Steps to r ecovery T o maximiz e heat r e covery at Meadowbank BB A f ocused on small specif ic measur es lik e developing cleaning pr oc edur es t o impr ove r e covery r a t es fr om g ener at or engine exhaust while also looking at the big g er pictur e T h ey had never off i cially f ormaliz ed their risk t oler anc e f or black out s said Allen T his is import ant because powerplant oper at ors do not pay f o r fuel but can f eel r esponsible f or out ag es so it is common that they run all engines at lower loads Although this burns mor e fuel it gives oper at ors an immediat e r eserve t o t ap int o if the load spik es or a g ener at or unexpect edly shut s down Allen and his t eam put a question t o Agnico Eagle s br as s How man y black out s do we w ant per y ear and how much money ar e we los ing during these black out s Is this bet t er than running all the engines lower As a r esult g ener at ors wer e run hot t e r at a higher load f act or impr oving heat r e covery r a t e s T hese and other chang es cut diesel use by r oughly two million litr es per y ear at Meadowbank without an y subst antial equip ment impr ovement s or upgr ades When it came time f or det ailed design of the cog ener ation plant at Meliadine Agnico Eagle s next pr oject in Nuna vut the compan y ag ain turned t o BB A ask ing the compan y t o incorpor at e the les sons of Meadowbank Right aw ay Agnico Eagle w ant ed t o in volve oper ations in the design pr oc es s and commis sioning of the power plant so Melia dine st aff knew how t o run the s y st ems pr operly t o achieve the desir ed heat r e covery r a t e s It s a har d one because the mor e we w ant t o r e cover the mor e the s y st ems become complex said Allen If the users don t oper at e the s y st ems corr ectly we can design the gr eat est powerplant but it will not be as eff icient as it s supposed t o T he s y st em BB A designed inject s thermal ener gy r e cover e d fr om the g enset s int o a hotw a t er loop that heat s the pr oc es sing plant and all other surf a c e building s connect ed t o the network A second loop continues on t o heat air in the under gr ound mine t o r oughly two or thr ee degr ees Celsius bef or e r eturning t o the plant wher e the cooled w a t er is heat ed up ag ain T he entir e heat distribution s y st em runs mor e than f i ve kilometr es in t o t al Allen said it r eliably heat s the surf a c e building s but r equir es some help t o heat the under gr ound mine when the t emper atur e dr ops below 25 Celsius T he t o t al eff iciency of the cog ener ation plant is about 80 per c ent ac cor ding t o Allen In other wor d s each kilogr am of diesel cont ains about 43 Meg ajoules F r om that about 19 Meg ajoules ar e con v ert ed t o electricity and another 16 Meg ajoules int o heat during the wint er said Allen Reliability is huge A crucial f act or t o consider with off grid powerplant s is r eli ability A g ener at or f ailur e can shut down pr oduction oper ation wide and that can g et expensive T o minimiz e this pr oblem Agnico Eagle implement ed load shedding which allows the oper at or t o run the engines at optimal loads t o g et the most eff i cient perf ormanc e fr om the g ener at ors If one engine inst antly st ops f or some pr oblem then y ou can load shed f or example the caf e t eria or the lodging or a c e rt ain part of the pr oc es s y o u know y ou can st op without aff ecting pr oductivity said Allen T her e w as no additional in vestment It w as just thinking about the network in a smart w a y If something does g o wr ong y ou just load shed a sect or that y o u ve chosen in adv anc e T his gives the oper at or time t o st art up a back up g ener at or and power r eturns t o aff ect ed ar eas minut es lat e r Agnico Eagle also built r eliability int o the Meliadine plant by pur chasing f i ve 5 6 meg aw at t high eff iciency W a rt sila g ener a t o rs T hese 7 2 0 r p m g enset s run at a low speed meaning les s wear and t ear on the engine and bet t er r eliability T h ey ar e also f i ve per c ent mor e eff icient than the 900 r p m g ener at ors at Meadowbank T his g ain in eff iciency tr anslat es t o r oughly 25 million litr es of diesel sa ved every y ear But it s mor e than that explained Allen Agnico Eagle can ship in fuel only f our months each y ear when the ic e g oes out of Hudson Bay so this r eduction means f ewer st or ag e t anks les s fuel t o tr ansport t o sit e by ship and f ewer trucks on the r oad It also tr anslat es t o a decr eased risk of spills and f ewer gr eenhouse g ases emit t ed T her e ar e a lot of adv ant ag es t o r educing diesel consumption when y o u r e up N o rth BB A made the busines s case f or the mor e expensive g enset s T her e w as mor e than diesel sa ving s t o consider with each behe moth 100 t onne g ener at or t o o Lower speed f or the same power means a big g er engine T h at s wh y it s mor e expensive said Allen Y ou also need mor e spac e in y our building a big g e r f oundation Agnico Eagle made the in vestment because the payback on what these g ener at ors c ost versus the g ener at ors at Meadowbank w as only about two y ears Meliadine s curr ent pr oject ed mine lif e is 12 y ears Get ting the g ener at ors t o sit e posed a f e w logistical chal leng es considering Nuna vut lacks a deep w at er port Each g e n er at or w as moved off a ship anchor ed in deep w a t er and ont o a multiax el tr ailer sit ting on a bar g e When this bar g e came t o land the tr ailers wer e t owed ont o the beach and then tr a v elled 35 kilometr es t o Meliadine Five g ener at ors as well as eight 50 t onne pr ef ab cog ener ation plant building s wer e moved this w a y A lat e summer in 2018 pushed back the schedule Fuels for the futur e F r om the very st art Agnico Eagle insist ed on de risking Meliadine by ensuring it s plant could be compatible with liquid natur al g as LNG and r enew able power T he r a tionale made sense if the mine uses man y t ens of millions of litr es of diesel per y ear and that pric e g oes up by even 0 50 the compan y is stuck and oper ating cost s incr ease by t ens of millions Dual fuel g ener at ors that run on both diesel and LNG alr eady exist ed on the mark et said Allen But the pr oblem is if y o u r e using dual fuel but running on diesel y o u r e actually thr ee per c ent les s eff icient while w aiting f or the pos sible incorpor ation of natur al g as a t a lat er dat e Af t er speaking t o man y manu f actur ers Finnish compan y W a rt sila pr oposed an option wher e Agnico Eagle could easily con v ert it s g ener at ors t o LNG at a lat er dat e T hey ar e eff icient as diesel engines but if y ou do w ant t o con v ert them t o dual fuel then y ou only t a k e two weeks y ou pay that money at that time f or con v ersion and y o u r e r eady t o oper at e on them said Allen T he compan y could st ag g er the g enset s wit chovers so the oper ation would not be aff ect ed T he plant can also int egr at e r enew able ener gy W e ve been doing int ernal studies on a wind f arm and we ha ve been working on that f or a couple of y ears no w said L a voie W e r e saying that we need t o ag ain k eep our minds open and look f or opportu nities T h at f l exibility t o alt er course with the winds of chang e means the long er Meliadine pr oduc es g old the mor e Agnico Eagle is r e w a r ded f or the up fr ont in vestment and planning it put int o it s cog ener ation plant CIM MayJune 2020 MaiJuin 2020 31 ener gy efciency