Boiler 'Attemperation'

[Raai2015]

Hi all , We have the boiler desuperheater control by Multiple nozzle desuperheater valve. I got a offer from two reupted supplier. Below are some details on design case.
Spray flow : 3,11tph
Spec density : 0,95
Cv @ 80% opening : 6,78
Dp offered : 0,3 bar
On the above i calcualted the DP , it was around 0.2 bar. Below are some opinions needed.
1, Both the suppliers give DP across the load same 0,3bar but with different CV --> My view is Different Cv (different opening) results in different DP in principle. May be they specify the max 0.3 bar in all load cases.
2, Interesting for me : this kind of valve (multiple nozzle) suppliers requires atleast 5 bar above the steam line. I was under impression 5 bar will the DP across the multiple nozzle valve. When they have 0,3bar DP across then why do they every time require 5 bar DP atleast?
3, I read somewhere , weber number is the indication of atomization and it needs to be above 12. Does anybody have calcualtion (Dr google is not much helpfull this time) of weber number?

 

[hacksaw]

Engineers don't offer opinions, there focus is on design, safe, reliable design, in compliance with establish standards where they apply,

opinions may be gotten from the street corner outside your office,

good luck,

 

[Raai2015]

hacksaw, But their technical bulletin says min 5 bar atleast. this i have written to them to clarify. but by chance any weber number calcualtion is available?
reg
Baskar

 

[Bahador_eshghi]

Hi
I am not an Desuperheater expert but maybe following information be helpful for you:
1- we normally calculate water consumption of desuper heater in several HRSG load cases including the worst case ( maximum flow ) and minimum flow ( as a boiler expert )
2- when steam temperature is at maximum ( normally summer condition or maximum post firing case ) desuper heater water flow will be maximum.
3- due to ability to temperature adjustments of the desuper heaters, minimum flow of water flow happens in a load case with 3 degree c temperature drop.
4- the supplier tries to offer the related valve to over come these high and low flows with an acceptable turn down ratio ( normally 1/30 )
maybe this is related to the pressure drops that you have mentioned.