First of all, after careful and careful inspection, it is confirmed that the instrument monitoring system is normal, and the change of the data of the four measuring points of the steam turbine is consistent, and the obvious vibration and abnormal sound are felt at the scene, and the first possibility is excluded; secondly, considering As mentioned above, the turbine and the inlet steam line have been affected by the failure. After checking the on-site piping system and the claws of the steam turbine, no obvious changes are found. Further, if static friction occurs, it will be accompanied by high-frequency vibration components. The third possibility is also ruled out; finally, in the second case, when the rotor is bent, the axial vibration will rise significantly, and when the component is loose or the shaft is cracked, the vibration phenomenon should be expressed as progressiveness and initial vibration is not obvious. Based on the above analysis, it can be judged that the cause of the vibration rise is caused by the sudden breakage of the turbine blade and the severe damage of the rotor dynamic balance. After the fault occurred, the system load was adjusted from 71500kg/h to 66000kg/h, the steam speed of the syngas compressor was adjusted from 12375r/min to 12060r/min, and the turbine shaft vibration value decreased from 77-79μm to 73-70μm. Bearing vibration has no abnormal development trend. After that, the fluctuation of the unit speed caused by the change of the load, the vibration value of the turbine also fluctuated, indicating that the vibration is very sensitive to the rotation speed, and the vibration value decreases with the decrease of the rotation speed, and rises with the increase of the rotation speed, further confirming the above analysis. in conclusion.
In order to further diagnose the cause of the vibration of the syngas compressor driving turbine, on March 22, 2007, the steam turbine was tested and diagnosed. Through on-site testing and comprehensive analysis of the vibration characteristic map, the following conclusions are drawn: 1 The failure of the steam turbine is caused by the mass loss on the rotor; 2 There is no evidence to prove that the fault is displaced from the previous squib and the center of the unit and The overhaul is not relevant; 3 this failure has nothing to do with process production and control of operating parameters. In view of this, the following suggestions are made: 1 In view of the current situation of the unit and the original, fuel and production arrangements, adhere to the operation, arrange parking maintenance as soon as possible; 2 strengthen the monitoring of the unit, conduct special management, and the relevant experts on the site should meet regularly; 3 authorized operators In the event of an emergency that jeopardizes the safety of the unit's equipment, it can be immediately shut down; 4 when the unit vibration rises slowly with the speed and load, or a small amount of fluctuations, report it in time; 5 when there is a problem with the peripheral or auxiliary machine, as long as it does not endanger the turbine Safety should not stop, otherwise it will not be able to open again; 6 try to stabilize the unit's speed and load and other process parameters of the unit; 7 properly adjust the temperature of the lubricating oil to ensure the normal operation of the bearing.
The condition adjustment based on long-period operation ensures that the unit can run to the planned maintenance time and avoid secondary damage to the unit. Adjust and optimize the unit and its process system. Control of inlet pressure of syngas compressor When the system fluctuates, the inlet pressure of the syngas compressor is automatically controlled to the local control, keeping the inlet pressure of the syngas compressor relatively stable. When the system pressure fluctuates, allow the inlet pressure vent valve to be vented a small amount. After the system returns to stability, slowly absorb the air release.
The control of the molecular sieve unit performs a peak shift on the pressure drop and the outlet temperature difference generated when the syngas molecular sieve (A/B tank) is switched, and the automatic switching is changed to manual operation to reduce the valve opening and closing rate. The molecular sieve inlet temperature was lowered from the original 4 ° C to 3 ° C. By extending the parallel time of the molecular sieve (A/B tank), it is ensured that the heat of the regenerated molecular sieve and the heat of adsorption are released under controlled conditions. The control hydrogen-nitrogen ratio of the compressor syngas circuit is controlled at 2195-311, and the heat load of the waste heat boiler, the gas distribution of the synthesis tower, and the gas volume are stabilized. The circulating water temperature is controlled at 27 to 29 ° C, which is about 2 ° C lower than the original operating temperature. On the basis of coordinating the circulating water volume of the whole plant, reduce the circulating cooling water volume of the urea plant, and increase the influent capacity of the ammonia plant by about 700t/h. The high turbine parking value is changed to 95μm, and the lubricating oil temperature is controlled at 45°C to avoid the lubricating oil. The temperature causes the unit to run unstable. The unit speed control is relatively stable under the working conditions, but the syngas compressor speed and vibration continue to rise, slowly open the compressor inlet 5018mm bypass valve, after the speed stabilizes or back, keep or close the bypass valve.
Concluding remarks After the instability of the steam compressor of the syngas compressor, the fault diagnosis technology is used to accurately analyze and judge the cause of the fault, which provides a scientific decision-making basis for the factory production and safe operation of the equipment. The continuous operation of the production equipment is ensured by adjusting the optimized working conditions; The dismantling results are consistent with the diagnostic analysis conclusions, and the unit is stable after the inspection.
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