Catalytic Feed Hydrotreater
Heater Performance Improvement
In February 2002, FIS carried out a Catalytic Feed Hydrotreater Heater (CFHT) revamp for a refinery situated in Illinois. CFHT heater is located in their Fluid Catalytic Cracking (FCC) unit. It is a natural draft vertical cylindrical furnace with a horizontal overhead convection section and three up fired low NOx natural draft burners. Client was facing repetitive tube failures in this heater and solicited Furnace Improvements (FIS) to find the root cause of tube failures. FIS was also requested to provide the design of the new convection section and rerate the heater.
Furnace Improvements carried out a thorough analysis of the heater and found that the existing convection section was designed with very tight design parameters. The heater had a very high heat flux that resulted in high skin temperatures and subsequent tube failures. The burners had a very high heat release rate, which led to long flames and flame impingement.
FIS redesigned the convection section within one week with a larger convection section that overcame the drawbacks in the original design. FIS also replaced the existing burners with six new low NOx burners and rerated the heater. FIS developed the detail engineering and fabrication drawings for the convection section and replacement of the burners. FIS also developed material and burner specifications, evaluated the vendor quotations, and witnessed the burner test.
Advantages of revamped design are as follows:
Convection section skin temperatures were reduced by 193 °F.
Thermal efficiency was improved by 6.2%.
Stack flue gas temperature was alleviated by almost 200 °F.
Heat flux and flue gas mass velocity in convection section were significantly curtailed.