It is desired that the whole pulp stays in a flotator sufficiently long, not too long not too short, to satisfy the flotation time. The anther tried to develop a new flotator to contribute in this respect.
After ascertaining that two principles of counter current flotation and mechanical agitation flotation may be combined in a cell by a test, he designed a new flotator named SEVONETT in memory of the Seventy One Birthdays of T.T., because the fundamental experiment with the basic form of the set of the rotor and the stator was completed just a day before his 71st birth day.
In the cell of the SEVONETT flotator there are several units of the rotor and the stator, arranged vertically with a certain intervals. The pulp is fed at the center of the highest rotor, and draws out from the bottom. Air is blown into the pulp under each rotor. The rotor is devided into two parts by a horizontal plate. The pulp is rotated by the upper part, and the rotated pulp is scooped out radially by the vertical vanes of the stator which surrounds the rotor. The air blown into the pulp under the rotor is broken into many tiny bubbles. The air bubbles are carried out by the flow of the pulp into the annular space between the contour surface of the stators and the inner wall of the cell, and ascend against the pulp flowing down. Here the counter current flotation is realized.
Several fundamental surveys and practical tests have shown that the SEVONETT flotator is competent for practical use.
The speed of flotation in the SEVONETT flotator is high by virtue of the counter current priciple of flotation. The machine is economical with respect to its size, power and floor space requirement, and repairing.
The type of the machine is a Vertical Multistage Mechanical Air Flotator.
At present there are three 1.8m × 1.8m SEVONETTs at the Akabira Coal Washing Plant and one 1.2m × 1.3m SEVONETT at the Ponbetsu Coal Washing Plant, Hokkaido, Japan. The Akabira plant is going to have another four SEVONETTs in near future.

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The problems to be solved in order to improve flotation results of KuRoKo (Complex Sulfide Ore in Japan) has been disscussed.
This article is aimed to reveal some features of flotation results of KuRoKo by data available from [Mining & Cyanidation Practice in Japan, 1968] Compiled by Japan Mining Industry Association, as it seems that separation of the are is fairly progressing.
By simple graphic analysis of relations between amounts of the same mineral contained in feed and products of mills in the table, it can be qualitatively found that the separating efficiency is not usually worse than the others, while products from high grade feed as KuRoKo tend to have more impurities, and that there are much possibility and necessary of better results in separation of that kind of ore, because of its relatively wide variation.

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From several years ago, we have had drastic instrument for the purpose of rationalization and effectuation at the each section, such as, crushing stage reduction and simplification by the Hydro-Cone-Crusher, introduction of the Swirl Cyclone in the H.M.S section, two-stage straight classification system with a cyclone in the grinding circut and overall adapation of the Warman flotator in the flotation section, while we have carried out several improvements of general mill section, Taishu concentrator.
In this paper, a breif discription of the outline and results of some improvements at the grinding, flotation section are made,
1) To deal with the increase of tonnge by the development of the Somen deposits, we have compounded the two concentrators which consist of Pb-Zn rich are and other one is Cu-Sp rich are concentrator, in order to recover valuable minerals, simplification of are treatment process and are transportation. Results are successful, 3.95 million yen merits in apparatus of transportation, 30 yen/ton cost down reagents, increased flotation recovery of low grade Cu-minerals, remarkable Ag recovery up are obtained.
2) To increaee with, the Pb flash flotation recovery, we have carried out the following matter which is diminution of Pb metal circulating load, grinding density of 1st mill and which is consideration of operational condition of the Unit Cells in the closed grinding circut.
3) As considering of shape and material of the ball mill liner, we have disccusion for shape the comparision with groove liner and wave liner and for material about high Mn steel and rubber at the point of wearing cost and total cost followed by the dealing ability and grindability at the grinding circut.
Results are as follows. Wave liner is better than groove liner and rubber liner is better than high Mn steel in the wearing cost but it followed diminution of grindability.

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