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Fundamental Research On Co-Treatment Of Chromic Wastes In High-Temperature Metallurgical Furnace

Posted on:2014-04-17Degree:MasterType:Thesis
Country:ChinaCandidate:C C PanFull Text:PDF
GTID:2251330401471222Subject:Iron and steel metallurgy
Abstract/Summary:PDF Full Text Request
Chromic wastes generally contain4%-10%chrome, which usually exist as trivalent chromium and hexavalent chromium. It mainly comes from chromic salt and stainless steel production. Hexavalent Chromium (Cr6+) has intense toxicity because of its strong oxidative effect that causes corrosion and destruction to organism. Chromic wastes have been included in the National Hazardous Waste List as a toxic waste.Present researches and technologies on non-toxic treatment and comprehensive utilization of chromic wastes were investigated. The results show that detoxification of chromic wastes is unsatisfactory and it is difficult for comprehensive treatment of the wastes to be promoted due to the shortage of co-treatment theory. In this paper, chromic waste toxicity and detoxification mechanism, also the properties and restrictive conditions of furnace and chrome waste in co-treatment are mainly studied. At last, a co-treatment technology by using BF and RKEF to treat chromic waste is developed based on the research cinclusions got above. Main results are as follow:(1) The activity model of a seven-component chromic slag was established. Cr2O3in slag is easily reacted with Na20and CaO at high temperature, but as the temperature drops, it will be oxidized to Cr Ⅵ, the valence with strong toxicity, and be released. This is the main reason that causes toxicity of chromic slag and unsatisfactory effect using present detoxification method. Reliable method of detoxification is to promote Cr2O3form Spinel with MgO and FeO by adjusting composition of the waste.(2) Temperture, basicity, MgO and FeO all have influence on the stable detoxification of chromic slag. In1700K, Percentage of Q2O3fixed into spinel can reach88.2%when the basicity is1.14and additional FeO reaches30%of the waste weight. Detoxification for stainless steel slag is similar with that of chromic slag. In1700K, percentage of Cr2O3fixed into spinel can reach62.6%and67%respectively with MgO and FeO when the basicity is1.45.(3) Co-treatment process of chromic wastes need these conditions including high temperature, reducing atmosphere and direct reduction. So these wastes can be co-treated in BF or RKEF for comprehensive reusing. Such restriction conditions as slagging system, thermal system, alkali-metal load and zinc load should be considered during designing co-treatment process. (4) Slagging system is the main constraint for co-treating chromic wastes in BF, and the optimal additive amount of chromic slag or stainless slag is less than27.2kg/t iron or76.2kg/t iron.(5) The new route for co-treating chromic wastes during smelting ferronickel in RKEF is proposed. The optimal additive amount of chromic slag or stainless slag is less than76.2kg/t iron or242kg/t iron. This new route has a greater potential for co-treating chromic wastes than BF.
Keywords/Search Tags:Chromic waste, High-temperature metallurgical furnace, Co-treatmenttechnology, Blast furnace, Rotary kiln-electric furnace
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