The Mystery Machine

I still remember my first technological contact with the cement industry: the clinker cooler. This astonishing machine for a good portion is responsible for my passion for the cement industry! Why is that? Because you can dive into the complexities of the cooling process of a cross-aerated packed layer of particles of different sizes endlessly … Even with the most elaborate knowledge and methodologies, this machine still evades a full technological exploration! Its function and performance is really hard to assess. Firstly, it never operates without being connected to the kiln (and that in counter flow of gas and solid particles) and this interface can never really be assessed by measurement correctly. Secondly, the efficiency of the heat transfer – and with that the main performance judgement on the cooler – is highly dependent on the granularity and density of the clinker product. To make it even more complicated: these clinker parameters are dependent on the kiln process, which itself is influenced by the cooling process again because the recuperated heat from the cooler influences the sintering process. So the cat bites its own tail here! And most astonishingly, the recuperation rate of a cooler gets higher the smaller the thermal efficiency of the kiln is! Still after so many years and clinker coolers in operation, experts around the world don’t seem to have resolved the classical question: is it better to run a shallow bed with fast cooling and short retention time in the cooler or is it better to run a high bed layer with slow cooling and long retention time? This can really get a process engineer wheeling and dealing, especially because clinker cooler performance is of utmost importance for the over-all efficiency of the kiln line.

Wishing you good recuperation,

Matthias Mersmann