Integrated technological and environmental solutions have become a key challenge for the iron and steel industry. The main ecological driving forces are:
As a result of repeated dust recycling to the LD (BOF) or EAF steel shop, the zinc content of the dust continually increases. Above a certain limit, various problems may arise such as shorter refractory lifetimes and ZnO caking in the cooler zones of the off-gas system. During certain phases of steelmaking, the zinc content of the emitted dust is typically in excess of 20%. We have therefore developed and installed a special on-line laser-based zinc measuring system in the latter's LD Works #3, which allows for the continual separation of these dust fractions and subsequent pelletizing. These pellets represent a valuable source of zinc for the industry and also reduce waste disposal costs.
Siemens VAI has developed a highly efficient sludge recycling process for wet dedusting systems. Following initial sedimentation in a settling pond, the sludge is filtered to reduce the total water content to about 30% by weight. The resulting filter cake is then thoroughly mixed with burnt lime. This reduces the water content, saves energy in the downstream thermal drying step and also serves as a binding agent for the subsequent granulation step. The final oven-dried product is pellets with a water content of less than 5%—strong enough to be stored, handled and charged into the converter together with scrap. Producers are thus able to recover ferrous components from the sludge and reduce their disposal costs.
Water is by far the earth's most important
natural resource. Therefore, it is essential that
all production facilities in an iron & steel works
must be optimized in respect to the interrelated
technical, economical and environmental demands.
This is also valid for industrial water streams
applied in cooling and offgas cleaning facilities,
etc.
Siemens VAI focuses on the installation of
technological solutions for the individual
production steps which minimize water consumption
and effluent emissions. In closed-loop systems, the
process water is recovered and treated in special
water treatment facilities. Outstanding examples of
this approach are the AIRFINE® Process
(agglomeration plants) and Siemens VAI's sludge
recycling system (BAUMCO® dedusting).
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