Since the vertical kiln cement plant uses the small ball mill, the grain size of raw material can greatly affect its capacity and quality. The smaller the particle size, the higher the yield and quality of the ball mill. On the contrary, the larger the particle size, the lower the output and quality of the mill, and the higher the power consumption.
The wear resistance of raw material refers to how easy the high energy ball mill is to grind the material. National standards stipulate that using Wi (kwh / t) represents the grinding index. The smaller the grinding index, the better the material is ground. The cement factory is accustomed to using the relative grindability coefficient to indicate how easy it is to grind the material. It uses the experimental small mill to compare the material to be tested with the standard sand to achieve the specified fineness value and calculate the time of grinding.
As for the dry grinding method, the moisture of raw material can affect ball mill capacity and quality. The higher the moisture content of the milled material will cause saturated or greasy so that the capacity and quality of ball grinding machine will be reduced. Thus, the raw material with high moisture should be dried before grinding through the ball mill machine.
If the temperature of the raw material and the impact friction of the grinding body is too high, the temperature inside the ball mill will be excessive and the ball will stick, which will reduces the ball mill capacity and affects the quality of ball mill. Meanwhile, The ball mill cylinder is affected by thermal expansion and affects the long-term safe operation of the ball mill. Therefore, you must strictly control the temperature of raw material.
For ball mills of the same specification, the closed circuit process yields 15-20% higher than the open circuit process. In the closed circuit operation, choosing the proper powder selection efficiency and cycle load rate is an important factor to increase the ball mill capacity.
Some grinding aid will affect the effect of grinding. Most commonly used grinding aids are organic substances with strong surface activity. In the processing of grinding, the grinding aid can be adsorbed with the raw material, and this will accelerate the crack propagation in the material pulverization, reduce the mutual adhesion between fine powders, improve the efficiency of grinding, and is conducive to the energy saving and high yield of the ball mill. The national standard stipulates that the grinding aid may be added during the cement production process, but the addition amount shall not exceed 1%.
Adding a little cement grinding aid to improve the effiency of ball mill grinding during the woking. Since an enterprise uses the cement grinding aid, the increase rate of ball mill has been increased more than 10%, the power consumption per unit can be reduced by about 10%, and the blending amount of mixed materials is increased by about 5%.
The moisture of raw material entering the plant should be strictly controlled and carefully reviewed, and the temperature of the grindled material should be strictly controlled within the scope of the process. In order to ensure the stable capacity of ball mill grinder, the comprehensive moisture of raw material should be less than 1%.
In order to ensure a virtuous cycle of internal ventilation, all ventilation ducts should be cleaned regularly under normal production conditions. The dust collector is cleaned once a week and the warehouse should be cleaned up when the machine stop. The pulverizer is ventilated, and the efficiency of the powder selection should be properly adjusted to ensure the steady improvement of the output and quality of ball grinding mill.
Increasing the ball load when the device configuration allows. According to the actual measurement of the grinding balls consumption per ton to determine the number of supplementary grinding balls. Supplementing the ball mill media according to changes in ball mill current, grinding sound, output and quality during daily production. Generally, a warehouse can be used with 3-4 grade balls, and fine grinding bins can be 2-3 grades.
During the control of production, our control of cement fineness mainly adopts sieve analysis method and cement specific surface area method. The 0.08mm sieve residue should be controlled in the range of 2.5% to 3%, and the specific surface area of cement should be controlled in the range of 360 to 375m2/kg.
Using the method of more broken and less grinding to control the size of raw material. The second is to control and track the particle size of the mixed materials to truly achieve the rationalization of various material sizes.
The steel balls are the important ball mill media. They produce abrasion and peeling by the collision friction between the steel ball and the material, and the balls of the ball mill. During the working of the ball mill, whether the grading of grinding steel ball is reasonable is related to the working efficiency of the ball mill equipment. Only ensuring a certain proportion of various balls can the grain size structure of the material be adapted to achieve a good grinding effect. Reasonably selecting the grading of ball mill ball is an indispensable measure to improve the quality of ball mill machine. Here we will see how we can get a reasonable grading of the ball mill media.
If you want to process hard rock materials, the grinding balls should have big impact, and the ball mill balls also need the big size. The harder raw materials, the larger diameter of steel ball is. The ball diameter of double-storage partition should be smaller than the single-layer compartment board of the same discharge section.
The ball mill ball ratio should be judged according to the effective length of the mill, whether it is equipped with roller press, feed size, lining material and structure, and the number of rotation speed. After installing the ball mill, ball mill size gears need to be meshed and the amount of processing is also gradually increasing. After the ball mill has been running normally for two or three days, check the meshing of the large and small gears. Until everything is OK, open the ball mill manhole cover and add the remaining 20% steel balls for the second time.
1.The friction between balls, balls and ore, balls and ball mill liner will increase the wear and tear of ball mill when it is normally operating. So you do not need to add a small ball under normal circumstances.
2.The steel ball in the ball mill are continuously wore during operating. In order to maintain the ball filling rate and the reasonable ratio of the ball, and stable operation of the ball mill, it is necessary to add ball mill balls to compensate for the wear.
3.The weight of the steel ball depends on its quality. While the quality of steel balls determine the capacity of ball mill grinder. The quality of the steel ball is calculated according to the amount of ore processed per ton (ie 0.8kg per ton of ore). The average steel ball needs to process one ton of ore (1kg-1.2kg).
In general, the ratio of ball mill ball is a complicated technical problem. Each concentrator must carefully analyze its actual situation. Through long-term research and accumulation, you can find the right match ratio for yourselves. Besides, the ball ratio also includes the size and quantity of grinding balls.
Dear Experts, I want to know about the GM size wise percentage distribution in a 2 chamber close circuit OPC ball mill. Mill dim. 3.4 x 12.5 Media load 128 MT high chrome Also let me know how do the supplier selected 80mm as max. Ball size in this mill? Please share the formula as well. Clinker feed size is 25mm with standard BWI & sp. gravity.
H there, These are just the basics if you want to accurately do it you have to fill it up to 80% BC and then do alongitudinal sieving and then correct the BC based on the results. The biggest ball determination is explained and it is based on material hardness and biggest size. Let me know if you need more info. Regards; FJalali
Thank you very much sir for this help. I was keen to know the media surface area in 1st and 2nd compartment also. You document helped me in knowing that also. Sir, Can you share the grinding balls standard surface area to be kept in raw mill and coal mill (monochamber)?
Dear Sagarhbt, Why are you concerned about surface area? I never hear about basing your ball charge on surface area! In your first compartment the grinding is not related to surface area at all and it is related to weight and number of impacts. In the second compartment the grinding is related to pass of contact or length of circumference (see attachment). But you should figure the ball charge base on how it is grinding along the length of the compartment. As I said before charge 80% of the weight base on one of the recommended ball charges and then take longitudinal samples and adjust based on the results. Let me know if you nedd ant help. Kind regards; FJALALI
Dear Sagarhbt, Why are you concerned about surface area? I never hear about basing your ball charge on surface area! In your first compartment the grinding is not related to surface area at all and it is related to weight and number of impacts. In the second compartment the grinding is related to pass of contact or length of circumference (see attachment).
But you should figure the ball charge base on how it is grinding along the length of the compartment. As I said before charge 80% of the weight base on one of the recommended ball charges and then take longitudinal samples and adjust based on the results.
The basic parameters used inball mill design (power calculations), rod mill or anytumbling millsizingare; material to be ground, characteristics, Bond Work Index, bulk density, specific density, desired mill tonnage capacity DTPH, operating % solids or pulp density, feed size as F80 and maximum chunk size, productsize as P80 and maximum and finally the type of circuit open/closed you are designing for.
In extracting fromNordberg Process Machinery Reference ManualI will also provide 2 Ball Mill Sizing (Design) example done by-hand from tables and charts. Today, much of this mill designing is done by computers,power modelsand others.These are a good back-to-basics exercises for those wanting to understand what is behind or inside the machines.
Open circuit grinding to a given surface area requires no more power than closed circuit grinding to the same surface area provided there is no objection to the natural top-size.If top-size must be limited in open circuit, power requirements rise drastically as allowable top-size is reduced and particle size distribution tends toward the finer sizes.
A wet grinding ball mill in closed circuit is to be fed 100 TPH of a material with a work index of 15 and a size distribution of 80% passing inch (6350 microns). The required product size distribution is to be 80% passing 100 mesh (149 microns). In order to determine the power requirement, the steps are as follows:
The ball mill motorpowerrequirement calculated above as 1400 HP is the power that must be applied at the mill drive in order to grind the tonnage of feed from one size distribution. The following shows how the size or select thematching mill required to draw this power is calculated from known tables the old fashion way.
The value of the angle a varies with the type of discharge, percent of critical speed, and grinding condition.In order to use the preceding equation, it is necessary to have considerable data on existing installations. Therefore, this approach has been simplified as follows:
Many grinding mill manufacturers specify diameter inside the liners whereas othersare specified per inside shell diameter. (Subtract 6 to obtain diameter inside liners.)Likewise, a similar confusion surrounds the length of a mill. Therefore, when comparing the size of a mill between competitive manufacturers, one should be aware that mill manufacturers do not observe a size convention.
Cement clinker is usually ground using a cement ball mill. This is essentially a large rotating drum containing grinding media - normally steel balls. As the drum rotates, the motion of the balls crushes the clinker. The drum rotates approximately once every couple of seconds.
Grinding systems are either 'open circuit' or 'closed circuit'. In an open circuit system, the feed rate of incoming clinker is adjusted to achieve the desired fineness of the product. In a closed circuit system, coarse particles are separated from the finer product and returned for further grinding.
This cement ball mill is mainly used in grinding cement finished products and raw materials and also suited to metallurgical, chemical, electricity etc. and other industrial mining enterprises. It could also be used to grind various ore materials and materials that is grindability.
Cement mill is a simplified level, out of the hollow shaft and grinding materials and other components, simplified for the long cylinder, cylinder equipped with a grinding, cylinder of steel plate, with steel liner and simplified fixed, grinding media generally steel ball, according to different tube diameters and a certain percentage of load in, section steel grinding media can also be used.
When the cylinder rotates, the material and the ball under the action of centrifugal force, close to the liner, due to the role of friction, the material and the ball into the cylinder a certain height, the gravity, the ball and materials while whereabouts of the ball crushing the material, while the relative liner material sliding friction occurs, the resulting abrasive material, grinding the material so as to achieve the purpose.
Material by the feeding device into the compound air evenly into the mill screw shaft first warehouse, the warehouse there are ladder liner or corrugated liner, built with different specifications steel ball, rotating cylinder produces centrifugal force to the ball a certain height After the fall, have severe impact on the material and abrasive. Coarse material in the first position to reach, after single-compartment plate into the second warehouse, the warehouse lined with flat lining, there are balls, the material to further grinding. Powder discharged through the discharge grate plate, complete the grinding operation.
Cylinder in the rotary process, the grinding phenomenon has slipped in the fall to the process of abrasive material in order to effectively use abrasive effect on the larger particle size is generally twenty head when finely ground, the body tube mill body with the diaphragm plate separated Sec, it becomes two-position, materials into the first position when the ball was crushed, the material into the second position when the end of the material for grinding steel, finely ground material passing from the discharge end of the discharge hollow shaft, the small particles of feed material for pulverized, as in II slag sand, coarse fly ash, mill shell could have no partitions, a single-chamber tube mill, grinding the volume of steel can also be segment.
To achieve good combustion and satisfactory flame formation, coal needs to be dried and ground to a proper degree of dryness and fineness. Drying of moisture in coal is achieved normally by ducting part of the kiln exhaust gas through the mill with inlet temperatures of up to 300C. Inert kiln exhaust gases with oxygen content of about 3-5% are most suitable for the intended purpose due to high risk of fire/explosion in fine coal. However, the provision for inertization of coal mill circuit and fine coal bins (with CO2, N2 or CO2+N2 to replace O2 which promotes spontaneous ignition of fine coal) is strongly recommended to be available. Gas analyzers and explosion vents are essentially provided in mill circuits to monitor the potential of fire/explosion and mitigate fire/explosion incident respectively. Drying and grinding are generally being done in either air swept ball mill or a vertical mill. The selection of mill system will depend mostly on the factors like initial capital cost, drying and grinding capacity required, cost of energy (power) etc.
Coal Fineness: It is understood generally that the finer we grind, the easy it is for burning. However, the fineness required will always be directed by where to fire and what type of coal it is and lastly the fineness will be dictated by the risk factor involved in finer grinding high volatile coals. The recommended fineness for coal verses volatile matter percentage is depicted in graph beside.
As understood from the above graph, the relationship between 90-micron and 200-micron residue is quite important as well. So, it is generally recommended to have 200-micron residue as low as possible, because coarse particles delays ignition, gives long flames in kiln (coating & ring issues), CO formation at kiln inlet, higher preheater exit temperatures (EGT). As a rule of thumb, the residue on 90-micron sieve should not be less than half of the volatile content for safety purpose. ie. R90>=1/2. Volatile Content %.
Coal Moisture: The degree of drying, and therefore the required mill outlet temperature (from 65-80 0C) will depend upon the type of coal ground. Some residual moisture in fine coal is recommended (Graph below) to minimize the potential of spontaneous ignition of fine coal, which will again vary for different coal types as below:
While considering the safe mill outlet temperature, care should be taken to avoid the temperatures below dew point of mill outlet gases, so that the condensation inside the bag filter and consequent material jamming problems can be avoided.
Important Note: If you chose to use different types of coal (having different rank) simultaneously or use coal and Petcoke, remember to grind them separately as per above guidelines and feed them from different fine coal bins in required proportion to kiln and pre-calciner as required.
Coal Grinding Operation Objectives and KPIs: Highly energy intensive unit operation of coal grinding is intended to provide a fine coal as a fuel for calcination and clinkerization. Coal grinding operation is monitored for following parameters to ensure objectivity and economy of operation.
Note: Proximate and ultimate analysis are generally provided by coal supplier. However, Proximate analysis, Determination of calorific value, Ash analysis, Hardgrove analysis and Abrasion analysis are done as and when required in plant laboratory or by a third party agency.
Mill Load (Kw or Amps). Mill sound/filling % (in ball mills). Mill Inlet Temperature (0C). Mill Outlet Temperature (0C). Gas flow through mill (m3/h) or mill fan power (kw) Mill DP, or inlet/outlet draft (mmH2O). Separator DP (mmH2O, mbar) and temperatures (0C). Bag filter DP (mmH2O, mbar), Temperature (0C).
Position of Explosion vents. Operational readiness of quick shutoff dampers. Inertization section readiness (N2, CO2 pressure in bars) Mill Inlet Temperature (0C). Mill Outlet, bag filter outlet Temperature (0C). O2 + CO Percent at bag filter outlet and in fine coal bins. Bag filter hopper and fine coal bin temperature (0C).
Mill Feeding: Consists of following activities Coal Crusher: Generally, require when ball mill is used for grinding and raw coal size is on higher side(>25mm). Conveying to Hoppers: Covered belt conveyors, horizontal or inclined are most suitable and commonly used for conveying. Metal Detector and Magnetic Separator Arrangement of metal detector and magnetic separator is integral part of feeding system in vertical roller mills and roller presses. Both are installed on mill feeding belt conveyor. Magnetic separator, separates out small metallic impurities from mill feed. While as metal detector signals the presence of metallic debris, which can damage the grinding path and give rise vibrations issues. Mill Feeding Hoppers Hoppers for coal, petcoke serve the purpose of providing a buffer storage for mill feed and a convenient arrangement for feeding to weigh feeders. Hoppers are generally designed to hold the requirements of one shift or more. Coal hoppers are generally steel hoppers with conical steep bottom (inclination >700), wide opening for discharge as possible to ensure mass flow of coal, mounted on load cells and/or equipped with level sensors to guide filling in auto mode. De-dusting bag filters needs to be installed at the top to vent air when material is fed to a hopper. Mill Feeders: Feeders for coal mill are generally installed directly under hoppers with rod gate in between. The feeders are generally 2 to 3 m long and discharge on to conveyor or feeding chute to mill. For coal mill feeding, table feeders, belt feeders, chain feeders and weigh feeders have been used. However, weigh feeders are the most commonly preferred to feed and report production counters. Metering on Feeders: Metering can be either direct (gravimetric) or indirect (Volumetric). In direct method of metering the material passes over a load cell installed in weigh feeder/apron feeder and the travel speed is monitored with installed tachometer. Weight and speed together determines the mass flow rate of material in metric tons per hour (t/hr). Alternatively, in some of the arrangements direct system consists of weigh feeder and its pre-feeder. Feed rate is generally controlled with the speed of weigh feeder belt, which is driven by a variable speed drive. Feed rate is monitored and controlled by a control panel generally supplied with weigh feeder. Set points are passed to control panel from CCR by Operator. In indirect metering system feed rate is determined by measuring cross section of material and rate at which it flows and taking into account bulk density of material.
Calibration and Drop Test Facilities: Provisions for drop test for calibration of weigh feeders are commonly available in cement plants to validate production figures. Although the weigh feeder calibration is not required frequently unless there is a disturbance in mechanical system due to various reason including maintenance. However, it is a common practice to validate feed rate through drop test periodically. Weigh feeders generally come with self-calibration devices. A simple way of 'self-calibration' is to have the hopper mounted on load cells, so that a weight loss for predefined time will be used for calibration purpose, and in this case calibration of hopper load cells needs to done at least once a year with standard weights.
Cold Air Locking at Mill Inlet: This is very important for coal mill, as ambient air throttling the drying capacity of mill as well as increases the oxygen content of kiln gases making it riskier. Oxygen percentage of more than 12-14% is considered catalyst for fire/explosion risk. Rotary feeders (gravel gate), double flap valve are used to stop/minimize cold air leakage into mill system. Cold air leakage percentage can be determined by measuring oxygen percentage at inlet and outlet of the circuit element.
Ball Mill: Single chamber ball mills (with classifying liners and dam ring) with drying chamber and static or dynamic separator are commonly existing for coal grinding in cement plant for one or more kilns as per capacity. Ball mill is a cylinder rotating at about 70-80% of critical speed on two trunnions in white metal bearings or slide shoe bearings for large capacity mills. Grinding media consists balls of 3-4 sizes (60mm-30mm) in designed proportions with large sizes in feed end and small sizes in discharge end. About 27 to 35 % volume of mill is filled with grinding media. Equilibrium charge is that charge where compensation for wear can be done by balls of one size only usually the largest size in the compartment. Grinding media could be made of forged steel, cast steel or even cast iron. To economize grinding media consumption, presently grinding media used are high chrome steel balls. Mill shell is lined with lining plates to protect it from wear, high chrome steel liners are now commonly preferred to give longer life. Ground material is swept out of the mill by hot air /gas of significant velocity (5-6 m/s), through separator and coarse fraction is returned to the system for regrinding and fine material passed to bag filter for collection.
Vertical Roller Mills: In Vertical Roller mill 2 - 4 rollers (lined with replaceable liners) turning on their axles press on a rotating grinding table (lined with replaceable liners) mounted on the yoke of a gear box. Pressure is exerted hydraulically. This mill also has a built in high efficiency separator above the rollers to reduce circulation loads and consequently reducing differential pressure across the mill. Feed material is directed onto the center of the table and is thrown outward by rotation under the rollers by centrifugal action. Material gets partially ground and as it falls over the edge of the table, where it is picked up by hot gases, and is separated into coarse fraction falling back on grinding table and fine fraction is carried with hot gases to product collector. The mill is started either with the rollers in lifted-up position, or with the hydro-pneumatic system at low pressure. In grinding mode, actual metal to metal contact should be prevented by limit switches or a mechanical stop and by consistent feed. In VRMs the material cycle time is usually less than a minute against several minutes for a ball mill or tube mill. Thus, control response should be accordingly faster. In case mill feed fails action should be taken within no more than 45 seconds or excessive vibration will cause mill shut-down. Moreover, the vertical mills are subject to vibrations if material is too dry to form a stable bed. Therefore, provision is made for controlled spray water inside the mill During mill operation magnetic separator and metal detector should be always functional to ensure to exclude tramp metal which can damage the grinding surfaces.
A mill is a grinder used to grind and blend solid or hard materials into smaller pieces by means of shear, impact and compression methods. Grinding mill machine is an essential part of many industrial processes, there are mainly five types of mills to cover more than 90% materials size-reduction applications.
Do you the difference between the ball mill, rod mills, SAG mill, tube mill, pebble mill? In the previous article, I made a comparison of ball mill and rod mill. Today, we will learn about the difference between SAG mill vs ball mill.
AG/SAG is short for autogenous mill and semi-autogenous mill, it combines with two functions of crushing and grinding, uses the ground material itself as the grinding media, through the mutual impact and grinding action to gradually reduce the material size. SAG mill is usually used to grind large pieces into small pieces, especially for the pre-processing of grinding circuits, thus also known as primary stage grinding machine. Based on the high throughput and coarse grind, AG mills produce coarse grinds often classify mill discharge with screens and trommel. SAG mills grinding media includes some large and hard rocks, filled rate of 9% 20%. SAG mill grind ores through impact, attrition, abrasion forces. In practice, for a given ore and equal processing conditions, the AG milling has a finer grind than SAG mills.
The working principle of the self-grinding machine is basically the same as the ball mill, the biggest difference is that the sag grinding machine uses the crushed material inside the cylinder as the grinding medium, the material constantly impacts and grinding to gradually pulverize. Sometimes, in order to improve the processing capacity of the mill, a small amount of steel balls be added appropriately, usually occupying 2-3% of the volume of the mill (that is semi-autogenous grinding).
High capacity Ability to grind multiple types of ore in various circuit configurations, reduces the complexity of maintenance and coordination. Compared with the traditional tumbling mill, the autogenous mill reduces the consumption of lining plates and grinding media, thus have a lower operation cost. The self-grinding machine can grind the material to 0.074mm in one time, and its content accounts for 20% ~ 50% of the total amount of the product. Grinding ratio can reach 4000 ~ 5000, more than ten times higher than ball, rod mill.
Ball mills are fine grinders, have horizontal ball mill and vertical ball mill, their cylinders are partially filled with steel balls, manganese balls, or ceramic balls. The material is ground to the required fineness by rotating the cylinder causing friction and impact. The internal machinery of the ball mill grinds the material into powder and continues to rotate if extremely high precision and precision is required.
The ball mill can be applied in the cement production plants, mineral processing plants and where the fine grinding of raw material is required. From the volume, the ball mill divide into industrial ball mill and laboratory use the small ball mill, sample grinding test. In addition, these mills also play an important role in cold welding, alloy production, and thermal power plant power production.
The biggest characteristic of the sag mill is that the crushing ratio is large. The particle size of the materials to be ground is 300 ~ 400mm, sometimes even larger, and the minimum particle size of the materials to be discharged can reach 0.1 mm. The calculation shows that the crushing ratio can reach 3000 ~ 4000, while the ball mills crushing ratio is smaller. The feed size is usually between 20-30mm and the product size is 0-3mm.
Both the autogenous grinding mill and the ball mill feed parts are welded with groove and embedded inner wear-resistant lining plate. As the sag mill does not contain grinding medium, the abrasion and impact on the equipment are relatively small.
The feed of the ball mill contains grinding balls. In order to effectively reduce the direct impact of materials on the ball mill feed bushing and improve the service life of the ball mill feed bushing, the feeding point of the groove in the feeding part of the ball mill must be as close to the side of the mill barrel as possible. And because the ball mill feed grain size is larger, ball mill feeding groove must have a larger slope and height, so that feed smooth.
Since the power of the autogenous tumbling mill is relatively small, it is appropriate to choose dynamic and static pressure bearing. The ball bearing liner is made of lead-based bearing alloy, and the back of the bearing is formed with a waist drum to form a contact centering structure, with the advantages of flexible movement. The bearing housing is lubricated by high pressure during start-up and stop-up, and the oil film is formed by static pressure. The journal is lifted up to prevent dry friction on the sliding surface, and the starting energy moment is reduced. The bearing lining is provided with a snake-shaped cooling water pipe, which can supply cooling water when necessary to reduce the temperature of the bearing bush. The cooling water pipe is made of red copper which has certain corrosion resistance.
Ball mill power is relatively large, the appropriate choice of hydrostatic sliding bearing. The main bearing bush is lined with babbitt alloy bush, each bush has two high-pressure oil chambers, high-pressure oil has been supplied to the oil chamber before and during the operation of the mill, the high-pressure oil enters the oil chamber through the shunting motor, and the static pressure oil film is compensated automatically to ensure the same oil film thickness To provide a continuous static pressure oil film for mill operation, to ensure that the journal and the bearing Bush are completely out of contact, thus greatly reducing the mill start-up load, and can reduce the impact on the mill transmission part, but also can avoid the abrasion of the bearing Bush, the service life of the bearing Bush is prolonged. The pressure indication of the high pressure oil circuit can be used to reflect the load of the mill indirectly. When the mill stops running, the high pressure oil will float the Journal, and the Journal will stop gradually in the bush, so that the Bush will not be abraded. Each main bearing is equipped with two temperature probe, dynamic monitoring of the bearing Bush temperature, when the temperature is greater than the specified temperature value, it can automatically alarm and stop grinding. In order to compensate for the change of the mill length due to temperature, there is a gap between the hollow journal at the feeding end and the bearing Bush width, which allows the journal to move axially on the bearing Bush. The two ends of the main bearing are sealed in an annular way and filled with grease through the lubricating oil pipe to prevent the leakage of the lubricating oil and the entry of dust.
The end cover of the autogenous mill is made of steel plate and welded into one body; the structure is simple, but the rigidity and strength are low; the liner of the autogenous mill is made of high manganese steel.
The end cover and the hollow shaft can be made into an integral or split type according to the actual situation of the project. No matter the integral or split type structure, the end cover and the hollow shaft are all made of Casting After rough machining, the key parts are detected by ultrasonic, and after finishing, the surface is detected by magnetic particle. The surface of the hollow shaft journal is Polished after machining. The end cover and the cylinder body are all connected by high-strength bolts. Strict process measures to control the machining accuracy of the joint surface stop, to ensure reliable connection and the concentricity of the two end journal after final assembly. According to the actual situation of the project, the cylinder can be made as a whole or divided, with a flanged connection and stop positioning. All welds are penetration welds, and all welds are inspected by ultrasonic nondestructive testing After welding, the whole Shell is returned to the furnace for tempering stress relief treatment, and after heat treatment, the shell surface is shot-peened. The lining plate of the ball mill is usually made of alloy material.
The transmission part comprises a gear and a gear, a gear housing, a gear housing and an accessory thereof. The big gear of the transmission part of the self-grinding machine fits on the hollow shaft of the discharge material, which is smaller in size, but the seal of the gear cover is not good, and the ore slurry easily enters the hollow shaft of the discharge material, causing the hollow shaft to wear.
The big gear of the ball mill fits on the mill shell, the size is bigger, the big gear is divided into half structure, the radial and axial run-out of the big gear are controlled within the national standard, the aging treatment is up to the standard, and the stress and deformation after processing are prevented. The big gear seal adopts the radial seal and the reinforced big gear shield. It is welded and manufactured in the workshop. The geometric size is controlled, the deformation is prevented and the sealing effect is ensured. The small gear transmission device adopts the cast iron base, the bearing base and the bearing cap are processed at the same time to reduce the vibration in operation. Large and small gear lubrication: The use of spray lubrication device timing quantitative forced spray lubrication, automatic control, no manual operation. The gear cover is welded by profile steel and high-quality steel plate. In order to enhance the stiffness of the gear cover, the finite element analysis is carried out, and the supporting structure is added in the weak part according to the analysis results.
The self-mill adopts the self-return device to realize the discharge of the mill. The self-returning device is located in the revolving part of the mill, and the material forms a self-circulation in the revolving part of the mill through the self-returning device, discharging the qualified material from the mill, leading the unqualified material back into the revolving part to participate in the grinding operation.
The ball mill adopts a discharge screen similar to the ball mill, and the function of blocking the internal medium of the overflow ball mill is accomplished inside the rotary part of the ball mill. The discharge screen is only responsible for forcing out a small amount of the medium that overflows into the discharge screen through the internal welding reverse spiral, to achieve forced discharge mill.
The slow drive consists of a brake motor, a coupling, a planetary reducer and a claw-type clutch. The device is connected to a pinion shaft and is used for mill maintenance and replacement of liners. In addition, after the mill is shut down for a long time, the slow-speed transmission device before starting the main motor can eliminate the eccentric load of the steel ball, loosen the consolidation of the steel ball and materials, ensure safe start, avoid overloading of the air clutch, and play a protective role. The slow-speed transmission device can realize the point-to-point reverse in the electronic control design. When connecting the main motor drive, the claw-type Clutch automatically disengages, the maintenance personnel should pay attention to the safety.
The slow drive device of the ball mill is provided with a rack and pinion structure, and the operating handle is moved to the side away from the cylinder body The utility model not only reduces the labor intensity but also ensures the safety of the operators.
Having an independent audit of your cement mill can identify opportunities for productivity improvements, including increasing production or lowering energy consumption. It is common to achieve a 5-10% gain in production by following mill audit recommendations.
Typically, an audit establishes the current conditions of the mill and identifies areas of possible improvement. This usually involves a full day for monitoring and collecting samples during mill operation, followed by a crash stop (i.e., without prior stopping of mill feed) for internal inspection. The audit provides an objective assessment of:
Samples are taken of feed, product and the separator circuits for subsequent evaluation of circulating load and separator efficiency, product performance and possibly feed grindability. It is also sometimes useful to perform a mill retention test.
In each chamber of the mill, measurements are taken of the effective diameter, length and height above the charge and powder level relative to the media. The average powder level is estimated by considering the chamber in segments, depending on the variation in the powder level across the length and diameter. The diaphragm slot pattern and average width, together with an overall estimate of the percentage of blockage, is noted. The presence, location and degree of coating is also noted.
Material samples along the mill length provide an important guide to chamber 1 effectiveness, while samples in chamber 2 length can identify problem areas such as buildup of nibs (3-5mm or larger clinker pieces). Data collected from these and the circuit samples can help determine the main parameters influencing cement grinding efficiency, such as media loading and grading as well as circulating load and separator efficiency.
With a cement additive business spanning more than 80 years, GCP Applied Technologies draws upon a database of more than 400 audits of cement grinding systems conducted during the last 25 years for our clients. Such a mill audit requires mutually agreed upon targets and benefits and pre-audit preparation for safety (including isolation, access, confined space working, etc.), personnel, sampling, equipment, as well as mill availability (both in operation and stopped).Get in Touch with Mechanic