4 replies to this topic

[NDJH]

Hey all,

We are about to commence commissioning of a Blow Case to Liquid Burner system using condensate. Condensate will be pressurised up in Blow Case and discharged to burners where liquid will be atomised at the burner tips and burnt (well thats the theory!).

Does anyone have experience with this operation? The last time the burners were used (pump transfer back then now Blow Case) burning liquid rain was observed. Obviously this is not wanted again.

Secondary issue - any tricks to reduce black smoke when burning condensate- considering only variable to play with really is the Blow case pressure.

many thanks

[JMW]

What is the viscosity of the condensate? and what is the optimum viscosity for the burner tips?
If the fuel is at all viscous then it may require heating to reduce the viscosity to the required value in which case the heater is controlled by measuring the viscosity of the fuel as it flows to the burner.
When the fuel passes through the burner tip it is supposed to atomise such that the optimum drop size and dispersion occurs. If this is correct then the droplets will disperse well and mix well with the air flow and will burn as completly as possible where it is intended to burn.
If the viscosity is too low then the droplets formed are very fine but they do not disperse well nor mix well with the air and therefore they tend to burn slowly, incompletely and in the region of the burner tips.
If the viscosity is too high then large droplets are formed which project across the combustion chamber and burn on the boiler tubes. AGain, poor mixing with the air flow and incomplete combustion.
In older style burner plant fuel samples are regulalry and routinely analysed to try and establish the EVT (Equi Viscous Temperature) which is the temperature at which the optimum viscosity is achieved (necessary because of quality changes), the EVT is then used as a set-point for temperature controlled heating. In this type of operation excess oxygen is used and visual flame inspection is also a necessity. Modern viscometers will handle even the dirtiest of oils and the resultant combustion is generally far more efficient and less polluting.

[NDJH]

Thanks very much for the response.

Our Basis of Design documentation does not state an optimum burner tip viscosity. It states that the system (blow cases and burners) can handle a range of fluids of differing density i.e. LPGs, condensate and seal oil etc..

It also states that the only requirement for atomisation is to have a back pressure of 2.5 bar at the burner tips. To me it seems like a big call that the back pressure is the only requirement necessary.

I had a feeling also that fluid properties (such as viscosity) would be significant. The viscosity of our condensate is approx 0.42cP. We are tied to this viscosity as our vessels dont have heat transfer capability.

Can you point me towards any literature on liquid atomisation?

cheers.

[Art Montemayor]

NDJH:

I have burned a lot of fuels around the world in my time. And the one burner I always had very good results with was the Hauck Burner. Their website is:

http://www.hauckburner.com/press.asp?ID=21&DB=press

I have burned the same quality of condensate that you describe with only mechanical atomization - and no problems. I generated steam with it and also used it in a direct-fired heater - again with no problems.

[NDJH]

NDJH:

I have burned a lot of fuels around the world in my time. And the one burner I always had very good results with was the Hauck Burner. Their website is:

http://www.hauckburner.com/press.asp?ID=21&DB=press

I have burned the same quality of condensate that you describe with only mechanical atomization - and no problems. I generated steam with it and also used it in a direct-fired heater - again with no problems.

Hi Art,
Thanks for the reply and useful information. Your response has given me abit more confidence in what we are about to undertake.

Our liquid burners are from Kaldair Limited and were installed in the 80s and have only been used once - unsuccessfully.

However, this was probably due to insufficient back pressure at the tips which prevented atomisation.

thanks again.