Key Technical Analysis of Ignition and Firing Operations in Trial Production of New Brick Production Lines

The trial production of a new brick production line is a complex engineering task involving multi-system coordination, including equipment commissioning, workforce skill development, and raw material adaptability. Successful trial production relies not only on efficient collaboration among workshops but also on an experienced technical leader and a highly responsible team. Based on extensive field tracking of several tunnel kiln production lines across different regions, this paper summarizes practical issues encountered during ignition, drying, and firing stages, and proposes targeted recommendations to improve ignition efficiency and reduce trial production losses.

1. Technical Specifications for Ignition Operation

Drawing on practical experience from multiple production lines and mature operating practices from annular kilns, this paper presents a rational set of technical specifications for ignition operation, aiming to coordinate process parameters, minimize errors, and control trial production losses.

1.1 Precise Control of Raw Material Calorific Value

During the ignition phase, the drying chamber and the firing kiln — especially the kiln cars, side walls, and roof of the brick firing system — absorb a substantial amount of heat. Therefore, when preparing internally fueled green bricks, the calorific value of the raw material should be appropriately increased, ideally within 450–500 kcal/kg. This range satisfies the heat demand for firing while providing surplus heat for drying. It is not necessary to blend large quantities of high‑calorific materials; only 10–15 kiln cars of bricks need to achieve this value. Excessively high calorific values can lead to uncontrollable kiln temperatures. Unlike annular kiln operation, external coal addition should be avoided during tunnel kiln ignition. The heat transfer efficiency of internal fuel is far superior to that of external coal, which also increases labor costs and may cause localized overheating. Once the ignition car ignites the adjacent brick car, the kiln temperature field can be rapidly established through thermal radiation and convection — an approach that integrates seamlessly with modern brick making machine automation, eliminating the need for external fuel.

1.2 Management of Residual Moisture and Setting Density

Before ignition, green bricks must be naturally dried for a sufficient period to minimize residual moisture. The drying chamber and storage tracks should be fully loaded with brick cars. The exhaust fan in the drying chamber can be activated in advance to circulate ambient air, further reducing moisture content. The lower the residual moisture of incoming bricks, the lower the thermal load on the preheating zone, facilitating rapid temperature rise. Meanwhile, setting density should not be excessively high, as this increases airflow resistance in both the drying chamber and the kiln, complicating commissioning. During the ignition phase, the average setting density is recommended to be 190–220 pieces/m³.

1.3 Firing Strategy: Low-Temperature, Long Firing

Ignition‑phase firing must achieve three objectives:
① supply stable heat to the drying chamber to enhance drying efficiency;
② ensure product quality;
③ rapidly establish a rational firing regime.
To this end, a “low-temperature, long firing” strategy is recommended, based on the following considerations:

• During initial ignition, the drying chamber temperature is low and cannot supply a large volume of low‑moisture bricks. The front section of the firing kiln must temporarily assist in drying, so its temperature rise rate should be moderated and the preheating zone appropriately lengthened. After a stable high‑temperature zone is formed inside the kiln, dampers are adjusted to gradually move the high‑temperature zone forward, shortening the preheating zone while delivering more heat to the drying chamber, enabling a smooth transition to normal production.
• At ignition, the kiln walls and roof are not fully dried and lack sufficient heat accumulation. “High‑temperature, fast firing” is inappropriate. Low‑temperature, long firing allows the kiln structure to accumulate heat gradually, forming a stable temperature profile. It also enables the ventilation system to be commissioned under varying loads, facilitating stepwise mastery of damper settings and system resistance characteristics.
• The ignition phase requires modification of the preset firing curve to identify a sintering curve that matches the raw material properties. Low‑temperature, long firing offers a wider adjustment margin, making it easier to detect firing patterns and prevent product defects caused by excessively low or high sintering temperatures.

This firing strategy is particularly compatible with advanced brick machine systems, as it reduces thermal shock and allows stable heat distribution across the kiln.

1.4 Hot Spot Localization and Temperature Control

The positioning of the high‑temperature zone (hot spot) is critical to firing operations. Reliance on the monitoring system alone is insufficient; flame color and behavior in the high‑temperature zone should also be observed to assess actual firing temperatures. Feedback from products exiting the kiln should be used to continuously adjust the sintering temperature. During ignition, the hot spot should be set slightly lower than the design temperature, with fine‑tuning performed after analyzing product quality — this effectively prevents overfired bricks.

The ignition of a new kiln involves multiple process subsystems: raw material preparation, drying, firing (the core brick firing system), and ventilation. Pre‑ignition preparation must be thorough, including a deep understanding of raw material characteristics and system status. Overconfidence should be avoided. Only through scientific control of key parameters and system‑level coordination can the success rate of ignition be improved and scrap rates reduced.

Conclusion
Drying and firing form an integrated, unified system. Operation should adhere to principles of system balance and progressive advancement, steadily increasing output while ensuring product quality. The “low‑temperature, long firing” approach offers broad adaptability to different raw materials, facilitates firing control, significantly reduces defect rates during commissioning, and accelerates the establishment of a stable firing process — ultimately enhancing the overall performance of your brick production machine and brick making machine.