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[Tdha]

Dear professionals,

 

I have some problems at my workplace and some confrontation with my boss.

I am working in an ethylene plant, that has twin-cell, induced draft cracking furnaces including mixed firing (40% of duty of heat is released by side wall burners, and 60% of it is done by floor burners). Our problem is, that recently we suffer from sevre fluctuation of oxygen content in flue gas and coil outlet temperatures. Symptoms:

- Fuel gas pressure is limited by SPH controller (needed duty is around 50% higher that we can produce by side wall burners)

- Oxygen content of flue gas sometimes fluctuates despite static operating and wheather conditions (there was no wind)

- Coil outlet temperatures are fluctuating (without any changes in fuel gas composition or wheather conditions)

 

The duty that side wall burners cannot produce must be taken by floor burners.

I suppose, that changes of coil outlet temperatures has been induced by changes in heat release, that has influenced the oxygen content measured in the stack (unfortunately not on the top of the fireboxes), and this is because of our inappropriate side wall burners.

Them configuration is quite simple - they have only primary air inlet that can be adjusted by a cowl manually.

As I checked them, most burners' flame shape seems good, but frequently they are hazy, orangey and we often suffer from flashback because of high hydrogen content of the fuel gas. The limit of SPH controller was not experienced before, according to the operators.

 

My opinion is, that the fuel gas nozzle and the venturi throat that would intended to entrain the needed combustion air to the burner tip can be the source of the problem. The continuous flashback may damaged the fuel jet nozzle/throat/inner side of burner tip (or caused coke deposits), but my boss is not willing to give order of disassemble them...

 

Has anyone experienced anything like that? What could also cause symtoms like this? Maybe I'm wrong.

Edited by Tdha, 13 June 2016 - 04:10 PM.

[raj1]

Tadha. u may be correct but not sure. The chance for the coke formation in burner tip or someother areas in burners seems very less as your fuel gas is hydrogen rich. Do this phenomena happens in both the sides? If it happens in single cell what is its effect on bridge wall temperature and combustible content in flue gas?  what is the feedstock ur using? Is there any high coke formation in particular cell comparing other cell? Which results in high fuel gas consumption(check fuel gas consumption/feed (MMBTU/KLB)? as u said fuel gas controllers are limited.