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Why Raw Material Fineness Matters for Tunnel Kiln Yield？

2026-05-13

Frequent Cracks in Tunnel Kiln Firing? The Root Cause Might Be Substandard Raw Material Fineness

In automated brick production lines, the yield rate of tunnel kiln firing is a key metric for factory profitability. However, many operators struggle with firing cracks, even after fine-tuning the kiln's temperature curves. In reality, the root cause is often not the kiln itself but the raw material preparation stage. Whether the raw material particle size can be consistently controlled at ≤2mm directly determines the internal stress and structural consistency of the green body.

1. How Inconsistent Particle Size Triggers Firing Cracks

When coarse particles exceeding 3mm are mixed into the raw material, they create physical "stress concentration points" inside the brick.

Differential Thermal Expansion: Coarse particles expand and contract at different rates than the surrounding fine powder, causing micro-cracks during cooling.
Reduced Plasticity Index: Insufficient crushing results in lower plasticity and poor density, making the body highly susceptible to structural cracking during the dehydration stage in the preheating zone.

2. High-Speed Fine Roller Crusher: Key Parameters for ≤2mm

To solve these cracking issues, a High Speed Fine Double Roller Crusher is essential for final processing before molding. Its technical consistency is supported by:

High Hardness Guarantee (HRC 60-62): Utilizing medium-manganese nodular cast iron ensures the roll gap does not expand rapidly due to wear under high pressure, maintaining long-term stability of output size.
Optimized Linear Speed (224-315 r/min): The shear and compressive forces generated by high-speed rotation crush small hard mineral spots, eliminating potential crack sources.

3. Selection Guide for Different Working Conditions

When selecting fine crushing equipment, parameters must match production capacity and material properties:

Small to Medium Lines: Models with 15-30t/h capacity are suitable. Focus on built-in safety protection blocks to prevent non-crushable objects from damaging the roller surface.
Large Automated Projects: High-output models (80-130t/h) are required, equipped with anti-blockage augers to handle clay materials with higher moisture content (sticky soil).

The quality ceiling of a tunnel kiln is determined by the floor of its raw material processing. By implementing crushers with HRC 60-62 high wear-resistant rollers and ≤2mm precise size control, factories can eliminate firing cracks, reduce maintenance downtime, and significantly enhance the surface finish of finished bricks.

Why Your Tunnel Kiln Brick Firing Fails: The Hidden Role of Proper Stacking Methods

Why customized clay plasticity determines brick and tile quality?

Related questions

How Does Full-Automatic Brick Unloading & Packaging Surpass the Limitations of Semi-Automatic Equipment?

The brick and tile industry is constantly moving toward large-scale and intelligent production. The upgrading of brick unloading and packaging technology is a key part of industrial transformation. Semi-automatic devices once promoted the mechanization progress of the industry, while fully automatic technology has surpassed all its limitations and led a new round of industrial reform.

There is no doubt that semi-automatic unloading and packaging machines made progress against traditional manual work. The combination of machinery and manual assistance improved working efficiency and relieved heavy labor work. Nevertheless, viewed from the whole industrial development trend, it is merely a transitional technology with inherent weaknesses.

Since core working steps require manual operation, production efficiency cannot be further improved. Manual errors and different operation habits will inevitably cause uneven packaging quality of finished bricks. Meanwhile, rising labor costs year by year have become a prominent obstacle for enterprises to realize long-term profit growth and development.

In contrast, mature fully automatic brick unloading and packaging technology perfectly overcomes all the above shortcomings. Adopting high-precision sensors and intelligent control modules, it realizes full-process unmanned operation. Every working link follows unified standards, so the packaging quality of each brick product keeps consistent and stable.

In terms of production capacity, fully automatic equipment runs in a continuous and high-speed state, delivering much higher output than semi-automatic machines. It effectively lifts the overall production capacity of brick production lines. Although the one-time purchase cost is higher, the sharp drop in labor costs creates more long-term economic advantages for manufacturers.

In addition, this advanced technology boasts outstanding adaptability. Operators can adjust working modes and parameters freely to match bricks of different sizes and types. Equipped with fault self-diagnosis, automatic repair and remote monitoring functions, the equipment operates more reliably and reduces unexpected downtime.

In conclusion, semi-automatic brick packaging equipment played an important transitional role in the early stage of industrial development. Fully automatic technology has completely broken through the bottlenecks of semi-automation in efficiency, quality, cost and adaptability. It has become the mainstream choice for modern brick factories and drives the entire brick and tile industry to achieve intelligent upgrading.

What Practical Methods Can Accelerate Fired Clay Brick Sintering Speed in Tunnel Kiln Production?

1.Strictly control fuel moisture content to improve coal ignition efficiency

Excess water in coal consumes massive heat for water evaporation after entering kiln, delays ignition time; damp coal agglomerates and reduces contact area with air to slow down combustion. Build rainproof coal storage shed to avoid coal soaking in rainy days; coal with excessive moisture must be air-dried or artificially dried before feeding into kiln.

2. Screen and crush raw coal to expand fuel contact area with air

All kiln-used coal needs pre-screening; large lump coal shall be fully crushed. Fine granular coal increases oxygen contact area, speeds up burning, and effectively lowers coke accumulation and black brick defects.

3. Standardize stacking layout & coal feeding rules with fixed quantitative parameters

Follow the operation rule: feed frequently with small dosage, add coal according to real-time kiln fire condition.

For full external combustion bricks: feeding circulation interval = 1.5 minutes/time
Temperature section 800~900℃: single feeding weight 0.1~0.2Kg
Temperature above 900℃ up to peak firing zone: single feeding weight 0.2~0.3Kg Reduce external coal consumption properly when internal combustion proportion of green brick rises. Keep the proportion of coal falling onto kiln bottom at the optimal value: 10%. Replace manual feeding with automatic coal feeder: save around 20% fuel consumption for even feeding. Over-large one-time feeding causes oxygen shortage and unstable kiln temperature.

4. Unify operation specifications of three working shifts to stabilize fire advancing speed

Inconsistent operation among shifts leads to fluctuating kiln temperature and uneven fire travel, resulting in extra fuel waste, unstable brick quality and limited output. Uniform operating standard ensures steady sintering rhythm.

5. Properly increase excess air volume under qualified firing temperature

On the premise of meeting required sinter temperature, raise surplus air reasonably to lift oxygen concentration inside firing zone, accelerate oxidation reaction and shorten sinter cycle.

6. Adopt low-temperature long-time firing technology for internal combustion bricks (especially high-internal-combustion bricks).

Rapid early heating makes green brick surface vitrify prematurely, seals internal pores and blocks oxygen penetration, causing incomplete or even stopped combustion of inner fuel.

Keep slow temperature rise at front section of firing zone to reserve open pores for continuous oxygen infiltration;
Maintain high temperature at middle & rear firing zone to burn out internal fuel completely, reduce finished brick faults including black core and indentation. This craft is defined as low-temperature long firing compared with high-temperature short firing process.

7. Transform solid bricks into hollow bricks to optimize inner oxygen supply

Hollow structure reserves holes inside bricks, greatly boosts contact between internal fuel and infiltrated oxygen. Hollow design is highly recommended especially for high internal combustion bricks to speed up inner fuel burning obviously.

How to quickly solve the core faults of a brick factory strip cutting machine?

The brick strip cutting machine serves as core processing equipment in fully automatic brick making production lines, responsible for cutting raw mud strips, compressing blanks and feeding strips to the brick cutter. Unexpected breakdowns will halt whole production and raise factory maintenance costs. Most malfunctions originate from faulty proximity sensors, unstarted air compressors and worn brake pads. Below are six frequent faults with actionable fixing steps for on-site maintenance technicians.

1. Strip cutter cannot cut mud strips

Fault reason: X2 proximity sensor fails to trigger induction or is broken; air compressor remains shut down without air supply.

Solution: Two workers cooperate for inspection. One manually blocks the X2 sensor, another checks the corresponding indicator lamp on I/O monitoring page of the touchscreen. If the X2 lamp stays off, replace the defective X2 sensor; meanwhile confirm the air compressor is powered on.

2. Cutter unable to compress mud blanks

Fault reason: X4 or X5 sensor loses induction or gets damaged.

Solution: Dismount X4 and X5 sensors one by one, test with ferromagnetic metal parts. No lighting during testing means sensor damage and needs replacement.

3.Continuous strip feeding while brick cutter never cuts blanks

Fault reason: Damaged or non-inductive X7 sensor, missing feeding-in-place feedback signal.

Solution: Carry out paired detection via touchscreen I/O interface. Block X7 manually, check indicator status; replace X7 if no light is on.

4. No strip feeding but brick cutter keeps cutting nonstop

Fault reason: X7 sensor is permanently triggered by constant induction, sending wrong position signal to PLC control system.

Solution: Adjust X7 mounting position and sensing distance to eliminate false continuous induction.

5. Mud strip feeds into position but cutting mechanism refuses to cut

Fault reason: X6 sensor malfunction or damage, no in-place signal transmitted to control unit.

Solution: Remove X6 sensor and test with iron accessories; replace the component when indicator does not light up.

6.Cutting unit returns home but fails to stop instantly or stops extremely slowly

Fault reason: Excessive abrasion on cutting motor brake lining leads to insufficient braking force.

Solution: Fine-tune brake pad clearance; replace severely worn brake pads if adjustment cannot solve the issue.

Conclusion: Daily regular calibration of all cutting machine sensors and periodic inspection of brake wear can drastically reduce unplanned downtime and maximize continuous brick output.

Why Temperature Fails to Prevent Winter Brick Collapse?

Humidity Control Is the Hidden Key of Tunnel Kiln Drying Chamber

In recent years, large-section tunnel kilns have achieved continuous output breakthroughs in the brick and tile industry. Many production lines have even far exceeded the designed production capacity. However, the stubborn problem of green brick collapse in winter drying processes has plagued most manufacturers and cannot be completely solved for a long time. Most technicians have long regarded exhaust temperature as the core standard to judge drying quality, believing that increasing the exhaust temperature can effectively avoid brick collapse. In actual production, most enterprises control the exhaust temperature above 30°C, and some even set the standard at 40°C or 50°C.

However, a large number of field production practices have overturned this traditional cognition. Many drying chambers with exhaust temperature exceeding 45°C still face severe winter brick collapse failures. This fully proves that exhaust temperature is not the decisive factor for green brick collapse. The real core parameter that determines the drying effect and avoids blank collapse is exhaust humidity.

The optimal exhaust humidity range for tunnel kiln drying chambers is 90%-100% (excluding 100% saturation). Within this range, the hot air can maintain the highest heat utilization rate, realize uniform and gentle dehydration of green bricks, and avoid structural damage caused by rapid drying or secondary moisture absorption. The higher the exhaust humidity (within the standard range), the higher the thermal efficiency of the drying system, which means no waste of hot air heat.

The biggest flaw of current domestic drying chamber design and operation is the lack of effective humidity detection and adjustment devices. Most production lines are only equipped with temperature monitoring equipment, without humidity meters installed. A small number of factories that have installed humidity meters still fail to solve the collapse problem due to the absence of supporting adjustment systems, making humidity detection a mere formality. Unreasonable humidity control leads to unstable drying atmosphere in the chamber, which is the fundamental reason for frequent winter brick collapse, even if the temperature index meets the standard.

To completely eliminate winter blank collapse, tunnel kiln production lines must abandon the single temperature control logic, take exhaust humidity regulation as the core, and match scientific exhaust mode and air volume design to build a stable and efficient drying environment.

What Are The Key Factors Affecting The Drying Efficiency Of Sintered Bricks?

Low drying efficiency is a common trouble for most sintered brick production lines. Many factories install high-temperature hot air systems for the drying chamber, yet still face slow drying speed, frequent cracking and deformation of bricks. In fact, the efficiency of sintered brick drying depends not merely on temperature, but the combined coordination of three core factors: temperature, humidity and airflow velocity of drying media. All these factors jointly affect heat transfer and moisture diffusion inside green bodies.

All elements influencing sintered brick drying act on heat transfer and mass transfer. Heat transfer efficiency is decided by the total heat the drying chamber can obtain per unit time, while diffusion efficiency depends on the migration and evaporation speed of moisture inside and outside green bodies. A widespread mistake in production is only raising hot air temperature while ignoring airflow and humidity control. This wrong operation leads to poor drying efficiency and restricts the overall output growth of the factory.

Air volume and airflow velocity are the most easily overlooked factors in sintered brick drying. Some lines supply high-temperature hot air, but the fan has insufficient air output. Hot air circulates slowly in the drying chamber, so even if the displayed temperature is high, each green body cannot get enough heat. Unbalanced heat and mass transfer result in extremely slow drying. On the contrary, production lines with moderate temperature but sufficient air volume can realize fast hot air circulation. Heat covers all green bodies evenly to complete uniform drying, delivering better product quality and higher output.

Humidity of drying media also plays a vital role. Excessively high humidity in the drying chamber will slow down surface water evaporation, block internal moisture discharge and cause internal cracks. If the humidity is too low, the green body surface will dry too fast and form a hard shell, which hinders internal moisture migration and results in hollowing and surface cracking.

Optimizing the sintered brick drying process is the most cost-effective way to boost factory benefits, much more effective than simply upgrading the firing section.

Production teams must abandon the outdated idea of valuing firing over drying. On the basis of low-moisture molding and standard green body stacking, adjust hot air temperature, air volume and humidity according to raw material features, and optimize drying curves in real time.

Scientific optimization of sintered brick drying can eliminate common drying defects, shorten production cycles and improve the rate of qualified products. It will thoroughly break the output and quality bottlenecks of sintered brick production, and help enterprises operate stably and gain maximum economic returns.

How Can A Sintered Brick Factory Reduce Fuel Costs To Achieve Energy Saving And Consumption Reduction?

Fuel cost is the largest variable expenditure in the production process of sintered bricks and the core factor determining the profit margin of brick factories. Unlike fixed costs such as equipment depreciation, staff salaries and certification amortization, fuel expenses fluctuate greatly due to regional raw material prices, fuel quality differences and batching technologies, ranging from $70 to $150 per ten thousand standard bricks in different regions.

Most sintered brick enterprises adopt calorific solid fuels including coal, coal gangue and fly ash. To achieve precise fuel cost control, brick plant managers must abandon the simple price comparison of fuel tonnage and adopt aunit calorific value cost accounting method, which is the key to scientific fuel procurement. For example, if 3000-kcal fuel is priced at $42 per ton and 3500-kcal high-quality fuel is $45 per ton, the latter has a lower actual calorific value unit price and higher combustion efficiency, which is more cost-effective in long-term production.

In addition to standardized procurement accounting, fuel quality inspection is indispensable. Unscrupulous suppliers often cut corners by falsifying calorific value data, insufficient weighing and excessive moisture content, which directly leads to insufficient brick firing, increased secondary fuel supplementation and hidden cost losses. Brick factories need to arrange special purchasers to track local real-time fuel market prices, screen stable and high-quality suppliers, and strictly inspect fuel weight, moisture and calorific value before warehousing to eliminate unqualified fuel materials.

The internal combustion batching ratio is the top priority of fuel cost control and quality management for sintered brick plants. For the once-setting and once-firing wet brick production process, unreasonable internal combustion proportion will trigger a huge cost chain reaction. Practical production data shows that insufficient internal combustion fuel will force enterprises to invest 3 times more external combustion fuel to meet the brick firing qualification standard. Worse still, mismatched batching will cause quality defects such as underfiring and unstable brick hardness, damage corporate market reputation and cause long-term operational losses.

Therefore, brick factories must formulate fixed internal combustion batching management systems based on local raw material characteristics and production equipment conditions. After repeated debugging to determine the optimal batching standard that requires no external combustion and avoids underfiring, the standard shall be strictly implemented in daily production. This can not only stabilize product quality fundamentally, but also maximize fuel utilization and effectively reduce the core production cost of sintered bricks.

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