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A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Separation Processes".

Deadline for manuscript submissions: 30 June 2026 | Viewed by 8068

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Special Issue Editors

Dr. Zhiyi Xiong

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Guest Editor

College of Mechanical and Transportation Engineering, China University of Petroleum Beijing, No.18, Fuxue Road, Changping District, Beijing 102249, China
Interests: multiphase flow process; separation equipment; modeling and simulation; centrifugal compressor performance and reliability

Dr. Xinwei Wang

E-Mail Website
Guest Editor

College of New Energy, China University of Petroleum (East China), No. 66, West Changjiang Road, Qingdao 266580, China
Interests: characterization of thermal properties under extreme conditions; theory and technology of heavy oil thermal recovery; comprehensive energy utilization technology for oil fields

Special Issue Information

Dear Colleagues,

This Special Issue on “Multiphase Flow Process and Separation Technology” mainly concerns research papers on new technologies of multiphase flow and separation equipment, new methods of research, theories of design, etc. Researchers are welcome to submit their papers. It is expected that the research methodology, including the research design, experimental methods, sample selection, and data analysis techniques, should be detailed; the main results should highlight the significance and novelty of the submissions.

Topic include, but are not limited to, the following:

The development of models or simulations or experiments of multiphase processes.
The development of models or simulations or experiments of separation equipment.
Design, analysis, optimization, and performance of novel separation technologies.
Simulation techniques, algorithms, or other tools for modeling and simulation.

Thank you, and I hope you consider participating in this Special Issue.

Dr. Zhiyi Xiong
Dr. Xinwei Wang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

multiphase flow process
separation equipment strengthening
new design
research method
gas–liquid–solid separation

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Published Papers (8 papers)

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Research

25 pages, 19561 KB

Open AccessArticle

Emergency Plugging and Killing of Blowout Preventer Failure

by Xuliang Zhang, Zhi Zhang, Qingfeng Li, Haitao Wang, Hangbo Cui, Hua Wang and Fumin Gao

Processes 2025, 13(12), 3959; https://doi.org/10.3390/pr13123959 (registering DOI) - 7 Dec 2025

Abstract

The blowout preventer (BOP) is the most important and the last line of safety defense in drilling engineering. Once a blowout occurs and the BOP fails, engineers will lose control of the entire wellbore pressure, and combustible fluids in the formation will continuously sprayed out, which can easily cause huge losses of life and property. At present, reliable and highly recognized emergency measures for BOP failure are lacking. Therefore, we propose a plugging method after the failure of the BOP that can maintain good control within the secondary well control. Numerical and experimental results indicate that using a small-to-medium displacement (1–2 m³/min) during the early stage of plugging and applying multiple plugging and killing cycles significantly improves plugging stability and killing efficiency. PEEK (polyether ether ketone) was selected as the bridging material for field plugging tests on full-scale blowout preventers, verifying its sealing effectiveness at pressures up to 80 MPa. Subsequently, the CFD–DEM was used to simulate the well killing process after plugging. This study mainly focused on the transportation of particles in a pipeline and the analysis of the process of well killing after plugging. The research results indicate that PEEK demonstrates sufficient pressure-bearing capacity under real blowout conditions. Also reveal that PEEK’s exceptional wear resistance and impact strength help maintain sealing stability during repeated particle–wall collisions, effectively reducing secondary erosion and prolonging the operational lifespan of temporary plugging structures. After undergoing six high-pressure tests of 70 MPa and two high-pressure tests of 80 MPa within 25 min, it remained intact. Both cylindrical and spherical particles can smoothly pass through the storage tank and double-bend pipeline at different displacements. Considering the retention effect of the plugging material, it is recommended to use 1–2 m³/min of pumping the plugging material at medium and small displacements in the early stage of plugging. During the process of plugging and killing, it is recommended to use alternating plugging and killing across multiple operations to prevent further blowouts to achieve the best plugging and killing effect. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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14 pages, 4297 KB

Open AccessArticle

Numerical Simulation of Natural Gas Waste Heat Recovery Through Hydrated Salt Particle Desorption in a Full-Size Moving Bed

by Liang Wang, Minghui Li, Yu Men, Yun Jia and Bin Ding

Processes 2025, 13(8), 2589; https://doi.org/10.3390/pr13082589 - 15 Aug 2025

Viewed by 604

Abstract

To achieve energy conservation, emission reduction, and green low-carbon goals for gas storage facilities, it is crucial to efficiently recover and utilize waste heat during gas injection while maintaining natural gas cooling rates. However, existing sensible and latent heat storage technologies cannot sustain long-term thermal storage or seasonal utilization of waste heat. Thermal chemical energy storage, with its high energy density and low thermal loss during prolonged storage, offers an effective solution for efficient recovery and long-term storage of waste heat in gas storage facilities. This study proposes a novel heat recovery method by combining a moving bed with mixed hydrated salts (CaCl₂·6H₂O and MgSO₄·7H₂O). By constructing both small-scale and full-scale three-dimensional models in Fluent, which couple the desorption and endothermic processes of hydrated salts, the study analyzes the temperature and flow fields within the moving bed during heat exchange, thereby verifying the feasibility of this approach. Furthermore, the effects of key parameters, including the inlet temperatures of hydrated salt particles and natural gas, flow velocity, and mass flow ratio on critical performance indicators such as the outlet temperatures of natural gas and hydrated salts, the overall heat transfer coefficient, the waste heat recovery efficiency, and the mass fraction of hydrated salt desorption are systematically investigated. The results indicate that in the small-scale model (1164 × 312 × 49 mm) the outlet temperatures of natural gas and mixed hydrated salts are 79.8 °C and 49.3 °C, respectively, with a waste heat recovery efficiency of only 33.6%. This low recovery rate is primarily due to the insufficient residence time of high-velocity natural gas (10.5 m·s⁻¹) and hydrated salt particles (2 mm·s⁻¹) in the moving bed, which limits heat exchange efficiency. In contrast, the full-scale moving bed (3000 × 1500 × 90 mm) not only accounts for variations in natural gas inlet temperature during the three-stage compression process but also allows for optimized operational adjustments. These optimizations ensure a natural gas outlet temperature of 41.3 °C, a hydrated salt outlet temperature of 82.5 °C, a significantly improved waste heat recovery efficiency of 94.2%, and a hydrated salt desorption mass fraction of 69.2%. This configuration enhances the safety of the gas injection system while maximizing both natural gas waste heat recovery and the efficient utilization of mixed hydrated salts. These findings provide essential theoretical guidance and data support for the effective recovery and seasonal utilization of waste heat in gas storage reservoirs. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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16 pages, 3729 KB

Open AccessArticle

Throttling Effect and Erosion Research of Ultra-High-Pressure Grease Nozzles

by Shaobo Feng, Zhixiong Xu, Hongtao Liu, Bao Zhang, Fumin Gao, Hongtao Jing and Pan Yang

Processes 2025, 13(8), 2555; https://doi.org/10.3390/pr13082555 - 13 Aug 2025

Viewed by 514

Abstract

To accommodate the extreme thermodynamic effects and erosion damage in throttling equipment for ultra-high-pressure natural gas wells (175 MPa), a coupled multiphase flow erosion numerical model for nozzles was established. This model incorporates a real gas compressibility factor correction and is based on the renormalized k-ε RNG (Renormalization Group k-epsilon model, a turbulence model that simulates the effects of vortices and rotation in the mean flow by modifying turbulent viscosity) turbulence model and the Discrete Phase Model (DPM, a multiphase flow model based on the Eulerian–Lagrangian framework). The study revealed that the nozzle flow characteristics follow an equal-percentage nonlinear regulation pattern. Choked flow occurs at the throttling orifice throat due to supersonic velocity (Ma ≈ 3.5), resulting in a mass flow rate governed solely by the upstream total pressure. The Joule–Thomson effect induces a drastic temperature drop of 273 K. The outlet temperature drops below the critical temperature for methane hydrate phase transition, thereby presenting a substantial risk of hydrate formation and ice blockage in the downstream outlet segment. Erosion analysis indicates that particles accumulate in the 180° backside region of the cage sleeve under the influence of secondary flow. At a 30% opening, micro-jet impact causes the maximum erosion rate to surge to 3.47 kg/(m²·s), while a minimum erosion rate is observed at a 50% opening. Across all opening levels, the maximum erosion rate consistently concentrates on the oblique section of the plunger front. Results demonstrate that removing the front chamfer of the plunger effectively improves the internal erosion profile. These findings provide a theoretical basis for the reliability design and risk prevention of surface equipment in deep ultra-high-pressure gas wells. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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17 pages, 4576 KB

Open AccessArticle

Experiment and Simulation on the Influence of Fire Radiation on the Evaporation of Liquefied Natural Gas

by Li Xiao, Fan Yang, Jing Tian, Wenqing Song and Cunyong Song

Processes 2025, 13(6), 1673; https://doi.org/10.3390/pr13061673 - 26 May 2025

Viewed by 1053

Abstract

With the introduction of the “dual carbon” strategy, public attention to green energy has surged, leading to a notable increase in the demand for natural gas. Consequently, the storage and transportation of liquefied natural gas (LNG) have emerged as critical aspects to ensure its safe and cost-effective utilization. For onshore LNG storage, LNG storage tanks play a pivotal role. However, in extreme scenarios such as fires, these tanks may be exposed to radiant heat, which not only jeopardizes their structural integrity but could also result in LNG leaks, triggering severe safety incidents and environmental disasters. Against this backdrop, this study delves into the evaporation characteristics of large-scale LNG storage tanks under fire radiation conditions. Given the unique properties of LNG and the similarity between the bubble-point lines and heat exchange curves of nitrogen and LNG, liquid nitrogen is employed as a substitute for LNG in experimental investigations to observe evaporation behaviors. Furthermore, the FLUENT 2022R1 software is utilized to conduct numerical simulations on a 160,000-cubic-meter LNG storage tank, aiming to model the intricate process of internal evaporation and the impact of environmental factors. The findings of this research aim to furnish a scientific basis for enhancing the storage safety of large-scale LNG storage tanks. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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16 pages, 11809 KB

Open AccessArticle

Multi-Layer Filter Material with a Superoleophobic Pore Size Gradient for the Coalescence Separation of Surfactant-Stabilized Oil-in-Water Emulsions

by Xingdong Wu, Ying Wang, Chengzhi Li, Lang Liu, Xiaowei Li and Cheng Chang

Processes 2025, 13(5), 1600; https://doi.org/10.3390/pr13051600 - 21 May 2025

Cited by 1 | Viewed by 963

Abstract

The performance of oil–water coalescence separation elements currently fails to meet the increasing demands of the oily wastewater treatment industry. To address this challenge, a series of fiber coalescing filters were developed through an underwater superoleophobic modification process using a simple impregnation technique. The effect of varying surface wettability on the separation efficiency of oil-in-water (O/W) emulsions stabilized with surfactants was investigated. The results demonstrate that, after undergoing underwater superoleophobic modification, the separation efficiency of the fiber filter material improved by 33.9%, the pressure drop was reduced by 46.1%, and the steady-state quality factor increased by 83.3%. Building upon these findings, an oil-repellent pore size gradient structure was introduced for the coalescence separation of surfactant-stabilized oil-in-water emulsions. This structure exhibited outstanding characteristics, including a low pressure drop and a high-quality factor. Furthermore, when processing emulsions stabilized with surfactants such as OP-10 (nonionic), CTAB (cationic), and SDS (anionic), the structure maintained high separation efficiencies of 93.6%, 96.4%, and 97.2%, respectively, after 10 cycles. Finally, based on experimental data and theoretical analysis, a separation mechanism for oil–water coalescence using superoleophobic pore size gradient filtration materials is proposed. This structure demonstrates significant potential for widespread application in liquid–liquid separation technologies. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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23 pages, 17410 KB

Open AccessArticle

Analysis and Optimization of Thermal Storage Performance of Thermocline Storage Tank with Different Water Distribution Structures

by Xinwei Wang, Longbin Duan, Genying Gao, Weibo Zheng, Dong Sun, Jinyu Li, Jing Fu and Riyi Lin

Processes 2025, 13(3), 629; https://doi.org/10.3390/pr13030629 - 22 Feb 2025

Cited by 3 | Viewed by 1912

Abstract

Energy storage is essential for solar energy utilization, and thermocline storage tanks are commonly used. To improve temperature stratification and storage efficiency, we investigated the effect of different water distributor configurations on tank stratification. We numerically analyzed the heat storage processes in hot water tanks with three water distribution configurations: star, antenna, and octagonal. Temperature stratification was evaluated based on thermocline thickness and storage efficiency. Thermal storage efficiency improves by 0.45% when the outlet direction of the water distributor matches the fluid’s motion direction during natural stratification. The energy storage process is categorized into three stages based on efficiency changes, with different factors affecting efficiency at each stage. In the initial stage, antenna-type and octagonal water distribution improve temperature uniformity along the axial section, reduce thermocline thickness, and enhance stratification. Final efficiency during this stage is primarily influenced by energy loss resulting from the mixing of hot and cold water. In the development stage, energy storage efficiency decreases mainly because the lower boundary of the thermocline reaches the exit, causing partial discharge of hot water. Among the three configurations, the octagonal water distribution exhibits the lowest energy loss, 6.4% lower than that of the star-type distribution. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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21 pages, 9485 KB

Open AccessArticle

Numerical Study of the Soil Temperature Field Affected by Natural Gas Pipeline Leakage

by Weichun Chang, Xiaolong Gu, Xiahua Zhang, Zenian Gou, Xin Zhang and Zhiyi Xiong

Processes 2025, 13(1), 36; https://doi.org/10.3390/pr13010036 - 27 Dec 2024

Cited by 1 | Viewed by 1145

Abstract

This study investigates the impact of natural gas pipeline leakage on the soil temperature field through numerical simulations. Physical and mathematical models were developed to analyze the temperature and flow field changes resulting from pipeline leaks. The study explores the influence of various leakage factors on the temperature distribution in the surrounding soil. Key findings include the identification of the buried pipeline temperature as a critical factor influencing the soil temperature gradient when surface temperatures are similar to the subsurface constant temperature. Upon leakage, the pressure distribution around the leak is symmetrical, with a higher pressure at the leak point, and the Joule–Thomson effect causes a rapid decrease in gas temperature, forming a permafrost zone. The study also reveals that increased transport pressure expands the permafrost area, with pressure playing a significant role in the temperature field distribution. Additionally, an increase in the leak orifice diameter accelerates the expansion of the permafrost area and reduces the time for temperature stabilization at monitoring points. Conversely, changes in the leak direction mainly affect the spatial distribution of the permafrost zone without significantly altering its size. The findings provide valuable insights for monitoring natural gas pipeline leaks through temperature field variations. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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21 pages, 10529 KB

Open AccessArticle

A Study on the Influence of Core Stability on the Coring Process of Long-Barrel Coring Tools

by Jiliang Liu, Jinsheng Sun, Guancheng Jiang and Yongjin Yu

Processes 2024, 12(12), 2847; https://doi.org/10.3390/pr12122847 - 12 Dec 2024

Viewed by 1259

Abstract

In the process of long-barrel coring, the improper selection of operating parameters can easily cause blocked deformation, violent vibration of the core, core fracture, and impact crushing, which lead to a reduction in the stability of the core and core harvesting rates. Accurate knowledge of the influence of relevant factors on core stability is the key to improving core harvesting rates. Therefore, in this study, a numerical calculation model for tight and fractured cores in a barrel was constructed based on the Drucker–Prager criterion, using the finite element method. A numerical calculation model of a core broken into a barrel was constructed using the discrete element method. A study was conducted on the influence law of core stability under different core lengths, rotational speeds, weights on bit, and well inclination angles. The influence of each factor on core stability was analysed based on the vibration displacement and stress distribution characteristics of the core. The calculations show that increasing the weight on bit and reducing the rotation speed can effectively reduce the radial vibration displacement and local stress in tight and fractured cores, reduce the possibility of core fracture or breakage, and improve core stability. When the well inclination angle is large, it can easily cause core deformation and wall sliding, generating large contact stress and radial vibration displacement, significantly reducing the core stability. A broken core has the worst stability and is easily compacted in the core barrel, producing secondary crushing and plugging effects. Increasing the core barrel length resulted in a more unstable core. Compared with single-barrel coring, the distortion of the core column under double-barrel coring was more evident. In addition, the coring process, cuttings distribution, and drill bit hydraulic characteristics were studied based on the CFD-DPM method. The conclusions of this study are of great significance for optimising coring operation parameters to further improve core stability and coring harvest rate. Full article

(This article belongs to the Special Issue Multiphase Flow Process and Separation Technology)

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