Waste heat recovery in ceramics

In ceramic kilns, a significant share of the supplied energy does not remain in the product. Instead, it leaves the process via exhaust gas and cooling air.

From a process engineering perspective, this is not an unavoidable loss. It is a usable energy stream.

Given current market conditions—volatile energy prices, increasing CO₂ costs, and pressure on supply security—utilising this energy is no longer optional. It is a direct lever to reduce operating costs and stabilise energy demand.

For this reason, Keramischer OFENBAU considers waste heat recovery from the outset when designing or modernising kiln systems.

Typical sources of recoverable heat include:
→ exhaust gases from the firing zone
→ hot air streams from the cooling zone

In continuous processes, these flows are relatively stable. This makes them especially suitable for systematic recovery.

From a technical standpoint, three approaches are commonly applied:

Process-integrated heat recovery
Hot gases are redirected within the kiln, usually from the firing zone to the preheating zone.
This reduces burner load, improves efficiency, and stabilises temperature gradients.

Cross-process heat utilisation
Recovered heat is used in adjacent steps, such as drying.
This reduces additional energy demand and improves the overall energy balance.

Indirect heat recovery via heat exchangers
If direct use is not feasible, heat exchangers transfer energy into secondary circuits (air or water).
This enables flexible use—for example in dryers or auxiliary heating—without affecting the firing process.

The effectiveness of these systems depends on proper integration, including:
→ matching heat supply and demand
→ considering gas composition and dust load
→ avoiding pressure losses
→ ensuring maintainability in continuous operation

When implemented correctly, waste heat recovery leads to:
→ lower energy consumption
→ reduced fuel or electricity demand
→ improved plant efficiency
→ more stable processes

Ultimately, this means:
less energy purchased, lower price risk, and more predictable operation.

Waste heat is not a secondary effect.
It is energy that has already been paid for—and should be used accordingly.