Waste heat recovery from industrial ovens, kilns, and calciners captures and reuses heat that would otherwise be lost, improving energy efficiency and reducing costs. These systems operate at high temperatures (often 200°C to over 1000°C), producing significant exhaust heat. Recovery methods include:

1. Heat Exchangers:
   • Recuperators: Transfer heat from exhaust gases to preheat incoming air or fuel, achieving 10-30% energy savings. Common in kilns and calciners.
   • Regenerators: Use ceramic media to store and transfer heat, ideal for cyclic processes like glass furnaces.
   • Plate or Shell-and-Tube Exchangers: Suitable for lower-temperature ovens, transferring heat to air, water, or thermal oils.
2. Boilers and Steam Generation:
   • Exhaust heat generates steam or hot water for process use or power generation via steam turbines. Common in cement kilns or large calciners.
   • Organic Rankine Cycle (ORC) systems convert lower-grade heat (100-300°C) into electricity, suitable for smaller ovens.
3. Direct Heat Reuse:
   • Hot exhaust gases preheat raw materials or fuel, reducing primary energy input. Used in ceramic kilns or metal calcining.
4. Cogeneration (CHP):
   • Combines heat and power generation, using waste heat for both process heating and electricity. Effective in continuous-operation calciners.

Benefits:

• Energy savings: 10-50% depending on system and temperature.
• Reduced emissions: Lower fuel use cuts CO2 and NOx.
• Cost savings: Reduced energy bills and potential incentives.

Challenges:

• High upfront costs for equipment like heat exchangers or ORC systems.
• Corrosion or fouling from exhaust gases, especially in chemical calciners.
• Process integration: Matching heat recovery to variable oven/kiln cycles.

Applications:

• Ovens: Food processing, drying, or curing recover low-grade heat for preheating or facility heating.
• Kilns: Cement, lime, or ceramic kilns use recuperators or boilers for preheating or steam.
• Calciners: Alumina or mineral processing leverage high-temperature heat for power generation or material preheating.