Recognize Hidden Process Bottlenecks in Fired Brick Production Line

For fired brick manufacturing, the whole production is a systematic project made up of connected process sections. Every production link interacts closely, just like the wooden boards forming a water bucket. The maximum water volume the bucket can hold depends on the shortest board instead of the longest one. This is the bucket short board principle, and it also applies fully to modern brick plant operation. The profit level of your brick factory is determined by its weakest process link. Many brick investors only focus on nominal output at the early planning stage, such as daily capacity of 500,000 or 800,000 pieces of bricks, annual output of 150 million or 200 million pieces. However, most of them ignore the actual total turnover quantity in the whole factory. The real daily turnover may reach 5 million to 8 million pieces, far higher than the nominal daily output.

1. Raw Material Stockyard

Some brick factories can directly mine shale or gangue on-site without a large raw material storage yard. If raw materials need to be transported from outside, you need multiple stockyards to hold raw materials equivalent to 500,000 bricks, not just one.

2. Raw Material Processing

The daily handling capacity of your raw material workshop must exceed the target daily brick output. Raw material crushing equipment only runs 8–10 hours per day. You need to select suitable brick making machine units: primary crushing or secondary crushing, single-shaft or double-shaft mixer, screen size, conveyor belt width and speed, magnetic separator layout and easy maintenance design. Even if you install large crushers and heavy motors, replacing hammerheads may take half a day or a full day without proper lifting tools. Many small brick plants only use loaders and manual work to move heavy screen plates, without overhead cranes or electric hoists. Mechanics frequently leave jobs due to heavy manual labor. This is a typical production bottleneck.

3. Aging Chamber & Fine Material Storage Bin

The aging chamber plays a critical role in stabilizing raw material performance. We recommend storage capacity supporting 72 hours of production, equal to 3 times your daily brick output. Even when crushing machines stop for 2 days of maintenance, sufficient aged raw materials can still support production for 500,000 bricks. For hard rock and sandy raw materials, anti-seepage design prevents uneven moisture (dry top and wet bottom). Installing soil shredders after aging and mixing will greatly improve raw material uniformity.

4. Extrusion and Forming

Material feeding, mixing, intensive stirring, extrusion, brick cutting and setting are well-known links in brick green body production. But raw material variations and product specifications require customized equipment parameters. A set of brick making machine that works well in one region may fail in another. For example, several brick plants built in Lanzhou copied the production experience from central and eastern China. Although they produced good-looking green bricks, they faced slow drying, slow firing, high reject rate and heavy cracking. Their actual output was far below expectation, which became a serious bottleneck.

5. Drying Chamber

Multiple tunnel kiln configurations are available: direct drying & direct firing, one drying + one firing, one drying + two firing, one drying + three firing, two drying + one firing. The optimal selection depends on raw material property and local climate. For shale and coal gangue with good plasticity used for solid bricks, direct drying and direct firing tunnel kiln for brick firing works well. A 3.6m × 110m or 120m kiln can achieve nearly 200,000 bricks per day. Never adopt direct drying & direct firing kilns for raw materials sensitive to drying shrinkage; this will create an almost unreparable bottleneck. In Kuitun, Xinjiang, extremely dry ambient air caused green body cracking immediately after cutting. The solution was lowering the height of the green body storage shed, surrounding it with curtains to raise local humidity, adopting a 1.5x brick setting scheme. The tracks and kiln cars were increased to 1.5 times the original quantity. Drying heat sources include flue gas drying, waste heat drying, combined flue gas & waste heat drying. Each solution has pros and cons. If raw materials contain high sulfur content, flue gas drying will contaminate bricks and raise environmental cost. Low-sulfur flue gas combined with waste heat delivers better drying effect, lower power and fuel consumption. Moisture exhaust modes include centralized exhaust, decentralized exhaust, segmented centralized exhaust, negative pressure exhaust and positive pressure exhaust. Pure centralized moisture exhaust is inefficient: high power consumption, excessive oxygen. The best solution combines decentralized and centralized exhaust, positive pressure as main and negative pressure as auxiliary. It avoids green body collapse, keeps low temperature and cuts power cost. Many rotary tunnel kilns have poorly designed drying sections; some exhaust fans consume 3–4 times power of the main kiln, which is a costly bottleneck.

6. Firing Process in Tunnel Kiln

Kiln performance, brick quality, output and coal consumption are mostly decided during kiln design and construction. There are many kiln types: masonry tunnel kiln, combined tunnel kiln, upper flue tunnel kiln, lower flue tunnel kiln, internal flue tunnel kiln, external flue tunnel kiln and rotary tunnel kiln. If we borrow the advantages of rotary tunnel kiln and solve cross-section temperature difference and kiln car burning problems of conventional tunnel kilns, tunnel kilns will become the best option. Rotary kiln holds around 300 bricks per cubic meter, while tunnel kiln can hold 400–500 bricks per cubic meter, featuring larger capacity, higher output and lower energy consumption. However, traditional tunnel kilns are limited by the structural bottleneck: bricks move while kiln body stays static. Breaking this long-existing limitation requires technological innovation.

7. Firing Technician Capability

Many old kiln operators only regard kiln work as watching flame color, which is wrong. A qualified firing technician is a kiln regulator. He must master kiln structure, air path, flue design, waste heat system, fan air volume, temperature monitoring, heat value, brick setting plan, kiln door and kiln car operation, drying chamber logic. He needs to adjust the whole system when parameters go wrong. Poor firing skill is a repairable bottleneck via training or personnel replacement. There is a common rule in brick production: 70% performance comes from brick setting, 30% comes from firing; 70% work is below the kiln, only 30% on the kiln. Excellent kiln operators analyze brick setting plans, raw material test reports and heat distribution. With the same kiln, brick setting and mixture heat value determine final brick quality. Operators are forbidden to feed coal at joints between kiln cars, and must not open fire peepholes at high-temperature kiln car joints. This will severely damage kiln cars. Kiln manufacturers should cancel peepholes in high-temperature joint zones. Kiln car burning is also related to kiln car insulation and trench air balance, which remains a major headache for many brick plants.

8. Kiln Car Unloading Track

We visited a brick factory with a 3.7m wide kiln designed for four drying + three firing. It only had one unloading track and one semi-automatic brick packing machine, with no extra space to add new tracks. After 5–6 years of operation, it could never run the full four-drying-three-firing mode; the maximum stable operation was two firing sections. The bottleneck came from insufficient unloading tracks. No matter how powerful your kiln is, you cannot ship finished bricks out. The number of unloading positions, packing positions, stopping positions and clamp parking positions must be calculated at the design phase. This planning defect is hard to fix later.

9. Finished Brick Storage Yard

Lack of finished yard is a widespread bottleneck. Many brick plants have limited land area while kiln capacity is large. They have to reduce kiln load in rainy seasons or off-seasons. Hollow bricks require more storage space, because construction projects often need hollow bricks after frame completion. Without enough yard, hollow brick production cannot run smoothly. This bottleneck is difficult to resolve after factory completion.

10. Raw Material Test & Environmental Compliance

Many investors skip raw material lab tests before construction. If raw material contains 4%–5% sulfur without alternative materials, this will become an insurmountable environmental bottleneck. New brick plants must carry out repeated raw material analysis. High calcium content causes brick deliquescence; high potassium oxide and magnesium oxide lead to white salt bloom on brick surface. Poor raw material quality directly weakens your market competitiveness.

11. Desulfurization Tower

A lot of brick plants rebuilt their desulfurization towers twice. Most desulfurization equipment suppliers lack knowledge of kiln structure and fluid mechanics. After tower installation, factories need to upgrade fan motors or suffer poor moisture exhaust and reduced output, creating new bottlenecks. Horizontal + vertical combined desulfurization and dust removal achieves better effect than single vertical type. The air inlet of desulfurization tower set slightly above kiln surface saves more power and matches fluid mechanics better than downward air intake.

12. Kiln Upgrade for Natural Gas Firing

Natural gas firing delivers the best environmental performance with low sulfur, nitrogen oxide and dust emission. Brick factory owners need to evaluate whether existing kilns can be modified for natural gas combustion, or whether new kilns need to reserve space for gas burning during design.

Conclusion

The capacity calculation formula for a fully functional tunnel kiln for brick firing:

① Raw material stock for multiple days of output;

② Raw material processing capacity ≥1.5 × daily output;

③ Aging chamber capacity for 2–3 × daily output;

④ Extrusion workshop to finish 1 × daily output within 8–12 hours;

⑤ Green body storage capacity for 1.5–2 × daily output;

⑥ Empty kiln car reserve ≥0.5 × daily output;

⑦ Drying chamber capacity for 1 × daily output;

⑧ Firing section capacity for 1 × daily output;

⑨ Finished brick transport track ≥0.75 × daily output;

⑩ Unloading station ≥0.3 × daily output;

⑪ Finished product yard for multiple days of output.

For a factory targeting 500,000 bricks per day, the total material turnover inside the whole line may reach 5 million pieces. Fired brick production is a complete system covering raw material preparation, processing, extrusion & setting, green body drying, firing and finished brick handling. Factory profit is always restricted by the weakest link.