Customised adsorption dryer replaces refrigeration dryer

Compressed air treatment according to the latest guidelines

The operator is a food & beverage manufacturer that specialises in coffee refinement, among other things. The compressed air is frequently used in production and comes into direct contact with the products (e.g. coffee granulate) at several points. The important certifications in the food industry and the specifications resulting from an audit required a stable pressure dew point (DTP) of below -40°C in order to maintain the desired compressed air class with a DTP of class 2 according to ISO 8573-1. In addition, 100% availability of compressed air in 24/7 operation was required. The compressed air station consists of several decentralised, oil-lubricated screw compressors that are fed to a manifold. In the past, the compressed air was dry at a degree of dryness of <3°C pressure dew point (DTP) and processed oil-free by means of an activated carbon adsorber. The operator took the opportunity of an upcoming refrigeration dryer repair to discuss a replacement with his specialised trade partner Wecker Druckluft and to work out a corresponding concept. The compressed air treatment had to meet the requirements of the audit and the latest guidelines in the food industry, as well as enable a trouble-free pressure dew point. There was also a special challenge: the low room height at the desired installation site precluded the installation of standard dryers of the required performance class.

Adsorption dryer with special construction height enables energy savings

BEKO TECHNOLOGIES is a long-standing partner of Wecker Druckluft and has a lot of experience in the food & beverage sector. Instead of a new refrigeration dryer, we recommended a custom-built EVERDRY FRA 6000 Eco adsorption dryer to the food producer, which fits into the space thanks to lower adsorbent tanks. There were two key success factors for the performance of a smaller built adsorption dryer compared to a standard size. Firstly, the Sorbead Air adsorbent from BASF selected for the application is approximately 20 % more efficient than conventional activated alumina. This efficiency of the high-performance adsorbent allowed the overall height of the adsorption dryer to be reduced by 30 cm while maintaining the same performance. The low desorption temperature of Sorbead Air reduces energy requirements during regeneration and offers a long service life due to its abrasion resistance and mechanical and thermal stability. The second success factor was a real added value of the EVERDRY FRA6000 Eco dryer - namely the use of steam, which is abundantly available at the operator's site. Heated ambient air is used to desorb the adsorbent, which is normally done by centrifugal fans and electric heaters in standard dryers. In this case, the steam heats the fan air via a steam heat exchanger. In this way, an already existing energy is used instead of generating thermal energy for desorption with expensive electrical power.

Higher compressed air class achieved

The operator was convinced by our concept and placed the order. The oil-lubricated screw compressors now go to the manifold and are followed by the EVERDRY FRA6000C Eco adsorption dryer and the activated carbon adsorber incl. corresponding filtration. Since June 2019, the plant has been running reliably and has even exceeded the operator's requirements. The pressure dew point is far better than required. The compressed air achieves a quality of compressed air class1-2-1 (previously 1-4-1) and is 50 times drier. Thus, not only the degree of dryness has been optimised, but also the absorption capacity of the oil vapour in the activated carbon adsorber. The quality and thus the production reliability are significantly more stable. The operator had subjected the adsorption dryer to a preliminary acceptance test at the BEKO TECHNOLOGIES plant in Netphen and at the same time the service technicians had been trained for the unit by Wecker Druckluft. In the course of commissioning, individual optimisations were made to the dryer programme in order to implement further customer requirements. The compressed air requirements are now state-of-the-art and the operator is optimally positioned for the future. Further joint projects are to follow.