(146a) Ethylene Cracking Heater Troubleshooting Tutorial

Cracking heaters represent the largest individual investment made in an ethylene plant.  The operation of the heaters greatly impacts the economic performance of the plant, so the incentive for maintaining cracking heaters in optimal operating and mechanical condition is significant.      

There are a number of issues that can detract from the optimal performance of a cracking heater and the life of its mechanical components. The occurrence of short run lengths, carburized or bowed tubes, process control excursions, poor yields, and capacity limitations can be indicative of basic problems that need to be rectified to optimize cracking heater performance.   

This paper will introduce methodologies for discovering performance deficiencies in cracking heaters and provide examples for practical solutions to common problems that result in degradation of cracking heater performance. Some of the troubleshooting tips that will be addressed are:

• Confirmation of hydrocarbon and fuel flow measurements using venturi and burner curves and corroboration of cracking conditions via feed and effluent analysis
• Correcting burner performance issues due to damage, fouling, pressure imbalances, tip mis-alignment/orientation, and air register setting using visual inspections and firebox combustion surveys
• Surveying tube metal temperatures to estimate heat flux profiles
• Analysis of startup, shutdown, and decoking procedures to identify manual operations that can shorten furnace run length and tube life 
• Inspection of coil support system condition and evaluation of coil maintenance procedures to ensure coil stresses are minimized
• Evaluation and rectification of process control performance deficiencies
• Visual inspection of firebox and convection casing for indications of refractory damage and intrusion of tramp air
• Impact of feed contaminants
• Detection and mitigation of convection section fouling/damage (process and flue gas side)