ТЕРМОДИНАМИЧЕСКОЕ МОДЕЛИРОВАНИЕ ВОССТАНОВЛЕНИЯ НИКЕЛЯ И ЖЕЛЕЗА ИЗ МНОГОКОМПОНЕНТНОГО СИЛИКАТНОГО РАСПЛАВА В ПРОЦЕССЕ БАРБОТАЖА. СООБЩЕНИЕ 3. ВОССТАНОВИТЕЛЬ – КОНВЕРТИРОВАННЫЙ ГАЗ

Abstract

Common  method  of  oxidized  nickel  ores  processing  includes  ore feeding in countercurrent with high-temperature waste gases, melting in bubbling zone of a two-zone furnace, supplying carbonaceous  fuel and oxygen-containing blasting to produce melt that is reduced by  solid  reducing  agent  in  plasma  zone  when  heated  with  nitrogen.  The  main disadvantages of this method are low nickel content in alloy and  presence  of  silicon,  carbon,  chromium  and  other  impurities.  To  improve quality of ferronickel, it is proposed to use converted natural gas  in  plasma  zone,  which,  when  processed  by  plasma,  is  not  only  a heat  carrier,  but  also  a  reducing  agent.  The  method  is  based  on  assumption that at melt bubbling, composition of gas in bubbles that reached  bath surface is close to equilibrium. Gas-reducing agent is obtained by  oxygen conversion of natural gas with ratio α equal to 0.25; 0.35 and  0.50  respectively  (T = 1823 K).  Based  on  calculations,  dependencies  of content of nickel and iron oxides in silicate melt, degree of their reduction, ratio of slag and metal and nickel content in the alloy on total  gas flow determined as the product of the gas amount in a single batch  and the number of calculation cycles, as well as the amount of nickel  and iron, reduced by a single portion of gas are revealed. Regardless of proportion of hydrogen and carbon monoxide in source gases, increase  in  their  consumption  monotonously  reduces  content  of  nickel  oxide  in  the  melt,  while  content  of  iron  oxide  initially  increases,  and  then  decreases.  When  melt  is  blown  with  natural  gas  conversion  products  with  α = 0.25,  reduction  process  takes  place  due  to  hydrogen,  effect  of  CO  is  insignificant.  Flow  rate  of  54 m 3 /t  of  gas  allows  to  achieve  98.5 %  degree  of  nickel  reduction,  content  of  nickel  oxide  in  melt  is  0.028 %, ratio of slag and metal is 46 units. At equal gas consumption,  with increase in proportions of CO 2 and H 2 O in the initial mixture, by  increasing α, values of metals reduction from melt deteriorate: valu es  of  C NiO and  C FeO and  ratio  of  slag  and  metal  increase,  and  degree  of  nickel  and  iron  reduction  decreases.  Comparison  of  results  with  previously  obtained  data  on  metals  reduction  from  similar  melts  by  carbon monoxide and hydrogen has shown that hydrogen has greater efficiency, somewhat worse results are demonstrated when converted gas  with α = 0.25 is applied. Nickel reduction by converted gas (α = 0.35)  to reduction rate of 88 %, which corresponds to its consumption of  60 m 3 /t,  is  more  effective  than  by  pure  CO.  However,  final  values  of  degree of reduction using converted gas reach 90 %, while for CO they  approach 100 %.