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Dive into the research topics where Nobuo Takeda is active.

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Featured researches published by Nobuo Takeda.


Water Science and Technology | 2010

Behaviour and adsorptive removal of siloxanes in sewage sludge biogas.

Kazuyuki Oshita; Y. Ishihara; Masaki Takaoka; Nobuo Takeda; Tadao Matsumoto; Shinsuke Morisawa; Akira Kitayama

We investigated the behaviour of siloxanes, which adversely affect biogas engines, as well as their concentration levels in sewage sludge biogas in Japan. We also performed experiments on the absorptive removal of siloxanes using various adsorbents and determined the main adsorbent characteristics required for the removal of siloxanes. The results of our study on the concentration and composition of siloxanes in biogas were similar to previous reports. Moreover, we found that the concentration of siloxanes changes in relation to the outside air temperature based on real-time measurements of siloxanes using a continuous analyser. We further speculated that the continuous analyser would accurately indicate the siloxane concentration in model biogas but overestimate the siloxane concentration in actual biogas because of positive interference by VOCs and other biogas components. In the siloxane adsorption experiment, the equilibrium uptake of both cyclic siloxanes, D4 and D5, was positively related to the BET-specific surface area of the adsorbents and the fraction of the external surface area taken up by relatively large diameter pores. We attributed the adsorption results to the fact that the siloxane molecules are generally larger than micropores; therefore, they are less susceptible to adsorption to micropores. Based on these results, we concluded that adsorbents with large BET-specific surface areas, especially those with a high external specific surface area and pores of relatively large diameters, are desired for the removal of siloxanes.


Waste Management | 2009

Comparison of two types of municipal solid waste incinerator fly ashes with different alkaline reagents in washing experiments

Fenfen Zhu; Masaki Takaoka; Kazuyuki Oshita; Nobuo Takeda

In this study, we propose a washing-calcination-conversion of washed fly ash into cement material with bottom ash (WCCB) system to reduce the amount of fly ash that must be specially treated so it can be used as raw cement material. Calcium hydroxide (Ca(OH)2) is widely used in air-pollution control devices of incinerators while sodium bicarbonate (NaHCO3) is not. We conducted single-, double-, and triple-washing experiments to compare the washing characteristics of two types of fly ash. Unlike NaHCO3 fly ash, Ca(OH)2 fly ash has almost twice as much washed residue and almost 2.5 times more chlorine after the same washing procedure. After washing once, the washing frequency is also important for NaHCO3 fly ash, while the mixing time and liquid/solid ratio are more critical for Ca(OH)2 fly ash. The use of NaHCO3 is more suitable for the WCCB system.


Chemosphere | 2010

Extraction of PCBs and water from river sediment using liquefied dimethyl ether as an extractant.

Kazuyuki Oshita; Masaki Takaoka; Sin-ichiro Kitade; Nobuo Takeda; Hideki Kanda; Hisao Makino; Tadao Matsumoto; Shinsuke Morisawa

We investigated whether polychlorinated biphenyls (PCBs) and water could be simultaneously removed from river sediment by solvent extraction using liquefied dimethyl ether (DME) as the extractant. DME exists in a gaseous state at normal temperature and pressure and can dissolve organic substances and some amount of water; therefore, liquefied DME under moderate pressure (0.6-0.8 MPa) at room temperature can be effectively used to extract PCBs and water from contaminated sediment, and it can be recovered from the extract and reused easily. First, we evaluated the PCB and water extraction characteristics of DME from contaminated sediment. We found that 99% of PCBs and 97% of water were simultaneously extracted from the sediment using liquefied DME at an extraction time of 4320 s and a liquefied DME/sediment ratio of 60 mL g(-1). The extraction rate of PCBs and water was expressed in terms of a pseudo-first-order reaction rate. Second, we estimated the amount of DME that was recovered after extraction. We found that 91-92% of DME could be recovered. In other words, approximately 5-10% of DME was lost during extraction and recovery. It is necessary to optimize this process in order to recover DME efficiently. The extraction efficiency of the recovered DME is similar to that of the pure DME. From the results, we conclude that solvent extraction using liquefied DME is suitable for extracting PCBs and water from contaminated sediment.


Drying Technology | 2011

Sewage Sludge Dewatering Process Using Liquefied Dimethyl Ether as Solid Fuel

Kazuyuki Oshita; Masaki Takaoka; Yusuke Nakajima; Shinsuke Morisawa; Hideki Kanda; Hisao Makino; Nobuo Takeda

This article describes the dewatering of sewage sludge using liquefied dimethyl ether (DME), which clarified the effect of sludge type and its particle size. Changes in the heating value of the dewatered sludge were also examined. In addition, the change in dewaterability upon reuse of the liquefied DME was investigated experimentally. Regardless of the nature of the sludge, its dewatering behavior was similar. The amount of dewatered water could be increased by decreasing the diameter of the sludge cake. Complete drying of the sludge cake via DME dewatering resulted in retention of approximately 96% of the heating value (17.7 MJ/kg-sludge) of the original sludge cake dry base (18.4 MJ/kg db). The DME could be recovered after extraction, and reuse experiments showed that liquefied DME dewatering performance was unchanged after five reuses.


Drying Technology | 2009

Dewatering a Superabsorbent Polymer Using Liquefied Dimethyl Ether

Hideki Kanda; Kazuyuki Oshita; Kazuya Takeda; Masaki Takaoka; Hisao Makino; Shinsuke Morisawa; Nobuo Takeda

In this study, we evaluated the applicability of the dimethyl ether (DME) dewatering method originally developed for high-moisture coal to superabsorbent polymer (SAP) and disposable diapers. It was found that liquefied DME successfully extracts water from SAP and disposable diapers. However, the polypropylene outer film and polyurethane used in diapers tended to dissolve in the liquefied DME and were subsequently released with the water discharged. These compounds are highly viscous, making it difficult to remove them from the drain outlet of the prototype. Therefore, the mechanics of the drain outlet should be considered in future studies.


Journal of Material Cycles and Waste Management | 2009

Characterization of trace constituents in landfill gas and a comparison of sites in Asia

Yuya Takuwa; Tadao Matsumoto; Kazuyuki Oshita; Masaki Takaoka; Shinsuke Morisawa; Nobuo Takeda


Analytical Sciences | 2012

Methods of Determining Lead Speciation in Fly Ash by X-ray Absorption Fine-Structure Spectroscopy and a Sequential Extraction Procedure

Atsushi Funatsuki; Masaki Takaoka; Kazuyuki Oshita; Nobuo Takeda


Journal of Material Cycles and Waste Management | 2009

Japan's waste management policies for dioxins and polychlorinated biphenyls

Hideto Yoshida; Kazuaki Takahashi; Nobuo Takeda; Shin-ichi Sakai


Journal of Material Cycles and Waste Management | 2012

Mercury emission from sewage sludge incineration in Japan

Masaki Takaoka; Shingo Domoto; Kazuyuki Oshita; Nobuo Takeda; Shinsuke Morisawa


Journal of Material Cycles and Waste Management | 2011

Current status of waste to power generation in Japan and resulting reduction of carbon dioxide emissions

Masaki Takaoka; Nobuo Takeda; Naruo Yamagata; Takahiro Masuda

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Hisao Makino

Central Research Institute of Electric Power Industry

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Hideto Yoshida

Japanese Ministry of the Environment

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