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New Technologies and Processes in Kilns

The sustainable development of the ceramic industry is facing severe challenges from the natural ecological environment, and the energy shortage is placing increasingly stringent demands on the development of the ceramic industry. Energy conservation, reduction of consumption, and minimizing pollution from ceramic kilns are the trends in ceramic production and essential conditions for the sustainable development of the ceramic industry. At the “Third International Ceramic Industry Development Forum” this year, Professor Zeng Lingke, a Ph.D. supervisor at South China University of Technology, outlined the direction for the development of new technologies and processes in Chinese ceramic kilns. This article summarizes his speech, hoping to enlighten professionals in the industry.

I. Kiln Structure
  1. Intermittent Kilns: High energy consumption, low output, and exhaust gas temperatures ranging from 600℃ to 860℃. Key factors affecting the uniformity of the temperature field in shuttle kilns:
    • Adopting new types of burners, such as isothermal burners, pulse burners, high-speed burners.
    • Adjusting the layout of burners.
    • Improving the placement of greenware.
    • Properly arranging flues.
    • Utilizing waste heat for shuttle kilns.
    • Selecting appropriate temperature detection points and control methods.
  2. Continuous Kilns
    • Tunnel Kilns: Large temperature differences, especially in the preheating zone. Kiln walls and kiln cars have a high heat storage capacity, resulting in high energy consumption (12000×4.18 kJ/kg of product). With the application of new technologies, energy consumption can be reduced to 1100-5200×4.18 kJ/kg. Key issues include detection and control of reducing firing atmospheres.
    • Roller Hearth Kilns: Lower energy consumption, as low as 200-300×4.18 kJ/kg of product. High production capacity: kiln length exceeds 220m, producing over 10000m²/day of wall and floor tiles. Properly controlling atomizing air pressure and combustion air volume, adjusting exhaust fan and hot air fan extraction rates, and setting up flame-blocking walls or flame-blocking plates to extend burner or flame length, improving the “ignition point.”

Structurally, converting kilns with a flat roof or entirely arched structure to those with arched structures in the firing zone can effectively reduce section temperature differences.

II. Insulation Technology
  • Heavy refractory bricks: Large mass, high heat capacity, high thermal conductivity. The external surface temperature of kiln walls can reach 400℃ or higher.
  • Lightweight insulation bricks: mullite lightweight bricks, high-alumina lightweight bricks, lightweight ceramic fibers.
    • Light in weight, small thermal conductivity, weight only 1/6 of lightweight materials, bulk density 1/25 of traditional refractory bricks, and heat storage capacity only 1/30 to 1/10 of brick-lined furnaces. Using lightweight ceramic fibers reduces the weight ratio between products and kiln furniture.
    • Fiber energy savings: total energy consumption decreases from 20.6% to 9.02%, achieving energy savings of 16.67%.

Fiber pulverization, research on pulverization resistance, and rational kiln wall structures enhance energy-saving effects.

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