Two-step Water Research Articles

Moving Brick Receiver–Reactor: A Solar Thermochemical Reactor and Process Design With a Solid–Solid Heat Exchanger and On-Demand Production of Hydrogen and/or Carbon Monoxide

Three crucial aspects still to be overcome to achieve commercial competitiveness of the solar thermochemical production of hydrogen and carbon monoxide are recuperating the heat from the solid phase, achieving continuous or on-demand production beyond the hours of sunshine, and scaling to commercial plant sizes. To tackle all three aspects, we propose a moving brick receiver–reactor (MBR2) design with a solid–solid heat exchanger. The MBR2 consists of porous bricks that are reversibly mounted on a high temperature transport mechanism, a receiver–reactor where the bricks are reduced by passing through the concentrated solar radiation, a solid–solid heat exchanger under partial vacuum in which the reduced bricks transfer heat to the oxidized bricks, a first storage for the reduced bricks, an oxidation reactor, and a second storage for the oxidized bricks. The bricks may be made of any nonvolatile redox material suitable for a thermochemical two-step (TS) water splitting (WS) or carbon dioxide splitting (CDS) cycle. A first thermodynamic analysis shows that the MBR2 may be able to achieve solar-to-chemical conversion efficiencies of approximately 0.25. Additionally, we identify the desired operating conditions and show that the heat exchanger efficiency has to be higher than the fraction of recombination in order to increase the conversion efficiency.

Water Splitting via Decoupled Photocatalytic Water Oxidation and Electrochemical Proton Reduction Mediated by Electron-Coupled-Proton Buffer.

Water splitting mediated by electron-coupled-proton buffer (ECPB) provides an efficient way to avoid gas mixing by separating oxygen evolution from hydrogen evolution in space and time. Though electrochemical and photoelectrochemcial water oxidation have been incorporated in such a two-step water splitting system, alternative ways to reduce the cost and energy input for decoupling two half-reactions are desired. Herein, we show the feasibility of photocatalytic oxygen evolution in a powder system with BiVO4 as a photocatalyst and polyoxometalate H3 PMo12 O40 as an electron and proton acceptor. The resulting reaction mixture was allowed to be directly used for the subsequent hydrogen evolution with the reduced H3 PMo12 O40 as electron and proton donors. Our system exhibits excellent stability in repeated oxygen and hydrogen evolution, which brings considerable convenience to decoupled water splitting.

SURFACE SOURCES OF CENTRALIZED DRINKING WATER SUPPLY: THEIR PURIFICATION FROM BIOCONTAMINATION AND PURIFIACTION EFFICIENCY DETERMINATION (WITH THE CITY OF SIMFEROPOL TAKEN AS AN EXAMPLE)

The paper demonstrates statistical analysis results of biocontamination of Simferopol water reservoirs of centralized drinking water supply sources. The biocontamination results were obtained by permanganate oxidizability factor. The analysis revealed a consistent patt ern of biocontamination distribution and its analytical description for four sources of centralized water supply. The paper also introduces models of this factor distribution for water purifi ed in water-purifi cation plants of the city of Simferopol (in clean-water reservoirs). The eff ectiveness of two-step water purifi cation scheme (horizontalstrainer chamber - high-rate trickling fi lter) from biocontamination is calculated. The research demonstrates a probability of exceeding permanganate oxidizability normative values for drinking water according to WHO and EU standards and according to drinking water requirements for this indicator in the Russian Federation. The required degree of permanganate oxidizability disposal at water treatment plants which will make the quality of drinking water meet WHO and EU standards is also defi ned.

Particle reactors for solar thermochemical processes

Utilization of solar thermal power for high temperature fuel production has the potential to significantly reduce the fossil fuel dependence of our current economy. Over the past two decades, remarkable progress has been made in the development of solar driven thermochemical reactors for the production of hydrogen and syngas as they are promising energy carriers for transportation, domestic and industrial applications. However, there are solar peculiarities in comparison to conventional thermochemical processes – high thermal flux density and frequent thermal transients because of the fluctuating insolation-, and conventional industrial thermochemical reactors are generally not suitable for solar driven reactors. Therefore, solar-specific modifications of reactor design are necessary to realize efficient solar driven thermochemical processes. In solar thermochemical reactors, the methods for solar-heating particulate solid feedstock to high temperatures can be broadly classified as solar “directly” and “indirectly” absorbing reactors. On solar thermochemical processes involving reacting solid particles at high temperatures, such as “solar two-step water splitting with metal oxides” and “solar gasification”, various types of solar directly and indirectly absorbing particle reactors have been developed. In this review, recent development of solar particle reactors for the above solar thermochemical processes is described.

A Study on Hydrogen Production with High Temperature Solar Heat Thermochemical Cycle by Heat Recovery

Two-step water splitting thermochemical cycle with CeO2/ZrO2 foam device was investigated by using a solar simulator composed of 2.5 kW Xe-Arc lamp and mirror reflector. The hydrogen production of CeO2/ZrO2 foam device depending on heat recovery of Thermal-Reduction step and Water-Decomposition step was analyzed, and the hydrogen production of CeO2/ZrO2 and NiFe2O4/ZrO2 foam devices was compared. Resultantly, the quantity of hydrogen generation increased by 52.02% when the carrier gas of Thermal-Reduction step is preheated to 200°C and, when the N2/steam is preheated to 200°C in the Water-Decomposition step, the quantity of hydrogen generation increased by 35.85%. Therefore, it is important to retrieve the heat from the highly heated gases discharged from each of the reaction spaces in order to increase the reaction temperature of each of the stages and thereby increasing the quantity of hydrogen generated through this.

4-4-5 45kW_ KIER太陽炉によるCeO_2/MPSZ反応デバイスを用いた水分解サイクルの太陽試験(4-4 太陽熱・水素製造,Session 4 新エネルギー)

4-4-5 45kW_ KIER太陽炉によるCeO_2/MPSZ反応デバイスを用いた水分解サイクルの太陽試験(4-4 太陽熱・水素製造,Session 4 新エネルギー)

4-9-3 オーストラリアCSIROソーラー集光設備を用いたロータリー式太陽反応炉による水素生産(4-9 太陽熱発電・水素製造1,Session 4 新エネルギー,研究発表)

4-9-3 オーストラリアCSIROソーラー集光設備を用いたロータリー式太陽反応炉による水素生産(4-9 太陽熱発電・水素製造1,Session 4 新エネルギー,研究発表)

4-2-1 レーザー加工による金属ドープCeO_2の反応表面積増大効果を用いた集光太陽熱利用水素生成反応促進(Session 4-2 太陽熱・熱分解)

4-2-1 レーザー加工による金属ドープCeO_2の反応表面積増大効果を用いた集光太陽熱利用水素生成反応促進(Session 4-2 太陽熱・熱分解)

4-10-4 フェライト内循環流動層反応器の光照射による二段階水熱分解(4-10 太陽熱発電・水素製造2,Session 4 新エネルギー,研究発表)

4-10-4 フェライト内循環流動層反応器の光照射による二段階水熱分解(4-10 太陽熱発電・水素製造2,Session 4 新エネルギー,研究発表)

4-2-1 二段階水分解反応を用いるソーラー水素生産用反応性セラミックスの開発(4-2 太陽熱発電・水素製造2,Session 4 新エネルギー,研究発表)

4-2-1 二段階水分解反応を用いるソーラー水素生産用反応性セラミックスの開発(4-2 太陽熱発電・水素製造2,Session 4 新エネルギー,研究発表)

4-3 二号機ロータリー式太陽反応炉(東工大提案)を用いたYSZ-Niフェライト固溶体による二段階水分解反応((1)太陽熱発電・水素製造1,Session 4 新エネルギー)

4-3 二号機ロータリー式太陽反応炉(東工大提案)を用いたYSZ-Niフェライト固溶体による二段階水分解反応((1)太陽熱発電・水素製造1,Session 4 新エネルギー)

On the diffusion coefficient calculation in two-step light water reactor core analysis

ABSTRACTThis paper presents consistent and rigorous accuracy assessments of various methods for calculating the diffusion coefficients in a two-step reactor core analysis of light water reactors (LWRs). The diffusion coefficients are significantly affected by the transport correction and critical spectrum calculations. There are various methods for the transport corrections (inflow/outflow/hybrid corrections) and critical spectrum calculations (B1/P1/CASMO-4E methods) so that it is necessary to decide the best combination to achieve a high accuracy in the transport/diffusion two-step analysis. Numerical tests are performed step-by-step to search for the best combination of the methods by comparing each other the transport one-step results, transport/diffusion two-step results, and Monte Carlo results. Numerical test results with a large and a small LWR core show that the combination of inflow transport correction and CASMO-4E critical spectrum calculation is most accurate than the other combinations in terms of eigenvalues and assembly power distributions.

The Water Load Test As a Measure of Gastric Interoception: Development of a Two-Stage Protocol and Application to a Healthy Female Population

The sensitivity for one’s own internal body signals (i.e., interoception) has been demonstrated to play an important role in the pathogenesis of eating and weight disorders. Most previous measures assessing interoceptive processing have not, or only partly, captured perception of hunger and satiety cues, which is a core aspect of interoceptive deficits in eating disorders. In addition, methods used to measure sensitivity to gastric signals are heterogeneous and findings inconsistent. The primary aim of the present study was to establish a standardised test to measure gastric interoception, and to provide normative data using a non-clinical adult sample. The two-step Water Load Test (WLT-II) involves ingestion of non-caloric water until perceived satiation (step 1) and until maximum fullness (step 2). The WLT-II consists of several variables: Besides volumes of water ingested until satiation and maximum fullness expressed in ml, percentage of satiation to maximum fullness is calculated as an individual index of gastric interoception that is not confounded with stomach capacity. Ninety-nine healthy women participated in the study. Measures included the WLT-II, the heartbeat tracking test, a self-report questionnaire assessing subjective sensations, and the Eating Disorder Inventory-2. Twenty-eight participants underwent test-retest of the WLT-II. Results suggest that the WLT-II is a valid and reliable measure of gastric interoception. Importantly, satiation volume and percentage of satiation to maximum fullness were strongly positively related to self-reported bulimic symptoms, indicating that the WLT-II could emerge as a useful clinical tool to measure interoceptive processing in the field of eating disorders.

A Novel Two-Step Water-Splitting Electrochemical Cycle for Hydrogen Production

We propose a novel electrochemical water-splitting cycle consisting of two-step electrochemical reactions for oxygen and hydrogen production by introducing an intermediate electrode. Two-step water electrolysis offers the following advantages: (i) higher-purity hydrogen can be obtained because hydrogen and oxygen gases are generated in different steps and (ii) high energy conversion efficiency for hydrogen production can be achieved by reducing the ohmic overpotential between the electrodes through the use of a thinner separator than a conventional one. Furthermore, a pulsed current can be supplied to the electrolysis cell, which leads to a low concentration overpotential by increasing the reacting species concentration in a diffusion layer. In the present study, manganese dioxide (MnO2) was selected as the intermediate electrode because its oxidation-reduction potential is located between the potentials of the hydrogen and oxygen evolution reactions.

4-3-4 CeO2系セラミックスを用いる集光太陽熱利用二段階水分解反応における表面積増大効果

4-3-4 CeO2系セラミックスを用いる集光太陽熱利用二段階水分解反応における表面積増大効果

Manganese-Substituted Polyoxometalate as an Effective Shuttle Redox Mediator in Z-Scheme Water Splitting under Visible Light.

In the present study, a polyoxometalate is for the first time applied as a shuttle redox in two-step (Z-Scheme) photocatalytic water splitting. Photocatalytic H2 evolution using a Mn-substituted polyoxometalate [SiW11 O39 Mn(II) (H2 O)](6-) as an electron donor proceeded over a Ru-loaded SrTiO3 :Rh photocatalyst under visible light with relatively high selectivity, accompanied by the stoichiometric production of its oxidized form [SiW11 O39 Mn(III) (H2 O)](5-) . Photocatalytic O2 evolution using the oxidized [SiW11 O39 Mn(III) (H2 O)](5-) as an electron acceptor proceeded over PtOx -loaded WO3 photocatalyst under visible light with relatively high quantum efficiency and selectivity, whereas the loading of effective PtOx cocatalyst was necessary to facilitate the reduction of polyoxometalate. Finally, a two-step water splitting into H2 and O2 was demonstrated under visible light using the couple of Mn-substituted polyoxometalate as shuttle redox between Ru/SrTiO3 :Rh and PtOx /WO3 photocatalysts, under mildly acidic conditions with pH≈4.5.

Pilot-scale solar reactor operation and characterization for fuel production via the Zn/ZnO thermochemical cycle

Successful demonstration and promising characterization of a solar reactor pilot plant for thermal reduction of ZnO as part of a two-step water and CO2 splitting cycle has been accomplished at the 100kWth scale in a 1MW solar furnace. The solar reactor pilot plant was operated for over 97h and achieved sustained reaction temperatures well above 2000K, while demonstrating ZnO dissociation rates as high as 28g/min totaling over 28kg of processed reactant during 13 full days of experimentation. In-situ, high temperature, flow visualization of the quartz window enabled the unimpeded operation of the solar reactor. As many as three consecutive full day experiments were conducted without complication. Solar power delivered to the reaction cavity ranged between 90 and 128kWth, at peak solar concentrations as high as 4671kW/m2. The products Zn and O2 were quenched with Ar(g) and recovered in a filter battery, where collected particles contained molar Zn-content as high as 44%. During experimentation, switching between product collection filter cartridges resulted in 54 unique experiments, where a maximum solar-to-chemical efficiency of 3% was recorded for the solar reactor. Robust characterization of the product quenching device revealed inherent limitations in its effectiveness, and thus solar-to-fuel energy conversion efficiency was limited to 0.24% if it would have been possible to supply 4640Ln/min of Ar(g). Further, only a limitation on available experimental time prohibited the demonstration of significantly higher dissociation rates, achievable with higher ZnO reactant feed rates. While the use of large volumes of quenching Ar(g) to separate the reaction products remains a significant obstacle to achieving higher solar-to-fuel efficiencies, demonstration of solar reactor technology at the pilot-scale represents significant progress toward the realization of industrial-scale solar fuels production.

Proton-Conducting Magnetic Coordination Polymers.

Three isostructural lanthanide-based two- dimensional coordination polymers (CPs) {[Ln2(L)3(H2O)2]n⋅2n CH3OH)⋅2n H2O} (Ln=Gd(3+) (1), Tb(3+) (2), Dy(3+) (3); H2L=cyclobutane-1,1-dicarboxylic acid) were synthesized by using a low molecular weight dicarboxylate ligand and characterized. Single-crystal structure analysis showed that in complexes 1-3 lanthanide centers are connected by μ3-bridging cyclobutanedicarboxylate ligands along the c axis to form a rod-shaped infinite 1D coordination chain, which is further linked with nearby chains by μ4-connected cyclobutanedicarboxylate ligands to form 2D CPs in the bc plane. Viewing the packing of the complexes down the b axis reveals that the lattice methanol molecules are located in the interlayer space between the adjacent 2D layers and form H-bonds with lattice and coordinated water molecules to form 1D chains. Magnetic properties of complexes 1-3 were thoroughly investigated. Complex 1 exhibits dominant ferromagnetic interaction between two nearby gadolinium centers and also acts as a cryogenic magnetic refrigerant having a significant magnetic entropy change of -ΔSm=32.8 J kg(-1) K(-1) for ΔH=7 T at 4 K (calculated from isothermal magnetization data). Complex 3 shows slow relaxation of magnetization below 10 K. Impedance analysis revealed that the complexes show humidity-dependent proton conductivity (σ=1.5×10(-5) S cm(-1) for 1, σ=2.07×10(-4) S cm(-1) for 2, and σ=1.1×10(-3) S cm(-1) for 3) at elevated temperature (>75 °C). They retain the conductivity for up to 10 h at high temperature and high humidity. Furthermore, the proton conductivity results were correlated with the number of water molecules from the water-vapor adsorption measurements. Water-vapor adsorption studies showed hysteretic and two-step water vapor adsorption (182,000 μL g(-1) for 1, 184,000 μL g(-1) for 2, and 1,874,000 μL g(-1) for 3) in the experimental pressure range. Simulation of water-vapor adsorption by the Monte Carlo method (for 1) confirmed the high density of adsorbed water molecules, preferentially in the interlayer space between the 2D layers.

Oxygen and hydrogen productivities and repeatable reactivity of 30-mol%-Fe-, Co-, Ni-, Mn-doped CeO2−δ for thermochemical two-step water-splitting cycle

The characteristics of oxygen/hydrogen productivity using 30-mol%-M (M = Fe, Co, Ni, Mn)-doped CeO2−δ (30-mol%-M-CeO2−δ) were studied for the thermochemical two-step water splitting cycle comprising TR (thermal reduction) at 1500 °C and WD (water decomposition) at 1150 °C. The reproducibility of oxygen evolution was evaluated using 30-mol%-M-CeO2−δ and the effects of different M dopants were compared in the TR temperature range of 1200–1500 °C. Two solid phases detected in the 30-mol%-M- CeO2−δ powders were involved in the redox reaction of the thermochemical two-step water splitting cycle. Among the M-CeO2−δ samples evaluated, Mn-doped CeO2−δ provided the most stable and reproducible results and the highest reactivity for oxygen evolution at all temperatures employed for the TR step of the thermochemical two-step water-splitting cycle.

Simulation of Flux Distributions on the Foam Absorber with Solar Reactor for Thermo-chemical Two-step Water Splitting H2 Production Cycle by the 45 kWth KIER Solar Furnace

Abstract The flux distributions on the device in the solar reactor with the solar furnace were studied. This study aims to understand of characters of concentrated sun rays through KIER solar furnace and design of device shape for uniform heat distribution on the device surface. For the calculation of heat flux on the device with the KIER solar furnace, the optical modeling program Soltrace was used. At first, the KIER 45 kWth solar furnace and flat disk type device shape was simulated for understand of past experimental results. And then 3 cylinder shape device model and 1 conical shape device model was suggested and the heat flux intensity on the device was calculated. Finally, 5 models which is including flat disk type device shape, 3 cylinder shape, and 1 conical shape device models was calculated and compared. The results show that the concentrated sun rays from dish and heat flux intensity are has a directional characteristic concentrated to normal direction than perpendicular direction. The results will be applied to next solar demonstrations which are design of new solar reactor and new device shape.