Application of an Internally Circulating Fluidized Bed for Windowed Solar Chemical Reactor with Direct Irradiation of Reacting Particles

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Tatsuya Kodama ◽  
Syu-ichi Enomoto ◽  
Tsuyoshi Hatamachi ◽  
Nobuyuki Gokon
Keyword(s):  
Fluidized Bed ◽  
Circulating Fluidized Bed ◽  
Chemical Reactor ◽  
Thermal Reduction ◽  
Storage Efficiency ◽  
Solar Reactor ◽  
Direct Irradiation ◽  
Thermochemical Processes ◽  
Reactor Operating ◽  
Reduction Of Metal Oxides

Solar thermochemical processes require the development of a high-temperature solar reactor operating at 1000–1500°C, such as solar gasification of coal and the thermal reduction of metal oxides as part of a two-step water splitting cycle. Here, we propose to apply “an internally circulating fluidized bed” for a windowed solar chemical reactor in which reacting particles are directly illuminated. The prototype reactor was constructed in a laboratory scale and demonstrated on CO2 gasification of coal coke using solar-simulated, concentrated visible light from a sun simulator as the energy source. About 12% of the maximum chemical storage efficiency was obtained by the solar-simulated gasification of the coke.

New Solar Water-Splitting Reactor With Ferrite Particles in an Internally Circulating Fluidized Bed

2007 ◽  
Author(s):  
Nobuyuki Gokon ◽  
Shingo Takahashi ◽  
Hiroki Yamamoto ◽  
Tatsuya Kodama
Keyword(s):  
Metal Oxide ◽  
Fluidized Bed ◽  
Water Splitting ◽  
Circulating Fluidized Bed ◽  
Thermal Reduction ◽  
Solar Irradiation ◽  
Solar Water Splitting ◽  
Oxide Particles ◽  
Efficient Heat Transfer ◽  
Reactor Operating

The thermal reduction of metal oxides as part of a thermochemical two-step water splitting cycle requires the development of a high temperature solar reactor operating at 1000–1500°C. Direct solar energy absorption by metal-oxide particles provides efficient heat transfer directly to the reaction site. This paper describes experimental results of a windowed thermochemical water-splitting reactor using an internally circulating fluidized bed of the reacting metal-oxide particles under direct solar irradiation. The reactor has a transparent quartz window on the top as aperture. The concentrated solar radiation passes downward through the window and directly heats the internally circulating fluidized bed of metal-oxide particles. Therefore, this reactor needs to be combined with a solar tower or beam down optics. NiFe2O4/m-ZrO2 (Ni-ferrite supported on zirconia) particles is loaded as the working redox material in the laboratory scale reactors, and thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally-reduced sample is oxidized back to Ni-ferrite with steam at 1000°C. As the results, the conversion of ferrite reached about 44% of maximum value in the reactor by 1kW of incident solar power. The effects of preheating temperature and particle size of NiFe2O4/m-ZrO2 were tested for thermal reduction of internally circulating fluidized bed in this paper.

New Solar Water-Splitting Reactor With Ferrite Particles in an Internally Circulating Fluidized Bed

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Nobuyuki Gokon ◽  
Shingo Takahashi ◽  
Hiroki Yamamoto ◽  
Tatsuya Kodama
Keyword(s):  
Metal Oxide ◽  
Fluidized Bed ◽  
Water Splitting ◽  
Circulating Fluidized Bed ◽  
Thermal Reduction ◽  
Beam Irradiation ◽  
Solar Water Splitting ◽  
Oxide Particles ◽  
Efficient Heat Transfer ◽  
Reactor Operating

The thermal reduction of metal oxides as part of a thermochemical two-step water-splitting cycle requires the development of a high-temperature solar reactor operating at 1000–1500°C. Direct solar energy absorption by metal-oxide particles provides direct efficient heat transfer to the reaction site. This paper describes the experimental results of a windowed small reactor using an internally circulating fluidized bed of reacting metal-oxide particles under direct solar-simulated Xe-beam irradiation. Concentrated Xe-beam irradiation directly heats the internally circulating fluidized bed of metal-oxide particles. NiFe2O4∕m‐ZrO2 (Ni-ferrite on zirconia support) particles are loaded as the working redox material and are thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally reduced sample is oxidized back to Ni-ferrite with steam at 1000°C. The conversion efficiency of ferrite reached 44% (±1.0%), which was achieved using the reactor at 1kW of incident Xe lamp power. The effects of preheating temperature and NiFe2O4∕m‐ZrO2 particle size on the performance of the reactor for thermal reduction using an internally circulating fluidized bed were evaluated.

Internally Circulating Fluidized Bed Reactor Using m-ZrO2 Supported NiFe2O4 Particles for Thermochemical Two-Step Water Splitting

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Nobuyuki Gokon ◽  
Hiroki Yamamoto ◽  
Nobuyuki Kondo ◽  
Tatsuya Kodama
Keyword(s):  
Fluidized Bed ◽  
Water Splitting ◽  
Gas Flow ◽  
Circulating Fluidized Bed ◽  
Fluidized Bed Reactor ◽  
Thermal Reduction ◽  
Input Power ◽  
Light Irradiation ◽  
Bed Temperature ◽  
N2 Flow Rate

A windowed internally circulating fluidized bed reactor was tested using m-ZrO2-supported NiFe2O4(NiFe2O4/m-ZrO2) particles as redox material for thermochemical two-step water splitting to produce hydrogen from water. The internally circulating fluidized bed of NiFe2O4/m-ZrO2 particles is directly heated by solar-simulated Xe light irradiation through a transparent quartz window mounted on top of the reactor. A sun simulator with three Xe lamps at laboratory scale has been newly installed in our laboratory for testing the fluidized bed reactor. The input power of incident Xe light can be scaled up to 2.6 kWth. Temperature distributions within the fluidized bed are measured under concentrated Xe light irradiation with an input power of 2.6 kWth. Hydrogen productivity and reactivity for the fluidized bed of NiFe2O4/m-ZrO2 particles are examined using two different reactors under the N2 flow rate and flow ratio, which yield a higher bed temperature. The feasibility of successive two-step water splitting using the fluidized bed reactor is examined by switching from N2 gas flow in the thermal reduction step to a steam/N2 gas mixture in the water decomposition step. It is confirmed that hydrogen production takes place in the single fluidized bed reactor by successive two-step water splitting.

Coal Coke Gasification in a Windowed Solar Chemical Reactor for Beam-Down Optics

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Tatsuya Kodama ◽  
Nobuyuki Gokon ◽  
Shu-ich Enomoto ◽  
Shouta Itoh ◽  
Tsuyoshi Hatamachi
Keyword(s):  
Size Fraction ◽  
Chemical Reactor ◽  
Power Input ◽  
Reaction Site ◽  
Coal Particles ◽  
Energy Peak ◽  
Thermochemical Processes ◽  
Efficient Heat Transfer ◽  
Co2 Flow ◽  
Reactor Operating

Solar thermochemical processes, such as solar gasification of coal, require the development of a high temperature solar reactor operating at temperatures above 1000°C. Direct solar energy absorption by reacting coal particles provides efficient heat transfer directly to the reaction site. In this work, a windowed reactor prototype designed for the beam-down optics was constructed at a laboratory scale and demonstrated for CO2 gasification of coal coke using concentrated visible light from a sun-simulator as the source of energy. Peak conversion of light energy to chemical fuel (CO) of 14% was obtained by irradiating a fluidized bed of 500–710 μm coal coke size fraction with a power input of about 1 kW and a CO2 flow-rate of 6.5 dm3 min−1 at normal conditions.

A Two-Step Water Splitting With Ferrite Particles and Its New Reactor Concept Using an Internally Circulating Fludized-Bed

Solar Energy ◽  
2006 ◽  
Author(s):  
Nobuyuki Gokon ◽  
Takayuki Mizuno ◽  
Shingo Takahashi ◽  
Tatsuya Kodama
Keyword(s):  
Fluidized Bed ◽  
Water Splitting ◽  
Circulating Fluidized Bed ◽  
Experimental Studies ◽  
Redox System ◽  
Chemical Reactor ◽  
Inert Atmosphere ◽  
Zro2 Particle ◽  
Concentrated Solar Radiation ◽  
Particle Bed

A thermochemical two-step water splitting cycle using a redox system of iron-based oxides or ferrites is one of the promising processes for converting and storing solar energy into a fuel in sunbelt regions. The ZrO2-supported ferrite (or the ferrite/ZrO2) powders exhibit superior performances on activity and repeatability of the cyclic reactions when compared to conventional unsupported ferrites. In the first step at 1400°C under an inert atmosphere, ferrite on ZrO2 support is thermally decomposed to the reduced phase of wustite that is oxidized back to ferrite on ZrO2 with steam in a separate second step at 1000°C. In this paper, a number of ZrO2-supporetd ferrites, Mn-, Mg-, Co-, Ni- and Co-Mn-ferrites, are examined on activity. The NiFe2O4/ZrO2 powder was found to have a greatest activity between them. This paper also describes a new concept of a windowed solar chemical reactor using an internally circulating fluidized bed of ferrite/ZrO2 particles. In this concept, concentrated solar radiation passes downwards through the transparent window and directly heats the internally circulating fluidized bed. The exploratory experimental studies on this reactor concept are carried out in a laboratory scale for the thermal decomposition of NiFe2O4/ZrO2 particle bed as part of two-step water splitting cycle.

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