Steel is used in many sectors such as the automobile production, construction, packaging and household appliances.

Steel production requires iron ore, coal, lime and iron-alloys, with gas emissions at each step.

1. Coke production (or coking)Coke is produced from coal in an airtight furnace. Coke is a material containing carbon that is almost pure and that is associated with lower levels of mineral elements. It is notably used as fuel in blast furnaces, to obtain cast iron which is subsequently transformed into steel.

The manufacturing of coke is accompanied by the emission of certain gases (hydrogen, methane gas, acetylene, ethylene, carbon oxides).

How is steel made?

Risks:CO (carbon monoxide, toxic) H2 (hydrogen, explosive)

Steel Industry

Application Note

Gazd’échappement

Airchaud

Gazd’échappement

400°

1800°

Laitier

Fonte

Minerai de fer,coke et castine

Airchaud

2. Blast furnaceHere, iron is extracted from its ore. Ore and coke solids are charged from the top through the blast tube. Hot air at 1200°C, blown into the pot furnace, causes coke combustion. Carbonic oxide will oxidize and form iron oxides (in other words it will absorb their oxygen and thereby isolate the iron), then descends down the furnace to become cast iron.

At the output of furnace, the residue, called blast furnace slag, floats on top of cast iron and is recycled or sent to other industrial sectors (cement works for example).

Blast furnace gas will be channelled through gas pipelines. The risk of explosion must be measured.

Risks: CO (carbon monoxide, toxic)H2 (hydrogen, explosive)

Blast furnace3. Refining (desulphurization unit)

This step will help remove the last unwanted elements, such as phosphorus or sulphur.

Risks:H2S (hydrogen sulphide, toxic)

Ore, coke

Exhaust gasesExhaust gases

Hot air Hot air

blast furnace slag

Cast iron

Charbon

Coke

Oxygène Convertisseur

Mineraide fer

Hautfourneau

Élaboration de l’alliage par élimination d’impuretés

Coulée

Fonte

Acier

5. Continuous or ingot castingThe molten steel continuously flows into a bottomless mould. While passing through the mould, it starts to solidify when it comes into contact with walls that are cooled with water. The moulded metal descends, guided by a set of rollers, and continues to cool. When it reaches the outlet, it is solidified and cut at the wanted lengths.

Risks: O2 deficiency (nitrogen line in the cellar)CO (near the steel gas meter)

6. Rolling millRolling is used to shape the material.

4. SteelThis step allows for cast iron to be turned into steel: the molten cast iron is poured over a bed of scrap and the unwanted elements (hydrogen sulphide, ammonia) contained in the cast iron are burnt by blowing pure oxygen, which will form carbon monoxide and produce heat.

This is how raw liquid steel, that is still imperfect, is obtained. It will then be refined by removing the remaining impurities.

When the carbon content of the molten bath is at the desired level, the alloying elements are added and the liquid steel is poured into a pre-heated ladle.

The steel gas is made up of 75% CO and 3% hydrogen.

Risks : CO (carbon monoxide, toxic)H2 (hydrogen, explosive)

Oxygen furnace

Oxygen

Ore

Blast furnace

Cast iron

Converter

Coal

Development of the alloy by eliminating impurities

Steel

ingot casting

The Fixed Gas Detection People

The Fixed Gas Detection People

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MX52

OLCT100

OLCT60

MX62

Oldham proposes The new OLCT 100 gas detector: designed for

explosive, toxic or oxygen gas detection, it is available as Wheatstone bridge output or 4-20mA version. ATEX certified, the OLCT 100 is available in ADF or intrinsically safe versions. SIL 2 certified according to EN5410, the OLCT 100 combines robustness, reliability and a longer service life.

The new OLCT 60 gas detector: available in ADF or intrinsically safe versions, with display, fixed or mobile versions for non-intrusive calibration to save considerable time during maintenance operations.

Warning, the presence of hydrogen interferes with the measurement of carbon. Thus 1000 ppm of H2 will generate a 450 ppm CO signal and could cause false alarms. At Oldham, we have developed a cell with low interference. From now on, 2000 ppm of H2 generates a signal of only 90 ppm CO. This enables you to: • have precise and reliable protection • obtain correct VLE and VME • prevent delayed alarms

MX 52 controller: certified to SIL 2 according to EN61511, this controller is available in a rack version that lets you monitor up to 16 measuring points. As an option, it has a standby power (435x315x120 mm), equipped with a 24V 12A charger and 24Ah batteries (Part number 6312888).

MX 62 numeric controller: certified to SIL3 according to EN50402 and allows connection of up to 64 sensors. Its modularity significantly reduces wiring costs and its reliability will ensure minimal maintenance.

Remember to include all required accessories.

SOLUTIONS AND BENEFITS

Discover our whole range of products atwww.oldhamgas.com

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