Bulletin of the Society of Sea Water Science, Japan
Online ISSN : 2185-9213
Print ISSN : 0369-4550
ISSN-L : 0369-4550
Volume 61, Issue 1
Displaying 1-9 of 9 articles from this issue
  • Ken-Ichiro SOTOWA
    2007 Volume 61 Issue 1 Pages 3-8
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    In a salt crystallization process, a large amount of energy is consumed for the evaporation of water. Since the amount rises almost proportionately with an increase in the production rate, the strategy for energy saving becomes more important in high-throughput processes. Typically, a reduction in energy cost was achieved by employing multi-effect processes and a heat exchanger network for heat recovery. In this study, a design support system for deriving an energy-efficient salt crystallization process was developed. Simultaneous optimization of multi-effect process and the heat exchanger network was tackled by combining the pinch technology and genetic algorithm. A four-effect process was used as an example process and its optimal design condition was derived using the system. Usually the vapor rising from a crystallizer is used to heat the crystallizer in the next stage. However, the solution indicated that for optimizing the energy efficiency, the vapor should be used to heat the brine or the mother liquor entering the crystallizer. One of the problems of the system was that it was impossible to pose limitations in the number of heat exchangers. Therefore, the system was modified in such a way that the optimal combination of hot and cold streams was derived by an exhaustive search method. The results obtained using the modified system showed a heat exchanger network similar to that obtained using the original system.
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  • Meguru KAMINOYAMA, Kazuhiko NISHI, Ryuta MISUMI
    2007 Volume 61 Issue 1 Pages 9-16
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    The influence of operating conditions on the crystal growth rate of salt particles was investigated to realize both a high suspension density and a high crystal growth rate, for in order to improve the efficiency of the salt crystallization process in an evaporation crystallizer. A semibatch-type, stirred vessel fitted with a draft tube was used as the crystallizer. First, a method of direct heating with a coil-heater set around the outer side of the draft tube was investigated in order to attain a high evaporation rate in the vessel. Subsequently, operating conditions, such as heating rate, γe, and the amount of initial injection of the seed crystals, M0, were investigated in order to attain both a high suspension density and a high crystal growth rate. It was clarified, as a result, that a crystal growth rate higher than 300μm/hr on the basis of D90 and a suspension density higher than 30 vol% ca n be maintained under the conditions of γe=804kg/hr, and M0=0.05 to 0.10kg. Thus, the feasibility of greatly improving the efficiency of the salt crystallization process in an industrial evaporation crystallizer was verified by these investigations.
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  • Kaoru ONOE, Masakazu MATSUMOTO, Yoshinari WADA, Masayuki WADA
    2007 Volume 61 Issue 1 Pages 17-23
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    The objective of this study is to investigate the adequate crystallization conditions that are suitable for the acceleration of crystallite growth of sodium chloride (NaCl) owing to the production of elementary-minute crystals under specified conditions such as higher suspension density and supersaturation. A mixing-type evaporation crystallizer that is easy to atably manipulate the vaporization condition of water was chosen as the experimental apparatus. NaCl crystals were grown by means of semi-batch type reaction in which the saturated NaCl solution was continuously supplied into the brine solution (evaporated seawater) including a specified weight of seed and fine crystals, and relation between the initial weight ratio of elementary-minute crystals based on seed crytsls (ξ) and NaCl crystallite growth were examined. A separable-type flask (1L) was used as the crystallization vessel. A propeller-type mixing impeller with four blades was installed in the vessel, and the mixing rate was set at 300min-1. The evaporated steam was condensed using the Liebig condenser and trapped within the beaker. The total salt concentration of brine (evaporated seawater) was 250g/kg and the ratio of NaCl to the total salt weight was set at 90wt%, and the evaporated solution (mother solution) was prepared at 4.7times concentration of brine. The vaporization rate of water was 0.011min-1, and NaCl concentration was maintained at 175g/kg. Initial weight ratio of seed crystals ([ωs]0) was changed in the range from 9.1 to 23.1wt% by the addition of seed crystals that have an average size of 324μm. ξ was changed in the range of 0.002-0.094 by the addition of minute crystals (average particle size: 8μm). Furthermore, an antisolvent (Et-OH) was added into the crystallizer, and elementary-minute crystals were generated in the suspension. Time changes in the physicochemical properties of both solution (mother solution weight, concentration of NaCl) and solid products (total weight, shape observation by a digital microscope, size distribution, and identification by XRD) were measured. Experimental results indicated the following 1) the crystallite growth of NaCl was accelerated owing to the production of elementary-minute crystals at 9.1wt% in [ωs]0, 2) when minute crystals (average particle size: 8μm) were supplied into the crystallizer at [ωs]0 of 16.7wt%, no acceleration of the crystallite growth was observed regardless of ξ, 3) when antisolvent (Et-OH) were added into the crystallizer at [ωs]0 of 16.7wt%, average crystal growth rate showed a maximum value at 0.024 in ξ, 4) under these experimental conditions, the deterioration of crystal purity was not observed accompanying the acceleration of crystal growth rate.
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  • Hiroshi TAKIYAMA, Kyoko KAWANA
    2007 Volume 61 Issue 1 Pages 24-28
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    Industrial crystallization should be carried out under high suspension conditions in order to obtain NaCl products efficiently. However, the nucleation rate rises under such conditions. Excess nuclei cause wide crystal size distribution (CSD) with a small mean size. Therefore, it is necessary to control the number of fine crystals in a crystallizer. This study focused on and discussed undersaturation operation with the NaCl-water system. Based on the experimental results, the destruction mechanisms of fine crystals were discussed and a novel operation technology for controlling the number of fine crystals was proposed. Undersaturation operation in this study was carried out by injection of dissolution water into the supersaturated solution. The following mechanisms contributed to the decrease in the number of fine crystals in the product by injection of dissolution water.(1) Preferential dissolution of fine crystals.(2) Inhibition of generation of fine crystals generated by crystal surfaces. It became clear that CSD was improved by the injection of dissolution water, and the injection operation strategy of dissolution water was proposed.
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  • Koji MASAOKA, Masami HASEGAWA
    2007 Volume 61 Issue 1 Pages 29-33
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    The effect of the number of suspended fine crystals in a mother liquid on the crystal growth rate of sodium chloride was studied using a fluidized-bed-type crystallizer, as a fundamental study for obtaining a high crystal growth rate. In the experiment, the increase in crystal weight caused by crystal growth was regarded as proportional to the elapsed time. The relationship between the number of fine crystals in the mother liquid and the ratio of the weight increase rate to the super-saturation was almost as linear. Therefore, the crystal growth rate basis on mass can be expressed as (dw/dt)av=(A+BNfine)Δ C. In addition, the effect of the high crystal growth rate on the amount of liquid inclusion was studied. Concerning the crystal products of every experimental condition, the difference of the decrease in crystal weight at 873K and at 413K was measured and regarded as the weight of water in the liquid inclusion. Concerning the results of the experiments, the increase in growth rate scarecely affected the weight of liquid inclusion in the crystal products.
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  • Kenji SHIMIZU
    2007 Volume 61 Issue 1 Pages 34-36
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    In the salt industry, the control method for production rate is not yet established because the crystal number substantially depends on the secondary nucleation, agglomeration and breakage under various crystallization conditions. In this work, the in situ measurement method of turbidity of suspended crystals in a crystallizer was proposed by using a light sensor. In NaCl evaporation crystallization, the relationship between the nucleation rate and the evaporation rate was obtained. This system may be useful for controlling the production rate and the design of the crystallizer.
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  • Izuru KAKUTA
    2007 Volume 61 Issue 1 Pages 38-53
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    Nowadays various anthropogenic pollutants including endocrine disrupting chemicals (EDCs) are widely spread in natural water. Most of the major rivers being flowed through urban and industrial areas or agricultural land, and the closed coastal seawater area fed by these rivers have become highly contaminated with some man-made substances and their by-products. The appropriate assessment of environmental impacts for coastal organisms is, therefore, is required.
    In order to understanding the effects of anthropogenic pollutants on fish and other organisms inhabiting coastal seawater areas, physiological, biochemical and immunological indicators were investigated. The major topics were the effects of deoxygenation, cement effluents, heavy metals and anthropogenic pollutants including EDCs.
    Bacterial composition in sediment, δ13C and δ15N values of benthic organisms, O2 consumption, renal erythropoietin and hepatic adenylate energy charge of fish were effective anoxic biomarkers. Hatching rate and the cough reaction frequency of fish were available as a biomarker of the pollution caused by cement effluents. Elemental compositions in the bioactive tissues of some organisms and the otoliths of fish were available for grasping of internal metal sequestration and its ecotoxicological relevance. As a mean of assessing anthropogenic pollution, it was advisable to investigate the relationship between hepatic microsomal cytochrome P-450 and brain acetylcholinesterase, or plasma total thyroxine or the phagicytic activity of granulocytes or gonad-somatic indices of flat fishes, for example, marbled sole.
    There were also reported a few instance on environmental bioremediation through marine algae and bacteria.
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  • Toshio SATO, Tomoyuki KUWABARA, Shushi SATO
    2007 Volume 61 Issue 1 Pages 54-65
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
    To avoid a food crisis caused by the population explosion, preservation of resources and the environment aswell as an increase in biological production in shallow seas are essential in Japan, which is surrounded by water.
    However, since resources and the environment have been harmed by the ocean dumping of fly ash (FA) and clinker ash (CL), gravel extraction for aggregate and industrial by-product, we developed waste use-concrete-blocks containing these wastes for seaweedbeds. Then we investigated the preservation of resources and the environment and the increase of biological production in shallow seas using these beds to solve these problems.
    In the first experiment, the durability and the strength of five mortar test pieces were measured to form a seaweedbed. The five test pieces were Plain (normal mortar), FA&CL, FA&CL+zeolite, FA&CL+molding sand and FA&CL+zeolite+molding sand. In the second experiment, harmful materials, extracted from FA&CLmortar test pieces by elution test were investigated to examine their influence on the marine environment and marine life.
    Furthermore, to investigate how well aquatic life can growon the mortar test pieces, the mortar test pieces wereimmersed in seawater, and then biomass of biofilm was measured the quantityof ATP, chlorophyll a, and FDA decomposition activity.
    The results of the first experiment showed that recycled waste-use-concrete containing FA, CL, molding sand and zeolite had sufficient strength for seaweed beds. The results of the second experiment showed that the test pieces were also safe forseaweed beds since there was hardly any trace of heavy metals or organic phosphorus detected. The results of last experiment were: (1) The quantity of ATP of three types of zeolite-molding sand system pieces (FA&CL+zeolite, FA&CL+molding sand and FA&CL+zeolite+molding sand) was almost equal to the Plain or larger than the Plain.(2) The quantity of chlorophyll a was FA&CL+molding sand>FA&CL+zeolite>FA&CL+zeolite+molding sand=FA&CL>Plain.(3) FAD decomposition activity was roughly the same as that of the Plain.
    Based on the above fundamental results, three types of large tes tconcrete-blocks were prepared: plain (normal concrete), FA&CL (concrete containing FA and CL as aggregate) and FA&CL+Zeolite+Fe including molding sand (concrete contained FA, CL, Zeolite and Fe including molding sand). Five blocks of each type formed each unit, and then, they were sunk in the test sea area at a depth of 5min two layers.After that, four diving surveys were conducted over a period of one year and nine months. In this investigation, the Quadrate Method was employed to measure the amount of seaweed and the Line Transect Method was used toobserve the swarm characteristics.
    In the results, the amount of seaweed on FA&CL+Zeolite+Fe including molding sand was equality or greater than that on the other two types of blocks. This means that aquatic life was able to suitably adhere and grow on the blocks containing FA&CL+Zeolite+Fe including molding sand. Furthermore, the amount of seaweed on the seaweed-bed was greater than thaton the adjacent seaweed-beds made of natural stones. As a result, the blocks made of FA&CL+Zeolite+Fe including molding sandaccelerate the formation of seaweed-beds, and therefore provide a good substrate for seaweed-beds.
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  • Display Term on Edible Salt (1)
    Noboru OGATA
    2007 Volume 61 Issue 1 Pages 66-68
    Published: 2007
    Released on J-STAGE: February 19, 2013
    JOURNAL FREE ACCESS
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