Good Day Dan

Assuming you want to aerate all the pads simultaneously, I would recommend a Roots blower, size 404 RAM-J. It would need a 20-25 HP motor. This will also handle an additonal 2 psig which you want for your PRV setting.

You can contact John Kolcun at R&M equipment, 610.495.9700 or e-mail JohnK@ramequipment.com for the details and prices.

Regards ■

With all due respect to Mr. Hauch -- Cement has been aerated and handled for a long time and there isn't much those of us who have spent a great deal of time in a cement facility don't know about it.

Why make your production plant into an R&D lab if you don't have to.

1 f/sec for Cement is a complete overkill and only costs you more money than you need to spend. ■

Minimum fluidization velocity (Umf) for standard cements is about 0.025 ft/sec. The amount of air that is introduced through the aeration pads must not fluidize the material in the bin. I generally use 1/4 of the Umf for this purpose. I also provide flow control at each of the aeration points to enable monitoring and adjustment.

Regards,

A. T. Agarwal

Consuting Engineer

Pneumatic Conveying Consulting Services

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Dan

Your application requires the right combination of air volume and pressure.

The blower recommended in my original post includes both the correct air volume and pressure rating for cement aeration pads in a silo.

Regards ■

Dan,

I gave only the air velocity in my last post. You can calculate the total air flow in cfm based on the cross sectional area of the bin.

For calculating the air pressure, I use the height of the material in the bin x the bulk density of the material. This will give the air pressure in lbs/cu ft.

Hope it helps.

Regards,

A. T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services

Emailolypcc@aol.com

Ph and Fax: 304 346 5125 ■

Dan

The bulk density of Finished Cement (OPC type) is typically 85 pounds per cubic foot. Taking this value times your material height results in a "break through" pressure per the following;

Height = 10 feet ............ Pressure equals 6 psig

Height = 20 feet ............ Pressure equals 12 psig

Height = 30 feet ............ Pressure equals 18 psig

and so on.

Pressure is not rated in pounds per cubic foot.

You haven't mentioned your bin height but I assume it's in the 20 to 30 foot range, maybe more?

A positive displacement blower usually has a max pressure differential of 15-18 psig but we typically never design an aeration system to break through the material head above the pads. Aeration blowers are usually in the 5-10 psig range for the application you have.

Aeration pads and air slides operate on the principle of fluidizing the material above the media to break the material friction and therefore encourage flow by gravity.

Give me an e-mail to my address below and I can make some more specific recommendations for you if you would like.

Regards, ■

Dan,

If the total pressure drop exceeds the pressure rating of the Roots lobe type blowers, I then use plant air for the aeration pads. Since plant air is generally at 100 psi, I use a pressure reducing valve to turn down the pressure.

Regards

Amrit T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Compressing air to 100 psig only to pipe it to a distant silo and then reduce the pressure to significantly less doesn't seem like a prudent thing to do.

Also - Care must be taken because plant air typically has moisture which will immediately plug the aeration devices and cause problems in the silo. ■

Using a new blower or an existing source of compressed air should be made on the basis of a process and cost study for the required air flow and air pressure. If the pressure exceeds the maximum rating of the Roots type blowers, other more expensive options for compressing air for the aeration pads such as screw compressors also are available. But the capital and operating cost of these will be much higher than that of using air from an existing air compressor, especially because the air flow requirements will be relatively small.

Regards,

Amrit T. Agarwal

Consulting Engineer

Pneumatic Conveying Consulting Services

Email: polypcc@aol.com

Ph and Fax: 304 346 5125 ■

Whether you use an existing compressor or a new unit, compressing air to 100 psig only to use it at 10-15 psig does not make sense. ■