The present invention relates to the slag processing, in particular for recovering iron from this byproduct.

Slag processing is disclosed in patent documents US 4 747 547, US 2013/0240415 and US 1 478 826.

EP 2 128 279 A1 describes a method for separating metal-containing fractions from slag comprising the successive steps of: Supplying the slag; processing the slag into fractions; pre-separating the fractions with a magnetic separator where substantially all iron-containing fractions are separated; and separating non-ferrous metal-containing fractions by using an eddy current separator.

WO 2009/089906 A1 describes a process for producing mortar or concrete comprising the steps of carbonating a fine fraction (24) of steel slag particles, containing a significant amount of y-dicalcium silicate, and then mixing at least this fine fraction (24) with at least a hydraulic binding agent and with water to produce said mortar or said concrete.

KR 2002 0074430 A describes a method and an apparatus for manufacturing aggregate using steelmaking slag is provided to use steelmaking slag as superior recycled product by installing a steelmaking slag recycling facility to crush steelmaking slag charged, remove foreign materials mixed in the slag, and age produced products, thereby remove sulfur.

Huiting Shen et al. analyzes and summarizes the generation, characteristics, and application of various slags, and discussed the potential effects of the slags on the environment as well as methods for recovery of metals from the slags.

WO 02/066164 A1 describes a facility for treating composite material containing metal as treating material, comprising a metal separator (22, 22a, 28) mounted upstream of an impact crushing mill (30, 50) -- and optionally an eddy current separator (54) mounted downstream of the impact crushing mill (30, 50) as device for separating the treating material by swirling.

Existing processes do not allow a complete recovery of iron from slag and are not fully integrated. They also not allow the separation of FeO.

An object of the present invention is to provide a complete recovering of iron from slag.

Another object is to effectively break slag, in particular slag of relatively important size, typically above 300 mm.

Another object is to separate and recover FeO from slag.

Those and other objects are achieved with the system of the invention according to claim 1, which comprises a

Grizzly feeder adapted to separate a slag fraction of less than 60 mm, a single rotor crusher adapted to crush a slag sub-fraction of 30 to 60 mm, a centrifugal crusher adapted to crush a slag sub-fraction of less than 30 mm, and a drum magnet and a material spreader that are adapted for sorting said sub-fraction of less than 30 mm.

The inventors have surprisingly found that an efficient and complete iron recovery can be obtained when handling the above cited slag fractions. The "less than 30 mm" fraction is particularily useful for separating FeO.

The invention also relates to a method process according to claim 5 for slag processing comprising the following steps

• separating a slag fraction of less than 60 mm,
• crushing a slag sub-fraction of 30 to 60 mm,
• crushing a slag sub-fraction of less than 30 mm,
• sorting said sub-fraction of less than 30 mm by spreading the slag and imparting a magnetic force on it.

The invention will be better understood in the present chapter, with an illustrated non-limiting example.

• Figure 1 represents one system according to the invention.
• Figure 2 illustrates an active free lime process
• Figure 3 is a transparent view of a hydraulic breaker according to the invention
• Figure 4 shows different positions of a hydraulic breaker according to the invention
• Figure 5 illustrates the combination of a machine and a hydraulic breaker

The different elements that constitute the system are discussed below:

Slag is fed to the hopper by front loader, excavator or dumper. From hopper and Grizzly feeder (1) fraction 0-60 (100) mm is separated from the flow to conveyor line to Special crusher (4) passing the Jaw Crusher (3). Fraction 60-800 mm goes into a drum screen (2).

Drum screen, diameter 2,2 m, is made of highly wear-resistant steel. Slag is divided into 60- 300 mm and over 300 mm fractions. (Opening of the screen can be on range 200 - 300 mm). Drum is supported with four rubber wheels. There are 2 x 22 kW electric gear motor drives.

The drum speed is variable.

From drum screen fraction app 60-300 mm goes into a conveyor line and to Jaw Crusher (3). Pieces over 300 mm will be crushed by hydraulic breaker (12).

Special crusher (4) is fed by fraction 30-60mm. This crusher breaks the slag guaranteeing complete metal recovery. Crushed material goes by conveyor line to the screen (5).

Robust Jaw Crusher (3) are designed for high performance, in order to achieve the lowest possible operating cost per ton of end product produced. Performance has been optimized through solid cavity design and kinematics. The robust Jaw Crusher feature a long stroke, optimized operating speed, and an aggressive motion of the pitman.

The crusher is fed by 60-300mm slag (no thicker metal pieces than 340mm). Materials are crushed in smaller fractions. Automatic metal piece control (AMPC) let unbroken pieces going thru without causing damage to Crusher. Materials continue with conveyor (6) to the inclined heavy-duty screen (5).

The screen is a horizontal with double decks. The top screen is very durable wire deck.

0-300 mm slag will be screened to 0 - 30 mm, 30 - 60 mm and 60 - 300 mm fractions.

These fractions are very important that magnetic separators can be adjusted to optimize separation. 60 - 300 mm fraction goes from top deck (over size) to magnet (7).

30 - 60 mm fraction goes from bottom deck (over size) to magnet (6).

0 - 30 mm fraction goes through bottom deck (under size) by conveyor line via surge bin () to the conveyor and to High-Speed Centrifugal crusher (11) and then to special magnet (9).

Magnet is for fraction 60 - 300 mm.

Magnet is belt drum magnet (7) where diameter of the drum is specified for this fraction. Inside of the drum is permanent magnet which position is fully adjustable.

Divider plate will guide steel scrap and slag to right conveyors. Position of the divider plate is fully adjustable.

Magnetic metal pieces will go to conveyor and to cleaning drum (8). Slag will go to conveyor and to the Jaw crusher.

Magnet for fraction 30 - 60 mm.

Magnet is belt drum magnet where diameter of the drum is specified for this fraction. Inside of the drum is permanent magnet which position is fully adjustable.

Divider plate will guide steel scrap and slag to right conveyors. Position of the divider plate is fully adjustable.

Magnetic metal pieces will go to conveyor and to cleaning drum (8). Slag > 30 mm will go to the Special crusher (4) and back to the screen (5).

Special crusher (4) for fraction 30-60mm crushing. This crusher breaks the slag guaranteeing complete metal recovery. Crushed material goes by conveyor line to the screen (5).

Magnetic metal pieces in fractions 30 - 60 and 60 - 300 are cleaned from slag residues in cleaning drum (8).

Magnetic metal pieces is fed to drum with conveyor. Diameter of the drum is 3.0 m. There are lifters, which lift metal pieces up. This rotation causes autogenous cleaning where falling of metal pieces will liberate slag residues. When metal pieces drop on steel bed on bottom there is very small amount of wearing.

Inside of the drum is manufactured with high wear-resistant steel.

In discharge end of the drum, there are two screening drums with openings #60 mm and #30 mm.

60 - 300 mm fraction falls out at the end of the drum, and it is ready to be loaded. Metal concentration in this product is high, usually above 85%.

30 -60 mm fraction goes to conveyor and to stockpile. Metal concentration in this product is still high, usually above 80%.

0 - 30 mm fraction goes to conveyor and to High-Speed Centrifugal crusher (11). Metallic iron is bound with the lime and that is why it need to be crushed by High-Speed Centrifugal crusher.

Cleaning Drum is supported with four rubber wheels.

The LF slag-processing utilizes a smaller equipment footprint since the slag is already in a small size and can be fed, screened, and run through a specialized centrifugal mill for crushing and metallic separation. To maximize the utilization of equipment capacity and reduce the footprint of the plant.

The plant process LF slag in the same high speed centrifugal crusher as the steel slag and then continue through the same processing equipment.

Because of the significant amount of calcium aluminate in ladle furnace slags, which is the main compound of ladle fluxes, the remaining LF slag fines after metal recovery are best used back in the Ladle Furnace as a fluxing agent.

These fluxes are widely used to clean steel production processes. Hence, using of ladle furnace slags as a part of ladle fluxes can be considered as an economic recovery for these materials.

The High-Speed Centrifugal crusher (11) is for crushing the steel slag in fraction 0-30 mm. This mill liberates rest of metallic pieces from lime and silicate. Crushed material goes by conveyor to the fine magnet (9).

With high performance impact (160 m/s) with a vertical shaft, outer and inner special rotors with special hard metal impact pins.

• The input material is fed from above into the center of the centrifugal mill. Material is thrown from the inner rotor to the opposite direction rotating outer rotor by high-speed centrifugal force.
• The input material hits to the outer rotor impact pins at high speed. This leads to an optimized impact resulting effective liberating for the metallic particles and pieces from the lime.
• The twin rotor eliminates the risk of clogging and allow high throughput rates.
• High throughput rates
• Reduced risk of clogging
• Directed material acceleration
• Optimal energy efficiency
• Reduced wearing of the materials
• Increase rapidly the recovery of Fe-metals from smaller than 30 mm slag fines
• Unique high-speed centrifugal mill with ring speed 160meter/second
• Twin rotors rotating in opposite directions
• Special hard metal impact pins
• No stacking
• Hydraulic cover opening for maintenance

Special magnet for fraction 0 - 30 mm.

Magnet is High Speed drum magnet with High Intensity magnet field, where diameter of the drum is specified for this fraction. Inside of the drum is permanent, high intensity magnet, which position is fully adjustable.

This enables the efficient separation of fine metal grains. There is electric motor drive and adjustable rotation speed.

Material spreaders expand the slag for the whole width of the magnet, in this way the magnet separation is more efficient, and flow can be higher. Material spreader is designed for the harsh environment against material sticking.

Divider plate will guide magnetic pieces and slag to right conveyors. Position of the divider plate is fully adjustable.

Metals 0 - 30 mm will go by conveyor to Flip flop screen (10) and to storage silos. Slag 0 - 5 mm will go by conveyor to storage silo.

Screen is a horizontal flip flop screen with one deck. The screen is very durable 60 mm rubber screen. Deck has surface area app 15 m2.

0-30 mm slag metals will be screened to 0-2 mm and 2 - 30 mm fractions. 2 - 30 mm fraction goes over the deck (over size) to conveyor and silo.

0-2 mm fraction goes through the deck (under size) by conveyor to the storage silo.

0-5 mm non-magnetic slag go to storage silo.

This machine is used for effectively braking slag of relatively important size, i.e. above 300 mm. Its main componets are described below (see also figures 3, 4 and 5).

1. a) Carrier machine: Stationary carrier machine with legs or mobile version with tracks. Power is produced by electric current or by diesel engine.
2. b) Chassis: This consists mainly of the main pipe in which the hammerhead and coupler operates.
3. c) Power train: This consists mainly of adouble luff, which operates on 2 slide bars. A hydraulic double acting main cylinder, which expands and lifts the hammerhead and coupler to the top of the chassis.
4. d) Hammer head: The hammer head runs inside the chassis and consists of several parts. One replaceable hammer point and one ballast block. Moreover, there is a carriage with rollers that control the hammer head as it falls freely through the base. which control the hammerhead as it falls freely through the chassis. The hammerhead weight is preferably between 4 and 8 tons. It may generate an impact energy between 200 000 and 400 000 Joules, depending on its weight and dropping height.
5. e) Coupler: The Power train activates a wire, which lifts the coupler. The coupler has electromagnet catcher. The magnet field activates when the coupler reaches the hammerhead and catcher attaches itself to the lifting tap. The coupler has a mechanical locking to prevent the head from falling in the event of a power failure.
6. f) Carrier machine coupler: The hydraulic coupler is the attachment to the carrier machine.

The following description refers to figure 4 which shows a basic work cycle. The breaker has a hydraulic drop hammer. The principle of operation is as follows:

1. 1. Place the hammer upon the surface of the object - 1
2. 2. The hydraulics of the carrier machine lifts the hammerhead to the top of the pipe -
3. 3. The coupler releases as it reaches the highest limitation of the chassis.
4. 4. When the coupler is released the hammerhead falls freely toward the object, upon which the hammer is placed -3
5. 5. When the hammerhead impacts the object, the energy from the hammerhead is transferred to the object and it will split depending upon the material.
6. 6. The coupler lowers onto the hammerhead - 4
7. 7. When the coupler reaches the hammer head it attaches itself to the lifting tap and the breaker is ready to repeat the process.

As the breaker to a large proportion only requires lifting the hammerhead the only other active force being the earth's gravitational force it means that this breaker is a very cost-effective tool. The hammerhead drops by its own weight on the object without the use of active propellants. Thus, the operation principle is free of the vibrations known from other splitting methods, which significantly extend the wear life of the carrier machine while improving.

The invention also concerns the production and stabilization of active free lime from slag tailings n fraction 0-5 mm.

The resulting product comes from the slag processing process. It is a unique ecological product which binds carbon dioxide from the air, because of the multiplied surface area.

The product can be recycled and 100% reused in replacing cement in concrete production.

1. 1. In the process slag tailings are grinded in to fraction below 50 microns.
2. 2. While the grinding of the slag, environmentally friendly ingredients are fed into slag. It helps deactivating active free lime from slag.
3. 3. For every ton of product used in replacement of cement in concrete production, CO2 emissions are reduced by 500 kg.