Steam boilers optimization strategy

[MedicineEng]

Hello everyone:

We have 3 steam boilers in our plant and right now we are struggling on setting up a proper optimization strategy.

The challenge is that one of the boiler is roughly double the size of the other 2.

When the boilers are the same size, a lead/lag strategy is relatively straight forward and equalizes the working times of each boiler, but when capacities are different the situation changes a little bit.

The boiler manufacturer established the cut it/cut out settings but after a period of analysis and observations, in some of the days we had boilers starting around 150 times in a 24 hours period. This is a recurrent situation.

Clearly the optimization strategy is not working, but the boiler supplier doesn't seem capable of providing a better one than the usual lead/lag with the poor results stated above.

Any ideas how can we optimize the system and reduce the huge amount of cycles in the boilers?

Thanks.

 

[GenB]

Are the burners modulatng? And what's the capacity 4:1 or better? What sizes are the boilers, what pressure trim and operating? What's the use flow in %, it looks that you have on.off operation. As it can be difficult, there are ways to improve performance.


General Blr. CA,USA

 

[MedicineEng]

GenB:
Yes, the burners are modulating
Boilers are 2x 1000KW and 1x2000KW.
Lead is working with a pressure setting of 8 bar with a hysteresis of 0.2
Lag 1 kicks in at 7.7 bar with a hysteresis of 0.5
Lag 2 kicks in a 3 bar with a hysteresis of 0.5

 

[chicopee]

Are these boilers for heating or process? Is their turn down ratios 4:1 or 10:1?
I remember a school district in which some of their heating boilers were cycling repeatedly and one solution was to reduce their firing rates and nozzle sizes.

 

[MedicineEng]

These boilers are for heating purposes.
I don't have the information regarding their turndown rations here with me.

I'll have to see the O&M manual for the boilers.

 

[chicopee]

You may want to look at reducing their firing rates first. The manuals should have some say on how to do that. Also contact the manufacturer of the burners for same information.