High-temperature pyrolysis modeling of a thermally thick biomass particle based on an MD-derived tar cracking model

Biomass pyrolysis in the thermally thick regime is an important thermochemical phenomenon encountered in many different types of reactors. In this paper, a particle-resolved algorithm for thermally thick biomass particle during high-temperature pyrolysis is established by using reactive molecular dynamics (MD) and computational fluid dynamics (CFD) methods. The temperature gradient inside the particle is computed with a heat transfer equation, and a multiphase flow algorithm is used to simulate the advection/diffusion both inside and outside the particle. Besides, to simulate the influence of intraparticle temperature gradient on the primary pyrolysis yields, a multistep kinetic scheme is used. Moreover, a new tar decomposition model is developed by reactive molecular dynamic simulations where every primary tar species in the multistep kinetic scheme cracks under high temperature. The integrated pyrolysis model is evaluated against a pyrolysis experiment of a centimeter-sized beech wood particle at 800 to 1050 \ub0C. The simulation results show a remarkable improvement in both light gas and tar yields compared with a simplified tar cracking model. Meanwhile, the MD tar cracking model also gives a more reasonable prediction of the species yield history, which avoids the appearance of unrealistically high peak values at the initial stage of pyrolysis. Based on the new results, the different roles of secondary tar cracking inside and outside the particle is studied. Finally, the model is also used to assess the influence of tar residence time and several other factors impacting the pyrolysis

The sun is no fun without rain : Physical environments affect how we feel about yellow across 55 countries

Across cultures, people associate colours with emotions. Here, we test the hypothesis that one driver of this cross-modal correspondence is the physical environment we live in. We focus on a prime example – the association of yellow with joy, – which conceivably arises because yellow is reminiscent of life-sustaining sunshine and pleasant weather. If so, this association should be especially strong in countries where sunny weather is a rare occurrence. We analysed yellow-joy associations of 6625 participants from 55 countries to investigate how yellow-joy associations varied geographically, climatologically, and seasonally. We assessed the distance to the equator, sunshine, precipitation, and daytime hours. Consistent with our hypotheses, participants who live further away from the equator and in rainier countries are more likely to associate yellow with joy. We did not find associations with seasonal variations. Our findings support a role for the physical environment in shaping the affective meaning of colour.Peer reviewe

High-temperature pyrolysis modeling of a thermally thick biomass particle based on an MD-derived tar cracking model

Biomass pyrolysis in the thermally thick regime is an important thermochemical phenomenon encountered in many different types of reactors. In this paper, a particle-resolved algorithm for thermally thick biomass particle during high-temperature pyrolysis is established by using reactive molecular dynamics (MD) and computational fluid dynamics (CFD) methods. The temperature gradient inside the particle is computed with a heat transfer equation, and a multiphase flow algorithm is used to simulate the advection/diffusion both inside and outside the particle. Besides, to simulate the influence of intraparticle temperature gradient on the primary pyrolysis yields, a multistep kinetic scheme is used. Moreover, a new tar decomposition model is developed by reactive molecular dynamic simulations where every primary tar species in the multistep kinetic scheme cracks under high temperature. The integrated pyrolysis model is evaluated against a pyrolysis experiment of a centimeter-sized beech wood particle at 800–1050 °C. The simulation results show a remarkable improvement in both light gas and tar yields compared with a simplified tar cracking model. Meanwhile, the MD tar cracking model also gives a more reasonable prediction of the species yield history, which avoids the appearance of unrealistically high peak values at the initial stage of pyrolysis. Based on the new results, the different roles of secondary tar cracking inside and outside the particle are studied. Finally, the model is also used to assess the influence of tar residence time and several other factors impacting the pyrolysis