Sustainability

Iron and Steel

Iron and Steel

Our calcium- and magnesium-based products and minerals are used throughout the iron- and steel-making process as binders or flux agents to form slag. Slag removes harmful impurities, such as silica, phosphorus and sulfur. Lhoist products also help improve productivity and enable you to comply more readily with environmental legislation.

Steel is one of the biggest drivers of the world economy since it plays a major role not only in the construction and automotive industries, but also in mechanical engineering applications. Global production in 2012 was approximately 1.55 billion tons, worth about US$1,000 billion. Every ton of steel requires 30 to 70kg of lime and 100 to 200kg of limestone to manufacture.

Iron ore mining

Lime is used in many mineral processing steps. In the thickening phase, it facilitates ore fines recovery. It also controls the pH value to adjust pulp viscosity when transportation by pipe is necessary. Adding hydrated lime at this stage to increase the pH also enables water purification since it increases the precipitation of iron ore fines that can then be reclaimed.

Iron ore agglomeration

Our experts are available to help you maximize the performance of your iron ore agglomeration plants, using our products for sinter and pellet making.

Increased sinter plant productivity

Finely-crushed limestone is used as a flux in iron ore sintering. It adjusts the overall chemistry of the iron burden and plays a vital role in the formation of slag in the blast furnace process. Lime-based binders - sometimes including special clays - increase sinter plant productivity. Higher percentages of ultra-fine ore can also be combined with lime-based products with no loss of productivity.

Pelletization

Pelletization involves the agglomeration of ultra-fine ores with other raw materials, such as coal, hydrated lime and limestone. After the materials have been homogenized in suitable quantities (for ideal mass balance), the mixture is sent to a disc or a pelletization drum. The result is an 8- to 18-mm diameter pellet that is burned at approximately 1,350°C to increase its mechanical resistance. Hydrated lime is an efficient alternative binder to high SiO2 bentonite.

Correct basicity for improved efficiency

In pellet plants, finely-crushed limestone and dolomite result in products with the desired basicity (ratio CaO + MgO vs. SiO2 ). 

Quality blast furnace slag

Dolomite provides MgO that the process requires to achieve proper fluidity of blast furnace slag.

Hot-metal desulfurization

Lhoist's fluidized milled quicklime is specifically formulated for application in injection-based hot metal desulfurization (HMD) stations and can be used with both ladle and torpedo cars. The injection of a mixture of our fluidized milled quicklime and metallic magnesium into hot metal offers a cost-effective and environmentally-friendly alternative to calcium carbide-based HMD.

 

Lhoist's fluidized milled quicklime:

  • reduces slag volume
  • halves iron losses because slag viscosity is lower
  • lowers cost compared to other reagents
  • is safe to handle and store, as is the resulting slag

Lime slag can also be recycled.

It can be:

  • co-injected with magnesium powder
  • mono-injected as a lime-magnesium blend, once processed in our dedicated mixing plants

We provide technical assistance and follow-up during trials and start-up. We also offer data analyses and on-going R&D support.

Crude steelmaking

Quality slag = Quality steel

Quicklime is an important active product in eliminating silica and phosphorus in both converters and electric arc furnaces. The lime, after having absorbed impurities, forms a basic slag more quickly. Good quality lime produces a high-quality slag, an environmentally-friendly result that is easy to handle and treat.  

Extended refractory life

You can enhance the steel refining process by adding soft- and/or hard-burnt dolime in either a pure form or in a lime-dolime mix. Dolime extends the lifespan of refractory linings in converters. It also protects them from the aggressive effects of certain impurities found in hot metals. Adding dolime creates MgO in solution in the slag. This provides excellent buffering capacity. Excess MgO protects refractories and tap holes, reducing the need for gunning and repairs.

Secondary metallurgy

Swift slag formation 

Tailored mixes of our lime and dolime ladle metallurgy products act in the formation of synthetic slags. Quicklime facilitates the creation of slag and increases sulfur elimination. Dolime offers swift slag formation and protects the refractory.

Increased productivity

Dolime increases process speed to boost productivity and improve the resulting steel. It also protects refractory linings. The reduction in downtime required for refractory repair and maintenance also enhances productivity.

Environmental processes

Economical compliance with legislation

Flue gas, water and steel by-products must be treated to meet strict emission levels. Our steel and environmental specialists can co-develop products with you to meet regulatory requirements effectively and economically. We can help you eliminate or market certain steel by-products. For example, non-recyclable dust collected in the furnace extraction system can be inertized and applied as a strengthening material in mines. Converter slag can also be valorized for use in other markets.

Iron sludge deoiling

The industry faces increasingly strict environmental regulation, raw material shortages and high metal prices. These challenges make the implementation of dedicated processes to treat metallurgical residues and recover their valuable contents even more important. Oily mill scale is a typical by-product in steel making. It is possible to recover its iron content efficiently without impeding the main iron-steel flowsheet.

Engineering and technology supplier to the iron and steel industry, Paul Wurth, worked with Lhoist to develop an innovative deoiling process using a low temperature pyrometallurgical approach.

The process :

  • is easy to integrate into a normal steelmaking flowsheet
  • requires no specific residue preparation before it is charged in the furnace
  • is flexible with regard to sludge analysis
  • offers high-quality iron oxide
  • provides deoiled oxide that is easy to handle and charge to the sinter plant
  • has no impact on the plant’s other steel processes.

Flue gas treatment

Very low flue gas emission levels are being enforced on the release of harmful pollutants such as acid gases, dioxins, furans and heavy metals. To meet these requirements, you need a highly effective reagent and process that can be incorporated into existing installations. For flue gas treatment in a dry sorption system, SO2 and other acid gases are neutralized using hydrated lime. Sorbacal® SP is a hydrated lime with a high pore volume. It has been specially developed to increase the efficiency of dry flue gas cleaning systems and reduce disposal costs of residues.

We deliver tailor-made mixtures of lime comprising activated carbon, lignite coke or special minerals to trap pollutants (e.g. dioxins and furans). The neutralizing effect of lime combined with the micro-pollutant capturing power of the additives eliminates the negative side effects associated with the injection of pure activated carbon.

Scrubbing flue gas is an alternative process to dry sorption. Sorbacal® reagents neutralize the acid gases in spray sorption and wet scrubbers.

Read more : www.sorbacal.com

 

Acidic water neutralization

Lhoist’s SLS 45 neutralizes the acidic water resulting from pickling, rinsing and flue gas scrubbing. It also assures an appropriate pH level and precipitates heavy metals. Following sedimentation, water can be recycled back into your process or returned to the sewage system.

Read more : www.neutralac.com

Sludge stabilization

Water treatment generates a certain amount of sludge. Adding lime slurry before filtration makes the sludge easier to filter. Post-conditioning of filter cakes or centrifuge sludge facilitates handling and disposal.

Converter flue gas containing dust is usually washed. You can treat the resulting sludge with lime and recycle the iron-containing material back into your process.

If the sludge cannot be recycled, it can be dried and solidified using milled quicklime, making it easier to handle, transport and store.