Minimum Transport Velocity Research Articles

Application of oscillation flow to horizontal gas–particle two-phase flow

The purpose of this study is to apply the oscillation flow induced by a combination of a circular cylinder and non-uniform soft fins to gas–solid two-phase flows to reduce the transport gas velocity and power consumption in a horizontal pipe. In order to evaluate the oscillation flow, several different sizes of square and circular cylinders are used to combine four pieces of soft fins with non-uniform lengths, which are mounted on the horizontal central plane in front of the particle supply. The test pipe comprises a horizontal acrylic pipe with a length of 5 m and an inside diameter of 80 mm. Spherical polyethylene particles with an average diameter of 2.3 mm and density of 978 kg/m3 were used as the test particles. The average gas velocity was 9–16 m/s, and the solid mass flow rate was 0.11–0.51 kg/s. It is found that the combination of a circular cylinder or square cylinder of L = 10 mm with non-uniform soft fins causes the lowest pressure drop and highest velocity fluctuation in the oscillation flow based on single-phase flow (gas only) measurement. Compared to conventional gas–solid two-phase flows, the reduction in the minimum transport velocity, pressure drop, power consumption, and additional pressure drop were obtained using a combination of a circular cylinder with non-uniform soft fins. This combination provides the highest reduction rates in the minimum conveying velocity and an additional pressure drop by approximately 10.0% and 34.1%, respectively. Based on particle image velocimetry measurements, the time-mean particle velocity and particle fluctuating velocity of a circular cylinder with non-uniform soft fins were higher than those of conventional flows near the bottom part of the pipe, thus easily accelerating and suspending particles near the pipe bottom, even at lower gas velocities.

An Enhanced Model for the prediction of Minimum Transport Conditions in Multiphase Flow Systems

Hydrocarbon production accompanied by the flow of sand from reservoirs is unavoidable as many of the formations are poorly consolidated. The deposition of the produced sand at low velocities or production of sand at very high velocity can pose serious challenges to the condition of the petroleum pipeline as it can lead to pipeline capacity reduction and degradation respectively. It is therefore important to investigate the minimum transport velocity that prevents sand deposition in the pipelines. In this study, the firefly optimization algorithm (FFA) was used in the development of the improved model for the prediction of minimum transport condition (MTC) in a multiphase pipeline. The model development was implemented using the MATLAB software package. The input parameters were sand concentration, particle diameter, viscosity, density and superficial velocity of the hydrocarbons. The developed model was observed to perform better than the base model with a R2 value of 0.9845 and 0.8149 for the developed model and base model respectively. The newly developed model was also compared with some existing models and the statistical measures show that the developed model gave a better performance. This enhanced model can be used for the prediction of MTC in multiphase pipelinesKeywords— Algorithms, Artificial Neural Network (ANN), Firefly algorithm (FFA), Minimum Transport Condition (MTC)

Investigation of cuttings transport in a horizontal well with high-speed visualization and electrical resistance tomography technique

In a horizontal well drilling operation, a part of generated drill cuttings tends to settle down at a lower annular section. Formation of sand bed causes several operational issues such as low rate of penetration and stuck drill pipe. In this study, a lab-scale experimental work is carried out to investigate hole cleaning in the extended reach and horizontal drilling operation. This work focuses on the visualization of the flow behaviour of drill cuttings in the horizontal annular section. A 6.16 m-long horizontal well test section with an outer diameter of 4.5 inch (11.43 cm) and an inner diameter of 2.5 inch (6.35 cm) is used in this study. Four non-Newtonian Herschel-Bulkley fluids are tested as the drilling mud. Solid glass beads of 2.5–3.0 mm with a density of 2650 kg/m3 are utilized as the drill cuttings with two different solid concentrations. The flow behaviour in the horizontal annular section is analyzed with a high-speed imaging technology at 2000 frames/second and electrical resistance tomography (ERT) technique. The effects of fluid rheology, fluid velocity, drill pipe rotation, and eccentricity on the cuttings transport are investigated. This study showed that an optimum drill pipe rotation of 80 RPM and a minimum transport performance number (TPN) of 70 is required for efficient hole cleaning in horizontal well section. This study also reveals that fluid rheology has a significant effect on the minimum transport velocity (MTV). A flow regime analysis revealed that a turbulent flow regime is required for effective hole cleaning without sand bed formation. The mechanistic three-layer model of cuttings transport is experimentally verified with high-speed visualization techniques. Furthermore, this study introduces the concept of estimating the instantaneous annular solid volume fraction by the ERT system as well as visualization of solid bed distribution in the annulus section.

Measurement and analysis of flow regimes transition by acoustic and electrostatic signals in vertical pneumatic conveying

Acoustic and electrostatic signals were used to detect and analyze the flow regimes transition in vertical pneumatic conveying from the scope of particle motion. It was found that the minimum acoustic energy and electrostatic accumulation appeared close to the minimum transport velocity. Furthermore, analysis of particle velocity based on electrostatic signals demonstrated that negative particle velocities appeared in plug flow since particles fell down between plugs, thus collision between falling particles and plug dominated and the energy fraction of collision increased with the decreasing gas velocity in plug flow. Finally, based on combination of different detection methods, two new flow regimes transition diagrams were developed. The one based on AE energy and pressure drop indicated different relationships between particle-wall interaction and energy loss in different flow regimes, while another one based on the electrostatic accumulation demonstrated the transition zone between the minimum transport velocity and flow regime transition velocity.

Investigation of sand transport in an undulated pipe using computational fluid dynamics

A CFD model has been implemented to investigate the effects the pipe undulation on sand transport. Of particular interest of the present study is the sand deposition in small angled V-inclined bend relevant to oil and gas subsea flowlines where sand deposition could be a major problem. The model used is the two-fluid Eulerian-Eulerian model with the granular temperature to tackle the solid phase properties. A number of sub-models for tackling solid-fluid and fluid-fluid interaction has been incorporated in the modelling frame work to capture the transition of flow regimes. The simulation results show that the seemingly small angled V-inclined has significant impact on sand disposition compared to the horizontal section. Sand is deposited at the downstream section of the V-inclined pipe at much higher velocities compared to the minimum transport velocity of the horizontal pipe.

A Hydrodynamic Study of a Fast‐Bed Dual Circulating Fluidized Bed for Chemical Looping Combustion

AbstractThis study explores the use of a dual interconnected circulating fluidized bed (CFB) for chemical looping combustion. This design can enhance gas–solid interactions, but it is difficult to control the solid transfer and circulation rates. With the use of a 1:1 scale cold‐flow model, an investigation determining the hydrodynamic behavior of the dual CFB system has been conducted. The cold‐flow system consists of two identical fast‐bed risers, each with an internal diameter of 100 mm and a height of 7 m. The simplified cold‐flow model is based on the chemical looping Pilot‐Scale Advanced CO2 Capture Technology (PACT) facility at Cranfield. Here, we have determined the minimum fluidization and transport velocities, and we have assessed the solid density profiles, transport capacity, and potential for the dilution by air/N2 leakage into the CO2 stream exiting the fuel reactor. The experimental procedure uses two different bed materials, molochite (ceramic clay) and FE100 (iron particles), and it satisfies the dynamic scaling laws to model the bed inventory within the system. The results indicate that the two fast‐bed risers share similar density and pressure profiles. Stable circulation can be achieved through pneumatic transport. The circulation rate of the system is flexible and can be adjusted by altering the fluidization velocity in the riser and by altering the bed inventory. The gas leakage from the loop seal to the cyclone was found to be sensitive to the bed height and fluidization velocity in the loop seal. However, by maintaining a loop‐seal bed height above 600 mm during operation, the outlet stream remains undiluted.

EXPERIMENTAL INVESTIGATION OF SAND MINIMUM TRANSPORT VELOCITY IN MULTIPHASE FLUID FLOW IN PIPES

The production of reservoir fluid through long tiebacks/pipelines has emerged as one of the cost effective alternative especially for many marginal fields which can now be produced as clusters into a common processing facility. However, sand is often co-produced with the reservoir fluid especially when produced from unconsolidated formations. The sand will settle to form beds along the bottom of the pipe if the fluid velocity is below the minimum transport velocity required (MTV). In order to prevent solid deposition and ensure flow assurance, it is therefore critical to identify and measure the MTV. Two approaches are generally recognised for development of solid minimum transport velocity models in pipelines, the analytical and empirical methods. Because of the complexities of multiphase flow, the analytical approach will often require some assumptions and inputs from empirical measurement. This study presents the results of the experimental investigation for minimum transport velocity (MTV) both in suspension and rolling. The minimum transport velocity was found to be greatly influenced by the flow patterns and pipe inclinations. It was observed that the slug flow provides better solid carrying capacity in pipes when compared with other observed flow patterns. It was also observed that the influence of pipe inclination diminishes beyond 20⁰. The acquired experimental data will ultimately provide a comprehensive data base for testing and validations of analytical models for improved accuracy. The justification for experimental work was evident from the inconsistent and inaccurate results obtained using existing analytical models for MTV predictions. http://dx.doi.org/10.4314/njt.v35i3.9

A generalized model to predict minimum particle transport velocities in multiphase air–water horizontal pipes

A new model is proposed to predict minimum flow rates required to constantly move particles in both intermittent and stratified flow regimes. The new model consists of a single‐phase flow model along with an appropriate length scale to be extended to multiphase flow regime. A comparison of the new model with experimental data in a multiphase air–water flow shows that the new model is able to predict minimum flow rates well for a wide range of operating conditions. The new model can capture the effects of particle size, particle concentration, and pipe size as confirmed by experimental data. A comparison of the new model with previously proposed models in the literature shows that the new model improves critical velocity predictions significantly. Moreover, the new model is the only model that takes into account the effect of particle concentration and can predict critical velocity in both intermittent and stratified flow regimes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2634–2646, 2015

Validated scale-up procedure to predict blockage condition for fluidized dense-phase pneumatic conveying systems

This paper presents results of an ongoing investigation into modelling fluidized dense-phase pneumatic conveying of powders. For the reliable design of dense-phase pneumatic conveying systems, an accurate estimation of the blockage boundary condition or the minimum transport velocity requirement is of significant importance. The existing empirical models for fine powder conveying in fluidized dense-phase mode are either based on only a particular pipeline and product or have not been tested for their accuracy under a wide range of scale-up conditions. In this paper, a validated test design procedure has been developed to accurately scale-up the blockage boundary with the help of a modelling format that employs solids loading ratio and Froude number at pipe inlet conditions using conveying data of two different samples of fly ash, electro-static precipitation (ESP) dust and cement (particle densities: 2197–3637kg/m3; loose poured bulk densities: 634–1070kg/m3; median size: 7–30μm). The developed models (in power function format) have been used to predict the blockage boundary for larger diameter and longer pipelines (e.g. models based on 69mm I.D.×168m long pipe have been scaled up to 105mm I.D. and 554m length). The predicted blockage boundaries for the scale-up conditions were found to provide better accuracy compared to the existing models.

Sand Transportations and Deposition Characteristics in Multiphase Flows in Pipelines

Sand management strategies become an important study to be performed as part of multiphase flow assurance assessments during oil and gas project life and especially for subsea multiphase flow network. This paper presents experimental works to investigate the sand transport characteristics and identify the sand minimum transport condition (MTC) in sand–water and sand–air–water flows in a horizontal and + 5 deg inclined pipelines. The used sand volume fraction, Cv, ranged from 1.61 × 10−5 up to 5.38 × 10−4. The sand minimum transport velocity in single-phase water flow was obtained visually and then compared with that calculated by previous correlations for slurry transport. It was found that in sand–water flow, the pipeline inclination had negligible effect on the minimum sand transport velocity. However, the transport characteristics of sand particles were found changed significantly by changing the pipe inclination, which could result in the change of air–water flow regime. It was observed that sand particles transport more efficiently in terrain slug than stratified wavy flow in +5 deg inclined pipes. The sand transport and settling boundary for different air–water flow regimes were generated for horizontal and +5 deg inclined pipeline.

High Speed Visualization of Pneumatic Conveying of Materials in Bypass System

Dense phase pneumatic conveying is preferable over dilute phase conveying in many industries as lower transport velocities are beneficial due to reduced attrition of the particles and reduced wear. However, dense phase conveying is critically dependent on the physical properties of the materials to be conveyed. For many materials which are either erosive or fragile, they do not exhibit the physical properties required to be conveyed reliably in a low velocity, dense phase flow regime. This can be serious problem in the food, chemical and pharmaceutical industries. One satisfactory approach which has been widely applied is the use of bypass systems. Bypass pneumatic conveying systems provide the capacity of transporting some materials that are not naturally suitable for dense phase flow. Bypass pneumatic conveying systems also provide a passive capability to reduce minimum particulate transport velocities. In this study, pneumatic conveying experiments were carried out in a 79 mm diameter main pipe with a 27 mm inner diameter bypass pipe with orifice plate flute arrangement. Alumina, fly ash and sand were conveyed in the tests. High speed camera visualization was employed to study the flow regimes of bypass pneumatic transport systems and investigate the mechanism of material blockage inhibition provided by these systems. For alumina and fly ash, it was found that particulate material blockages were inhibited in bypass systems due to the air penetration into the particulate volume as a result of orifice plate airflow resistance. For the bypass pneumatic conveying of sand, the splitting of a long plug into two smaller plugs was observed. One of the primary concerns of bypass system is the wear of the bypass line. Material such as alumina is inherently abrasive by nature. For internal bypass systems, there is limited ability to monitor the state of the inner bypass tube while in operation. The particle velocity in the pipeline has been measured from the high speed video of the flow. The experimental result also showed that the conveying velocity of bypass system is much lower when compared conventional single bore pipelines. Based on the models developed for the assessment of service life of pneumatic conveying pipelines, the thickness loss of the bypass pipe has been estimated. It has been estimated that for a 3mm bypass tube wall thickness, a wear hole is created in approximately 2.5 years for a particle velocity of 3 m/s and 4 months for a particle velocity of 10 m/s.

An Experimental Modeling of Cuttings Transport for an Iranian Directional and Horizontal Well Drilling

This article has experimentally investigated and modeled the influence of variables such as hole angle, fluid rheology, cuttings size, circulation rate, and annular size on cuttings transport velocity using the concept of minimum transport velocity (MTV). The proposed method was checked against field values and has produced excellent results. The results obtained from this model were compared with Larsen's (1997) model and insignificant differences were observed. The result shows that this work can be utilized as a superior tool in drilling of directional and horizontal wells in Iran.

The minimum transport velocity of colloidal silica suspensions

A 26 mm N.B. horizontal pipe loop has been used to study the transport velocity of aqueous dispersions of colloidal silica. At low electrolyte concentrations the silica spheres form a stable dispersion, while at high electrolyte concentration particle aggregates are readily formed. Two measurement techniques have been used to study the critical transport velocity; (i) flow visualisation, and (ii) ultrasonic Doppler velocity profiling. Both measurement techniques show agreement in identifying the critical transport velocity. The study has shown that the critical transport velocity can be reduced when the suspension is transformed from a dispersed ( d 50=0.8 μm) to an aggregated ( d 50=4.6 μm) state. Such behaviour is related to the introduction of inter-floc flow through aggregates, enhancing the turbulence intensity of the fluid.

A pipeline transport correlation for slurries with small but dense particles

AbstractMost correlations/models for minimum transport or critical velocity of slurry were developed for slurries composed of particles greater than ∼100–200 µm diameter with narrow particle‐size distributions which is typical of the minerals industry. Many other process industries handle smaller particles. In particular waste slurries at the U.S. Department of Energy's Hanford Site have broad size distributions and significant fractions of smaller particles. Despite the size of these wastes, recent studies at Pacific Northwest National Laboratory indicate that the small particles might be of sufficient density to pose a significant risk for pipeline deposition and plugging. To allow predictive assessment of deposition of fine dense particles for waste slurry transport at the U.S. DOE Hanford site, a pipeline‐transport correlation for critical velocity was developed using a simple power‐law between two dimensionless numbers important for slurry transport, the deposition Froude and Archimedes numbers. The correlation accords well with experimental data for slurries with Archimedes numbers <80 and is an adequate pipeline design guide for processing Hanford waste slurry.

On the circulating boiling bed energy

Energy losses through gas filtration in a circulating boiling bed have been analyzed. The expression of the power needed for sustaining the internal circulation of particles has been obtained. On this basis the theoretical dependence for determining the carrying capacity of the flow and the lower boundary of existence of a circulating boiling bed (minimum transport velocity) has been established. Simple engineering formulas for calculating the bed drag and the maximum transport velocity have been obtained.

Fluidization and Flow Regimes of Titaniferous Solids

Physical properties of ilmenite and titania slag particlesproperties such as particle density, bulk density, packed-bed voidage and sphericityhave been determined for narrow size fractions ranging from 50 to 850 μm of each material. Particle sphericities measured by image analysis decrease with particle size. A comparison with other techniques shows that image analysis predicts lower values of sphericity. For both materials, the minimum fluidizing velocity, Umf, and transport velocity, Utr, were determined in air at room temperature and atmospheric pressure. The measured minimum fluidizing velocities are higher for ilmenite particles than for slag particles because the density and sphericity of the ilmenite are higher. Separate correlations for Umf, based on a simplified version of the Ergun equation, were fitted for ilmenite and slag particles. Both of these correlations tend to underestimate the minimum fluidizing velocity for small (<50-μm) particles. The experimental values of the transport velocity were fitted to a single equation, which predicts Utr for both materials with a maximum deviation not exceeding 8%. Flow-regime maps for the upward transport of Cl2−ilmenite and Cl2−slag systems at 1000 °C and 0.1 MPa were constructed.

Application of the minimum transport velocity model for drag-reducing polymers

The objective of this work is to acquire further insight into the procedure for predicting the minimum fluid velocity, which is required to transport cuttings from a directional well. The minimum transport velocity model (MTV) was used for drag-reducing polymers such as xanthan gum (XG). A series of experiments to evaluate the predictions of the model were conducted using water, aqueous solutions of polyanionic celluose (PAC) and xanthan gum (XG). The experiments conducted in a 4-m-long and 8-cm-diameter test section with recirculation facilities. The tests were carried out by measuring critical velocities, which are required to initiate the motion of sand bed particles. Four sand beds with different particle size ranges were used in the experiments. The model predictions were compared to the experimental results. The model predictions of critical velocity show satisfactory agreement with the measured data.

Percolation flux and transport velocity in the unsaturated zone, Yucca Mountain, Nevada

The percolation flux for borehole USW UZ-14 was calculated from 14C residence times of pore water and water content of cores measured in the laboratory. Transport velocity is calculated from the depth interval between two points divided by the difference in 14C residence times. Two methods were used to calculate the flux and velocity. The first method uses the 14C data and cumulative water content data directly in the incremental intervals in the Paintbrush nonwelded unit and the Topopah Spring welded unit. The second method uses the regression relation for 14C data and cumulative water content data for the entire Paintbrush nonwelded unit and the Topopah Spring Tuff/Topopah Spring welded unit. Using the first method, for the Paintbrush nonwelded unit in borehole USW UZ-14 percolation flux ranges from 2.3 to 41.0 mm/a. Transport velocity ranges from 1.2 to 40.6 cm/a. For the Topopah Spring welded unit percolation flux ranges from 0.9 to 5.8 mm/a in the 8 incremental intervals calculated. Transport velocity ranges from 1.4 to 7.3 cm/a in the 8 incremental intervals. Using the second method, average percolation flux in the Paintbrush nonwelded unit for 6 boreholes ranges from 0.9 to 4.0 mm/a at the 95% confidence level. Average transport velocity ranges from 0.6 to 2.6 cm/a. For the Topopah Spring welded unit and Topopah Spring Tuff, average percolation flux in 5 boreholes ranges from 1.3 to 3.2 mm/a. Average transport velocity ranges from 1.6 to 4.0 cm/a. Both the average percolation flux and average transport velocity in the PTn are smaller than in the TS/TSw. However, the average minimum and average maximum values for the percolation flux in the TS/TSw are within the PTn average range. Therefore, differences in the percolation flux in the two units are not significant. On the other hand, average, average minimum, and average maximum transport velocities in the TS/TSw unit are all larger than the PTn values, implying a larger transport velocity for the TS/TSw although there is a small overlap.

Predicting transport velocities

The minimum transport velocity is defined as the minimum gas velocity required for the vertical, dilute phase transport of particles. Literature data for this characteristic gas velocity are correlated in terms of particle properties. Then, it is shown that the same type of correlation holds for transport velocities governing transition toward fast fluidization. The similarity of these equations suggests that coarse particles can be carried over only in the fast fluidization regime. On the contrary, in a limited range of gas velocities, finer solids can be transported with different flow regimes, depending upon solids feed rate to the column. In that case, the solids feed rate governs transition to fast fluidization.

Minimum Transport Velocity of Gas-Solid Two-Phase Flow in a Pipe Bend.

Studying the limiting gas velocity at which conveying is possible in a state in which particles are not stagnant on the wall of the pipe, called 'minimum transport velocity', is very important in terms of saving energy for transportation. However, relating to a pipe bend, concepts concerning the minimum transport velocity are few up to this time since the particle motions in the pipe bend are very complicated. From such viewpoints in this paper a basic model equation of the minimum velocity in the pipe bend is first introduced for the dilute phase flow in conventional pneumatic conveyance. Next, the minimum velocities are measured in an actual transport experiment for coarse particles. By analyzing the measured data, an unknown in the basic equation is determined and an empirical equation of the minimum velocity is provided. The experiments are carried out on the condition that the curvature radiuses of the right-angled bend from the horizontal to the vertical are 300, 500 and 700 mm, the pipe line is 10 m long and 50 mm in diameter, and the conveyed particle is Polyethylene pellet with particle diameter of 3.4 mm.