Authors, continuously from 3rd and 4th reports, have made clear up the effects of surfactants in O.A. method.
Especially in this report, they have discussed the relative merits of surfactant addition test in comparison with blank test, considering the relation between ash of clean coal by O.A. method, to be exact, ash of de-oil pellet and several factors, for example quantity of surfactant (Fig. 1), one of binder oil (Fig. 2) and mean size of the coal (Fig. 3).
Besides, as the pre-treatment method of O.A. one, they have brought forward and discussed the usage of alkali in order to improve de-ash efficiency (Fig. 4-Fig. 7).

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Most of the limestone produced is used as raw material for cement, iron and steel industries, and various civil engineering projects. Some of the limestone used which is of very high grade could be more profitably used for paper filler than for cement manufacture. The present paper was thus focused on problems related to limestone pulverization for paper filler production.
1) Limestone of high grade purity and whiteness was pulverized by Tower Mill Pulverizer in a dry system.
2) Tests were performed under various conditions in order to determine the one most suitable for the pulverization of limestone.
3) The particle size distribution analysis was performed by the Sedimentation Balance.
4) The most suitable pulverizing condition was as follows;
The weight of the pulverizing medium (steel ball) was 40 kg, the number of revolution of blower was 1260 rum and the weight of feed (limestone) was 3.5 kg.

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