rm立磨培训

Gas Flow
The required gas flow of the roller mill depends on the following factors: Discharge and transport of the ground material, basically the principle of functioning of the mill Drying of the material to be ground Use of available maximum hot gas amount mill in Order to recycle Energy Maximum temperature of hot gas before mill
grinding table discharge ring hot gas channel
pendulum flap
Nozzle Ring
The gas velocity has also an infect of the grain size will be drop into the bucket elevator or will be lifted up to the separator.
tie rods water injection
nozzle ring
grinding table hydraulic skid
drive unit
hydraulic cylinder
parts of the mill:
dam ring extension clamping plates for table liner fixing
advantages
low space for the grinding plant
disadvantages
high energy requirements
high wear on the complicated parts of the mill
no chance to separate high wear causing materials out
grinding path
grinding table
retaining plate
expansion bolt
grinding table insulation
parts of the mill:
nozzle ring
wear protection for nozzle ring segment
Material Distribution
ring diagram
12 10 8 6 4 2
in the mill housing
[*10³g/m³ ] dust per hot gas
Edge of the grinding table
Edge of the nozzle ring
Nozzle Ring Adjustment
The adjustable nozzle ring supports the reduction of internal material circuit, thus mainly product material is being transported to the separator pneumatically. This has the effect of lowering the pressure loss (drop) as well as the imperative gas amount and minimizing the power requirement.
Material Movement
on the grinding table
… by adjusting the plough
Material Movement
on the grinding table
… by adjusting the plough … in depends of the elevation … and in depends of the grain size … it is possible to force the material passing two one none … rollers before it dropped in the nozzle ring
overrunning main clutch drive
coupling main with guard gear box
Mill Main Drive
(1) … the value of the load torque depends on the hydraulic pressure set for the rollers (2) … periodic load variation (up to ± 35 %), depend on the hydraulic pressure, frequency <5 Hz main motor dimensioning
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Grinding Process
Parts of the mill
Parts of a POLYSIUS Roller Mill
separator
confining air system
roller Pair dismounting device mill housing
roller pair
adjustable segment of nozzle ring (box)
nozzle ring adjusting device inner part of nozzle ring
parts of the mill:
mill drive
auxiliary gear box auxiliary drive
Internal Material Circuit
level lV
Sankey diagram
lll ll l
material load
Material Distribution
velocity [m/s]
40 36 32 28 24 20 16 12 08 04 00
velocity vectors coloured by velocity magnitude
Internal Material Circuit
The material is being transported to the separator by the gas flow coming from the nozzle ring. Operation only by the internal material circuit is suitable for coal mills or for roller mills with low throughputs.
Note: The gas flow for material discharge must not fall below the
required minimum amount of gas. The maximum gas temperature amounts normally to 450 º C. For specific wet material an assembling for up to 550 °C is possible.
External Material Circuit
The gas velocity in the nozzle ring can be specifically minimized so that not all the material is entrained by the gas, but a large portion falls through the nozzle ring onto the discharge ring rotating with the grinding table.
Nozzle Ring
The gas velocity will be reduced when the open cross section of the nozzle ring is enlarged.
mill housing nozzle ring adjustment box
At the same time the “natural” pressure loos of the Mill will drop. The amount of material falling dropping through the nozzle ring increases.
Fturn … turning motion force Frad … centrifugal force = m * R * w² Fres … resulting force
Frad
Fres
Fturn Ffri
Ffri
… friction between table and material and internal friction of the material
In the nozzle ring it will be decided what material will be lifted to the separator to be check there for the right grinding success.
The nozzle ring cross–section is adjustable from outside. The hot gas velocity in the nozzle ring is a decisive parameter for the grinding process.
External Material Circuit
advantages
The energy-saving mechanical transport by bucket elevator reduces the pneumatic transportation of material in the roller mill itself.
This certain amount of material falls through the nozzle ring to the discharge ring. Over a discharge chute the material gets to a bucket elevator which transports it back to the inlet feed chute or to the separator inlet.
0 10 20 30 40 50 60 70 80 90 100 [%]
Dam Ring Adjustment
in relation to the wear
Process Parameter
Material Balance
vaporising of water
Material Circuits
Nozzle Ring
adjustable gas speed
maximum gas flow for raw material grinding:
usually: adjustable between 15 and 35 m/s
Material Movement
on the grinding table
[%] 200
T TN
180 160
140
120
(1) TL
(2)
TN 100
T … torque
TA
wenku.baidu.com
80 60 40
T N … rated torque
T L … load torque n … speed
T A … break-away torque 20
nN … rated speed
0
time n nN
according the material distribution
Nozzle Ring
bottleneck
The nozzle ring is the ”bottleneck” in the roller mill. Here, the hot gas stream emerges at a high velocity, enables to take up crushed material.