Quicklime
Rotary valves can be designed to operate at 250 C which would accommodate the one-pipe system that you described but it would certainly not represent the most cost-effective solution to your problem.
Three small(er) stand-alone systems provide more operational flexibility, no question. Depending on the material flow properties there are several possibilities for three-pipe systems:
1) Pressure dilute-phase conveyance using solids eductors (no moving parts). This approach would save not only on installation costs but on maintenance costs as well.
2) Vacuum dilute-phase conveyance. The conveying air must be filtered and cooled before entering the blower suction.
3) Dense-phase conveyance using a blowtank. Blowtanks mean batch transfer, the choice here would be a single tank or twin tanks (in parallel or in series).
Regards,
Dennis Hauch ■
Quicklime
I agree. Eductors are used to move free flowing powders, chips and aggregates at temperatures exceeding 1000 degrees Centigrade. Eductors have no moving parts, are self feeding, create a negative pressure at the product inlet, can suck material from a pit and can be generally trouble free in operation. ■
Quicklime
I have attached a drawing of an eductor.
Attachments
eductJPEG:forum_attachments/file_container/educt.jpg (BMP)
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Multiple pick-up points
We are providing layout work for a dilute phase pneumatic conveying system to carry quicklime fines from 3 kilns.
The quicklime will be screened after exiting the kiln. The temp of the quicklime fines will be about 250 C.
The density of the quicklime fines is about 50 pounds per cubic foot.
We want to use one conveying line to pick-up the fines from the three kilns. The kilns are in a straight row, on 60 foot centers. The carrying pipe will be a nominal 6 inch. The flow velocity will be about 5000 feet per minute.
We will put a rotary airlock on the pipe at each load point, with a vent to handle any carry-over air from the conveying system.
The conveying rate from each kiln screen for fines is 6666 pound per hour, for a total from the three at 20,000 pounds per hour.
Can we simultaneously pick up from the 3 points (each feeding 6666 lb/hr), or do we need to stagger the feed times (by putting a surge hopper with level controls between the screen and rotary airlock, and each feeding then 20,000 pounds per hour on their cycle.)? ■