Taking the molten iron pretreatment of torpedo mixed iron tank car as an example, Figure 1 shows the refractory materials used for molten iron pretreatment. When pretreating molten iron, the pretreatment agent is sprayed into the molten iron through a spray gun with a carrier gas (nitrogen or air). In order to improve the pretreatment efficiency, a stirring gas is sprayed into the molten iron through a nozzle, or the molten iron is stirred with a stirrer, so that the pretreatment agent and the molten iron are fully mixed, the reaction process is accelerated and the reaction is fully completed.
When desiliconization is carried out, an iron oxide (FeO) pretreatment agent is used. Generally, rolled steel scale or iron ore is used as an oxygen source in the pretreatment process, and lime (CaO) is used to adjust the slag alkalinity. When dephosphorization is carried out, lime (CaO-CaF2-FeO) or soda ash (Na2CO3) pretreatment agents are generally used. When desulfurization is carried out, lime (CaO-CaF2 and CaC2) is used. Various pretreatment agents have a strong corrosive effect on refractory materials. Especially among the soda ash pretreatment agents, Na2O has a good dephosphorization and desulfurization effect, but its melting point is very low (852℃), and it has a strong corrosive effect on refractory materials. Na2O is also a strong oxidant that can oxidize graphite and silicon carbide. When using lime pretreatment agents, lime (CaO), fluorite (CaF2) and iron oxide (Fe2O3) are mixed. Iron oxide and fluorite have a strong corrosive effect on refractory materials, but their corrosive effect is lighter than Na2O. In addition, due to the addition of lime during the treatment process, the alkalinity of the slag changes greatly, from acidic slag to alkaline slag, and the refractory materials are corroded by acidic slag and alkaline slag.
1-Dolomite refractory; 2-High alumina refractory; 3-Magnesium refractory; 4-Sealing brick; 5-Breathable brick; 6-CaC2 spray gun
During the pretreatment of molten iron, the erosion and damage to the refractory are mainly:
(1) Strong scouring and wear of high-temperature molten iron and slag;
(2) Chemical erosion of various pretreatment agents;
(3) Penetration and erosion of slag;
(4) Temperature changes caused by intermittent operation.
Therefore, the requirements for refractory materials for molten iron pretreatment are:
(1) High high temperature strength and wear resistance;
(2) Resistance to erosion of various pretreatment agents;
(3) Good resistance to slag erosion;
(4) Good thermal shock resistance, no cracking, peeling and flakes;
(5) Convenient for on-site application and construction, less pollution to the environment.
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