Air Swept Tubular Dryer

[Locar]

My small company recently purchased an Air Swept Tubular dryer for drying a product from 70% solids to 99.5% solids. Downstream of the dryer is a bag house/dust collector. The exhaust fan has VFD that operates at whatever amps are necessary to pull the desired vacuum. A debate has started internally about the most energy efficient way to operate the dryer. Side A maintains that the exhaust fan should pull the minimum amount of air possible across to do the job and not cause condensation in the dust collector. This mean heating as little air as possible. Side B maintains that is less critical, since with the water "boils off" it undergoes a large charge in volume and the exhaust fan doesn't care what it moves to pull the vacuum.

Can anyone offer any guidance in how to calculate which side is right? Or does anyone have experience with this type of dryer?

 

[rmw]

It seems like you are asking two questions.

The fan is going to pull whatever it gets to maintain the vacuum it is asked to control, assuming it is properly sized to get the job done.

On the other hand, whatever it gets from the process is going to have a substantial amount of water vapor mixed with the air, so if condensation in the baghouse is a problem, it is going to be there whatever.

It looks to me like your problem is trying to determine what is needed to be accomplished. The fan should pull no more flow than that actually required to dry the material which will mean that moisture flows through the baghouse to the fan. Pulling anything more than that is wasted horsepower. Any less is insufficient drying.

Am I missing something?

rmw