This adiabatic combustor type with a vertical tube convection section is another option for recovery of heat to natural circulation steam generation.
This design incorporates the steam and mud drums with the vertical heat recovery surface eliminating the circulation pumps. The tubes are usually 2" (50 mm) bare tubing to resist the deposits of the dust-laden environment of fluid catalytic cracking and residue fluid catalytic cracking units.
The advantages of this design include:
- Combustor style provides better CO destruction than water-wall units
- Supplemental fuel use is significantly less than water-wall units
- Bare tubes resist the dust fouling of regeneration gas streams
- The catalyst fines are collected in hoppers to protect downstream equipment
- The heat recovery surface is a boiler style convection section with the same degree of maintenance requirements
- Natural circulation means no additional maintenance for boiler feed water circulation pumps.