The purposes of this paper are to evaluate the properties of flocculation and sedimentation of Aluminum Calcium Hydrates which are made by reaction of AlCl₃, and Ca (OH) ₂ at pH 11.0 or above, and to explore implementation of a closed system using these compounds.
We studied with Cold Soda Pulp (CGP) and Sodium Base High Yield Sulphite Pulp (HCGP) effluents.
The Results are summarized as follows :
1. It was found that treatment with Aluminum Calcium Compounds was relatively superior in COD removal to the Aluminum Hydroxid Method and the Massive Lime Method, and sludges from this treatment could be used closedly.
2. Changes of Aluminum Calcium Compound in this closed system are elucidated by Xray analysis.
3. In this closed system, supplies of AlCl₃ and CaO are very small because soluble Al₂O₃ and CaO are saved by carbonating the first thickner effluent below pH about 8.5.
4. Drainage properties of this sludge are superior to the Alminum Hydroxide Method and comparable to the Massive Lime Method.
5. This closed system is effected by other compouds (for example, S, SiO₂, Mg, ); sulpher reacts with Aluminum Calcium Hydrates, and SiO₂, Mg, react with Ca (OH) ₂ to form 3 CaO·E SiO₂, Mg (OH) ₂

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Comparison of corrosion activities, boiling-point rise, and swelling values of the waste liquors from the five different methods of magnesium-base semichemical pulp was made and discussed here. Remarkable weight loss of the killed steel was found in the waste liquors with low pH as shown in Fig. 1, but no weight loss of the stainless steel used for the test was observed. When the acidic liquors were neutralized with alkali, corrosion decreased considerably as shown in Fig. 2. However, the order of weight loss in both tests corresponded to the order of the pH value of the original waste liquors as follows : Two-components>High-yield sulfite>Magnefite>Vapor-phase magnefite>Slurry.
As shown in Fig. 4, except the viscosities of the waste liquor from the magnefite method, it was found that the higher the organic content of the supernatant liquor, the higher the viscosity within a range of 10 to 47% solids of the waste liquors. Prominent increase in viscosities of the five waste liquors with 60% solids was observed. The order of viscosities at 60% solids was quite different from that of viscosities at 47% solids and as follows : High-yield sulfite> Two-components>Slurry>Magnefite>Vapor-phase magnefite. On the other hand, difference in boiling-point rise between the five waste liquors was small.
Out of the five waste liquors with 47% solids, the two-components liquor revealed an unusually high swelling value, but those of the other four seemed to be considerably affected by the viscosity of the respective liquor. However, the order of swelling values of the five waste liquors with 60% solids was found to be completely accordant with the order of viscosities of the corresponding waste liquors described above. As a whole, findings presented here suggest that the magnefite or the vapor-phase magnefite method may be more preferable than the others within a range of the experiments studied.

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