Study On Comprehensive Treatment Of Metallurgical Wastes In Steel Work

At present China’s iron & steel industry’s development direction is to make the environment-friendly, green ecologicalization, high efficiency and comprehensive utilize the resources. Sintering flue gas, coking wastewater and steel slag are the main wastes of integrated steel companies. Effective handling these wastes is the main important task. However, the past researching work about handling wastes is essentially in isolation, without taking into account the inner link between the three parts, therefore there is no major breakthrough of the treatment process. In the paper the experiments were done, the mechanisms of desulfurization in sintering, flue gas and handling coking wastewater using steel slag were analyzed.In order to study the distribution of Sulphur in sintering, the equipment which named as small-sintering test has been invented. The results have shown that it can simulate the sintering process very well. It is a new method for researching on the sintering production process. Because of less material and low labor intensity, the experiment can be operated independently by one man.About 60-90% SO2 emissions came from the sintering production process in metallurgical enterprises. Lime is not only an indispensable raw material for sintering production process, but also commonly used as desulfurization agent. The high active lime can be got by calcining limestone in vacuum condition. The activity of lime is related to the calcination’s temperature and time. The best process condition for prepare high active lime is calcining limestone in vacuum at 950℃for 60 minutes. The activity of lime is corresponding related to special surface area and special porosity. The activity of lime can be accurately determined by temperature rising rate method. This method is not only with simple operation, benefit to environment, but also with well reproducibility. The sintering production process is significantly impacted by the activity of lime. The high activity of the lime is favorable for the formation of fine acicular and acicular structure calcium ferrite. The sinter’s grade, intensity and the yield are increased with the rase of lime’s activity. The sulfur assignment during sintering production process is greatly affected by the activity of lime. Sulphur content in sinter will increase with the increase of the activity of lime, but it is still satisfactory for technology standard of high quality sinters, the SO2 emissions from the flue gas can be reduced. The testing results of mineragraphic microscope and scanning electron microscopy (SEM) indicate that the Sulphur existences as CaS, and mainly distributes in the spiracle region of sinter.The SO2 gas is a kind of acidic gas, while a large amounts of alkaline substances in coking wastewater, such as ammonia, the chemical reactions will take place when they meet together. The results show that the SO2 in sintering flue gas can be effectively removed by coking wastewater. The SO2 content in Sintering flue gas can meet the discharge standards. Sintering flue gas can decrease the pH value of coking wastewater, which provides favorable conditions for the following treatment of wastewater via iron-carbon internal electrolysis method.Iron-carbon internal electrolysis method is an effective effluent disposal method which has been developing a few years. Metallization pellets with high carbon content (MPHC) has been success made from steel slag, iron powder, coal powder and a little of bonding agents. This preparation process integrates sponge iron preparation and the activated carbon preparation process. A number of sponge iron and activated carbon are uniform distribution in the MPHC. The results show that phenols and cyanide in coking wastewater can be effective removed by the MPHC, and the COD has certain degeneration, but the degradation of nitrogen is bad. The MPHC exhibited remarkable performance for the degradation of coking wastewater than steel 45#, cast iron and sponge iron. The results of GC-MS and FT-IR indicate that the degradation of organic pollutants in coking wastewater by the MPHC is not simply adsorption, but is removed complete by galvanic cell reaction.The results of the distribution of Sulphur during sintering production process and the degradation mechanism of coking wastewater by the MPHC indicate that a new method was explored for removing the SO2 of sintering flue gas by comprehensive utilization of coking wastewater, then coking wastewater will be treated by the MPHC. Theoretical basis were provided for the integrated steelworks’ to treat main wastes such as the sintering flue gas, coking wastewater and steel slag at highly effective and more economy.