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Wakkanai, Japan

Kurokawa A.,Hokkaido University | Togawa J.,Wakkanai Green Factory Co. | Nabeshima Y.,Hokkaido University | Nagano K.,Hokkaido University
Kagaku Kogaku Ronbunshu | Year: 2011

Isotherms Moisture absorption by porous materials with mesopores and micropores is generally evaluated by measurement of the water adsorption isotherm and analysis of the pore distribution by the nitrogen adsorption method using completely dry samples. In practical use, however, the adsorbent contains some water depending on the environmental conditions. To evaluate the pore distribution accompanied by the water adsorption, the nitrogen adsorption method was modified by using a frozen sample, which was dipped into liquid nitrogen after the water adsorption had reached equilibrium. Water adsorption was found to proceed from the smaller to the larger pores as relative humidity increased. The pore distribution at the relative humidity above which pores were completely occupied by absorbed water was shown visually on a histogram. © 2011 The Society of Chemical Engineers, Japan. Source


Kurokawa A.,Hokkaido University | Togawa J.,Wakkanai Green Factory Co. | Nabeshima Y.,Hokkaido University | Nagano K.,Hokkaido University
Kagaku Kogaku Ronbunshu | Year: 2011

Wakkanai siliceous shale (WSS) is a natural mesoporous material that has high performance of moisture adsorption/desorption in response to relative humidity. The authors have previously applied the technique of impregnation with chloride to enhance the water adsorption performance; and in the present study the moisture sorption mechanism with chloride impregnation was examined by DSC analysis. It was found that the adsorbed water in the pores was divided present in three forms: non-freezing water, freezable bound water and free water. The free water peak was not observed at water content below 320 mg/g. This water content was also consistent with the maximum amount of water adsorbed without surface wetting, which was estimated from color change of WSS surface at various water contents. In addition, from the measurement by a modified nitrogen adsorption method, it was visually shown that the mechanism of moisture sorption gradually proceeded from the smaller mesopores. Moreover, the NaCl impregnation was applied to other porous materials. From the experimental results, the impregnation of silica gel with NaCl is not effective, because of the structural weakness. Therefore the stability of the material to impregnation is an important factor. © 2011 The Society of Chemical Engineers, Japan. Source


Nakabayashi S.,Hokkaido University | Nagano K.,Hokkaido University | Togawa J.,Wakkanai Green Factory Co. | Nakamura M.,Hokkaido University | Kurokawa A.,Wakkanai Green Factory Co.
Kagaku Kogaku Ronbunshu | Year: 2010

Wakkanai siliceous shale, a natural mesoporous material, is impregnated with lithium chloride, calcium chloride and sodium chloride solutions to improve its moisture adsorption capacity. However, excess impregnation leads to elution of sorbed moisture from pores to the surface under humid conditions, and the surface of the sample becomes wet. To determine appropriate concentrations of impregnating chlorides, the surface wettedness of the chloride-impregnated shale was estimated from the surface color changes of samples exposed to 75%RH air by using a digital scanner. The appropriate concentrations of lithium chloride and calcium chloride for the shale were 4 and 5 wt%, respectively. Moreover, the maximum moisture sorption of the shale impregnated with the appropriate chloride concentration agreed with the moisture retention predicted from the mesopore volume. This indicates that, in order to avoid elution of the chloride solution to the surface, the maximum moisture sorption of the chloride-impregnated shale should be smaller than the mesopore volume. © 2010 The Society of Chemical Engineers, Japan. Source


Nakabayashi S.,Hokkaido University | Nagano K.,Hokkaido University | Nakamura M.,Hokkaido University | Togawa J.,Wakkanai Green Factory Co. | Kurokawa A.,Wakkanai Green Factory Co.
Adsorption | Year: 2011

The aim of this study is the development of a new adsorbent for the desiccant material which can be regenerated by the domestic exhaust heat by using natural mesoporous material, Wakkanai siliceous shale. To improve this shale's performance to adsorb/desorb the water vapor, lithium chloride, calcium chloride or sodium chloride was supported into the mesopores by impregnating with each chloride solution. Especially sodium chloride was effective to increase the water vapor adsorption amount 5-7 times of that of natural shale in the relative humidity range from 50 to 70%. Moreover, the appropriate impregnating concentrations were determined as 5wt% from the relationship between the maximum water vapor adsorption amount and the mesopore volume. Based on these results, a new desiccant filter has been developed by impregnated original paper with lithium chloride and sodium chloride. This paper contained shale powder in the synthetic fibers. The dehumidification performance of this filter was evaluated under the simulated summer condition in Tokyo. From the cyclic adsorption/regeneration test, this shale and chlorides filter could adsorb and desorb 60 g/h water vapor repeatedly at the regeneration temperature of 40°C. On the other hand, a silica gel filter and a zeolite filter adsorbed and desorbed only 10 g/h and 25 g/h, respectively. These results suggested that the shale impregnated with the chlorides has the best dehumidification ability as a new desiccant material. Further, the desiccant filter made from the shale will achieve the effective use of the low temperature exhaust heat. © 2011 Springer Science+Business Media, LLC. Source

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