CO Boiler Convection Replacement
The refinery had a carbon monoxide (CO) boiler in their Fluid Catalytic Cracking (FCC) Unit. The CO boiler was more than 40 years old. The CO boiler’s convection section is used to preheat the FCC charge and also generate superheated steam at 600 psig/710°F. The boiler had three problems: (1) low economizer tube metal temperatures were reaching dew point levels (2) high super heated steam temperature (3) problems with tube supports in the hottest zones.
The refinery approached Furnace Improvements to provide thermal design for replacing the convection section of the CO boiler. Furnace Improvements carried out the engineering study for replacing the convection section. We conducted a detailed operation analysis of the existing CO boiler and built a model of the existing design. With the model built, we were able to simulate the current operating conditions and predict the heater performance for the future operating conditions. We developed a better design overcoming the drawbacks in the existing CO heaters. The convection section was redesigned to:
Increase FCC feed flow
Improve CO Boiler efficiency
Prevent cold end corrosion of economizer
Eliminate flow distribution problems
The new design was developed retaining the existing soot blower locations, same platform elevations, and without any additional firing requirement. The detailed engineering drawings of the convection section vendor were also reviewed. The proposed revamp took care of all the issues with the existing CO boiler. It was estimated to save the client almost $550,000 per year. The boiler was commissioned in March 2003 and is running continuously now.