Refractory material for electric zinc smelting furnace and zinc leaching slag volatilization kiln
January 13, 2021
The electric zinc smelting furnace is actually a resistance arc furnace. The electric energy supplied by the graphite electrode is converted into heat energy through the material slope and slag resistance to keep the slag temperature at 1250~1350℃. The furnace gas composed of zinc vapor and CO after electrothermal reaction enters the condenser to condense the zinc vapor into liquid zinc. The slag is mostly furnace slag with basicity of 0.75~1.25.
The electric zinc smelting furnace masonry is built at the top of the spherical furnace at a temperature of 1200~1300℃. Generally, high alumina bricks or heat-resistant castable materials are selected. High alumina bricks are selected for the side wall above the slag line. The erosion and scouring effect of slag below the slag line is strong. The bottom of the furnace is flat bottomed with clay bricks, magnesia and brine, and aluminium-chrome (slag) bricks or aluminium-alumina spinel bricks.
In view of the zinc smelting electric furnace to raw material adaptability, short process, less investment, fast construction, environmental pollution is easy to control, so suitable for the area with rich power resources, especially suitable for electric furnace capacity in 2000~2500kV·A small and medium-sized zinc plant selection.
Hydrometallurgical zinc smelting is the most important zinc production method in China. But acid leaching residue still contains a lot of zinc, lead, indium, gallium and other oxides or sulfides, so the rotary volatile kiln is used to treat the leaching residue for recovery.
Rotary kiln is a general steel cylinder, lined with refractory brick, furnace body and horizontal plane into 3°~5° inclination, kiln length of 30~58m, kiln diameter of 2.0~3.6m, the speed of 0.6~1.2r/min.
The working principle of pyrometallurgical zinc from acid leach residue is to mix acid leach residue and coke particles in a certain proportion, use it to reduce and exothermic reaction, distillation in rotary kiln, reduce and gasify zinc, and then condense zinc vapor to prepare zinc metal. The rotary kiln can be divided into four stages from feeding to slagging along the direction of kiln length: dryer, pre-tropical zone, high temperate zone and cooling zone. Due to the oxidation of zinc vapor and the combustion of carbon, the temperature in the high temperate zone of the kiln is between 1000~1300℃, the temperature at the end of the kiln is between 650~750℃, and the temperature at the exit of the kiln residue is between 750~900℃. The flue gas of kiln is oxidized atmosphere. The furnace charge in the kiln is in the high temperature and constantly rolling running state, the physical and chemical reaction in the kiln is intense and complex, the kiln lining is seriously worn, and the kiln body life is very short.
The main factors affecting the life of kiln body are as follows:
(1) Structure size of kiln body. If the inner diameter of high temperate zone is too small, the volume strength in this area will be large, leading to the increase of thermal stress and the deformation of the cylinder, so the rotary kiln should tend to be large.
(2) Masonry quality. Brick seam is much and wide, easy to be eroded by molten slag, now more use of large brick and implementation of dry laying bricks or stones.
(3) Selection of kiln lining materials. In the process of production, the kiln lining is subjected to the combined action of thermal stress, mechanical erosion wear and reducing atmosphere, and the erosion rate of refractory material is very fast, the clay brick is the fastest, and the magnesia-alumina brick, magnesia-alumina brick, chromium slag brick and magnesia-alumina brick are slower. According to the cause of kiln lining damage, kiln lining materials must have the following properties: 1) high thermal shock resistance; 2) High porosity; 3) It has strong reduction resistance, which is the most important aspect.
Therefore, magnesia-alumina brick, chromium slag brick and magnesia-alumina brick should be selected for other belts besides clay brick in dry zone. At present, the magnesia-aluminium-chromium brick has achieved good application effect in zinc volatilization kiln.