Furnace Excessive Fumes

[Vikram 1971]

Currently I'm involved in a steel Re-heating continuous furnace project for heating billet , scraps. It's pulverized Coal fired having two zones - soaking and heating zones.
Secondary air of soaking zone burner is preheated (recovered heat from Draft)

The problem is that whenever coal concentration is increased in the primary air, excessive fumes starts forming (I don't know if fumes is the right word.. Maybe it's POC. its between flame and fumes.)

These fumes are so problematic that it blinds the workers which unable them to perform the job.
Reducing the coal concentration partially solves the blinding problem but after sometimes it leads to a large decrease in the required temperature in the soaking zone. Halting the flow.

Things is have Tried
1.) Changing burners - I thought that maybe problem is with preheated secondary air.
2.) Changing air ratios - not very promising results.

 

[arunmrao]

Have you considered changing fuel. Why pulverized coal ?? You can consider Cng!!
I am converting ladle preheated from diesel to Cng

 

[TugboatEng]

Any halogenated substances present in coatings and such will create acid gasses when burned and those will cause great discomfort and harm for your workers.

 

[Dhurjati Sen]

The problem could be in the burner assembly and not just the burners. Check the burner manual and look for the issue there.

DHURJATI SEN

 

[Tmoose]

In facilities burning pulverized coal the coal feed rate and primary air flow are mutually controlled. Air/fuel ratio. The adjustment of the inter-linked controls is called "characterization."

If your furnace has such systems, perhaps a factory technician needs to be involved.

I do get the feeling there will resistance to anything that appears to reduce "production."

 

[Vikram 1971]

Furnaces require some percentage of excess air depending on load to prevent smoke

I have tried changing the excess air but still no results. Actually it isn't smoke, maybe it's an extension to the flame as you can see in the figure given below( Sorry for bad drawing). What is more troubling is why these foggy Fumes/POCs are moving in the opposite direction??
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The problem could be in the burner assembly and not just the burners. Check the burner manual and look for the issue there.

I have checked the manual, there isn't thing like this but most of the burner related problem are due to coal flow. Could this be the problem??
I'm using volumetric screw feeder, maybe it's giving somewhat pulsating coal fuel? Could this be the issue??
​

In facilities burning pulverized coal the coal feed rate and primary air flow are mutually controlled. Air/fuel ratio. The adjustment of the inter-linked controls is called "characterization."

If your furnace has such systems, perhaps a factory technician needs to be involved.

I have tried changing the primary air/fuel ratio but I didn't get any promising results. But those Fumes/Flame/Fog tends to reduce when the primary air supply is decreased but it lead to choking of primary air. Secondary air has no effect on this.
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[link Vikram 1971]These fumes are so problematic that it blinds the workers which unable them to perform the job.[/url]

Another data point explaining why stuff doesn't get made in N. America any more.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."