Case 14 Improving FCC Expander Reliability Under Off-Design Conditions

CASE 14 IMPROVING FCC EXPANDER RELIABILITY UNDER OFF-DESIGN CONDITIONS  

Rotating machinery usually performs efficiently if it works under design point conditions. However, off-design conditions require a predictive model of the machine s performance. In a FCC power train system, mass flow deviation is quite common for adjusting production capacity to meet the requirements of petrochemical product markets. 

There are many reasons for significant investment in FCC power trains and, thus, power train maintenance. These power recovery machines handle catalyst-laden gas at high temperature. Because the recovery system is connected to the processing plant, the steam pipe network and the electrical power grid, a power train upset is likely to rapidly extend from the FCC unit to the entire plant. 

Evaluating off-design performance is strongly recommended for the purpose of improving the operating reliability of both power recovery sets and processing plants. To do this evaluation, a simulation analysis should be based on velocity diagrams, the law of similarity, and expander performance maps. 

It would be an understatement to say that the gas expander turbine forms a major part of the power train. Evaluating off-design performance for the expander installed in the Sinopec Jinan Oil Refinery is presented as an example of an appropriate evaluation method. It should be noted that calculations are based on actual field measurements and plant experience. 

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