Twin Shaft Regenerative The Cimprogetti TSR is a two-shaft vertical kiln which utilizes the regenerative process for lime calcination. When one shaft operates in the burning mode, the other shaft operates in the regeneration (nonburning) mode. Each shaft operates for an equal amount of time in the burning and regeneration modes. There are two distinguishing characteristics of the TSR kiln: the parallel flow of hot gases and stone in the burning zone, which allows a mild burning of the limestone without over-burning, and the regenerative preheating of all combustion air using the limestone contained in the preheating zone of the kiln (in the non-burning shaft) as a heat accumulator. The two shafts are alternately loaded from the top, with pre-weighted limestone charges. The fuel is introduced to only one of the two shafts at a time, at the upper side of the burning zone where the material is still un-calcined and can absorb most of the heat released by the combustion. The combustion gases travel downwards, in parallel flow with the material and leave the burning shaft through the crossover channel, entering the nonburning shaft travelling upwards in counter flow with the stone. The off-gases then cross the freshly loaded limestone in the pre-heating zone located in the upper part of the non-burning shaft, where they transfer most of their residual heat, before being vented off. The heat transferred, as above said, is then recovered in the next cycle, from the combustion air entering from the top, when that given shaft will shift to burning mode. The shifting between burning and non-burning modes is called “inversion” and it takes place at set intervals. In the lower part of the TSR kiln, the hot lime lumps are progressively cooled down by cooling air introduced from the bottom of both shafts so as to be handled with standard conveying equipment. 4 LIMESTONE CHARGING COMBUSTION AIR EXHAUST GAS TO FILTER BURNING SHAFT CO-CURRENT FLOW NON-BURNING SHAFT COUNTER-CURRENT HEAT RECOVERY LIME COOLING AIR FUEL LIME DISCHARGE process
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