First of all, it is better to indicate the required dryness of the air by the dew point temperature at a certain pressure.

In your case, where you are applying a roots blower, the pressure can be maximum 1 bar(o) # 2 bar(a)

Depending on the required dryness there are options in this order:

-cooling the compressed air at the given pressure and draining the condensed water. The RH is then still 100% and the amount of resdual water vapor is depending on the cooled temperature.

-freezing cooler, suitable to a dew point of 3 degrC. (Just above freezing).

As the air is heated up after cooling, the RH stays below 100%

-Adsorption dryer, suitable for dew point temperatures to even -70 degrC, resulting in very dry air at ambient temperatures.

Example:

Ambient air:

Temperature = 40 degrC

pressure = 1 bar(a)

RH = 100%

Compressed air:

dew point temperature -30 degrC

pressure 2 bar(a)

RH = 100%

Airflow 5000 cfm # 9000 m3/hr

Condensed water mass = approx. 458 ltr/hr

Heated to ambient temperature of 40 degrC, the RH becomes approx. 0.4%

Have a look at:

href="http://productpagesct.atlascopco.com/ProductPages.asp?MASTER=PP%20MASTER%20MD&Lng=EN&Country=US" target="blank">http://productpagesct.atlascopco.com...=EN&Country=US

Have a nice day

Teus

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dryair (PDF)

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Hello LF Pumping Dryer,

Teus is absolutely on the correct track to stear you toward defining the inlet and final conditions in terms of pressures, temperatures and RH, Dry and wet bulb values. You will have a much better chance in getting someone to quote you a suitable dryer.

Now, having said that, I can share a little experience with drying air, or gas in low pressure systems. As a rule of thumb inlet drying is very expensive as any device that either cools and then drops the water out or any absorption molecular type dryer will incur pressure losses. At inlet conditions that will make them very large since a typical position displacement blower or compressor will want no more than 50mBar pressure drop.

When you look at the blower discharge the world opens up a little. Here both technologies become more managable and less expensive. If you have chilled water try using a water cooled heat exchanger followed by a water trap. You can hot rod this combination by placing another heat exchanger into the system and put steam into the coils. This raises the temperature and thus also lowers the moisture value. Here is a link to a company that has helped me in various occasions with custom cooling and drying applications. Ask for Paul Boedecker, he is an expert at this. http://www.xchanger.com/productstv.htm

The other road is using a dessicant type adsorption dryer. This is commonly used in the compressed air treatment of shop or plant air world and there are many manufacturers out there who can help you. They usually are still quite large and consume a bit of power as one of two bottles is always in active use while the other one dries out by heating it up.

Good luck,

Ralf ■