CEE Jan-Mar 2012

Alr·S.ponlt (AS) Muiii·Stl&t (MSC) MSC t CC can be separately controlled, and thus the dwell time extended to a total of up to 15 minutes. An elegant side effect of the PREPOL SC is that due to the transport control by means of air blast nozzles no mechanical internal fittings or moving parts are necessary inside the reaction chamber. Figure B. PREPOL© calcining systems. Based on many years of experience in cement plant engineering Polysius AG is now able to offer its customers a future-oriented sustainable overall concept for the use of solid secondary fuels. calcining of the raw meal and is therefore the determining factor for the calciner's dimensions. For this reason, various suspension flow calciners are available according to fuel properties (Figure 8). These will allow a control of the combustion temperature and atmosphere so that it is also possible to reduce the NOxemissions. In order to ensure the burnout of slow-reacting substitute or primary fuels it is not only necessary to support the dwell time inside the calciner with a suitable distance required for calcinations and burnout but if necessary, by using a additional burning chamber. For a long time now, especially for slow-reacting fuels such as biomass, petroleum coke or anthracite, the CC precombustion chamber is used, where in the centre of a vortex flow and with an initial supply of pure tertiary air high temperatures develop starting the combustion . For the use of low calorific, large-sized substitute fuels the dwell time in the short hot zone is insufficient. Therefore, a precombustion chamber, the so-called "step combustor", has been especially developed for the high feed rate of low calorific, large-sized substitute fuels (Figure 9). The typical retention time of 4 - 8 seconds of a previously described suspension flow Handling and storage calciner (cf. Figure. 8) is grossly insufficient for the safe burnout of such slow-reacting substitute fuels. Therefore, in the "step combustor" and as a function of the substitute fuel quality, the transport and discharge rates Cement processing requires a constant mass flow equal quality of raw material as well as lofted reSidual calctner terh.:uy air with meal 2-3 mtn lgmtton + burnout drytng • pyrolysiS HCF < 300 11m No mechanlcalrnstallaltOns - only fixed au ldnnons separate ltghl from h~avy unburnt fractiom and feeds the matennl mto lh~ calclncr by controllf'd \IPp\ Figure 9. Principle of PREPOL© "Step Combustor". Figure 10. Truck unloading station for reception and storage as well as feeding the ca/ciner process with max. 80 mm RDF at preheating or supply refined SRF to the main burner. 44