Tungsten tailings brick

The calcified brick factory of Xihuashan Tungsten Mine was completed in 1989. It was put into mass production in 1990. It produces calcified bricks from tailings and lime. The annual production of bricks reaches 10 million pieces, and the annual profit is more than 200,000 yuan.

First, the main raw materials and quality requirements

Calcified brick is also known as lime sand brick. Its main raw material is tailings and lime. The tailings are tailings produced by Xihuashan tungsten ore. The chemical composition and particle size distribution are shown in Table 1 and Table 2.

Table 1 Tail sand size composition table

Table 2 Table of chemical composition of tailings (%)

The tailings account for more than 80% of the total amount of calcified bricks. It is necessary to ensure that the content of silica in the tailings is more than 65%. In addition, the tailings are not allowed to contain agglomerated clay blocks, and the finely dispersed fine-grained soil content is not allowed. It should be less than 10% of the total amount; the content of water-soluble potassium and sodium oxide should not exceed 2%; the particle size requirement is 0.31.2mm>65%, +1.2mm<5%, -0.15mm does not exceed 30%, and the tail Sand does not allow the presence of large and small pebbles, slag, grass roots, bark and other debris.

Lime: Lime must be fresh (bulk) of lime, and the content of calcium oxide should be greater than 65% efficient, magnesium oxide content should be less than 5% of the low magnesium lime, while the burnt lime and lime should be burnt separately under Less than 5% and 15% are optimal, and the fineness requirement is -0.097 mm>95%.

Second, the production process

After the lime is processed and pulverized, it is mixed with the tailing sand for removing impurities, stirred with water, and then digested into a warehouse, pressed and formed, and steamed to become a finished product.

In the process of mixing sand and sand, in order to disperse the sand and sand to achieve uniform mixing, mechanical agitation should be used to enlarge the contact surface of ash and sand, control the amount of water added, and the lime can be fully digested to generate as much hydration as possible. product. The theoretical water addition amount is 33.13% of the effective calcium oxide content. When digested in an open container, the actual water addition amount is 1-2 times of the theoretical water addition amount; the mixing digestion time is generally within 30 minutes, and the temperature needs to be controlled above 55 °C.

Brick forming is an important means to ensure the quality of calcified bricks. Calcified bricks are formed by semi-dry pressing, and the moisture content is only 8% to 10%. To ensure that the weight of the brick reaches 2.75 ~ 2.89kg / block, the ultimate forming pressure must reach 20MPa (or 200kg / cm ² ) or more, the filling depth is 80 ~ 85mm, the finished product size is 240mm × 115mm × 53mm.

Autoclaved curing generally uses a saturated vapor pressure of 0.8 MPa (or 8 kg/cm ² ) and autoclaved for 6 h.

After testing, the indicators of the finished product meet the requirements of the national standard brick No. 150, in line with the national building materials radiological protection standards, which can be widely used in the construction industry.