Hydrodynamic cavitation (HC) is an emerging, energy-efficient process intensification technology with potential to enhance efficiency, yield, and sustainability across key refinery operations. By generating controlled microscale shear, turbulence, and localized thermal–mechanical effects - within RAPTECH´s CaviFlow® units - HC can improve mixing, mass and heat transfer, reaction kinetics, and feedstock conditioning. This review evaluates HC integration opportunities across crude desalting, delayed coking, fluid catalytic cracking, hydrotreating, alkylation, and residuum upgrading, with emphasis on mechanistic understanding, equipment configuration, and operational constraints.
Recent practical results—including residuum blending and upgrading—demonstrate measurable benefits in heavy fuel oil blending with alternative fuels. Cavitation-assisted blending of HFO with 20% FAME has shown improved viscosity, density, sediment content, and stability indices, as well as reduced cat-fines and modest fuel consumption improvements. These findings highlight HC’s relevance not only for refinery processes but also for the maritime/bunker fuel sector, particularly in the context of ISO 8217:2024, which permits marine fuels containing up to 100% FAME. The results reflect a broader industry trend toward low-carbon, renewable, and more variable feedstocks.
Overall, HC and RAPTECH´s CaviFlow® units present a promising pathway to improve processability, reduce energy requirements, and support the transition toward more sustainable refinery and marine fuel systems. While most data originate from laboratory and pilot-scale studies, emerging demonstrations—including residuum blending and upgrading—underline HC’s potential for practical industrial deployment.
Keywords: Hydrodynamic cavitation, Refinery conversion, Process intensification, Heavy oil upgrading, Delayed coking, Fluid catalytic cracking, Hydrotreating, Residuum blending
1. Introduction
Refinery conversion processes are central to transforming crude oil into transport fuels, petrochemical feedstocks, and high-value products. Efficiency and product quality are often limited by feedstock heterogeneity, catalyst deactivation, fouling, and mass transferconstraints. The increasing use of heavy and extra-heavy crude oils, which constitute a significant portion of recoverable global reserves, presents additional challenges due to high viscosity, low API gravity (<20°), and elevated asphaltene content [1]. These properties hinder heat and mass transfer, accelerate fouling, and increase coke formation in thermal andcatalytic processes.
Hydrodynamic cavitation (HC) has emerged as apromising process intensification strategy. It generates controlled microbubbles, localized hotspots, extreme shear, and pressure gradients, which can enhance chemical reactions, phase dispersion, and mass transfer. Compared to conventional mechanical mixing or chemical additives, HC represents apotentially energy-efficient and low-chemical approach to addressing refinery bottlenecks [2]. HC can be combined with catalysts, surfactants, mild oxidants (e.g., H₂O₂, ozone), or UV irradiation to further improve reaction efficiency and cleaner processing outcomes [2].
Mechanistically, cavitation can induce molecular-level modifications in hydrocarbons, including asphaltene disaggregation, partialcracking, and rheological property changes, which improve feedstock handlingand reaction efficiency [3]. Scaling HC to industrial operations is challenging due to the absence of a standardized method to quantify cavitation intensity across different fluids an require high capital and operational costs [1,4]. Evidence from laboratory and pilotstudies suggests HC can improve processability and efficiency, although full-scale industrial validation remains limited.
HC-assisted processes may offer operational and environmental benefits, including reduced energy consumption, enhanced throughput, and lower greenhouse gas emissions. They can complement conventional upgrading methods, which are often energy-intensive and rd reactor designs. The cavitation number has been proposed as a systematic parameter to optimize reactor design and bridge experimental data with practical applications.
2. High-Impact Hydrodynamic Cavitation Opportunities
2.1 Crude Desalting (CDU)
Integrating HC at the desalter inlet can enhance oil–water dispersion and salt removal. Micro-turbulence, shear, and localized pressure fluctuations promote breakup of stable emulsions, generating fine, uniform droplets that improve water–oil contact and accelerate coalescence. This can result in lower residual salt content, reduced fouling and corrosion, and improved heat-exchange performance [2]. HC units can be implemented as compact inline skids with minimal modifications to existing desalting infrastructure.
2.2 Delayed Coking (DCU)
Applying HC to vacuum residue before coker heaters can improve feed homogenization and induce mild pre-upgrading effects. Shear, micro-mixing, and localized thermal–mechanical activation promote partial asphaltene disaggregation and viscosity reduction, enabling more uniform thermal cracking [5,3]. Pilot-scale studies have reported improvements in heater stability, reductions in coke deposition, and modest increases in liquid product yields when HC is integrated upstream of the coker. Maintaining the appropriate cavitation intensity is essential to avoid excessive pre-cracking, particularly in highly aromatic or unstable feeds [1,3]. Proper HC system design and optimization of operating conditions are therefore critical for safe and effective implementation.
2.3 Fluid Catalytic Cracking Unit (FCCU)
Pre-conditioning heavy feeds (e.g., vacuum gas oil or residue) via HC may enhance feed homogenization and partially disrupt asphaltene- and metal-rich aggregates, potentially lowering the effective contaminant load that contributes to CCR formation [6]. The intense shear and micro-mixing generated by cavitation can also improve dispersion, mass transfer, and overall feed rheology, which may support higher conversion efficiency and reduced fouling tendencies. These effects have been demonstrated at pilot scale, but no publicly available data confirm full-scale FCC implementation to date. Integrating HC upstream of an FCC unit requires careful engineering of the feed injection interface, including pressure, temperature, metallurgy, and compatibility with existing preheat and feed distribution systems.
2.4 Hydrotreaters (DHT, CNHT, NHT)
HC-assisted hydrogen–oil pre-mixing can improve H₂ dispersion and interfacial contact, potentially enhancing desulfurization, nitrogen removal, and olefin saturation [2,8]. Micro-turbulence and shear increase available interfacial area, mitigating mass-transfer limitations that reduce catalyst effectiveness. Pilot validation is recommended to optimize cavitation severity, residence time, and module integration. Properly engineered HC modules—pressure-rated skids with materials compatible with process conditions—may support higher per-pass conversion and improved catalyst longevity.
2.5 Jet Fuel Caustic Treating (JCTU)
In jet fuel caustic treating, HC intensifies contact between caustic solution and hydrocarbons, improving mercaptan extraction and product stability. Micro-mixing and high interfacial renewal may reduce caustic consumption while maintaining or enhancing sweetening performance. Inline HC systems allow straight forward retrofitting with minimal process disruption.
2.6 Alkylation Units (H₂SO₄ ALKY)
HC can enhance acid–hydrocarbon contact in alkylation units, promoting more uniform reaction conditions and potentially improving octane number and product yield [6]. High shear, micro-turbulence, and pressure fluctuations accelerate acid-catalyzed reactions. Implementation requires rigorous materials selection, corrosion-resistant design, and strict safety protocols. Pilot-scale validation is recommended before full-scale adoption.
2.7 Residuum Upgrading & Blending
Hydrodynamic cavitation (HC) can support both blending and partial upgrading of heavy residua and vacuum residues by enhancing dispersion, reducing viscosity, and improving overall fuel stability.
Upgrading applications
For upgrading, cavitation promotes asphaltene disaggregation, mild cracking, viscosity reduction, a shift toward lighter fractions, and sludge minimization [2–4]. HC-assisted residuum treatment has been shown to be more cost-effective than acoustic cavitation for pilot-scale operations and may enhance bitumen properties, desulfurization, and emulsion stability in applications such as FCC feedstocks, hydrotreaters, and marine fuels [4,7,8]. While most reported benefits derive from lab and pilot scales, proper control of cavitation intensity and residence time is critical for safe and effective implementation.
Blending applications
In blending operations, HC promotes the formation of fine, stable dispersions between heavy oils and lower-viscosity components such as biodiesel or pyrolysis oils. The high shear and micro-turbulence generated during cavitation improve miscibility, reduce the propensity for phase separation, and enhance homogeneity during storage and handling.
Independent testing at Bureau Veritas and data-physics laboratories confirmed these improvements. Table 1 summarizes a comparison of HFO 380 blended with 20% biodiesel (FAME) using conventional hand blending (HD) and cavitation-assisted blending (CF) with Raptech’s CaviFlow® system. The cavitation-assisted method produced measurable improvements in density, viscosity, sulfur content, ash content, sediment levels, and mean stability index (MSI), while also reducing cat-fines concentration. Engine testing by FVTR GmbH additionally reported a modest (~1%) reduction in fuel consumption for the cavitation-treated HFO–20% FAME blend.
Depending on vessel size, operational profile, and fuel pricing, such property improvements can translate into meaningful operational benefits in the maritime sector, where heavy fuel oil remains a dominant energy source.
Table 1. Comparison of HFO 380 blended with 20% biodiesel (FAME) using conventional hand blending (HD) and cavitation-assisted blending (CF).
(1) Heavy oils with °API < 22.3 are typically classified as “heavy fuel oil.”
(2) Although the flash point decreased, both blends remain well above ISO 8217 minimum limits for residual marine fuels, ensuring compliance with safety regulations.
3. Conclusion
Hydrodynamic cavitation represents a versatile process-intensification tool capable of addressing several persistent challenges in petroleum refining, including feedstock heterogeneity,mass-transfer limitations, fouling, and the processing of high-viscosity residues. Across crude desalting, thermal and catalytic conversion units, caustic treating, and alkylation, HC offers opportunities to improve dispersion, reaction uniformity, and operational stability while potentially reducingenergy consumption and environmental impact.
The promising results demonstrated for residuum upgrading and cavitation-assisted blending—particularly the improved handling and stability of HFO–FAME mixtures— underscore HC’s relevance as both the refining and maritime/bunker fuelsectors transition toward more diverse and renewable fuel streams. The introduction of ISO 8217:2024 [9], enabling marine fuels containing up to 100% FAME, further amplifies the need for technologies that canstabilize mixtures of heavy petroleum fractions with alternative fuels. HC’sability to reduce viscosity, improve phase stability, and mitigate sediment andcontaminant issues positions it as a practical enabler in this evolvinglandscape.
Successful industrial adoption will depend on:
Although current evidence is predominantlypilot-scale, HC-assisted heavy oil treatment and fuel blending demonstrate encouraging pathways for increasing refinery efficiency, enabling alternativefuel integration, and supporting broader decarbonization and sustainabilityobjectives [4]. These benefits are directly applicable to the maritime/bunker fuel sector, providing operational, environmental, and fuel quality improvements.
Author: Dr. Ahmad Saylam | RAPTECH Eberswalde GmbH
References
Recent practical results—including residuum blending and upgrading—demonstrate measurable benefits in heavy fuel oil blending with alternative fuels. Cavitation-assisted blending of HFO with 20% FAME has shown improved viscosity, density, sediment content, and stability indices, as well as reduced cat-fines and modest fuel consumption improvements. These findings highlight HC’s relevance not only for refinery processes but also for the maritime/bunker fuel sector, particularly in the context of ISO 8217:2024, which permits marine fuels containing up to 100% FAME. The results reflect a broader industry trend toward low-carbon, renewable, and more variable feedstocks.
Overall, HC and RAPTECH´s CaviFlow® units present a promising pathway to improve processability, reduce energy requirements, and support the transition toward more sustainable refinery and marine fuel systems. While most data originate from laboratory and pilot-scale studies, emerging demonstrations—including residuum blending and upgrading—underline HC’s potential for practical industrial deployment.
Keywords: Hydrodynamic cavitation, Refinery conversion, Process intensification, Heavy oil upgrading, Delayed coking, Fluid catalytic cracking, Hydrotreating, Residuum blending
1. Introduction
Refinery conversion processes are central to transforming crude oil into transport fuels, petrochemical feedstocks, and high-value products. Efficiency and product quality are often limited by feedstock heterogeneity, catalyst deactivation, fouling, and mass transferconstraints. The increasing use of heavy and extra-heavy crude oils, which constitute a significant portion of recoverable global reserves, presents additional challenges due to high viscosity, low API gravity (<20°), and elevated asphaltene content [1]. These properties hinder heat and mass transfer, accelerate fouling, and increase coke formation in thermal andcatalytic processes.
Hydrodynamic cavitation (HC) has emerged as apromising process intensification strategy. It generates controlled microbubbles, localized hotspots, extreme shear, and pressure gradients, which can enhance chemical reactions, phase dispersion, and mass transfer. Compared to conventional mechanical mixing or chemical additives, HC represents apotentially energy-efficient and low-chemical approach to addressing refinery bottlenecks [2]. HC can be combined with catalysts, surfactants, mild oxidants (e.g., H₂O₂, ozone), or UV irradiation to further improve reaction efficiency and cleaner processing outcomes [2].
Mechanistically, cavitation can induce molecular-level modifications in hydrocarbons, including asphaltene disaggregation, partialcracking, and rheological property changes, which improve feedstock handlingand reaction efficiency [3]. Scaling HC to industrial operations is challenging due to the absence of a standardized method to quantify cavitation intensity across different fluids an require high capital and operational costs [1,4]. Evidence from laboratory and pilotstudies suggests HC can improve processability and efficiency, although full-scale industrial validation remains limited.
HC-assisted processes may offer operational and environmental benefits, including reduced energy consumption, enhanced throughput, and lower greenhouse gas emissions. They can complement conventional upgrading methods, which are often energy-intensive and rd reactor designs. The cavitation number has been proposed as a systematic parameter to optimize reactor design and bridge experimental data with practical applications.
2. High-Impact Hydrodynamic Cavitation Opportunities
2.1 Crude Desalting (CDU)
Integrating HC at the desalter inlet can enhance oil–water dispersion and salt removal. Micro-turbulence, shear, and localized pressure fluctuations promote breakup of stable emulsions, generating fine, uniform droplets that improve water–oil contact and accelerate coalescence. This can result in lower residual salt content, reduced fouling and corrosion, and improved heat-exchange performance [2]. HC units can be implemented as compact inline skids with minimal modifications to existing desalting infrastructure.
2.2 Delayed Coking (DCU)
Applying HC to vacuum residue before coker heaters can improve feed homogenization and induce mild pre-upgrading effects. Shear, micro-mixing, and localized thermal–mechanical activation promote partial asphaltene disaggregation and viscosity reduction, enabling more uniform thermal cracking [5,3]. Pilot-scale studies have reported improvements in heater stability, reductions in coke deposition, and modest increases in liquid product yields when HC is integrated upstream of the coker. Maintaining the appropriate cavitation intensity is essential to avoid excessive pre-cracking, particularly in highly aromatic or unstable feeds [1,3]. Proper HC system design and optimization of operating conditions are therefore critical for safe and effective implementation.
2.3 Fluid Catalytic Cracking Unit (FCCU)
Pre-conditioning heavy feeds (e.g., vacuum gas oil or residue) via HC may enhance feed homogenization and partially disrupt asphaltene- and metal-rich aggregates, potentially lowering the effective contaminant load that contributes to CCR formation [6]. The intense shear and micro-mixing generated by cavitation can also improve dispersion, mass transfer, and overall feed rheology, which may support higher conversion efficiency and reduced fouling tendencies. These effects have been demonstrated at pilot scale, but no publicly available data confirm full-scale FCC implementation to date. Integrating HC upstream of an FCC unit requires careful engineering of the feed injection interface, including pressure, temperature, metallurgy, and compatibility with existing preheat and feed distribution systems.
2.4 Hydrotreaters (DHT, CNHT, NHT)
HC-assisted hydrogen–oil pre-mixing can improve H₂ dispersion and interfacial contact, potentially enhancing desulfurization, nitrogen removal, and olefin saturation [2,8]. Micro-turbulence and shear increase available interfacial area, mitigating mass-transfer limitations that reduce catalyst effectiveness. Pilot validation is recommended to optimize cavitation severity, residence time, and module integration. Properly engineered HC modules—pressure-rated skids with materials compatible with process conditions—may support higher per-pass conversion and improved catalyst longevity.
2.5 Jet Fuel Caustic Treating (JCTU)
In jet fuel caustic treating, HC intensifies contact between caustic solution and hydrocarbons, improving mercaptan extraction and product stability. Micro-mixing and high interfacial renewal may reduce caustic consumption while maintaining or enhancing sweetening performance. Inline HC systems allow straight forward retrofitting with minimal process disruption.
2.6 Alkylation Units (H₂SO₄ ALKY)
HC can enhance acid–hydrocarbon contact in alkylation units, promoting more uniform reaction conditions and potentially improving octane number and product yield [6]. High shear, micro-turbulence, and pressure fluctuations accelerate acid-catalyzed reactions. Implementation requires rigorous materials selection, corrosion-resistant design, and strict safety protocols. Pilot-scale validation is recommended before full-scale adoption.
2.7 Residuum Upgrading & Blending
Hydrodynamic cavitation (HC) can support both blending and partial upgrading of heavy residua and vacuum residues by enhancing dispersion, reducing viscosity, and improving overall fuel stability.
Upgrading applications
For upgrading, cavitation promotes asphaltene disaggregation, mild cracking, viscosity reduction, a shift toward lighter fractions, and sludge minimization [2–4]. HC-assisted residuum treatment has been shown to be more cost-effective than acoustic cavitation for pilot-scale operations and may enhance bitumen properties, desulfurization, and emulsion stability in applications such as FCC feedstocks, hydrotreaters, and marine fuels [4,7,8]. While most reported benefits derive from lab and pilot scales, proper control of cavitation intensity and residence time is critical for safe and effective implementation.
Blending applications
In blending operations, HC promotes the formation of fine, stable dispersions between heavy oils and lower-viscosity components such as biodiesel or pyrolysis oils. The high shear and micro-turbulence generated during cavitation improve miscibility, reduce the propensity for phase separation, and enhance homogeneity during storage and handling.
Independent testing at Bureau Veritas and data-physics laboratories confirmed these improvements. Table 1 summarizes a comparison of HFO 380 blended with 20% biodiesel (FAME) using conventional hand blending (HD) and cavitation-assisted blending (CF) with Raptech’s CaviFlow® system. The cavitation-assisted method produced measurable improvements in density, viscosity, sulfur content, ash content, sediment levels, and mean stability index (MSI), while also reducing cat-fines concentration. Engine testing by FVTR GmbH additionally reported a modest (~1%) reduction in fuel consumption for the cavitation-treated HFO–20% FAME blend.
Depending on vessel size, operational profile, and fuel pricing, such property improvements can translate into meaningful operational benefits in the maritime sector, where heavy fuel oil remains a dominant energy source.
Table 1. Comparison of HFO 380 blended with 20% biodiesel (FAME) using conventional hand blending (HD) and cavitation-assisted blending (CF).
| Parameter | Unit | Blending (HD) | Blending (CF) | Improvement (%) |
|---|---|---|---|---|
| Density at 50°C | kg/m³ | 948.7 | 945.5 | 0.3 |
| °API @ 60 °F (1) | - | 13.83 | 14.32 | 3.5 |
| Kinematic Viscosity at 50°C | cSt | 109.2 | 94.72 | 13 |
| Sulfur Content | % (m/m) | 1.35 | 1.33 | 1.5 |
| Ash Content | % (m/m) | 0.024 | 0.023 | 4 |
| Pour Point | °C | -15 | -15 | 0 |
| Flash Point | °C | 129.5 | 103.5 | -20 (2) |
| Total Sediment Potential | % (m/m) | 0.04 | 0.03 | 25 |
| Total Sediment Existent | % (m/m) | 0.03 | 0.02 | 33 |
| Mean Stability Index (MSI) | - | 0.24 | 0.19 | 26 |
| Cat Fines (Al&Si) | mg/kg | 9 | 6 | 50 |
(1) Heavy oils with °API < 22.3 are typically classified as “heavy fuel oil.”
(2) Although the flash point decreased, both blends remain well above ISO 8217 minimum limits for residual marine fuels, ensuring compliance with safety regulations.
3. Conclusion
Hydrodynamic cavitation represents a versatile process-intensification tool capable of addressing several persistent challenges in petroleum refining, including feedstock heterogeneity,mass-transfer limitations, fouling, and the processing of high-viscosity residues. Across crude desalting, thermal and catalytic conversion units, caustic treating, and alkylation, HC offers opportunities to improve dispersion, reaction uniformity, and operational stability while potentially reducingenergy consumption and environmental impact.
The promising results demonstrated for residuum upgrading and cavitation-assisted blending—particularly the improved handling and stability of HFO–FAME mixtures— underscore HC’s relevance as both the refining and maritime/bunker fuelsectors transition toward more diverse and renewable fuel streams. The introduction of ISO 8217:2024 [9], enabling marine fuels containing up to 100% FAME, further amplifies the need for technologies that canstabilize mixtures of heavy petroleum fractions with alternative fuels. HC’sability to reduce viscosity, improve phase stability, and mitigate sediment andcontaminant issues positions it as a practical enabler in this evolvinglandscape.
Successful industrial adoption will depend on:
- Precise control of cavitation intensity to balance efficiency gains with equipment integrity.
- Ensuring compatibility with high-temperature, corrosive, or high-viscosity process streams.
- Integrating HC modules into existing refinery configurations without disrupting critical process control.
Although current evidence is predominantlypilot-scale, HC-assisted heavy oil treatment and fuel blending demonstrate encouraging pathways for increasing refinery efficiency, enabling alternativefuel integration, and supporting broader decarbonization and sustainabilityobjectives [4]. These benefits are directly applicable to the maritime/bunker fuel sector, providing operational, environmental, and fuel quality improvements.
Author: Dr. Ahmad Saylam | RAPTECH Eberswalde GmbH
References
- Demirbas, A.; Bafail, A.; Nizami, A.-S. Heavy oil upgrading: Unlocking the future fuel supply. Petroleum Science and Technology, 2016, 34(4), 303–308. DOI: 10.1080/10916466.2015.1136949.
- Panda, D.; Saharan, V. K.; Manickam, S. Controlled Hydrodynamic Cavitation: A Review of Recent Advances and Perspectives for Greener Processing. Processes, 2020, 8, 220. DOI: 10.3390/pr8020220.
- Kuimov, D.; Minkin, M.; Yurov, A.; Lukyanov, A. Current State of Research on the Mechanism of Cavitation Effects in the Treatment of Liquid Petroleum Products—Review and Proposals for Further Research. Fluids, 2023, 8, 172. DOI: 10.3390/fluids8060172.
- Neelima, N. V.; Bhattacharya, S.; Holkar, C. R.; Jadhav, A. J.; Pandit, A. B.; Pinjari, D. V. Cavitation-Assisted Transformations in Bitumen Processing: A Review. Industrial & Engineering Chemistry Research, 2024, 63, 6047–6065. DOI: 10.1021/acs.iecr.4c00785.
- Wan, C.; Wang, R.; Zhou, W.; Li, L. Experimental study on viscosity reduction of heavy oil by hydrogen donors using a cavitating jet. RSC Advances, 2019, 9, 2509–2515. DOI: 10.1039/C8RA08087A.
- Stebeleva, O. P.; Minakov, A. V. Application of Cavitation in Oil Processing: An Overview of Mechanisms and Results of Treatment. ACS Omega, 2021. DOI: 10.1021/acsomega.1c05858.
- Davudov, D.; Ghanbarnezhad Moghanloo, R. A systematic comparison of various upgrading techniques for heavy oil. Journal of Petroleum Science and Engineering, 2017, 156, 623–632. DOI: 10.1016/j.petrol.2017.05.014.
- Cako, E.; Wang, Z.; Castro-Muñoz, R.; Rayaroth, M. P.; Boczkaj, G. Cavitation based cleaner technologies for biodiesel production and processing of hydrocarbon streams: A perspective on key fundamentals, missing process data and economic feasibility – A review. Ultrasonics Sonochemistry, 2022, 88, 106081. DOI: 10.1016/j.ultsonch.2022.106081.
- CIMAC Fuels Working Group. CIMAC Guideline: Marine fuels containing FAME — ISO 8217:2024. CIMAC, 2024.
