Global Stone Ore Blending for
Rotary Kiln
Global Stone Tenn Luttrell
Introduction
„
Global Stone Tenn Luttrell was originally founded in
1979 and is located in Eastern Tennessee.
„
GSTL is a producer of High Chemical Quicklime,
Construction Aggregates and Pulverized Limestone
products.
Ore Body
„
Tennessee Division of Geology identifies GSTL’s ore body as the Chickamauga
Limestone Group.
„
The limestone ore body lies at a 35 degree southeasterly slant and is
approximately 50 to 75 feet thick.
„
The ore body has two distinct limestone strata:
–
A Zone (Underground) contributes consistent high CaCO3 characteristics.
–
C Zone (Surface) contributes moderate CaCO3 characteristics and is
cyclic in consistency.
„
Each zone calcines distinctly:
– A Zone has a moderate calcination integrity (easily fractures within the
kiln).
– C Zone has a high calcination integrity (does not fracture as easily within
the kiln).
A-Zone Underground
Surface
Mined Out
Surface Mine
Shale Layer
5
600 Ft
6
High Calcium A
Zone Seam is
approximately 50'
to 75' feet thick
7
8
Shale Layer
Each heading is 50' wide by 50'
high. Following the ore
our tunnels are approximately 1.5
miles in length.
C-Zone Surface Mine
Purpose - Why We Blend
„
Quality
–
–
–
„
Production
–
–
„
A Zone is used to maintain / improve chemical quality.
C Zone is being utilized as kiln feed in the stone blending process, that on a
stand alone basis would not qualify.
GSTL is committed to maintaining / improving quality in the stone blending
process.
The stone blending process enables us to blend two distinct limestone
strata which improves kiln productivity.
Reduction of LKD (kiln by-product) production is accomplished by stone
blending.
Mine Life
–
A Zone and C Zone must be effectively and efficiently used together to
maximize mine and plant life.
Determining Projections
„
„
„
„
Determine quality from each mine location using
drill cuttings.
Log quality components in “Location Projection”
file.
From “Location Projection” place Mean, Standard
Deviation, and estimated tonnage into “Chemical
Balance” worksheet.
From “Chemical Balance” worksheet place
average from each mine location into “Incremental
Blend” worksheet.
Drill Samples
„
Bench drill on C
Zone surface
bench. This stone
will be tested in lab
and matched with
jumbo drill samples
from the A Zone
underground mine.
Sample Results
Blend Worksheet
Blend#
Date
Incremental
Beginning
Ending
40
hrs
Incremental Hours is time building surge. After Surge is built it will be released to A/B piles
Tonnage
Tonnage
23702
0
Quality
97.4
1083
0
A
Underground
6w#2
Location
weekly
5/21/2003
29443
0
0
0
92.7
92.8
Portal 3
floor
West Pit
0
0
0.0
0.0
West Pit
West Pit
Primary
Quality
97.4
92.7
92.8
0.0
0.0
Tonnage
23702
1083
29443
0
0
94.81
54228
20000
2309049
100350.8
2732016
0
0
Trucks
474.04
21.66
588.86
0
0
94.81
Target = 96
5141416
1084.56
Incremental Tonnage
Incremental Tonnage and Tonnage must match for blend to work
Kiln Feed Piles (A or B)
mine prod min =
Surge Quality
daily kiln output
0.57*(1-((lkd%+waste%)/100)
Secondary
Target Standard
Deviation equals 0.2 to
0.4
35248.2
10710
1530
18979.8
Process operator will be measured
on Standard Deviation
Chemical Fines
weekly kiln stone requirement based on 14% waste and 750 tons / day
Process
„
„
„
„
Blasting and hauling from designated
locations. These locations are determined and
projections made on the “Incremental Blend”
worksheet.
Building primary surge pile and sampling to
insure blend quality and consistency.
Cascading action to homogenize ore blend.
Building secondary surge pile and sampling
to measure blend quality and consistency.
A-Zone Underground Mine
Process
C-Zone Surface Mine Process
„
The determined mine
locations (A-Zone &
C-Zone) are hauled to
the primary crusher in
appropriate ratios for
blending.
The Blending Begins
„
Truck dumping into
crusher. Since stone is
coming from multiple
locations, stone is
blending together to
homogenize before
reaching primary
surge. This helps
narrow Standard
Deviation.
Stage One Blending - Primary
Surge Pile
Surge Pile Blending Diagram
„
As inner cone falls
into feeder, the
concentric circles will
cut strata lines of
different stone
chemistries. This will
blend stone to a more
homogeneous mixture.
When incremental blending it is important to take the time and build the pile according to the incremental time
you set. After desired tonnage is reached, then run into feeders and let cascading action blend material.
Do not set blend and run feeders at same time. This will cause slip streaming of material through inner cone
and will cancel effect of cascading action.
Shape of inner cone as it feeds into feeder
Outer Pile Skirt
Outer Pile Skirt
Material Flow into feeder
Chemical strata lines that cascade
into inner cone causing blending action
Automatic Belt Sampler Obtaining
Sample After Primary Surge
„
Ore production
samples are taken and
analyzed during
production to measure
the success of each
primary surge pile
blend.
Stone Composition by Location
„
GSTL has reduced the
UG (A-Zone) stone
consumption by
approximately 36%
since implementing
the stone blending
process.
Before Stone Blending Program (Jun'02)
43%
57%
C-Zone
A-Zone
After Stone Blending Program (Jun'04)
21%
79%
C-Zone
A-Zone
Stage Two Blending - Secondary
Surge Pile
Automatic Belt Sampler Obtaining
Sample After Secondary Surge.
„
„
Samples are taken
before kiln’s stone bin
to measure target
quality and std dev
success.
We use an automatic
belt sampler to obtain
samples in a set
periodic manner.
Kiln Production Gains
„
„
Successful stone blending
enables us to improve kiln
productivity while
maintaining product
quality.
Reduced LKD production
is a very important benefit
of the stone blending
program.
Before Stone Blending Program ('02)
60
50
40
30
20
10
0
57
15
A-Zone
LKD
15% = 36,750 Tons/LKD
After Stone Blending Program ('04)
60
50
40
30
20
10
0
21
12.4
A-Zone
LKD
12.4% = 30,380 Tons/LKD
Repeatability Curve
Goal is to fall into the Target Deviation boundaries. This signifys the success of your blend target and that you are
repeating. This will show up in kiln performance. Kiln will not deal with cyclic quality of feed resulting in better output
quality, consistent product output, and reduced LKD.
Target Deviation Boundary
Actual Deviation Boundary
Actual Deviation Boundary
Y
Mean
X
f(x) =
1
STD x (2 x pi)1/2
x
e-1/2 (( X - mean) / STD)2
„
The challenge is to take moderate
quality CaCO3 stone (C-Zone)
and mix with a higher quality
CaCO3 stone (A-Zone) to achieve
a homogeneous mix that falls
within Target Quality & Std Dev
Boundary. The mining and kiln
production benefits of a
successful stone blending
program far out weigh the cost of
blending implementation and
maintenance.
Conclusion
„
The goal of the stone blending program is to
create a homogeneous stone mixture as feed for
the rotary kiln. This is accomplished by
continuously narrowing stone chemistry variation
toward a set standard deviation, then
demonstrating repeatability of performance. The
degree of repeatability attained determines the
derived mining benefits, product quality and kiln
productivity.