Lifting Pipe Research Articles

Simulation of special-shaped graded particulate hydraulic transport in deep-sea mining scenarios

Hydrodynamic transport is crucial in deep-sea mining engineering for conveying materials. This study investigates the impact of various particle shapes on slurry transport efficiency and flow characteristics at higher concentrations. A numerical method combining computational fluid dynamics (CFD) and the discrete element method (DEM) within the Euler-Lagrange framework is employed to simulate the flow and hydrodynamic properties of graded heterogeneous coarse particles in a deep-sea hydraulic lift pipe. The reliability of the simulations is verified through comparisons, focusing on feed concentration and particle gradation effects on dynamic characteristics and flow patterns. The study quantitatively analyzes concentration distributions under various flow regimes for different particle shapes and conveying concentrations in a vertical pipeline system. Flow characteristics under clogging conditions are described, considering flow transition and concentration distribution. Additionally, conditions for stable transportation are discussed concerning particle forces and transport reliability.

Experimental study on hydrate blockage formation and decomposition in gas-dominated Fluctuating pipes

Current research pertaining to hydrate flow assurance in the transportation of deep-sea natural gas through undulating pipelines remains sparse. Employing a novel undulating pipeline equipped with multipoint-distributed sensors, we delve to the processes of hydrate generation, migration, deposition, blockage, and decomposition. Our findings reveal that the upward inclination sections of both lifting and underlying pipes are particularly vulnerable to hydrate blockage. The lifting pipe is not conducive to hydrate deposition and blockage, whereas the underlying pipe poses a heightened risk for hydrate formation. Increasing subcooling leads to a reduction in blockage duration and sloughing frequency, alongside an extension in decomposition time. Furthermore, increasing the water injection rate and pipeline curvature prolongs the blockage of the lifting pipe. However, the impact of the water injection rate on the underlying pipe is negligible. Increasing pipeline curvature promotes the blockage of the underlying pipe. We propose models that encapsulate hydrate blockage and decomposition based on varying gas–liquid distributions. This research fills the gap in the study of hydrate blockage and decomposition in undulating pipelines and provides a reference for monitoring hydrate risks in natural-gas transmission pipelines.

Investigation on fatigue crack propagation failure mechanism of hydraulic lifting pipe in deep‐ocean natural gas hydrate exploitation

AbstractIn deep‐ocean natural gas hydrate exploitation operation, the fatigue failure mechanism has attracted more and more attention from scholars, but it has not been effectively disclosed. Therefore, in this work, a multifield coupling and multiple‐nonlinear vibration model of lifting pipe is established, which can accurately determine the alternating stress of deep‐ocean lifting pipe. Second, according to Forman theory, the calculation method of crack propagation length and depth on the surface of a deep‐water riser is established, which is verified by the comparison between the experimental and theoretical model calculation results. The results demonstrate that, first, the effect of residual stress in the welded joint of deep‐ocean lifting pipe should be considered in the later parameter influence analysis. Second, the fatigue growth life of deep‐water pipe with small outflow velocity is mainly determined by tensile stress, and that is determined by both tensile stress and bending stress with large outflow velocity. Third, more attention should be paid to the vibration of the lower pipe on‐site to reduce its vibration frequency and vibration stress amplitude, which can effectively reduce the surface crack propagation state of the deep‐ocean pipe and improve the service life of the pipe. Fourth, properly adjusting the tension coefficient of the tensioner during field operation can effectively improve the safety of the pipe, and the optimal tension coefficient is related to the configuration of the deep‐ocean pipe system, which can be analyzed and determined by the model.

Fluidization characteristics of iron ore powder in fluidized bed

The fluidization characteristics of iron powder were studied on a self-made cold fluidized bed in the laboratory. The pressure distributed in the axial inside the lifting pipe of a fluidized bed gradually decreases to a constant value from underbody to roof. As the gas flow rate in the fluidized bed increases, the pressure on each axial section first increases and then decreases. When the inflation numbers are fixed, as the operating gas speed increases, the pressure on the same height segment decreases. When the operating gas speed of a fluidized bed is constant, the pressure increases with the increase of inflation numbers. The pressure at different bed heights is affected differently by the operating air speed: at the underbody of the bed, the pressure rapidly decreases with increasing operating airspeed. As the cross-sectional height increases, the influence of operating gas speed on pressure gradually decreases. As the charge increases, the pressure at the underbody of the fluidized bed rises rapidly, while the pressure at the roof changes gently. When iron ore fine powder is fluidized, distribution in axes of particle concentration shows an uneven distribution of upper dilute and lower dense. Under a certain loading number, increasing the operating airspeed will reduce the average concentration of granules in each axial section of the entire bed, and the particle concentration distribution in that section will become uniform. As the number of charges increases, the average concentration of granules in the riser increases, and the difference in particle concentration between the underbody and roof parts of the riser decreases.

Determination of active concentrations and velocities of phases in airlift three-phase flows

A one-dimensional ascending steady flow of a mixture of air, water, and solids in a vertical lift lift pipe is considered. As a physical model, this three-phase flow is represented as the compatible movement of the pulp (a mixture of liquid and solid particles) and compressed air in the form of shells. It is assumed that the lifting of solid material is carried out by liquid plugs that move in the intervals between the air shells. The purpose of the work is to determine the actual concentrations and velocities of the phases as one of the important hydrodynamic characteristics of the flow. The method of statistical averaging of these characteristics is used, similar to the theoretical-probabilistic method of averaging in the theory of turbulence, the basis of which is the transition from consideration of a single flow to consideration of a statistical set of similar flows carried out under almost identical conditions. The actual phase concentrations in any given live current section are considered in terms of the unconditional probability of one or another phase passing through the section. To determine the true velocities of the phases, hydraulic continuity equations are used, containing probability-averaged hydrodynamic quantities and describing each phase individually as some continuum in the statistical sense. In this case, the true velocity of a phase in any given live section is defined as the statistical average of the velocity, provided that this phase clearly intersects the section. The expressions obtained for the real concentrations and velocities of the phases form the theoretical basis for the construction of a hydraulic mathematical model of the three-phase flow with respect to the problem of airlift calculation.

Surge and lifting analysis of internal transmission gas–liquid two-phase flow lifting pipe

The gas–liquid two-phase flow inside large aspect ratio lifting pipes is often characterized by a complex flow pattern, potentially causing coupling vibration of the lifting pipe. And produce a surge effect, aggravating the vibration of the lifting pipe and thus affecting its fatigue life and the lifting performance of the pipe. In this paper, a combination of numerical simulation and experiment is used to investigate the effects of inlet flow rate (Q) and tube diameter (D) on the vibration and lifting performance of the lifting tube. The obtained conclusions are as follows: with an increase in the inlet gas flow rate, the amplitude of the lifting pipe increases, and the lifting flow increases; with an increase in pipe diameter, the amplitude of the lifting pipe decreases and the overall lifting performance increases. According to the numerical simulation and experimental results, when D = 40 mm lifting pipe at the intake flow between Q = 50-60 L/min, the impact of surge effect is the least, and the liquid lifting quality also reaches the best state at this time, The research presented in this paper provides a reference for the selection of parameters for lifting pipes in engineering applications.

Vibration stability of a lifting pipe transporting solid–liquid two phase flow

A new mathematical model is developed to investigate the vibration stability of a lifting pipe induced by solid–liquid two phase flow. Three different slip models and the momentum conservation theorem are introduced to describe the slip characteristics of solid particles in two phase flow, which are coupled with the pipe vibration equations to establish a new governing equation and solved using the harmonic differential quadrature method. The mathematical model is validated by published data for the single-liquid flow case. Numerical results show that the slip model has noticeable effects on two phase flow-induced pipe vibration performance. The transport concentration of solid particles has a significant effect on the stability characteristic; however, the effect of particle size is very limited. The pipe flow mass ratio and the gravity coefficient are also key parameters affecting two phase flow-induced pipe vibration performance.

Full-Loop Study of a Pilot-Scale Dual Fluidized Bed Cold Flow System: Hydrodynamic Simulation

Computational particle fluid dynamics (CPFD) simulations of three-dimensional cold-flow gas-solid flow were performed for a pilot-scale dual-circulating fluidized bed (DCFB) using Barracuda Virtual Reactor® 17.4.0. This DCFB system is a fluidized bed gasifier used in a calcium-loop gasification process to produce a hydrogen-rich gas with CO2 capture. The effects of different bubble bed inlet airflow rates and different solid inventories on the full-loop pressure distribution and particle concentration distribution were compared. The increase in the bubble bed inlet airflow rate significantly increases the pressure in the bubble bed and lift pipe, and the increase in the solids inventory significantly increases the pressure where the solids are tightly packed. For long-term operation, the appropriate combination of parameters should be found to maintain a stable particle seal at the loopseals.

Multi-field coupling multiple nonlinear vibration model and fatigue failure mechanism of deep-ocean mining hydraulic lifting pipe

Multi-field coupling multiple nonlinear vibration model and fatigue failure mechanism of deep-ocean mining hydraulic lifting pipe

Studying the solution of the system of differential equations obtained in simulation of gas-lift process by the relaxation method

Using the relation method for the system of first order, two-dimensional hyperbolic type partial differential equations describing the motion of gas liquid gas mixture corresponding to gas-lift process of oil production in an annular and lifting pipe, we consider a boundary condition problem. In this problem the existence a boundary condition problem. In this problem the existence of the solution with respect to the equations of motion is studied and it is shown that when constructing the solution of this problem by means of boundary conditions, it is impossible to determine the coefficients of positive degrees of the parameter ε. For this reason, the solution is sought in the form of a series using negative degrees of the parameter ε.

Study on vibration characteristics of ship mining system under composite load

The load that borne by ship mining system is very complex. The vibration of lifting pipe can be significantly affected by ocean current and wind load, which has a key impact on material lifting, ore bin storage and ship towing. Considering the composite load condition, the vibration control equation of mining ship is established based on the transverse swing mechanism of ship hull, and the variation law of transverse disturbance is obtained. The dynamic equation is constructed according to the bearing characteristics of the lifting system and the D’Alembert principle. The Wilson method is used to analyze and obtain the transverse vibration spectrum response of the lifting pipe under different wind loads, hull disturbance velocity and water depth. Based on the analogy method and hammering method, the vibration feedback test-bed of the lifting system is built, and the time-domain and frequency-domain vibration characteristics of the lifting pipe model under different water depths are obtained. The results show that in shallow water, the disturbance of mining ship and the composite load of ocean current are the key factors affecting the vibration amplitude of lifting pipe respectively. With the increase of water depth, the characteristic frequency and amplitude of the system decrease, and the amplitude gradually presents a discontinuous phenomenon.

Numerical method for determining the coefficient of hydraulic resistance two-phase flow in a gas lift well

The process of stationary movement of a gas-liquid mixture in the lifting pipe of a gas-lift well is considered. To describe this two-phase flow, a mathematical model is proposed that includes the equation of flow motion and the continuity equation for each phase. The presented model is transformed to a single nonlinear ordinary differential equation with respect to pressure. Within the framework of the obtained model, the task is set to determine the hydraulic resistance coefficient of a two-phase flow according to an additionally specified condition with respect to pressure. An additional condition, presented in the form of a nonlinear algebraic equation, is transformed into an ordinary differential equation with respect to an unknown coefficient of hydraulic resistance by applying the method of differentiation by parameter. The solution of the resulting Cauchy problem is determined by the finite difference method. Based on the proposed computational algorithm, numerical experiments were carried out for model data. Keywords: gas lift; two-phase flow; hydraulic resistance coefficient; parameter differentiation method; finite difference method.

Simulating Thermal Interaction of Gas Production Wells with Relict Gas Hydrate-Bearing Permafrost

The thermal interaction of a gas production well with ice-rich permafrost that bears relict gas hydrates is simulated in Ansys Fluent using the enthalpy formulation of the Stefan problem. The model admits phase changes of pore ice and hydrate (ice melting and gas hydrate dissociation) upon permafrost thawing. The solution is derived from the energy conservation within the modeling domain by solving a quasilinear thermal conductivity equation. The calculations are determined for a well completion with three casing strings and the heat insulation of a gas lifting pipe down to a depth of 55 m. The thermal parameters of permafrost are selected according to laboratory and field measurements from the Bovanenkovo gas-condensate field in the Yamal Peninsula. The modeling results refer to the Bovanenkovo field area and include the size of the thawing zone around wells, with regard to free methane release as a result of gas hydrate dissociation in degrading permafrost. The radius of thawing around a gas well with noninsulated lifting pipes operating for 30 years may reach 10 m or more, while in the case of insulated lifting pipes, no thawing is expected. As predicted by the modeling for the Bovanenkovo field, methane emission upon the dissociation of gas hydrates caused by permafrost thawing around producing gas wells may reach 400,000–500,000 m3 over 30 years.

Multi-field coupling nonlinear vibration characteristics of hydraulic lifting pipe in deep-ocean mining

To address the problem of flow-induced vibration failure of lifting pipe in deep-ocean hydraulic mining, a multi-field coupling nonlinear vibration model of deep-ocean mining lifting pipe was established by using finite element method, energy method and Hamiltonian variational principle. The longitudinal-lateral coupling effect, external current vortex-induced effect and internal fluid pulsation effect were considered, and the numerical solution of the nonlinear vibration model of lifting pipe was realized with the Newmark-β method, Newton Raphson method and finite volume method. Using the same structural parameters, the correctness and effectiveness of the proposed model were verified by comparing with the simulated experimental measurement data in the literature. On this basis, the influence of the buffer station mass and wave parameter on the vibration response characteristics and nonlinear behavior of the lifting pipe were explored. The results show that the vibration frequency of the lifting pipe near the upper end is higher, and the vibration of the pipe string near the lower end is chaotic. With the increase of the buffer station mass, the in-line flow offset and root mean square stress of the lifting pipe decrease, and the axial force on its top end is greater. Under the higher mass of buffer station, the longitudinal vibration of the lifting pipe tends to quasi-periodic motion of the ring, but the vibration amplitude is larger. Small period and large amplitude waves have obvious influences on the vibration, stress and top axial force of the lifting pipe, and make its longitudinal vibration gradually transition from chaotic motion to quasi-periodic motion.

Dynamic Characteristics of Lifting Pipe on a Retrofitted Mining Vessel

Lifting pipe used in deep ocean mining is the tool to transport mineral from seabed to vessel. In this study, a vessel was retrofitted as an experimental ship for deep ocean mining with a U-type lifting pipe installed on the right side of vessel. Assuming pipe as a rigid structure, the impact of pipe on movements of vessel were discussed based on frequency domain method for hydrodynamic analysis.

Study on vessel–pipe coupling dynamic behavior under regular waves in deep sea mining process

A indirect time-domain coupling dynamic mathematical model of mining vessel–lifting pipe was established by combining the analysis method of mining vessel and lifting pipe in this paper. The vessel–pipe coupling experiments under various wave conditions were performed at the China National Ocean Technology Center, and a dynamic computer simulation of the coupled model was conducted to verify the effectiveness of the experiment and simulation. To simulate the coupling dynamic behavior, we established the hydrodynamic model of the vessel using AQWA software to determine the response amplitude operators (RAOs). Subsequently, the obtained RAO matrix was merged into an OrcaFlex model to analyze the dynamics of the mining vessel–lifting pipe interaction. In addition, the influencing factors of vessel–pipe coupling dynamics were estimated quantitatively, including regular wave, buffer mass, and sailing velocity. The findings show that the coupling effect has a significant impact on the vessel–pipe dynamic behavior, which has a strong relevance with surface waves, but a weak relevance with sailing velocity. In the process of changing the wave direction from 180° to 90°, the tension at the top of the pipeline increases by 19.31% and the coupling time decreases by 66.67%.

Investigation on Damage to Optical Fiber Cables Caused by Freezing and Thawing of Water in a Lifting Pipe

Investigation on Damage to Optical Fiber Cables Caused by Freezing and Thawing of Water in a Lifting Pipe

Analysis of longitudinal coupling dynamic characteristics of deep sea mining vessel and stepped lifting pipe

In deep-sea mining, the coupling dynamic response between the mining vessel and the lifting pipe is a significant problem, which directly affects the structural design of the lifting system and the safety of field operation. The characteristics of coupled motion model have not been fully considered in the existing research. Therefore, this paper uses time-domain coupled numerical model as the research object, considering ocean current, surface wave, pipe dynamics and vessel-pipe contact mechanics, to study the dynamic behavior of the lifting pipe and mining vessel during the process of deep-sea mining using AQWA and OrcaFlex softwares. The response amplitude operator (RAO) is used to compare the measured and simulations dynamic response of the mining vessel. There is a very good agreement in RAO between the experiments and simulations. The coupling simulation results show that the coupling effect has a significant effect on the time domain dynamic response of the lifting pipe, but has little effect on the average effective tension and longitudinal amplitude along the pipe length. The research results of this paper are of great significance to the safety design of deep-sea mining lifting system and the planning of deep-sea operation activities.

Study on structure optimization of a bubble cap against erosion wear of an S Zorb desulfurization reactor distribution plate

Bubble cap structures are researched for the particle erosion wear of the distribution plate (tray for short) in an S Zorb desulfurization reactor. The semi-empirical model of erosion wear prediction of gas–solid two-phase flow is revised by means of erosion wear experiments at high temperature and high speed. According to the revised erosion wear, the influence of the h0 (the distance from the bottom of the bubble cap to the tray), h1 (distance from the outlet of the lifting pipe to the top of the bubble cap interface), N (the number of cavities), d0 (the inner diameter of bubble cap) on erosion wear of trays are studied. The results show that a smaller h0 will make the erosion degree of the tray more serious; it is recommended to keep h0 = 17 mm. A larger h1 will alleviate the erosion wear degree of adsorbent particles on the tray, but considering the efficiency of the reaction, h1 = 36 mm is more appropriate. The increase of N reduces the erosion wear less but enhances the fluid disturbance and makes the erosion wear area unstable; so, N should be kept at 10. The increase of d0 reduces the velocity and density of fluid impacting the tray, thus reducing the erosion wear degree, which is an effective means.

CFD-DEM Simulation of Backflow Blockage of Deep-Sea Multistage Pump

The multistage centrifugal pump is the critical component of mineral resources lifting in deep-sea mining. The reflux of nodules in the lifting pipe caused by the emergency pump stop can easily cause the pump to clog. In this paper, coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM co-simulations) are used to clarify the solid-liquid two-phase flow in two-stage centrifugal pumps under different particle sizes (10–20, 20–30, 30–40, 40–50 mm) with constant particle concentration. The movement and accumulation behaviour of particles in different flow fields (pipeline to pump, the first to the second pump stage) is investigated. Meanwhile, the effect of particle size and particle reflux velocity on the blockage of the flow channel in the pump was investigated. Particle accumulation in the pump was observed to determine the key factors affecting the pump’s reflux capacity. The residual mass of particles in the pump at different particle sizes was counted. Simultaneously, the percentage of residual mass of 10–20 mm particles in the pump was compared between the experiment and the simulation with an acceptable tolerance of within 10%. In addition, pressure changes in the blockage-prone section were also investigated. A comparison between experiments and simulations verifies the consistency of the trend on the pump inlet pressure when clogged with 50 mm particles. It was found that larger particles in the range of 10–30 mm can better ensure the pump’s reflux performance.