Analysis of Key Technologies for Energy Saving, Consumption Reduction and Green Low‑Carbon Production in Clay Brick Plants
Under the wave of green & low‑carbon and smart manufacturing, fired brick enterprises must achieve carbon peak and carbon neutrality goals while improving capacity and quality. The fire advance rate directly determines kiln output. In most cases, hollow bricks have a faster fire advance rate than solid bricks, but under certain conditions, hollow bricks can fire slower than solid bricks. Based on practical tunnel kiln production experience, this article deeply analyzes the core factors affecting the fire advance rate, and integrates industry hotspots such as solid waste utilization, prefabricated building blocks, and sponge city paving materials, helping enterprises achieve energy saving and clean production.
I. Unreasonable Green Stack Structure: Poor Preheating is the First “Stumbling Block"
The stacking principle of “dense on top, sparse at the bottom; dense at the sides, sparse in the middle" is the foundation for fast firing. The flue passages and green body dimensions must be well coordinated – too few or too many flues, too wide or too narrow gaps, or improper spacing between bricks will seriously slow down the fire advance rate. Gaps between the stack and the kiln roof/walls should be minimized. Special note: Many manufacturers stack most bricks with holes facing upward, with few or no horizontal holes. This obstructs hot air from penetrating through the green body, causing a large temperature difference inside and outside the stack, naturally reducing the fire advance rate. For large‑void‑rate products (e.g., KM blocks), the hole layout must be optimized to facilitate hot gas flow, which is also an important aspect of digital twin simulation in the industrial internet.
II. Improper Draft Pressure or Damper Shape: Oxygen Deficiency in the Firing Zone Lowers the Speed
Draft pressure directly affects the oxygen supply for firing and the preheating of the stack. When the pressure is too low, the firing zone will suffer from varying degrees of oxygen deficiency; part of the heat energy floats upward, the forward force weakens, and the heat exchange rate in the preheating zone decreases – thus the fire advance rate slows down. Principle for determining optimal draft pressure: ensure that the firing zone reaches adequate temperature, and that the top and both sides of the brick stack show no underfired bricks. Then gradually increase the draft pressure. Through repeated observation of bricks and fire, the optimal draft pressure data for your specific kiln can be determined.
The damper (Hafeng damper) shape also significantly influences the fire advance rate. Currently, different kiln operators use various damper configurations, leading to inconsistent speeds. It is recommended to use more dampers (all dampers except those near the kiln entrance and 5m~8m in front of the firing zone). Two common shapes are:
Trapezoidal damper pattern: Highest at the entrance end, then gradually lower toward the firing zone. This maximizes thermal efficiency and provides sufficient heating and preheating space, suitable for pursuing a high fire advance rate.
Bridge‑shaped damper pattern: The first 2–3 dampers at the entrance end are low, then gradually raised to the highest in the middle, and slowly lowered again toward the rear. This pattern reduces the risk of moisture regain and condensation, and lowers the occurrence of firing cracks and explosive defects, making it especially suitable for high‑void‑rate thin‑wall products. However, the fire advance rate is slightly lower than with the trapezoidal pattern. Under the requirement of environmentally friendly & efficient production, the bridge‑shaped pattern can be combined with low‑calorific‑value internal fuel to achieve stable, high‑quality output.
III. Non‑standard Internal Fuel Blending: The Root Cause of Large Temperature Fluctuations
Standardized internal fuel blending stabilizes the fire advance rate, saves auxiliary fuel, and enables sustainable high‑quality firing. The key is proper blending ratio and uniform, stable calorific value. In reality, some enterprises neglect internal fuel blending, resulting in fluctuating calorific values, drastic changes in fire advance rate and firing temperature, forcing operators to adjust frequently, which can easily produce defective products.
How to determine the internal fuel blending amount for hollow bricks? Taking KP1 and KP2 perforated bricks as an example, the calorific value required for normal firing is lower than that for solid bricks, generally 285 kcal/kg ~ 350 kcal/kg. The reason is that the relatively faster fire advance rate lengthens the firing zone, creating a “low‑temperature long‑firing" condition: the firing temperature is 20°C~45°C lower than for solid bricks, while the holding time is extended by more than 20%. This is the main reason why ordinary hollow bricks need less internal fuel. For large‑void‑rate KM blocks, the story is different. As the void ratio increases, the solid mass per unit volume decreases, but the heat transfer and self‑combustion conditions become more complex, so the internal fuel blending amount actually needs to be increased appropriately. This technical detail is especially important when utilizing solid waste (e.g., coal gangue, fly ash, construction waste as internal fuel), effectively reducing production costs and contributing to urban renewal and sponge city construction.
IV. Conclusion: Systematic Optimization to Seize the High Ground of Green Fired Bricks
Increasing the fire advance rate is not a single action but requires systematic optimization of three aspects: green stack structure, draft pressure and damper shape, and internal fuel blending ratio, as well as differentiated management for products with different void ratios. The industry is rapidly moving toward digital twins and industrial internet enabled transformation, using sensors to monitor fire advance rate, kiln temperature and pressure distribution in real time, thus achieving smart manufacturing and clean production. It is recommended that brick plants, in the context of carbon peak and carbon neutrality, actively replace part of the raw fuel with solid waste, promote high‑void‑rate blocks for prefabricated buildings, and strictly implement energy saving technical specifications, thereby maintaining both technical leadership and environmental compliance in the fierce market competition.
