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Innovative and cost advanced Electric Steelmaking

for the Construction Sector

Apfel, Jens1，Beile, Hannes1，Joerg Schwoerer1

1Primetals Technologies Germany GmbH

Abstract：This paper outlines the latest developments and design improvements of the most efficient electric arc

furnace: The EAF Quantum. Since more than four years this revolutionary furnace concept proves its reliability and

outstanding efficiency.

For the Vietnamese market, new sizes, design features, and automation levels have been added to gain even more

flexibility in terms of input material, scrap logistics, and operator and maintenance friendliness.

In combination with modern casting and rolling technologies, the EAF Quantum perfectly serves both mini mill long

and flat. This innovative and cost advanced Electric Steelmaking could also have a big impact in terms of conversion

costs for the construction sector. As in China many new meltshops are currently built with scrap preheating capabilities

also Vietnam needs to be prepared for future overcapacities and respective imports from China.

Keywords：Electric Steelmaking, preheating, efficiency, shaft furnace, mini mill, EAF

1. Introduction

In previous years, productivity was the main focus for the steel industry as the market was booming and the steel producers

were output oriented. But the situation changed and the market downturn forced the industry to work on the efficiency of

the equipment and the steel producers became cost oriented. Additionally, more and more countries worldwide are

implementing new rules and regulations not only concerning energy efficiency and CO2 emissions, but also with respect

to hazardous off gas emissions. Most of the steel manufacturers producing large volumes of steel are using the integrated

production via blast furnace and basic oxygen furnace with high CO2 emissions. So there is a clear trend around the world

to change to EAF steelmaking. The preferred EAF technology should have the following characteristics:

Low in electrical energy consumption

Low in CO2 and other hazardous emissions

Flexible in raw material input

Highly automated process

High availability of the plant

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The Quantum technology shows all these characteristics and is a very good solution for modern steelmaking under today’s

tough conditions in the steel industry.

2. Basic Quantum principles

The preheating shaft of the Quantum furnace is loaded with scrap by a tilting scrap container which is mounted on an

elevator (1). The scrap container itself is automatically loaded by a rectangular scrap bucket which has been filled before

on the scrap yard. The scrap charging is operated automatically. The preheated scrap is charged into the liquid steel bath

in several batches. The scrap is molten by electrical power input and oxygen injection through two top lances. The furnace

shell itself can be tilted for tapping and deslagging with four cylinders, while the roof and shaft are fixed. Fluxes and alloys

can be added through the roof and into the ladle during tapping.

Figure 1: General view of Quantum EAF from tapping side

Elevator for scrap skip

The Quantum EAF is a combination of many long proven technologies . The elevator is similar to the ones used at

blast furnaces. At the Tyasa plant in Mexico this elevator is operating since 2014 without any disturbance.

Scrap Retaining Finger System

The scrap retaining finger system has been optimized compared to the system used in the finger shaft furnaces. The

fingers can be retracted completely from the shaft while charging. The finger surface is protected by special steel

plates which can resist the mechanical impact of charging.

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Figure 2: Scrap retaining finger system of Quantum EAF

FAST Tapping System

Another special feature of Quantum EAF is the FAST (Furnace Advanced Slag Free Tapping) tapping system. The tap

hole is arranged in a way that it is separated from the liquid steel bath by a siphon. This installation has several advatages.

Steel can be tapped slag free since the slag cannot pass the siphon. The tap hole can be refilled under power on. Tapping

is possible under power on as well. As a consequence the set-up time (downtime for tapping, charging, taphole refilling

etc.) of the Quantum EAF is about 4 minutes per heat.

Figure 3: Schematic drawing of FAST tapping system, FAST installation at Tyasa, Mexico

Furnace shell movement

As all the shaft structure is fixed installed, the shell has to be manipulated for tapping and deslagging (if required). This is

realized in a manner that the shell is sitting on base frame with cylinders and guides, allowing the shell to be tilted in both

directions –tapping and slag side.

The gantry with the electrode lifting system and the lance holders for the oxygen and carbon lance is not tilting, but only

swinging out for electrode slipping and fast roof center piece exchange. Heavy stress from furnace tilting like the gantry at

the conventional EAF with all its consequences on support and bearing, high current cables, etc. is not required. For

maintenance reasons, a simple shell transfer and moving concept reduces furnace movements and improves system

maintenance aspects through quick shell exchange.

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Figure 4: (a) Ladle car with ladle ; (b) Ladle car before shell change; (c) Ladle car with shell in pick up position; (d)

Ladle car with shell in maintenance position

The transfer car is acting as tapping car as well as shell transfer car. The sequence of shell exchange is show in the figure

9. In order to pick up the shell from the frame, the car has to be placed into the exchange position, underneath the shell.

The shell will be lowered by means of the cylinder and guide system. When sitting on the car, the shell is free and can be

moved outside the furnace area for refractory maintenance or shell exchange.

Figure 5- (a) Ladle car in shell change position; (b) Ladle car with shell in maintenance position

In order to prepare the furnace for restart, the shell can be loaded with remaining liquid steel or scrap prior moving to the

operating position. Once again in operating position, the cylinder and guide system is moved up and then connecting the

base frame with the shell.

3. Electrical energy consumption of Quantum EAF

Electrical energy consumption is one of the highest cost factor in electric arc furnace steelmaking. Therefore we can find

here the biggest potential for cost saving. The following figure shows the electrical energy consumption in correlation to

the oxygen consumption for different kinds of EAF technologies. The Quantum EAF is among the lowest energy

consumption furnaces with 310 kWh/t and 25 Nm3/t

a. b.

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Figure 6: Electrical energy consumption vs oxygen consumption for different EAF technologies

4. Raw material flexibility

Of course the Quantum is designed for 100 % scrap charging since only under these conditions the preheating shows its

biggest benefit. But also all other materials can be charged to the Quantum, either with the scrap or continuously fed

through the 5th hole in the roof.

Scrap specification is basically as for other conventional furnaces. Scrap pieces should not be longer than 1,5 m. Not more

than 500 kg per scrap piece. Sheets should not be thicker than 50 mm. There are some restrictions on the scrap density.

Charge material with high bulk density like shredded scrap should only be used up to a certain percentage. Otherwise the

scrap in the shaft is not enough permeable for the off gases from the furnace. The pressure drop along the shaft is too high

and so mainly false air is entering the EAF. Basically all materials shown in the following table can be charged to the

Quantum EAF.

Table 1: Material usable in a Quantum EAF

Material Iron met. (%) Carbon (%) Gangue (%) Bulk Density (t/m3) Temperature (°C)

Scrap < 0.2 < 3 0.4 – 1.0 Ambient temp.

Coal based DRI 80 – 85 % 0.1 – 0.3 3 – 9 1.5 – 1,8 Ambient temp.

Gas based DRI 80 – 85 % 1.8 – 2.4 3 – 9 1.5 – 1,8 Ambient temp.

Hot gas based DRI 80 – 85 % 1.8 – 2.4 3 – 9 1.5 – 1,8 500 – 600

HBI 80 – 85 % 1.2 – 1.8 3 – 9 2,2 – 2,6 Ambient temp.

Pig iron 92 – 95 % 3.5 – 4.2 - 3.5 – 4 Ambient temp.

Hot metal 92 – 95 % 3.5 – 4.2 - 1200 - 1300

The amount of non-scrap material which can be used has technical and economical limitations. At least 50 % scrap should

be used to have enough benefit from preheating. DRI and HBI can be charged through the roof and can be molten easily

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due to the high hot heel of the Quantum EAF. Even hot metal can be charged with a launder through the slag door but not

more than 30 % of the charge mix. The following picture shows the possibilities for charging different kinds of material

into the Quantum EAF.

Figure 7: Hot metal feeding through door and DRI feeding through roof into Quantum EAF

5. Automation at Quantum EAF – a big step towards Industry 4.0

At the Quantum EAF the degree of automation is very high. Human interaction is mainly done from the operators pulpit.

All major process steps can be operated completely in automatic mode.

Table 2: Process steps at Quantum EAF with automation

Process step Mode of operation Comment

Scrap loading in bucket manual Crane driver on scrap yard

Scrap loading into skip on elevator automatic Moveable hopper

Charging of skip into shaft automatic According to operating diagram

Charging from finger into bath automatic According to operating diagram

Oxygen/carbon injection automatic Top lances controlled by slag monitoring

Tapping semi automatic Proposed by system done by operator

Tap hole filling automatic Automatic sand filling device

Off-gas system and post

combustion

automatic Controlled by continuous off-gas and temperature

measurement

Sample and temperature taking automatic By manipulator through a roof opening

Slag door cleaning manual With forklift

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The plant under construction in Bangladesh is equipped with a fully automated scrap yard. Only the scrap cranes are still

manned. Due to space restriction the scrap yard has a kind of carousel for the scrap buckets. The movement and the loading

of the skip on the elevator are fully automatic. The buckets are driving along the different boxes for different scrap grades

and are loaded by crane handling. At the Quantum the bucket is taken by a crane and unloaded into the skip on the elevator.

With an automatic hydraulic coupling system the bucket is opened and scrap is falling into the skip on the elevator.

Afterwards the bucket is put back to the bucket car. The following picture shows the scrap yard at GPH.

Figure 8: Overview GPH scrap yard with automation

6. Environmental Aspects

Stack emissions

All EAF technologies melting scrap generate emissions of CO, NOx, organic compounds like dioxins and furans.

Especially the organic emissions are linked to contaminations of scrap with oil, grease and colour paintings. In case of

scrap preheating the organic compounds are difficult to burn completely just by a simple post combustion with false air

like in conventional arc furnaces. Therefore all scrap preheating furnaces need a post-combustion chamber with burners

installed to heat up the off-gas to values up to 850 °C to minimize dioxin and furans but also carbon monoxide. The

principle of minimizing organic emissions including dioxins and furans consists of three steps and is shown in the following

figure.

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Figure 9: Principle of dioxin and furan mitigation in the stack emissions of EAF

The dedusting system for a Quantum EAF therefore looks as shown in the following figure.

Figure 10: Schematic arrangement of Quantum Dedusting Plant

With the described system all environmental aspects can be covered. For low dioxin and furan emissions

(< 0,1 ng TE/Nm3) an optional activated carbon injection system may be required.

Noise emissions

The biggest noise source at the EAF is the short circuit of the electrodes with the scrap during beginning of meltdown.

Once all scrap is molten the noise level comes down significantly. During refining the noise level of a conventional EAF

is the lowest during one heat.

At Quantum EAF with its hot heel of about 70 % of the tap weight, the scrap is mainly molten indirectly while heating up

the hot heel. This process is similar to the refining stage of a conventional EAF and therefore the noise level of a Quantum

is lower than for a conventional EAF. The following figure shows the noise levels for both types of EAF over one heat in

5 m distance to the slag door.

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Figure 11: Noise level (sound pressure level) of conventional EAF and Quantum EAF

7. Quantum References and upcoming projects

Quantum Technology is available in different sizes from 70 to 150 t tapping weight. A 100 t installation is in operation in

Tyasa, Mexico. One project is under execution in Bangladesh and three more projects just started in China. The following

table shows the characteristics of these five Quantum furnaces.

8. Conclusion

Quantum EAF is a proven technology with various sizes and product mixes. All kinds of raw material can be charged to

the Quantum, but economic feasibility for each charge mix has to be proven. Electrical energy consumption can be reduced

significantly through scrap preheating, while other benefits like electrode consumption and low refractory consumption

help to reduce operating costs. In addition all environmental obligations can be fulfilled. Especially noise emissions are

lower than from a conventional EAF.

Quantum is a furnace which can be operated almost fully automated. From scrap charging to tapping all steps are at least

semi-automatic and need just confirmation by the operator. This is a big step into the direction of Industry 4.0 and will

have a big impact on the production of steel for the Vietnamese construction sector.