of Technology for Extracting Valuable Metals from Industrial Sludge
(Joint Program to Promote Technological Development with the Private Sectors)
RITE-TORANOMON LABORATORY in The Japan Research and Development Center for Metals
RITE-AGEO LABORATORY in Mitsui Mining & Smelting Co.
RITE-KAWASAKI LABORATORY in NKK Co.
In the technological development in fiscal 2001, process designing, bench-scale experiments, and process evaluation were carried out for each of the following processes:
1. Hybrid coarse separation;
2. Small-to-medium-scale smelting reduction;
3. Large-scale smelting reduction.
In the development of hybrid coarse separation, the electrodialysis concentration method and the water evaporation method utilizing low-temperature waste heat were compared regarding their performance in concentrating fluorine-containing effluent. It was found that to adopt the multi-stage water evaporation method is most appropriate. Based on this result, its treatment flow was designed and trial calculation of its cost was performed. Further, economy of the CaF2 and hydrofluoric acid recovery methods was evaluated at a plant scale of treating 150 m3 of fluorine-containing effluent per day.
In the development of small-to-medium-scale smelting reduction, bench-scale experiments were carried out six times, and its operational stability was confirmed. Based on this result, trial calculation of its cost was performed, and its economy was evaluated as a function of waste treatment cost. The trial calculation revealed that the investment would be recovered within approximately 1.8 years when the industrial waste treatment cost was 37,500 yen per ton.
In the development of large-scale smelting reduction, bench-scale experiments of smelting reduction were carried out six times, The reduction behavior and fluorine behavior were summarized, using the value of (heat required for smelting)/(input heat - radiation heat) as an index. The effects of theoretical combustion temperatures were clarified and the operating conditions were optimized. Based on this result, economy of the process combined with hybrid coarse separation was evaluated. The trial calculation revealed that the investment on the CaF2 recovery method would be recovered within approximately 2.7 years when the industrial waste treatment cost was 37,500 yen per ton. Also, it was indicated that the hydrofluoric-acid recovery method would achieve better economy.
In industrial application, it is important to closely watch the state of the industrial waste treatment market, site condition of a plant, and trends in legal regulations.