Cavitation Reactor Research Articles

Effect of working fluid temperature on flow characteristics of jet cavitation reactor

Effect of working fluid temperature on flow characteristics of jet cavitation reactor

Methyl ester production process from palm fatty acid distillate using hydrodynamic cavitation reactors in series with solid acid catalyst

This study aims to optimize the reduction of free fatty acids (FFAs) in palm fatty acid distillate (PFAD) using hydrodynamic cavitation reactors (HCRs) in series and a solid acid catalyst for biodiesel production. Hydrodynamic cavitation is used to accelerate the esterification of FFAs using a heterogeneous acid catalyst. There are three HCRs units, and each HCR composed of a 3D-printed rotor and stator, is separated by flanges and equipped with a basket for holding Amberlyst-15 catalyst. Through response surface methodology (RSM), the esterification process is optimized by adjusting its optimal parameters, namely, methanol (2–12 wt%), circulation time (30–170 min), and rotor speed (1000–3000 rpm). The optimal conditions for achieving a maximum methyl ester purity of 89.76 wt% in converting FFA in first-step esterified oil are 9 wt% methanol (molar ratio of methanol to oil of 4:1), 133 min of circulation time, and 2000 rpm of rotor speed. An 82.48 wt% biodiesel yield is achieved from the HCRs in series under the optimal conditions. Scanning electron microscope images reveal that after the esterification process, there are minor cracks and defects on the catalyst’s resin surface, indicating the presence of residual reactants. Further examination of the catalyst after the esterification process, reveals an average absorption pore diameter of 341.41 Å and BET surface area of approximately 41.68 m2/g. Although there were slight physical changes in the catalyst, HCRs technology offers a viable FFA reduction process that could enhance biodiesel production efficiency. Moreover, the optimized conditions achieved in this study contribute to the advancement of biodiesel production processes and provide insights into the performance of the catalyst used.

Study on the characteristics of cavitation and COD removal of an addendum rotational hydrodynamic cavitation reactors

AbstractThis paper presented an addendum rotational hydrodynamic cavitation reactors (ARHCR) that enabled circumferential shear cavitation, axial cavitation, and the Venturi effect, thus increasing cavitation efficiency. The experiments on hydroxyl (·OH) release and chemical oxygen demand (COD) removal demonstrate the feasibility of cavitation performance characterization and COD removal rate. The findings indicate that the COD removal rate can reach a maximum value of 28% or 30% with an increase in flow rate or rotating speed, respectively. Specifically, the maximum values were achieved at a rotation speed of 2,500 rpm or a flow rate of 1.0 m3·h−1. Based on the mechanism of the addendum cavitation, the wedge angles, and the crucial structural parameters, were examined for optimizing cavitation performance. The results revealed that the cavitation number and cavitation bubble were significantly influenced by wedge angles, as well as the efficiency of cavitation energy. The mechanical shear of fluid was enhanced by wedge angles, resulting in constant compression and release of fluid with increased kinetic energy. This led to stronger effects on bulge blocks, and the formation of vortexes that rebounded constantly, resulting in lower pressure areas and expanded regions of cavitation. Among the wedge angles tested, the wedge angle of 15° exhibited the highest cavitation bubbles with a maximum value of 46%. This was 31% higher than the grooves‐type cavitator reported. Furthermore, the cavitation performance was extremely improved with a wedge angle of 15°, as corresponding with the maximum efficiency of cavitation energy. These explorations provide references for the removal of COD in industrial and agricultural wastewater, as well as the development of novel reactors for wastewater treatment.

Cavitation intensity prediction and optimization for a Venturi cavitation reactor using deep learning

The Venturi reactor, widely used in process intensification through hydrodynamic cavitation technology, has proven highly effective in various chemical and environmental applications. The cavitation intensity of a Venturi is primarily influenced by shape parameters such as the convergent angle (β1), throat diameter (dth), throat length (lth), and divergent angle (β2). However, the impact of these parameters on cavitation intensity has not been sufficiently clarified. In this study, the structural optimization of a Venturi reactor was accomplished by integrating deep neural networks with particle swarm optimization. The Cavitation Intensity Prediction Network model, which combines artificial neural networks and numerical simulation, was used to establish the nonlinear relationship between shape parameters and cavitation intensity. Partial dependence plots and individual conditional expectation plots were utilized to clarify the influence of each parameter. The findings reveal that the cavitation intensity of the optimal Venturi is 2.76 times greater than that of the original design. Reducing β1 resulted in a swift conversion of static pressure into dynamic pressure, but it also caused an uneven distribution of fluid velocity. To reduce this unevenness and allow the dynamic pressure in the throat to reach its peak, which is advantageous for cavitation generation, lth should be extended. dth directly influenced the efficiency of converting static pressure into dynamic pressure and was a key factor in determining cavitation intensity. β2 indirectly impacted cavitation intensity by modulating the space available for cavitation development. The insights gained from this study may provide valuable guidance for designing Venturis in process intensification applications.

Optimization of Rotational Hydrodynamic Cavitation Reactor Geometry

A Rotary-Pulsation Apparatus (RPA), also known in the literature as a Rotational Hydrodynamic Cavitation Reactor (RHCR), is a device which typically consists of a rotating mechanism that generates pulsations or vibrations within a fluid. This can be achieved through various means such as mechanical agitation, pneumatic pulses, or hydraulic forces. It is widely used in food, chemical, pharmaceutical, and microbiological industries to improve the mixing of different fluids, dispersion, pasteurization, and sterilization. In the present paper, a CFD study was conducted to develop and optimize the geometry of the RPA’s rotor and stator to induce cavitation in the fluid flow. The effect of cavitation has the potential to improve dispersion and emulsion properties and to significantly reduce operation pressure, in comparison to conventional mixing systems.

Experimental investigation of chocked cavitation flow and its oscillation mechanism in jet pump cavitation reactors under limited operation stage

Experiments were conducted in this study to investigate the chocked cavitation characteristics and its oscillation mechanism in jet pump cavitation reactors (JPCR) under limited operation stage (LOS) utilizing a synchronous measurement system. The pulsation characteristics of cavitation in JPCR under various inlet and outlet pressures were analyzed by the processed high-speed camera images. Furthermore, correlation between cavitation and pressure pulsation as well as the mechanism of cavitation oscillation in JPCR under LOS are elucidated based on synchronized measurements. The results reveal that the typical jet choked cavitation flow field can be divided into three characteristic regions, i.e., stability region, oscillation region and collapse region. Changes in flow parameters cause variations in the areas of these three regions and shift the initial and collapse positions of cavitation. The time-averaged length of cavitation clouds varies linearly with the absolute pressure ratio at the outlet, corresponding to both stable and unstable LOS. Notably, the results reveal a clear correlation between the grayscale of cavitation clouds and pressure fluctuations over time, identifying the inverse pressure gradient as the primary cause of cavitation oscillation in the throat tube during unstable LOS.

Response surface optimization of a single-step castor oil-based biodiesel production process using a stator-rotor hydrodynamic cavitation reactor.

In order to combat environmental pollution and the depletion of non-renewable fuels, feasible, eco-friendly, and sustainable biodiesel production from non-edible oil crops must be augmented. This study is the first to intensify biodiesel production from castor oil using a self-manufactured cylindrical stator-rotor hydrodynamic cavitation reactor. In order to model and optimize the biodiesel yield, a response surface methodology based on a 1/2 fraction-three-level face center composite design of three levels and five experimental factors was used. The predicted ideal operating parameters were found to be 52.51°C, 1164.8rpm rotor speed, 27.43min, 8.4:1 methanol-to-oil molar ratio, and 0.89% KOH concentration. That yielded 95.51% biodiesel with a 99% fatty acid methyl ester content. It recorded a relatively low energy consumption and high cavitation yield of 6.09 × 105J and 12 × 10-3g/J, respectively. The generated biodiesel and bio-/petro-diesel blends had good fuel qualities that were on par with global norms and commercially available Egyptian petro-diesel. The preliminary cost analysis assured the feasibility of the applied process.

Advanced Processes in Water Treatment: Synergistic Effects of Hydrodynamic Cavitation and Cold Plasma on Rhodamine B Dye Degradation

The increasing pollution of water bodies, due to the constant release of highly toxic and non-biodegradable organic pollutants, requires innovative solutions for environmental remediation and wastewater treatment. In this study, the effectiveness of different Advanced Oxidation Processes (AOPs) for the purification of water contaminated with Rhodamine B (RhB) dye at a concentration of 5 mg/L were investigated and compared. Using the classical ozonation strategy as a benchmark treatment, the research showed over 99% degradation of RhB within 4 min in a laboratory-scale batch setup with a capacity of 0.2 L. In contrast, a “chemical-free” process exploiting ultrasound (US) technology achieved a 72% degradation rate within 60 min. Further experiments were conducted using a pilot-scale rotor-stator hydrodynamic cavitation (HC) reactor on a 15 L solution leading to 33% of RhB removal in the presence of hydrogen peroxide (H2O2) at 75 mg/L. However, the use of an innovative cavitational reactor, which hybridizes HC with cold plasma, showed remarkable efficiency and achieved 97% degradation of RhB in just 5 min when treating a 5 L solution at an inlet pressure of 20 bar in a loop configuration. In addition, a degradation rate of 58% was observed in a flow-through configuration, emphasising the robustness and scalability of the HC/electrical discharge (ED) plasma technology. These results underline the potential of hybrid HC/ED plasma technology as an intensified and scalable process for the purification of water, as it offers a catalyst- and oxidant-free protocol.

Introducing a Promising New Disinfection Technology for the Fonce River in Colombia

Urban wastewater disinfection is a critical component of environmental sustainability and human health. Current technologies for this are often costly and inaccessible to many communities. Typically, this treatment is carried out by chemical processes, with chlorination being the most common despite the potential for harmful disinfection byproducts. However, the emergence of promising alternatives, such as physical processes that utilize hydrodynamic cavitation reactors (HCRs), offers significant energy and environmental benefits. Based on this, the Fundación Universitaria San Gil, UNISANGIL, has developed a technology that utilizes hydrodynamic cavitation (HC) to disinfect urban wastewater samples discharged into the Fonce river in San Gil, Santander, Colombia. The primary objective of this research was to test the ability of a hydrodynamic cavitation system to reduce total coliforms and fecal coliforms (E. coli) in a 200 L tank containing 12.5 L of domestic urban wastewater diluted in 187.5 L of non-residual water. The methodology consisted of three steps: HCR design and simulation, HC implementation, and disinfection measurement. The experiments were conducted with a Venturi-type HCR, designed with computational fluid dynamics, and tested with wastewater samples from one of the ten discharges that flow into the river. The results obtained for a system with a flow capacity of 0.00625 m3/s show an average growth inhibition rate of 31.72 %, 59.45 %, and 84.53 % for one, ten, and twenty water recirculation, respectively, with an energy efficiency of 2327.6 CFU/J. The highest results reach a Growth Inhibition Rate (GIR) of 93.40 %, a Logarithmic Reduction (LR) of 1.18 for Total Coliforms, and a GIR of 95.12 % and an LR of 1.31 for E. coli. Finally, it is concluded that this technology holds great promise for efficiency and operational viability, with further testing required to realize its potential.

Experimental investigation on cavitation performance of the annular-slit rotational hydrodynamic cavitation reactor

Experimental investigation on cavitation performance of the annular-slit rotational hydrodynamic cavitation reactor

Unveiling the roles of turbulence characteristics on the degradation of methylene blue by the activation of H2O2 through vortex-based hydrodynamic cavitation under neutral condition

Presently, fast degradation of organic wastewater has been achieved by the synergetic method of hydrodynamic cavitation and H2O2 at a laboratory scale, while the physico-chemical effect, especially the turbulence characteristics on the degradation process remains lacking. This paper presents investigation on the degradation of dyeing wastewater containing methylene blue (MB) under neutral condition, within a vortex-based hydrodynamic cavitation (VBHC) reactor. Operating conditions are firstly optimized and then used to collaborate with H2O2 to study the synergetic effects of this hybrid treatment method. The turbulence characteristics are subsequently obtained by a computational fluid dynamics (CFD) simulation, and the correlation between them and the degradation process of MB is revealed. The results indicate that the highest degradation rate of 91.95 % is achieved under optimal conditions. Higher inlet pressure (4.5 bar) owns the thickest vapor volume fraction, greatest vapor transfer rate, and largest size of cloud cavity in the vortex core region, indicating the strongest cavitation intensity; meanwhile, moderate solution temperature (30 ℃) also favors for the greatest cavitation intensity inside the reactor. The optimal cavitation intensity activates the considerable production of reactive oxygen species, and results in good consistency with the MB degradation performance, which predominately occurs in the annular region around the vortex rope. This research unveils the rationale behind the physical essences of the VBHC process and its influence on the degradation efficacy of MB, which can provide reliable guidance for further development of cavitational reactors to degrade organic pollutants by the VBHC/H2O2 hybrid treatment method.

Degradation of Procion Golden Yellow H-R Dye Using Ultrasound Combined with Advanced Oxidation Process

The current study aims to degrade Procion Golden Yellow H-R through ultrasound-induced cavitation coupled with various oxidants. A comprehensive investigation was conducted to examine the impact of parameters, specifically pH, power, and frequency, on the extent of degradation. The primary aim was to optimize degradation by solely utilizing a cavitation reactor where only 23.8% degradation was observed under the established optimum conditions of pH 2.5, frequency of 22 kHz, and power of 200 W. The investigation of the combined process of cavitation with H2O2, Fenton reagent (H2O2/Fe2+), NaOCl, and potassium persulphate (KPS) was subsequently conducted under optimized conditions. The combined operations greatly enhanced degradation with the use of H2O2 loading of 0.1 g/L leading to 53.3% degradation and the H2O2/Fe2+ ratio of 1:0.25 resulting in 94.6% degradation, while the NaOCl quantum of 0.075 g/L yielded 90% degradation and the KPS quantity of 2 g/L resulted in 97.5% degradation in the specific combinations. A toxicity test on two bacterial strains, Staphylococcus aureus and Escherichia coli, was carried out using the original dye solution and after treatment. The various individual and combination processes were compared using the parameters of cavitational yield and total treatment cost. The study elucidates that combining ultrasonic cavitation with KPS is an effective method for treating wastewater containing Procion Golden Yellow H-R dye, especially when implemented at a larger scale of operation.

Ozonation degradation of wastewater using rotational hydrodynamic cavitation reactor with a conical rotor

ABSTRACT Water pollution caused by an abusive discharge of dye-containing wastewater leads to serious ecological risks. Conventional wastewater treatment methods have shortcomings of incomplete degradation, long-time treatment and secondary pollution. For the first time, a rotational hydrodynamic cavitation reactor (RHCR) equipped with a conical rotor has been designed to enhance the ozonation process for effective degradation of pollutants. The effects of rotational speed, discharge voltage, gas flow rate, liquid flow rate and initial pH on methylene blue (MB) degradation were deeply investigated. The optimised conditions were initial pH = 9, rotational speed = 1800 rpm, discharge voltage = 9.3 kV, gas flow rate = 60 mL/min and liquid flow rate = 80 mL/min. With the integration of ozonation and cavitation in RHCR, the MB degradation efficiency reached 95.2%, which was 15.6% higher than that of the individual ozonation method. The degradation process was proven to track the first-order kinetic model, with the reaction rate and synergy index were 0.232 min−1 and 1.78, respectively. Through the quenching experiments, it can be confirmed that the contribution proportion of hydroxyl radical during degradation was increased by 8.7% due to the enhancement of cavitation. A required energy consumption of 74.7 kWh/order/m3 and a total expense of 8.7 $/m3 were calculated. The energy consumption of the RHCR was approximately 80% lower than that of the recently reported degradation system combining ozonation and cavitation, with total expense reduced by 52%. The findings of this work provide a new water treatment method and offered theoretical references for the design of RHCR.

Evaluation of operational parameters and technology readiness for enhanced management of oilfield produced water treated by ozonation

Managing oilfield produced water (OPW) is a significant challenge for the petrochemical industry due to the high daily volumes generated and strict disposal limits for oil and grease (O&G) content. O&G levels are influenced by organic compounds known as naphthenic acids (NAs). This study explored ozonation to degrade cyclohexane carboxylic acid (CHCA, a model compound for NAs) present in a synthetic OPW matrix and reduce O&G in real OPW from offshore platforms. Experiments were conducted on four ozonation prototypes with varying effluent capacities: a simplified bench-scale prototype (200 mL), an extended bench-scale prototype (400 mL to 800 mL), a hydrodynamic cavitation reactor with Venturi (5 L), and a pilot unit reactor (25 L to 80 L). CHCA degradation ranged from 91 % to 100 % under optimized conditions for each prototype. Additionally, the ozonation treatment met the Brazilian National Environment Council’s disposal requirements for OPW in oceanic regions, achieving an O&G content below 29 mg/L within 30 min at natural pH. The energy required for degradation (ERC) decreased from 729.2 kWh/m3 to 30.3 kWh/m3 as ozonation scaled up from the simplified bench-scale system (200 mL) to the pilot scale (80 L). For real OPW, the ERC was even lower at 34.5 kWh/m3. These findings demonstrate the effectiveness of ozonation in treating OPW and underscore the importance of multi-scale studies to evaluate the technical and economic viability of this treatment technology. This contributes to the sustainable management of industrial waste even in space-restricted installations such as offshore oil production facilities.

Rotor–stator hydrodynamic cavitation reactor for intensification of castor oil biodiesel production

AbstractNowadays, the intensification of the production of biodiesel from non-edible oil crops is mandatory to overcome petrol-fuel depletion and environmental pollution. For the first time, enhanced biodiesel production from castor oil via rotor–stator hydrodynamic cavitation has been studied in this work. Response surface methodology based on one-factor-at-a-time design of experiments was employed for modelling and optimizing the biodiesel yield and the decrease in feedstock viscosity, density, and total acid number (TAN). The predicted optimum parameters of 8.15:1 methanol:oil (M:O), 1499 rpm, 29.38 min, 48.43 °C, and a KOH catalyst concentration of 0.74 wt.% resulted in a 96% biodiesel yield with a concomitant decrease in viscosity, density, and TAN of approximately 95%, 5.12%, and 90.02%, respectively. According to the results of the breakthrough kinetic calculations, the reaction is pseudo-second order, with the activation energy, frequency factor, and reaction rate constant being 0.23 M−1 min−1, 18.77 kJ/mol, and 6.32 M−1 min−1, respectively. The fuel properties of the produced biodiesel and bio-petro-diesel blends were good, comparable to international standards and the marketed Egyptian petro-diesel.

Study on cavitation and pulsation characteristics of a novel rotor-radial groove hydrodynamic cavitation reactor

Abstract Hydrodynamic cavitation is widely used in many fields such as water treatment, impact rock breaking, and food preparation. The performance of hydrodynamic cavitation is closely related to its internal flow field. In the present study, cavitation flow field was analyzed by computational fluid dynamics in the reactor. The cavitation performance of the rotor is evaluated under different operating conditions. The time frequency distribution of pressure pulsation is studied. The pressure increases at the connection point between the local low-pressure area and the mainstream low-pressure area. Cavitation bubbles collapsed at the tail end of the cavity to form a local void area. The blade frequency amplitude of pressure pulsation shows the significant periodic change. The blade frequency amplitude decreases along the flow direction. The effect of the fluid outlet led to the increase in the second-order harmonic frequency amplitude. The research results could provide theoretical support for the research of cavitation mechanism of cavitation equipment.

Investigation on the cavitation characteristic of a novel cylindrical rotational hydrodynamic cavitation reactor

Hydrodynamic cavitation reactors are of great promise for the applications of chemical process intensification and water treatment. In this work, a novel cylindrical rotational hydrodynamic cavitation reactor (CRHCR) with rectangular grooves and oblique tooth protrusions on the rotor surface was studied. The three-dimensional characterization of cavitation within the CRHCR was observed from the front and left views by the high-speed camera experiments. Interestingly, a new phenomenon of simultaneous formation of the attached cavitation and shear cavitation was found in the CRHCR. The synergistic effect of attached cavitation and shear cavitation contributes to the enhancement of the cavitation performance of CRHCR. In addition, the evolution of attached cavitation is explored. It is found that attached cavitation forms a trapezoidal-shaped cavitation cloud in the groove, which undergoes three various stages: incipient, development, and collapse. Finally, the pulsation frequency and cavitation intensity of shear cavitation in the chamber were investigated. The results show that the cavitation pulsation frequency is the same at the same rotational speed in the chamber near diverse oblique teeth. As the rotational speed increases, the cavitation pulsation frequency increases linearly. These findings in this paper are of great benefit to understanding the mechanism of the cavitation effect of CRHCR.

Removal of per- and polyfluoroalkyl substances (PFAS) from wastewater using the hydrodynamic cavitation on a chip concept

The elimination of micropollutants such as highly fluorinated substances, including per- and polyfluoroalkyl substances (PFAS), in wastewater treatment plants has been receiving growing attention due to the urgent need to minimize their adverse effects on natural water and associated ecosystems. Conventional treatment methods often fall short in effectively removing PFAS. In this study, the Hydrodynamic Cavitation on a Chip concept (HCOC) was utilized to degrade 11 common PFAS variants (PFAS11) for the first time in three different hydrodynamic cavitation reactor set-ups, each enhanced with surface modifications involving roughness elements. Stockholm municipal wastewater treated by a Membrane BioReactor (MBR) process was subjected to fully developed cavitating flow treatment using the three distinct microscale hydrodynamic cavitation (HC) reactors. The obtained results indicate that the chemical-free HCOC technique employed in this study has a significant potential in the degradation of nearly all investigated PFAS11 compounds at a notable rate of 36.1 % while the combination with MBR process can prevent blockage within the fluidic channels, enabling continuous operation with high throughput processing rates. Our proposed methodology demonstrated promising results in eliminating PFAS and could contribute to advancements in the use of microscale HC to treat micropollutants in wastewater. These findings could be a major leap in water treatment technologies addressing the global burden of resource-efficient micropollutant water treatment.

Quantification of phenol degradation using hydrodynamic cavitation‐based packed bed reactor based on glass balls

AbstractThe current study presents a novel and effective cavitation technique for the degradation of phenol using a hydrodynamic cavitation‐based packed bed reactor (HCPBR). Several operational parameters, including fluid velocity, hydrogen peroxide (H2O2) generation (18.06 μM of H2O2 in 60 min), and initial phenol concentration, have been studied using a HCPBR. The effective parameters for phenol degradation were found to be a fluid velocity of 85.15 m/s and an initial phenol concentration of 20 ppm. It was also noted that the presence of a glass marble‐bed (15.35%) in the cavitation reactor exhibits a substantial effect on the degradation of phenol compared to the absence of a glass marble‐bed (2.91%). The investigation also examined the effect of combining hydrodynamic cavitation with chemical oxidation processes, specifically H2O2, persulfate (Na2S2O8 and K2S2O8), and titanium dioxide, on the extent of phenol degradation. Persulfate was shown to have a significant effect on phenol degradation at 1 g/L. To clarify if free radical attack is the driving force behind degradation, the impact of radical scavengers such as n‐butanol has also been examined. Toxicological assessments revealed that, for lentil meristematic cells, the therapy was quite cytotoxic, but it needs to be improved to eliminate its genotoxic side effects. Overall, the experiment clearly demonstrated the effectiveness of the HCPBR for phenol degradation.

Investigations on cavitation flow and vorticity transport in a jet pump cavitation reactor with variable area ratios

Hydrodynamic cavitation (HC) has emerged as a promising technology for water disinfection. Interestingly, when subjected to specific cavitation pressures, jet pump cavitation reactors (JPCRs) exhibit effective water treatment capabilities. This study investigated the cavitation flow and vorticty transport in a JPCR with various area ratios by utilizing computational fluid dynamics. The results reveal that cavitation is more likely to occur within the JPCR as the area ratio becomes smaller. While as the area ratio decreases, the limit flow ratio also decreases, leading to a reduced operational range for the JPCR. During the cavitation inception stage, only a few bubbles with limited travel distances are generated at the throat inlet. A stable cavitation layer developed between the throat and downstream wall during the limited cavitation stage. In this phase, the primary flow carried the bubbles towards the outlet. In addition, it was found that the vortex stretching, compression expansion, and baroclinic torque terms primarily influence the vorticity transport equation in this context. This work may provide a reference value to the design of JPCRs for water treatment.