What does the Green Cement Plant include? Part 1

In a two-part series, Robert Shenk, FLSmidth, provides an overview of what ‘green’ cement plants could look like in a not-so-distant future - starting with Quarry to Packing and dispatch. 

 

Quarry 

 

While total transformation of the quarry is not foreseen in the near future, there will be some key differences. First, the electrification of material extraction and transport – switching from diesel to electric-powered vehicles in the quarry is a relatively simple way to reduce carbon emissions in this part of the cement process. In fact, a recent pilot project at a Swedish quarry realised a 98% reduction in carbon emissions through the use of electric machinery.  Furthermore, the quarry may become a lonely place because many of these electric vehicles will also be fully autonomous. 

This electrification will require additional power sources, but in the next decade, more cement plants are expected to take control of their energy supply by building wind and solar installations on site. This will ensure that they have the clean energy needed to power not just their quarry operations but increase electrification throughout the plant.   

Besides the quiet from electric engines, quarries may not appear as busy as in the ‘peak clinker’ years, thanks to the increased uptake of supplementary cementitious materials (SCMs), including calcined clay, which is discussed in further detail in part two of this series.  

Crushing

Crushing operations will be smarter and more efficient, taking advantage of Industry 4.0 technology to conserve energy and maximise availability. Machine learning-driven vision systems will help prevent blockages, while an emphasis on hard-wearing parts and easy maintenance will ensure minimum downtime. 

Stockpile management

More efficient blending will enable greater chemistry control and grinding efficiency – so the emphasis on this section of the plant will be on advanced stockpile visualisation technologies. The equipment might look the same, but quality control will be vastly refined thanks to the use of software programmes like QCX/BlendExpert™ Pile and Mill, which help cement plant operators gain greater control over their raw mill feed. 3D modelling and fast, precise analysis provide the greatest possible insights into stockpile composition, enabling the optimisation of blending with minimal effort. All of this means that the raw material will be preparedtomaximizethe utilization of SCMs.

Raw grinding 

 
Raw grinding operations will be focused on vertical roller mills, which are able to achieve greater energy efficiency, increased productivity and high availability. Additionally, the control potential for VRMs (when the main drive is equipped with a VFD) is far superior than for ball mills or even hydraulic roller presses. This enables a greater degree of optimisation, which in turn improves kiln stability and facilitates increased use of alternative fuels and the use of more diverse raw materials. 

Cement mills 

 
Like the raw mill, cement plants will continue to move towards more efficient grinding technologies and away from ball mills. Vertical roller mills will be equipped with variable speed drives and enable the flexibility needed by the cement plant of the future, which is more likely to require regular recipe changes to accommodate the use of a variety of SCMs. Through utilization of the most efficient technology, precious kWs shall be preserved for additional decarbonization measures. 

Hot gas generators will be decarbonised, either through electrification or by using waste heat from elsewhere in the plant. Advanced blend control applications will help ensure a larger clinker substitution, while maintaining quality targets. 

Pyroprocess 

 
The biggest changes to the plant will be seen in the kiln. First, less clinker will be produced in proportion to cement production, replaced in increasing quantities by SCMs. Secondly, the fuel make-up will continue to evolve, taking advantage of advanced burners and other combustion technologies to co-fire a mix of alternative fuels including waste products, biomass, newly engineered fuels from waste streams, oxygen enrichment (so-called oxyfuel injection) and even hydrogen. Precision dosing will enable careful kiln control to maximise clinker quality, while solutions like the HOTDISC® Combustion Device will enable a wide range of fuels to be used. It is worth noting that 100% fossil fuel replacement is possible with existing technologies, but it may take another decade or more for the waste streams to catch up with demand. In addition, the green cement plant of the future will have to consider how green these alternative fuels actually are. 

Waste heat will also be utilised, not just in the pyroprocess but also in other areas of the plant, for example to replace hot gas generators.  Waste heat from the clinker production process will be captured and used to offset the remaining energy demands of the plant.   

Material transport 

In many areas around the plant and for loading, unloading and dosing, material transport will move from mechanical to pneumatic. This not only ensures a clean and safe environment, it also enables higher capacity conveying with greater precision and control.  

Packing and dispatch 

Flexibility will be required here, as in the cement mill, to accommodate the variety of cement mixes produced. Automated packing, palletising and loading technology will not only facilitate the quick and easy packing of a variety of products, but will also help to remove the safety risks of manual operation. 

The vision 

Cement producers must begin to consider how the changes outlined above could work in their plants, and the measures that need to be taken to meet emissions targets. 

The cement industry has pioneered new technologies, set itself very high standards, and has done so before climate change agreements obligated it to. Collectively, the industry has incredible power to make a difference in the global campaign to reduce warming. As often declared in superhero movies, “with great power comes great responsibility”. When reflecting on the ambitious goals of the cement industry and the requirements for Green Cement Solutions, the lyrics from one of my favourite bands come to mind – “And nothing else matters.”