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 elements446888

boundary & 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

0.100

1.000

10.000

100.000

0.1 1 10 100 1000 10000 100000 1000000 10000000

Np (Without B affes ) Np (With B affes )

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%

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 Engineeringvol. 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