Production of Refractory Bricks and Red Bricks

In the process of recovering fluorite by branch flotation from the tailings of the Shaodong Lead-Zinc Concentrator in Hunan Province, the overflow from the first-stage flotation tailings after classification by a hydrocyclone mainly consists of silica and alumina, with a refractoriness of 1680°C. Using this overflow product, mixed with a certain amount of clay clinker (2.361 mm) and binder clay, after blending, molding, and natural air-drying, the mixture was dried at 80°C and 120°C, and then fired in a reheat furnace to obtain the final product. Its properties were tested and found to meet the national standards for refractory bricks used in blast furnaces. In the flotation process for fluorite recovery, part of the tailings from the cleaning stage is rich in silica and calcium fluoride. Returning these tailings to the fluorite flotation circuit would affect the quality of the fluorite concentrate, so they are discharged as a separate tailings stream. To make rational use of this tailings stream, tests were conducted to produce red bricks. The tailings were mixed with clay in a ratio of 3:2, then dried (120°C, 4 h) and fired (1000°C, 3 h) to obtain finished products.

5.1.2.2 Production of Autoclaved Silicate Bricks
The Yinshan Lead-Zinc Mine, subordinate to Jiangxi Copper Corporation, has built a tailings brick plant with an annual output of 10 million bricks, using tailings to produce autoclaved silicate bricks. The production process flow is shown in Figure 5-4.

Technical requirements of the process:
(1) Mix ratio: 85% tailings, 15% lime;
(2) Mass fraction of calcium oxide: above 65%;
(3) Digestion temperature: above 80°C;
(4) Digestion time: 6 h.

(5) Steam pressure: 0.8 MPa;
(6) Steam temperature: above 170 °C.

The finished bricks produced have high strength and an attractive appearance. Test results show a compressive strength of 18–21 MPa, a flexural strength of 3.7–5.5 MPa, and good frost resistance (passing 17 freeze‑thaw cycles). All other physical and mechanical properties meet the requirements for use. The measured performance corresponds to Grade 150 according to the national standard, which is higher than that of ordinary clay bricks. These bricks can be widely used in general industrial and civil construction.