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Masaoka K.,Yokohama National University | Masaoka K.,Research Institute of Salt and Sea Water Science | Misumi R.,Yokohama National University | Nishi K.,Yokohama National University | Kaminoyama M.,Yokohama National University
Journal of Chemical Engineering of Japan | Year: 2014

To develop a new industrial crystallization operation or crystallizer capable of realizing a higher crystal growth rate, a method of enhancing apparent crystal growth through the use of fine-crystal adhesion was examined using a classified bed-type crystallizer. We were able to clarify the effects of incorporating a pump for applying shear stress to a supersaturated mother solution along the path between the supersaturating section and the crystal growth section of the apparatus. A fine-generator pump was found to be effective at creating a discharge flow from the path, stimulating nucleation by impeller-based agitation, and recycling the solution back into the path. We found that the number of fine crystals could not be increased significantly with crystallization in a normal classified bed-type crystallizer that excludes the use of a fine-generator pump, whereas these parameters were controllable using the fine-generator pump. As an indicator of the output of the fine-generator pump, we defined the agitation rate m3/m3, which is expressed as the ratio of the flow rates between the fine-generator pump and the circulation pump. The fine-generator pump is effective at enhancing crystal growth rates at agitation rates of less than 1 m3/m3 and at an operational degree of saturation of less than 1.4 g/L. The most effective agitation rate was found to be 0.5 m3/m3, and it was independent of the degree of saturation. The maximum crystal growth rate was found to be 160 μm/h at a degree of saturation of 1.4 g/L, which was about three times greater than the maximum crystal growth rate without the use of the fine generator. These results are effective for the actual method of enhancing apparent crystal growth, although elucidation of the mechanism based on the phenomenological model is necessary. © 2014 The Society of Chemical Engineers, Japan. Source


Noda Y.,Research Institute of Salt and Sea Water Science | Noda Y.,Yokohama National University | Asada T.,Research Institute of Salt and Sea Water Science | Kobayashi K.,Yokohama National University
Bunseki Kagaku | Year: 2010

In order to respond to the Japanese positive list system for residual agricultural chemicals in salt products, 116 agricultural chemicals were selected. For a scientific certification of safety compliance, an analytical method for all 116 residual agricultural chemicals in salt should be developed. In the present study, a simultaneous determination method for agricultural chemicals in salt by gas chromatography/mass spectrometry (GC/MS) was examined. Mixtures of agricultural chemicals were added to salt samples, and they were extracted by solid phase extraction (SPE). Among four SPE sorbents examined, a styrene-divinylbenzene copolymer (PS-2) column showed the best performance, where 94 agricultural chemicals could be successfully extracted. By the improved method with PS-2 column, 94 agricultural chemicals could be successfully detected with the recoveries higher than 70%, and relative standard deviations within 20%. Detection limits of targeted chemicals were less than 0.01 mg/kg. © 2010 The Japan Society for Analytical Chemistry. Source


Masaoka K.,Research Institute of Salt and Sea Water Science | Hasegawa M.,Research Institute of Salt and Sea Water Science
Kagaku Kogaku Ronbunshu | Year: 2012

To develop a method to simultaneously estimate the properties of salt (sodium chloride) products, namely, moisture content, mean particle size, and magnesium content, we conducted a basic test and a demonstration test. In the basic test, the relationships between these properties and the diffuse reflectance of salt products were examined on the basis of infrared diffuse reflectance of spectra recorded using a spectrophotometer. At all wavelengths, the diffuse reflectance of salt was found to change with changes in each property; and the degree to which each property contributes to changes in the diffuse reflectance depends upon the wavelength. Equations to predict the value of each property from the diffuse reflectance of multiple wavelengths were created from the relationships between each property and the spectrum data. Next, to create the optimum combination for simultaneous estimation, we selected the seven wavelengths that best average the prediction accuracies. In the demonstration test, the seven selected wavelengths were applied to a commercially available infrared analyzer. The effects of impurity content (other than magnesium) or any deviation in the mean particle size on the absorbance were found to be insignificant within the quality range of the manufactured salt product. Analytical curves that predict each property from the absorbance at the seven wavelengths were also created. These analytical curves showed good prediction accuracies. © 2012 The Society of Chemical Engineers, Japan. Source


Masaoka K.,Research Institute of Salt and Sea Water Science | Yoshikawa N.,Research Institute of Salt and Sea Water Science | Hasegawa M.,Research Institute of Salt and Sea Water Science | Misumi R.,Yokohama National University | And 2 more authors.
Journal of Chemical Engineering of Japan | Year: 2016

Effects of the feed location on crystal growth and agglomeration using a model of a classified bed type crystallizer were examined. Semi-batch crystallization tests were examined with a feed from one of various feed locations. The particle size distribution and the number of the product particles were measured. From the results of the investigations, it was concluded that a feed positioned inside the slurry phase of the crystallizer affects the crystal growth and agglomeration phenomena, though the knowledge about phenomena of ne crystals is inadequate. Positioning the feed within the slurry phase increases the crystal growth rate slightly at the bottom of the slurry phase, as well as the agglomeration of the seed crystals, by increasing the degree of supersaturation at the inlet to the crystallizer. However, when the feed is positioned in the upper part of the slurry phase, the feed interferes with the agglomeration by reducing the concentration of the mother solution. It was thought that we can control the size of the crystals that form in the crystallizer by moving the location of the feed to a point within the slurry phase. © 2016 The Society of Chemical Engineers, Japan. Source

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