Engineering Study of DHT Charge Heater (F-1)
Furnace Improvements (FIS) was employed by a refinery in Illinois to carry out an engineering study on their DHT Charge Heater (F-1). The client wanted to improve the thermal efficiency of their Distillate Hydrotreater Charge Heater. The client was also facing positive pressure and capacity limitation issue in the heater.
The design heat duty of the heater was 38.2 MMBtu/hr. The client provided FIS with 1 year of operating data. The following observations were made from data analysis:
The total feed flow rate did not match with the sum of individual pass feed flowrates.
Feed inlet temperature was 148°F below the design inlet temperature.
Feed outlet temperature was 177°F lower than the design outlet temperature.
The heater was operating with positive draft at arch at high firing rates.
FIS revamp scheme consisted of:
A new larger convection section
A new stack having same diameter and elevation as existing
A new pneumatic operated stack damper
Advantages of revamped design are as follows:
The maximum flue gas mass velocity through convection section is alleviated by 48%
A lower flue gas pressure drop of 0.328” WC is observed in the new convection section
Flue gas temperature leaving the convection section is reduced by 202°F
The efficiency of the heater increased by 8.4%