Working principle and structure characteristics of vertical millDate: 2019-06-28 Views:
1. The main equipment of the vertical mill system is:
The invention relates to a hydraulic device, a grinding roller lubricating device, a speed reducer lubricating device, a sealing fan, a mill water spraying device, a rotary air lock valve, a vibration feeding machine, a vertical grinding and selecting device, a grinding main motor, a grinding main speed reducer, a main motor thin oil station and a slag discharging bucket.
II. Working principle of vertical mill:
the matched material is sent to the grinding disc from the feeding port, the grinding disc is rotated under the driving of the main motor, the material is dispersed around the grinding disc due to the action of the centrifugal force, the shearing force of the grinding roller on the material is converted into the material extrusion and the grinding is carried out under the action of the gravity of the grinding roller and the application of the grinding force, a part of the large particles fall into the nozzle ring, the grinding cavity is scraped out by the scraper, and the rotation is generated at the same time by the friction force of the material; the high-temperature waste gas from the kiln tail or the hot-blast stove is driven by the nozzle ring to generate a vortex wind, the material is preheated and dried, and the material to be ground is under the pumping force of the exhaust fan, to suspend the material in accordance with a certain fineness requirement into the ring of the powder-selecting machine The amount of material and the amount of feed are controlled parameters, which are stable under normal conditions, so the change of pressure difference directly reflects the amount of circulating material in the grinding cavity. The pressure difference of grinder should be stable under normal working conditions, which indicates that the amount of incoming and outgoing grinding materials is in dynamic balance and the circulation load is stable. Once this balance is destroyed, the cycle load changes and the pressure difference changes. If the change of pressure difference can not be controlled in time and effectively, it will inevitably bring adverse consequences to the operation process, mainly in the following cases:
The main results are as follows: (1) the decrease of pressure difference shows that the amount of incoming material is less than the amount of grinding material, the circulation load is reduced, the thickness of the material bed becomes thinner gradually, and vibration will occur when the material is thin to the limit.
(2) the increasing pressure difference indicates that the amount of incoming material is larger than that of grinding material, and the circulation load is increasing, which will eventually lead to instability of the material bed or serious slag spitting, resulting in full grinding and vibration shutdown. The reason for the increase of pressure difference is that the amount of incoming material is larger than that of grinding material, which is not caused by uncontrolled feeding, but because of the unreasonable process links, resulting in the decrease of the amount of grinding material. The grinding material should be a fine and qualified product. If the grinding effect of the bed is poor, the amount of grinding materials will inevitably decrease and the circulation will increase; if the grinding effect is very good, but the efficiency of powder selection is low, it will also lead to the reduction of grinding materials.
The following factors affect the crushing effect:
(1) The tightening force of the hydraulic tension device, under the condition that the other factors are unchanged, the greater the tension force of the hydraulic tension device, the larger the positive pressure acting on the material in the material bed, and the better the crushing effect. But the high tension will increase the chance of vibration, and the motor current will increase accordingly. Therefore, the operator shall take into account the setting value of the tension force according to the material's easy to meet, the output and the fineness index, the formation of the material bed and the control thickness and vibration.
(2) the thickness of the material bed;
Under the premise that the tension force has been determined, the effect of bearing the fixed pressure is different with different thickness of the material bed. Especially for materials with different fragility, the required failure stress is different, so the optimal value of bed thickness is different.
(3) the extrusion working face of grinding disk and roller;
In the production process, with the wear of the grinding disk and the roller, the crushing effect will decrease. Due to various reasons, the extrusion face between the disc and the roll is protruding and concave, which will lead to the phenomenon of local overcrushing and insufficient local extrusion pressure, resulting in poor crushing effect. Therefore, it is best to replace the grinding disk and roller liner together, otherwise it will reduce the crushing effect.
(4) the fragility of materials;
The fragility of the material has a great influence on the crushing effect. The type selection design of the vertical mill is based on the test data and output requirements of the raw materials used to determine the specifications and models. It is worth noting here that when the same mill is used in different mines and different fragile raw materials, attention should be paid to adjusting the relevant parameters in time to avoid the change of pressure difference. Separation effect is one of the main factors affecting cyclic load. It refers to the timely separation and discharge of materials that have met the fineness requirements. The separation effect depends on the fluid flow field composed of the speed of the separator and the wind speed in the mill. In general, the speed of the separator is increased and the grinding product is produced. Reduce with the separator speed set. The wind speed in the mill is increased, and the grinding product becomes coarse. The two parameters are generally stable and balanced.
4. The main economic and technical indexes of the vertical mill and the main economic and technical indexes of the vertical mill are production, power consumption, chemical composition qualification rate, product fineness, moisture, etc.
(1) The main factors that affect the fineness of the product are the speed of the separator and the wind speed of the unit, and the general wind speed cannot be adjusted arbitrarily, so the main means of controlling the rotation speed of the separator is the product fineness control. The separator is a variable-frequency stepless speed-regulating, the higher the rotating speed, and the finer the fineness of the product. The fineness of the product of vertical mill is very uniform, but it cannot be too fine. It shall be controlled within the required range, and the ideal fineness shall be 9% ~ 12% (0.08 mm sieve). The product is too thin, which is not easy to operate and cause waste.
(2)One factor that affects the product moisture is the air temperature and the other is the air volume. The air volume is basically constant and should not be changed randomly. Therefore, the grinding air temperature determines the material grinding water.
(3)In addition to the properties of the material itself, the factors affecting the mill output are mainly the reasonable cooperation of the tensioning pressure and the thickness of the material layer. The higher the tightening pressure, the greater the grinding capacity, the thinner the material layer, the better the grinding effect. However, production must be pursued on the premise of smooth operation, otherwise, it is contrary to the intention. Of course, the ventilation in the mill shall meet the requirements.
(4) the power consumption of the product is closely related to the output of the mill. The higher the output, the lower the unit power consumption. In addition, it is related to the reasonable use of air, the output is low and the air volume is very large, which is bound to increase the power consumption of the fan, so the ventilation volume should be adjusted reasonably. Under the premise of satisfying the wind speed of the nozzle ring and the dust concentration of the out-of-wear air volume, the excessive air volume should not be used.
II. The advantages of vertical mill in production are better than those of tube mill:
1. Taiwan time has high output, low power consumption and low energy consumption.
2. The process operation is simple, preheating, grinding and lifting in one, the process is short and the occupation area is small.
3. The self-protection property is provided with auxiliary facilities such as the reducer thin oil station, the hydraulic station, the grinding roller lubrication and the water spraying device.
4. The material is ground under variable pressure
5. Dynamic and static powder separation adjusts product quality and has higher grinding efficiency.
6. The maintenance is small and the wear part is small, which is convenient for maintenance and maintenance.
3. The performance characteristics of the vertical mill are as follows:
1. The operation cost is low:
The main results are as follows: (1) the grinding efficiency is high, the vertical grinding roller and the material bed are used to crush the ground material, the energy consumption of the grinding system is low, the power consumption of the grinding system is 40 ≤ 50% lower than that of the ball milling system, and with the increase of the humidity of the raw material, the power saving effect is more remarkable.
(2) the metal loss is small, the special material for liner and roller is used, the service life is long, the operation cost is reduced, and the utilization rate is high;
(3) equipped with external circulation device, it can further reduce the power consumption;
(4) the particle size of the grinding material is large, which can reach about 5% of the diameter of the grinding roller, which is generally 40 × 100 mm, so the secondary grinding can be saved by large and medium-sized vertical grinding.
2. Construction costs are low:
The main results are as follows:
(1) compared with the ball milling system, the vertical grinding process is simple, the occupation area can be reduced by about 50%, the construction cost can be reduced by about 70%, the construction area is small and the space occupied is less.
(2) the vertical mill integrates the crushing, drying, grinding and grading to be integrated, the system is simple, and the layout is compact. Can be arranged in the open air, so that the construction cost is low.
3. Easy and reliable operation:
The main results are as follows: (1) equipped with automatic control device, remote control can be realized, and the operation is simple and easy.
(2)Since there is a device to prevent direct contact between the roller sleeve and the grinding plate lining plate, it is required to avoid severe vibration due to breakage.
4. Strong drying capacity:Vertical mill uses gas to transport materials. When grinding materials with large moisture, the inlet air temperature can be controlled to make the product reach the final water content. The materials with water content up to 12~15%can be dried in the vertical mill. Even if the ball mill is dried, only the materials with water content of 3~4%can be dried.
5. Stable product quality:stable product quality and uniform particle grading. It is easy to detect and control the particle size and chemical composition of the product, and the product quality is stable.
6. Convenient maintenance: convenient maintenance, through maintenance cylinder, flip arm, roll sleeve, liner can be replaced in a very short period of time.
7. Energy-saving and environmental protection:small vibration, low noise, less dust, clean operation environment and environmental protection requirements.
Fourth, the operation guiding ideology grinding operation is mainly wind, material, work balance, give full play to the best technological parameters of vertical grinding.
A, air: from kiln tail (hot blast stove) exhaust gas, up preheating, drying, lifting function; depends on whether the ventilation generated by the tail exhaust fan matches the feed quantity.
B, material: limestone, shale (clay) and iron powder are generally used to grind in a certain proportion. Mainly consider the particle size of grinding materials, particle grindability, moisture.
C, work: grinding pressure comes from roll weight, shearing force of material, grinding of material and material extrusion, grinding pressure should match feed quantity.
V. Performance characteristics of vertical mill
1. The relative sliding difference between the grinding disk and the roller is small, so the speed of the grinding stone is faster and the working pressure of the roller is higher, so the output is higher than that of other types of roller under the same specifications.
2. At the same time, the material is dried, ground and selected, the technological process is simple and the noise is low.
3. It is suitable for air sweeping and partial material external circulation system, which can greatly reduce the ventilation and power consumption of the system.
4. the inner ventilation ring gap can be adjusted flexibly according to the distribution of disk materials in order to reduce ventilation resistance and power consumption.
5, for four-roll vertical grinding, the grinding roller can be pressurized separately or four-roll at the same time to meet the needs of the change of the material bed. If the opposite roller is pressurized separately, different working pressure can be selected to run, so that a pair of grinding rollers with low working pressure have the dual function of preparing the material bed and grinding powder, which plays an important role in keeping the stability of the material bed when grinding the material which is difficult to grind under the higher working pressure.
6. The grinding roller can be lifted and lowered automatically to realize no-load starting, so as to reduce the starting torque of the motor.
7. The roller mill can be turned out of the housing by turning the roller cylinder for maintenance.
8, the high efficiency cage powder separator is installed, the fine adjustment is sensitive, the adaptability to load is strong, and the powder separation efficiency can reach more than 90%.
9, the cost of operation and maintenance is low.
10. Less investment in one line