High-efficiency Reactor Research Articles

Effect of the Ultrasonic Irradiation on the Cr(VI) Electroreduction Process in a Tubular Electrochemical Flow Reactor

The electroplating, leather tanning, and textile industries are facilities that discharge wastewaters contaminated with high concentrations of Cr(VI), which is carcinogenic and has negative health effects. Low-cost technologies to remove this pollutant must be generated with high-efficiency reactors. Electrochemical Cr(VI) reduction is a low-cost alternative process, which has been studied and applied with success at the laboratory level. In this work, the hydrodynamic behavior of the fluid into the sonoelectrochemical tubular flow reactor with spiral-helicoid-wire low-cost electrode material (carbon steel) was evaluated. The fluid behavior was evaluated by computational fluid dynamics (CFD). In addition, the dispersion the reactor was evaluated experimentally and by CFD. The reactor presented large dispersion that was considered into the model to describe the sonoelectrochemical process to reduce the Cr(VI) in wastewaters. Moreover, an empirical model to describe the electrochemical reduction of the Cr(V...

SCC and corrosion evaluations of the F/M steels for a supercritical water reactor

As one of the Generation IV nuclear reactors, a supercritical water cooled reactor (SCWR) is being considered as a candidate reactor due to its high thermal efficiency and simple reactor design without steam generators and steam separators. For the application of a structural material to a core’s internals and a fuel cladding, the material should be evaluated in terms of its corrosion and stress corrosion cracking susceptibility. Stress corrosion cracking and general corrosion tests of ferritic–martensitic (F/M) steels, high Ni alloys and an oxide dispersion strengthened (ODS) alloy were performed. Stress corrosion cracking (SCC) was not observed on the fractured surface of the T 91 steel in the supercritical water at 500, 550 and 600 °C. As the test temperature increased, the ultimate tensile strength (UTS) and yield strength (YS) of T 91 decreased, and a high dissolved oxygen level induced corrosion and low ductility. The F/M steels showed a high corrosion rate whereas the Ni base alloys showed a little corrosion at 500 and 550 °C. Corrosion rate of the F/M steels at 600 °C test was up to three times larger than that at 500 °C. A thin layer composed of Mo and Ni seems to retard the Cr diffusion into the out layer of the corrosion product of T 92 and T 122.

High Efficient Capacitance Coupled Plasma Reactor for Enhanced Surface Reaction

Capacitance-coupled plasma reactors are widely used in the semiconductor industry for the plasma enhanced processes. The specific optimization of the electrode design and reactor construction is most critical to optimize the plasma process in general. This article explores the recent breakthroughs and advancements of the-state-of-the-art plasma technology of recent DryScrub patents and studies. I propose a new interpretation of the Paschen Curves with applications to current industrial practices.

Novel microfibrous composite bed reactor: high efficiency H2production from NH3 with potential for portable fuel cell power supplies

A novel microfibrous composite bed reactor was developed and was demonstrated for high efficiency hydrogen production by the decomposition of ammonia at moderate temperatures in portable fuel cell power system applications. By using a high-speed and low-cost papermaking technology combined with a subsequent sintering process, sinter-locked three-dimensional microfibrous networks consisting of approximately 3 vol% 8 microm (dia.) nickel microfibers were utilized to entrap approximately 35 vol% 100-200 microm dia. porous Al(2)O(3) support particulates. A CeO(2) promoter and active Ni component were then dispersed onto the pore surface of the entrapped Al(2)O(3) support particulates by a stepwise incipient wetness impregnation method. The microfibrous structure took advantage of a large void volume, entirely open structure, high heat/mass transfer, high permeability, good thermal stability, and unique form factors. Addition of ceria significantly promoted the low-temperature activity of Ni/Al(2)O(3) catalyst particulates incorporated into the micorfibrous structure. The use of fine particles of catalyst significantly attenuated the intraparticle mass transport limitations. As a result, the present novel microfibrous composite bed reactor provided excellent activity and structure stability in ammonia decomposition, as well as low pressure drop and high efficiency reactor design. At a 90% conversion of a 145 sccm ammonia feed rate, the microfibrous entrapped Ni/CeO(2)-Al(2)O(3) catalyst composite bed could provide a 4-fold reduction of catalytic bed volume and a 5-fold reduction of catalytic bed weight (or 9-fold reduction of catalyst dosage), while leading to a reduction of reaction temperature of 100 degrees C, compared to a packed bed with 2 mm dia. Ni/CeO(2)-Al(2)O(3) catalyst pellets. This composite bed was capable of producing roughly 22 W of hydrogen power, with an ammonia conversion of 99% at 600 degrees C in a bed volume of 0.5 cm(3) throughout a 100 h continuous test. These initial and promising results established that the microfibrous nickel-based catalyst composites were effective for high efficiency production of hydrogen by ammonia decomposition, while achieving a significant reduction of overall catalytic bed weight and volume. We anticipate our assay to be a new point for small-scale hydrogen production, where the microfibrous catalytic reactors considered in isolation can satisfy several of the most fundamental criteria needed for useful operation.

High Efficient Capacitance Coupled Plasma Reactor for Enhanced Surface Reaction

not Available.

Subchannel Analysis to Investigate the Fuel Assembly for the Supercritical-water-cooled Power Reactor

The supercritical-water-cooled power reactor (SCPR) is expected to reduce power costs compared with those of current LWRs because of its high thermal efficiency and simple reactor system. The high thermal efficiency is obtained by supercritical pressure water cooling. The fuel cladding surface temperature increases locally due to a synergistic effect from the increased coolant temperature, the expanded flow deflection due to coolant density change and the decreased heat transfer coefficient, if the coolant flow distribution is non-uniform in the fuel assembly. Therefore, the SCPR fuel assembly is designed using a subchannel analysis code based on the SILFEED code for BWRs. The SCPR fuel assembly has many square-shaped water rods. The fuel rods are arranged around these water rods. The fuel rod pitch and diameter are 11.2 mm and 10.2 mm, respectively. Since coolant flow distribution in the fuel assembly strongly depends on the gap width between the fuel rod and the water rod, the proper gap width is examined. Subchannel analysis shows that the coolant flow distribution becomes uniform when the gap width is 1.0 mm. The maximum fuel cladding surface temperature is lower than 600°C and the temperature margin of the fuel cladding is increased in the design.

Subchannel Analysis to Investigate the Fuel Assembly for the Supercritical-water-cooled Power Reactor

The supercritical-water-cooled power reactor (SCPR) is expected to reduce power costs compared with those of current LWRs because of its high thermal efficiency and simple reactor system. The high thermal efficiency is obtained by supercritical pressure water cooling. The fuel cladding surface temperature increases locally due to a synergistic effect from the increased coolant temperature, the expanded flow deflection due to coolant density change and the decreased heat transfer coefficient, if the coolant flow distribution is non-uniform in the fuel assembly. Therefore, the SCPR fuel assembly is designed using a subchannel analysis code based on the SILFEED code for BWRs. The SCPR fuel assembly has many square-shaped water rods. The fuel rods are arranged around these water rods. The fuel rod pitch and diameter are 11.2 mm and 10.2 mm, respectively. Since coolant flow distribution in the fuel assembly strongly depends on the gap width between the fuel rod and the water rod, the proper gap width is examined. Subchannel analysis shows that the coolant flow distribution becomes uniform when the gap width is 1.0 mm. The maximum fuel cladding surface temperature is lower than 600°C and the temperature margin of the fuel cladding is increased in the design.

A High-Efficiency Reactor for the Pulsed Plasma Conversion of Methane

The authors recently developed a high-frequency pulsed plasma process for methane conversion to acetylene and hydrogen using a co-axial cylindrical (CAC) type of reactor. The energy efficiency represented by methane conversion rate per unit input energy has been improved so that such a pulsed plasma has potential for commercial acetylene production. A pulsed plasma consists of a pulsed corona discharge and a pulsed spark discharge. Most of energy is injected over the duration of the pulsed spark discharge. Methane conversion using this kind of pulsed plasma is a kind of pyrolysis enhanced by the pulsed spark discharge. In this study, a point-to-point (PTP) type of reactor that can produce a discharge channel over the duration of a pulse discharge was used for the pulsed plasma conversion of methane. The energy efficiency and carbon formation on electrodes have been improved. The influences of pulse frequency and pulse voltage on methane conversion rate and product selectivity were investigated. The features of methane conversion using PTP and CAC reactors were discussed.

Lateral solids dispersion in a high-density riser with swirling air flow

Lateral mixing of solids in a high-density riser is investigated by a phosphor tracer method. The lateral solids dispersion is determined by measuring the solids RTD at different radii using point sources for tracer injection. A two-dimensional dispersion model describes the measured RTD curves satisfactorily. The cross-sectional average solids fraction has the dominant effect on the lateral solids mixing in the high-density riser. The lateral Peclet number increases exponentially with the solids fraction and is not sensitive to gas velocity and solids circulation rate. The lateral Peclet number in high-density riser is over 1200, indicating that the lateral mass transfer is a limitation factor for the application of high-density riser as a high efficient reactor. Correlation of the lateral Peclet numbers fits the experimental data well. When swirling air is introduced into the riser, the lateral Peclet number decreases and the lateral solids mixing is intensified by the swirling flow.

High efficiency reactor for the biooxidation of ferrous iron

The biooxidation of ferrous iron is a potential industrial process in the regeneration of ferric iron, in hydrometallurgical leaching operations and in the removal of H 2S in combustible gases. Another field of application is the treatment of acid mine drainage water. The aim of this work was the design of a continuous reactor for a high efficiency ferrous iron biooxidation capable of attaining the oxidation rates demanded by industrial processes for a minimum-sized reactor. Some criteria of design come from the data of former studies. The bioreactor consists of a 1249 mm high and 84 mm diameter column randomly packed with siliceous stone particles with inlets for fresh medium and air at the bottom. The present work studies the influence of air and liquid flow rates on the ferrous iron biooxidation in a flooded packed bed bioreactor. Starting from the data of this study, kinetics, and oxygen concentration in the outlet gas, it was deduced that the biooxidation process was limited by the availability of oxygen in the liquid medium. The free-swimming cells concentration was measured in the outlet solution for different operating conditions. It was observed that once the biofilm has been formed, a variation in the liquid flow rate does not alter the biomass attached to the packing. The highest ferric productivity attained was 11.25 g/L·h.

Flow-Induced Accident and Transient Analyses of a Direct-Cycle, Light-Water-Cooled, Fast Breeder Reactor Operating at Supercritical Pressure.

This paper deals with the safety design of a light-water-cooled fast breeder reactor operating at supercritical pressure (SCFBR) hich has the advantages of high thermal efficiency and simple reactor system. A new computer code was developed and five important flow-induced events were analyzed for the 1,245 M We SCFBR with two coolant loops. A core flow rate must be maintained for the safety of once-through type plant. Thus this reactor has two high-pressure auxiliary feedwater, four low pressure coolant injection and automatic depressurization systems. They are activated by the emergency signals of the decrease in coolant flow rate. The feedwater pumps should have fly-wheels for prolonging the coast-down time. It has been found that the peak cladding surface temperature of fuel rods does not exceed the allowable temperature under the accidents of the total loss of feedwater flow and feedwater pump shaft seizure. The minimum deterioration heat flux ratio satisfies the criterion under the transients of the ...

新型転換炉「ふげん」用炉内中性子検出器の開発

In the Prototype Heavy Water Reactor "Fugen", Zircaloy-2 is used as in-core structural material for neutron economy. In-core neutron detectors for the Local Power Monitor are placed in heavy water moderator of 50°C. Such "Fugen" in-core conditions bring a high level thermal neutron flux environment, which burns away the neutron conversion material (235U) in the detector more rapidly compared to that of the light water reactors. Therefore, it was strongly required to realize a neutron detector which could work for a long time under such environment.To resolve this unexperienced subject, the authors started to develop an advanced in-core neutron detector for "Fugen" by adopting various technologies, The developed neutron detectors have smart structures and excellent characteristics such as (1) light weight structure to avoid gas displacement due to γ-heating, (2) structure of assembling detectors in a Zircaloy-2 tube, (3) wide range and linear current measuring performance and (4) long life performance by the use of mixed uranium (235U+234U). This kind of in-core neutron detector is now in the reactor core of "Fugen" nuclear power plant and is contributing to the high-efficient reactor operation.

Investigation of the velocity field in the space above the reactor bed for dehydrogenating ethylbenzene and butylenes

1. The velocity fields were measured in the volume above the bed of model reaction equipment, with fixed catalyst beds of diameters 100, 200, 250, and 600 mrm for all three designs of distributors. 2. It was found that similarity of velocity distribution is not maintained on increasing the model size. 3. Further investigation is necessary to determine the hydraulic modelling criteria for high-efficiency reactor and adsorption equipment.