a study on the grinding process of hmx using fluid energy ... · a study on the grinding process of...
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A Study on the Grinding Process of HMX A Study on the Grinding Process of HMX using Fluid Energy Millusing Fluid Energy Mill
JooJoo SeungSeung ChaeChae, , HyounHyoun--SooSoo Kim,Kim, Jin Rae Jin Rae ChoCho
A g e n c y f o r D e f e n s e A g e n c y f o r D e f e n s e D e v e l o p m e n t ( A D D )D e v e l o p m e n t ( A D D )
Y u s e u n gY u s e u n g
P . O . B o xP . O . B o x
3 53 5 -- 4 2 , 4 2 , D a e j e o nD a e j e o n , K o r e a, K o r e a
High Explosives Group, ADD
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IntroductionIntroduction
Characteristics of HMX
�1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane
(Octogen), C4 H8 N8 O8
�High performance explosive�6 differential class�Dv = 9.1 km/s�Sensitive of Impact and Friction→Coated it with polymer binder and plasticizer
H2C N
N
H2C N
O2N
CH2
N NO2
CH2
NO2
NO2
High Explosives Group, ADDRef) ICT database & MIL-DTL-45444C
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IntroductionIntroduction
Aim of this study
�Study on the grinding process of HMX using fluid
energy mill
�Find the optimum operating parameters for the
purpose of average particle sizes below 5�in t he
process of HMX grinding
High Explosives Group, ADD
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BackgroundBackgroundProcess of Grinding through jet�Type I
- relatively hard material (ex, Silica sand)- the mechanism of separation through attrition- the separation of particles occur primarily within the surface or in the edge- the characteristics of the particles are maintained throughout the process of
separation- progressively as the quantitative amount of the larger particles diminish,
there occurs a dramatic production of the smaller sized particles simultaneously
- during the grinding process, the formation of particle distribution retains and maintains a similar format
High Explosives Group, ADDRef) Y.Mori, G.Jim
b
o, J. C h e m . E n g . O f J a p a n , 22, 363 (1958)
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BackgroundBackground
Process of Grinding through jet
�Type II- relatively soft material (ex, Sulfur)
- the mechanism of separation through fracture- when the particles are exposed to a greater amount of internal stress than
it’s capacity and are thus fractured and broken down into smaller particles subsequently
- all particles become smaller compared to its original size and the status of particle distribution is also gravitated towards the smaller side
High Explosives Group, ADDRef) Y.Mori, G.Jim
b
o, J. C h e m . E n g . O f J a p a n , 22, 363 (1958)
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Schematic diagram of Fluid Energy Mill (JSchematic diagram of Fluid Energy Mill (J--OO--M)M)
Com pressorC.A Dryer
Hum idityCheck
Surge Tank
C.A Heater
Ejector
Packed Scrubber W et Scrubber Bag Filter Cyclone
J-O-M
M anom eter
Feeder
High Explosives Group, ADD
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Calibration curves of Volumetric feederCalibration curves of Volumetric feeder
RPM
0 200 400 600 800 1000
Feed
ing
rate
(g/m
in.)
0
200
400
600
800
1000
HMX class-AHMX class-CHMX class-F
High Explosives Group, ADD
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The effect of the grinding materialThe effect of the grinding material’’s feed rates feed rate
Feed rate (g/min.)
Ave
rage
par
ticle
siz
e (m
m)
0
1
2
3
4
5
46 500 1055600
High Explosives Group, ADD
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The effect of feed air pressureThe effect of feed air pressure
Feed air pressure (kPa)
400 500 600 700 800
Aver
age
parti
cle
size
(mm
)
0
1
2
3
4
5
feed rate = 500g/min., mill air pressure = 672.2 kPa
High Explosives Group, ADD
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The effect of mill air pressure at constant feed rateThe effect of mill air pressure at constant feed rate
Mill air pressure (kPa)
0 200 400 600 800
Ave
rage
par
ticle
siz
e (m
m)
0
4
8
12
16
20
feed air pressure = 344.7 kPafeed air pressure = 482.6 kPafeed air pressure = 715.0 kPa
High Explosives Group, ADD
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The grinding result according to variations in mill pressureThe grinding result according to variations in mill pressure
Volume equivalant diameter (μm)
0.1 1 10 100 1000 10000
Diff
eren
tial p
roba
bilit
y
0
2
4
6
8
10
Cum
mul
ativ
e pr
obab
ility
(%)
0
20
40
60
80
100
Volumetrice equvalent diamter (μm)
0.1 1 10 100 1000
Cum
ulat
ive
prob
abiti
ty (%
)
0
20
40
60
80
100
Diff
eren
tial p
roba
bilit
y
0
2
4
6
8
10
Volumetrice equvalent diamter (μm)
0.1 1 10 100 1000
Diff
eren
tial p
roba
bilit
y
0
2
4
6
8
10
Cum
ulat
ive
prob
abiti
ty (%
)
0
20
40
60
80
100
Before Grinding
Volumetrice equvalent diamter (μm)
0.1 1 10 100 1000D
iffer
entia
l pro
babi
lity
0
2
4
6
8
10
Cum
ulat
ive
prob
abiti
ty (%
)
0
20
40
60
80
100
Mill pressure : 70kPa
Mill pressure : 200kPaMill pressure : 340kPa
Type II
Type I
Type II
High Explosives Group, ADD
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Volumetric equivalant diameter (μm)
0.1 1 10 100
Diff
eren
tial p
roba
bilit
y
0
2
4
6
8
10
Cum
ulat
ive
prob
abilit
y (%
)
0
20
40
60
80
100
Class-C : 2.91μmClass-F : 2.83μmClass-A : 2.89μm
High Explosives Group, ADD
The grinding results of The grinding results of HMXsHMXs with respect to with respect to average particle size variationaverage particle size variation
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Pre & Post Grinding process SEM images of HMXPre & Post Grinding process SEM images of HMX
Before Grinding After Grinding
High Explosives Group, ADD
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ConclusionsConclusions
- The particle size and distribution were greatly influenced by mill air-pressure, but feed air-pressure and feed rate had little effect.
- When the air-pressure exceeds 340kPa, we can stably obtain an average fine-powder particle size below 3�regardless of feed rate.
- Under the normal circumstances and conditions within the operation of the JOM, with increase in air pressure, we were able discern the co-existence of the 2 different types of grinding mechanisms.
High Explosives Group, ADD
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ConclusionsConclusions
- Through the SEM image analysis, the fine-powder particles which underwent grinding were found to have a smooth surface and clean surface.
- We judge this to contribute towards the added insensitivity of the plastic bonded explosive’s characteristics.
High Explosives Group, ADD