Alumina Bed Research Articles

Experimental determination of friction coefficient and mobilization force for a laterally confined granular column

The case of a cylindrical container filled with granular material is a basic situation where the presence of the cylindrical wall induces horizontal pressure and hence, shearing forces (caused by friction between the container wall and the granular bed). Under certain circumstances, a finite length of the granular column in a housing cylindrical container can stand in the vertical position unsupported at the bottom end, held only by the frictional forces at the wall. When an axial load is applied at one end of the bed and increased slowly, the whole granular column starts to slide at a critical load value, called herein the mobilization force. Since this scenario is of significant practical interest (e.g. in caissons construction or in the design of silos), the experimental determination of the related parameters is of great importance for the development of suitable simulation models. In this paper, experimental methodologies for in-situ measurement of the mobilization force and the Coulomb’s friction coefficient between the granular material and the wall of the housing cylinder are presented in detail. Practical and convenient experimental set-ups that require only a few pieces of readily available and easily operated test equipment are proposed to measure these parameters. Results from a series of example experiments conducted on a granular alumina bed packed in a rigid plastic cylinder illustrate the performance and validity of the proposed experimental methods.

Hybrid filtration combustion of natural gas and coal

Rich and ultrarich combustion of natural gas in a porous medium composed of aleatory coal particles and alumina spheres was studied experimentally to evaluate the suitability of the concept for hydrogen and syngas production. Temperature, velocity and chemical products of the combustion waves were recorded experimentally in two stages: (1) natural gas in an inert porous medium at filtration velocities of 12, 15 and 19cm/s for equivalence ratios (φ) from φ=1.0 to φ=3.8; (2) natural gas in a porous medium composed of coal and alumina particles for a range of volume coal fractions from 0 to 75% at φ=2.3, and a filtration velocity of 15cm/s. It was observed that the flame temperatures and hydrogen yields were increased with the increase of filtration velocity in inert porous media. In hybrid porous media the flame temperature decreased with an increase of coal fraction, and hydrogen and carbon monoxide were dominant partial oxidation products. Syngas yield in hybrid filtration combustion was found to be essentially higher than for the inert porous medium case. The maximum hydrogen conversion for the hybrid coal and alumina bed was ∼55% for a volumetric coal content of 75%.

Bio-oil and bio-char from low temperature pyrolysis of spent grains using activated alumina

The pyrolysis of wheat and barley spent grains resulting from bio-ethanol and beer production respectively was investigated at temperatures between 460 and 540°C using an activated alumina bed. The results showed that the bio-oil yield and quality depend principally on the applied temperature where pyrolysis at 460°C leaves a bio-oil with lower nitrogen content in comparison with the original spent grains and low oxygen content. The viscosity profile of the spent grains indicated that activated alumina could promote liquefaction and prevent charring of the structure between 400 and 460°C. The biochar contains about 10–12% of original carbon and 13–20% of starting nitrogen resulting very attractive as a soil amendment and for carbon sequestration. Overall, value can be added to the spent grains opening a new market in bio-fuel production without the needs of external energy. The bio-oil from spent grains could meet about 9% of the renewable obligation in the UK.

Bentonite as an Alternative Adsorbent for the Purification of Styrene Monomer: Adsorption Kinetics, Equilibrium and Process Design

Some problems have been reported regarding the purification of styrene monomer by adsorption onto alumina beds, making this process both difficult and expensive. A study of the adsorption equilibrium and kinetics of t-butylcatechol (TBC) and water onto an alternative adsorbent, bentonite, is presented herein. Experimental equilibrium and kinetic measurements onto silica gel and commercial alumina are also included in order to compare the equilibrium capacities and adsorption rates. In addition, process design and economic evaluation of the adsorption process using bentonite as an adsorbent are also included.

The hybrid plasma–catalytic process for non-oxidative methane coupling to ethylene and ethane

Non-oxidative methane coupling in hybrid plasma–catalytic reactors was studied. The hybrid system which combined the gliding discharge (GD) and mobile (spouted) bed of catalyst particles revealed high efficiency in the methane conversion. Two catalysts from Pt and Pd supported by alumina ceramics were prepared and tested. The methane conversion was investigated in two GD reactors supplied by 1-phase or 3-phase circuits (50 Hz). In a homogeneous gas system and with a mobile bed of alumina–ceramic particles, mainly acetylene was produced from the CH 4 + H 2 mixture with none or a minor share of other C 2 hydrocarbons. The formation of non-volatile products (mainly soot) was also observed. In the presence of Pt and Pd catalysts, the soot formation was strongly reduced. Owing to these catalysts, ethylene and ethane became the main gaseous products replacing a major part of acetylene.

Cotton Stalk Combustion in a Circulating Fluidized Bed

AbstractThe basic properties of cotton stalk (CS) of length 10–100 mm and its ash were investigated. Studies concerning the combustion characteristics of CS were performed in a circulating fluidized bed (CFB) test facility with a heat input of 0.5 MW. According to previous cold tests, there is very little segregation during the mixing of CS with this size profile and bed material at a fluidization number of N > 7, but the hot experimental results indicate that slight segregation has a small effect on the steady combustion of the dense region. Experiments were carried out with the aim of investigating the effects of operating conditions on the axial temperature and gas concentration profiles along the combustor height, as well as the emission performance and combustion efficiency of the CFB. The experimental results indicate it is difficult to react alumina bed material with alkali metals from CS ash following 26 h of combustion. The overall conclusions appear to indicate that the application of circulating fluidized bed boilers to fire pure CS of length 10–100 mm, is feasible.

알루미나 컬럼에서 2-propylpiperidine-1-carbodithioate 착체의 흡착에 의한 수용액중에서 구리(II)의 고상추출

A novel approach has been developed for the solid phase extraction of copper(II) based on the adsorp- tion of its 2-propylpiperidine-1-carbodithioate complex on alumina column. The effect of various parameters such as acidity, sample volume, interfering ions, etc., were studied in detail. The adsorbed complex could be easily eluted using polyethylene glycol-sulfuric acid mixture and the concentration of copper has been determined using visible spec- trophotometry. The calibration graph was linear in the range 0-1 µgmL copper(II) with a detection limit of 5 µgL . A highest preconcentration factor of 25 could be obtained for 250 mL sample volume using glass wool as support for the alumina bed adsorbent. Copper(II) could be effectively separated from other ions such as nickel, cobalt, zinc, chlo- ride, sulfate, nitrate, etc., and the method has been successfully applied to study the recovery of copper in electroplating waste water and spiked water samples.

Experimental studies on cotton stalk combustion in a fluidized bed

Abstract The present work reports studies on the mixing and combustion characteristics of cotton stalk (CS) with 10–100 mm in length in a fluidized bed. Effects of length and initial weight percentage of CS, diameter of alumina bed material as well as gas velocity on the mixing characteristics of CS with alumina were investigated. CS can mix well with 0.6–1 mm alumina at fluidization number N =3–8. Fluidized bed combustion of pure CS was conducted in a 0.2 MW th test facility. The concentrations of major gaseous pollutants (CO, SO 2 and NO) in flue (stack) gas were measured. The combustion efficiency of CS is over 99.5%. Additionally, the experiments researched the agglomeration characteristics of bed materials: silica sand and alumina. SEM/EDX analyses on silica samples suggest that the high alkali metals content may cause the formation of the coating around silica particles. The coating consists of compounds with low melting temperature and can result in the bed agglomeration. By contrast, alumina is difficult to react with alkali metals from CS ash after 38 h combustion.

Experimental study on cotton stalk combustion in a circulating fluidized bed

This paper summarizes the results of an experimental study on cotton stalk (CS) combustion in a circulating fluidized bed. The mixing and fluidizing characteristics of binary mixture of CS with 10–100 mm in length and alumina bed material with a certain size distribution in a cold test facility were studied. The results show that CS by itself cannot fluidize, and adding inert bed material can improve the fluidization condition. CS can mix well with alumina at fluidization number N = 3–7. As N is more than 7, there will exist a little more segregation. The study concerning combustion characteristics of pure CS was performed on a circulating fluidized bed with a heat input of 0.5 MW. The effects of fluidizing velocity, secondary air flow and gas flow to the loop seal on the bed temperature profiles were investigated. Although there is a little more segregation at N higher than 7 in the cold tests, the hot experimental results indicate that slight segregation has little effect on the steady combustion of the dense region. In this study, the concentrations of major gaseous pollutants (CO, SO 2 and NO) in flue (stack) gas were measured.

Hybrid gas-liquid electrical discharge for degradation of organic pollutants in aqueous solution

Hybrid gas-liquid electrical discharge for degradation of phenol was investigated. The removal rate increased with decreasing the phenol initial concentration and adding some catalysts, such as Fe2+, Fe3+and H2O2. Augmenting the particle diameter of activated alumina or exchanging beadings as padding would lead to the reduction of the removal rate of phenol. Local discharge promoted the phenol degradation in the thin water film. And the space-time distribution of gas-liquid phases was more uniform and the contact areas of activated species generated from the discharge and the pollutant molecules were much wider due to the effect of the activated alumina bed.

中心装入粒子の密度や摩擦特性が高炉内固体粒子流れと炉芯挙動に与える影響の数値解析

A center coke charging method from the top of blast furnace is known for a novel approach to burden distribution and coal combustion. This method is considered as one of the key technologies for keeping gas permeability of deadman in the lower part of blast furnace and producing iron liquid with a stable furnace operation. In recent years, the center charging method is also expected as improving the unsteady behavior with bridging/slipping of solid bed in low reducing agents operation of blast furnace. In the present study, a center charging method with different particle density or friction coefficients is carried out numerically by using a 3-dimensional Discrete Element Method (DEM). Before the numerical analysis, an experimental approach using a two-dimensional cold model is also examined. Alumina sphere was used as representative particle of coke/ore packed bed and the glass sphere was for the center charge. From the experiment, it was found that the height of deadman is reduced dramatically by using the center charging method with the glass sphere. This experimental result was compared with the numerical approach, although the gas flow was not considered in the numerical method. In the numerical results, the void fraction was calculated more precisely compared to the previous numerical two-dimensional calculation. Almost uniform particle flow distribution called a piston flow pattern was fairly maintained by the numerical center charging method, and as the result, the height of deadman was also confirmed reduced numerically compared to the alumina bed only. This result was qualitatively coincident with the experimental flow pattern except for the particle velocity descending faster in the experimental center-charging region, which could be available for the operation of deadman control.

Comparison of adsorption characteristics according to polarity difference of acetone vapor and toluene vapor on silica–alumina fixed-bed reactor

Adsorption characteristics of acetone vapor and toluene vapor on silica–alumina were investigated using a fixed-bed reactor. The equilibrium adsorption capacity of acetone vapor on silica–alumina was about four times higher than that of toluene vapor because of polarity difference between adsorbent and adsorbate. As inlet concentration and linear velocity were increased, MTZ (mass transfer zone) and LUB (length of unused bed) were increased. In binary vapor systems, the phenomenon of “roll-up” was observed in the breakthrough curves. Thus the more strongly adsorbed adsorbate (acetone) displaces the weaker adsorbate (toluene), leading to a rise in the effluent concentration of the less strongly adsorbed adsorbate above the inlet concentration. Temperature changes in silica–alumina bed during adsorption of acetone vapor and toluene vapor were occurred near 30 min and the increase of temperature by adsorption heat was in the range of 6–7 °C.

Catalytic Effects of Metals on the Conversion of Methane in Gliding Discharges

AbstractPlasma‐catalytic methane conversion was studied under gliding‐discharge conditions using a mobile (spouted) catalytic bed of fine particles. A new model of the GD reactor was tested for the non‐oxidative methane coupling using alumina‐supported catalysts containing Cu, Ni, Ag or Pt resistant against the plasma action. C2 hydrocarbons, besides hydrogen, were the main products, with some amounts of non‐volatile substances (mainly soot). With Cu/Al2O3, Ni/Al2O3, Ag/Al2O3, and alumina beds, acetylene was mainly produced from the CH4 + H2 mixture with none or a minor share of other C2 hydrocarbons. Using Pt/Al2O3, an increased ethylene and ethane content was found with lower acetylene content. magnified image

Removal of phenol by activated alumina bed in pulsed high-voltage electric field

A new process for removing the pollutants in aqueous solution-activated alumina bed in pulsed high-voltage electric field was investigated for the removal of phenol under different conditions. The experimental results indicated the increase in removal rate with increasing applied voltage, increasing pH value of the solution, aeration, and adding Fe 2 +. The removal rate of phenol could reach 72.1% when air aeration flow rate was 1200 ml/min, and 88.2% when 0.05 mmol/LFe 2 + was added into the solution under the conditions of applied voltage 25 kV, initial phenol concentration of 5 mg/L, and initial pH value 5.5. The addition of sodium carbonate reduced the phenol removal rate. In the pulsed high-voltage electric field, local discharge occurred at the surface of activated alumina, which promoted phenol degradation in the thin water film. At the same time, the space-time distribution of gas-liquid phases was more uniform and the contact areas of the activated species generated from the discharge and the pollutant molecules were much wider due to the effect of the activated alumina bed. The synthetical effects of the pulsed high-voltage electric field and the activated alumina particles accelerated phenol degradation.

Fluidized-Bed Combustion Characteristics of Cedar Pellets by Using an Alternative Bed Material

The agglomeration of bed material is a serious problem during biomass combustion. In this paper, an alternative bed material (porous alumina) was used to prevent defluidization and to improve efficiency during cedar pellet combustion. During the tests, we observed that porous alumina was more difficult to agglomerate than silica sand, because of its specific properties. The volatile matter from cedar pellets mostly burned in the dense bed when the porous alumina was employed, as porous alumina captured part of the volatile matter released from the fuel pellets. Therefore, the temperature of the alumina bed was higher than that of silica sand under the same experimental conditions (fuel feed rate and air feed rate), and the temperature gradient in the freeboard region using the former was larger than that using the latter. In addition, the temperature distribution in the horizontal direction was notably uniform. When silica sand was used as a bed material, the CO concentration sharply decreased with the height in the freeboard region. In the horizontal direction, the maximum CO concentration was found in the middle of the bed. By contrast, the height of the combustor had a minor influence on the CO concentration when porous alumina was used as the bed material. Our experimental results also showed that NOx emission was not affected by the type of bed material.

Chlorobiphenyl Constituents of Aroclor 1268, Chlorofen, Clophen T 64, KC-600, and KC-1000 Technical Formulations

All 209 chlorobiphenyls (CBs) theoretically possible and potentially present in relatively highly chlorinated types of technical CB formulations of Aroclor 1268, Chlorofen, Clophen T 64, KC-600, and KC-1000 have been quantified using isotope dilution techniques and high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). CB constituents of Aroclor 1268, Chlorofen, Clophen T 64, KC-600, and KC-1000 could be separated, detected, identified and quantified as “bulk CBs,” using a capillary column (60 m length × 0.25 mm i.d.) coated by 8% phenyl polycarborane-siloxane (HT-8PCB, SGE, Australia) liquid phase for GC coupled to HRMS, into 111, 78, 126, 137, and 148 peaks, respectively, which covered 140, 100, 158, 169, and 180 possible CB congeners. 87, 60, 99, 110, and 121 peaks represented single CB congeners in Aroclor 1268, Chlorofen, Clophen T 64, KC-600, and KC-1000, respectively, while 34, 18, 27, 27, and 27 peaks represented 53, 40, 59, 59, and 59 co-eluting CBs. After enrichment procedures using multilayer silica beds, alumina beds, and carbon-impregnated silica beds in glass columns, all four planar non-ortho CBs and all eight mono-ortho CBs (but with the exception of CB no. 123 in Chlorofen) could be quantified in all five technical CB formulations examined. The planar non- and mono-ortho CBs content of Aroclor 1268, Chlorofen, Clophen T 64, KC-600 and KC-1000 were 6.2, 7.0, 47, 120, 470 μ g/g and 220, 410, 34,000, 12,000, 5900 μ g/g, respectively, and their 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalents (2,3,7,8-TeCDD TEQs) were 31, 390, 710, 260, 1900 ng-TEQ/g and 35, 99, 5900, 2600, 8900 ng-TEQ/g, and the total 2,3,7,8-TeCDD TEQs of planar CBs were 66, 490, 6600, 2900, and 11,000 ng-TEQ/g.

The Prediction of the Emissivity and Thermal Conductivity of Powder Beds

A simple model for estimating the emissivity of the surface of a powder bed by knowing only the bed porosity and its solid emissivity is presented. Estimates by the model are compared with experimental measurements for powder beds of alumina, silicon carbide, and iron. Agreement within the uncertainty of the measurements of ±10% is obtained. A view factor that adopts the predicted emissivity of the powder beds into its term is suggested for the calculation of the conductivity by radiation. For the prediction of the thermal conductivity of the powder beds, the authors compared the existing models in literature. They rederived the Zehner-Schlünder equation (1970) and made some modifications to it. Comparison of predictions by this equation with 424 measured values shows the predictions to be accurate to within a ±30% relative error.

The Prediction of the Emissivity and Thermal Conductivity of Powder Beds

A simple model for estimating the emissivity of the surface of a powder bed by knowing only the bed porosity and its solid emissivity is presented. Estimates by the model are compared with experimental measurements for powder beds of alumina, silicon carbide, and iron. Agreement within the uncertainty of the measurements of±10% is obtained. A view factor that adopts the predicted emissivity of the powder beds into its term is suggested for the calculation of the conductivity by radiation. For the prediction of the thermal conductivity of the powder beds, the authors compared the existing models in literature. They rederived the Zehner-Schlunder equation (1970) and made some modifications to it. Comparison of predictions by this equation with 424 measured values shows the predictions to be accurate to within a ±30% relative error.

A Study of the Dehydrochlorination of 1,2-Dichloropropane over Silica−Alumina Catalysts

The conversions of 1,2-dichloropropane (12dcp), 1,3-dichloropropane (13dcp), and allyl chloride (3-chloropropene, 3cp) over a silica−alumina bed have been investigated. Both 12dcp and 13dcp undergo dehydrochlorination above 500 K, mainly resulting in the two 1-chloropropene (1cp) geometric isomers, which, above 650 K, further eliminate HCl to give propyne and burn in the presence of oxygen. Small amounts of 3cp were also observed. 12dcp was found to react more rapidly than 13dcp. The conversion of 3cp gives essentially COx above 700 K and small amounts of benzene in the range 600−700 K. The reaction order is zero. The activation energy for the conversion of 12dcp was found to be 14.4 kcal/mol (60.6 kJ/mol). IR data show that a reversible adsorption step is followed by a nucleophilic substitution by an active surface oxide species, giving rise to an alkoxide species. The slow step is likely the E1 elimination of the alkoxide. The conversion of the primary 3-chloro-1-propyl carbenium ion to a 1-chloro-2-propyl carbenium ion plays a relevant role. The catalyst deactivates progressively at 523 K, its activity being nearly halved after 4 h, but it attains a plateau after 7 h. At higher temperatures, the stable total conversion of 12dcp was obtained after 10 h.

Incineration Characteristics of Dye Sludge in a Fluidized Bed Incinerator.

Incineration experiments are carried out to investigate the agglomeration characteristics of bed materials during fluidized bed incineration of dye sludge in a lab-scale system. With several criteria, the agglomeration potential is assessed during a 26 hr-operation. Silica sand and alumina sand are used as a bed material in the experiment. Above a temperature of 800°C, the fluidized bed of silica sand shows agglomeration behavior instantaneously resulting in serious channeling and defluidization during fluidized bed incineration of dye sludge. In the case of an alumina bed material, steady-combustion can be achieved during a 26 hr-operation.