firing diesel oil with atomising steam

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FPSO
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firing diesel oil with atomising steam

Postby FPSO » Wed Apr 13, 2011 2:43 pm

I know that diesel oil shouldn't be fired in a boiler using atomising steam, but why not?
Can someone give a proper explanation?

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JollyJack
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Re: firing diesel oil with atomising steam

Postby JollyJack » Thu Apr 14, 2011 10:02 am

I don't know why anyone would use diesel oil in a boiler. Todays cost of MGO in Rotterdam is $1027 a tonne, down from $1065 on the 11th. IFO 380 is $641 today, down from $660 on the 11th.

However, may I refer you to Reeds Steam Engineering Knowledge, Vol 9, page 54, which says, in part,

"Fig 1.31 shows the business end of the relatively recent Y-jet steam atomising oil burner that is finding increased favour for water tube boilers for the following reasons:

1. Deposits are greatly reduced, hence soot blowing and water washing of the gas surfaces need not be carried out as frequently as before. (18 months or more between cleaning has been found possible)

2. Atomisation and combustion are greatly improved.

3. % CO2 is increased (% O2 reading has been lowered to 1% or below) hence boiler efficiency is greatly improved.

(My note, great for Inert Gas systems on tankers)

4. Atomisation is excellent over a wide range of loads and the turn-down ratio is as high as 20:1 and above.

5. With improved combustion and turndown ratio, refractory problems are reduced."

The differences between IFO and MGO as a boiler fuel, apart from price, are sulphur content and viscosity. Sulphur in MGO is generally less than 0.05%. The cost of 1% Sulphur IFO380 is currently $703 in Rotterdam, slightly more that the cheaper stuff at $641. 1% sulphur fuel will be mandated by MARPOL Annex VI by (I think, without looking it up) 2015. Steam atomising reduces the need to lower viscosity to 11 CTS, so you don't need to use nearly as much steam to heat the stuff, it can be blasted in at (eg) 180CTS, as long as it can be persuaded to flow. (you need to heat IFO 380 to around 135C to get 11 CTS, but it will flow well enough at 50 C)
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Big Pete
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Re: firing diesel oil with atomising steam

Postby Big Pete » Sat Jun 18, 2011 12:42 pm

Professor Thompson of Newcastle University did a lot of research on burning various liquid fuels emulsified with water in boilers and engines and found increases of efficiency of 10 to 15% reductions in surplus air required and improved emmission levels, & less carbon deposits. Unfortunatly he found very few people willing to take up the idea. I heard a lecture by him in Sunderland about 30 years ago, while attending South Shields College for my extra Chiefs. Fascinating stuff.
There were some thoughts that the water droplets emulsified in the oil "exploded" in the heat of the engine/boiler. performing a secondary, much finer atomisation of the fuel, and also a possibility that the water was involved in an intermediate combustion stage before all the Carbon was burnt to CO2 and all the Hydrogen to H2O. for instance high temperature water molecules can dissassociate back into Oxygen and hydrogen, the released Oxygen could then burn the carbon in the fuel and the free Hydrogen later burn in the combustion air, lots of theories.
However, he got practical results.

I am not sure why you shouldn't use atomising steam in a Diesel oil fired boiler, but i have never sailed with steam atomisation so I wouldn't know!! Soeone else out here shoud though.

With regard to burning diesel oil in boilers, it has been mandatory in all European Union Ports and anchorages to burn fuel with less than 0.1% Sulpur since 1st January 2010, in both boilers and generators.
It is also Mandatory to burn low Sulphur MDO or MGO in Californian Ports and at Sea off the coast.


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JollyJack
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Re: firing diesel oil with atomising steam

Postby JollyJack » Mon Jun 20, 2011 6:15 am

Canada has ratified Annex VI (clean air) of Marpol and as from 12 August 2012, it will be illegal to burn fuel with a sulphur content of more than 1% within 200 miles of the east coast of Canada and the USA.
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carbob
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Re: firing diesel oil with atomising steam

Postby carbob » Sun Oct 02, 2011 8:01 am

I don't think it is a question that you shouldn't fire diesel oil in a boiler with atomizing steam, but rather, why would you? The whole idea of the steam atomizing is to break up, atomize as it were, the incoming fuel droplets for better ignition of the boiler's normal heavy fuel oil. With diesel oil, this level of atomization is not really required.

We use atomizing steam burners here (top-firing Mitsubishi MAC-25 boilers), and for cold firing, you have no choice but start the boilers firing on atomizing air. Once you have pressure on the boiler, you change over to atomizing steam and then change-over to HFO. So the firing period for diesel on steam is very short, cost prohibitive otherwise. Unless you are trading in an ECA and have no choice, but then you would probably fire with atomizing air methinks.

Don't know if this helps.

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Re: firing diesel oil with atomising steam

Postby hamal » Thu Oct 06, 2011 9:31 am

In European or selected U.S. ports you have to run the boiler on LSMGO or MDO with atomizing steam. I have done the same with Mitsubishi and Volcano burners without any issue. The atomizing air is used when the atomizing steam is out of order / pressure range (cold starting or steam pressure loss).

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Madzng
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Re: firing diesel oil with atomising steam

Postby Madzng » Mon Nov 21, 2011 7:55 am

My first post in a while.. have read through this topic and want to add the following;

I have attached an information sheet sent out by Aalborg a couple years ago, this should be useful information for the operation of any boiler burner on distalate fuel. The leaflet also touches on why steam should not be used with these fuels.

I think the biggest reason for not using atomising steam with distalate fuel is the flash point.

7 bar saturated steam is approx 165 degrees C, based upon current legislation the minimum flash point for these types of fuel is 60 degrees.

As Carbob said, in the past there has never been the option to use atomising steam when flashing up the plant from cold, now we have to run the boilers in ECA areas on distilate. I hope we dont hear of any disasters where people have ignored these old warnings and continued to use atomising steam.

As the global demands for diesel increase the flash point will become closer to that of automotive diesel (55 degrees C). Several flag states, owners and Class societies are investigating the implications of reducing the minimum flash point of fuels used down to this automotive limit of 55 degrees in order to prevent the big squeeze and inevitable price increase put upon the industry by the oil majors.

Check the regulations, check your boilers and dont wait until the last minute before consulting your boiler maker for any available safety modifications. Dont assume that because you dont have a steam atomising burner that you dont need to modify or change procedures when running your boiler on distilate fuels.

Hope that this helps..

The lowering of the minimum flash point of fuels used in engine rooms could be a whole topic in itsef. Any points of view?
Attachments
12-FuelchangetoMDOMGO-09JAN09.pdf
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carbob
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Re: firing diesel oil with atomising steam

Postby carbob » Mon Nov 21, 2011 2:02 pm

Just as an aside; earlier this year, I went to the boiler manufacturer (Mitsubishi) to see if they had sprayer tips with smaller holes for use with LSMDO/MGO. The sprayers we have in service now could pass coal through them! The quote that came back included parts for the atomizers, sprayers, limit switches, and flame eyes, and a service engineer to reprogram the Boiler Control System, $167,500 USD. I only asked for a couple of sprayer tips..............

Needless to say, this was knocked on the head. Hopefully, I won't have to produce the paperwork for an inspector of we fail an emissions test.


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