comprehensive utilization and discussion of iron and steel metallurgical slag

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Comprehensive utilization and discussion of Iron and steel metallurgicalslag

Xinlong Yang1,a, Huixin Dai2,b*, Xiang Li3,c

1,2,3Faculty of Land Resource Engineering, un!ing "ni#ersity of $cience and %ec&nology,

un!ing, '())3, +&ina

ayxl()1-1'3.co!, bd&x''//-sina.co!, c0))2lx-1'3.co!

Key words: Ferrous !etallurgy blast furnace slag oxide scale co!re&ensi#e utili4ation

Abstract. In recent years, the steel industry is in decline. To reduce environmental pollution,

increase corporate profits and promote the sustainable development of China's steel industry,

developing steel metallurgical slag’s comprehensive utilization has a very important significance.

This article describe the present situation and problems in China's steel metallurgy slagcomprehensive utilization, and reach the conclusion that the present method should be improved

and the new method of comprehensive utilization should be further developed.

Introduction

China has the largest steel output in the world. In 2!2 China's crude steel output has reached "!#

million tons. To promote the development of iron and steel enterprises, effectively using a large

number of metallurgical slags in the process of iron and steel smelting and reducing environmental

pollution have more important significance.

The main metallurgy slag consist of blast furnace slag, steel slag, iron o$ide scale, scrap iron, redmud, ash blast furnace and gas dust, etc. The first three is the main waste of iron and steel

metallurgy. This paper focuses on these three solid slags% discuss their present comprehensive

utilization’s e$isting problems.

Blast furnace slag and steel slag utilization

&last furnace slag comes from blast furnace discharge. teel slag comes from steelma(ing

process which is divided into converter slag and electric furnace slag. The main chemical

composition of blast furnace slag and steel slag is i)2, Ca), *l2)+, g) and n), etc. -!2/. The

utilization ways of the two slags are similar.

Building materials applications. *fter water 0uenching cooling, blast furnace slag and steel slagwill form the vitreous mineral crystal. tudy shows that both (inds of slag containing active mineral

such as C2 and C+. &last furnace slag and steel slag, therefore, need to be added e$citing agent to

inspire the potential hydraulic activity. *fter adding silicate cement clin(er, gypsum, and blast

furnace slag can produce blast furnace slag cement% teel slag adding zeolite or fly ash can produce

steel slag fly ash cement and steel slag cement. 1esearch shows that the slag micro powder and steel

slag powder can be e0uivalent to replace all (inds of concrete.

sing their hydraulic gelation properties, blast furnace slag can be made as slag bric(, sintering

bric(, slag ceramics and other building materials by deep processing. *lso, the steel slag can be

widely used in producing steel slag bric(, laying foundations, engineering bac(fill and di(e and

dam construction, etc.The recovery of valuable elements. 3$cept 4e element, other valuable elements also contain in

blast furnace slag. uch as titaniferous slag, which content high titanium in 2! to 2+5. *t present

the enrichment methods of titanium which has been studied mainly include6 e$tracting TiCl 7 from

Advanced Materials Research Vols. 807-809 (2013) pp 2328-2331Online available since 2013/Sep/10 at www.scientific.net © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.807-809.2328

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blast furnace slag by high temperature carbonization and low temperature selective chlorination%

8lasma melting reduction produce titanium silicon alloy from titanium blast furnace slag% 1ecover

titanium by ammonium sulfate melting method -2/.

&ecause of contains a lot of steel, steel slag can be recycled. The basic flow of recovery is bro(en

screening magnetic separation. To achieve high recovery rate of steel slag, plant often use

multiple stage crushing process. Through magnetic separation, slag and steel’s iron grade average in

more than 995.

Used for flux in the iron making. teel slag mainly used for sintering flu$ and the flu$ of

ironma(ing in the iron ma(ing.

intered flu$ was mostly limestone, when Ca), g) and iron o$ide in converter steel slag

content in 7:95 -+/. Therefore, steel slag, after the fine grinding, can replace part of limestone as

the sintering burden. ;oining steel slag can not only improve the permeability of sinter bed, ma(e

Ca) easily react with iron ores, increase the li0uid phase in sintering process and increase the sinter

drum strength% but also reduce the inta(e of limestone, reduce heat absorption of CaC)+

decomposition, improve sintering temperature relatively.teel slag can be added to the blast furnace as ironma(ing flu$. <ithout carbonate decomposition,

Ca) and g) in steel slag can have the effect of the limestone flu$ in ironma(ing process. It can

reduce the amount of limestone and dolomite, reduce the consumption of co(e, and recycle iron

components of steel slag.

Agricultural production applications. Containing in &last furnace slag and steel slag, Ca, 8, i,

g and other elements, which is crops need, can be used for ma(ing silicon fertilizer,

calciummagnesia phosphate fertilizer and other fertilizers. ilicon is needed by rice. *nd silicon

fertilizer made of two (inds of slag contained a lot of citrate acid soluble silicon which can easily be

absorbed by rice. This silicon can ma(e up for the inade0uacy of natural silicon in soil. *fter

absorbing silicon, rice can deposit this silicon on the leaf epidermis cells, inhibit plant transpiration,

raise photosynthetic rate. o applying blast furnace slag and steel slag silicon fertilizer into the rice

paddies can improve rice growth and increase yield.

&last furnace slag and steel slag contents more al(aline compound such as Ca) and g). o it

can be applied into the acidic soil to use as acidic soil conditioner.

Used for treatment of wastewater and waste gas. <ith high basicity, porous, large surface and

density, steel slag=s price is low. o it can be used in the processing of industrial waste water and

waste gas.

To purify waste water, steel slag is mainly used its good filtration and adsorption properties.

tudy shows that the surface of the steel slag with negative charge, can adsorption of cationic. teelslag has better removal effection to some anionic compounds such as Congo red -7/.

teel slag can be used to handle acid gases by made into slurry. *l(aline substances which is

contained steel slag react with )2 on the absorption of acid gases. tudies have shown that in

serum, )2 and >2) react and generates >)+. >)+

decomposed into )+2 and >?. Iron and

manganese o$ide in serum can let )+2 o$idize to )7

2, and desulphurize waste gas. Ca) and i)2

in steel slag will @oin hydration reaction at the same time% accelerate the process of absorption of

)2.

Iron oxide scale utilization

Auring hot rolling or forging, steel can react with o$ygen in the air and produce large amounts of

iron o$ide scales. 4e content is high Bup to :D5E in o$ide iron scale. Iron o$ide scales can be

used in metallurgy, chemical industry and the preparation of the use of permanent magnets, etc.

Advanced Materials Research Vols. 807-809 2329



Used as sintering and antioxidant. &ecause the iron content is high, iron o$ide scales is often used

as a raw material to return to the sintering, ironma(ing and steelma(ing process.

4e) in the iron o$ide scales is as good as sintering material reducing agent. o the scales can be

added in sintering material to ma(e 4e) turn to 4e2)+ to improve the level of sintering temperature.

o the scales can improve the drum inde$ and the grade of sinter. any sintering plant use the

scales into the sintering process. &ut the iron o$ide oil content is higher. Aeoiling must be carried

out before use.

3$cept for sintering, iron o$ide can also be mi$ed with other ferrous materials after grinding to

produce metallized pellets and cold consolidation pellets. *fter balling, pellets turn to pelletizing

production in annular furnace% after bri0uetting and calcining in low temperature, pressure ball can

be directly into the ironma(ing.

cales may also used as o$idant assisted in electric furnace steelma(ing or converter steelma(ing

slag agent after dehydration. In addition, iron o$ide can produce silicon alloy, steelma(ing

deo$idizing agent and additives.

The preparation of high purity ferric oxide. 4errite is used as a basis to create the magnetic fieldin the electronics industry. 4e2)+ content is higher, so scales can be used in the preparation of

permanent magnetic ferrite.

Iron o$ide scales’ processing methods are screeningdry magnetic separation and screeningfine

grindingo$idation. creeningdry magnetic separation method need removing oil and drying scales

first, screening, and selecting with a belt magnetic separator. 8roduct is used as permanent magnet

ferrite underburnt clin(er. creeningfine grindingo$idation method is to put the scales sieving

after fine grinding to 9 microns below. Then put the powder into the o$idative (iln. 4e +)7 is

o$idated 4e2)+. 8roduct is used as highgrade permanent magnetic ferrite materials.

Iron o$ide scales is suitable in the chemical industry as a raw material to produce iron o$ide red.

*t present, most iron o$ide red was produced by li0uid phase precipitation method.

iscussions of steel metallurgical slag utilization existing problems

Blast furnace slag and steel slag. <ith the development of construction industry and the huge

demand of high strength cement and high strength concrete, steel slag cement with relatively poor

mechanical properties can't meet the needs of a large number of buildings. Ary granulating

technology -9/ will granulate blast furnace slag to granulating slag. &y forced cooling and steam

heat e$change, the process output low temperature furnace slag and middle temperature steam. This

method, recycling heat and simultaneous produce cement, succeed in high efficient utilization of

waste residue, should get further development.

teel slag can be used to instead of limestone in sintered material, but it containing 8, two (indsof harmful elements. *fter adding steel slag in the sinter, these two elements will be into the closed

cycle of smelting, and ma(e pig iron brittle. If 8 and can be removed before sintering, it can

reduce the enrichment of harmful elements in smelting cycle and improve the 0uality of sinter.

Iron oxide scales. intering process which put iron o$ide scales as sinter feed ingredients are

comple$ and e$pensive. Finc o$ide contained in scales may grow nodules in blast furnace and

affect the life of blast furnace. <hen it was added in sintering material, chlorine can react with zinc

o$ide during sintering and generate volatile FnCl2. 4or sinter, half of zinc can be removed in this

reaction.

Iron o$ide scales scales have some impurities% bring some difficulties for the production of high

purity ferric o$ide. &y combining magnetic separation method and o$idation method, the purity of

the product could be further improved.

2330 Environmental Protection and Resources Exploitation



!onclusions

Comprehensive utilization of metallurgical slag should be used with less investment, technology

diversification and products diversification. Comprehensive utilization with high efficiency and

energy saving is related to science and technology, and wor(ers need to indepth study of this

problem.

Acknowledgements

This study was supported by the Gational Gatural cience 4oundation of China BHrant

Go.9!2#72E.

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Advanced Materials Research Vols. 807-809 2331



Environmental Protection and Resources Exploitation

10.4028/www.scientific.net/AMR.807-809

Comprehensive Utilization and Discussion of Iron and Steel Metallurgical Slag

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comprehensive utilization and discussion of iron and steel metallurgical slag

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