The core idea to reduce heat loss of the tunnel kiln is "plugging air leaks, improving efficiency, and recycling waste heat". Specifically, it can be approached from four aspects: improving kiln body insulation, optimizing sealing structures, recovering waste heat, and upgrading kiln cars and kiln furniture.
I. Strengthen kiln body insulation to reduce surface heat loss.
This is the most direct measure to reduce surface heat loss, with the focus on upgrading insulation materials and structures.
Select high-efficiency insulation materials: Replace traditional lightweight clay bricks with ceramic fiber modules or high-purity alumina hollow sphere bricks. These materials feature lower thermal conductivity and can greatly reduce the temperature difference between the inner and outer kiln walls.
Optimize insulation layer structure: Adopt a "multi-layer composite insulation" design. For example, ceramic fiber for the inner layer, lightweight insulating bricks for the middle layer, and insulating coating for the outer layer to cut conductive and radiative heat loss through the kiln wall.
Control kiln body surface temperature: Through renovation, keep the kiln shell surface temperature below 60°C (at an ambient temperature of 25°C). This can significantly reduce surface heat dissipation and improve the working environment in the workshop.
II. Optimize sealing design to eliminate heat leakage through gaps
Targeting critical areas such as kiln doors and assembly joints, heat leakage can be reduced via physical sealing and structural improvements.
Improve kiln door sealing: Inflatable seals (such as silicone airbags) are adopted for the kiln doors at the inlet and outlet ends. When the door is closed, the airbag inflates and expands to closely fit the edge of the kiln door. This replaces traditional asbestos rope sealing and reduces heat and cold exchange during door opening and closing.
Seal kiln body assembly joints: Install flexible metal sealing strips at segmented joints of the kiln body or fill with high-temperature sealant to prevent leakage of high-temperature flue gas through gaps. Quick-opening structures with sealing rings are used for inspection ports and temperature measuring ports, which shall be closed and tightened promptly when not in use.
Reduce kiln door opening frequency: Optimize production scheduling to arrange kiln car loading and unloading in batches and shorten the kiln door opening duration. Where conditions permit, add a "buffer chamber" outside the kiln door to prevent direct influx of cold air when the door is opened.
III. Recover waste heat from the cooling zone to improve heat utilization efficiency
Waste heat from the cooling zone is an important "recoverable resource". Energy consumption can be directly reduced by recovering it with dedicated equipment.
Preheat combustion air: Install tubular heat exchangers or regenerative heat exchangers in the cooling zone. Use hot air from the cooling zone to heat cold air for combustion, raising the temperature of combustion air to 200–400°C and cutting fuel consumption.
Heat process water or workshop space: Route waste heat from the cooling zone into a waste heat boiler to generate hot water or steam. It can be used for workshop heating, domestic water for staff, or as a heat source for other production processes.
Preheat green bodies: In some scenarios, waste heat from the cooling zone can be ducted into the green body drying workshop to replace part of the drying heat source, realizing cascade utilization of heat energy.
IV. Improve kiln cars and kiln furniture to reduce mobile heat absorption loss
Optimize both material selection and structure to address the inherent heat absorption of kiln cars and kiln furniture.
Lightweight kiln car design: Adopt lightweight high-temperature resistant materials (such as silicon carbide and mullite) for kiln car frames and lining bricks to reduce heat storage of the kiln car itself and cut heat absorption loss.
Optimize kiln furniture structure: Use thin-walled kiln furniture (such as thin-walled saggers and perforated batts) to reduce the volume and weight of kiln furniture while maintaining load-bearing capacity, lowering its proportion of heat absorption. Promote the "sagger-free firing" technology, placing products directly on rollers or supports to eliminate heat absorption by saggers.
Recover waste heat from kiln cars: Install waste heat recovery hoods in the kiln car cooling zone to capture heat dissipated by kiln cars. The recovered heat can be used for preheating combustion air or workshop heating, avoiding waste of such heat.
