Liquid Feed Rate Research Articles

A Thermodynamic Analysis of a Proton Exchange Membrane Electrolyzer

A thermodynamic, first law analysis was conducted to understand the temperature of a proton exchange membrane electrolyzer when operated at a constant voltage and feed water flow rate. When using the electrolyzer voltage, current, liquid water feed rate and temperature, the electrolyzer operating temperature can be calculated. Heat losses can also be accounted for but are currently neglected. Carpet plots show the resulting electrolyzer temperature under varying conditions. The calculated temperatures are in very good agreement with measurements conducted in our laboratories.

A Thermodynamic Analysis of a Proton Exchange Membrane Electrolyzer

A thermodynamic, first law analysis was conducted to understand the temperature of a proton exchange membrane electrolyzer when operated at a constant voltage and feed water flow rate. When using the electrolyzer voltage, current, liquid water feed rate and temperature, the electrolyzer operating temperature can be calculated. Heat losses can also be accounted for but are currently neglected. Carpet plots show the resulting electrolyzer temperature under varying conditions. The calculated temperatures are in very good agreement with measurements conducted in our laboratories.

Single feed droplet–catalyst particle collision in a liquid containing gas–solid fluidized bed to convert fructose to value-added chemicals

Carbohydrates, comprising C6 sugars, dehydrate to form furfural (FUR) and 5- hydroxymethyl furfural (HMF). HMF is an intermediate for value-added specialty chemicals like 2,5-diformyl furan (DFF) and 2,5-furandi carboxylic acid, a monomer for polyethylene furaonate. Atomizing sugar solutions into catalytic fluidized beds operating beyond the caramelization temperature, Tcarm, accelerates reaction rates while avoiding humins, which are color forming agents characteristic of liquid phase processes. However, droplets partially coat particles in the spray zone and agglomerate due to liquid cohesive forces, which reduces heat transfer rates at the micro-scale and degrades reaction rates at the macro-scale. Here, we developed a CFD model to study the collision between a single feed droplet and a catalytic particle above Tcarm. We focused on evaluating the evaporation rate and heat transfer between the droplet and particle to promote vaporization the liquid feed, and assessing the impact of bed temperature, liquid feed rate, and superficial gas velocity. The highest DFF and furfural selectivity obtained are 17% and 24%, respectively, and these values are correlated to the maximum coke formation and agglomeration of 0.6% and 12g. However, the corresponding heat transfer and mass transfer are among the lowest values of 40% and 0.5W.

Liquid Atomization in Rotary Slinger Injectors: Role of Liquid Delivery Manifold

In rotary injectors, the method of liquid delivery can play an important role in the quality of liquid atomization. In slingers, which are employed in small gas turbine engines, the liquid delivery manifold is a key component in the atomizer assembly, which not only delivers the liquid to the atomizer but also acts as a fuel metering device. In the present work, we investigate the liquid atomization in a slinger atomizer with a focus on the effect of the number of liquid delivery ports and port size in the static manifold. Different optical diagnostics are employed to visualize primary liquid breakup and measure droplet size. The results showed that, at a low liquid feed rate, a smaller number of injection ports or port size promotes supercritical breakup (annular liquid exit and disintegration) at an orifice exit such that the breakup length and droplet size are smaller. Also, hole-to-hole variation in the liquid breakup mode is noticed, which refers to different breakup mechanisms in adjacent slinger orifices. On the other hand, Coriolis-induced film breakup is promoted when the liquid feed rate increases. The present study highlights that the design of the delivery manifold can potentially influence spray performance in slinger injectors.

Experimental investigation on liquid breakup regimes and spray characteristics in slinger atomizers with various injection orifices

Slinger atomizers, known as one type of rotary atomizers, have been widely applied in various small gas turbine engines. The fuel can be well atomized by taking advantage of the high rotational speed of the turbine shaft. The geometric characteristics of the injection orifice play an important role in determining the atomization performance of the slingers. The breakup regimes and the droplet size of the slinger atomizers with slot-shaped orifices have rarely reported in the past. Herein, three types of slinger atomizers with different orifice shapes and orifice diameters are tested at rotational speeds of 8000–20 000 rpm and liquid feed rates of 4 up to 20 g/s. High-speed shadowgraph imaging, high-speed digital imaging, and planar Mie technologies are applied to provide the spray breakup process, liquid film injection features, and droplet distribution, respectively. Spray visualizations show that the orifice diameters strongly affect the breakup modes, whereas the orifice shapes have a slight effect. The variation regarding droplet sizing under different heights from the slinger plane is analyzed. The uniformity of the droplet distribution in slot-shaped slinger atomizers is better than that in round-shaped slinger atomizers. Moreover, the smaller orifice diameter results in a small Sauter mean diameter (SMD) for the slinger atomizers with slot-shaped orifices. Finally, a mathematical expression is obtained to predict non-dimensional droplet size (SMD/d) for different slinger atomizers. The present results appear to be the first systematic investigation of the spray characteristics in slinger atomizers with slot-shaped orifices.

Large-Scale and Highly Efficient Production of Ultrafine PVA Fibers by Electro-Centrifugal Spinning for NH3 Adsorption.

Ultrafine Polyvinyl alcohol (PVA) fibers have an outstanding potential in various applications, especially in absorbing fields. In this manuscript, an electrostatic-field-assisted centrifugal spinning system was designed to improve the production efficiency of ultrafine PVA fibers from PVA aqueous solution for NH3 adsorption. It was established that the fiber production efficiency using this self-designed system could be about 1000 times higher over traditional electrospinning system. The produced PVA fibers establish high morphology homogeneity. The impact of processing variables of the constructed spinning system including rotation speed, needle size, liquid feeding rate, and voltage on fiber morphology and diameter was systematically investigated by SEM studies. To acquire homogeneous ultrafine PVA fiber membranes, the orthogonal experiment was also conducted to optimize the spinning process parameters. The impact weight of different studied parameters on the spinning performance was thus provided. The experimental results showed that the morphology of micro/nano-fibers can be well controlled by adjusting the spinning process parameters. Ultrafine PVA fibers with the diameter of 2.55 μm were successfully obtained applying the parameters, including rotation speed (6500 rpm), needle size (0.51 mm), feeding rate (3000 mL h-1), and voltage (20 kV). Furthermore, the obtained ultrafine PVA fiber mat was demonstrated to be capable of selectively adsorbing NH3 gas relative to CO2, thus making it promising for NH3 storage and other environmental purification applications.

Outdoor direct solar-driven massive photo-thermo-catalytic reforming of methanol into hydrogen at lower temperature

Solar-driven massive fuel production technology with the utilization of photo-thermo-catalytic method is emerging as a future energy development trend. This paper is aimed at establishing an outdoor flow photo-thermo-catalytic system of reforming methanol into hydrogen at low temperature to explore the outdoor operation condition for future commercial applications. Moreover, a massive preparation process is designed to fabricate CuO/ZnO/ZrO2 (CZZ) nanocatalysts with the solar full-spectrum absorption of 91.4%. Under the optimal liquid feeding rate and the water/methanol molar ratio, the solar-to-chemical conversion efficiency can reach 10.7% under a low temperature of 422K when the direct irradiation intensity is 700 W/m2, which is 5.2% higher than that of the experimental basic research at the same temperature.

Modeling of a Continuous Carbonation Reactor for CaCO3 Precipitation

To stop global warming well below 2°C, a rapid decarbonization of our economy, including the industrial sector is required—reaching net-zero GHG emissions in 2050. CO2 mineralization processes, capturing CO2 from industrial point sources and trapping it as carbonate minerals, have the potential to store climate-relevant amounts of CO2. To get there, the potential processes have to be designed and developed, with the help of a process model that can support the process scale-up and optimization. In this work, a process model describing a gas-liquid-solid continuous cristallizer for CO2 absorption into an aqueous ammonium nitrate solution and CaCO3 precipitation has been developed. It consists of the relevant material balances, of a speciation model, and a population balance equation. While several of the model parameters can be obtained from the literature, a few have been estimated by fitting a comprehensive set of experimental data presented earlier. In particular, the process quantities used for parameter estimation are the CO2 mass transfer rate, the calcium carbonate crystallization rate, and the average particle size of the CaCO3 product crystals. The accuracy of the model, particularly in reproducing mass transfer rates and average particle sizes, has been assessed. Interestingly, it has been shown that the dominating mechanism for crystal formation is primary rather than secondary nucleation. The validated model has been used to explore the effect of the different operating conditions on various key performance indicators so as to gain a deeper insight into the process performance and potential. It has been shown that the CO2 absorption efficiency is mainly affected by the feed stoichiometry and the gas feed rate, whereas the CO2 capture and precipitation efficiency are controlled by the liquid phase composition and the residence time; increasing the calcium concentration in the feed is obviously one way to improve the efficiency. Moreover, we could show that the particle size tends to increase with calcium concentration and to decrease with liquid feed rate and supersaturation of the solution.

Experimental investigation and modeling of atomization aspects in spray drying for production of pharmaceuticals with inhalable size

This paper reports on some theoretical and experimental investigation of spray drying technology to produce dry powdery pharmaceuticals for healing application via inhalation. A numerical simulation of the atomizing gas flow pattern in the vicinity of two-fluid nozzle is presented, which is then used to identify the key parameters of the spray drying process, namely the velocity of the atomizing gas in relation to liquid feed rate. The range of permissible atomizing gas velocities was determined and the effect of the atomizing gas velocity on the size of the resulting particles was quantified. Consequently, the method for the production of microparticles with an average size of 2.6 µm and a fairly narrow size distribution has been proposed.

Effect of orifice size on liquid breakup dynamics and spray characteristics in slinger atomizers

The ability of the rotary slingers to achieve fuel atomization by employing the rotational speed of the turbine shaft obviates the use of high-pressure fuel pump and makes those a popular choice for small gas turbine engines. Such atomizers contain arrays of orifices on their outer periphery for injection of the liquid into the combustion chambers. In the present work, we experimentally investigate the influence of the choice of orifice size on primary liquid breakup dynamics and spray characteristics in slinger atomizers. Three slinger discs with the same disc size and number of orifices but with different orifice size, d o (= 1 mm, 1.5 mm, and 2 mm) are examined in a high-speed slinger test rig for a range of rotational speed (2000–10,000 rpm) and liquid feed rate (0.2–1 lpm). The operating conditions are relevant to part-load and engine relighting conditions for which the selection of geometric parameters of the injector may play a crucial role in achieving the atomizer performance. In the current work, the liquid breakup process in the vicinity of the slinger orifices was visualized using front light illumination technique, whereas the pulse-shadowgraph technique was employed for droplet sizing. It is found that smaller orifice size promotes column mode of liquid breakup which results in larger primary liquid breakup length and subsequently results in larger Sauter mean diameter. The results highlight that the orifice size is an important design parameter as the liquid atomization in slinger atomizers is sensitive to the selection of orifice size especially for lower range of rotational speeds.

Switching from batch to continuous granulation: A case study of metoprolol succinate ER tablets

Continuous manufacturing (CM) has been used to produce several immediate release drug products. No extended-release (ER) product manufactured employing CM technology has been approved yet. This study investigated the critical aspects of switching from the batch mode of high shear granulation to the continuous operation of twin-screw granulation for extended-release tablets. Metoprolol succinate ER tablets was used as a model ER formulation for this purpose. A central composite design (CCD) was employed to determine the effects of high shear granulator (HSG) parameters, namely impeller speed, granulation time, and binder liquid feeding rate, on the critical granulation characteristics important for product performance. These critical granulation characteristics served as a guide for switching from the batch processing to the continuous operation for achieving the same breaking strength and dissolution for this ER metoprolol tablets.The granulation time was the most critical factor affecting the bulk properties of granules which contributed to tablet dissolution. The higher density and lower compressibility of granules were attained at the longest granulation time of 5.4 min with the fastest liquid feeding rate of 75 g/min. The granules’ density was the primary factor negatively affecting the dissolution of metoprolol tablets. However, the breaking strength of tablets confounded the effect of granules density on metoprolol dissolution. Switching the processing parameters of high shear granulation to twin-screw granulation achieved similar dissolution profiles (F2 greater than 50). The screw speed was not found to affect bulk properties of granules. The root cause of granulation failures in twin-screw granulation, such as premature consolidation, excessive swelling, poor cohesion, inconsistent shearing effects, and formation of deformed agglomerates, were identified. In conclusion, the use of critical granulation characteristics through a performance-based approach of ER tablets facilitated the switching of manufacturing of an ER formulation form batch to continuous operation.

Effect of Liquid Feeding Rate on Carbonation of Precipitated Calcium Carbonate via Continuous Method

Precipitated calcium carbonate (PCC) is an innovative product generated from lime that significantly offers various functional characteristics in fulfilling numerous market demand. PCC is produced by hydrating high-calcium quicklime resulting slurry so-called milk-of-lime and reacting the slurry with carbon dioxide (CO2) via carbonation process. The resulting PCC product is extremely white and typically has a uniform narrow particle size distribution. PCC is available in various crystal morphologies and sizes, which can be tailored to optimize performance in a specific application. The final properties of the PCC can be diversified by controlling processing parameters. In this current work, effect of liquid air pressure corresponding to feeding rate on a formation of PCC was investigated. In enhancing the product yield, the quicklime was initially converted into a solution containing calcium ion (Ca2+) using natural promoter agent. Subsequently, CO2 gas was continuously supplied into the Ca-rich ionic solution, thus inducing carbonation reaction to form PCC. This present work showed the carbonation time of producing PCC was effectively reduced as a function of feeding rate from 15 minutes at 10 psi to only 7 minutes at 50 psi. The PCC yield slightly increased from 19 g to 23 g with increasing the feeding rate from 10 psi to 50 psi, respectively. Morphologically, the PCC particles were dominated by rhombohedral structures at various feeding rates with an indication of intergrowth mechanism. This current finding signified the increasing feeding rate offered a significant reduction of PCC production time that might be efficiently applied by the industrial manufacturers.

Effect of environmental temperature on CO2 selective absorption characteristics by ionic liquid electrospray in flow system

In this study, the effect of ambient temperature on ionic liquid electrospray is experimentally clarified for the selective absorption of CO2 in a flow system with 1-ethyl-3-methylimidazolium acetate. The physical properties of ionic liquids, such as viscosity and surface tension are dependent significantly on the liquid temperature. The spray mode transition voltage increases with temperature primarily because of the decrease in viscosity. Moreover, the ionic liquid feeding rate increases the threshold voltage for the spray mode transition when the liquid temperature is higher. The ionic liquid electrospray enhances selective CO2 absorption in the flow system, and the initial decay of CO2 concentration increases with applied voltage, indicating that widely spread ultrafine droplets of ionic liquid are continuously generated. Although the CO2 reaction rate increases with temperature, the CO2 absorption in the spraying chamber at the steady state is lower because of the lower solubility at higher temperatures.

Simulation of Onset of the Capillary Surface Wave in the Ultrasonic Atomizer.

The novel drug delivery system refers to the formulations and technologies for transporting a pharmaceutical compound in the body as it is needed to safely achieve its desired therapeutic effects. In this study, the onset vibrational amplitude of capillary surface waves for ultrasonic atomization spray is explained based on Faraday instability. Using ultrasonic frequency, the vibrational amplitude approached a critical point, and the liquid surface broke up into tiny drops. The micro-droplets were are steadily and continuously formed after the liquid feeding rate was optimized. The simulation study reported a minimum vibrational amplitude or onset value of 0.38 μm at 500 kHz frequency. The required minimum energy to atomize the drops was simulated by COMSOL Multiphysics simulation software. The simulation result agreed well with the numerical results of a subharmonic vibrational model that ocurred at 250 kHz frequency on the liquid surface. This newly designed single frequency ultrasonic atomizer showed its true physical characteristic of resonance on the fluid surface plane. Hence, this research will contribute to the future development of a single-frequency ultrasonic nebulizer and mechatronics for the generation of uniform atomized droplets.

Numerical Analysis of Ultrasonic Nebulizer for Onset Amplitude of Vibration with Atomization Experimental Results

In this study, the onset amplitude of the initial capillary surface wave for ultrasonic atomization of fluids has been implemented. The design and characterization of 485 kHz microfabricated silicon-based ultrasonic nozzles are presented for the concept of economic energy development. Each nozzle is composed of a silicon resonator and a piezoelectric drive section consisting of three Fourier horns. The required minimum energy to atomize liquid droplets is verified by COMSOL Multiphysics simulation software to clarify experimental data. The simulation study reports a minimum vibrational amplitude (onset) of 0.365 μm at the device bottom under the designated frequency of 485 kHz. The experimental study agrees well with the suggested frequency and the amplitude concerning the corresponding surface vibrational velocity in simulation. While operating, the deionized water was initially atomized into microdroplets at the given electrode voltage of 5.96 V. Microdroplets are steadily and continuously formed after the liquid feeding rate is optimized. This newly designed ultrasonic atomizer facilitates the development of capillary surface wave resonance at a designated frequency. A required vibrational amplitude and finite electric driving voltage promote not only the modern development in the green energy industry, but also the exploration of noninvasive, microencapsulated drug delivery and local spray needs.

Optimization of Spray-Drying Process with Response Surface Methodology (RSM) for Preparing High Quality Graphene Oxide Slurry

The “Drying-redissolution” method is promising for the industrial production of high-concentration well-dispersed graphene oxide slurry (GOS). As the potential key step in this method, the spray drying process requires a statistical investigation which guides the large-scale preparation of graphene oxide powder (GOP). This work systematically studies the effects of operating parameters, including nozzle airflow rate (439–895 L·h−1), atomization pressure (0.5–0.7 MPa), and liquid feed rate (3.0–9.0 mL·min−1), by using the response surface methodology integrated Box–Behnken design (RSM–BBD), aiming to produce GOP with high yield and easy re-dispersion. The optimized spray drying condition is predicted to be 439 L·h−1, 0.59 MPa, and 9.0 mL·min−1, at which a powder yield of 70.45% can be achieved. The experimentally obtained GOP has an average particle size of 11.65 μm and the low crumpling degree of the particle morphology results in the good re-dispersibility (97.95%) and excellent adsorption performance (244.1 mg·g−1) of GOP. The GOS prepared by the spray-dried GOP possess low viscosity and high exfoliation efficiency with a single-layer fraction up to 90.8%, exhibiting good prospects for application. This work first applied the RSM–BBD model on the spray drying process of GO, and evidenced the possibility of producing high-quality GO slurry with the “drying-redissolution” method.

Production of ZSM-5 zeolites using rotating packed bed: Impact mechanism and process synthesis studies

In this study, hierarchical ZSM-5 zeolites are hydrothermally prepared using rotating packed bed (RPB) in premixing process (gelation stage). The impact mechanisms of RPB on the zeolite growth process are investigated. It is found that the zeolite precursor obtained by RPB contains abundant bubbles, and aluminosilicate aggregates in the precursor are broken and dispersed uniformly, which is beneficial for the uniform and fast growth of zeolite. Additionally, the effects of various RPB-premix process parameters, including rotation speed, premixing time, and liquid feed rate on the particle sizes of ZSM-5 are systematically investigated. The prepared ZSM-5 zeolites by RPB-premix route exhibit smaller particle sizes, narrower particle size distributions, larger specific surface areas, richer pore structure, and more acid amount compared with those by traditional premix treatment. Therefore, this study provides a novel approach for the synthesis of high-performance ZSM-5 zeolites.

Resolving Anodic Current and Temperature Distributions in a Polymer Electrolyte Membrane Water Electrolysis Cell Using a Pseudo-Two-Phase Computational Fluid Dynamics Model

Expanding upon our prior experimental work, we constructed a three-dimensional model of a polymer electrolyte membrane water electrolyzer using computational fluid dynamics. We applied the assumption of pseudo-two-phase flow, the flow of two phases with equal velocity. Experimental data were used to obtain parameters and to determine the conditions under which this model was valid. Anodic distributions of current density, temperature, liquid saturation, and relative humidity were obtained at various flow rates. The overall current density and temperature difference from inlet to outlet at the anode agreed strongly with experimental measurements under most circumstances. This verification allowed us to further examine the apparent gas coverage calculated from experimental and model temperature data. Results suggested a low liquid saturation and low relative humidity at the anode due to the consumption of liquid water and water vapor. However, we questioned the accuracy of the pseudo-two-phase assumption at low water feed rates. We concluded that the model was applicable to systems with liquid water feed rates greater than 0.6 ml min−1 cm−2. Therefore, it is a fair screening method that can advise which operating conditions lead to excessive temperatures or drying at the anode, thereby promoting the longevity of the membrane and catalyst.

Characterization of electrical current and liquid droplets deposition area in a capillary electrospray

A comprehensive study was conducted to investigate the effects of applied voltage, distance between needle tip and counter electrode, liquid flow rate, pH and conductivity of water on the electrical current in a capillary electro-spray. Atomic Force Microscopy (AFM) was employed to measure the size distribution of water droplets, which presented a mean diameter of 299 ​± ​76 ​nm. Statistical analysis using three-way ANOVA and nonlinear multivariate regression model were employed to study the interactions of applied voltage, distance between needle tip and counter electrode, and liquid feed rate with electrical current, and to develop regression equations to predict the current. It was found that electrical current was significantly (p ​< ​0.05) influenced by applied voltage (0 to ±10 ​KV) and the distance (2, 3 and 4 ​cm), but not by the liquid feed rate (1–10 ​μl/min) within the range investigated in this work. A water contact indicator was employed for the first time in the electrospray system to investigate the effect of parameters mentioned above on the liquid droplets deposition area. The experimental data demonstrated that increasing the distance of the capillary needle, liquid feed rate, pH, and conductivity, resulted in increased electrosprayed area.

Coriolis-induced liquid breakup and spray evolution in a rotary slinger atomizer: Experiments and analysis

Understanding the physics of primary liquid breakup process and its correlation with the evolution of spray characteristics in a rotary slinger atomizer is the goal of the present research. Experiments were conducted in a high-speed slinger test rig that houses a static liquid delivery manifold to uniformly supply the liquid to the rotating slinger disc that contains a single row of orifices carved on its peripheral surface for liquid injection.The atomizer was operated for a wide range of conditions by varying the rotational speed and liquid feed rate. The liquid breakup structure at the exit of the slinger orifices was visualized using front light illumination technique, while the droplet size was measured at different radial stations away from the slinger surface by application of the Interferometric Laser Imaging for Droplet Sizing (ILIDS) technique. The visualization images highlighted strong influence of Coriolis force as the liquid tends to accumulate on one side of the channel (that is opposite to the rotational direction) for all cases. It was observed that while the liquid thickness is smaller for higher rotational speed, it does not vary much with liquid feed rate at the same speed and, instead, in such case the span of the liquid is wider. A theoretical analysis was developed to describe the in-channel liquid behaviour that accounts for the effect of Coriolis and surface tension forces. Interestingly, the theory could explain the above observations. The differences in the predictions in comparison to the analysis by Dahm et al. (2006a) was attributed to the assumption of annular film flow in the latter. The liquid breakup mode (stream, sheet or transition mode) could be described by Coriolis Bond number (Bo) that refers to the ratio of Coriolis to surface tension forces and proportional to the spread parameter (span to thickness ratio), while the liquid breakup regimes were identified on a Bo−q plot, where q is the liquid to air momentum flux ratio. The variation of characteristic droplet sizes with both rotational speed and feed rate were examined, and again some interesting trends are identified. The correlation between liquid breakup mode/regime with the measured droplet size was established using the above non-dimensional numbers.