Nickel sulfide formation from nickel-containing steel residuals in the glass batch has been assumed for some time. Melting trials were carried out with a soda-lime-silica glass batch containing steel particles with 20% nickel. Five steps can be distinguished: sweating out the less noble elements; formation of a mixed iron nickel sulfide phase in equilibrium with the remaining iron nickel alloy; enrichment of nickel in the alloy and the sulfide phase,until complete elimination of iron; sulfidation of the remaining pure nickel and formation of a nickel-rich sulfide; oxidation to NiS. The reaction cascade found experimentally is confirmed by the authors own thermodynamic calculations. Literature data show that nickel sulfides containing more sulfur than 1:1 composition are not stable in the melt and decompose in a small "explosion".
