Development of the adsorbent for heat storage system using iron and steel making slag as source material

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The heat storage system using water vapor adsorption to zeolite materials is getting much attention because of extremely high energy density and flexibility of process. The composition of zeolite A can be shown as M_XAl_XSi_<1-X>・nH_O. The hydrophiic property of zeolite A is excellent because of high Al/Si ration in the zeolite A. The blast furnace slag mainly consists of SiO_2, Al_2O_3, CaO and MgO. Since Ca and Mg can be introduced to zeolite A as M, the blast furnace slag is a promising candidate for source materials of zeolite A. In the present work, the alkali hydrothermal process for production of zeolite A from the blast furnace slag as a source material was investigated. The following results were obtained;1.Zeolite A can be synthesized from SiO_2-Al_2O_3-CaO slag by hydrothermal treatment in the conditions;Temperature: 328-393NaOH: 0.5-3 MNaOH solution : slag (source material): 15 (mug)2.The zeolite A synthesized by the hydrothermal process was thermally stable up to 873 K.3.In order to obtain zeolite A from blast furnace slag in the hydrothermal process, the adjustment of composition was needed. It was required to decrease the content of CaO+MgO in the blast furnace slag. The less the content of CaO+MgO, The more the ratio of zeolite A to total products after hydrothermal synthesis.4.The rate of the hydrothermal reaction increased by using the ball-mill-type chamber.5.It was confirmed that the zeolite A obtained in the present work was applicable to the heat storage system because endothermic reaction was observed during the heating of the zeolite A.