The first step in this project consisted of defining the project's strategy (biomass boiler to validate the model, characteristics of the fixed bed model, implementation).
The biomass boiler on which to build the model was chosen: a spreader stoker. In this type of biomass boilers, the biomass is fed from over the fixed bed, adding extra complexity yo the model. On the other hand, this will allow the building of a model better adapted to any biomass boiler.
The next step was the definition of the fixed bed model features. We envisioned a model able to deal with multiple materials (wood, straw, waste), combining Eulerian and Lagrangian approaches. The final purpose was to improve the detail of Eulerian models without substantially increasing the computational cost. After the definition of the fixed bed model characteristics, we developed it.
Simultaneously to the development of the fixed bed model, we built the freeboard CFD model. This model solves the multiphasic fluid flow, turbulence, heat transfer, radiation, and chemical reaction in the freeboard.
The next step was the coupling between the fixed bed and the freeboard models. The coupling between both models must consider all the mass (particles), energy and species transfer between the fixed bed and the freeboard. Novel algorithms were developed to manage the coupling between both models.
Finally, we integrated the fixed bed and freeboard models into one model. This makes the model's resolution more compact and robust than other approaches in which the freeboard and the fixed bed are solved with different software. This final model was applied to two real biomass spread stoker boilers with different sizes (25 MWth and 50 MWe). In both cases, the comparison of the numerical results with the measurements was satisfactory.
The main result obtained by DT4Biomass has been the elaboration of an innovative, affordable and accurate model for the integral simulation of biomass boilers. Additionally, nablaDot has increased its know-how about the simulation of thermochemical processes of biomass and the application of Lagrangian models to simulate complex phenomena. Finally, the DT4Biomass project has increased the Innovative Associate's competencies.
nablaDot will present an article at the 29th European Biomass Conference (EUBCE 2021) about the biomass boiler model developed. Additionally, we aim the publication of 2-3 articles in international scientific journals. In parallel, nablaDot will disseminate the DT4Biomass through its website and social networks (LinkedIn, Twitter).
nablaDot has also envisioned an ambitious plan to exploit the results. nablaDot will present the model's features to companies working in the biomass boiler sector and other companies related to biomass thermochemical equipment (pellets manufacture, gasification, pyrolysis, bio-refineries, etc.). Additionally, nablaDot expects to prepare several R&D proposals to increase the biomass boiler model's functionalities (such as the heat transfer simulation at the convective pass and other phenomena like fouling or corrosion) or the elaboration of reduced-order models (ROM) from CFD biomass boiler simulations. Those models can be solved in real-time. This feature allows their integration into platforms for the control and management of biomass boilers. Therefore, DT4Biomass has been only nablaDot's first step to contribute to the bioenergy sector's digitalization.
