Diesel fired boiler turn down

[nicolai]

Hello folks
Our boiler is rated for steam production of 2500 kg /hr @ 10 bar
The diesel burner is rated also for production of 2500 kg/hr steam and turn down ratio of 4

Our steam demand fluctuate between 200 kg /hr and 900 kg/hr

What is concerns and possible consequences of operating diesel fired boiler out of its turn down range?

 

[LittleInch]

I would guess potential excess temperature, cooking of the burners/ flame out or thermal cycling if the burners turn on and off many times an hour at minimum diesel flow.

Ask the vendor if there are ways to isolate sets of burners maybe?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[chicopee]

About your question, would that be to operate at low firing rate or at high firing rate? and what would be the reason to ask such question? If you operate at high firing all the time eventho. the steam demand is low then a few things pop in my mind which are: one wasted fuel, excessive stack temperature, three refractory wear and tear, steam pressure and temperature increase, safety valves popping.

 

[chicopee]

and increase in make up water, increase in chemical treatment and increase in blowdown frequency.

 

[LittleInch]

A lot depends on how sophisticated the control system is. If it won't turn down beyond 25% then you could end up venting a lot of steam.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

For liquid burners, poor atomisation of the liquid stream could also lead to poor combustion, soot and maybe even likelihood of explosion with accumulation of uncombusted liquid fuel. If your upper limit is 900kg/hr, change out the burner for a rated capacity of 1000kg/hr with a 5:1 turndown capability. That is, assuming you cannot modify to add an auxiliary low range burner or vendors cannot offer to change out this existing burner to enable a 12:1 turndown.

 

[crshears]

Maybe I'm missing something, and perhaps ultimately it doesn't make a difference, except to operating cost...but why fire a boiler with something certified as Diesel fuel? Or did you simply mean oil-fired? There is after all a price attached to guaranteeing a cetane index for a fuel, not to mention a much higher degree of cleanliness, freedom from moisture, and so on; generally speaking, boiler fuel systems tend to be a bit more forgiving than Diesel engine fuel systems.

OP reads "diesel burner is" which I take to mean there's only one; if that is in fact the case, since 900/200 = 4.5, you clearly have to achieve a greater turndown ratio, something in the order of > 6:1, so you will neither overproduce steam at minimum consumption rates or be unable to maintain steam pressure at maximum consumption rates. If the BTU rating of the burner is too great, what LittleInch and chicopee said; repetitive burner cycling on and off will waste energy in unnecessary purges, thermal cycling will fatigue the refractory, etc., etc.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[chicopee]

A lot of people can actually use #2 fuel oil as diesel fuel in their vehicles which is against the law in the USA; in the case of the OP it is either terminology or perhaps due to compatibility between both fuels, diesel is actually used which I doubt.