Optimising Stirred Milling Technology

By integrating this advanced technology into conventional ball mill and roller press systems, both significant energy savings and capacity increases can be achieved without compromising product quality.

A comprehensive case study involving the implementation of Pamir technology in a white cement production line demonstrates the practical benefits of this approach. Sampling and mass balance analyses were conducted to model the existing equipment and predict performance improvements under various scenarios. Simulation studies revealed potential capacity increases of up to 60% and specific energy consumption reductions, with energy savings correlating with the extent of Pamir mill usage. The study highlights the potential of Pamir technology to make cement production more energy-efficient and cost-effective. By adopting such modern grinding technologies, the cement industry can achieve significant operational enhancements and contribute to sustainability goals.

Introduction

In the cement industry, the process from raw material preparation to final grinding consumes an average of 110 kWh of energy per t of cement, with more than 60% of this energy used for raw material and cement grinding. Given that a significant portion of energy is expended in grinding circuits, improving energy efficiency in these circuits can significantly reduce operational costs. Energy savings can be achieved through the optimisation of operational parameters and the integration of new grinding technologies.

Modernising existing grinding circuits with new technologies and implementing high-energy efficiency equipment are essential strategies for reducing energy costs. High-performance air separators and pre-crusher systems have significantly increased grinding circuit capacity and reduced energy consumption per t of cement. In 1984, high-pressure roller presses were developed, proving more energy-efficient than other conventional grinding methods. When used as a pre-crusher before ball mills, roller presses create micro-cracks in the material, facilitating easier grinding and increasing ball mill capacity, thus reducing specific energy consumption.

Addressing the optimisation in existing grinding circuits containing ball mills, roller presses or vertical roller mills, Minerva Engineering has developed flow diagrams utilising Pamir milling technology. These diagrams aim to combine the efficient fine grinding of dry stirred mills to provide either low energy consumption or production increase. This approach is expected to yield significant energy savings and improved product quality, marking a new era in the cement industry. The energy efficiency of dry stirred mills in fine grinding has been demonstrated in laboratory and pilot-scale tests, proving advantageous for achieving the required product fineness and quality.

Proposed flow diagrams involve feeding classified products from roller presses or vertical mills directly into dry stirred mills. This combination enables the target fineness to be achieved in a more energy-efficient way. When combined with roller presses or vertical mills, the dry stirred mill provides at least a 20% reduction in energy consumption per t compared to existing ball mill systems, without compromising product quality.

With rising energy costs and the imperative to reduce the carbon footprint in cement production, the use of clinker substitutes is becoming essential, necessitating finer grinding. Over the next decade, energy efficiency will become increasingly important in cement grinding lines. The Pamir technology, which allows for efficient energy use, is poised to play a significant role in this process.

In an existing operation, the implementation of the Pamir technology starts with a performance evaluation of the current performance, which is determined through data collection during steady state operational conditions. The sampling study around the circuit and inside the ball mill with crash stop is achieved. Both the full particle size distribution of each stream and the Blaine measurements are completed to use for mass balancing of the whole circuit. Following the mass balance study, the data is used for modelling of the individual equipment in the circuit. Once the modelling is completed, the simulation of the circuit is conducted for varying scenarios of Pamir use. In this context, the model structure of the Pamir mill obtained from different industrial operations or from the pilot test run is utilised.

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Read the article online at: https://www.worldcement.com/special-reports/19112024/optimising-stirred-milling-technology/