D8.3 Assessment of calciner test results

Between the different calciner configurations, described in D8.1, the in-line calciner is the best option for the operation in oxyfuel mode. A few considerations are reported to confirm that the calciner rig in Stuttgart University represents quite closely the industrial situation both in air calcination mode and in oxyfuel mode; the same for the difficult task to measure real values of temperature, inevitably biased by radiant heat, because it is possible to assume that similar deviations are included in the industrial measured values; the difference between the real temperature value and the measured one should not be higher than 40 °C. Consequently it is possible to consider the results obtained by the tests done in work package WP8 in different conditions as meaningful and useful to supply quantitative information to be used in the mathematical model developed in WP6. Effects on calcination degree consequent to temperature, residence time, CO2 concentration, raw meal fineness, water vapor have been evaluated. The main finding is that decarbonation takes place in an oxyfuel mode at temperatures that are higher than those registered for air calcination: the difference is in the order of 50 °C, and the temperature absolute value of calcination in oxyfuel mode is evaluated to be around 920 °C. This value is critical from the technological point of view and may be a possible cause of anomalous coatings. This aspect can’t be analyzed with the available equipment and will be matter of studies during future full scale tests. The other parameters have also influence on the calcination process but all of them need the support of temperature to reach an acceptable degree of calcination.