劉 醇一

Abstract One of the solutions to energy problems is the reuse of waste heat. One way to reuse waste heat is to use latent heat storage materials. Erythritol, of which melting point is the temperature range between 100 and 200°C, has attracted much attention as latent heat storage materials. However, as usual erythritol shows the large supercooling, its supercooling degree must be decreased to use for latent heat storage material. To achieve this, we have investigated the mixed erythritol with fatty acids as addition agents. Samples were prepared by physically mixing of erythritol and fatty acids such as (lauric acid, myristic acid, palmitic acid, and stearic acid). In this study, differential scanning calorimeter (DSC) was used (to evaluate the sample temperature program: 30→140→0→30°C, heating rate: 5°C/min, atmosphere: N₂ gas). The degree of supercooling was calculated from the DSC curve. And also, a camera was used to capture and discuss the freezing process. The erythritol physically mixed with fatty acids showed a higher freezing point and lower degree of supercooling than pure erythritol. The mixing myristic acid with erythritol significantly lowers the supercooling degree. The erythritol sample with palmitic acid or stearic acid did not show as low supercooling degree as that with myristic acid. Additionally, with lauric acid or myristic acid, the erythritol sample solidified simultaneously, while sample solidified separately with palmitic acid or stearic acid added. In summary, it was found that physical mixing of fatty acids and erythritol decreased in the supercooling degree. Furthermore, the crystallization temperatures of the sample with lauric acid or myristic acid were altered by changing the fatty acids.

Large storage capacity of ammonia (NH₃) on bis(fluorosulfonyl)amide (FSA) salts were observed using the pressure-swing method (0.1–0.5 MPa).

<p>The effect of LiCl and LiOH on the hydration of MgO was investigated by XRD and FT-IR measurements, which can help to identify dopants that can effectively catalyze the Mg(OH)₂ dehydration and MgO hydration processes.</p>

This research focuses on dehydration / hydration of magnesium hydroxide as a chemical heat storage material. Previous studies have reported that the use of additives in magnesium hydroxide improved the dehydration / hydration reactivity. However, additives used in previous studies have had problems in terms of environmental impact and cost. Therefore, the purpose of this study is to search for safe and inexpensive additives. We have selected citrate compounds as an inexpensive and safe additive. The effect of the additive was verified by measuring the dehydration / hydration reaction of magnesium hydroxide using a thermogravimetric instrument. Furthermore, XRD was used for sample characterization. As a result, the most improved reactivity was confirmed in the sample using sodium citrate as an additive. SC5 (molar ratio, magnesium hydroxide: sodium citrate dihydrate = 100: 5) decreased the dehydration peak temperature by about 31ºC compared to pure magnesium hydroxide. Sodium citrate dihydrate was found to undergo thermal degradation during sample heating. Then, when the repeated reaction test was implemented, the improvement of the dehydration rate after the 2nd time was confirmed. These results indicate that the product of thermal decomposition of sodium citrate dihydrate is effective as an additive.

Best Student Poster Award 受賞（評価対象14件中1件）

A lithium orthosilicate/carbon dioxide (Li4SiO4/CO2) reaction system is proposed for use in thermochemical energy storage (TcES) and chemical heat pump (CHP) systems at around 700 C-omicron. Carbonation of Li4SiO4 exothermically produces lithium carbonate (Li2CO3) and lithium metasilicate (Li2SiO3). Decarbonation of these products is used for heat storage, and carbonation is used for heat output in a TcES system. A Li4SiO4 sample around 20 pm in diameter was prepared from Li2CO3 and SiO2 using a solid-state reaction method. To determine the reactivity of the sample, Li4SiO4 carbonation and decarbonation experiments were conducted under CO2 at several pressures in a closed reactor using thermogravimetric analysis. The Li4SiO4 sample's carbonation and decarbonation performance was sufficient for use as a TcES material at around 700 C-omicron. In addition, both reaction temperatures of Li4SiO4 varied with the CO2 pressure. The durability under repeated Li4SiO4 carbonation and decarbonation was tested using temperature swing and pressure swing methods. Both methods showed that the Li4SiO4 sample has sufficient durability. These results indicate that the temperature for heat storage and heat output by carbonation and decarbonation, respectively, could be controlled by controlling the CO2 pressure. Li4SiO4/CO2 can be used not only for TcES but also in CHPs. The volumetric and gravimetric thermal energy densities of Li4SiO4 for TcES were found to be 750 kJ L-1 and 780 kJ kg(-1), where the porosity of Li4SiO4 was assumed to be 59%. When the reaction system was used as a CHP, and heat stored at 650 C-omicron was warmed and output at 700 C-omicron, 14% of the heat supplied by carbonation was needed for self-heating of the material from 650 to 700 C-omicron, and the volumetric and gravimetric thermal energy densities for heat output were calculated as 650 kJ L-1 and 670 kJ kg-1, respectively. (C) 2017 Elsevier Ltd. All rights reserved.

This paper investigates the use of expanded graphite (EG) as a thermal conductivity enhancer for packed bed reactor materials in a chemical heat storage/pump system based on magnesium hydroxide (Mg(OH)(2)) dehydration and magnesium oxide (MgO) hydration reactions. Composites of Mg(OH)(2) powder mixed with EG (hereafter termed EM composites) were developed by varying the mass mixing ratios of Mg(OH)(2) to EG (psi). EM composites and pure Mg(OH)(2) powder were compacted in slab configurations (width 20 mm x length 100 mm x variable thickness 20-38 mm) and the thermal conductivities of the slabs were measured as a function of the slab density and psi. Using EG as a thermal conductivity enhancer in the composite improved the thermal conductivity of the EM slab six-fold relative to that using pure Mg(OH)(2). Evaluation of the thermal effusivity and chemical heat storage capacity showed that EM prepared with a mass ratio of psi = 8 allowed achievement of good heat transfer performance without negatively impacting the chemical heat storage capacity.

A chemical heat storage (CHS) material that utilizes waste heat (with temperatures over 450 degrees C) from industrial plants, thermal generation plants, and nuclear power plants was developed. Calcium hydroxide (Ca(OH)(2)) was selected as the CHS material because it decomposes at temperatures over 450 degrees C under atmospheric pressure. A support that holds the CHS material dispersed in micrometer-sized clusters was needed to prohibit Ca(OH)(2) agglomeration; this support also permitted the moldability of the Ca(OH)(2) material for loading into practical heat-exchange reactors. Vermiculite was selected as the support for Ca(OH)(2) because of its high porosity, chemical stability, and low cost. Using the impregnation method, composite materials were developed, which consisted of Ca(OH)(2) and vermiculite. The reaction performance was then studied with thermal gravimetric analysis (TGA). It was confirmed that, in comparison with the original Ca(OH)(2), the reaction rate of the composite material was enhanced because of the incorporated vermiculite. (C) 2015 Elsevier Ltd. All rights reserved.

A chemical heat storage (CHS) material that utilizes waste heat (with temperatures over 450 degrees C) from industrial plants, thermal generation plants, and nuclear power plants was developed. Calcium hydroxide (Ca(OH)(2)) was selected as the CHS material because it decomposes at temperatures over 450 degrees C under atmospheric pressure. A support that holds the CHS material dispersed in micrometer-sized clusters was needed to prohibit Ca(OH)(2) agglomeration; this support also permitted the moldability of the Ca(OH)(2) material for loading into practical heat-exchange reactors. Vermiculite was selected as the support for Ca(OH)(2) because of its high porosity, chemical stability, and low cost. Using the impregnation method, composite materials were developed, which consisted of Ca(OH)(2) and vermiculite. The reaction performance was then studied with thermal gravimetric analysis (TGA). It was confirmed that, in comparison with the original Ca(OH)(2), the reaction rate of the composite material was enhanced because of the incorporated vermiculite. (C) 2015 Elsevier Ltd. All rights reserved.

A novel candidate chemical heat storage material having higher reaction performance and higher thermal conductivity used for magnesium oxide/water chemical heat pump was developed in this study. The material, called EML, was obtained by mixing pure Mg(OH)(2) with expanded graphite (EG) and lithium bromide (LiBr), which offer higher thermal conductivity and reactivity, respectively. With the aim to achieve a high energy density, the EML composite was compressed into figure of the EML tablet (phi 7.1 mm x thickness 3.5 mm). The compression force did not degrade the reaction conversion, and furthermore it enabled us to achieve best heat storage and output performances. The EML tablet could store heat of 815.4 MJ m(tab)(-3) at 300 degrees C within 120 min, which corresponded to almost 4.4 times higher the heat output of the EML composite, and therefore, the EML tablet is the solution which releases more heat in a shorter time. A relatively larger volumetric gross heat output was also recorded for the EML tablet, which was greater than one attained for the EML composite at certain temperatures. As a consequence, it is expected that the EML tablet could respond more quickly to sudden demand of heat from users. It was concluded that the EML tablet demonstrated superior performances. (C) 2015 Elsevier Ltd. All rights reserved.

An active carbon recycling energy system (ACRES) based on carbon recycling has been proposed as a new energy transformation system. This energy transformation system reduces the carbon dioxide (CO2) emissions in the atmosphere during the iron-making process. An experimental study for electrochemical CO production by CO2 electrolysis based on the ACRES concept was carried out using a tubular solid oxide electrolysis cell. Experimental results show that the CO and oxygen (O-2) production rates at 800, 850, and 900 degrees C were almost proportional to the current passing through the cell. Both ionic conductivity and the chemical kinetics of CO2 decomposition increased with increasing temperature. The highest current density and CO production rate at 900 degrees C were 2.97 mA/cm(2) and 0.78 mu mol/(min cm(2)), respectively. On the basis of the electrolytic characteristics of the cell, the scale of the combined ACRES CO2 electrolysis/iron-making system was estimated. (C) 2015 Elsevier Ltd. All rights reserved.

The reaction performance of a novel chemical heat storage composite as thermal energy storage medium were evaluated for use in a magnesium oxide/water chemical heat pump. The composite, called EML, is composed of pure Mg(OH)(2) powder and support materials, including LiBr and expanded graphite to improve reactivity and heat transfer, respectively. The heat storage and heat output capacities of the EML composites were evaluated based on laboratory experiments of dehydration and hydration processes for various molar mixing ratios a of LiBr to Mg(OH)(2) using the thermogravimetric method. The heat storage and heat output capacity of the EML composites increased with increasing a. The EML composite with alpha = 0.100 was estimated to be able to store 1.3 times the heat stored in pure Mg(OH)(2) powder after 30 min. Based on these evaluations, the EML composites exhibited sufficient heat storage, heat output capacity, and good mold-ability for practical use in a heat exchange reactor. The EML composite was accordingly confirmed as a candidate material for use in chemical heat pumps. Thus, potential use of the EML composite in a magnesium oxide/water chemical heat pump coupled with a small nuclear reactor for district heating systems was evaluated based on the experimental results. (C) 2014 Elsevier Ltd. All rights reserved.

A heat recovery system based on thermal energy storage from the iron-making process at medium temperature range (200-300 degrees C) is presented. For an efficient waste heat recovery system the selection of suitable thermal energy storage material is essential. Accordingly, a new candidate for a chemical heat storage material used in a magnesium oxide/water chemical heat pump at medium-temperature was developed in this study. The new composite, named EML, was fabricated by mixing pure magnesium hydroxide with lithium bromide and expanded graphite, which are employed as reactivity and heat transfer enhancers, respectively. The effects of mass mixing ratios w of EG to Mg(OH)(2) on dehydration and hydration were investigated by a thermogravimetric (TG) method, with the result that the w of 0.83 was the optimal mass mixing ratio for the EML composite. Thereby the heat output capacities of the EML composite (w = 0.83) were evaluated with varying reaction vapor pressure and hydration temperature. Heat output capacity per unit initial weight of the EML composite (w = 0.83) was calculated as 1168.7 kJ kg(EML)(-1) at a hydration temperature of 110 degrees C and reaction vapor pressure of 57.8 kPa. This value was 1.2 times higher than the corresponding heat output capacity of pure Mg(OH)(2) powder (958.5 kJ kg(Mg(OH)2)(-1)). This result showed that the EML composite has sufficient heat output capacity and mold-ability provided by EG for practical use in a heat exchange reactor. Thus, this composite could potentially be used as chemical heat storage materials for thermal heat storage.

New composite materials were developed for application in chemical heat storage (CHS) systems based on the calcium oxide/water/calcium hydroxide (CaO/H2O/Ca(OH)(2)) reaction. It was found that the mixtures of expanded graphite (EG) and Ca(OH)(2) enhance the reaction performance and moldability, which are important factors for the application in a packed-bed CHS heat exchanger. The reaction kinetics was investigated by thermogravimetric analysis. The maximum mean heat output of a mixture containing 11 wt% EG was 1.76 kW (kg-material)(-1), which is twice as high as that of the pure Ca(OH)(2) (0.85 kW (kg-material)(-1)). A repetitive dehydration-hydration experiment was carried out and it was confirmed that the positive effect of EG was preserved during the investigated 10 cycles. Therefore, based on our results, these composite materials can enhance the thermal performance of the CaO/H2O/Ca(OH)(2) reaction cycle in CHS systems.

Efficient carbon dioxide (CO2) reduction into carbon monoxide (CO) is required to establish a smart iron-making process based on an active carbon recycling energy system (iACRES). A disk-type solid oxide electrolysis cell (SOEC) was prepared and examined experimentally for application to the CO2 reduction process in iACRES. A SOEC with a cathode vertical bar electrolyte vertical bar anode structure of Ni-YSZ vertical bar YSZ vertical bar La0.6Sr0.4Co0.2Fe0.8O3-delta. was fabricated. The electrolysis of carbon dioxide was conducted at 800-900 degrees C. A current density of 107.1 mA cm(-2) was measured between the cathode and anode at 900 degrees C and at 2.52 V. The production rates of CO and O-2 were in agreement with the theoretical values determined using Faraday's law. Evaluation of iACRES using the experimental results indicated that an estimated 0.73 high-temperature gas cooled reactor units as the primary energy source for CO2 reduction and a SOEC surface area of 0.098 km(2) were required for the reduction of 30% CO2 in blast furnace gas emitted from a conventional blast furnace.

Magnesium oxide/water/magnesium hydroxide (MgO/H2O/Mg(OH)(2)) heat storage system using a composite material mixed with Mg(OH)(2) and expanded graphite (EG), named as EM, was discussed experimentally and numerically. Thermal performance of EM tablet of 10 mm diameter and 7 mm thickness was evaluated by packed bed reactor experiments. Thermal performance of a packed bed of pure Mg(OH)2 pellets (diameter of pellet of 2 mm and 5-10 mm length) was compared with one of EM in the same experimental reactor. It was observed that the higher effective thermal conductivity of the bed of EM tablets contributed on enhancing the heat storage performance of the packed bed reactor. The effect of thermal conductivity enhancement of thermochemical heat storage materials was discussed numerically. The numerical model was utilized for a preliminary investigation on the behavior of a larger system, made of bundles of chemical heat storage units (CHSU), designed as pipes (length of 2 m) containing a packed bed of CHS material. It was shown that CHSU charged with EM tablets was capable to be utilized for recovery waste heat from the cooling down process of continuous casting of steel slabs.

A composite chemical heat storage material, EMC, comprising a mixture of expanded graphite (EG), magnesium hydroxide (Mg(OH)(2)), and calcium chloride (CaCl2) has been developed as a magnesium oxide/water chemical heat pump reactant. The reaction kinetic characterization of the optimized EMC (which was an optimized mixing weight ratio of the material) was conducted. From BET and thermal conductivity measurements, it was confirmed that an optimized EMC had a higher specific surface area and thermal conductivity values than pure Mg(OH)(2) on adding EG. The durability of the optimized EMC was also investigated by thermobalance and XRD experiments. EMC maintained enough reacted conversion and unchanged crystal structure throughout the repetitive experiment. The film diffusion control model was suggested as a dominant reaction process for MgO hydration by kinetic analysis of experimental results. In conclusion, the optimized EMC showed shorter dehydration time corresponding to the heat storage process period and enhanced hydration conversion corresponding to the heat output capacity than pure Mg(OH)(2) on adding EG, a moldable and porous carbon material, and a CaCl2 hydrophilic material.

In this work, chemical heat storage is proposed for the accumulation of the surplus thermal energy generated by a nuclear reactor during low demand of electricity and its re-utilization for the peak demands. Thermal energy is converted into chemical energy or vice versa by operating a reversible chemical reaction, consisting in the dehydration of magnesium hydroxide (Mg(OH)(2)) and the hydration of magnesium oxide (MgO). It is required that thermal energy has to be released promptly in order to follow the demand of electricity. To satisfy these features, the thermal conductivity of Mg(OH)(2) and MgO has been enhanced by using expanded graphite (EG). A composite material, named EM, was obtained by mixing Mg(OH)(2) and EG in a water suspension. After drying of the mixture, EM was compressed in figure of tablets (diameter of 10 mm, thickness of around 6 mm). The reactivity of the packed bed of EM tablets was and studied experimentally in order to determine its heat storage and heat output performances and compared to a packed bed made of pure Mg(OH)(2) pellets. From the experimental results of stored heat and heat power output, it was possible to estimate the amounts of Mg(OH)(2) and EM required for the peak shaving of electricity in a nuclear power station. A Rankine cycle in the power station has been modified to include a chemical heat storage reactor. The range of admissible variation of electrical power output from the steam turbine was estimated from the enthalpy and mass balances under the heat storage and heat output operation modes, respectively. The volume of EM tablets required to store the same amount of thermal energy of Mg(OH)(2) pellets resulted 13.6% smaller. (C) 2015 The Authors. Published by Elsevier Ltd.

The chemical heat storage/chemical heat pump technology (CHS/CHP) based on the reversible gas-solid chemical reactions between magnesium oxide, water, and magnesium hydroxide (MgO/H2O/Mg(OH)(2)) requires enhanced thermal conductivity for the packed bed reactors. A composite material of expanded graphite (EG) and Mg(OH)(2), EM8, was prepared. Mg(OH)(2) and EG, used in the preparation of EM8, were mixed at the optimal mass mixing ratio of 8:1. EM8 was then compressed into a cylindrical block with dimensions matching that of the reactor of a CHP apparatus (diameter phi(reactor) = 48 min, height Z(reactor) = 48 mm). The dehydration and hydration reactions, corresponding to the heat storage and heat output mode of the CHP, were carried out using the apparatus by inserting the EMS block directly into the reactor. The results were compared with those obtained under the same reaction conditions by filling the reactor with a packed bed of Mg(OH)(2) pellets. The results show that after 120 min of dehydration at 400 degrees C, the EMS block had a volumetric heat storage (q(d,v)) of 747 MJ m(bed)(-3), while that for the bed of Mg(OH)(2) pellets was 502 MJ m(bed)(-3). After 60 min of hydration at water vapor pressure of 361 kPa, the EM8 block had a gross heat output (q(h,v)) of 911 MJ m(bed)(-3), while that for the bed of Mg(OH)(2) pellets was 497 MJ m(bed)(-3). Kinetic analysis for the hydration reaction indicated that in the EMS block, the hydration rate was controlled by mass transfer for P-h &lt; 101 kPa, while it was controlled by heat transfer for P-h &gt; 101 kPa. (C) 2014 Elsevier Ltd. All rights reserved.

The dehydration and hydration behaviors of Mg-Co mixed hydroxides and the effect of LiCl addition were studied to develop a new material for chemical heat storage. The formation of the mixed hydroxides and LiCl addition were expected to reduce the dehydration temperature of authentic magnesium hydroxide; this temperature corresponds to that of heat-storage operation. That the dehydration temperature of Mg-Co mixed hydroxides was found to be approximately 280 degrees C, which was lower than that of authentic magnesium hydroxide. The mixed hydroxides showed higher hydration reactivities than authentic magnesium oxide at 110 degrees C with 57.8 kPa of water vapor after dehydration at 300 degrees C. The dehydration temperatures of Mg-Co mixed hydroxides were lowered by LiCl addition. LiCl-added Mg-Co mixed hydroxides showed higher hydration reactivities than the usual Mg-Co mixed oxides after dehydration at 250 degrees C. The heat-output performance of LiCl/Mg0.95Co0.(05)(OH)(2) was estimated as 715 kJ kg(-1) after dehydration at 250 degrees C. These results indicated that Mg-Co mixed hydroxides can be used to utilize industrial waste heat between 250 degrees C and 300 degrees C.

A new candidate for a chemical heat storage material used in a magnesium oxide-water chemical heat pump at medium- temperature (200-300 degrees C) was developed. The new composite, named EML, was fabricated by mixing pure magnesium hydroxide (Mg(OH)(2)) with lithium bromide (LiBr) and expanded graphite, which are employed as reactivity and heat transfer enhancers, respectively. The effects of mixing mole ratios of LiBr-to-Mg(OH)(2), alpha, on both dehydration and hydration were kinetically investigated by a thermogravimetric method. It was experimentally demonstrated that the reacted mole fractions of dehydration and hydration increased with increasing alpha value. Further, the activation energy, E-a, of the dehydration process was significantly reduced for the EML with high alpha. Therefore, it was concluded that the E-a values determined here are dependent on alpha. Further, the EML composite showed cyclic ability with repeat reactions over five cycles. Thus, this composite can be used as a chemical heat storage material because of its ability to store heat at medium-temperatures ranging from 220 to 300 degrees C.

A new energy transformation system based on carbon recycling is proposed called the active carbon recycling energy system (ACRES). A high-temperature gas reactor was used as the main energy source for ACRES. An experimental study based on the ACRES concept of carbon monoxide (CO) regeneration via high-temperature reduction of carbon dioxide (CO2) was carried out using a tubular solid oxide electrolysis cell employing Ni-LSM cermet vertical bar YSZ vertical bar YSZ-LSM as the cathode vertical bar electrolyte vertical bar anode. The current density increased with increasing CO2 concentration at the cathode, which was attributed to a decrease in cathode activation and concentration overpotential. Current density, as well as the CO and oxygen (O-2) production rates, increased with increasing operating temperature. The highest CO and O-2 production rates of 1.24 and 0.64 mu mol/min cm(2), respectively, were measured at 900 degrees C. Based on the electrolytic characteristics of the cell, the scale of a combined ACRES CO2 electrolysis/iron production facility was estimated. (C) 2013 Elsevier B.V. All rights reserved.

A chemical heat storage composite material (EMC), a mixture of expanded graphite (EG), magnesium hydroxide (Mg(OH)(2)), and calcium chloride (CaCl2), was developed as a magnesium oxide/water chemical heat pump reactant. The potential of the EMC was confirmed and optimized mixing weight ratio between EG and Mg(OH)(2) was suggested in previous study. In this study, the optimization of mixing molar ratio between Mg(OH)(2) and CaCl2 for practical application was conducted; total six kinds of EMC mixtures, which have different mixing molar ratio from 0, to 0.01 to 0.20 with optimized mixing weight ratio, were prepared then dehydration and hydration experiments were carried out. From experimental results, it was confirmed that hydration reacted conversion was increased as increasing amount of CaCl2 in an EMC and the optimized mixing molar ratio was suggested as mixing molar ratio, alpha, is 0.1 at mixing weight ratio, n, is 0.8 by considering chemical rate constant and reacted conversion. Hydration under various vapor pressures and temperatures of optimized EMC was also conducted and optimized EMC showed better performance than pure Mg(OH)(2). Finally, the heat output performance of optimized EMC was estimated numerically. In conclusion, optimized EMC performed better on dehydration and hydration than pure Mg(OH)(2) by adding EG, which has high thermal conductivity and large specific surface, and CaCl2, which has hydrophilic property. (C) 2014 Published by Elsevier Ltd.

Expanded graphite (EG) was used to enhance the thermal conductivity in the packed bed reactors of magnesium oxide water (MgO-H2O) chemical heat pumps (CHP). An expanded graphite magnesium hydroxide composite (EM) was obtained by mixing a precursor CHP material of magnesium hydroxide (Mg(OH)(2)) powder and EG. The composite was pelletized to achieve a diameter (phi) of 7.1 mm and thickness (I) ranging of 3.5-4.5 mm. Mg(OH)(2) dehydration and MgO hydration in the EM pellets were investigated on the packed bed reactor of a 100-W-scale CHP experimental apparatus. The temperatures measured in the packed beds of the EM pellets, as well as the dehydration and hydration kinetics, were compared with the results obtained using a packed bed of pure Mg(OH)(2) pellets (phi = 1.9 mm, l = 5-10 mm). The thermochemical performances of the EM pellets were analyzed as a function of the mass mixing ratio of Mg(OH)(2) to EG (4:1, 8:1, and 16:1) used for preparing the EM. In both dehydration and hydration, the EM pellets showed a higher reaction rate and more homogeneous temperature distribution in the packed bed than did the pure Mg(OH)(2) pellets. Consequently, a greater final material conversion was achieved. A higher reactivity enhancement was measured with the addition of a greater quantity of EG in the EM preparation. From the experimental results, it was calculated that the bed comprising EM pellets (having a mass mixing ratio of 8:1) had a heat-storage capacity of 881 kJ/kg(Mg(OH)2), gross heat output of 714 kJ kg(Mg(OH)2), and mean power output rate of 132 W/kg(Mg(OH)2). These values were higher correspondingly than the 755, 505, and 94 W/kg(Mg(OH)2) values calculated for the bed comprising pure Mg(OH)(2) pellets. It was demonstrated that the EM pellets had higher reactivity than pure Mg(OH)(2) pellets because of their higher thermal conductivity. (C) 2013 Elsevier Ltd. All rights reserved.

The reaction performance enhancement of a chemical heat-storage material for a magnesium oxide/water chemical heat pump was discussed. A new composite, denoted as EML, was developed by mixing pure magnesium hydroxide with lithium bromide and expanded graphite, which were employed as reactivity and heat transfer enhancers, respectively. With respect to pure magnesium hydroxide powder, the EML composite showed higher reaction rates for dehydration and hydration transformations; further, the EML could dehydrate and hydrate at the same reaction temperature (200 degrees C). Addition of LiBr was found to decrease the estimated activation energy in the dehydration. The heat output capacity of the EML composite calculated at a hydration temperature of 110 degrees C was 1405.3 kJ kg(-1), which was higher than that of pure MgO. It was established that the newly developed EML composite is a promising candidate for novel chemical heat-storage materials for chemical heat pumps at working temperatures of 200-300 degrees C. (C) 2013 Elsevier Ltd. All rights reserved.

The chemical heat pump is a promising technology for the recovery of waste heat from industrial processes or cogeneration systems. It can be used for storing the surplus heat during low demand periods and release it for shaving the peaks of heat demand, with a benefit for the overall system efficiency. In this work, a packed bed reactor chemical heat pump based on the dehydration and hydration of magnesium hydroxide has been investigated. Due to its high thermal conductivity, expanded graphite was mixed with magnesium hydroxide to enhance heat transfer. The composite material, named EM, was developed and tested experimentally in order to understand the effects of expanded graphite on the chemical reactions occurring in the packed bed reactor. (C) 2013 Elsevier Ltd. All rights reserved.

A method of producing a composite hydrogen permeation membrane using a reverse buildup method has been proposed for a membrane fuel reformer. A 1- to 5-m-thick palladium alloy membrane and a nickel metal support layer were prepared by the proposed method. The uniqueness of the proposed method is that the palladium alloy layer was formed first, and the metal support layer was subsequently built on the alloy layer. This study demonstrates the production of the composite membrane by using a palladium-silver alloy and evaluates the performance of the produced membrane as a hydrogen permeation membrane. Hydrogen permeability of the composite membrane was measured under different values of pressure and temperature. It was reasonable to assume that hydrogen decomposed into hydrogen atoms on the surface of the composite membrane and that the hydrogen atoms permeated through the composite membrane. A permeability equation has been proposed, and the economic performance of the composite membrane has been discussed using experimental results.

Lithium chloride-modified magnesium hydroxide is a candidate material for thermochemical energy storage. In this work, the effects of lithium chloride mixing ratio, hydration temperature, and water vapor pressure on the hydration behavior of the material are investigated. Heat output densities for all experimental conditions are evaluated. The heat output density per unit weight of lithium chloride-modified magnesium hydroxide, at a molar mixing ratio of 0.10 mol of lithium chloride per mol of magnesium hydroxide, is 1.40 × 103 kJ kg-1 at a hydration temperature of 110 C and a water vapor pressure of 57.8 kPa. This value is higher than the heat output density of authentic magnesium hydroxide. © 2013 American Chemical Society.

Lithium chloride (LiCl) modified magnesium hydroxide (Mg(OH)(2)) is a potential new material for chemical heat pumps. However, there is insufficient information concerning its dehydration and hydration behavior. In this study, the dehydration and hydration reactions, corresponding to the heat storage and the heat output operations, respectively, of authentic Mg(OH)(2) and LiCl-modified Mg(OH)(2) were investigated by thermogravimetric methods and near infrared spectroscopy. The dehydration of authentic Mg(OH)(2) proceeded as a one-step reaction. In contrast, the dehydration of LiCl-modified Mg(OH)(2) occurred in two steps. The dehydration reaction rates were increased by LiCl modification of the Mg(OH)(2) surface, while the activation energy for the first-order dehydration reaction was lowered. The mechanism for the hydration reaction of magnesium oxide (MgO) was different to that for the hydration of LiCl-modified MgO. This difference was explained by the effect of the LiCl on the MgO particle surface. (C) 2011 Elsevier Ltd. All rights reserved.

A composite chemical heat storage material (EMC) comprising a mixture of expanded graphite (EG), magnesium hydroxide (Mg(OH)(2)), and calcium chloride (CaCl2) was developed as a magnesium oxide/water chemical heat pump reactant. The optimization of a mixing weight ratio between the Mg(OH)(2) content of EMC and EMC itself was discussed from the viewpoints of both heat storage capacity and reactivity by considering the reaction rate constants from a kinetic analysis. It was confirmed that the dehydration reactivity of EMC increased as the mixing weight ratio decreased; however, the heat capacity of the EMC unit mass decreased. A multiplied factor consisting of the multiplied value dehydration rate constant and mixing weight ratio was introduced. It was suggested that a weight ratio of approximately 0.80 was the optimized value when the mixing molar ratio between CaCl2 and Mg(OH)(2) was 0.10. Dehydration of EMC with an optimized mixing weight ratio and dehydration of pure Mg(OH)2 were conducted under various temperatures to compare the reaction rate constants of each material. From this study, it was demonstrated that EMC performed better on dehydration than pure Mg(OH)(2). (C) 2012 Elsevier Ltd. All rights reserved.