Mixing Behavior of Natural Gas and Hydrogen in a High‐Efficiency Vane (HEV) Static Mixer

This study investigates the blending characteristics of natural gas (NG) and hydrogen in a Kenics static mixer using computational fluid dynamics. The effectiveness of the adopted numerical model is experimentally validated. The scenario of high-pressure, long-distance NG pipelines is considered, and the Soave–Redlich–Kwong equation of state is applied. The mixing uniformity and pressure loss are adopted as evaluation criteria to analyze the impact of factors such as the deflection angle of spiral blades, the number of blades, the length-to-diameter ratio, the hydrogen blending ratio (HBR), the pipeline pressure, and the temperature on mixer performance, followed by structural optimization of the mixer. It is found that a Kenics static mixer with two spiral blades, a length-to-diameter ratio of 2, and a deflection angle of 135° can achieve a mixing uniformity of 95% at the blade outlet while minimizing pressure loss. Increasing the HBR helps improve the mixing uniformity but also increases the pressure loss of the mixer. Increasing the pipeline pressure while keeping the hydrogen mole fraction constant enhances the mixing uniformity but also increases the pressure loss. Increasing the gas temperature reduces the mixing uniformity and the pressure loss. Overall, pipeline pressure and temperature changes have a minimal impact on the mixing characteristics. Under high-pressure conditions, the use of a real gas model is essential. This study provides theoretical guidance for the design of static mixers for hydrogen blending in high-pressure NG pipelines.

The global transition to clean and sustainable energy sources has sparked interest in hydrogen as a potential solution to reduce greenhouse gas emissions. Efficient and safe transportation of hydrogen is crucial for its integration into the energy network. One approach is utilizing existing natural gas infrastructure, but it introduces unique challenges. Hydrogen has distinct characteristics that pose potential hazards, requiring careful consideration for safe transportation through natural gas pipelines. Moreover, the absence of field data on component failure rates adds to the existing uncertainty in Quantitative Risk Assessment (QRA) for hydrogen transportation. QRA plays a vital role in enabling the safe deployment of hydrogen transportation through existing pipelines and is increasingly integrated into the permitting process. The lack of data impedes the comprehensive understanding of risks associated with hydrogen transportation. This paper aims not only to analyse the effects of hydrogen blending ratios on gas dispersion, release rates, jet fires, and explosions in natural gas pipelines, but also highlight the disparities in leak frequencies currently used for hydrogen or blended hydrogen. A QRA for hydrogen blending in natural gas pipelines is novel and timely because the behaviour of hydrogen in natural gas pipelines, a novel process with potential hazards, is not fully understood. Conducting a thorough QRA on hydrogen blending in gas pipelines, our study reveals innovative insights: higher blending ratios reduce release rates, impact safe distances, and maintain stable flame lengths. Despite an elevated explosion risk, scenarios remained below lethal overpressure values. This paper offers unique contributions to safety considerations in hydrogen transportation, guiding stakeholders toward informed decisions for a secure and sustainable energy future.

Performance analysis of coaxial shear static mixer for hydrogen blending into natural gas

Hydrogen blending of natural gas is an effective way to achieve carbon neutrality. In order to evaluate the influence of different static mixers on the mixing performance of natural gas and hydrogen, numerical simulation methods were used to analyze in detail the effects of SMX-type static mixers, LPD-type static mixers, and KSM-type static mixers on the mixing uniformity, internal flow field structure, and pressure loss of natural gas and hydrogen. The results show that in terms of blending uniformity, SMX static mixer > LPD static mixer > KSM static mixer. Based on flow characteristics, the spiral plate of the KSM static mixer reduces the time and opportunity for air flow to contact each other, the two elliptical plates of the LPD static mixer promote the mixing of the mixed gas to generate eddy current, and the SMX static mixer can realize the mixing in two dimensions: flow direction and radial direction. For pressure loss, the pressure loss of the three static mixers increased with the increase in the number of mixing units and basically showed a linear increase, and the pressure loss of the LPD static mixer was about twice that of the SMX static mixer and the KSM static mixer.

As a cost-effective transitional strategy, the integrated utilization and transportation of hydrogen and natural gas have gained significant attention as a viable pathway toward carbon neutrality. However, hydrogen's low density, viscosity, and calorific value cause upward migration and accumulation in pipelines, raising embrittlement risks. Its high diffusion and leakage rates also pose significant safety challenges. To address hydrogen-natural gas blending challenges, achieving uniform mixing is crucial. This study systematically examines hydrogen-methane mixing in T-junction pipelines via numerical simulations, analyzing hydrogen mixing ratios (HMR: 10-25%) and methane flow rates (4-10 m/s) to assess flow and mixing dynamics. The coefficient of variation (COV) quantifies mixing uniformity with spatial and temporal analyses, optimizing hydrogen injection for rapid, homogeneous mixing. The key findings are as follows: (1) The uniform mixing length (the minimum axial distance required for the first pipeline cross-section to achieve 95% mixing uniformity) decreases inversely with the HMR, from 100 D to 20.875 D (D represents the pipeline diameter) as the HMR rises from 10% to 25%. (2) Analysis of initial uniform mixing time (defined as the duration required for the first pipeline cross-section to achieve 95% mixing uniformity) shows significant reduction with increasing HMR. While methane flow rate has a less pronounced effect, it nevertheless contributes to reducing the outlet uniform mixing time (defined as the time required to attain 95% mixing uniformity at the pipeline outlet). (3) A fundamental trade-off in engineering applications is established: increasing the HMR reduces mixing length but extends overall mixing time (difference between outlet and initial mixing times), while higher methane flow rates shorten overall mixing time at the cost of increased mixing length. The primary objective of this research is to elucidate the fundamental fluid dynamics of hydrogen-methane mixtures in T-junction pipelines, providing scientific insights for the safe and efficient operation of hydrogen-blended natural gas pipeline systems.

Insight into the effects of hydrogen on inside-valve flow and Joule-Thomson characteristics of hydrogen-blended natural gas: A numerical study

The transportation of hydrogen is a weak link in the large‐scale development of the hydrogen energy industry. Injecting hydrogen into the natural gas pipeline network for transportation is an efficient way to achieve the large‐scale, long‐distance, and low‐cost transportation of hydrogen. Hydrogen can lead to hydrogen embrittlement in natural gas pipelines and cause safety incidents if hydrogen and natural gas are not mixed uniformly. Therefore, it is necessary to study the blending process and blending uniformity of hydrogen and natural gas. In this study, a three‐dimensional model of the hydrogen‐injected natural gas pipeline was constructed. The effects of hydrogen injection inlet and turbulator configuration on the mixing process of hydrogen and natural gas were investigated using a computational fluid dynamics approach. The results show that increasing the number of hydrogen injection inlets shortens the distance L98% of uniform mixing of hydrogen and natural gas. Increasing the radial distance r from the initial hydrogen mixing positions to the center of the pipeline will shorten the distance for uniform gas mixing in the pipeline. The addition of turbulator configurations in the pipeline significantly reduces the distance to uniform gas mixing. Changing the distance Lturb from the turbulator to the initial mixing position further shortens the distance between hydrogen and natural gas mixing uniformly. The results of this study provide a reference for the structural design of the hydrogen–natural gas mixing pipeline and the gas distribution state during the mixing process.

Introduction Structural Types and Construction Static Mixers from Tubes or Short Pipes Static Mixers of Plates or Sheets Helical Static Mixers Wire Matrix Turbulators Effects of Static Mixers on Momentum Transfer Flow Structure Pressure Drop Gas-Holdup Liquid Velocity Mixing Mass Transfer in Presence of Static Mixers Heat Transfer Using Static Mixers Scale-up Considerations Concluding Remarks Nomenclature References

The static mixer is a non-moving structure used for mixing fluid medium in the pipeline, and structural parameters are important factors affecting the mixing effect. Due to the unclear influence of structural parameters on mixing uniformity for dredged mud and curing agent mixed by static mixers, the motion mode of fluid medium and the influence of unit number and deflection angle between adjacent units on the mixing uniformity are studied by multiphase flow simulation. The results show that the fluid in the cross-plate panel static mixer exhibits an alternating spiral forward motion mode, and the coefficient of uniformity of dredged mud and curing agent can be reduced by 26% - 98% after mixing. Under the conditions that the deflection angle is less than or equal to 60°, the mixing uniformity of the cross-plate panel static mixer with 2 pieces is better than that with 4 pieces. The mixing uniformity increases with the increase of the number of units. There is an optimal deflection angle between adjacent units, and too small or too large deflection angle will lead to the decrease of mixing uniformity. The study will help to optimize the structure of the existing pneumatic flow mixing device and improve the mixing effect.

Geometry optimization of a deswirler for cyclone separator in terms of pressure drop using CFD and artificial neural network

A novel static mixer for blending hydrogen into natural gas pipelines

BACKGROUND Mixing is one of the most important unit operations in process industries. Owing to the low energy consumption and high continuity, static mixers are widely used in chemical and biochemical industries. The structure of static mixers determines the flow pattern within the device, which directly influences the mixing performance. Therefore, optimizing the geometry of mixing elements is critical for enhancing mixing efficiency. This study proposes a novel curved‐sheet typed static mixer with symmetrical folded blades (CSFB) and investigates its mixing performance using computational fluid dynamics (CFD). RESULTS The CSFB static mixer with six mixing elements achieved a mixedness of 99.5% at an inlet Reynolds number (Re in ) of 2500. Its distributive and dispersive mixing performance outperformed the Kenics, LPD and Komax static mixers. The CSFB static mixer achieved complete homogeneity within a shorter distance than the other static mixers. Additionally, the flow resistance of the CSFB mixer was lower than that of a high‐mixing performance CBF static mixer with asymmetrically arranged blades. CONCLUSION The multiblade structure of the CSFB mixing element enhanced radial flow and promoted the rapid mixing of fluids. The perforated blades reduced pressure drop by minimizing the collision between the fluid and blades. Compared with the previously reported high‐mixing performance CBF static mixer with asymmetric blades, the CSFB static mixer achieved complete mixing at a lower pressure drop. © 2025 Society of Chemical Industry (SCI).

The total pressure drop in horizontal wells is considered to consist of reversible (acceleration) and irreversible (wall friction, perforation roughness, mixing effects) pressure drop. The fundamental equations for pressure drop are presented along with relationships used for pipe junction flow. Experiments on a perforated pipe with 144 perforations, geometrically similar with wellbore casing (12 SPF, 60° phasing), are presented and analyzed. The results are applied to a typical horizontal oil well in the North Sea. It was found that the total pressure drop consists typically of 80 percent wall friction, IS percent mixing effects (including perforation roughness) and 5 percent pressure drop due to acceleration.

Viscous liquids have to be homogenized in continuous operations in many branches of processing industries; and therefore, fluid mixing plays a critical role in the success or failure of many industrial processes. The use of static mixers has been utilized over a wide range of applications from simple blending to complex chemical reactions. Generally, a static mixer consists of a number of equal stationary units, placed on the inside of a pipe or channel in order to promote mixing of flowing fluid streams. These mixers have low maintenance and operating costs, low space requirements and no moving parts. A range of designs exists for a wide range of specific applications. The shape of the elements determines the character of the fluid motion and thus determines the effectiveness of the mixer. There are several key parameters in the design procedure of a static mixer. Some of the most important ones are: the degree of mixing of working fluids, pressure drop across the mixer, and residence time distribution of fluid elements. An ideal static mixer provides a highly mixed material with low pressure drop and similar traveling history for all fluid elements. To choose a static mixer for a given application or in order to design a new static mixer, besides experimentation, it is possible to use powerful computational fluid dynamics (CFD) tools to study the performance of static mixers. This paper extends previous studies by the authors on industrial static mixers and illustrates how static mixing processes of single-phase viscous liquids can be simulated numerically. Using different measuring tools, the global performance and costs of two static mixers are studied.

CFD and lower order mechanistic models for gas-liquid flow in NETmix: Pressure drop and gas hold-up