1 reply to this topic

[ryn376]

We have a vacuum rotary dryer (even though I said exchanger above, the question is relevant for both) where steam is being sent to the agitator. Due to temperature sensitivity of the product, the maximum temperature to the agitator can only be 250F (15 psig). We have steam at 120 psig in the plant and we need to get it down to <15 psig. The vendor suggested that we may need a desuperheater in this situation. I realize that if we assume isenthalpic expansion from 120 psig to 15 psig that the temperature would be ~307 F. But how important is the desuperheater. Can we just put the regulator slightly farther away or assume that the condensate inside the agitator will make it superheated (dropping the temperature)?

[IGC]

I mean, a basic desuperheater is water injection into the steam line to bring it down to temperature.  If your product is really sensitive to maximum temperature, surely you'd want to make sure you stay below the maximum temp?

 

If you put the regulator further away then you run the risk of condensing in the line which could lead to water hammer.  

 

Wouldn't the amount of condensate be reduced in the dryer if you are supplying hotter steam?  You could also end up with hot spots on the wall of the dryer then.