بازیافت فلز از سرباره فولاد BOF توسط روش کاهش کربوترميک

Metal Recovery from BOF Steel Slag by Carbo-thermic Reduction

چکیده

1- مقدمه

2- آزمایشات

2-1- تهیه و آماده سازی سرباره

2-2- طبقه بندی و روش آزمایش

3- یافته ها و بحث و گفتگو

4- نتیجه گیری

منابع

چکیده

سرباره فولاد BOF یک محصول فرعی در صنعت فولاد سازی محسوب می شود.اهمیت سرباره BOF برای صنعت و محیط زیست بسیار ارزشمند است . در مطالعه حاضر، روش احياي کربوترميک سرباره BOF و نیز احیاء فازهای حاوی Fe و P(همانند اکسید و ترکیبات دیگر) همراه با تاثیر افزودن AL2O3 بر فازهای احیاء ، مورد بحث و بررسی قرار خواهد گرفت از دو روشِ XRD و EPMA جهت طبقه بندیِ این سرباره نیز استفاده خواهد شد و در مجموع، چنین نتیجه گیری شده که تحت کنترلِ شرایط آزمایش، احتمال تصفیه و بازیابیِ Fe بسیار زیاد است

4- نتیجه گیری

بازیابی فلز از یک سرباره معمولی BOF با پایه بالا ،با کمک روش احياي کربوترميک در این مطالعه مورد بررسی قرار گرفت.احیاء اکسیدهایFe,P همراه با روش های بهینه سازی جهت بازیابی و احیاء آهن فلزیِ خلوص بالا ، مورد بررسی قرار گرفتندشکل گیری و رشدِ Fe و تاثیرAl2O3 بر احیاء، بررسی شدند باافزودن مقدار C،فاز حاویP از سرباره با فلز تغییر یافته و با کنترل C،می توان از آلوده شدن Fe از سوی P در شرایط روش احياي کربوترميک جلوگیری نمود لذا توصیه می شود نسبت مولیِ C به P در اکسیدهای آهن، جهت به حداقل رسانیدن مقدار P در Fe فلزی، برار با 1:1 قرار گیرد.

Abstract

BOF steel slag is a main by-product in steelmaking. The valorization of BOF slag is good for the industry and the environment. In the present study, the carbo-thermic reduction of BOF slag has been investigated, the reduction of Fe and P containing phases (i. e. oxide and compounds) is discussed, and the effects of Al2O3 additions on the reduction process are described. XRD and EPMA have been applied for characterizing the slag. We conclude that, by controlling the test conditions, it is possible to purify the recovered Fe.

4- Conclusions

Metal recovery from a typical BOF slag with high basicity has been studied by carbothermic reduction. The reduction of Fe oxides and P oxides has been discussed, and optimized process conditions to recover high-grade metallic iron (>98 wt%) have been proposed. The formation and growth of the extracted metallic Fe has been observed, and the effects of Al2O3 on the reduction have been investigated. With increasing C addition, the P-rich phase changes from slag to metal. By controlling C addition, it is possible to avoid contamination of metallic Fe by P during carbothermic reduction. It is suggested to keep the mole ratio of C to O in the iron oxides as 1:1, in order to minimize the P content in the metallic Fe.

تصویری از مقاله ترجمه و تایپ شده در نرم افزار ورد

بازیافت فلز از سرباره فولاد BOF توسط روش کاهش کربوترميک

Metal Recovery from BOF Steel Slag by Carbo-thermic Reduction

بررسی فرایندهای بازیابی فلز از سرباره های فولاد

Study of the Processes of Metal Recovery from Steel Slags

چکیده

1- مقدمه

2- مفاهیم اصلی

3- یافته ها و مباحثات

4- نتیجه گیری

منابع

چکیده

روش های فرآوری ضایعات و پس ماندها در سرباره های فولاد سازی از اهمیت بالایی برخوردار است طرحِ احیاء دو مرحله ایِ فلزات از سرباره های دور ریز با کمک شیوه های احیاء در شرایط آزمایشگاهی، مورد بررسی قرار گرفته است پارامترهای احیائی که با ماکزیمم بازیابیِ فلزات از سرباره ها در ارتباط باشد نیز به تازگی شناسایی گردیده است همچنین، مطالعاتی نیز بر روی بازیابیِ فاز مایع و جامدِ نمونه های سرباره در دمای بین 1000 تا 1500 درجه س، انجام گرفته و نتایجِ مدل سازی ترمودینامیک و فرآوری سرباره در دمای بالا، نشان می دهند می توان به بازیابی سرباره های فاز جامد در شریط حضور مونواکسید کربن با دمای بالا جهت دستیابی به قطعات فلزیِ مجزا، امیدوار بود

4- نتیجه گیری

با انجام آنالیز فیزیکی-شیمیایی بر روی سرباره های دور ریزZMW، توانستیم توزیعِ غیر همگنِ ترکیبات شیمیایی و حضور فازهای پیچیدهِ ترکیبات حاوی آهن و عاری از آهن را تعیین نمائیم. نتایج حاصل از تفکیکِ نمونه ها بعد از عملیات حرارتی نیز نشان از بهبود بازدهیِ فلزات ، بعد از احیا داشته البته به شرطی که دمای احیا، افزایش یابد( جدول4)ترکیبات مغناطیسیِ به دست آمده در فرآیند تفکیک، نه تنها حاوی فلزاتِ احیا شده بوده بلکه دی اکسیدهایِ فلزی را نیز در بر دارد غلظت بالای ترکیبات مغناطیسی نشان می دهند که تفکیک و جداسازیِ فلزاتِ احیا نشده از سرباره تنها در دمای بین 1200 تا 1300 درجه س به علت افزایش قابلیت مغناطیسی پذیریِ سرباره و نیز تفکیک کریستال ها در هر فاز، بهبود می یابد. حضور دی اکسیدهای فلزی نشان می دهند که توسعهِ فناوری های موجود جهت تولید هرچه بهتر فلزات احیا شده و تفکیک آن از سرباره، بسیار حائز اهمیت خواهد بود.

Abstract

The methods of waste processing and salvaging are considered for steelmaking slags. The dump slags of the Zlatoust metallurgical works are analyzed. A scheme of two-stage metal reduction from the dump slags using the reduction– melting scheme is developed and tested under laboratory conditions. The reduction parameters that correspond to the maximum recovery of a metallic component from the slags are found. Experimental researches included experiments on solid-phase and liquid-phase recovery of slag samples at temperatures of 1000-1500°C. The results of thermodynamic modeling and experimental high-temperature slag processing allow speaking about the advisability of preliminary solid-phase recovery slag in the atmosphere of carbon monoxide with subsequent high-temperature (liquid phase) recovery to obtain the separate metal fractions.

4- Conclusion

When performing a physicochemical analysis of the ZMW dump slags, we detected a significantly nonuniform distribution of chemical components and the presence of complex phases of iron-free and iron-containing compounds. The results obtained from repeated magnetic separation of the specimens after heat treatment also point to an improvement in the efficiency with which metals are reduced when the reduction temperature is increased (Table 4). The magnetic component obtained in the separation process contains not only reduced metal, but also metal-bearing oxides. The high concentration of magnetic material indicates that the separation of the unreduced iron-bearing material from the slags improves at 1200 and 1300°C due to the increase in the slag magnetic susceptibility and isolation of the crystals of these phases. The presence of metal-bearing oxides shows that it is necessary to develop a technology for further reducing metals from the separated magnetic part of slag.

تصویری از مقاله ترجمه و تایپ شده در نرم افزار ورد

بررسی فرایندهای بازیابی فلز از سرباره های فولاد

Study of the Processes of Metal Recovery from Steel Slags

مروری بر کاربرد سرباره و لجن های به دست آمده از صنایع فولاد سازی

An overview of utilization of slag and sludge from steel industries

Abstract

Significant quantities of sludge and slag are generated as waste material or byproduct every day from steel industries. They usually contain considerable quantities of valuable metals and materials. It is generally possible to recover some values by physical or chemical mineral processing techniques such as crushing, grinding, classification, hydrocyclone, magnetic separation, flotation, leaching or roasting. Transforming these solid wastes from one form to another to be reused either by the same production unit or by different industrial installation are very much essential not only for conserving metals and mineral resources but also for protecting the environment. This paper analyzes the characterization, beneficiation and utilization aspects of blast furnace flue dust, blast furnace sludge, LD sludge and LD slag generated at modern steel plants.

1 Introduction

Integrated steel plants utilize mostly five materials such as raw materials, air, water, fuel and power to produce steel. During the production of steel, 2–4 t of wastes are being generated per tonne of steel produced. The various solid wastes in the form of slags and sludges that are emerged from steel plants are blast furnace slag, blast furnace flue dust and sludge, Linz–Donawitz (LD) converter slag, LD sludge, LD dust, mill scale, mill sludge, acetylene sludge, etc. The solids and liquid wastes generated from a steel plant are shown in Table 1. The composition of these materials vary widely depending on the source of generation but usually contains some useful resources such as iron, carbon, calcium, zinc, lead, etc., which can be recovered and reused in a judicious manner. Besides that, some slag and sludge contain a notable amount of heavy metals and release of them to earth may cause some environmental problems. The harmful components like As, Cd and Hg, etc. are highly objectionable from the pollution point of view. So, the simple disposals of these wastes are becoming less attractive which not only occupies plenty of land but also increases the disposal costs. Therefore, it is desirable to recover the valuables and utilize these wastes. However, detailed scientific investigation is necessary to establish the scope of the problems associated with recovering the valuable materials from different slags and sludge and the proposed utilizations are to be carefully evaluated.

Steel plant slags mainly include blast furnace slag and steel melting slag (open hearth or LD process slag). Various efforts have been made on the utilization of blast furnace and steel slags. These are competitive raw materials for industrial mineral industry. A comparison of the qualities between air-cooled blast furnace slag and natural sand, LD slag and natural sand, LD slag and gravel or crushed stones shows that they are equivalent. The special processing of slag sometimes produces products originating from the rock and mineral industries. Therefore, lot of studies has been made for the concrete, plastering and environmental technology industries (Kolb and Leipold, 1993). Today blast furnace slag has found a wide application in cement production and marketed as Port land blast furnace slag cement (PBFS). Since blast furnace slag contains little iron and high calcium oxide content with similar composition of clinker, it can be safely used along with the clinker and gypsum for production of cement.

LD slag is a byproduct of steel industry, which comes from pig iron refining processing using LD converters. Because of its physical, chemical and mineralogical properties, it can be used as a substitute for aggregates in civil engineering projects. LD slag has the useful components like CaO, MgO with high basicities (CaO/SiO2) of above 3.0. LD slag therefore has high fluxing capacity and is being charged in the blast furnace due to easy melt and better utilization of calcium values. In the European countries, 30% of such slags are recycled into the blast furnace. However, the most harmful components in the LD slag is P&S which are to be removed before use either in sintering plant or blast furnace. LD slag, used in blast furnace at Bhilai Steel Plant, India was therefore discontinued due to sulphur and phosphorus content (Sharma et al., 1993). The slag is however not suitable in cement making due to the presence of high percentage of iron oxide. In many instances it is usually subjected to metal recovery before its application in steel and iron industries.

Most of the materials of sludge and dusts from steel industries are recycled through sinter making in more advanced countries. The recycled wastes also have some effect on sinter quality, strength and productivity. The recycling is generally controlled depending on the analysis of the waste material. In the direct use of the steel plant wastes, a briquetting plant was commissioned at National Steel Corporation, Great Lake to recycle 300,000 metric tonnes of waste materials such as BOF sludge, BF dust and sludge, LD sludge, mill scale and other materials (Landow et al., 1997). A number of technologies have been developed to allow better utilization of Fe-bearing steel plant fines in primary operations. Methods ranging from simple agglomeration techniques to new hot metal production processes for treating the dust materials are cited which are useful in pretreating the waste materials to make them more amenable to recycling in iron and steel making operations. These processes involve thermal, hydrometallurgical and physical beneficiation methods.

The process byproduct of mill scale from the rolling process containing >70% Fe is generally recycled into the sintering plant. Generally, 70–100% mill scale containing high iron is being recycled through either briquetting or sintering route with out any difficulties. In some cases, de-oiling of the material is required. Rolling mill sludge is the fine particles, which takes the oil portion along with the rolling cooling water. Recycling of these particles are challenging due to very high oil content. The reduction of oily mill scale sludge along with blast furnace flue dust in laboratory experiments and in a pilot plant rotary kiln has indicated that it is possible to reduce oily mill scale sludge to sponge iron in the rotary kiln (Eriksson et al., 1999).

The extent of generation, characterization and utility of various sludge and slags with a review of number of methods for the recovery of valuables or recycle in the plant from such materials have been summarized.