Gas Flow Rate Research Articles

Effect of Deposition Temperature on Zn Interstitials and Oxygen Vacancies in RF-Sputtered ZnO Thin Films and Thin Film-Transistors.

ZnO thin films were deposited using RF sputtering by varying the argon:oxygen gas flow rates and substrate temperatures. Structural, optical and electrical characterization of ZnO thin films were systematically carried out using X-Ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, X-Ray photoelectron spectroscopy (XPS) and Hall measurements. Film deposited at room temperature and annealed at 300 °C exhibited low O2 incorporation with localized defects and a high percentage of Zn interstitials. A large crystalline size and fewer grain boundaries resulted in a high Hall mobility of 46.09 cm2/V-s Deposition at higher substrate temperatures resulted in improvement in O2 incorporation through the annihilation of localized defects and decrease in oxygen vacancies and Zn interstitials. Urbach tails within the bandgap were identified using the absorption spectrum and compared with the % defects from XPS. Bottom-gate thin-film transistors were subsequently fabricated on a SiO2/p-Si substrate using the combination of RF sputtering, wet etching and photolithography. Variation in the substrate temperature showed performance enhancement in terms of the leakage current, threshold voltage, sub-threshold swing and ION/IOFF ratio. Thin-film transistor (TFT) devices deposited at 300 °C resulted in an O2-rich surface through chemisorption, which led to a reduction in the leakage current of up to 10-12 A and a 10-fold reduction in the sub-threshold swing (SS) from 30 V to 2.8 V. Further TFT optimization was carried out by reducing the ZnO thickness to 50 nm, which resulted in a field-effect mobility of 1.1 cm2/V-s and ION/IOFF ratio of 105.

Investigation on metal vapor characteristics and keyhole/melt pool dynamics in high-power laser welding with side gas flow

High-power laser welding processes involve intense interactions between the laser beam and the base material, resulting in severe welding defects such as humping, spattering, and undercutting. Utilizing side gas flow may provide an effective approach for minimizing these defects. However, the effects of side gas flow on the dynamic behavior and weld formation necessitate further investigation. In this study, an innovative analysis of metal vapor characteristics and keyhole/melt pool dynamics in high-power laser welding with side gas flow is presented, combining experimental and simulation results. A three-dimensional transient fluid flow model was developed, uniquely integrating an adaptive heat source, evaporation-condensation processes, and metal vapor energy attenuation to provide a novel perspective on the effects of side gas flow in high-power laser welding. The results display that side gas flow could suppress plasma, increase thermal input to the melt pool, and intensify the flow of liquid metal toward the pool bottom during high power laser welding, thereby enhancing weld seam penetration. The numerical results indicate that variations in flow rate significantly impact metal vapor morphology, with higher flow rates reducing both the average area and height of the metal vapor and effectively suppressing the size of metal vapor/plasma. When the side gas flow rate is 20 l/min, with the gas flow impact point located at the keyhole opening and the nozzle height set to 3 mm, the side gas flow significantly enhances the depth-to-width ratio of the weld seam in 316L stainless steel laser welding. This work can provide guidance for suppression of weld defects in high-power laser welding of medium-thick steel components, which has important theoretical significance and application value.

A numerical study of double flow focusing micro-jets

Purpose Double flow-focusing nozzles (DFFNs) form a coaxial flow of primary liquid with micro-crystalline samples, surrounded by secondary liquid and focusing gas. This paper aims to develop an experimentally validated numerical model and assess the performance of micro-jets from a DFFN as a function of various operating parameters for the water–ethanol–helium system, revealing the jet's stability, diameter, length and velocity. Design/methodology/approach The physical model is formulated in the mixture-continuum formulation, which includes coupled mass, momentum and species transport equations. The model is numerically formulated within the finite volume method–volume of fluid approach and implemented in OpenFOAM to allow for a non-linear variation of the fluid's material properties as a function of the mixture concentration. The numerical results are compared with the experimental data. Findings A sensitivity study of jets with Reynolds numbers between 12 and 60, Weber numbers between 4 and 120 and capillary numbers between 0.2 and 2.0 was performed. It was observed that jet diameters and lengths get larger with increased primary and secondary fluid flow rates. Increasing gas flow rates produces thinner, shorter and faster jets. Previously considered pre-mixed and linear mixing models substantially differ from the accurate representation of the water–ethanol mixing dynamics in DFFNs. The authors demonstrated that Jouyban–Acree mixing model fits the experimental data much better. Originality/value The mixing of primary and secondary liquids in the jet produced by DFFN is numerically modelled for the first time. This study provides novel insights into mixing dynamics in such micro-jets, which can be used to improve the design of DFFNs.

CO2 capture enhancement by metal oxides impregnated coal fly ash: a breakthrough adsorption study.

Coal fired power plants are significant contributors to CO2 emissions and produce solid waste in the form of coal fly ash, posing severe environmental challenges. This study explores the application of dry-impregnated coal fly ash for CO2 capture from gas stream. The modification of coal fly ash was achieved using alkaline earth metal oxides, specifically CaO and MgO, to alter its physical and chemical properties. Characterization techniques like X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and BET (Brunauer-Emmett-Teller) analysis were employed for physio-chemical changes in the adsorbent. Breakthrough experiments were conducted using a laboratory-scale fixed packed-bed reactor to assess the influence of temperature and gas flow rate on CO2 adsorption. Among the synthesized sorbents, calcium oxide-impregnated ash showed the highest CO2 uptake capacity, achieving 9.41mg/g at 30°C and a flow rate of 20 L/hr under atmospheric pressure. Isotherm modeling indicated a heterogeneous adsorbent surface, with the data best fitting the Sips isotherm model. Furthermore, the adsorption data conformed well to the Yoon-Nelson and Thomas kinetic models, affirming their relevance in characterizing the adsorption process under varying conditions. This research emphasizes the potential of coal fly ash-an abundant, cost-free material-as an effective CO2 adsorbent, contributing to both CO2 mitigation and landfill waste reduction.

Investigation of Churn and Annular Flow Transition Boundaries in Vertical Upward Gas-Water Two-Phase Flow

ABSTRACT Flow patterns in two-phase flow in vertical upward pipes are crucial for predicting phase distribution, flow transitions, and stability. Existing studies on churn to annular flow transitions primarily focus on flow rates, physical parameters, pressure, and temperature, often overlooking pipe diameter. This study addresses this gap using a multiphase pipe flow experimental setup to examine transitions under varying pipe diameters, gas flow rates, and liquid flow rates. Results show that with a constant liquid flow rate, increasing pipe diameter requires a higher gas flow rate to form annular flow, leading to greater pressure gradients and smoother fluctuations. Conversely, with a constant gas flow rate, larger pipe diameters decrease the liquid flow rate needed for annular flow, resulting in smaller pressure gradients and smoother fluctuations. Smaller pipe diameters make annular flow formation easier, with smaller pressure gradients but larger fluctuations. A novel churn-annular flow transition boundary model was developed, considering factors like gas shear force, surface tension, gravity, viscous force, and pressure gradient. Evaluated with 804 experimental data sets, the new model’s prediction accuracy exceeds 98.19%, outperforming traditional models with 53.92%-86.27% accuracy, enhancing applicability across varying diameters.

Modelling pressure dynamics in a gas pipeline with an in-line sampling

Gas pipelines, whether main, field, or urban, often operate in non-stationary modes. Changes in the operating modes of pumping stations, equipment start-up and shutdown, an in-line sampling or pumping and various factors are causes of instability of pressure, velocity, gas flow rate. Main pipelines are complex engineering systems with the pipeline itself being the main element. Fail-safety is the major factor in the operation of this system. Ensuring operational safety requires studying the movement regimes of the transported medium, particularly study of the dynamics of pressure duringstart-up or shutdown and at specific extraction points. This article aims to build a mathematical model and study the pressure dynamics in a gas pipeline with a sampling point. The theory of non-stationary motion liquid in round pipes has been strongly developed in the works of I. A. Charnyj. These works consider a large complex of engineering tasks taking into account viscous properties of the transported medium and pipe resistance in the hydraulic approximation. In the article on the basis of I. A. Charnyj's researches on the motion of real liquid in circular pipes the equation in partial derivatives of hyperbolic type is compiled. The equation describes the unsteady pressure of a horizontal section of gas pipeline with an extraction point. Using the Dirac delta function allows the formulation of the problem in the form of a single equation. Pressures are set at the ends of a given section, and the initial velocity is related to the Dirac delta function. By applying the finite Fourier sine transform, the partial differential equation is transformed into an ordinary differential equation and solved. Solution of equation is vision of a solution to the initial task. Inverse transform formulas based on Fourier theory allowed us to proceed to the solution of this task. Explicit dependences for the dynamics of unsteady pressure are obtained. The qualitative analysis of the formulas indicates the wave motion of a medium during the initial phase of operation, transitioning into a stationary mode after a brief period. The duration of the transition period depends on factors such as the hydraulic resistance coefficient and the velocity of the transported medium. Coefficient of hydraulic resistance and the velocity of the transported medium are the main factors. An example is considered for a horizontal section under isothermal flow conditions. With assumed numerical parameters, the transition to a stationary state occurs approximately 17 minutes after the process begins, as illustrated in the graphs provided in the article. Engineers can use mathematical models of the liquid and gas motion through pipes in the design of pipelines, as well as in solving tasks that arise during their operation. These tasks include monitoring the condition of the pipeline system, optimizing the operation, accumulation capacity estimates and others.

Prediction of Welding Mode for the Effect of Plasma Gas Flow Rate on the Mechanical and Microstructural Characteristics of Plasma Arc Welded Titanium Alloy Joints

Prediction of Welding Mode for the Effect of Plasma Gas Flow Rate on the Mechanical and Microstructural Characteristics of Plasma Arc Welded Titanium Alloy Joints

Macrokinetics of ammonium sulfite oxidation inhibited by sodium thiosulfate in wet ammonium flue gas desulfurization

AbstractThe oxidation of ammonium sulfite must be inhibited to improve the economy and cycle performance of the ammonia flue gas desulfurization process. A stirred bubbling reactor was used to investigate the macrokinetics of oxidation inhibition of ammonium sulfite by sodium thiosulfate in wet ammonia desulfurization. The effects of initial concentration, Na2S2O3 concentration, pH value, gas flow rate, and temperature on the oxidation rate were discussed. The results show that the apparent activation energy of the reaction is 37.3 kJ/mol. The macrokinetics equation of sodium thiosulfate inhibiting sulfite oxidation in the ammonia desulfurization process was established. Combined with the kinetic model, it is inferred that the rate of sodium thiosulfate inhibiting ammonium sulfite oxidation is controlled by the intrinsic chemical reaction. The results can provide a reference for the regeneration of ammonium sulfite in the wet ammonia desulfurization process.

Air Leakages at Microvalves: Pressure Decay Measurements and Extended Continuum Modelling of Knudsen Flows

To improve the performance of valves in relation to the leakage rate, a comprehensive evaluation of the valve characteristics and behavior during pressure exposure is important. Often, these low gas flow rates below 0.1 cm3/min cannot be accurately measured with conventional flow sensors. This paper presents a small and low-cost test rig for measuring gas leakage rates accurately, even far below 0.1 cm3/min, with the pressure decay method. These leakage flows are substantiated with a flow model, where we demonstrate the feasibility of modeling those gas flows with an extended Navier–Stokes framework to obtain more accurate theoretical predictions. As expected, the comparison to the experimental results proves that the classical Navier–Stokes system is unsuitable for modeling Knudsen flows. Hence, self-diffusion of gas, a wall-slip boundary condition, and an effective mean free path model were introduced in a physically evident manner. In terms of the calculated mass flow, while self-diffusion and slip boundary conditions explain deviations from the classical Navier–Stokes equation for Knudsen numbers already smaller than 1, the effective mean free path model has an effect, especially when Kn > 1. For simplified conditions, an analytical solution was presented and compared to the results of an OpenFOAM CFD-solver for flow rates through more complex gap-flow geometries of the flap valve. Hereby, acceptable deviations between 10% and 20% were observed. A comparison with measurement results was carried out. The reproducibility of the measurement method was verified by comparing multiple measurements of one silicon microvalve sample to a state-of-the-art flow sensor. Three geometrically similar passive silicon microvalves were measured with air overpressure decreasing from 15 kPa relative to atmospheric pressure. Maximum gas volume flowing in a blocking direction of 1–26 µL/min with high reproducibility and marginal noise were observed.

Study on the Continuous Whole Process Preparation of Peptizable Pseudoboehmite by High Gravity Strengthening Reaction of CO2 and Heat Transfer.

The preparation of highly peptizable pseudoboehmite faces challenges such as slow reaction rate, prolonged aging times leading to poor peptization performance, and difficulty in achieving continuous production. In this study, a novel approach was proposed involving a high gravity reactor to enhance carbonation reaction control for pseudoboehmite nucleation, a high gravity steam heating process, and a continuous aging process in pipelines. By coupling these three processes, the continuous whole process production of highly peptizable pseudoboehmite under high gravity conditions was achieved. First, the effect of high gravity reactor enhancement on the reaction and the resulting solid phase was investigated. Second, the impact of aging temperature and time on the solid phase formed at different reaction end points was studied using high gravity and steam heating of the liquid phase. Furthermore, the influence of synthesis conditions on the peptization performance of pseudoboehmite was extensively examined. Finally, the nucleation and growth mechanisms of pseudoboehmite under high gravity conditions were analyzed. It was found that increasing high gravity factor, CO2 gas flow rate, and CO2 content accelerated carbonation reaction rate, promoting pseudoboehmite crystal nucleation. Increasing aging temperature and time facilitated the growth of pseudoboehmite nuclei and improved peptization performance. The high gravity device altered the gas-liquid phase contact state of traditional kettle-type equipment, reducing the reaction time and heating time from minutes to seconds, thus achieving the continuous whole process production of pseudoboehmite with a peptization index of 100% from sodium aluminate solution by kiln flue gas.

Optimization of Hydrogen Utilization and Process Efficiency in the Direct Reduction of Iron Oxide Pellets: A Comprehensive Analysis of Processing Parameters and Pellet Composition

The article deals with the H2 consumption for different processing conditions and the composition of the processed pellets during the direct reduction process. The experiments are carried out at 600–1300 °C, with gas pressures of 1–5 bar, gas flow rates of 1–5 L min−1, and basicity indices of 0 to 2.15. Pellets with different compositions of TiO2, Al2O3, CaO, and SiO2 are analyzed. The gas flow rate is crucial, with 0–10 L min−1 leading to an H2 consumption of 0–5.1 kg H2/kg pellet. The gas pressure (0–10 bar) increases the H2 consumption from 0 to 5.1 kg H2/kg pellet. Higher temperatures (600–1300 °C) reduce H2 consumption from 5.1 to 0 kg H2/kg pellet, most efficiently at 950–1050 °C, where it decreases from 0.22 to 0.10 kg H2/kg pellet. An increase in TiO2 content from 0% to 0.92% lowers H2 consumption from 0.22 to 0.10 kg H2/kg pellet, while a higher Fe content (61–67.5%) also reduces it. An increase in SiO2 content from 0% to 3% increases H2 consumption from 0 to 5.1 kg H2/kg pellet. Porosity structure influences H2 consumption, with the average pore size decreasing from 2.83 to 0.436 mm with increasing TiO2 content, suggesting that micropores increase H2 consumption and macropores decrease it.

Influence of Absorbent Composition and Operating Parameters on CO2 Removal Efficiency Using Aqueous Blends of 1-Dimethylamino-2-propanol in Tray Column

The CO2 absorption performance in aqueous blends of monoethanolamine (MEA)—1-dimethylamino-2-propanol (DMA2P) and piperazine (PZ)—DMA2P was investigated using a bench-scale tray column under atmospheric pressure. The removal efficiency of CO2 (ηCO2) and the overall volumetric mass transfer coefficient (KGav) in DMA2P-MEA and DMA2P-PZ solutions were determined at 313.2 K. The simulated flue gas was composed of 15% (mole fraction) CO2 and 85% N2. The effects of inlet gas flow rate (G), absorbent composition (w), inlet liquid flow rate (L), and plate number (NP) on ηCO2 and KGav were demonstrated. Our results showed that the absorption of CO2 in DMA2P aqueous solution can be accelerated by the addition of MEA/PZ in a tray column, and both ηCO2 and KGav can be significantly improved.

Improved wear and corrosion resistance of magnesium AZ80 alloy prepared by laser surface remelting

Laser surface remelting (LSR) is a laser-based surface treatment method. In the LSR process, microstructural defects such as cracks and porosity are suppressed in addition to grain refinement, and the mechanical properties are improved. The present research investigated the effects of LSR parameters on the microstructure, wear, and corrosion behavior of Mg AZ80 alloy. The results showed that in LSR, the coarse-grained (29.8 μm) structure of AZ80 was transformed into a fine-grained structure (3.1 μm) with no microstructural defects. The evaporation of Mg during LSR and the formation of Al-rich and Mg-poor phases are the most important challenges in the surface treatment of AZ80. This limitation was solved by optimizing the LSR parameters, which included a gas flow rate of 2 L min−1, pulse duration of 3 ms, scanning speed of 3 mm s−1, pulse frequency of 8 Hz, and heat input of 64 J mm−1. The prevention of Mg evaporation was associated with the elimination of porosity and cracks, reducing of the solidification range, and uniform distribution of β-Mg17Al12 precipitation phases in α-Mg refined grains. The tribological behavior of the laser-treated region showed that the COF, depth of the wear scar, wear rate, and wear volume loss were reduced by 18%, 48%, 37%, and 66%, respectively, compared to AZ80. This result is attributed to the refinement of α-Mg grains and the uniform distribution of β-Mg17Al12 in the laser-treated region. The results of the polarization curves of the corrosion test in 3.5 wt% NaCl solution showed that the optimal laser-treated region with the lowest corrosion current density (34.68 × 10−6 μA.cm−2) and highest self-corrosion potential (1.425 V) exhibited the highest corrosion resistance. A slight change in the breakdown potential current slope in the laser-treated region indicates the formation of a protective film on the surface after the completion of LSR, which increases corrosion resistance.

Hydrogen-Rich Syngas Production in a Ce0.9Zr0.05Y0.05O2−δ/Ag and Molten Carbonates Membrane Reactor

This study proposes a new dense membrane for selectively separating CO2 and O2 at high temperatures and simultaneously producing syngas. The membrane consists of a cermet-type material infiltrated with a ternary carbonate phase. Initially, the co-doped ceria of composition Ce0.9Zr0.05Y0.05O2−δ (CZY) was synthesized by using the conventional solid-state reaction method. Then, the ceramic was mixed with commercial silver powders using a ball milling process and subsequently uniaxially pressed and sintered to form the disk-shaped cermet. The dense membrane was finally formed via the infiltration of molten salts into the porous cermet supports. At high temperatures (700–850 °C), the membranes exhibit CO2/N2 and O2/N2 permselectivity and a high permeation flux under different CO2 concentrations in the feed and sweeping gas flow rates. The observed permeation properties make its use viable for CO2 valorization via the oxy-CO2 reforming of methane, wherein both CO2 and O2 permeated gases were effectively utilized to produce hydrogen-rich syngas (H2 + CO) through a catalytic membrane reactor arrangement at different temperatures ranging from 700 to 850 °C. The effect of the ceramic filler in the cermet is discussed, and continuous permeation testing, up to 115 h, demonstrated the membrane’s superior chemical and thermal stability by confirming the absence of any chemical interaction between the material and the carbonates as well as the absence of significant sintering concerns with the pure silver.

Dynamics of change in the polytropic exponent in the expansion stroke of diesel

In the article is considered the problem of achieving the optimal duration of the working stroke of a diesel engine piston during the expansion process and obtaining the maximum efficiency coefficient (EC). For this purpose, a hypothesis was put forward about the pumping action of the piston on the flow of expanding gases during the power stroke of an diesel internal combustion engine (ICE) as the piston moves from upper dead point (UDP) to bottom dead point (BDP).At a certain moment of expansion, the rate of the flow of expanding gases turns out to be equal to the rate with which the same flow is slowed down by the moving piston.The equality of these rates leads to the formation of a flow break line and has a significant impact on the nature of the change in the polytropic exponent; the value of the exponent becomes equal to one: n = 1. This indicates that the optimum duration of the engine’s working stroke has been achieved and corresponds to the maximum power that can be removed during the diesel engine’s operating cycle. An experimental relation was obtained between the initial p1 and final p2 pressures in the cylinder during gas expansion with the gas flow rate and the rate of deceleration of this flow due to the pumping action of the piston. An equation for the continuity of gas flow has been compiled for the process of gas expansion in the cylinder of an ICE with closed gas exchange organs. Based on this equation, the numericalvalue of the acceleration of gravity in the cylinder of ICE is obtained: gф ≈ 8,7 м/с2 < g, which confirms the pumping action of the piston. A theoretical (and graphical) dependence of the polytropic process exponent on the flow rate of expanding gases is obtained. The dependence allows to calculate the polytropic exponent and establish the gas relaxation period, indicating the achievement of the optimal duration of the piston stroke.

Stability analysis of CO2 microbubble for CO2 sequestration and mobility control in enhanced oil recovery

This study addresses the challenge of CO2 microbubble stability in enhanced oil recovery (EOR), with a focus on the combined effects of surfactant concentration, brine concentration, brine-oil ratio, and gas flow rate. Microbubble destabilization, driven by phase separation and improper brine-oil ratios, is a critical issue in EOR. The novelty of this research lies in the use of Acacia concinna, a natural, non-ionic surfactant, to enhance microbubble stability sustainably. The study systematically investigates foamability, drainage kinetics, surface tension, rheology, and bubble size distribution to assess microbubble stability. The results showed that increasing surfactant concentration and brine-oil ratio significantly impacted foam stability and bubble size distribution, with optimal stability conditions observed at 2 wt% surfactant concentration (53.6 min), 5000 ppm brine concentration (47.6 min), a brine-oil ratio of 1:2 (52.4 min), and a CO2 gas flow rate of 1 lpm. Key findings also indicate that increasing NaCl concentration from 5000 to 20,000 ppm caused an increase in microbubble diameter, while higher gas flow rates reduced bubble size. The work introduces new empirical correlations for predicting bubble size distribution based on column diameter, surfactant and brine concentrations, viscosity, density, and gas superficial velocity. These correlations provide a more accurate means of optimizing EOR processes, improving oil recovery efficiency while enhancing CO2 sequestration, contributing to both energy production and environmental sustainability.

Elucidating flow-directed 98% CO2 absorption using millimeter-sized coiled flow inverters: Nanocellulose-aided sustainable scope

The Sustainable Development Goals (SDGs) adopted by the United Nations drive the global efforts to discover a sustainable carbon capture method for the reduction of anthropogenic CO2 emissions. Concentrated alkanolamine solutions are being used as CO2 capture mediums for batch processes amid several disadvantages, such as energy intensiveness and poor efficiency. In this work, millimeter-sized coiled flow inverters (CFI) have been explored as a point-source CO2 capture tool for highly efficient, continuous operations. Solvent and CO2 gas flow rates are found to dictate the slug flow regime and, more specfically, slug lengths. High interfacial area and residence time remain the driving factors for enhanced CO2 capture using CFI. About 98% CO2 absorption efficiency has been achieved for 3% aqueous diethanolamine solution in CFI . The efficacy of nanocellulose, a sustainable nanomaterial has been unearthed for CO2 capture at low flow rate.

Dehydration by Pervaporation of an Organic Solution for the Direct Synthesis of Diethyl Carbonate

Pervaporation has been a central subject in the research community within the scope of the further development of energy- and cost-efficient alternatives to conventional liquid–liquid separation technologies. The potential eligibility of four commercial membranes (ZEBREX ZX0, PERVAPTM 4155-80, PERVAPTM 4100, PERVAPTM 4101) for use in an integrated dehydration application of a diethyl carbonate/water/ethanol mixture by pervaporation was assessed experimentally. The impact of feed concentration, operating temperature, pressure, and sweep gas flow rate on membrane separation performance, including permeation flux, permeate quality, selectivity, and permeance, was thoroughly investigated. Applying the ZX0 membrane delivered the best qualities of all tested membranes of the permeate stream, with a water concentration of mostly >98%. In comparing the water flux, the ZX0 membrane remained reasonably competitive with the polymer membranes. Furthermore, the sweep gas volume flow rate and the operating temperature were identified as influencing the flux significantly but not the product composition. At the same time, the feed concentration of water also influenced the water purity within the permeate. The experiments were monitored with a partial least squares model, allowing a quick assessment of obtained samples while delivering accurate results.

Piperazine-Based Mixed Solvents for CO2 Capture in Bubble-Column Scrubbers and Regeneration Heat

This work used piperazine (PZ) as a base solvent, blended individually with five amines, which were monoethanolamine (MEA), secondary amines (DIPAs), tertiary amines (TEAs), stereo amines (AMPs), and diethylenetriamine (DETA), to prepare mixed solvents at the desired concentrations as the test solvents. A continuous bubble-column scrubber with one stage (1 s) was first used for the test. Six parameters were selected, including the type of mixed solvent (A), the ratio of mixed solvents (B), the solvent feed rate (C), the gas flow rate (D), the concentration of the mixed solvents (E), and the liquid temperature (F), each one having five levels. Using the Taguchi experimental design, only 25 runs were required. The outcome data, such as the absorption efficiency (EF), the absorption rate (RA), the overall mass-transfer coefficient (KGa), and the absorption factor (φ), could be determined under steady-state conditions. The optimal mixed solvents were found to be A1 (PZ + MEA) and A2 (PZ + DIPA). The parameter importance and optimal conditions for EF, RA, KGa, and ϕ were determined separately; the verification of all optimal conditions was successful. This analysis found that the importance of the parameters was D > C > A > E > B > F, and the gas flow rate (D) was the most important factor. Subsequently, multiple-stage scrubbers were used to capture CO2. Comparing 1 s and 3 s (three-stage scrubber), EF, RA, KGa, and φ increased by 33%, 29%, 22%, and 38%, respectively. The desorption tests for the four optimal scrubbed solutions, including multiple stages, showed that the heat of regeneration for the three scrubbers was 3.57–8.93 GJ/t, in the temperature range of 110–130 °C, while A2 was the best solvent. Finally, the heat regeneration mechanism was also discussed in this work.

Fluodynamics of a column filled with glass rings using the air-water system

In the present work, the fluidynamics of an absorption tower with a filling of glass rings is shown. The study was done by the variation in pressure drop with the flow rates of liquid (water) and gas (atmospheric air). The influences of the two flows were analyzed and ranges were identified where the flooding and the dragging of the liquid occur. A critical point is also presented, indicating the maximum limit of the combination between the two flows, Qwater/Qair, which must be used in the operation of the tower