Co-primary thermolysis molecular modeling simulation of lignin and subbituminous coal via a reactive coarse-grained simplification

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 thermolysis 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.

► We develop a novel modeling approach to visualize lignin and subbituminous coal co-pyrolysis. ► The approach uses reactive coarse-graining. ► The individual pyrolysis yields were calculated using CPD. ► After devolatilization, radicals are separated according to molecular weight into two layers. ► The results shown are the radicals that will evolve into the different devolatilization products.