Type Of Carrier Gas Research Articles

Heat release performance and evolution of CaO particles under fluidization for CaO/Ca(OH)2 thermochemical heat storage

The fluidized bed reactor has been recognized for large-scale CaO/Ca(OH)2 heat storage system. In this work, the effects of critical factors such as particle size, fluidization number, steam concentration in hydration, initial temperature, cycle number and type of carrier gas on heat release performance of CaO in the fluidized bed reactor were experimentally investigated. CaO under fluidization state exhibits excellent cyclic stability on the heat release performance. The decay in heat release temperature of CaO under fluidization state is less 10% of that under static state. With increasing the cycle number, the heat release temperature of CaO using N2 as carrier gas decreases because of the rapid expansion of particles. After 20 cycles with N2 as carrier gas, the average particle size of CaO increases by 46.2% and the hydration conversion of CaO reaches above 95%. The hydration conversion of CaO experienced 20 cycles using air as carrier gas is 20% lower than that using N2 as carrier gas due to the presence of CO2 in air. The experimental investigation of CaO/Ca(OH)2 heat storage provides an important reference for the development of CaO/Ca(OH)2 system using the fluidized bed reactor.

Pyrolysis of Ligustrum vulgare waste and the effects of various operating parameters on bio-oil upgrading

In this work, the pyrolysis of biomass obtained from Ligustrum vulgare (LV) waste is examined with a focus on the yield and quality of the produced bio-oil. Effects of different operating parameters of the time and pyrolysis temperature, type and flow rate of carrier gas, and the use of different catalysts on the yield and composition of the produced bio-oil were studied. The TG analyses show that in pyrolysis temperature range of 200 to 600°C about 75 wt% of the LV waste decreased and converted to liquid or gas products. The produced bio-oil was characterized by FTIR, GC, and GC-MS analyses. Total 55 compounds were identified in the produced bio-oils by GC-MS analysis. The main components of the produced bio-oils are acetic acid (16%), 2-propanon 1-hydroxy (16%), formic acid (15.5%), ethanol (6%), 1-propen-2-Ol (6%), and phenol (5.22%). The maximum yield of produced bio-oil is about 30 wt% which obtained in pyrolysis temperature of 500°C, 120-min pyrolysis time, N2 carrier gas with flow rate of 60 ml/min, and use of CaO as the catalyst.

Effect of in-flight particle behavior on the morphology of flame sprayed Er2O3 splats

The morphology and microstructure of splats impact the comprehensive capability of a new coating methodology called chelate flame spraying (CFS). This study addresses the quantitative characterization of the spread morphologies of flame sprayed Er2O3 splats directly deposited under different spray conditions on aluminum alloy substrates with a mirror finish. The influence of the in-flight particle temperature and velocity, carrier gas type, and carrier gas ratio on the solidification mechanism of molten droplets was investigated. Image analysis methods were employed to identify single splats from the morphology observed with field-emission scanning electron microscopy (FE-SEM). In addition, Er2O3 films were synthesized on an Al–Mg alloy (A5052) substrate using N2 or O2 as the carrier gas. When O2 was used as the carrier gas, 109-μm-thick films were deposited on the A5052 substrate. The cross-sectional porosity of the films was 3.8%. In contrast, films with 101-μm thickness were synthesized on the A5052 substrate when N2 was used as the carrier gas. The cross-sectional porosity of these films was 13.8%. The results showed that the carrier gas type (N2) and carrier gas ratio had a significant effect on the flattening behavior of the molten droplets. A spraying method combined with multidimensional modes is proposed to control the morphology of the splats.

Effects of carrier gas on the properties of soot produced by ethylene pyrolysis

Herein, we investigate the mechanism of soot formation produced by controlled-temperature pyrolysis of ethylene in Ar, He, or N2 and analyze the size distributions of soot particles to understand soot aggregation and nucleation behavior. Additionally, we probe the reactivity of soot, revealing that soot particles were highly unlikely to react with molecules of the above carrier gases. The use of Ar is demonstrated to promote soot production, facilitate crystalline growth, and increase the diameter of primary soot particles, while the use of He has an opposite effect, which is ascribed to the large size of the former molecules and the small size of the latter ones. Consequently, the soot generation mechanism is found to be affected by carrier gas type.

Study of silicon nitride deposition in III-N MOVPE reactors

Si3N4 deposition from silane and ammonia in a number of III-N MOVPE reactors of various sizes was studied in a wide range of reactor conditions. It was revealed that Si3N4 deposition rate depends on temperature, pressure, carrier gas type, and ammonia concentration. Deposition rate rises with temperature up to 1050–1100 °C in a manner typical for temperature-activated processes, but under any studied conditions, including the 800–850 °C range, it is strictly linear with SiH4 concentration indicating the absence of high-order parasitic reactions at high temperature and surface passivation at low temperature. For a low-volume reactor the higher the pressure is, the faster the deposition is both for N2 and H2 carrier gases. For large reactors the dependence is non-monotonic. At temperature above 900 °C using H2 as a carrier gas results in a higher Si3N4 deposition rate than when using N2. If nitrogen is used as a carrier gas, deposition rate gradually rises with ammonia concentration. If hydrogen is used, deposition rate rapidly rises with ammonia concentration and then gradually falls. If hydrogen-nitrogen mixture is used as a carrier gas, deposition rate changes in a linear manner with the mole fraction of hydrogen in the carrier gas.

Microwave energy inductive fluidized metal particles discharge behavior and its potential utilization in reaction intensification

Microwave-induced metal discharge (MMD) technology offers a novel methodology for efficient gas-phase catalytic reaction due to its unique heating effect, plasma effect and discharge effect. Herein, we successfully used a special kind of uniformly distributed particles with synergistic microwave-induced fluidized-metal discharge (MFD) effect. A lab-scale atmospheric quartz tube fluidized bed reactor was designed. Apparatus like high-speed camera, fiber spectrometer and infrared thermometer were used to record the discharge phenomena. The effects of operating conditions such as gas velocity, microwave power, carrier gas type, and metal type on the discharge behavior were investigated in detail. Subsequently, the MFD was applied into the methane dry reform reaction (MDR) with excellent conversion compared with the conventional heating conditions. Gratifyingly, the metal particles can both be the converter of microwave and the catalyst of the reaction. The reported conclusion provides a novel way to intensification the reaction process and utilize microwave energy.

On the Influences of Carrier Gas Type and Flow Rate on CVD Synthesis of CNTs from Postconsumer Polyethylene

Multiwall carbon nanotubes (MWCNTs) were generated from recycled low-density polyethylene (LDPE). The polymer was pyrolyzed at 800 °C in inert atmospheres, and the gaseous pyrolyzates—light hydroca...

Distinctive Features of Graphene Synthesized in a Plasma Jet Created by a DC Plasma Torch.

Synthesis of graphene materials in a plasma stream from an up to 40 kW direct current (DC) plasma torch is investigated. These materials are created by means of the conversion of hydrocarbons under the pressure 350–710 Torr without using catalysts, without additional processes of inter-substrate transfer and the elimination of impurities. Helium and argon are used as plasma-forming gas, propane, butane, methane, and acetylene are used as carbon precursors. Electron microscopy and Raman imaging show that synthesis products represent an assembly of flakes varying in the thickness and the level of deformity. An occurrence of hydrogen in the graphene flakes is discovered by X-ray photoelectron spectroscopy, thermal analysis, and express-gravimetry. Its quantity depends on the type of carrier gas. Quasi-one-dimensional approach under the local thermodynamic equilibrium was used to investigate the evolution of the composition of helium and argon plasma jets with hydrocarbon addition. Hydrogen atoms appear in the hydrogen-rich argon jet under higher temperature. This shows that solid particles live longer in the hydrogen-rich environment compared with the helium case providing some enlargement of graphene with less hydrogen in its structure. In conclusion, graphene in flakes appears because of the volumetric synthesis in the hydrogen environment. The most promising directions of the practical use of graphеne flakes are apparently related to structural ceramics.

Remediation of pyrene contaminated soil by double dielectric barrier discharge plasma technology: Performance optimization and evaluation

Polycyclic aromatic hydrocarbons (PAHs) in soil are not only detrimental to environment but also to human health. Double dielectric barrier discharge (DDBD) plasma reactor used for the remediation of pyrene contaminated soil was studied. The performance of DDBD reactor was optimized with influential parameters including applied voltage, type of carrier gas, air feeding rate as well as pyrene initial concentration. The analysis of variance (ANOVA) results showed that input energy had a great effect on pyrene remediation efficiency followed by pyrene initial concentration, while, the effect of air feeding rate was insignificant. More specifically, the remediation efficiency of pyrene under air, nitrogen and argon as carrier gas were approximately 79.7, 40.7 and 38.2% respectively. Pyrene remediation efficiency is favored at high level of applied voltages and low level of pyrene initial concentration (10 mgkg−1) and air feeding rate (0.85 L/min). Moreover, computation of the energy efficiency of the DDBD system disclosed that an optimal applied voltage (35.8 kV) and higher initial pyrene concentration (200 mgkg−1) favored the high energy efficiency. A regression model predicting pyrene remediation under DDBD plasma condition was developed using the data from a face-centered central composite design (FCCD) experiment. Finally, the residual toxicity analysis depicted that the respiratory activity increased more than 21 times (from 0.04 to 0.849 mg O2 g−1) with a pyrene remediation efficiency of 81.1%. The study demonstrated the DDBD plasma technology is a promising method not only for high efficiency of pyrene remediation, but also recovering biological function without changing the physical-chemical properties of soil.

(Ga,In)N/GaN light emitting diodes with a tunnel junction and a rough n-contact layer grown by metalorganic chemical vapor deposition

Tunnel junctions (TJs) are envisaged as potential solutions to improve the electrical injection efficiency of nitride emitters in the visible as well as in the UV range. Indeed TJs would solve the issues related to the poor contact with the top p type nitride layer, replacing it by an n type one. But if metal-organic chemical vapor deposition (MOCVD) is chosen to grow the n side of the TJ on a LED, one faces the problem of a potential re-passivation by hydrogen of the underlying p type layer. We propose a TJ epitaxial process whereby low growth temperatures, high growth rates and the type of carrier gas will minimize hydrogen incorporation in the underlying layers. In this view, n++/p++ GaN TJs with and without an (Ga,In)N intermediate layer are grown by MOCVD at varying temperatures (800°C and 1080°C), using N2 as a carrier gas under a very high growth rate of 2.5μm/h on top of blue (Ga,In)N/GaN LEDs. The LEDs made under N2 carrier gas and lower temperature growth conditions are operational without the need for further thermal activation of the Mg acceptors. The light emission intensity from the top surface of the TJ-LEDs is improved compared to the reference LED without TJ: besides the more efficient carrier injection this is also attributable to the larger photon extraction efficiency because of the rough surface of the low temperature grown n-GaN contact layer of the TJ-LEDs.

Decomposition of high concentration benzene (produced in paper and painting industries) and its byproducts, methane and carbon dioxide, using plate gliding arc.

High concentration benzene production in paper and painting industries is a restrictive problem in production line of companies. In this study, removal of high concentrated benzene produced in painting companies was investigated using a Plate Gliding Arc (PGA) reactor. Decomposition of methane and carbon dioxide as the most predominate byproducts of benzene decomposition was also studied using (PGA) reactor. The effect of several parameters such as input power, feed gas flow rate, type of carrier gas, and [CH4/CO2] flow ratio was studied by two series of experiments. The results show significant conversion (>70%) of high concentration benzene (74000ppm) without using any catalyst. Selectivity of CO2 and CO was 88% and 10% respectively showing complete oxidation of benzene. The maximum conversion of CH4 and CO2 reached 52% and 69%, respectively by using optimum ratio of 3:4. The main results of this study proved removal of high concentration benzene using a low-energy-density reactor. Furthermore, an optimum value for efficient conversion of methane and carbon dioxide was achieved and the energy density of the PGA reactor was evaluated, which shows a good promise for industrial applications.

GaN quality evolution according to carrier gas for the nucleation layer and buffer layer

The effect of the carrier gas type on the crystal quality of GaN is investigated in detail. Compared with a single carrier gas (H2 or N2), the employment of N2 during the nucleation layer and H2 in the high temperature buffer layer growth process will lead to smoother surface, stronger photoluminescence spectral strength, and lower threading dislocation density. Furthermore, it is found that conical and snowflake-like protrusions appear on the surface for the sample under pure N2 atmosphere.

Adsorption capacity of phenanthrene and pyrene to engineered carbon-based adsorbents produced from sewage sludge or sewage sludge-biomass mixture in various gaseous conditions

Adsorption of phenanthrene (PHE) and pyrene (PYR) by engineered carbon-based adsorbents produced from sewage sludge in an atmosphere of nitrogen (N2) or carbon dioxide (CO2) at temperatures of 500, 600, and 700 °C was investigated. The addition of willow to the SSL decreased the biochar adsorption capacity. However, there was an increase in the adsorption capacity after changing N2 to CO2. The addition of willow to SSL and the type of carrier gas affected the mechanism of adsorption. The adsorption of PHE and PYR on the SSL-derived adsorbents produced in N2 occurred through pore filling. The adsorption on the SSL-derived adsorbents with willow followed the mechanism of π-π electron-donor-acceptor (EDA) interactions and hydrophobic interactions. A similar mechanism was observed with regard to the biochars produced from SSL in atmosphere of CO2. For the SSL-derived adsorbents with willow in CO2, the adsorption mechanism was observed to vary between PHE and PYR.

Production and functionalization of carbon nanotubes for application in membrane synthesis for natural gas separation

Abstract In this study, carbon nanotubes (CNTs) were produced using catalyst-assisted chemical vapour deposition method. Ferrocene was used as the catalyst. Effects of carbon sources (acetylene and methane) and production conditions (temperature and type of carrier gas) on the quality of as-produced CNTs were investigated using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), electronic precision balance (EPB) and raman spectroscopy. The best of as-produced CNTs was purified and functionalized using carboxylation protocol. The surface chemistry, thermal stability, textural property and crystallinity of functionalized CNTs (FCNTs) were obtained using Fourier transform infrared spectroscopy (FTIR), Thermo-gravimetric analysis (TGA), N2 physisorption at 77 K and X-ray diffraction (XRD), respectively. CNT produced from methane and argon at 900 °C has the best quality with ID/IG ratio of 0.17 while the CNT produced from acetylene and mixture of argon and hydrogen at 1000 °C has the highest yield of 1.78 mg/s. FTIR confirms successful functionalization of CNTs. The degree of functionalization obtained from TGA is consistent with that of EPB. N2 physisorption at 77 bK indicates increase in pore volume and average pore size of the FCNTs indicating more adsorption sites for the adsorbate. Thereby suggesting that FCNT could be a good filler in membrane synthesis for gas separation.

Application of different carrying gases and ratio between sewage sludge and willow for engineered (smart) biochar production

We investigated the physicochemical properties of biochar produced at 500, 600, and 700 °C from sewage sludge (SSL) and SSL with willow (8:2 and 6:4, w/w). The effect of carrier gas type (N2 or CO2) on the biochars properties was examined. The pH, electrical conductivity (EC), specific surface area (SBET), elemental composition (CHNO), and mineral composition (XRD), as well as functional groups (FT-IR/PAS) were identified and determined.Replace the N2 by CO2 as carrier gas influenced the properties of the all produced biochars. CO2 had an effect on reducing the process efficiency as well as pH and EC in the SSL-derived biochars. Changes in the elemental composition (H and O content) were also noted after change of carrier gases. In the biochars obtained in a CO2, a negative correlation was found between EC and pyrolysis temperature. In the biochars produced from SSL and willow, apart from similar changes to those observed for the biochars made from SSL in the presence of CO2, changes in the surface properties were additionally noted. The biochar obtained in a CO2 atmosphere had higher SBET values (from 19 to 47%) than the respective biochars produced in an N2 atmosphere.

Simulation of the multi-component process gas flow for the explanation of oxidation during laser cladding

Usually the process gas flow rates and the process gas types are not regarded as the primary process parameters of the laser cladding process. Herein it is shown, how the melt pool surface oxidation can be significantly reduced by the change of the carrier gas type, by a reduced carrier gas flow rate and by minor changes in the powder nozzle design. However, the absorptivity may decrease concurrently by up to 15%. A simulation model for the gas flow and the powder particle flow between the powder nozzle and the melt pool surface has been developed, which reveals the volume percentage of different gas types and so the quality of the shield gas atmosphere. Additionally, the powder particle distribution and the attenuation of the laser beam by the powder particles can be simulated. The simulation results are confirmed by experimental measurements of the powder particle density distribution in the working plane, by measurements of the oxygen volume percentage at the workpiece surface, by high-speed camera images of the melt pool surface and by absorptivity measurements, which show the effect of oxidation on the process.

КОМПЛЕКСНАЯ ДЕСУЛЬФУРАЦИЯ И ДЕГАЗАЦИЯ ЧУГУНА МАГНИЕМ

The aim of the work is a theoretical and experimental study of the behavior of oxygen, hydrogen and nitrogen in iron during desulfurization with its granulated magnesium. A computational and analytical assessment of the formation and floating of gas bubbles during the introduction of dispersed magnesium into a metal melt in an argon jet is performed. It has been established by calculation that when dispersed magnesium is introduced into the cast iron in an argon jet, through a lance with a nozzle diameter of 7 mm to a depth of 3 m, argon bubbles with a diameter of 25 mm are formed. The thermodynamic probability of the processes of interaction of magnesium with oxygen, nitrogen and hydrogen during desulfurization of cast iron has been established. It has been established that the processes of desulfurization and deoxidation of iron occur throughout the entire range of pressures under study, and the formation of magnesium nitride is possible only with an excess pressure in the gas-metal system at a depth of molten iron more than 1.4 meters. Experiments in industrial conditions revealed the features of the removal of oxygen, nitrogen and hydrogen from cast iron during desulfurization of the melt with dispersed magnesium in a stream of various carrier gases. It was established experimentally that the type of carrier gas has a decisive influence on the by-pass degassing of the iron during its desulfurization by injecting granular magnesium. When using nitrogen or argon as a carrier gas, the hydrogen content in cast iron is reduced by 50-70%.

Determination of Water Evaporation Rates in Gas Diffusion Layers of Fuel Cells

The efficiency of polymer electrolyte fuel cells is closely linked to effective heat and water management. Evaporation of water in the gas diffusion layers (GDL) is an important process influencing water management and can even be used for evaporative cooling. In this study, evaporation rates in Toray-GDL materials are obtained for different temperatures, gas flow rates, carrier gases and water saturation levels. Evaporation rates are correlated with water distribution profiles in the GDL, obtained using X-ray tomographic microscopy imaging. The influence of temperature on the evaporation rates is predicted by considering the effect of temperature on vapor diffusion alone. However, changing the carrier gas type points to a deviation from diffusive-driven vapor transport, which could be due to entrainment of gas inside the GDL, among other factors.

Effect of catalyst contact mode and gas atmosphere during catalytic pyrolysis of waste plastics

In the present study, polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET) were pyrolyzed using HZSM-5 zeolite in a tandem micro-pyrolyzer to investigate the effects of plastic type, catalyst and feedstock contact mode, as well as the type of carrier gas on product distribution. Among the four plastics, PS produced highest aromatic yields up to 85% whereas PE and PP mainly produced aliphatic hydrocarbons. In comparison to ex-situ pyrolysis, in-situ pyrolysis of the plastics produced more solid residue but also promoted the formation of aromatic hydrocarbons, except PS. For PS, ex-situ pyrolysis produced a higher yield of aromatics than in-situ pyrolysis, mostly contributed by high styrene yield. During in-situ pyrolysis, the catalyst reduced the decomposition temperatures of the plastics in the order of PE, PP, PS and PET from high to low. Hydrogen carrier gas reduced solid residue and also increased the selectivity of single ring aromatics in comparison to inert pyrolysis. Hydrogen was more beneficial to PS and PET than PE and PP in terms of reducing coke yield and increasing hydrocarbon yield. The present study also showed that catalytically co-pyrolyzing PS and PE, or PET and PE increases the yield of aromatics and reduces the yield of solid residue due to hydrogen transfer from PE to PS or PET and alkylation reactions among the plastic-derivatives.

Amine-functionalized titanium metal organic framework for photochemical vapor generation for determination of selenium by inductively coupled plasma optical emission spectrometry

Metal organic framework MIL-125-NH2 was used as a photocatalyst for the photochemical vapor generation to establish an efficient and accurate method for highly sensitive determination of trace selenium by inductively coupled plasma optical emission spectrometry. The mixture of Se (IV) and Se (VI), MIL-125-NH2 nanoparticles and a low molecular weight organic acid was mixed to generate gaseous selenium-containing species which was separated from its liquid phase and transported to inductively coupled plasma optical emission spectrometer for determination. Influencing factors including carrier gas flow rate, type and concentration of catalyst, type and concentration of organic acid, UV irradiation time and power, and sample pH were carefully studied. Under the optimized conditions, a catalytic efficiency of more than 80% was achieved. The limits of detection for Se (IV) and Se (VI) were found to be the same and as low as 0.3ng/mL. The relative standard deviation of Se (IV) and Se (VI) was 2.7% and 2.1% at 20ng/mL (n=11), respectively. The accuracy of the method was evaluated by analysis of natural mineral water and certified reference materials.