Application of Gyratory Sifters and Screeners to Food - K-Tron

Application of Gyratory Sifters and
Screeners to Food Processing
April 2014
PRESENTATION OUTLINE
1. Factors Affecting Screening Performance
a) Material Characteristics
b) Screen Opening Selection
c) Blinding
d) Screen Motion
2. How to Specify Screening Performance
a) Product Quality
b) Screening Efficiency
3. Examples of Food Screening Application
2 pg.
What is Screening?
ROTEX No. 48, built around 1910 for flour screening
3 pg.
Basic Types of Screening
Scalping
Fines Removal
Grading (Sizing)
SCALPING
Coarse Scalping Removing trash,
scale or agglomerated material
which is 50%+ coarser than the
nominal feed
Close Scalping
Final product or shipping
screens that remove a small
amount of coarse material
Oversize typically 5%
or less
5 pg.
FINES REMOVAL
Removing a small amount of fine
material from a feedstock.
Typical applications are
dedusting and final product
cleaning prior to shipping.
Fines typically less
than 10% of the
feedstock
6 pg.
Grading
KEY FACTORS AFFECTING SCREENING
PERFORMANCE
•
•
•
•
8 pg.
Material Characteristics
Screen Opening Selection
Blinding
Types of Screen Motion
KEY FACTORS - Material Characteristics
•
•
•
•
•
•
•
9 pg.
Particle Size Distribution
Bulk Density
Particle Shape
Flowability
Friability
Surface Moisture or Oil Content
Static Charge
SIEVE ANALYSIS
Test Sieves are identified by a
sieve number or by the opening
of the wire mesh.
An ISO/U.S. #10 sieve has an
opening of 2 mm or 2000 microns.
10 pg.
PARTICLE SIZE DISTRIBUTION
U.S. Sieve No. Opening (mm) % Retained
10
2.00
4.8%
16
1.18
18.8%
30
0.60
26.3%
60
0.25
28.1%
100
0.15
11.3%
Pan
10.7%
100.0%
11 pg.
PSD and CAPACITY
Fines
Removal
Range
Grading
Range
Scalping
Range
cit
pa
Ca
y
Typical Particle Size Distribution
Screen Opening
Smaller
Larger
Screening is a Volumetric Process
For effective screening,
the screener must
stratify the feed and
provide enough area to
allow the fines to pass
through the screen
openings.
Screening is a Volumetric Process
As capacities increase,
bed depths build up
and separations take
place further down the
screen surface
Screening is a Volumetric Process
There is a point at
which the bed depth
is so great that the
screener can no
longer make effective
separations
KEY FACTORS AFFECTING
PERFORMANCE
•
•
•
•
16 pg.
Material Characteristics
Screen Opening Selection
Blinding
Types of Screen Motion
17 pg.
SAME OPENING
DIFFERENT WIRE DIAMETERS
Opening
One Mesh
65% Open
Area
18 pg.
40% Open
Area
SCREEN COMPARISON TABLE
Mesh
Wire Diameter
Opening
% Open Area
10
0.020” (0.51)
0.080” (2.03)
64.0%
10
0.025” (0.64)
0.075” (1.91)
56.3%
10
0.028” (0.71)
0.072” (1.83)
51.8%
10
0.032” (0.81)
0.068” (1.73)
46.2%
Number 10 U.S. Sieve……….….2.00 mm
Number 10 Tyler Sieve………….1.68 mm
KEY FACTORS AFFECTING
PERFORMANCE
•
•
•
•
20 pg.
Material Characteristics
Screen Opening Selection
Blinding
Types of Screen Motion
BLINDING
The reduction in open area of a screen surface caused by plugging or
coating.
Plugging by Near-Size
21 pg.
Bridging by oil,
moisture or static
SCREEN BLINDING
Capacity
% Blinding
22 pg.
ANTI-BLINDING BALL MESH
CLEANING SYSTEM
23 pg.
KEY FACTORS AFFECTING
PERFORMANCE
•
•
•
•
24 pg.
Material Characteristics
Screen Opening Selection
Blinding
Types of Screen Motion
SCREENER MOTIONS & TYPES
Rectangular Gyratory
Round Gyratory
Centrifugal
Round Vibratory
Inclined Vibratory
Horizontal Vibratory
HOW DOES ROTEX WORK?
UNLIKE VIBRATORY SCREENERS, ROTEX USES
A GYRATORY-RECIPROCATING MOTION, WITH
NO VERTICAL COMPONENT.
THIS MOTION:
-CIRCULAR MOTION AT THE FEED END
-ELLIPTICAL MOTION IN THE CENTRE
-LINEAR MOTION AT THE DISCHARGE END
-CIRCULAR MOTION SPREADS THE PRODUCT
-ELLIPTICAL MOTION CONVEYS AND STRATIFIES
-LINEAR MOTION REMOVES NEARSIZE
EXTREME
FINES INTERMEDIATES
NEARSIZE
STROKE & MOTION – GYRATORY RECIPROCATING
Stage 1: Circular motion at the feed end.
STAGE 1
STAGE 2
• Spreads feed the full width of the screen.
• Stratifies & conveys.
• No mechanical feeding required.
Stage 2: Elliptical motion in the centre section.
• Long stroke elliptical action.
• Promotes stratification.
• Good conveying.
Stage 3: Linear motion at the discharge end.
STAGE 3
• Near linear sifting motion.
• Effective removal of near size happens in this
area, promoting higher efficiency.
GYRATORY-RECIPROCATING MOTION vs. VIBRATORY MOTION
• Product remains in contact with
mesh/plate at all times
• Product bounces down the deck,
losing contact at times.
• When stratified, product is not
remixed.
• Product doesn’t stratify well, as
vibration remixes fractions.
• Increases effective area: product
doesn’t spend any time ‘airborne’
and miss screen area.
• Reduced effective area: when
product is ‘airborne’ it cannot be
screened, so misses screen area.
SCREENING ACCURACY
Production Screening is NOT
a “black and white” separation!
29 pg.
PERCENT RETAINED
FINES
500
PRODUCT
OVERSIZE
1000
SIEVE OPENING (MICRONS)
30 pg.
100% ACCURATE SCREENER
Screener
PAN
31 pg.
500
FINES ANALYSIS
500
1000
PRODUCT ANALYSIS
1000
OVERS ANALYSIS
THE “TRADE-OFF” IN SCREENING
High Product Quality?
or
High Production Rate?
32 pg.
PERCENT RETAINED
FINES
PRODUCT
OVERSIZE
1000
TOP DECK: 1030 
500
BOTTOM DECK: 540  SIEVE OPENING (MICRONS)
Screener
High Production
On-Spec
33 pg.
TOP DECK: 1030
BOTTOM DECK: 540
Gyratory Screener
High Production
On-Spec
PAN
34 pg.
500
FINES ANALYSIS
500
1000
PRODUCT ANALYSIS
1000
OVERS ANALYSIS
LOW PRODUCT YIELD
TOP DECK: 1030
BOTTOM DECK: 650
Vibrating
Screener
PAN
500
FINES ANALYSIS
35 pg.
500
1000
PRODUCT ANALYSIS
VIBRATING Screener
High Production
On-Spec
1000
OVERS ANALYSIS
LOW PRODUCT QUALITY
TOP DECK: 1300
BOTTOM DECK: 540
Vibrating
Screener
PAN
500
FINES ANALYSIS
36 pg.
500
1000
PRODUCT ANALYSIS
VIBRATING Screener
High Production
On-Spec
1000
OVERS ANALYSIS
Virgin Feed
100 TPH
25% Oversize
Effect of Screener Efficiency
on Milling Circuit Loads
Milled Overs
MILL
SCREENER
Screened Overs
(to recycle mill)
Screened Product
100 TPH
0% Oversize
37 pg.
Screener
Efficiency
Mill
Recycle
Load
Total
Screener
Load
100%
25 TPH
125 TPH
90%
36 TPH
136 TPH
80%
50 TPH
150 TPH
70%
68 TPH
168 TPH
ROTEX Primary Markets
Industrial Mineral Processing
Chemical Processing / Fertilizers
Plastics Processing
Agribusiness
Food Processing
Food Processing Segments
•
•
•
•
Breading and Cereal
Coffee Tea and Cocoa
• Corn Processing
Flavorings and Spice
• Flour
• Ingredients
• Milk Powder
Miscellaneous Food
Processing
SUGAR APPLICATION
Sugar Grading
Typical grading:
1. -14/+30 mesh (-1.4/+0.6mm) - fine granulated
2. -30/+80 mesh (-0.6/+0.18mm) - extra fine
3. -80 mesh (-0.18mm) - fine confectioners
Specialty Screening for Specific Product Specs.
40
3/28/2002
SUGAR APPLICATION
Sugar Grading (continued)
Rotex Advantages
1. Standard in sugar industry
2. Sifting motion produces accurate and
efficient separations
3. Ball mesh cleaning controls near-size blinding
Features
1. Gentle action minimizes screen tears
2. Cleanable sanitary designs
3. Easy disassembly for quick cleanout
4. Totally enclosed - positive sealing
41
3/28/2002
FLOUR APPLICATION
Oversize Removal Operation
10 to 40 mesh (2 to 0.4 mm) range
5,000 Kg/h/m² Typical @ 30 mesh range
Synthetic screen clothing
Rates higher with stainless steel screens
Rates higher with larger openings
FLOUR SCREENING
ROTEX Advantages
Gentle Gyratory Screening Action
“Sifts” rather than “forces” material
Will not break up foreign objects
No pilling of product
Ball mesh cleaning
Cleanable Sanitary Designs
Totally enclosed - positive sealing
Easily disassembled for quick cleanout
USERS-FLOUR
Campbell Soup
Domino’s Pizza
Nabisco
Pillsbury
Quaker Oats
EDIBLE SALT
Application Data
Edible salts have tight specifications
Pretzel Salt: -14US / +20US
Table Salt: -40US / +70US
Flour Salt: -70US
SALT USER LIST
AKZO Salt
AM Salt
Canadian Salt Ltd.
Cargill Salt
Domtar
Moab Salt Co.
Morton Salt
Sal Fibras Pilco S.A.
Sherkat Tolidi Ghaza