Flax Straw Char-CO 2 Gasification Kinetics and its Inhibition Studies with CO Thilakavathi Mani and Nader Mahinpey* Department of Chemical and Petroleum Engineering, Schulich School of Engineering, The University of Calgary, Calgary, Alberta, Canada, T2N 1N4 Char gasification has been studied in different ways with different feedstock; however, the fundamental studies about the variation of char reactivity with different combination of parameters are still required in order to design the biomass char gasification process in large scale unit. In this work, char from flax straw pyrolysis was used for gasification with different partial pressure of CO 2 , different temperature and particle size. Results showed that 375-m particle sizes of char has higher reactivity compared to other particle sizes and the inhibition effect was also less at 375-m particle size. Kinetic parameters varied for gasification reaction with different particle sizes and the average activation energy was 196 kJ/mol and the order of the reaction was approximately 1. Inhibition studies with the addition of CO in the gasifying agent proved that CO molecules interfere significantly and reduced the reactivity. ANOVA test showed that the temperature plays a vital role in char reactivity. The particle sizes of 375 and 800 m along with the CO 2 partial pressure of 0.35 bars are the best combination for achieving the maximum reactivity. Keywords: char gasification, flax straw, inhibition, kinetics, particle size, reactivity INTRODUCTION B iomass is one of the largest sources of energy reserves in the world. The advantages of being CO 2 neutral, having low sulfur content, and being easy to transport make biomass a dominant choice for the replacement of fossil fuels (Demirbas, 2001; Naik et al., 2010). Biomass consists primarily of cellulose, hemicellulose and lignin. Cellulose is composed of monomers of glucose, a six sugar linked by ˇ (1–4) glycoside bonds. Hemi- cellulose is a highly branched carbohydrate and is composed of both hexose and pentose sugar. Lignin is macromolecular in nature with phenolic character; it is helical and contains ether and carbon–carbon linkages (Scott and Piskorz, 1984; Czernik and Bridgwater, 2004). Gasification process consists of two main reactions: the initial rapid devolatilisation of biomass or coal pro- duces char, tar and gases and the subsequent gasification of the produced char (Paviet et al., 2008). Research into the fundamen- tal aspects of the char gasification process has evidently identified the rate of gasification of char as a significant factor controlling coal or biomass gasification behaviour. This is mainly due to the relatively slow kinetics of the char reaction with CO 2 under gasi- fication conditions (Roberts et al., 2010; Zhang et al., 2010). An extensive literature is available on the reactivity and the heteroge- neous kinetics of coal and coal char gasification and combustion. However, the number of studies on lignocellulosic char reactivity is comparatively much smaller. Actually, the properties of char from coal and lignocellulosic biomass differs in many aspects such as reactivity, ash content, pore sizes, etc. (Di Blasi, 2009). There- fore, studies on the reactivity of lignocellulosic char are essential for the design and development of gasifiers that work based on the biomass feed stocks. Char gasification characteristics are mainly dependent on the nature of biomass and operating conditions. Several factors influ- ence the gasification rates such as particle size, char porosity, mineral content of the char, temperature and partial pressure of the gasifying agents (Ollero et al., 2002; Cetin et al., 2005). Stud- ies of char reactivity, useful for kinetic analysis, are mainly based on thermogravimetric measurements (Gomez-Barea et al., 2005, 2006). Reactivity determined using TGA may deviate from that observed in commercial equipment, when fuel particles undergo rapid heating during devolatilisation. Under controlled condi- tions, the study of char gasification such as TGA can provide ∗ Author to whom correspondence may be addressed. Department of Chemical and Petroleum Engineering, Schulich School of Engineering, The University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4. E-mail address: nader.mahinpey@ucalgary.ca Can. J. Chem. Eng. 9999:1–7, 2012 © 2012 Canadian Society for Chemical Engineering DOI 10.1002/cjce.21696 Published online in Wiley Online Library (wileyonlinelibrary.com). | VOLUME 9999, 2012 | | THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING | 1 |