S (Fe,t) --> X1 (O2,t) --> X2 (O2,kat) --> X3 (NaOH, недостаток) --> X4 (NaOH, недостаток) --> X5
S+Fe=FeS 2FeS+3O2=2FeO+2SO2 2SO2+O2=2SO3 SO3+NaOH=NaHSO4 NaHSO4+NaOH=Na2SO4+H2O