In the H2020 DryFiciency project, a novel closed loop compression heat pump (HP) prototype was developed and integrated into a brick drying process (see figure 1) at the production site of Wienerberger Österreich in Uttendorf, Austria, and operated first-time in industrial environment at heat supply temperatures up to 160°C.
The HP prototype uses innovative components including eight piston compressors (HBC 511) developed by former Viking Heat Engines (now: Heaten AS) 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 with a maximum heat output of 279 kW. Most operational experience was gathered at heat sink temperatures of 140°C and 120°C, which represents the required site conditions. 570 hours were collected at elevated temperature levels from 150°C up to 160°C. The heat output reached up to 297 kW.
Figure 1: Integration layout of the HP assisted brick dryer (temperatures indicate the design point of the heat pump)
Benefits
The coefficient of performance (CoP) ranged from 5.0 at 120°C (heat sink outlet) and 84°C (heat source outlet) to 2.2 at 160°C (heat sink outlet) and 89°C (heat source outlet). Figure 2 compares the performance of the DryFiciency HP with that of other industrial heat pumps.
By switching from natural gas, energy savings of up to 83% were achieved, leading to a reduction of 600 tons of carbon emissions annually.
Figure 2: Performance of the DryFiciency heat pump compared with other industrial heat pumps
Key facts
| Dryer type | Tunnel dryer |
| Drying product(s) | Brick |
| Drying medium | Hot air |
| Operation | Continuous |
| Product conveying | Carts |
| Heating medium temperature | 70-200°C |
| Heat sources | Absorption heat pump (AHP), waste heat from kiln, DryF HP |
| Heat pump capacity | Approx. 400 kW |
| Flow temperature heat pump | 160°C |
| Refrigerant | R1336mzz(Z) |
| Drying time | several hours |
| Start of operation | 2019 |
| Capacity | 3500 kg/h water evaporation |
| Dryer Dimensions | n.a. |
| Outlet condition drying medium | 50°C (60% RH) |
| Direct heat recovery | No |
| Heat source for heat pump | Absorption heat pump (AHP) |
| Challenges | High CAPEX for HP and its integration on-site (required e.g. opening of roof), development of suitable lubrication oil |
| Tracked parameters | Tunnel dryer/kiln: relative humidity (RH) of dryer, temp. of hot air from kiln, volume flows of hot air, etc. Scrubber: RH, standard volume flow & outlet temp. of wet air from dryer, electric consumption of wet air fans, temp./RH of exhaust air, AHP: Inlet/outlet temp. and electric consumpt. of desorber, outlet/inlet temp. and volume flow of hot water; etc. DryF HP: outlet temp. of hot air from dryer, speed and electric consumption of recirculation fan at HP, inlet temp. of hot air into dryer |
More information
This information was extracted by AIT as scientific coordinator of the DryFiciency project.
For further insights into the configuration of the heat pump cycle, compressor prototypes and lubrication oil used, please refer to the document here (from page 6 onwards)
Additional information on the integration, commissioning and operation phase of the novel heat pump dryer system, is compiled here (from page 7 and page 14 onwards).
Key findings from the techno-economic assessment performed are included here (from page 19 onwards)
Watch the Dryficiency heat pump demonstrator in action here.