This report describes a study conducted to analyze those factors related to the economization of the multistage flash evaporator used for seawater conversion and to calculate the optimum conditions for the operation of the evaporator.
As the result of this study, the for mulas obtained were as follows:
(1) N_opt.=0.16·C^0.5·E^0.158
(2) τ_opt.=1920·C^-0.5·E^-0.129
(3) γ_{m opt.}=375·C^-0.5·E^-0.158· {exp (0.88/E^0.029)-1}^-1
(4) F_opt.=0.0181+0.0332·γ_{m opt.}
where
N_opt.: optimum number of stages [-]
τ_opt.: optimum rate of product per unit area of condenser surfaces [kg/m²h]
γ_{m opt.}: optimum average temperature difference at outlet terminal of tubes in condensers [°C]
F_opt.: optimum ratio of steam consumption [kg of heating steam/kg of product]
C: unit cost of steam [¥/ton]
E: plant capacity [kg/h]

View full abstract

A study was conducted on the precipitation recovery of strontium from brine. In this study, the precipitation behavior of strontium was traced by using radioactive isotope ⁸⁹Sr, and those of calcium and magnesium by EDTA titration.
The separation of magnesium was carried out by applying the difference in the solubility among calcium, strontium and magnesium bicarbonate contained in the solution saturated with carbon dioxide. By bubbling carbon dioxide into slag containing carbonates, about 80% of magnesium was dissolved. After removing the most part of magnesium by carbon dioxide, strontium was separated by adding sodium hydroxide at temperature 80°C. By this procedure, more than 70% of calcium was precipitated as hydroxide, and the precipitation of residual magnesium was complete.
Strontium was then separated as sulfate by adding ammonium sulfate.
The over-all chemical recovery of strontium amounted to 55-60% after the abovementioned separation process.

View full abstract

For the improvement of quality of common salt and the protection of corrosion of salt making equipments, various methods have been studied by several groups of workers in recent years. The present investigation of the behaviors of iron on salt making process was undertaken in order to make a choice of the emphasis point and estimation of the effects to application of these methods, and to develop the methods for improving the quality of common salt. The examination was chiefly carried out in two factories of a common type in the Setonaikai district, Japan. The resuts were as follows:
1) The existence form of iron in salt making process was chiefly solid, and soluble iron was usually little except in bittern: Therefore, it is possible to remove most of these irons by filtration.
2) Inorganic iron. was accompanied by calcium sulfate, and therefore iron was decreased in the process of removing suspended calcium sulfate.
3) Iron in brine was regulated by the concentration operation by addition of crystal seed of calcium sulfate. But it was suggested that this operation was effective to the corrosion protection because of degassification of dissolved oxygen.
4) The material balance of iron in salt making process was obtained, the Contamintion of iron was, chiefly occured at evaporator, preheator and brine, and this iron was displaced chiefly to bittern and its slurry.
5) The salt washer using mother liquor was effective to the uniformity of iron content and the removal of iron in salt up to about 1 ppm. But tri-iron tetroxide (blackish granulated impurity) was not removed sufficiently.
6) The corrosion product on the wall of evaporating part of evaporator was chiefly detected as tri-iron teroxide and partially detected iron as carbide and iron oxychloride. The corrosion product on the wall of liquid part of evaporator was presumed as ferric hydroxide. Blackish granulated impurity in common salt was considered originate in the wall of evaporator, and reddish colloidal impurity was probably originated in the wall of liquid part of evaporator, preheator, and other contacted parts with liquid.
7) The Corrosion rate of evaporator calculated from these results was that mild steel was 0.26 mm/y, mild steel coated with wood was 0.09 mm/y, and cast iron was 0.06 mm/y. Corrosion cathodic protection with zinc was effective in any evaporator.

View full abstract

The author conducted tests on the compacting and unconfined compressive strength and soundness of the soil samples which had been added sodium chloride (0.2-3% weight) and portland cement (3-10% weight).
The compressive strength was measured after these soil samples packed in vinyl film were cured for 6 days at 20°C and were immersed in water for one day. The results obtained from the above tests were as follows;
1) When added sodium chloride and cement, their optimum moisture content decreased, but their maximum dry density increased as compared with the values obtained when none of sodium chloride and cement were added.
2) The degree of compressive strength and dry density increased with addition of sodium chloride, and it showed the maximum value when 1% salt was added.
3) On the execution of soil cement pavement in Hofu City, the addition of 7% cement was required in order to obtain the compressive strength of 30kg/cm². When sodium chloride was added, however, it was possible to obtain this strength by adding 4.5% cement.
4) As a consequence, it is possible to save about 20% of the cost of construction if sodium chloride is added to soil cement.

View full abstract