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Digital twin for biomass boilers

Periodic Reporting for period 1 - DT4BIOMASS (Digital twin for biomass boilers)

Período documentado: 2019-12-15 hasta 2021-01-14

DT4Biomass (Digital Twin for Biomass Boilers) aims to contribute to the biomass sector's digitalization, specifically biomass boilers' simulation.
Biomass boilers manufacturers (SMEs and midcaps) often base their design processes on their experience, trial-error methodologies and relatively simple calculation tools. With this methodology, reasonable solutions are found, but they might be far from the optimal solution. Computational fluid dynamics (CFD) is a powerful tool for designing and optimizing all types of boilers. Until now, CFD has been used mainly for the modelling of fossil-fuel boilers. The bigger size of the fossil-fuel boilers and a more (relative) simplicity of the required CFD models make it more affordable to apply these techniques.

DT4Biomass has developed complete and accurate biomass boiler models to overcome these barriers, based on computational fluid dynamics techniques, which can be easily adapted to simulate any biomass boiler. Additionally, and not least, the elaborated models are relatively simple to implement and affordable (reasonable computational resources) for manufacturing SMEs. The ultimate goal is to ensure that manufacturing SMEs and companies operating biomass boilers can incorporate these tools into their design process to optimize their biomass boiler's performance.
The application of the developed tools can contribute to some of the next-generation biomass boilers' challenges: the reduction of polluting gases (NOx, CO, HCl or SO2) and particulate matter emissions, the increase of the boiler's efficiency, the improvement of the predictive maintenance (fouling, slagging, corrosion) and the enhancement of the boiler flexibility (to use different biomass fuels and to adapt to the electric demand curve). Some of these new requirements for biomass boilers are already included in the European legislation (EU Directive 2018/2001).
Manufacturing better biomass boilers will increase the share of biomass energy in energy consumption, avoid the risks associated with this technology, and contribute to the climate neutrality target aimed by the European Union by 2050. Additionally, the objectives of DT4Biomass are aligned to the following Sustainable Development Goals: SDG7 (Affordable and Clean Energy), SDG9 (Industry, Innovation and Infrastructure) and SDG12 (Responsible consumption and production).
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.
The DT4Biomass progress beyond state of the art is summarized in the application and development of CFD Lagrangian methods to simulate complex phenomena. The developed method can calculate the diameter of each particle along all the combustion process. This allows obtaining a higher accuracy in the calculation since the particle's size is an essential parameter for the fixed bed's phenomena (heat transfer, drying, devolatilization, heterogeneous combustion).
The main advantage of these Lagrangian models is that they are affordable from the point of view of computational resources needed. This is paramount to support the adoption of advanced simulation techniques by the manufacturing industry and boilers operators.

The main expected impact of DT4Biomass is supporting nablaDot to become a relevant actor in the digitalization of the bioenergy sector. This new business line is expected to contribute to the internationalization of the nablaDot's activities, generate 50% of the current turnover of nablaDot and create three jobs in the medium term (three years).

The digitalization of the biomass sector is essential for deploying this renewable energy that will be essential in the transition to climate neutrality. The activities developed in DT4Biomass will contribute to these digitalization requirements, supporting the development of more efficient and resilient equipment and facilities. Thus, DT4Biomass aims to support the following Sustainable Development Goals: SDG7 (Affordable and Clean Energy), SDG9 (Industry, Innovation and Infrastructure) and SDG12 (Responsible consumption and production).
Flue gas temperature contours calculated
Detail of the nitrogen oxides concentration calculated
Detail of the oxygen concentration calculated
Detail of the flue gas temperature contours calculated
Detail of the carbon monoxide contours concentration calculated
Oxygen concentration contours calculated
Scheme of the biomass boiler modelled