Industrial drying is an energy intensive process, but a lot of thermal energy could be recovered from the dryer outlet by condensing drained moisture. As the accompanying temperature drop is rather low in relation to the recovered heat flow, especially if the desired drying input temperature is not too high, by using heat pumps, substantially energy savings, up to 70% could be realized.

Despite it is not the only way, integrating heat pumps facilitate the realization of (partially) closed cycle drying processes. In case of completely closed drying cycles advantages such as the avoidance of annoying odor or environmental load of contaminants can be exploited. Moreover, other gases than air can be applied in order to avoid the drawbacks of oxygen: fire or explosion risk or product degradation. Another promising possibility is to utilize the condensate, but in some cases additional costs due to the need of cleaning before discharge could be caused.



During the last few decades a lot of academic research was performed on heat pump dryers (HPDs) to reduce energy consumption. However, reliable industrial applications are still exceptional.

To explain the state of the art, to demonstrate the potential energy savings by integrating heat pumps in drying processes and to investigate the technical and economic feasibility of integration of heat pumps in existing industrial drying processes a practical oriented research project within the CORNET frame has been submitted, accepted for funding and executed.

Project title: Energetic and environmental optimization of drying processes by integration of heat pumps HP4Drying (HP4Drying – www.hp4drying.eu)

Research frame: CORNET with project partners in Belgium (Flanders) and Germany, also funded by the Flemish (VLAIO) and German (AiF) governments

During the symposium, about this theme you can expect to:

- Learn about the state of the art of heat pumps assisted drying.
- Attend a real life lab scale demonstration on a HPD test and demo setup and the opportunity to visit it in the lab, located close to the conference room.
- Take the results of several industrial case studies on existing drying processes (wood, bricks, sludge, pig blood, milk powder) with you. Note that not only electrically driven heat pumps have been evaluated! - Learn about the promising posibilities of microwave drying.

Many drying processes e.g. the 2 spray dryers, subject of HP4Drying case studies, are operated a temperature levels up to 220^oC which cannot be reached by current heat pumps.

Because of a finished project, CORNET W2Pheat (From waste heat to process heat), research group TEI is following new developments in high temperature heat pumps and is involved in projects and project applications in this field.

Two interesting developments will be presented: Thermoacoustic heat pump technology and a chemical heat transformer, both able to deliver process heat at 200^oC or even higher.

Many industrial processes are discontinue in such a way they discharge an excess of (waste) heat while a later, process heat is needed. A typical example is in the ceramic industry where there often is a time shift between the heat discharge of the kilns and the heat demand for drying.

A new project proposal (within the Flemish TETRA as well as the European CORNET frame) has been submitted to formulate an answer on following questions:

- On which temperature levels can heat be stored and recovered? Link to available materials and systems (water, steam, PCMs, salts, chemical reactions…)
- Charging and discharging times (thermal flow related to capacity)
- Efficiency as a function of storage time
- Life time of materials (included equipment), safety…
- Integration and control of thermal energy storage system
- Outcome of cost/benefit analysis, derived from real life case studies
- Heat/cold production when electricity is cheap combined with storage.
- Way to the expected energy transition (phase out of fossil fuels)?

Some boundary conditions:
- Temperature levels from < -100°C to over 1000°C
- Time shifts from < 1 hour up to several days (seasonal storage out of the project scope)
- No temperature lift required (use of heat pumps out of the project scope)


The state of the art on thermal storage will be proposed by a leading research organization. The project evaluation result (accepted for funding/rejected) will not be available yet. If accepted, project results will be presented on the next edition of this conference.