Tugas Syarief (1006704764)Corex Prosses

8/3/2019 Tugas Syarief (1006704764)Corex Prosses

1/9

COREX Process

COREX consists of two reactors, the reduction shaft and the melter-gasifier. The reduction shaft

is placed above the melter-gasifier and reduced iron bearing material descends by gravity. The volume

of the reduction shaft and the melter-gasifier is about 600 m3 and 2200 m3 respectively.

Reduction Shaft :

Iron ore, pellets and additives (limestone and dolomite) are continuously charged into thereduction shaft via lock hopper system located on the top of the shaft. Some amount of coke is also

added to the shaft to avoid clustering of the burden inside the shaft due to sticking of ore/pellets and to

maintain adequate bed permeability. The reduction gas is injected through the bustle located about 5

meters above the bottom of the shaft at 850C and over 3-bar pressure. The specific reduction gas flowis about 1200Nm3/ton of iron bearing burden charged to the shaft. The gas moves in the counter

current direction to the top of the shaft and exits from the shaft at around 250C. About 5-6% of coke is

also added to the shaft to avoid clustering of the burden inside the shaft due to sticking of ore/pelletsand to maintain adequate bed permeability. The iron bearing material gets reduced to over 95%

metallization in the shaft and is termed as DRI. Subsequently, six screws discharge the DRI from the

reduction shaft into the melter-gasifier. The metallization degree of the DRI and the calcination of theadditives are strongly dependent on the following parameters:

Amount and quality of the reduction gas flow

Temperature of the reduction gas

Reducibility of the iron bearing burden

Average particle size and the distribution of the solids charged


2/9

Metal Gasifier :

The melter-gasifier can largely be divided into three reaction zones

Gaseous free board zone (upper part or dome)

Char bed (middle part above oxygen tuyeres)

Hearth zone (lower part below oxygen tuyeres)

Due to continuous gas flow through the char bed, there also exists a fluidized bed in the

transition area between the char bed and the free board zone.

The hot DRI at around 600-800 C along with partially calcined limestone and dolomite are

continuously fed into the melter-gasifier through DRI down pipes. The DRI down pipes are uniformlydistributed along the circumference near the top of the melter-gasifier so as to ensure uniform

distribution of material over the char bed. Additionally non-coking coal, quartzite and required quantity

of coke are continuously charged by means of lock hopper system. The operating pressure, in themelter-gasifier is in excess of 3 bars. Oxygen plays a vital role in COREX process for generation of

heat and reduction gases. It is injected through the tuyeres, which gasifies the coal char generates CO.

The hot gases ascend upward through the char bed. The sensible heat of the gases is transferred to thechar bed, which is utilized for melting iron and slag and other metallurgical reactions. The hot metal

and slag are collected in the hearth. The efficiency of the furnace depends largely on the distribution of

this gas in the char bed and utilization of the sensible heat of the gas. The dome temperature maintained

between maintained between 1000C to 1100C, which assures cracking of all the volatile matter

releases from the coal. The gas generated inside the melter-gasifier contains fine dust particles, whichare separated in hot gas cyclones. The dust collected in the cyclones is recycled back to the melter-

gasifier through the dust burners, where the dust is combusted with additional oxygen injected throughthe burners. There are four such dust burners located around the circumference of the melter-gasifier

above the char bed. The gas from the melter-gasifier is cooled to the reduction gas temperature (850C)

through the addition of cooling gas. A major part of this gas is subsequently fed to the reduction shaft.The excess gas is used to control the plant pressure. This excess gas and the reduction shaft top gas are

mixed prior to the take over point and is termed as COREX export gas. The export gas has high net

calorific value of approximately 7,500 8000 kJ/m (STP). This gas is suitable for use for a wide range


3/9

of applications like power generation etc.

Typical usage of materials :

Coal use in the C 1000 plant is about 900 kg/thm. The oxygen requirment is 540 Nm3/thm.

The production of export gas is around 11.5 Gj/thm. A small amount of electricity is required, 60

kWh/tonne. On the basis of these data, the Spesific energy consumption (SEC) of the C - 1000 plantcan be calculated to be 15.5 17.5 Gj/thm. (All the calculation of the Spesific energy consumption

(SEC) of smelting reduction processes are summarized in Table)

Table 1 : Materials for the production of 1000 kg hot metal at a COREX plant

Process Energy

carrier

Input Low case

(Gj/thm)bHigh case

(Gj/thm)

COREX Coal

other fuel

Oxygen

Electricity demandExport gas

Export steamSEC

0.88 t

0.71 t

60 kWh-11.5 Gj

25.5

1.2

0.4-11.5

15.6

28.2

2.8

0.5-12.9

17.5

Process Chemistry :

Corex is a two reactor but three-stage process. The blast furnace concept has been used,virtually splitting it into two at the cohesive zone interface. Accordingly a Corex plant has shaft unit,

where iron ore pellets (with or without some closely sized lump ore) is reduced by gases emanating

from the second unit to make hot sponge iron (first stage). This is mechanically transferred to the

second unit or Melter-Gasifier where it is melted and carburised (second stage) by injection of bothcoal and oxygen. In the upper part of the Melter-Gasifier a fluidised bed of coal char is maintained

(third stage), where any CO2 or H2O is converted to CO and H2. Since there is practically no CO2 or

H2O in the gas leaving the Melter-Gasifier, we say that the degree of post combustion of Corex gas iszero, resulting in a gas rich in chemical energy.

Reaction in Reduction Shaft :

Following are the primary reactions taking place inside the reduction shaft:

Reduction of iron oxide by CO and H2 and transforming the iron oxides to metallic iron.

Fe2O3 Fe3O4 FeO Fe

Calcination of Limestone and Dolomite

CaCO3 CaO+CO2 (endothermic)

CaCO3.MgCO3CaO.MgO+2CO2 (endothermic)

Carbon deposition reaction and formation of Fe3C

2CO CO2+C (exothermic)

3Fe+2CO Fe3C+CO2 (exothermic)


4/9

Out of the above mentioned reactions, reduction of iron oxide by H2 and calcination reactionsare endothermic. On the other hand, reduction of iron oxide by CO gas and carbon deposition reactions

are exothermic in nature.

The reduction gas is almost fully desulphurized in the shaft due to the presence of the burnt lime anddolomite according to the following reactions:

CaO + H2S CaS + H2OMgO + H2S MgS + H2O

Low content of hydrogen sulphide of the top gas is important with respect to the further usage of the

COREX gas.

Reaction in Melter Gasifier :

Following are the reactions taking place in melter-gasifier:

Drying of Coal(100 oC)

Devolatilisation of coal (200 oC to 950 oC) and liberation of methane and higher hydrocarbons.

Decomposition of volatile matter

Due to higher temperature prevailing in the melter-gasifier free board zone, the hydrocarbons

are cracked intohydrogen and elementary carbon

CnHm = nC + (m/2)H2

It is desirable that all higher hydrocarbons are cracked in the free board zone so as to assuregeneration of a good quality reduction gas. Maintaining dome temperature between 1000 oC to 1100

oC ensures the same.

Other reactions in the free board zone are:

CO2 + C = 2CO (Boudouard Reaction)

H2O + C = CO + H2 (Water Gas Reaction)

CO + H2O = CO2 + H2 (Shift Reaction) Decomposition of the undecomposed limestone and dolomite.

Residual Reduction of the iron oxide.

Direct reduction of FeO int the DRI takes place by carbon in the char bed.

Combustion of coal char by oxygen.


5/9

Burning of the coal char takes place near the tuyeres. The maximum temperature inside the

melter-gasifier exists in front of the tuyeres. The following carbon gasification reactions takes place in

the tuyeres area.

2C + O2 = 2CO

2CO + O2 = 2CO2C + CO2 = 2CO

Melting and formation of hot metal and slag respectively.

A typical analysis of COREX hot metal and slag is give in table 2 & 3

The typical analysis of various gases produced in COREX process is dive in table 4

The efficiency of the COREX process depends on the following parameters:

Size and chemical analysis of the raw especially the coal Low C02 percentage in the reduction gas so as to ensure higher metallization of the DRI

Optimum distribution of oxygen between the tuyeres and dust burners

Permeability of the char bed

High system pressure

Higher melting rate operation


6/9

COREX process use in the world

Development of the COREX process dates back to the 1980s and was performed by Voest-

Alpine (Germany/Austria). The first commercial COREX unit was constructed between 1985

and 1987 at ISCORs Pretoria works, after first testing the process in Germany. The plant hadvarious problems (due to inexperience) after the start-up in December 1987. After

reconstruction and de-bugging, the plant has been successfully in operation since 1989 and was

given over to ISCOR(capacity 300,000-ktpa). Reconstruction of some parts and new operationconditions improved the performance greatly, leading to production of high quality iron, and

high productivity and availability. The plant demonstrated to be economically attractive, with

30% lower production costs than the blast furnace on site, despite the low capacity of theCOREX unit. The clean excess fuel gas is used on site in furnaces and coke ovens. The COREX

process proved to be very flexible(with respect to the fuel rate, and additives addition),insensitive to high alkali content of the ore (and burden), and easy to operate.

The preliminary success of the first COREX plant lead to the decision to build a larger COREX

(C-2000, 650,000 tonnes per year) in South Africa by Saldanha Steel, a subsidiary of ISCOR.

Saldanha Steel is now a part of Mittal Steel South Africa which in turn is part of global steelcompany Arcelor-Mittal. In 1998, ISCOR decided to close the Corex-based Pretoria plant due

to an unprofitable economic situation. The off-gases of the new COREX unit will be used to

produce 800,000 tonnes per year of DRI, following a similar design to that at HANBO Steel,

South Korea. This decision also seems to be based on the environmental performance of theCOREX process, as the site is located near a nature preserve. This plant, which includes a thin

slab caster, began operation in January 1999.

Since 1995 a COREX plant has been in operation in the Republic of Korea, with twice the

capacity of the South African plant (C-2000). South Koreas Pohang Iron and Steel Co. has a

600,000-700,000 ton per year unit COREX plant. Several more orders have been placed for C-2000 plants in India, South Korea, and South Africa.

The Chinese steel producer Baosteel Pudong Iron and Steel Co. Ltd. (For Short Pudong steel) at

Luojing, near Shanghai started up a Corex C-3000 plant in early November 2007, with a

nominal production capacity of 1.5 million tons of hot metal per year. The project wascompleted under the management of Siemens Metals Technologies within a period of 29

months.

The latest generation of Corex plants, the C-3000, is ideally suited for integration into green- or

brown-field steel works projects. It can replace the blast furnace, or can be used as a source of

virgin iron for minimills. The economics of the Corex plant already provide an answer to futurescrap and coke shortages, and the continually increasing demands placed on steel quality.

Another alternative is the installation of a Corex C-3000 plant as a stand-alone merchant plant

for the production of hot metal and/or pig iron.


7/9

In the United States, Geneva Steel has joined Air Products and Centerior Energy in a

Department of Energy project to demonstrate the commercial viability of the Corex process inthe United States.

World's Largest Corex Ironmaking Plant setup by the Chinese steel producer Baosteel Pudong

Iron and Steel Co. Ltd.

Corex Process in India

The COREX C-2000 Plant/Module 01 at Jindal Vijaynagar Steel Ltd., Tornagallu, Karnataka,

India, Successfully started on August 8, 1999. Jindal Vijaynagar Steel Limited (JVSL) project islocated in the midst of the rich iron ore belt of Bellary- Hospet in Karnataka.The JVSL project is

conceived as the one of the most modern, technologically efficient Greenfield plant with a capacity of

1.6 mt per annum.

As a highlight of this proven technology, more than 75% of the nominal capacity was reached

shortly after start-up. The excellent hot metal quality fulfils the requirements of the LD(BOF) shop.

The plant was installed by VOEST-ALPINE INDUSTRIENLAGENBAU (VAI), a company of thelisted VA Technologic AG. This was the forth plant which was put in operation for the production of

hot metal based on VAIs proprietary COREX technology. It is planned that the COREX export gas will

be used for electrical power generation and for heating purposes within the steel complex. Hot metalfrom the COREX plant is processed to high quality steel in two 130 t LD(BOF) converters. The slag

produced by the COREX plant is processed in the granulation plant and will be sold to cement industry.


8/9

The steel making facility (BOF-CCP shop) include two 120 T convertors and two single castersof latest design and state of art facility from Mannesmann Demag of Germany. The quality slab

produced will be suitable for hot strip mill which has been engineered by Daniel United of

USA, incorporating the latest technology of coil box and a 250 T walking beam furnace fromStein Heurty. A third generation mill is equipped with state of art electrical automation from

Cegelac, USA and has all modern control features and equipment, to produce internationally

competitive quality strips of 1.6mm to 12mm thickness up to a width 1250 mm.The JVSLproject is visualised on co-generation concept and the unique feature of the project is its

technology-cum-management model. Jindal Praxair Oxygen Company Limited, the joint

venture company, supplies oxygen to the COREX plant. COREX off-gases will be used to

produce power by another joint venture company, Jindal Tractebel Power Company Limited.An overview ofJVSLCOREX Plant

Rated capacity : 1.6 million tpa

No. of units : 2 Module C-2000Major units : Coal Blending Station Coal

Drying Plant Stock House

COREX Tower Cast HouseWater recirculation System

Gas Cleaning and

Distribution System SlagGranulation Plant

Salient Technical features : Use of non-coking coal.

Availability of COREX gas of

medium calorific value foruse as fuel in the steel plant

as well as Power Plant.

Environment friendlyprocess.


9/9

Reference :

Smelting Reduction for Iron Making

by A. K. Jouhari, 2002 (Pages 44-58)

Future technologies For energy-efficient Iron and steel making

by De beer, Worrell & Blok , 1998

http://www.industry.siemens.com/metals-mining/en/Ironmaking/corex.htm

http://jpcindiansteel.nic.in/corex.asp

Article by M. Gojic and S. Kozuh, Faculty of Metallurgy, University of Zagreb, on

Development of Direct Reduction Processes and Smelting Reduction Processes for the

Steel Production

Report by Lynn Price, Dian Phylipsen, Ernst Worrell on Energy Use and Carbon DioxideEmissions in the Steel Sector in Key Developing Countries

Tugas Syarief (1006704764)Corex Prosses

Documents

Transcript of Tugas Syarief (1006704764)Corex Prosses