PLD: De-oiling of Iron Sludge

Environmental Technologies – Residue Treatment

Recycling Technologies

PLD: De-oiling of Iron Sludge

With increasingly severe environ-mental legislation, shortage of raw material supply and high metal prices, the implementation of dedicated processes for treat ing metallurgical residues and recov-ering their valuable contents becomes more and more relevant. Oily sludge and scales are part of these residues. Today it is possible to recover their iron content in an efficient way without impeding the main iron-steel flowsheet.

Paul Wurth, engineering and tech-nology supplier for the iron and steel industry, and Lhoist, lead-ing producer of calcium oxide and magnesium oxide based chemicals, developed an innovative process based on a low temperature pyro-metallurgical approach.

Lack of dedicated solutions

As a general rule, an integrated steelworks with a steel produc-tion of 4 – 8 mtpy generates 10 000 – 20 000 t of oily sludge and scales yearly.

Internal recycling at the sinter plant is limited because of the generation of dioxins and deflagra-tion issues in the electro per-cipitator (ESP). Recycling at the converter requires charge prepa-ration (briquettes) and may be detrimental to a smooth convert-ing process as well as to the steel quality (sulphur content). The retreatment through other spe-cific routes most often requires high temperatures (pyrolisis). And if such residues were landfilled, increasing costs and environmen-tal liabilities would be engaged.

Paul Wurth Lhoist solution

The respective metallurgical and chemical expertise of Paul Wurth and Lhoist led to the development of a low temperature process using lime, thus providing an effi-cient and economical solution to steelmakers.

In this process, a combination of exothermal chemical reactions and a controlled oxidation process ena-

before treatment after treatment

Oily sludge Lime

Gas treatment

Dust

MHF

De-oiled iron oxide

Sinter plant

PLD = Paul Wurth Lhoist De-oiling process

Environmental Technologies – Residue Treatment

bles the complete destruction of the hydrocarbons contained in the oily by-products and the recovery of premium iron oxide, ready to be re-used in the sinter plant.

The patented Paul Wurth Lhoist De-oiling (PLD) process is based on a close mixing of the residues together with a specific lime (Lhoist specification) inside a Paul Wurth Furnace.

Thanks to a specially designed low temperature Multiple Hearth Furnace (MHF) and a controlled mixing, the lime reacts with the water contained in the residue, inducing a quick temperature rise, followed by a 1 hour lasting com-plete oxidation (at a temperature <500° C) of organic materials. Ad-ditional energy is only requested to initiate the operation and dur-ing maintenance stops.

The exhaust gases are treated in an appropriate gas treatment system in order to comply with local emissions regulation.

Iron oxide mixed with a proportion of calcium carbonate and calcium hydroxide is recovered at the bottom of the furnace.

Paul Wurth Lhoist De-oiling process data

Key characteristics: ` compact MHF with insulated steel casing

` 6 – 8 hearths ` 3.5 – 5 m internal diameter

Gross mass balance: ` input quantity: typically 25 / 100 ktpy oily residue

` input analysis (typical, wet base): 2 ~ 20 % oil, 10 ~ 35 % moisture, 35 ~ 60 % Fe, 2 ~ 5 % gangue

` input lime: 5 – 10 % ` output quantity: approx. 25 / 100 ktpy

` output form: dust ` residual oil content < 0.1 %

` Low process temperature (<500°C)•Flexible operation•Limited refractory amount•Limited SO2 emissions

` Easy maintenance furnace and compact design

` Stable process and controlled operating conditions•Individual control of

temperatures zones•Efficient mixing between

materials•Residence time easy to

control

Applications of Paul Wurth Lhoist De-oiling process

Apart from oily sludge and resi dues generated in any inte grated steelplant, the PLD process can find inter esting appli-cations for treating oily by-prod-ucts coming from the non-ferrous smelting and refining industry, or from polluted soils.

Advantages of Paul Wurth Lhoist De-oiling process

` Easy to integrate inside a normal steelmaking flowsheet

•No specific preparation of the residue before being charged in the furnace

•Flexibility regarding sludge analysis

•High quality of output iron oxide

•Deoiled oxide easy to handle and charge to sinterplant

•No impact on the other steel processes of the plant

- Steel quality not impacted (no additional S charged to BOF)

` Avoid any environmental cost or liability

•Landfilling avoided

•Destruction of oily sludge odor

•Off-gas emissions in accord ance with the European regulation

` Auto-thermal process. Use of energy source only dur-ing maintenance stops, plant start-up and for low oil bearing by-products (<3%)

0

500

1000

1500

2000

2500

3000

IN OUT

kW

Furnace heat balance for 4t/h oily scale (fresh)4% oil - 20% H2O - 5% CaO

Oil oxidationIron oxidationCaO hydratation + carbonatationFuel gas

Heat lossesWater vaporisationSolid sensible heatGas sensible heat

� PAUL WURTH

Based in Luxembourg since its creation in 1870, Paul Wurth is mainly active in engineering for the iron & steel industry and the non-ferrous metals sector. With a portfolio of about 600 patented inventions, the company is one of the world leaders in the design and supply of complete plants, systems and processes as well as mechanical equipment for the ironmaking sector. At regional level, Paul Wurth specialized in the management and coordination of large civil construction projects.With a dedicated staff of more than 1500 collaborators, Paul Wurth is active worldwide, operating subsidiaries in the main iron and steelmaking regions of the world.

� LHOIST

Lhoist, Belgium based company, is the world leader for calcium oxide and magnesium oxide based reagents and a major supplier of the steel industry for these products including specialty products for metal desulfuration and flue gas treatment.Overall, the company is a the key solution supplier in metallurgy, mining, building & road construction, flue gas, water, sludge and waste treatment, glass, pulp & paper, chemicals and agriculture.The very strong R&D commitment of the company towards environmental issues has allowed Lhoist to bring innovative solutions to solve several of the key environmental challenges in air, water, sludge and waste treatment.Lhoist is strongly renowned by the major steel producers and has a commercial presence in more than 20 countries covering all continents in order to serve them for the best.

Engineering & Technology worldwide

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Non Contractual Data: Paul Wurth believes that the data contained in this folder are correct and accurate, but cannot guarantee same or better performances for any specific site without a detailed quote. Patents and Patents pending. — Paul Wurth equipment and processes are protected in many countries by patents.

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Paul Wurth S.A.32, rue d’Alsace • L-1122 LuxembourgPhone: (+352) 4970-1 • Fax: (+352) 4970-2209paulwurth@paulwurth.com • www.paulwurth.com

VCA**CER

TIFIED SAFETY SYSTEM

VINCOTTE

ISO 9001ISO 14001

BUREAU VERI TASCerti�cation

N° BXL 05000141 / N° BEL BXL 153669

Lhoist Group28 , rue Charles Dubois • B-1342 Ottignies-Louvain-la-NeuvePhone: (+32) 10 230 744 • info@lhoist.com

Subsidiaries: Brazil, Chile, Czech Republic, Germany, India, Italy, Japan, Korea, Mexico, P.R. China, Russia, South Africa, Taiwan, Ukraine, U.S.A., Vietnam

Subsidiaries: Benelux, Brazil, Czech Republic, Denmark, Finland, France, Germany, India, Mexico, Poland, Russia, Slovak Republic, Spain, Sweden, United Kingdom, U.S.A.

LIFE11 ENV/LU/000855 - PLDProject supported by the European Commission Coordinating beneficiary: Paul Wurth S.A. (Luxembourg) Associated beneficiary: S.A. Lhoist R&D (Belgium)www.pld-life.eu