Optimum Gas Flow Rate Research Articles

Development of Alditol Acetate Derivatives for the Determination of 15N-Enriched Amino Sugars by Gas Chromatography-Combustion-Isotope Ratio Mass Spectrometry.

Amino sugars can be used as indices to evaluate the role of soil microorganisms in active nitrogen (N) cycling in soil. This paper details the assessment of the suitability of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for the analysis of 15N-enriched amino sugars as alditol acetate derivatives prior to application of a novel 15N stable isotope probing (SIP) approach to amino sugars. The efficient derivatization and cleanup of alditol acetate derivatives for GC was achieved using commercially available amino sugars, including glucosamine, mannosamine, galactosamine, and muramic acid, as laboratory standards. A VF-23ms stationary phase was found to produce optimal separations of all four compounds. The structure of the alditol acetate derivatives was confirmed using gas chromatography/mass spectrometry (GC/MS). For GC-C-IRMS determinations, implementation of a two-point normalization confirmed the optimal carrier gas flow rate to be 1.7 mL min-1. Linearity of δ15N value determinations up to δ15Nt of 469 ± 3.1‰ (where δ15Nt is the independently measured δ15N value) was confirmed when 30 nmol N was injected on-column, with the direction of deviation from δ15Nt at low sample amount dependent on the 15N abundance of the analyte. Observed between- and within-run memory effects were significant ( P < 0.007) when a highly enriched standard (469 ± 3.1‰) was run; therefore, analytical run order and variation in 15N enrichment of analytes within the same sample must be considered. The investigated parameters have confirmed the isotopic robustness of alditol acetate derivatives of amino sugars for the GC-C-IRMS analysis of 15N-enriched amino sugars in terms of linearity over an enrichment range (natural abundance to 469 ± 3.1‰) with on-column analyte amount over 30 nmol N.

Synthesis of Gold Nanoparticles with Ultrasonic Spray Pyrolysis and its Feasibility for Ink-Jet Printing on Paper

Background: The bulk production of Gold Nanoparticles (AuNPs) and their concentrated ink, with desirable properties such as morphology, purity, stability and final Au concentration, remains a challenge. Objective: (i) Synthesis of AuNPs through Ultrasonic Spray Pyrolysis (USP) from different precursors. (ii) Preparation of their concentrated ink and (iii) Test their feasibility for ink jet printing onto a glossy paper substrate. Method: Initially, two different start materials were used - precursor: Gold Chloride with its nanoparticles as C-AuNPs, and Gold Acetate with its nanoparticles as A-AuNPs stabilised with PVP40 in deionised water. The concentrated ink was prepared from both AuNPs, and filtered up to the [Au] of 1000 ppm. Ink-jet printing was performed, and the obtained patterns were analysed through SEM. Results: The [Au] in the obtained solutions, determined through ICP-OES analysis, was, for CAuNPs, about 100 ppm, and 150 ppm for A-AuNPs. In the case of C-AuNPs the solution was rose, and for A-AuNPs violet. TEM investigation revealed that C-AuNPs dominated in a circular shape with size about 18 nm; contrary to this, A-AuNPs were mostly in ellipsoid shape, with size in the longitudinal direction of about 36 nm. EDX analyses detected 99.9 wt. % of Au in both AuNPs, which is evidence that these were of high purity. Due to different AuNPs` sizes and [Au], the colloidal solutions showed maximum absorbance wavelength of 532 nm for C-AuNPs and 528 nm for A-AuNPs. SEM results showed that A-AuNPs were significantly better for printing on the paper substrate than C-AuNPs, due to their ellipsoidal shape, as the flow behaviour had been much smoother through the nozzle as compared to the circular shape. The printed area with A-AuNPs reflected in better incorporation of nanoparticles on the paper surface and high-density connectivity among AuNPs. Conclusions: C-AuNPs and A-AuNPs were synthesised successfully under optimum parameters of evaporation temperature, reaction temperature and gas flow rates. The spherical shape of C-AuNPs as compared to the ellipsoidal nature of A-AuNPs was due to the rapid sintering of Gold Chloride at a higher temperature of 300ºC as compared to Gold Acetate.

Effect of impregnated activated carbon on carbon dioxide adsorption performance for biohydrogen purification

The challenge in biohydrogen (bio-H2) production is the presence of low hydrogen purity, which contains a high concentration of carbon dioxide (CO2). Bio-H2 purification systems are required to produce high-purity hydrogen for industrial applications, such as adsorption for CO2 removal. This study tested the effect of impregnated activated carbon (AC) and feed gas flow rate on CO2 adsorption performance. Different types of adsorbents were synthesized by impregnating the chemical on AC, such as potassium iodide, potassium hydroxide, copper (II) sulfate, sodium carbonate, and zinc acetate. The feed gas flow rate was varied in the range of 0.25–1.0 L min−1 by using synthetic bio-H2 gas, that is, mixing the gas with 50 vol.% H2 and 50 vol.% CO2. The CO2 adsorption performances of the synthesized adsorbents were evaluated in terms of breakthrough time and adsorption capacity. To evaluate the reusability of the adsorbents, adsorption–desorption cycles were conducted for several times. For desorption, atmospheric air was used to remove the adsorbed CO2 from the adsorbents. The effect of air flow rate on CO2 desorption was assessed by setting the air flow rate to be between 100 and 350 L min−1. The impregnated AC with zinc acetate displayed the highest adsorption capacity of 63.61 mg CO2/g adsorbent and the longest breakthrough time of 25.7 min. The optimum feed gas flow rate was 0.25 L min−1, thereby demonstrating that the lowest feed gas flow rate resulted in the highest adsorption capacity. Moreover, desorption was faster at higher air flow rates.

Development of a Novel Micro Photoionization Detector for Rapid Volatile Organic Compounds Measurement.

The simulation of the gas flow field and electrostatic field in the photoionization detector by COMSOL was conducted based on principle investigation in the present study. Under the guidance of simulation results, structural optimization was carried out to significantly reduce the dead volume of the ionization chamber, and finally, the relationship between offset voltage and collection efficiency was obtained which led to a remarkable increase in the collection efficiency of charged ions in the photoionization detector. Then an ionization chamber with low interference and fast response was developed. Then experiment was performed with toluene as a VOCs gas under the condition of optimal gas flow rate of 50 ml, UV lamp ionization energy of 10.86 eV. The results showed that the ion collection efficiency reached 91% at a bias voltage of 150 V. Moreover, a preferred linearity of 99.99% was obtained, and a ppb level of LOD can be achieved. The determination results well-fitted the relationship between offset voltage and the response value obtained in the simulation.

Experimental Investigation and Numerical analysis of SO2 Removal Using Polypropylene Membrane Contactor

In this study, polypropylene membrane contactor is designed for SO2 absorption of simulated flue gas. Water and the aqueous solution of Na2SO3 are used as an absorbent. Absorption performance of the longitudinal module is compared to novel transversal membrane contactor module. The result shows that the transversal configuration of hollow fiber module significantly enhances absorption performance over conventional longitudinal configuration. Absorption flux of SO2 in aqueous Na2SO2 is 1.8 times higher than water at optimum Na2SO3 concentration and gas flow rate. According to performance stability test, polypropylene hollow fiber membrane is successfully operated for 15 hours maintaining average absorption flux of 20 x 10−5 mol.m−2.s−1. Numerical simulation shows good agreement with physical absorption data.

Transversal Submerged Membrane Contactor for Simultaneous Absorption and Desorption of CO2 During Natural Gas Sweetening Process

In this work, a unique transversal submerged membrane contactor is used for CO2 removal. The developed configuration is aimed to provide the possibility to perform simultaneous absorption and desorption of carbon dioxide in a single module. In addition, this configuration is expected to reduce the solvent circulation which is the major obstacle encountered in separated absorption-desorption unit. The module contains a number of polypropylene hollow fiber membranes arranged perpendicularly to the longitudinal axis in which the fibers are submerged into a solvent. Pure water which is placed in the shell of the module is used as the solvent. The effects of operating parameters such as gas flow rate (40-80 ml/min) and operating time on membrane performance are investigated. In addition, the simultaneous absorption-desorption process is compared to the separated ones. Results revealed that CO2 removal is significantly affected by the gas flow rate. The optimum gas flow rate is 60 ml/min (vacuum pressure of 60.5 kPa) with >80% CO2 absorption and desorption efficiencies. During a long-term operation, the separation efficiencies are decreased after 200 minutes of operation which may be associated with membrane wetting phenomenon. The simultaneous absorption-desorption process shows a higher separation efficiency rather than the separated process.

Investigation on the Fluid Flow and Decarburization Process in the RH Process

In the current study, mathematical models were developed to predict the fluid flow and motion of gas bubbles in the RH degasser. The multiphase model volume of fluid was employed to simulate the free surface in the vacuum chamber, while injected argon bubbles were treated as discrete-phase particles and tracked using the discrete-phase model. The expansion of argon bubbles was considered. The variation of the liquid level in the vacuum chamber and the effect of the number of nozzles on the recirculation rate were discussed in detail. The optimal number of nozzles was 6. Furthermore, the decarburization process was simulated by considering three reaction sites: the free surface, inner sites of the liquid steel in the vacuum chamber, and the bubble surface. The carbon contents predicted by the decarburization model were well validated by the measured results in the literature. The effect of the gas flow rate on the decarburization process was also investigated. With the increasing gas flow rate, the carbon content gradually decreased, and then reached the steady state. The optimal gas flow rate was 2400 L/min, which was explained by the comparison of the decarburization rate constants. Meanwhile, the decarburization reaction was in a quick decarburization stage for the first 7 minutes, and for the next 13 minutes, the decarburization rate constant rapidly decreased.

Study on the Preparation of Plasma-Modified Fly Ash Catalyst and Its De⁻NOX Mechanism.

Fly ash and bentonite were mixed in a certain proportion as raw materials to prepare a denitration catalyst. In previous studies, it has been concluded that fly ash-type catalysts can provide significant catalytic activity for denitrification after being modified with oxygen. In this study, the effect of plasma conditions on the denitration performance of the catalyst was investigated from the aspects of plasma modification power, modification time, and the flow rate of the gas. Boehm titration and infrared analysis systems were used to characterize the performance of the catalyst. The experimental results show that the optimal modification power is 60 W, the optimal modification time is 20 min, and the optimal gas flow rate is 40 mL/min.

CO2 conversion in non-thermal plasma and plasma/g-C3N4 catalyst hybrid processes

Carbon dioxide conversion at atmosphere pressure and low temperature has been studied in a cylindrical dielectric barrier discharge (DBD) reactor. Pure CO2 feed flows to the discharge zone and typical filamentary discharges were obtained in each half-cycle of the applied voltage. The gas temperature increased with discharge time and discharge power, which was found to affect the CO2 decomposition deeply. As the DBD reactor was cooled to ambient temperature, both the conversion of CO2 and the CO yield were enhanced. Especially the energy efficiencies changed slightly with the increase of discharge power and were much higher in cooling condition comparing to those without cooling. At a discharge power of 40 W, the energy efficiency under cooling condition was approximately six times more than that without cooling. Gas flow rate was observed to affect CO2 conversion and 0.1 L min−1 was obtained as optimum gas flow rate under cooling condition. In addition, the CO2 conversion rate in plasma/g-C3N4 catalyst hybrid system was twice times as that in plasma-alone system. In case of cooling, the existence of g-C3N4 catalyst contributed to a 47% increase of CO2 conversion compared to the sole plasma process. The maximum energy-efficiency with g-C3N4 was 0.26 mmol kJ−1 at 20 W, which increased by 157% compared to that without g-C3N4. The synergistic effect of DBD plasma with g-C3N4 on pure CO2 conversion was verified.

Composite CVOCs Removal in a Combined System of Nonthermal Plasma and a Biotrickling Filter

A coupling system of nonthermal plasma and a biotrickling filter was used to remove a gas mixture of chlorobenzene (CB) and dichloromethane (DCE). The effects of inlet gas concentration and gas flow rate on the removal of the target pollutants in the coupling system were investigated at the frequency of 10000 Hz and specific input energy (SIE) of 6111 J·L-1. Furthermore, the advantages of the plasma-bio-coupled system were revealed by analyzing the relationship between the degradation products and SIE, biomass, or biodiversity in the biotrickling filter. The results showed that when the SIE and gas flow rate were constant, increasing the initial concentration would decrease the removal efficiency of the mixed gas. The optimal appropriate gas flow rate was 0.71 L·min-1 when considering the cost. The CO2 production amount, CO2 selectivity, and chloride ion concentration increased with the increase of SIE when both the CB and DCE concentrations were 500 mg·m-3 and the gas flow rate was 0.71 L·min-1. The protein content of the biofilter column gradually increased as the reactor operation progressed, and the biomass of the lower layer was higher than that of the upper layer. The high-throughput sequencing analysis showed that the biological community in the biotrickling filter keeped rich and diversified.

Effect of direct air injection through anode in plasma electrolysis process for batik dye wastewater treatment

Plasma electrolysis has been proved have much higher effectivity in degrading complex pollutant contained in batik dye wastewater. This study aims to investigate the effect of gas bubbles with air injection of plasma electrolysis in decolorization process. A new method to form bubbles using injection of air directly through anode with a tiny hole of glass tube is proposed. This research work presents the effects of gas injection rates on various phenomena such as electrical power of discharge pulses, concentration of OH radicals, and the decolorization percentage of remazol red as the dye waste in a batch reactor system. Experimental results showed that direct injection of air through anode can reduce the required energy for plasma generation significantly compared to non gas injection. Energy consumption for discharge plasma was observed lowered at higher rates of gas injected. Optimum gas flow rate at different voltage has been evaluated based on the physical and chemical characteristics of plasma. At higher required energy due to higher operation voltage used, the required gas injection rate to effectively degrade the waste was found higher.

Gas–liquid mass transfer and flow phenomena in the Peirce–Smith converter: a water model study

A water model with a geometric similarity ratio of 1:5 was developed to investigate the gas-liquid mass transfer and flow characteristics in a Peirce-Smith converter. A gas mixture of CO2 and Ar was injected into a NaOH solution bath. The flow field, volumetric mass transfer coefficient per unit volume (Ak/V; where A is the contact area between phases, V is the volume, and k is the mass transfer coefficient), and gas utilization ratio (eta) were then measured at different gas flow rates and blow angles. The results showed that the flow field could be divided into five regions, i.e., injection, strong loop, weak loop, splashing, and dead zone. Whereas the Ak/V of the bath increased and then decreased with increasing gas flow rate, and eta steadily increased. When the converter was rotated clockwise, both Ak/V and eta increased. However, the flow condition deteriorated when the gas flow rate and blow angle were drastically increased. Therefore, these parameters must be controlled to optimal conditions. In the proposed model, the optimal gas flow rate and blow angle were 7.5 m(3)center dot h(-1) and 10A degrees, respectively.

Experimental investigation of salmon blends and sesame wood chips as alternative fuel

ABSTRACTThe present investigation elaborates on the exhaust emission and diesel fuel savings from a multicylinder diesel engine operated in dual fuel mode utilizing salmon biodiesel and sesame wood generated producer gas at different loads (0, 2, 4, 6, 8, and 10 kW) under an optimum producer gas flow rate of 19.72 kg/h. The results of this investigation depicted that both nitric oxide and smoke emission were reduced, while carbon monoxide, carbon dioxide, and hydrocarbon emission increased for dual mode in contrast to single fuel operating mode. Increase in biodiesel blend percentage shows a reducing curve for all the emission parameters in comparison to diesel fuel for all test conditions in dual fuel mode. Therefore, for optimum producer gas flow rate of 19.72 kg/h, it might be inferred that sesame generated producer gas with salmon biodiesel may be able to substitute for the conventional diesel for reducing greenhouse emission without much engine modification.

Influence of Inorganic Matter in Biomass on the Catalytic Production of Aromatics and Olefins in a Fluidized-Bed Reactor

Catalytic fast pyrolysis (CFP) conversions of sugarcane bagasse (pretreated and untreated, or “raw”) over HZSM-5 zeolite catalyst were conducted in a fluidized-bed reactor to compare the hydrocarbons yields and selectivities of pretreated and raw biomass materials in order to determine the effect of inorganic matter on the aromatics and olefins yields. The effects of reaction temperature and sweeping gas flow rate (SGFR) on aromatics and olefins yields and selectivities were studied. The results showed that a maximum aromatics yield of 12.41% carbon was obtained during CFP of pretreated sugarcane bagasse at an optimum gas flow rate of 2.5 L min–1 and temperature of 500 °C. The highest olefins yield was 10.89% carbon under the same CFP conditions. Benzene and ethylene were the dominant compounds in the aromatics and olefins, respectively. The highest selectivities to benzene and ethylene were 46.44% and 45.45% carbon, respectively. Slightly lower aromatics and olefins yields of 11.77% and 9.9%, respectively, were obtained from CFP of untreated biomass. In the final step, the yields of aromatics and olefins for the raw and treated sugarcane bagasse were compared, and in addition the yields and selectivities at optimum conditions were compared. The results suggest that inorganic matter has an inhibiting effect on hydrocarbons production and also causes catalyst deactivation by blocking the catalyst pores. It is evident that removal of inorganic matter would increase both liquid and hydrocarbons yields during CFP over HZSM-5. Hydrocarbons yields and selectivities were found to depend not only on temperature and SGFR but also on the severity of the treatment process.

Effect of hydrogen gas addition on combustion characteristics of pulverized coal

A promising approach to decrease CO2 emissions from blast furnaces during ironmaking is to blow a reducing gas containing hydrogen into blast furnaces from their tuyeres. However, the combustion behavior of pulverized coal in the presence of a hydrogen-containing gas has not been elucidated. In this work, the combustion experiments of pulverized coal using a drop tube furnace were carried out to investigate the effect of H2 gas addition on the combustibility of pulverized coal. The combustion ratio of char particles in the presence of H2 gas (when introduced at a flow rate of 0.10L/min) was larger than that in the absence of H2 gas. This is because of the enhanced release of volatile matter from coal and the combustion of char due to an increase in the temperature of the coal particles, which was caused by the drastic combustion of H2 gas. The combustion ratio of char particles when H2 gas was added at flow rates higher than 0.21L/min was considerably smaller than that obtained when H2 gas was not added. It was found that the combustibility of coal was enhanced when an optimum H2 gas flow rate was used.

Well performance optimization for gas lift operation in a heterogeneous reservoir by fine zonation and different well type integration

In this study, an integrated optimization procedure was proposed for well performance analysis in a heterogeneous oil field from southwest Iran. Proposed integrated strategy optimizes well performance in an iterative manner, while fluid properties, geological and petrophysical data were analyzed separately by new advanced methods. Subsequently, integrated solution was introduced by integrating various well types geometry and fine zonation of the target formation. Combination between each zone and each well type was based on three potential oil bearing zones predefined by well log data analysis. Target formation, the Sarvak formation limestone, was divided into 10 different zones and much more subzones according to the geological and petrophysical data. Afterwards, 17 wells with various geometries were modeled in the upscaled reservoir model. Fluid properties and reservoir characteristics were also obtained and analyzed from different samples taken from target formation. Results of applying the proposed integration strategy defined that the maximum production rate occurs while water cut does not exceed 10%. Performed analysis also suggest 15 MPa as the optimal value of the surface gas lift pressure and state that the gas oil ratio should not exceed this ratio at the flowing wells bottom condition. Sensitivity analysis on tube size expresses 4.67-inches tube as the optimum value. Meanwhile, sensitivity analysis on flow rate represents that optimal value of this parameter shows high sensitivity to changes in production index. Results showed that 7% change in production index will make 4% changes in optimal gas flow rate value.

Conversion of carbon dioxide to carbon monoxide by pulse dielectric barrier discharge plasma

The conversion of carbon dioxide (CO2) to carbon monoxide (CO) was investigated in a non-thermal plasma dielectric barrier discharge (DBD) reactor, and the effects of different process conditions on the CO2 conversion were investigated. The results showed that the increase of input power could optimize the conversion of CO2 to CO. The CO2 conversion and CO yield were negatively correlated with the gas flow rate, but there was an optimum gas flow rate, that made the CO selectivity best. The carrier gas (N2, Ar) was conducive to the conversion of CO2, and the effect of N2 as carrier gas was better than Ar. The conversion of CO2 to CO was enhanced by addition of the catalyst (5A molecular sieve).

Effect of Gas Flowrate on Nucleation Mechanism of MWCNTs for a Compound Catalyst

Activation of the catalyst particles during a CVD process can be anticipated from the carbon feeding rate. In this study, Fe2O3/Al2O3 catalyst was synthesized with uniformly dispersed iron over alumina support for onward production of multiwalled carbon nanotubes (MWCNTs) in a fluidized bed chemical CVD reactor. The effect of the ethylene flowrate on catalytic activity of the compound catalyst and morphology of the as-grown MWCNTs was also investigated in this study. The dispersed active phases of the catalyst and optimized gas flowrate helped in improving the tube morphology and prevented the aggregation of the as-grown MWCNTs. The flowrates, below 100 sccm, did not provide sufficient reactants to interact with the catalyst for production of defect-free CNT structures. Above 100 sccm, concentration of the carbon precursor did not show notable influence on decomposition rate of the gas molecules. The most promising results on growth and structural properties of MWCNTs were gained at ethylene flowrate of 100 sccm. At this flowrate, the ratio of G and D intensity peaks (IG/ID) was deliberated about 1.40, which indicates the growth of graphitic structures of MWCNTs.

Role of the carrier gas flow rate in monolayer MoS2 growth by modified chemical vapor deposition

Monolayer molybdenum disulfide (MoS2) has attracted much attention because of the variety of potential applications. However, its controlled growth is still a great challenge. Here, we report a modified chemical vapor deposition method to grow monolayer MoS2. We observed that the quality of the MoS2 crystals could be greatly improved by tuning the carrier gas flow rate during the heating stage. This subtle modification prevents the uncontrollable reaction between the precursors, a critical factor for the growth of high-quality monolayer MoS2. Based on an optimized gas flow rate, the MoS2 coverage and flake size can be controlled by adjusting the growth time.

Effect of snorkel shape on the fluid flow during RH degassing process: mathematical modelling

A mathematical model was developed to investigate the effect of snorkel shape on the recirculation rate and the erosion of the lining refractory during RH degassing process. A particle image velocimetry technique was used to measure the velocity distribution in a water modelling experiment. The calculated results were well validated with the measured ones. In the mathematical model, the interfaces between the molten steel and the gas phase, and the motion of argon bubbles were simulated and tracked using VOF + DPM model by which the argon bubbles were treated as the discrete phase in the molten steel and the top gas phase, and the top gas phase was treated as a second continuous phase. It was found that the recirculation rate of the molten steel with oval snorkels was significantly larger than that with round snorkels. For round snorkels, the optimum gas flow rate was 1800 L min−1 and it was 2800 L min−1 for oval snorkels. Furthermore, the volume distribution of the argon in the radial direction of the up-snorkel with oval snorkels was much more homogeneous than that with round snorkels. Meanwhile, the predicted maximum wall shear stress showed that the bottom and the sidewall of the ladle with round snorkels were more seriously eroded than that with oval snorkels. Therefore, the oval snorkel was beneficial to improve the service life of the RH degasser.