Cement Energy Environment

39 One of the currently strongest debated topics worldwide is climate change and measures to stop it. Against the background of its 7 % contribution to global CO 2 emissions, the cement industry bears a major responsibility not only for the present but also for future generations. Oxyfuel technology is based on the replacement of ambient air for the clinker production process by entering pure oxygen into the front zone of the cooler in order to remove the nitrogen portion in the air with the result that the CO 2 concentration in the kiln off-gas reaches values of 90 % and above. This allows for a significantly more efficient CO 2 separation as the basis for CO 2 treatment downstream the process, be it utilization or storage. However, the advantage of reducing the exhaust gas to a practically pure CO 2 stream unfortunately leaves the The contribution of clinker substitution to sustainability is manifold. The environmental impact is obvious with respect to CO 2 emissions and energy demand. Process- polysius ® pure oxyfuel –CO 2 capturing by oxygen based kiln operation polysius ® activated clay production of resources and energy saving clinker substitutes preheater with too little gas to operate the cyclones. In the first generation oxyfuel process, this is countered by a complex gas recirculation system from the preheater exhaust gas to the cooler with heat exchanging, de- dusting and condensation process steps. With the second generation polysius ® pure oxyfuel process, this gas recirculation can be dispensed with significant savings for both, investment and operating costs. A further advantage is that this process is also suitable for retrofitting existing kiln systems. The polysius ® pure oxyfuel process has been developed up to a technical level which justifies the building of a demonstration and testing plant with a capacity of several hundred tons of clinker per day. Accordingly, the technology is part of several ongoing commercial proposals (Figure 2). related CO 2 emissions of conventional cement production can be reduced by up to 40 % through the polysius ® activated clay technology. Figure 2: The oxyfuel process of the first generation (equipment in blue and red) allows kiln operation with pure O 2 but requires gas recirculation (red equipment). polysius® pure oxyfuel process operation is without gas recirculation, retrofittable and developed up to industrial-size demonstration and testing plants. Several measures allow to cope with the significantly reduced gas stream.