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In the present work, LDHs-derived Ni–Al nanosheet arrays (NiAl/NA) were successfully synthesized via a one-step hydrothermal method, and applied in the steam-reforming of glycerol reaction for enhanced and stable hydrogen production. The physicochemical properties of catalysts were characterized using various techniques, including XRD, SEM–EDS, XPS, N2-physisorption, Raman, and TG–DTG. The results indicate that smooth and cross-linked Ni–Al mixed metal oxide nanosheets were orderly and perpendicularly grown on the Ni foam substrate. The SEM line scan characterization reveals the metal concentration gradient from the bottom to the top of nanosheet, which leads to distinctly optimized Ni valence states and an optimized binding strength to oxygen species. Owing to the improved reducibility and more exposed active sites afforded by its array structures, the NiAl/NA catalyst shows enhanced glycerol conversion (83.1%) and a higher H2 yield (85.4%), as well as longer stability (1000 min), compared to the traditional Ni–Al nanosheet powder. According to the characterization results of spent catalysts and to density functional theory (DFT) calculations, coke deposition is effectively suppressed via array construction, with only 1.25 wt.% of amorphous carbons formed on NiAl/NA catalyst via CO disproportionation.

Co@C-N with hierarchical pores and highly active sites is synthesized by the pyrolysis of an ionic liquid@metal–organic framework.

Biodegradable plastics, such as poly(lactic acid) (PLA), are considered the alternative for alleviating the environmental issues caused by the accumulation of petroleum-based plastic wastes. However, PLA is relatively expensive, and its natural degradation is slow. Therefore, upcycling instead of disposing of PLA should be more favorable for sustainability. Herein, we studied the selective methanolysis of PLA to produce methyl lactate (ML) catalyzed by a new molecular catalyst, tetramethylammonium fluoride (TMAF), with superior thermal and chemical stability and excellent catalytic performance. The complete methanolytic depolymerization of the commercial PLA pellets, 4043D, 6060D, 6202D, and 2500HP, was achieved within a short reaction time ( gel permeation chromatography (GPC) and Nuclear Magnetic Resonance (NMR) spectrometry were used to investigate the mechanism of the PLA depolymerization in the methanol solvent. F - was found to be the active center of the TMAF catalyst. A possible random scission depolymerization pathway of the TMAF catalyzed methanolysis of PLA was proposed.

Secondary doping has a long history of use in conductivity enhancement in poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS). However, very little research has addressed its detrimental effect on application performance of PEDOT : PSS in organic solar cells. Herein, it was shown that the uneven drying of secondary dopant-water mixture results in a nonuniform/continuous film structure, causing severe damage to the device efficiencies (dropping about 8 and 23 % for poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) : 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC) and poly[(2,6-(4,8-bis(5-(2-ethylhexyl)-4-fluorothiophen-2-yl)benzo[1,2-b:4,5-b']dithio-phene))-co-(1,3-di(5-thiophene-2-yl)-5,7-bis(2-ethylhexyl)-benzo[1,2-c:4,5-c']dithiophene-4,8-dione))](PM6) : (3,9-bis(1-oxo-2-methylene-3-(1,1-dicyanomethylene)-5,6-difluoroindanone)-5,5,11,11-tetrakis(4-n-hexylphenyl)-dithieno[2,3d:2',3'd']-s-indaceno[1,2b:5,6b']dithiophene (IT-4F) cells, respectively) and thermal stabilities. Moreover, a simple yet robust dialysis treatment was proposed to solve the issue of noncontinuity and retain the secondary doping's advantages of quinoid structure simultaneously, thus demonstrating a significant enhancement in device performance. This study will be of great importance to the future exploration of the next generation of post-treatment strategy.

Three Ni/CaxFeyO (x/y = 2:1, 1:1, 1:2) catalysts are prepared by impregnation method and applied in steam reforming of acetic acid as the model compound of bio-oil for hydrogen production. The effects of reaction temperature, steam to carbon ratio (S/C), liquid hourly space velocity (LHSV) on gas contents and H2 yield are carefully investigated and optimized. The fresh and used catalysts are characterized by BET, XRD, H2-TPR, CO2-TPD, SEM and TG methods. The experimental and characterization results show that the Ni/CaFe2O4 catalyst displays the best activity and stability among the three catalysts, providing 92.1% of H2 yield under S/C = 5, LHSV = 3.4 h−1 and at 600 °C. The strong interaction between Ni and CaFe2O4 support result in the formation of Ni–Fe alloy and Ca2Fe2O5, which shows the synergistic effects on the resistant to carbon deposition and metal sintering, thereby improving the activity and stability of the Ni/CaFe2O4 catalyst.

As a natural fluorescent material, the practical application of lignin fluorescence was hindered due to the low fluorescence quantum yield (QY). Inspired by its aggregation fluorescence behavior, the effect of microstructure-scale on lignin fluorescence was studied from two levels, the molecular weight and colloidal sphere. It was demonstrated that with the decrease of lignin microstructure-scale, the non-radiative dissipation and reabsorption effect of lignin fluorescence would be weak, resulting in high emission efficiency. On this basis, hydrogenolysis was used to obtain small molecular fragments and reduce content of reabsorbing groups of lignin, of which the QY was greatly increased by 35 times to about 12%. In addition, the emission peak of lignin was the fluorescence addition of its main structural units. The long-wavelength emission peak was often the illusion from the reabsorption effect but not duo to the formation of conjugated structure. This work provided a potential method for the preparation of high QY lignin and an in-depth understanding of lignin fluorescence.

A high-performance catalyst is the key to selectively convert lignin into aromatic monomers. In this study, Ru@N-doped carbon catalysts were prepared in situ by a two-stage pyrolysis of a mixture o...

Particle coating is a very important step in many industrial production processes as the particle coating layers may fix surfaces with unique advantages. Given the limitation and disadvantages of the existing simulation methods, a coupled CFD–DEM–CVD multi-physical field model for particle-coating simulations has been established taking into account the velocity field, temperature field, concentration field, and deposition model. In this model, gas behavior and chemical reactions are simulated in the CFD frame based on the conservation laws of mass, momentum, and energy. The particle behavior is simulated in the DEM frame based on the gas–solid interphase force model and contact force model. The deposition behavior is simulated in the CVD frame based on the particle movement–adhesion–deposition model. The coupled model can be implemented in Fluent-EDEM software with their user definition function and application programming interface. The particle coating process involving the pyrolysis of acetylene was investigated, and the effect of bed temperature and inlet gas velocity on deposition rate and coating efficiency were investigated based on the proposed model with adjustable deposition coefficients. Both the average deposition layer mass and the average deposition layer thickness were found to be proportional to the elapsed time and increased at the rate of about 1.05 × 10−2 mg/s and 3.45 × 10−4 mm/s, respectively, setting the inlet gas velocity to 11 m/s and bed temperature to 1680 K. A higher temperature and larger inlet gas velocity lead to a larger deposition rate, but the coating efficiency decreases because of limits imposed by the chemical reaction. At a bed temperature of 1280 K, the average deposition rate is 7.40 × 10−3 mg/s when the inlet gas velocity is set to 11 m/s, which is about double the deposition rate when the inlet gas velocity is set as 5 m/s. The proposed model can provide some guidance for the operating conditions and parameters design of the spouted bed in actual coating settings and can also be further developed as a basic model of mechanisms to integrate detailed information across multiple scales.

High value-added utilization of plastic waste has historically been a problem, which has driven researchers to make long-term and unremitting efforts to tackle it. High-performance carbon based solid acid (CSA) was prepared from polyvinyl chloride (PVC) and polyethylene (PE) in different proportions. The small amount of chlorine is still residual on the edge of graphitic carbon sheets after co-carbonization and sulfonation. Strong electronegative –Cl group and the high-density phenolic –OH group, double-adsorption group, are covalently bonded to the edges of the graphitic carbon sheets, contributing to the decrystallization of cellulose to a large extent. Meanwhile, PVC and PE-derived CSAs have significantly higher –SO3H group density than PVC-derived CSA and cellulose-derived CSA. These are obviously beneficial to the improvement of hydrolysis activity, which can be attributed to structural optimization caused by co-carbonization PVC and PE. The CSA with a mixture of 80% proportions has great catalytic activity and repeatability.

Particle mixing is a very important process in many industrial reactors. It is important to consider how to quantify the particle mixing behavior accurately under different conditions. In this paper, the drawbacks of traditional mixing indexes, such as Lacey index are discussed, and then a novel particle mixing index, without grid dependency and particle color dependency was proposed based on the neighbor distance method and coordination number concept. Its characteristics such as parameters selection, calculation method and multi-direction were discussed in details. The proposed mixing index was used for investigating particle mixing behavior in the multiple-spouted bed under conditions of different gas velocity ratios and different particle density ratios. The experimental results have been used to validate the simulation results at first. It is found that the improved mixing index is more superior and effective compared with the traditional mixing index methods, and suitable for the investigation of particle mixing behavior. It was indicated that the density ratio is a key factor to influence particle mixing process. The novel particle mixing index without grid dependency and particle color dependency is recommended to study particle mixing behavior in other particulate processes in the future.

Plug flow receives attention due to its advantages of low particle attrition, low pipeline wear and low energy consumption. A novel non-mechanical draft tube type feeder (DTF) for plug formation has been proposed in our previous study for vertical plug conveying of coarse particles. We further investigate the influence of key geometry parameter of the DTF on plug formation for different particle diameter. Furthermore, we attempt to extend the application of PIV technique to evaluate plug velocity in pneumatic plug conveying. Experiments for vertical plug formation are conducted with glass beads of three kinds of particle diameter (i.e. 6 mm, 4 mm and 2 mm). Plug formation characteristics are examined in terms of flow pattern in riser pipe, solids mass flowrate and pressure fluctuation. The experimental results show that four main features of plug flow pattern in the riser pipe are observed. Solids mass flowrate displays good linear relation to superficial gas velocity forthe same particle diameter in the plug flow regime, even with different relative entrainment height. Some interesting phenomena are observed for the pressure fluctuation. Plug velocity is successfully obtained by PIV technique with high temporal resolution. The present study provides a further understanding of the flow pattern and dynamic behavior of coarse particles in vertical plug formation with the draft tube type feeder.

Plug flow attracts continuous interest due to its advantages of low particle attrition, low pipeline wear and low energy consumption. A novel non-mechanical draft tube type feeder (DTF) has been proposed in our previous work for vertical plug conveying of coarse particles. Detailed particle motion behaviors and plug formation mechanisms in the draft tube type feeder are investigated by the combined approach of Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) in the present study. The CFD-DEM method based on local averaging of granular matter is used to deal with fluid cell sizes smaller than particle sizes under the specific conditions. The applicability of the model is verified by comparing the calculated results with the experimental results of vertical plug formation of 6 mm glass beads in a draft tube type feeder, in terms of plug flow pattern, pressure drop and solid mass flow rate. Detailed analysis of the particle entrainment in feeder container, flow properties at riser inlet and natural plug formation in riser are then carried out. It is found that both gas and particle flows result in entrainment effect on particles, respectively, through fluid-particle and particle-particle interactions. The linear increase of solid mass flow rate with superficial gas velocity is closely related to the linear increase of particle vertical velocity at riser inlet. Plug formation is achieved in a natural way, which shows the features of self-organization phenomenon. Particle concentration is a key parameter in this self-organization process. This study provides some insights into the natural plug formation of coarse particles in a non-mechanical feeder. The model should be useful to study the gas-solid flow of coarse particles in a confined domain with complex geometry, where the fluid cell size may be smaller than the particle size.

The present work focused on fundamentally modelling of the fluidized bed chemical vapor deposition (FB-CVD) process, which is the extensively used method to prepare TRISO particles and other types coated particles, aimed at optimizing and scaling up of the coated fuel particles fabrication technology using a mechanistic approach rather than empirical knowledge. Based on the experimental observation of the coating process, the population balance model (PBM) was used to describe the size distribution of nanoparticles in the FB-CVD process. The deposition rate model related to nanoparticle size distribution was developed based on the homogeneous and heterogeneous deposition coexistence mechanism. Furthermore, on a macroscopic scale, the computational fluid dynamics (CFD) and discrete element method (DEM) were coupled with the deposition rate model, establishing a multiscale simulation platform for simulating the FB-CVD particle coating process. In this proposed CFD-DEM-PBM model, the mass, momentum, and energy transfer, along with chemical reaction, nanoparticle formation, deposition along homogeneous and heterogeneous pathways were considered and simulated accordingly. The preliminary study has been conducted successfully and indicates that the proposed multiscale model has clear and important significance for investigating the particle coating process. However, it should be noted that the model parameters still need to be experimentally refined in the future.

A series of carbon-based solid acids (CSAs) were respectively prepared by the different relative proportions of cellulose and lignin to simulate biomass, and employed to hydrolyze cellulose. The influence of relative proportions of cellulose and lignin on mixture-derived CSA (MCSA) has been investigated in detail. Differences in the structure and performance of MCSAs were found to be obvious. The microcrystalline structure parameters, adsorption capability and hydrolysis activity of MCSA present regular variation trend with the increase of cellulose proportions, which can be attributed to the interaction of cellulose and lignin during co-carbonization. When cellulose proportion is 50%, the co-carbonization is at a turning point, the carbon skeleton of MCSA is more flexible and disordered with larger interlamellar spacing and more C O C bond. Meanwhile, MCSA exhibits remarkable adsorption capability, and the hydrolysis activity is comparable to that of cellulose-derived CSA.

Absorber sphere pneumatic conveying is a special application of pneumatic conveying technique in the pebble bed High Temperature Gas-Cooled Reactor (HTGR or HTR). Granular discharge through a vertical pipe with a bend outlet is one of the control modes to determine solid mass flowrate which is an important parameter for the design of absorber sphere pneumatic conveying. Granular discharge rate through the vertical pipe with a bend outlet in the small absorber sphere system are investigated by discrete element method simulation. The effect of geometry parameters on discharge rate, the discharge rate fluctuation in the vertical pipe, and the effect of friction on steady discharge rate ( W s ) are analyzed and discussed. The phenomena of discharge rate fluctuation in the vertical pipe are observed, which are mainly resulted from the evolution of the average downward granular velocity. The steady discharge rate decreases rapidly with sliding friction coefficient increasing from 0.125 to 0.5, and gradually saturates with the friction coefficient further increasing from 0.5 to 1. It is interesting that the linear relation between W s 2/5 and pipe internal diameter D with zero intercept are found for the vertical pipe discharge with a bend outlet, which is different from the orifice discharge through a hopper or silo with none-zero intercept. A correlation similar to Beverloo’s correlation is developed to predict the steady discharge rate through the vertical pipe with a bend outlet. These results are helpful for the design of sphere discharge rate through the vertical pipe with a bend outlet in the small absorber sphere system of the pebble bed HTGR.

Raw Gas generated from LCPG (lump coal pressurized gasifier) contains quantities of organics including methane so that it is not suitable as syngas. A process was proposed to solve this problem, and Aspen Plus was used to discuss its possibility that Raw Gas was reformed to clean syngas through introducing oxygen on the principle of thermodynamic equilibrium. The simulation results reveal that almost all organics are completely converted to simple substances such as hydrogen and carbon monoxide whether or not to preheat. Raw Syngas and wastewater no longer contain various organic pollutants eliminated difficultly besides very small amounts of ammonia and hydrogen sulfide, which certainly simplifies the purification and post-treatment processes. A Raw Syngas with H 2 /CO ratio of 2.0 was attained under the operating condition of 2.35 Mpa and 918 °C. Such H 2 /CO ratio is higher than those of coal gas derived from existing gasification technologies. Meanwhile, the total yield and content of the effective gas (CO + H 2 ) have been increased to 1109 m 3 /t and 72.0% respectively in the preheating process, and GE (gasification efficiency) rises to 84.8%. The OC (oxygen consumption), CC (coal consumption) and SC (steam consumption) have been reduced by 47.3%, 50.7% and 49.4% respectively compared with LCPG. In addition, the feasibility of this process was further verified with kinetic simulation.

The gas-solid hydrodynamics of coarse particles in a two-dimensional spouted bed (2DSB) are measured using 6 mm glass beads to obtain quantitative experimental results. A one-dimensional mathematical model based on gas-solid mass and momentum balance is used to characterize the spout-annulus interaction and to further interpret the experimental results. The superficial velocity and static bed height are in the range of 2.58 to 4.39 m/s and 8.0 to 13.3 cm, respectively. Pressure fluctuation periodicity of the bed pressure drop is characterized by power spectral density (PSD) analysis. The whole-field particle velocity profiles in 2DSB are obtained by high speed CCD camera and PIV technique. The results show that particle motion in the spout in the present 2DSB experiments is dominated by the balance of drag force, solid stress and gravitation. The existence of obvious solid stress from particle impaction and friction leads to energy dissipation, which limits the increase of vertical particle velocity along the spout axis ( v yc ) in the spout and results in a flat stage of v yc with slight fluctuation near the bottom of the fountain. The solid stress also contributes to the nearly flat peak of lateral profile of downward particle velocity in the annulus. These detailed results are helpful for understanding the gas hydrodynamics and particle motion behavior of coarse particles in 2DSB, and for verification of the extended CFD-DEM coupling method for particle size approaching fluid cell size.

Plug flow receives attention because of its advantage to reduce particle attrition, pipe wear and energy consumption. A novel non-mechanical draft tube type feeder (DTF) for plug formation is proposed in this study for vertical plug conveying of coarse particles. Particles in the feeder are entrained by gas stream through draft tube direct into the bottom of riser pipe. The plug formation experiments with coarse particles (glass beads particle diameter 4.0 mm) are conducted with this novel feeder. Plug formation characteristics are investigated by solids mass flowrate, high frequency pressure fluctuations and high-speed camera measurements. Power spectral density analysis is used to characterize frequency distribution of the high frequency pressure fluctuations. The experimental results show that natural plug formation is successfully achieved by the DTF for the superficial gas velocity ug in the range of 4.86 to 10.16 m/s. A “particle cloud” is initially formed by particles entrainment effect in the bottom of riser, then its porosity decreases and length increases by further particles entrainment and pickup to form a plug. The solids mass flowrate shows a good linear relation to the gas mass flowrate. The plug length shows to be stochastic in a certain range around 0.11 m, which is mainly attributed to the natural plug formation characteristics of the DTF. This study provides a natural plug formation feeder for vertical plug conveying of coarse particles. The feeder might be used for high temperature and/or high pressure operation environment in which high reliability is required. It might also be used to simplify the feeding device for vertical plug conveying of coarse particles.

The selective cleavage of C–O bond in lignin is the key to convert them into aromatic compounds and then to produce liquid fuels and chemicals. N-doped carbon nanosheets were obtained by direct pyrolysis of glucosamine hydrochloride (GAH) and melamine. Highly-dispersed and small-sized Ru nanoparticles (NPs) supported N-doped carbon by impregnation method, which can efficiently convert lignin to obtain 40.70% aromatic monomers. It was 2.3 times than that of the commercial catalyst (Ru/C) and the catalyst could be used at least five runs with an insignificant loss in the yield of aromatic monomers. The morphology, specific surface area, nitrogen species and content of supports could be tuned by controlling the weight of melamine. The results showed that the melamine and GAH were condensed to form layered graphitic carbon nitride (g-C3N4) and a carbon skeleton at 600 °C, respectively. Then, the produced N from the decomposition of g-C3N4 at high temperature (>700 °C) could improve nitrogen concentration, increase the specific area and result in the graphene-like wrinkled morphology. The presence of pyridinic N not only served as metal coordination sites to stabilize and disperse Ru NPs but also enhanced the proportions of Ru0 through the electronic interactions. The DFT calculations implied that the pyridinic N contributed to the highest adsorption energy for 2-phenoxy-1-phenethanol (PPE) and a reduction of the disassociation energy for Calkyl–O bond compared with graphite N and pure C.

In order to solve the problem that loading chlorine could reduce the density of -SO3H group and inhibit the increase of catalytic activity, three strategies were adopted to realize the simultaneous chlorination and oxidation modification of carbon-based solid acid, using cheap and easily available NaClO and highly reactive coal as raw materials. The results show that the involvement of NaClO changes the structure of coal-based solid acid from three aspects: loading of chlorine, increase of −COOH group and improvement of aromaticity. It is worth mentioning that −COOH group plays a dual role in both adsorption and hydrolysis, which has a compensation effect on -SO3H group and -Cl group. The structural improvement prominently enhances the hydrolysis of cellulose. Moreover, −COOH group and -Cl group with induced effect can significantly improve the stability of solid acid.

Pyrolysis techniques can provide a way to convert polyvinyl chloride (PVC) waste into high value liquids and gases. The inexpensive pyrolysis residue was used to successfully prepare a carbon-based solid acid (CSA) bearing –Cl functional group by a simple process, which has been shown to be highly effective for hydrolyzing microcrystalline cellulose into reducing sugars. The structure, acidic functional group density and catalytic activity of PVC-derived CSA (PCSA) were investigated. The results showed that the carbonization time has an important influence on the structure and properties of the PCSA, especially in a lower temperature range. There was a compensation effect between the carbonization temperature and time on the structure and the activity of PCSA. Phenolic-OH and –Cl groups acted as double cellulose-binding sites and together improved the adsorbability of PCSA, which is much higher than that of traditional CSA and other CSAs bearing –Cl groups. The high hydrolytic activity was determined by the adequate density of the –SO3H group, the excellent adsorption property, and the entire structure of the PCSA.

Pneumatic conveying of absorber spheres in the pebble-bed high-temperature gas-cooled reactor is a special application of pneumatic conveying technique in the nuclear engineering. It may be regarded as an intermittent circulation of absorber spheres between the side reflector boring and the storage bin in the reactor. The whole process consists of several sub-processes, e.g., the granular discharge from the sphere storage bin into the boring, granular discharge from the side reflector boring into the feeder, particle entrainment in the feeder, sphere conveying in the transport pipe, and gas-solid separation in the storage bin. We give a brief summary of the experimental and discrete element simulation work done recently at the Institute of Nuclear and New Energy Technology of Tsinghua University, mainly from the viewpoint of gas-solid flow and granular flow. CFD-DEM coupling simulation is recently conducted to investigate the coarse particle conveying in the small absorber sphere system. We present some CFD-DEM simulation results of coarse particle conveying in ambient air and high-pressure helium gas. Based on the needs of engineering practice and scientific research, some research requirements are suggested. Further work is still needed, to make a comprehensive understanding of the conveying process, and to optimize the design and operation of the conveying system.

The pressure drop of gas-solid flow for absorber sphere pneumatic conveying is important for the design and operation of the gas circulator. The simplified one-dimension model is introduced to predict the pressure drop of gas- solid flow for absorber sphere pneumatic conveying. The pressure drop of gas-solid flow in the vertical pipe is the main component part of the total gas-solid flow for absorber sphere conveying. The pressure drop of gas-solid flow for absorber sphere conveying in the vertical pipe with the inside diameter 47 mm and conveying height 23 m is predicted by the simplified model. The superficial gas velocity considered is in the range of 1.5 to 3.0 times of the terminal velocity of a single particle. The solid mass flow rate considered is in the range of 0.2 to 1.2 kg/s. Particle velocity, solid friction factor and solid mass flow rate are important parameters to predict pressure drop of vertical pipe. The typical empirical correlations of particle velocity and solid friction factor reported in the literature are adopted to predict the pressure drop of vertical pipe. The superficial gas velocity for absorber sphere conveying is suggested to be two times of the terminal velocity of a single particle. For the suggested superficial gas velocity, the predicted pressure drop of vertical pipe by using empirical correlations is in the range of 15 to 20 kPa and 31 to 50 kPa for solid mass flow rate at 0.2 kg/s and 1.2 kg/s, respectively. For the suggested superficial gas velocity, the relatively conservative predicted pressure drop of vertical pipe is in the range of 20 to 78 kPa for solid mass flow rate in the range of 0.2 to 1.2 kg/s. Further work is needed to verify the pressure drop model and to modify the key parameters for absorber sphere conveying in helium.

The effect of CaO on the NH3 + NO + O2 reaction system at 650–850 °C was investigated. High CO2 concentration was added to investigate the effect of CaCO3 on this reaction system also. Experimental results showed that CaO had a strong catalytic effect on NH3 decomposition, NH3 oxidation by O2 to NO, and NO reduction by NH3 in the absence of O2. The overall effect of CaO on the NO + NH3 + O2 reaction was to enhance NH3 oxidation by O2 to produce more NO. A small amount of NO2 and no N2O was detected in the outlet gas stream over CaO in the NH3 + NO + O2 reaction. NO2 formation decreased with temperature increase. NO2 formation in the NH3 + NO + O2 reaction over CaO was attributed to the oxidization of NH3 and NO by O2. The performance of CaCO3 was different from CaO. NH3 decomposition was promoted, but NH3 oxidation to NO was inhibited after CaO was converted to CaCO3. No catalytic activity for NO reduction was detected in NO + NH3 reaction over CaCO3, but strong activity for NH3 decomposition was observed. NO and NH3 outlet concentration over CaCO3 in the NH3 + NO + O2 reaction was lower and higher, respectively, than that of CaO, which was mainly due to the difference of CaO and CaCO3 for NH3 oxidation. NO2 formation was inhibited, but N2O was observed over CaCO3. N2O formation increased with temperature increase at 650–750 °C, and then decreased at 750–850 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

Nitrous oxide (N2O) is a significant greenhouse gas and its emissions from fluidized bed combustion systems can be controlled using catalytic conversion and decomposition. The catalytic decomposition of N2O was studied in a quartz fixed-bed reactor at 450–700 °C. The low-cost catalyst was prepared from fly ash and iron oxides, and was characterized in terms of the BET specific surface area and XRD. This study showed that both the Fe content on the catalyst surface and the calcination temperature during the preparation of the catalyst should be optimized in order to significantly improve the catalyst performance when used for N2O decomposition. The influences of O2, H2O, CO2 and SO2 on the N2O decomposition were investigated at the most reactive temperature. Experimental results showed that O2 had a small negative effect on the catalytic activity, while CO2 had no obvious effect on the N2O decomposition. The N2O conversion was still high even when H2O was present. However, the N2O conversion dropped sharply when H2O and O2 were both present. The catalytic activity was reduced by SO2 because of its reaction with the catalyst. The difference between the N2O conversion with H2O present and with both H2O and O2 present was analyzed in order to determine the N2O decomposition mechanism. Two mechanisms for the N2O catalytic decomposition mechanism have been considered, of which the one with formation of oxygen atoms at two sites with migration and recombination shows better agreement with our experimental results. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

The effect of sulfated CaO on NO reduction by NH3 in the presence of excess oxygen was investigated to evaluate the potential of simultaneous SO2 and NO removal at the temperature range of 700−850 ...

The potential of the sorbent-catalysts prepared from three low cost materials, i.e., the lime, fly ash and some industrial waste material containing iron oxide, have been investigated for simultaneous removal of SO2 and NO x from flue gas in the temperature range 700–850 °C. NH3 was chosen as the reducing agent for NO reduction in this study. Experimental results showed that SO2 and NO could be simultaneously removed efficiently in the absence of O2 at the temperature window of 700–800 °C. The effect of product layer generated from SO2 removal on NO removal was not obvious. NO removal efficiency was strongly inhibited by O2, which was attributed to the partial oxidation of NH3 to NO over the sorbent-catalysts in the presence of oxygen. Neither NO2 nor N2O by-product was detected both in the absence and presence of O2. Three routes were suggested to overcome the negative effect of O2.

In the high-temperature gas-cooled reactor pebble-bed module (HTR-PM), absorber sphere shutdown system is the second shutdown system. Absorber spheres are transported back to storage vessel by pneumatic conveying when reactor needs to be started. The restart reliability of absorber sphere pneumatic conveying is quite important. Experimental system for absorber sphere pneumatic conveying has been built to investigate the gas-solid flow characteristics of pneumatic conveying. Restart experiments were conducted to study the restart performance of pneumatic conveying. Ambient air was used as source gas and absorber sphere was replaced by glass sphere. The inlet steady gas velocity of the sphere feeder was in the range of 17∼27 m/s. Pneumatic conveying could be restarted in all the experiments, which showed the good reliability of the pneumatic conveying process. The maximum relative deviation of the spheres pile heights in the riser was 4.1%, which showed a good repeatability. Pressure drop of feeder during steady stage was in the range of 4∼8 kPa. Furthermore, the restart experiments were also conducted in the full scale experimental system with helium as the source gas and the pressure of 2 MPa, the results also showed the good reliability of pneumatic conveying process.Copyright © 2014 by ASME

The absorber ball shutdown system is a key system and related to reactivity control in HTR-PM, which has once achieved power regulation and cold shutdown of the nuclear reactor. Passive drive mechanism of absorber ball shutdown system has been designed for HTR-PM reactor safety before. Ball dropping valve can be automatically opened by gravity when loss of offsite power happens, then a mass of balls with BC4 fall into reactor core for function implementation. Therefore drive mechanism reliability is fairly important for absorber ball shutdown system in HTR-PM. Experiments on passive drive mechanism have been carried out in this study. Falling distance and falling time of drive mechanism have been recorded and analyzed with and without absorber ball, as well as at ambient temperature and in the heating conditions. Experimental results demonstrate that designed passive drive mechanism can shift reliably. Ball dropping valve can freely open each time without absorber balls in the storage vessel. Basically present design of passive drive mechanism for absorber ball shutdown system can meet the requirement of actual reactor application.Copyright © 2013 by ASME

The sphere feeder is an important component of the absorber sphere shutdown system for absorber sphere conveying. Absorber sphere is entrained and fluidized in the feeder by conveying gas to form gas-solid flow. The effect of feeder inner structure, i.e. the draft tube height, on the feeding performance was investigated. Experiments were conducted in the positive pressure conveying system with ambient air as the source gas. The glass sphere was used to replace the absorber sphere. Three types of feeder inner draft tube relative position were considered. Five combinations of the draft tube height were tested with feeder inlet air velocity in the range of 15∼30 m/s. Experimental results showed that feeder inner draft tube height played an important role on the feeding performance. Different characteristics for the starting process of the sphere conveying were observed. The difference of sphere blown away pressure and steady conveying pressure could be reduced to about 5 kPa, which was negligible from the view point of conveying blower selection in engineering application. Sphere stagnation region was observed near the bottom of the feeder. The obvious boundary of stagnated sphere and fluidized sphere was formed for the steady conveying. Two types of control model were observed for sphere steady feeding rate. One was that the sphere steady feeding rate was determined by sphere flow through the orifice. The other was that the sphere steady feeding rate was determined by gas-sphere fluidization and entrainment. These results were important for optimization sphere feeder design.Copyright © 2013 by ASME

Visualization experiments were conducted in a positive pressure system to investigate the starting process characteristics of the absorber sphere pneumatic conveying. The ambient air was used as the source gas. The absorber sphere was replaced by the glass sphere. Spouted spheres flow was observed at the early stage of the starting process. With the increase of feeder inlet gas flow rate with time after starting the blower, the amount of fluidized spheres in the riser pipe first increased gradually and then decreased to the steady conveying state. The steady conveying was achieved as the feeder inlet gas flow rate was up to the maximum. A peak pressure was observed at the feeder gas inlet. The sphere blown away pressure was approximately 20 kPa higher than the steady conveying pressure. The time lasted for the pressure higher than the steady conveying pressure was about 10 s. The process for spheres blown away at the early stage of the starting process was more difficult than the steady conveying. The pressure increase and the duration characteristics should be taken into account for the blower pressure parameters design in the practical engineering application.