IV. Refractory materials for lead smelting
The smelting of lead basically adopts the sintering-blast furnace method (i.e. roasting-reduction smelting method). The furnace types are blast furnace, closed lead-zinc blast furnace, oxygen bottom blowing lead smelting furnace and KIVCET direct lead smelting furnace.
(1) Blast furnace, vertical cylindrical, the upper working layer of the furnace body is made of clay bricks; the middle working layer is generally made of magnesia bricks, magnesia-chrome bricks or chrome bricks; the temperature of the lower part of the furnace body and the tuyere area is 1300℃, and some parts are 1500℃. The use conditions are harsh and there is water cooling plate protection. The working layer generally uses dense clay bricks, high-alumina bricks or magnesia-chrome bricks, or high-alumina castables. The working layer of the furnace is made of magnesia bricks, magnesia-chrome bricks or chrome bricks. Due to the high density and strong permeability of lead liquid, it is easy to make the furnace bottom bricks float up. Therefore, high-aluminum phosphate combined with ramming material is used to ram the furnace hearth, which has a better effect.
(2) The closed lead-zinc blast furnace is a new type of furnace for processing lead-zinc oxide ore or lead-zinc mixed sulfide ore. It is a thermal equipment for directly smelting and producing lead and zinc. It consists of a closed blast furnace, a condenser (i.e., lead mist chamber) and a flue. The working layer of the furnace hearth and the lining of the water-cooled plate at the waist of the furnace are generally built with magnesia-chrome bricks. The furnace top and the inclined lining at the connection with the lead mist chamber are generally cast on site with high-aluminum cement refractory castables, and can also be made into prefabricated blocks for hoisting and masonry.
The bottom and top of the lead mist chamber are built with dense clay bricks, and can also be poured with refractory castables. The side walls are subjected to the scouring and chemical erosion of lead mist and are damaged quickly. They are built with clay combined with silicon carbide bricks. The bottom and top of the lead-zinc separation chamber are generally built with dense clay bricks. The bottom of the lead liquid flow trough and the lead outlet trough are built with high-alumina bricks with an Al2O2 content of 65%, and the trough wall is built with magnesia-chrome bricks or chrome bricks. It can also be cast with castables of the same material to form a trough lining with strong integrity. The trough cover is prefabricated with high-alumina cement castables.
(3) Oxygen bottom blowing lead smelting furnace, a thermal equipment for directly smelting lead with lead concentrate. It is in the shape of a long cylinder, placed horizontally on two support rings, and can be rotated 90°. The furnace is about 22m long and is divided into a reduction zone and an oxidation zone, with a partition wall between the two. There are holes in the lower part to connect the two zones. The oxidation zone is equipped with an oxygen nozzle and a charging port is provided above. The reduction zone is equipped with a sleeve nozzle, etc. The molten pool, slag line area, partition wall, charging port and furnace wall opposite the nozzle of the lead smelting furnace are generally built with molten cast magnesia-chrome bricks, and the rest are built with directly bonded magnesia-chrome bricks or fired magnesia-chrome bricks.
(4) The direct lead smelting furnace of the Kifset process combines roasting and smelting in the same furnace. It consists of a straight cylindrical smelting tower and an electric furnace. The two share a furnace chamber and are separated by a water-cooled partition wall. The partition wall is inserted into the molten pool to a depth of 200~400mm. The electric furnace lining and the high-temperature area of the smelting tower of this furnace are subject to high temperature and chemical erosion. The slag line, electrode holes and partition walls inserted into the molten pool are damaged quickly. Therefore, the working layer of the furnace is all built with magnesia-chrome bricks, and the vulnerable parts are also protected by water-cooled copper sleeves. The water-cooled plate partition wall can also be welded with anchor nails on the plate, and magnesia-chrome amorphous refractory materials can be poured or rammed.
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