process control technology for optimum performance

process control technology for optimum performance

We offer a wide range of technologies designed to optimise the performance of your cement plant or mineral processing operations. Whether you are looking to cut energy and maintenance costs, lift your productivity or automate your machinery, we can help.

Weve been supporting the cement industry for 135 years and the mining industry for decades. This has provided us with a unique awareness of current market needs and an unmatched understanding of plant processes.

An efficient operation is a successful one. Weve always worked closely with our customers and we understand the challenges you are facing today: the competitive global environment, rising energy costs, tighter emissions and high staff costs. To survive, and indeed thrive, you need to keep costs low while lifting your performance.

Thats where we can help. We offer a wide range of process control and optimisation technologies to improve virtually every aspect of your operation. We can help you lift throughout/output, cut energy costs, reduce downtime and much more.

When you embark on the digital journey you want a partner that provides the complete range of automation and integration products, solutions and services. With the help of our ECS process control solutions and the expert knowledge of our engineers and support staff, we deliver real digital effectiveness to your plant and equipment. By automating your processes youll be able to ensure your plant is always working at its full potential while alleviating the risks of process instability and inconsistent quality. That means a stronger performance with less downtime and lower maintenance costs.

The first step to improving the performance of your plant is understanding exactly what is going on inside it. Of course, thats easier said than done when you are dealing with extremely harsh and sometimes unpredictable conditions. But the good news is we offer a range of technological solutions that can assist. These will allow you to closely monitor conditions inside your kiln or mill, track energy usage, and much more. Once your operators know exactly what is going on inside your plant and how your equipment is performing, they, or their plant managers, will be able to make better decisions to ensure peak performance in maintained.

Digital goes beyond just adopting separate pieces of technology though it needs to be key to solving the business issue of improving productivity and margins across your value chain. We provide a number of technologies that are at the forefront of this trend. Greater digitisation will help drive greater productivity in your operations by reducing operating costs, lifting throughput and stabilising your processes and product quality. It also increases the scope for remote control of plant and equipment.

That also results in better process safety through earlier identification of problems. Your operators will become more effective as they only focus on key parameters. And you will gain increased process understanding as clear, real-time information is available at your fingertips.

One of the biggest challenges for any mineral processing or cement production operation is managing energy usage. High power or fuel bills can sap your profitability and there is ever-present pressure to rein in emissions. We offer a number of solutions that can help you monitor and reduce energy usage by ensuring your plant and equipment are operating as efficiently as possible. You will also have the tools to see exactly where your energy is being consumed within the entire process.

When you choose FLSmidth, you get more than just a product. Everything we do is backed by our expert teams of process engineers, project managers and support staff. Weve got a proven track record of delivering on time and can upgrade your equipment and systems with little to no downtime to avoid production losses. Once our solution is installed, youll also have access to round the clock support and troubleshooting from our team, so you can be confident well always be there to help.

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.

ball mill charge - grinding & classification circuits - metallurgist & mineral processing engineer

ball mill charge - grinding & classification circuits - metallurgist & mineral processing engineer

The crop load of ball mill. It =ore + mill medium +water. But usually, it was used in a percentage formation. So how to calculate this percentage. I know this is really a basic question, but it puzzled me, for most books and papers just use it but nor explain it.

The ball charge and ore charge volume is a variable, subject to what is the target for that operation. The type of mill also is a factor as if it is an overflow mill (subject to the diameter of the discharge port) is usually up to about 40-45%. If it is a grate discharge you will have more flexibility of the total charge. Ball size and ball grade is determined by the feed ore size and hardness, plus the PH level of the slurry. The ball charge is determined by the operator targeting the balance between grind and throughput, the higher the ball charge the more aggressive the milling becomes. With softer oxide ores lower ball charges are usual however the harder sulphides does need more media energies to meet the P80 target and an acceptable throughput. These comments are very broad and very much dependent on individual operator priorities. There are too many variables to cover every case in this forum. I will however mention that "spawling" has been now greatly reduced due to new media technologies and breakage of media in high ball charges is able to be overcome. High ball charges in ball mills does open that danger of media breakage through higher ball on ball incidents - now this is not the problem that it was previously.

DISCLAIMER: Material presented on the 911METALLURGIST.COM FORUMS is intended for information purposes only and does not constitute advice. The 911METALLURGIST.COM and 911METALLURGY CORP tries to provide content that is true and accurate as of the date of writing; however, we give no assurance or warranty regarding the accuracy, timeliness, or applicability of any of the contents. Visitors to the 911METALLURGIST.COM website should not act upon the websites content or information without first seeking appropriate professional advice. 911METALLURGY CORP accepts no responsibility for and excludes all liability in connection with browsing this website, use of information or downloading any materials from it, including but not limited to any liability for errors, inaccuracies, omissions, or misleading statements. The information at this website might include opinions or views which, unless expressly stated otherwise, are not necessarily those of the 911METALLURGIST.COM or 911METALLURGY CORP or any associated company or any person in relation to whom they would have any liability or responsibility.

ball charge and grinding efficiency - grinding & classification circuits - metallurgist & mineral processing engineer

ball charge and grinding efficiency - grinding & classification circuits - metallurgist & mineral processing engineer

What is the effect of low ball % full on grinding efficiency?One of our clients is thinking of the future and has bought a ball mill that will be the right size someday, but is very large now.I know what happens to mill power from adjustments to % critical speed and % balls charge. What I don't know is what happens to grinding efficiency as ball charge % filling is lowered. For example does a grinding between two given sizes that takes 6 kW/tonne at 40% full take 8 kW/tonne or some other number at 20% full?

The volume of grinding media in a mill is directly related to grinding efficiency. The higher the volume of grinding media the more effective the grind. Balls must be added to maintain the media load and mill power draw. The power draw increases as balls are added and decreases as media wears down: add balls.

Higher ball loads will result in finer grind but dont overcharge. If throughput of slurry to BM decreases the mill power draw will increase because balls grinding against balls are drawing more power: finer grind.

I totally agree with you that the low charge rate directly affects the grinding efficiency, but in here there is another thing we have, that shouldn't be overlooked, it is the power consumption, at low charge rates below 20% the power consumption increase by 6-15% for the ball mills.

A difference (duty vs. maximum) of 5% to 10% is fairly typical and you would likely struggle to perceive an energy efficiency difference between the two operating points. Beyond this, the situation may change.

The 40% vs. 20% is a very large difference in ball charge. Under these conditions I would agree your slurry pool is going to be large and this is likely to cause issues from both a power draw and power efficiency perspective. This is not easy to quantify without more detailed analysis/benchmarking.

This shouldn't be a show-stopper, as you say, the mill is oversized so the duty throughput/grind size should be attainable, albeit the exact milling conditions/power efficiency may be difficult to pin-point.

If this is a concern, and if the client has already bought the mill, your options may be limited. One option could be to install a grate possibly with high capacity pulp lifters, to minimize the slurry pool at 20% ball charge. The grate could later be removed to allow for operation at higher ball charges. Obviously this creates its own set of separate issues.

Actually, you need to differentiate between capacity and grinding efficiency. At a lower load capacity will be reduced but grinding efficiency will increase. There are only a few examples of this (most sites go for throughput rather than efficiency) but it has been shown to hold true for overflow mills.

With very low ball charge (less than 20 %) and low slurry density power draw will increase because of increasing toe angle and also more lifting. Also with low ball charge slurry pool will reduce grinding efficiency. Beside lower ball charge will increase P80 of ball mill because of less number of impacts but mean residence time will increase by lower ball charge because of more volume to occupy. I think at last in this situation, power consumption will increase.

You missed the point that the feed rate is lower so the residence time is longer so the product size is not necessarily larger. By the way, circuit product size is not determined by the mill but by the classifier. The mill performance will affect the circulating load.

I don't get why you think that the toe angle will increase and there will be more lifting. I don't understand why the slurry density would be any lower. Why would it change (or in mill that controls it why would the target change)?

All overflow ball mills operate with slurry pooling. Do not confuse with a AG/SAG mill where pooling can be detrimental. In ball mills all the media is balls with a high SG so the impact of pooling is not as large. Additionally, in ball mills grinding is primarily through cascading not cataracting (compared to an AG.SAG) so the slurry pool is not a factor unless density is high, which leads to viscosity issues.

I have been told at a few sites I visited where the ball level is lower (e.g. 25%) that they operate at that level because they don't need the power. What they have observed is that the specific energy is lower and that the media and liner consumption is lower.

Of course all the ball mills operate in slurry pooling conditions but with low ball charge it will be larger than before so it will affect the P80 (Ball mill Product 80 % passing not circuit product) badly and it will increase. He had mentioned adding water to classifier underflow; this work will reduce slurry density. With low slurry density (under 60% solid percentages) because of more charge liberation to lift, the shoulder angle will increase (more lifting). High ball charge will result in developing toe position and because of high ball charge after a certain point of charge level; power draw will decrease so with lower ball charge there will be no toe developing.

The throughput of mill will decrease with the time;The P80 in the discharge of the Mill, will increase because of the high time of particle residence in the Mill, and for this reason the grinding will be lower efficient.The power specific consumption will increase, due to the lower feed rate.

I don't know where you got the low mill density of 60% but I don't see that in the postings above. I don't agree that the lower ball charge will lead to a higher P80 because the feed rate will be lower and pooling does not affect cascading action so low impacts will not be affected. Yes, the number of impacts will be lower but that affects capacity not efficiency. What is important for efficiency is the location of the energy spectra (high impacts vs. low impact). For ball mills low impact is more important because of the smaller particles.

You state that the residence time will increase so what is your evidence that P80 will increase? Yes, the feed rate is lower but so is the power. If the power drops more than the tonnage then the specific energy will be lower.

The only thing I will add to this discussion is that I have been to plants where they operate at low load (-25%) because they don't need to have the capacity. They do it to save energy and reduce media consumption. None of them have complained of low efficiency. So, based on my experience, tell your client that they will be fine.

Quite an interesting discussion here, with many different views! Why is efficiency important anyway? How would you define it? What would be the measured benefit? Would is matter if commodity prices were depressed? What would be considered "high" and what would be considered "low"?

I agree 100% with you regarding low loaded mills with good, even great, efficiency.In fact, some studies point out the importance of reaching this "optimal" load % that necessarily isnt this common heard 28-30% value.

I just want to add that more than a fixed load %, its important to keep the balance between both mill's chambers. In my experience Ive seen engineers planning and making calculations for a grinding media reload in Chamber 1, not considering at all the load % on Chamber 2. What happens next? : You have a wonderfully filled chamber 1, but your Chamber 2 isnt able to keep the pace with Chamber 1; in fact, you just unbalanced your mill.Just want to say that the mill will work as good as your worst chamber.

Low ball ratio is not the same as low mill density. If the slurry density falls below 80% then the slurry will not adhere to the balls and there will be no further abrasion grinding (only impact grinding).

Reducing the ball charge will reduce the grinding capacity, and the comment on installing a grate discharge is a good one as it will let ore out sooner, thus minimizing overgrinding, which will occur if the mill is (temporally) too big, or one chamber is too big in a multi chamber mill. But the reduction is not a direct reduction (50% fewer balls 50% less grinding) as there is a factor from the liner role in grinding.

There is no need to add low grade ore or to change to a grate discharge. There will not be any vacant space because this is (I assume) an overflow mill so by definition will be full. Adjusting the ball charge to meet the capacity demand will ensure that it is not overgrinding (if it is overgrinding then it has more capacity than needed and the ball charge can be reduced). In order to maintain good efficiency the grinding circuit should maintain a good circulating load (e.g. 250%).

I was doing some research trying to see if anything has been published in this area. These papers are more applicable to the cement industry and less applicable to the minerals industry, but they are interesting nonetheless:

Obviously there are numerous potential inaccuracies and uncertainties associated with commercial mineral processing operations and a handful of case studies with conflicting conclusions is not a convincing design basis.

If your project is sensitive to grinding efficiency (I'll let you decide the economics), it would be prudent to assume your project may initially have a lower grinding efficiency and put in controls to help mitigate this risk (if indeed it is an issue). As I said previously, to give a quantitative answer more detailed analysis/benchmarking is required.

If you maintain a high ball charge with low tonnage, you'll overgrind. So you can low the ball charge, these means less interaction mineral particle with steel balls so reduce grinding, but also it means that you bed density will be lower, since you'll reduce the steel (7,75 kg/m) and replaced with mineral slurry (let say 2,0 kg/m for copper mineral) to maintain the volume, thus reducing energy consumption.

But there some worth to point out and it is the consequences of not evaluating the degree of the lowering. As he mentioned paper of David S. Fortsch (2006), when lowering the ball charge to less than 25% volume the energy efficiency goes down for that operation in particularly. And it also make sense, just imagine that you're feeding the ball mill with a high P80, that needs more cataracting than cascading, a you just low the ball mill to a point that cataracting is heavily reduced.

So every operation needs to evaluate particularly the degree of ball charge, and sure there's and optimal minimum, and variables like L/D ratio, Mill Size, and feed particle size had a strong effect on this optimum value.

If the ball charge rate is between 8-12%, it will be SAG mill. If it is more than this, it will be ball mill. SAG Mill's effect is mainly crush the big ores and then use ball mill to grinding the small ores.

Ball size will also affect the grind P80. Efficiency is in part determined by the Axb value of the ore. A small lab mill can give guidance on the influence of ore strength and ball size. Larger balls will increase P80 in ball mill, thereby reducing overgrinding. If you believe the entry ball size sets the initial point on ball population and exit size is fixed, since the ball wear is near linear, in some camps, this raises the P80 = can only result in grinding larger rock.

SAG & Ball mill % ball contentSAG % ore contentSAG grate size and end mill design including grate geometry, location, shape, pan cavity, recycle % in pan cavity, et. al.SAG lifter and end cone geometry - can change SAG mill performance more than 20%-50% depending on P80 transfer size and Axb, some of which is published and some will be published at SAG 2015.SAG mill wear rates and performance changes with wear morphology, grate details, mill speed changes and optimization with speed controlBall feed sizeSAG mill water flow rateSAG mill power vs. wear geometry - maximizing kW-hr/ton & tons/hour in combinationSAG mill liner change-out life/cycle vs. tons/kg consumed

Ball mill liner efficiency based on liner geometry and its influence on kW-hours/ton, total tons/life cycle, and P80 transfer to cyclones. Ball mill grind is based on different principle; it has some attributes similar to SAG mill optimization. SAG mill breaks with stirring the kidney at optimized kidney specific gravity and maximum stir rate per mill revolution, whereas ball mill breaks down ore with increasing particle-to-ball interaction.

In dry cement ball mills, there are studies done in the past which clearly shows that energy saving make sense reducing 1chamber ball mill filling degree. This thread-shore level is considered between 20 and 21%. Below that level mill production/consumption curve do not make more sense increasing the specific energy consumption instead of lower it.

Give me actual data of you grinding flowsheet: feed size, product size, power of mill motor, capacity, ball size, numbers & diameter of hydrocyclone ball charge, mill speed. I'm calculate optimum capacity you flowsheet.

DISCLAIMER: Material presented on the 911METALLURGIST.COM FORUMS is intended for information purposes only and does not constitute advice. The 911METALLURGIST.COM and 911METALLURGY CORP tries to provide content that is true and accurate as of the date of writing; however, we give no assurance or warranty regarding the accuracy, timeliness, or applicability of any of the contents. Visitors to the 911METALLURGIST.COM website should not act upon the websites content or information without first seeking appropriate professional advice. 911METALLURGY CORP accepts no responsibility for and excludes all liability in connection with browsing this website, use of information or downloading any materials from it, including but not limited to any liability for errors, inaccuracies, omissions, or misleading statements. The information at this website might include opinions or views which, unless expressly stated otherwise, are not necessarily those of the 911METALLURGIST.COM or 911METALLURGY CORP or any associated company or any person in relation to whom they would have any liability or responsibility.

ball mill | henan deya machinery co., ltd

ball mill | henan deya machinery co., ltd

The quality of the installation is the key to ensure the normal operation of the ball mill. The installation method and sequence for all types of ball mills are roughly the same. To ensure smooth operation of the ball mill and to reduce the risk to the building, the ball mill must be installed on a reinforced concrete foundation of 2.5 to 3 times of its weight. The foundation should be laid on solid soil and should be at least 40-50 cm away from the workshops foundation. Read more

The final stages of comminution are performed in tumbling mills using steel balls as the grinding medium and so designated ball mills. Since balls have a greater surface area per unit weight than rods, they are better suited for fine finishing. The term ball mill is restricted to those having a length to diameter ratio of 1.5 to 1 and less. Ball mills in which the length to diameter ratio is between 3 and 5 are designated tube mills. These are sometimes divided into several longitudinal compartments, each having a different charge composition; the charges can be steel balls or rods, or pebbles, and they are often used dry to grind cement clinker, gypsum, and phosphate. Tube mills having only one compartment and a charge of hard, screened ore particles as the grinding medium are known as pebble mills. They are widely used in the South African gold mines. Since the weight of pebbles per unit volume is 35-55% of that of steel balls, and as the power input is directly proportional to the volume weight of the grinding medium, the power input and capacity of pebble mills are correspondingly lower. Thus in a given grinding circuit, for a certain feed rate, a pebble mill would be much larger than a ball mill, with correspondingly higher operating cost. However, it is claimed that the increment in capital cost can be justified economically by a reduction in operating cost attributed to the lower cost of the grinding medium. This may, however, be partially offset by higher energy cost per tonne of finished product. Read more

Ball mill is key equipment for grinding in mineral processing plant, it is widely used in cement, silicate, new-type building material, refractory material, fertilizer, ore dressing of ferrous metal and non-ferrous metal, glass ceramics etc.There are dry grinding and wet grinding, ball mill can be divided into tabular type and flowing type according to different forms of discharging materials.

The ball mill is a horizontal rotating device transmitted by the outer gear. The materials are transferred to the grinding chamber through the quill shaft. There are ladder liners and ripple liners and different specifications of steel balls in the chamber. The centrifugal force caused by rotation of barrel brings the steel balls to a certain height and impact and grind the materials. The ground materials are discharged through the discharging board thus the grinding process is finished.

Pebble mills are similar to ball mills except that the grinding media is closely sized rocks or pebbles.Pebble milling is a form of autogenous milling as no steel media is used in the process however, the type of rocks used are selected more carefully than in convention AG milling.

ball mill for cement grinding process

ball mill for cement grinding process

MQ series ball mills are mainly used in grinding operations in mining, cement, refractory, chemical and other industries. According to the discharging method, it is divided into MQG series dry type lattice ball mill, MQS series wet type lattice ball mill, MQY series wet overflow type ball mill, MQZ series peripheral discharge type ball mill; according to the type of liner, it is divided into A series (high manganese steel lining). Plate, magnetic lining) standard type and B series (rubber lining, high aluminum lining, silica lining, ceramic lining) energy-saving type; according to the transmission mode is divided into edge drive ball mill and center drive ball mill.

When Ball Mill is working, raw material enters the mill cylinder through the hollow shaft of the feed. The inside of the cylinder is filled with grinding media of various diameters (steel balls, steel segments, etc.); when the cylinder rotates around the horizontal axis at a certain speed, Under the action of centrifugal force and friction force, the medium and the raw material in the cylinder will drop or roll off the inner wall of the cylinder when the gravity of the cylinder reaches a certain height.

When material particle gravity is greater than centrifugal force, they will be crushed due to the impact force. At the same time, during the operation of the mill, the sliding movement of the grinding media to each other also produces a grinding effect on the raw materials. The rest material is discharged through a discharge hollow shaft. Due to the constant uniform feeding, the pressure causes the material in the cylinder to move from the feed end to the discharge end. During wet grinding, the material is carried away by the water flow; during dry grinding, the material is taken away by the airflow drawn out of the cylinder.

When Ball Mill is running, the raw material enters the mill cylinder through the hollow shaft of the feed. The inside of the cylinder is filled with grinding media of various diameters (steel balls, steel segments, etc.); when the cylinder rotates around the horizontal axis at a certain speed, Under the action of centrifugal force and friction force, raw material in the cylinder will drop or roll off the inner wall of the cylinder when the gravity of the cylinder reaches a certain height. When their own gravity is greater than the centrifugal force, they will be crushed due to the impact force. ore. At the same time, during the operation of the mill, the sliding movement of the grinding media to each other also produces a grinding effect on the raw materials. The ground material is discharged through a discharge hollow shaft. Due to the constant uniform feeding, pressure will causes the material in the cylinder to move from feed end to discharge end. During wet grinding, material is carried away by water flow; during dry grinding, raw material is taken away by the airflow drawn out of cylinder.

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optimization of continuous ball mills used for finish-grinding of cement by varying the l/d ratio, ball charge filling ratio, ball size and residence time - sciencedirect

optimization of continuous ball mills used for finish-grinding of cement by varying the l/d ratio, ball charge filling ratio, ball size and residence time - sciencedirect

During the last decade, semi-finish-grinding plants have been used more and more for the energy efficient grinding of high-quality cement. In 1999, it was found that by decreasing the ball charge filling ratio it was possible to lower the specific energy demand for grinding significantly.

It was obvious, too, that the L/D ratio influences the specific energy demand and the mill throughput as well. Therefore, a huge test program was carried with a semi-industrial ball mill, which was operated in closed circuit. The mass-specific surface area of the two feed materials (intermediate product) used were quite typical for industrial semi-finish grinding plants. The values were 2200 and 3000 cm2/g according to Blaine. The product finenesses were 3000 and 3800 cm2/g, respectively. The L/D ratio of the ball mill was varied in four steps of 1.75, 2.1, 2.79 and 3.49, and the ball charge filling ratio was varied in three steps of 15%, 20% and 25%. The experiments clearly indicated that the optimal L/D ratio and the optimal ball charge filling ratio are different for each feed fineness.

The influence of the ball charge grading on the specific energy demand, characterised by the average ball diameter, was tested by means of a discontinuous laboratory ball mill. The results showed that by using a finer ball grading the specific energy demand could be lowered considerably.

The obtained results can be explained well by theoretical considerations regarding the ruling stress intensity and the number of stress events. The stress intensity expressed as the power input per ball is dependent on the ball diameter to the third power and only slightly dependent on the inner diameter of the mill. The number of stresses can be characterised by the average retention time of the ground material inside the mill if the ball charge grading remains unchanged. The optimal retention time depends not only on the feed material and the desired comminution result but also on the ball charge filling ratio and particularly on the L/D ratio. On the basis of the present results and considerations, a specific optimisation of ball mills in semi-finish-grinding plants can be done.

magotteaux automatic ball charger (abc) - sciencedirect

magotteaux automatic ball charger (abc) - sciencedirect

The Magotteaux Automatic Ball Charger (ABC) optimizes ball mill performance by controlling ball addition. Each ABC consists of a storage hopper, vibrating feeder, load cells, local control electronics and computer link to the grinding process. The system continuously monitors absorbed power, feed rate and ball consumption to calculate the proper ball addition rate to maintain optimum mill power. Advantages of the ABC include optimized grinding through mill power control, reduced operator involvement, and real time adjustment of ball consumption rates relative to the abrasiveness off the current mill feed.

how to improve cement ball mill performance in closed circuit grinding system

how to improve cement ball mill performance in closed circuit grinding system

There are many factors that may affect the ball mills working efficiency and product quality during the operation. In this article, we will discuss the measures that can improve the ball mills performance.

The particle size of the feed material is an important process parameter that restricts the grinding efficiency of the ball mill. Due to the different physical and chemical properties and microhardness of the materials (the grindability of materials in raw meals decreases in clinkers), the clinker discharged from the cement kiln must be pretreated to reduce its particle size so as to increase the output and reduce the power consumption of the ball mill.

From table 1 we can learn that if the particle size of the feed material is reduced from 25 mm to less than 2 mm, the mill output can be increased by at least 60%, which is relatively consistent with the actual production.

There are two methods for clinker pretreatment: pre-crushing and pre-grinding. 1) The pre-crushing uses a crusher to crush the clinker before grinding, which can reduce the diameter of clinker particle to 5 ~ 8mm. 2) The pre-grinding adds a roller press to the cement grinding system. In this system, the clinker is extruded circularly, dispersed and separated, and becomes powder with diameter less than 2 mm;

The gradation of grinding media is also an important factor in improving the efficiency of ball mills. A reasonable gradation can only be calculated after analyzing the performance of the mill, the property of the feed material, and equipment layout in the closed-circuit grinding system.

The size of the grinding media is calculated based on the grinding capacity of the mill and the size of the feed material. Because of the complex movement of the grinding media and the material in the mill, and because the actual production situation of each cement plant is different, it is difficult to determine a universally applicable grading rule. Only through long-term production practice can we get the appropriate gradation scheme.

The gradation of grinding media is constantly changing in the process of mill operation, and the wear law of different size of grinding media is also different. Therefore, the supplementary of grinding media can only keep the loading capacity relatively balanced, but can not keep the gradation consistent.

The stable grinding process largely depends on the material of grinding medium. Different materials of grinding media lead to different wear consumption. If the hardness and wear resistance of the grinding media are poor, it is easy to deform and crack during the operation, which not only affects the grinding efficiency and blocks the grate gap, but also makes the partition device difficult to discharge material, and finally leads to the deterioration of the mill operation. Therefore, improving the quality of the grinding media is an effective way to ensure the long-term stable operation of the mill, otherwise, no matter how reasonable the grading scheme is, it is difficult to ensure that the expected grinding effect can always be achieved.

Once the grinding media and other equipment is properly selected for the grinding system, then the gradation can be determined according to the particle size of the feed material. However, no matter how reasonable the grading scheme is, it is always relative.

The ball bearing height of ball mills can be different due to different specifications, diameters, rotating speeds and liner forms of the ball mills. And the potential energy produced by different height of the ball is completely different. Therefore, the reasonable grinding ball diameter should not only match with the mill specifications, but also adapt to the liner form of the mill.

Large size mills with lifting liner bring grinding balls to higher heights and generate stronger impact force, so the diameter of grinding balls can be smaller. The ball diameter should be different according to the aging degree of the inner liner: new liners bring grinding balls to higher height, so the ball size can be smaller.

It can be seen from the experiment that when a grinding ball with a diameter of 70 mm falls freely from the height of 40 cm, its potential energy can completely crush a clinker particle with a diameter of 25 mm. Therefore, the minimum ball diameter should be selected on the premise of sufficient impact energy to increase the number of grinding balls, increase the impact times of balls on materials, and improve the grinding efficiency.

Table 2 and table 3 show the relationship between the material particle size and the grinding ball diameter for reference only. When determining the ball diameter, it is necessary to adjust it according to the cement plants own situation.

energy efficient cement ball mill from flsmidth

energy efficient cement ball mill from flsmidth

You decide whether to operate the mill in open or closed circuit, with or without a pre-grinder and with side or central drive, according to your plant layout and end product specifications. Even the lining types are tailored to your operating parameters.

In addition, the large through-flow areas enable the mill to operate with large volumes of venting air and a low pressure drop across the mill. This reduces the energy consumption of the mill ventilation fan and keeps your energy costs down.

The mill is based on standard modules and can be adapted to your plant layout, end product specifications and drive type. The horizontal slide shoe bearing design enables much simpler foundations and reduced installation height, making installation quicker and less expensive.

Our shell linings are designed to suit the task at hand. In our two-compartment cement mills, the first compartment (for coarse grinding) has a step lining suitable for large grinding media. It protects the shell while ensuring optimum lifting of the mill charge. In the second compartment (and also in our one-compartment cement mills) we use a corrugated lining designed to obtain the maximum power absorption and grinding efficiency. For special applications, we can supply a classifying shell lining for fine grinding in the mill.

In fact, the entire mill is protected with bolted on lining plates designed for the specific wear faced by each part of the mill. This attention to detail ensures both minimal wear and easy maintenance. When a wear part has reached the end of its life, it is easily replaced.

The grinding media are supplied in various sizes to ensure optimum grinding efficiency. The STANEX diaphragm is designed to maximise the effective grinding area, enabling a higher throughput. It is fitted with adjustable lifters to ensure the material levels in each compartment are right. Best of all, the STANEX diaphragm works for all applications, even when material flow rates are high and the mill feed is moist.

The mills are typically driven by our FLSmidth MAAG LGDX side drive - gearing rated to the latest proven AGMA standards. The mill drive is provided with an auxiliary drive for slow turning of the mill. The LGDX includes two independent lubrication systems, one which services the girth gear guard and intakes more dust, and a second which supplies oil for the fast-rotating gearing and bearings and stays clean. If requested, however, the mills can be provided with a central drive: the FLSmidth MAAG CPU planetary gearbox. The mill design differs slightly, depending on whether the side or central drive is chosen.

Each grinding compartment has two man-hole covers to give easy access for maintenance. As there are minimal moving parts, the maintenance requirement is low and simple changes like replacing wear linings and topping up grinding media can be completed quickly and easily. Horizontal slide shoe bearings prevent oil spillages from the casing and offers easy replacement of slide shoes.

Buying a new mill is a huge investment. With over a century of ball mill experience and more than 4000 installations worldwide, rest assured we have the expertise to deliver the right solution for your project. Our ball mill is based on standard modules and the highly flexible design can be adapted to your requirements. The mill comprises the following parts.

The mill body consists of an all-welded mill shell and a T-sectional welded-up slide ring at either end, the cylindrical part of which is welded onto the ends of the shell. The mill shell has four manholes, two for each grinding compartment.

Each slide ring runs in a bearing with two self-aligning and hydrodynamically lubricated slide shoes. One of the slide shoes at the drive end holds the mill in axial direction. In the others, the slide rings can move freely in axial direction to allow for longitudinal thermal expansion and contraction of the mill body.

The slide shoes are water-cooled, and each bearing is provided with a panel-enclosed lubrication unit including oil tank, motorised low- and high-pressure oil pumps, as well as an oil conditioning circuit with motorised pump for heating/cooling and filtration of the oil.

The stationary steel plate inlet duct leads the venting air into the mill. It is equipped with a manually operated throttle valve and a pressure monitor to adjust the pressure at the inlet end, thus preventing dust emission from the inlet. The feed chute is lined with bolted-on wear plates and slopes down through the air duct to the mill inlet opening.

The more control you have over the mill, the better your grinding efficiency is likely to be. Our ball mills include monitoring systems to continuously measure the material and air temperatures as well as the pressure at the mill exit. The venting of the mill is adjusted by a damper in the inlet to the mill fan. And the material fill level is continuously monitored by means of sensors. For ball mills operating in closed circuit, the circulation load is monitored by weighing the flow of reject material from the separator. These measures ensure you achieve optimum mill performance, giving you the quality, efficiency, safetyand reliability that you need.

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.

cement finish milling (part 1: introduction & history)

cement finish milling (part 1: introduction & history)

Cement is manufactured by heating a mixture of ground limestone and other minerals containing silica, alumina, and iron up to around 1450 C in a rotary kiln. At this temperature, the oxides of these minerals chemically transform into calcium silicate, calcium aluminate, and calcium aluminoferrite crystals. This intermediate product forms nodules, called clinker, which is then cooled and finely ground with gypsum (added for set-time control), limestone, supplementary cementitious materials, and specialised grinding aids which improve mill energy consumption and performance to produce cement.

The finish mill system in cement manufacturing is the second to last major stage in the process, where the feed material is reduced in size from as large as several centimeters in diameter, down to less than 100 microns (typically less than 10% retained on 45 microns). This is accomplished by grinding with the use of either ball mills or vertical roller mills, sometimes in combination with a roll press.

This operation typically consumes somewhere between 30 to 50 kWh per tonne of cement produced, and is the single largest point of consumption of electrical power in the process. Although concrete is the most sustainable building material available [1], with over 4 billion tonnes of cement produced and consumed world-wide, optimisation of the grinding process can provide significant reductions in energy consumption and environmental impacts.

As concrete became the preferred building material, it became readily apparent that in order to meet the increasing demand, improvements in grinding technologies and operational efficiencies were required.

Early hydraulic cements were relatively soft and readily ground by the technology of the day using millstones. The emergence of portland cements in the late 1840's presented a challenge however, due to the hardness of the clinker, resulting in a coarse cement product (with up to over 20% over 100 microns). This resulting cement was slow to hydrate and prone to issues with expansion due to large free-lime crystals. It wasnt until improved quality of steels were developed and the introduction of the ball mill in the late 19th century that grinding technology improved, allowing for a four-fold increase in compressive strengths during the 20th century [2] where finer grinding was needed to improve concrete performance and meet construction schedule demands.

Although ball mills were first introduced in the 1860s, the main progress was made during the 1870s to 1900s in Germany, where its growing cement and chemical industries increased the demand for finer grinding [3]. The first tumbling mill to gain reasonable acceptance was designed by the Sachsenberg brothers and Bruckner and built by Gruson's Workshop in 1885, which was subsequently acquired by the Krupp Company.

The mill consisted of a drum lined with stepped steel plate with 60-100 mm steel balls. Fines were discharged from the mill through apertures in the plates, with coarse material in the discharge screened and reintroduced through slits between the plates.

The initial product on the early mills was particularly coarse, due to large aperture sizes necessary to prevent blockages, which led to a modification to discharge product through an end trunnion in the early 1900s to improve performance up to a couple tonnes per hour. Around this same time, F.L. Smidth and Co. was rapidly growing through contracts to build cement plants and acquired the rights to a tube mill from a French inventor, selling it worldwide after redesigning it.

A modern ball mill is a horizontal cylinder thats partially filled with high-chrome martensitic steel balls that rotates on its axis imparting a tumbling and cascading action to the balls. Material is fed through the mill inlet and initially crushed by impact forces and then ground finer by attrition (chipping and abrasion) forces between the balls.

An early approach to grinding was the use of a short tumbling mill to break the large clinker down to the size of grit and then a long tube mill to grind the grit down to powder. The next development involved the combination of those two stages into one piece of equipment, known as the multi-compartment mill, in Germany.

Modern ball mills are usually divided into two chambers, separated by an intermediate diaphragm, allowing the use of different sized grinding media to focus the crushing action in the first chamber, and attrition in the second. The ball mill shell is protected by carefully designed wear-resistant liners which promote lifting action to the ball charge in the first chamber, and cascading action in the second. Liners in the second chamber are sometimes designed to classify the balls so that the larger balls tend toward the central partition and smaller balls tend toward the outlet.

Balls diameters are typically 50-80 mm in the first chamber and 15-40 mm in the second chamber, where the ball charge design must be optimised based on the inlet material size, material hardness, and the desired size reduction. The ball charge typically occupies around 30%-36% of the volume of the mill, depending on the mill motor power and desired energy consumption and production rates. Air is pulled through the mill by an induction fan to control material throughput and temperature.

To solve the issue of large particulate in the discharge, the industry looked to closed-circuit operation with an air classifier to collect the fine particles as one product and recycle the larger particles back to the mill. As early as 1885, Mumford and Moodie secured a patent for an air separator being used in the flour industry.

This type of circuit started a trend which became common practice in the 1920s after Sturtevant developed an air classifier for the tobacco industry. Its adoption, which became commonplace by the 1950's, led not only to improved cement performance, but increases to production and energy efficiency by as much as 25% due to reductions in over-grinding. Development of the separator has continued from the so-called first generation to the current third generation of high-efficiency separators.

The first generation separators are very similar to the Mumford-Moodie design with one motor driving a distribution plate, the main fan, and an auxiliary fan. The second generation incorporated an external fan and external cyclones but gained only marginal improvement in classification efficiency. The modern generation of high efficiency separators, led by the development of the O-Sepa by Onoda Cement Co. in Japan in the 1970s, has an external fan which draws significantly more air through a rotating cage, increasing the ratio of air to material and the size of the open area in the classification zone to greatly increase efficiency.

Around this same time in the late 1970's and early 1980's, Professor Schonert developed and patented the key requirements for size reduction of many particles by compression of the particle bed using high pressure grinding rolls, first licensed to Polysius. The incorporation of this as a pre-crushing stage to ball mills with high efficiency separators led to circuits that were even more efficient and versatile. The roller press consists of a pair of rollers set 0.25 to 1.25 apart rotating against each other, through which the feed is introduced and compressed at up to 300 MPa. The material emerges as a cake of highly fractured particles and can reduce energy consumption of a ball mill by 20 to 40%.

Another major development was in 1906 by Grueber with the initial stages of what would become the vertical roller mill for grinding coal in Germany. In 1927 the first Loesche mill was patented which featured a rotating grinding track that used centrifugal force to push the grinding stock outwards from the center of the mill under high pressure roller wheels and into the airstream of the internal air classifier. This mill was adapted in the late 1930s for grinding raw mix and cement. However, it wasnt until the 1960s where rapid development in optimisation and up-sizing led to its increasing popularity in cement production, and not until the early 2000s that it began to become popular for cement grinding, due to higher grinding capacities and around 25% lower power consumption compared to the ball mill.

One of the most significant developments for the cement industry dates back to 1931, when an attempt was made to mix carbon black in concrete to make a darker middle lane on U.S. Route 1, in Avon for passing. Initially, the carbon black did not disperse well and rose to the surface giving the concrete a mottled appearance. Dewey & Almy (acquired by W.R. Grace in 1954 and later leading to GCP Applied Technologies) developed and produced a product called TDA (Tuckers Dispersing Agent) which helped the dispersion of carbon black and led to better workability and strength.

TDA was then tried in cement finish mills where it was found to improve mill operability with higher throughput and better product fineness, strength, and flowability, due to the dry dispersion of cement powder. The initial commercial versions of TDA were based on modified lignosulphonates and this began the modern grinding aid industry as well as leading to the development of water reducing admixtures. By the early 1960s amine acetates and acetic acid were also being used in grinding aids, and then glycols in the late 1960s and early 1970s. The 1990's saw the introduction of performance enhancing grinding aids which are continuing development to optimise particular mill circuits and product performances.

One of the biggest challenges faced in the grinding industries was matching an appropriate mill and motor to the required feed rate, product size, and material grindability. This led to Allis-Chalmers Company establishing a research laboratory in 1930 where Fred Bond further developed the theory of comminution by introducing Bonds Work Index in 1952 (to be continued)

modular and portable grinding station plug and grind classic cemengal: engineering, equipment and assembly for the cement industry. experts in grinding station

modular and portable grinding station plug and grind classic cemengal: engineering, equipment and assembly for the cement industry. experts in grinding station

The P&G number #1 container bin farm includes 4 bins with its dedicated weightfeeders. This allows you to use clinker, gypsum and two other additions (fly ash, slag, limestone or puzzolan). If one or no additions are required you will have 2 or 3 bins of clinker for extra storage capacity.

The container number #2 has a 450kW ball mill of extreme simplicity to ensure maximum reliability and low maintenance. Nevertheless todays most advanced technology has been used in its conception and construction. This ball mill is ready to be installed as it comes on a flat-rack container.

The container number #4 has a horizontal silo with a total storage capacity of 30Tm. The filters special design allows using the hopper as a cement silo. Cement is reclaimed by 3 screw conveyors which carry it to a one spout packing machine and/or the optional bulk-loading silo.

The container number #6 has the electrical and control room that includes all the necessary equipment to run the plant. An extremely simple control panel helps the operator avoid making mistake during operation.

The P&G number #1 container bin farm includes 4 bins with its dedicated weightfeeders. This allows you to use clinker, gypsum and two other additions (fly ash, slag, limestone or puzzolan). If one or no additions are required you will have 2 or 3 bins of clinker for extra storage capacity.

The container number #2 has a 450kW ball mill of extreme simplicity to ensure maximum reliability and low maintenance. Nevertheless todays most advanced technology has been used in its conception and construction. This ball mill is ready to be installed as it comes on a flat-rack container.

The container number #4 has a horizontal silo with a total storage capacity of 30Tm. The filters special design allows using the hopper as a cement silo. Cement is reclaimed by 3 screw conveyors which carry it to a one spout packing machine and/or the optional bulk-loading silo.

The container number #6 has the electrical and control room that includes all the necessary equipment to run the plant. An extremely simple control panel helps the operator avoid making mistake during operation.

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