Furnace Improvements (FIS) was hired to perform a turnkey NOx Reduction revamp on an Alky Unit Heater (H-2). The target NOx emission rate was 0.035 lb/MMBtu (HHV). The Alky Heater is a vertical cylindrical heater with a design heat duty of 55 MMBtu/hr. The heater efficiency was very low at 66%.

Excess oxygen in the firebox was very high at 8.5%. The heater floor was in bad shape. The heater did not have any stack damper for draft control.

FIS’ scope included finalization of thermal design and engineering, procurement of material, fabrication, supply and field installation of the heater.

FIS’ scope of services included:

• Modification of Existing Floor:

The existing floor was in poor condition and needed to be replaced. The burners were fitted on a smaller burner circle diameter to increase the reliability of the heater by minimizing the flame impingement.

• Install Eight New Ultra Low NOx Burners (ULNB):

FIS rerated the heater using ULNB to reduce NOx emissions. The burners are fired vertically upwards and the NOx emissions are 0.018 lbs/MMBtu. The burners were housed in a common air plenum with a central air intake. The air intake was provided with a manual damper.

• Install New Convection Module:

Existing convection section efficiency was very low due to high flue gas
temperatures leaving the section. The flue gas temperature decreased to 520oF from 680oF by replacing the convection section.  FIS supplied and installed an upgraded convection section.

• Installation of New Stack and Damper:

FIS replaced the existing stack and installed O2 and temperature indicators for better control of oxygen levels and temperatures exiting the stack. The new stack was provided with connected ladders and platforms. The existing stack did not have a damper for draft control. The stack damper is operated pneumatically. Minimum limit stop has been provided on the linkage side of the damper frame, so as to prevent it from being fully closed. A position transmitter has been provided to know the damper opening position. The stack damper is provided to ensure that the draft at arch is maintained at the design level of (-) 0.1” WC under all operating conditions.

After the revamp, the efficiency increased by 20%. The total cost of the project for the design services, engineering services, fabrication and installation was $1,560,000. The project payout was estimated to be less than 2 years. This heater was successfully commissioned in March 2008.