Pollution by waste from melts used in hardening, carburising and nitriding steel, and from heat-treatment melts contg. alkali nitrite/nitrate, is prevented by common destruction of (1) cyanides, cyanates and complex cyanides (I)and of (2) nitrates and nitrites (II). Powdery mixts contg (I) and (II) are reacted with one another, in molten or sinter sintered conditions, using a wt. ratio (II):(I)2.1(4), and reducing excess (II) by reaction with C or C-contg. substances in molten phase. Mixts of powdered salts are heated at least to formation of melt, partic. when C is added after reaction of (I) and (II), or powdered salts contg. (I) or (II) may be introduced into stirred melt of the other cpd gp. Reduction with C may be effected also during reaction of salt mixts. esp. at 50 degrees C above their melting temp.
展开▼
