roller mills by siebtechnik tema. crushing & milling equipment
Our roller mills are capable of comminuting very hard through to soft products homogeneously and with a minimum fine material content, depending on requirements, to a reduction ratio of between 1:5 and 1:1.5 and our double-roller mills to a Mohs hardness of up to approx. 8.5.
With the double-roller mill, all brittle materials, such as, for example, ores, clinker, limestone, gypsum, aluminium oxide, glass, can be reduced in size up to a Mohs hardness of approx. 8.5 with a reduction ratio from 1:2 to 1:5.
Comminution occurs between a rotating roller and a flexibly supported crushing wall mainly through compressive and shear stress. The fed material is drawn in through the rotating roller by means of shear and compressive stress until it can pass through the smallest opening between the roller and crushing wall.
The single-roller mill has a crushing roller provided with crushing strips. The crushing strips can be lined to improve the feeding behaviour, which additionally improves the throughput with a final product that becomes coarser. The crushing wall with mounted crushing jaws is supported by springs, so that protection is ensured against overloading and minor foreign bodies. It can also be adjusted via threaded spindles to set the end product fineness.
Crushing is done between two counter-rotating rollers mainly through compressive and shear stress. The smooth crushing rollers are arranged on opposite sides, one of them being fixed to the housing and the other arranged flexibly. The flexibly appointed crushing roller can be moved via a spindle in order to thus set the opening between the two rollers infinitely variably. To protect the crusher from minor foreign bodies, the flexible roller is supported by spring packages that can be adjusted to meet requirements in the prestressing force. The two crushing rollers are driven by a V-belt drive.
The double-roller mills are executed by us in two versions: In the laboratory version, the machine is equipped with a tamper-proof feeding funnel, the base frame with integrated control system and the safety-monitored collecting box.
In the laboratory version, the complete upper section of the housing can be swung open once the quick release has been actuated, so that the crushing chamber can be subjected to rapid inspection/cleaning in order to prevent any cross-contamination between the samples.
vertical roller mills
With the many advantages vertical roller mills offer, we continually develop our VRM offering with the latest upgrades, including the OKTM Mill and the ATOX Coal Mill. The OKTM Mill skilfully comminutes raw material, cement and slag. It features a patented roller and table design and concrete mill stands instead of traditional, heavy steel structures.
The OKTM Mills flexible design makes it possible to operate it with a number of rollers out of service while still reaching 60 to 70 percent of the normal operation output, minimising production losses.
The compact and long-lasting ATOX Coal Mill has the capability to grind virtually all types of raw coal, to your desired fineness. It is suitable for feed materials with varying moisture percentages, handling abrasive and sticky raw coal with ease.
The cement industrys focus on energy reduction has made vertical roller mills particularly compelling. Grinding systems in cement production make up approximately 85 to 90 percent of total plant electrical energy consumption. As vertical roller mills are 30 to 50 percent more efficient than other grinding solutions, they give cement plant owners a great opportunity to
When it comes to grinding raw coal, savings in specific energy consumption can be achieved with vertical roller mills. Specific energy consumption depends on the grindability of the raw coal and the coal meal fineness required. A dynamic separator that ensures high separation efficiency also helps to reduce specific energy use.
FLSmidth provides sustainable productivity to the global mining and cement industries. We deliver market-leading engineering, equipment and service solutions that enable our customers to improve performance, drive down costs and reduce environmental impact. Our operations span the globe and we are close to 10,200 employees, present in more than 60 countries. In 2020, FLSmidth generated revenue of DKK 16.4 billion. MissionZero is our sustainability ambition towards zero emissions in mining and cement by 2030.
roller mill - feed mill machinery glossary
Roller mills accomplish size reduction through a combination
of forces and design features. If the rolls rotate at the
same speed, compression is the primary force used. If the
rolls rotate at different speeds, shearing and compression
are the primary forces used. If the rolls are grooved, a tearing
or grinding component is introduced. There is little noise
or dust pollution associated with properly designed and maintained
roller mills. Their slower operating speeds do not generate
heat, and there is very little moisture loss. Particles produced
tend to be uniform in size; that is, very little fine material
is generated. The shape of the particles tends to be irregular,
more cubic or rectangular than spherical. The irregular shape
of the particles means they do not pack as well. For similar-sized
particles, bulk density of material ground on a roller mill
will be about 5 to 15 percent less than material ground by
- little or no effect on fiber
- particles tend to be irregular in shape and dimension
- may have high initial cost (depends on system design)
- when required, maintenance can be expensive
There are many manufacturers of roller mills, but they all share the following design features shown adjacent picture:
- a delivery device to supply a constant and uniform amount of the material to be ground
- a pair of rolls mounted horizontally in a rigid frame
- one roll is fixed in position and the other can be moved closer to or further from the fixed roll
- the rolls counter rotate either at the same speed or one may rotate faster; roll surface may be smooth or have various grooves or corrugations
- bar; pairs of rolls may be placed on top of one another in a frame.
To ensure optimum operation, material must be introduced between the rolls in a uniform and constant manner. The simplest feeder is a bin hopper with an agitator located inside it and a manually set discharge gate. This type of feeder is best suited for coarse processing. For grinding operations, a roll feeder is suggested. In this type of feeder, the roll is located below the bin hopper and has a manually set or automatic adjustable discharge gate. If the gate is adjusted automatically, it will be slaved to the amperage load of the main motor of the roller mill.
The rolls that make up a pair will be 9 to 12 inches (23 to 30.5
cm) in diameter, and their ratio of length to diameter can
be as great as 4:1. It is very important to maintain the alignment
between the roll pairs. Sizing of the material is dependent
upon the gap between the rolls along their length. If this
gap is not uniform, mill performance will suffer, leading
to increased maintenance costs, reduced throughput, and overall
increased operation costs. The gap may be adjusted manually
or automatically through the use of pneumatic or hydraulic
cylinders operated through a computer or programmable controller.
Each pair of rolls is counter rotating. For improved size reduction
one of the rolls rotates faster. This results in a differential
in speed between the roll pair. Typical differentials range
from 1.2:1 to 2.0:1 (fast to slow). Typical roll speeds would
be 1,300 feet per minute (~ 395 m/min) for a 9-inch (~23 cm) roll to 3,140 feet per minute (~957 m/min) for
a 12-inch (~30.5 cm) roll. Usually a single motor is
used to power a two high roll pair, with either belt or chain
reduction supplying the differential. In a three high roll
pair, the bottom pair will have a separate drive motor. In
addition, the roll faces can be grooved to further take advantage
of the speed differential and improve size reduction.
By placing (stacking) pairs of rolls on top of one another, two
or three high, it is possible to reduce particle sizes down
to 500 microns, duplicating the size-reducing capability of
a hammermill for grain. For coarse reduction of grain, a roller
mill may have a significant advantage (perhaps as high as
85 percent) over a hammermill in terms of throughput/kwh of
energy. For cereal grains processed to typical sizes (600
to 900 microns) for the feed industry, the advantage is about
30 to 50 percent. This translates into reduced operating expense.