Basic refractories mainly refer to refractory materials mainly composed of magnesium oxide and calcium oxide, which have strong corrosion resistance to alkaline slag, and are mainly used in open hearth furnaces, oxygen-blown converters, electric furnaces, non-ferrous metal smelting equipment and some high-temperature on the device.
Detailed explanation of the main production process steps
(1) Crushing: First, the large particle raw materials are crushed into small particles by the jaw crusher, and then further crushed into smaller particles by the roller crusher or cone crusher. This process produces crusher noise (N2-1) and raw material dust (G2-1).
(2) Screening: The processed granular materials are lifted to the screening machine by the bucket elevator for screening. After screening, the raw materials that meet the specifications enter the respective silos, and the raw materials that do not meet the specifications continue to be crushed. This process produces screening machine noise (N2-2) and raw material dust (G2-2).
(3) Crushing: Some products need to be ground into powders below 200-300 mesh by Raymond mill, and then enter their respective silos. This process produces Raymond machine noise (N2-3) and raw material dust (G2-3).
(4) Batching: After the powder in the high-level silo is accurately weighed according to a certain ratio by the automatic batching system, it is sent into the mixer through the feeder, and at the same time, the weighed binder (mainly for pulp, dextrin and water) are also added to the mixer. 40% of the powder in the high-level silo is the powder produced by crushing, and 60% is the purchased specification material. At this stage, the vibrating feeder will generate certain noise (N2-4), and dust (G2-4) will also be generated during the feeding process.
(5) Magnetic separation: use the different magnetic properties of mineral particles to separate in an uneven magnetic field to remove impurities such as iron and titanium. If there are impurities such as iron in the powder, the iron will be oxidized during the firing process of the refractory bricks, which will cause spots on the surface of the refractory bricks and affect the appearance of the refractory bricks. This process will produce certain dust (G2-5) and solid waste (S2-1).
(6) Mixing: In the forced mixer, materials with different components and particle sizes are mixed and extruded with an appropriate amount of binder to achieve uniform distribution and full wetting, and then enter the mud in the form of mud. in the can. Certain noise (N2-5) and dust (G2-6) will be produced during the mixing process.
(7) Molding: Send the mud mixed in the mud tank to the pressing molding workshop with a manual flatbed truck, and press it into bricks with a friction press, and the pressing power is provided by the air compressor station. Some products with special requirements for shape and performance are formed by vibration forming machine. This process will generate friction press noise and vibration forming noise (N2-6).
(8) Drying: Put the pressed bricks on the kiln car, and dry them in electric drying kiln and waste heat drying kiln respectively according to different product performance requirements. The waste heat drying kiln uses the hot flue gas in the tunnel kiln to dry the bricks. dry. When the waste heat boiler is used for drying, since the hot flue gas of the tunnel kiln is used for heating, air pollutants such as SO2, NOx and dust will be produced (G2-7).
The drying process can be divided into four stages:
The first stage is the heating stage. Generally, the heating period is very short, and the temperature of the embryo body rises to the wet bulb temperature;
The second stage is the constant drying stage. This stage excludes a large amount of water, and the evaporation of water occurs on the surface of the embryo body, and the evaporation rate is equal;
The third stage is the deceleration drying stage. With the extension of the drying time or the decrease of the water content of the embryo body, the effective evaporation area on the surface of the embryo body will gradually decrease, and the drying speed will gradually decrease;
The fourth stage is the low-speed and balanced drying stage. The drying speed gradually approaches zero, and finally the moisture content of the embryo body no longer decreases.
(9) Firing: The dried bricks are then pushed into high-temperature kilns by electric trailers and hydraulic carts for firing. According to different product performance requirements, they are fired in tunnel kilns and shuttle kilns respectively. At present, natural gas is mostly used as fuel in the tunnel kiln, which is sprayed into the tunnel kiln through the nozzle in the middle of the kiln body, fully mixed and burned, and the firing temperature in the kiln is about 1800°C. When firing in a tunnel kiln, if a steam boiler is used to burn coal as fuel, more smoke, SO2 and NOx (G2-8) and cinder solid waste (S2-2) will be produced; Smoke, SO2 and NOx (G2-9) will be produced. The shuttle kiln uses clean energy natural gas for heating, and some products need to be fired under the protection of nitrogen. When fired in a shuttle kiln, a small amount of smoke, SO2 and NOx (G2-10) will be produced.