Re: Lime Conveying Best Practice
Expansion chambers are used to slow down the terminal velocity of the conveying system to help with air / material separation. If you do away with the chambers, you risk overloading the vent filters if the lime silo is full.
There are simple designs for expansion chambers which are also wear resistant designs.
The build up from moisture can be eliminated either by using an effecient design of air lock device to prevent the moisture from migrating upstream or putting a vent system on the causticizer to pull off the damp vapors.
Hammertek elbows are just one of many designs available to replace traditional long radius sweeps in a conveying system. ■
Re: Lime Conveying Best Practice
Hello Jack
Thank you for your reply. Can I trouble you again or anyone else for some further advise:
1) How can we mitigate risks of overloading the vent filters if we do away with the expansion chambers?
2) Can you lead me to some good wear resistant designs of expansion chambers?
3) How do you compare the reliability of air locks to air vents? By air vents I assume you refer to wet scrubbers as simple pipe vents are known to get blocked by moist lime.
4) Can you lead me to some good air lock designs and technical info including reliability and maintenance requirements?
Regards
VJKumar ■
Re: Lime Conveying Best Practice
The simplest and often best form of expansion chamber is a simple pipe discharge box where a horizontal section of pipe is cut away on the bottom and the pipe is expanded to a larger width and length so the outlert os approximately 0.7m x 0.9m or something similar. This forms a radial type of design which is very good for abrasion resistance.
To avoid flter overload, the filter can be raised from the roof of the silo or internal baffles can be fitted which means the height to which the silo can be filled may be limited. The total layout should be reviewed in light of the silo diameter, fill pipe location, filter size, etc.
There are no doubt many equipment suppliers who suscribe to this forum and will be happy to offer their hardware as suggestions to your application.
If you wish, you can e-mail me directly to my address below and I can give you some specific recommendations if you wish.
Wet scrubbers is one solution to removing the moisture and I believe venturi scrubbers are another choice.
Regards ■
Lime Conveying best practice
The lime system at Kwinana has a number of problems contributing to lime spillage. Dry lime from delivery truck is unloaded into silos using compressed air. Lime travels throgh piping and into an expansion chamber then via air gravity conveyors into a main Tank. This is later transferred into a Day Bin using an air lift through similar expansion chambers and air gravity conveyors.
PROBLEMS:
Dust collector located on the Day Bin does not work properly and may be undersized.
Lime spills through holes in expansion chamber, and other high wear areas including bends.
Lime spills through vents
Possibility of lime spills through straight sections of the piping
Dry lime from the Day Bin is transferred through screw feeders then through screw conveyors into the Causticiser Tanks.
PROBLEMS:
The hot vapours in the causticiser tank causes a positive pressure and moisture backs up into the screw feeder
The screw feeders frequently block up due to moist lime built up
The conveyor trough fills with lime while the screw feeder operates causing covers to dislodge and resulting in lime emissions.
Wet scrubbers on the Causticiser tanks have been removed due to maintenance issues.
We have done some investigations and found that expansion chambers are not typical equipment. Some refineries are using Hammertak elbows instead at bends. Can we do away with the expansion chambers? Any comments on the maintenance problems with the wet scrubber ? What type of equipment or design changes is recommended for this system?
VJKumar ■