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Advanced cement grinding with ‘reduced circuit’: Florian Grassl, PM-Technologies GmbH (Austria)

Filmed at Cemtech Europe 2015, 20-23 September, Intercontinental Hotel, Vienna, Austria.

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Thanks for your introduction, ladies and gentlemen I want to welcome you, today I want to tell you some facts about the plants cement grinding with ball mills and high efficiency classifiers. At the beginning I just want to give you a short overview about the company profile of PM-Technologies.

PM-Technologies was founded in the early years of the 1990s in Austria. Today we're operating on the worldwide market as an engineering partner and assistance supplier to the cement, and the mineral industry. We're able to handle a complete turnkey projects including the delivery, the commissioning, direction work, but we also do smaller scopes for example only basic engineering, process engineering, design study.

So this is always depending on the demand of each customer of each project. The main competence of PM-Technologies was since the beginning the optimization of existing systems this means we do not like to deliver complete new green field plants this is not our approach. Our approach is really depthtinisation[sp] of such plants, of old plants of new plants it is our target to bring every plant to its optimum solution, to its optimum performance, apart from the grinding systems which the actual title of today.

We have the second main focus and this is the optimization of kiln and preheater plants. So only a short introduction the requirements in the cement industry especially for this kiln plants. There can be very different from one customer to the other from one market to the other. It can be for example of a classic clinker production increase.

It can be use of alternative fuels like today in Central Europe increase in emission limits. So the demands are very individual and this tasks we want to find an individual solution for this demands. The first step when we are requested for help is always a very detailed bottleneck evaluation re-engineering of this existing operation, of the conditions this individual plant.

Then we have different solutions for example we do modifications at the second stages. We have solution for new consim lime of optimization of consim. We have in the lower pre-heat area the step 2 hot meal bypass system. It is very useful if you have problems in operation, or if you want to use SNCR system.

We have solutions for chlorine bypass system, gas kiln system and also hot meal bypass system, they cleaning in the chamber, cleaning in the sealing, this can be very important. And we have all this key equipment you need in the preheater for example this potential theoretic the guideline for the upper cyclone stages So let us come to the grinding plants.

As an introduction to this topic, I want to tell you how PM Technologies entered this field and it started with the development of a new and a unique classifier that is called the Classiclon it was initially developed for the mineral industry that means it was used for producing high quality powders for ultra fine powders different minerals like chips or a limestone or synthetic powders and the new idea of this classifier you can see here in the picture it is ADS router to technology ADS stands for Aero Dynamics Seperation and this is because our plates they look a little bit like the wing of an aeroplane this means we do not use just flat bars or bench bars or even round steel we really use this shaped plates and the idea was very simple, every classified has this one key part, it has this one most important part, we call it the heart of the machine and it was intention if we managed to improve this part, the total classifier performance will increase and this is the rest of out of this development.

So what is not the principle? What is the difference between a conventional router and this ADS technology You see here the comparison between a conventional router at an upper picture and the ADS plate. When you think now about the physic principle of classification, this is always the difference of the draft force it is caused by the outflow and of the centrifugal force which is caused by the turning router and every particulate to choose depending on it's size if it follows the draft force into the router, then it is in the fine fraction.

Or if it follows, if it is rejected by the centrifugal force, then it is rechecked at the classifier. And then you see here now the comparison, the airflow, the ground force in the conventional machine, it is very a straight way, it is a very easy way, it enters directly to router inside.

At ADS plate it makes a curve. This means the airflow has to overtake the router. Also the particle has to overtake the router. And as you can imagine, it is much more difficult to overtake this router, then to enter very straight. So if it's not the draft force itself, not the forces itself is very important just to enter the particles.

And with this technology we manage to have a better interaction. This means we need lower draft force and also lower centrifugal force for getting the better separation efficiency. So in total we have two benefits, we have really better separation efficiency a very sharp separation efficiency on the other hand we have less rotation speeds and less rotation speeds is a very big benefit on the mechanical side.

Because you have lower load on the plates, you have lower air, you have lower energy consumption. So let's come back to the development of the classiclon for the cement grinding plants. This was hard in the mineral industry, it was very successful more and more customers was asking, can't we apply this for the large scale machine for the cement grinding, and then we started this develop and in the year 2001, the first classiclon was installed in commission for a cement plant.

Since then we've developed different housing types. Here you can see two in the picture. We have developed the spiral housing with this classiclon for cement grinding, we have a compact housing gas inlet from the bottom and we have a very unique design, if this is kind of a great or fit of an existing classifier.

This means we use the second generation classifier, the housing and then existing plant we cut the roof, we put the tunnel out, we put our new router unit or new puring unit inside. This is very cost effect solution because the housing can remain, the cyclones can remain. The ventilation can remain, the total steel structure can remain.

So very cost effective solution for getting the best possible classifier performance. Until to date, they are operating more than 20 classiclon machines, in the cement grinding plants, really all of them we have to first setup internal parts. This means use very steady and very proven design.

We spend really high efforts and protection. The first real unit we ever replaced was 10 years in daily operation. We have the second reference for a grinding it is in operation today, since six years, and no part was exchange until that. so what is the function of first generation classifer compared second generationI have prepared here an example, you see the difference of the efficiency.

Generally it's quite easy, to bet the separation of efficiency of a first generation classifier it leads in more fine particles are going to the final product. Less particles are rejected in an unnecessary way this is imperfect, and in this example the comparison shows if you apply the same particles to be washed in the same feed materials.

In this example 27% are going with the second generation classifier to the product, if a high efficiency classifier provided the same feed material 38% would go to the final product. This would be a huge increase on the production rate, but this is only a theoritic example because if you have to think about the real sytem, you have to think on the total grinding plant in the end it still cut the grinding plant not the classifier plant.

In order to have the total field, you have to think about this circulation loads. I have a practice example from before, the low efficiency classifier. 100% are entering the circulation load, 260 are recirculated due to the bad separation, and the total mill throughput is 3.6. So 360% is circulation load, if you are plan a high efficiency classifier the same example as before.

Due to the better separation efficiency less particles are recirculated, only 160 in this example. Also the finest of the reject is lower because before you had this unnecessary recirculation of the fine particles now they are all in the final product, that means for the mill itself there is very big change you have lower circulation load, lower mill throughput and you have lower finest at the beginning of the mill.

Now this example from before it is a totally changed situation, if you do nothing else, just put the new classifier and then try to increase the feed rate what will happen? The circulation load will get higher and higher again the mill fineness at the beginning is lower, and it will get even lower.

Also the finest at the outlet will decrease if the finest at the mill outlet decreases the classifies is not provided with the fine part has no chance it cannot do its job and sort out the fine particles. That means it is a totally changed situation from this example from before.

This huge increase on the production rate it will not happen in the reality because you have to optimize this total system. If you do nothing just replace the classifier. The mill will not work efficient also the classifier will not work so efficient because all there equipment was not designed for this status.

In this picture I've written all the parameters that may be necessary may be important for such a grinding plant. So, please you don't have to read too much. That's just to show you how complex such a system is in reality. If you exchange one big part, this will have influence in all the settings.

All the settings are interacting with each other. That means if you want to open such a system, you cannot simply exchange one main part and so nothing else. You really have to focus on the total grinding plant. And this is the approach of PM technologies, we want to find an optimization of the total plant.

The first step again is always a detail plant assessment a bottleneck evaluation. We want to know before what is necessary to improve the total performance, only after this step we define the necessary changes. Of course the classifier this is always mandatory, for a state of the art cement grinding system a high efficiency classifier is mandatory, this is the basis and then we focus into grinding process, together with the grinding process you have to focusing in all the setting because they are interacting each other and please don't understand wrong, I don't want to say that you have to exchange very much parts you do not have to exchange all the liners or the diaphragms this is not necessary but you have to define some single steps that maybe necessary, in one plant that can be a simple adoption of the bolt charge which is very easy the other plant may be a relocation of the intermediate wall if necessary maybe you have just to kill just some slots in the outlet world to open some slots.

So where at different solutions can be necessary, and what they learned is that there's only one common thing for each power mill. Each power mill is individual. It means you can have the same set up in one plant, the same machine from the same supplier. In the other plant it may work totally different, because you have other clinker quality, you have other additives.

The final product quality is different, you have other accessory treatment are not reacting the same. So, this is very important to really find an individual solution for each of these plants. You cannot apply one solution for the outer plant even it's totally same middle. In the end this is a target to reach optimum conditions both for the coal mill, and for the classifier, and this is what we call to reduce climbing circuit.

We call it our philosophy and this means we want to avoid a very high material re-circulation, I know that in the earlier years with older systems, it was necessary to have quite a high material re-circulation. This was based on the fact of the behavior of the old classifier of old systems.

If a high efficiency classifier have totally different potentials you have other demands. You have not the re-circulation of different particles, and this is big potential you have to use that in the formula. If you want to catch this potential you have to focus really hard on the grinding process this means an adaption of deport charge you have to optimize the wrong define grinding power, you have to increase the retention time, you have to secure a good mill filling ever such basic figures they are so important and in the end it is the target to increase the finesse at the middle outlet.

We have here figure that this, if you needed the middle outlet half of the finesse of the final product. For example if you to produce 4000 plain cement at the middle outlet you should have at least 2000 plane then you have this reduce circulation the the mill converter on it's optimal conditions, also the classifier will work on it's optimal conditions and in the end you will catch the total potential of the system you will improve the total performance.

Okay up to this theoretically part of this come to some references. In 2013, we installed a new classifying system including classiclon classifier and back filter in Finland, and here we replace the second generation classifier system with cyclone. We had two targets. We had two demands in this system.

On the one hand of course the increase on the production rate like always. On the hand with the old system they had strong problems with the temperature, they have problem with the cement quality and also in the ball mill. Therefore we decided to put in this back filter system which here it is posible to suck in up to 100% of fresh air, totally automated.

Due to that we could reduce the water injection in the ball mill, they had very much water injection. The cuttings inside the ball mill, they reduce completely, there is no cuttings on the liners, anymore no cuttings in the diaphragm. Therefore we could increase, we could use another board chart and together with the operating conditions they increased in the ball mill in the classifier, with this reduce[xx] cooling capacity, in total the increase for for their main production type which is cement with more than 5, 000 plane increase to 20% compared to second generation classifying system.

The second reference it was in Germany in the year 2009, and this was a system with pre-grinding device and the ball mill. The pre-grinding device will cause a roller press. At the bottleneck evaluation, we came to defect and all the systems were not working good. The classifier had bad efficiency the ball mill it has no setting for the pre-grinding device.

Also the roller press the long was not working so efficient, so in the end we start a new classifier system, we applied this reduced roller press and then we redefined the role and define grinding power in the ball mill. This means we just moved intermediate diaphragm you put in a totally other port charge and then we optimize the little bit with the automation roller press no big investment in the end the production increase was very good, because all the equipment all the main equipment, could work on it's optimum conditions the roller press, the ball mill and the classifier, for the main production type which is cement with 4000 plane the increase was 18%.

And for a high quality production with 5000 plane the increase was more than 40%. So now we are quite at the end of my presentation I want to give you a short overview of what PM Technologies offers you. We have for you a detailed evaluation of your existing system a bottleneck evaluation, we want to define a tailor made solution and the reason for your system. With our classiclon can offer you the best possible classifying technology on the market.

And we offer you an overall optimization of the grinding plant, and this must be hand in hand with all the equipment, hand in hand with the customer. The benefits for the customer secure due to the tailor made solution we reach low carpics values. The high quality equipment means low maintenance cost, remember the 10 years of lifetime of loyalty low maintenance cost low effort and of course an increase in the production rate and increase of the overall performance.

Now, I really at the end and I hope you have no doubt about the philosophy if you have any question please don't hesitate to ask thank you.

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