Optimization of calciners in the cement industry

1 Schematic representation of a combustion chamber for burning large-sized, solid secondary fuels that are difficult to ignite

2 Schematic sequence of the calculation of shredded tyre combustion

3 Diagram of calciner with split feeding of fuel, air and meal before shredded tyres are injected

4 Flow velocities in the calciner

5 Trajectories of the shredded tyres during combustion

6 CO concentration in the calciner when shredded tyres are burnt

7 Oxygen concentration in the calciner when shredded tyres are burnt

8 Oxygen and CO concentration in the calciner after increasing the tertiary air volume

Modern pyro-line with inline-calciner and tertiary air duct

Summary: In recent years, most developments in burning systems for the manufacturing of cement have concerned the calciner. Apart from its original function of calcining the raw meal, the system was given increasingly often the task of burning the highest possible proportion of secondary fuels, which are often supplied in large pieces. This imposes difficult challenges for the designing of calciners, because the reliable ignition and burn-out of lumpy secondary fuels often demands design features that run contrary to the requirements of achieving a high and consistent degree of raw meal calcination. As a consequence, system optimization measures are necessary. Their successful performance requires detailed understanding of the process, which can be gained with the aid of CFD (Computational Fluid Dynamics) methods. The simulation also allows part of the calciner optimization to be performed at a reasonable price on the computer, thus avoiding repeated modification of the production equipment itself. This article describes important aspects of the objective and concludes with an example of CFD-aided optimization of a calciner to enable the use of shredded tyres.

1 Development status of pyroprocessing technology

Since calciner technology was introduced in the 1960s, there has been no comparable leap in the pyroprocessing technology for the manufacturing of cement. Steinbiss in [1] provides a good overview of earlier developments in calciner technology, as well as a prediction of the economic prospects of burning residual materials. Apart from some innovations in the mechanical technology of grinding systems [2–8], there have been some developments in the field of burning technology as regarding calciner and cooler technology [9–15]. While the new...