Rich H2 Research Articles

Synergistic catalytic biomass-H2O gasification for H2 production and biochar etching mechanism: Experimental and DFT studies

Biomass-H2O gasification facilitated by multi-metal synergistic catalysis for H2 production. Oxygen transfer, carbon dissolution, lateral/vertical etching mechanism, and hydrogen production capacity of biomass self-contained K and added Ni catalytic gasification were studied through biomass loaded with K and Ni pyrolysis, biochar gasification experiments, and DFT calculations. The H2 yield from KNi catalytic gasification was 67.09 mmol/g (increased by 13.51%). Driven by *OH, K migrates and transforms from the inside of the carbon matrix to form active sites (CK), increasing carbon defects (40–50%) and reactivity. The vertical etching ability of Ni on biochar is enhanced from outside to inside (forming NiC and CK to reduce carbon dissolution energy barrier) and the gasification reaction rate is increased. The competition between the strong attraction of Ni on OH and the van der Waals force of K on OH leads to a 7.7% increase in the energy barrier of the rate-determining step (H transfer). The work enhances the understanding of the multi-metal catalytic gasification of rich H2 and provides a foundation for developing catalytic gasification technology.

The feasibility and performance of using producer gas as a gasifying medium

The gasification process in a 20-kW downdraft gasifier is investigated using Computational Fluid Dynamics. The research aims to examine the feasibility of air and producer gas co-injectionas a gasifying medium on the performance of the whole process. To this end, the effect of varying the injected amount of the producer gas on producer gas composition, emissions, H2 production, producer gas yield and higher heating value (HHV), the gasification, and carbon conversion efficiencies are reported. The results reveal promising findings for boosting the producer hydrogen amounts, and the corresponding heating values, with lower CO2 levels. The ratio of the injected producer gas (within the gasifying medium) to the total required amount of air for gasification is defined by z (eqn. (10)), and it is found that optimum z values are around (0.25–0.5). For the same working conditions of moisture content (MC), feedstock, and equivalence ratio (ER), the gasifying medium of z= (0.25–0.5) has higher HHV, gasification, and carbon conversion efficiencies than air gasification up to 33%, 31%, and 19% respectively. Additionally, for the same optimum range of z, it is found that the producer gas yield, and H2 production are higher than air gasification by 10%, and 34% respectively, with a reduction in CO2 by 18%. Consequently, the research presents a significant potential for higher yield, rich H2, and CO2-free syngas production, while demonstrating a promising novelty and technique that is applicable to any sort of the gasification units’ type and capacity.

Investigation of CO2 and CH4 capture from syngas in adsorption process and breakthrough modeling by modified Lattice-Boltzmann mesoscale method

A modified Lattice Boltzmann method (LBM) was developed to model and analyze the transient flow and multi-component adsorption in a dispersive packed bed column of activated carbon as a new kind of meso-scale modeling. The model using D2Q9 (two dimensions and 9 speed) lattice solves the two-dimensional space, convection-dispersion adsorption model for the CO2–CH4 mixture in rich H2 at transient condition. The sink/source term model was considered as the adsorption/desorption kinetic rate based on Extended Langmuir theory for multicomponent mixture. The mole balances in the solid phase were considered as the lumped kinetic model of adsorption-desorption reaction. The results of the developed model was presented as the flow velocity and molar fractions of the components in axial and radial directions of the bed as well as breakthrough curves of CO2 and CH4 from their mixture in H2 gas stream under pressures of 3 and 5 bar and inlet linear velocities of 0.01, 0.04, 0.08 and 0.1m/min. The breakthrough curves were validated with the experimental data and the average absolute relative deviations (AARD) were calculated for both components. In addition, the results of LBM were compared with finite difference method in which AARDs were dtermined as 3% and 8% for CO2,4% and 7% for CH4 , by LBM and FDM, respectively.

Optimizing the Reaction Pathway by Active Site Regulation in the CdS/Fe2O3 Z-Scheme Heterojunction System for Highly Selective Photocatalytic Benzylamine Oxidation Integrated with H2 Production

Simultaneous photocatalytic H2 production and preparation of high-value chemicals by the selective oxidation of organic substances is of great significance for solar energy utilization and conversion. Herein, a Pt-modified 2D/2D CdS/Fe2O3 Z-scheme heterojunction was dexterously designed for photocatalytic dehydrogenation coupling of benzylamine with high performance and product selectivity. The Z-scheme charge transfer in CdS/Fe2O3 greatly boosts charge separation and maintains the strong redox capacity of photogenerated electrons and holes. Impressively, the loading of the Pt cocatalyst not only provides rich H2 production active sites to further accelerate charge separation and H2 production kinetics but also facilitates the condensation of N-benzylideneamine with benzylamine for N-benzylidenebenzylamine production and NH3 releasing. The selectivity for C═N coupling products is significantly enhanced and the C–C coupling side reaction is greatly suppressed. With sufficient benzylamine substrate and visible light irradiation, the optimal Pt/CdS/Fe2O3 composite displays a high H2 production rate of 39.4 mmol h–1 g–1 with a quantum efficiency of 32.81% at 420 nm, and the selectivity of benzylamine oxidation to N-benzylidenebenzylamine is above 90%.

H2-rich syngas from glycerol dry reforming over Ni-based catalysts supported on alumina from aluminum dross

The performance of Ni-based catalyst supported on γ-Al2O3 for glycerol dry reforming (GDR) reaction was investigated in the current study. γ-Al2O3 was prepared from aluminum dross (AD) before use as catalyst support. Al2O3 was extracted using three different techniques assisted with ultrasonication: acid leaching with ammonia precipitation, acid leaching with re-precipitation of HCl, and alkaline leaching with ammonium hydrogen carbonate. The results show that extracted γ-Al2O3 3 (EGA3) with the highest purity and the surface area of 267.5 m2 g−1 was produced from acid leaching with ammonia precipitation technique at a calcination temperature of 800 °C. A series of Ni/EGA3 (5%, 10%, 15% and 20%) catalysts were tested and it was found that the catalytic activity was increased in the order of 5%Ni/EGA3 < 10%Ni/EGA3 < 20%Ni/EGA3 < 15%Ni/EGA3. 15%Ni/EGA3 catalyst has the highest catalytic activity due to the excellent distribution of Ni on the EGA support, high specific surface area of the support and high catalyst's basicity. In addition, the strong Ni-EGA3 interaction of the 15%Ni/EGA3 catalyst suppressed the carbon formation with the catalyst having the lowest carbon deposition value of 25.51% during the GDR reaction carried out for 8 h. Studies on the GDR reaction catalytic activities revealed that 15%Ni/EGA3 achieved the maximum catalytic activity with 56.7% glycerol conversion, 44.7% H2 yield, and 40.6% CO yield at 800 °C and CGR of 1:1. The H2:CO ratio obtained in this study was approximately 1.2–1.5 throughout the reaction, depicting a relatively rich H2 syngas product. Overall, the strong interaction between Ni and EGA3 ensured stable Ni particles that can mitigate carbon deposits, thereby enhancing the catalytic activity.

Rich H2 catalytic oxidation as a novel methodology for the evaluation of mass transport properties of 3D printed catalyst supports

In this work, we propose a novel methodology for the evaluation of the external mass transfer properties of 3D printed catalyst supports. This protocol relies on the use of a lab scale SLA 3D printer with a resin characterized by a high heat deflection temperature (HDT) for the manufacturing of samples at a lower price and with higher accuracy than equivalent metallic 3D printed structures. Periodic open cellular structure (POCS) samples with Tetrakaidecahedron unit cells (TKKD) were 3D printed and catalytically activated by depositing a 3% Pd/CeO2 washcoat by spin-coating. The washcoat was then consolidated with a two-step heat treatment composed by in-situ calcination in N2 and reduction in N2/H2 stream. Catalytic tests of rich H2 combustion showed the possibility to reach the external mass transfer control at temperatures below the resin HDT. Sherwood numbers were eventually estimated from the oxygen conversions under full external mass transfer control assuming a PFR behaviour. To validate the methodology, 3D printed replicas of open cell foams were also tested, and the results were successfully compared against a well-established literature correlation. Moreover, a one-to-one comparison was performed between the Sherwood numbers of a resin 3D printed structure, tested with the proposed methodology, and a metallic 3D printed structure, tested with the conventional CO oxidation approach. The two methods lead to superimposed results, thus providing the experimental evidence of the equivalence of the two methodologies for the evaluation of the external mass transport properties of complex catalyst substrates.

The enhanced rich H2 from co-gasification of torrefied biomass and low rank coal: The comparison of dry/wet torrefaction, synergetic effect and prediction

In this study, the enhanced rich H2 gas was produced via the co-gasification of torrefied biomass and low-rank coal in the fixed bed reactor. The properties of wet/dry torrefied char was compared, and then the synergetic effect between dry/wet torrefied char and the low rank coal during the gasification were analyzed to study the enhancing effect of torrefaction on the H2 yield. Moreover, the co-pyrolysis reactivity and kinetic analysis were investigated to further determine the synergetic mechanism. The results showed that the change of fundamental compositions in biomass after torrefaction, especially, the removal of cellulose played an important role in the enhancement of H2. Thus, dry torrefaction was more beneficial for improving H2 yield than the wet one. Besides, an obviously synergetic effect was observed from coal and dry torrefied biomass in their ratio 1:1 and 3:1, which was mainly due to the catalytic role of alkali and alkaline earth metallic species, and the transfer of active OH and H radicals from the torrefied biomass to the coal. The co-pyrolysis reactivity and kinetic analysis further proved the synergetic effect on reducing activation energy.

2-biofuels (H2 and CH4) production from anaerobic digestion of biscuits wastewater: Experimental study and techno-economic analysis

The up-flow anaerobic hybrid reactor (UAHR) was simultaneously employed for 2-biofuels (H2 and CH4) production from solely biscuits wastewater (BW) industry and a mixture of BW with domestic sewage (DS) at a mixing ratio of 3:1 respectively. The UAHR was fed with BW and operated at an organic loading rate (OLR) of 21.9 ± 1.7 gCOD/L/d., and hydraulic retention time (HRT) of 12.0 h. The module achieved volumetric hydrogen production rate (VHPR) and hydrogen yield (HY) of 0.95 ± 0.13 L/L reactor/d., and 118.6 ± 22.3 mL/gCODremoved respectively. A substantial deterioration in the H2 productivity was occurred after 94 days of continuous-feed operation, due to the inhibition effect of long-chain fatty acids (LCFAs). DS was integrated into the BW at mixing ratio of 3.0 (BW):1.0 (DS) where the UAHR was continuously operated at OLRs of 7.95 and 4.45 gCOD/L/d., achieving H2 and CH4 yields of 414.2 ± 38.1 and 318.5 ± 23.5 mL/gCOD removed, respectively. The payback periods for the production of biogas rich CH4 and H2 were 7.1 and 5.7 y respectively.

Effect of 2-step energy release on direct detonation initiation by a point energy source in a rich H2–NO2/N2O4 mixture

In the present study, direct detonation initiation by a point energy source in a rich H2–NO2/N2O4–Ar mixture has been investigated using high-resolution one-dimensional numerical simulations performed with detailed chemistry. In particular, the effect of the 2-step energy release profile on the critical initiation energy and the dynamics of the failure process has been studied for the first time. Three reduced reaction models exhibiting a similar first step of energy release but a second step of different strengths have been employed. As the second step of heat release is strengthened, the overall behavior gets closer and closer to a 1-step process. It was found that the critical initiation energy for successful detonation initiation decreases as the second step of heat release is strengthened and the width of the overall heat release pulse is reduced. This feature has been investigated by studying the competition between chemical heat release and unsteadiness along the path of Lagrangian particles. The decrease of the critical initiation energy for stronger second step of heat release seems to be a result of the decrease of the sensitivity of this second step to unsteadiness-induced quenching behind a decaying shock wave. In view of the present results and previous experimental observations on propagating and diffracting detonation in H2–NO2/N2O4(–Ar) mixtures, it seems that the 2-step energy release presenting the specific characteristics observed in rich H2–NO2/N2O4(–Ar) mixtures, i.e. a strong and rapid first step and a weak and slow second step, constitutes a feature which is not essential for detonation propagation but makes detonation direct initiation and transmission to open space more difficult.

UTILIZATION OF LACTIC ACID RICH MEDIUM AND CASSAVA STARCH WASTEWATER FOR BIOLOGICAL HYDROGEN PRODUCTION

H2 production from lactic acid rich medium and H2 production from cassava starch wastewater by isolated bacteria were investigated. The isolation of H2 producing bacteria from heat treated sludge was carried out. The H2 production from lactic acid rich medium which used 1.5 g/L sodium acetate, 1.5 g/L sodium lactate and 1 g/L sucrose as carbon sources. The effects of inoculums size of 10, 20, 30 and 40 % (v/v) and incubation temperature of 35, 45 and 55oC using cassava starch wastewater as the substrate on H2 production by isolation strains were investigated. Results showed 6 isolated strains i.e. isolation code of MK01to MK06 indicated the H2 production capability when cultured in lactic acid rich medium. However, 3 isolated strains i.e. MK01, MK04, and MK06 were preferred to use as seed inoculums for further experiments depend on a high H2 production capacity obtained. Results indicated that the optimal condition of H2 production from cassava starch wastewater was 30% (v/v) inoculum size of MK06 under 35oC of incubation temperature. The maximum H2 production potential, H2 yield and H2 production rate of 4.20 L H2/L medium, 1.47 L H2/g substrate consumed, and 14.00 mL H2/L/h was obtained. Identification and characterization of MK06 were investigated using 16S rRNA gene sequence analysis followed by phylogenetic analysis. The 100% similarity of 16S rDNA compare with closely related species was indicated Klebsiella pneumoniae subsp. pneumoniae DSM 30104(T).

The LaCo1−xVxO3 Catalyst for CO Oxidation in Rich H2 Stream

The LaCo1−xVxO3 catalysts for CO oxidation in H2 rich stream were studied. These perovskite-type oxides with variable amounts of vanadium (x = 0, 0.05 and 0.1) were synthesized by modified citrate method. It was found that the modification in LaCoO3 perovskite after vanadium addition affected directly the structure and morphology leading to decrease in the crystallite size and increase in BET surface area. XPS results confirmed quantitatively the higher presence of V4+ species at the surface of the modified perovskite. The existence of Co2+ was reported to facilitate the interplay between Co2+/Co3+ and V5+/V4+ redox couples, which can enhance the lattice oxygen mobility and create interfacial active sites of CoOx/V2O5. Tests during 20 h on stream at 250 °C showed excellent stability, high resistance to coke deposition and no sintering. Perovskite modified by addition of vanadium LaCo1−xVxO3 for preferential CO oxidation in H2-rich stream.

Gas reforming and tar decomposition performance of nickel oxide (NiO)/SBA-15 catalyst in gasification of woody biomass

ABSTRACTIn the gasification of biomass, it is necessary to limit the amount of by-product tar and increase the yields of hydrogen (H2) and carbon monoxide (CO) (syngas). Therefore, we conducted gasification and reforming experiments on woody biomass using an electric tubular furnace, to evaluate the gas reforming and tar decomposition performance of a NiO/SBA-15 catalyst. As a result, we found that this catalyst is effective for H2 production. It is believed that the increase in H2 volume due to the catalyst occurs through a steam reforming reaction involving hydrocarbons, including methane (CH4), and the water-gas shift reaction. With respect to the influence of the gasifying agent on the reforming effect of the catalyst, the amount of generated carbon dioxide (CO2) and hydrogen (H2) increases because the shift reaction is promoted by supplying steam. On the other hand, it was inferred that the shift reaction rarely occurred because it approaches equilibrium by supplying O2. Furthermore, it is suggested that light aromatic hydrocarbons are decomposed by the catalyst.Implications: The mesoporous silica catalyst NiO/SBA-15 was highly effective for H2 production and decomposition of light aromatic compounds in the gasification of woody biomass. In the catalyst reaction, supplying steam promoted H2 production. From thermodynamic analysis and discussion, it was also inferred that supplying O2 might prevent the water gas shift reaction. The results are useful for designing a process needed for rich H2 production and gas refining process for further use of syngas.

Unravelling the Nature of the Active Species as well as the Doping Effect over Cu/Ce-Based Catalyst for Carbon Monoxide Preferential Oxidation

The active sites of a mixed Cu/Ce material and the doping effect of typical element (iron, Fe) on the active species and the catalytic behavior of Cu/Ce for CO preferential oxidation in rich H2 (CO...

Low Temperature Growth of Germanium on Silicon Using RF-PECVD for Electronic and Optoelectronic Application

In order to address the high demand for CMOS scaling, novel structures and new materials are being introduced at a rapid pace for the silicon industry in the recent years. It is very critical for nanoscale devices such as (FinFETs) and nanowire FETs (NW-FETs) to employ channel materials with high electron and hole mobility. Therefore, Germanium has returned to the picture with its high bulk hole and electron mobility, which are approximately four and two times higher than conventional Si channel, respectively. Moreover, Ge has a room temperature direct band gap of 0.8 eV (~ 1.55 µm) which is only separated by 0.14 eV from its indirect band gap (0.67 eV) and therefore it acts as a strong absorber in the near-infrared light spectrum. This allows for simultaneous fabrication of photodetectors and Si CMOS receiver circuits in a monolithically integrated fashion. However, fundamental issues with Ge such as the lack of stable germanium native oxide, its water solubility, and the poor physical and electrical properties of high κ oxide/Ge interfaces make it difficult to fabricate high-quality electronic or optoelectronic devices. Furthermore, heteroepitaxial growth of high-quality films on silicon is very challenging due to the 4.2% lattice mismatch between the two materials. Several research groups have reported high quality Ge layers on Si, however, temperatures as high as 650 ̊ C were used in performing the epitaxial deposition. The goal of this work is to deposit a Ge layer with low surface roughness and an acceptable threading dislocation density (TDD < 107 cm-2) values at low deposition temperature. In this paper, a low temperature deposition of germanium films on silicon is performed using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD). A two-step temperature technique and different GeH4 flow rates have been employed during the deposition process. The structural, the electrical and the optical properties of 700 nm Ge films have been investigated. Study of the surface morphology of low temperature Ge seed layer revealed that a surface roughness as low as 0.5 nm can be achieved with in-situ low temperature annealing in rich H2 chamber. Also, the Fast Fourier Transform pattern taken at the same area imaged by TEM for the seed layer exhibited crystalline nature due to the hydrogen induced crystallization. Furthermore, study of the post annealed Ge layers at different temperatures in H2 and N2 gas ambient revealed an improved electrical and transport properties of the films treated at T<600⁰ C. Also, samples annealed at 550⁰ C show the lowest threading dislocation density (TDD) of ~1x106 cm-2. In addition, metal-oxide-semiconductor capacitors (MOSCAPs) and metal-semiconductor-metal photodetector (MSM) are fabricated based on Ge growth using the low-temperature two step deposition technique. For MOSCAPs, the electrical characteristics of 9 nm Al2O3/i-Ge/Si MOSCAPs exhibits n-type (p-channel) behavior and normal high frequency C–V responses. In addition to CV measurements, the gate leakage vs applied voltage is measured and discussed. The Ge/high-κ interface trap density vs. surface potential is extracted with peak value of ~ 1x1012 eV-1 cm-2. For MSM photodetectors fabricated using low temperature Ge layer grown directly on Si, the possibility to suppress leakage current in Ge MSM detectors have been investigated by inserting large band gap material. A 5-20nm layer of n-type Si:H is used as a barrier layer to engineer the SHB. Results revealed that ~4 order of magnitude reduction of dark current is achieved by inserting ~20nm layer of a- Si:H. Furthermore, the photo response of the detector is tested under 1310 nm laser light. A responsivities of 0.9 A/W is achieved at 1 V reverse bias for detector fabricated with 20nm barrier layer compared to 0.5A/w of the one without barrier layer. The low temperature processing of Ge/Si demonstrates a great potential for p-channel transistors and optical detectors applications in monolithically integrated CMOS platform.

An expeirmental investigation into mechanism of high temperature steam gasification of wastewater sewage sludge

High temperature steam gasification experiments were conducted to gasify sludge in an electrically heated tubular furnace at 650, 750, 850, 950, and 1050?C. The obtained results develop a mechanistic understanding on steam gasification of sludge from starting constituents to final products. The introduction of steam led to a steam reforming of the tar and CnHm compounds, and a partial gasification of the solid char and CH4, which contributed to the generation of rich H2 and CO. The steam gasification process can be divided into three significant stages. As temperature increased, a decreasing absorbance amount of C-Har and C-O and a large reduction of C = O were accompanied with an evident reduction of tar yield and an increasing gas yield, especially the increase of H2 and CO contents. The H2 and CO were the indicator for the occurrence of tar and CnHm steam reforming. In addition, more micro-pores generated in solid char and a sharp increase of Brunauer-Emmett-Teller (BET) surface from 24.2 m2g?1 to 75.4 m2g?1 showed the occurrence of char decomposition. An increasing content of polycyclic aromatic hydrocarbons (PAH) with 2 and 3 rings and a significant decrease of PAH with 4-6 rings in tar showed the tar cracking and reforming of non-condensable intermediates.

Low temperature deposition of germanium on silicon using Radio Frequency Plasma Enhanced Chemical Vapor Deposition

In this paper, a low temperature deposition of germanium (Ge) films on silicon (Si) is performed using Radio Frequency Plasma Enhanced Chemical Vapor Deposition (RF-PECVD). A two-step temperature technique and different GeH4 flow rates have been employed during the deposition process. The structural and the optical properties of 700nm Ge films have been investigated using high resolution scanning electron microscopy, atomic force microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and variable angle spectroscopic ellipsometry. Study of the surface morphology of low temperature Ge seed layer revealed that a surface roughness as low as 0.5nm can be achieved with in-situ low temperature annealing in rich H2 chamber. Also, the fast Fourier transform pattern taken at the same area imaged by TEM for the seed layer exhibited crystalline nature due to the hydrogen induced crystallization. In addition, the RF-PECVD method promotes the nanocrystals growth at low temperature via plasma contribution. The XRD data shows that polycrystalline Ge layers with four different orientation and average crystallizes size of 43nm on Si substrate is achieved. Furthermore, the post annealing treatment of the films at T<600°C enhances its electrical and transport characteristics. The optical characteristics of the Ge-on-Si shows high absorption coefficient (approximately one order of magnitude higher than bulk Ge at 1.5μm) in the near-infrared (1.5–1.6μm).

Demonstrating feasibility of a high temperature polymer electrolyte membrane fuel cell operation with natural gas reformate composition

Experimental data on the performance of a single cell PBI-based HT-PEMFC operated with a fuel composition similar to natural gas reformate and oxygen enriched cathode air are presented. A test studying the effect of CO2, H2O and CO in the fuel on fuel cell performance revealed that the presence of CO2 mainly worsens mass transport, H2O improves proton conduction and CO influences reaction kinetics as well as causing mass transport limitations. A small increase of the O2 concentration in the oxidant provided a boost on performance. Electrical efficiency of the fuel cell was improved from 36.6% with H2/air operation up to 38.2% with synthetic reformate gas/30% O2 enriched air. Three 1000 h long-term tests at constant load conditions were performed. The first test showed a degradation rate of −21.4 μV/h and was operated with H2/30% O2. The second test was performed with the same kind of MEA but different fuel composition (54% H2, 15% CO2 and 31% H2O) and exhibited a reduction of the degradation rate to −5.5 μV/h. The main reason for this lifetime improvement is H2O because its transport from anode to cathode may sweep along PA that soaks catalyst active sites and limits HOR. Moreover, water in rich H2 reformate streams also relieves formation of CO from CO2 via RWGS. The third test was performed with a different kind of MEA (extra PTFE content in GDE) but the same fuel composition than the second one. A higher degradation rate of −22.2 μV/h was observed but it was mainly caused by unprotected shut-downs during operation. Two preliminary long-term tests were also performed with a fuel composition similar to natural gas reformate (54% H2, 14% CO2, 1% CO and 31% H2O). These latest tests revealed that the fuel cell should be operated at higher temperatures to diminish CO catalyst coverage, and that anode purge with dry gases avoids water condensation in gas pipes. In addition, CO poisoning on anode catalyst is time dependent and operation at high current densities enhances CO catalyst coverage.

Cheese whey management by catalytic steam reforming and aqueous phase reforming

Cheese whey is a yellowish liquid by-product of the cheese making process. Owing to its high BOD and COD values, this feedstock should not be directly discharged into the environment without appropriate treatment. The management of this wastewater has become an important issue, and new treatments must be sought. This work addresses the valorisation of cheese whey by steam reforming and aqueous phase reforming. The catalytic steam reforming of cheese whey turned out to be a promising valorisation route for H2 production from this effluent. This process enabled the organic compounds present in the cheese whey to be transformed into a rich H2 gas (35% of the C of the feed was transformed into a gas with 70vol.% of H2). This significantly reduced the amount of carbon present in the original feedstock, producing an almost carbon-free liquid stream. The aqueous phase reforming of cheese whey allowed 35% of the carbon present in the whey to be transformed into gases and 45% into valuable liquids. The gas was principally made up of H2 and CO2, while a mixture of added-value liquids such as aldehydes, carboxylic acids, alcohols and ketones constituted the liquid phase. However, both valorisation routes produced a substantial amount of solid. The formation of this solid was promoted by the presence of salts in the original feedstock and caused operational problems for both valorisation processes. In addition, it hampered gas production in the case of steam reforming and reduced gas and liquid formation when using aqueous phase reforming as the valorisation route. The filtration of cheese whey slightly decreased the solid formation in both processes due to the reduction of proteins and fats, both of which partly contribute to such formation. Less solid was formed in the experiments conducted with lactose than in those conducted with whole and with filtered cheese whey.

Characterization of initiator dynamics in a rotating detonation combustor

The performance of a tangentially-injecting initiator tube of a rotating detonation combustor (RDC) is assessed for a range of initiator conditions. Two initiator fuels are evaluated for a range of RDC channel pressures, and channel widths to determine the effect on the blast wave generated by the initiator tube. Blast wave trajectories exhibit asymmetric bias in the initiator injection (forward) direction. The energy content is estimated by fitting the blast wave trajectory to a theoretical model for blast propagation. Maximum energy deposition is achieved for a rich H2–O2 initiator mixture (ϕ>2), which provides twice the energy deposition of the highest performing C2H4–O2 mixture. The highest recorded initiator energy deposition is an order of magnitude smaller than the critical value to directly initiate detonation in a stoichiometric H2–air mixture, precluding direct initiation for this configuration. RDC initiation behavior is assessed for a near-stoichiometric H2–air mixture using the highest-performing initiator tube setting, and verifies the absence of direct initiation. A complex, transitory period follows the subcritical initiation event and culminates in stable detonation rotation within several milliseconds.

Quantification of extinction mechanism in counterflow premixed flames

The extinction mechanisms of stretched premixed flames have been investigated numerically for the fuels of CH4, C3H8, H2, CO and for the mixture fuels of CH4+H2 and CO+H2 by adopting symmetric double premixed flames in a counterflow configuration. The local equilibrium temperature concept was used as a measure of energy loss or gain in order to quantify the extinction mechanism by preferential diffusion and/or incomplete reaction. The energy loss ratio from preferential diffusion arising from non-unity Lewis number and the loss ratio from incomplete reaction were calculated at various equivalence ratios near flame extinction. The results showed that the extinction of lean H2, CH4, CH4+H2, CO+H2, and rich C3H8 premixed flames was caused by incomplete reaction due to insufficient reaction time, indicating that the effective Lewis number was smaller than unity, while the effect of preferential diffusion resulted in energy gain. However, the extinction of rich H2, CH4, CH4+H2, CO+H2, and lean C3H8 premixed flames was affected by the combined effects of preferential diffusion and incomplete reaction indicating that the effective Lewis number was larger than unity. In CO premixed flames, incomplete reaction was dominant in both lean and rich cases due to the effective Lewis number close to unity. The effect of H2 mixing to CO is found to be quite significant as compared to CH4+H2 cases, which can alter the flame behavior of CO flames to that of H2.