EFFECT OF SAND DISTRIBUTION ON EROSION IN ANNULAR THREE- PHASE FLOW Quamrul H. Mazumder, Siamack A. Shirazi, and Brenton S. McLaury Erosion/Corrosion Research Center (E/CRC) Mechanical Engineering Department The University of Tulsa April 1, 2004 Overview Introduction Objective Background Mechanistic Model Development Experimental Investigation of Erosion Experimental Investigation of Sand Distribution Summary and Conclusion Introduction Erosion in fluid handling equipment is a major problem in several industries due to entrained solid particles in the fluid Introduction Erosion is a process by which material is removed from a solid surface due to mechanical effects such as impingement of solid particles on a surface Erosion can cause severe damage to the piping and equipment wall, resulting in loss of equipment and production downtime Erosion phenomenon is complicated due to a wide range of parameters such as fluid properties, solid particle size and distribution in flow, wall materials, geometry, etc. Introduction Elbows and Plugged Tees are geometries that are used to redirect fluid and are susceptible to erosion damage. Introduction (Continued) Prediction of erosion in multiphase flow is a complex problem due to lack of understanding of the particle impact velocity that causes erosion Particle impact velocity depends upon the geometry, carrying fluid velocity, flow pattern, particle size and distribution The complexity of erosion prediction increases significantly for three phase flow (gas, liquid and solid) Among different flow patterns, severe erosion damage occurs in annular flow with high gas and low liquid velocities Objectives The Objective of this work is to investigate erosion behavior in behavior in annular three-phase flow ( solid/ liquid/ gas) Investigate solid particle (sand) distribution and its effect on erosion in annular flow. Investigate erosion behavior in horizontal and vertical flow. Develop a mechanistic erosion prediction model to predict erosion in annular flow Background Most of the currently available erosion prediction models are based on empirical data Accuracy of these models are limited to certain flow conditions and are not general Erosion Corrosion Research Center (E/CRC) of The University of Tulsa developed a semi- mechanistic model based on empirical data and CFD model to predict erosion The model uses characteristic particle impact velocity to calculate erosion Background (continued) The E/CRC model for calculating maximum penetration rate for an elbow or tee can be written as 1.73 WV h FMFSFPFr / D L 2 (D / D ) 0 –h = penetration rate in mm/year or mpy –FM = empirical constant related to material hardness –FS = empirical sand sharpness factor –FP = penetration factor for steel based in 1” pipe diameter, (m/kg) –Fr/D = penetration factor for long radius elbows –W = sand production rate, (kg/s) –VL = characteristic particle impact velocity, (m/s) –D = pipe diameter, (in mm) –D0 = 25.4 mm Background (continued) For a given geometry, material, sand sharpness, sand rate, the erosion prediction equation can be written as h KVL 1.73 Where VL is the characteristic particle impact velocity. • A method for calculating the characteristic impact velocity was developed by using a simple model for stagnation layer in pipe geometry • The stagnation zone is a region where the particles must travel and penetrate to strike the pipe wall to cause erosion Background (E/CRC Model) Stagnation Equivalent Stagnation Length Zone L Particle Initial Position Tee Stagnation Zone vo x Elbow Present Work We are proposing a new Mechanistic Model to calculate characteristic initial particle velocity Vo. The mechanistic model velocity calculation is based on theory of two phase flow. The mechanistic model will use flow velocities and sand distribution in the flow The mechanistic model attempts to shed more light on the physics of erosion phenomenon Mechanistic model is expected to be more reliable and general compared to the semi- empirical model Schematic of Annular Flow VFilm Vdroplet Annular Liquid Film Thickness, * Sand Particles in the film Entrained Sand Particles and Liquid Droplets in The Gas Core Region DCore Mechanistic Model Development The proposed mechanistic model for sand particle initial characteristic velocity is: Vo = (Mass fraction of sand in film x Vfilm) + (Mass fraction of sand in gas core x Vd) Assuming sand concentration (mass of sand/ mass of liquid) is uniform in annular flow Vo = (Mass fraction of liquid in film x Vfilm) + (Mass fraction of liquid in gas core x Vd) Vo = (1-E)Vfilm + E x Vd Where, E = Fraction of liquid entrained in the gas core Vfilm = Average liquid film velocity (ft/sec) Vd = Average liquid droplet velocity (ft/sec) Liquid Film and Droplet Velocity Calculations Vfilm and entrainment fraction were calculated based on two phase flow model developed by Ansari (1989) at TUFFP A simplified method for calculating droplet velocity was developed as the effect of sand particles in the droplets are higher on erosion Calculated mean centerline droplet velocities were compared to Dukler (1994) droplet velocity measurements and showed good agreement Comparison of Calculated and Experimental Droplet Velocities 45 Re(Liq.) = 750 (Calculated) Re(Liq.) = 750 (Dukler) Droplet Velocity (m/sec) Re(Liq.)=3000 (Calculated) 35 Re(Liq.)=3000 (Dukler) 25 15 15 20 25 30 35 Superficial Gas Velocity ( m/sec) Comparison of Measured Erosion with E/CRC Semi-empirical and Mechanistic Models Mechanistic model was compared with erosion data reported by Salama (1998) and Bourgoyne (1989) Bourgoyne erosion data was for high gas velocities and low liquid rates with 350 micron sand The above erosion data reported by Salama were gathered at DNV and AEA for • One and two-inch flow loops • Carbon Steel and Stainless Steel • Annular, slug and bubble flows • Two different sand sizes (150 and 350 microns) Comparison of Measured Erosion with New Mechanistic Model Predictions Mech.Model Superficial Superficial Elbow Sand Measured Predicted Liq. Vel. Gas Vel. Dia. Size Erosion Erosion V SL (m/sec) V SG (m/sec) (mm) (Micron) (mm/kg) (mm/kg) Note 1 30 49 150 5.52E-04 8.93E-04 1 0.5 30 49 150 2.46E-03 1.45E-03 1 5.8 20 49 150 5.19E-05 5.48E-05 1 3.1 20 49 150 6.93E-05 1.20E-04 1 5 15 49 150 6.38E-05 1.11E-05 1 1 15 49 150 1.47E-04 1.09E-04 1 1.5 14.4 26.5 250 2.30E-04 5.38E-04 2 1.5 14.6 26.5 250 4.20E-04 5.58E-04 2 2.1 34 26.5 250 2.83E-03 3.79E-03 2 1 35 26.5 250 6.56E-03 5.78E-03 2 0.5 34.3 26.5 250 7.20E-03 6.92E-03 2 0.7 37 26.5 250 8.03E-03 7.38E-03 2 0.5 38.5 26.5 250 8.03E-03 8.84E-03 2 1.5 44 26.5 250 1.05E-02 8.23E-03 2 0.6 51 26.5 250 1.34E-02 1.52E-02 2 0.7 52 26.5 250 1.33E-02 1.51E-02 2 (1) Fluid: air/ water at 2 bar, Material: Carbon Steel (Brinell Hardness 160) (2) Fluid: nitrogen/water at 7 bars, Material: Duplex Stainless Steel Experimental Investigation of Erosion Erosion experiments were conducted at E/CRC using two different one-inch multiphase flow loops with Lf / D = 70 and Lf / D = 160 One-inch elbow specimen was used during the erosion experiment Examined the effects of variables on erosion –Liquid and gas velocities –Inclination angle (Horizontal, Vertical) E/CRC Multiphase Flow Loop (One inch Lf/D 70) Test Cell (Vertical) Air to Compressors Slurry Tank Drain (Liq+Sand) 5.5 ft Air From Compressors 6.2 ft Mixing Zone Test Cell Horizontal E/CRC Multiphase Flow Loop (One inch Lf/D 160) Filter Cyclone Separator Test Cell-Ver Slurry Tank 13 ft Water Tank Test Cell- Hor Drain 13.3 ft Flowmeter Compressors Test Cell Erosion Specimen Measured Horizontal and Vertical Erosion at Vsg=30.48 m/sec, Vsl=0.30 m/sec 1.3 L/ D =7 0 : V e rt ic a l L/ D =7 0 : H o rizo nt a l Normalized Mass Loss 1.0 L/ D =16 0 : V e rt ic a l L/ D =16 0 : H o rizo nt a l 0.8 Vertical 0.5 FLOW Horiz 0.3 0.0 0.0 3.0 6.0 9.0 12.0 15.0 Sand Throughput (Kilograms) Comparison of Horizontal and Vertical Erosion Vsg=22.86 m/sec, Vsl = 0.30 m/sec, Lf/D=160 Normalized Mass Loss 1.0 Horizontal Vertical 0.8 Vertical Vertical 0.5 FLOW FLOW 0.3 Horiz Horiz 0.0 0.0 4.0 8.0 12.0 16.0 20.0 24.0 Sand Throughput (Kilograms) Sand Distribution in Multiphase Flow Sand Entrainment Liquid droplets Liquid Film Sand Particles Vertical flow Horizontal Flow More sand particles in horizontal annular liquid film Intrusive Probe Used for Sand Sampling Sand and Liquid Distribution in Vertical Pipe Percent Sand and Water Vsg=30.48 m/sec, Vsl = 0.30 m/sec, Lf/D=160 6 M easured liquid/to tal liquid thro ughput M easured sand/to tal sand thro ughput 5 4 3 2 1 0 1 2 3 4 5 Probe Location Sand and Liquid Distribution in Horizontal Pipe Vsg=30.48 m/sec, Vsl = 0.30 m/sec, Lf/D=160 5 Measured sand/total sand throughput 4 Probe location Measured liquid/total liquid throughput 3 2 1 0 1 2 3 4 5 Percent Sand and Water Sand and Liquid Distribution in Vertical Pipe Vsg= 22.86 m/sec, Vsl = 0.30 m/sec, Lf/D=160 4 Percent Sand and Water M easured liquid/to tal liquid thro ughput M easured sand/to tal sand thro ughput 3 2 1 0 1 2 3 4 5 Probe Location Sand and Liquid Distribution in Horizontal Pipe Vsg= 22.86 m/sec, Vsl = 0.30 m/sec, Lf/D=160 5 M easured sand/to tal sand thro ughput M easured liquid/to tal liquid thro ughput Probe location 4 3 2 1 0 2 4 6 8 Percent Sand and Water Measured Horizontal and Vertical Erosion at Vsg=30.48 m/sec, Vsl=0.30 m/sec 1.3 Percent Sand and Water 6 M easured liquid/to tal liquid thro ughput M easured sand/to tal sand thro ughput 5 L/ D =7 0 : V e rt ic a l 4 L/ D =7 0 : H o rizo nt a l Normalized Mass Loss 3 1.0 L/ D =16 0 : V e rt ic a l 2 L/ D =16 0 : H o rizo nt a l 1 0 0.8 1 2 3 Probe Location 4 5 5 Measured sand/total 0.5 4 sand throughput Probe location Measured liquid/total liquid throughput 3 2 0.3 1 0 1 2 3 4 5 Percent Sand and Water 0.0 0.0 3.0 6.0 9.0 12.0 15.0 Sand Throughput (Kilograms) Comparison of Horizontal and Vertical Erosion Vsg=22.86 m/sec, Vsl = 0.30 m/sec, Lf/D=160 4 Percent Sand and Water M easured liquid/to tal liquid thro ughput M easured sand/to tal sand thro ughput 3 Normalized Mass Loss 1.0 Horizontal 2 1 Vertical 0 0.8 1 2 3 4 Probe Location 5 5 M easured sand/to tal sand thro ughput M easured liquid/to tal liquid thro ughput 0.5 Probe location 4 3 2 0.3 1 0 2 4 6 8 Percent Sand and Water 0.0 0.0 4.0 8.0 12.0 16.0 20.0 24.0 Sand Throughput (Kilograms) Summary and Conclusions Mechanistic erosion prediction model has been developed for annular three- phase flow Mechanistic model predictions showed good agreement with experimental results in the literature Different erosion rates were observed Between Lf /D=70 and Lf /D=160 flow loops Higher erosion was observed in the vertical specimen compared to the horizontal specimen.
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