CEE Jan-Mar 2012

.. The initial designed capacity of the plant was 1,400 tpd , which was upgraded to 2,000 tpd through modifications and utilizing inherent capacities available. The clinkerization capacity was intended to be further enhanced from 2,000 tpd to 2,400 tpd. At the time of study, average specific fuel and power consumption were about 800 - 850 kcal/kg clinker and about 95 - 100 kWh/t cement respectively. 5. TECHNICAL AUDIT FOR CAPACITY EVALUATION. After preliminary data collection, measurements and evaluation study, the capacity and the potential was established. Emphasis was first given to establish the potential of clinkerization capacity. Subsequently, potential of other unit operations were established for balancing the capacities. • Kiln The kiln size was assessed at operating capacity. The kiln filling at operating speed of 4.5 rpm was 15.0%. The specific volumetric and thermal loading was 5.2 tld/m 3 and 3.3 Gcal/hr/m 2 and the retention time was 21.7 min. At enhanced production of 2,400 tpd, the kiln specific volumetric and thermal loading worked out as 6.3 t/d/m 3 and 3.7 Gcal/hr/m 2 respectively, which are within acceptable limit. At a kiln speed of 5 rpm, the kiln filling worked out as 16.3% and retention time as 19.5 min. • Pre-heater System Preheater consists of 5 stage pre-heater with swirl type calciner. Cyclone diameter are: Cyclone Size, mm 1 2 x4,000 2 5,800 3 5,800 4 2 x4,300 5 6,300 Preheater was operated at high pressure of 850 mmWG at preheater outlet and high gas temperature of 354 Deg C. The preheater fan was operating at a specific gas volume of 1.6 Nm 3 / kg clinker. • Calciner Calciner was studied for the requirement of residence time for fuel combustion and heat transfer for material calcination. Based on the active volume of calciner, mixing chamber and calciner loop, the residence time for coal combustion worked out to be 4.17 sec at 2,000 tpd and 3.5 sec at 2.400 tpd. • Cooler, Cooler ESP & Cooling air fans The installed cooler was a conventional grate cooler with fixed inlet and effective grate of 36 m 2 . At 2,400 tpd the cooler loading worked out to be 66.7 tpd/m 2 , which is very high. It was recommended to increase the area by installing additional grate to reduce the cooler loading below 45 tpd/m 2 and additional cooling air fans. Existing duct from cooler to cooler ESP was severely damaged leading to excessive leakage. The cooling air had to be restricted at 1.50 - 1.55 Nm 3 / kg of clinker at 100% ESP fan speed. With addition of third grate a new duct was recommended to be installed from cooler to cooler ESP. The vent duct and take off area was suitably recommended to handle the extra vent air volume at increased production. • Tertiary air duct (TAD) Hot air velocity in the existing tertiary air duct worked out to be 20 m/s and 24 m/s at 2,000 tpd and 2,400 tpd clinker production respectively. The velocity at the TAD take off point worked out to be 4.00 m/s and 4.8 m/s at the two production capacities. Hence, existing tertiary air duct diameter and take off area was found suitable for 2,400 tpd production. However to reduce pressure drop across the system it was recommended to realign the TAD by making the duct inclined and reduce existing 2 number 90° bends in order to reduce the pressure drop. It was discussed and planned to be executed in second phase for further improvement. • Observations on pyro processing system. Following observations were made on the pyro processing system: • Pressure drop across each cyclone was high at existing production except for cyclone 2 & 3. • Draught at top cyclone outlet was expected to exceed 1200 mmWG at 2400 tpd against normally accepted value of 850 mmWG • Temperature drop across bottom two cyclones was not significant. It could be due to internal recirculation of material since dip tube is missing in fifth cyclone. • Even without Dip tube in Cyclone 5, pressure drop was measured as 165 mmWG As this pressure drop also accounts for most of the calciner duct, it was acceptable. 9