Influence Of Gas Flow Rate Research Articles

Investigation on the Transport Characteristics of Typical Biological Slender Particles in a Pilot-Scale Rotary Dryer

The transport characteristics of cut tobacco as a typical biological wet slender particle were investigated in a pilot-scale rotary cylinder. Effect of solids and gas flow rate, moisture content of particles and rotating speed of cylinder was analyzed. The adaptability of the classical Friedman model for predicting average residence time of these type particles was also investigated. The result shows that the gas flow rate, moisture content of particles as well as rotating speed of cylinder have a significant influence on the axis transport velocity and forward step per cycle of cut tobacco in rotary cylinder. It’s difficult for Friedman model to accurately describe influence of gas flow rate and moisture content on transport of cut tobacco, which was associated with the particle characterize and influence of moisture content on the fluidity of particles.

Inclusion Removal at the Free Surface of Steel Bath by Bubble Flotation

In the present work, physical model experiments were carried out to clarify the inclusion removal at the free surface of steel bath. Polyethylene particles were used to simulate the non-wetting inclusions like alumina and silica. The influence of gas flow rate and bubble size on the inclusion removal at the free surface was evaluated. It is demonstrated that not all particles are removed when they arrive at the free surface of liquid bath, and those which are not removed will get back to the bath. It is found an annular particle layer is formed by the removed particles at free surface, which can capture other particles arriving at the free surface. However, the attachment of particles to the annular particle layer is not stable, and re-entrainment of particles occurs at high gas flow rate. It is shown the overall particle removal is determined by a balance of removal and re-entrainment. The particle removal constant increases with the increase in the gas flow rate, but decreases with the increase in bubble size. The equilibrium concentration of particles increases with the increase in gas flow rate and bubble size.

Simulation study of biobutanol production in a polymer-loaded two-phase partitioning bioreactor (PL-TPPB): Model development

The conventional two-phase partitioning bioreactor (TPPB) containing an organic solvent as a second phase was found to be hardly efficient for biobutanol production because of the relatively low partitioning coefficient of butanol between the organic solvent and aqueous solution. Polymer bead was alternatively employed as the second phase in the TPPB, and Dowex Optipore L-493, a copolymer of styrene and divinyl benzene, was chosen as the optimum polymer because it shows the highest partitioning coefficients of butanol, acetone, ethanol and butyric acid against the aqueous phase among candidate polymers. The mass transfer coefficients of compounds from the aqueous phase into polymer beads were experimentally determined with respect to agitation speed. The mass transfer coefficient related to the stripping of volatile compounds by nitrogen gas was also determined, and the influence of gas flow rate turned out to be greater than that of the agitation speed, though both influences were remarkable. A mathematical model for the TPPB containing the polymer beads was suggested and as many as 40 parameters were cited from other publications or determined in this study. This mathematical model will be subsequently used for the detailed simulation study.

Effect of oil concentration and residence time on the biodegradation of α-pinene vapours in two-liquid phase suspended-growth bioreactors

Recently, research on the use of binary aqueous-organic liquid phase systems for the treatment of polluted air has significantly increased. This paper reports the removal of α-pinene from a waste air stream in a continuous stirred tank bioreactor (CSTB), using either a single-liquid aqueous phase or a mixed aqueous-organic liquid phase. The influence of gas flow rate, load and pollutant concentration was evaluated as well as the effect of the organic to aqueous phase ratio. Continuous experiments were carried out at different inlet α-pinene concentrations, ranging between 0.03 and 25.1 g m⁻³ and at four different flow rates, corresponding to residence times (RTs) of 120 s, 60 s, 36 s and 26 s. The maximum elimination capacities (ECs) reached in the CSTB were 382 g m⁻³ h⁻¹ (without silicone oil) and 608 g m⁻³ h⁻¹ (with 5%v/v silicone oil), corresponding to a 1.6-fold improvement using an aqueous-organic liquid phase. During shock-loads experiments, the performance and stability of the CSTB were enhanced with 5% silicone oil, quickly recovering almost 100% removal efficiency (RE), when pre-shock conditions were restored. The addition of silicone oil acted as a buffer for high α-pinene loads, showing a more stable behaviour in the case of two-liquid-phase systems.

Study of Graphene Growth by Gas-Source Molecular Beam Epitaxy Using Cracked Ethanol: Influence of Gas Flow Rate on Graphitic Material Deposition

To understand what is going on during graphene growth by gas-source molecular beam epitaxy with cracked ethanol and to gain insights into how to optimize this growth method to produce high-quality graphene, we investigated the influence of gas flow rate on the growth rate. From the core-level photoelectron intensities, we found that the deposition rate decreases with increasing gas supply rate. We introduced growth efficiency using the photoelectron intensities and environmental pressure of the growth system during ethanol supply and found that the efficiency decreases with increasing supply rate. To understand this phenomenon, we supplied the cracked ethanol to the previously deposited graphitic material on the substrate and found that the graphitic material was removed from the substrate surface. These results indicate that, under the supply of cracked ethanol, deposition and etching of graphitic material occur simultaneously. This process of competitive reactions, deposition and etching, results in the extremely low growth rate, and the reactions are almost balanced at our growth condition.

Study of Graphene Growth by Gas-Source Molecular Beam Epitaxy Using Cracked Ethanol: Influence of Gas Flow Rate on Graphitic Material Deposition

Study of Graphene Growth by Gas-Source Molecular Beam Epitaxy Using Cracked Ethanol: Influence of Gas Flow Rate on Graphitic Material Deposition

In-Situ Measurement of In-Plane Temperature Distribution in a Single-Cell Polymer Electrolyte Fuel Cell Using Thermograph

To clarify the mechanism of combined phenomena of heat, mass and electric charge transfers in a single-cell polymer electrolyte fuel cell (PEFC), it is necessary to measure in-plane temperature distribution of a single-cell PEFC when it is run, i.e., generating power. The measurement by thermograph assists to investigate the influence of gas flow rate at inlet and gas channel pitch of separator on in-plane temperature distribution and power generation performance. As a result, the higher temperature region is observed near the outlet of cell when the excess ratio of gas flow is set due to the convective heat transfer by excess oxygen flow in gas channel at the cathode. When the gas flow is set at stoichiometric, in-plane temperature distribution becomes even and high power generation performance can be achieved. The other observation is that the total voltage is increased and temperature in observation area is dropped with decreasing gas channel pitch of separator irrespective of gas flow rate.

Effect Assessment of Surface Treatment and Gas Channel Pitch of Separator on In-Plane Temperature Distribution and Power Generation Performance of a Single-Cell Polymer Electrolyte Fuel Cell

To clarify the impact of surface treatment and gas channel pitch of separator on in-plane temperature distribution and power generation performance of a single-cell polymer electrolyte fuel cell (PEFC), we have measured the in-plane temperature distribution on backside of separator at cathode by thermograph under the power generation with the operation of relative humidity of supply gas of 100 %. We have also investigated the influence of gas flow rate at inlet of the single-cell PEFC on heat transfer phenomena and power generation performance. As a result, the best power generation performance is obtained for the gas channel pitch of 1.0 mm irrespective of surface treatment of separator. The power generation performance of hydrophobic separator is better than that of hydrophilic separator since the performance of discharging the water produced in gas channel is better and the pressure loss of gas channel caused by gas flow is smaller. The temperature drop at the last turned edge of gas channel in observation area with increasing gas flow rate for hydrophobic separator is larger compared with hydrophilic separator by 1-2°C. The higher improvement of power generation performance due to increasing gas flow rate is obtained for gas channel pitch of 1.0 mm compared with gas channel pitch of 0.5 mm irrespective of surface treatment of separator.

Mixing Models for Slag Covered, Argon Stirred Ladles

Ninety-five percent bulk mixing times were determined experimentally in water models (D=0.30 m and D=0.60 m respectively) of a 140 T industrial ladle fitted with dual ‘plugs’ (located diametrically opposite at mid bath radius position) in the presence of an overlying, second phase liquid. Experiments were conducted to investigate the influences of gas flow rate, liquid depth, thickness of the upper phase liquid together with the latter's physical properties on mixing time. Within the range of variables studied, it is observed that besides gas flow rate, liquid depth and vessel radius, thickness of the upper phase liquid has the most significant bearing on mixing times. In contrast, considerably less pronounced effect of density and viscosity on mixing was noted. Dimensional analysis and regression of the experimental data show that 95% bulk mixing times in slag covered, dual plug fitted ladles can be described, in terms of relevant dimensionless groups, via: [Equation]in which, Q is the gas flow rate, L is the depth of liquid, R is the vessel radius, ΔL is the thickness of the overlying liquid, ρL is the density of the bulk liquid and νs is the kinematic viscosity of the upper or slag phase.Mixing correlations applicable to slag covered, dual plug fitted ladle and its slag free counterpart were found to bear striking similarity. This, as a possibility, suggests that embodying an additional factor, (<6(ΔL/L)0.3νs0.033(Δρ/ρL)−0.044) into a mixing correlation applicable to a slag free, gas stirred ladle, a correlation for an equivalent slag covered system can be derived. The hypothesis has been tested against axi-symmetrical gas stirred ladle system and towards this, relevant experimental measurements, mixing correlations etc. reported on such systems were applied. These suggest that 95% bulk mixing time in slag covered, axisymmetrical ladles can indeed be predicted reasonably well embodying the aforementioned addition factor into an existing correlation applicable to an equivalent slag free system.

Influence of gas flow rates on the formation of III‐nitride nanowires

AbstractThis study achieved catalytic growth of gallium nitride nanowires (GaN‐NWs) and indium gallium nitride nanowires (InxGa1‐xN‐NWs) by the horizontal furnace chemical vapour deposition (HF‐CVD) method at the temperature of 900 °C and 550 °C, respectively. The morphologies and structures of III‐nitride nanowires depended on the gas flow rates were studied. Comparing the growth mechanisms of GaN‐NWs and InxGa1‐xN‐NWs, the vapour‐solid (VS) mechanism is dominant in GaN nanowires, except with a low ammonium flow rate, and the vapour‐liquid‐solid (VLS) mechanism is dominant in InxGa1‐xN nanowires. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Study on the Flow Field around Two Parallel Moving Bubbles and Interaction Between Bubbles Rising in CMC Solutions by PIV

The flow fields surrounding two parallel moving bubbles rising from two identical orifices submerged in non-Newtonian fluid of carboxymethylcellulose (CMC) solution of three different mass concentration were measured experimentally by the use of particle image velocimetry (PIV). The influences of gas flowrate, solution mass concentration, orifice interval and the angle between two bubble centers line and vertical direction on the flow field surrounding bubbles were discussed respectively by analyzing the velocity vector, velocity contours as well as individual velocity components. The results show that the liquid velocity both in front of two bubbles and behind increases with gas flowrate duo to shear-thinning effect of previous bubbles, whereas decreases with the increase of CMC concentration due to the increase of drag force acting on bubbles. The effect of the orifice interval on the flow field around two moving bubbles becomes gradually obvious as the interval becomes closer. Moreover, two adjacent side-by-side bubbles repulse each other during rising, leading to the practical interval between them increased somewhat above the orifice interval. When the distance between bubbles is less than the orifice interval l0 mm, the interaction between two neighboring bubbles changed from mutual repellence to attraction with the decrease of the angle of the line of linking two bubble centers to the vertical direction.

The Influence of Gas Flow Rate on the Growth of YBCO Films Prepared by TFA-MOD

As reported by some authors, during the high temperature firing heat treatment step of TFA-MOD process, the gas flow rate on film surfaces, which is directly related to the transfers of water and the product HF gas, is one of the most important parameters influencing YBCO film nucleation and growth. In our experiments, this influence was investigated by a rotating method rather than changing the volume gas flow directly. As the rotating speed of the sample holder increased, relative gas flow rate on film surfaces increased, and quite high values could be reached without consumption of much gas. It was found that microstructure, texture, superconducting properties of YBCO films were evidently dependent on the rotating speed. With increasing the rotating speed, critical current density of YBCO films converted from precursor films in different quality could be enhanced to around 3 MA/cm2, the c-axis lattice parameter of YBCO unit cell was slightly reduced and the texture of the epitaxial films was improved, while the ratio of a-axis/c-axis oriented grains first increased and then decreased again.

Modeling of Nonequilibrium Air Plasma Generation by Transversal Gas Discharge

The mathematical model of nonequilibrium air plasma at atmospheric pressure has been presented. Theoretical investigation of nonequilibrium plasma interaction with turbulent gas flow has been performed for the case of transversal gas discharge taking into account 3-D geometry of the conjugated problem. The calculated results have been compared with the experimental data and have shown good results. Influence of gas flow rate on the discharge characteristics has been analyzed. Differences in the calculated and measured electron temperature values observed are explained.

Influence of Gas Flow Rate on Liquid Distribution in Trickle-Beds Using Perforated Plates as Liquid Distributors

Two wire mesh tomography devices and a liquid collector were used to study the influence of the gas flow rate on liquid distribution when fluids distribution on top of the reactor is ensured by a perforated plate. In opposition to most of the studies realized by other authors, conditions in which the gas has a negative impact in liquid distribution were evidenced. Indeed, the obtained results show that the influence of gas flow rate depends on the quality of the initial distribution, as the gas forces the liquid to “respect” the distribution imposed at the top of the reactor. Finally, a comparison between the two measuring techniques shows the limitations of the liquid collector and the improper conclusions to which its use could lead.

Biofiltration of ethylbenzene vapours: Influence of the packing material

In order to investigate suitable packing materials, a soil amendment composed of granular high mineralized peat (35% organic content) locally available has been evaluated as carrier material for biofiltration of volatile organic compounds in air by comparison with a fibrous peat (95% organic content). Both supports were tested to eliminate ethylbenzene from air streams in laboratory-scale reactors inoculated with a two-month conditioned culture. In pseudo-steady state operation, experiments at various ethylbenzene inlet loads (ILs) were carried out. Maximum elimination capacity of about 120 g m −3 h −1 for an IL of 135 g m −3 h −1 was obtained for the fibrous peat. The soil amendment reactor achieved a maximum elimination capacity of about 45 g m −3 h −1 for an inlet load of 55 g m −3 h −1. Ottengraf–van den Oever model was applied to the prediction of the performance of both biofilters. The influence of gas flow rate was also studied: the fibrous peat reactor kept near complete removal efficiency for empty bed residence times greater than 1 min. For the soil amendment reactor, an empty bed residence time greater than 2 min was needed to achieve adequate removal efficiency. Concentration profiles along the biofilter were also compared: elimination occurred in the whole fibrous peat biofilter, while in the soil amendment reactor the biodegradation only occurred in the first 65% part of the biofilter. Results indicated that soil amendment material, previously selected to increase the organic content, would have potential application as biofilter carrier to treat moderate VOC inlet loads.

Influence of gas flow rate on the microstructure and mechanical properties of hydroxyapatite coatings fabricated by gas tunnel type plasma spraying

Gas tunnel type plasma torch was used to spray hydroxyapatite (HA) coatings on 304 stainless steel substrate at different plasma gas (Ar) flow rates (100–170 l/min). Microstructure was observed by scanning electron microscope and phase analysis by X-ray diffraction. The mechanical properties such as hardness and abrasive wear resistance of HA coatings sprayed at different gas flow rates were investigated. The results showed that the gas flow rates affect greatly the microstructure and mechanical properties of HA coatings. Crystallinity increased and porosity decreased as the gas flow rate increased. Hardness and abrasion resistance increased as the gas flow rates increased.

Performance optimization of the fungal biodegradation of α-pinene in gas-phase biofilter

A Ophiostoma species using α-pinene as the sole source of carbon and energy converted it into biomass, carbon dioxide and water. The strain was inoculated in a biofilter fed α-pinene polluted air, and it remained the dominant biocatalyst throughout the study. Near complete removal was observed up to a load of 100 g m −3 h −1, while 89% removal efficiency was reached at an elimination capacity of 143 g m −3 h −1. The influence of gas flow rate, pollutant concentration and load was evaluated. For a similar load, the highest removal efficiency and corresponding elimination capacity were reached at the lowest flow rate and at an inlet concentration of 2.47 g m −3. Oxygen had a significant effect on the removal efficiency since the maximum α-pinene degradation rate exceeded 187 g m −3 h −1 at 45% oxygen in the inlet air suggesting that at high loads oxygen transfer becomes limiting. Biokinetic studies led to a good fit between experimental data and mathematical equations, yielding a calculated maximum α-pinene degradation rate of 198.42 g m −3 h −1 with a half-velocity constant, K S, of 0.76 g m −3.

Numerical and experimental investigation on the thermofluid fields induced by a pen-like atmospheric nonthermal plasma torch

The present paper carried out the numerical simulation and experimental study of the thermofluid fields induced by a pen-like atmospheric nonthermal plasma torch, which is a very simple device to produce atmospheric plasma and has been successfully applied for surface treatment to improve the hydrophilic properties of plastic film and polyethylene. The device consists of a small cylindrical stainless steel pipe with 6.5 mm diameter and 170 mm length inserted into a ceramic tube as the inner electrode. A ring outer electrode made of stainless steel is fixed at near the edge of the ceramic. The 13.56 MHz RF power was applied between the two electrodes to produce a surface discharge. The power into the torch is 60 W. The driving gas is argon and the flow rate varies in the range of 3–12 L min −1. Fundamental research results describing the major features of the flow fields induced by the plasma torch are provided in the present study. The stress is laid on the investigation of the influence of gas flow rate, which is one of important operation conditions, on the flow fields excited by the plasma torch. The principal results show that as the power input is fixed the increase of the gas flow rate will reduce the plasma temperature. The plasma penetration length stretching toward the atmospheric surroundings is also found to be closely related with the gas flow rate. Experimental confirmation by measuring the rotational temperature using optical spectroscopic method has been carried out, and a reasonable agreement between calculation and experiment has been obtained. These results provide fundamental understanding of the thermofluid fields induced by a pen-like atmospheric plasma torch, and also build up a basic predictive capability by numerical simulations to perform the further detailed investigation for practical applications in future.

Microbial biomass production from rice straw hydrolysate in airlift bioreactors

Rice straw is a by-product of rice production, and a great bioresource as raw biomass material for manufacturing value-adding protein for animal feedstock, which has been paid more and more attention. In the present work, utilizing rice straw hydrolysate as a substrate for microbial biomass production in 11.5 L external-loop airlift bioreactors was investigated. Rice straw hydrolysate obtained through acid-hydrolyzing rice straw was used for the culture of yeast Candida arborea AS1.257. The influences of gas flow rate, initial liquid volume, hole diameter of gas sparger and numbers of sieve plates on microbial biomass production were examined. The best results in the external-loop airlift bioreactor were obtained under 9.0 L initial liquid volume, 1.1 (v/v)/min gas flow rate during culture time of 0–24 h and 1.4 (v/v)/min gas flow rate of 24–48 h at 29 ± 1 °C. The addition of the sieve plates in the riser of the external-loop airlift bioreactor increased productivity. After 48 h, under optimized operation conditions, crude protein productivity with one sieve and two sieves were 13.6 mg/mL and 13.7 mg/mL, respectively, comparing 12.7 mg/mL without sieves in the airlift bioreactor and 11.7 mg/mL in the in the 10-L mechanically stirred tank bioreactor. It is feasible to operate the external-loop airlift bioreactors and possible to reduce the production cost for microbial biomass production from the rice straw hydrolysate.

Flue Gas Treatment for SO2 Removal with Air-Sparged Hydrocyclone Technology

Laboratory results from an initial study on the removal of SO2 from gas mixtures are reported using air-sparged hydrocyclone (ASH) technology. Tap water and alkaline solutions were used for absorption, and the influence of gas flow rate, water flow rate, and length of the ASH unit were investigated. The research results indicate thatthe air-sparged hydrocyclone can be used as a highly efficient absorber for SO2 emissions. The ASH allows for 97% SO2 removal using water alone for sulfur dioxide content in the gas phase of 5 g/m3. All SO2 is removed in weakly alkaline solution (0.01 mol NaOH/dm3).