RHI Mr Services Bulletin 1 2012-Data

7/27/2019 RHI Mr Services Bulletin 1 2012-Data

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RHI Bulletin>1>2012The Journal of Refractory Innovations

Steel Edition

DELTEK Eco Gaskets and

Insulation for Flow Control

Products

COMPAC ROX A93MAS-15

Application in CAS-OB Bells

Gas Purging Lance Design

Optimization

CAS-OB Process


2/642 1>2012The Journal of Refractory Innovations

RHI Bulletin 1/2012

Steel Edition

Published by: RHI AG, Vienna, Austria

Chief Editor: Bernd Buchberger

Executive Editor: Alexander Maranitsch

Technical Writer: Clare McFarlane

Proofreaders: Bernd Buchberger, Clare McFarlane

Project Manager: Ulla Kuttner

Photography, Graphics

and Production: Christoph Brandner, Stefanie Puschenjak

Design and Typesetting: Universal Druckerei GmbH, Leoben, Austria

Printers: Universal Druckerei GmbH, Leoben, Austria

Contact: Ulla Kuttner

RHI AG, Technology Center

Magnesitstrasse 2

8700 Leoben, Austria

E-mail: [email protected]

Tel: +43 (0) 502 13-5300

Fax: +43 (0) 502 13-5237

www.rhi-ag.com

The products, processes, technologies, or tradenames in the

RHI Bulletin may be the subject of intellectual property rights

held by RHI AG or other companies.


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RHI worldwide

> 3

Opening Ceremony for the New Tundish WaterModel Took Place

Austria >> The tundish water modelling facility at the Technology

Center Leoben (Austria) was recently inaugurated and initial simula-

tions have already been executed using scaled customer tundish

geometries.Water modelling will assist in understanding flow phenomena in

the tundish as well as supplement CFD simulations. As an integral

part of RHIs Tundish Technology Solutions, water modelling will

serve to optimize existing products and develop new technologies

dedicated to the increasing demand for clean steel production. The

overall aim of the tundish water modelling facility is to realize tailor-

made solutions for RHIs customers that meet the quality and safety

requirements.

MARVO Successfully Completes First Turn-around of 2012 at the MiRO Refinery in Karlsruhe

Germany >> MARVO GmbH services were provided at the MiRO

combustion engineering works in the petroleum coke area. Calcined

petroleum coke is processed in the coker on a rotating staged hearth,

by extreme heat treatment up to 1400 C, to produce special con-

verted coke grades. These high quality calcinate grades are mainly

required for the industrial production of electrodes used in carbon

baking furnaces.

The soaking pit cone section of this installation was lined with

COMPAC SOL M64COR-6, RESISTAL SK60C, and DIDURIT M60-6 pre-

cast components. The sidewalls and parts of the turntable were

reconstructed using COMPAC SOL M64COR-6 and DIDURIT M60-6precast components.

The installation also features rabbles that convey the final pet coke

from the turntable via the cone into the coke cooler. These rabbles

were relined with DIPLASTIT 259 during the installations turnaround,

providing excellent abrasion resistance in this high wear area.

New Bag Filter Systems and Hardening Gratefor the RHI Hochfilzen Plant

Austria >> In order to achieve future exhaust gas limits at RHIsHochfilzen plant (Austria), the existing rotary kiln exhaust gas treat-

ment facility (cyclone separation and gas washing system) will be

upgraded to a bag filter system. Concurrently, the hardening grate

unit, which has now reached the end of its service life (built in 1958),

will be replaced and modified for use with a downstream bag dust

filter. The hardening grate required to harden briquettes will also be

used to preheat raw magnesite following the conversion.

The aims of the 8.6 million project are to reduce dust emission to

< 10 mg/Nm (future BAT limit 20 mg/Nm obligatory as of 2013),

decrease air leakage by approximately 12000 m/hour by decoupling

the hardening grate from the Lepol kiln, reliably maintain low levels

of SO2 in the exhaust gas, utilize waste heat from the kiln exhaust

gas to preheat the raw magnesite, and increase the rotary kiln per-

formance by approximately 4.5%. Commissioning is scheduled for

November 2012.

RHI at AISTech 2012USA >> Together with approximately

435 other exhibitors, RHI and INTER-

STOP took part in the Association for

Iron and Steel Technology (AISTech)

2012 conference and exhibition, which

ran from May 710 in Atlanta (USA). In

addition to presenting the INTERSTOP

Metering Nozzle Changer MNC at the

trade fair, numerous lectures were also

given by RHI personnel from both Aus-

tria and the US.

AISTech is the largest steel trade fair

held in America with more than 6000 vis-

itors recorded at this years event.

New Snorkel ProductionRecord at RHIs Dalian Plant

China >>In 2011, the RHI Dalian plant(China) achieved a new plant record of

1717 prefabricated RH degasser snorkel

pieces. This figure was the result of high

domestic demand as well as increasing

orders from customers worldwide. Prefab-

ricated snorkels were delivered to the

USA, Japan, India, Brazil, and other coun-

tries where RHIs products are successful-

ly used in various RH degassers.

The future outlook is also promising;

driven by an increased demand for high-

quality steel the use of prefabricated snor-

kels from Dalian will increase accordingly.

Therefore RHI is already proactive in pro-

viding the necessary capacity expansion.

Sales budgets forecast a total turnover of

more than 12 million in 2012 for this

profitable business.

Tailor-Made TundishSolutions

Austria >> Once more it has been prov-

en that thermochemical simulations are

an extraordinary tool to predict wear

phenomena of tundish wear linings. By

considering the various aspects that lead

to premature chemical wear, the linings

and boundary conditions of several cus-

tomers on all continents have been ana-lysed and optimized. Tailor-made tundish

wear lining mixes adjusted to customer

conditions, including thermochemical

investigations, are another step forward

in RHIs technology leadership.


4/644 As a major cornerstone of

the companys backward integration

strategy, RHI purchased the SMA Miner-

als company in Porsgrunn (Norway) in

2011. Concurrently, it was decided to

build a new state of the art MgO smelt-

er at this location.

By investing in buildings, smelting

furnaces, treatment facilities, and infra-

structure, it will be possible in future to

produce around 50000 tonnes of the

highest quality fused magnesia annual-ly, independent of the Chinese raw

materials market, chiefly for RHIs own

use.

The total investment costs for the proj-

ect are approximately 72.5 million, of

which 9.8 million were spent in 2011.

Test operations will start in stages in

August 2012, with full production

scheduled for October 2012.Lifetime Record of New EAF Burner Bricks inNorth America

USA >> RHI recently completed a trial using ANCARBON TB008 in

the high wear burner area of an EAF. The ANCARBON TB008 brickreplaced the high wearing competitor brick (MgO-C) in this demand-

ing furnace area. The results were spectacular; the newly developed

brick achieved 440 heats with 254304 mm remaining from the origi-

nal brick length of 457 mm, as compared to the former competitor

brick that was normally replaced after around 250300 heats in this

high wear zone without any residual thickness. The original trial tar-

get for the high wear zone was 500 heats, so the ANCARBON TB008

will exceed this significantly.

The additional good news from this trial is the customer has

ordered approximately 20 tonnes of this new brick for ongoing

installations in each of the two EAF furnaces. The customer has also

requested RHI submit a quote for 609 mm long ANCARBON TB008

bricks for the slag door area, since the customer considers the

ANCARBON TB008 to be perfectly suited for this application.

This latest development was especially designed for the high wear

rates in the EAF burner area. It is a further development of success-

fully implemented grades for the high wear areas in ladles and

BOFs, which were introduced on the Brazilian market 3 years ago. To

outperform a local competitor, RHI developed highly oxidation and

slag resistant grades based on special antioxidant addition and high

quality raw materials. These results provided the basis for the subse-

quent development of ANCARBON TB008. To withstand the high oxi-

dative attack, special additives were used. On oxygen attack, these

compounds form liquid phases with MgO or other oxidic compo-

nents of the brick and protect the carbon from oxidation by coveringthe pore surface with a thin film. For further trials, several grades

have been developed for EAF, BOF, and ladle applications. Already

well established and tested grades with these special additives are

ANCARBON F1T14B, ANCARBON F3T14B, and ANCARBON F6T14B

for ladle and BOF applications.

CEMENTTECH China HostsMore Than 400 ExhibitorsIncluding RHI

China >> For the 13th time, CEMENT-

TECH (China International Cement

Industry Exhibition) was a meeting point

for experts and companies from the

Asian region. Held at the Beijing Exhibi-

tion Center (China), from March 2830,

2012, this international cement industry

trade fair was host to more than 400

exhibitors from mainland China, the

USA, and Europe and brought together

the most advanced international tech-

nology and equipment. The event was

visited by more than 10000 people and

included topics such as mine explora-

tion, powder processing, cement manu-

facturing, as well as concrete products

and their construction.

The RHI stand focused on four major

topics: In-house high-grade sinter pro-

duction (HQM98), established standardbrands (ANKRAL ZC, ANKRAL RC, and

ANKRAL DC), high-grade refractories

based on HQM98 (ANKRAL R1, ANKRAL

R2, and ANKRAL Z1), and new products

such as ANKRAL R8.

Record Campaign Life of 1091 Heats in40-Tonne EAF at AML

India >> Adhunik Metaliks Ltd., (AML) achieved the highest cam-paign life of 1091 heats from October 1, 2011, to November 20, 2011,

in their 40-tonne EAF using RHI refractory bricks and monolithics.

The previous average campaign life was 850 heats; however, it was

extended beyond 100 heats by reengineering the slag conditions

based on mutual interactions between AML and RHI as well as

through using RHIs ANKERJET NP12 T gunning mix. The brick

brand installed was ANCARBON F6T10.

RHI have a supply management contract with AML for the EAF. At

the contract startup, an EAF lifetime of around 550 heats had been

reached with other suppliers. Currently, the lining installation is

supervised by RHI and the EAF refractory maintenance, namely gun-

ning and fettling, is also performed under RHI supervision. On occa-

sion, the local RHI India team also provides refractory expertise to

improve the EAF performance.

AML is located near Rourkela in Eastern India and is part of

Adhunik group who are also engaged in the mining and power

sectors.


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Production Capacity Increase at RHIs TriebenPlant

Austria >> To meet further organic growth in the nonferrous busi-

ness area, 2 million has been invested in the Trieben plant (Aus-

tria). The annual capacity limit of Trieben was approximately 53000

tonnes of basic high-fired shaped products, depending on the prod-

uct mix. However, by investing in a new press and a modern brickmilling machine, the production capacity has been increased to

63000 tonnes per annum. Following test operations in March 2012,

the new facilities were officially commissioned on April 19, 2012.

RHIs First Quarter Results for 2012Austria >> RHI started 2012 with an improved revenues and earn-

ings situation in the first quarter: Revenues increased 5.6% to

436.9 million in the first quarter of 2012, comparable to the equiva-

lent period in 2011. The EBIT of the first quarter increased by 15.1%

to 33.6 million compared with the reference period of 2011 and the

EBIT margin improved from 7.1% to 7.7%. The net profit even rose

by 74.9% up to 32 million.

While sales volume in the Steel Division fell slightly by 1.3% in

comparison with the first quarter of 2011, revenues were up 6.2% as

price increases were implemented.

Steel EBIT amounted to 12.8 million in the first quarter, after

6.1 million in the prior-year reference period.

The sales volume in the Industrial Division dropped 5.9% in com-

parison with the first quarter of 2011 because the cement business

was weaker. The recovery of the markets back to precrisis levels is

proceeding, but they still show a highly diverse picture depending

on region and industry segment. Revenues of the Industrial Divi-sion, at 143.0 million in the first quarter of 2012, fell slightly short

of the 144.6 million revenues recorded in the first quarter of 2011.

EBIT amounted to 13.1 million in the first quarter, after 15.8 mil-

lion in the prior-year reference period.

Outlook: In a stable macroeconomic environment and with

unchanged foreign currency exchange rates, RHI expects similar

revenue levels for the Steel Division in the second quarter and sig-

nificantly higher revenues in the Industrial Division. Price increases

and the cost cutting programme initiated in 2012 in combination

with a positive contribution to earnings of the higher level of back-

ward integration leads RHI to expect a higher margin for the entire

year 2012 than in the past financial year.

> 5

Fourth Tunnel Kiln and Addi-tional Capacity Extensionsat the Dalian Plant

China >> Owing to strong growth in the

Asia-Pacific region, it is necessary to

increase the production capacity of basic

high-fired bricks at the Dalian plant

(China) by an additional 35000 tonnes

per year. To achieve this requirement,

14.7 million has been invested in a

fourth tunnel kiln and additional facilities

for crushing, mixing, pressing, and fin-

ishing. The kiln was fired up at the

beginning of June and production using

the new facilities will commence in mid-

July 2012.

RHI Participates atALUMINIUM BRAZIL

Brazil >> The nonferrous sector in Brazil

is a very important market for RHI.

Therefore, at the recent ALUMINIUM

BRAZIL, which ran from April 2426, in

Sao Paulo (Brazil), RHI not only had a

stand at the exposition but also present-

ed at the conference. The event, focusing

on a wide range of aluminium-associat-

ed products and services, was held for

the first time in Brazil and immediately

received international praise.

Rotary Kiln Preheater Filter at Breitenau WillProvide Enviromental Benefits

Austria >> At RHIs raw material and production plant in Breitenau

(Austria) the existing electrostatic precipitator in rotary kiln 3 will be

replaced with a bag dust filter. In addition, a raw magnesite preheat-

er will be installed prior to the filter in order to recover waste heat

and enable the bag filter system to function.

The total project costs are 3.5 million, of which 0.6 million

were spent in 2011. The project aims are to reduce dust emission to< 10 mg/Nm (future BAT limit 20 mg/Nm obligatory as of 2013), use

waste heat in order to increase energy efficiency, preheat the raw

magnesite and save approximately 2000000 Nm of natural gas per

annum (corresponding to 4000 tonnes of CO2), as well as decrease

NOx emissions through primary measures.

Second Magnesia RotaryKiln at RHIs Eskisehir Plant

Turkey >> Chinas export policy, com-

bined with a high demand for magnesia,

is leading to price increases and the

occasional shortage of high-quality mag-

nesia. To alleviate this scenario, RHI is

expanding its own production of sintered

magnesia in Turkey. A second rotary kiln

at Magnesit Anonim Sirketi (MAS) in

Eskisehir (Turkey) will enable the addi-

tional production of approximately 76000

tonnes of sintered magnesia per annum

and decrease the need to purchase this

material at expensive prices.

The total investment costs for this new

rotary kiln facility are approximately 19

million, of which 6.14 million werespent in 2011. An additional 4.75 mil-

lion is estimated for raw magnesite sup-

ply. The test operation will start in

August 2012, with full production

planned for September 1, 2012.


6/646 RHI has published its first sus-tainability report according to the report-

ing standards of the Global Reporting Initi-

ative (GRI), thereby taking a major step

towards systematically dealing with sus-

tainability. The report titled We write sus-

tainable (hi)stories contains comprehen-

sive data and facts on good corporate gov-

ernance, product responsibility, environ-

ment and energy, employees, health and

safety, and social responsibility as well as

targets for the coming years. An electronic

version of this report is available on RHIs

website www.rhi-ag.com at Group/Sustain-

ability.

RHI will publish a sustainability report-

ing according to GRI on an annual basis in

the future, in order to regularly report on

trends, developments, and achievements.

Nonferrous Metal Topics Presented at TheMinerals, Metals and Materials Society Con-ference

USA >> The 141st TMS Annual Meeting and Exhibition took place at

the Swan and Dolphin Hotel Resort in Orlando, Florida (USA). More

than 4000 of the worlds top materials science and engineering pro-

fessionals participated in this event from March 1115, 2012. RHI

presented three technical topics during the conference: High-perfor-

mance brands for the nonferrous metals industry, slide gate systems

for copper tapping, and the chemical wear of basic brick linings in

the nonferrous industry.

The main interest for RHI, in addition to the light metal processing

of aluminium, centred on the event International Smelting Technol-

ogy Symposium: Incorporating the 6th Advances in Sulfide Smelting

Symposium. Many of the participants are very well known to RHI

as they are part of the customer base (e.g., Boliden, Umicore, Cam-

pine, Metallo, Vale, Xstrata, Stillwater, Atlantic Copper, KCM, Mopa-

ni, and Eramet) or OEMs (Outotec, Xstrata Technologies, Mintek,ANDRITZ Maerz, Kumera, Pyromet, Hatch, and SNC-Lavalin) RHI is

working with during daily business.

RHI was also represented at the TMS 2012 Exhibition along with

approximately 100 different technical and analytical companies

working in the pyrometallurgical processing and mining industry.

EBT Taphole Lifetime Increased WithSYNCARBON TB028

SYNCARBON TB028 is a new brand for EAFs, developed to with-stand the high wear rates in EBT tapholes. The carbon-bonded grade

is based on high-quality MgO and graphite in combination with spe-

cial antioxidants. Whilst the addition of antioxidants is a well-known

practice to increase the oxidation behaviour of resin-bonded bricks,

it hadnt previously been applied to such brick types due to the good

intrinsic properties provided by carbon bonding. However, especially

for EBT taphole applications, the use of antioxidants provides advan-

tages such as increased bonding strength and oxidation resistance.

Further improvements to the brick properties were achieved by

impregnation to reduce pore volume and increase the carbon yield

after coking (during operation). This impregnation also improves the

carbon matrix of the entire brick. A new environmentally friendly

carbon binder was used for the carbon bonding and impregnation.

The results of recent trials at three customers have confirmed the

benefits of this brand. At Ferrostal Labedy Sp.z o.o.(Poland) the

standard lifetime of the cylindrical design EBT taphole was ~ 120

heats, which was increased to ~ 170 heats after implementing a con-

ical EBT taphole made from standard grades. However, a further life-

time increase to ~ 205 heats and a new EBT lifetime record was

achieved using SYNCARBON TB028. An EBT lifetime record was

also realized at Stahl Gerlafingen AG (Switzerland) where the num-

ber of heats with the conical EBT taphole was increased to ~ 200

with SYNCARBON TB028 from 130 with the standard conical EBT. In

addition, a new EAF vessel lifetime record of 628 heats was achieved

with SYNCARBON TB028 in the EAF slag zone at Elektrostahlwerke

Grditz GmbH (Germany), where previously the average lifetime of

the EAF vessel had been approximately 500 heats.

RHI Provides the Main Spon-sorship for MagMin 2012 in

SalzburgAustria >> The most important conference

for the magnesia industry, the Magnesia

Minerals Conference (MagMin), took place

from May 1416, 2012, in Salzburg (Austria).

This annual global conference brings

together around 200 producers, dealers,

buyers, and other partners linked with the

magnesia industry in a setting focused on

speeches, panel discussions, field trips, and

networking opportunities.

This year Salzburg was chosen as the

conference venue and with its long-estab-

lished presence in the area, RHI was delight-

ed to act as the principal sponsor.

On May 14, a field trip provided the

opportunity for delegates to visit RHIs plant

in Hochfilzen, where alpine magnesite is

mined and processed into high-quality sin-

ter. More than 60 participants toured the

mining and production facilities where

refractory mixes for the steel industry are

manufactured.

Board Member Manfred Hdl officially

opened MagMin on May 15 with his wel-

coming speech and outlined in his presenta-

tion the strategic focus of RHIs backward

integration strategy, including the business

rationale behind the two recent raw materi-

als acquisitions in Ireland and Norway.


7/64> 7

Subscription Service

and Contributions

We encourage you, our customers and inter-

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Furthermore, to receive the RHI Bulletin free of

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E-mail: [email protected]: +43 (0) 502 13-5300

Fax: +43 (0) 502 13-5237

Contents 8 Comparison of Basic Oxygen Furnace

Bottom Gas Purging Options

16 New Oxycarbide Refractory Products

Demonstrate Outstanding Properties

First Practical Results

20 Customer-Specific Analysis of

Steelmaking Slags to Provide Process

and Refractory Lining Lifetime

Improvements in Steel Treatment Ladles

and EAFs

26 Gas Purging Lances: Improving

Established Technology

34 Microscopic Examination of Premature

Wear Caused by Joint Opening andVertical Crack Formation in Magnesia-

Carbon Steel Treatment Ladle Linings

39 Thermomechanical Steel Ladle

Simulation Including a Mohr-Coulomb

Plasticity Failure Model

44 Consequences of REACH on the Use of

Ceramic Mineral Fibres

50 Resource EfficiencyGlobal Context,European Policy Initiatives, and RHIs

Responses

55 Full Integration of INTERSTOP Flow

Control Technology into RHI

58 Dynamic Refractory Wear Test Method

for Magnesia-Carbon Products

Editorial

Yours sincerely

Bernd Buchberger

Corporate Research and Development

RHI AG

Sustainability has always been integral in RHIs approach to

business, taking long-term responsibility for environmental,

economic, and social activities at a global level. However, in

recent months sustainability management has been restructured

at the company, with Management Board members strategically

engaged in sustainable value creation. At a time when raw mate-

rial availability and continually rising costs of raw materials,

energy, and climate control have such a significant impact, sus-

tainability at RHI is focusing on resource and energy efficiency as

well as health, safety, and talent management, as exemplified in

the first annual sustainability report published in April 2012.

In this edition of the Bulletin a number of papers describe RHIs

direct commitment to sustainability including contributions to

resource efficiency in the context of European policy initiatives.

RHIs proactive measures to address health and safety concerns

regarding certain ceramic mineral fibres used for high-tempera-

ture insulation are also detailed in an article describing REACH

legislation.

Many of the additional articles highlight product developments

and system improvements that can reduce specific refractory con-

sumption as well as provide energy savings. For example a new

oxycarbide refractory material is introduced that demonstrates

excellent material properties including chemical and thermal

shock resistance. The first trial results illustrate how the lifetime

of CAS-OB bells can be doubled using this refractory, which is

also suitable for various steel treatment, hot metal, and foundry

applications. In a paper detailing customer-specific analyses of

steelmaking slags, various tools are discussed that enable the

slag composition to be optimized, improving both lining lifetimes

and metallurgical processes. Further papers describe improve-

ments to gas purging lances, the development of a dynamic

refractory wear test to improve quantitative evaluation of refrac-

tory dissolution, and a comprehensive overview of gas bottom

purging in BOFs.

Innovation was recognized by the European Commission as an

essential precondition to improve resource efficiency and sustain-

able raw material supply. At RHI the Power of Innovation has

been pivotal in the corporate strategy for many years and I hope

the Bulletin provides a forum in which the advances realized

through this approach, including those directly relating to

resource efficiency, can reach a wide audience.

In closing, I would like to thank all the authors involved in this

edition, many who regularly take time to write articles for the

Bulletin. I am also very grateful to the editorial team members,

whose continued commitment make this publication possible.

> 7


8/648 1 > 2012, pp. 815

Thomas Kollmann, Christoph Jandl, Johannes Schenk, Herbert Mizelli, Wolfgang Hfer, Andreas Viertauer and Martin

Hiebler

Comparison of Basic Oxygen Furnace Bottom

Gas Purging OptionsIntroductionA higher level of product sophistication (e.g., clean steel,

interstitial-free, and ultra low carbon steel grades) and

unstable charging materialsdependent on the raw mate-

rial situation (e.g., availability and fluctuating prices)

require an economically optimized BOF process operation.

In the early 1980s most of the steel plants, especially in

Europe, made a decision to switch from the original LD

process technology (using only a top blowing oxygen lance)

to a process operating with a top blowing oxygen lance in

combination with a bottom inert gas purging system (Fig-

ure 1) [13].

Worldwide, different BOF philosophies (Figure 2) are in

operation using different bottom gas purging plug types,

arrangements, blowing practices, flow rate regulation sys-

tems, and patterns.

Figure 1. Variety and application frequency of oxygen steelmaking processes worldwide [4]. Abbreviations include Linz-Donawitz (LD),Linz-Donawitz bottom stirring (LD-BS), Linz-Donawitz oxygen bottom (Nippon Steel) (LD-OB), Klckner oxygen bottom Maxhtte(KOBM), and oxygen bottom Maxhtte (OBM).

Figure 2. Oxygen steelmaking processes [5]. Abbreviations include oxygen bottom Maxhtte (OBM), which is equivalent to Q-BOP.

150

120

90

60

30

0

100

80

60

40

20

0

No.ofsteelplants

Top only Soft Strong Combined Bottom only

Cumulativeshare[%]

LD LD-BS

Ar/N2 O2/CO2 O2/CnHm

LD-OB LD-OB KOBM

O2/CnHm O2/CnHm

OBM

Top-blown

(BOF) process

Top lance plus

permeable elements in bottom

Top lance plus

uncooled bottom tuyeres

Top lance plus

cooled bottom tuyeres

Bottom-blown

(OBM or Q-BOP) process

Hydrocarbon Hydrocarbon

Oxygen Oxygen

N2N2

ArAr

Oxygen lance Oxygen lanceOxygen lance Oxygen lance

n No. of steel plants using

specific process

n Cumulative share


9/64

RHI Bulletin >1 > 2012

> 9

Benefits of Bottom Gas Purging

The internal motivation to install bottom gas purging sys-

tems was nearly identical all over the world: The fundamen-

tal reasons were to improve metallurgical results and guar-

antee a highly effective and efficient oxygen steel produc-

tion at the lowest costs (Figure 3) [68].

The common benefits of vessel bottom purging are listed inTable I. By enhancing mass and heat transfer, the gas purg-

ing system influences the equilibrium conditions in the steel

bath during the refining process enabling the system to

approach equilibrium at the end of blowing. As a result

decarburization and dephosphorization are considerably

improved. Table II shows a detailed overview of the realized

metallurgical results with a bottom gas purging system

compared to the original LD process without bottom gas

purging [12,13].

Influence of Gas Type and Purging Rate

The indicator for an efficient gas purging performance is

the product of the dissolved carbon [C] and oxygen [O]. Due

to the purging plug availability, inert gas supply, and plug

regulation system (linked to the set flow rate patterns),

[C] x [O] levels < 25 x 10-4 are realized without any problems

(Figure 4) [14,15].

Benefits Benefits in detail

High quality and economical steelproduction

>> Minimization of the tap-to-tap time>> Reduction of the re-blow rate

numbers>> Lower (Fet), [P] levels, and [Mn]

oxidation loss

Realization of lower [C] x [O] levels/pCOvalues

>> Less deoxidation agents (e.g., Al)are required

>> Minimization of the RH degassingoperation (cost saving)

Improved steel bath homogenization/kinetic and temperature distribution

>> Shorter and quicker reaction path-ways between the slag and steelbath (better conditions for scrap/fluxadditive melting, and higher scrap/hot metal ratio)

>> Improved process control (higher

accuracy of the tapping temperatureand element levels)>> Improved steel yield and flux addi-

tive levels (reduced slag volume andslopping material)

Table I. General benefits of gas bottom purging [911]

Parameter With bottomgas purging

Without bottomgas purging

(Fet) in slag (wt.%) 1820 > 20

[C] at end of blowing (ppm) 300400 > 400

[O] at end of blowing (ppm) 500650 > 650[P] at end of blowing (ppm) 60120 > 120

Aluminium consumption fordeoxidation (kg/tonne)

1.52 > 2

Re-blow rate (%) 1018 > 18

Tap-to-tap time (min) 3035 > 35

Table II. Metallurgical benefits of bottom gas purging.Figure 3. Advantages of BOF bottom purging.

Figure 4. Comparison of carbon and oxygen content at the end of blowing with and without bottom gas purging [15].

Argon and nitrogen are used as inert bottom purging gases.

Inert in this case means that no (i.e., argon) or hardly any

(i.e., nitrogen) reaction with other dissolved elements in the

steel bath takes place even at the highest temperatures.

Optimization ofBOF process

Enhancedproductivity

Cost savings

Bottompurging

Carbon [%]

1600

1400

1200

1000

800

600

400

200

0

Oxygen[ppm]

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14

pCOn Without bottom purging

n With bottom purging

37.5

25.0

12.5

[C] x [O]

0.5 1.51.0


10/64

RHI Bulletin > 1> 2012

10


11/64


> 11

To realize good bath kinetics, the aim is to achieve small

bubbles with a long dwell period in the liquid steel bath

while jetting should be avoided. Steel plants that operate

on the tuyere philosophy have the opportunity to drill and

set new tuyeres during a campaign. The function of the tuy-

eres is nearly identically to a SHP and the tuyeres are

installed at defined drilled bottom positions. These posi-tions are preset by the gas connection points on the steel

shell bottom. Since the bottom lining moves during heat

up, as a result of thermal expansion, the bottom purging

system is activated (i.e., drilled) after 50100 lining heats.

However, installation takes several hours to complete per

tuyere, with associated production loss and vessel cooling.

Typically, the implemented tuyeres are set at very high flow

rates using three to four tuyeres per vessel in combination

with an excessive slag splashing practice. An example of a

circular tuyere arrangement (starting with four tuyeres) with

defined positions for the second drilling during the cam-

paign is depicted in Figure 7.

Commonly, 813 purging plugs (i.e., MHPs or SHPs) are

installed per vessel, set with an average total purging inten-

sity of 1 Nm3

/tonne per heat. The high gas flow ratesthrough the individual tuyeres result from the very low

number of tuyeres, typically three or four per vessel, and

guarantee purging through any slag layer present on the

vessel bottom, irrespective of its thickness. As a result jet-

ting can occur, leading to poor bath kinetics and poorer

metallurgical results in comparison to the outcome

achieved with SHPs or MHPs. The average [C] x [O] levels

obtained with various purging plug types are shown in

Figure 8.

Figure 7. Concept for tuyere installation.

Parameter MHP SHP Tuyere

Relative price Medium Low High

Bubble characteristics Well distributed small bubbles Ineffectively distributed large bubbles Ineffectively distributed large bubbles

Breakthrough safety High Low Low

Blocking Likely to reopen Likely to remain blocked Likely to reopen

Average flow rate range per plug (l/min) 2001400 2001200 20003500

Average total flow rate consumptionper heat (Nm3/t)

0.81.2 0.81.2 > 1.5

Average pipe diameter range (mm) 12 48 1.53.8

Number of pipes per plug 12, 24, 32 1 1

Open gas section per plug (mm2) 9.4100.5 12.650.3 100120

Average wear rate (mm/heat) 0.40 0.42 0.400.45

Number of plugs per vessel 812 813 34

Additional information >> Less plug blocking potential>> Less infiltration affinity>> Reopening during a campaign

(purging availability increased)>> Installation during relining procedure

>> Economically priced>> Increased plug blocking potential

during a campaign>> Installation during the relining

procedure

>> Defined drilling positions>> Complicated installation procedure>> Installation during campaign startup

period>> No purging availability at campaign

start (installation after 50100 liningheats)

>> Poor bath agitation caused by veryhigh flow rates (jetting)

Table III. Characteristics of MHPs, SHPs, and tuyeres.

Positions for second drill

Figure 8. Average [C] x [O] levels achieved with different purgingplug types.

Purging plug types

35.0

30.0

25.0

20.0

15.0

10.0

5.0

0.0

Average[C]x[O]levelx10-4

MHP SHP Tuyere

22.0

24.5

33.0


12/64


12 > Bottom maintenance philosophy.

>> Inert gas purity (primarily the {O2} level).

>> Tapping temperature.

>> Lining concept (quality and initial brick length).

Maintenance Strategy

To stabilize wear, slag splashing or coating are imple-

mented as bottom maintenance philosophies. However,

due to very thick or too sticky slag layers (related to the

(MgO) level in the slag) in combination with very intense

bottom maintenance or discontinuous production, the

Figure 9. (a) MHPs and (b) SHPs installed in an elliptical arrangement.

Figure 10. Inert purging gas distribution influenced by slag coating. (a) thick slag layer formed over the bottom and (b) thick slag layerextending across the bottom and up the vessel walls.

(a) (b)

(a)

Quality Quality

(b)

Inert gas distribution

Slag

Liquid steel

Slag coating caused byslag splashing

N2/Ar N2/ArN2/Ar N2/Ar


13/64


> 13

bottom purging elements may become blocked and in the

worst case they never reopen (bottom build up). If the slag

layer formed is more than 50100 mm, effective gas purg-

ing is not possible. As a result the inert gas diffuses

between the lining and the slag layer along the barrel to

the vessels upper cone or mouth. The purging gas

streaming, dependent on the slag layer build up, is pic-

tured in Figure 10. This type of phenomenon has been

seen and verified using natural gas, identifiable by a flame

(combustion reaction), which was detected coming out of

the areas described.

Remedies to counteract this phenomenon include:

>> Immediately stopping slag coating until the plugs are

visibly open again.

>> Bottom burning with an oxygen lance using hot metal

or heating agents such as coke or FeSi to free the bot-

tom of the solidified slag layer.

Furthermore, the level of bottom gas purging availability is

limited by the slag layer that has formed (i.e, height and

consistency) and the slag splashing frequency. If the bot-

tom is completely covered with slag, the [C] x [O] levels

increase considerably, becoming close to the range

detected when operating only with a top blowing lance.

Furthermore, the effect leads to unstable [C] x [O] levels

during the vessel campaign. The influence of the slag

splashing rate on the obtained average [C] x [O] levels is

listed in Table IV. It is evident that an increase in the slag

splashing rate corresponds with a simultaneous rise of the

average [C] x [O] levels.

Slag splashing rate (%) Average [C] x [O] level range (10-4)

1015 2026

20 2528

40 3033

Table IV. Influence of the slag splashing rate on the average[C] x [O] levels.

Figure 11. Relationship between the lining maintenance strategy and the [C] x [O] levels. (a) without bottom maintenance, (b) 1015%slag splashing during the entire campaign, and (c) > 60% slag splashing when the bottom gas purging system was activated followedby 100% slag splashing when bottom gas purging had shutdown.

Lining heats without bottom maintenance Lining heats with 1015% slag splashing rate

Shutdown of the bottom gas

purging system between 1500

and 1700 lining heats

40

35

30

25

20

15

10

5

0

40

35

30

25

20

15

10

5

0

[C]x[O]levelx

10-4

[C]x[O]levelx

10-4

1000 1500 2000 2500 3000 3500 4000 1000 1500 2000 2500 3000 3500 40000 0500 500

Lining heats with > 60% slag splashing rate

Shutdown of the bottom gas purging system

between 3000 and 4000 lining heats

40

35

30

25

20

15

10

5

0

[C]x[O]levelx10-4

1000 1500 2000 2500 3000 3500 40000 500

For a more detailed understanding of this phenomenon,

three different bottom maintenance strategies and their

influence on the [C] x [O] levels were investigated including

the lower and upper [C] x [O] levels and their average

course during a campaign (Figure 11).

(a) (b)

(c)


14/64


14 > Without bottom maintenance.

>> With slag splashing (rate between 1015%) during the

entire campaign.

>> With slag splashing (rate of > 60%) when the bottom gas

purging system was activated and a 100% slag splashing

rate to achieve the highest vessel lifetimes after the bot-

tom gas purging had shutdown.

Without bottom maintenance it was observed that the [C] x

[O] levels were in a range between 1527 x 10 -4 while the bot-

tom gas purging system was activated. After the bottom gas

purging system had been shutdown due to bottom premature

wear, the values drifted to levels of 3037 x 10-4. A slag splash-

ing rate between 1015% resulted in higher vessel lifetimes

and slightly increased average [C] x [O] levels and ranges,

compared to gas purging with no bottom maintenance, as a

result of plug blocking and wear; however, the upper [C] x [O]

levels were not as high as those detected when no bottom gas

purging system was operational. For example, at advanced

vessel lifetimes, the [C] x [O] values tended to the upper limit

of more than 25 x 10-4. Using a slag splashing practice of 60%

corresponded to a very wide range of [C] x [O] levels between

2037 x 10-4 from the initial stage of the campaign life to the

end of the bottom gas purging system activation. Further-

more, from a metallurgical point of view, the process was very

unstable leading to potentially very high re-blow numbers and

rising metallurgical treatment times and costs for secondary

metallurgy during the campaign period. Therefore, a consist-

ently reliable bottom gas purging efficiency (< 25 x 10-4) and

plug availability was not achievable with this maintenance

strategy. Finally, the bottom gas purging system was shut-

down after 3000 and 3500 lining heats due to premature bot-tom wear. Afterwards an intensive slag splashing programme

was carried out (rate of 100%) aiming for vessel lifetimes of

more than 10000 heats per campaign. During this stage the

[C] x [O] levels exceeded 30 x 10-4.

Potential Plug Lifetime

The critical plug thickness for closing is defined differently

for each steel plant and ranges from nearly zero to about

200 mm. The initial height of the implemented bottom gas

purging plugs is influenced by the BOF bottom design, ves-

sel capacity, and the installed purging plug type (production

length limitation of the brick press). Bottom bricks are man-

ufactured from MgO-C brands and contain 10 or 14 wt.%

(residual carbon) with an initial length between 800

1200 mm. Two different philosophies for the bottom brick

lining design are in operation:

>> Using the same quality material for the areas surround-

ing the plug and the rest of the bottom.

>> Using a different quality material for the areas surround-

ing the plug and the rest of the bottom (higher lev-

els in the surrounding plug areas).

The advantage of using lower levels in the bricks sur-

rounding the plugs is:

>> An increase in the wettability that leads to better condi-

tions for slag adherence (slag coating /splashing).

Whilst the advantages of using higher levels in the sur-

rounding bricks include:

>> Better thermal conductivity.

>> More resistant to thermal stress.

In addition, the wear rate of the plug and surrounding area

is about 0.1 mm/heat lower when the area surrounding the

plug contains higher levels than it is for bottom lining

designs where the same grade is used for the surrounding

area and plug (Figure 12).

OutlookIn the future, a purging plug should provide very high inert

gas purging availability during the entire vessel lifetime and

achieve average [C] x [O] levels between 2025 x 10 -4. The

goal of steel plants to increase vessel lifetimes whilst lower-

ing maintenance practices and costs has demanded purging

plugs with reduced wear rates. Figure 13 demonstrates the

relationship between the calculated number of achievable

heats per campaign and the initial plug brick length for

Figure 13. Influence of the initial plug length and plug wear rateon the number of achievable heats.

Initial plug length [mm]

8000

7000

6000

5000

4000

3000

2000

1000

0

Achievableheats

500 700 900 1100 1300 1500

Wear rate [mm/heat]

n 0.18n 0.25

n 0.40

Figure 12. Comparision of plug and surrounding brick wear ratewhen the same or different material is used for the plug and sur-rounding bricks.

0.6

0.5

0.4

0.3

0.2

0.1

0.0

Averagewearofplugandsurroundingarea

[mm/heat]

Different material for plugsand surrounding bricks

(higher )

Same material for plugsand surrounding bricks

0.44D 0.1

0.54


15/64


> 15

References

[1] Kreulitsch, H., Krieger, W., Antlinger, K. and Jungreithmeier, A. Der LD-Prozesse - ein kologisch optimiertes Verfahren. Neue Htte. 1992, 37,

313321.

[2] Kohtani, T., Kudou K., Murakami, S., Okimori., M., Nakajima, M. and Aoki, H. On the Metallurgical and Blowing Characteristics of the LD-OB Pro-

cess. Iron and Steelmaker. 1982, 9, No. 12, 2833.

[3] Wallner, F. and Fritz, E. Fifty Years of Oxygen-Converter Steelmaking. Metallurgical Plant and Technology International. 2002, 6, 3843.

[4] Hsken R., Fechner, R. and Cappel, J. Use of Hot Metal With High Phosphorus Content in Combined Blowing BOF Converters. Iron and Steel

Technology. 2011, 8, No. 11, 4658.

[5] Fruehan, R. (Ed) The Making, Shaping and Treating of Steel: Volume 1 - Steelmaking and Refining. 11 th edition;AIST Publications: Warrendale,

1998.

[6] Cappel, J. and Wnnenbeg, K. Cost-Saving Operation and Optimization on Metallurgical Reactions in BOF Practice. Iron and Steel Technology.

2008, 5, No. 11, 6673.

[7] Cappel, J. and Wnnenberg, K. Kostengnstige Arbeitsweise und optimierte metallurgische Reaktionen beim Sauerstoffaufblasverfahren. Stahl

und Eisen. 1988, 128, No. 9, 5566.[8] Bruckhaus, R. and Lachmund, H. Stirring Strategy to Meet the Highest Metallurgical Requirements in the BOF Process. Iron and Steel Techno-

logy. 2007, 4, No. 11, 4450.

[9] Krieger, W., Hubner, F., Patuzzi, A. and Apfolterer, R. LD-Prozess mit Bodensplung Manahmen, Mglichkeiten, Ergebnisse. Stahl und Eisen.

1985, 105, No. 12, 673678.

[10] Fiege, L., Schiel, V., Schrer, H., Weber, L. and Delhey, H-M. Einfluss des Bodensplens auf die metallurgischen Ergebnisse in den LD-Stahlwerk-

en der Krupp Stahl AG. Stahl und Eisen.1983, 103, No. 4, 159164.

[11] Krieger, W. and Poferl, G. Metallurgische und betriebliche Vorteile des LD-Prozesses mit Bodensplung. Weiterbildungsunterlagen VOEST, Linz,

1982.

[12] Gudenau, H. Praktikum zur Metallurgie, RWTH Aachen, Germany, 2002.

[13] Chigwedu, C., Kempken, J. and Pluschkell, W. A New Approach for Dynamic Simulation of the BOF Process. Stahl and Eisen. 2006, 126, No. 12,

2531.

[14] Schoeman, E., Wagner, A., Ebner, A. and Berger, M. Implementation of Basic Oxygen Furnace Bottom Purging at Mittal Steel Newcastle. RHI

Bulletin. 2006, No. 2, 711.[15] Kollmann, T. Influence of Bottom Purging on the Metallurgical Results, Masters Thesis, University of Leoben, Austria, 2010.

[16] Hiebler, H. and Krieger, W. Metallurgie des LD-Prozesses. BHM. 1992, 137, 256262.

[17] Selines, R. Selection of Stirring and Shrouding Gases for Steelmaking Applications, Union Carbide Cooperation, New York, 1988.

http://www.praxair.com/praxair.nsf/0/FC4072B3D78AB3B5852573A8006EDB4A/$file/StirringandShroudingGases.pdf

[18] Genma, N., Soejima, T., Kobayashi, J., Matsumoto, H., Matsui, H. and Fujimoto, H. Application of CO as Bottom Stirring Gas in Combined Blown

Converter. Presented at 110th ISIJ Meeting, Niigata University, Japan, October 1985, Lecture No. S989.

[19] Messina, C. Slag Splashing in the BOF- Worldwide Status, Practise and Results. Iron and Steel Engineer. 1996, 73, 1719.

[20] Mills, K., Su, Y., Fox, A., Li, Z., Thackray, H. and Tsai, H. A Review of Slag Splashing, ISIJ International, 2005, 45, No. 5, 619633.

Authors

Thomas Kollmann, RHI AG, Steel Division, Mlheim-Krlich, Germany.

Christoph Jandl, RHI AG, Steel Division, Vienna, Austria.

Johannes Schenk, Chair of Metallurgy, University of Leoben, Austria.

Herbert Mizelli, voestalpine Stahl GmbH, Linz, Austria.

Wolfgang Hfer, voestalpine Stahl GmbH, Linz, Austria.

Andreas Viertauer, Siemens VAI Metals Technologies GmbH, Linz, Austria.

Martin Hiebler, Siemens VAI Metals Technologies GmbH, Linz, Austria.

Corresponding author: Thomas Kollmann, [email protected]

three different wear rates. If the aim is 5000 heats per cam-

paign (critical residual brick thickness of 100 mm for plug

closing), the plug wear has to be 0.18 mm per heat with an

initial length of 1000 mm. Currently, the average wear rates

are in the range of 0.250.45 mm/heat. Therefore, RHI is

focused on developing a new generation of purging plugs

in the next few years that meet the requirements of steel

plant customers.


16/6416 1 > 2012, pp. 1619

Jrgen Schtz, Alexander Maranitsch and Milos Blajs

New Oxycarbide Refractory Products

Demonstrate Outstanding PropertiesFirst

Practical ResultsIntroduction

The initial idea behind the development of a new refractory

material was to replace the traditional calcium aluminate

cement used as a binder in alumina-based refractory casta-

bles (e.g., low cement (LC) and ultra low cement (ULC)

mixes). Therefore, a new binding system was developed

that avoids the disadvantages of the calcium aluminate

cement. Refractory cement is not only an expensive raw

material for bonding refractory products, it also has multi-

ple disadvantages during application including:

>> Decrease in refractoriness (CaO forms low melting phas-

es with other oxidic raw materials used for refractories).

>> Time consuming curing, drying, and heating up proce-

dures.

>> Energy intensive drying and dehydration of the Ca-

hydrate phases.

Taking these facts into account, RHI developed a new type

of alumina-based refractory material for hot metal and steel

applications, comprising different carbon carriers, antioxi-

dants, a special liquid binder, and in certain cases silicon

carbide.

Philosophy of the New Oxycarbide ProductRange

All oxycarbide products are completely cement-free con-

cretes that use a separate, special type of binder. Due to

the absence of Ca-hydrate phases there is no chemically

bonded water in the fluidized mix and cured product. There-

fore, a safe and rapid heating up is possible, including for

thick lined sections. The absence of CaO also guarantees a

much higher refractoriness. Furthermore, the special binder

creates a completely different pore structure. The matrix

structure is microporous with an average pore size approxi-

mately one-tenth that of traditional cement-bonded systems

(Figure 1). This results in completely different material prop-

erties and facilitates water evaporation.

Very complex reactions between the different carbon carriers,

antioxidants, and binder generate a product with superior

characteristics at high temperatures. These include:

>> Excellent thermal shock resistance.

>> High chemical resistance against acidic as well as basic

slag attack.

>> Hot erosion and corrosion resistance.

Oxycarbide Product Properties

Refractoriness Under Load

When compared to LC-bonded castables based on the same

raw materials, the oxycarbide products demonstrate a 200

300 C higher refractoriness under load (Figure 2). Outstand-

ing hot modulus of rupture (HMOR) values (> 25 N/mm2 at

1500 C) have also been measured.

The presences of carbon additives in the matrix in combina-

tion with the microporous structure leads to a product with

more ductile characteristics, which is distinct from the very

brittle nature of traditional sintered ceramic materials. The

carbon present also eliminates the formation of glassy phases,

whereas the micropores inhibit cracks from spreading.

Thermal Shock Resistance

As shown in Figure 3, absolutely no cracks were visible after

rapidly heating up (Figure 4) a wellblock with the new

Figure 2. Comparison of the refractoriness under load of lowcement castables (LCC) with oxycarbide mixes based on thesame raw materials and prefired at 1500 C.

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

Expansion[%]

Temperature [C]1200 1500 18000 300 600 900

n Bauxite LCC (T0.5 1464 C)

n Oxycarbide bauxite (T0.5 > 1704 C)

n Corundum LCC (T0.5 1681 C)

n Oxycarbide corundum (T0.5 > 1750 C)

Load: 0.1 N/mm2

Figure 1. Oxycarbide matrix prefired at 1500 C.

20 m


17/64


> 17

oxycarbide bonding. In contrast, all standard cement-

bonded blocks showed crack formation under the same test

conditions, namely the blocks were heated up to 1700 C in

5 hours from one side under oxidizing conditions. The

excellent thermal shock resistance makes the oxycarbide

products applicable for a diverse range of processes.

Chemical Resistance

Another remarkable characteristic of the newly developed

oxycarbide material is that it shows only a very thin decar-

burized zone of a few millimetres below the surface. Due to

the carbon content in the refractory products, the wettability

by steel, hot metal, and slag is strongly reduced. This prop-

erty in combination with the microporous structure results

in a much higher corrosion and infiltration resistance,

including a reduced infiltration depth, compared to standard

LC and ULC castables. Susceptibility to sulphur attack

depends mainly on the cement-derived CaO content in tra-

ditional LC and ULC mixes; however, because there is no

cement in the oxycarbide products the sulphur resistance is

excellent.

Heating Up

In contrast to cement-bonded castables, there are two

essential advantages when heating up and drying the oxy-

carbide products:

>> A much faster heating up rate is possible.

>> A lower overall temperature is necessary to dry out the

refractory castable.

These two benefits are illustrated in the drying behaviour

curves shown in Figure 5, comparing cement and oxycar-

bide-bonded castables.

In the case of LC and ULC mixes, the different Ca-hydratephases created while curing the cement significantly affect

the heating up process. A slow heating up rate, with hold-

ing times at several temperatures, is necessary to dehy-

drate these phases. The total removal of the chemically

bonded water happens at a temperature up to 600 C. It

has to be taken into consideration that this temperature

has to be reached throughout the entire refractory con-

crete installation to avoid any risk of damage during the

heating up process. Depending on the application area

and furnace geometry, this is difficult to realize and some-

times very long heating up schedules are necessary. In

contrast, a temperature of ~ 150 C is high enough to dry

the new oxycarbide products. This remarkable advantage

results in a significant reduction of the heating up energy

and time as well as an associated reduction in CO2 emis-

sions.

Following the development and determination of the excel-

lent physical properties, the first practical tests were under-

taken with the oxycarbide products. The very aggressive

operation conditions of the CAS-OB process were chosen

for the initial service evaluation to provide significant prac-

tical test results.

The CAS-OB ProcessThe CAS-OB process (composition adjustment by sealed

argon bubbling-oxygen blowing) was developed by Nippon

Steel Corporation (Figures 6 and 7). During the process it is

possible to add all the necessary alloying elements into the

melt through a slag-free surface in the absence of atmos-

pheric air. This is achieved by immersing a bell into the

steel bath above an argon purging element. The bell also

enables oxygen to be lanced simultaneously with the addi-

tion of aluminium. In the resulting exothermic reaction,

Al2O3 is formed and considerable amounts of heat are gen-

erated; it is estimated that temperatures of around 2000 CFigure 3. Cross section of an oxycarbide wellblock heated up to1700 C in 5 hours.

Figure 5. Comparison of the dehydration curves for cement-bonded versus oxycarbide-bonded materials.

100

90

80

70

60

50

40

30

20

10

0

Emittedwater[%]

Time [hours]

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.00

Figure 4. Heating up curve used to compare the thermal shockresistance of oxycarbide-bonded and standard cement-bondedwellblocks. The wellblocks were heated to 1700 C from one sidein 5 hours under oxidizing conditions.

1800

1500

1200

900

600

300

0

Temperature[C]

Time [hours]

0 1 2 3 4 5 6 7 8 9 10

n Oxycarbide

n Cement (8 wt.%)


18/64


18 > Homogenization and adjustment of the molten steel

composition and temperature.

>> No oxidation and loss of added alloying elements pro-

viding an exact and reproducible chemical composition

of the steel melt.

>> Effective method for attaining clean steel.

Production of CAS-OB Bells Using the NewOxycarbide Material

Typically, the CAS-OB bells consist of two parts: The so-

called wine glass or upper part is protected by refractory

only on the inside whilst the polo or lower part is steel

reinforced refractory material. Since only the lower part is

dipped into the steel bath during the CAS-OB process, this

part is the most stressed by extremely high temperatures,

thermal shock, as well as chemical erosion and corrosion.

Twelve hours after casting the lower bell section withapproximately 2.5 tonnes of the oxycarbide brand COMPAC

ROX A93MAS-15, it can be heated up and dried out. Since

the material doesnt contain any cement, it is not necessary

to have the prolonged curing time required for all cement-

bonded products. Furthermore, because there are no Ca-

hydrate phases in oxycarbide products the drying and

heating up time can also be reduced dramatically. In addition

to the described advanced physical properties, other very

important advantages of the newly designed products are

time, cost, and energy savings, as well as a reduction in CO2

emissions.

After drying, both parts of the bell are assembled together

and finished prior to application (Figure 8).

Trial ResultsCOMPAC ROX A93MAS-15 Instal-

lation in CAS-OB Bells at SSAB Tunnplt

The Oxycarbide Bells in Operation

In 1992, SSAB Tunnplt AB (Lule, Sweden) took the decision

to build a new ladle treatment station. The CAS-OB process

was chosen and the startup took place in August 1993. At

SSAB, the treatment time is up to 25 minutes per heat for

a ladle capacity of 130 tonnes.

One major cost factor of the CAS-OB process is the refractory

material for the bell. This material is stressed by huge ther-mal cycles between each heat, which can limit the lifetime of

the bell (Figure 9). Periods of lower production and many

stoppages and standstills can also have a negative influence

on bell performance because the bells cool down completely

and are heated up very rapidly when they are dipped into the

hot steel again. This results in enormous thermal shock.

Figure 7. CAS-OB process in operation. Figure 9. Magnesia-based competitor material after 17 heats inoperation.

Figure 8. CAS-OB bell in production.Figure 6. Image of the CAS-OB process.

Upper part

Lower part

Ladle

Bell

Argon gas purgingelement

Slag

Melt


19/64


> 19

Practical Results

Compared with standard competitor bells, the lifetime could

be doubled using COMPAC ROX A93MAS-15 (Figures 10

and 11). In general at SSAB Tunnplt there is no mainte-

nance, intermediate repair, or gunning of the CAS-OB bells.

The bells can be operated at different heights, which means

that after the first segment is worn (~ 400 mm of the lower

part), the bell is dipped deeper into the steel bath. Up to

three segments can be used in this manner. In comparison

to other steel producers who also use the CAS-OB technol-

ogy, the SSAB bells are relatively small and the treatment

time and ratio of Ca/Si treatment is long and intensive. In

addition, the chemical heating up is greater than at other

CAS-OB plants. Therefore, a direct comparison of the life-

time and performance of bells between different CAS-OB

plants is difficult. However, whilst the magnesia-based com-

petitor bells were destroyed by vertical cracks mainly

caused by thermal shock, the oxycarbide bells showed

absolutely no cracks until the end of operation and were

only slowly worn by hot corrosion and chemical dissolution

(Figure 12).

An additional significant advantage of the bells installed

with the oxycarbide material was a clean inner and outer

surface of the bell since the carbon and carbide content of

the oxycarbide product has an antiwetting effect (see Figure

12). As a result slag and oxides formed during the steel

treatment do not stick to the refractory surface in contrast

to the bells based on other raw materials. For this reason

no additional slag treatment with CaO-CaF2 or CaO-B2O3 is

necessary.

Conclusion

The superior properties including extremely good thermal

shock resistance, a microporous structure, the antiwetting

effect resulting from carbon and carbides, reduced brittle-

ness, and high hot strength caused by in situ carbide forma-

tion make the oxycarbide products highly suitable for differ-

ent steel treatment, hot metal, and foundry applications.

Currently, hot metal application field trials including blast

furnace runner systems (i.e., main runners, hot metal and

slag runners, tilters, skimmers, and spouts), torpedo cars

(i.e., mouth and impact areas), and hot metal ladles (i.e.,

bottom or full monolithic linings, spout areas, and well-

blocks) are planned or running.

In several steel plants the oxycarbide castables have been

installed for diverse applications including RH degasser

snorkels, CAS-OB bells, and steel ladles (i.e., full monolithic

lining or segments such as bottoms, sidewalls with and

without monolithic slag zones). Whilst there are no final

trial results at this stage, comparisons with traditional

installed linings are providing a very optimistic outlook for

these new products. In addition to the aforementioned tri-

als, prefabricated parts (e.g., wellblocks, and pocket blocks)

are in operation and showing very good results. On occa-

sions, the large and thick dimensions of refractory products

can cause problems during the heating up and for these

applications the oxycarbide bonding is proving to be an

ideal solution. Additional sectors where oxycarbide prod-

ucts can be used include the foundry industry for long cam-

paign cupolas as well as transport ladles.

Authors

Jrgen Schtz, RHI AG, Steel Division, Mlheim-Krlich, Germany.

Alexander Maranitsch, RHI AG, Steel Division, Vienna, Austria.

Milos Blajs, RHI AG, Technology Center, Leoben, Austria.

Corresponding author: Jrgen Schtz, [email protected]

Figure 10. COMPAC ROX A93MAS-15 bell after 52 heats.

Figure 11. COMPAC ROX A93MAS-15 bell after 64 heats.

Figure 12. COMPAC ROX A93MAS-15 bell after 35 heats. Abso-lutely no cracks and slag are visible.


20/6420 1 > 2012, pp. 2025


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> 21

If the initial composition of the process slag is MgO under-

saturated, corrosion of the MgO-C lining by dissolution of

the MgO component occurs. Doloma linings require MgO

and CaO saturation of the slag. The amount of MgO that

will be corroded can be calculated from the slag mass bal-

ance and can be compensated by the appropriate addition

of MgO-containing material in order to decrease magnesia

lining wear. The maximum amount of MgO corroded from

the lining is estimated from equation 1 as the difference

between the MgO slag saturation level and the actual MgO

input into the slag (equation 2):

xrefr MgO mrefr loss max = [xlime MgO mlime +xdolo MgO mdolo + xCa aluminate MgO mCa aluminate +

xtaphole filling sand MgO mtaphole filling sand +(2)

xcarryover MgO mcarryover] xsaturated slag MgO mslag

For example, a 1 wt.% MgO increase in the slag during ladle

treatment indicates a MgO loss from the refractory lining of

approximately 0.1 kg/tonnesteel, which is equivalent to a 1020

kg MgO loss per heat depending on the ladle volume. This

MgO loss corresponds with observed MgO lining wear rates

of 14 mm per heat and lining lifetimes of 50150 heats.

The slag corrosion potential or presaturation level MgO*,can also be expressed as the difference between the MgOcontent of the added slag formers and the slag saturation

level in wt.% (equations 3 and 4):

MgO* = (xlime MgO mlime + xdolo MgO mdolo +

xCa aluminate MgO mCa aluminate + xtaphole filling sand MgO

mtaphole filling sand + xcarryover MgO mcarryover)/mslag (3)

xsaturated slag MgO

Or if slag analysis data is available:

MgO* = xinitial analysed slag MgO xsaturated slag MgO (4)

The presaturation level is often more informative than the

analysed level of a slag sample taken during ladle treatment

as a certain amount of MgO from the lining may have dis-

solved at very low initial presaturation levels before the

slag was sampled.

MgO Saturation of Slags

The MgO saturation concentration of a particular process

slag,xsaturated slag MgO, can be estimated from empirical mod-

els, for example the Schrmann and Kolm model [1], the

Park and Lee model [2] (Figure 2), the Kwong model [3], and

Pretorius ISD diagrams [4]. Both the Park and Lee, and Pre-

torius and Carlisle models are based on the basicity ratio,

Bi, of the slag (Table II). B i represents the ratio between the

Table I. Composition ranges and input masses of slag formers added to the steel treatment ladle. * indicates the range of mass inputto produce CaO-SiO2-rich slags or CaO-Al2O3-rich slags for steel treatment.

Slag formers CaO

(wt.%)

MgO

(wt.%)

SiO2(wt.%)

Fe2O3(wt.%)

Al2O3(wt.%)

Mass*

(kg/tonnesteel)

Lime 8995 14 12 010

Raw dolomite > 2830 > 1820 SiO2 + Fe2O3 + Al2O3 < 45 05

Dolomitic lime 5660 3740 SiO2 + Fe2O3 + Al2O3 < 24 05

Bauxite 2.57 27 7482

Synthetic calcium aluminate slag A 040 2735 < 8.0 < 5.0 010

Synthetic calcium aluminate slag B 040 2026 15 < 1.0 010

Synthetic slag modifier C 10 0.5 3337 0.5 5.0 05

Fluorspar < 1.5 < 18.3 < 0.02 CaF2 > 80 05

Synthetic lime-CaF2 mix 66 1 4 0.5 CaF2 > 34 05

Olivine taphole filling sand 0.53 4050 3945 69 0.53 0.51.5

EAF slag carryover 3045 515 1535 1540 210 05

Al, FeSi oxidation products FeSi: 100 Al: 100 15

Table II. Common basicity ratios from metallurgical guidelinesused in slag operations.

Basicity parameter Application

B2 CaO/SiO2B3 CaO/(SiO2+Al2O3) Oxidized slags, EAF, ladle

B4 (CaO+MgO)/(SiO2+Al2O3) Oxidized slags, AOD

B5

(CaO+MgO)/(SiO2+Al2O3+FeO+MnO) Reduced slags in ladle (FeO + MnOconsidered)

(CaO+MgO)/(SiO2+Al2O3+CaF2) Reduced slags in ladles (FeO + MnOneglected), desulphurization slags

Figure 2. MgO saturation limits of CaO-SiO2-Al2O3slags accord-ing to the models of Schrmann and Kolm [1], Park and Lee [2],and Pretorius and Carlisle [4]. Abbreviations include magnesiumaluminate (MA).

Basicity B3 = CaO/(SiO2+Al2O3)

16

14

12

10

8

6

4

2

0

MgOsaturation[%]

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

n Pretorius and Carlisle (1999)

n Schrmann and Kolm (1986)

n Park and Lee (1996)

T = 1600 C

MA spinel

Mg wustite

Mg wustite

+ Ca2SiO4


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22


23/64


> 23

the slag, which is achieved at high slag basicity levels. Sul-

phide capacity slightly increases with the MgO content in

CaO-SiO2 slags if SiO2 is not too low [7]; however, this effect

vanishes at low SiO2. Therefore, an appropriate MgO con-

tent in the ladle slag near to saturation is also beneficial for

the desulphurization process with CaO-SiO2-rich slags, or at

least no negative impact on desulphurization has been

reported.

Visualization of Slag Compositions

Process Slags in Electric Arc Furnaces

Steelmakers often request the optimum slag composition

suitable for steel melting and refinement during secondary

metallurgy that also maximizes the lining lifetime. The visu-

alization of analysed slag compositions provides valuable

information in order to characterize and evaluate particular

process conditions.

MgO saturation of the process slag in an EAF is not only ben-

eficial for the MgO-based lining but is also a necessary pre-

requisite for efficient slag foaming, as the presence of fine

solid MgO particles increases the slag viscosity to the appro-

priate level for foaming. The increased volume of the foam-

ing slag helps to decrease energy losses by arc radiation to

the sidewalls, increase energy transfer from the arc to the

melt, and improve energy efficiency of the EAF process.

Figures for unusually high refractory lining wear may be due

to poor slag composition control, although the mean MgO

saturation level of the slag appears to be at the appropriate

value. An example of slag compositions from a 60-tonne EAF

where the SiO2 and MgO contents scattered independently,

indicating a high influence due to sand, concrete, and other

contaminating additives in the scrap, as well as MgO input

from gunning and repair mixes and lining bricks, is shown in

Figure 5. A variance of the SiO2 mass input into the slag is

not uncommon; however, due to unusually low amounts of

lime and dololime in the EAF the SiO2 composition scatter

was significant because under these circumstances the corro-

sion potential of high SiO2 slags is intensified. A lack of slag

volume may also increase lining wear due to arc radiation.

Therefore, increasing the mass of both lime and dololime to

act as SiO2 buffering slag formers was recommended in this

case. Increasing the slag mass also improved slag foaming

and electric arc shielding.

Slag analysis from an 80-tonne EAF indicated MgO under-

saturation in all the EAF slag samples (Figure 6). In this case

replacement of lime by dololime was suggested in order to

achieve 9 wt.% MgO saturation. In contrast, the analysis of

slags from a 60-tonne EAF, where mixtures of lime and

MgO-containing slag conditioners were used, revealed reg-

ularly saturated slags with good foaming properties and a

minimum lining corrosion potential.

The amount of proposed dololime addition in Figure 6 was

calculated using MgO mass balance (see equation 1) and

the analogous CaO mass balance. The difference between

the analysed slag composition and the target MgO-satu-

rated composition was used to determine the necessary

correction to the slag former input by mass balance.

A further example shows slag samples from a 100-tonne

EAF where there was high control of the slag composition

so the MgO level was very close to saturation, although the

Figure 5. Visualization of EAF slag analysis with respect to MgOsaturation levels indicating an initial poor control of the slag com-position due to a low input of lime/dololime into the 60-tonne EAFand improved slag undersaturation over the course of the analy-sis. Saturation lines calculated with the thermochemical FactSage

software [6]. Analysis and target values in wt.%.

Figure 6. Visualization of EAF slag analysis with respect to MgOsaturation indicating consistent MgO-undersaturated slags froman 80-tonne EAF when 100% lime was used as a slag former ver-sus slags from a 60-tonne EAF where efficient MgO slag condi-tioning had been implemented. Analysis and target values inwt.%.

SiO2

MgO FeO

SiO2

MgO FeO

Under-saturated

Under-saturated

Saturated Saturated

SiO2

FeO

MgO

CaO

SiO2

FeO

MgO

CaO

Analysis Target

MgO 3.0 9.0

Al2O3 8.7 8.0

SiO2 12.6 12.0

CaO 34.8 33.0

Cr2O3 1.9 1.5

MnO 5.0 5.0

FeO 32.7 30

Analysis Target

MgO 14.8 14.0

Al2O3 5.2 5.0

SiO2 18.5 17.0

CaO 36.3 35.0

Cr2O3 1.1 1.5

MnO 5.6 6.6

FeO 15.8 19.0

Lime (kg) 430

Dololime (kg) 560

Lime (kg) 2900

Dololime (kg) 0

Correction to lime (kg) -906

Additional dololime (kg) 1236

Correction to lime (kg) 600


EAF Q1/2010

EAF Q2/2010

EAF Q3/2010

n Saturation line, 35 wt.% CaO, 1600 C


l Recent slag analysis

l Target slag composition

80-tonne EAF, 2007

60-tonne EAF, 2011







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24 2. However, the large vari-

ance in FeO, due to poor oxidation control by oxygen and

carbon injection, generated a high proportion of very oxi-

dized slags with a definite lining corrosion potential. In

addition, the slag viscosity dropped at high FeO levels and

the slag foaming index decreased. However, adjustment of

the slag former input improved the MgO saturation figures

in the fourth quarter of 2009 due to an increase in the CaO

level (see Figure 7).

Process Slags in Steel Treatment Ladles

The ladle slag composition is adjusted to the type of steel

killing strategy after tapping the BOF or EAF: Al-killed steels

require a calcium aluminate slag with low SiO2 activity in

order to avoid reduction of SiO2 by Al added to the steel

melt. Mixed Al-Si-killed and Si-killed steels are usually cov-

ered by a calcium-silicate(-alumina) slag (Figure 8). The total

FeO and MnO concentration should be low, in the ideal case< 2 wt.%, to avoid any mass exchange between the slag and

melt (e.g., oxidation of Si and Al by FeO and MnO).

For both slag types, high magnesia lining lifetimes require

high MgO slag activity. In the case of high calcium silicate

saturated slags, the Ca2SiO4 and/or Ca3SiO5 levels are close

to the MgO periclase saturation values of 712 % MgO. In

the case of high calcium aluminate slags there is double

saturation with lime and periclase at 712 wt.% MgO (Fig-

ure 8). The common metallurgical rules for optimum slag

composition reflect these saturation figures: B3 near 1.5 (red

line in Figure 8), or B5 > 1.6 for a CaO-SiO2-Al2O3 slag, and

B5 > 1.8 for a CaO-Al2O3-rich slag.

The assessment of slag analysis data for Si-killed steels

from a 40-tonne ladle (Figure 9) showed remarkable

Figure 8. Visualization of slag analysis from an 80-tonne ladle (Si-killed steels) and a 150-tonne ladle (Al-killed steels) showing theimportant saturation fields at 1600 C and basicity values B3=

CaO/(Al2O3+SiO2) = 1.5. Saturation lines calculated with the ther-mochemical FactSage software [6]. Stability fields at 5 wt.% MgOfrom [8]. Abbreviations include Ca2SiO4 (C2S) and Ca3SiO5 (C3S).

Figure 7. Visualization of slag analysis from a 100-tonne EAFwith respect to MgO saturation indicating a significant propor-tion of high FeO-containing slags due to suboptimum control ofthe oxygen versus carbon injection. Saturation lines calculatedwith the thermochemical FactSage software [6]. Analysis andtarget values in wt.%.

SiO2

CaO FeO

SiO2

CaO Al2O3

Under-saturated

Saturated

CaO/SiO2 = 2

CaO/(SiO2+Al2O3) = 1.5

Analysis Target

MgO 4.6 8.0

Al2O3 2.5 3.0

SiO2 12.3 12.0

CaO 31.4 35

Cr2O3 0 0

MnO 4.6 4.0

FeO 34.6 30.0

Lime (kg) 4000

Dololime (kg) 0

Correction to lime (kg) -455


EAF Q1/2009

EAF Q2/2009

n Saturation line, 5 wt.% MgO, 1550 C





80-tonne ladle

150-tonne ladle

SiO2

FeO

MgO

CaO

SiO2

Al2O3

MgO

CaO

EAF Q3/2009

EAF Q4/2009

MgO+

free

CaO

Figure 9. Visualization of slag analysis from a 40-tonne ladle (Si-

killed steels) indicating MgO saturated and undersaturated ladle

slags during the steel treatment process. Stability fields at 10 wt.%

MgO from [8]. Abbreviations include Ca2SiO4 (C2S) and Ca3SiO5

(C3S). Analysis and target values in wt.%.

SiO2

CaO Al2O3

SiO2

Al2O3

MgO

CaO

Analysis Target

MgO 9 11

Al2O3 30 26

SiO2 15 14

CaO 43 47

B3 0.956 1.542

CaO (%) 4

MgO (%) 2

Al2O3 (%) -4

Slag samples

n MgO saturation, 10 wt.% MgO, 1600 C

n Ca2SiO4, Ca3SiO5 saturation,

10 wt.% MgO, 1600 C

n CaO saturation, 10 wt.% MgO, 1600 C



MgO+

freeCaO

FeO + MnO < 1.5 wt.%

Sum 97 wt.%102 wt.%

Correction

n MgO saturation, 5 wt.% MgO, 1600 C

n Ca2SiO4, Ca3SiO5 saturation, 5 wt.% MgO, 1600 C

n CaO saturation, 5 wt.% MgO, 1600 C

wt.%

SiO

2 w

t.%Al2O

3

wt.%

SiO

2

wt.%

Al2O

3


25/64


> 25

agreement between some heats and the calculated satura-

tion lines. This indicated that undersaturated ladle slags

with a variable initial Al2O3 content dissolved MgO from the

lining until MgO saturation was reached. Other slags

remained MgO undersaturated at the Ca2SiO4 saturation

line. Although most slag samples were MgO saturated, an

increase of the initial MgO concentration in the slag formers

could be effective in decreasing ladle lining wear.

Materials for MgO Slag Conditioning

Metallurgically used lime and synthetic slag formers based

on calcium aluminates only contain a few wt.% MgO (see

Table I). As a result, the initial MgO content of the slag in an

EAF or steel treatment ladle might be too low to prevent

corrosion of the lining material. In this case the addition of

MgO is recommended and there are various MgO-contain-

ing mineral sources available on the market. RHI provides

high-quality dolomite and magnesia sinter in order to mod-

ify the slag composition, improve slag operation, and

increase the lining lifetime in EAFs as well as transport and

refinement ladles (Table III).

References

[1] Schrmann, E. and Kolm, I. Mathematische Beschreibung der MgO-Sttigung in komplexen Stahlwerksschlacken beim Gleichgewicht mit

flssigem Eisen. Steel Research. 1986, 57, 712.

[2] Park, J. and Lee, K. Reaction Equilibria Between Liquid Iron and CaO-Al2O3-MgOsat-SiO2-FetO-MnO-P2O5 Slag. Proceedings 79th Steelmaking

Conference, Iron and Steel Society, Pittsburgh, USA, March 2427, 1996, pp. 165171.

[3] Kwong, K., Bennett, J., Krabbe, R. and Thomas, H. Thermodynamic Calculations Predicting MgO Saturated EAF Slag for Use in EAF SteelProduction. The Minerals, Metals & Materials Society. Supplemental Proceedings. Materials Characterization, Computation and Modeling. 2009,

Vol. 2, 6370.

[4] Pretorius, E.B. and Carlisle, R.C. Foamy Slag Fundamentals and Their Practical Application to EAF Steelmaking. Iron and Steelmaker. 1999, 26, No.

10, 7988.

[5] Brggmann, C. and Ptschke, J. Contribution to the Slagging of MgO in Secondary Metallurgical Slags. Presented at 53rd International Colloquium

on Refractories, Aachen, Germany, Sept., 89, 2010, pp. 145149.

[6] Bale, C., Chartrand, P., Degterov, S., Eriksson, G., Hack, K., Ben Mahfoud, R., Melanon, J., Pelton, A. and Petersen, S. FactSage Thermochemical

Software and Databases. Calphad. 2002, 26, No. 2, 189228.

[7] Taniguchi, Y., Sano, N. and Seetharaman, S. Sulphide Capacities of CaOAl2O3SiO2MgOMnO Slags in the Temperature Range 16731773 K.

ISIJ International. 2009, 49, No. 2, 156163.

[8] Schlackenatlas, Slag Atlas; VDEh., Ed.; Verlag Stahleisen: Dsseldorf, 1981.

AuthorsMarcus Kirschen, RHI AG, Steel Division, Vienna, Austria.

Simo Pedro de Oliveira, RHI Refratrios Brasil, Belo Horizonte, Brazil.

Elshad Shikhmetov, RHI U.S., Ltd., USA.

Matthias Hck, RHI AG, Steel Division, Vienna, Austria.

Corresponding author: Marcus Kirschen, [email protected]

Summary

Assessment of slag mass balances and visualization of slag

analyses provide essential information to optimize slag

compositions and improve both the lining lifetime and mul-

tiple metallurgical processes. Using various tools, RHI is

able to provide this customer-specific analysis, enabling tai-

lored recommendations to be made regarding slag adjust-

ment using slag formers. In EAFs, where the slag composi-tion can vary widely due to contaminants in the input mate-

rial, visualizing slag analysis enables, for example, the lin-

ing lifetime as well as slag foaming to be improved. MgO

mass balance of process slags has also been effectively

used to increase the lining lifetime in steel treatment ladles,

whilst the visualization of slag compositions enables slags

to be precisely examined in relation to the type of killing

strategy adopted in the ladle.

Table III. Materials provided by RHI for MgO slag conditioning.Abbreviations include loss on ignition (LOI).

Material and origin Size(mm)

LOI(wt.%)

CaO(wt.%)

MgO(wt.%)

SiO2(wt.%)

Fe2O3(wt.%)

Al2O3(wt.%)

Raw dolomite,Marone (Italy)

16 47.7 30.9 21.2 0.13 0.1 0.1

SLAGDOL, sintereddoloma, Marone (Italy)

01 58.5 39.5 1.0 0.5 0.5

PENTADOL 5-15,sintered doloma,Marone (Italy)

413 58.5 39.5 1.0 0.5 0.5

Magnesia brickets

HL15, Hochfilzen(Austria)

2050 39.3 8.3 45.2 0.7 3.4 0.3

KAUSTER RKM-S,

Radenthein (Austria)

16 2.5 8.3 56.0 23.5 3.4 6.2


26/6426 1 > 2012, pp. 2633

Bernd Trummer, Bianca Heid, M

RHI Mr Services Bulletin 1 2012-Data

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