Re: Pneumatically Conveying Of Ultrafine Caco3
Joe,
I had done a cost comparison of dilute Vs dense phase conveying of CaCO3 sometime back, based on Net Present Value. This study concluded that dense phase was more economical. Investment for dilute phase was about twice than that for dilute phase, and the operating cost was about the same considering both utilities and maintenance costs. Solids to air ratio for dense phase was about 20 Vs about 5 for dilute phase. This ratio offset the higher air pressure needed for dense phase with higher cfm needed for dilute phase.
In addition to economics, system performance also is a critical parameter for decision making. Low velocity and much less air flow improves system performance by reducing product aeration problems at the receiving end and in the body vent of the rotary valve used as a feeding device.
My recommendation would be that you use dense phase.
A. T. Agarwal
Consulting Engineer
Pneumatic Conveying Consultants
polypcc@aol.com
www.powderandbulk.com/pcc ■
Carbonate Blowing
I agree, dense phase is your solution.
We have designed (and redesigned!) carbonate blowing lines and dense phase is more energy efficient if designed well. But in reality, I don't think energy efficiency is your main concern - the difference is not staggering. Better, faster deaeration before packing will reduce your operating costs and that is more important!
However there are some pitfalls:-
1. You should purchase a dedicated compressor providing air at a pressure just above that which you need for conveying, because if you take the air from the plant main or a standard 7 bar machine then let the pressure down through a regulator and choked flow nozzle, you are throwing away most of the energy before it gets to the pipeline - so your net energy usage will be much higher than lean phase. Most system suppliers will encourage you to use plant air, because that way their quotation does not include a compressor so the system looks cheaper to buy and they are more likely to get the contract!
2. You should use a stepped bore pipeline - increase in bore size along the length to compensate air expansion as pressure falls - for best efficiency and minimum plug velocity at the end.
3. Watch the blowdown - the emptying of the high pressure air from the tank aloong the pipeline at the end of the blow! This is a high velocity lean phase operation and if not properly controlled, will undo all the advantages!
4. Be careful of the entry of the pipeline into the receiving hopper - proper choice of geometry is critical here!
There are other pitfalls as well, but if done properly it will control your problems. Our handbook on pneumatic conveying might help you or maybe we can talk. Drop me an email on bm08@gre.ac.uk
Mike. ■
Densphase Conveying Ultrafine Caco3
At Clyde Materials Handling, have conveyed a lot of CaCO3 in many different grades both by dense phase and medium or two phase. For your short distance low tonnage requirement our regular densPhase Pump system would be fine. We could convey either capacity in a 3' pipeline with solids air ratio in the 20:1 region.
If areation of the material is a particular problem, we could look at full pipe conveying, which has a slightly higher capitol cost but potentially uses less conveying air since the conveying pipeline remains full, there is no blowdown as mentioned by one of the other respondants, unless the system must be emptied for maintenance or product change etc.
If you would like us to quote the system for you please contact me at (513) 576 9200, or email gcooper@clydematerials.com
Regards,
Graham C. Cooper ■
Clyde
Good to hear from you guys.
I hope everything is fine in Doncaster. if yow run into wear issues call me.
marco ■
Energy Use In Kwh By Loading Rate Μ.
Energy reduction with patented automatic by-pass valve;www.q-engineering.com ■
Pneumatically Conveying of Ultrafine CaCO3
Hi there,
we are installing in the near future a plant extension for the ultrafine grinding and classifying of CaCO3.
The final product has to be conveyed pneumatically from the filter to the final product silos. Actually we use dilute phase systems but the finer the product the more problems we get with aerated product, especially at the packing stage.
That's why I thought about dense phase.
Dense Phase in my opinion consumes more energy as Dilute Phase because we have to provide pressure air which is expensive. This is only a feeling and so I would like to ask whether somebody could give me out of his experience an energy estimation for both systems and more important some pro and cons for ultrafine CaCO3 and the different conveing systems.
Our final products will be:
a) 700kg/h of 98%<3micron
b) 3000kg/h 98% < 10micron
The distance is approx. 50m and the height approx. 30m.
Thanx a lot
Joe ■