Journal of Analytical and Applied Pyrolysis 108 (2014) 203–211 Contents lists available at ScienceDirect Journal of Analytical and Applied Pyrolysis journal h om epage: www.elsevier.com/locate/jaap Co-pyrolysis reaction rates and activation energies of West Virginia coal and cherry pit blends Pablo Yangali a , Ana M. Celaya a , Jillian L. Goldfarb b,∗ a Department of Chemical Engineering, University of New Hampshire, 33 Academic Way, Durham, NH 03824, United States b Department of Mechanical Engineering and Division of Materials Science & Engineering, Boston University, 15 St. Mary’s Street, Brookline, MA 02446, United States a r t i c l e i n f o Article history: Received 2 December 2013 Accepted 27 April 2014 Available online 5 May 2014 Keywords: Biomass–coal blends Co-pyrolysis Activation energy Derivative thermogravimetry a b s t r a c t Bringing our society to a carbon-neutral, clean-energy future is an evolutionary process that must com- bine technological advances with available infrastructure. By co-firing biomass in existing coal-fired power plants, we can utilize standing equipment to increase the share of renewables in energy gener- ation portfolios. This study investigates the pyrolysis behavior of blends of sweet cherry pit stones and a West Virginia coal using thermogravimetric analysis at a heating rate of 100 K/min under nitrogen to determine mass loss rates and global activation energies as a function of blend composition. Derivative thermogravimetric curves show two distinct peaks for the fuel blends at temperatures corresponding to peaks for the pure cherry pits and coal. The peak mass loss rates for blends are higher than predicted using an additive scheme at the lower temperature peak and lower than predicted at the higher tem- perature peak. Global activation energies determined using a first order Arrhenius equation were higher than predicted by a linear addition scheme at lower temperatures, and lower than predicted at higher temperatures, suggesting that the incorporation of the cherry pit biomass may promote devolatilization of the coal at lower temperatures. © 2014 Elsevier B.V. All rights reserved. 1. Introduction To increase the share of renewables in their energy portfo- lios and reduce their pollutant emissions, coal-fired power plants worldwide are co-firing biomass in varying proportions with coal [1]. This is especially useful when it comes to abating SO x emis- sions that result from burning the highly sulfurous coals mined in the United States. In West Virginia, where coal mining is a driving factor of the state’s economy, over 93% of the electricity generated comes from coal [2]. While this statistic is likely to remain high for the foreseeable future, one way to increase the use of biomass for energy generation in the immediate time frame is as a blended feedstock in coal-fired boilers. In this study, we look at the pyrolytic behavior of blends of a commercial West Virginia coal and sweet cherry pits using thermogravimetric analysis. During the thermochemical conversion of coal and biomass, devolatilization can account for the majority of the solids’ weight loss, depending on the organic constituents of the fuel [3,4]. The evolution of gaseous products and tars, and the formation of ∗ Corresponding author. Tel.: +1 617 353 3883. E-mail addresses: JillianLGoldfarb@gmail.com, jilliang@bu.edu (J.L. Goldfarb). carbonaceous chars during pyrolysis, result from the depolymer- ization, vaporization and cross-linking of the solid fuel matrix. While both coal and biomass undergo pyrolysis as an initial (and often rate-limiting) step to eventual combustion, the rates and temperatures at which the reactions occur can be significantly dif- ferent [5,6]. Moreover, when two solid fuels are blended, debate exists over whether or not the thermal devolatilization of the blend occurs as the independent summation of the reactions of both fuels, or if reaction synergies exist that promote the devolatilization of the solid having the more condensed structure (in this case, coal) because of reactions occurring in the more volatile component [7]. Some conclude that the rates and activation energies of pyrolysis of coal–biomass blends are the linear addition of each component’s independent behavior, that is, that no interactions exist between the biomass and coal [8,9]. Others find evidence for synergistic reac- tions between the solids, negating a simple linear addition model for activation energies to predict blend behavior. This evidence comes in the form of non-additive natures of the kinetic param- eters such as activation energies, and also the products formed upon of co-pyrolysis. Some groups find that the yields of specific volatile products are not proportional to the yields experienced upon pyrolysis of components separately [10–15]. The mechanisms underlying this behavior are unclear; Aboyade et al. [16] provide http://dx.doi.org/10.1016/j.jaap.2014.04.015 0165-2370/© 2014 Elsevier B.V. All rights reserved.