Constant Gas Flow Research Articles

Novel three-phase steam–air plasma torch for gasification of high-caloric waste

Research results are presented for an AC electric arc that burns a mixture of steam and air in a three-phase high-voltage plasma torch and can be implemented to produce plasma for plastic waste gasification. The dependences of electric parameters on the ratio of the steam to air mass flows (H2O/air ∼1–6) at an approximately constant total mass flow of the plasma-forming gas are obtained during several experiments. During the experiments, the arc parameters were as follows: voltage drop of 1.0–1.8kV, current of ∼28.5A and power of ∼52–86kW. The thermal efficiency of the plasma torch was ∼94–95%. CCD cameras operating at 4000fps were used to determine the average discharge length of ∼798mm. Photography with a high shutter speed (1/8000s) was used to determine the average arc diameter (∼4.47mm). Arc temperatures were calculated (10,000–11,500K) using the thermodynamic equilibrium approach. Experimental results indicate that increases in the steam content of the steam–air plasma lead to a reduction of the arc’s temperature and electrical conductivity. Using an equilibrium approach, the main parameters of plasma gasification were estimated: syngas yield (3.62–3.48m3/kg), composition (H2 – 55.5–62.5, CO – 32.8–34.1vol.%) and energy consumption (11.0–12.3MJ/kg).

Gas threshold pressure and gas permeability of silo concrete specimens for a low- and intermediate-level waste disposal facility in Korea

In order to simulate gas migration at an underground disposal facility, the characteristics of a medium such as the gas threshold pressure and gas permeability need to be measured in advance. In this study, the gas threshold pressure and gas permeability of silo concrete specimens for a Korean LILW (Low- and Intermediate-Level Waste) disposal facility were measured. The concrete specimens had the same composition as the concrete used in the construction of the silo. The gas threshold pressure was measured by injecting a constant gas flow into cross sections of the specimens. To measure the gas permeability, selected pressures were applied to the specimens and the apparent permeability was calculated using the Hagen-Poiseuille equation. The intrinsic permeability was calculated with the Klinkenberg empirical equation. The gas threshold pressure and gas permeability ranged from 30 to 40bar and from 10−17 to 10−18m2, respectively.

A criterion of similarity and transition to turbulence for electric arc flows

A method is suggested for determining the similarity criterion and the criterion of transition of an electric arc flow in a plasmatron channel from a laminar regime to a turbulent one (equivalent Reynolds number) that does not require using any reference temperature. Application of this method to the available experimental data on the transition to turbulence demonstrates its correctness and efficiency. The critical value of the proposed similarity criterion corresponding to the boundary of the transition from a laminar regime to a turbulent one has been revealed. A marginal curve separating the regions of the laminar and turbulent regimes of the plasma flow has been plotted in the space of the operating plasmatron parameters. A phenomenon of a double change of the electric arc flow regime with electric current rise upon constant plasma-forming gas flow rate has been discovered.

Pseudo Steady State Gas Flow in Tight Reservoir under Dual Mechanism Flow

Gas reservoirs with low permeability (k<0.1 mD) are among the unconventional reservoirs and are commonly termed as Tight Gas Reservoirs. In conventional gas reservoirs that have high permeability, the flow of gas is basically controlled by the reservoir permeability and it is calculated using the Darcy equation. In these reservoirs, gas flow due to gas diffusion is ignored compared to Darcy flow. However, diffusion phenomenon has a significant impact on the gas flow in tight gas reservoirs and the mechanism of gas diffusion can no longer be ignored in comparison to Darcy flow. In this study, a dual mechanism based on Darcy flow as well as diffusion is used for the gas flow modeling in tight gas reservoirs. The diffusivity equation is obtained using this method that it indicates the gas flow in a porous media. The conventional dry gas pseudo pressure function is not able to linearize the diffusivity equation including diffusion effect. Subsequently, a new real gas pseudo pressure function is used and a novel real gas pseudo time function is introduced. These pseudo functions consider changes in gas properties with pressure and linearize the diffusivity equation. The linear diffusivity equation is solved analytically for constant gas flow boundary condition under Pseudo Steady State (PSS) situation. Then, pseudo steady state analytical solution, based on new functions of pseudo pressure and pseudo time, is obtained. The calculation of reservoir parameters such as permeability, effective diffusion coefficient and original gas in place (OGIP) using reservoir data is the first application of analytical solution. Reservoir data is required to analysis the results of application of introduced model in low permeability gas reservoir.

Study of Dust Sampler System Based on Single Neuron PID

The sampling flow will be decreased by the weakness of filterable membrane permeability after the dust sampler working for period of time. It seriously affects the measurement accuracy, so keeping the dust sampler working under the constant gas flow is important. Gas flow can be adjusted accurately in time to ensure constant flow based on single neuron adaptive PLC algorithm and PWM technique. Apply ZigBee wireless communication technology on indoor positioning and remote monitoring.

Mathematical modeling of a three-phase trickle bed reactor

The transient behavior in a three-phase trickle bed reactor system (N2/H2O-KCl/activated carbon, 298 K, 1.01 bar) was evaluated using a dynamic tracer method. The system operated with liquid and gas phases flowing downward with constant gas flow Q G = 2.50 x 10-6 m³ s-1 and the liquid phase flow (Q L) varying in the range from 4.25x10-6 m³ s-1 to 0.50x10-6 m³ s-1. The evolution of the KCl concentration in the aqueous liquid phase was measured at the outlet of the reactor in response to the concentration increase at reactor inlet. A mathematical model was formulated and the solutions of the equations fitted to the measured tracer concentrations. The order of magnitude of the axial dispersion, liquid-solid mass transfer and partial wetting efficiency coefficients were estimated based on a numerical optimization procedure where the initial values of these coefficients, obtained by empirical correlations, were modified by comparing experimental and calculated tracer concentrations. The final optimized values of the coefficients were calculated by the minimization of a quadratic objective function. Three correlations were proposed to estimate the parameters values under the conditions employed. By comparing experimental and predicted tracer concentration step evolutions under different operating conditions the model was validated.

Accurate and adjustable calibration gas flow by switching permeation and diffusion devices

A new method for generating adjustable concentrations of calibration gases from permeation and diffusion devices is described. The method achieves high accuracy by maintaining the source device at a constant temperature and pressure and in a constant gas flow. It involves switching the gas stream and subsequently smoothing it to generate dilutions of up to 100 with a relative uncertainty of ±2%. Its dynamic performance has been modelled and its performance under steady-state conditions has been validated.

Enhanced NOx removal from flue gas by an integrated process of chemical absorption coupled with two-stage biological reduction using immobilized microorganisms

An integrated process of metal chelate absorption coupled with two stage bio-reduction using immobilized cultures has been proposed to continuously removal of NOx, and the effects of SO2, NO and O2 concentration, gas/liquid flow rate on NOx removal efficiency were investigated. Although nitrogen-containing components, such as Fe(II)EDTA-NO, NO2− and NO3− in the scrubbing solution, inhibited the bio-reduction of Fe(III)EDTA obviously, it was feasible to abate the inhibition effect by using the two stage bio-reduction system, and thus to improve NOx removal efficiency. The removal efficiency decreased slowly with the increase of SO2, O2, NO concentration and gas flow rate, and increased with the increase of liquid flow rate. Continuously operating for 18 days, a high removal efficiency around 95% was reached by using the two-stage bio-reduction system with immobilized microorganisms, while the value decreased to 85% after 5 days of operation by using the suspended microorganisms, at a constant gas flow rate of 60L/h containing 424–450mg/m3 NO, 2428–2532mg/m3 SO2 and 3% O2.

Separation of CO2 from the CO2/N2 mixed gas through ionic liquid membranes at the high feed concentration

Separation of CO2 from the CO2/N2 mixtures through ionic liquid membrane was carried out in this study. The CO2 volume fractions (XCO2) at feed side were 0.3–0.5. The microporous polyvinylidine fluoride (PVDF) membrane and two species of ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]), were used as the material for supported membrane and room temperature ionic liquids, respectively. The PVDF membranes were impregnated with the ionic liquids. The total pressures at the feed side were varied from 1.05 to 1.21atm. The experiment was performed under constant temperature at 40°C. The gas flow rates of CO2/N2 mixed gas at feed side were varied in range of 100–300mlmin−1. The effects of total pressure difference, the total flow rate at the feed side and the CO2 concentration were investigated. It was found that the higher permeability of CO2 was obtained from the lower total pressure differential conditions. The feed flow rates do not have the significant effect on permeability of N2. The [bmim][PF6] and [bmim][Tf2N] liquid membrane are given the equivalent CO2/N2 selectivity for XCO2=0.5 even though the feed gas flow rate was adjusted. The carrier saturation inside the ionic liquid membrane at high CO2 concentration and high pressure difference constrain the permeation of CO2. The highest selectivity was obtained in the case of XCO2=0.3 at constant total pressure difference and feed gas flow rate.

A novel brush feeder for the pneumatic delivery of dispersed small particles at steady feed rates

Abstract A novel particle feeding system capable of pneumatically dispensing dispersed particles at low and consistent feed rates has been developed. The feeder is based on a rotating brush that continually cleans the outlet orifice in a hopper filled with particles. The system was designed specifically for biomass particles that have been milled and sieved to less than 150 μm as a feedstock for laboratory scale aerosol flow reactors. This feedstock often contains a large fraction of high aspect ratio particles that form obstructions in many conventional feeding systems. In addition to biomass, the feeder has successfully fed all particles less than 150 μm that have been tested. Feed rates varying from 4.25 to 2420 mg/min have been obtained with spray dried algae at a constant carrier gas flow of 0.75 slpm, and steady and consistent feeding with milled switchgrass has been demonstrated. The design, construction, and preliminary testing of the feeding system are presented in this paper.

Effect of flow rate conditions on bubble formation

An experimental study has been carried out on bubble generation by means of air injection through an orifice submerged in water. An orifice, drilled in an hydrophobic horizontal plate and a radius a=1mm, have been used to investigate the effect of the flow rate working conditions on the bubble formation process; a wide range of volumetric gas flow rates (2.0×10⩽Q⩽1.8×104mm3/s) has been used, including different chamber volumes before the injection orifice.Two volumetric gas flow rates are apparent: the one into the experimental setup, which could be assumed as a constant, and a higher one into de bubble through the injection orifice; there is a first and significant time step with zero gas flow through the orifice. This drives to two different working conditions, named: constant volumetric gas flow rate, when both flow rates are equal, and non-constant volumetric gas flow rate, when both flow rates are different. First, a short experimental study, for constant volumetric gas flow rate, is presented; it represents a link between both working conditions. The main part of the work are devoted to non-constant volumetric gas flow rate and, it showed that the experimental data can be reduced approximately to a single bubble volume/flow rate relationship, as in the case of constant volumetric gas flow rate, if the properly scaled volumetric gas flow rate is used. Finally a simplified model, to estimate this proper volumetric gas flow rate, is presented and checked experimentally.

The Fuzzy-PID Algorithm Apply to the Constant Gas Flow Control of the Dust Sampler

The Sampling flow will be decreased because the permeability weakness of filterable membrane after the dust sampler working for a period of time. It seriously affects the accuracy of measurement, so we should keep the dust sampler working under the constant gas flow. The stable, rapidness and accuracy constant sampling can be achieved based on the application of fuzzy-PID algorithm and the adoption of PWM technique. It has carried on design to the dust sampler control system from selecting the hardware and designing the software to data processing and errors analysis, and discussing the preferable performance of the dust sample control system.

Environmental effects in kelvin force microscopy of modified diamond surfaces

We have explored the effects of atmospheric environment on Kelvin force microscopy (KFM) measurements of potential difference between different regions of test polycrystalline diamond surfaces. The diamond films were deposited by microwave plasma-assisted chemical vapor deposition, which naturally produces hydrogen terminations on the surface of the films formed. Selected regions were patterned by electron-beam lithography and chemical terminations of oxygen or fluorine were created by exposure to an oxygen or fluorine plasma source. For KFM imaging, the samples were mounted in a hood with a constant flow of helium gas. Successive images were taken over a 5-h period showing the effect of the environment on KFM imaging. We conclude that the helium flow removes water molecules adsorbed on the surface of the samples, resulting in differences in surface potential between adjacent regions. The degree of water removal is different for surfaces with different terminations. The results highlight the importance of taking into account the atmospheric environment when carrying out KFM analysis.

Weldability and joining characteristics of AISI 430/AISI 1040 steels using keyhole plasma arc welding

AISI 430 and AISI 1040 steel couples were welded using the keyhole plasma-transferred arc (KPTA) welding process. Welded joints were manufactured using three different traverse speeds (0.01, 0.02 and 0.03 m/min) under three different welding currents (130, 135 and 140 A) at a constant plasma gas flow rate (1.1 l/min) and a shielding gas rate (25 l/min). In order to determine the microstructural changes that occurred, the interface regions of the welded specimens were examined by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Energy Dispersive Spectrometry (EDS) after KPTA welding. Microhardness, V-notch Charpy and tensile tests were conducted to determine the mechanical properties of the welded specimens.

Simulation of Blast Furnace Operation with Intensive Hydrogen Injection

Recent years various trials to decrease carbon dioxide emission from iron and steelmaking industries have been made. One of these trials is utilization of hydrogen in blast furnace process, and this study performed numerical simulation of blast furnace operation with hydrogen injection through tuyere. The simulations were carried out under the conditions of constant bosh gas flow rate, adiabatic flame temperature and hot metal temperature. The simulation results showed that the temperature level in the stack part was decreased with increase in the hydrogen injection ratio. This resulted in the lowering of the top gas temperature and retarded the reduction of iron oxide especially one of magnetite. The injection of the hydrogen remarkably decreased the coke rate. The converted reducing agent rate, that is sum of coke rate and six times (molecular weight ratio of carbon to hydrogen gas) as hydrogen rate showed small change. Although this decrease in coke rate deteriorated the permeability of the burden materials in the furnace, pressure drop in the furnace was reduced. Since the molar flow rate of the reducing gas was kept constant, the decrease in the gas density due to the increase in the hydrogen content was mainly considered to lead the decrease in the pressure drop. The water gas shift reaction played an important role in the generation of the field of gas composition, thus this reaction has to be carefully discussed for further utilization of hydrogen in blast furnace.

Gas Channel Optimisation for PEM Fuel Cell using the Lattice Boltzmann Method

A scheme for two-phase flow with large density differences using the lattice Boltzmann method (LBM) was applied to investigate the optimum gas channel design for water drainage. Three different channel geometries were used: rectangular, trapezoidal, and triangular with constant gas flow rate and a droplet initially placed at the corner. The results show that the rectangular channel offers the best water removal characteristics under a moderate pressure drop. When using hydrophilic gas channels, a larger droplet is drawn up, which may induce better fuel cell performance. The cases of both channels with the same cross-section area, height and width are discussed.

Effect of the Gmaw and the Gmaw-P Welding Processes on Microstructure, Hardness, Tensile and Impact Strength of Aisi 1030 Steel Joints Fabricated by ASP316L Austenitic Stainless Steel Filler Metal

Effect of the Gmaw and the Gmaw-P Welding Processes on Microstructure, Hardness, Tensile and Impact Strength of Aisi 1030 Steel Joints Fabricated by ASP316L Austenitic Stainless Steel Filler Metal In this study, medium-carbon steel (AISI 1030) plates of 10 mm thickness, were welded by using the synergic controlled pulsed (GMAW-P) and manual gas metal arc (GMAW) welding techniques. Constant wire feed speed, voltage, welding speed and gas flow rates (3.2 m/min, 22.5 V, 4 mm/s, 16 1/min) and ASP316L austenitic stainless steel filler metal were used in these techniques. The interface appearances of the welded samples were examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-Ray diffraction (X-RD). In order to determine mechanical properties of samples, the tensile, impact and microhardness tests were conducted. The GMAW-P joints of AISI 1030 steel couples showed superior tensile strength, less grain growth and narrower heat affected zone (HAZ) when compared with GMAW joints, and this was mainly due to lower heat input, fine fusion zone grain and higher fusion hardness.

Dynamic analysis of the absorption/desorption loop of a carbon capture plant using an object-oriented approach

Post-combustion capture of CO2 is regarded as a possible technology in order to reduce CO2 emission to the atmosphere. This paper provides a dynamic analysis of the absorption/desorption loop of a carbon capture plant with the help of a simulation model, built using the object-oriented Modelica Library Thermal Separation. The solvent used is an amino-acid salt.The dynamic behaviour is investigated for a reduction in regeneration heat flow rate but constant flue gas flow rate. Hereby four different control strategies are compared, one keeping the lean solvent loading constant, one keeping the solvent flow rate constant, one where flue gas bypasses the capture plant and a last one where an additional solvent tank is introduced. The simulation shows i.e. that for a constant lean solvent loading the response of the absorbed CO2 flow rate is much faster than for a constant solvent flow rate.Also the effect on the dynamic behaviour is investigated, comparing the whole cycle model to a stand-alone desorber model and to a stand-alone absorber model respectively. It was found that the dynamic responses on a short time scale are very similiar, but different on a long time scale.

Palladium‐catalyzed dehalogenation of 5‐halopyrazoles

AbstractA new and efficient method for the dehalogenation of 5‐halopyrazoles was developed by using the catalytic amount of palladium (II) chloride and triphenylphosphine as a ligand at reflux under constant flow of hydrogen gas. The reaction gave the corresponding pyrazole products in good to excellent yields (≥83%). J. Heterocyclic Chem., (2012).

Regional lung opening and closing pressures in patients with acute lung injury

PurposeIn acute lung injury (ALI), the application of positive end-expiratory pressure (PEEP) is known to prevent the alveoli from cyclic collapse and reopening and to homogenize ventilation. The setting of adequate PEEP could be optimized by the knowledge of regional lung opening and closing pressures at the bedside. The aim of our study was to determine regional opening and closing pressures in ventilated patients by electrical impedance tomography (EIT). Materials and MethodsEight patients with healthy lungs and 18 patients with ALI were studied. A low-flow inflation and deflation maneuver with constant gas flow was performed. Regional opening and closing pressures were calculated for every pixel of the EIT scan. These pressures were defined as those values of global airway pressure at which the lung areas opened up or started to close. ResultsInjured lungs exhibited significantly higher regional opening pressures compared with healthy lungs (P < .05). In ALI, significantly higher opening pressures were found in the dependent lung regions. Regional closing pressures did not significantly differ between healthy and injured lungs. ConclusionsRegional lung opening and closing pressures can be assessed by EIT. This information may facilitate the setting of adequate PEEP levels in patients in future.