| 摘要 |
PROBLEM TO BE SOLVED: To regenerate sludge as a value-added source with a low treatment cost by washing sludge generated in a zinc phosphate chemical treatment process with pure water followed by sintering it under a specific condition. SOLUTION: Sludge generated in a zinc phosphate chemical treatment process of a cold drawn steel plate and a zinc-plated steel plate in particular is washed with 5-25 times by weight, preferably 10-20 times by weight of water or pure water for not less than 3 minutes and then dehydrated to give sludge having a water content of not more than 50 wt.%, preferably not more than 20 wt.%, The sludge is sintered at 300-900 deg.C for 30-180 minutes, preferably 90-120 minutes to produce a phosphate-containing pigment having water soluble content of 0.1-0.3 wt.%, average diameter of 2-10μm, true specific gravity of 1.9-2.3 whereby it is possible to avoid expenditure due to disposal of the sludge or issue of disposal and to reuse the sludge as a useful source.
|
