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Clay manufacturing can be either via a dry or wet/slurry process. Manufacture is comprised of a number of phases; extraction, blending (where necessary), crushing and drying. Each stage requires certain competencies and machinery to ensure that we always offer the most optimum product for each application. Clay is tested regularly throughout the manufacturing process to ensure product consistency.
Investigating and developing a clay mine
In each deposit, multiple strata are found comprised of clays that vary in terms of particle size, distribution, chemistry, mineralogy and surface area. They also differ widely from geographic location to location.
Mining is carried out using excavators and load-hauling trucks. With a bench-mining technique, each stratum of clay is quarried separately and segregated in storage sheds for aging.
Clay is aged for 3-12 months, depending on the category of the clay and time required for it to offer maximum benefit. Plasticity and rheological characteristics are modified as oxidation of organic and non-organic constituents takes place. This impacts the clays’ chemical and physical properties. The moisture content of freshly mined clay is between 18% and 22%. After aging, the moisture content ranges from 13% to 18%.
How clay is processed?
Aged raw clays are blended carefully according to pre-determined formulations to provide a product with a consistent and predictable range of characteristics and behaviors. The first stage in processing is to crush the blended clay into smaller, more regular lumps (about 5 cm in size) via a primary feeder crusher and secondary roll crusher. This is sold as shredded or disintegrated clay and has a moisture content of around 16%.
In the dry process, putting the clay through a fluid bed dryer reduces the moisture content to between 10% and 12%. This product can be sold as mechanically dried clay or is sent to the roller mill to be further processed and made into air-floated clay.
Wet or slurry process
The wet or slurry process uses the same primary and secondary crushers as the dry process. However, rather than a blend of raw clays being loaded into the primary crusher, raw clays are placed in a batch hopper in a certain order so that different clays enter the process first for each batch. These are then fed into a blunger via conveyor belt. The blunger contains hot water and predetermined chemicals, depending upon the product being made. Clays loaded first react with the chemicals to enable the digestion of organics and lignins which form part of their composition. Other clays follow as determined and required. The blunger mixes for a programmed period of time. Control checks are made to test gravity and carry out screen analysis.
The material is then transferred to 0.06 mm scalper screens. From there it is pumped over several 0.175 mm finish screens, put through a ferro filter and moved into a storage tank where it is examined.
After checking its specifications, the material is mixed to increase its consistency for shipping. Products are transported as 61% solids or higher via tank truck or tankcars.