Cement and Energy

space, and the new kiln hood with tertiary air take off was adapted to suit the new clinker cooler. An increase in throughput from 1300 tpd to 3000 tpd (with a maximum of 3300 tpd) required higher rotation speeds so that the kiln dri ve was replaced. The girth gear and beari ng system remained unchanged. In order to achieve better control of the false air, the old kiln inlet seal was also repl aced by an improved new design during conversion work. The grate cooler was completely changed to a new Mulden type cooler to suit the increased throughput, and its cooling area was increased. Larger fans with fixed-silencers and new Mulden type grate plates were also installed to assist the cooling. The mechanical grate dri ves were also replaced by hydraulic units. Parallel to the increasing demand of the coal dust and raw meal, one raw mill LM 46.4 with capacity of 250 tpd and a LOESCHE coal mjll LM 16.2 D with capacity of 12 tph were installed. The capacity of the fl ow control gates underneath the storage silos was increased to 250 tph . A new ELEX electrostatic precipitator was installed behind the raw meal mm and rotary kiln. According to the gas fl ow quantity, one chamber was added to existing two chambered electrostatic precipitator in the clinker cooler unit. The heart of this conversion project is the conversion of the four-stage cyclone preheater to a four-stage ACT– PASEC precalcining system. In the following description, the conversion is broken down and described in three construction stages. Stage I During this phase the ex1stmg tower structure was widened by 7.25m . Because the existing preheater tower II is made of concrete, the new extension was rigidly con nected to the existing steel preheater I. The calciner and the cyclones of the second line were installed during the erection of the tower structure. This conversion phase in no way interfered with the operation and could therefore be carried out while the kiln was working. A specially-designed foundation slab on which this structure now rests was attached rigidly to the existing tower foundation by special horizon tal anchors. From the design analysis point of view the modified tower structure can be seen as a single structure. Stage II Production was stopped before the start of thi s phase. The existing double cyclone, and cyclones 2 and 3 were completely dismantled. Only the pre-existing cyclone 4 was reused. Stage III Some portion of the required connecting lines was prepared in conversion phase I, so that during this phase only the meal and gas ducts remained to be connected. The main dimension of the extension is only 7.25m by 15m. Operation of the system has also shown that sufficient free access has been provided to the cyclones in the preheater tower. Commissioning By April 1995, the erection was sufficientl y completed to start the cold tests on the system. Part of this process was the tests of the raw grinding system, coal . grinding system, raw meal feed system, rotary kiln and cl inker transport system and their interaction with the control system. The control system is a freely programmable PLC-based system with four visual display units for each kiln line. After eliminating some faults regarding bi g and smaller motors, start-up was effected at the end of May 1995. Due to the similarities of kiln line I and the newest version of the existing visualisation system, the new kiln line has been operated by the plant' s own operating personnel since the start-up time. Operating Results According to specification, the system is designed for a guaranteed production of 3000 tpd of well-burnt cl inker. However, the cri tical components, such as the hot gas fan have suffi cient reserve for the system to be able to perform at over 3300 tpd. The guaranteed heat consumption was 730 kcal/kg (3056 kJ/kg) in which a measuring tolerance of 1.5 per cent was agreed in the 8