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BEST AVAILABLE TECHNIQUES ON THE PRODUCTION OF IRON AND STEEL. Group 9. IRON AND STEEL INDUSTRY. This BREF covers the processes involved in the production of iron and steel in integrated steelworks. Iron and steel are important products that are widely used.

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iron and steel industry
IRON AND STEEL INDUSTRY
  • This BREF covers the processes involved in the production of iron and steel in integrated steelworks.
  • Iron and steel are important products that are widely used.
  • The production of crude steel in the European Union stood about 20% of world production.
steel production in the eu
STEEL PRODUCTION IN THE EU
  • The figure shows Germany to have the largest steel industry in Europe.
environmental relevance of the iron and steel industry
ENVIRONMENTAL RELEVANCE OF THE IRON AND STEEL INDUSTRY
  • The iron and steel industry is highly intensive both in materials and energy.
  • Only about half of the input results in crude steel and the other half are solids residues and off gases. *
  • Air pollution remains to be the most important issue of this sector.
  • Copper and nickel emissions to air from electric arc fournaces are also of significant relevance.
best available techniques
BEST AVAILABLE TECHNIQUES
  • Best available techniques are defined as:
    • Techniques

Include both the technology used and the design, built, maintenance and operation installation.

    • Available

Techniques developed in the relevant industrial sector, under economically and technically viable conditions.

    • Best

Most effective.

basic oxygen steelmaking and casting
BASIC OXYGEN STEELMAKING AND CASTING
  • Two thirds of crude steel are produced via the basic oxygen furnace (BOF).
  • The primary raw materials are liquid hot metal from blast furnace and steel scrap.
  • Raw materials are charged into the Basic oxygen furnace vessel.
  • Oxygen (99,5% pure) is blown into the BOF at supersonic velocities in order to oxidizes the carbon and silicon contained in the hot metal liberating great quantities of heat which melts the scrap.
bof bat
BOF-BAT

Process-integrated measures

  • PI.1 Energy recovery from the BOF gas.
  • PI.2 Lowering the zinc-content of scrap.
  • PI.3 On-line sampling and analysis of steel.

End-of-pipe techniques

  • EP.1 Primary de-dusting.
  • EP.2 Particulate matter abatement from pig iron pre-treatment.
  • EP.3 Secondary de-dusting.
  • EP.4 Dust hot-briquetting and recycling.
  • EP.5 Treatment of wastewater from wet de-dusting.
  • EP.6 Treatment of wastewater from continuous casting.
bof bat1
BOF-BAT
  • PI.1 Energy recovery from the BOF gas.

Generally, two systems can be used to recover energy from the BOF gas:

Combustion of BOF gas in the converter gas duct and subsequent recovery of the sensible heat in a waste heat boiler.

Suppression of BOF gas combustion and storage of the BOF gas in a gasholder for subsequent use.

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BOF-BAT
  • PI.2 Lowering the zinc content of scrap

A high zinc content in the blast furnace has an adverse affect on correct operation. This zinc mainly originates from the scrap charged into the basic oxygen furnace. The release of Zn can fluctuate strongly from one cast to another. The same problem, but to a lesser extent, applies to lead (Pb) or cadmium (Cd).

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BOF-BAT
  • PI.3 On-line sampling and steel analysis

Oxygen steelmaking is a batch process. In order to monitor progress samples are taken from the steel bath for analysis. It used to be necessary to interrupt oxygen blowing and tilt the BOF in order to take the sample. This was a time consuming process and it increased emissions from the BOF. In a modern plant samples are taken on-line during oxygen blowing by means of a sub-lance.

bof bat4
BOF-BAT
  • EP.1 Primary de-dusting

During oxygen blowing, BOF gas is generated.This gas is loaded with a large amount of particulate matter. The BOF gas is recovered for use as a fuel. Primary de-dusting is usually performed by venturi-type scrubbers (approximately 90% of the plants) or dry electrostatic precipitators. Prior to the venturi or the ESP, coarse particulates are usually removed by means of a deflector

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BOF-BAT
  • EP.2 Particulate matter abatement from pig iron pre-treatment
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BOF-BAT
  • EP.3 De-dusting of secondary off-gases

Secondary off-gases result from following operations:

Reladling and deslagging of hot metal.

BOF charging.

Tapping of liquid steel and slag from BOF (converters). Secondary metallurgy and tapping operations.

Handling of additives.

Continuous casting.

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BOF-BAT
  • EP.4 Dust hot-briquetting and recycling with recovery of high Zn concentrated pellets for

external

reuse.

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BOF-BAT
  • EP.5 Treatment of wastewater from wet de-dusting

In most oxygen steelmaking plants, scrubbers are used to reduce emissions to air from the primary gas flow. This potentially transfers pollution from air to water so the wastewater generated is usually recycled and treated before discharge. The water from the scrubbers mainly contains suspended solids; Zinc and lead being the main heavy metals present.

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BOF-BAT
  • EP.6 Treatment of wastewater from continuous casting.
electric steelmaking and casting
ELECTRIC STEELMAKING AND CASTING
  • Electric arc furnaces (EAF) play an important and increasing role in modern steel works concepts.
  • Today the percentage of electric arc furnace steel of the overall steel production in the EU are 35,3%.
  • In Italy and Spain the production of EAF steel is higher than steel production via BOF.
eaf bat
EAF-BAT

Process-integrated measures:

  • PI.1 EAF process optimisation.
  • PI.2 Scrap preheating.
  • PI.3 Closed loop water cooling system.

End-of-pipe techniques:

  • EP.1 Advanced emission collection systems.
  • EP.2 Efficient post-combustion in combination with advanced off gas treatment.
  • EP.3 Injection of lignite coke powder for off gas treatment.
  • EP.4 Recycling of EAF slags.
  • EP.5 Recycling of EAF dusts.
eaf bat1
EAF-BAT
  • PI.1 EAF process optimisation
eaf bat2
EAF-BAT
  • PI.2 Scrap preheating
eaf bat3
EAF-BAT
  • PI. 3 Closed loop water cooling system

The most relevant use of water considered here is the water used for the cooling of the elements of the furnace. Additionally, some water may be used for the cooling of waste gas or in the secondary metallurgy section.

eaf bat4
EAF-BAT
  • EP.1 Advanced emission collection systems

The primary and secondary emissions to air are of high relevance. The available abatement techniques should be fed with the raw emissions as complete as possible. Thus the collection of the emissions is important. The combination of 4th hole (in case of three electrodes) respectively of 2nd hole (in case of one electrode) direct extraction with hood systems (or furnace enclosure) or total building evacuation are the most favorite systems.

eaf bat5
EAF-BAT
  • EP.2 Efficient post-combustion in combination with advanced off gas treatment

Post combustion in the furnace is developed to use a maximum of chemical energy of the CO in the furnace and to improve the energy balance, but CO and H2 are never completely oxidised in the furnace; for this reason, it needs post combustion.

eaf bat6
EAF-BAT
  • EP.3 Injection of lignite coke powder for off gas treatment

In order to reduce organic micropollutants in the total off gas (primary and secondary emissions), especially PCDD/F lignite coke powder can be dosed to the duct before the bag filters.

eaf bat7
EAF-BAT
  • EP.4 EAF slag recycling

EAF slag can be regarded as an artificial rock, similar to natural rock, consisting of iron-oxides (FeO), lime (CaO), silicium-oxide (SiO2), and other oxides (MgO, Al2O3, MnO) EAF slags are characterised by high strength, good weathering resistance, and also high resistance against polishing. They also have properties, that make them suitable for use in hydraulic engineering.

eaf bat8
EAF-BAT
  • EP.5 EAF dust recyling

There are two method of dust recycling:

  • Recycling of precipitated dusts
  • Zinc recovery and removal of heavy metals
emerging techniques and future developments
EMERGING TECHNIQUES AND FUTURE DEVELOPMENTS
  • Scrap sorting.

The emissions of organochlorine compounds can be reduced by minimising the input with the scrap.

This compounds are contained in several technical devices like washing machines, hair driers, cooker hoods, fluorescent lamps…

emerging techniques and future developments1
EMERGING TECHNIQUES AND FUTURE DEVELOPMENTS
  • New furnace concepts.

In recent years new furnace types have been introduced that might be realised at industrial scale.

COMELT EAF

comelt eaf
COMELT EAF

ADVANTAGES

  • Integrated shaft scrap preheating.
  • Complete off gas collection.
  • A lowered sound level.
  • High productivity.
  • Reduction of total energy consuption.
  • Reduction of electrode consuption.
  • Reduction in maintenance costs.