The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jingyun Wang - One of the best experts on this subject based on the ideXlab platform.
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Supercritical fluids at subduction zones evidence formation condition and physicochemical properties
Earth-Science Reviews, 2017Co-Authors: Huaiwei Ni, Li Zhang, Xiaolin Xiong, Jingyun WangAbstract:Abstract There is a general consensus that at subduction zones, mass transfer from the subducted slab to the overlying mantle wedge is mediated by a hydrous mobile phase. However, it is under intense debate whether this phase is an aqueous fluid, hydrous silicate melt, or Supercritical fluid with intermediate composition (H 2 O concentration in the range of 30 wt%–70 wt%). Supercritical fluids, with fluid-like viscosity and melt-like wetting and element-carrying capability, are an ideal agent for chemical transport at subduction zones. After clarifying the phase relations of silicate-H 2 O systems and the definition of Supercritical fluids, this contribution reviews existing evidence for the presence of Supercritical fluids at subduction zones, mostly from experimental investigation of phase relations of mineral-H 2 O and rock-H 2 O systems and the atomic structure and physicochemical properties of Supercritical fluids. H 2 O-rich multi-phase solid inclusions from continental subduction zones, once their bulk water contents can be confirmed, may provide a direct record of Supercritical fluids. Experimental results generally indicate that Supercritical fluids can derive from the slab at 160 km depth, but there is still significant discrepancy between different studies on H 2 O-saturated solidus, fluid-melt critical curve, and the second critical end point (SCEP). Some novel experimental methods are proposed to resolve the controversies over the formation condition of Supercritical fluids. The special physicochemical properties of Supercritical fluids arise fundamentally from their intermediate composition and intermediate degree of polymerization that are distinctive from aqueous fluids or silicate melts. Probing the structure and properties of Supercritical fluids, which are required for understanding of their petrological and chemical behavior and geophysical characteristics, relies mainly on in situ spectroscopy, but first-principles molecular dynamics is becoming a potentially powerful alternative approach.
Takeo Iwai - One of the best experts on this subject based on the ideXlab platform.
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general corrosion properties of modified pnc1520 austenitic stainless steel in Supercritical water as a fuel cladding candidate material for Supercritical water reactor
Advances in Science and Technology, 2010Co-Authors: Yoshihisa Nakazono, Takeo IwaiAbstract:The Super-Critical Water-cooled Reactor (SCWR) has been designed and investigated because of its high thermal efficiency and plant simplification. As the operating temperature of Supercritical water reactor will be between 280°C and 620°C with a pressure of 25MPa, the selection of materials is difficult and important. The PNC1520 austenitic stainless steel developed by Japan Atomic Energy Agency (JAEA) as a nuclear fuel cladding material for a Na-cooled fast breeder reactor. The corrosion data of PNC1520 in Supercritical water (SCW) is required but does not exist. The purpose of the present study is to research the corrosion properties for PNC1520 austenitic stainless steel in Supercritical water. The Supercritical water corrosion test was performed for the standard PNC1520 (1520S), the Ti-additional type of PNC1520 (1520Ti) and the Zr-additional type of PNC1520 (1520Zr) by using a Supercritical water autoclave. In view of general corrosion, 1520Zr may have larger possibility than 1520S and 1520Ti to adopt a Supercritical water reactor core fuel cladding.
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general corrosion properties of modified pnc1520 austenitic stainless steel in Supercritical water as a fuel cladding candidate material for Supercritical water reactor
Journal of Physics: Conference Series, 2010Co-Authors: Yoshihisa Nakazono, Takeo IwaiAbstract:The Super-Critical Water-cooled Reactor (SCWR) has been designed and investigated because of its high thermal efficiency and plant simplification. There are some advantages including the use of a single phase coolant with high enthalpy but there are numerous potential problems, particularly with materials. As the operating temperature of Supercritical water reactor will be between 280°C and 620°C with a pressure of 25MPa, the selection of materials is difficult and important. Austenitic stainless steels were selected for possible use in Supercritical water systems because of their corrosion resistance and radiation resistance. The PNC1520 austenitic stainless steel developed by Japan Atomic Energy Agency (JAEA) as a nuclear fuel cladding material for a Na-cooled fast breeder reactor. The corrosion data of PNC1520 in Supercritical water (SCW) is required but does not exist. The purpose of the present study is to research the corrosion properties for PNC1520 austenitic stainless steel in Supercritical water. The Supercritical water corrosion test was performed for the standard PNC1520 (1520S) and the Ti-additional type of PNC1520 (1520Ti) by using a Supercritical water autoclave. Corrosion tests on the austenitic 1520S and 1520Ti steels in Supercritical water were performed at 400, 500 and 600°C with exposures up to 1000h. The amount of weight gain, weight loss and weight of scale were evaluated after the corrosion test in Supercritical water for both austenitic steels. After 1000h corrosion test performed, the weight gains of both austenitic stainless steels were less than 2 g/m2 at 400°C and 500°C . But both weight gain and weight loss of 1520Ti were larger than those of 1520S at 600°C . By increasing the temperature to 600°C, the surface of 1520Ti was covered with magnetite formed in Supercritical water and dissolution of the steel alloying elements has been observed. In view of corrosion, 1520S may have larger possibility than 1520Ti to adopt a Supercritical water reactor core fuel cladding.
Hongtao Wang - One of the best experts on this subject based on the ideXlab platform.
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optimization of Supercritical phase and combined Supercritical subcritical conversion of lignocellulose for hexose production by using a flow reaction system
Bioresource Technology, 2012Co-Authors: Yan Zhao, Jinwen Liu, Hongtao WangAbstract:A flow reaction system was utilized to investigate lignocellulose conversion using combined Supercritical/subcritical conditions for hexose production. Initially, investigation of cellulose hydrolysis in Supercritical water and optimization of reaction parameters were done. Oligosaccharide yields reached over 30% at cellulose concentrations of 3-5 gL(-1) and reaction times of 6-10s at 375 °C, and 2.5-4 gL(-1) and 8-10s at 380 °C. Temperatures above 380 °C were not appropriate for the Supercritical phase in the combined process. Subsequently, conversion of lignocellulosic materials under combined Supercritical/subcritical conditions was studied. Around 30% hexose was produced from corn stalks under the optimal parameters for Supercritical (380 °C, 23-24 MPa, 9-10s) and subcritical (240 °C, 8-9 MPa, 45-50s) phases. Flow systems utilizing the combined Supercritical/subcritical technology present a promising method for lignocellulosic conversion. The results of this study provide an important guide for the operational optimization and practical application of the proposed system.
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combined Supercritical and subcritical conversion of cellulose for fermentable hexose production in a flow reaction system
Chemical Engineering Journal, 2011Co-Authors: Yan Zhao, Hongtao Wang, Hao WangAbstract:Abstract Using research on a batch system as basis, a flow reactor was designed and applied in the combined Supercritical and subcritical hydrolysis of cellulose for fermentable hexose production. The results show that when the Supercritical parameters were maintained, the hexose yield first increased with the rise in subcritical temperature, and then decreased after the maximum yield was obtained. This maximum yield of fermentable hexoses from cellulose was 31.5% ± 1.4%, which was obtained under the following conditions: cellulose concentration of 3.53 ± 0.24 g L −1 , Supercritical temperature of 380 °C, Supercritical reaction time of 9.70 ± 0.66 s, subcritical temperature of 240 °C, and subcritical reaction time of 48.49 ± 3.31 s. The appropriate ranges of cellulose concentration (around 3.5 g L −1 ) and reaction time (9–10 s for Supercritical process and 45–50 s for subcritical process), which depended on the flows of water and material sludge, were also crucial in obtaining a high hexose yield. Compared with the batch system, the flow reaction system can yield a reasonable amount of hexose from cellulose hydrolysis and proved to be considerably promising for practical applications, especially for combined Supercritical and subcritical technology on lignocellulosic resources.
Yukihiko Matsumura - One of the best experts on this subject based on the ideXlab platform.
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state of the art of biodiesel production under Supercritical conditions
Progress in Energy and Combustion Science, 2017Co-Authors: Obie Farobie, Yukihiko MatsumuraAbstract:Abstract This paper reviews the current status of biodiesel production mainly under Supercritical conditions. Various methods such as homogeneous acid- and alkali-catalyzed transesterification, heterogeneous acid and alkali-catalyzed transesterification, enzyme-catalyzed transesterification, and Supercritical reactions have been employed so far to synthesize biodiesel. Herein, we review the reaction mechanisms and experimental results for these approaches. Recently, Supercritical biodiesel production has undergone a vigorous development as the technology offers several advantages over other methods, including the fact that it does not require a catalyst, short residence time, high reaction rate, no pretreatment requirement, and applicability to a wide variety of feedstock. This technology was first designed for biodiesel production using methanol and ethanol. Biodiesel production without glycerol as a byproduct is attractive and has been achieved using Supercritical methyl acetate and dimethyl carbonate (DMC). Most recently, biodiesel production in Supercritical tert-butyl methyl ether (MTBE) has been developed also. In this review, Supercritical biodiesel production will be discussed in detail. Empirical rate expressions are derived for biodiesel production in Supercritical methanol, ethanol, methyl acetate, DMC, and MTBE in this study for the first time. These rate equations are critical to predicting biodiesel yields and to comparing the reaction behaviors in different solvents. Lastly challenges for improving energy recovery in Supercritical biodiesel production and recommendations for future work are provided.
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Supercritical water treatment of biomass for energy and material recovery
Combustion Science and Technology, 2006Co-Authors: Yukihiko Matsumura, Kazuhide Okuda, Seiichi Takami, Satoshi Ohara, Mitsuo Umetsu, Mitsuru Sasaki, Tadafumi AdschiriAbstract:ABSTRACT Supercritical water liquefaction and gasification is reviewed with the introduction of some recent findings by the authors. Supercritical water gasification is suitable for recovery of energy from wet biomass while Supercritical water liquefaction opens the door to effective treatment of biomass species in terms of material recovery. Cellulose, one of the main components of biomass, is completely dissolved in Supercritical water. Once dissolved, reaction of cellulose can take place swiftly by hydrolysis and pyrolysis. The hydrolysis reaction, otherwise slower than pyrolysis due to the mass transfer limitation, is faster than decomposition in Supercritical water, and a possibility of efficient glucose recovery has been shown. Once dissolved, super saturation is kept when the solution is cooled down, and swift hydrolysis by enzyme is also possible. Lignin can be also converted into specialty chemicals by using Supercritical cresol/water mixture as a solvent. Dissolution of cellulose also enables ef...
Yan Zhao - One of the best experts on this subject based on the ideXlab platform.
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optimization of Supercritical phase and combined Supercritical subcritical conversion of lignocellulose for hexose production by using a flow reaction system
Bioresource Technology, 2012Co-Authors: Yan Zhao, Jinwen Liu, Hongtao WangAbstract:A flow reaction system was utilized to investigate lignocellulose conversion using combined Supercritical/subcritical conditions for hexose production. Initially, investigation of cellulose hydrolysis in Supercritical water and optimization of reaction parameters were done. Oligosaccharide yields reached over 30% at cellulose concentrations of 3-5 gL(-1) and reaction times of 6-10s at 375 °C, and 2.5-4 gL(-1) and 8-10s at 380 °C. Temperatures above 380 °C were not appropriate for the Supercritical phase in the combined process. Subsequently, conversion of lignocellulosic materials under combined Supercritical/subcritical conditions was studied. Around 30% hexose was produced from corn stalks under the optimal parameters for Supercritical (380 °C, 23-24 MPa, 9-10s) and subcritical (240 °C, 8-9 MPa, 45-50s) phases. Flow systems utilizing the combined Supercritical/subcritical technology present a promising method for lignocellulosic conversion. The results of this study provide an important guide for the operational optimization and practical application of the proposed system.
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combined Supercritical and subcritical conversion of cellulose for fermentable hexose production in a flow reaction system
Chemical Engineering Journal, 2011Co-Authors: Yan Zhao, Hongtao Wang, Hao WangAbstract:Abstract Using research on a batch system as basis, a flow reactor was designed and applied in the combined Supercritical and subcritical hydrolysis of cellulose for fermentable hexose production. The results show that when the Supercritical parameters were maintained, the hexose yield first increased with the rise in subcritical temperature, and then decreased after the maximum yield was obtained. This maximum yield of fermentable hexoses from cellulose was 31.5% ± 1.4%, which was obtained under the following conditions: cellulose concentration of 3.53 ± 0.24 g L −1 , Supercritical temperature of 380 °C, Supercritical reaction time of 9.70 ± 0.66 s, subcritical temperature of 240 °C, and subcritical reaction time of 48.49 ± 3.31 s. The appropriate ranges of cellulose concentration (around 3.5 g L −1 ) and reaction time (9–10 s for Supercritical process and 45–50 s for subcritical process), which depended on the flows of water and material sludge, were also crucial in obtaining a high hexose yield. Compared with the batch system, the flow reaction system can yield a reasonable amount of hexose from cellulose hydrolysis and proved to be considerably promising for practical applications, especially for combined Supercritical and subcritical technology on lignocellulosic resources.
