Low-Temperature Firing Defect in Brick Kilns – Phenomena, Causes and Remedial Measures
Low-temperature calcination defect is one of the most frequent technical problems in automatic brick kiln production and continuous brick firing processes. When the working temperature of the kiln calcination zone drops below the standard range, fired brick bodies in the high-temperature firing section will present a red or dark red appearance. This typical underfiring issue directly produces unqualified green bricks with low compression strength and poor weather resistance, severely affecting brick finished product quality and factory production efficiency. Timely on-site adjustment is essential for brick plant stable operation and defect control.
Professional on-site emergency operation protocols are formulated for low-temperature firing faults in industrial tunnel kilns and ring kilns. Once insufficient kiln temperature and underfired brick signs are observed, kiln operators need to immediately lower the kiln air damper, fully close all open kiln doors to reduce excess air infiltration, and strengthen fuel supply work. Sustained feeding of high-quality bituminous coal or auxiliary firewood can effectively raise and stabilize kiln temperature, rebuild balanced combustion conditions in the calcination zone, and quickly eliminate low-temperature firing risks in commercial brick production.
Three major root causes lead to persistent low-temperature calcination in industrial brick kilns
First, the application of low-calorific-value raw coal results in insufficient combustion heat and weak firing power.
In actual internal combustion brick production, low-quality coal with low heat value features unique applicability, which can replace part of clay raw materials to optimize blank forming. The targeted solution is to adopt frequent quantitative coal feeding to maintain stable combustion heat, cooperating with high-resistance brick stack arrangement to limit excessive excess air flow inside the kiln.
Second, manual fire judgment deviation is a critical human factor for kiln temperature failure.
Due to insufficient light on rainy days and at night, professional kiln workers are prone to misjudge weak firing flames as normal combustion status, resulting in unrecognized low kiln temperature and large-scale underfired brick defects.
Third, unreasonable kiln ventilation parameter setting causes excessive cold air intake, which is common in external combustion brick firing processes.
Ultra-low brick stack ventilation resistance, ultra-short kiln door opening distance and excessively raised air dampers will lead to massive cold air entering the kiln chamber, taking away combustion heat and reducing effective calcination temperature. Standardized solutions include closing adjacent kiln doors in the firing zone, properly lowering damper height, suspending brick discharging and shielding partial finished brick stacks in severe conditions, and standardizing kiln door opening specifications to avoid irregular operation.
