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How to Control Tunnel Kiln Temperature and Prevent Brick Stack Collapse in Brick Production？

2026-06-10
In modern brick and tile production, precise temperature control of tunnel kilns is the key to qualified finished products and efficient production. The thermal system adjustment of tunnel kilns is a dynamic optimization process. Production personnel adjust multiple flexible production factors according to product specifications and process requirements to optimize the internal thermal system of the kiln. The conventional temperature adjustment methods in actual production include fan frequency modulation for smoke exhaust, heat dissipation and kiln door ventilation, pipeline gate opening adjustment, kiln car feeding speed control, and kiln top coal feeding regulation.
Only when the tunnel kiln meets stable operating conditions can accurate temperature control and continuous production be guaranteed. Firstly, the internal combustion heat of brick blanks must be consistent without obvious deviation, which is the foundation of stable kiln temperature. Secondly, the temperature of each functional zone of the kiln (preheating, firing, cooling) must be controlled within the standard fluctuation range to avoid under-firing or over-firing of products. Thirdly, maintain a stable feeding rhythm, fix production varieties and internal combustion proportioning parameters, ensure uniform kiln car entry intervals, and stabilize the heat absorption efficiency of brick blanks in key firing zones. Fourthly, keep the physical and chemical properties of raw brick blanks stable to ensure consistent firing conditions.
Brick stack collapse is a major bottleneck restricting tunnel kiln production efficiency. Once the stack collapses in the high-temperature operating section of the kiln, forced kiln shutdown is inevitable. Manual treatment in high-temperature environments not only reduces production efficiency but also brings serious safety hazards to operators. The root causes of stack collapse can be summarized into four categories: improper stacking leading to unstable stack structure and loose displacement during operation; excessive residual moisture of brick blanks after drying; track deformation and settlement causing kiln car inclination and stack collapse; and falling refractory linings of kiln walls and roofs causing mechanical jamming and stack damage.
To solve the problem of brick stack collapse and realize stable temperature control, targeted improvement measures must be implemented in production management. First, strengthen the quality control of the drying process, strictly detect and control the moisture content of brick blanks before entering the kiln to eliminate collapse caused by excessive moisture. Second, standardize manual and mechanical stacking operations, strictly implement the flat, straight and stable stacking standards to enhance the overall firmness of brick stacks. Third, establish a regular kiln equipment inspection mechanism, regularly check the flatness of kiln operation tracks and the integrity of kiln wall and roof refractory bricks, and timely handle deformed, damaged and fallen parts to avoid secondary faults. Meanwhile, once feeding abnormalities are found on site, operation suspension and fault inspection shall be carried out immediately to prevent fault expansion.
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Related questions
1
Why Do Tunnel Kilns Have Large-Area Overburning and Severe Brick Sticking?
In modern automated brick and tile production lines, tunnel kiln firing quality is the core index that determines finished brick qualification rate and overall production profit. Large-area overburning defects and severe green brick sticking are typical frequent faults in tunnel kiln mass production. These quality issues not only ruin brick and tile finished quality but also cause unnecessary material waste and unexpected production shutdown losses. This article comprehensively analyzes all potential root causes of tunnel kiln overburning and brick adhesion, and compares defect mechanisms with ring kilns, helping brick manufacturers carry out fast and accuratekiln fault troubleshooting and production optimization.
Excessive internal combustion heat of green bricks is the most fundamental material-induced cause of firing overburning and adhesion. In standard brick and tile manufacturing processes, green blanks are formulated with a certain proportion of internal fuel to support self-firing. Once the internal combustible content is too high, the extra heat released during high-temperature sintering will far exceed the standard process temperature required for brick forming. In the relatively closed high-temperature operating environment of tunnel kilns, redundant heat cannot be dissipated timely, resulting in over-fired brick surfaces and tight mutual adhesion between adjacent green bricks.
Imperfect ventilation system configuration is the key environmental factor triggering large-scale overburning faults. A qualified tunnel kiln air supply and exhaust system relies on precise alignment between brick stack ventilation channels and kiln wall exhaust ducts to form balanced hot air circulation and stable temperature fields. Any duct misalignment or blocked ventilation passages will sharply reduce the kiln’s overall heat dissipation capacity. Accumulated internal combustion heat erupts violently in the high-temperature firing zone, creating localized ultra-high temperature zones that lead to widespread brick overburning and severe sticking problems.
Unreasonable reserved gaps between brick stacks and the kiln main body is a easily neglected structural defect in daily kiln operation. The brick and tile industry has a clear standard: the gap between brick stacks, kiln walls and kiln roofs must not exceed 80mm. Excessively large gaps directly cause air short-circuiting in the kiln: more than 80% of circulating and cooling air flows rapidly through the peripheral gaps, while the inner area of brick stacks stays in a static air state. Insufficient preheating makes green bricks unable to adapt to the high-temperature sintering environment, and instant intense internal combustion after entering the high-temperature zone finally causes overburning and blank adhesion.
Non-standard brick stacking technology directly hinders internal heat exchange and air convection inside brick stacks. Excessively dense stacking layouts and insufficient reserved ventilation gaps between adjacent stacks completely block vertical and horizontal air flow. Heat generated by blank internal combustion is fully trapped inside the dense brick stack, forming local ultra-high temperature areas. Under such conditions, brick surfaces precipitate liquid phases in advance, which is the direct cause of persistent sticking and large-area overburning phenomena.
Irregular manual operation and unreasonable process adjustment are critical human factors leading to recurrent firing defects. To pursue higher daily output or simply stabilize flame position, many operators adopt improper gate control strategies, including overusing near gates, refusing to lift far gates properly, and allowing excessive fan suction to press down gate height. These wrong operations disrupt the standard firing temperature curve, shorten the reasonable heat preservation period of green bricks, and trigger premature liquid phase sintering, forming irreversible overburning and brick adhesion faults.
Mismatched kiln body structural parameters are the essential equipment-level cause of poor firing quality. If the tunnel kiln is manufactured with an overly short body, the effective length of the preheating zone and high-temperature roasting zone will be insufficient. Green bricks cannot complete gradual, gradient temperature rise preheating, and directly rush into the high-temperature firing zone. The sharp temperature difference leads to instantaneous intense combustion of internal fuel, causing overall temperature field imbalance and large-area firing overburning and sticking defects.
Compared with tunnel kilns, traditional ring kilns have more concentrated and single causes of overburning and sticking. The four core fault factors include excessive internal combustion heat of green blanks, insufficient preheating zone design length, unreasonable high near-gate operation habits, and inadequate overall kiln exhaust suction, which cover almost all common ring kiln firing adhesion problems.
2
How Drying Sensitivity Coefficient Governs Hot Air Temperature Setting of Fired Brick Green Bodies?
The fundamental reason for adopting differentiated hot air temperature in fired brick drying lies in the varying drying sensitivity of raw materials. The drying sensitivity coefficient is positively correlated with the plasticity index of brick raw materials. Raw materials with high plasticity index have strong drying sensitivity, slow internal water migration, and high risk of drying cracks, which require lower hot air temperature and longer drying time; low-sensitivity raw materials can adapt to high-temperature rapid drying.
This raw material characteristic directly guides the hierarchical setting of drying chamber hot air temperature. Low-sensitivity raw materials with a coefficient less than 1 have uniform water evaporation and extremely low cracking risk, so the hot air temperature can be raised to 120℃-125℃. This high-temperature drying mode only requires a drying cycle of 12-20 hours, achieving the highest production efficiency while ensuring drying quality.
For medium-sensitivity raw materials with a drying sensitivity coefficient of 1 to 2, temperature setting must be strictly classified by brick type. Solid bricks with dense internal structure have high water resistance, suitable for 100℃-120℃ hot air drying; hollow bricks with porous structure are prone to stress concentration, so the temperature needs to be reduced to 80℃-100℃ to ensure gradual and balanced dehydration. Correspondingly, the drying time of such raw materials is extended to 20-32 hours with the change of temperature parameters.
In industrial production, blind high-temperature drying for high-sensitivity raw materials (coefficient > 2) is prohibited. Such raw materials have severe unbalanced internal and external water loss, and can only adopt low-temperature slow drying with extended drying time up to 32-48 hours. Unreasonable temperature matching will directly lead to a surge in defective bricks and waste production energy consumption.
Scientific temperature differentiation also matches fixed energy consumption standards for brick drying. Evaporating 1kg of green brick water consumes 1300kcal of heat (equivalent to 0.186kg standard coal), and requires 33m³ of 30℃ hot air to take away water vapor. Reasonable temperature adjustment based on raw material sensitivity can avoid excessive heat waste caused by blind high temperature and incomplete dehydration caused by low temperature, realizing energy-saving and efficient drying.
In addition, the green brick forming moisture will affect the temperature adaptation effect. Properly reducing forming moisture (2 percentage points for lean raw materials, 4-6 percentage points for fat raw materials) can double green brick strength, reduce drying shrinkage, and make the raw materials more adaptable to differentiated hot air temperature drying, further reducing the risk of quality defects.
3
Is An Automatic Brick Stacking Machine Worth It? 3-Year ROI and Cost Analysis
For overseas brick plant owners, high labor costs, unstable manual brick stacking, and excessive brick damage rates are the top operational pain points that severely reduce factory profit margins. Most brick factory operators struggle to decide whether to purchase an automatic brick stacking machine, worried about high upfront equipment investment. In practical brick production operations, a fully automatic brick palletizing machine can perfectly replace 6 to 8 on-site manual stacking workers. For medium-sized and large-scale automated brick plants, the one-time investment of an automatic brick stacking machine can be fully recovered within 2 to 3 years. After crossing the ROI payback period, the equipment delivers stable 24-hour production, zero manual operation errors, and long-term operational cost savings, making it one of the most cost-effective profit-upgrading equipment for modern brick factories.

Manual Brick Stacking vs Automatic Brick Stacking Machine: Full Cost and Benefit Comparison

1. Labor Cost Gap

Traditional manual brick stacking relies entirely on 8 to 10 skilled workers to complete green brick stacking, placement and kiln entry work. Overseas brick manufacturing industries are currently facing universal challenges: rising local labor wages, high worker turnover rates, and unstable on-site attendance. Unstandardized manual operation easily causes misplaced bricks, irregular stacking, green brick collision damage and low production efficiency. These manual drawbacks not only lower finished brick quality but also delay delivery cycles and increase daily factory management costs.
In comparison, an automatic brick stacking machine only requires one-time upfront equipment investment, with no recurring labor expenses. The automated stacking equipment features ultra-low daily power consumption and requires almost no manual intervention. It supports non-stop 24-hour industrial production all year round, completely solving the problems of worker rest, attendance instability and high labor costs, and maximizing the effective production capacity of the brick production line.

2. Product Quality & Defect Rate Optimization

Manual brick stacking quality is greatly affected by worker proficiency, physical fatigue and operational attitude. Long-time repetitive work inevitably causes uneven green brick stacking, collision deformation and surface damage. Statistical data of overseas brick plants shows that manual stacking leads to a monthly brick defective and damage rate of 3% to 5%, bringing huge invisible economic losses to brick factory operations.
Equipped with precision servo positioning and standardized mechanical stacking procedures, the automatic brick stacking machine fundamentally eliminates human errors in brick production. It maintains consistent stacking accuracy and neat placement of green bricks every day, effectively reducing the monthly brick damage rate by 3%-5%. Stable and high-quality finished brick products greatly enhance market competitiveness, helping brick factories win more local construction project orders and long-term cooperative customers.

3. Exact 3-Year ROI Calculation for Brick Plants

For medium and large-scale brick plants with stable daily output, continuous order supply and formal standardized operation, the comprehensive benefits brought by the automatic brick stacking machine are extremely prominent. The saved labor costs, reduced brick scrap losses, and improved production efficiency can fully offset the one-time equipment investment, realizing complete cost recovery within 2 to 3 years, which is a stable and low-risk industrial investment.
After the 2-3 year payback period, the automatic brick stacking machine enters a pure profit stage. The equipment continuously reduces factory labor costs and product scrap rates, and effectively increases daily output and production efficiency. In the long run, it greatly optimizes the overall production cost structure of the brick plant and significantly improves the net profit margin of brick manufacturing.

Frequently Asked Questions About Automatic Brick Stacking Machines

Q1: Are automatic brick setting machines suitable for small brick factories?

Yes. Small brick factories with a daily output of over 8,000 standard bricks are very suitable for installing automatic brick stacking machines. Although small-scale brick plants have lower production capacity than large factories, the long-term savings in labor costs and the reduction of brick damage losses can bring stable and reliable investment returns. It is a forward-looking upgrade choice for small brick factories that plan to expand production scale and improve automation level.

Q2: Is the daily maintenance of automatic brick setting machines complicated?

Automatic brick stacking machines adopt simplified and wear-resistant industrial structure design, with ultra-low failure rate and stable long-term operation performance. The daily maintenance work is simple, labor-saving and time-efficient, requiring no professional senior technical personnel. Factory staff can master all daily inspection, cleaning and maintenance skills through basic free training, with extremely low later operation and maintenance costs.
For all formal overseas brick plants with stable production demands and long-term operation plans, investing in an automatic brick stacking machine is absolutely worthwhile. This automated brick stacking equipment perfectly solves the core pain points of high manual labor costs, unstable brick quality and high product scrap rates, helping traditional brick factories realize standardized, intelligent and low-cost production. It is an essential upgrade equipment for modern brick plants to reduce operational costs and increase long-term profits.
4
How Optimized Kiln Ventilation and Heat Exchange Reduce Energy Consumption in Fired Brick Production？
High energy consumption is one of the biggest operational challenges for modern tunnel kiln brick plants and automatic clay brick production lines worldwide. For brick manufacturers aiming to cut operational costs and boost profit margins, optimizing tunnel kiln ventilation and internal heat exchange is the most practical, cost-efficient solution to lower fuel consumption while stabilizing brick firing quality. Mastering core kiln airflow and heat exchange principles is essential for low-carbon, energy-saving brick manufacturing operations.
The entire firing process in a tunnel kiln is a continuous circulating heat exchange process between unfired green brick blanks and high-temperature flue gas generated by fuel combustion. During mass production, fuel combustion releases massive thermal energy, which transfers to brick blanks to raise their internal temperature gradually. Once the temperature reaches the critical standard for chemical reactions of raw materials including clay, shale, coal gangue and fly ash, all internal components of brick blanks react completely, forming high-quality qualified solid bricks and hollow fired bricks.
Airflow circulation penetrates every key stage of brick firing, making it an indispensable element for normal kiln operation. Fuel combustion requires sufficient oxygen, which is delivered to the high-temperature firing zone by preheated airflow from the kiln cooling zone; the preheated hot air further accelerates full fuel combustion and improves combustion efficiency. High-temperature flue gas serves as the primary heat transfer medium, responsible for preheating wet brick blanks and sustaining constant firing temperature in the firing zone. After sintering, high-temperature finished bricks are cooled to room temperature by incoming cold airflow for smooth kiln discharge. In addition, the removal of residual moisture from wet green bricks and continuous preheating of dry blanks entirely rely on hot flue gas flowing from the firing zone to the preheating zone.
It is evident that stable, orderly gas flow is the basic guarantee for complete brick sintering. To fundamentally cut down the energy consumption of brick production with gas-fired tunnel kiln equipment, manufacturers must prioritize optimizing two core indicators: kiln ventilation efficiency and internal heat exchange performance. Scientific airflow management eliminates incomplete fuel combustion and invalid heat loss, enabling low-energy, high-yield, high-stability operation for all types of brick factories.
Professional kiln energy saving does not rely on blind fuel reduction, which easily causes unqualified brick products. Instead, it focuses on improving the overall heat transfer efficiency inside the kiln through optimized ventilation and heat exchange systems. This technology maximizes the thermal utilization rate of fuel combustion, avoids repeated heating and redundant fuel waste, effectively reduces comprehensive production costs, and helps brick manufacturing enterprises comply with global green and low-carbon building material production standards.
5
What Is the Correct Low-Temperature Preheating Wind Brake Adjustment for Tunnel Kiln Brick Firing?
Many brick factory owners, production technicians and procurement customers frequently ask this question: what is the standard adjustment method for low-temperature preheating wind brakes on tunnel kilns, and how does it affect brick firing quality and production output? In tunnel kiln automatic firing systems, the low-temperature preheating zone (from kiln entry to 560℃) is the most critical stage to prevent green brick cracking and stabilize subsequent high-temperature firing. The opening size, quantity combination and brake shape of low-temperature preheating wind brakes directly control the total circulating air volume, flue gas flow speed and temperature distribution in the front kiln section. Correct wind brake adjustment is the simplest and most effective way to stabilize firing speed, eliminate preheating defects and improve finished brick yield in daily tunnel kiln operation.
Low-temperature preheating wind brakes refer to the group of wind brakes installed at parking spaces 1 to 10 of the tunnel kiln, covering the temperature range from ambient inlet temperature to 560℃. The total opening degree of all wind brakes determines the overall preheating air volume of the tunnel kiln, while the different opening combinations of individual wind brakes can precisely adjust the temperature of each front-section parking space. Reasonable adjustment ensures uniform preheating of green bricks, avoiding common quality problems such as uneven heating, local overheating, or insufficient preheating that easily cause brick cracking and deformation after firing.
Low-temperature preheating wind brake opening has strict industrial standardized calculation rules to avoid unnecessary air pressure loss and ensure maximum heat exchange efficiency.
The maximum lifting height of a single wind brake is limited to the radius of the wind brake body. The number of fully opened wind brakes is calculated by squaring the multiple of the total flue duct diameter and the single wind brake diameter. For example, when the total flue duct diameter is 1.2m and the single wind brake diameter is 0.4m, the diameter multiple is 3, and the standard number of full-open wind brakes is 9. If adopting an average half-open state, 18 wind brakes (9 pairs) are required for matching, which completely eliminates air pressure loss on the wind brake structure.
When using variable frequency fans for automatic tunnel kiln control, operators must fully open the ventilation area of all low-temperature preheating wind brakes.
Partially closed wind brakes will cause severe air pressure loss and wind energy waste, making the fan frequency conversion adjustment ineffective and unable to accurately control the drying air volume and kiln temperature. Only fully opened wind brakes can ensure that the fan operating power is completely applied to internal flue gas circulation and heat exchange, realizing precise and sensitive automatic temperature control.
It is crucial to match exclusive wind brake shapes and opening standards according to different brick types and green brick states in automatic firing production. Hollow bricks, porous bricks, and standard solid bricks have different thermal expansion rates and heat resistance, so they cannot adopt the same wind brake scheme. In addition, wet green bricks and dry green bricks require completely different preheating parameters, which means their wind brake opening degrees and shapes must be adjusted separately. In actual production, if the fan speed has been reduced to the lower limit that meets drying room air demand but the firing speed is still too fast, adjusting the wind brake shape and opening is the most effective solution to balance drying air pressure, air volume and kiln firing speed.
The working principle of low-temperature preheating wind brakes is to control the flow rate and residence time of high-temperature flue gas inside the preheating zone. A larger wind brake opening allows more high-temperature flue gas to pass through and extends the heat exchange time between hot flue gas and green bricks, effectively raising the local kiln temperature. Conversely, a smaller opening reduces flue gas flow and lowers preheating temperature. Scientific and graded wind brake opening configuration forms a stable gradient temperature curve in the preheating zone, eliminates green brick cracking caused by uneven temperature difference, and significantly improves tunnel kiln production stability and finished brick qualification rate.
6
What Are the Correct Drying Room Parameters for Clay, Fly Ash, Shale and Coal Gangue Bricks?
Improper drying room parameters are the leading cause of brick rewetting, surface cracking, low green brick strength and high kiln loss in professional brick and tile manufacturing. For B2B brick factories and global building material suppliers, matching accurate drying room parameters to different raw materials and brick styles is the core key to stable brick product quality and high production yield. Unlike ordinary industrial drying processes, professional brick drying requires strictly customized temperature, humidity, airflow and exhaust standards based on raw material drying characteristics to meet standardized brick production requirements.
The hot air temperature inside the brick drying room must be scientifically adjusted according to the unique drying tolerance of different brick raw materials. For conventional clay hollow bricks and sintered fly ash bricks, the optimal drying room hot air temperature is controlled between 60℃ and 80℃, which prevents rapid dehydration and avoids common surface cracks on green bricks. For shale and coal gangue raw materials with a drying sensitivity coefficient of 1 to 2, differentiated drying parameter settings are essential: solid bricks made of these materials adopt a drying temperature of 100℃ to 120℃, while hollow bricks of the same raw materials apply a milder temperature range of 80℃ to 100℃. For low-sensitivity shale bricks and coal gangue bricks with a drying sensitivity coefficient below 1, the drying room temperature can be increased to 120℃ to 125℃, realizing efficient and thorough brick dehydration without causing any quality risks.
Stable exhaust and airflow parameters ensure uniform drying effects for all green bricks in the drying room. The standard exhaust gas temperature of a qualified brick drying room is maintained at 35℃ to 45℃, with a relative humidity stably kept at 90% to 95%. The internal air flow speed of the drying room is steadily controlled at 1.5m/s to 4.5m/s, ensuring even heat and moisture exchange for every batch of bricks. In addition, mud material preheating during hot water or steam mixing needs to be kept at 45℃ to 60℃. This step optimizes raw material plasticity and lays a solid foundation for subsequent stable brick drying operations.
A critical operational rule that all professional brick production lines must strictly follow: the temperature of green bricks entering the artificial drying room must be higher than the humidity temperature of the gas discharged from the kiln inlet. This core technical standard completely prevents green brick reabsorbing moisture, effectively solving common brick quality problems such as peeling, blistering and uneven hardness. Our integrated brick and tile production equipment supports full intelligent drying parameter adjustment, realizing one-click switching of drying room schemes for different raw materials and brick specifications, and providing consistent high-quality brick products for global B2B bulk procurement orders.
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