The development of fossil-free technologies is essential to tackle climate change. Today, there are acute demands to accelerate the development of low-carbon technologies such as oxyfuel combustion and biomass gasification. Numerical simulations can potentially substitute costly trial-and-error scale-up procedures and drastically accelerate the process development in a cost-efficient manner. However, the simulation tools can be useful only if the critical sub-models that describe physical and chemical phenomena are sufficiently accurate. This project, which is funded by Vetenskapsrådet, aims to improve the understanding of heat and mass transfer inside and around reacting porous particles and to provide simple sub-models that can be implemented in industry-relevant simulations. The project will be executed through the investigation with PR-DNS (particle-resolved direct numerical simulation) of single particles. The detailed insight from the PR-DNS will be used to develop sub-models that can describe the observed effects without having to solve additional differential equations. The first stage of this project aims to study the effect of porosity on a singular particle under varying non-isothermal conditions. This will be done by carrying out a sweep of applicable Reynolds and Biot numbers for both a non-porous and porous particle. Then the resulting Nusselt number and drag for a non-porous and porous particle will be compared. In a second stage it will be investigated how the different categories of heterogeneous reactions (equimolar or non-equimolar; exothermal, endothermal, or thermally neutral) affect the intra-particle transport phenomena and result in different overall reaction rates. To isolate the effects of mass transfer and heat transfer, first, the analyses will be carried out without the consideration of temperature changes (isothermal case). Then, the second series of studies will consider the heat of reaction and the temperature changes to investigate the combined effects of heat and mass transfer.