Gas Absorption Rate Research Articles

Experimental study on gas hydrate generation in a thermal-kinetic binary promotion system

ABSTRACT The primary measure for the prevention and control of coal and gas protrusion is gas extraction. However, various factors, such as coal seam conditions, drilling construction, and extraction management, have led to poor gas management. Therefore, the method of transforming gaseous gas into solid hydrate provides a new direction for the prevention and control of coal and gas herniation. In this paper, the factors that influence gas hydrate solidification and its influence law are explored. A thermo-kinetic binary promotion system was constructed by combining thermo-kinetic promoters, and experiments on gas hydrate generation under the thermo-kinetic binary system were carried out. The effects of four thermodynamic accelerators (CP, THF, TBAB, HCFC-141b) compounded with the kinetic accelerator SDS on the gas hydrate generation characteristics were determined. The experimental results show that among the four thermodynamic promoters, THF and SDS have the best synergistic effect, and the optimal mass concentration ratio of the two is 21.2 wt% THF + 8.6 wt% SDS. The gas pressure in the reactor decreased by a maximum of 2.788 MPa within 500 min in this experimental system, and the absorption rate of gas reached 55.41%, which indicates a more pronounced hydration promotion effect.

CO2 solubility and absorption rate analysis of a mixed poly(oxymethylene) dimethyl ethers (PODE3–5) solution

Efficient and economical carbon capture is critical to counteract the diverse problems of global warming. In this work, the solubility of carbon dioxide (CO2) in different poly(oxymethylene) dimethyl ethers (PODE) solutions was experimentally investigated at temperatures from 278.15 to 308.15 K and pressures up to 1.2 MPa. The Henry's law constants of CO2 in the PODE system were determined and compared with other types of physical absorbents, which revealed PODE3–5 has great CO2 absorption ability in terms of molar and mass fraction. Meanwhile, the initial absorption rate of the physical absorption process of PODE3–5 was calculated and compared with commercially available absorbents using a gas absorption rate relationship. It was shown that the absorption rate of PODE3–5 in the CO2 absorption process is faster than that of other commercial absorbents. The CO2 solubility data of PODE3–5 were also correlated using the Jou-Mather model and the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state model, and the recycling performance of the PODE3–5 absorbent was tested.

Critical role of lattice vacancies in pressure-induced phase transitions of baroplastic diblock copolymers.

Baroplastic diblock copolymers exhibit order-disorder transitions and melt upon compression at low temperatures, in some cases even at ambient temperatures. Their unique low-temperature processability makes them promising candidates for sustainable polymeric materials. Despite their potential, however, the molecular mechanisms governing the pressure-induced phase transitions of these copolymers remain largely unexplored. This study develops a compressible self-consistent field theory for baroplastic copolymers based on a simple lattice vacancy model that explicitly incorporates voids to account for compressibility. The theory shows that the selective presence of voids in compressible domains stabilizes the ordered phase, while a reduction of voids under compression leads to the order-disorder transition. In addition, this work demonstrates for the first time the critical role of gas absorption rates in each segment in the pressure-induced order-disorder transition of baroplastic diblock copolymers. These findings have significant implications for the rational design of baroplastic polymers with tailored low-temperature processability.

Supplemental impact of silymarin in growing pig diet on the growth performance, total tract digestibility, faecal microflora, faecal noxious gas emission and absorption rate in blood.

The research was done to examine the impact of dietary silymarin on growth performance, total tract digestibility, faecal microbial, faecal gas emissionand absorption rate in blood of growing pigs. Experiment 1: a total of 140 growing pigs (24.47 ± 2.49 kg) were used in a 6-week trial. There were four dietary treatment groups (sevenreplicate pens/treatment, five pigs/pen) and treatment diets composed of corn, soybean meal (SBM), distillers dried grains with solubles (DDGS), and rapeseed meal-based basal diets with 0%, 0.025%, 0.050%and 0.10% of micelle silymarinrespectively. Experiment 2: A total of 18 pigs were divided into six treatment groups. Treatment diets: TRT1, TRT2 and TRT3 were basal diets with 30, 150and 300 g powdered silymarinrespectively; and TRT4, TRT5 and TRT6 were basal diets with 30, 150and 300 g micelle-type silymarinrespectively. Average daily gain (ADG) tended to increase (p < 0.10) at Week 3 and overall experiment after silymarin addition. Overall ADG and average daily feed intake are also intended to improve (p < 0.10) linearly in this study. During Week 6, growing pigs fed silymarin showed linearly increased (p < 0.05) apparent total tract digestibility (ATTD) of dry matter, nitrogenand energy. Dietary silymarin supplementation increased (p < 0.10) linearly the faecal Lactobacillus count at Week 3 while Escherichia coli count was linearly decreased at both the 3rdweek (p < 0.05) and 6thweek (p < 0.10). Silymarin supplementation showed no effect on faecal gas emissions. A higher (p < 0.05) absorption rate in the blood was found in micelle-type silymarin compared to powdered silymarin after the 1st, 2nd, 4th, 8th, 12thand 24th h of feeding. Results suggest that silymarin in a corn-SBM-DDGS-rapeseed meal-based diet may help to improve ADG, FI, ATTDand faecal microflora in growing pigs. And absorption rate in the blood of pig is higher in micelle-type silymarin.

A Predictive Methodology to Determine the Rate of Gas Evolution in Hydrocarbon Systems at Elevated Pressures

The rate of gas evolution (volumetric mass transfer coefficient) is a critical parameter in understanding and predicting gas–liquid separation, especially in the energy industry. This work led to the development of an empirical correlation to determine the mass transfer coefficient based on the dead oil properties and energy dissipation. The approach was evaluated using published n-dodecane data. The empirical correlation was tested for model and crude oils using experimental data for the rate of gas evolution and absorption under varying levels of energy dissipation and from liquids of varying viscosities. The energy dissipated in the liquid was varied by changing the mixing speed from 25 to 500 rpm. The rate of gas evolution/absorption was measured using one model oil (Exxsol D-110) and three crude oils (crudes A, B, and C) of varying viscosities at elevated pressure (3.45 MPa) and at two different temperatures (298.15 and 348.15 K), while pure methane was used as the gas phase. The mass transfer coefficient determined for each liquid was correlated with an empirical equation based on the kinematic viscosity and energy dissipation, similar to the Lamont and Scott model. This work also evaluated the impact of inlet conditioning (multiple shear environments) on gas evolution. In gas–liquid separators, varying levels of energy dissipation are encountered. For example, high levels of energy are encountered in inlet conditioning devices, followed by lower levels of energy within the separator. Thus, the impact on the rate of gas evolution when an initial shear pulse (high energy dissipation) was applied prior to the gas evolution stage was investigated. The initial shear pulse increased the rate of gas evolution in all cases. This work provides an approach for estimating the rate of mass transfer in hydrocarbons, and it provides insight into cases where different levels of energy dissipation are experienced.

Optimization Study of CO2 Gas Absorption with NaOH Absorbent Continuous System in Raschig Ring Packing Column Using Box–Behnken Design

Increasing CO2 gas emissions results in climate change by increasing air temperature and worsening environmental problems. It is necessary to control CO2 gas in the air to overcome this. This research aims to optimize the absorption of CO2 gas in the air with 0.1 M NaOH absorbent in the column of the Raschig ring stuffing material using the response surface methodology (RSM). This research was conducted using a continuous system of three independent variables by varying the contact time (10–80 min), the flow rate of NaOH absorbent (2–5 L/min), and the flow rate of CO2 gas (1–5 L/min). The response variables in this study were the absorption rate (L/min) and mass transfer coefficient, while the air flow rate was constant at 20 L/min. Air and CO2 gas mix before absorption occurs and flow into the Raschig ring packing column so that contact occurs with the NaOH absorbent. Mass transfer of CO2 gas occurs into the NaOH absorbent, resulting in absorption. The results showed that the effect of contact time (min), the flow rate of NaOH absorbent (L/min), and CO2 gas flow rate individually and the interaction on CO2 absorption rate and mass transfer coefficient were very significant at a p-value of 0.05. Chemical absorption of CO2 also occurred due to the reaction between CO2 and OH- to form CO32− and HCO3−, so the pH decreased, and the reaction was a function of pH. Optimization using Design Expert 13 RSM Box–Behnken Design (BBD) yielded optimal conditions at an absorption time of 80 min, NaOH absorbent flow rate of 5 L/min, CO2 gas flow rate of 5 L/min, absorption rate of CO2 gas of 3.97 L/min, and CO2 gas mass transfer coefficient of 1.443 mol/min m2 atm, with the desirability of 0.999 (≈100%).

CO2 and H2S absorption in aqueous MDEA with ethylene glycol: Electrolyte NRTL, rate-based process model and pilot plant experimental validation

Acid gas absorption with aqueous amines is an important industrial technology for natural or flue gas treatment. To lower the high energy required for the regeneration process it has previously been proposed to replace a significant part of the water by a physical co-solvent with a lower specific heat. To investigate this idea, as well as the overall impact of adding a physical co-solvent, a detailed process model for CO2 and H2S absorption using an aqueous mixture of N-methyl diethanolamine (MDEA) – ethylene glycol (EG) is developed based on lab-scale experimental measurements of physical, thermodynamic, and kinetic properties. Those experiments indicate that the addition of EG reduces the solubility of the acid gases and that, despite the higher viscosity of the solvent, the impact on the rate of acid gas absorption is minor. Pilot plant tests further confirmed this. The vapor-liquid equilibrium (VLE) experiments were used to regress the thermodynamic electrolyte e-NRTL (Non-Random Two-Liquid) model parameters. In parallel, the kinetic measurements allowed to develop a rate-based model. All models were implemented in a commercial process simulator that was validated with high-pressure absorption–regeneration pilot tests with the solvent composition of 34 wt% MDEA, 44.5 wt% EG and 21.5 wt% H2O and with the raw gas composition of 2.5 mol% H2S and 2.5 mol% CO2. Comparison with aqueous MDEA (50 wt% MDEA, and 50 wt% H2O) shows that a reduction of 25 % in reboiler duty can be obtained when adding EG. Nevertheless, an 80 % increase in solvent flow rate is needed to get a similar acid gas absorption performance, and a higher co-absorption of hydrocarbons is observed.

Ethanol Gas Concentration Detection System Based on Infrared Spectrum

Based on the absorption mechanism of infrared spectrum of ethanol gas, a detection system is designed to detect the concentration of ethanol gas quickly and accurately. Based on the Beer-Lambert law and the absorption rate of ethanol gas in the near-infrared band, the LED with the center wavelength of 1300 nm is selected as the light source, and then the cascaded air chamber is designed, and the light source driving circuit and detecting circuit are designed and made.

A review on hydrothermal liquefaction of algal biomass on process parameters, purification and applications

Algae, a potential biomass feedstock with a faster growth rate and capability of greenhouse gas absorption, mitigates the limitations of the first- and second-generation feedstock in bio-oil production. hydrothermal liquefaction (HTL) is known to be an active method capable of producing substantial energy resources. In HTL, biomass undergoes thermal depolymerization in the presence of water, at around 280 °C–350 °C following subcritical and near supercritical conditions to produce chemical compounds such as alkanes, nitrogenates, esters, phenolics, etc. The primary product, “Biocrude/Bio-oil” obtained from the reaction, is identified as the essential fuel source after processing and also as a distinct value-added chemical source, along with biochar and biogas as co-products. This review outlines a range of routes available for thermochemical conversion of the algal biomass. It also provides a better understanding of the reaction mechanism like depolymerization, decomposition, and re-polymerization, operating conditions like temperature, pressure, the quantity of catalyst required, and the solvent used in the process. The review also highlights the yield achieved by altering the aforementioned parameters, comparing and presenting them as a collective result.

Promoting methane hydrate formation with expanded graphite additives: Application to solidified natural gas storage

Solidified natural gas storage (SNG) using hydrate can provide environmentally friendly, highly compact and non explosive mode of NG storage at mild storage conditions. The efficient and rapid formation of natural gas hydrate is of great significance to the industrial application of SNG. In this work, in order to improve the gas storage capacity and absorption rate of CH4 hydrate, experiments were carried by adding expanded graphite (EG) with sodium dodecyl sulfate (SDS) with a pressure range of 5.0–8.0 MPa and a temperature of 273.2 K. The results indicate that EG can not only promote the formation of hydrate by promoting the nucleation of hydrate, but also accelerated the growth of hydrate by enhancing hydration heat transfer. EG system (0.05 wt%, 0.08 wt%, and 0.10 wt%) enabled faster hydrate formation than a liquid water system, with a content of 0.08 wt% optimal for the enhancement of hydrate formation. In the combination of EG (0.08 wt%) and SDS solution, EG + 0.03 wt% SDS system can improve the kinetics of hydrate formation to the greatest extent; the maximum gas storage capacity reached 190.4 STP/g H2O, and the maximum gas storage speed reached 20.84 cm3·g−1·min−1 at 273.2 K and 6 MPa. Compared with the SDS system, the maximum methane uptake and rates of EG + 0.03 wt% SDS system increased by 11.90% ~ 26.18% and 15.09% ~ 51.67% under different pressures respectively. At relatively low pressure, the hydrate can achieve a saturation of ~90% in EG + 0.03 wt% SDS system. On the other hand, compared with other carbon materials such as graphite and carbon nanotubes, the gas storage capacity and average gas storage rate of EG system were 1.12–1.37 times and 1.67–30.17 times higher, respectively, under similar temperature and pressure conditions. Therefore, a collaborative mode of enhancing gas concentration, nucleation site and heat transfer efficiency at the gas–liquid interface of hydrate reaction with only one material (EG) was proposed to promote the formation of hydrate. Further study on the promotion mechanism of EG and amplification experiments are expected to provide an effective way for the commercial application of SNG process in future work.

Influence of THF and THF/SDS on the Kinetics of CO2 Hydrate Formation Under Stirring

Hydrate-based gas separation is a potential technology for CO2 recovery and storage, and its products can be used for fire prevention and control in mines. Promoters are often employed to accelerate or moderate hydrate formation. In this study, experiments were performed to examine the effects of different concentrations of the thermodynamic promoter tetrahydrofuran (THF) and kinetic promoter sodium dodecyl sulphate (SDS) on CO2 hydrate formation under stirring. The results showed that THF significantly shortens the induction time of CO2 hydrates; however, because THF occupies a large cavity in the hydrate structure, it also reduces the gas absorption and hydrate formation rate. SDS has no obvious effect on the induction time of hydrates, but it can increase the gas storage density and hydrate formation rate. Using THF and SDS together consumed more CO2 than using THF alone or pure water. The peak gas consumption rate was 2.3 times that of the THF system. The hydrate formation efficiency was improved by including both THF and SDS, which maximized both the hydrate formation rate and total gas uptake.

Hydrogenation Dynamics Process of Single-Wall Carbon Nanotube Twisted

In some of the technological applications (electromechanical oscillators and mechanical actuators for artificial muscles, for instance), carbon nanotubes (CNT) are subjected to large deformations. Although this frequently happens in the air, there are only a few studies about the interaction of deformed CNT with the atmosphere and the dynamics of these processes. We have investigated, through fully atomistic reactive molecular dynamics simulations, the process of hydrogenation of highly twisted CNT. Our results show that the effective hydrogenation ratio is directly related to the twist angle values. This could be used to control the rates of gas absorption in CNT.

Extinguishing Characteristics of a Pool Fire with a Rubber Balloon Filled with Inert Gases

In this study, an extinguishing method using a rubber balloon filled with inert gas is proposed against fires in confined space such as spacecraft and space station. The proposed method has a possibility to increase extinguishing effectiveness of inert gas and decrease its volume amount needed for firefighting. In order to clarify the extinguishing characteristics, the blowoff experiments have been performed under normal gravity condition. CO2, N2, Ar and Ar + N2 mixture gases were used as an extinguishing gas and ethanol, 1-butanol and n-heptane were used to form a pool fire. The fuel pan diameters were varied from 47 mm to 94 mm. From the experimental results, it is found that there exists the extinguishment limit, which indicates the minimum inert gas volume needed for achieving flame extinguishment with the rubber balloon. By using the magnitude of the extinguishment limit value, the extinguishing ability of inert gas in the rubber balloon extinguishment can be evaluated. As a result, the effectiveness ranking of the inert gas in rubber balloon extinguishment agrees well with that of cup-burner tests. Moreover, it is found that when the size of the pool fire (fuel pan diameter) is same, the value of the lower heating value of fuel divided by the inert gas heat capacity at the extinguishment limit shows a certain constant value independent of inert gas and fuel species. As a result, the extinguishment limit of the rubber balloon extinguishing method is considered to be determined due to the balance between the heat release rate of the pool fire and the heat absorption rate of inert gas released from the bursting balloon. Thus, a rubber balloon can be used as an extinguishing capsule, by which a high concentration inert gas is easily delivered to the flame. In addition, it is much easier to grasp heat capacity effect of inert gas on flame extinguishment than the conventional methods, such as the cup-burner test.

Research of Titanium Saturation with Gas and Feature of Ceramic Layer Formation Using the Oxidative Constructing Approach

Abstract—Samples made of titanium grade BT 1-0 in the form of disks were subjected to isothermal aging at 875°C with access to atmospheric air for 2, 4, 6, 7, and 13 days. As a result of XRD, it was established that the oxide layer is rutile TiO2. The metal blank absorbs oxygen and nitrogen from atmospheric air, which are concentrated in the surface layer. The increase in the mass of oxygen going to the formation of rutile is 96–98 wt % of the total amount of gas absorbed. The rest of the absorbed gas (2–4 wt %) is contained in the metal blank in the form of solid solutions. The gas absorption rate of a titanium blank is proportional to the rate of rutile formation. The process kinetics for each of the sample surfaces (side and end), which is described by an exponential law, is determined. At the initial stage of the oxidation process, the surface geometry does not affect the rate of formation of the ceramic layer of rutile; subsequently, there is an “acceleration” of rutile growth on the end surface.

INVESTIGATION OF THE EFFECT OF ELECTRIC FIELD ON CO2 ABSORPTION IN WATER/Fe3O4 NANOFLUID

Abstract In this study, a novel strategy for controlling the mass transfer rate in a gas-liquid system was reported and used for the industrially important system of CO2 absorption. The strategy used Fe3O4 nanoparticles in the liquid phase and also exerting an external electric field. To demonstrate this approach, a unique experimental set up was applied to form a falling liquid film, which was water, to be in contact with the gas phase, which was pure carbon dioxide. Nanofluid with concentrations less than 0.03% by volume and field intensities of 133, 200, 266 kV/m were used in this study. Experimental results showed that the external electric field was able to remarkably enhance the gas absorption rate in dilute nanofluids, while it deteriorated mass transfer in concentrated nanofluids. In order to explain the results, the viscosity of the nanofluid was also experimentally measured in the presence of the electric field.

Numerical simulation of welding fume lung dosimetry

Exposures to airborne particles and toxic gases generated by welding fabrication activities will potentially lead to various diseases. Accurate information on the transport and deposition of such aerosols in the respiratory system is critically needed for precise health risk assessments. To address the data demand mentioned above, a multiscale computational fluid-particle dynamics (CFPD) model was developed in this study. Specifically, a virtual fabrication shop was integrated with a virtual human in the numerical model to evaluate the effects of ventilation condition, particle size, and gas species on the lung uptakes of those welding fume particles and gases. Welding fume particle and gases transmission, transport, and deposition have been simulated and analyzed starting from the emission source to the subject-specific human respiratory system via oral inhalation. Spherical iron particles with diameters of 100, 190, and 830 nm were simulated. The transport and absorption of NOx and CO were predicted too. Steady-state inhalation with 11.87 L/min was applied with two different air filter ventilation conditions. The numerical results indicate that the ventilation condition can significantly influence welding gas transport and deposition. The pulmonary gas absorption rate is much higher at poor ventilation conditions. The air-tissue absorption coefficient is another crucial factor that can impact pulmonary gas absorption. The total particle deposition fractions (TDFs) from mouth/nose to generation 6 (G6) are less than 18.0%, and particles mostly deposit in the oral cavity. Regional and local particle deposition data demonstrate that particles tend to enter the two upper lobes more than the other three lobes. In summary, this study paves the way to build a personalized in silico tool based on CFPD models for noninvasive precise health risk assessments associated with different welding activities.

Enhancement in specific absorption rate by solvent microencapsulation

Microencapsulation of liquid solvents (MECS) has been proposed as a means of increasing the rate of absorption in gas separation processes. Surface renewal theory was used to rigorously quantify the increase in absorption microencapsulation could provide, compared to traditional packed columns. The results indicate that, for chemical solvents, gas flux will be similar in the two cases, while for physical solvents gas flux into MECS may be larger, owing to the reduction in spatial scales. However, previous publications may have overestimated the increase in surface area that microencapsulation can provide by approximately 3‐10 times. Internal fluid flow inside fluidized MECS was also studied, and it was found that gas flux will be similar for stationary and fluidized particles. Overall, microencapsulation can be expected to increase gas absorption rates by approximately an order of magnitude for chemical solvents, and up to 2 orders of magnitude for physical solvents. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4066–4079, 2018

Dynamic measurement of liquid‐phase mass transfer coefficient and significance on the SO2 absorption rate

AbstractLiquid‐phase mass transfer coefficient is important for characterization of gas–liquid reactors and relevant to the modelling of gas absorption rate. Both direct and indirect methods have been used to obtain this coefficient. However, these methods have not been compared on the same basis. Liquid‐phase mass transfer coefficients were measured in three ways—(a) CO2 absorption into water, (b) SO2 absorption into 1 kmol m−3 of HCl, and (c) O2 absorption into Na2SO3—and then normalized to the coefficient for SO2. Based on transient experiments, the normalized values for liquid‐phase mass transfer coefficient obtained from three methods are in turn of . The fluxes of SO2 predicted from three methods were further compared with the experimental values measured in SO2‐NaOH system. The fluxes predicted from agreed well with the experimental values, whereas those from and were significantly lower or higher. Therefore, the liquid‐phase mass transfer coefficient is preferably obtained from the targeted gas. Modelling on the flux of SO2 demonstrates the transition of controlling regions against pH. At pH above 4, the gas side resistance is larger than the liquid side, whereas at pH below 4, the gas side resistance is smaller than the liquid side.

Impacts of CaO Solid Particles in Carbon Dioxide Absorption Process from Ship Emission with NaOH Solution

CO2 emitted from ship exhaust is one of the major sources of atmospheric pollution. In order to reduce ship CO2 emissions, this paper comes up with the idea of recovering CO2 from ship exhaust by NaOH solution and improves the absorption rate by adding CaO solid particles. The effect mechanism of CaO solid particles on CO2 absorption efficiency is analyzed in detail, and the mathematical model is deduced and the CaO enhancement factor is calculated through experiments. Experiment result demonstrates that the effect of CaO solid particles on the absorption of CO2 in alkali solution is significant. The absorption rate of pure CO2 gas, the simulated ship exhaust gas and 6135AZG marine diesel engine emission can be increased by 10%, 15.85% and 10.30%, respectively. So it can be seen that CaO solid particles play an important role in improving the absorption efficiency of ship CO2 emission.

A frequency quantum interpretation of the surface renewal model of mass transfer.

The surface of a turbulent liquid is visualized as consisting of a large number of chaotic eddies or liquid elements. Assuming that surface elements of a particular age have renewal frequencies that are integral multiples of a fundamental frequency quantum, and further assuming that the renewal frequency distribution is of the Boltzmann type, performing a population balance for these elements leads to the Danckwerts surface age distribution. The basic quantum is what has been traditionally called the rate of surface renewal. The Higbie surface age distribution follows if the renewal frequency distribution of such elements is assumed to be continuous. Four age distributions, which reflect different start-up conditions of the absorption process, are then used to analyse transient physical gas absorption into a large volume of liquid, assuming negligible gas-side mass-transfer resistance. The first two are different versions of the Danckwerts model, the third one is based on the uniform and Higbie distributions, while the fourth one is a mixed distribution. For the four cases, theoretical expressions are derived for the rates of gas absorption and dissolved-gas transfer to the bulk liquid. Under transient conditions, these two rates are not equal and have an inverse relationship. However, with the progress of absorption towards steady state, they approach one another. Assuming steady-state conditions, the conventional one-parameter Danckwerts age distribution is generalized to a two-parameter age distribution. Like the two-parameter logarithmic normal distribution, this distribution can also capture the bell-shaped nature of the distribution of the ages of surface elements observed experimentally in air–sea gas and heat exchange. Estimates of the liquid-side mass-transfer coefficient made using these two distributions for the absorption of hydrogen and oxygen in water are very close to one another and are comparable to experimental values reported in the literature.