World Cement interviewed Fives for their thoughts on the topic of grinding & milling.
1) What do you see as the main challenges facing the grinding operations of cement manufacturers today? How can these be resolved?
As well the consideration of production costs and carbon footprints, one key issue is energy consumption. For reference, the grinding process represents a significant part of a cement plant’s electrical demand, in the range of 50 to 70% of the total integrated plant’s needs. Therefore, limiting grinding power demand is a major industry focus. The end-product evolution is another key issue to address, with respect to the expansion of the cement additives range and cement/clinker ratio, as well as the emergence of ultra-fine products in the cement industry. It appears then that the solutions are to be found in versatile technologies, with low-energy consumption, and the capability to adapt to a wide range of raw materials, which come with their own constraints such as grain size variation, moisture content, grindability, etc.
The FCB Horomill® grinding system can help provide a solution to these challenges, offering low energy consumption and high flexibility and end-product quality for an optimised cement/clinker ratio.
2) What factors should be considered by cement manufacturers when making the choice between using ball mills or in-bed compression in their operations?
In-bed compression mills are the way to meet the energy consumption reduction targets, and are in addition, a pledge of product quality provided that they are used alongside a high efficiency separator. With a wide range of applications, in-bed compression mills are also more adapted to process substitution materials requiring drying. Indeed, in such a field, ball mills may quickly reach their limits (for example mill choking due to diaphragm clogging).
Nevertheless, in some instances, for raw meal grinding, the conventional ball mill remains a more appropriate solution, in particular in cases where there are large differences in the physical properties (grindability) of the different components in the raw mix or high abrasiveness of some components. With this perspective, Fives has developed a complete range of flash drying solutions in order to extend the moisture acceptance level of its ball mill portfolio to typically up to 8% moisture content of fresh feed.
3) What steps can be taken to ensure high separator performance?
Bearing in mind that the high efficiency separators principle relies on the opposition of the drag force versus centrifugal force in a rotating cage, it is above all, very important that the classifier is properly ventilated, regardless of the mill operation requirements. Thus, it is more advantageous when the classifier is set in an independent circuit than the mill itself. Another parameter that influences the classifier performance is the material load, and it is therefore very beneficial to have full control of the total feed of the classifier, whether through a separator’s rejects metering system (impact flow meter or other weighing device) or the feed control itself, such as measurement of the absorbed power of the bucket elevator for instance. Whether it is associated with the FCB Horomill or with a ball mill, the FCB TSV™ Classifier is set in an independent circuit, allowing ventilation and feed control.
Last but not least, as the use of clinker substitution materials is spreading, thus involving the corresponding drying requirements, it is important to consider the water vapour evacuation, which means setting the classifier, and possibly the associated flash dryer, in a ventilated circuit with a properly sized exhaust filter.
4) What advantages do modular grinding systems offer over more conventional set-ups?
Besides a quick installation set-up and corresponding savings at the erection stage, and provided that they can achieve the expected production performances, modular grinding systems allow quick access to some markets. This implies that time has been taken in the design process to ensure the grinding system effectively meets these new market requirements, yet this is in general, contradictory with the standardisation of the modular concept. In this regard, the FCB FLAG™ Station has been designed for flexibility in terms of raw material types (particle size, moisture content, etc.) and finish products’ variety (recipe, fineness, etc.) Therefore, this not only allows quick market access but can still also adapt to market changes in the long term.
5) What role do you see for digital technologies, such as process automation solutions, in the grinding sector?
As a grinding equipment and plants supplier, the main digital technologies we have developed are the automation solutions allowing grinding plants to be operated in a fully automatic mode. This is highly recommended with regards to bed compression technologies as they are generally more dynamic and reactive systems, which require more close and accurate control than a conventional ball mill. Fully automated systems allow for the management of raw material quality variations and a large range of finish products, in a very smooth and safe way. In addition, automation relieves operators of the increasingly high responsibility of daily operations and allows them to focus on more valuable tasks.
Another field of development in the remote services, aimed at supporting customers in their daily operations, is predictive maintenance and troubleshooting. This kind of development has shown its relevance during the pandemic.
6) Looking to the future – what do you see as the next steps in terms of grinding technology? What advances can we expect to see over the coming years?
For some years, cement producers have been facing climate change challenges increasing the complexity of their installations so that they can be set-up and operated in a sustainable manner. Suppliers are adapting and complying with these challenging requirements, developing flexible solutions with high levels of energy efficiency, emission control and product quality. In addition to the limitation of the environmental impact in terms of emissions, this evolution should positively help reduce the use of natural resources by their substitution with by-products or recycled materials.
Read the article online at: https://www.worldcement.com/special-reports/15042021/back-to-the-grind-world-cement-grinding-qa-with-fives/