Recent Improvements at Hosokura Lead Smelter and Refinery
597
front
side
Fig. 3 Hood of short rotary furnace
the floor around the short rotary furnaces is kept much cleaner compared to the
previous dusty environment. As a result, the blood lead concentrations of the workers
are decreasing.
Treatment of Wastewater Containing Fluorine at High
Concentration
Regulation of Fluorine in Hosokura Wastewater Treatment
Careful attention must be paid to the fluorine concentration in wastewater in Hosokura
area. Japanese standard of fluorine concentration of effluent water discharged from
the plant is 8 mg/L. But in Hosokura area, stricter regulation, 6 mg/L, is established
by regional ordinance.
Wastewater Containing Fluorine at High Concentration
in Lead Smelting
Figure 4 shows the process flow of the anode slime treatment. The anode slimes
generated in the lead electrorefining process contain H 2 SiF 6 (hydrofluorosilicic acid)
as the electrolyte. The anode slimes are melted and reduced in a short rotary furnace,
where H 2 SiF 6 is decomposed. HF (hydrogen fluoride) is transferred to exhaust gas.