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The dry recovery of valuable scrap from the residual slag at the production of Stainless Steel and Ferro-Alloys using the Sensor Separation Technique. The RecCo-Marilyn Process. Jan Groothoff (M. of Sc.) S3R Company Asian Stainless Steel Conference in Shanghai May 2006. Index

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The dry recovery of valuable scrap from the residual slag at the production of Stainless Steel and

Ferro-Alloys using the Sensor Separation Technique.

The RecCo-Marilyn Process

Jan Groothoff (M. of Sc.)

S3R Company

Asian Stainless Steel Conference

in Shanghai

May 2006




Present recovery techniques for scrap

Key-elements of the RecCo-Marilyn concept


The sensor technique

Benefits of recovery of scrap

Advantages of the dry recovery rocess

Introduction of S3R Company

Pictures of recovered scrap

Pictures of the first installed plant in Taiwan

Biography of Jan Groothoff



  • Presently all stainless steel mills are rapidly increasing their production.
  • Stainless steel scrap is an essential feedstock for the stainless steel production.
  • (€ 1500 ton f.o.b. Rotterdam). The higher the price; the lower the quality!
  • Consequently maximum recovery of own residual scrap from slag with known quality is very essential.
  • Conventional producers have slag quantities of 30-40% of steel making tonnages, containing 6-12% retrievable scrap.

Page 1 of 2



  • After removing the obvious easy to recover sculls > 250mm, the remaining slag has an approximate particle size distribution of:

2% 250 - 600mm

8% 80 - 250mm

±25% retrievable scrap

25% 10 - 80mm

65% 0 - 10mm (±3-4% scrap)

Page 2 of 2


2. Present recovery techniques for scrap

  • • Traditional mining recovery techniques for high grade ore are mostly used:
    • - Jaw crushing
    • - Screening
    • - Hand picking
    • - Peripheral discharge wet grinding rod mill
    • - Wet overflow ball mill
    • - Classifiers
    • - Humphrey spirals
    • - Cyclones
    • - Settling ponds
  • Largest problem: avoiding Cr 6+ penetration in ground water
  • Results:
    • - High degree of recovery
    • - High quality of scrap
    • - Large problem of dumping unreusable slag

Page 1 of 3


2. Present recovery techniques for scrap

  • • Modifications to the wet processing route
    • - Dry crushing with impactor + vertical shaft crusher
    • - Hand picking
    • - Wet jigging for the final recovery of scrap
  • Results:
    • - Still using water
    • - No recovery of fine material

Page 2 of 3


2. Present recovery techniques for scrap

  • • Dry cone crushing only + magnetic recovery
    • - Not processing > 50 mm
    • - Not processing < 15 mm
  • Results:
    • - Not efficient
    • - Missing 4-6% of retrievable scrap!

Page 3 of 3


3. Key elements of the RecCo-Marilyn dry recovery process

  • Dry recovery of scrap from slag.
  • Latest crushing and screening techniques.
  • Tailor made sensor separation of scrap on 2 fractions till 15 mm (modules 1-3).
  • Dry crushing and grinding of fines to retrieve the last scrap fraction > 1 mm (module 4).
  • Step 5 = a newly engineered processing technique using very high density neodyn magnets and a special modified crusher to retrieve 3-4% Fe from the initial removed
  • 0-10 mm (wet) slag.
  • Re circulate the slag fines into the 0-10 mm fines for usage in civil works.
  • - Fine slag has Cr 6+ value < 1 ppm!
  • - Volume stability is 2,5%; which is well under the 5% limit.
  • Step by step module approach.

Page 1 of 4


3. Key elements of the RecCo-Marilyn dry recovery process

  • The most simple processing plant (module 1-3) version (semi-mobile) has:
    • 1) 1 (mobile) 2 deck screen with scalping grid (for dry slag) or a disc-screen (for very wet slag); cap. 120t/hr
    • 2) 1 (semi-mobile) impactor on skids + magnet with 2 sensors (fixed plant); cap. 50t/hr
    • 3) 1 hand picking station
    • 4) 1 bar sizer
    • 5) 1 two deck sizer screen
    • 6) 1 sensor separator + hopper + feeding conveyor + 2 outlet conveyors
    • 7) connecting conveyors
    • The complete version is module 4 and 5, includes dry crushing and screening.
    • This module will atleast recover 4 percent extra scrap of the total input.

Page 2 of 4


4. Results

  • 6-12% scrap recovery from total slag input.
  • High quality scrap. 80% pure metal.
  • Densities 6-7 tons per m3!
  • Re-usable slag product in civil works.
  • Environmental acceptable process.

5. The sensor technique

Metal containing slag of a defined size distribution is routed onto a fast moving conveyor (3-5 m/sec). Nearly at the end of this conveyor, the material is routed over an electric field. Each metal piece causes a damping disturbance of this field which is measured by a sensor. This signal is send to a processing unit (computer) which in sequence activates air valves located below the material flow of the sorting unit. Finally the activated air will blow out the programmed material (metal pieces).


6. Benefits of recovery of scrap


> 800.000 t/yr steel production (UHP electric arc furnace + Converter)

> 300.000 t/yr slag + sculls > 250mm

> 274.000 t/yr slag excl sculls

Dry processing according “RecCo-Marilyn” process results in:

> 24000 t/yr scrap (1-250mm) + 250.000 tons of reusable (0-10 mm) slag

> 2000 t/month scrap

> Internal value of recovered scrap < 250mm

± 80% x scrap price = 80% x € 1.000/ton* = € 800/t *= low estimate

> 2.000 t x € 800/t = ± $ 2 M/month

Total recovered scrap value = $ 2 M / month = $ 24 M / yr

Page 1 of 2


6. Benefits of recovery of scrap

  • Conclusions:
  • Recycling is very worth-wile.
  • 70% of the total scrap is relatively easy to retrieve by hand picking and magnet separation.
  • The other 30% recovery requires high-technology
  • (Eastern countries mostly miss these 30%).
  • This is still $ 7 m/yr of the above mentioned $ 24 m/yr.
  • A large quantity of scrap is in the fraction 15-25mm. This can hardly be recovered
  • by hand picking.
  • The second largest fraction is in the 1-15mm fraction.
  • The basics of the described techniques are also applicable
  • for Ferro-Alloys recovery, such as ferro-chrome, ferro-titan and others.

Page 2 of 2


7. Advantages of this dry process

  • CAPEX (Capital expenditure) is substantially less than the CAPEX required for the wet milling route.
  • There is no slag disposal problem as the process produces reusable 0-10mm dry slag.
  • Treatment with FeSO4 will convert Cr6+ into Cr3+, eliminating the undesired hazard of Cr6+.
  • The plant can be built on permanent or semi-mobile configurations in accordance to our 4-step module approach.
  • No large concrete foundations are required.
  • No water treatment installation. No risk of contaminated water entering the environment.
  • Dust-free sorting plant.

8. Introduction of S3R Company

  • S3R, Stainless Steel Scrap Recovery, is a strategic alliance of 3 companies who have combined their know how, engineering and production facilities to market the dry recovery concept.

RecCo BV (Recycling Consultancy), based in Aerdenhout and Akersloot, the Netherlands, has specialised know-how in engineering and management of the recovery of non-ferrous and ferrous metals from slag. Recco BV has now established a strategic alliance with Mous BV, a well established metal construction company, for building their designs. This includes products for s3R and Recco Contracts.

Hofung Technology, based in Beijing, China is an expert in bringing together the needs of chinese clients with specialised technology and equipment suppliers outside China.

Evergoed NV, Investment company based in The Hague.

Page 1 of 2


8. Introduction of S3R Company


- Will provide stainless steel and ferro-alloys producers tailor made recovery proposals

conform the RecCo-Marilyn concept.

- Will build and sell the sensors and offer auxiliary equipment.

- S3R was founded in 2005 and has sold in 2005 the first concept and equipment to a Taiwaneese customer. In Februari 2006 S3R signed a contract to supply basic engineering and key components to the largest stainless steel producer in the world, Tisco company based in Taiyuan China. This plant will process 760.000 ton of slag / year.

S3R is based in Akersloot, The Netherlands and has a branchoffice in Beijing.

See for more details our brochure and we are happy to see you at our stand.

Thank you for your attention and I will be happy to answer your questions.

Page 2 of 2


11. Biography Jan Groothoff

• Jan Groothoff (60 years of age) is a Dutch mining engineer (University of Delft, The Netherlands) and served 17

years in one of the largest steel slag processing companies in the world, Heckett Multiserv. During this period

he managed as regional director and local manager large slag recycling operations in the Netherlands (Corus),

Luxemburg (Arbed), Scandinavia (Fundia, SSAB, Nirosta), Russia (MMK), Slovakia (USX) and Czech Republic (Nova

Hut). These operations were mostly at carbon steel producers.

• At the Corus works in IJmuiden he developed the licensed coolant scrap production, which converts slittings

from the hot and cold rolling mills into high quality coolant nodules for the vacuum degasser.

• In 2003 he started his own consultancy company RecCo BV, specialized in the recovery of ferrous and non-ferrous

metals from waste streams. RecCo BV worked together with a client in the Netherlands, which has a 20 year

experience in recovery of non-ferro mix metals from shredder waste and incinerator slag. In their works, hightech

technologies are used to recover and seperate the non-ferrous mixed metals into seperate base metals. One

of these techniques is sensor separation. A semi-mobile and a fully mobile sensor machine were developed to

carry out extensive pilot plant test to recover stainless steel scrap from slag streams.

• In 2005 S3R BV was then established to further develop, market and sell turnkey dry recycling proposals to

potential clients in the stainless steel/non-ferro producing industry.

• Mr. Jan Groothoff is the managing director of S3R BV, with Recco BV as major shareholder. He developed for S3R

BV the now license applied for Recco-Marilyn dry recycling concept for the recovery of stainless steel/ferro alloys

from slag.

• First project was sold in 2005 to a Taiwanese customer for a 75 t/hr single shift/day plant.

• Second project was sold february 2006 to Tisco (China) for a 150 t/hr 2 shift/day plant in taiyuan.