19
Innovations for a better world. Numerical study of the flow of rice grains in a whitener Master project in industry Wenyi SONG, EPFL Innovations for a better world.
Innovations for a better world.
Numerical study of the flow
of rice grains in a whitenerMaster project in industry
Wenyi SONG, EPFL
Innovations for a better world.
2
Who is Bühler?
Rice whitener project | Wenyi SONG | 2019-06-19
06:30 07:15
07:00 07:30
10:00
12:00
15:00
18:00
19:00
20:00
3
The rice whitening process
Rice whitener project | Wenyi SONG | 2019-06-19
Typically 12% is the bran composition by weight in brown rice
https://www.chowhound.com/food-news/176585/whats-
the-difference-between-white-rice-and-brown-rice/
4
The rice whitener
• Capacity = 3500 to 8000 kg/h
• Tip-speed = 10.5 to 15 m/s (~700 rpm)
• Milling gap = 80% grain length (~10 mm)
Rice whitener project | Wenyi SONG | 2019-06-19
5
Project roadmap
Experimental study
1. Spherical particles
2. Rice grains
Numerical study
1. Spherical particles
2. Polyhedron particles
Validation of model
1. Comparison of data:
• Global motion
• Particle velocity
• Bulk angle
• Torque
2. Determination of
simulation parameters:
• Friction coefficients
Model applied to
industrial machine
Useful information on
process:
• Flow behavior
• Stress distribution
• Correlation between
process result and
simulated stress
distribution
Goal
Effective bran removal &
decreased breakage rate
Rice whitener project | Wenyi SONG | 2019-06-19
6
Experimental setup
a. Light source
b. Photo diode rotation speed
c. Couette cell
d. Fast camera particle flow
e. Power source
Rice whitener project | Wenyi SONG | 2019-06-19
a
b
d c
e
7
Numerical Setup
Feature Setting
Number of particles 3531 spherical or
4733 rice-shaped
Weight of particles 71 g
Height of gap 5.4, 8.1, 8.4 cm
Number of corners 50
Rotational speed 210, 375, 425 rpm
Normal Force Hysteretic Linear Spring
Tangential Force Linear Spring Coulomb Limit
Hardware resources 16 cores & Quadro GV100
Rice whitener project | Wenyi SONG | 2019-06-19
Polyhedron
5.4, 8.1, 8.4 cm
8
Particle properties
Particle Density
[kg/m3]
Young’s modulus
[GPa]
Poisson ratio
[-]
POM* 1420 3.2 0.44
Rice grain** 1500 1 0.25
Interaction Particle - Particle Particle - Boundary
Static friction coef.** 0.28 0.3/0.5
Restitution coef.** 0.5 0.5
POM particles (d=3 mm)
Rice grains (l=6.7 mm, w=1.8 mm)
*Values from http://www.dmh.at/materials/product/42_pom400/ and Polymer Properties Database
**Values obtained from http://doi.org/10.1016/j.apt.2018.02.021
Rice whitener project | Wenyi SONG | 2019-06-19
9
Results for POM particles
Global motion of POM particles
Rice whitener project | Wenyi SONG | 2019-06-19
Experiment, 375 rpm
10
Results for POM particles
Flow pattern of POM particles
Rice whitener project | Wenyi SONG | 2019-06-19
Experiment, 375 rpm
11
Results for POM particles
Particle trajectories
Rice whitener project | Wenyi SONG | 2019-06-19
Experiment, 375 rpm
12
Results for POM particles
Mean particle velocity at outer layer of the gap
Rice whitener project | Wenyi SONG | 2019-06-19
SimulationExperiment
13
Results for rice grains
Global motion of rice grains
Rice whitener project | Wenyi SONG | 2019-06-19
Experiment, 205 rpm
14
Results for rice grains
Profile of rice grains
Rice whitener project | Wenyi SONG | 2019-06-19
Slope: -0.73
Experiment, 205 rpm
Slope: -0.78
Simulation, 210 rpm
15
POM vs. rice grains
Normal and tangential contact forces from DEM
Rice whitener project | Wenyi SONG | 2019-06-19
Rice grainsSpherical POM
16
Results for rice grains
Normal and tangential collision velocity and stress from DEM
Rice whitener project | Wenyi SONG | 2019-06-19
Collision stressCollision velocity
17
Conclusion
• Several flow features of spherical particles and rice grains have been
successfully extracted and analysed, i.e.:
o Global flow patterns;
o Particle trajectories and velocities;
o Global particle-particle collision statistics.
• Experiment with simplified geometry acts as a calibration/validation
method for the DEM numerical model.
Rice whitener project | Wenyi SONG | 2019-06-19
Tangential stress
18
Outlook
• With desktop experiment:
o Determine suitable parameters for the numerical simulation.
o Analyse the motion of rice grains.
o Analyse the contact force distribution of rice grains.
• With industrial machine:
o Study global flow behaviour of rice grains.
o Correlate simulated stress distributions with bran removal
efficiency observed in industry.
o Enable breakage model in the simulation.
o Propose suitable improvements of the process.
Rice whitener project | Wenyi SONG | 2019-06-19
Maximum Tangential Force
Thank you for your attention.
