NWGD Symposium 2024

On Thursday 3 October 2024 the (Nederlandse Werkgoep Drogen) NWGD organised its annual symposium on Wageningen Campus. This years’ theme was: “Drying with high energy efficiency and for better products”. In total about 90 participants registered for the event. Besides regular presentations also 6 PhD students pitched their research project. Maarten Schutyser, chair of the NWGD, introduced the day with an introduction to the NWGD society, its activities and the program.

Sebastiaan Tsirakos (Friesland Campina) presented about an innovative energy recovery system for spray drying designed in collaboration with Atlas Copco. In this system most of the sensible heat is recovered from the exhaust air by an indirect heat exchanger while latent heat is recovered by a direct heat exchanger, heat pumps, compressors and condensing heaters, respectively. This system can save up to 70% of the energy consumed in spray dryers. The major challenges are the CAPEX, spatial footprint and microbial growth in air exhaust heat exchangers. Research on risk management of microbial growth in condensing heat exchangers and selecting an existing dryer for further development of the system are the steps ahead.   

Paul Deckers (Bodec) gave an update on agitated thin film (ATF) dryer development. The ATF dryer dries products at the boiling point as a film under reduced pressure. Bodec tested a broad range of products in their ATF dryer. Roughly, three quarters of those products are dried successful or need a bit further optimization. However, liquids with high fat content, complex molecules or high viscosity cannot be dried using the ATFD. Compared to conventional dryers (i.e. small-scale spray dryer, drum dryer and vacuum drum dryer), ATFD showed a better extraction of colour compound from algae. Further, potentially up top 75% of the energy can be recovered using vapour recompression. At the moment, a third large scale ATFD unit is in development.

Evelien Maaskant (Wageningen Food & Biobased Research) presented about the importance of drying for making biobased plastics. As fossil-based plastics negatively impact our environment, transition to plastics that are biobased and do not accumulate in nature is recommended. Regular plastics accumulate in nature as their polymers cannot be easily broken down by bacteria. This is why biobased polymers ideally have molecular structures similar to natural polymers, e.g. often biobased polymers are esters. Polyesters can be made by polycondensation and subsequent solid-state postcondensation with drying to fully complete the reaction. The solid-state postcondensation is done in a vacuum tumble dryer and provides bioplastics of high quality.

Subsequently, the 6 pitch presentations were held:

• The influence of dextrose equivalent value of maltodextrin on d-limonene retention during the encapsulation process by spray drying by   Ana Jauhari (WUR)
• Single droplet drying to steer particle agglomeration during spray drying by Nienke Eijkelboom (WUR)
• A multi-scale investigation on protein addition toward steering agglomeration and yield in spray drying by Anneloes van Boven (WUR)
• Corona wind generation in electrohydrodynamic (EHD) drying by Judith Ham (WUR)
• Numerical Modelling of a Single Droplet Drying by Sanaz Aghaei (TU/e)
• Agglomeration and the effect of fines particle size by Suzan de Leeuw (WUR)

After lunch Andreas Bück (Fau Erlangen-Nurnberg) gave a presentation entitled: “(Toward) superheated steam spray drying (SSD)”.  SSD is in principle similar to convective drying, but operates at much higher process temperatures. There is no mass transfer resistance in the gas phase. The knowledge gap that is being studied, is the time scale of the locking time – the moment that the surface of a droplet becomes solid, and what the properties/ structures of the droplet are. This is done by modelling. It was found that with SSD, the locking point is earlier, which results in larger particles. The centre of the particles has a lower volume fraction of product than the surface. This effect is stronger with higher steam temperatures. The next step for this research is doing experiments with a spray dryer and looking into realistic space designs.

Rick Kirpestein (ISPT/Vsquare Tech bv) presented the potential of “Drying drying air” using zeolite. Dehumidifying drying air is beneficial because production will not be affected by varying outdoor air conditions. In desiccant drying typically silica composite is used to absorb moisture from the drying air. This absorption of moisture simultaneously results in heating of the drying air. Replacing silica by zeolite results in a higher temperature of the drying air as zeolite has a higher temperature limit. Zeolite can result in an energy reduction up to 40-50%. Drying using zeolite was already investigated around twenty years ago but is now becoming more interesting because energy prices are rising.

Kevin van Koerten (NIZO) presented about the new pilot-scale spray dryer with novel air distribution system installed at NIZO food research. The novel air distribution is designed as a circular chamber with 8 inlets with a separator at the back to prevent circulation flows. The air flows through perforated plates when going in the chamber for uniform distribution. The pressure drop of the airflow is influenced by the openness of the perforated plates. A low pressure drop (least openness) that still leads to an homogeneous air distribution is desired. Besides this, the vanes influence the downward velocity and with that the fouling of the dryer.

Henk Roelevink and Joep Bom (HAI & Notilyze) presented the importance of data science in saving water and energy in powder factories. The first step in data science is creating a digital log sheet. After checking the quality of the collected data, the data can be used to find correlations, make predictions and create real time charts and dashboards. Artificial intelligence can help to find the best way to run the factory and minimize the water and energy usage.   

Joanne Siccama (Wageningen Food & Biobased Research) presented about superheated steam drying (SHS) technology. SHS drying is often operated at higher than ambient pressures but can also be operated at reduced pressure to dry heat sensitive products. The steam can be easily recycled to reduce energy use such that only 10-20% of the energy of conventional air drying is needed. Other advantages of SHS drying are that the drying rate is high, oxidation is avoided, and the process can be easily electrified. Two options for applying SHS drying in the paper industry are being evaluated within the EU project SteamDry, i.e. conductive or convective SHS drying. Current challenges are ensuring high steam quality and minimizing fouling (by prevention and removal).

At the end of the program, the three award winners were announced. Nienke Eijkelboom won the pitch award and Ana Jauhari and Sanaz Aghae won the two poster awards. The symposium was concluded with a tasteful vegetarian dinner.

This report & pictures were made by WUR students Janine Bekebrede, Eline Kroon and Sven Nijveen and Martijn de Ruijter.