Continuous experiment regarding hydrogen production by coal/CaO reaction with steam (I) gas products

The AER (absorption enhanced reforming) process, based on the dual fluidized bed steam gasification process, uses a bed material which, apart from its function as heat carrier, acts as a CO 2 transporting agent and selectively transfers CO 2 from the gasification reactor to the combustion reactor. Thus, a hydrogen-rich gas is produced (H 2 55...70 vol.-% db , CH 4 8...13 vol.-% db , CO 5...11 vol.-% db as well as CO 2 7...20 vol.-% db ). Seven different CaO containing bed materials were tested for their principal applicability to the AER process with special focus on their influence on tar production. The amount of tars was generally found to be five times lower than with conventional gasification (at 850°C) despite the low gasification temperatures (600-700°C). Due to these low gasification temperatures, biomass with high alkali contents (e.g., straw), indicating a low ash melting point (< 800°C), can be used under AER conditions. In summary, the AER process is very effective owing to the integration of the heat of the chemical reaction of CO 2 with CaO and the water-gas shift reaction, which are both exothermic, into the gasification and the internal reforming of primary and secondary tars, which cuts off the formation of higher tars.

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“…Many activities were undertaken in this field of research to produce a hydrogen-rich gas [8,9] and to remove CO 2 from a gas stream [10,11].…”

Section: Adsorption Enhanced Reforming Processmentioning

confidence: 99%

In Situ CO₂ Capture in a Dual Fluidized Bed Biomass Steam Gasifier – Bed Material and Fuel Variation

et al. 2009

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“…By adding calcium-based absorbents into the coal gasifier, coal conversion reaches 90 % and the concentration of H 2 more than 80 vol.-% in a batch microreactor at 873-973 K and 12-105 MPa [1][2][3]. Recently, continuous coal gasification experiments at a bench scale were conducted with CaO as the absorbent in the range of 0.1-6.0 MPa and 923 K [4,5], the H 2 concentration reached 77 vol.-%, and only 2 vol.-% CO 2 and not more than 1 vol.-% CO were detected.…”

Section: Introductionmentioning

confidence: 99%

“…Up to now, the EDC model has mainly been adopted in simple systems of gas turbulent combustion, such as the combustion of H 2 , CO, CH 4 , or their mixtures, and the formation of NO x , when the turbulent mixing rate and the reaction rate are comparable [26-28, 30, 31]. The coal gasification system is complicated since it consists of gas-solid two-phase flow with a complicated net reaction, and simulation work of coal gasification using EDC as the turbulencechemistry model has not been reported.…”

Section: Introductionmentioning

confidence: 99%

“…The coal gasification system is complicated since it consists of gas-solid two-phase flow with a complicated net reaction, and simulation work of coal gasification using EDC as the turbulencechemistry model has not been reported. However, in the simulation of the present process of fluidized-bed coal steam gasification with in situ CO 2 fixation, the EDC model is successfully suggested as a turbulence-chemistry interaction model since the operating temperature is at least 150 K lower than that of traditional gasifiers [4,9,32], which results in relatively lower reaction rates in the gasifier, as well as turbulent mixing. Finite rate reactions also need to be considered.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen Production from a Fluidized‐bed Coal Gasifier with In Situ Fixation of CO₂–Part I: Numerical Model

Lü

Zhang

et al. 2008

Chem Eng & Technol

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In order to attempt to eliminate global warming effects, it is highly desirable that new technologies with lower or zero emission of CO 2 to the environment are developed. In this work, a high-pressure fluidized-bed coal gasifier for H 2 production with in situ fixation of CO 2 is simulated by a comprehensive two-dimensional model. The Eddy Dissipation Concept (EDC) model is first adopted in the pulverized coal gasification model to simultaneously describe the turbulent mixing and detailed chemical kinetics. The developed model is verified with experimental results. The simulated concentrations for the gas product agree well with the experimental data. The simulated distributions for gas temperature and velocity correlate well with the reaction mechanism and experimental phenomena.

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“…19 In this technology, the gasification and WGS reaction are combined in one reactor, with simultaneous absorption of CO 2 and other pollutants to increase the hydrogen yield, while maintaining a relatively low reaction temperature of 900 K. One of the latest developments in gasification technology is the Carbo-V process (CHOREN Technologies GmbH) designed to produce tar-free syngas for H 2 or liquid fuel. 20 The advantage of Carbo-V process over the normal gasifier is that it increases efficiency (>80%).…”

mentioning

confidence: 99%

Hydrogen Production from Renewables

Navarro¹,

Sánchez-Sánchez²,

Álvarez-Galván³

et al. 2005

Encyclopedia of Inorganic Chemistry

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Hydrogen is considered to be critical for energy and environmental sustainability. However, as hydrogen is currently produced from fossil fuels, it emits large amounts of carbon dioxide along the reforming steps. The technical challenges to achieve a stable hydrogen economy include improving process efficiencies, lowering the cost of production, and harnessing renewable sources for hydrogen production. Lignocellulosic biomass is one of the most abundant forms of renewable resources. When this precursor is used, virtually no net greenhouse gas emissions result because a natural cycle is maintained, in which carbon is extracted from the atmosphere during plant growth and is released during hydrogen production. This article focuses on recent developments in biomass and biomass‐derived product conversion to H 2 . The second option explored here is the conversion of solar energy into hydrogen via water‐splitting processes assisted by two‐step metal‐oxide thermochemical cycles or by photosemiconductor catalysts. The conversion of solar energy into a clean fuel (H 2 ) is the most promising technology for the future because large quantities of hydrogen can potentially be generated in a clean and sustainable manner. Undoubtedly, the conversion of solar energy into H 2 is one of the greatest challenges scientists are facing in the twenty first century. A survey is presented of the advances made in the development of metal oxide redox pairs since the pioneering work by Nakamura in 1977 and in the development of photocatalysts for water splitting under visible light since the first work of Fujishima and Honda in 1972. The very high thermal reduction temperature used for the metal oxide redox pairs developed until now leads to severe sintering, melting, and vaporization of materials, decreasing the efficiency and durability in the cyclic operation. Consequently, the application of material science and engineering to the development of materials with lower reduction temperature and high water‐splitting ability is still a challenge in this scientific area and an overview of the progress is provided in this article. On the other hand, there are still major challenges in the development of photocatalysts with improved efficiencies for hydrogen production from water using solar energy. An overview is provided in this article of research strategies and approaches adopted in the search for photocatalysts for water splitting under visible light (new photocatalyst materials and the control of the synthesis of materials for customizing the crystallinity, electronic structure, and morphology of catalysts at nanometric scale).

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Continuous experiment regarding hydrogen production by coal/CaO reaction with steam (I) gas products

Cited by 95 publications

References 6 publications

In Situ CO₂ Capture in a Dual Fluidized Bed Biomass Steam Gasifier – Bed Material and Fuel Variation

In Situ CO₂ Capture in a Dual Fluidized Bed Biomass Steam Gasifier – Bed Material and Fuel Variation

Hydrogen Production from a Fluidized‐bed Coal Gasifier with In Situ Fixation of CO₂–Part I: Numerical Model

Hydrogen Production from Renewables

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Continuous experiment regarding hydrogen production by coal/CaO reaction with steam (I) gas products

Cited by 95 publications

References 6 publications

In Situ CO2 Capture in a Dual Fluidized Bed Biomass Steam Gasifier – Bed Material and Fuel Variation

In Situ CO2 Capture in a Dual Fluidized Bed Biomass Steam Gasifier – Bed Material and Fuel Variation

Hydrogen Production from a Fluidized‐bed Coal Gasifier with In Situ Fixation of CO2–Part I: Numerical Model

Hydrogen Production from Renewables

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In Situ CO₂ Capture in a Dual Fluidized Bed Biomass Steam Gasifier – Bed Material and Fuel Variation

In Situ CO₂ Capture in a Dual Fluidized Bed Biomass Steam Gasifier – Bed Material and Fuel Variation

Hydrogen Production from a Fluidized‐bed Coal Gasifier with In Situ Fixation of CO₂–Part I: Numerical Model