In brick production, brick dryer and kiln are the primary energy consumers, which, even in modern facilities, are predominantly powered by natural gas. Wienerberger, a leading supplier of bricks, has partnered with AIT Austrian Institute of Technology GmbH to implement an electrified brick plant. This system utilizes also three compression heat pumps to optimize the brick drying process.
Production process and heat pump integration
In state-of-the-art brick dryers, the hot exhaust air from the kiln’s cooling zone is used to pre-dry the bricks in a tunnel dryer before the firing process. However, in an electrified kiln, the absence of flue gases results in less available exhaust air and thus reduced energy for drying. To compensate, additional heat sources must be harnessed to dry the bricks to the desired residual moisture content. For this purpose, three compression heat pumps are installed.
Furthermore, the brick dryer is extended in length to allow for longer dwell times, enabling lower drying temperatures that are more manageable for heat pumps. The dryer itself utilizes three distinct heat sources to provide the energy required for drying:
- Internal heating elements: These are distributed along the length of the dryer and powered by the heat pump circuit.
- Ambient air: Preheated using the heat pumps and an external heat exchanger.
- Exhaust air from the kiln’s cooling zone: This is mixed with preheated ambient air and introduced into the rear section of the dryer.
Rotary cone fans ensure uniform distribution of the drying air along the dryer and through the brick stack. The latent heat in the warm, moist exhaust air from the dryer is recovered via an air scrubber and used as a source for the heat pumps.
Figure 1: Sketch of the dryer and its energy supply
The operation of three compression heat pumps started in early 2025 and is monitored by an extended measurement campaign.
Key facts
| Dryer type | Tunnel dryer |
| Drying product(s) | Bricks |
| Drying medium | Air |
| Operation | Continuous and Discontinuous |
| Product conveying | Carts |
| Heating medium temperature | 70-200°C |
| Heat sources | Heat pumps, kiln exhaust air |
| Heat pump capacity | 3×1,2 MW |
| Flow temperature heat pump | 90 °C |
| Refrigerant | Ammonia |
| Drying time | 1-2 days |
| Start of operation | 2025 |
| Capacity | 3500 kg/h water evaporation |
| Dimensions | 70x12x5m |
| Outlet condition drying medium | 40°C, 90% relative humidity |
| Direct heat recovery | No |
| Heat source for heat pump | Scrubber using latent heat in exhaust air |
| Challenges | Variating production schedule, retrofit of an existing plant |
| Tracked parameters | Temperatures, COPs, specific energy consumption, specific air consumption, relative humidity |
More information
This information was extracted by AIT as scientific partner of the GreenBricks project. More information is provided here.