Agrana is a leading Austrian company adding value to agricultural commodities by producing a wide range of industrial products for the processing sector. It operates many dryers in its 54 sugar and starch factories for product and by-product drying, which are currently mainly fossil-fired, although heat recovery options are being implemented wherever feasible.
In the DryFiciency project, Agrana makes a major step towards increasing the share of renewable energy in its production facilities. A novel closed loop compression heat pump system is developed and integrated in one of the company’s starch drying process at the production site of Agrana Stärke GmbH in Pischelsdorf, Lower Austria, and demonstrated first-time in industrial environment at heat supply temperatures up to 160°C.
DESCRIPTION OF HEAT PUMP ASSISTED BRICK DRYING PROCESS:
The bricks are dried in a continuous process in a tunnel dryer. Air that flows counter-currently to the bricks is used as drying agent. The moisture content of the bricks is reduced from 28% (at the time of entering the dryer) to 2%. The drying air in the tunnel is heated by internal heat exchanger surfaces, which are supplied with water with 90°C by a heat recovery cycle. The heat pump also uses the heat recovery cycle as its heat source. The evaporator is integrated before the heat exchangers. The heat pump provides hot air via an intermediate circuit, heat supply temperatures up to 160°C can be reached there. The hot air is fed into the outlet zone of the tunnel dryer, where the highest temperatures are required. The heat pump acts as a booster for the heat recovery cycle.
DESCRIPTION OF HEAT PUMP DEMONSTRATOR
The DryFiciency heat pump demonstrator placed in a container has a heating capacity of around 400 kW. It replaces a natural gas burner and shall lead to end energy savings of up to 84% and reductions in CO₂ emissions of about 80%.
The heat pump is realized as twin-cycle configuration with two refrigerant cycles. This configuration is more efficient when dealing with a wide operating range. It also offers advantages in terms of start-up behavior and approval due to the lower refrigerant charge per circuit.
The heat pump prototype uses novel piston compressors (HBC 511) developed by Viking Heat Engines, based on a proven, heavy-duty design in collaboration with the world’s largest engine design company, AVL. They are engineered to operate at very high pressures and internal temperatures (>160°C) and are compatible with all common refrigerants of the 3rd and 4th generations e.g. HFOs like OpteonMZTM from Chemours as used in this heat pump demonstrator for brick drying.
The piston compressors have an internal oil circuit with oil filter and preheater and show very low internal friction through exclusive use of low-friction bearings.
They also have an efficient integrated water-cooled synchronous motor (PMM) and reach a high isentropic and volumetric efficiency over a broad range of operating conditions by utilizing a variable speed operation. For their lubrication, a novel lubricant is provided by FUCHS.
The DryFiciency heat pump demonstrator for brick drying started its trial operation in autumn 2019. Extensive monitoring of the operation is currently performed to evaluate its efficiency and other important process parameters, as well as the stability of refrigerant and lubricant when exposed to high temperature levels.
Within DryFiciency, demonstrations in industrial drying have been pioneered as the drying processes are very energy intensive and offer huge potential for energy efficiency. The DryFiciency high temperature heat pump demonstrator installed at the Wienerberger brick production facility in Uttendorf, Austria replaces a natural gas burner and has been shown to lead to energy savings of up to 80 per cent and reductions in CO₂ emissions of about 80 per cent.
You can see the DryFiciency heat pump technology in action here:
If you want to know more about the DryFiciency heat pump technology, please contact the project coordinator.