P r o c e s sing plant s ha ve the r eput ation of being ener gy inef f icient but a r e c ent study has put some har d numbers on their ener gy usag e Af t er in vestig ating thr ee industrial grinding mill cir cuit s oper at ed by Agnico Eagle Goldex Division Mine Canadian Malartic and N e w Gold N e w Af t on Mine r esear chers concluded on a v er ag e 7 9 per c ent of the supplied electrical ener gy w a s con v ert ed t o heat absorbed by the slurry eight per c ent w as lost thr ough the drive s y st em and appr o ximat e ly two per c ent w a s tr ansmit t ed t o the ambient air Only nine per c ent of the input ener gy w as actually used f or grinding In this r e g a r d not much has chang ed in a very long time As the lead author of the paper Br eaking down ener gy con sumption in industrial grinding mills published in CIM Journal V olume 10 Number 4 2019 J o c e lyn Bouchar d a U niversit e L a v al as sociat e pr of es sor of chemical engineering believes ther e ar e eas y eff iciencies t o be g ained and ener gy t o be sa ved CIM Mag azine spok e t o Bouchar d and ask ed him about making pr oc es sing plant s mor e eff icient CIM What can mineral pr ocessing operations do to impr ove their ef ficiency Bouchar d A g ood example is ball mills In most of the oper a tions y ou can pr oc es s a lit tle bit mor e mat erial if y ou f ind the optimum oper ating point with r oughly the same amount of ener gy so the plant ener gy output will not chang e but the amount of mat erial y ou ar e pr oc es sing is gr eat e r If y ou look at the ener gy per t onnes y ou ar e using it s g oing t o be a lower num ber T his I think is a g ood st arting point Y ou try t o maximiz e y our as set utiliz ation and use y our equipment t o a maximum capacity Just with that y ou can pr obably impr ove the ener gy consumption f i gur es by an y thing fr om f i ve t o 15 per c ent Fif t een per c ent could be a bit of a str et ch but fr om a simulation we ar e conducting curr ently I would say f i ve t o 12 per c ent is r e a sonable CIM Could you explain how you achieve this optimization Bouchar d T her e ar e man y thing s y ou can do Of t en people will t a r g et a c e rt ain pr oduct siz e that is based on off line labor at ory work that has been done prior t o the pr oject or is being r outinely done every f e w months just t o check if they ar e t a r g eting the right particle siz e But this t a r g et should be changing all the time perhaps every six hours every 12 hours or even every hour depending on the char act eristics of the or e y ou ar e cur r ently pr oc es sing If y ou measur e online or even off line mor e fr equently ask am I in the right t a r g et and r eadjust that t a r g et y ou may be able t o pr oc es s mor e or e Y ou ar e pr obably t a r g eting a pr oduct siz e that is much smaller than y ou actually need t o r each y our gr ade r e covery t a r g et f or y our f inal conc entr at e or even r each the r e covery in a g old plant F or inst anc e typical v alues ar e 7 5 micr ons If y ou just g et the 7 5 micr ons t o 80 or 82 or 83 micr ons y ou might ha ve f i ve 10 or 12 per c ent les s power utiliz ation in y our plant so it mak es a hug e diff er enc e CIM Does changing the size af fect anything else Bouchar d If y ou ar e alr eady at the right t a r g et then y ou can not pr oc es s mor e Y ou ca n pr oc es s slightly mor e but not by changing the t a r g et One w a y t o do it is t o s y st ematically moni t or and contr ol the entir e distribution online W e ha ve sensors that can do that 38 CIM Magazine V ol 15 No 3 Courtesy of Jocelyn Bouchar d Finding ef ficiency thr ough better housekeeping Paying attention to pr ocess contr ol leads to significant savings for mineral pr ocessing plants By Car olyn Gruske