Extending homogeneous fluidization flow regime of Geldart-A particles by exerting axial uniform and steady magnetic field

The homogeneous/particulate fluidization flow regime is particularly suitable for handling the various gas–solid contact processes encountered in the chemical and energy industry.This work aimed to extend such a regime of Geldart-A particles by exerting the axial uniform and steady magnetic field.Under the action of the magnetic field,the overall homogeneous fluidization regime of Geldart-A magnetizable particles became composed of two parts:inherent homogeneous fluidization and newly-created magnetic stabilization.Since the former remained almost unchanged whereas the latter became broader as the magnetic field intensity increased,the overall homogeneous fluidization regime could be extended remarkably.As for Geldart-A nonmagnetizable particles,certain amount of magnetizable particles had to be premixed to transmit the magnetic stabilization.Among others,the mere addition of magnetizable particles could broaden the homogeneous fluidization regime.The added content of magnetizable particles had an optimal value with smaller/lighter ones working better.The added magnetizable particles might raise the ratio between the interparticle force and the particle gravity.After the magnetic field was exerted,the homogeneous fluidization regime was further expanded due to the formation of magnetic stabilization flow regime.The more the added magnetizable particles,the better the magnetic performance and the broader the overall homogeneous fluidization regime.Smaller/lighter magnetizable particles were preferred to maximize the magnetic performance and extend the overall homogeneous fluidization regime.This phenomenon could be ascribed to that the added magnetizable particles themselves became more Geldart-A than-B type as their density or size decreased.

Operating range of magnetic stabilization flow regime for magnetized fluidized bed with Geldart-B magnetizable and nonmagnetizable particles

The magnetic stabilization flow regime could also be created forGeldart-Bnonmagnetizable particles pro-vided some magnetizable particles are introduced and the magnetic field is applied.This study aimed toexplore the size(d_(pM))and density(ρ_(pM))effects of magnetizable particles on its operating range.The upperlimit(Umb;)could not be determined from the △P_(b)-U_(g)↓curve but could from analyzing the variation of △P_(b)-fluctuation with increasing U_(g).Due to the variation of U_(mfH)(lower limit)with d_(pM) and ppw,both U_(mbH)-U_(mfH) and(U_(mbH)-U_(mfH))/U_(mfH) were used to quantify the operating range of magnetic stabilization.U_(mbH)-U_(mfH) varied hardly with ρ_(pM) but increased significantly with decreasing ρ_(pM).(U_(mbH)-U_(mfH))/U_(mfH)increased as d_(pM) or ρ_(pM) decreased.lt was more difficult for the nonmagnetizable particles to escape fromthe network formed by the smaller/lighter magnetizable particles.For the same magnitude of change,dp had a stronger effect than ρ_(pM) on(U_(mbH)-U_(mfH))/U_(mfH).Neither U_(mbH)-U_(mfH) nor(U_(mbH)-U_(mfH):)/Uma variedmonotonously with the minimum fluidization velocity of the magnetizable particles,indicating that nostraightforward criterion for matching the magnetizable particles to the given nonmagnetizable particlescould be established based on their minimum fluidization velocities to maximize the operating range ofmagnetic stabilization.

Magnetic field stabilization system designed for the cold-atom coherent population-trapping clock

Accurate control of magnetic fields is crucial for cold-atom experiments,often necessitating custom-designed control systems due to limitations in commercially available power supplies.Here,we demonstrate precise and flexible control of a static magnetic field by employing a field-programmable gate array and a feedback loop.This setup enables us to maintain exceptionally stable current with a fractional stability of 1 ppm within 30 s.The error signal of the feedback loop exhibited a noise level of 10^(-5)A·Hz^(-1/2)for control bandwidths below 10 k Hz.Utilizing this precise magnetic field control system,we investigate the second-order Zeeman shift in the context of cold-atom coherent population-trapping (CPT)clocks.Our analysis reveals the second-order Zeeman coefficient to be 574.21 Hz/G^(2),with an uncertainty of 1.36 Hz/G^(2).Consequently,the magnetic field stabilization system we developed allows us to achieve a second-order Zeeman shift below10^(-14),surpassing the long-term stability of current cold-atom CPT clocks.

Synthesis of Diphenyl Carbonate over the Magnetic Catalysts Pd/La_(1-x)Pb_xMnO_3 (x=0.2-0.7)

The magnetic perovskite-supported palladium catalysts Pd/Lal_xPbxMnO3 （x = 0.2-0.7） were prepared and used for the oxidative carbonylation of phenol to diphenyl carbonate. The synthesized catalysts were characterized by the X-ray diffraction （XRD）, surface area measurement BET, vibration sample magnetometer （VSM） and tem- perature-programmed reduction （TPR）. The experimental results demonstrated that the magnetic Pd/La1-xPbxMnO3 （x = 0.4-0.5） obtain relative better catalytic activity. It can be explained by higher concentration of oxygen vacan- cies, larger amount and better mobility of lattice oxygen of their support. Furthermore, these samples possess suffi- cient saturated magnetization. Thus, Pd/La1-xPbxMnO3 （x = 0.4-0.5） may be suitable for operation in the magneti- cally stabilized bed reactor.

Collecting aerosol in airflow with a magnetically stabilized fluidized bed

A magnetically stabilized fluidized bed (MSB) is a highly efficient filter that takes the advantage of both fluidized beds and fixed beds. This paper presents the research to collect aerosol in airflow with a MSB. The filtering model of MSB is established with its parameters including magnetic Geld intensity, gas superficial velocity, average grain-size, and bed height on the collection efficiency of MSB. The model is verified by experiments.

Axial Liquid Dispersion Characteristics in Magnetically Stabilized Bed

Axial liquid dispersion was experimentally studied in liquid-solid and gas-liquid-solid magnetically stabilized beds using the ferromagnetic catalyst of SRNA-4 as the solid phase. The effects of operating factors and fluid characters, such as superficial liquid velocity, superficial gas velocity, magnetic field intensity, liquid viscosity and surface tension, on axial dispersion coefficients of liquid were investigated. The dispersion coefficients increased with the increase of superficial liquid velocity and superficial gas velocity, and decreased with the increase of liquid viscosity, liquid surface tension and magnetic field intensity. A correlation equation of Peclet number was obtained for both liquid-solid and gas-liquid-solid magnetically stabilized bed.

Synthesis, Crystal Structure, Fluorescence, Thermal Stability and Magnetic Properties of the Dinuclear Manganese(Ⅱ) Complex [Mn_2(L)_2(2,2'-bipy)_2(H_2O)_5]_2·3H_2O

A new dinuclear manganese complex [Mn2（L）2（2,2＇-bipy）2（H2O）512·3H2O has been synthesized with MnSO4·H2O, 2,2＇-bibenzoic acid （H2L） and 2,2＇-bipyridine（2,2＇-bipy） in the mixed solvent ethanol and water. It crystallizes in monoclinic, space group Pi with a = 9.9944（10）, b = 21.939（2）, c = 25.628（3） A, a = 108.429（3）, β = 100.613（4）, 7 = 102.821（3）°, V = 4997.9（9） A3, Dc= 1.355 g/cm^3, Z = 2, F（000） = 2108, GOOF = 1.074, the R= 0.0626 and wR= 0.1531. The structure of the complex contains two [Mn2（L）2（2,2＇-bipy）2] units, ten coordinated H2O molecules and three uncoordinated H2O molecules. The fluorescence, thermal stability and magnetic properties of the complex were investigated.

Synthesis of magnetically modified palygorskite composite for immobilization of Candida sp. 99–125 lipase via adsorption

Magnetically modified palygorskite composites were synthesized with γ-Fe2O3 dispersing on the external surface of clay mineral. The magnetic clay was characterized with Fourier transform infrared, X-ray diffrac- tion, transmission electron microscopy, and vibrating sample magnetometer. Candida sp. 99-125 lipase was immobilized on magnetic palygorskite composites by physical adsorption with enzyme loading of 41.5 mg· g^-1 support and enzyme activity of 2631.6 U· （g support）^-1. The immobilized lipase exhibit better thermal and broader pH stability and excellent reusabilitV compared with free lipase.

Hydrothermal Synthesis, Crystal Structure, Thermal Stability and Magnetic Properties of a Dinuclear Copper(Ⅱ) Complex

A new dinuclear copper（Ⅱ） complex [Cu（CH3COO）（C7H5N4）（H2O）]2·3.5H2 O has been hydrothermally synthesized with copper acetate, o-acetamidobenzoic acid and 3-（pyridin-2-yl）-1,2,4-triazole. It crystallizes in the monoclinic space group P21/c, with a = 12.0188（7）, b = 13.7993（8）, c = 8.7488（5） A, β = 101.7350（10）o, V = 1420.67（14） A3, D3 c = 1.568 g/cm, Z = 1, F（000） = 690, the final GOOF = 1.145, R = 0.0437, and w R = 0.1097. The crystal structure shows that the whole molecule consists of two copper ions bridged by two μ2-η1：η0 3-（pyridin-2-yl）-1,2,4-triazole anions. The coordination environment of Cu（Ⅱ） ion is Cu O2N3, giving a distorted square pyramidal geometry. The thermal stability and magnetic properties of the complex were investigated.

Effects of terbium sulfide addition on magnetic properties,microstructure and thermal stability of sintered Nd-Fe--B magnets

To increase coercivity and thermal stability of sintered Nd–Fe–B magnets for high-temperature applications, a novel terbium sulfide powder is added into（Pr（0.25）Nd（0.75））（30.6）Cu（0.15）Fe（bal）B1（wt.%） basic magnets. The effects of the addition of terbium sulfide on magnetic properties, microstructure, and thermal stability of sintered Nd–Fe–B magnets are investigated.The experimental results show that by adding 3 wt.% Tb2S3, the coercivity of the magnet is remarkably increased by about 54% without a considerable reduction in remanence and maximum energy product. By means of the electron probe microanalyzer（EPMA） technology, it is observed that Tb is mainly present in the outer region of 2：14：1 matrix grains and forms a well-developed Tb-shell phase, resulting in enhancement of HA, which accounts for the coercivity enhancement.Moreover, compared with Tb2S3-free magnets, the reversible temperature coefficients of remanence（α） and coercivity（β） and the irreversible flux loss of magnetic flow（hirr） values of Tb2S3-added magnets are improved, indicating that the thermal stability of the magnets is also effectively improved.

Magnetic Properties and Thermal Stability of Pr_(1-x)La_xCo_(5-y)Alloys

Pr1-xLaxCo5-y (x=0, 0.15. 0.25, 0.35,1.0, y=0.5, 0.7, 0.9, 1.0) alloys were investigated. The effect of the variation of x and y on magnetic properties and thermal stability of the alloys were studied. The magnetic properties for the Pr0.85La0.15Co4.3 and Pr0.75La0.25Co4.1 magnets are iHc=368 kA/m, Br=0.91 T, (BH)max=145.6 kJ/m3, αBr=-0.03%/℃ and iHc=568 kA/m,Br=0.8 T, (BH)max=127.2 kJ/m3,αBr,=-0.06%/℃, respectively The phase structures of as-cast alloys and magnets were investigated

Hollow FeCoNiAl microspheres with stabilized magnetic properties for microwave absorption

Development of high-performance microwave absorption materials(MAM)with stabilized magnetic properties at high temperatures is specifically essential but remains challenging.Moreover,the Snoke's limitation restrains the microwave absorption(MA)property of magnetic materials.Modulating alloy components is considered an effective way to solve the aforementioned problems.Herein,a hollow medium-entropy FeCoNiAl alloy with a stable magnetic property is prepared via simple spray-drying and two-step annealing for efficient MA.FeCoNiAl exhibited an ultrabroad effective absorption band(EAB)of 5.84 GHz(12.16–18 GHz)at a thickness of just 1.6 mm,revealing an excellent absorption capability.Furthermore,the MA mechanism of FeCoNiAl is comprehensively investigated via off-axis holography.Finally,the electromagnetic properties,antioxidant properties,and residual magnetism at high temperatures of FeCoNiAl alloys are summarized in detail,providing new insights into the preparation of MAM operating at elevated temperatures.

An ab initio study of niobium (n=2-11) clusters: structure, stability and magnetism

The ground-state configurations of the Nbn （n = 2-11） clusters are studied through the first-principles calculations. It is found that niobium clusters （n = 2-11） tend to form compact structures with low symmetry. The clusters with 4, 8 and 10 atoms axe found to be magic and have relatively large highest occupied-lowest unoccupied molecular orbital （HOMO-LUMO） gaps. The Nbn clusters possess low magnetic moments, which exhibit an odd-even oscillational character. The analyses of calculated electronic density and population of the lowest-energy niobium clusters for n =2, 3, 5, 7, 9, 11 show that the total magnetic moments of Nbn originate mainly from a few Nb atoms with longer spacings between them in most cases, while they are located on two Nb atoms for n = 2, 3, 5. The total magnetic moments come mainly from the 4d local moments but with the exception of the Nb5 cluster.

MHD Stability Analysis and Flow Controls of Liquid Metal Free Surface Film Flows as Fusion Reactor PFCs

Numerical and experimental investigation results on the magnetohydrodynamics（MHD） film flows along flat and curved bottom surfaces are summarized in this study. A simplified modeling has been developed to study the liquid metal MHD film state, which has been validated by the existing experimental results. Numerical results on how the inlet velocity（V）, the chute width（W） and the inlet film thickness（d0） affect the MHD film flow state are obtained. MHD stability analysis results are also provided in this study. The results show that strong magnetic fields make the stable V decrease several times compared to the case with no magnetic field,especially small radial magnetic fields（Bn） will have a significant impact on the MHD film flow state. Based on the above numerical and MHD stability analysis results flow control methods are proposed for flat and curved MHD film flows. For curved film flow we firstly proposed a new multi-layers MHD film flow system with a solid metal mesh to get the stable MHD film flows along the curved bottom surface. Experiments on flat and curved MHD film flows are also carried out and some firstly observed results are achieved.

Advances in Application of New Catalytic Materials in Petroleum Refining and Petrochemicals Production

This article introduces the solid acid catalyst for isobutene/butylenes alkylation, the HTS Ti/Si zeolite for ammonoxidation of cyclohexanone and the noncrystalline alloy catalyst and magnetically stabi- lized bed for hydrofining of caprolactam that were developed recently by SINOPEC Research Institute of Petroleum Processing (RIPP).

Removal of dust from flue gas in magnetically stabilized fluidized bed

A magnetically stabilized fluidized bed （MSFB,Ф 500mm×2100mm） was designed to study dust removal from flue gas. Based on the mechanism of dust removal in a fixed bed, the effects on collection efficiency of magnetic field intensity, ratio of flue gas velocity to minimum fluidization velocity, bed height, and particle average diameter, were investigated. Then feasible methods for MSFB to better remove dust were proposed. Over 95 % of dust removal with MSFB can be achieved, when stable fluidization is maintained and when magnetic particles are frequently renewed.

An overview of separation by magnetically stabilized beds:State-of-the-art and potential applications

This article deals with problems relevant to implementation of magnetically stabilized beds （MSB） as separation devices. The main issues discussed are： bed mechanics, bed structure, possibilities to create controllable filter media, etc. As examples several separation techniques are discussed： dust filtration-magnetic and non-magnetic, ion-exchange, copper cementation, yeast filtration from biological liquids, particle separation by density and magnetic properties, dangerous wastes removal. Only key publications will be quoted that provide a basis for further reading and study and relevant information.

L-S mass transfer in G-L-S countercurrent magnetically stabilized bed with amorphous alloy SRNA-4 catalyst

Liquid-solid （L-S） mass transfer coefficients （Ks） were characterized in a gas-liquid-solid （G-L-S） three-phase countercurrent magnetically stabilized bed （MSB） using amorphous alloy SRNA-4 as the solid phase. Effects of superficial liquid velocity, superficial gas velocity, magnetic field strength, liquid viscosity and surface tension were investigated. Experimental results indicated that the external magnetic field increased Ks in three-phase MSB, as compared to those in conventional G-L-S fluidized beds; that Ks increased with magnetic field strength, superficial gas and liquid velocities and decreased with liquid viscosity and surface tension; and that Ks showed uniform axial and radial distributions except for small increases close to the wall. Dimensionless correlations were established to estimate Ks of the G-L-S countercurrent MSB using SRNA-4 catalyst, with an average error of 3.6%.

Magnetically stabilized bed reactor for selective hydrogenation of olefins in reformate with amorphous nickel alloy catalyst

A magnetically stabilized bed （MSB） reactor for selective hydrogenation of olefins in reformate was developed by combining the advantages of MSB and amorphous nickel alloy catalyst. The effects of operating conditions, such as temperature, pressure, liquid space velocity, hydrogen-to-oil ratio, and magnetic field intensity on the reaction were studied. A mathematical model of MSB reactor for hydrogenation of olefins in reformate was established. A reforming flow scheme with a post-hydrogenation MSB reactor was proposed. Finally, MSB hydrogenation was compared with clay treatment and conventional post-hydrogenation.

Magnetically stabilized bed dust filters—Analysis through variable length scale approach

Magnetically stabilized beds are packed beds subjected to fluid-driven deformation and controlled by magnetically induced interparticle forces. This paper deals with magnetically stabilized beds as deformable porous media and describes their application in dust filtration. The Richardson-Zaki scaling law, U/Ut = ε^n describes the field controlled bed expansion via the exponent n, that yields a porosity-dependent flow length scale dc = dpε^n. The paper addresses two issues： （i） deformation characteristics by assuming homogeneous bed expansion and a definition of bed variable flow length scale; （ii） dust filtration characteristics such as filter coefficient, specific deposit and filtration efficiency expressed in terms of the variable flow length scale and illustrated by experimental data.