Weekly Topic (11.14-11.20): Problems encountered in the operation of smoke exhaust systems and improvement measures

The main reason affecting the long-term operation of the flue gas turbine is scaling on the turbine, which causes high vibrations and forces it to stop for maintenance. To control scaling, I believe it is essential to pay attention to regulating the amount of fine particles in the flue gas; this is primarily influenced by the operating conditions of the regenerator and the three-spin system. In particular, technical upgrades usually result in an increase in capacity, which leads to the systems operating under high loads and thus an increase in the amount of fine particles in the flue gas, affecting the turbine’s operation. In addition, strict control is exercised to ensure that the inlet of the smoke extractor does not experience excessive temperature or pressure, thereby reducing fluctuations in the system.

This post was last edited by lijianhuai on 2011-11-17 08:49. The flue gas turbine in catalytic cracking is a key device for reducing energy consumption in such units. In my unit, the main issue with the flue gas turbine relates to its catalyst structure; in order to reduce this structural problem, the cooling steam used for the rotor was changed to superheated steam, but this did not yield significant results as the structural issue persisted. To ensure the long-term operation of the unit and reduce the frequency of failures in the flue gas turbine, after it had been in operation for 10 months, manual maintenance was carried out, primarily involving the replacement of the turbine rotor and the cleaning of its blade structure. My unit has spare rotors available.

1. Structural improvement of the leaf lock plate. 2. Improvements to the smoke extractor condensate line and the disc cooling steam system. 3. Pay attention to the cleaning of the copper tubes in the condenser.

To reduce failures and ensure safe production, many facilities conduct regular shutdown inspections of the smoke extractors on an annual basis, which helps to lower the incidence of sudden accidents involving these extractors.

The last edit to this post was made by yulanggongwu on 2011-11-17 at 08:53. Offline sampling at the three inlets and outlets is used to analyze dust levels; however, the offline analysis results obtained by our unit seem to differ significantly from the actual values. It would be better to use online analysis for real-time monitoring, so that adjustments can be made promptly when there are significant deviations from the designed parameters； In terms of vibration monitoring, regular analysis is necessary, especially regarding changes in the first harmonic frequency. When there are sudden changes in this frequency, it is important to analyze them in conjunction with changes in other frequencies as well as the actual conditions on site, and take appropriate measures to prevent errors in shutdown due to problems with the instruments ； Some facilities have attempted to clean the fouling on the rotor catalysts online by adjusting temperature without shutting down the system. However, since the effectiveness of this cleaning method is unpredictable, it is necessary to shut down the main fan and have plans in place to handle increased vibrations that may occur after cleaning.

Regarding the decrease in performance caused by scaling on the smoke extractor, cleaning is necessary. The conventional methods of maintenance, which involve replacing the rotor of the smoke extractor and cleaning its blade structure, require shutting down the equipment, which is quite troublesome. Does anyone have any good suggestions for carrying out repairs without shutting down the machine?

What we encountered was fouling on the blades and erosion at the blade roots; by replacing them with high-efficiency triple rotors, we reduced the dust concentration as well as the size of large dust particles in the flue gas, and now the system is operating well

I’ve always wanted to ask: how many flue gas dust control units are appropriate after a three-stage centrifuge? I have another question: why can’t a soot blower be installed at the inlet of the smoke extractor?

Pollution and scaling of the copper tubes in the condenser reduce the heat transfer coefficient and lower the vacuum level, affecting the thermal efficiency of the unit and resulting in insufficient output; therefore, a series of cleaning measures must be taken.

The blades should be cleaned regularly; in some facilities, the rotor is replaced after it stops working, but this approach is not advisable as it takes time and incurs high maintenance costs. After shutting down, simply open the stator blades and clean the fouling on both the stator and rotor blades. For the very hard scale on the moving blades, it can be heated first using welding; the temperature should be controlled with a thermometer, after which the scale will crack on its own. Finally, the remaining scale can be removed by using a small grinder. It’s sufficient to keep each blade as clean as possible; there’s no need to worry about wearing away the coating, as it won’t be subject to erosion as long as it remains scaled. We are not applying coatings to the scaled areas of our rotors, which saves a lot of money; applying coatings to those areas is completely useless. After cleaning, it usually works fine when powered on. The cleaning and maintenance process now takes only one day to complete, compared to three days before.