4 8 C a n adi a n M inin g J o ur n a l J un eJ u l y 2014 w w w c a n adi a nminin gj o ur n a l co m I nn o va t i v e A Dr y G r a v i t y C o n cen t ra t o r h a s b e en de v e lo p e d f o r min era l dep osi ts w h er e wa t er i s n o t a va i l a b le w h er e t h er e a r e co m p et in g in t er es ts f o r a limi t e d wa t er s u p p l y o r f o r j ur i s dic t io n s w h er e t h e u s e o f c ya nide i s pr o h i bit e d I n t h e c ur r en t g lo b a l en v ir o nm en t p r e cio u s m et a l minin g co m p a nies a r e a l s o s t r ug g lin g w i t h hig h c a p i t a l a n d o p era t in g cos ts a n d b e c a u s e o f t hi s n e w a n d inn o va t i v e wa ys t o h e l p m a k e minin g m o r e p r o f i t a b le a r e a l wa ys w e lco m e B e c a u s e o f t hi s w e f e e l t h a t i t s a g o o d t im e t o t a k e a lo o k a t dr y g ra v i t y co n cen t ra t io n Of a l l o f t h e uni t o p era t io n s in min e r a l p r o c e s s i n g g r a v i t y c o n c e n t r a t i o n h a s t h e lo w es t c a p i t a l a n d o p era t in g cos ts a n d in t h e w o r d s o f P enn sy l va ni a S t a t e U ni v er si t y M in era l P r o ces sin g P r o f es s o r F ra n k A p l a n G ra v i t y C o n cen t ra t io n f o r e co n o mic r e a s o n s i s a p p lic a b le w h er e t h e si t u a t io n dic t a t es t h e le a s t exp en di t ur e o f m o n e y A Hydraulics Systems Appr oach T o co m e u p w i t h a n o v e l dr y co n cen t ra t o r a dif f er en t a p p r o ac h wa s t o co n sider t h e dr y g ra v i t y p r o ces s in t er m s o f a h y dra u lic sys t em w i t h t w o f lo w r eg io n s W i t h a h y dra u lics a p p r o ac h a n d em p lo y in g A ir S izin g a n d D u s t C o l le c t io n f o r m u l a s t h e T er min a l V e lo ci t y o f p a r t ic les f o r t h es e t hr e e f lo w r eg io n s c a n b e def in e d b y f o r m u l a s t h a t p r o v ide t h e m a in va r i a b les r e q uir e d f o r dr y g ra v i t y s ep a ra t io n s I n t h e I n t er m e di a t e Flo w R eg io n m os t f in e dr y s o lid s c a n b e aera t e d w i t h lo w p r es s ur e a ir On ce aera t e d t h e y w i l l f lo w li k e a f l uid I n p n eum a t ic co n v e y in g f in es aera t io n i s t h e b a si s u p o n w hic h co mm er ci a l l y a va i l a b le a ir ac t i va t e d g ra v i t y co n v e y o r s co mm o n l y r ef er r e d t o a s a ir s lides o p era t e Th e y a r e em p lo y e d in dr y in d u s t r i a l min era l p l a n ts t o em p t y ra i l c a r s s t o r a g e b in s a n d t o co n v e y m a t er i a l s b et w e en dr y p r o ces s o p era t io n s Th e y a r e a va i l a b le in sizes t h a t va r y b et w e en f o ur a n d 24 in c h es w ide r e q uir e 2 t o 6 deg r e e s lo p es if t h e e le va t io n i s a va i l a b le len gt h s c a n b e u p t o o n e mi le a n d t h e y c a n co n v e y a va r iet y o f lo w a n d hig h b u l k den si t y m a t er i a l s G en era l l y t h e hig h er b u l k den si t y m a t e r i a l s c a n o n l y b e co n v e y e d in t h e f in er p a r t ic le sizes S in ce m os t p r e cio u s m et a l o r es a r e in t h e 1400 t o 1900 kgc u b ic m et er ra n g e w i t h li b era t io n sizes f in er t h a n 100 m es h a ir s lide co n v e y o r s c a n b e r e adi l y ad a p t e d a s dr y g ra v i t y co n cen t ra t o r s Air Slide Conveyors S in ce t h e 1880s m a n y va r i a t io n s o f t h e a ir s lide dr y g ra v i t y co n cen t ra t o r co n cep t h a v e b e en p a t en t e d in t h e U ni t e d S t a t es V er y f e w t w o o f t h es e p a t en ts h a s m ade i t t o a co mm er ci a l p r o d uc t io n s t a g e Thi s m a y b e b e c a u s e t h e va r i a b les r e q uir e d t o ac hie v e co mm er ci a liza t io n w er e n o t p r o p er l y def in e d Th os e p a t en t des cr i p t io n s s h o w m a t e r i a l f e d t o co n v e y e d b y a n d di s c h a r g e d t o a s ep a ra t io n de v ice W h a t wa s mi s sin g w er e t h e f r o n ten d m a t er i a l p r ep a ra t io n a n d t h e s ep a ra t io n s t eps W A T E RLES S WONDER Innov ative device offers solution to growing problem By George Rodger and T ony Mariutti PO WER A dry system will tak e 833 times less energy to move an equiv alent volume of air than it would tak e for w ater 12 kgcubic metres for air compared to 1000 kg cubic metres for w ater W A TER Only requires 70 to 90 kg of w ater per ton of ore for dust suppression W et processes gener ally require two to three tons of w ater per ton of ore Air is a compressible fuid that can replace w ater VISCOSITY OF AIR Depending on the temper ature the viscosity of air is 28 to 90 times lower than it is for w ater T hat effectively eliminates surface tension and viscosity agglomer ation effects in the dry concentr ation of miner als Reagents are not required Vibr ation is not required when air is the fuid medium All of the process support equipment is current technology DR Y GRA VITY AD V ANT A GES IN ADDITION T O LO W CAPIT AL AND OPERA TING COSTS A DR Y GRA VITY CONCENTRA TION PRO CESS HAS A NUMBER OF INHERENT AD V ANT A GES SUCH AS THE FLO W REGIONS ARE DESCRIBED AS FOLLO WS T urbulent 10000 to 1000 micron particle size r ange Intermediate 1000 to 100 micron particle size r ange and THESE ARE A constant for particle shapes Specifc gr avity and P article size Only in the Streamline Region does the viscosity of air become a v ariable V ARIBLE INCLINE LOW PRESSURE AIR CHAMBER POROUS MEDIA GENERALIZED AIRSLIDE DRA WING LOW PRESSURE AIR SUPPL Y