Automation of excess steam condenser unit.

[Fahad3608]

Greetings,

We have an excess steam condenser unit that needs to be automated in order to avoid having huge amounts of condensate and effectively utilize the steam's energy as much as we can. Unfortunately, we couldn't due to hammering issue. Please refer to the attached word doc for further explanation, and advice accordingly.

Thanks,

 

[TD2K]

I don't see how you are "effectively utilize the steam's energy", you are just rejecting it to air aren't you?

You said that the hammering starts when you get steam in the outlet condensate line. The LP steam is stated to be 60 psig so the outlet steam/condensate has to be in the area of 300F. The control range is shown as 160 to 200F, is it not starting up additional fans fast enough?

 

[Fahad3608]

Burning fuel to generate steam and then discharge it to condensate through the aforementioned excess steam condensers is not practical at all, the board operator in the Central Control Room CCR is placing the PCV-1 and PCV-2 on MANUAL mode to get rid of the hammering issue. what I have observed is when we place the system on AUTO mode severe hammering will start. I am doubting about the control philosophy and as well what you have mentioned that fans will take time to start. therefore, steam/condensate will appear. I think it is a design issue and we need to resolve it ASAP to avoid this bad practice of wasting the steam energy.

your feedback is highly appreciated

thanks !

 

[TD2K]

I seem to recall an article many years ago about a surface condenser for excess steam that appeared similar to yours that had problems with water hammer and it was addressed by a change in their fan control logic. Unfortunately, I don't recall the specifics or the article and a quick search didn't find anything.

Have you talked to the equipment vendor? Does the equipment data sheet indicate the transient nature of the steam flow and air temperatures? The picture you attached seems to suggest a significant sized unit. Unfortunately, a lot of these units are specified at the design condition and the wide range of operating conditions it has to operate at are not included for the equipment vendor to consider.

 

[Mutt]

Maybe I don't fully understand the system but I would have had the PCV2 upstream of the air coolers. PCV1 would have a setpoint of 60psig and PCV2 slightly higher, say 67psig such that when PCV2 is opening, PCV1 should be about closed. That way you minimise steam waste. You only condense the excess during upsets. You may need to allow constant slip of steam - minimum opening of the PCV1 say 2-3% - to the air coolers to keep them warm so that there is no thermal shock if demand on the LP header can drop suddenly and need to vent for short period until PCV1 closes. A steam trap (or condensate separator) downstream of the air coolers to make sure don't throw steam away will suffice on that side.