# case study on effects on performance of dry ash conveying without using air drye

Questions & Answerscase study on effects on performance of dry ash conveying without using air drye
Cas Staff asked 4 years ago

If we do not use an air dryer with our transport air compressor, which is used in dry ash piping conveying system, what are the problems that can arise in the conveying system?

Site location is nearer to coastal region and RH more than 70.

Cas Staff answered 4 years ago

Hi Sam,

First, I am no expert in dry ash conveying systems. But I can say you will probably not have any problems with condensate water in your application.

I assume the following, please correct me if I’m wrong:

* The dry ash that you are conveying is hot ash, around 150 degrees Celsius
* The compressed air leaves the compressor at about 50 – 60 degrees Celsius
* The compressed air at the end of the conveying pipe is 30 degrees Celsius and 1 bar (atmospheric pressure).

Why no condensate problems? Let me explain.. To understand, you need to know three things:

1) Wet air condenses when the Relative Humidity (RH) reaches 100%.

2) When compressing air, RH rises. When de-compressing air, RH falls.

3) When cooling down air, RH rises, when heating up air, RH falls.

Above 3 points are basic physic laws.

The compressor sucks in wet outside air (RH 70%). The air is compressed and cooled (normally in an compressor after cooler, built-in in the compressor).

* 5 – 7 bar
* 50 degrees Celsius
* 100% Relative Humidity

(by the way, in the after cooler of your compressor, a lot of water will condense. This water is removed by a simple condensate trap.). This means that the water leaving your compressor has 100% Relative Humidity, in other words, it’s on the edge of condensing to water…

Now, when you use this air in your dry ash conveying system, two things will happen:

* the compressed air will heat up because of the hot ash

* the compressed air will expand in the conveying pipes, until it ultimately reaches the end of the pipe and is blown off to atmospheric pressure.

Both things work in our advantage: the heating up of the compressed air will lower relative humidity. And the expansion of the compressed air will also lower the relative humidity.

So both things work to your advantage and will actually create (very) dry air. For this reason I think you will have no problems with condensate water in your conveying system.

Good luck! If you have any more questions, please let me know.

disclaimer: this is my personal opinion, I cannot be held responsible for any problems or costs.