Introduction：
In the production of sintered bricks using tunnel kilns, the design and execution of temperature curves are critical for product quality and production stability. In practice, management often requires strict adherence to the theoretical temperature curve. However, significant differences frequently exist between the theoretical and actual curves. This article systematically analyzes the sources of these two curves, reasons for their differences, and provides management recommendations.

Origin and Characteristics of the Theoretical Temperature Curve：
The theoretical temperature curve is developed by equipment designers based on raw material chemical properties and small-scale trial firing tests, considering factors such as:
1. Chemical composition of raw materials (SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO, K₂O, Na₂O, etc.);
2. Refractoriness, sintering temperature range, and physical properties of raw materials;
3. Particle size distribution under laboratory conditions (generally below 0.5 mm);
4. Optimal heating rate and sintering temperature determined through trial firing;
Key Features:
(1) Used in the design phase to guide kiln structure and process parameters;
(2) Represents ideal trends for heating, holding, and cooling stages;
(3) Provides a reference for kiln operators during production.

Formation and Influencing Factors of the Actual Temperature Curve:
The actual temperature curve reflects real-time thermal conditions inside the kiln, influenced by:
(1) Coarser particle size in production (typically 2-3 mm), affecting plasticity and sintering performance;
(2) Low fine material proportion due to high crushing costs;
(3) Variations in forming moisture, drying quality, and residual moisture in green bricks;
(4) Stacking method (e.g., grid stacking) causing significant internal and external temperature differences;
(5) Kiln structure, sealing conditions, and uneven air distribution;
(6) Seasonal ambient temperature fluctuations;
(7) Variations in fuel calorific value and operational habits;
As a result, it is difficult for the actual curve to completely coincide with the theoretical curve, especially during critical stages such as drying, preheating, and sintering.

Case Study: Brick Explosion Phenomenon:
Theoretically, heating can be accelerated after reaching 120°C in the drying zone to prevent steam expansion and brick explosions. However, in actual production, explosions may still occur between 200-300°C due to:
(1) Insufficient airflow within the brick stack, hindering moisture removal;
(2) High temperatures in external air passages, creating large temperature differences;
(3) Residual moisture rapidly vaporizing under high temperatures.

Management Recommendations:
(1) Recognize the limitations of theoretical curves and adjust production strategies accordingly;
(2) Strengthen raw material control, manage particle size distribution to balance cost and process requirements;
(3) Optimize stacking methods to reduce internal temperature differences;
(4) Enhance monitoring of airflow and temperature distribution, dynamically adjust parameters;
(5) Implement zoned and staged temperature control strategies for critical areas;
(6) Train operators to understand differences between theoretical and actual curves, improving kiln control;

Conclusion:
The theoretical temperature curve serves as an essential reference for tunnel kiln design and operation but must be applied flexibly based on actual production conditions. Scientifically combining both theoretical and actual curves is key to ensuring brick quality, reducing production risks, and improving energy efficiency.