Journal of Analytical and Applied Pyrolysis 95 (2012) 101–111 Contents lists available at SciVerse ScienceDirect Journal of Analytical and Applied Pyrolysis journa l h o me page: www.elsevier.com/locate/jaap Co-primary thermolysis molecular modeling simulation of lignin and subbituminous coal via a reactive coarse-grained simplification Josep O. Pou a , Yesica E. Alvarez b , Justin K. Watson c , Jonathan P. Mathews b,∗ , Sarma Pisupati b a Departament d’Enginyeria Química, Escola Tècnica Superior IQS, Via Augusta 390, 08017 Barcelona, Spain b John and Willie Leone Family Department of Energy and Mineral Engineering, and the EMS Energy Institute, The Pennsylvania State University, 126 Hosler Building, University Park, PA 16802, USA c The Applied Research Laboratory, The Pennsylvania State University, University Park, PA 16802, USA a r t i c l e i n f o Article history: Received 31 January 2011 Accepted 17 January 2012 Available online 28 January 2012 Keywords: Biomass Devolatilization Co-pyrolysis CPD Wyodak coal Synergy a b s t r a c t Co-pyrolysis of coal and biomass is one immediate approach to reduce net carbon dioxide emissions from heat and power generation. Interestingly there is often co-pyrolysis synergy, commonly enhancing tar and gas yields. To explore the synergy mechanisms requires the ability to predict yields and explore thermol- ysis of coal and biomass chemistry. The current state-of-knowledge allows individual yield predictions through mathematical modeling, and creation of large-scale molecular representations of lignin (as a biomass simplification) and coal. Yet there is no means of coupling these molecular representations and predicted yields. Here a reactive coarse-grained simulation is used to generate 2D lattice representations from complex large-scale subbituminous coal and generic hardwood lignin structural representations. The chemical percolation devolatilization (CPD) model was used to predict yields of chars and tars/gases during pyrolysis. Scripting within a molecular modeling environment generates the reactive 2D lattice in molecular modeling space and also simulates the primary thermolysis within the lattice to achieve the desired yields through a breaking of labile cross-links between “un-reactive” structural nodes. The approach is used to visualize the dynamic yield differentials between lignin and a subbituminous coal and to generate radical fragments that can be used to explore synergistic interactions. In this paper the coarse-graining and thermolysis processes are described. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The main contributor to anthropogenic CO 2 emissions is the energy sector [1]. Worldwide CO 2 emissions from energy repre- sented 60% of the anthropogenic CO 2 emissions in 2007 [1]. One immediate approach to reduce the carbon-intensity is the co-firing of coal with biomass in existing utilities. The combustion (or gasifi- cation) of biomass reduces the effective CO 2 emissions [2,3] while also reducing fly-ash [2], SO 2 [4–6], and NO x emissions [2,5]. The co-pyrolysis of coal and biomass has been widely stud- ied. Mixing coal with biomass can improve fuel reactivity [7,8] and is a possible approach to utilize urban, industrial and agricul- tural wastes. Several studies investigated co-firing with different biomass sources [9] or waste materials such as: sludge waters [4], tires [10], plastic wastes [11], cattle manure [12,13] or nut shells [6,9]. Under certain conditions there is evidence to support syn- ergy in the co-pyrolysis producing enhanced gas and tar yields that would improve fuel reactivity. Others however determined ∗ Corresponding author. E-mail address: jpm10@psu.edu (J.P. Mathews). the properties simply to be the sum of the fractional proper- ties of the individual components [14]. In general those studies that found synergy [6,15–18] were performed at devolatilization temperatures between 400 and 800 ◦ C and at low heating rates (10–20 ◦ C/min). Also, the studies that find evidence of synergistic effects used a biomass fraction of less than 50% by mass. Vuthaluru [14] concludes that there is an additive behavior using biomass con- tributions from 50% to 90% by mass. Sonobe et al. [19] found synergy between lignite and corncob when the analysis used a fixed-bed reactor but additive behavior if the same conditions were evalu- ated with a TGA approach. Unfortunately, given the complexity of the structure of coals and complexities of pyrolysis, the tools do not exist to investigate the possible synergistic interactions of these entities using molecular modeling approaches. This paper addresses this issue by developing a method that enables reactive coarse-grained pyrolysis of a subbituminous coal and biomass (represented by lignin). Lignin is a major compo- nent in terrestrial biomass and has a direct evolutionary linkage to peat and lignitic coals. Thus its devolatilization is similar to low- rank coal pyrolysis [20,21]. A Powder River Basin coal was selected because this region accounted for 44% of the total U.S. production in 2007 [22,23]. Most of this coal (93%) was exported to 48 States 0165-2370/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.jaap.2012.01.013