Termodinamica

Fuel 84 (2005) 569–575 www.fuelfirst.com

Thermochemical characteristics of sugar cane bagasse pellets
¨ ¨ Catharina Erlicha,*, Marcus Ohmanb,1, Emilia Bjornbomc,2, Torsten H. Franssona,3
Department of Energy Technology, Royal Institute of Technology, Brinellvagen 60, 100 44 Stockholm, Sweden b ˚ ˚ Energy Technology and Thermal Process Chemistry, Umea University, 901 87 Umea, Sweden cDepartment of Chemical Engineering and Technology, Royal Institute of Technology, 100 44 Stockholm, Sweden Received 7 April 2004; received in revised form 7 October 2004; accepted 13 October 2004 Available online 10 November 2004
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Abstract Pelletisation facilitates utilisation of sugar cane bagasse as a fuel and storage for year-round electricity generation. The present work determines thermochemicalcharacteristics of bagasse pellets of different sizes and origins, using various temperatures (600, 750 and 900 8C) and gas flow rates (4, 7 and 10 L/min) with varying concentrations of oxygen (5, 10 and 15%) in mixtures with nitrogen. Of major interest are the effects of raw material, origin and size of pellets, and the treatment conditions on the rate of pyrolysis and the structure andreactivity of char in combustion. The char yield of the larger pellets of high-ash content bagasse was practically independent of treatment conditions. Smaller pellets gave better mechanical stability of the char but lower reactivity. q 2004 Elsevier Ltd. All rights reserved.
Keywords: Flaming pyrolysis; Pellets; Bagasse; Gasification

1. Introduction Sugar cane residues are largely available in sugarproducing countries such as Brazil, India, Cuba, Mexico and China. The heat needed for concentrating the sugar-rich juice is usually produced from combustion of cane residues in a steam power plant within the factory. The sugarcane residues can be divided into bagasse and cane trash [1,2]. Bagasse is the fibrous material left over after pressing out the sugar-rich juice. Cane trash consists of topsand leaves that in traditional sugar cane harvesting are burned off in the field before picking the cane stem. As environmental awareness has increased worldwide, this technique has in many countries been substituted by ‘green’ harvesting techniques, i.e. separating the tops and leaves mechanically and thus increasing the biomass residues from sugar cane [2].
* Corresponding author. Tel.: C46 8 7907468; fax: C46 8 20 4161. E-mail addresses: erlich@energy.kth.se (C. Erlich), marcus.ohman@ ¨ ¨ chem.umu.se (M. Ohman), emilia@ket.kth.se (E. Bjornbom), fransson@ energy.kth.se (T.H. Fransson). 1 Tel.: C46 90 786 6324; fax: C46 90 786 9195. 2 Tel.: C46 8 790 8256. 3 Tel.: C46 8 790 7475; fax: C46 8 20 4161. 0016-2361/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.fuel.2004.10.005

Bagasse has a high moisture content (50%) and is often burned at low steam parameters to create a balance between the needed process heat and combusted bagasse to avoid a disposal problem [3]. As the sugar industry is seasonal, many processes have not been designed to provide excess energy in form of electricity to the national grid. Due to the increasing energy demand worldwideit is feasible to improve the steam generation process to better utilize the bagasse, and to deliver electricity to the grid year-round by supplementary burning cane trash or wood during offseason. A serious problem with bagasse is that it is a nonuniform voluminous material and applying it to modern combustion or gasification technologies may be difficult. In fluidised beds it tends to float on top ofthe bed instead of mixing with the bed-material. Pelletising the bagasse is a way of improving the fuel handling, transportation, conversion and also allowing for storage for off-season utilisation. Wood pellets are already commercialised and the utilisation in heat power plants as well as for residential heating has increased significantly during the recent years. Wood pellet production in...