolyzer with processing capacity 10 kg h 1 of coal. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Poly-generation; Coal pyrolysis; Solid heat carrier 1. Introduction Pyrolysis and combustion are the two common types for coal utilization. The utilization efficiency of coal will be improved greatly when the two types are integrated reason- ably. Because the circulating fluidized bed (CFB) combus- tion technique has developed quickly recently, it provides a base for the integration. High-temperature ash from the CFB boiler is used as solid heat carrier to provide heat for the coal pyrolysis, getting gas and tar. The semi-coke from the moving-bed pyrolyzer returns to the CFB boiler to generate electricity and provide heat. Thus, poly-gener- ation of heat, power, gas and tar can be realized in a system by coupling CFB combustion with coal pyrolysis [1]. Modeling work of coal pyrolysis has been widely inves- tigated, and many useful results have been obtained. With the deeper understanding of coal molecular structure in recent years, some models on coal pyrolysis have been reported, such as CPD model, Flash Chain model and FG-DVC model, etc. [2–4]. Moving-bed pyrolyzer of coal pyrolysis with solid heat carrier is one of the most impor- tant parts of the poly-generation system, as it determines whether the combinatorial system runs steady or not. Con- siderable experimental investigation on coal pyrolysis with solid heat carrier has been conducted over the years [5–7], however the relative simulation work is scarcely reported. He [8] reported the calculation and analysis of heat and mass transfer on lignite pyrolysis with solid heat carrier. A moving-bed reactor model based on the theory of flow and heat transfer in non-sintered porous media was devel- oped [9]. However, ash and coal was considered as one unit to describe the heat transfer between solid and pyrolysis gas in the model, which was not an accurate assumption. As a result, the reliability of the prediction on coal particle temperature remains questionable. The present model is based on the heat transfer theory of gas–solid–solid three phases. The multiple-reaction model is applied in the model to forecast the volatile evolution, gas, tar yield and temper- ature distribution in the pyrolyzer. The model is shown to 0016-2361/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2007.06.022 * Corresponding author. Address: State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, PR China. Tel./fax: +86 351 4072379. E-mail address: liangp@sxicc.ac.cn (P. Liang). www.fuelfirst.com Available online at www.sciencedirect.com Fuel 87 (2008) 435–442