Some Study related to Refractory Waste Management in Sweden : A move towards a greener and sustainable Swedish steel industry

University essay from KTH/Materialvetenskap

Abstract: Decades  ago,  1  ton  of  steel  required  80  kg  of  refractory  material.  While  the  scenario  has completely changed over the years. Today, 1 ton of steel needs approximately 11 kg of refractory material   depending   on   the   steelworks.   Refractories   are   accustomed   to   high-temperature processes,  for  example,  producing  steel,  glass,  etc.  The amount of  spent  refractories has  also increased  with the increase in demand for its production. For the manufacturing of refractories, there is a tremendous use of virgin raw materials but with the increase in price and reducing raw material   sources,   it  will   be  difficult  to   continue  in  that   way  in  the  future.  While,  the environmental  concerns  in  steel  industries  are  increasing  on  a  rapid  scale  such  as  global environmental pollution, natural  resource conservation, and the most important increase in cost for  landfilling.  Therefore,  achieving  zero  waste  and  proper  usage  of  material  from  spent refractories is necessary for economic and environmental reasons in future. This project work focuses on collecting information regarding the refractory waste management for  aid  towards   more   sustainable  Swedish  steel  industries.  The  project  is  carried  out  in collaboration  with  KTH  Royal  Institute  of  Technology  and  the  Swedish  steel  producers association  Jernkontoret.  This  work  focuses  on  a   survey   of  well-known  Swedish  steel companies Sandvik Materials Technology (SMT) AB and Höganäs AB. The scientific work concentrates on the investigation of MgO-C bricks mixed waste, collected from Mireco AB, up to a grain size of 20 mm. Three samples of varying compositions and different grain sizes were collected  from  the  recycling  site  and  processed  for  carbon  reduction.  On  several  trails,  the maximum  carbon  elimination  was  achieved at a  temperature higher than  800°C with holding time longer than 5h. The fines underwent mechanical pressing of 40 MPa to form pellets of 16 mm and 32 mm in diameter. The main traced elements of MgO, SiO2, CaO, Al2O3  and Fe2O3  can be utilized for applications in the agricultural industry. MgO is present in the maximum quantity (70-80%).  By  possible  extraction  of  MgO  from  the  fines  can  be  employed  in  the  crucible industry,  construction industry  and steel  industry for slag  formation. The MgO  in the form of supplements for magnesium deficient soils or calcium magnesium oxide for neutralizing the pH of  the  soil  by  balancing  the  acidity  can  be  employed.  The  compatibility of the  fines can be helpful  to  resolve  transportation  issues and benefit  convenient addition to processes. Overall, this  work  brings  to  the  fore  a  high  potential  for  using  such  waste  refractory  materials  forapplications besides landfilling with an emphasis on agriculture.

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