Division 11

BAT is to prevent or reduce diffuse dust emissions from materials storage, handling and transport by using one or a combination of the techniques mentioned below.

If abatement techniques are used, BAT is to optimise the capture efficiency and subsequent cleaning through appropriate techniques such as those mentioned below. Preference is given to the collection of the dust emissions nearest to the source.

1. I..

   General techniques include:

   • the setting up within the EMS of the steelworks of an associated diffuse dust action plan;

   • consideration of temporary cessation of certain operations where they are identified as a source of PM₁₀ causing a high ambient reading; in order to do this, it will be necessary to have sufficient PM₁₀ monitors, with associated wind direction and strength monitoring, to be able to triangulate and identify key sources of fine dust.

2. II..

   Techniques for the prevention of dust releases during the handling and transport of bulk raw materials include:

   • orientation of long stockpiles in the direction of the prevailing wind

   • installing wind barriers or using natural terrain to provide shelter

   • controlling the moisture content of the material delivered

   • careful attention to procedures to avoid the unnecessary handling of materials and long unenclosed drops

   • adequate containment on conveyors and in hoppers, etc.

   • the use of dust-suppressing water sprays, with additives such as latex, where appropriate

   • rigorous maintenance standards for equipment

   • high standards of housekeeping, in particular the cleaning and damping of roads

   • the use of mobile and stationary vacuum cleaning equipment

   • dust suppression or dust extraction and the use of a bag filter cleaning plant to abate sources of significant dust generation

   • the application of emissions-reduced sweeping cars for carrying out the routine cleaning of hard surfaced roads.

3. III..

   Techniques for materials delivery, storage and reclamation activities include:

   • total enclosure of unloading hoppers in a building equipped with filtered air extraction for dusty materials, or hoppers should be fitted with dust baffles and the unloading grids coupled to a dust extraction and cleaning system

   • limiting the drop heights if possible to a maximum of 0,5 m

   • the use of water sprays (preferably using recycled water) for dust suppression

   • where necessary, the fitting of storage bins with filter units to control dust

   • the use of totally enclosed devices for reclamation from bins

   • where necessary, the storage of scrap in covered, and hard surfaced areas to reduce the risk of ground contamination (using just in time delivery to minimise the size of the yard and hence emissions)

   • minimisation of the disturbance of stockpiles

   • restriction of the height and a controlling of the general shape of stockpiles

   • the use of in-building or in-vessel storage, rather than external stockpiles, if the scale of storage is appropriate

   • the creation of windbreaks by natural terrain, banks of earth or the planting of long grass and evergreen trees in open areas to capture and absorb dust without suffering long-term harm

   • hydro-seeding of waste tips and slag heaps

   • implementation of a greening of the site by covering unused areas with top soil and planting grass, shrubs and other ground covering vegetation

   • the moistening of the surface using durable dust-binding substances

   • the covering of the surface with tarpaulins or coating (e.g. latex) stockpiles

   • the application of storage with retaining walls to reduce the exposed surface

   • when necessary, a measure could be to include impermeable surfaces with concrete and drainage.

4. IV..

   Where fuel and raw materials are delivered by sea and dust releases could be significant, some techniques include:

   • use by operators of self-discharge vessels or enclosed continuous unloaders. Otherwise, dust generated by grab-type ship unloaders should be minimised through a combination of ensuring adequate moisture content of the material is delivered, by minimising drop heights and by using water sprays or fine water fogs at the mouth of the ship unloader hopper

   • avoiding seawater in spraying ores or fluxes as this results in a fouling of sinter plant electrostatic precipitators with sodium chloride. Additional chlorine input in the raw materials may also lead to rising emissions (e.g. of polychlorinated dibenzodioxins/furans (PCDD/F)) and hamper filter dust recirculation

   • storage of powdered carbon, lime and calcium carbide in sealed silos and conveying them pneumatically or storing and transferring them in sealed bags.

5. V..

   Train or truck unloading techniques include:

   • if necessary due to dust emission formation, use of dedicated unloading equipment with a generally enclosed design.

6. VI..

   For highly drift-sensitive materials which may lead to significant dust release, some techniques include:

   • use of transfer points, vibrating screens, crushers, hoppers and the like, which may be totally enclosed and extracted to a bag filter plant

   • use of central or local vacuum cleaning systems rather than washing down for the removal of spillage, since the effects are restricted to one medium and the recycling of spilt material is simplified.

7. VII..

   Techniques for the handling and processing of slag include:

   • keeping stockpiles of slag granulate damp for slag handling and processing since dried blast furnace slag and steel slag can give rise to dust

   • use of enclosed slag-crushing equipment fitted with efficient extraction and bag filters to reduce dust emissions.

8. VIII..

   Techniques for handling scrap include:

   • providing scrap storage under cover and/or on concrete floors to minimise dust lift-off caused by vehicle movements

9. IX..

   Techniques to consider during material transport include:

   • the minimisation of points of access from public highways

   • the employment of wheel-cleaning equipment to prevent the carryover of mud and dust onto public roads

   • the application of hard surfaces to the transport roads (concrete or asphalt) to minimise the generation of dust clouds during materials transport and the cleaning of roads

   • the restriction of vehicles to designated routes by fences, ditches or banks of recycled slag

   • the damping of dusty routes by water sprays, e.g. at slag-handling operations

   • ensuring that transport vehicles are not overfull, so as to prevent any spillage

   • ensuring that transport vehicles are sheeted to cover the material carried

   • the minimisation of numbers of transfers

   • use of closed or enclosed conveyors

   • use of tubular conveyors, where possible, to minimise material losses by changes of direction across sites usually provided by the discharge of materials from one belt onto another

   • good practice techniques for molten metal transfer and ladle handling

   • dedusting of conveyor transfer points.