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In situ composition measurements of Bunsen reaction solution by radiation probes

放射線プローブによるブンゼン反応溶液の組成計測法

久保 真治; 長家 康展

Kubo, Shinji; Nagaya, Yasunobu

熱化学法ISプロセスを実現するためには、化学プロセスの安全性,操作性を確保するうえでの必須技術である溶液組成計測法の開発が重要課題である。複数の放射線をプローブとする組成計測方法(マルチ放射線プローブ法)を用いることにより、従来法にはない優れた特徴(多成分溶液を連続計測,センサーが非接触で高温高腐食環境に耐える,簡便な実施)を持つオンライン組成計測法の確立が期待できる。ISプロセスの主要流体であるブンゼン反応溶液(ヨウ化水素相溶液,硫酸相溶液)を用い、マルチ放射線プローブ法の適用性を検証するためのラボスケール測定実験を行った。ヨウ化水素相溶液では、中性子水分計によって、高速中性子(カリフォルニウム線源)照射による熱中性子カウント値を取得した。供試溶液を、水,ヨウ化水素酸溶液,ポリヨウ化水素酸と変えると、溶液中の水素原子体積濃度とカウント値に相関が認められた。硫酸相溶液に混入したヨウ素を定量するため、二種類の$$gamma$$線密度計(セシウム線源及びバリウム線源)の出力を取得したところ、両者の出力値相関よりヨウ素混入の影響を検知することができた。これらにより、マルチ放射線プローブ法によるヨウ化水素相溶液組成及び硫酸相溶液組成の定量的測定の可能性を示した。

Measuring equipments are integral to chemical process controls. A stable hydrogen production by the Iodine-Sulfur thermochemical water-splitting process is relatively difficult because of lack of existing in situ composition measurement techniques for multiple components and corrosive solution. Composition regulations of Bunsen reaction solution is particularly important, since a closed cycle system provided with this process causes that the many streams with different composition return to this section. Accordingly Bunsen solution becomes changeable composition. Radiation probes have a potential for applications to determine this multiple component solution while the non-contact approach avoids the corrosive issues. Moreover the probes have features of the promptness, contact-less and sequential use. Laboratory scale experiments to evaluate these possibilities of the measurement were conducted with use of simulated Bunsen solution, HIx solution and H$$_{2}$$SO$$_{4}$$ solution, containing HI, I$$_{2}$$, H$$_{2}$$SO$$_{4}$$ and H$$_{2}$$O and sealed radiation sources. Radiations were counted, which were interacted with the solutions in various compositions around room temperature contained in vessels. For HIx solution, the obtained counting rates were correlated with hydrogen volume concentrations; moreover, the application of the Monte Carlo method suggests possibilities that the detector responses for HIx solution by the radiation probes are predictable. For H$$_{2}$$SO$$_{4}$$ solution, iodine atoms had significant influences on the relationship between output values of two $$gamma$$-ray density meters, cesium source as higher energy and barium source as lower energy. This results suggest that the neutron-ray probe, the $$gamma$$-ray probes of both lower energy and higher energy have possibilities to determine the composition of Bunsen solution of HIx and H$$_{2}$$SO$$_{4}$$ solutions.

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