Performance Improvement of Vacuum Heater
FIS was approached by a refinery in Illinois for Vacuum Heater performance improvement study. Client also wanted to revamp the heater to handle Canadian Crude and reduce NOx emissions.
The Vacuum heater was a natural draft horizontal cabin heater with horizontal convection section and a top mounted stack. FIS reviewed the design and operations of the heater and discovered following major issues:
The heater was facing coking problem
Average temperature drop was 40°F in the transfer line from vacuum heater to vacuum distillation tower, which is very high
Flow distribution through each pass was not uniform
On FIS recommendation client decided to build a new Vacuum heater using existing heater foundation. The new heater is 4 ft wider. This vacuum heater is horizontal tube box with a convection section. It is designed for a heat duty of 42.8 MMBtu/hr and an efficiency of 90%.
Salient features of the new heater are as follows:
The convection section of the heater has steam generation coils and boiler feed water coils along with the process coils.
The heater is designed as a gas firing unit.
The flue gas temperature leaving the economizer is alleviated by 72°F to 400°F.
The heater is designed for the overall fuel efficiency of 90% (LHV).