Heat Recover Steam Generator (HRSG) Ramping Rate

[norzul]

Hi,

We just procured 4 HRSGs for our cogen project. It has supplementary firing (SF) capabilities. Without firing the production is about 50 ton/hr. With SF, 95 t/h. The ramping rate is 15 ton/hr per minute. Is this quite typical for this size of HRSG?

I've checked our existing boilers (MCR=105 ton/hr), the ramping rate is 20 ton/hr per minute. Puzzle me, coz all the while I thought the ramp rate for HRSG should be higher than the conventional boiler..???

Any advise?

Thanks

norzul

 

[norzul]

Hi,

Any info on this...??

Thanks

norzul

 

[davefitz]

norzul,
The ramping rate permitted by a boiler will vary depending on (a) the fuel fired (b)whether it is operated at constant or variable throttle pressure and (c) if the outelt steam is saturated or superheated.

You had indicated that your existing boilers can operate at a ramp rate of 20% MCR/minute. That is very fast. I assume they are oil or gas fired and operate at constant pressure and output saturated steam. If it outputs superheated steam, I would expect a lower limit on the ramp rate of 10%/minute. A variable pressure boiler with superheated outlet steam might have a limit of 5%/minute, and a lower limt if the max permitted deviation in main steam temperature was limited to +- 6 C.

 

[norzul]

TQ Davefitz,

I tend to agree with yu. But the ramping rate that I quoted was based on the actual boiler equipment datasheet. Our boiler is gas fired, producing steam at constant pressure (40bar+405C) and off course superheat.

Thanks

norzul