Grinding accounts for more than 60% of the electrical power demand during cement production while also being of the greatest importance for the final product quality. With today’s and tomorrow’s challenges regarding energy and resource efficiency in mind, grinding within the cement industry needs to be rethought. New concepts and new technological approaches towards efficient comminution are required. ECRA’s Future Grinding Technologies Project is based on two pillars: The first is a systematical approach towards new technologies for grinding in the cement industry. The second is the development of new and useable modelling tools for better understanding and optimised operation of comminution technologies. 

In 2014 the European Cement Research Academy (ECRA) started its cross-sectoral research project “Future Grinding Technologies” in order to optimise and develop comminution technology for the cement industry and also for other related sectors. As a first step, ECRA conducted a pre-study in which available comminution technologies were analysed, and information was collected within a database which documented more than 140 different entries, covering the known comminution technologies on the market. All technologies compiled in the database belong to different industry- or laboratory sectors and also reflect techniques of different development stages (e.g. industrial-, semi-industrial-, laboratory-scaled mills and crushers as well as patents). The data filed in the database was taken from literature studies, web researches, scientific articles and practical experience with different technologies where available. Each single entry was equipped with specific data about quality aspects, flexibility aspects regarding feed, operation behaviour, maintenance aspects, efficiency aspects and environmental impacts. All main categories were subdivided into sub-criteria to improve the information content.  

Currently, the ECRA database is being transformed into a web-based version which can be used by all ECRA members for further investigation as well as a knowledge library of grinding. 

The database was evaluated in a further step using the so called analytic hierarchy process which compares datasets with a cement-based reference in a pairwise-comparison. The final score is influenced by different weightings of sub-criteria and main categories. The cement-based reference takes into account all state-of-the-art technologies for grinding in the cement industry. This includes data on ball mills, vertical mills, high pressure grinding rolls and Horomills. 

Based on this, all types of scenarios can be analysed by flexibly tuning the different weights of the main and sub-categories and criteria. Based on a large number of analyses, the cement-based reference was confirmed as the best generalist to solve all comminution tasks in cement plants. But some interesting grinding machines were also detected which show advantages in certain areas.  

As a result, the next step will be to investigate the combination of mills that work extremely efficiently in certain application areas. The aim is to combine the advantages of the individual machines and thus generate a highly efficient grinding system. A study is currently being prepared to show how a universal grinding system can cover both the raw grinding and the cement grinding sectors. This grinding system consists of a highly efficient fine crushing unit, a conventional grinding unit for a medium fineness, and a fine grinding unit. All three units consist of mills that can be considered best in class within their small operating range. 

In this universal grinding unit, raw grinding is to be realised by the crusher as well as the conventional grinding unit, and cement grinding by the conventional as well as the ultra-fine grinding unit. In this study, mass flows as well as heat balances will be considered under various scenarios involving different raw materials and end products. In cement grinding, the principle of separate fine grinding will be used. Intermediate products with different finenesses will be produced and then mixed to achieve a particle size distribution that corresponds to that of a ball mill cement. In order to work as energy-efficiently as possible, most of the intermediate products will be produced on the conventional grinding unit. This can be, for example, a vertical roller mill, a high-pressure grinding roll mill or a Horomill, which all produce medium fine products very energy efficiently. The ultra-fine intermediate products will be produced in a fine grinding unit such as a dry stirred media mill.    

At the end of the study, the aim is to draw up a technical requirements profile in order to be able to estimate the investment and operating costs of such a plant. 

In addition to the ECRA database, a flow-sheet simulation is also being developed in this project which will enable the user to predict particle size distributions and the corresponding energy consumption of grinding circuits. This work is being carried out by the University of Braunschweig at the Institute of Particle Technology, where ECRA has established an academic Chair entitled ”Future Grinding Technology in the Cement Industry and Related Industries” under the leadership of Professor Arno Kwade.  

The tool, which is in the final stages of development, can simulate grinding circuits with different mills and classifiers. Currently, classic ball mills, high-pressure grinding rolls and dry-stirred media mills as well as classifiers have been integrated. The goal at the end of the development is to have an easy-to-use tool with which it is possible to make predictions for grinding circuits.