Friday, February 5, 16 The Produced Water Society Seminar 2016 1 MECHANISMS FOR FLOTATION OF FINE OIL DROPLETS Hank Rawlins, Technical Director eProcess Technologies Friday, February 5, 16 The Produced Water Society Seminar 2016 2 Presenter - Hank Rawlins [email protected] • eProcess – Technical Director • Metallurgical Engineer (PhD, P.E.) • 25 years experience • Facilities Sand Management Systems • Compact Separation Technology • Produced Water Treatment Systems • Fifty Publications • (former) Chair of SPE Separations Technical Section • Adjunct at Montana Tech Friday, February 5, 16 The Produced Water Society Seminar 2016 3 Topside Focus Areas WATER SOLIDS OIL GAS TREATMENT REMOVAL/HANDLING PRODUCTION PRODUCTION Desander Systems Wellhead Desander Partial Processing Wellhead Gas Desander Deoiler Systems Dual Pot Filters Preseparation Dehydration Compact Degasser Systems IGF/DGF Systems Sand Washing Systems Compact Production Systems (CPS) Sump Caissons Collection | Transport | Store Extended Well Test PacKages (EWT) Friday, February 5, 16 The Produced Water Society Seminar 2016 4 Outline • Mineral and Oil Flotation • Bubble/Droplet Buoyancy • Bubble Generation & Sizes • Bubble-Droplet Attachment Profiles • Free Energy Minimization • Water-Oil-Gas Interfacial Tension Properties • Attachment Mechanism Model & Results • Production Factors Affecting IFT • Summary Friday, February 5, 16 The Produced Water Society Seminar 2016 5 Mineral Froth Flotation Selective separation of hydrophobic minerals from hydrophilic • Desired mineral is chemically altered to make hydrophobic then floated The single more important unit operation in upgrading sulfide ores Developed in late 1880’s in UK and Australia Uses both mechanical and hydraulic flotation cells Copper flotation at Asarco’s Mission mine (www.tucsoncitizen.com) PGM flotation in South Africa (www.flsmidth.com) Friday, February 5, 16 The Produced Water Society Seminar 2016 6 Particle-Bubble Attachment Collector chemical added to improve hydrophobicity -38 micron coal particles in single layer on air bubbles (SME Froth Flotation – A Century of Innovation) 175 micron coal particles on air bubbles forming clusters (SME Froth Flotation – A Century of Innovation) Galena conditioned with xanthate showing point attachment on air bubbles (www.tecmin.wordpress.com) Friday, February 5, 16 The Produced Water Society Seminar 2016 7 Why Do We Use Flotation? In upstream oil & gas Primarily for water cleanup • Not selective separation for oil recovery Use mechanical and hydraulic cells Air bubble rise faster than oil droplets • Bubble flotation reduces residence time versus straight gravity separation • Reduces footprint and size of separation equipment Also less consumables - especially compared to filters www.netl.doe.gov Friday, February 5, 16 The Produced Water Society Seminar 2016 8 Bubble/Droplet Buoyancy Want largest bubble for rise rate but strong bubble-droplet bond to 300 prevent detachment 280 Gas Bubble Oil Droplet 260 P=0.5 bar Small gas bubbles and oil droplets 240 T=35° C 220 Water: 10% salinity OIl: 30 API nearly spherical (use Stokes Law) 200 Gas : 18 MW Stokes’ relationship valid for: 180 • Dilute suspensions and Re<0.1 160 • Re<1.0 (~10% error) 140 120 2 Velocity (cm/min) ρlu∞d p gd p (ρl − ρ p ) 100 Re v∞ = = 18 80 µ µl l 60 BubbleStokes Region 40 Example at right: DropletStokes Region • v = 5.8v 20 bubble droplet 0 • 100 µm bubble + 100 µm droplet = 0 50 100 150 200 250 126µm combined = 5.3X Drop or Bubble Diameter (µm) • 100 µm bubble + 10 µm droplet = 101µm combined = 576X Friday, February 5, 16 The Produced Water Society Seminar 2016 9 Oil Naturally Floats on Water There are constraints! • Limited footprint • Limited weight • Motion sensitivity • Oil shear sensitivity • Methane flotation gas • Hypersaline water Friday, February 5, 16 The Produced Water Society Seminar 2016 10 Bubble Generation & Sizes Myriad of ways to generate and introduce bubbles into flotation: • Shear pumps, eductors, shatter plates, nozzles, porous frits, cavitation tubes, dissolution/nucleation, fluidic oscillators, air sparged cyclone, etc. Variety of recommended bubble sizes: • Millibubble (10-3), microbubble (10-6), nanobubble (10-9), picobubble (10-12) • …opening in the market for femtobubble (10-15) technology! What size is really needed? (Does size matter?) Friday, February 5, 16 The Produced Water Society Seminar 2016 11 Deep Thoughts …or I think too much while fly fishing Does bubble size matter, or is amount more important? • Probably population/flux/swarm-density What size bubble is really need to capture fine (10 µm) droplets? • If flotation is primary treatment, droplet size is probably 50 microns • If flotation is secondary, after deoilers, droplet size is probably 10-20 microns What is the strongest attachment for bubble-droplet? • We don’t want to lose (detach) captured droplet What is main difference between oil droplet and mineral particle flotation, from a micro point of view? • Oil naturally floats and is naturally hydrophobic (that’s a big help!) • Oil droplets shear and coalesce (rocks don’t) • More interestingly – an oil droplet is deformable and can flow to adapt to bubble surface • What is thermodynamic stable state once bubble-droplet attach? Friday, February 5, 16 The Produced Water Society Seminar 2016 12 Attachment Profiles Various possible mechanisms l Oil e Initial contact v Droplet Oil droplets a r t in streamline f o Streamline n o i t Gas c Gas bubble Nucleate e Bubble r i nucleation coalescence D Gas Bubble Oil droplet in Oil droplets and Full or partial turbulent Gas bubble Gas bubble gas bubbles encapsulation, or Oil film (or) Oil lens (or) Point wake aggregate “mat” growth Attachment rising point contact (a) (b) (c) (d) What drives oil to form film, lens, or point attachment? Friday, February 5, 16 The Produced Water Society Seminar 2016 13 Single Attachment Profiles l Oil Forward Gas e Initial contact v Droplet Encapsulation Bubble a r t f o Streamline n o i t Gas Droplet c e Bubble Reverse r i Encapsulation D Internal Lens Oil film (or) Oil lens (or) Point Attachment Mixed Lens Friday, February 5, 16 The Produced Water Society Seminar 2016 14 Free Energy Minimization Thermodynamic Stable State Bubble ΔV ⎛ ∂G ⎞ γ = ⎜ ⎟ Forward Gas 0 ⎝ ∂A ⎠P,T ,n Encapsulation Bubble Gaggregate < (Gbubble + Gdroplet ) Droplet + Drop Full Reverse Encapsulation Volume < + Internal +Drop Full Lens Volume γ og Abubble +γ ow Aoilfilm − γ wg Abubble + γ ow Adrop < 0 + Drop Partial ( ) ( ) Mixed Lens Volume Friday, February 5, 16 The Produced Water Society Seminar 2016 15 Produced Water ρ & µ 1.20 1.8 1.6 1.15 1.4 1.2 1.10 1.0 1.05 0.8 0.6 1.00 0.4 Produced Water Viscosity (cP) at 14.7 psia Produced Water Specific Gravity at 14.7 psia 0.95 0.2 0 5 10 15 20 25 20 30 40 50 60 70 80 90 Total dissolved solids (wt. %) Temperature (°C) Friday, February 5, 16 The Produced Water Society Seminar 2016 16 Water-Hydrocarbon IFT 80 58 75 53 70 48 65 43 60 Interfacial Tension (dyne/cm) at 14.7 psia Interfacial Tension (dyne/cm) at 14.7 psia 55 38 20 30 40 50 60 70 80 90 20 30 40 50 60 70 80 90 Temperature (°C) Temperature (°C) Friday, February 5, 16 The Produced Water Society Seminar 2016 17 Hydrocarbon Gas-Liquid IFT 30 29 28 27 26 Interfacial Tension (dyne/cm) at 14.7 psia 25 20 30 40 50 60 70 80 90 Temperature (°C) Friday, February 5, 16 The Produced Water Society Seminar 2016 18 Spreading Coefficient Not really useful for this exercise -6.0 Decreased Cn S -6.5 20% NaCl o = γ wg −γ ow −γ og -7.0 10% NaCl γ wg > (γ ow +γ og ) 5% NaCl 0% NaCl -7.5 Indicates spreading of oil droplet along gas-water interface -8.0 n-dodecane does not wet the -8.5 methane-water interface, but Spreading Coeff. (dyne/cm) at 14.7 psia Dodecane-Methane-Water System forms a definite contact angle -9.0 20 30 40 50 60 70 80 90 Surfactant that lowers γow may be Temperature (°C) necessary Friday, February 5, 16 The Produced Water Society Seminar 2016 19 Attachment Mechanism 0% Salinity, 25°C 6.0E-10 5.0E-10 Forward Encapsulation Reverse Encapsulation 4.0E-10 Internal Lens 3.0E-10 Mixed Lens 2.0E-10 1.0E-10 0.0E+00 -1.0E-10 -2.0E-10 -3.0E-10 Net Free Energy Change (J) -4.0E-10 Salinity: 0% -5.0E-10 Temp: 25°C -6.0E-10 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 ddrop/dbubble Friday, February 5, 16 The Produced Water Society Seminar 2016 20 Attachment Mechanism 20% Salinity, 25°C 6.0E-10 5.0E-10 Forward Encapsulation Reverse Encapsulation 4.0E-10 Internal Lens 3.0E-10 Mixed Lens 2.0E-10 1.0E-10 0.0E+00 -1.0E-10 -2.0E-10 -3.0E-10 Net Free Energy Change (J) -4.0E-10 Salinity: 20% -5.0E-10 Temp: 25°C -6.0E-10 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 ddrop/dbubble Friday, February 5, 16 The Produced Water Society Seminar 2016 21 Attachment Mechanism 0% Salinity, 60°C 6.0E-10 5.0E-10 Forward Encapsulation Reverse Encapsulation 4.0E-10 Internal Lens 3.0E-10 Mixed Lens 2.0E-10 1.0E-10 0.0E+00 -1.0E-10 -2.0E-10 -3.0E-10 Net Free Energy Change (J) -4.0E-10 Salinity: 0% -5.0E-10 Temp: 60°C -6.0E-10 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 ddrop/dbubble Friday, February 5, 16 The Produced Water Society Seminar 2016 22 Attachment Mechanism 20% Salinity, 60°C 6.0E-10 5.0E-10 Forward Encapsulation Reverse Encapsulation 4.0E-10 Internal Lens 3.0E-10 Mixed Lens 2.0E-10 1.0E-10 0.0E+00 -1.0E-10 -2.0E-10 -3.0E-10 Net Free Energy Change (J) -4.0E-10 Salinity: 20% -5.0E-10 Temp: 60°C -6.0E-10 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 ddrop/dbubble Friday, February 5, 16 The Produced