Magnetic Separator
Dear Houdeh,
It is necessary to know the magnetic properties of your worn mill balls to make a convenient magnetic circuit from either permanent magnets or electromagnets.We can also give our advises about the conveyor belt needed for this application accordingly.
If you can send a sample to our following address we may propose the most convenient and optimum solution for your problem. We have many, many applications on this subject for cement factories, ceramic and gypsum plants, etc.
Yours Truly,
Mustafa Kemal Yunel
Address: YUNEL ELEKTROMEKANIK Co.Ltd.
CANKIRI YOLU 26. Km.
AKYURT 06750
ANKARA/TURKEY
PHONE :+903128475200
FAX :+903128475205
e-mail : sales@yunel.com
URL : www.yunel.com
www.yunel.com.tr ■
Re: Magnet For Scrap Removal
Dear Mr. B. Houdeh
As I understand you intend to remove worn out balls from the reject material being conveyed by the belt conveyor. I presume the material is common steel for balls. That means from magnetisation point of view it is similar to common structural steel.
I suggest you to write to the manufacturer of magnetic separators and you will get many quotations. However, I would like to draw your attention to the following point.
1) The type of separator will depend upon the diameter and weight of the ball. The designer / manufacturer of magnetic separator will take care of this aspect.
2) The type will also depend upon the frequency of removal. This means in one shift how many balls are expected to be removed.
3) The spherical ball is the worst shape for removal by magnetic separator. For the ball to be extracted, first it gets magnetised during its passage under the magnetic separator. This magnetisation is opposite in polarity. This creates the extraction force.
4) The extraction force depends upon the flux density and flux gradient. The entire process of magnetisation and pulling out is to occur in fraction or say 1 or 1.5 seconds.
5) The effectiveness of the removal greatly depends upon the time available. This means one should try to keep the conveyor belt as slow as possible. For conventional shape 1 mps will give best results, in conjunction with magnetic separator of reasonable length and price. For the spherical shape you might have to use still slower speed.
The above are the general guidelines. The magnetic separator designer / supplier will make the necessary calculations and will come out with specific values and recommendations.
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyors.
Author of Book : Belt Feeder Design and Hopper Bin Silo
Advisor / Consultant for Bulk Material Handling System & Issues.
Pune, India.
Tel.: 0091 (0)20 25871916 ■
Re: Magnet For Scrap Removal
Dear Mr. Mulani,
Thank you for the info with guidelines for selecting a proper magnet. Indeed in our case we have a suspended electro magnet in use for scrap removal which has been installed to remove more or less bolts and nuts and some worn out balls from the SAG mill rejects redirected into it. This is a SE 730 suspended electromagnet with a Gauss density of about 192 Gauss at 350 mm from the electromagnet surface. At the moment there is no pebble crusher (cone crusher) in the rejects circuit and the reject material from the SAG mill is recirculated directly into the SAG mill but we intend to install a pebble crusher so we are obliged to use an appropriate magnet in line with it in order to remove completely the worn balls from the stream.
Any assistance in selecting the right electromagnet for the task is greatly acknowledged.
Best regards,
Babak Houdeh ■
Magnet For Scrap Removal
Dear Mr. Babakhoudeh,
Only installing magnet will not serve the purpose. You have to install metal detector along with magnet. As regards selection you may refer the matter to supplier. They are the best guide.
Regards.
A.Banerjee ■
Untitled
Dear Babak,
Looking at previous answers and adding my own, I come to the following. The story from Mr. Mulani is the right one. In my opinion you should install the magnet in such case always inline with the conveyorbelt. Balls are the most difficult shape to attract. Funny item is that if the ball is e.g. diameter 5 mm or 25 mm, there is no difference in attraction height. Both balls will be caught at the same distance. The force index of a steel ball is 3000. Shape is always the same, weight and size differ.
Our 15 kW magnet attracts a ball of 25 mm diameter at a distance of 290 mm. Our 23 kW magnet attracts a ball at 380 mm.
Our smallest electro magnet is suitable for 800 mm beltwidth, and attracts the ball at 200 mm.
This is always measured in non-moving situation, under the center of the magnet, without product on top.
So there comes the advise to always open up the product layer as much as possible, which only occurs with inline situation at the end of the product conveyor. Then the magnet starts and catches the Fe-parts from the free fall situation. In this case the resistance against pulling out is less then when the magnet has to attract the part through the complete layer of product.
Note that the drive drum of the product conveyor (under the magnet) always must be from SUS (non-magnetic) material.
Our 800 mm electromagnet (3,3 kW) has 340 Gauss at 350 mm (in warm situation) from the magnet surface. So your current SE730 magnet is much to weak to have succes.
With beltspeed 1,5 m/s, beltwidth 650 mm, and quite heavy product, I would suggest to take at least oversized magnet 3,3 kW for 800 mm belt or better 5,8 kW for 1000 mm belt. Place it inline and keep it only about 200 mm from the belt. Then you can be quite succesfull to also separate the balls.
Then you could think of install another magnet after the overbelt magnet. E.g. a headrollermagnet or metal detector or something else to get more clean product.
Goodluck in your quest !
Regards,
Eugene ■
All
Gentle men,
I had faced the same problem in one of the installations. Some of the options are
1. To ensure 100% tramp free feed to cone crusher:
Try a twin magnetic separator, one cross belt and one inline (in same conveyor) at the discharge pulley where the material is opened up (flattened). also add a metal detector as a fail safe option
2. Use Metal detector:
Use a metal detector + mag sep in loop and use the metal detector signal to boost the gauss temporarily. depends on the avl conveyor length/time to boost gauss
3. Use metal detector + diverter gate:
Self Explanatory/ cheap /efficient
Some more suggestions:
Keep the belt as low as possible, say below 1m/s
SAG mill broken balls are the hardest thing to remove using a mag sep due to various factors like, shape factor, speed, roll back if conveyor is not horizontal.
Very few installations in world is having a pebble crusher in sag mill recirculation circuit. if you know any alternate solution/working plant kindly pass on info. ■
Competent Supplier
Dear Sir,
I spoke with someone from http://www.goudsmit.eu
They produce these type of magnets themselves and can deliver tailor made or
in complete machines.
With regards,
Niels Dijkstra ■
Magnetic Separator
For this talk to Eries, or Dings. They sell this equipment, and will provide you with free and accurate sizing. ■
Re: Magnet For Scrap Removal
this is done often in south africa.
here they are called skats,removed with magnet installed above the belt.
contact mark@magnetech.co.za ■
Re: Magnet For Scrap Removal
You can ask a company for this information in this field. ■
Magnet For Scrap Removal
Dear Bulcoholics,
Would you please help us in selection of an appropriate magnet for worn ball removal in a reject belt conveyor from a SAG mill?
Flow rate of reject material: max. 207 t/h
Max. size of scrap metal balls: 50 mm
Speed of rejects belt conveyor:1.51 m/sec.
Belt width:650 mm
Length: 16,800 mm
It would be appreciated if you also advise any suggestion about the most appropriate width or speed of the belt.
Kind regards,
B. Houdeh ■