Reference Document on Best Available Techniques in the Ferrous Metals Processing Industry A.2 Processes and Techniques A.1 General Information A.3 Consumption

Reference Document on Best Available Techniques in the Ferrous Metals Processing Industry

A.2 Processes and Techniques

A.1 General Information

A.3 Consumption and Emission Levels

A.5 BAT

A.6 Emerging Techniques

A.4 Techniques

EUROPEAN COMMISSION

Grupo 3:

Abad González, Soraya

Prada Uña, Raquel

Rodríguez Gutiérrez , Cristina

Villacorta Asensio, Milagros

Best Available Techniques in the Ferrous Metals Processing Industry

EUROPEAN COMMISSION

Gestión AmbientalCurso 2007-08





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION

Asignatura: Gestión Ambiental - Curso 2007-2008


A.1 Wire

Hot and Cold Formed Products covered by this BREF:

We´re going to talk about WIRE





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.2 Processes and Techn.

A.2 WireA.2.1 Wire Drawing Process

A typical wire drawing process line comprises the following steps:

• Pre-treatment of the wire rod (mechanical descaling, pickling).• Dry or wet drawing (usually several drafts with decreasing die sizes).• Heat treatment (continuous-/discontinuos annealing, patenting, oil hardening).• Finishing.

Wire drawing is a process in which wire rods/wires are reduced in size by drawing them through cone-shaped openings of a smaller cross section, so called dies.

The input usually is wire rod of diameters raging from 5.5 to 16.0 mm obtained from hot rolling mills in form of coils.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION



A.2 Wire A.2.1.1 Wire Rod Preparation

Air-cooling after rolling produces an iron oxide-layer (scale) on the wire rod surface. This layer is very hard, brittle and not deformable and must therefore be removed before any further processing can take place.

Two techniques for descaling wire rods are applied:

A.2.1.2 Drawing

Dry Drawing of WireDry drawing is typically used to draw wire rod (> 5.5 mm) to a product diameter of 1 - 2 mm .

Wet Drawing of Wire Wet drawing is typically used to draw wire with an intermediate product diameter of 1 - 2 mm to final diameter.

Mechanical descaling

Chemical pickling





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION



A.2 WireA.2.1.3 Heat Treatment of Wire

• Heat treatment of wire has different goals. • Different types of heat treatment are available depending on the type of steel and the final use. • Heat treatment also thermally removes soap and lubricant residues. • A considerable percentage of the output of the wire industry does not need any heat-treatment.

Annealing is one of the different methods to re-obtain a suited crystal shape.

Batch Annealing of Low Carbon Steel Wire. Continuous (In-Line) Annealing of Low Carbon Steel Wire. Continuous (In-Line) Annealing of Stainless Steel Wire.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION



A.2 WirePatenting • Patenting is a heat-treatment method typically used for high-carbon and alloyed steel products to create a special crystal structure, which allows easy further deformation.• Patenting is done by heating the wire to 850 - 1000 °C, then cooling fast to 450 - 600 °C.• Patenting is usually done continuously.Stress-relieving

The goal of stress-relieving is to remove internalstresses in the wire caused by a previous processing steps, without changing the shape and structure of the steel crystal.

Stress-relieving can be done at various temperatures (200 - 500 °C), dependent on the desired characteristics of the final product.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION



A.2 WireA.2.1.4 In- line Pickling

• In-line pickling is a typical operation after heat-treatment and/or before hot-dip coating of wire.• It is used to clean the wire and to remove metal oxides. • The wire is passed continuously through one or more acid baths. • The pickling takes place in a very short time (a few seconds).• After pickling the wire is rinsed in water.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire PlantA.3.1 Mass Stream Overview

Input/Output balance for a wire mill.

A.3 Emission Levels





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3.2 Wire Rod PreparationA.3.2.1 Mechanical Descaling of Wire RodMechanical descaling brings about solid waste:• Scale, mainly consisting of iron oxide (FeO and Fe3O4)• Traces of other metal oxides

A.3 Wire Plant

A.3 Emission Levels





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.2.2 Chemical Descaling/Pickling of Wire Rod • In chemical descaling liquid waste is generated in form of spent HCl or H2SO4 acid.• Aerosols can from mechanically when the wire rod is allowed to drip off.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.2.3 Application of Soap Carrier • Consumption and emissions associated with the application of soap carrier vary in dependence of the type of soap carrier, thickness applied and the wire rod diameter. No quantitative data is available at the moment.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.3 Drawing of Wire A.3.3.1 Dry Drawing• Dry drawing activities leave spent lubricant: mainly consisting of the drawing soap itself contaminated by degradation products.• Also soap dust arises, which can be controlled by proper encapsulation and filtering of the extracted air.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.3.2 Wet Drawing• Wet drawing is done in a watery emulsion of soap or oil is gradually contaminated by dragin of various products from previous process steps.The result is that the wet drawing lubricant needs to be replaced from time to time: The replacement frequency can be lowered by continuous removal of some of the contaminants by decantation or filtration.• Other waste streams are broken dies and cooling tower blowdown.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.4 Heat Treatment of Wire A.3.4.1 Batch Annealing/Bell and Pot Furnaces• Emissions from batch annealing furnaces comprises: - The combustion products from the firing - A small flow of the protective atmosphere (purge) containing decomposition products of the lubricant





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.4.2 Continuous Annealing/Molten Lead Bath• This process leads to solid wastes in the form of lead oxides and lead contaminated bath cover material.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.4.3 Patenting• Wastes and emissions are: - Air emissions arise from the furnace. Fresh air is mixed with the hot exhaust gas of the oven in order to convert the CO to CO2, prior to emission into the atmosphere. NOx and SO2 are negligible in this stream: reducing atmosphere/fuel is free of sulphur - Solid waste is generated by the lead bath as lead oxides and spent bath cover material - Waste water is formed in the quench bath





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.4.4 Oil Hardening & Tempering • Waste and emissions are dependent on: - The method of heating - The quench medium - The reheating method





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.4.5 Annealing of Stainless Steel Wire • A quantitative mass balance cannot be given.

A.3.4.6 Stress Relieving • The most important application is stress relieving of PC-strand: reinforcement wire that will be used in prestressed concrete.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.3 Wire Plant

A.3 Emission Levels

A.3.5 Noise Issues in a Wire Plant

The main sources of noise in wire processes are:

- Rotating equipment - Air-wipes or air-brushes which clean the wire using compressed air can have a high frequency noise - Pay-off units of wire rod have a particular repetitive noise - Burners of ovens





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION

A.4 Wire Mill


A.4.1 Storage and Handling of Raw Materials and AuxiliaresDescription:• All storage tanks for both fresh and spent acid must be equipped with a sealed secondary containment.• This secondary containment must be protected with an acid-resistant coating.• The loading and unloading area for the acids any potential leak is directly discharged to the waste water treatment plant.

A.4.2 Mechanical DescalingA.4.2.1 External Recycling of ScaleDescription:• The scale from mechanical descaling of wire consists mainly of metal oxides ( which is oild and water free).• This scale can be recycling to recovery the iron content.• Recycling is done or not depends to the interests of the industry.Main achieved environmental benefits: • Reduction to waste.

Reference Document on Best Available Techniques in the Ferrous Metals Processing Industy

A.4 Techniques





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION

A.4 Wire Mill


Hoods

Lateral extractions

A.4 Techniques

A.4.3. Chemical Descaling/ Pickling of Wire RodA.4.3.1 Optimum Range of Operation for HCl Pickling BathsMain achieved environmental benefits: • Reduction of acid emissions to air.

A.4.3.2 Pickling Tank Fume ControlDescription:Vapour and aerosols comming off tanks can be controlled by:Main achieved environmental benefits: • Reduction of acid vapours and aerosols emissions Reduction of fugitive emissions.• Improvement of working environment, protection of installation and equipment

A.4.3.3 Treatment of Extracted Air from Pickling Tank Fume Control

Description:

For reduction of acid vapour, droplets or aerosols emission can be used– Demister (for H2SO4) or scrubber (for HCl)

Main achieved environmental benefits: • Reduction of acid vapour, droplets and aerosols emissions.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION

A.4 Wire Mill


A.4 Techniques

A.4.3.4 Cascade PicklingMain achieved environmental benefits: • Reduced consumption of fresh acid• Reduced spent acid (waste)

A.4.3.5 Minimizing Carry-out from PicklingMain achieved environmental benefits:• Reduced carry-out of acid, reduced consumption of fresh acid• Reduced spent acid (waste)• Reduced pickling loss.

A.4.3.6 Separation and Reuse of Free Acid FractionMain achieved environmental benefits:• Reduced consumption of fresh acid• Reduced spent acid (waste)





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4.3.7 Regeneration of Spent AcidMain achieved environmental benefits:• Reduction of acidic waste

A.4.3.8 Reuse of Spent Acid as Secondary Raw materialMain achieved environmental benefits:• Reduction of acidic waste

A.4.3.9 Minimize Rinsing Water Consumption by Cascade RinsingMain achieved environmental benefits:• Reduction of water consumption

A.4 Wire Mill

A.4 Techniques





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4 Wire MillA.4.4 Shot Blast Descaling: Separation of Scale and Blast mediaDescription:• The shot blast system causes the scale to break and fall off the base metal

The blast cabinet descaling operationThe reclaim system retrieve the used shot and dust from the descaling operation The recycling system separating the shot particles from the contaminants and dust the cleaned shot particles are returned to a storage system

Main achieved environmental benefits:• Scale is collected separately and can be reused• Consumption of shot-blasting media is reducedA.4 Techniques





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4 Wire MillA.4.5 Dry DrawingA.4.5.1 Control of Air Emissions /Treatment of Extracted AirDescription:• A hood or cover is installed above of the parts (of machine) in contact with wire• The air within the cover is extracted• The extracted air can be treated by a filterMain achieved environmental benefits:• Reduction of emissions to air• Improvement of working enviroment limit the spread of lubricant-dust over the area around the drawing machine

A.4.5.2 Closed Loop for Cooling WaterDescription:The drawing operation heats both wire and drawing die both the dies and the wire are water cooled. To reuse the cooling water Wet cooling tower Main achieved environmental benefits:• Reduction water consumption

A.4 Techniques





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4 Wire Mill

A.4 Techniques

A.4.6 Wet DrawingA.4.6.1 Closing loop for cooling waterDescription:• The drawing operation heats both wire and drawing die through friction of the wire. • This heat is taken up by the lubricantMain achieved environmental benefits:• Reduced water consumption.

A.4.6.2 Cleaning of drawing lubricant/coolantDescription:Wire drawing lubricants, water-miscible oil emulsions or straight oils, accumulate metal fines during operationMain achieved environmental benefits:• Reduccion of waste drawing lubricant





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4 Wire Mill

A.4 Techniques

A.4.6.3 Treatment and Disposal of Waste Drawing Lubricant: Soap Emulsions

Description:• In case the quantities are small compared to other waste waters of the plant, the spent lubricant is mixed with otherwaste waters. •If the quantities are comparably big, the spent lubricants are treated separately by coagulation and precipitation, coagulation and flotation, membrane filtration, evaporation or other suited methods.

Main achieved environmental benefits:

• Reduced emissions to water

A.4.7 Batch Annealing of WireA.4.7.1 Burn Purge of Protective GasDescription:In order to keep an over-pressure in the "pots" or "bells", a fraction of the protective gas is continuously purged. Main achieved environmental benefits: Reduced emissions to air





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4 Wire Mill

A.4 Techniques

A.4.8 Continuous (in-line) Annealing of Low Carbon WireA.4.8.1 Lead-bath: Good HousekeepingDescription:• Maintain a protective layer or cover on the lead-bath • Prevent formation of dust while removing impurities from the lead-bath • Minimize drag-out of lead with the wire by using an anthracite gravel wipe or similar immediately after the lead bath• Apply a method that minimizes / eliminates the spread of lead dust that is possibly dragged out with the wire. Main achieved environmental benefits:• Reduce emissions from lead bath

A.4.8.2 Recycling of Pb- containing residues•Description:• Some Pb-containing residues originate from the Pb-bath. These residues should be stored separately and protected from rain and wind.• The wire industry depends on subcontractors for the final disposal or recycling of these residues.Main achieved environmental benefits:• Reduced waste disposal





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4 Wire Mill

A.4 Techniques

A.4.8.3 Operation of Quench Bath and treatment of waste water from quench baths in-line annealingDescription: As the water quality requirements for this bath are generally low, it is advised to use recuperated water for this purpose or to operate the quench bath in closed loop.Main achieved environmental benefits:• Reduced emissions to water

A.4.9 PatentingA.4.9.1 Optimised Operation of the OvenDescription: A slightly substochiometric mixture is used in the burners. In this way, all O2 is excluded from the oven atmosphere, in order to minimize the formation of iron oxides at the wire surface Excess CO must be converted to CO2 by adding air in a controlled way to the hot exhaust of the oven.Main achieved environmental benefits:• Reduced consumption in following process steps• Reduced CO-content





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.4 Wire Mill

A.4 Techniques

A.4.10 Oil Hardening and TemperingA.4.10.1 Oil Hardening and TemperingDescription:• Evacuation of the oil mist and removal from the extracted airMain achieved environmental benefits:• Reduction of fugitive air emissions, especially oil emissions.

A.4.11 Heat Treatment of Wire (Different Processes)A.4.11.1 Inductive Heating of wire Description:• The wire to be heated is guided through a coil; in this coil a magnetic field is generated.• The applicability of inductive heating is highly dependent on wire material, wire diameter and required temperature increase:Main achieved environmental benefits:• Air emissions from combustion are avoided in the plant





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.5 Wire Plant

A.5 BAT

For batch pickling, the following techniques are considered to be BAT:• HCl pickling: close monitoring of bath parameters: temperature and concentration.• In the case of high vapour emission: installation of lateral extraction and possibly treating of the extraction air for both new and existing installations. To reduce acid consumption, amounts of acidic wastes and waste water, the following techniques are considered to be BAT:• Cascade Pickling or reclamation of free acid fraction and reuse in pickling plant.• External regeneration of spent acid. • Recycling of spent acid as secondary raw material. Non-acid descaling if quality requirements allow.• Countercurrent cascade rinsingFor wet drawing lubricants, the following measures are considered to be BAT:• Cleaning and reuse of drawing lubricant.• Treatment of spent lubricant to reduce oil content in the discharge and/or to reduce wastevolume.• Treatment of discharge water fraction.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.5 Wire Plant

A.5 BAT

The best available techniques to reduce cooling water consumption are closed cooling-water loops for dry and wet drawing.

Burning of the protective gas purge is considered to be BAT for all batch annealing furnaces, continuous annealing furnaces for stainless steel and furnaces used in oil hardening and tempering

For continuous annealing of low carbon wire and patenting, the following measures are considered to be BAT:• Recycling of Pb-containing wastes in non-ferrous metals industry• Closed loop operation of quench bath.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION


A.6 Wire Plant


Acid regeneration process such as electrodialysis / bipolar membrane technology are under development or being tested. This technology which converts all acid again to free acid and metals to hydroxides is much too young / not proven / too expensive From analogy with more traditional membrane processes, a short membrane life is expected.





A.5 BAT


A.4 Techniques

EUROPEAN COMMISSION

Grupo 3:

Abad González, Soraya

Prada Uña, Raquel

Rodríguez Gutiérrez , Cristina

Villacorta Asensio, Milagros

Best Available Techniques in the Ferrous Metals Processing Industry

EUROPEAN COMMISSION

Gestión AmbientalCurso 2007-08

Documents

Reference Document on Best Available Techniques in the Ferrous Metals Processing Industry A.2 Processes and Techniques A.1 General Information A.3 Consumption