Vertical roller mill has the advantages of high efficiency, low energy consumption, low noise, large drying capacity , product fineness easy to adjust , easy no dust pollution and maintenance, reliable operation . Especially in large grinding process, to fully meet customer needs. Widely used in metallurgy, electric power , cement , chemicals , ceramics, non-metallic minerals , plant desulfurization , slag grinding mass of materials , slag , slag , coal, cement clinker , glass, quartz , limestone and other industries and ultrafine powder grinding .
Since the vertical roller mill tensioning device is packing system, oil tanks are not automatically inferior vena flow, after all the mill shut down or in the repair process, for the framework to enhance or decrease the pressure required to do the following:
The central control system enables the main parameters to be controlled accurately, achieving the coordination of the mill and other devices, high reproducibility of the same particle fineness and high production stability of the entrre mill system.
The central control syste is capable of monitoring the operating conditions of the mill system, such as the mill vibration, grinding roller pressure, oil temperature, and mill temperature. Protection setting can avoid personnel caused damage to the service life of the vertical roller mill.
Thanks to Mr. Osama Aly Ahmed who inspired me to write this article. He mentioned that we have to understand the complete grinding process. Therefore, I would like to provide some briefly information about the grinding process. Please consider that this is only my point of view and is based on my knowledge/experience. It is not an absolute benchmark. Readers should re-think the provided information.
The airflow is an important parameter which effects the duration/resting time of the particles in the mill. The airflow should be set at the correct rate. Every grinding system should have a design airflow. A wrong airflow setting is the most common problem in grinding systems. A too high flow generates a too high pressure loss. It can also decrease the classifying efficiency depending on the classifier type and size. A too low airflow decreases the capacity and generates an overload of the mill. Furthermore, it is recommended to adjust the particle size by changing the classifier and the mill speed instead of changing the airflow. An airflow controller is also important to keep the airflow stable. If the system has no airflow controller, the particle size would change if the material feeding would be increased due to the airflow drop, even when the classifier and the mill speed does not change. A reproducibility of the product quality might be difficult.
In the vertical roller mill (VRM) the air is discharged from the ported air ring with high velocities. These high velocities are required to prevent coarse material dropping through the air ring into the air channel and ensure that they are thrown back into the center of the grinding table. A too small flow cross section causes a higher pressure loss and therefore requires a higher fan capacity. Another problem that can be caused by too high velocities is the worn out of the internal component of the grinding system. The dust loaded air will act like a sand blast at too high velocities.
After each roller pass the ground material is removed from the grinding track and transported by the airflow to the classifier. The coarser particles which dont pass the classifier continue to circulate in grinding chamber until they are reduced to the required product fineness and finally discharged from the classifier. This is the main cycle. If fewer cycles are repeated, the grinding process will be more efficent which means that the particles dont stay too long in the grinding chamber. If the cycles are repeated to often, the amount of fines in the product increases unnecessary and the curve of the particle size distribution will be not steep. In the VRM the raw material is fed to the center of the grinding table. Due to centrifugal forces the material moves outward from the middle of the grinding table. After a while the material passes the grinding rollers, falls over the edge of the table and only then comes into contact with the airflow. A too thick product bed between roller and grinding table will cause higher electrical power consumption of the mill.
Furthermore, the grinding process with a dry surface is much better and avoids also slipping of the rollers on the product bed between roller and grinding table/ring. This insures a better grinding process.
In the VRM the forces are generated by spring pressure, hydraulic or hydro-pneumatic systems and transmitted by the shaft and plain/anti friction bearings in the roller. The higher the material thickness between roller and grinding table the higher is the required force.
In the VRM the track is a rotating table. The vertical forces are applied downwards by the roller and get compensated by the rotating grinding table. The forces act at several points around the circular line of the track. Large gear units with heavy segment-thrust-bearings are required to resist the vertical grinding forces. Irregular forces will cause a rotary fluctuation and a rumbling of the mill.
An efficient grinding process requires a continuous rolling motion of the roller on the grinding track without slippery. Slippery increases the friction on the feed material. The amount of fines increases. Slippery increases also the power consumption for operating the mill and causes more wear on the grinding element.
In the VRM the rolling line of the roller and grinding track are not parallel to each other. There is only one line which has an exact rolling motion between roller and grinding track. All other lines have a certain amount of slippery (faster or slower than the corresponding contact lines on the track).
The size of the chunks/particles that can be drawn-in/stuck between the roller and its track depends on the depth of the product bed, the frictional condition and the entry angel between the roller and the track. Referring to the draw-in condition a curved track allows a bigger entry angel. The bigger the angel, the better is the draw in condition of the material.
On the way of the material to get between the roller and track there are forces that act on the chunks/particles that can weather be a benefit or a disadvantage for the draw-in conditions. On the VRM the particles on the way from the center to the edge of the grinding table are dealing with centrifugal acceleration which brings it radially outwards to the edge and the coriolis acceleration which moves the particles in the tangential direction which is the opposite to the rotating direction.
Wearing parts should not be left in the machine until they have entirely worn away. They should be changed when the operating performance of the machine gets worse. Lower grinding capacity and unquiet running are typical characteristics. Smoothing the surface of the grinding elements is the simplest way to restore the normal operation condition, if the grinding elements are uncomplicated and can be removed quickly (Depending on the grinding system). Of course, from the viewpoint of a high availability of a grinding plant it is required that wearing parts can quickly be exchanged.
Also, a too high velocity rate in the mill chamber can act like a sandblast and can generate a higher worn out of the mill parts. I often have seen customers changing the duct work without taking care of the proper diameter. A few millimeters smaller will increase the velocity while having the same airflow rate.
LUM Series Ultrafine Vertical Grinding Mill is designed on the basis of many years' experience in grinding mill production. It adopts the Taiwanese grinding roller technology and German powder separating technology. The ultrafine vertical grinding mill integrates ultrafine powder grinding, grading, powder collecting and transporting.
Feed particle size: 0-10mm Production capacity: 5-18 tons / hour Applicable materials: calcite, marble, limestone, talc, dolomite, barite, kaolin, wollastonite, gypsum, feldspar, pyrophylite and other non-metallic mineral ores.
It owns many independent patents, such as multi-rotor classifier, special design of grinding curve and variable frequency motor, etc. All of these make it lead the trend of the milling industry in the world.
The dedicated grinding mill for high quality, huge capacity ultra-fine powder production, the best choice for ultra fine powder processing industry powder site can reach 10-20um D97 by first separation, 4-5um D97 by secondary seperation, capacity 5-30tons per hour.
Using GCC to replace the PCC, it saved the production cost. We have signed a long-term supply agreement with them. The production of PCC will cause the pollution. It is not good for the environment. Zenith LUM1125 mill meet the environmental protection standard. More and more customers choose our GCC powder.
Our three-stage spur gear unit with torque split, the MAAG GEAR MAX Drive system uses two equal drive units to deliver power up to 15,000 kW for your vertical roller mill. Weve taken the expertise in gear technologies and manufacturing weve built up over the last 100 years and applied them to this modular drive concept specifically for vertical mills.The matched drive units, torque split, reliable components and our proven track record make our MAX Drive an ideal fit for cement and slag grinding bringing maximum power to your vertical roller mill.
The modular concept of the MAAG GEAR MAX Drive System allow for a compact arrangement without unnecessarily increasing the complexity of monitoring and the connection to the power grid. The two drive units include a vertical asynchronous motor directly flanged to the casing and are each connected to a central girth gear.
When both drives are running, the MAX Drive has a power range from 5,000 to 15,000 kW. You can also operate just one drive, allowing you to continue production at reduced output while performing maintenance on the other drive unit or half of the rollers.
The power behind our MAX Drive comes from two equal gear units that operate the girth gear around the central part on two flanks. These twin gear units transmit powerfrom the electric motors to the grinding table and reduce the motors speed to precisely what you require for the grinding process.
In addition to enabling its compact size, the torque split of our three-stage MAAG GEAR MAX Drive ensures that the total torque to the mill is always equally distributed between the two pinions. The highly flexible couplings used in the MAX Drive automatically equalise any torque imbalances between the two pinions ensuring equal load distribution between the two gear trains in each drive unit. The coupling also allows you to adjust the correct timing between the output pinions and the central girth gear and guarantees smooth operations through its damping of torque peaks and adaptable stiffness.
The pinions are also self-aligning, providing full tooth contact, even if there is a small run-out failure at the girth gear set-up. The self-alignment is made possible by a crowned toothing between the pinion and pinion shaft.
Mounted on the output disc, the central part of the MAX Drive System supports the grinding table, while a tilting-pad thrust bearing absorbs the static and dynamic grinding forces. With a design adapted from our well-proven MAAG GEAR WPU and WPV gear units, the thrust bearing for the MAAG GEAR MAX Drive System consists of thrust pads lined with Babbitt metal. The bearing is hydrostatically and hydrodynamically lubricated by high- and low-pressure oil pumps and the temperature is continuously monitored.
We use the latest machines and manufacturing processes, ensuring all parts are fit-for-use and free from defects. Our girth gears are made from fabricated steel, which produces a homogeneous crystal structure in the base material of the toothing, contributing to higher fatigue- and wear-resistance. Additionally, our in-house heat treatment eliminates internal stresses in the toothings. You can have confidence in the durability and reliability of the MAX Drive System and its components.
Our comprehensive documentation for the MAAG GEAR product line allows us to supply spare parts for all gear units since 1926 giving you confidence that your MAX Drive System will be in good repair for decades to come.
Manufacturing the complete drive system ensures the ideal adjustment between the main motors and all geared parts and lets us efficiently customise the MAX Drive System to meet your specific requirements. The drive system is available as standard solution or can be customised to suit your unique operational needs.
Made up of two or four segments, the girth gear of the MAX Drive is a fabricated design and is manufactured to be more fatigue- and wear-resistant. The ring with the toothing is a high-quality alloy steel that is rolled and bent, while the rib is made out of ordinary carbon steel and welded to the ring.
The compact gearbox of our MAAG GEAR MAX Drive System is powered by a vertical electric motor, adapted from a standard design to specifically fit this application. It is a squirrel cage asynchronous motor mounted directly on top of the gear casing, removing the need for any complicated onsite alignment.
In order to protect the girth gear from dust, we developed a new sealing concept that decouples the drives from the central part. A labyrinth seal, brush and dust protection shield are installed between the mill table and girth gear guard, along with rubber sealing to protect the central part and gear unit. These safeguards allow the drive system to run smoothly and decrease servicing.
The oil supply units for our vertical roller mill gear units and drive systems includes low-pressure pumps to feed bearings and toothings with filtered and cooled lubrication oil. If required, high-pressure pumps supply the oil for the thrust bearing from a separated compartment of the tank filled with filtered oil from the low-pressure part. Using only clean oil on the high-pressure side allows us to improve the lifespan of the pumps.
The maintenance drive is integrated in one of the gear trains and allows you to rotate the mill table very slowly. This simplifies maintenance work at your vertical roller mill, including replacing lining plates or rebuilding surfaces through welding.
All of our gear units and drive systems are equipped with unparalleled condition monitoring sensors. Normally, these types of sensors keep an eye on critical operating parameters like bearing temperatures, casing vibrations, etc. and trigger a mill shutdown in the case of exceedances.
Our condition monitoring system does much more. It lets you set up condition-based preventive maintenance that uses continuous monitoring and data analysis to detect wear and tear at an early stage. With this enhanced information, we help you plan maintenance and servicing in advance reducing downtime and keeping your plant running smoothly.
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.
Vertical Roller Mill is our newly-launched product which is applied as a solution to the technical issues such as low output and high energy consumption in the ordinary industry. This new type product is developed based on years of production and development on the pulverizer through analyzing and researching the strengths and weakness of both foreign and domestic products of its kind. Its performance has entered into the leading level among the international products of its kind. Vertical Roller Mill is a new type advanced pulverizing equipment featuring good performance and drying function. Integrated with drying, pulverizing and powder-selection, Vertical Roller Mill is widely applied in cement, chemical, coal and electric power industries. It has become the mainstream equipment in the pulverizing industry.
The equipment integrates the functions of crushing, drying, grinding, powder separating and transportation, featuring simple system and compact layout, with the floor space of about 50% of that of the ball-milling system. And it can be arranged outdoors so as to greatly reduce the investment costs. The system design is simple and reasonable, saving unnecessary equipment investment so as to reduce total investment of the equipment.
Less wear: The roller does not contact the grinding plate directly and the roller and grinding plate are made of high-quality materials. Therefore, they enjoy longer service life and less wear. High efficiency: The grinding rollers can directly grind materials on the grinding plate, featuring lower energy consumption (30% ~ 40% lower than that of ball-milling systems).
The equipment is provided with an expert automatic control system, realizing free switching between remote and local control to achieve easy operation and save labor costs.
The equipment can operate stably with little vibration, so its noise is fairly low. The system is wholly sealed and works under negative pressure, free of dust spillover and environmentally friendly, with the emission meeting the national standard.
The main motor drives the grinding plate by the reducer, simultaneously the hot air enters the vertical mill body from the air inlet and the materials drop on the grinding plate center from the feed opening and evenly move outwards due to centrifugal force. The materials are ground by grinding rollers when passing through the grinding area on the grinding plate, and large size materials will be directly crushed while the fine materials will form a material bed by extrusion for further inter granular crushing. The crushed materials will continue to move towards the mill edge until being taken away by the strong air flow at the vane and collected by the dust collector, while larger material particles will again fall onto the grinding plate for repeated grinding; the coarse particles in the air flow will drop back onto the grinding plate for further grinding when passing through the upper separator under the action of the rotor blade, with the qualified fine powder flowing out of the grinding plate with the air flow and then collected and discharged by the system powder collector as finished powder product. However, the iron blocks and other wastes mixed in the materials will move along with the materials towards the edge of the grinding plate due to their own weight and fall into the lower chamber and then be discharged out of the slag discharge opening by the scraping plate at the bottom of the mill tray (commonly known as scumming).
The vertical roller mill (VRM) is a type of grinding machine for raw material processing and cement grinding in the cement manufacturing process. In recent years, the VRM cement mill has been equipped in more and more cement plants around the world because of its features like high energy efficiency, low pollutant generation, small floor area, etc.
The VRM cement mill has a more complex structure than other types of cement mills, so we need to ensure the following aspects are normal during the operation, or the machine may not be able to function well.
Too thick material layer will reduce the grinding efficiency of the vertical roller mill. When the pressure difference of the mill reaches the limit, the material layer will collapse and affect the operation of the main motor and the discharge system.
There are many factors that may make mill body vibrate, including the grinding pressure, material layer thickness, air volume and temperature, accumulator pressure, wear condition of the roller and the grinding plate, etc.
The grinding pressure of the mill should be adjusted according to the fed quantity, the particle size, and the grindability of the material. It must be well controlled to maintain the thickness of the material layer, reduce the vibration of the mill body, and ensure that the stable operation of the mill.
Increasing the grinding pressure will improve the grinding capacity of the mill, but the grinding capacity will stop increasing when the grinding pressure reaches a certain critical point. If the set pressure of the hydraulic cylinder is too high, it will only increase the driving force and accelerate the wear of parts, but not improve the grinding capacity.
On the other hand, too high grinding pressure will cause the thickness of the material layer to decrease, which further leads to the increase of the vibrating speed of the mill and accelerates the wear speed of the parts.
The gas temperature at the discharging port can be increased by increasing the opening of the hot air door and reducing the opening of the circulating air door. However, when the gas temperature exceeds 130 , the equipment will also be damaged. For example, the dividing wheel at the lower part of the cyclone will expand and get stuck, and the lubricating grease of the grinding roller will dry and crack, which is also unfavorable to the tail dust collection bag.
In vertical roller mills, the air volume in the mill is determined by the material feed rate. The air volume can be controlled by adjusting the power of the circulating fan of the mill or the opening of the exhaust fan at the kiln tail.
If the air volume is too large, the pressure difference in the mill and the current of the main motor will decrease, the thickness of the material layer will become thin, and the vibration degree of the mill body will become strong.
If the air volume of the system is too small, the thickness of the material layer, the pressure difference in the mill, and the current of the main motor will increase, and so will the vibration speed of the mill.
When operating the vertical roller mill, the operator must control the inlet and outlet air valves to make the air volume of the system in a balanced state, so as not to affect the air pressure at the back end of the rotary kiln.Get in Touch with Mechanic