Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the ac...Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the activated sludge process, despite their long operating times. However, population increases have created a demand for more efficient means of wastewater treatment, Fluidization has been demonstrated to in- crease the efficiency of many processes in chemical and biochemical engineering, but it has not been widely used in large-scale wastewater treatment. At the University of Western Ontario, the circulating fluidized-bed bioreactor （CFBBR） was developed for treating wastewater. In this process, carrier particles develop a biofilm composed of bacteria and other microbes. The excellent mixing and mass transfer characteristics inherent to fluidization make this process very effective at treating both municipal and industrial wastewater. Studies of lab- and pilot-scale systems showed that the CFBBR can remove over 90% of the influent organic matter and 80% of the nitrogen, and produces less than one-third as much biological sludge as the activated sludge process. Due to its high efficiency, the CFBBR can also be used to treat wastewaters with high organic solid concentrations, which are more difficult to treat with conventional methods because they require longer residence times; the CFBBR can also be used to reduce the system size and footprint. In addition, it is much better at handling and recovering from dynamic loadings （i.e., varying influent volume and concentrations） than current systems. Overall, the CFBBR has been shown to be a very effective means of treating wastewa- ter, and to be capable of treating larger volumes of wastewater using a smaller reactor volume and a shorter residence time. In addition, its compact design holds potential for more geographically localized and isolat- ed wastewater treatment systems.展开更多
Abstract： In order to improve the reactivity of Na2CO3/Al2O3 sorbent with CO2, a new sorbent showing high reactivity was developed by doping Na2CO3/Al2O3 with TiO2 using impregnation. Fourteen multi-cycle carbonation...Abstract： In order to improve the reactivity of Na2CO3/Al2O3 sorbent with CO2, a new sorbent showing high reactivity was developed by doping Na2CO3/Al2O3 with TiO2 using impregnation. Fourteen multi-cycle carbonation/regeneration tests of the sorbent were carried out in a fluidized-bed reactor and the sorbent was characterized by X-ray diffraction and nitrogen adsorption. It is confirmed that TiO2 shows a positive effect on the adsorption process of Na2CO3 and the reaction rate is observed to increase significantly, especially in the first 10 min. Moreover, TiO2 is stable within the temperature range of the process and no other Ti-compounds are detected. The carbonation products are NaHCO3 and Na5H3 （CO3 ）4. The surface area and the pore volume of the sorbent keep stable after 14 cycles. The Fourier transform infrared spectroscopy and the X-ray photoelectron spectroscopy are used to analyze the effect mechanism of TiO2 on CO2 adsorption process of Na2CO3/Al2O3.展开更多
This work was conducted to evaluate whether Ca-bearing additives used during coal combustion can also help with the retention of some other elements. This work was focused on the evaluation of bottom ashes collected d...This work was conducted to evaluate whether Ca-bearing additives used during coal combustion can also help with the retention of some other elements. This work was focused on the evaluation of bottom ashes collected during four full-scale combustion tests at an operating thermal fluidized-bed power station. Bottom ashes were preferred to fly ashes for the study to avoid interference from condensation processes usually occurring in the post-combustion zone. This work focused on the behaviors of S, Cl, Br, As, Mn, V, Cr, Ni, Cu,Zn, W, and Pb. Strong positive correlations with CaO content in bottom ashes were observed（for all four combustion tests） for S, As, Cl and Br（R = 0.917-0.999）. Strong inverse proportionality was calculated between the contents of Pb, Zn, Ni, Cr and Mn and CaO, so these elements showed association to materials other than Ca-bearing compounds（e.g., to aluminosilicates, organic matter, etc.）. Somewhat unclear behaviors were observed for W, Cu, and V. Their correlation coefficients were evaluated as statistically ＂not significant＂, i.e., these elements were not thought to be significantly associated with CaO. It was also discovered that major enrichment of CaO in the finest bottom ash fractions could be advantageously used for simple separation of elements strongly associated with these fractions, mainly S and As, but also Cl or Br. Removal of5% of the finest ash particles brings about a decrease in As concentration down to 77%-80% of its original bulk ash content, which can be conveniently used e.g., when high As content complicates further ash utilization.展开更多
The reaction behavior of oil sand from Inner Mongolia（China） were studied in a fluidizedbed pyrolysis process,and a comparative study was conducted on the properties of the liquid products obtained through fluidized...The reaction behavior of oil sand from Inner Mongolia（China） were studied in a fluidizedbed pyrolysis process,and a comparative study was conducted on the properties of the liquid products obtained through fluidized-bed pyrolysis of oil sand and the native bitumen obtained by solvent extraction.The results indicated that the fluidized-bed pyrolysis,a feasible carbon rejection process,can be used to upgrade oil sand.The reaction temperature and time were found to be the key operating parameters affecting the product distribution and yields in fluidized-bed pyrolysis of oil sand.The optimal temperature was 490℃ and the most suitable reaction time was 5 min.Under these operation conditions,the maximum yield of liquid product was 80wt%.In addition,the pyrolysis kinetics of oil sand at different heating rates of 5,10,20 and 30℃/min was investigated using a thermogravimetric analyzer（TGA）.展开更多
In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and h...In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.展开更多
Performance of the oxidative coupling of methane in fluidized-bed reactor was experimentally investigated using Mn-Na2WO4/SiO2,La2O3/CaO and La2O3-SrO/CaO catalysts.These catalysts were found to be stable,especially M...Performance of the oxidative coupling of methane in fluidized-bed reactor was experimentally investigated using Mn-Na2WO4/SiO2,La2O3/CaO and La2O3-SrO/CaO catalysts.These catalysts were found to be stable,especially Mn-Na2WO4/SiO2 catalyst.The effect of sodium content of this catalyst was analyzed and the challenge of catalyst agglomeration was addressed using proper catalyst composition of 2%Mn2.2%Na2WO4/SiO2.For other two catalysts,the effect of Lanthanum-Strontium content was analyzed and 10%La2O 3-20%SrO/CaO catalyst was found to provide higher ethylene yield than La2O3/CaO catalyst.Furthermore,the effect of operating parameters such as temperature and methane to oxygen ratio were also reviewed.The highest ethylene and ethane （C2） yield was achieved with the lowest methane to oxygen ratio around 2.40.5% selectivity to ethylene and ethane and 41% methane conversion were achieved over La2O3-SrO/CaO catalyst while over Mn-Na2WO4 /SiO2 catalyst,40% and 48% were recorded,respectively.Moreover,the consecutive effects of nitrogen dilution,ethylene to ethane production ratio and other performance indicators on the down-stream process units were qualitatively discussed and Mn-Na2WO4/SiO2 catalyst showed a better performance in the reactor and process scale analysis.展开更多
For the synthesis of single-walled carbon nanotubes （SWCNTs） from CH4 over a Fe/MgO catalyst, we proposed a coupled Downer-turbulent fluidized-bed （TFB） reactor to enhance the selectivity and yield （or production...For the synthesis of single-walled carbon nanotubes （SWCNTs） from CH4 over a Fe/MgO catalyst, we proposed a coupled Downer-turbulent fluidized-bed （TFB） reactor to enhance the selectivity and yield （or production rate） of SWCNTs. By controlling a very short catalyst residence time （1-3 s） in the Downer, only part of Fe oxides can be reduced to form Fe nano particles （NPs） available for the growth of SWCNTs. The percentage of unreduced Fe oxides increased and the yield of SWCNTs decreased accordingly with the increase of catalyst feeding rate in Downer. SWCNTs were preferentially grown on the catalyst surface and inhibited the sintering of the Fe crystallites which would be formed thereafter in the downstream TFB, evidenced by TEM, Raman and TGA. The coupled Downer-turbulent fluidized-bed reactor technology allowed higher selectivity and higher production rate of SWCNTs as compared to TFB alone.展开更多
A mathematical model is developed for an industrial acrylonitrile fluidized-bed reactor based on arti-ficial neural networks. A new algorithm, which combines the characteristics of both genetic algorithm (GA) andgener...A mathematical model is developed for an industrial acrylonitrile fluidized-bed reactor based on arti-ficial neural networks. A new algorithm, which combines the characteristics of both genetic algorithm (GA) andgeneralized delta-rule (GDR) is used to train artificial neural network (ANN) in order to avoid search terminatedat a local optimal solution. For searching the global optimum, a new algorithm called SM-GA, incorporating ad-vantages of both simplex method (SM)and GA, is proposed and applied to optimize the operating conditions of anacrylonitrile fluidized-bed reactor in industry.展开更多
Objective To investigate the reduction of chlorination by-products （CBPs） precursors using the fluidized-bed biofdm reactor （FBBR）. Methods Reduction of total organic carbon （TOC）, ultraviolet absorbance （UV254...Objective To investigate the reduction of chlorination by-products （CBPs） precursors using the fluidized-bed biofdm reactor （FBBR）. Methods Reduction of total organic carbon （TOC）, ultraviolet absorbance （UV254）, tfihalomethane （THM） formation potential （THMFP）, haloacetic acid （HAA） formation potential （HAAFP）, and ammonia in FBBR were evaluated in detail. Results The reduction of TOC or UV254 was low, on average 12.6% and 4.7%, respectively, while the reduction of THMFP and HAAFP was significant. The reduction of ammonia was 30%-40% even below 3℃, however, it could quickly rise to over 50% above 3℃. Conclusions The FBBR effectively reduces CBPs and ammonia in drinking water even at low temperature and seems to be a very promising and competitive drinking water reactor for polluted surface source waters, especially in China.展开更多
This article presents a mathematical model of heat and mass transfer for the process of fluidized-bed spray granulation, which can be applied in the analysis of bed temperature profile, temperature and humidity of out...This article presents a mathematical model of heat and mass transfer for the process of fluidized-bed spray granulation, which can be applied in the analysis of bed temperature profile, temperature and humidity of outlet gas and moisture content of particles. Effects of operation parameters on the batch granulation are investigated. The theoretical calculation agrees reasonably well with the experimental data.展开更多
Controlled-release coated urea(CRCU)is an important agrochemical in precision farming,with its effectiveness reliant on the quality of the coating film and the nutrient-release kinetics.This study explores the use of ...Controlled-release coated urea(CRCU)is an important agrochemical in precision farming,with its effectiveness reliant on the quality of the coating film and the nutrient-release kinetics.This study explores the use of a chemically modified lignocellulosic biopolymer derived from almond shells as a coating material for producing CRCU using Wurster fluidized-bed equipment.The study examines how process parameters—namely fluidized-bed temperature(T_(fb)),spray rate(R_(spray)),fluidizing-air flow rate(Q_(air)),and atomizing-air pressure(P_(air))—influence coating quality and nutrient-release kinetics.These are assessed through the inter-particle coefficient of coating mass variance(CMV)and the diffusion coefficient,respectively.The mechanism of nutrient release was studied using the Ritger and Peppas empirical model,specifically by calculating the diffusional exponent,n,for all samples.A Response Surface Methodology(RSM)approach coupled with a CCRD was applied to plan the experiments,perform statistical analysis,predict outcomes,and optimize the process conditions.The Analysis of Variance indicated that Tfb significantly impacts the studied parameters.Optimal coating quality(CMV=6.7%)was achieved under conditions of T_(fb)=75℃,Q_(air)=80 m^(3)/h,R_(spray)=0.17 mL/s,and P_(air)=3.1 bar.The optimum diffusion coefficient(2.2×10^(-1)cm^(2)/s)was obtained at T_(fb)=78℃,Q_(air)=75 m^(3)/h,R_(spray)=0.125 mL/s,and P_(air)=3.2 bar.The experimental and predicted responses showed close agreement that validates the regression models for predicting quality of coating films and kinetics of nutrient-release.Based on the n values,some samples exhibited Fickian diffusion,while others followed a non-Fickian nutrient-release mechanism.展开更多
In this paper, the clustering behavior of solid particles in a two-dimensional （2D） liquid-solid fluidized-bed was studied by using the charge coupled devices （CCD） imaging measuring and processing technique and w...In this paper, the clustering behavior of solid particles in a two-dimensional （2D） liquid-solid fluidized-bed was studied by using the charge coupled devices （CCD） imaging measuring and processing technique and was characterized by fractal analysis. CCD images show that the distribution of solid particles in the 2D liquid-solid fluidised-bed is not uniform and self-organization behavior of solid particles was observed under the present experimental conditions. The solid particles move up in the 2D fluidized-bed in groups or clusters whose configurations are often in the form of horizontal strands. The box fractal dimension of the cluster images in the 2D liquid-solid fluidized-bed increases with the rising of solid holdup and reduces with the increment of solid particle diameter and superficial liquid velocity. At given solid holdup and solid particle size, the lighter particles show smaller fractal dimensions.展开更多
Coating of particulate materials in fluidized beds is a widely used technique to eliminate particle agglomeration,provide slow release of an active substance,or protect active ingredients.When thin polymer shells are ...Coating of particulate materials in fluidized beds is a widely used technique to eliminate particle agglomeration,provide slow release of an active substance,or protect active ingredients.When thin polymer shells are applied on a particle surface,it is important to determine the process parameters that provide coating uniformity.In this study,the degree of coverage,defined as the fraction of the coated surface of the particles,is proposed as a quantitative criterion of coating uniformity.A new model for the batch fluidized-bed coating process is presented.The model allows prediction of the function of particle distribution according to the degree of coverage at a given process time and thereby enables assessment of coating uniformity.An algorithm for the numerical solution of model equations for a batch fluidized-bed coater is described.The influences of the main process parameters on the coating uniformity were shown.展开更多
The reduction of carbon dioxide to methane by hydrogen("CO2 methanation")using renewable energy is a promising process for recycling CO2.Better catalysts and better reactors are both required for the practic...The reduction of carbon dioxide to methane by hydrogen("CO2 methanation")using renewable energy is a promising process for recycling CO2.Better catalysts and better reactors are both required for the practical application of CO2 methanation.This study examines how the operating parameters affect CO2 methanation in a highly efficient fluidized-bed reactor.We first measured the kinetics of the CO2 methanation reaction using an NiMgW catalyst,which has been reported to exhibit superior catalytic performance.We then developed a fluidized-bed reactor model based on an earlier model for CO2 methanation.The fluidized bed model indicated that the NiMgW was indeed superior to two other previously studied catalysts in terms of faster conversion of reactants and higher concentrations of product CH4 throughout the reactor.The overall rate of production of CH4 increased with temperature and H2/CO2 ratio and decreased as the inlet reactant flow rate,catalyst particle diameter,and catalyst particle sphericity increased.展开更多
The influence of reduction conditions on carbon deposition during fiuidized-bed pre-reduction of iron ore fines was investigated experimentally.The results showed that reduction temperature and the composition of redu...The influence of reduction conditions on carbon deposition during fiuidized-bed pre-reduction of iron ore fines was investigated experimentally.The results showed that reduction temperature and the composition of reducing gases had a significant effect on the rate of carbon deposition and the type of carbon deposits (graphite and Fe3C).Low reduction temperature,high CO content,and addition of H2favored the deposition of carbon,especially graphite.The reduction conditions also significantly affected the surface morphology of the as-reduced iron ore fines.As the amount of deposited graphite increased,the formation of fibrous iron disappeared and graphite filaments were observed.The pre-reduced iron ore fines were further fiuidized in pure CO at 850℃ for final reduction.The results showed that graphite could suppress the formation of fibrous iron and decrease the surface viscosity,thereby inhibiting agglomeration during the final high-temperature reduction stage.Reactions that consume the deposited carbon during the final high-temperature reduction were identified and graphite was shown to be more reactive than Fe3C.To enhance the application of fluidization technology in producing sponge iron,a novel solid-state high-temperature reduction method via deposited carbon was proposed and demonstrated to be feasible.展开更多
Temperature is a critical factor influencing the performance of coal catalytic hydrogasification in bubbling fluidized bed gasifiers.Numerical simulations at various temperatures(1023 K,1073 K,1123 K,and 1173 K)are co...Temperature is a critical factor influencing the performance of coal catalytic hydrogasification in bubbling fluidized bed gasifiers.Numerical simulations at various temperatures(1023 K,1073 K,1123 K,and 1173 K)are conducted to elucidate the mechanisms by which temperature affects bubble size,global reaction performance,and particle-scale reactivity.The simulation results indicate that bubble size increases at elevated temperatures,while H_(2)-char hydrogasification reactivity is enhanced.Particle trajectory analyses reveal that particles sized between 100 and 250μm undergo intense char hydrogasification in the dense phase,contributing to the formation of hot spots.To assess the impact of temperature on the particle-scale flow-transfer-reaction process,the dimensionless quantities of Reynolds,Nusselt,and Sherwood numbers,along with the solids dispersion coefficient,are calculated.It is found that higher temperatures inhibit bubble-induced mass and heat transfer.In general,3 MPa,1123 K,and 3-4 fluidization numbers are identified as the optimal conditions for particles ranging from 0 to350μm.These findings provide valuable insights into the inherent interactions between temperature and gas-particle reaction.展开更多
In order to solve the shortcomings of MoO_(3)/γ-Al_(2)O_(3)catalyst for sulfur-resistant methanation,a segmented plasma fluidized bed reactor was designed,where plasma discharge zone and the fluidization zone were se...In order to solve the shortcomings of MoO_(3)/γ-Al_(2)O_(3)catalyst for sulfur-resistant methanation,a segmented plasma fluidized bed reactor was designed,where plasma discharge zone and the fluidization zone were separated under higher discharge power.At the bed height of 30 mm,the gas velocity of 0.10 m·s^(-1)can provide a better fluidization state.The suitable discharge results can be achieved when the input power is 27 W and the discharge interval is 2.0 mm.With the extension of catalyst plasma treatment time,the conversion of CO decreases,but the selectivity of CH_(4)increases.Combined with N_(2)physical adsorption-desorption,XRD,TEM,Raman,TGA and TPR characterization,it was found that the active components of the catalyst are uniformly dispersed on the γ-Al_(2)O_(3)support.After plasma treatment,tetrahedral Mo species was used as the active center,and the interaction between Mo and the carrier was strengthened.It provides a novel approach for preparing catalyst with dielectric barrier discharge(DBD)fluidized bed reactor.展开更多
The size and distribution patterns of bubbles within a laboratory-scale coarse-particle flotation column were examined using a high-speed camera-based dynamic measurement system.The effects of operational parameters s...The size and distribution patterns of bubbles within a laboratory-scale coarse-particle flotation column were examined using a high-speed camera-based dynamic measurement system.The effects of operational parameters such as superficial water velocity,air-flow rate,and frother dosage on bubble-size and distribution characteristics were investigated.This study aims to provide theoretical support for enabling fluidized-bed flotation within coarse-particle flotation columns.The results show that negative pressure for air inspiratory and bubble formation is generated by passing a high-speed jet through a throat,and the greatest number of bubbles are observed under natural inspiratory state at an air-liquid ratio of 1:3-1:2.5.Increasing the air-flow rate transforms the bubble diameter distribution from a peaked distribution to a more uniform distribution.Furthermore,the frother narrows the range of bubble-size distribution.A positive correlation exists between the bubble Sauter diameter and air-flow rate,with the bubble Sauter diameter bearing a negative correlation with the superficial water velocity and frother concentration.展开更多
Due to their low cost,environmental friendliness and high energy density,the lithium-sulfur batteries(LSB)have been regarded as a promising alternative for the next generation of rechargeable battery systems.However,t...Due to their low cost,environmental friendliness and high energy density,the lithium-sulfur batteries(LSB)have been regarded as a promising alternative for the next generation of rechargeable battery systems.However,the practical application of LSB is seriously hampered by its short cycle life and high self-charge owing to the apparent shuttle effect of soluble lithium polysulfides.Using MgSO_(4)@MgO composite as both template and dopant,template-guided S-doped mesoporous graphene(SMG)is prepared via the fluidized-bed chemical vapor deposition method.As the polypropylene(PP)modifier,SMG with high specific surface area,abundant mesoporous structures and moderate S doping content offers a wealth of physical and chemical adsorptive sites and reduced interfacial contact resistance,thereby restraining the serious shuttle effects of lithium polysulfides.Consequently,the LSB configured with mesoporous graphene(MG)as S host material and SMG as a separator modifier exhibits an enhanced electrochemical performance with a high average capacity of 955.64 mA h g^(-1) at 1C and a small capacity decay rate of 0.109%per cycle.Additionally,the density functional theory(DFT)calculation models have been rationally constructed and demonstrated that the doped S atoms in SMG possess higher binding energy to lithium polysulfides than that in MG,indicating that the SMG/PP separator can effectively capture soluble lithium polysulfides via chemical binding forces.This work would provide valuable insight into developing a versatile carbon-based separator modifier for LSB.展开更多
文摘Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the activated sludge process, despite their long operating times. However, population increases have created a demand for more efficient means of wastewater treatment, Fluidization has been demonstrated to in- crease the efficiency of many processes in chemical and biochemical engineering, but it has not been widely used in large-scale wastewater treatment. At the University of Western Ontario, the circulating fluidized-bed bioreactor （CFBBR） was developed for treating wastewater. In this process, carrier particles develop a biofilm composed of bacteria and other microbes. The excellent mixing and mass transfer characteristics inherent to fluidization make this process very effective at treating both municipal and industrial wastewater. Studies of lab- and pilot-scale systems showed that the CFBBR can remove over 90% of the influent organic matter and 80% of the nitrogen, and produces less than one-third as much biological sludge as the activated sludge process. Due to its high efficiency, the CFBBR can also be used to treat wastewaters with high organic solid concentrations, which are more difficult to treat with conventional methods because they require longer residence times; the CFBBR can also be used to reduce the system size and footprint. In addition, it is much better at handling and recovering from dynamic loadings （i.e., varying influent volume and concentrations） than current systems. Overall, the CFBBR has been shown to be a very effective means of treating wastewa- ter, and to be capable of treating larger volumes of wastewater using a smaller reactor volume and a shorter residence time. In addition, its compact design holds potential for more geographically localized and isolat- ed wastewater treatment systems.
基金The National Natural Science Foundation of China(No.51476030)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20130092110006)
文摘Abstract： In order to improve the reactivity of Na2CO3/Al2O3 sorbent with CO2, a new sorbent showing high reactivity was developed by doping Na2CO3/Al2O3 with TiO2 using impregnation. Fourteen multi-cycle carbonation/regeneration tests of the sorbent were carried out in a fluidized-bed reactor and the sorbent was characterized by X-ray diffraction and nitrogen adsorption. It is confirmed that TiO2 shows a positive effect on the adsorption process of Na2CO3 and the reaction rate is observed to increase significantly, especially in the first 10 min. Moreover, TiO2 is stable within the temperature range of the process and no other Ti-compounds are detected. The carbonation products are NaHCO3 and Na5H3 （CO3 ）4. The surface area and the pore volume of the sorbent keep stable after 14 cycles. The Fourier transform infrared spectroscopy and the X-ray photoelectron spectroscopy are used to analyze the effect mechanism of TiO2 on CO2 adsorption process of Na2CO3/Al2O3.
基金supported by project no. CZ.1.05/2.1.00/03.0069 (ENET-Energy Units for Utilization of Non Traditional Energy Sources)supported by LO 1203 (Regional Material and Technology Research Centre)
文摘This work was conducted to evaluate whether Ca-bearing additives used during coal combustion can also help with the retention of some other elements. This work was focused on the evaluation of bottom ashes collected during four full-scale combustion tests at an operating thermal fluidized-bed power station. Bottom ashes were preferred to fly ashes for the study to avoid interference from condensation processes usually occurring in the post-combustion zone. This work focused on the behaviors of S, Cl, Br, As, Mn, V, Cr, Ni, Cu,Zn, W, and Pb. Strong positive correlations with CaO content in bottom ashes were observed（for all four combustion tests） for S, As, Cl and Br（R = 0.917-0.999）. Strong inverse proportionality was calculated between the contents of Pb, Zn, Ni, Cr and Mn and CaO, so these elements showed association to materials other than Ca-bearing compounds（e.g., to aluminosilicates, organic matter, etc.）. Somewhat unclear behaviors were observed for W, Cu, and V. Their correlation coefficients were evaluated as statistically ＂not significant＂, i.e., these elements were not thought to be significantly associated with CaO. It was also discovered that major enrichment of CaO in the finest bottom ash fractions could be advantageously used for simple separation of elements strongly associated with these fractions, mainly S and As, but also Cl or Br. Removal of5% of the finest ash particles brings about a decrease in As concentration down to 77%-80% of its original bulk ash content, which can be conveniently used e.g., when high As content complicates further ash utilization.
基金the financial support provided by the National Science Foundation of China (21176252)the China National Petroleum Science Research Program (2011B-2404-01)
文摘The reaction behavior of oil sand from Inner Mongolia（China） were studied in a fluidizedbed pyrolysis process,and a comparative study was conducted on the properties of the liquid products obtained through fluidized-bed pyrolysis of oil sand and the native bitumen obtained by solvent extraction.The results indicated that the fluidized-bed pyrolysis,a feasible carbon rejection process,can be used to upgrade oil sand.The reaction temperature and time were found to be the key operating parameters affecting the product distribution and yields in fluidized-bed pyrolysis of oil sand.The optimal temperature was 490℃ and the most suitable reaction time was 5 min.Under these operation conditions,the maximum yield of liquid product was 80wt%.In addition,the pyrolysis kinetics of oil sand at different heating rates of 5,10,20 and 30℃/min was investigated using a thermogravimetric analyzer（TGA）.
文摘In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.
基金supported by the Deutsche Forschungsgemeinschaft (DFG)
文摘Performance of the oxidative coupling of methane in fluidized-bed reactor was experimentally investigated using Mn-Na2WO4/SiO2,La2O3/CaO and La2O3-SrO/CaO catalysts.These catalysts were found to be stable,especially Mn-Na2WO4/SiO2 catalyst.The effect of sodium content of this catalyst was analyzed and the challenge of catalyst agglomeration was addressed using proper catalyst composition of 2%Mn2.2%Na2WO4/SiO2.For other two catalysts,the effect of Lanthanum-Strontium content was analyzed and 10%La2O 3-20%SrO/CaO catalyst was found to provide higher ethylene yield than La2O3/CaO catalyst.Furthermore,the effect of operating parameters such as temperature and methane to oxygen ratio were also reviewed.The highest ethylene and ethane （C2） yield was achieved with the lowest methane to oxygen ratio around 2.40.5% selectivity to ethylene and ethane and 41% methane conversion were achieved over La2O3-SrO/CaO catalyst while over Mn-Na2WO4 /SiO2 catalyst,40% and 48% were recorded,respectively.Moreover,the consecutive effects of nitrogen dilution,ethylene to ethane production ratio and other performance indicators on the down-stream process units were qualitatively discussed and Mn-Na2WO4/SiO2 catalyst showed a better performance in the reactor and process scale analysis.
基金supported by the Chinese National Key Program (Grant No. 2011CB932602)Natural Science Foundation of China (Key Program, 51236004)the Beijing Key Scientific Program (D12110300160000)
文摘For the synthesis of single-walled carbon nanotubes （SWCNTs） from CH4 over a Fe/MgO catalyst, we proposed a coupled Downer-turbulent fluidized-bed （TFB） reactor to enhance the selectivity and yield （or production rate） of SWCNTs. By controlling a very short catalyst residence time （1-3 s） in the Downer, only part of Fe oxides can be reduced to form Fe nano particles （NPs） available for the growth of SWCNTs. The percentage of unreduced Fe oxides increased and the yield of SWCNTs decreased accordingly with the increase of catalyst feeding rate in Downer. SWCNTs were preferentially grown on the catalyst surface and inhibited the sintering of the Fe crystallites which would be formed thereafter in the downstream TFB, evidenced by TEM, Raman and TGA. The coupled Downer-turbulent fluidized-bed reactor technology allowed higher selectivity and higher production rate of SWCNTs as compared to TFB alone.
文摘A mathematical model is developed for an industrial acrylonitrile fluidized-bed reactor based on arti-ficial neural networks. A new algorithm, which combines the characteristics of both genetic algorithm (GA) andgeneralized delta-rule (GDR) is used to train artificial neural network (ANN) in order to avoid search terminatedat a local optimal solution. For searching the global optimum, a new algorithm called SM-GA, incorporating ad-vantages of both simplex method (SM)and GA, is proposed and applied to optimize the operating conditions of anacrylonitrile fluidized-bed reactor in industry.
基金This work was supported by National Natural Science Foundation of China (No. 50408006).
文摘Objective To investigate the reduction of chlorination by-products （CBPs） precursors using the fluidized-bed biofdm reactor （FBBR）. Methods Reduction of total organic carbon （TOC）, ultraviolet absorbance （UV254）, tfihalomethane （THM） formation potential （THMFP）, haloacetic acid （HAA） formation potential （HAAFP）, and ammonia in FBBR were evaluated in detail. Results The reduction of TOC or UV254 was low, on average 12.6% and 4.7%, respectively, while the reduction of THMFP and HAAFP was significant. The reduction of ammonia was 30%-40% even below 3℃, however, it could quickly rise to over 50% above 3℃. Conclusions The FBBR effectively reduces CBPs and ammonia in drinking water even at low temperature and seems to be a very promising and competitive drinking water reactor for polluted surface source waters, especially in China.
文摘This article presents a mathematical model of heat and mass transfer for the process of fluidized-bed spray granulation, which can be applied in the analysis of bed temperature profile, temperature and humidity of outlet gas and moisture content of particles. Effects of operation parameters on the batch granulation are investigated. The theoretical calculation agrees reasonably well with the experimental data.
基金supported and funded by the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University(IMSIU)(grant number IMSIU-DDRSP2502).
文摘Controlled-release coated urea(CRCU)is an important agrochemical in precision farming,with its effectiveness reliant on the quality of the coating film and the nutrient-release kinetics.This study explores the use of a chemically modified lignocellulosic biopolymer derived from almond shells as a coating material for producing CRCU using Wurster fluidized-bed equipment.The study examines how process parameters—namely fluidized-bed temperature(T_(fb)),spray rate(R_(spray)),fluidizing-air flow rate(Q_(air)),and atomizing-air pressure(P_(air))—influence coating quality and nutrient-release kinetics.These are assessed through the inter-particle coefficient of coating mass variance(CMV)and the diffusion coefficient,respectively.The mechanism of nutrient release was studied using the Ritger and Peppas empirical model,specifically by calculating the diffusional exponent,n,for all samples.A Response Surface Methodology(RSM)approach coupled with a CCRD was applied to plan the experiments,perform statistical analysis,predict outcomes,and optimize the process conditions.The Analysis of Variance indicated that Tfb significantly impacts the studied parameters.Optimal coating quality(CMV=6.7%)was achieved under conditions of T_(fb)=75℃,Q_(air)=80 m^(3)/h,R_(spray)=0.17 mL/s,and P_(air)=3.1 bar.The optimum diffusion coefficient(2.2×10^(-1)cm^(2)/s)was obtained at T_(fb)=78℃,Q_(air)=75 m^(3)/h,R_(spray)=0.125 mL/s,and P_(air)=3.2 bar.The experimental and predicted responses showed close agreement that validates the regression models for predicting quality of coating films and kinetics of nutrient-release.Based on the n values,some samples exhibited Fickian diffusion,while others followed a non-Fickian nutrient-release mechanism.
基金the National Natural Science Foundation of China(Grant No.20576091)Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT).
文摘In this paper, the clustering behavior of solid particles in a two-dimensional （2D） liquid-solid fluidized-bed was studied by using the charge coupled devices （CCD） imaging measuring and processing technique and was characterized by fractal analysis. CCD images show that the distribution of solid particles in the 2D liquid-solid fluidised-bed is not uniform and self-organization behavior of solid particles was observed under the present experimental conditions. The solid particles move up in the 2D fluidized-bed in groups or clusters whose configurations are often in the form of horizontal strands. The box fractal dimension of the cluster images in the 2D liquid-solid fluidized-bed increases with the rising of solid holdup and reduces with the increment of solid particle diameter and superficial liquid velocity. At given solid holdup and solid particle size, the lighter particles show smaller fractal dimensions.
基金supported by the Council on Grants of the President of the Russian Federation(Grant No.SP-1951.2021.1).
文摘Coating of particulate materials in fluidized beds is a widely used technique to eliminate particle agglomeration,provide slow release of an active substance,or protect active ingredients.When thin polymer shells are applied on a particle surface,it is important to determine the process parameters that provide coating uniformity.In this study,the degree of coverage,defined as the fraction of the coated surface of the particles,is proposed as a quantitative criterion of coating uniformity.A new model for the batch fluidized-bed coating process is presented.The model allows prediction of the function of particle distribution according to the degree of coverage at a given process time and thereby enables assessment of coating uniformity.An algorithm for the numerical solution of model equations for a batch fluidized-bed coater is described.The influences of the main process parameters on the coating uniformity were shown.
基金We acknowledge funding from the National Research Founda-tion(NRF),Prime Minister's Office,Singapore under its Campus for Research Excellence and Technological Enterprise(CREATE) program,and the 2nd Intra-CREATE Seed Collaboration Grant(NRF2017-ITS002-013).
文摘The reduction of carbon dioxide to methane by hydrogen("CO2 methanation")using renewable energy is a promising process for recycling CO2.Better catalysts and better reactors are both required for the practical application of CO2 methanation.This study examines how the operating parameters affect CO2 methanation in a highly efficient fluidized-bed reactor.We first measured the kinetics of the CO2 methanation reaction using an NiMgW catalyst,which has been reported to exhibit superior catalytic performance.We then developed a fluidized-bed reactor model based on an earlier model for CO2 methanation.The fluidized bed model indicated that the NiMgW was indeed superior to two other previously studied catalysts in terms of faster conversion of reactants and higher concentrations of product CH4 throughout the reactor.The overall rate of production of CH4 increased with temperature and H2/CO2 ratio and decreased as the inlet reactant flow rate,catalyst particle diameter,and catalyst particle sphericity increased.
基金The authors gratefully acknowledge financial support from the National Natural Science Foundation of China (Grant No. 21736010).
文摘The influence of reduction conditions on carbon deposition during fiuidized-bed pre-reduction of iron ore fines was investigated experimentally.The results showed that reduction temperature and the composition of reducing gases had a significant effect on the rate of carbon deposition and the type of carbon deposits (graphite and Fe3C).Low reduction temperature,high CO content,and addition of H2favored the deposition of carbon,especially graphite.The reduction conditions also significantly affected the surface morphology of the as-reduced iron ore fines.As the amount of deposited graphite increased,the formation of fibrous iron disappeared and graphite filaments were observed.The pre-reduced iron ore fines were further fiuidized in pure CO at 850℃ for final reduction.The results showed that graphite could suppress the formation of fibrous iron and decrease the surface viscosity,thereby inhibiting agglomeration during the final high-temperature reduction stage.Reactions that consume the deposited carbon during the final high-temperature reduction were identified and graphite was shown to be more reactive than Fe3C.To enhance the application of fluidization technology in producing sponge iron,a novel solid-state high-temperature reduction method via deposited carbon was proposed and demonstrated to be feasible.
基金supported by the National Natural Science Foundation of China(22308170).
文摘Temperature is a critical factor influencing the performance of coal catalytic hydrogasification in bubbling fluidized bed gasifiers.Numerical simulations at various temperatures(1023 K,1073 K,1123 K,and 1173 K)are conducted to elucidate the mechanisms by which temperature affects bubble size,global reaction performance,and particle-scale reactivity.The simulation results indicate that bubble size increases at elevated temperatures,while H_(2)-char hydrogasification reactivity is enhanced.Particle trajectory analyses reveal that particles sized between 100 and 250μm undergo intense char hydrogasification in the dense phase,contributing to the formation of hot spots.To assess the impact of temperature on the particle-scale flow-transfer-reaction process,the dimensionless quantities of Reynolds,Nusselt,and Sherwood numbers,along with the solids dispersion coefficient,are calculated.It is found that higher temperatures inhibit bubble-induced mass and heat transfer.In general,3 MPa,1123 K,and 3-4 fluidization numbers are identified as the optimal conditions for particles ranging from 0 to350μm.These findings provide valuable insights into the inherent interactions between temperature and gas-particle reaction.
基金supported by the National Natural Science Foundation of China(22178255).
文摘In order to solve the shortcomings of MoO_(3)/γ-Al_(2)O_(3)catalyst for sulfur-resistant methanation,a segmented plasma fluidized bed reactor was designed,where plasma discharge zone and the fluidization zone were separated under higher discharge power.At the bed height of 30 mm,the gas velocity of 0.10 m·s^(-1)can provide a better fluidization state.The suitable discharge results can be achieved when the input power is 27 W and the discharge interval is 2.0 mm.With the extension of catalyst plasma treatment time,the conversion of CO decreases,but the selectivity of CH_(4)increases.Combined with N_(2)physical adsorption-desorption,XRD,TEM,Raman,TGA and TPR characterization,it was found that the active components of the catalyst are uniformly dispersed on the γ-Al_(2)O_(3)support.After plasma treatment,tetrahedral Mo species was used as the active center,and the interaction between Mo and the carrier was strengthened.It provides a novel approach for preparing catalyst with dielectric barrier discharge(DBD)fluidized bed reactor.
基金supported by the National Key R&D Program of China(Nos.2023YFC3904202,2022YFC2904500)Major Science and Technology Program of Yunnan Province,China(No.202202AB080012).
文摘The size and distribution patterns of bubbles within a laboratory-scale coarse-particle flotation column were examined using a high-speed camera-based dynamic measurement system.The effects of operational parameters such as superficial water velocity,air-flow rate,and frother dosage on bubble-size and distribution characteristics were investigated.This study aims to provide theoretical support for enabling fluidized-bed flotation within coarse-particle flotation columns.The results show that negative pressure for air inspiratory and bubble formation is generated by passing a high-speed jet through a throat,and the greatest number of bubbles are observed under natural inspiratory state at an air-liquid ratio of 1:3-1:2.5.Increasing the air-flow rate transforms the bubble diameter distribution from a peaked distribution to a more uniform distribution.Furthermore,the frother narrows the range of bubble-size distribution.A positive correlation exists between the bubble Sauter diameter and air-flow rate,with the bubble Sauter diameter bearing a negative correlation with the superficial water velocity and frother concentration.
基金supported by the Science Foundation of China University of Petroleum,Beijing(No.ZX20230047)Open Research Fund of State Key Laboratory of Coking Coal Exploitation and Comprehensive Utilization,China Pingmei Shenma Group(No.41040220201308).
文摘Due to their low cost,environmental friendliness and high energy density,the lithium-sulfur batteries(LSB)have been regarded as a promising alternative for the next generation of rechargeable battery systems.However,the practical application of LSB is seriously hampered by its short cycle life and high self-charge owing to the apparent shuttle effect of soluble lithium polysulfides.Using MgSO_(4)@MgO composite as both template and dopant,template-guided S-doped mesoporous graphene(SMG)is prepared via the fluidized-bed chemical vapor deposition method.As the polypropylene(PP)modifier,SMG with high specific surface area,abundant mesoporous structures and moderate S doping content offers a wealth of physical and chemical adsorptive sites and reduced interfacial contact resistance,thereby restraining the serious shuttle effects of lithium polysulfides.Consequently,the LSB configured with mesoporous graphene(MG)as S host material and SMG as a separator modifier exhibits an enhanced electrochemical performance with a high average capacity of 955.64 mA h g^(-1) at 1C and a small capacity decay rate of 0.109%per cycle.Additionally,the density functional theory(DFT)calculation models have been rationally constructed and demonstrated that the doped S atoms in SMG possess higher binding energy to lithium polysulfides than that in MG,indicating that the SMG/PP separator can effectively capture soluble lithium polysulfides via chemical binding forces.This work would provide valuable insight into developing a versatile carbon-based separator modifier for LSB.
