As part of the H2020 DryFiciency project, a novel closed loop compression heat pump (HP) prototype was developed, integrated into a starch drying process (see figure 1) at the production site of Agrana Stärke GmbH in Pischelsdorf, Austria, and operated first-time in industrial environment at heat supply temperatures up to 160°C.
Innovative components are applied in the DryFiciency HP prototype including a modified semi-hermetic screw compressor technology (from proven HS series) by Bitzer and a novel lubricant developed by FUCHS. R1336mzz(Z), supplied by Chemours under the trade name OpteonMZTM, is used as refrigerant. It is non-flammable, non-toxic and not subject to the F-gas regulation, and proofed well-suited for high temperature applications with heat supply temperatures up to 160°C.
Heat pump demonstrator
The heat pump demonstrator was implemented in a twin cycle configuration and completed over 4,000 operating hours covering heat supply temperatures from 90°C to 160°C, reaching a maximum heat output of 373 kW. Most operational experience was gathered at heat sink temperatures of 134°C, 155°C, and 130°C, which represent the required site conditions. Ca. 900 hours were collected at supply temperatures from 150° to max. 160°C.
Figure 1: Integration layout for the HP assisted starch dryer (temperatures indicate the design point of the heat pump)
Benefits
The coefficient of performance (COP) of the demonstrator ranges from 3.1 at 121°C (heat sink outlet) and 62°C (heat source outlet) to 2.7 at 153°C (heat sink outlet) and 73°C (heat source outlet). Figure 2 compares the performance of the DryFiciency HP with that of other industrial heat pumps.
Figure 2: Performance of the DryFiciency heat pump compared with other industrial heat pumps
Replacing natural gas, end energy savings of ca. 2,400 MWh/a were achieved leading to a yearly reduction in carbon emissions of 660 tons.
Key facts
| Dryer type | Flash dryer |
| Drying product(s) | Starch |
| Drying medium | Hot air |
| Operation | Continuous drying process |
| Product conveying | Air |
| Heating medium temperature | Up to 160°C provided by heat pump, residual heating by steam |
| Heat sources | Heat pump, steam |
| Heat pump capacity | Approx. 400 kW |
| Flow temperature heat pump | Up to 160°C |
| Refrigerant | R1336mzz(Z) |
| Drying time | Seconds |
| Start of operation | 2020 |
| Capacity | 5,4 to 7 t/h water evaporation |
| Dryer Dimensions | n.a. |
| Outlet condition drying medium | 52°C (48% relative humidity) |
| Direct heat recovery | No |
| Heat source for heat pump | Water in a heat recovery cycle |
| Challenges | High CAPEX, development of suitable lubrication oil |
| Tracked parameters | Steam (mass flow, temp., pressure); drying agent (volumetric flow, relative humidity & temp. at dryer inlet and outlet), HP: electric power, water mass flow on evaporator and condenser side, secondary side inlet and outlet temp.; product: mass flow |
More information
This information was extracted by AIT as scientific coordinator of the DryFiciency project.
For further insights into the heat pump cycle configuration, compressor prototype and lubrication oil used, please refer to the document here (from page 6 onwards)
Additonal information on the integration, commissioning and operation phase of the novel heat pump dryer system, is compiled here (from page 11 resp. 15 onwards).
Key findings from the techno-economic assessment performed please are included here (from page 19 onwards)
Watch the Dryficiency heat pump demonstrator in action here.