Analysis of key links in the brick production process

Analysis of key links in the brick production process

A complete brick-making process can be regarded as a precise "assembly line". It starts from processing raw materials and ends with the final output of finished bricks with qualified strength. The quality control of several core links directly determines the success or failure of the final product.

The first step: raw material preparation and processing

This is the cornerstone of the entire process. The goal is to obtain "brick mud" with uniform composition, moderate dryness and moisture, and suitable particles.

Raw material crushing and screening: If hard raw materials such as gangue and shale are used, they must be crushed first by a crusher and then screened to ensure that the particle size meets the subsequent process requirements. Excessively large particles will seriously affect the quality of the bricks.

Batching and mixing: According to the product strength requirements, clay (or shale, fly ash and other main materials) are mixed with an appropriate amount of water and internal fuel (such as coal powder) in precise proportions. Stirring must be sufficient and even so that the water and raw material particles are completely integrated to form a mixture with a consistent texture.

Aging (stuffing): The mixed raw materials are piled in the aging warehouse and left to rest for a period of time (usually 24-72 hours). This process allows moisture to fully penetrate into the raw material particles, improving their plasticity, making subsequent molding easier and making the bricks less likely to crack.

The second step: brick forming

This is a critical step in giving the brick its shape and initial strength.

Vacuum extrusion: The aged raw materials are fed into the vacuum extruder. In the extruder, part of the air is removed from the raw material first (to reduce bubbles and stratification inside the brick), and then under the strong thrust of the spiral reamer, it is continuously extruded through the mouth (die) of a specific shape and size to form a dense "mud strip". Vacuum degree and extrusion pressure are the core control parameters of this link.

Cutting and coding: The extruded continuous clay strips are cut into independent wet bricks according to the set length by the automatic brick cutting machine. Subsequently, the wet bricks are neatly stacked on the kiln car or curing pallet by a robot or manually to prepare for the next step.

The third step: brick drying

Freshly formed wet bricks have high water content and very low strength, and most of the water must be removed through drying.

Drying principle: Send the stacked wet bricks into the drying room (tunnel drying room or chamber drying room), and use the waste heat of the kiln or an independent hot air system to slowly and steadily evaporate the moisture in the bricks under controlled temperature, humidity and wind speed conditions.

Key Control: Drying speed is critical. If it is too fast, the surface of the brick will shrink too fast and the internal moisture will not come out, causing cracks; if it is too slow, it will affect production efficiency. The moisture content of dried bricks needs to be reduced to a very low level (such as less than 6%) before they can be fired.

The fourth step: high temperature roasting and cooling

This is the core link that makes the brick undergo qualitative changes and obtain ultimate strength and durability.

Roasting: The dry billet is fed into a tunnel kiln or a wheel kiln, and undergoes multiple stages such as preheating, heating, insulation, and cooling at high temperatures (usually 950°C-1100°C). At high temperatures, the chemical components in the raw materials react and melt, and the particles are firmly bonded to sinter the bricks and obtain high strength.

Cooling: After baking, the bricks must be cooled slowly and at a controlled rate in the kiln. Rapid cooling will cause stress inside the brick and cause cracking. The temperature of the cooled bricks needs to drop to close to room temperature before they can be taken out of the kiln.

Summary: everything is interrelated and the emphasis is on control.

The four major links of the brick-making process are closely connected, and the quality of the previous process directly determines the success or failure of the next process. If the raw materials are uneven, molding will be prone to defects; if drying is not well controlled, roasting will inevitably produce waste products. Therefore, the core of modern brick-making management lies in the precise control and recording of key parameters in each link (such as raw material ratio, vacuum degree, drying temperature and humidity, and roasting temperature curve). Understanding and controlling these key links is the only way to achieve stable production, improve product quality and reduce costs.