Description
What is MPH medium speed coal
mill
The MPH mill
manufactured by our company has absorbed the advantages of MPS mill
and HP mill, and removed their respective shortcomings. We
optimized the design on structure thus develop the new type
of coal mill. MPH medium-speed coal mill is mainly composed of the
following parts of central coal drop pipe, separator, spring
loading device, grinding roller, middle-frame, grinding disk,
nozzle ring, scraper, lower-frame, lower- frame seal ring,
planetary gear reducer, lubricant station, coupling,
motor.
How the
MPH medium coal mill works
The MPH medium
speed coal mill is the type of roller mill with stressing
extensively. The motor acts on the main reducer to drives the
grinding disk to rotate and the rotation of the disk brings the
three grinding rollers which are evenly distributed at 120 degree
to rotate themselves. The raw coal falls through the coal pipe down
the disk, and moves along the radial direction towards the
circumference under the effect of centrifugal force, evenly enters
the disk roller path then is grinded between the roller and the
disk tile. This grinding system is enclosed in the middle frame.
The grinding pressure is automatically applied by the spring
loading installed on the mid-frame and is adjusted according to the
coal grade. The grinding pressure and the themselves weight of the
grinding parts are all applied to the reducer and then transmitted
to the foundation. These three grinding rollers are evenly
separated on the grinding disk roller-path and fixed on the middle
frame by two trunnions, and roller arm can be adjusted to incline
12-15 degrees along the radial direction by the trunnion to get to
the change of materials thickness and the angle change caused of
the yearly working wear between the roller and disk.
The hot air used
to delivering the pulverized coal and drying raw coal blows into
the mill from the hot air inlet in which the static pressure is
transformed into dynamic pressure by the nozzle ring outside the
disk, and blows the pulverized coal at the speed of 75-90 m/s into
the separator above the coal mill, and simultaneously the raw coal
is dried out by strong stirring happening here. The raw coal not
completely grinded is blown back to disk. The unbreakable iron
blocks or gangue will fall into the hot air chamber located at the
lower part of the disk, and these foreign matters are scraped into
the waste bin by the scraper fixed on the disk support and
discharged from the mill.
After the
pulverized coal enters the separator at the upper part of the mill,
the coal meeting the fineness requirements is selected out
and delivered to the coal bin through the output pipe located in
the separator, however the coarse coal returns to the disk for
grinding through the lower part of the separator.
What is
the shortcomings of MPS Mill and HP Mill
1.The
shortcomings of MPS mill
1) It is difficult
to overhaul the mill roller. For the MPS mill is loading through
triangular pressure frame, and with which the roller is connected
by hinge shaft. When the overhaul is performed the connection
between the roller and the pressing frame are firstly removed and
then the roller is just taken out, during which the steps are
intricacy and the overhaul is heavy.
2)The hydraulic
loading is adopted. For the hydraulic cylinder always moving up and
down in a long time will cause of the short life of the seal, and
which is often required to replace the seal. If the replacement is
not done in time it will lead to oil leakage thus will seriously
pollute environment.
2.The shortcomings
of HP mill
The output of the
mill will seriously decrease after the mill operates for years. For
the roller works in linear contact, the grinding parts will be worn
after working many years, which will cause of the unstable contact
among the grinding parts thus it leads to decrease the
output.
What is
the feature of MPH medium speed coal mill
1. The roller
diameter is big, rolling resistance is small, and the grinding
condition is good so the output characteristic is excellent and the
power consumption is low.
2.The stable
output, easy adjustment, low noise, small vibration and evenly wear
of grinding parts.
The roller, roller
arm and trunnion are connected to the middle frame in which the
roller can be adjusted among the range of 12~15 degrees so that the
roller can be well adapted to the changes caused by the thickness
of the material layer, the feeding particle and the wear of
grinding parts. In addition, the loading force is automatically
controlled by the spring loading change. As the thickness of the
material layer increased the loading force correspondingly
increases thus the good grinding effect is achieved.
3.The coal mill
can start and stop in the condition of no-load.
4.The stable
output at post-worn period
MPH mill that is
similar to MPS mill has good tile curvature of the roller and disk,
and good matches in the ends to ensure excellent grinding effect.
In the post-worn period of grinding parts, the output of the mill
is slightly affected, which only decrease 5% lower than normal
operation. This is the main advantage of MPH coal mill. For the HP
medium speed coal mill it has the liner contact at working
therefore the output will be reduced by 10%-20% in the post-worn
period.
5.The grinding
parts is made of various materials to lengthen service
life
The roller bed and disk grate of MPH mill are made of high chromium
cast iron, hard nickel cast iron (Ni-Hard IV) or lay-welding hard
carbide metals which can also be reversed to use to make sure of
the longer service life and ensure long-term stable
operation.
6.The big output
and little waste
The speed of air
vortex is 70-90m/s in the mill which can fully hold the material to
be grinded. Only the non-grindable waste can be excluded from the
mill and the waste is less which reduces the workload of the
maintenance in operation.
7.The easy
maintenance
As the spring
variation automatically loading is adopted the roller can be
overhauled by taking it over directly. The mill is easy to overhaul
with low cost.
8.The low
operating cost
The traditional MPS mill adopts hydraulic
loading. For the hydraulic loading requires to frequently replace
of seal or hydraulic cylinder leaking will result in serious
environmental pollution and the operating costs is increased. In
addition the hydraulic station runs overtime and the energy
consumption is increased.
