CFD modeling of mixing and suspension in pulp stock ... - ESSS

CFD modeling of mixing and suspension
in pulp stock chests for recycling paper
Caroline Satye Martins Nakama
Nicolas Spogis
Song Won Park

PRESENTATION TOPICS
• Company Overview:
Polytechnic School of University of Sao Paulo
• Problem Description;
• Methodology;
• Goals;
• Conclusion and next steps.

Problem Description
The pulp desintegration has the highest
operational cost in the recycling paper
industry. The power consumption in the
pulper is directly related with the
impellers design, water/fiber quantities in
the chest, rotor velocity,
fiber/contaminants separation and the
segregation of the good quality fibers.
State-of-the-art: Spogis;Nunhes (2009)
Fiber pulp chest application: Bhole;Ford;Bennington(2009) Ford;Ein-
Mozaffari;Bennington(2006) Kor;Prince;Fletcher (2008) Oshinowo;Bakker(2002)
Ramasubramanian;Shiffler;Jayachandran(2008) Roux, Jean-Claude. (2001)
Saeed;Ein-Mozaffari;Upreti(2008)

IPPEL INDUSTRIAL CASE
• Simulating the chest with water and
fiber as homogeneous fluid.
• Isothermal flow
• Steady state
• Two domains
– Fixed chest
– Impeller rotating at 550 rpm
– Interface Frozen Rotor
• Batch

chest geometry

Impeller geometry
Removing sharpiness

meshes
Number of elements
446888

oundary & conditions
• Rotor domain:
- Rotational, 550 rpm
- Axis Y
- Turbulence RNG k-ε
• Chest domain:
- Stationary
- Turbulence RNG k-ε
• Interface between the domains:
– Frozen Rotor
– Pitch Change – Specified Pitch Angles:
• Pitch Angle Side 1 – 360°
• Pitch Angle Side 2 – 360°
- Interface 1
- Interface 2

preliminary results

preliminary results
Resultado dos valores de torque e potência
para cada simulação
Rotação Geometria Torque (Nm) Potência (W)
138 Com corte lateral 1053,5 458,0
275 Com corte lateral 4247,31 926,7
275 Sem corte lateral 4251,51 927,6
550 Com corte lateral 16296,79 3555,7
Sem corte lateral significa tanque com simetria
cilindrica em lugar de uma parede chata

case with baffles Re=10

case with baffles Re=100000

case without baffles Re=10

case without baffles Re=100000

obviously, this is extreme
conditions,
Re= 10 and 100000
the sketch has some kind of
baffles and the original industrial
chest has not baffles. We need
some design of baffles to
redesign the chest

Np versus Re
Np without
Baffes Np with Baffes Re Np increase
32.517 33.582 1 3.28%
3.220 3.304 10 2.60%
1.052 1.062 100 1.03%
0.687 0.734 1000 6.93%
0.581 0.593 10000 2.08%
0.557 0.612 100000 9.83%
0.579 0.604 1000000 4.25%
100.000
10.000
1.000
0.100
0.1 1 10 100 1000 10000 100000 1000000 10000000
Np (Without B affes ) Np (With B affes )

Conclusion and next steps
• Study of MultiFrontier for automatic redesign of the impeller
and the baffles. IPPEL is asking us for the continuing
improvements
GOALS:
• First step: reduction of 15 % of energy consumption without
fiber loss increase;
• Second step: increase of fiber segregation, that is, increase
of contaminants discharges with fiber quality increase.

for mathematical modeling please see:
• Bhole, M.; Ford, C.; Bennington, C.P.J. Characterization of Axial Flow Impellers in Pulp Fibre
Suspensions. Chemical Engineering Research and Design vol. 87 (4A), pp. 648–653. 2009.
• Ford, C.; Ein-Mozaffari, F.; Bennington, C. P. J.; Taghipour, F. Simulation of Mixing Dynamics in Agitated
Pulp Stock Chests using CFD. AIChE J. vol. 52, num. 10, pp. 3562-3569. 2006.
• Kor, Y. K.; Prince, R. G. H.; Fletcher, D. F. Using CFD to Identify Means of Reducing Power Consumption
for Mixing and Suspension in Paper Pulp Stock Chests. Asia-Pacific Journal of Chemical Engineering
vol. 3, num. 2, pp. 144-150. 2008.
• Oshinowo, L. M.; Bakker, A. CFD Modeling of Solids Suspensions in Stirred Tanks. Symposium on
Computational Modeling of Metals, Minerals and Materials, TMS Annual Meeting, Seattle, WA. February
17-21, 2002.
• Pakzad, L.; Ein-Mozaffari, F.; Chan, P. Using Computational Fluid Dynamics Modeling to Study the
Mixing of Pseudoplastic Fluids with a Scaba 6SRGT Impeller. Chemical Engineering and Processing vol.
47, num. 12, pp. 2218–2227. 2008.
• Ramasubramanian, M. K.; Shiffler, D. A.; Jayachandran, A. A Computational Fluid Dynamics Modeling
and Experimental Study of the Mixing Process for the Dispersion of the Synthetic Fibers in Wet-Lay
Forming. Journal of Engineered Fibers and Fabrics vol. 3, num. 1, pp. 11-20. 2008.
• Roux, Jean-Claude. Stock Preparation Part 1 – Pulp Treatment Processes. 12th Fundamental Research
Symposium, Oxford. September, 2001.
• Saeed, S.; Ein-Mozaffari, F.; Upreti, S. R. Using Computational Fluid Dynamics To Study the Dynamic
Behavior of the Continuous Mixing of Herschel-Bulkley Fluids. Ind. Eng. Chem. Res.vol. 47, num. 19, pp.
7465–7475. 2008.
• Spogis, N.; Nunhez, J.R. Design of a High-Efficiency Hydrofoil Through the Use of Computational Fluid
Dynamics and Multiobjective Optimization. AIChE J. vol. 55, num. 7, pp. 1723-1735. 2009.

Thank you