The Experts below are selected from a list of 33954 Experts worldwide ranked by ideXlab platform
Rikard Gebart - One of the best experts on this subject based on the ideXlab platform.
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Performance of a Pilot-Scale Entrained-Flow Black Liquor Gasifier
2016Co-Authors: Yawer Jafri, Kawnish Kirtania, Erik Furusjö, Rikard GebartAbstract:Pilot-scale entrained flow gasification experiments were carried out at the 3 MWth LTU Green Fuels black liquor gasification (BLG) plant, using ∼140 tons of Kraft black liquor (BL) with a dry solids content of ∼72.5%. Comprehensive mass and energy balances were performed to quantify process performance under varying pressure, load, and oxygen/Fuel ratio. Carbon conversion efficiency of the BLG process was 98.3%–99.2% and did not vary systematically in response to process changes. The unconverted carbon is almost exclusively present as dissolved organic carbon in the green liquor (GL) stream. GL is an aqueous solution of sodium carbonate and sodium sulfide used to recover the inorganic pulping chemicals present in BL for reuse in the pulp mill. A small fraction of syngas CO is converted to formate ions dissolved in GL through reaction with hydroxide ions. Unconverted carbon present in GL solids is insignificant. Syngas produced is subsequently upgraded to methanol and dimethyl ether (DME) in an integrated Fuel Synthesis facility. Concentration of H2 in syngas is not significantly affected by operating point changes in the domain investigated, while CO and CO2 concentrations are. Syngas hydrocarbon concentration values are typically in the single-digit parts per million (ppm) with the exception of C6H6, which was present at 16–127 ppm. CH4 is present at 0.5%–1.2%, with lower concentrations at higher temperatures, and shows good correlation with C6H6. A quantity of 24%–27% of BL sulfur ended up in the syngas as 1.5%–1.7% H2S and 64–72 ppm COS. Cold gas efficiencies (CGEs) on a lower heating value (LHV) basis, when including syngas CH4, were 52%–55% and decreased at higher temperature. CGEs on an LHV basis, when considering only H2 and CO with a sulfur-free BL heating value relevant for catalytic syngas upgrading, were 58%–60% and showed the opposite temperature dependence. Good mass and energy balance closures show the figures presented to be reliable. The results obtained from this study demonstrate process stability at varying operating conditions and can be further used for techno-economic analysis and design purposes
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influence of process parameters on the performance of an oxygen blown entrained flow biomass gasifier
Fuel, 2015Co-Authors: Fredrik Weiland, Esbjorn Pettersson, Henry Hedman, Henrik Wiinikka, Jonas Wennebro, Rikard GebartAbstract:Abstract Pressurized, O 2 blown, entrained flow gasification of pulverized forest residues followed by methanol production is an interesting option for synthetic Fuels that has been particularly investigated in the Nordic countries. In order to optimize gasification plant efficiency, it is important to understand the influence of different operating conditions. In this work, a pressurized O 2 blown and entrained flow biomass gasification pilot plant was used to study the effect of four important process variables; (i) the O 2 stoichiometric ratio ( λ ), (ii) the load of the gasifier, (iii) the gasifier pressure, and (iv) the Fuel particle size. Commercially available stem wood Fuels were used and the process was characterized with respect to the resulting process temperature, the syngas yield, the Fuel conversion and the gasification process efficiency. It was found that CH 4 constituted a significant fraction of the syngas heating value at process temperatures below 1400 °C. If the syngas is intended for catalytic upgrading to a synthetic motor Fuel where CO and H 2 are the only important syngas species, the process should be optimized aiming for a process temperature slightly above 1400 °C in order to reduce the energetic losses to CH 4 and C 6 H 6 . This resulted in a cold gas efficiency (based only on CO and H 2 ) of 70%. The H 2 /CO ratio was experimentally determined within the range 0.45–0.61. Thus, the syngas requires shifting in order to increase the syngas composition of H 2 prior to Fuel Synthesis.
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Experimental investigation of an industrial scale black liquor gasifier. Part 2: Influence of quench operation on product gas composition
Fuel, 2012Co-Authors: Henrik Wiinikka, Esbjorn Pettersson, Magnus Marklund, Per Carlsson, Carola Grönberg, Marcus Lidman, Rikard GebartAbstract:Pressurised black liquor gasification combined either with a gas turbine or a catalytic Fuel Synthesis process is a novel technique for production of green electricity or second generation motor Fuels. The composition of the gas produced in the gasifier may be important for the performance of either the gas turbine or the catalytic Fuel Synthesis process and different operating parameters of the gasifier may affect the composition of the produced gas. The aim of this study was to investigate the influence of some operating parameters on the final gas composition with special attention on the performance of the quench in the gasifier. The results show that system pressure, oxygen/black liquor flow rate ratio and the primary spray flow rate in the quench significantly affect the final gas composition. Furthermore, depending on the cooling rate in the quench, the hot reactor gas composition prior to the quench could either be preserved (high cooling rate) yielding the same final gas composition after the quench as in the hot reactor or shifted (low cooling rate) towards a higher concentration of H2 and CO2.
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experimental investigation of an industrial scale black liquor gasifier 1 the effect of reactor operation parameters on product gas composition
Fuel, 2010Co-Authors: Per Carlsson, Esbjorn Pettersson, Magnus Marklund, Henrik Wiinikka, Carola Grönberg, Marcus Lidman, Rikard GebartAbstract:Abstract A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient Fuel Synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO 2 , CO, H 2 , CH 4 , H 2 S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.
Junwang Tang - One of the best experts on this subject based on the ideXlab platform.
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synergistic effect of surface oxygen vacancies and interfacial charge transfer on fe iii bi2moo6 for efficient photocatalysis
Applied Catalysis B-environmental, 2019Co-Authors: Huidong Shen, Xiang Sun, Wenwen Xue, Ayoola Shoneye, Lei Luo, Danjun Wang, Jianguo Wang, Junwang TangAbstract:Abstract Novel Fe(III) clusters grafted Bi2MoO6 nanosheets with surface oxygen vacancies (denoted as F/BMO-SOVs) heterostructured composite have been firstly fabricated via a reliable calcination process combined with impregnation approach. The surface oxygen vacancies (SOVs) in Bi2MoO6 were formed due to controlled calcination process. The presence of Fe (III) clusters was confirmed by HRTEM, XPS, and UV–vis DRS. Under visible light irradiation, the optimum molar ratio of 15% F/BMO-SOVs achieved 93.4% degradation efficiency of phenol within 180 min, representing nearly 80 times higher activity than the pure Bi2MoO6, confirmed by both absorption spectrum and TOC measurement. The dramatically enhanced photocatalytic activity is attributed to the synergistic effect between the SOVs, Fe(III) clusters and Bi2MoO6, which not only narrows the band gap, improving the visible light response ability, but also facilitates the direct interfacial charge transfer (IFCT) from the SOVs to the surface Fe(III) clusters, greatly promoting the efficient separation of photogenerated electron-hole pairs. According to the trapping experiments and ESR measurements results, ·O2−, ·OH, and h+ all participated in the phenol photodegradation process over F/BMO-SOVs. Thus, this work not only provides a synergistic effect between SOVs, Fe(III) clusters and Bi2MoO6 involving an IFCT process, but also proposes an efficient approach to fabricating highly active photocatalysts in environmental remediation and solar Fuel Synthesis.
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mimicking natural photoSynthesis solar to renewable h2 Fuel Synthesis by z scheme water splitting systems
Chemical Reviews, 2018Co-Authors: Yiou Wang, Hajime Suzuki, Osamu Tomita, David James Martin, Masanobu Higashi, Dan Kong, Junwang TangAbstract:Visible light-driven water splitting using cheap and robust photocatalysts is one of the most exciting ways to produce clean and renewable energy for future generations. Cutting edge research within the field focuses on so-called “Z-scheme” systems, which are inspired by the photosystem II–photosystem I (PSII/PSI) coupling from natural photoSynthesis. A Z-scheme system comprises two photocatalysts and generates two sets of charge carriers, splitting water into its constituent parts, hydrogen and oxygen, at separate locations. This is not only more efficient than using a single photocatalyst, but practically it could also be safer. Researchers within the field are constantly aiming to bring systems toward industrial level efficiencies by maximizing light absorption of the materials, engineering more stable redox couples, and also searching for new hydrogen and oxygen evolution cocatalysts. This review provides an in-depth survey of relevant Z-schemes from past to present, with particular focus on mechanist...
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visible light driven heterojunction photocatalysts for water splitting a critical review
Energy and Environmental Science, 2015Co-Authors: Savio J A Moniz, David James Martin, Stephen A Shevlin, Z X Guo, Junwang TangAbstract:Solar driven catalysis on semiconductors to produce clean chemical Fuels, such as hydrogen, is widely considered as a promising route to mitigate environmental issues caused by the combustion of fossil Fuels and to meet increasing worldwide demands for energy. The major limiting factors affecting the efficiency of solar Fuel Synthesis include; (i) light absorption, (ii) charge separation and transport and (iii) surface chemical reaction; therefore substantial efforts have been put into solving these problems. In particular, the loading of co-catalysts or secondary semiconductors that can act as either electron or hole acceptors for improved charge separation is a promising strategy, leading to the adaptation of a junction architecture. Research related to semiconductor junction photocatalysts has developed very rapidly and there are a few comprehensive reviews in which the strategy is discussed (A. Kudo and Y. Miseki, Chemical Society Reviews, 2009, 38, 253–278, K. Li, D. Martin, and J. Tang, Chinese Journal of Catalysis, 2011, 32, 879–890, R. Marschall, Advanced Functional Materials, 2014, 24, 2421–2440). This critical review seeks to give an overview of the concept of heterojunction construction and more importantly, the current state-of-the art for the efficient, visible-light driven junction water splitting photo(electro)catalysts reported over the past ten years. For water splitting, these include BiVO4, Fe2O3, Cu2O and C3N4, which have attracted increasing attention. Experimental observations of the proposed charge transfer mechanism across the semiconductor/semiconductor/metal junctions and the resultant activity enhancement are discussed. In parallel, recent successes in the theoretical modelling of semiconductor electronic structures at interfaces and how these explain the functionality of the junction structures is highlighted.
Zhigang Zou - One of the best experts on this subject based on the ideXlab platform.
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series of znsn oh 6 polyhedra enhanced co2 dissociation activation and crystal facet based homojunction boosting solar Fuel Synthesis
Inorganic Chemistry, 2017Co-Authors: Lanqin Tang, Yong Zhou, Zong-yan Zhao, Xiaoyong Wang, Min Xiao, Zhigang ZouAbstract:A series of ZnSn(OH)6 polyhedra are successfully explored with well-controlled area ratio of the exposed {100} and {111} facets. Band alignment of the exposed facet-based homojunction of the elegant polyhedron facilitates spatial separation of photogenerated electrons and holes on {111} and {100} surfaces, respectively. Optimal area ratio of {100} to {111} is the prerequisite for pronounced CO2 photocatalytic performance of high-symmetry cuboctahedra into methane (CH4). The synergistic effect of the excess electron accumulation and simultaneously the enhanced CO2 absorption and low dissociation activation energy on {111} reduction sites promote the yield of CO2 photocatalytic conversion product.
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hexahedron prism anchored octahedronal ceo2 crystal facet based homojunction promoting efficient solar Fuel Synthesis
Journal of the American Chemical Society, 2015Co-Authors: Ping Li, Yong Zhou, Zong-yan Zhao, Xiaoyong Wang, Min Xiao, Qinfeng Xu, Zhigang ZouAbstract:An unprecedented, crystal facet-based CeO2 homojunction consisting of hexahedron prism-anchored octahedron with exposed prism surface of {100} facets and octahedron surface of {111} facets was fabricated through solution-based crystallographic-oriented epitaxial growth. The photocatalysis experiment reveals that growth of the prism arm on octahedron allows to activate inert CeO2 octahedron for an increase in phototocatalytic reduction of CO2 into methane. The pronounced photocatalytic performance is attributed to a synergistic effect of the following three factors: (1) band alignment of the {100} and {111} drives electrons and holes to octahedron and prism surfaces, respectively, aiming to reach the most stable energy configuration and leading to a spatial charge separation for long duration; (2) crystallographic-oriented epitaxial growth of the CeO2 hexahedron prism arm on the octahedron verified by the interfacial lattice fringe provides convenient and fast channels for the photogenerated carrier transp...
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Hexahedron Prism-Anchored Octahedronal CeO2: Crystal Facet-Based Homojunction Promoting Efficient Solar Fuel Synthesis.
Journal of the American Chemical Society, 2015Co-Authors: Yong Zhou, Zong-yan Zhao, Xiaoyong Wang, Min Xiao, Zhigang ZouAbstract:An unprecedented, crystal facet-based CeO2 homojunction consisting of hexahedron prism-anchored octahedron with exposed prism surface of {100} facets and octahedron surface of {111} facets was fabricated through solution-based crystallographic-oriented epitaxial growth. The photocatalysis experiment reveals that growth of the prism arm on octahedron allows to activate inert CeO2 octahedron for an increase in phototocatalytic reduction of CO2 into methane. The pronounced photocatalytic performance is attributed to a synergistic effect of the following three factors: (1) band alignment of the {100} and {111} drives electrons and holes to octahedron and prism surfaces, respectively, aiming to reach the most stable energy configuration and leading to a spatial charge separation for long duration; (2) crystallographic-oriented epitaxial growth of the CeO2 hexahedron prism arm on the octahedron verified by the interfacial lattice fringe provides convenient and fast channels for the photogenerated carrier transportation between two units of homojuntion; (3) different effective mass of electrons and holes on {100} and {111} faces leads to high charge carrier mobility, more facilitating the charge separation. The proposed facet-based homojunction in this work may provide a new concept for the efficient separation and fast transfer of photoinduced charge carriers and enhancement of the photocatalytic performance.
Paul C Mcintyre - One of the best experts on this subject based on the ideXlab platform.
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atomic layer deposited tunnel oxide stabilizes silicon photoanodes for water oxidation
Nature Materials, 2011Co-Authors: Yi Wei Chen, Jonathan D Prange, Simon Duhnen, Yohan Park, Marika Gunji, Christopher E D Chidsey, Paul C McintyreAbstract:Electrochemical energy can be produced by using solar energy to oxidize water, providing an abundant source of electrons, which are needed in Fuel Synthesis. The operation of an efficient and stable semiconductor nanocomposite anode, made of a protective TiO2 layer that protects a silicon substrate during photoelectrochemical water oxidation in both dark and light conditions, is now reported.
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atomic layer deposited tunnel oxide stabilizes silicon photoanodes for water oxidation
Nature Materials, 2011Co-Authors: Yi Wei Chen, Jonathan D Prange, Simon Duhnen, Yohan Park, Marika Gunji, Christopher E D Chidsey, Paul C McintyreAbstract:A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in Fuel Synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable Fuels. Silicon, an earth-abundant element and an efficient photovoltaic material, is protected by atomic layer deposition (ALD) of a highly uniform, 2 nm thick layer of titanium dioxide (TiO(2)) and then coated with an optically transmitting layer of a known catalyst (3 nm iridium). Photoelectrochemical water oxidation was observed to occur below the reversible potential whereas dark electrochemical water oxidation was found to have low-to-moderate overpotentials at all pH values, resulting in an inferred photovoltage of ~550 mV. Water oxidation is sustained at these anodes for many hours in harsh pH and oxidative environments whereas comparable silicon anodes without the TiO(2) coating quickly fail. The desirable electrochemical efficiency and corrosion resistance of these anodes is made possible by the low electron-tunnelling resistance (<0.006 Ω cm(2) for p(+)-Si) and uniform thickness of atomic-layer deposited TiO(2).
Henrik Wiinikka - One of the best experts on this subject based on the ideXlab platform.
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influence of process parameters on the performance of an oxygen blown entrained flow biomass gasifier
Fuel, 2015Co-Authors: Fredrik Weiland, Esbjorn Pettersson, Henry Hedman, Henrik Wiinikka, Jonas Wennebro, Rikard GebartAbstract:Abstract Pressurized, O 2 blown, entrained flow gasification of pulverized forest residues followed by methanol production is an interesting option for synthetic Fuels that has been particularly investigated in the Nordic countries. In order to optimize gasification plant efficiency, it is important to understand the influence of different operating conditions. In this work, a pressurized O 2 blown and entrained flow biomass gasification pilot plant was used to study the effect of four important process variables; (i) the O 2 stoichiometric ratio ( λ ), (ii) the load of the gasifier, (iii) the gasifier pressure, and (iv) the Fuel particle size. Commercially available stem wood Fuels were used and the process was characterized with respect to the resulting process temperature, the syngas yield, the Fuel conversion and the gasification process efficiency. It was found that CH 4 constituted a significant fraction of the syngas heating value at process temperatures below 1400 °C. If the syngas is intended for catalytic upgrading to a synthetic motor Fuel where CO and H 2 are the only important syngas species, the process should be optimized aiming for a process temperature slightly above 1400 °C in order to reduce the energetic losses to CH 4 and C 6 H 6 . This resulted in a cold gas efficiency (based only on CO and H 2 ) of 70%. The H 2 /CO ratio was experimentally determined within the range 0.45–0.61. Thus, the syngas requires shifting in order to increase the syngas composition of H 2 prior to Fuel Synthesis.
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Experimental investigation of an industrial scale black liquor gasifier. Part 2: Influence of quench operation on product gas composition
Fuel, 2012Co-Authors: Henrik Wiinikka, Esbjorn Pettersson, Magnus Marklund, Per Carlsson, Carola Grönberg, Marcus Lidman, Rikard GebartAbstract:Pressurised black liquor gasification combined either with a gas turbine or a catalytic Fuel Synthesis process is a novel technique for production of green electricity or second generation motor Fuels. The composition of the gas produced in the gasifier may be important for the performance of either the gas turbine or the catalytic Fuel Synthesis process and different operating parameters of the gasifier may affect the composition of the produced gas. The aim of this study was to investigate the influence of some operating parameters on the final gas composition with special attention on the performance of the quench in the gasifier. The results show that system pressure, oxygen/black liquor flow rate ratio and the primary spray flow rate in the quench significantly affect the final gas composition. Furthermore, depending on the cooling rate in the quench, the hot reactor gas composition prior to the quench could either be preserved (high cooling rate) yielding the same final gas composition after the quench as in the hot reactor or shifted (low cooling rate) towards a higher concentration of H2 and CO2.
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experimental investigation of an industrial scale black liquor gasifier 1 the effect of reactor operation parameters on product gas composition
Fuel, 2010Co-Authors: Per Carlsson, Esbjorn Pettersson, Magnus Marklund, Henrik Wiinikka, Carola Grönberg, Marcus Lidman, Rikard GebartAbstract:Abstract A novel technology to mitigate the climate changes and improve energy security is Pressurized Entrained flow High Temperature Black Liquor Gasification (PEHT-BLG) in combination with an efficient Fuel Synthesis using the resulting syngas. In order to optimise the technology for use in a pulp and paper mill based biorefinery, it is of great importance to understand how the operational parameters of the gasifier affect the product gas composition. The present paper is based on experiments where gas samples were withdrawn from the hot part of a 3 MW entrained flow pressurized black liquor gasifier of semi industrial scale using a high temperature gas sampling system. Specifically, the influence of process conditions on product gas composition (CO 2 , CO, H 2 , CH 4 , H 2 S, and COS) were examined by systematically varying the operational parameters: system pressure, oxygen to black liquor equivalence ratio, black liquor flow rate to pressure ratio and black liquor pre-heat temperature. Due to the harsh environment inside the gasification reactor, gas sampling is a challenging task. However, for the purpose of the current study, a specially designed high temperature gas sampling system was successfully developed and used. The results, obtained from two separate experimental campaigns, show that all of the investigated operational parameters have a significant influence on the product gas composition and present valuable information about to the process characteristics.
