OneWhat happened to the accidentOn March 10, 2017, the company shut down the kiln for 20 days for maintenance according to the annual plan. At that time, the kiln bricks were inspected and measured, and it was found that the kiln bricks from 57 meters to 60 meters had partial peeling, the thinnest part was 140mm, and the thickness of other bricks around was about 190mm. After discussion by the process team, it was decided that the refractory bricks in the area were planned to be replaced during the kiln maintenance in September. From April 30th to May 10th, the kiln is planned to be shut down for 10 days. At that time, the 57-60-meter kiln bricks were inspected and measured again, and no signs of deterioration were found. It was decided whether the refractory bricks in the area would be replaced as originally planned during the kiln overhaul in September. At 10:55 on May 11, the current fluctuation value of the kiln main motor in the production process suddenly rose from 124A to 490A, and the pressure of the hydraulic retaining wheel increased from 359MPa fluctuates to 9MPa. Process, mechanical, electrical and other professionals went to the site to inspect and judged that the kiln skin was uneven. Since then, although the process has been adjusted many times, the problems of large fluctuations in kiln current and hydraulic retaining wheel pressure have not been alleviated. At 0:28 on May 24, it rained heavily in the factory area, and at 5:48 it was found that the clinker roller breaking current was high, and at 5:53, the "carcass sweep" showed that there was a 400 high temperature point at 57 meters, and the on-site measurement was 371. Open axial fan cooling;On June 11, the carcass temperature remained at 340-390 at 57-64 m. From 7:30 on June 12 to 19:30 on June 13, external power was cut off due to the maintenance of the substation of the Power Supply Bureau, and the waste heat was used to generate electricity to ensure the operation of the kiln. At 19:23 on June 13, the external power supply was normal, and the kiln operator on duty operated according to the operation plan of switching external electricity: at 19:47, the output was reduced from 360t h to 100t h. 19:48 stop the kiln tail coal powder and close the coal injection pipe valve of the decomposition furnace, and burn the SP kiln. At 19:49, the kiln head was called the jump stop, and the kiln head was reopened at 19:51. 19:49-19:50 kiln speed from 4r min to 10r/min。19:52 Due to the high kiln current, the kiln speed is increased to 20r/min。19:58 Stop the coal mill. 20:02 Stop at the kiln bucket. At 20:05, when the main motor of the kiln was about to be stopped, the central control found that the local temperature was as high as 567 at 57 meters of the carcass. Call the post to the scene to confirm, the post found that there was a reddish phenomenon at 57 meters of the kiln carcass, and immediately reported to the central control and relevant personnel, and the company leaders approved the stop of the kiln for processing. At 20:06 on June 13, the kiln was stopped, and the company organized personnel to replace the refractory bricks of the kiln 57-64 metersAfter 75 hours of emergency repair, production resumed at 18:47 on June 17.
IIAnalysis of the cause of the accident(1) The direct cause is that the 57-72 meter bricks in the kiln have been used for 6 years since they were put into operation in October 2011, and the replacement cycle has been reached. And in the kiln maintenance process in March this year, it has been found that there is local spalling. However, due to the luck mentality, insufficient ideological attention and insufficient experience, the kiln bricks were not replaced in time, resulting in the occurrence of brick accidents. (2) Indirect reason 1, the company's purchased limestone composition fluctuates greatly, resulting in large fluctuations in the composition of raw meal into the kiln, resulting in large fluctuations in the thermal process of the production process, which affects the life of the kiln refractory bricks. 2. When switching external electricity, in order to protect the coal injection hose at the end of the kiln, the SP kiln is burned, and the pulverized coal at the kiln head is weighed to jump for 1 minute, resulting in a cold and hot temperature in the kiln, which is very damaging to the kiln bricks. 3. When switching external power, the kiln speed decreases too fast, resulting in an increase in the thermal vibration of the kiln, which is more damaging to the kiln bricks. 3. Accident prevention and rectification measuresIn response to this accident, the following preventive measures are formulated:
When the kiln is stopped for maintenance in the month, the refractory bricks of 64 meters to 72 meters in the kiln are replaced, and the large gear ring and wheel belt of the kiln are adjusted to solve the problem of kiln vibration and large slippage of the wheel belt.
2. The center of gravity of management is shifted forward, and the acceptance and homogenization of incoming limestone are strictly controlled, so as to reduce the fluctuation of raw materials and improve the thermal stability of the kiln. 3. Improve the importance of process management: take timely and decisive measures to deal with the process problems existing in the daily production process to minimize the risk of accidents in production. 4. Standardize the management of refractories: conscientiously do a good job in the inspection of refractories. Comprehensively consider the operating cycle, measured thickness, operating conditions and risk size of refractory bricks to avoid similar problems. 5. Take this as an example, organize review and reflection within the company, draw inferences from one another, learn lessons, and prevent similar accidents from occurring.