Agrana - Food industry

AGRANA operates many dryers in its 54 sugar and starch factories for product and by-product drying. The air or steam drying processes are usually heated by natural gas. While heat recovery from the exhaust gas is common, significant amounts of energy cannot be recovered due to lack of appropriate heat sinks. By boosting the temperature level with an industrial heat pump, a considerable amount of energy can be recirculated into the process. Some applications would even allow for closed-loop-dryers at the proposed temperature levels. In these cases, thermal energy would only be required during the start-up phase; during stationary conditions heat pumps could provide all of the required thermal energy. AGRANA’s name is synonymous with refinement of natural, renewable raw materials. During this project major steps will made towards increasing the share of renewable energy in AGRANA’s production. 



A closed loop heat pump will be integrated in the continuous starch drying process at AGRANA in Pischelsdorf, Austria. The drying process requires hot air at 158°C as drying agent. Currently, the air is preheated in several heat exchangers: first, hot water from a waste heat recovery cycle is used, then, steam is applied to reach the final temperature. The heat recovery cycle will also be used as heat source for the heat pump to gain more energy from waste heat. The heat exchanger supplied by the heat pump will be integrated between the two existing ones.

In this DryFiciency closed loop heat pump demonstrator, innovative components adapted exclusively for the project are applied: a modified semi-hermetic screw compressor by Bitzer and a novel lubricant developed by FUCHS. OpteonMZ (HFO-1336mzz-Z) supplied by Chemours is used as refrigerant. The Bitzer screw compressor is based on the company’s proven HS series, which was adapted to fit the requirements of high-temperature applications up to 160°C. It has a two-shaft rotary displacement design with high efficiency profile geometry. The compressor is optimized for parallel operation with up to six compressor units, allows optimal capacity adjustment and has minimal energy requirements under full and part load. It is further equipped with a high efficiency suction gas cooled motor and a high efficiency rotor profile. To guarantee durability, miscibility, wear protection and viscosity required by the compressor, a novel lubricant was developed by FUCHS.

The heat pump demonstrator will have a heating capacity of around 400 kW, which is about 10% of the dryer’s heat demand. The heat supply temperatures will be in the range of 110-160°C. The heat pump demonstrator plant shall decrease end energy consumption by 2200 MWh/a and CO₂ emissions by 500 t/a. 

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