pre-heating of fuel oil

UmerKhalid

Dear All,

I have a query if you could help.
I want to pre-heat fuel oil before entering furnace,
I wanted to know if there is any reference that what could be the maximum temperature of pre-heating an oil if its flash point is 60oC.

HVACNUT

A Tiger Loop is good for preheating, and nozzle line heaters are available. What issue are you having?

Jamie Hall

Why would you want to do that? Assuming that you are using #2 fuel oil? Is your tank outside?

EBEBRATT-Ed

#2 oil is seldom preheated

#4 oil will "usually" burne cold but 120-130F may be necessary for good combustion. It does not usually require heat to be pumped.

If your dealing with #6 oil tank temperature should be maintained at 90-100 degrees for pumping. For combustion a temperature of 160-220 may be needed depending on what kind of burner you are using. Air atomizing burners would require higher temps 200F and above, steam atomizing and rotary burners would require less temp

MaxMercy

Jamie Hall said:

Why would you want to do that? Assuming that you are using #2 fuel oil?

He's talking *maximum* temperature.. He doesn't just want to warm the oil, he wants to get it HOT. I suspect he's got an idea in his head that preheating oil to just below its flashpoint might "supercharge" his efficiency...

John

Jamie Hall

MaxMercy said:

Jamie Hall said:

Why would you want to do that? Assuming that you are using #2 fuel oil?

He's talking *maximum* temperature.. He doesn't just want to warm the oil, he wants to get it HOT. I suspect he's got an idea in his head that preheating oil to just below its flashpoint might "supercharge" his efficiency...

John

That it might. That it might. Ever seen the effect of a small oil spray hitting something hot, like, say, an exhaust flue? One can get a lot of heat that way. Of course it doesn't last long...

EdTheHeaterMan

I believe if the idea has merit, and there is an economical way to accomplish it, someone would have already invented it, patented it, marketed it, made a fortune on it, and we would all have preheated oil burners.

STEVEusaPA

They make nozzle line heaters for oil, Carlin specifically. Any testing done at BL or by any manufacturer, preheats the oil to 100°. Easy to add to a burner.
And you will burn more efficiently.
The question to solve is preheating the oil, efficiency gain vs. electricity used.

But again, why? What's the goal.

Robert O'Brien

Heating fuel reduces viscosity and size of atomized droplets. Buderus Blue Flame heated the fuel to 148F, Carlin H2L used a heater to allow proper atomization at pressures below 100 PSI on low fire. Not sure how much if anything can be gained from doing this in a standard burner?

Jamie Hall

And there is a further question here -- what is the actual temperature of the fuel when it reaches the nozzle in a standard oil burner? The amount of fuel going through almost any oil burner is too small to create any sort of cooling effect, and I'd be mightily surprised if the nozzle weren't at least somewhat warm, and thus would heat the fuel.

(This is a factor in diesel engines, and is one reason (among many) why starting a cold diesel can be an exercise in patience -- or frustration).

HVACNUT

Hey @UmerKhalid! You wanna get in on this?

EBEBRATT-Ed

Any heat added to the oil is not lost it ends up in the fire box.

But the only practical reason to heat oil is to be able to pump it (usually #4 & #6 oil only) or to burn it.

I have seen #6 oil which at 50 degrees a can of it tipped upside down will not pour but heated to 200F for an air atomizing burner it's thinner than water. And the fuel oil in the storage tank has to be 90-100 deg to pump it.

I will never forget the smell of it and don't miss it one bit. It's the closest thing to roofing tar there is. Get some on your work boots or hands it will take gasoline to disolve it

UGH

ScottSecor

It has been many years since I worked with #4 and #6 oils that required heaters so my memory could certainly be fuzzy. Also, we work on very few oil burners as of late, so I may be way off on my opinions.

I suspect the 'standard' #2 oil burner mounted oil pump is designed for heating oil within a 'normal' temperaure range. I'm guessing normal oil temperature is 35 to 100 degrees F. I belive with oil temperatures above or below this range the oil viscousity would change and the flow rates might change as a result. I'm guessing with say 200 degree oil the #2 oil would be much thinner and perhaps flow woul d be reduced?

As an aside we used to take care of an oil fired outdoor scotch marine type "oil" (not hydronic) boiler that heated above ground tanks that were used for a blacktop plant. The #2 PowerFlame oil burner struggled when the outdide temperature dropped below freezing and the (heated) oil tank cooled. The boiler was filled with some sort of oil (maybe #2???) and it was circulated to the three or four vertical tanks that had coils inside them. This was at least twenty years ago, but I seem to remember the boiler oil (not water) temperature was around 300 or 350F. Unfortunately this plant closed years ago,

kcopp

I do remember that when they were "experimenting" w direct venting/balanced flue oil boiler that oil temperature was critical for their operation.
-Cold oil from an uninsulated basement oil tank...
-Intake air from outside especially when is very cold <10F
And trying to atomize that spray into a combustion chamber would have all sorts of issues.
Warming it up helped matters... cleaner combustion.

EBEBRATT-Ed

@ScottSecor

Oil temp has a big effect on viscosity and flow rate. The funny thing is if I remember right higher temp and lower viscosity causes the oil to spin more in the nozzle and reduces the firing rate. Lower temp and higher viscosity causes the oil to go straight through the nozzle (less spin) and increases the flow rate.

This is the opposite of what one would think....it doesn't make sense. I think this is only true with the oil between certain temperature ranges

@kcopp warmer oil and warmer fuel does burn better. But warmer air is less dense that cooler air so at a given air setting the burner fan delivers less warm air (and less oxygen) than cooler air.

TAG

I have no idea what temp the oil ends up being ... whenever I bought a house PA with oil, my old school oil guy always installed a tiger and looped the lines -- the exit from the tiger to the top of the furnace. My last place had two older furnace and an old oil water heater.

UmerKhalid

Dear All,

Sorry for late reply.
And I should have clarified it.
I am using fuel # 6
AS you know it is preheated before burning, I wanted to know any reference of the standard used for the maximum temperature to which it can be pre-heated.
i have heard that it should not be higher than 30oC from its flash point.
Is it correct?

UmerKhalid

Another thing is that the heater is natural draft. It is being used for distillation of Gasoline and HSD mixture.

UmerKhalid

Jamie Hall said:

Why would you want to do that? Assuming that you are using #2 fuel oil? Is your tank outside?

I am using #6 fuel

UmerKhalid

EBEBRATT-Ed said:

#2 oil is seldom preheated

#4 oil will "usually" burne cold but 120-130F may be necessary for good combustion. It does not usually require heat to be pumped.

If your dealing with #6 oil tank temperature should be maintained at 90-100 degrees for pumping. For combustion a temperature of 160-220 may be needed depending on what kind of burner you are using. Air atomizing burners would require higher temps 200F and above, steam atomizing and rotary burners would require less temp

I am using #6 oil, and it is air atomized, I wanted to know the maximum limit I can pre-heat the oil, is there are standard?

UmerKhalid

HVACNUT said:

A Tiger Loop is good for preheating, and nozzle line heaters are available. What issue are you having?

I am using #6 oil, I wanted to know any reference of the standard used for the maximum temperature to which it can be pre-heated.
i have heard that it should not be higher than 30oC from its flash point.
Is it correct?

retiredguy

Preheating the #6 fuel oil above it's ability to flow through the tubing to the burner nozzle makes very little sense. The quality of the #6 fuel oil will determine the maximum temperature required to produce a good flow. In a hospital that we serviced I would occasionally have to raise the final temperature of the fuel oil to the maximum limit setting of 240F to get the oil to the nozzle. The burners were North American MFG using air atomized burners. Yes, I always hated working on #6 fuel burners. When you got it on your clothes it was almost impossible to clean them. And of course you always carry a worn out pair of #6 fuel oil boots just for that occasion.

Derheatmeister

I have a contact that works for the German company Weisshaupt..
He is well versed on the Large burners and understand combustion !
What temp are you currently preheating the # 6 oil to ?
I will be exhibiting in Las Vegas at the AHR 2022 at which point i will bring up this subject with him.

ScottSecor

If memory serves me we used to set the thermostats on the electric heaters at 200F. On some systems they had low pressure steam coils in the underground oil tanks, realistically the coils were about 212 F and the oil in the tanks was more like 125 or 150 degrees F.

Jamie Hall

Don't know about land based -- but in marine use the fuel was heated with exhaust steam or with an auxiliary boiler. Not more than 250, I'd say, and usually much less.

EBEBRATT-Ed

@UmerKhalid

See the attached. It auto ignites at 407C so if you say 300C + the flash point that sounds about right. I imagine that it would also depend on what pressure the oil is under.

I doubt heating it over 250F would improve combustion at all.

Changing from air atomizing to steam atomizing might help

UmerKhalid

Another thing is that th

Derheatmeister said:

I have a contact that works for the German company Weisshaupt..
He is well versed on the Large burners and understand combustion !
What temp are you currently preheating the # 6 oil to ?
I will be exhibiting in Las Vegas at the AHR 2022 at which point i will bring up this subject with him.

I am heating the oil at 240F but it is not burning properly.

UmerKhalid

ScottSecor said:

If memory serves me we used to set the thermostats on the electric heaters at 200F. On some systems they had low pressure steam coils in the underground oil tanks, realistically the coils were about 212 F and the oil in the tanks was more like 125 or 150 degrees F.

i haved increased the temperature to 240F with cold air atomization, but the firing is not proper.

UmerKhalid

Jamie Hall said:

Don't know about land based -- but in marine use the fuel was heated with exhaust steam or with an auxiliary boiler. Not more than 250, I'd say, and usually much less.

the problem is i don't have steam and I am using air atomization.

Derheatmeister

UmerKhalid said:

ScottSecor said:

If memory serves me we used to set the thermostats on the electric heaters at 200F. On some systems they had low pressure steam coils in the underground oil tanks, realistically the coils were about 212 F and the oil in the tanks was more like 125 or 150 degrees F.

i haved increased the temperature to 240F with cold air atomization, but the firing is not proper.

@UmerKhalid
Some questions..
Please Explain ..."Not firing Proper"..Light off ?
Do you have a "Print out" of the combustion results and what values are you trying to accieve ?
Have the Values that you are trying to accieve been meet in the past ?
Is This a new or preexisting setup?
Is the combustion testing equipment calibrated ?
What size is the burner ? Was it Made/ Matched up/Setup for the Chamber ?
Can you see the Flame pattern ? Are the flames hitting the back of the Chamber and curling back?
Spray Pattern in deg ?
Nozzle size?
Combustion Air temp ?
Are there Possible combustion air contaminats in the combustion air?
Humidity levels of the combustion air?
Altitude of install?
Oil pressure?
Air shutter adjustments ?
Is the Quality of the # 6 oil adhereing to a standard ? Sulfur levels ?
Do you have any support from the manufacturer of the Burner / distillation Equipment ?
This sounds like a larger install and you may need to reach out to Distillation Industrie experts..

Some pictures of the Burner setup would be nice.

UmerKhalid

@Derheatmeister
Not proper firing means the oil is driping inside the heater.
I don't have all the data right now.
it is a new system and the heater vendor is also available, but he is still trying to find the solution.
My actual question was to find any ASTM standard for the pre-heating temperature.

The vendor said to increase the temperature of oil pre-heating to 400F, it wanted to know if it is allowed?
Because I read somewhere that the temperature should not be more than 86F above its flash point i.e. in this case not above 200F.
But I could not find any reference, so the idea is actually to find the reference of a standard.

retiredguy

If you answer most of @Derheatmeister's questions, we may be able to help find an answer to your problem. More information required.

Jamie Hall

There may be an ASTM standard for preheating #6. I rather doubt it. There may also be an NFPA standard.

There is also such a thing as common sense: if you heat a fuel above its flash point, and if for any reason it comes in contact with air, it is going to...

FLASH!

Surprise!

Which means that if you have a leak in a fuel line containing fuel above its flash point it is going to burn. If this is a drip, it's a minor consideration provided your housekeeping is good. If it's a spray, I hope you have CO2 or Halon flooding available.