Norihisa Chitose

Radiolysis of aqueous phenol solutions with nanoparticles. 1. Phenol degradation and TOC removal in solutions containing TiO2 induced by UV, γ-ray and electron beams

Aqueous phenol solutions containing TiO(2) nanoparticles were irradiated with ultraviolet (UV), gamma-ray and electron beams. Organic compounds were fully removed by each type of radiation in the presence of the particles. The absorbed energy of the ionizing radiation (gamma-ray and electron beams) needed for removal was much lower than that of UV photocatalysis. Phenol was decomposed by the ionizing radiation in the absence of the nanoparticles and the addition of TiO(2) had no significant effect on phenol decomposition rate. Instead, total organic carbon (TOC) removal using the ionizing radiation was accelerated drastically by TiO(2). It is suggested that TiO(2) particles affect the intermediate compounds produced through the decomposition of phenol. The amount of removed TOC per absorbed energy were compared in the absence and the presence of TiO(2) nanoparticles. Radiolysis with the nanoparticles showed consistently high rate and high efficiency of TOC removal.

Development of Intermediate-Temperature SOFC Module Using Doped Lanthanum Gallate

An intermediate temperature solid oxide fuel cell (SOFC) module was developed using electrochemically active cells composed of (La, Sr)(Ga, Mg, Co)O 3 electrolyte, Ni-(Ce, Sm)O 2 anode, and (Sm, Sr)CoO 3 cathode. Seal-less planar type stack design was employed. The first generation module successfully provided the output power of I kW with thermal self-sustainability below 800°C. Maximum electrical efficiency obtained with this module was 43%[LHV] together with the corresponding fuel utilization of 78%. Dynamic performance tests demonstrated the capability of output power alteration from 0.6 to 1 kW while maintaining a high electrical conversion efficiency. Further testing and modification of the module for methane fuel utilization are in progress.

SOFC Module and System Development by Means of Sealless Metallic Separators with Lanthanum Gallate Electrolyte

The third-generation 1-kW e -class module was developed with an automatic control system. A conversion efficiency of 48% ac/lower heating value [ac/LHV] was achieved with an exhaust heat recovery unit. An endurance test using the third-generation 1-kW e module was done for over 1000 h and no degradation of the power generation performance was observed. In parallel, a single-cell unit, which includes one cell and two metallic separators, was tested for over 10000 h and the degradation rate of the terminal voltage was found to be 1-2%/1000 h. In the direction of scale-up, a triple-stack module of 3-kW e output was developed. A partial load as well as excess loads on the module were tested and the output power of 1-5 kW e was attained under thermally self-sustainable conditions. It was found that a high efficiency of 55% dc/lower heating value [dc/LHV] was obtained under stable operation. Ongoing research of the fourth-generation 1-kW e module has resulted in the conversion efficiency of 58% [dc/LHV].

Computational Fluid Dynamic Analysis of a Seal-Less Solid Oxide Fuel Cell Stack

Combined heat and power generation systems accommodating intermediate temperature (600-800°C) solid oxide fuel cell (SOFC) modules have been developed by Mitsubishi Materials Corporation and The Kansai Electric Power Co., Inc. High overall efficiency system units are designed in such a way that their output power can be modularized by altering the number of stacks inside the SOFC modules. The seal-less design concept is adopted to build generic stacks made up of stainless steel separators and disk-type planar electrolyte-supported cells. Innovative stack design together with its precise integration with the hot balance of plant components inside the SOFC module requires a number of design iterations supported by carefully planned experiments. In order to achieve improved levels of efficiency and reliability via optimum number of iterative cycles, we believe that the computational techniques offer significant advantages. In this work, a commercial computational fluid dynamics code is employed for solving the conservation of mass, momentum, and energy equations with an additional electrochemical submodel to simulate the coupled multiphysics processes in a generic SOFC stack. This approach proved to be effective in providing necessary guidance for identifying problem areas in the stack design and estimating the stack performance via less expensive numerical experiments. The results of the computational model are also compared with data I obtained by experimental measurements.

Development of Intermediate-Temperature Solid Oxide Fuel Cells Using Doped Lanthanum Gallate Electrolyte

Intermediate-temperature(IT) solid oxide fuel cells(SOFCs) were developed using lanthanum gallate electrolyte, samarium cobaltite cathode and the cermet anode of nickel and ceria. High efficiency operation below 800°C was enabled using planar disk type cells with unique seal less stack design. The first 10 kW-class combined heat and power (CHP) system provided AC output power of 10 kW with electrical and overall efficiency of 41 and 82 %HHV, respectively. Optimization of cell-stack components to increase the output power density is in progress.

A Unique Seal-Less Solid Oxide Fuel Cell Stack and Its CFD Analysis

Combined Heat and Power (CHP) generation units based on intermediate temperature (600∼800°C) solid oxide fuel cell (SOFC) modules have been collaboratively developed by Mitsubishi Materials Corporation and The Kansai Electric Power Co., Inc. Currently, hydrocarbon fuel utilising units designed to produce modular power outputs up to 10 kWe-AC with overall efficiencies greater than 80% (HHV) are being tested. A unique seal-less stack concept is adopted to build SOFC modules accommodating multiple stacks incorporated of stainless steel separators and disk-type planar electrolyte-supported cells. In order to advance the current technology to achieve improved levels of efficiency and reliability, through design iterations, computational modelling tools are being heavily utilised. This contribution will describe the results of coupled computational fluid dynamics (CFD) analysis performed on our fourth-generation 1 kW class SOFC stack. A commercially available CFD code is employed for solving the governing equations for conservation of mass, momentum and energy. In addition, a local electrochemical reaction model is coupled to the rest of the transport processes that take place within the SOFC stack. It is found that the CFD based multi-physics model is capable of providing necessary and proper guidance for identifying problem areas in designing multi-cell SOFC stacks. The stack performance is also estimated by calibrating the computational model against data obtained by experimental measurements.Copyright