Candidate measures for integrated pollution prevention and control presented in this section usually concern more than one environmental medium or one input at a time. The primary intention of a technique, though, usually aims towards the protection of a single sphere4 (eg.
protection of air quality, reduction/use of solid wastes, improvement of energy efficiency or productivity). Table 4-1 gives an overview of modern techniques applied within the secondary steel industry both for production purposes and for environmental protection purposes. Each technique is provided with a reference mark, which helps to identify the according section in the text. The table depicts the qualitative and quantitative tendencies of effects caused by the
4 Inter alia caused by the fact, that regulations on environmental protection focused on controlling releases into separate media for a long time.
different techniques on the media and on resource consumption, or resource saving (use). All the techniques listed with a reference mark are candidates for BAT. Cross media effects of techniques can be identified by indications of several effects on media or resources. Most of the listed modern techniques are applied within production plants of the secondary steel industry in Germany.
The techniques in the Table are divided into 4 groups. Each part represents a group of techniques, either primary applying to a particular medium or mainly to improve production technology itself.
The first set of measures contains modern techniques, introduced within the last two decades in order to improve production technology, mainly with respect to productivity and cost efficiency. These techniques also include measures aiming towards a reduction in energy consumption within the steelmaking process, as a reduction in total or specific energy consumption usually implies a reduction in costs. Also modern concepts concerning the furnace technology itself are presented.
Sets two, three, and four represent techniques, that have been mainly implemented to comply with demands on environmental protection, but eventually also to use valuable outputs besides the steel. Set two deals with techniques concerning chiefly the protection of the medium air.
Set three looks at different methods for the preparation or treatment of solid releases, that result from the steelmaking process (eg. slags, precipitated dusts, refractory breaks). Set four draws up possible measures for the handling of water flows possibly used or generated in the steelmaking process.
The construction of Table 4-1 shows available techniques in the rows, grouped the above mentioned way. In the columns are indicated qualitative environmental effects of each technique on the media, i.e. impacts on the amount of resulting emissions (eg. prevention), impacts on the consumption of energy and inputs, the effects on the collection performance for emissions into the different media, as well as the abatement potential for emissions for each medium (control). The columns "Collection of process emissions" and "Abatement of process emissions" are mainly related to the medium air, as for this medium primary measures to avoid the waste gas yield are not available and for this reason collection and abatement of the resulting emissions is the most important task. The consumption of input and energy is considered in two categories, "Consp. intern" and "Conspt. extern", to separate internal (within an EAF plant including secondary metallurgy) from external (eg. external dust treatment processes) effects. Furthermore, the effects of the techniques on the productivity and on the noise performance of electric steelmaking plants are indicated, too. The final three categories assign the techniques to the groups state of the art, retrofit measure, and emerging
technique. The indicated effects on the different media are not complete, but selected with respect to important impacts. The use of Table 4-1 is explained by means of the example G5.
Generally, arrows down (ê) indicate savings of inputs or energy and a reduction of emissions into media. They also show effects of abatement measures with relieving tendencies for the environment. On the contrary, arrows up (é) indicate an increase of emissions, consumption, etc. G5, the use of foaming slag practice, has several impacts on the production process. With respect to process emissions into the medium soil, it has two contrary effects. On the one hand, it saves refractory material by protecting the furnace lining from extreme heat radiation.
This means a lower amount of refractory breaks possibly has to be land-filled or treated (soil ê), it also means a saving of intern inputs (lining, conspt. intern ê). On the other hand, foaming slag has a lower density than normal slag, so the volume of slag initially obtained increases (soil é), possibly leading to problems in plants using bucket, for the moment [50].
However, the tapped slag is also degassing again in the slag bed and partially reducing its volume. Furthermore, foaming slag practice decreases the required energy input by a better heat transfer (conspt. intern ê). It increases productivity and can be considered as a retrofit measure as well as state of the art in modern (commercial steel) electric steelmaking.
Moreover, Table 4-2 depicts selected data for examples of electric steelmaking plants in Germany. It provides, in anticipation of the rest of this chapter, information on applied technologies within German electric steelmaking plants.
Table 4-1: Available Techniques for Integrated Pollution Prevention and Control (1)
Table 4-1: Available Techniques for Integrated Pollution Prevention and Control (2)
Table 4-2: Selected data for electric steelmaking plants in Germany (1)
Table 4-2: Selected data for electric steelmaking plants in Germany (2)
PSAG, Peine GMH GmbH
Georgsmarienhütte
Stahlwerke Thüringen GmbH, Unterwellenborn
In operation since 1995 1994 1995
Furnace type DC Produced steel grades carbon steel carbon steel carbon steel
Tapping weight [t] 100 125 120
Nominal apparent power of current transformer [MVA]
140 130 120
Raw materials scrap scrap scrap
Cooling system water cooled side walls and roofs
water cooled side walls and roofs
water cooled side walls and roofs
Tapping system EBT EBT EBT
Capacity [t/a] 750,000 600,000 600,000
Additional burners gas burners oxygen gas burners oxygen/natural gas burners (7)
Additional fuels coal coal coal
Emission collection measures 2nd hole, hood
2nd hole, roof hood
2nd hole, ladle furnace dedust-ing, big furnace enclosure Off gas cleaning system post combustion
chamber with Energy aspects recovery of waste gas
heat
recovery of waste gas heat
water cooled ducts Secondary metallurgy ladle furnace
vacuum degassing
ladle furnace vacuum degassing
ladle furnace
4.3 General developments in modern production technology (including energy