Flow Rate Of Mixed Gas Research Articles

Experimental testing and geometric optimization of a domestic cooker burning 80%Natural-Gas+20%Hydrogen

In urban pipelines, blending hydrogen into natural gas has been considered as an effective way of hydrogen usage to reduce carbon emission on household appliances. However, few studies, especially experimental ones are dedicated to address the characteristics of a typical domestic cooker due to the transition from natural gas to 20%hydrogen-enriched natural gas. This study experimentally investigated the changes in terms of the gas flow rate, flame temperature, heat transfer and emission characteristics of a domestic cooker as a result of such transition.Using a self-developed gas blending system, the flow rates of the both the mixed fuel and its components are obtained. The data shows that after blending hydrogen, the mixed gas flow rate becomes higher. Compared to the original cooker burning natural gas, hydrogen blending results in a decreased natural gas flow rate, leading to lower carbon emission. In addition, the thermal input to the cooker is lowered and hydrogen blending leads both the inner and outer combustion zones of the flame to shorten while the flame temperature to increase.As an attempt to optimize the performance of the cooker, the effects of wok stand height on heat transfer efficiency and NO/NOx/CO emissions are examined. It is found that the cooker fueled by 20%hydrogen-enriched natural gas exhibits lower heat transfer efficiency, higher NO/NOx emissions and lower CO emission. According to the fact that the heat transfer efficiency increases at lower wok stand height, the wok stand height is lowered from its original 7 cm–6 cm and 5 cm. The finding indicates that when the wok stand height is moderately decreased to 6 cm, NO/NOx emissions decrease and CO emission is only marginally increased. This study proposes that when natural gas is replaced by 20%hydrogen-enriched natural gas on a swirl flame cooker, the wok stand height can be slightly lowered to exploit the advantages of blended hydrogen combustion.

Optimization for biohydrogen purification process by chemical absorption techniques

Palm oil decanter cake and crude glycerol, which are characterized by their highly biodegradable organic content and nutrient-rich composition, are attractive ingredients for biohydrogen production. In this experiment, we investigated (1) how to produce hydrogen more effectively by co-fermenting palm oil decanter cake and crude glycerol and (2) how to improve the quality of the hydrogen gas produced via chemical absorption technology. This study was divided into two parts. In the first part, the co-fermentation was conducted with a fixed decanter cake concentration of 1% total solids (TS) w/v and variable crude glycerol concentrations (0.25–2.0% w/v). The results showed that maximum biohydrogen production was achieved with 2.0% w/v crude glycerol, which had a hydrogen yield of 131 L kg−1 TSadded and a hydrogen productivity of 1310 mL L−1 d−1. In the second part of the experiment, biohydrogen purification was conducted using the chemical absorption technique by varying four different alkaline solutions: mono ethanolamine (MEA), ammonia (NH3), sodium hydroxide (NaOH), and potassium hydroxide (KOH). The highest hydrogen purity of 98.9% v/v was reached with the MEA solution at a 5 M concentration and a 280 mL min−1 feed mixed gas flow rate for an absorption time of 5 min. However, to achieve sustainable waste management in palm oil mill plants, the feasibility of integrating the biohydrogen production process with palm oil mill effluent from the biogas plants and applying a hydrogen gas quality improvement system need to be investigated further.

Controllable Fabrication of Vertical Graphene with Tunable Growth Nature by Remote Plasma-Enhanced Chemical Vapor Deposition.

As an important member of the graphene family, vertical graphene (VG) has broad applications like field emission, energy storage, and sensors owing to its fascinating physical and chemical properties. Among various fabrication methods for VG, plasma enhanced chemical vapor deposition (PECVD) is most employed because of the fast growth rate at relatively low temperature for the high-quality VG. However, to date, relations between growth manner of VG and growth parameters such as growth temperature, dosage of gaseous carbon source, and electric power to generate plasma are still less known, which in turn hinder the massive production of VG for further applications. In this study, the growth behavior of VG was studied as functions of temperature, plasma power, and gas composition (or chamber pressure). It was found that the growth behavior of VG is sensitive to the growth conditions mentioned above. Although conditions with high growth temperature, large flow rate of mixed gas of methane and carrier gases, and high plasma power may be helpful for the fast growth of VG, brunching of VG is simultaneously enhanced, which in turn decreases the vertical growth nature of VG. High-quality VG can be achieved by optimizing the growth parameters. It was revealed that the vertical growth nature of VG is governed by the electric field at the interfacial layer between VG and the substrate, for which its strength is influenced by the density of plasma. These findings are important for the general understanding of the VG growth and provided a feasible way for the controllable fabrication of VG using the remote PECVD method which is usually believed to be unsuitable for the fabrication of VG.

Preparation and kinetics study of silica adsorbent derived from geothermal waste impregnated with chitosan for gas separation of CO2 and CH4

Gas separation of CO2 from mixed gas has been implemented in several methods, such as adsorption using activated carbon, zeolite, and silica adsorbents. This study aims to investigate the use of silica as an adsorbent by impregnating it with chitosan and using cetyltrimethylammonium bromide (CTAB) as a surfactant. A kinetics analysis was carried out using the modified silica from mixed gas, and the artificial composition of CO2 and CH4 was conducted using a volume ratio of 30:70. The adsorbent was characterized by fourier-transform infrared spectroscopy, scanning electron microscope-energy dispersive X-ray, and Brunauer–Emmett–Teller analysis before and after adsorption. The CO2 adsorption capacity (qt) was obtained at 61.334 mg/g with 60.6% CO2 removal using a mass ratio of CTAB:sodium silicate at 3% w/w, volume ratio of HCl:sodium silicate at 2% v/v, and mixed gas flow rate of 130 mL/min at room temperature and ambient pressure of 25 °C, and 1 atm. The kinetics was observed using a pseudo-first- and second-order model with kf and R2 of 0.1591/min and 0.7339, and 0.0019 g/mg.min and 0.9979, respectively. The results showed that the pseudo-second-order kinetic model represents the CO2 adsorption on chitosan-modified silica adsorbent. However, the rate constant is lower than that of the pseudo-first-order kinetic model.

Underground coal seam gas displacement by injecting nitrogen: Field test and effect prediction

The existing ground well gas injection displacement engineering shows that the technology of displacement by injecting gas is a coal gas stimulation technology with good application effect. Based on the field test of underground nitrogen injection to promote the discharge of coal seam gas in Liuzhuang coal mine, Anhui Province, China, the variation laws of the flow rate of mixed gas, the composition of mixed gas, the pure flow rate of methane in gas producing borehole are analyzed. Meanwhile, the laws of “discharging while injecting” and conventional emission are compared and analyzed. The results show that the injected nitrogen with a higher pressure than the coal seam gas can effectively increase the pressure gradient between the fracture and the gas-producing boundary, improving the mixed flow dynamics inside the coal seam. Compared with the mixed gas flow rate at the end of conventional emissions, the average mixed gas flow rates in each gas producing borehole after injecting nitrogen increase by 2.20 ~ 5.83 times, and the average pure flow rates of CH4 increase by 1.42 ~ 2.66 times. The technology of displacement by injecting nitrogen can significantly promote gas emission from coal seam. Compared to the prediction values of conventional emission in the corresponding gas producing boreholes, the total gas emission increase by 64.9%, 222.5%, 132.3% and 149.1% under the condition of displacement intervention, respectively. The output process of underground coal seam gas displacement by injecting nitrogen can be divided into two stages approximately. In stage I, driven by the pressure gradient, CH4 in the original free state is the main product. While in stage II, the desorbed CH4 from adsorbed state is the main product driven by the concentration gradient. In addition, a back-propagation artificial neural network is applied to the effect prediction of coal seam gas displacement by injecting nitrogen. The root mean square error of gas pure flow rate in each gas producing boreholes is 0.0075, 0.0266, 0.0492 and 0.0379 respectively, which is in good agreement with the actual measured values. It shows that the application of artificial neural network to the prediction of nitrogen injection displacement effect is feasible.

Experimental study on water recovery and SO 2 permeability of ceramic membranes with different pore sizes

In this study, the water recovery performance from flue gas with ceramic membrane tubes of different pore sizes 30, 50, and 200 nm was experimentally studied. The effects of flue gas temperature, flue gas flow rate, water coolant temperature, and water coolant flow rate on the water recovery performance were analyzed. In addition, in the experimental study of SO2 permeability, the pH of the water coolant inlet and outlet was measured using a pH meter to analyze the SO2 permeability of ceramic membranes during the water recovery process. The results show that the water recovery performance of the 50 nm pore size ceramic membrane is better than that of the other two types of ceramic membrane in most cases. The maximum amount of reclaimed water and the highest water recovery rate are 4.82 kg/(m2·h) and 80.3%, respectively. Under the same SO2 concentration condition, the SO2 permeation flux of the 30 nm pore size ceramic membrane is smallest, and that of the 200 nm membrane is the largest. When the SO2/N2 mixed gas flow rate is 6 L/min, the SO2 permeation flux of the 30 and 200 nm membranes is 0.407 and 0.635 mmol/(m2·h), respectively. The ceramic membrane with smaller pore size can block more SO2 permeation, while the ceramic membrane with larger pore size can remove SO2 better.

A Novel CMUT-Based Resonant Biochemical Sensor Using Electrospinning Technology

In this paper, a novel capacitive micromachined ultrasonic transducer (CMUT)-based resonant biochemical sensor is presented to detect SO2 with a sensitive polymer layer functionalized by electrospinning technology. The electrospinning technology is proposed as an innovative functionalization method to fabricate nano reticular polymer fibers with the diameters of 50–500 nm on the movable plates of the CMUTs. The surface topography of electrospun nanofibers and the impedance properties of functionalized CMUTs are characterized. The CMUT-based resonant biochemical sensor is packaged to detect SO2 in the experiments. Its resonant frequency shifts vary against the variation of SO2 concentration. The influences of the mixed gas flow rate are also analyzed. These show that the proposed sensor has good volume sensitivity and frequency stability.

Characterization of Coal Fly Ash Based Adsorbent for CO2 Removal

The study of CO2 removal from air-CO2 mixture using coal fly ash (CFA) based adsorbent has been conducted. The sieved CFA was calcined at various temperature (200, 300 and 400 °C) for 4 hours. The calcined adsorbent pellets were characterized before utilizing in CO2 removal. Result suggested that calcination temperature slightly affected the yield of adsorbents. Increasing calcination temperature decreased the density and bulk density; but increased the percentage of adsorbed moisture of the adsorbents. SEM micrograph revealed various shape and size of the adsorbent and matched the result of XRD pattern and EDS analysis. The characterized adsorbents then were utilized to remove CO2 in an adsorption column. The inlet mixture contained 35%-vol of CO2 with flow rate of mixed gas of 200 ml/min. The highest removal was accomplished by using CFA based adsorbent pellet with particle size of 140 mesh, calcination temperature 300 °C for 4 hours. The CO2 removal efficiency was 71.43% with adsorbent capacity of 8.027 mg CO2/g adsorbent.

Experimental and numerical study on the transition conditions and influencing factors of hetero-/homogeneous reaction for H2/Air mixture in micro catalytic combustor

Premixed combustion of Hydrogen/Air in a rectangular micro-catalytic combustor was investigated experimentally and numerically. The distribution of OH radicals in the combustor was observed by Plane Laser-Induced Fluorescence (PLIF). A method for determining the transition process of reaction types in the combustor by measuring temperature variation was proposed. The effects of combustor height and mixed gas flow rate on the transition characteristics of reaction type were analyzed and the results demonstrated that the reaction type would transform with the change of equivalence ratio between the coupled hetero-/homogeneous reaction (catalytic and gas phase reaction) and the pure heterogeneous reaction (pure catalytic reaction). The critical equivalence ratio from coupled hetero-/homogeneous reaction transforming into pure heterogeneous reaction is ФA. The critical equivalence ratio from pure heterogeneous reaction to coupled hetero-/homogeneous reaction is ФB. At different combustor heights and mixed gas flow rates, ФA is always less than ФB. When the height of combustor increases, the critical equivalence ratio ФA decreases while the critical equivalence ratio ФB increases. The critical equivalence ratios ФA and ФB both decrease with the increase of mixed gas flow rate. Heat loss on the combustor outer wall has an important influence on the transformation of reaction type.

Purification of Biohydrogen Produced From Palm Oil Mill Effluent Fermentation for Fuel Cell Application

Fermentation of palm oil mill effluent (POME) produces biohydrogen in a mixture at a specific set condition. This research was conducted to purify the produced mixed biohydrogen via absorption and membrane techniques. Three different solvents, methyl ethanolamine (MEA), ammonia (NH3) and potassium hydroxide (KOH) solutions, were used in absorption technique. The highest H2 purity was found using 1M MEA solution with 5.0 ml/s feed mixed gas flow rate at 60 minutes absorption time. Meanwhile, the purified biohydrogen using a polysulfone membrane had the highest H2 purity at 2~3 bar operating pressure. Upon testing with proton exchange membrane fuel cell (PEMFC), the highest current and power produced at 100% H2 were 1.66 A and 8.1 W, while the lowest were produced at 50/50 vol% H2/CO2 (0.32 A and 0.49 W). These results proved that both purification techniques have significant potential for H2 purification efficiency.

Synthesis and characterization of helium-charged titanium hydride films deposited by direct current magnetron sputtering with mixed gas

Controllable helium-containing TiH2 phase films were prepared on Si (100) substances by magnetron sputtering with hydrogen-helium-argon mixed gas, in order to investigate the helium behavior in titanium tritide. The TiHxHe films were characterized by ion beam analysis (IBA) in which elastic recoil detection (ERD) and Rutherford backscattering spectrometry (RBS) methods are included, X-ray diffraction (XRD) and scanning electron microscope (SEM). It is found that with the increase in the relative hydrogen flow rate (QH: QAr) under the fixed helium flow and sputtering pressure, the hydrogen concentration in TiHxHe films increases at first, and then decreases. Though the hydrogen concentration in TiHxHe films can be greatly increased by increasing the total sputtering pressure, excessive sputtering pressure will deteriorate the crystallization quality. Although the helium concentration mainly relies on the relative helium flow rate of mixed gas during sputtering, the increase of the relative helium flow rate will reduce the concentration of hydrogen in films at fixed sputtering pressure dramatically. Fortunately, suitable relative hydrogen flow and sputtering pressure can maintain a high concentration of hydrogen in the films. Thus TiHxHe films with controllable hydrogen and helium content can be achieved.

Controllable deformation of salt water-filled carbon nanotubes using an electric field with application to molecular sieving

Precisely controlling the deformation of carbon nanotubes (CNTs) has practical application in the development of nanoscale functional devices, although it is a challenging task. Here, we propose a novel method to guide the deformation of CNTs through filling them with salt water and applying an electric field. With the electric field along the axial direction, the height of CNTs is enlarged by the axial electric force due to the internal ions and polar water molecules. Under an electric field with two mutually orthogonal components, the transverse electric force could further induce the bending deformation of CNTs. Based on the classical rod and beam theories, two mechanical models are constructed to verify and quantitatively describe the relationships between the tension and bending deformations of CNTs and the electric field intensity. Moreover, by means of the electric field-driven tension behavior of CNTs, we design a stretchable molecular sieve to control the flow rate of mixed gas and collect a single high-purity gas. The present work opens up new avenues in the design and fabrication of nanoscale controlling units.

Experimental study of CO2 absorption in aqueous MEA and MDEA solutions enhanced by nanoparticles

The nanofluids based on MEA and MDEA solutions were prepared using ultrasonic dispersion method without any surfactant addition to study the influence of nanoparticles on the CO2 absorption by MEA and MDEA in the bubbling reactor. The influences of various factors including solid loading of nanoparticles, nanoparticle size, nanoparticle type, total volume flow rate of mixed gas and initial CO2 volume fraction on the CO2 absorption were investigated. Although the reaction rates of MEA-CO2 and MDEA-CO2 were different, the findings about the influence of nanoparticles based on MDEA solution were similar to that based on MEA solution. Most of tested nanoparticles could remarkably improve the gas–liquid mass transfer during the CO2 absorption process. The CO2 absorption enhancement factor increased with the increase of the solid loading of nanoparticles up to a maximum value and then decreased. The CO2 absorption enhancement factor based on the MEA solution for larger nanoparticles was greater than that for smaller nanoparticles. On the other hand, the absorption enhancement effect of nanoparticles based on the MDEA solution depends highly on the type of nanoparticle. It is also found that the enhancement factor based on the MDEA solution increased with the increase of the total volume flow rate of mixed gas or the initial CO2 volume fraction.

Effect Parameters of Ozonation of Dicamba in Aqueous Solution

The ozonation of dicamba in aqueous solution has been investigated in a bubble reactor in laboratory. The overall kinetics involved mass transfer step and reaction step are analyzed through two impact factors such as production percentage of O3 in mixed gas and flow rate of the mixed gas. The experimental results show that ozonation process can effectively degrade dicamba in aqueous solution. The reaction step and mass transfer step are both influenced by the changing of production percentage of O3. k value, the pseudo-first-order rate constant, increases sharply as the production percentage of O3 is rased from 40% to 50%. While the production percentage of O3 is in the range of 50%~70%, the increase of k value is slow. The concentration of O3 in liquid phase reaches an extreme value after the production percentage increases to a certain extent, which resulting in such trend. While the production percentage of O3 is fixed as 70%, k value is not basically affected by the changing of the mixed gas flow rate.

Ag(II)를 매개체로 사용하는 전기화학적 매개산화에 의한 NOx제거

The effects of the applied current density, the concentration, the scrubbing liquid flow rate and the NO-air mixed gas flow rate on the NO removal efficiency were investigated by using mediated electrochemical oxidation (MEO). Results showed that the NO removal efficiency increased with increasing the applied current density. The effect of the concentration on the NO removal efficiency was negligibly small in the concentration of above 0.1 M. When the scrubbing liquid flow rate increased, the NO removal efficiency was gradually increased. On the other hands, the NO removal efficiency decreased with increasing the NO-air mixed gas flow rate. As a result of the treatment of NO-air mixed gas by using the MEO process with the optimum operating condition and the chemical absorption process using 3 M solution as a scrubbing liquid, the removal efficiency of NO and was achieved as 95% and 63%, respectively.

Study of nanosized Zinc Oxide on Cu–Zn alloy substrate using Taguchi method

A Cu–Zn alloy with about 30 wt.% Zn was used as substrate for the growth of nanosized zinc oxides (ZnO). Before growth of ZnO, a Ni layer was coated on the substrate by electrodeposition technique. This Ni layer was used as a barrier against the diffusion of Zn and as a promoter for the growth of nanosized ZnO. The variables for the ZnO growth contained current density and time for electrodeposition of Ni layer, growth temperature, growth time, mixed gas flow rate, gas ratio of O 2/CH 4, flow rate of N 2 gas for carrying H 2O vapor, and temperature of water for producing H 2O vapor. The nanosized ZnOs were characterized by a scanning electron microscope for morphology and an energy dispersive X-ray spectroscope for composition. The Taguchi method was used to find the optimum parameters for optimizing the growth of nanosized ZnOs. The result showed that the optimum conditions are: 6 A/dm 2 of electrodeposition current density, 30 s of electrodeposition time, 800 °C of growth temperature, 30 min of growth time, 100 sccm of mixed gas flow rate, 1:2 of O 2/CH 4 ratio, 300 sccm of N 2 gas, and 55 °C of water.

Thermal behavior and effect of heat treatment in an inert gas on oxidized carbon microcoils

Vapor-grown carbon micro-coils were oxidation-treated under a low O 2 flow rate at 450–820°C to enhance the chemically activated sites on the surface. The thermal characteristics of the oxidation-treated carbon coils were then examined. The starting temperature of weight loss in air was decreased by the oxidation treatment. The lowest starting temperature at which weight loss was observed was 420°C under the following conditions; (a) a mixed gas flow rate of O 2=5 sccm (sccm means standard cubic centimetre/min) and Ar=50 sccm, (b) an oxidation treatment temperature of 600°C, and (c) a treatment time of 120 min. This lowest temperature was 120°C lower than that of the source carbon coils observed at 540°C. The band area of the endothermic peak on the DTA analysis significantly increased due to the post-heat treatment in Ar+N 2 after oxidation treatment of the source carbon coils and attained a maximum value of 290 mV s/g, which was about 15 times that of the as-oxidized carbon coils without post-heat treatment. The microstructures, such as pits, holes, etc., present on the surface of the post-heat treated carbon coils after oxidation treatment were changed to more complex morphologies with the occurrence of more numerous pits, holes, etc., than that of the as-oxidized carbon coils.

The effect of substrate surface temperature on the morphology and quality of diamond films produced by the oxyacetylene combustion method

Diamond films were synthesized using an oxyacetylene flame on a molybdenum substrate mounted on a water-cooled copper block. The morphology and quality of the synthetic diamond films produced depend on several factors including the substrate temperature, gas flow rates and their ratio, and substrate position. The substrate temperature profile was shown to be influenced by the coolant flow rate, nozzle size, substrate position on the heat sink, substrate position in the combustion flame, and the total flow rate of mixed gas (acetylene and oxygen). In this paper, the effects of substrate temperature and nozzle size on the morphology and quality of diamond films are discussed. Fine-gage thermocouples were used to measure the temperature distribution in the substrate during the process. Scanning electron microscopy of the produced diamond films is used to show the variation of crystal morphology.

Parametric Effects on the Substrate Temperature Profile in Oxy-Acetylene Flames

In the oxy-acetylene combustion method, the quality and morphology of the diamond film depends on a variety of factors, including the substrate surface temperature, gas flow rates and their ratio, and substrate position. Due to the nature of the oxy-acetylene flame, surface temperature of the substrate varies in the radial direction. The substrate temperature profile, in turn, is influenced by the coolant flow rate, nozzle size, substrate position on the heat sink, substrate position in the combustion flame, and the total flow rate of mixed gas (acetylene and oxygen). In this article, temperature measurements using fine-gauge thermocouples were made to characterize the influence of these parameters on the substrate temperature profile.

Kinetics of the Reduction of Cupric Ion in Ammonia Solution by Sulfur Dioxide

AbstractThe reduction of cupric ion in ammonia solution by aqueous sulfur dioxide was studied. Each run was carried out at constant initial cupric concentration, stirred rate and total mixed gas flow rate. The effect of temperature, partial pressure of sulfur dioxide in gas phase and cupric ion concentration of the solution was investigated.The reaction of Cu3++SO2(aq.)→Cu++SO42− was carried out by bubbling mixed gas (SO2/N2) through the aqueous ammonia complex of copper (II). The color change for the system was from deep blue, green, yellow to white. The pH values in the system changed from 10 to 4. The product of the reaction was identified by the analyses of IR spectrum and X‐ray diffraction, having the formula of 7Cu2SO3· 2CuSO3·3(NH4)2SO3·24H2O.The kinetic model of the reduction was proposed as:–d[Cu2+]/dt = k exp(–E/RT)[Cu2+]α[SO2%]According to the experiments, the parameters were determined as:α=1.64±0.03, þ=1.20, E=13.7 Kcal/mol and k = (1.77±0.20)×1010 (g‐equ./ℓ)−0.64min−2.