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Gentlemen, I have been tasked with a job and I am at a loss as I have never had to direct offload cement and lime kiln dust directly onto a sludge lagoon scheduled to be stabilized/solidified.

The site is in a remote rural area with no room for storage silos or feed equipment, although the specifications do call for such equiment and accurate measurement of S/S reagents. The only viable process is to direct offload pneumatically from the delivery trucks and treat the desired treatment cells. Distance to the cells is not an issue as it will be 50-75 m at most. My problem is the determination of cement and lime kiln dust delivered to the cells. Is there a method to measure or at least approximate the feed rates and total mass being delivered from the trucks? Measurement is critical as too little or too much reagent will be detrimental to stabilization or the budget... Dust control will be the next challenge.

I suppose we could weigh the trucks before and after delivery, but it is a remote location and I have no idea how far I could find truck scales. This approach would not provide "real-time" measurement, and would mandate adjustment of the sludge volumes to be treated depending on the total mass of reagents delivered. Are there any other options?

Thanks in advance from a bulk conveyance neophyte.

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Felix,

You can calculate the weight of material transferred by the pneumatic conveying system from the energy used for this transfer. For this calculation you will need to first calculate the blower power consumption using the conveying pressure and air flow. The second calculation will then be to co-relate this power consumption to the solids flow rate.

Regards,

Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting

Charleston, WV, USA

Email: polypcc@aol.com

Ph 304 346 5125 ■

Dear FelixM,

Unloading pressure (or power) is not a reliable indicator for the unloaded mass of cement.

This parameter changes with the conveying length and with the set rpm of the on board compressor.

However, there is a much easier method, which is used by all the cement bulk trailer drivers that I have met.

When the cement bulk trailer is loaded, the loaded cement mass is measured by the weigh scale at the loading site. (basis for the invoice)

The trailer has air suspension on the rear axles.

The pressure in the bellows is a direct and proportional measurement related to the cement mass in the tank plus the weight of the trailer itself.

The difference in wheel suspension pressure with an empty tank and the wheel suspension pressure with a loaded tank with a known load represents the loaded cement mass.

When the suspension pressure is decreased f.i. to (pempty + ploaded)/2 , half the loaded cement mass is then unloaded.

Or:

When the suspension pressure difference is decreased f.i. to (ploaded - pempty)/3 , two third of the loaded cement mass is then unloaded.

Requirement is that the unit has air suspension on the rear axles. A manometer (if not already installed) is mounted easily.

Estimated inaccuracy can be approx.10%.

Have a nice day

Teus ■