Thermal oxidizer high fire flame detection 1

[SCouture]

Hi,

My thermal oxidizer is in operation for 5 months. We oxidize process waste air (use as combustion air) and wastewater. Our burner is a North american with a 5:1 turndown ratio using oil#6 . Our thermal oxidizer go from low fire (2500 CFM of air) to high fire (9000 CFM of air) about 6 times per day for 1 hour. It was working well since the beginning. Since 3 weeks, every time we go to high fire, we trip on flame failure due to bad detection of the flame after 5,10,50 minutes (never the same). Our scanners (2) are working in good conditions. It seems that the flame has just move away from the burner down the furnace. I can't reajust the scanner due to the design. What can cause the flame to move away from the burner?

Pressure drop across the burner?
Atomizing steam?
Oil pressure?

Thanks

 

[Combustor1]

SCouture,

This is not easy say without all the data. When you set a burner up it is important that you keep setup information pressures and flows and temperatures of air and fuel at low fire and high fire. When something goes wrong at least you can revert back to the initial setup.

Flame scanners - if you have self checking scanners then the shutters can fail sometimes hours after startup and cause the burner to trip.

All of the 3 items you listed could be a cause for flame to move off the nozzle. But there are other items you will need to check, Oil temperature, clinkers developing inside the chamber and air and oil flows. You could even have an equipment problem check your oil atomizer/nozzle and your refractory tile.

Next step is to call a North American rep - and this time get a complete setup chart.


Good Luck!


Combuster

 

[unclesyd]

Just for curiosity are you doing any radiographic inspection near the scanners?
Make sure you have a proper electric ground?
The self checking scanners are very sensitive to electrical problems.
Are you having thunderstorms in the area?

We have a Thermal Reducing unit that uses natural gas with air and NOX as the oxidizer. When we increased capacity when had to tune the controls for the two burners where they wouldn't push the UV portion of the flame outside the vision of the scanners.

 

[airheadmw]

Sounds like a control issue. Does the unit have a ratio valve that tracks the amount of fuel input or does the combustion air modulator operates without a process signal?