Sweep Gas Flow Rate Research Articles

Sweep gas flow effect on membrane reactor performance for hydrogen production from high-temperature water-gas shift reaction

The sweep gas flow effect on hydrogen production via water-gas shift reaction (WGSR) using a membrane reactor (MR) was studied numerically in this work. The sweep gas flow rate was used as the primary parameter while the effects of flow pattern, inlet temperature, size, and gas type in the permeation side on MR performance were examined in detail. Using CO conversion and H2 recovery to characterize the MR performance, it was found that the sweep gas flow with inlet/outlet ports arranged on the same side (parallel flow mode) is the optimal design providing higher CO conversion, H2 recovery and lower reaction temperature compared with the other examined flow pattern designs. By varying the sweep gas flow inlet temperature the sweep gas flow can serve as cooling or heating fluid in the reactor. For both cooling and heating cases reactor performance could be degraded due to lower catalyst activity and reversed WGSR, respectively. For the H2-selective MR, the sweep gas type does not affect the MR performance under the same operating conditions. By changing the size of the permeation side it was found that H2 recovery could be improved by permeation side reduction without significantly affecting the CO conversion.

Mathematical Modeling of Hydrogen Production via Methanol‐Steam Reforming with Heat‐Coupled and Membrane‐Assisted Reactors

AbstractHydrogen production and purification via methanol‐steam reforming was studied in a membrane reactor coupled with a catalytic combustor heat supply, applying 1D non‐isothermal mathematical models. Both mass and heat transfer behaviors were evaluated simultaneously in three reactor components. Based on data of methanol conversion, hydrogen recovery, and carbon monoxide selectivity, the membrane reactor performance was found to be controlled by the methanol‐air flow rate in the combustor, reformer operating pressure, and sweep gas flow rate. Higher hydrogen permeation driving force leads to high reformer operating pressure and sweep gas flow rate. Methanol conversion is enhanced compared with a conventional reactor under the same operation conditions with increased hydrogen removal from the reformer.

Catalytic pyrolysis of Eremurus spectabilis for bio-oil production in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and character

Conventional slow pyrolysis of Eremurus spectabilis samples has been performed in a fixed-bed tubular reactor with (tincal, colemanite and ulexite) and without catalyst in the temperature range between 350 and 550 °C with heating rates of 10, 30, 50 °C/min. The yields of bio-char, bio-oil and gas produced, as well as the compositions of the resulting bio-oils were determined by elemental analysis, Fourier transform infrared spectroscopy (FT-IR) and gas chromatography/mass spectrometry (GC–MS). The effects of pyrolysis parameters such as heating rate, temperature, catalyst type, sweeping gas flow rate and particle size (Dp) on product yields were investigated. The results show that temperature and catalyst are the main factors that effect the conversion of E. spectabilis into solid, liquid and gaseous products. The highest liquid yield of 38.14% including aqueous phase was achieved with ulexite catalyst at 500 °C temperature at a heating rate of 50 °C/min when 0.224 > Dp > 0.150 mm particle size raw material and 100 mL/min of sweeping gas flow rate were used. Ninety-one and ninety-seven different compounds have been identified by GC–MS in bio-oils obtained at 350 and 550 °C respectively.

Insensible water loss through adult extracorporeal membrane oxygenation circuit: an in vitro study.

Patients on extracorporeal membrane oxygenation (ECMO) are critically ill, and fluid balance need to be managed as accurately as possible. Previous studies have focused on insensible water loss through neonatal ECMO circuit and showed that water loss through the ECMO circuit was correlated with the sweep-gas flow rates. Current study is the first study focusing on insensible water loss through adult ECMO circuit. An in vitro extracorporeal circuit consisting of Jostra Quadrox D membrane oxygenator and centrifugal pump was primed with normal saline. The amount of water loss through the ECMO circuit was found to be linearly correlated with the sweep-gas flow rate and fluid temperature. For every liter per minute of sweep-gas flow at 37°C, 0.046 ml/min of water will be lost, and for every change of fluid temperature by 1°C, water content loss will be changed by 0.0026 ml/min by multiple linear regression (R = 0.996). The average daily water loss for every liter per minute of sweep-gas flow at 33, 34, 35, 36, 37, 38, and 39°C were 51.3, 55, 58.8, 62.5, 66.2, 70.0, and 73.7 ml/day, respectively.

Three-dimensional numerical modeling on high pressure membrane reactors for high temperature water-gas shift reaction

This study presents a three-dimensional numerical model that simulates the H2 production from coal-derived syngas via a water-gas shift reaction in membrane reactors. The reactor was operated at a temperature of 900 °C, the typical syngas temperature at gasifier exit. The effects of membrane permeance, syngas composition, reactant residence time, sweep gas flow rate and steam-to-carbon (S/C) ratio on reactor performance were examined. Using CO conversion and H2 recovery to characterize the reactor performance, it was found that the reactor performance can be enhanced using higher sweep gas flow rate, membrane permeance and S/C ratio. However, CO conversion and H2 recovery limiting values were found when these parameters were further increased. The numerical results also indicated that the reactor performance degraded with increasing CO2 content in the syngas composition.

Solid state polymerization of bisphenol A polycarbonate: Effect of the crystallization method and polymerization conditions

A study on the effect of the crystallization method on the solid state polymerization (SSP) process of bisphenol A polycarbonate has been performed. Prepolymer samples were crystallized via four different techniques (solvent induced, shear induced, organic salt induced, and thermal crystallization) and SSP progress was checked by measuring the molecular weight increase. The fastest polymerization rate was obtained with prepolymers crystallized with acetone. The reaction rates were correlated with the crystallinity and plasticization of solvents, which both affected the chain mobility. The experiments conducted using different sweep gas flow rates and different particle sizes showed that, for the acetone‐crystallized prepolymers, the reaction rate was limited by the by‐product diffusion inside the polymer particles and from the surface of the particles into the sweep gas. 1H‐nuclear magnetic resonance analysis proved that polymers prepared through a solid state process had a consistently lower content of Fries rearrangement by‐products with respect to commercial samples obtained by standard melt polycondensation methods. POLYM. ENG. SCI., 55:1024–1029, 2015. © 2014 Society of Plastics Engineers

Nitrogenous emissions from the catalytic pyrolysis of waste rigid polyurethane foam

In this paper, we focus on the release of nitrogenous species from waste rigid polyurethane foam (WRPUF) during thermal conversion. Pyrolysis of WRPUF was experimentally studied to determine the effects of four operational parameters, temperature, particle size, sweeping gas flow rate and catalyst supplied, on the partitioning of the fuel nitrogen among nitrogen species. Experiments were performed using a bench-scale fixed-bed reactor and the important findings of this research include the following. (1) Five nitrogen-containing species, N2, NH3, HCN, NO2 and NO, were found in gas-phase product and N2 is dominant. (2) Tar N is retained as heterocyclic compounds, nitrile, or amine functional groups bonded to aromatic rings, and 4-[(4-aminophenyl)methyl]aniline is the main nitrogen-containing compound. (3) CaO has a good performance on increasing N2 production and decreasing NOx precursors. (4) The sweeping gas (Ar) flow rate and catalyst supplied were the most important parameters on affecting the N-containing species release. Whatever gaseous nitrogen, tar N or char N, they were significantly affected by sweeping gas flow rate, catalyst supplied or their interaction.

A simulation study on methanol steam reforming in the silica membrane reactor for hydrogen production

The main aim of this study is the presentation of a quantitative operating analysis of silica membrane reactor for carrying out the methanol steam reforming reaction to produce hydrogen. For this, a 1-dimensional isothermal model is developed and the simulation study is carried out for evaluating the catalyst loading, sweep gas flow rate and silica membrane hydrogen selectivity effects on silica MR performance in terms of methanol conversion and hydrogen recovery. These parameters effects are investigated at different reaction temperatures and pressures. The model validation results show good agreement with literature experimental data. As a main consequence, simulation results indicate that the catalyst loading and sweep gas flow rate have positive effects on silica MR performance. However, this result is devoted to lower catalyst contents (<3g) and sweep factor values (SF < 6). Moreover, the increase of silica membrane hydrogen selectivity increases the hydrogen recovery and methanol conversion. However, the improvement of membrane hydrogen selectivity in lower hydrogen permeance ranges cannot be more useful on silica MR performance in MSR reaction. According to the reaction pressure effect on silica MR performance, methanol conversion trends are various at different orders of hydrogen permeance.

Fast Pyrolysis of Pine Wood Chip in a Free Fall Reactor: The Effect of Pyrolysis Temperature and Sweep Gas Flow Rate

A lab-scale free fall reactor was employed for fast pyrolysis of pine wood chip at a temperature range from 550 to 750°C with a sweep gas flow rate of 20 or 500 mL/min. With increasing the pyrolysis temperature from 550 to 750°C, the gas yields were significantly enhanced, but the liquid yields were reduced. The highest gas yield, 67.3 wt%, was obtained after pyrolysis at 750°C with a sweep gas flow rate of 20 mL/min, while the highest liquid yield, 46.8 wt%, was obtained at 550°C with a sweep gas flow rate of 500 mL/min. Unexpectedly, char yields increased with increasing sweep gas flow rate. The gas products and liquid products after fast pyrolysis were analyzed by gas chromatography and gas chromatograph-mass spectrometry, respectively.

Efficient Splitting of CO2 in an Isothermal Redox Cycle Based on Ceria

An isothermal thermochemical cycle to split CO2 based on nonstoichiometric reduction and oxidation of ceria is demonstrated. Carbon monoxide is produced via an oxygen partial pressure swing by alternating inert sweep gas and CO2 flows over the ceria. The rates of reduction and oxidation at 1500 °C in a porous ceria particle bed are measured for sweep gas and CO2 flow rates from 50 to 600 mL min–1 g–1 and analyzed to identify cycle operating conditions (gas flow rates and reduction and oxidation durations) that maximize process efficiency. For a solar reactor assumed to operate at 3000 suns concentration and with 90% of the sensible heat of the gases recovered, the optimal cycle uses 150 mL min–1 g–1 sweep gas and 50 mL min–1 g–1 CO2 at reduction and oxidation periods of 100 and 155 s, respectively. This cycle is demonstrated in an IR imaging furnace over 102 cycles, yielding a stable average rate of CO production of 0.079 μmol s–1 g–1 and a projected reactor efficiency of 4%. The optimal conditions apply at large scale if the flow rates are scaled in proportion to the ceria mass.

Condensation studies in membrane evaporation and sweeping gas membrane distillation

Vapor transfer is an important phenomenon in various thermally driven membrane processes such as membrane distillation (MD), membrane evaporation and membrane condensation. In this study, we explore the mass transfer phenomena in sweeping gas membrane distillation (SGMD) by systematically investigating the effects of operational parameters on the process performance. It is found that mass transfer in SGMD is principally determined by both the evaporation temperature and the sweeping gas flow rate, and is significantly influenced by the operational parameters (i.e. fluid velocities) through multiple effects, including the boundary layer effect on both sides of the membrane, and the temperature polarization effect. We also prove that at low gas flow rates (i.e. insufficient gas vapor-holding capacity) the sweeping gas becomes saturated and water vapor forms droplets due to condensation on the gas side of the membrane. To the best of our knowledge, this is the first study reporting the interesting mass transfer phenomena in terms of vapor condensation and droplet re-evaporation in SGMD, which are of great significance for the heat and mass transfer in many thermally driven membrane processes using stripping gas.

Concentration of glycerol from dilute glycerol wastewater using sweeping gas membrane distillation

In this work, experimental results for the concentration of dilute glycerol wastewater using membrane distillation (MD) with a microporous hydrophobic flat-sheet PTFE membrane are reported. Experiments were performed using the sweeping gas mode of the MD (SGMD) process. The effects of various operating variables, such as feed temperature, glycerol concentration in aqueous phase, feed flow rate and sweeping gas flow rate were studied. A Taguchi analysis has been performed on the experimental results which determined the effects and contribution of each of the factors on the distillate flux and the interactions between the operating variables. Results showed that the most influential factor was feed temperature. The second significant contribution was observed for the sweeping gas flow rate. Feed concentration had a negative effect on the distillate flux. At optimum conditions (i.e. 65°C, 400mL/min, 1mass%, and 0.453Nm3/h), the Taguchi model predicted the value of the response (the distillate flux) as 20.93L/m2h, which had good agreement with the experimental results.

Fixed-bed catalytic and non-catalytic empty fruit bunch biomass pyrolysis

An attempt to the global clarion call to explore for an alternative source of environmentally friendly, renewable and cheaper energy (fuel) source than the conventional fossil fuel, was made in this study. This involved testing the effects of three catalysts (potassium carbonate K2CO3, calcium hydroxide Ca(OH)2 and magnesium oxide MgO) in the empty fruit bunch (EFB) pyrolysis on the product yields. The Ca(OH)2 catalyzed EFB pyrolysis gave the maximum percentage yield (42.64%) of bio-oil. The maximum bio-oil percentage yield from the Ca(OH)2 catalyzed EFB pyrolysis was obtained at pyrolysis temperature of 600°C, sweeping gas flow rate of 200mL/min and using 10wt.% of the catalyst. The GC–MS analysis of the Ca(OH)2 catalyzed EFB pyrolysis showed an increase (10.68%) in the desirable phenolic content and a reduction (35.21%) in the undesirable acidic components of the bio-oils when compared with the phenolic (16.74%) and acidic (42.88%) components of non catalyzed EFB pyrolysis bio-oil. This study has revealed that the quantity and quality of bio-oils can be improved using Ca(OH)2 catalyzed biomass pyrolysis.

Pyrolysis of apricot kernel shell in a fixed-bed reactor: Characterization of bio-oil and char

The pyrolysis of apricot kernel shell was studied for determining the main characteristics and quantities of liquid and solid products. Experiments were carried out in a static atmosphere with heating rates of 10°C/min and 50°C/min, pyrolysis temperatures of 400, 450, 500 and 550°C and sweep gas flow rates of 50–200cm3/min. The maximum bio-oil and char yields were 26.3 (500°C) and 35.2% (400°C), respectively. The TG-DTG analyses were applied on the raw material to investigate the thermal degradation of apricot kernel shell. The elemental analysis and heating value of the bio-oils were determined, and then the chemical composition of the bio-oil was investigated using chromatographic and spectroscopic techniques such as column chromatography, 1H NMR, and FTIR. In addition, the char was characterized by elemental, BET and scanning electron microscopy (SEM) analyses. According to the experimental results the liquid products can be used as liquid fuels and the solid product seems to be suitable for adsorption purposes due to its high surface area.

Veno-venous extracorporeal CO2 removal for the treatment of severe respiratory acidosis: pathophysiological and technical considerations.

IntroductionWhile non-invasive ventilation aimed at avoiding intubation has become the modality of choice to treat mild to moderate acute respiratory acidosis, many severely acidotic patients (pH <7.20) still need intubation. Extracorporeal veno-venous CO2 removal (ECCO2R) could prove to be an alternative. The present animal study tested in a systematic fashion technical requirements for successful ECCO2R in terms of cannula size, blood and sweep gas flow.MethodsECCO2R with a 0.98 m2 surface oxygenator was performed in six acidotic (pH <7.20) pigs using either a 14.5 French (Fr) or a 19Fr catheter, with sweep gas flow rates of 8 and 16 L/minute, respectively. During each experiment the blood flow was incrementally increased to a maximum of 400 mL/minute (14.5Fr catheter) and 1000 mL/minute (19Fr catheter).ResultsAmelioration of severe respiratory acidosis was only feasible when blood flow rates of 750 to 1000 mL/minute (19Fr catheter) were used. Maximal CO2-elimination was 146.1 ± 22.6 mL/minute, while pH increased from 7.13 ± 0.08 to 7.41 ± 0.07 (blood flow of 1000 mL/minute; sweep gas flow 16 L/minute). Accordingly, a sweep gas flow of 8 L/minute resulted in a maximal CO2-elimination rate of 138.0 ± 16.9 mL/minute. The 14.5Fr catheter allowed a maximum CO2 elimination rate of 77.9 mL/minute, which did not result in the normalization of pH.ConclusionsVeno-venous ECCO2R may serve as a treatment option for severe respiratory acidosis. In this porcine model, ECCO2R was most effective when using blood flow rates ranging between 750 and 1000 mL/minute, while an increase in sweep gas flow from 8 to 16 L/minute had less impact on ECCO2R in this setting.

Biomass pyrolysis in a fixed-bed reactor: Effects of pyrolysis parameters on product yields and characterization of products

Slow pyrolysis of eastern giant fennel (Ferula orientalis L.) stalks has been performed in a fixed-bed tubular reactor with (ZnO, Al2O3) and without catalyst at six different temperatures ranging from 350 °C to 600 °C with heating rates of 15, 30, 50 °C/min. The amounts of bio-char, bio-oil and gas produced, as well as the compositions of the resulting bio-oils were determined by FT-IR and GC–MS. The effects of pyrolysis parameters such as temperature, catalyst and ratio of catalyst, particle size (Dp) and sweeping gas flow rate on product yields were investigated. According to results, temperature and catalyst seem to be the main factors effecting the conversion of F. orientalis L. into solid, liquid and gaseous products. The highest liquid yield (45.22%) including water was obtained with 15% zinc oxide catalyst at 500 °C temperature at a heating rate of 50 °C/min when 0.224 > Dp > 0.150 mm particle size raw material and 100 cm3/min of sweeping gas flow rate were used.

Production and fuel quality upgradation of pyrolytic bio-oil from Jatropha Curcas de-oiled seed cake

The work is aimed at conversion of non-edible jatropha curcas de-oiled seed cake (the residue left after extraction of oil from the seed) into bio-oil and bio-char through pyrolysis process. A fluidized bed pyrolysis system with maximum feed rate of 12g/min was designed and fabricated. The particle size range, sweep gas flow rate and operating temperature were optimized as 0.5mm–0.99mm, 8L/min and 450°C respectively for obtaining maximum yield of bio-oil (48%) and bio-char (35.1%). The crude bio-oil has lower viscosity (1.98cSt), higher moisture content (31%) and higher density (1040kg/m3) as compared to commercial petro-diesel. The crude bio-oil was upgraded to make it suitable for engine application. The moisture content of the crude bio-oil was removed about 3% by weight using Na2SO4 as a reagent. The heavier fractions, tar, moisture and inorganic materials were removed from the crude oil by distillation in the temperature range of 40°C–80°C. The density, viscosity and moisture content of the upgraded bio-oil decreased to 1030kg/m3, 1.77cSt and 25% respectively.

Production and Characterization of Bio-Chars and Bio-Oils Formed by Pyrolysis of Persian Hogweed (Heracleum persicum Desf.) in A Fixed-Bed Reactor

Pyrolysis of Persian Hogweed (Heracleum persicum Desf.) stalks were performed in a fixed-bed tubular reactor with (K2CO3, ZnCl2) and without catalyst at three different temperatures (400, 500 and 600 oC) with a constant heating rate of 50 oC/min. and with a constant sweeping gas (N2) flow rate of 100 cm3/min. The amounts of bio-char, bio-oil and gas produced were calculated and the compositions of the obtained bio-oils were characterized by GC-MS. The effects of pyrolysis parameters such as temperature and catalyst on the product yields were investigated. According to the results, both temperature and catalyst had significant effects on the conversion of Heracleum persicum Desf. into bio-chars, bio-oils and gaseous products. The highest bio-oil yield of 41.42% by weight including aqeous phase was achieved with 10% potassium carbonate catalyst at 500 oC. 71 different compounds were identified by GC-MS in the bio-oils obtained at 500 oC.

Modeling of CO2 Stripping in a Hollow Fiber Membrane Contactor for CO2 Capture

Membrane stripping is a promising method for carbon dioxide (CO2) desorption with low energy demand. We developed a mathematical model to simulate the CO2 stripping from the CO2-rich monoethanolamine (MEA) solvent in a hollow fiber membrane contactor. The modeling results agreed well with literature experimental results. To improve the understanding and facilitate the optimization of the membrane based CO2 stripping process, we investigated the effects of different operating variables including liquid flow velocity, sweeping gas flow rate, regeneration pressure, and temperature on CO2 desorption performance. The effects of membrane’s length and diameter of membrane fiber on CO2 desorption were also studied. Results showed that increasing membrane’s length will improve CO2 stripping performance, but not infinitely, because of the thermodynamic limitation of absorbent, and shorter membrane module is preferred for thinner membrane. Membranes with a smaller diameter favor CO2 desorption. To predict the influe...

Supported Rh nanoparticles on CaO–SiO2 binary systems for the reforming of methane by carbon dioxide in membrane reactors

A set of Rh catalysts supported on a binary CaO–SiO2 system with different CaO content was prepared to investigate their textural and structural properties, Rh particle size, and catalytic performance in the dry reforming of methane reaction.The Rh nanoparticles and nanocrystalline structures in the reduced catalysts were characterized through HRTEM and CO chemisorption. EDX mapping showed that CaO is uniformly distributed on SiO2 and that no segregation is detected between them. Rh nanoparticles of about 1–2.6nm were observed. These particle sizes indicate that Rh is well dispersed on the catalyst surface and that no agglomeration exists.The incorporation of the promoter (CaO) to the silica support induced an increase in the metal dispersion from 8% in Rh/SiO2 to 22–80% in Rh/CaO–SiO2 catalysts. However, the Rh dispersion decreased as the CaO loading also increased in the binary supports.For the high CaO load solids, a high stability was observed after 80h on stream for the dry reforming of methane. In addition, the solid with 27% CaO presented the higher methane reaction rate. As a consequence, this solid was selected for its application in a membrane reactor under different conditions.The increase of methane conversion with reaction pressure at high sweep gas flow rate indicates that the separation efficiency of the Pd membrane is sufficiently high to dominate the performance of Pd membrane reactors under those conditions.