Flow Regimes in Bubble Columns with and without Internals: A Review

Hydrodynamics characterization in terms offlow regime behavior is a crucial task to enhance the design of bubble column reactors and scaling up related methodologies.This review presents recent studies on the typicalflow regimes established in bubble columns.Some effort is also provided to introduce relevant definitions pertaining to thisfield,namely,that of“void fraction”and related(local,chordal,cross-sectional and volumetric)variants.Experimental studies involving different parameters that affect design and operating conditions are also discussed in detail.In the second part of the review,the attention is shifted to cases with internals of various types(perfo-rated plates,baffles,vibrating helical springs,mixers,and heat exchanger tubes)immersed in the bubble columns.It is shown that the presence of these elements has a limited influence on the global column hydrodynamics.However,they can make the homogeneousflow regime more stable in terms of transition gas velocity and transi-tion holdup value.The last section is used to highlight gaps which have not beenfilled yet and future directions of investigation.

Consolidation of high replacement ratio stone column-reinforced ground:Analytical solutions incorporating clogging effect

The utilization of stone columns has emerged as a popular ground improvement strategy,whereas the drainage performance can be adversely hampered by clogging effect.Despite the ample progress of calculation methods for the consolidation of stone column-improved ground,theoretical investigations into the clogging effect have not been thoroughly explored.Furthermore,it is imperative to involve the column consolidation deformation to mitigate computational error on the consolidation of composite ground with high replacement ratios.In this context,an analytical model accounting for the initial clogging and coupled time and depth-dependent clogging of stone columns is established.Then,the resulting governing equations and analytical solutions are obtained under a new flow continuity relationship to incorporate column consolidation deformation.The accuracy and reliability of the proposed model are illustrated by degradation analysis and case studies with good agreements.Subsequently,the computed results of the current study are juxtaposed against the existing models,and an in-depth assessment of the impacts of several crucial parameters on the consolidation behavior is conducted.The results reveal that ignoring column consolidation deformation leads to an overestimate of the consolidation rate,with maximum error reaching up to 16%as the replacement ratio increases.Furthermore,the initial clogging also has a significant influence on the consolidation performance.Additionally,the increment of depth and time-clogging factors a and b will induce a noticeable retardation of the consolidation process,particularly in the later stage.

Visual experimental study of nanofluids application to promote CO_(2) absorption in a bubble column

The addition of dispersed-phase nanoparticles in the liquid phase can enhance the gas-liquid transfer process as the suspended nanoparticles affect the transfer process inside the fluid through microdisturbance or micro-convection effects.In this article,a high-speed digital camera was used to visualize the bubble behavior of CO_(2) in pure water and nanofluids to examine the effects of CO_(2) gas flow rate,nanoparticle solid content and type on the bubble behavior in the fluids.The CO_(2) absorption performance in three water-based nanofluids were compared in a bubbler.And the mass transfer characteristics during CO_(2) bubble absorption and the reasons for the enhanced gas-liquid mass transfer effect of nanoparticles were analyzed.The results showed that the presence of nanoparticles affected the formation process of bubbles in the fluid,shortened the bubble detachment time,reduced the detachment diameter,effectively increased the gas-liquid contact area,and improved the bubbles detachment frequency.The system with MCM-41 corresponded to a higher overall mass transfer coefficient.Uncalined MCM-41 contained surfactant that enhanced foaming behavior in water.This prevented the transfer of CO_(2) to some extent,and the CO_(2) absorption by uncalined MCM-41/H_(2)O was 5.34%higher than that by pure water.Compared with SiO_(2) nanoparticles with the same particle size and the same composition,MCM-41 had a higher adsorption capacity and better hydrophilicity due to its larger specific surface area and rich porous structure,which was more favorable to accelerate the collision between nanoparticles and CO_(2) bubbles to cause micro-convection.Under the condition of 0.1%(mass)solid content,the enhancement of CO_(2) absorption process by MCM-41 nanoparticles was more significant and improved by 16.9%compared with pure water.

Comparative impact behaviours of ultra high performance concrete columns reinforced with polypropylene vs steel fibres

Polypropylene(PP) fibres have primarily used to control shrinkage cracks or mitigate explosive spalling in concrete structures exposed to fire or subjected to impact/blast loads, with limited investigations on capacity improvement. This study unveils the possibility of using PP micro-fibres to improve the impact behaviour of fibre-reinforced ultra-high-performance concrete(FRUHPC) columns. Results show that the addition of fibres significantly improves the impact behaviour of FRUHPC columns by shifting the failure mechanism from brittle shear to favourable flexural failure. The addition of steel or PP fibres affected the impact responses differently. Steel fibres considerably increased the peak impact force(up to 18%) while PP micro-fibres slightly increased the peak(3%-4%). FRUHPC significantly reduced the maximum midheight displacement by up to 30%(under 20°impact) and substantially improved the displacement recovery by up to 100%(under 20° impact). FRUHPC with steel fibres significantly improved the energy absorption while those with PP micro-fibres reduced the energy absorption, which is different from the effect of PP-macro fibre reported in the literature. The optimal fibre content for micro-PP fibres is 1% due to its minimal fibre usage and low peak and residual displacement. This study highlights the potential of FRUHPC as a promising material for impact-resistant structures by creating a more favourable flexural failure mechanism, enhancing ductility and toughness under impact loading, and advancing the understanding of the role of fibres in structural performance.

Experimental Study on the Axial Compression Performance of Bamboo Scrimber Columns Embedded with Steel Reinforcing Bars

In this paper,a new type of bamboo scrimber column embedded with steel bars(rebars)was proposed,and the compression performance was improved by pre-embedding rebars during the preparation of the columns.The effects of the slenderness ratio and the reinforcement ratio on the axial compression performance of reinforced bamboo scrimber columns were studied by axial compression tests on 28 specimens.The results showed that the increase in the slenderness ratio had a significant negative effect on the axial compression performance of the columns.When the slenderness ratio increased from 19.63 to 51.96,the failure mode changed from strength failure to buckling failure,and the maximum bearing capacity decreased by 43.03%.The axial compression performance of the reinforced bamboo scrimber columns did not significantly improve at a slenderness ratio of 19.63,but the opposite was true at slenderness ratios of 36.95 and 51.96.When the reinforcement ratio increased from 0%to 4.52%,the bearing capacity of those with a slenderness ratio of 51.96 increased by up to 16.99%,and the stiffness and ductility were also improved.Finally,based on existing specifications,two modification parameters,the overall elastic modulus Ec and the combined strength fcc,were introduced to establish a calculation method for the bearing capacity of the reinforced bamboo scrimber columns.The calculation results were compared with the test results,and the results showed that the proposed calculation models can more accurately predict the bearing capacity.

Numerical Analysis of Cold-Formed Thin-Walled Steel Short Columns with Pitting Corrosion during Bridge Construction

Pitting corrosion is harmful during bridge construction,which will lead to uneven roughness of steel surfaces and reduce the thickness of steel.Hence,the effect of pitting corrosion on the mechanical properties of cold-formed thin-walled steel stub columns is studied,and the empirical formulas are established through regression fitting to predict the ultimate load of web and flange under pitting corrosion.In detail,the failure modes and load-displacement curves of specimens with different locations,area ratios,and depths are obtained through a large number of non-linear finite element analysis.As for the specimens with pitting corrosion on the web,all the specimens are subject to local buckling failure,and the failure mode will not change with pitting corrosion,but the failure location will change with pitting corrosion location;the size,location,and area ratio of pitting corrosion have little influence on the ultimate load of cold-formed thin-walled steel short columns,but the loss rate of pitting corrosion section area has a greater impact on the ultimate bearing capacity.As for the specimen with flange pitting corrosion,the location and area ratio of pitting corrosion have less influence on the ultimate load of cold-formed thin-walled steel short columns,and the section area loss rate has greater influence on the ultimate bearing capacity;the impact of web pitting corrosion on the ultimate load is greater than that of flange pitting corrosion under the same condition of pitting corrosion section area.The prediction formulas of limit load which are suitable for pitting corrosion of web and flange are established,which can provide a reference for performance evaluation of corroded cold-formed thin-walled steel.

An Affordable and Easily Accessible Approach for Acrylonitrile Monomer Purification through a Simple Column Technique

This manuscript presents a dataset detailing a method for purifying monomers. Purification plays a crucial role in every chemical process, as it leads to an improvement in product quality through the removal of impurities. The primary method for monomer purification, like acrylonitrile (AN), is the distillation technique. However, this technique is unsafe and hard to set up or handle. A straightforward, risk-free, low-cost method like the column technique resolves these issues. A simple column technique demonstrated the successful execution of purifying AN. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) analyses confirmed that AN was successfully purified, with purity reaching 99.8%. FTIR spectra revealed changes in the position and intensity of the stretching vibration peaks after purification. Also, the functional groups of the inhibitor monomethyl ether of hydroquinone (MeHQ) were undetected after purification. Furthermore, after purification, NMR spectra revealed the absence of aromatic protons and carbons associated with MeHQ. In conclusion, the column technique is a successful and inexpensive way to purify AN monomers. This makes it useful for a wide range of applications, especially in polymerization reactions where MeHQ needs to be removed to prevent self-polymerization during the initiation process.

Comprehensive analysis of phenolic composition and antioxidant mechanisms in Gymnema sylvestre extracts using LC-MS and column chromatography

Recent studies have highlighted the potential of plant extracts as therapeutic agents for managing oxidative stress and related disorders.This study aims to elucidate the phenolic composition and antioxidant properties of Gymnema sylvestre extracts.Ethanolic reflux extraction followed by column chromatography was employed to isolate phenolic compounds.The total phenolic and flavonoid contents were quantified using the Folin–Ciocalteu and aluminum chloride colorimetric methods,respectively.Antioxidant activities were assessed by DPPH,ABTS scavenging assays and the ferric reducing antioxidant power(FRAP)assay.High-Performance Liquid Chromatography(HPLC)with a C18 column and Thermo TSQ Quantum Access Max(LC-MS)were used to determine the levels of gymnemic acid and identify other potential phenolic compounds.The analysis revealed significant antioxidant activities in the fractions.Fraction A showed the highest DPPH and ABTS scavenging activities,and Fraction C demonstrated the highest ferric reducing power.LC-MS analysis identified several phenolic compounds,indicating that these are major contributors to the antioxidant efficacy of the extract.This study provides a detailed phenolic profile and confirms the strong antioxidant potential of Gymnema sylvestre leaf extract,supporting its therapeutic use and further investigation.

Modelling and Sizing of a Floor Reinforced by Ballasted Columns Intended to Support a Tank

This work aims to study the modeling and sizing of a floor reinforced by ballasted columns. We are studying the system of reinforcement by ballasted columns because this technique is able to replace deep foundations that are technically difficult to realize and their cost is higher. The modelling and dimensioning of foundations on a ballasted column will be an important contribution to the state of the art of this method because it will highlight the mode of transfer of loads, and will expose the induced deformations by also allowing to verification criteria of bearing capacity and allowable settlement according to geometric information of the model. The columns on a substrate located at 9 m have a length of 9 m and a diameter of 40 cm and were obtained by incorporating ballast of granular class 0/31.5 of internal friction angle of 38˚ and a density weight of 21 kN/m3. The choice of this method is based on the geotechnical characteristics of the initial soil. Thus, identification and characterization tests were carried out to estimate the bearing capacity and the settlement giving respectively 125 kPa and 57 cm. These results show the ground does not have sufficient mechanical properties to withstand the loads transmitted by the tank. By adopting the reinforcement of the soil with ballasted columns, numerical calculations show that after applying a load equal to 265.1 KPa, 20 cm vertical settlement and 17 cm horizontal displacement were obtained. This is in the tolerable deformation range for our tank, namely, less than 20 cm. Analytically, in addition to reducing settlement, ballasted columns, Due to their high stiffness, they have effectively contributed to the increase of the permissible soil stress up to 257 kPa.

Simultaneous Adsorption of Aqueous Pb2+, Cu2+, Zn2+, and Cd2+ Using Surfactant-Modified and Unmodified Activated Carbon in a Fixed Bed Column

The goal of this work is to improve the simultaneous removal of Pb2+, Cu2+, Zn2+, and Cd2+ ions from synthetic wastewater in a fixed bed column by incorporating sodium dodecyl sulfate (SDS) onto the surface of activated carbon made from coconut shells. The activated carbons were characterized using Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy-energy dispersive x-ray (SEM-EDX). The adsorption column dynamics were studied by varying the flow rates (5, 10 and 15 mL/min), bed heights (10, 15 and 20 cm), and initial concentrations (50, 150, and 250 mg/L). The activated carbon has a pore volume of 0.715 cm3/g and a BET-specific surface area of 1410 m2/g. Sodium dodecyl sulfate (SDS) surfactant incorporation onto the surface of the activated carbon enhances its capacity for simultaneous adsorption of Pb2+, Cu2+, Zn2+, and Cd2+ from the aqueous medium. The affinity of the heavy metals to both unmodified (AC) and modified (AC-SDS) activated carbons followed the order of Pb2+ > Cu2+ > Zn2+ > Cd2+. The dynamic adsorption of the column depends on the flow rate, bed height, initial metal concentration, and SDS surface modification. With a 5 mL/min flow rate, a 20 cm bed height, and a 50 mg/L initial metal concentration, a maximum break-through time of 150 minutes for the unmodified activated carbon (AC) and 180 minutes for the SDS-modified activated carbon (AC-SDS) was reached.

Nonlinear Time History Analysis for the Different Column Orientations under Seismic Wave Synthetic Approach

The significant impact of earthquakes on human lives and the built environment underscores the extensive human and economic losses caused by structural collapses. Over the years, researchers have focused on improving seismic design to mitigate earthquake-induced damages and enhance structural performance. In this study, a specific reinforced concrete (RC) frame structure at Kyungpook National University, designed for educational purposes, is analyzed as a representative case. Utilizing SAP 2000, the research conducts a nonlinear time history analysis to assess the structural performance under seismic conditions. The primary objective is to evaluate the influence of different column section designs, while maintaining identical column section areas, on structural behavior. The study employs two distinct seismic waves from Abeno (ABN) and Takatori (TKT) for the analysis, comparing the structural performance under varying seismic conditions. Key aspects examined include displacement, base shear force, base moment, joint radians, and layer displacement angle. This research is anticipated to serve as a valuable reference for seismic restraint reinforcement work on RC buildings, enriching the methods used for evaluating structures through nonlinear time history analysis based on the synthetic seismic wave approach.

装配式建筑梁柱节点疲劳损伤检测方法研究

常规的装配式建筑梁柱节点疲劳损伤检测主要采用梁柱图像分析实现,忽略了节点内部损伤的影响,导致检测结果相对变化量系数与实际系数的差值较大。本文对装配式建筑梁柱节点疲劳损伤检测方法进行了研究,于装配式建筑梁柱周围布置测点对梁柱节点的应变状态进行分析;根据分析结果,结合梁柱内部能量耗散值,计算节点疲劳损伤能量系数;将该系数作为节点应变能密度因子分析节点轴向力,由此得出检测的梁柱节点疲劳损伤值。实验结果表明,所提方法应用后梁柱节点疲劳损伤检测结果表现出的相对变化量系数差值较小,检测结果准确率较高,满足了装配式建筑梁柱安全运维工作的现实需求。

Column leaching process of rare earth and aluminum from weathered crust elution-deposited rare earth ore with ammonium salts

In order to better understand the leaching process of rare earth （RE） and aluminum （Al） from the weathered crust elutiondepositedRE ore, the mass transfer of RE and Al in column leaching was investigated using the chromatographic plate theory. Theresults show that a higher initial ammonium concentration in a certain range can enhance the mass transfer process. pH of leachingagent in the range of 2 to 8 almost has no effect on the mass transfer efficiency of RE, but plays a positive role in the mass transferefficiency of Al under strong acidic condition （pH〈4）. There is an optimum flow rate that makes the highest mass transfer efficiency.The optimum leaching condition of RE is the leaching agent pH of 4？8, ammonium concentration of 0.4 mol/L and flow rate of0.5 mL/min. The mass transfer efficiencies of RE and Al both follow the order： （NH4）2SO4〈NH4Cl〈NH4NO3, implying thecomplexing ability of anion.

Capillary Electrochromatography Using C_8 Open Tubular Column Prepared by Sol-Gel Technique

Open tubthar C8 columns were prepared by sol-gel technology and used in the electrochromatographic separations.

Forming method of wick structure for heat column

The intensified boiling and condensation wick structures of heat column were designed and manufactured by ploughing-extrusion （P-E） machining method.The forming process and mechanism were analyzed.The results show that the P-E depth plays a decisive role in forming of wick structure.The larger the P-E depth is,the better the surface characteristics are.Only when the groove spacing is in a certain range,superior surface structure can be formed in the wick.The better enhancement boiling structure forms at P-E depth of 0.3 mm,ringed groove spacing of 0.4 mm,and interior angle of radial groove of 3°;the better enhancement condensation structure forms at P-E depth of 0.3 mm,ringed groove spacing of 0.4 mm,and axial grooves spacing of π/3 mm.

Mass transfer process in replacement-column purification device in zinc hydrometallurgy

It is important to remove the impurities, such as copper and cadmium, from leaching solution in zinc hydrometallurgy. To improve purification efficiency, a replacement-column purification device was proposed and its mass transfer characteristics and purification efficiency were experimentally studied. The results show that purification efficiency increases with the decrease of the zinc powder diameter and decreases with the increase of solution velocity. If appropriate structure and operation parameters are used, it is possible to make purification efficiency more than 99%, but the diameter of zinc powder should be larger than 0.45 mm. For the velocity of 0.05-0.7 cm/s, mass transfer coefficient kc is in the range of 3.94×10-7-2.76×10-6 m/s, and increases with the decrease of zinc powder diameter and the increase of solution velocity. Moreover, it can be derived by mass transfer correlations of Sherwood number:Sh=0.1069Re0.5Sc0.33, for 0.3<Re<6.

Determination of Sulphonylurea Glimepiride in Dog Serum by RP-HPLC with Pre-column Derivatization

Aim A simple, sensitive and rapid RP HPLC method with pre column derivatization has been developed for the determination of sulphonylurea glimepiride in dog serum. Methods The sulphonylurea glimepiride was extracted from the dog serum using dichlromethane followed by derivatization with DNBF for 20 min at 100℃. The solvent was then evaporated at 60℃ under nitrogen, and the residue was taken up in 100 μL of mobile phase consisting of acetonitrile water (75∶30, v/v). The separation was performed on a Hypersil BDS C18 column with a flow rate of 0 8 mL·min -1 , and the ultraviolet detector wavelength was set at 350 nm. Results Extraction recovery ranged from 75.9% to 83.2%, and methodological recovery was between 96.5% and 109.3%. Within day RSD ranged from 1.5% to 6.3%, and inter day RSD was between 2 9% and 14.8%. The method showed good linearity (R=0.9998). Conclusion The method was simple, convenient and sensitive. The reaction of derivatization was reproducible.

Experimental study on concrete columns hybrid reinforced by steel and FRP bars under seismic loading

In order to study the dynamic behavior of hybrid reinforced concrete columns, shaking table tests of three concrete columns with equal initial stiffness were conducted.The longitudinal reinforcements include an ordinary steel bar,a steel-fiber reinforced polymer（FRP） composite bar（SFCB）, and hybrid reinforcement（steel bar and FRP bar, CH）. Test results show that the peak ground acceleration（PGA） responses of different columns are similar to each other. For an ordinary reinforced concrete（RC） column, the plastic strain of the steel bar develops rapidly after the PGA of the input ground motion reaches 100 cm / s^2, and the corresponding residual strain develops dramatically. For a SFCB column, even after the peak strain reaches 0. 015, the residual strain is below 5 × 10^- 4. For the hybrid column C-H,the residual strain of the FRP bar is similar to that of the SFCB column. In general, concrete columns with hybrid steel and FRP bar reinforcement can achieve smaller residual deformation, and the SFCB reinforced columns can be constructed in extreme environments, such as offshore bridges, due to good anti-corrosion performance.

Ultimate flexural strength of normal section of FRP-confined RC circular columns

Numerical analysis is carried out to study the sectional properties of the fiber-reinforced polymer（FRP）-confined reinforced concrete（RC）circular columns. The axial load ratio, the FRP confinement ratio and the longitudinal reinforcement characteristic value are the three main parameters that can influence the neutral axis depth when concrete compression strain reaches an ultimate value. The formula for computing the central angle θ, corresponding to the compression zone, is established according to the data regression of the numerical analysis results. The numerical analysis results demonstrate that the concrete stress enhancement from transverse confinement and strain hardening of the longitudinal reinforcement can cause a much greater flexural strength than that defined by the design code. Based on the analytical studies and the test results of 36 large scale columns, the formula to calculate the flexural strength when columns fail under seismic loading is proposed, and the calculated results agree well with the test results. Finally, parametric studies are conducted on a typical column with different axial load ratios, longitudinal reinforcement characteristic value and FRP confinement ratios. Analysis of the results shows that the calculated flexural strength can be increased by 50% compared to that of unconfined columns defined by the code.

Seismic strengthening of reinforced concrete columns damaged by rebar corrosion using combined CFRP and steel jacket

In order to study the effectiveness of combined carbon fiber-reinforced polymer （CFRP） sheets and steel jacket in strengthening the seismic performance of corrosion-damaged reinforced concrete （RC） columns, twelve reinforced concrete columns are tested under combined lateral cyclic displacement excursions and constant axial load. The variables studied in this program include effects of corrosion degree of the rebars, level of axial load, the amount of CFRP sheets and steel jacket. The results indicate that the combined CFRP and steel jacket retrofitting technique is effective in improving load-carrying, ductility and energy absorption capacity of the columns. Compared with the corrosion-damaged RC column, the lateral load and the ductility factor of many strengthened columns increase more than 90% and 100%, respectively. The formulae for the calculation of the yielding load, the maximum lateral load and the displacement ductility factor of the strengthened columns under combined constant axial load and cyclically increasing lateral loading are developed. The test results are also compared with the results obtained from the proposed formulae. A good agreement between calculated values and experimental results is observed.