Ramp rates of chain-grate coal fired shell boilers (saturated steam)

[KleinPete]

Hi All

First post here.

I am attempting to model the dynamic response of two industrial shell boilers that are connected to a single header (1x14.5 t/h and 1x20t/h 10barg). The boilers are typical chain grate and are coal fired. I am looking for some general rules of thumb regarding the ramp rates of such boilers, in order to follow a fairly dynamic load. I have seen numbers of quoted 1-2%MCR/min? Would this be realistic for such shell boilers in both ramping up and ramping down?

I know the water volume and mass of steel in the boiler examples in terms of thermal lag, but I have no info on how fast you can actually ramp up/down the coal feedrate. Any advice would be greatly appreciated


Kind Regards
Peter

 

[goutam_freelance]

The permissible ramp rate is determined by type of drum/tube connection as well as other factors. The manufacturers can give better data.
But for reference for rolled drum/tube connection the allowable temperature change rate is 56 deg C per hour. This is to prevent leakage in drum/tube joints due to differential thermal expansion due to uneven heating.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/

 

[KleinPete]

Thanks for the info. When you mention 56 degC per hour are you talking about the warm-up/cool-down phase for the boiler? Or am I missing something?

If the boiler is already operating under load at a 10 barg setpoint and then the steam demand is suddenly ramped up/down, I am looking to get an idea of how quickly a typical chain-grate firetube boiler in the 10-20t/h range could respond, in terms of steam output ramp rate %MCR/min to balance the pressure again.

 

[goutam_freelance]

Loading rate for PF fired boilers are in the range of 3-5% per minute. Since chain grate boilers will have larger thermal inertia an loading rate of 1-2% MCR/min is a reasonable assumption. But as I said boiler suppliers can give more specific data.

Engineers, think what we have done to the environment !

https://www.linkedin.com/in/goutam-das-59743b30/