The digitization of the manufacturing industry is essential to improve its efficiency and competitiveness. However, the digitization of the biomass sector is scarce, compared to other sectors. This article presents the work carried out to develop a digital twin of a fundamental equipment/process in biomass pellets manufacturing, such as the drying of the raw biomass. In particular, the digital twin is focused on a rotary dryer, commonly employed in pellets manufacturing, not only in the biomass sector but also in others like food or pharmaceutical sectors. A rotary dryer reduces the humidity in particulate matter through direct contact with flue gases from fossil or renewable fuels combustion (biomass). The combustion gases are mixed with air and recirculated gases from the rotary dryer to obtain a stream of gases whose temperature should not exceed 400 ºC, since higher temperatures could damage the material to be dried. The design and operation of a rotary dryer present significant challenges, mainly because it must be flexible enough to adapt to a multitude of operating modes. The digital twin elaborated combine detailed modelling of the rotary dryer, system simulation for the integration (optimization and control) of the equipment in the overall thermal process of the plant, and data analytics of the operation (for monitoring and maintenance). The developed models are solved in real-time, and the digital twin can be accessed on the cloud. The digital twin will support the design, production and operation phases of the rotary dryer. It will help the manufacturer company design faster and more reliable, better integrate the equipment in the customers’ general process, and provide an optimal configuration of the process (maximization of production with the lowest energy consumption), improving the customer experience. In addition, the manufacturer company will obtain insights through the results of simulation and data analysis, which can facilitate the development of new designs. In summary, this work describes the design and elaboration of a digital twin of a fundamental part of the manufacturing process of biomass pellets, and it proves the benefits of a tool like that in the biomass sector. This work has been carried out under the framework of the European project, DIGITbrain, being part of the second wave of DIGITbrain Experiments https://digitbrain.eu/2nd-wave-of-digitbrain-experiments/