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Magazine
Efficiently Achieving the Optimum Particle Size
What does the term "optimal particle" mean, and what technological factors determine its properties?
Gudrun Ding: An optimal particle precisely meets the requirements of downstream processes or the planned application. This includes size, shape, density, homogeneity, surface, solubility, and mechanical stability. To achieve this, the formulation, process and system design must be perfectly coordinated. At the same time, energy consumption must always be taken into account.
The specific material properties of the initial materials and the target parameters of the end product determine the choice of process. Particle formation itself depends on factors such as solubility, stickiness and primary particle size. In terms of process technology, this can be controlled via air velocity, temperature and humidity, while a suitable plant geometry additionally supports particle formation.
Where is the greatest potential for energy savings in thermal processes such as drying, agglomeration or coating?
Gudrun Ding: All of the methods mentioned are essentially drying processes. The energy requirement depends primarily on the amount of water to be evaporated. Spray drying or granulation, with typical solids contents of 30 to 50 percent, consumes the most energy. During agglomeration, only enough moisture is added until the desired particle size and shape are achieved. When coating, the amount of film to be applied depends on the particle size: The finer the product, the more coating material is required. When functional properties are required, low-concentration polymer solutions are often used. These are dispersions with a high water content, which consequently require more energy for evaporation. Potential savings can be achieved by setting the solids content of moist masses or suspensions as high as possible and optimally coordinating the process parameters, i.e. air velocity, temperature and humidity. Partial recirculation of process air to reuse waste heat and moisture also contributes to energy efficiency. Furthermore, additional savings can be achieved by selecting the process gas and system pressure, for example in circulation processes under vacuum or with superheated steam.
How can high particle quality be combined with energy-efficient process control?
Gudrun Ding: The use of existing energy sources in the overall system is essential. In a closed energy concept, all energy flows are analysed, bundled and fed back into the process via heat exchangers. In fluidised bed processes, for example, the residual heat from the exhaust air and the energy from the atomisation gas are recovered and used to preheat the supply air. This ‘heat swing’ is an integral part of the planning of new systems, provided that the temperature gradient is sufficiently high. Depending on the process, heat recovery of up to 30 percent can be achieved in winter, and around 15 percent in summer due to lower temperature differences.
Furthermore, efficiency can be increased through the use of heat pumps. They increase the energy level of the collected residual heat so that it can be used not only for the process itself, but also for upstream applications such as water heating or building heating.
Are there any practical examples where an optimised system or process concept has significantly reduced energy consumption?
Gudrun Ding: Saving energy is particularly effective when it is approached holistically. In addition to the thermal efficiency of the process, we always also consider the entire product chain. For our customers, the carbon footprint of a product is considered along the entire production chain – from raw materials to the final product ready for consumption. For example, a higher bulk density with the same product output can reduce the carbon footprint because less packaging material, storage space and transport volume are required. Similarly, a more compact particle structure can reduce hygroscopicity (moisture absorption), eliminating the need for costly coated packaging. These examples demonstrate how important it is to take a comprehensive and unbiased view of product and process development in order to exploit the full savings potential.
What role do digitalisation, sensor technology and data analysis play in energy optimisation?
Gudrun Ding: Accurate recording and analysis of process data is the key to greater efficiency. Automated processes can help save energy even when starting up and shutting down systems. Optimally adjusted controllers prevent fluctuations in the process and ensure consistent product quality. Continuous analysis of measurement data makes it possible to identify potential for optimisation at an early stage and avoid downtime.
What developments are on the horizon in the field of energy-efficient powder and granulate processes?
Gudrun Ding: The use of superheated steam as a process gas offers great opportunities – it allows for better energy utilisation and is particularly suitable for oxidation-sensitive materials. Although high product temperatures can have a limiting effect, the potential is enormous and is being further researched. Another approach is to use the heat generated by exothermic processes directly for the drying step, thereby reducing energy consumption. Sustainability remains the most important driver of innovation and energy-efficient processes are a key element of this progress.
What framework conditions does the industry need in order to fully exploit this potential?
Gudrun Ding: The technological possibilities are there. It is crucial that companies are given planning security for their investments. The energy transition offers great opportunities for innovation, but this requires a reliable long-term political framework.
About Glatt Ingenieurtechnik GmbH
Glatt Ingenieurtechnik GmbH, based in Weimar, German, is part of the internationally operating Glatt Group. The company develops and implements systems and processes for the production and refinement of powders, granulates and particles for the food, chemical and pharmaceutical industries.
For additional information:
Gudrun Ding
Head of PTF-New Technologies
Glatt Ingenieurtechnik GmbH
Nordstraße 12
99427 Weimar, Germany
