pilot plant handling and rheological behavior of...
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Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
PILOT PLANT HANDLING AND RHEOLOGICAL BEHAVIOR OF COLLOIDAL
PETROLEUM COKE-IN-WATER FUEL SUSPENSIONS
Gustavo NUÑEZ†, Hidekel OLMEDO, Nelson ROJAS, Suyin TORRES, María BRICEÑO Nano Dispersions Technology Inc.
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Nano Dispersions Technology, Inc.
• Small high-tech company that develops products based on colloidal and nanodispersions using a top-down approach
• Located in the City of Knowledge since 2007, a
Science Park in Panama sponsored by the UN and the EU
We have developed a mainly colloidal suspension of petroleum coke in water We are designing a manufacturing plant to provide 40 MW in a commercial boiler
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
There are increasing piles of petcoke around the world.
Fuel oil price is heavily affecting the economy of many power plants
There are increasing piles of petcoke around the world. Fuel oil price: 16 US$/MMBTU
Petcoke price: 2 US$/MMBTU
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Proof of concept has been successful
Colloidal Petcoke in Water (CPW): Low volatile content petcoke ignites easily and produces a stable flame, without a support fuel
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Commercial grind to specifications – 200 mesh
Wet-comminution grind
• Most particles are colloidal • Virtually no sedimentation
for weeks
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Is it possible to handle and atomize this material? Is it going to drain from a tank?
Fuel composition: Petcoke: 61 % w/w Additives: 0.3 % w/w Water: 38.7 % w/w
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Evaluation of rheological behavior: • Rotational rheometer (parallel plates) – steady state,
and dynamic oscillatory tests (sample volume < 2 mL) • Pipe viscometer (1/2” to 1”, sample volume 200 L,
laminar flow, 28 ºC – 32 ºC) • Tank drainage
The truth about this (and many!) VPF: Repeatability is acceptable (max. error < 10 %) but reproducibility is pretty bad, specially for larger volumes
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Rotational rheometry – parallel plates Viscosity as a function of temperature
This material is homogeneous and stable to sedimentation
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Rotational rheometry – parallel plates Material functions
Steady state and dynamic tests: • Yield stress, σy: 0.5 Pa • Phase angle, δ: 20º – 25º • Relaxation time, λ: 0.016 s
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Pipe viscometry
γ = 32QπD3
143+ d lnQ
d ln p!
"#
$
%&
τ =D −Δp( )4L
ReMR: 1 - 200
Slip or lubricated flow
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Pipe viscometer Material functions
• Yield stress, σy ≈ 23 Pa • Slope of shear thinning region, n: 0.3086
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Data fitting
Carreau model
Bingham model η =
σ y
γ+µ∞
η =ηo −η∞
1+ λ γ( )2( )1−n2
+η∞
Fitted parameter:
ηo and η∞
No fitted parameters
(µ∞= η∞)
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Combination of methods and models (shear rate: 2 to 800 s-1)
Lack of reproducibility: Shear history and microbubbles
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Viscosity for engineering design
Viscosity for pumping (< 100 s-1): ηo ( ≈ 500 mPa.s) Viscosity for atomization (100 s-1): 200 mPa.s – 400 mPa.s
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Ongoing investigation – tank drainage
Uneven surface observed in tanks of 1 L – 2000 L, gravity drainage or pumped
Undrained volume depends on tank shape and outlet diameter
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Preliminary results - rectangular and cubical tanks
1 2
θ θ
W 2W
d d
Tank 1: • θ is constant after
uneven surface onset • Drainage is gradual,
faster for larger d
Tank 2: • θ increases after uneven surface
onset • Drainage is fast the first few
seconds, then stops completely
Ho Ho
The free surface relaxes slowly (> 1 h)
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
Preliminary results
Tank 1
Tank 2
More work is necessary in order to establish operational criteria
D
d
Rectangular tank
Cubic tank
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013
CONCLUSIONS • The observed pipe behavior may be interpreted as a
lubricated flow in which the continuous phase migrates to the wall, thereby reducing friction.
• Acknowledging this phenomenon has a positive impact in equipment costs and handling operations.
Viscoplastic Fluids: From Theory to Application IFPEN, Rueil-Malmaison 18 – 21 November 2013