Energy Consumption in Copper Smelting: A New AsianHorse in the Race

P. COURSOL,1,5 P.J. MACKEY,2 J.P.T. KAPUSTA,3

and N. CARDONA VALENCIA4

1.—5N Plus Inc., Montreal, QC, Canada. 2.—P.J. Mackey Technology, Inc., Kirkland, QC, Canada.3.—BBA Inc., Montreal, QC, Canada. 4.—Deltamet Consulting, Pointe-Claire, QC, Canada.5.—e-mail: pascal.coursol@5nplus.com

After a marked improvement in energy consumption in copper smelting dur-ing the past few decades, technology development has been slowing down inthe Americas and in Europe. Innovation, however, is still required to furtherreduce energy consumption while complying with stringent environmentalregulations. The bottom blowing smelting technology being developed inChina shows success and promise. The general configuration of the bathsmelting vessel, the design of high-pressure injectors, and the concentrateaddition system are described and discussed in this article with respect tothose used in other technologies. The bottom blowing technology is shown tobe operating at a temperature in the range of 1160–1180�C, which is thelowest reported temperature range for a modern copper smelting process. Inthis article, it is suggested that top feeding of filter cake concentrate, which isalso used in other technologies, has a positive effect in reducing the oxidationpotential of the slag (p(O2)) while increasing the FeS solubility in slag. Thisreduction in p(O2) lowers the magnetite liquidus of the slag, while the in-creased solubility of FeS in slag helps toward reaching very low copper levelsin flotation slag tailings. The application of high-pressure injectors allows forthe use of high levels of oxygen enrichment with no requirements for punch-ing. Using a standard modeling approach from the authors’ previous studies,this article discusses these aspects and compares the energy consumption ofthe bottom blowing technology with that of other leading flash and bathsmelting technologies, namely: flash smelting, Noranda/Teniente Converter,TSL (Isasmelt [Glencore Technology Pty. Ltd., Brisbane, Queensland, Aus-tralia]/Outotec), and the Mitsubishi Process (Mitsubishi Materials Corpora-tion, Tokyo, Japan).

INTRODUCTION

One of the biggest business stories of 2014 wasthe huge drop in the price of oil. Thus, the WestTexas Intermediate oil price dropped amid an oilsurplus and lower demand by almost 50% from ap-proximately $100/barrel in the middle of 2014 toaround $50/barrel by early 2015. For a large energyconsumer such as a copper smelter, this providedsome relief to ever rising operating costs. However,analysts expect some rebound in the oil price laterthis year or into 2016. Hence, energy consumptionin smelting, examined in this article for a number of

technology configurations, remains an importanttopic for copper smelters.

The first published concept of bottom blowingsmelting for nonferrous metals dates back to 1974and the paper by Paul E. Queneau and ReinhardtSchuhmann1 titled ‘‘The Q-S Continuous OxygenConverter.’’ The authors explained that the Q-Soxygen process invention was a response to thechallenges of the time (first oil crisis resulting inhigh oil prices and pressure to fix sulfur dioxidegases) to increase process efficiency by a systematicuse of oxygen with a substantial correspondingreduction in fossil fuel usage. Queneau and

JOM, Vol. 67, No. 5, 2015

DOI: 10.1007/s11837-015-1380-1� 2015 The Minerals, Metals & Materials Society

1066 (Published online March 18, 2015)

Schuhmann adopted the following key concepts intheir process design:

� Continuity—to limit capital and operating costs� Autogenous—by using oxygen to lower energy

and fossil fuel consumption� Single off-gas of minimal volume—to lower costs

of sulfur fixation� Bottom blowing—to attain optimal solid–liquid–

gas contact� Countercurrent flow of matte and slag—to

achieve bath oxidation and slag reduction in asingle vessel

� An elongated, kiln-like vessel—to improve heatand mass transfer.

In 1989, Queneau2 provided historical insights intothe conceptual phase of the Q-S process develop-ment mentioning that a key driver that triggeredthe search for a new nonferrous smelting processwas the invention of the Savard–Lee shrouded in-jector and its success in steel refining. In fact,Queneau and Schuhmann3 had filed their patent in1973 and entered into a collaborative agreementwith Savard, Lee, and Canadian Liquid Air thatsame year, forming QSOP Inc. (Queneau–Schuh-mann Oxygen Process).

With a lack of interest from the copper industry,QSOP found support from Werner Schwartz ofLurgi, leading to a QSOP-Lurgi agreement in 1974for the development of the QSL (Queneau–Schuh-mann–Lurgi) lead smelting reactor. After 15 yearsof efforts in the laboratory and in pilot and demon-stration plants, including further developments ofthe Savard–Lee injectors, the QSL became the firstbottom blown smelting vessel commercialized innonferrous pyrometallurgy with lead smelting re-actors installed in 1990 in Canada (Trail Smelter ofCominco Ltd.), Germany (Stolberg Smelter of Ber-zelius), and China (Baiyin Smelter of CNIEC), andin 1991 in Korea (Onsan Smelter of Korea Zinc). Amore complete story of the QSL development frompatent to commercial implementation was reportedby Kapusta and Lee.4

The Chinese industry developed its own bottomblowing reactor in the 1990s. China NonferrousMetal Industry’s Foreign Engineering and Con-struction Co. Ltd. and China ENFI Engineering(ENFI) first piloted their ShuiKouShan (SKS) leadsmelting technology in 1999 at the ShuiKouShanlead smelter in Hunan Province. Commercial engi-neering and construction took place in 2001 andsuccessful commissioning in 2002. The SKS copperprocess was first adopted in 2001 and commissionedcommercially at the Sin Quyen Copper Complex inVietnam in 2008 with a capacity of just 10,000 t/a ofanode copper. The second implementation of thetechnology, and first in China, took place in 2008 atthe Dongying Fangyuan Nonferrous Metals Co.,Ltd. (Dongying) with an original copper concentratesmelting capacity of 32 dry t/h or 55,000 t/a of an-ode copper.5,6

The number of SKS lead reactors in China quicklygrew after 2002; Stephens7 reported that the SKSlead furnace had been described ‘‘as the smeltingsection of a QSL reactor.’’ As for the SKS copperfurnace, Kaixi Jiang et al.5 described it as similar indesign to the Noranda Reactor, contrasting with thefact that ‘‘the air in the copper matte layer is blowninto the furnace via the oxygen guns set in thefurnace bottom.’’ These oxygen ‘‘guns’’ are essen-tially Savard–Lee-type shrouded injectors withcompressed air as shrouding gas. The process atDongying is now known as the bottom blowingsmelting (BBS) process. Several other copper smel-ters in China have since adopted the SKS/BBStechnology. It has also been reported that the tech-nology is being evaluated as an alternative for somecopper smelters in Chile.

The goal of this article is to discuss the SKS/BBStechnology features and to evaluate the energy re-quirements for this technology compared with othermodern smelting technology. To do so, the approachused by Kellogg and Henderson8 and Coursolet al.9,10 is used. In this approach, all technologiesare compared on the same basis, with the sameconcentrate, flux and coal composition, this allowsevaluating both the electrical and thermal energyrequired to operate a smelter from concentrate toanode for a given technology.

BOTTOM BLOWING SMELTINGTECHNOLOGY (SKS/BBS)

General Description

The SKS/BBS reactor, as shown in Fig. 1, is acylindrical vessel with gravity top feeding of wetconcentrate through several ports. The injectors areall located on one side of the furnace, whereas theoff-gas mouth, matte, and slag tap holes are on theopposite side. This arrangement creates a two-zonebath: an agitated oxidation zone below the feedports and a quiescent settling zone above the mattetap hole. Two auxiliary burners are located on eachend wall and are used during start-up or stand-by.The mouth is small compared with existing bathsmelting reactors because operating at high oxygen

Fig. 1. Schematics of SKS/BBS copper process from Yao andJiang.11

Energy Consumption in Copper Smelting: A New Asian Horse in the Race 1067

enrichment produces lower volumes of process off-gases.

Cui et al.12 provided a complete description of thebottom blown oxygen smelting process at Dongying.The cylindrical furnace is 4.4 m in diameter by16.5 m in length. The oxygen ‘‘lances’’ are positionedin two rows at the bottom of the furnace with fivelances in the lower row at 7� to the vertical and thefour lances in the upper row at 22�. This provides a15� angle between the two rows. A photograph of theDongying furnace is given in Fig. 2.

The oxygen lances or guns used to inject the blastare Savard–Lee-type shrouded injectors with simi-lar design and configuration as the original QSLinjectors developed by Lurgi and Air Liquide in the1970s.4 The tips of the injectors are built with agear-like design as shown on Fig. 3a (drawing) andFig. 3b and c (photographs) for the reactors built byENFI. The principle of the lances is to inject high-oxygen-enriched air or pure oxygen in the centralbore and first or two annuli of grooves and a coolingmedium in the outer ring of grooves (e.g., air or ni-trogen). All streams are injected at sonic velocity.The lance design at Dongying has been slightlymodified to reduce the pressure requirement of theoxygen streams to achieve sonic velocity.13

The oxygen enrichment achieved to date with theSKS/BBS reactors is in the range 50–75%, which issignificantly higher than for the current Noranda

reactor and Teniente converter operations. Theoriginal design capacity of the Dongying furnacewas 55,000 t/a of anode copper at 55% oxygen, andits current capacity has reached 100,000 t/a as theoxygen enrichment reached 75%.

The inherent low level of nitrogen in the blast isfrequently perceived as a weakness of high-oxygeninjection due to the diminished mixing of the bath. Acomparison with the operating oxygen top-blown–nitrogen-bottom stirred vessel at Vale’s Copper Cliffsmelter in Sudbury is opportune at this point.Marcuson, Diaz, and Davies reported the use of fiveporous plugs, each with nitrogen flow rates of14 Nm3/h.16 The total flow rate of nitrogen for stir-ring was 70 Nm3/h, which was evidently sufficientto provide stirring in a 135-t semiblister bath (cor-responding to a specific blowing rate of 0.52 Nm3/h/tof the melt). In this later case, the top blown oxygenflow rate was approximately 5330 Nm3/h. With anSKS/BBS furnace operating at 75% oxygen, the to-tal blast rate is approximately 19,160 Nm3/h, cor-responding to the Dongying vessel to a specificblowing rate of 70 Nm3/h/t of melt. These conditionsprovide nitrogen in the order of 4,790 Nm3/h forstirring, a sizeable amount compared with the por-ous plugs in the Copper Cliff case. By comparison,the Noranda Process reactor in Canada has aspecific blowing rate of about 130 Nm3/h/t of melt.

The lance life was reported in 2013 by XiaohongHao et al. to be 30–60 days14 and in 2014 by JohnnyZhang et al. to be up to 6 months.17 This discrep-ancy highlights the importance of a proper lancedesign to ensure sonic velocity is achieved, and acontrolled bath chemistry and temperature isneeded to limit lance and refractory wear.

Dongying has achieved the most advanced devel-opments in the operation of its SKS/BBS furnace.This operation has therefore been selected in thisarticle as the reference for energy comparison of theSKS/BBS furnace to the Noranda and Tenientereactors.

Process Chemistry

Although most modern smelting vessels accom-plish a similar task of producing a high-gradeFig. 2. SKS/BBS furnace at Dongying (Source: Yao and Jiang.11)

Fig. 3. (a) Drawing of lance tip from Hao et al.,14 and (b, c) Photographs from July 2013 ENFI presentation.15

Coursol, Mackey, Kapusta, and Valencia1068

matte, the chemistry can vary significantly from onetechnology to another. In the BBS furnace case,several factors seem to affect positively slag chem-istry, leading to low copper levels in the furnace slagand favorable oxygen consumption figures. A few ofthese aspects are discussed next.

Impact of Matte Grade

The smelting furnace matte grade is importantfor the process chemistry. A matte grade higherthan 77% leads to higher soluble copper in slag inthe oxidic form, whereas operating at a matte gradelower that 70% leads to moderate copper levels inslag, predominantly in the form of soluble sulfidiccopper.18 In the BBS process, the operating mattegrade is in a range where the lowest soluble lossesare observed, which is generally between 70 and75% Cu.18 A reasonably low total copper in slag isobserved in the BBS furnace, indicating less than5 wt.% matte entrained in slag.6 Given that theapproach taken for slag cleaning is by milling andflotation, a high copper recovery is expected, with acopper content in tailings reported at 0.26%.6

FeS Solubility in Slag and Impact on CopperRecovery

The bulk sulfur content in slag of the BBS reactorwas reported to be 1.7 wt.%,6 whereas the bulkcopper content of the slag was reported to be2.9 wt.%.6 These numbers appear low from the au-thors’ viewpoint and are expected to vary as afunction of slag quality and matte grade. If one as-sumes all copper is present as matte entrained in theslag, then the %Cu/%S ratio should be maintained at3.4. If a significant level of copper oxide is present inthe slag, then the ratio should be higher. In the BBSfurnace, the %Cu/%S ratio is 1.71, indicating thatanother sulfide species is soluble or entrained in theslag. Previous publications have discussed FeS so-lubility in copper smelting slag and its sig-nificance.18,19 Figure 4 shows the sulfur solubility

trend as function of the matte grade for different Fe/SiO2 ratios in slag from a bath reactor such as theTeniente Converter. The thermodynamic calcula-tions assume all sulfur is soluble as FeS, but thecopper sulfidic dissolution is yet to be modeled ap-propriately. At 70% matte grade and a Fe/SiO2 ratioof 1.8, the expected %S soluble in slag is 0.7 wt.%,which is lower than the level of 1.1 wt.% reported byZhao et al.6 for the BBS slag, which must account forboth Cu and Fe sulfidic dissolution.

The sulfur solubility in slag can have a positiveimpact by forming recoverable matte droplets dur-ing slag cooling and solidification, if the slag is so-lidified at a sufficiently low cooling rate.20 Figure 5ashows the microstructure of a rapidly cooled slagsample, in which sulfide exsolution led to a phe-nomenon called ‘‘copper fog.’’ In the copper fog for-mation, the small sulfide particles are trappedbetween olivine and terminal glass (final slag tosolidify in a glassy state during the solidificationprocess) and are quite hard to recover by millingand flotation. On the contrary, when the slag is so-lidified under a controlled slow cooling rate, aspracticed by several smelters worldwide, this re-sults in a much coarser microstructure and thegrowth of droplets (e.g., due to coalescence phe-nomena). Hence, higher Cu recoveries can be ob-tained. Figure 5b shows a coarse microstructurewith matte droplets formed during cooling slag anda large entrained matte droplet with sulfide exso-lution texture.

Feeding on Slag Instead of Submerged Injection

In the BBS furnace case, the fresh feed is added asa wet concentrate onto the slag surface. Under theseconditions, it is conceivable to obtain a lower p(O2) inthe slag than in the matte because of the addition offresh concentrate from the top, as long as mixing isadequate, yet not overly intense. With more intensemixing, the p(O2) of both phases would be nearly thesame (closer to equilibrium). Melting of the concen-trate within the slag can contribute to maintainingthe dissolved copper oxide content to quite low levelsand, furthermore, to controlling the magnetite levelof the slag. In the BBS furnace case, the reducedbath agitation due to the higher oxygen enrichmentand lower blowing rates (or, a lower total off-gasvolume expressed as m3/m3 of melt) can provide fa-vorable conditions in the slag to minimize the slagliquidus (lower p(O2) and a higher level of solubleFeS). Although the Teniente Converter with sub-merged injection generally operates near 1225–1250�C, the Noranda Reactor and the Isasmelt fur-nace (Glencore Technology Pty. Ltd., Brisbane,Queensland, Australia) using wet feed addition fromthe top operate at 1200�C and 1180�C, respectively,which can lead to a significant improvement in therefractory protection and heat balance of these ves-sels. The BBS technology, operating with top feedingand high oxygen enrichment levels, seems to push

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.5 2.0 3.5 5.0 6.5 8.0 9.5

%S

in S

lag

as F

eS

%Fe in matte

Fe/SiO2=1.6Fe/SiO2=1.4Fe/SiO2=1.8

Fig. 4. Calculated sulfur solubility (as FeS) in the Teniente converterslag. Effect of Fe/SiO2 ratio and %Fe in matte at T = 1250�C.(p(SO2) = 0.25 atm, [Al2O3]slag = 4.0 wt%, [ZnO]slag = 2.1 wt.%,[MgO]slag = 0.8 wt.%, [CaO]slag = 0.8 wt.%).19

Energy Consumption in Copper Smelting: A New Asian Horse in the Race 1069

the concept observed in other top feeding technolo-gies toward a reduced mixing intensity, leading toeven lower operating temperatures, reported to be inthe 1160–1180�C range.6–17

Operating at High Oxygen Enrichment

Higher oxygen enrichment has the benefit of re-leasing more heat during the smelting process and ofallowing more reverts or low-grade materials to berecycled in the smelting vessel. It also has the ad-vantage of providing a lower mixing level in thesmelting vessel and reducing the off-gas volume. Oneshould also note that these conditions reduce the riskof foaming during periods when the slag containsexcessive levels of solid magnetite. One drawback ofusing high oxygen enrichment is the increase inOPEX and CAPEX for oxygen production.

Oxygen Usage in Copper Smelting

From practical experience with modern smeltingtechnologies, the oxygen usage factor (or oxygenefficiency) in most technologies is in the 95–99%range. Although much lower oxygen usage per ton-ne of concentrate can apparently be observed insome cases, clearly an oxygen efficiency over 100%is not possible. Differences can be explained by thefactors discussed next. It is noted that a lowerspecific oxygen consumption was observed in theBBS furnace case.17

When concentrate is fed to a smelting unit from thetop (Noranda Reactor, El Teniente Converter, BBSfurnace, etc.), the freeboard air or gas can react withthe concentrate if sufficient oxygen is available. Thisphenomenon is illustrated by reactions 1 and 2. Thechalcopyrite, bornite, and chalcocite present in theconcentrate can be oxidized following similar me-chanisms. Although this is not the major oxidationmechanism, it can make a significant difference inspecific oxygen consumption for a given feed.

The concentrate mineralogy obviously has a sig-nificant impact on the oxygen requirements. Main-ly, the input FeS2 and FeS equivalent are very

important, as most of the remaining iron sulfideneeds to be oxidized during converting. This is il-lustrated by reaction 3.

The mineralogy of reverts added to the smeltingunit can also lower tonnage oxygen usage and SO2

generation. For example, adding metallic copper inthe form of reverts, copper scrap, or spent anodescan reduce both the SO2 produced during smeltingand tonnage oxygen usage. This can be referred toas ‘‘sulfur sequestration’’ and obviously has an im-pact on the FeS oxidation mechanism, changingfrom reaction 3 to 4. Similarly, Cu2O contained inreverts from the converter aisle or anode furnacesrepresent a source of oxygen and therefore can alsosignificantly reduce tonnage oxygen consumption.This is illustrated by reaction 5.

Finally, in a deficient heat balance situation, cokeaddition is used for closing the heat balance. Most ofthis coke entering the smelting unit exits as CO2 gaswith trace levels of CO; hence, the oxygen requiredfor this reaction contributes to the total specific O2

consumption.

FeS2ð ÞfeedþO2ðfreeboardÞ ¼ FeSð ÞmatteþSO2 (1)

FeSð Þfeedþ3=2O2ðfreeboardÞ ¼ FeOð ÞslagþSO2 (2)

FeSð Þmatteþ3=2 O2 ¼ FeOð ÞslagþSO2 (3)

FeSð Þmatteþ2 Cuð ÞmatteþO2 ¼ FeOð Þslagþ Cu2Sð Þmatte

(4)

FeSð ÞmatteþCu2O ¼ FeOð Þslagþ Cu2Sð Þmatte (5)

The preceding discussion is helpful in under-standing the lower published and observed oxygen

Fig. 5. (a) Fine microstructure showing ‘‘copper fog’’ (bright dots). (b) Coarser microstructure obtained by slow cooling of the slag, leading to highcopper recovery by flotation (Cu2S and Cu-Fe sulfide [bright phases], fayalite [gray columnar crystals], terminal glass [dark gray phase betweenthe fayalite blades], and magnetite crystals [intermediate grey crystals shown in (b)]).

Coursol, Mackey, Kapusta, and Valencia1070

use in the BBS furnace compared with the Noran-da–Teniente reactor as indicated by Zhang et al.17

METHODOLOGY-ENERGY CALCULATIONS

The methodology adopted to evaluate smeltingenergy in this study was based in part on the ap-proach used by Kellogg and Henderson,8 which wasreviewed for modern smelting technologies byCoursol et al.9,10 In these last two studies, the au-thors reviewed the energy consumption (electricaland thermal) and compared modern technologyperformances in specific configurations, processcopper concentrate, and finished anodes. In total, 12different flowsheet configurations were compared. AMetsim model (METSIM; Proware, Tucson, AZ)previously developed by Tripathi et al.21 was usedas a basis for designing several other models and forcomparing technologies on the same basis. Heat andmass balance and energy consumption data werethen computed for each process for subsequentanalysis and comparison. Process ‘‘boundary limits’’were as follows: Inputs: wet concentrate, flux, andother consumables delivered to the smelter daybins; and Outputs: copper anodes, sulfuric acid, acidplant tail gas, cleaned fugitive gas released to at-mosphere, and cleaned slag. Waste heat recoveryfrom process gas streams was included as part of thestudy. In this work, the same approach was used tocompare the BBS technology with other moderntechnologies. Energy consumption in auxiliary unitoperations and energy equivalent for process sup-plies were computed from a set of unit energy con-sumption factors. These are presented in Table Ibased on data from Refs. 9 and 10.

Appropriate data were also taken from Kelloggand Henderson,8 and updated information was usedin other cases. Examples of auxiliary unit op-erations include producing tonnage oxygen, com-pressing Peirce Smith Converter (PSC) injection air,delivering low-pressure air to burners, moving pro-cess off-gas, drying concentrate and other materials,and transporting and injecting fine solids suspendedin a stream of gas (dense phase transportation ofsolid particulates).

The standard conditions used for the calculationof energy requirements for each of the chosen pro-cesses are presented in Table II and are identical tothe ones taken in previous studies.9,10 These pro-cesses include the assay of a standard copper con-centrate and the data relative to fluxes and fuels.

Table I. Unit energy parameters used in this study

Item Unit energy References

Steam dryer 2 t steam/t water evaporated 9Conversion of steam to electricity at smelter 6.25 kg of steam/kWha 9Tonnage oxygen production (300 kPa) 285 kWh/t of oxygen 22Tonnage oxygen production (600 kPa) 321 kWh/t of oxygen AuthorsCompress tuyere air (�600 kPa) 0.126 kWh/Nm3 AuthorsCompress tuyere air (�110 kPa) 0.05 kWh/Nm3 8Compress lance air (�60 kPa) 0.03 kWh/Nm3 9Process off-gases handling 0.0085 kWh/Nm3 9Fan-secondary gases 0.002 kWh/Nm3 24Furnace cooling water 3 kWh/t Cu 9Matte granulation and handling 9 kWh/t of matte 9Slag granulation and handling 3 kWh/t of slag 9Matte comminution and handling 10 kWh/t of matte 9Lighting and miscellaneous power (allowance) 30 kWh/t of Cu 8Acid plant operation (double contact) [(646.8/%SO2) + 63.7] kWh/t of acid 8Energy-Flux (90 MJ + 3 kWh)/t of flux 8Energy-limestone calcination (CaO flux) 7000 MJ/t of CaO 9Energy-wear steel in slag milling 20.7 MJ/kg of steel 23Energy-pig iron 15.5 MJ/kg of pig iron 9

aBased on a rate of 5 kg steam/kWh and an operational efficiency of 80% to account for potential losses on start-up/standby, etc.

Table II. Standard conditions used in the Metsimmodel

Item and data

Concentrate analysis (dry basis): 30.5% Cu, 28.5% Fe,31.5% S, 5% SiO2, 2% Al2O3

Concentrate moisture content: 10% H2OFlux analysis (dry basis): 88% SiO2, 2% CaO, 6% Al2O3,2% MgO, and 2% Fe3O4

Flux moisture: 3% H2ONatural gas: 37.3 MJ/Nm3

Coal: 28.4 MJ/kgAmbient conditions: 0�C, 760 mmHg

Energy Consumption in Copper Smelting: A New Asian Horse in the Race 1071

Brief Description of Processes Assumptions(Noranda Reactor Versus BBS Technology)

Each process route also included the following‘‘standard’’ unit operations: (I) complete secondarygas collection and cleaning, (II) anode refining andcasting, and (III) process gas treatment in a double-contact acid plant with acid delivery to storagetanks. As noted above, heat recovery from processoff-gases was also used. Concentrate and other solidprocess streams requiring drying were treated insteam dryers using waste heat steam. Surplussteam was assumed to generate electricity. Theflowsheet configuration used for the BBS processwas identical to the configuration used for the No-randa Process by Coursol et al.10 Figure 6 shows theflowsheet configuration used in both the NorandaReactor and the BBS furnace cases for the massbalance calculations.

In both simulations, Noranda and BBS, a feedrate of 126.8 t/h of a standard filter cake concen-trate was assumed (10% moisture, 114 t/h dry ba-sis), were fed to the smelting vessel. The total heatlosses for both smelting units were fixed at 7 MW.The two flowsheet had the exact same configura-tions as shown in Fig. 6. A few differences in processdata between the two cases are listed next.

In the Noranda Reactor case, with normal tuyeretechnology (low pressure and nonshrouded), theoxygen enrichment is limited to 45 vol.% to mini-mize risks on tuyere line integrity. The maximalcoke addition to the vessel is limited to ap-proximately 2 t/h from practical experience. In thissimulation, the Fe/SiO2 ratio in the slag was set to1.42. The final copper losses in slag tailings wereassumed to be 0.39 wt.% at a slag concentrate grade

of 37 wt.% Cu.25 With an oxygen enrichment of 43%,the heat balance was closed with a slag temperatureof 1244�C. These conditions, given as a reference,are the same conditions as presented by Coursolet al.10

In the BBS furnace case, with shrouded tuyeres,it is possible to achieve oxygen enrichment as highas 75 vol.%. By using this technology allowing forhigher oxygen enrichment, the coke addition in thesmelting unit was reduced to zero, and the slagconcentrate grade was reduced to 15 wt.% Cu al-lowing a lower %Cu in slag tailings (0.26 wt.%) to beassumed. The lower grade of slag concentrate pro-vides a greater tonnage of cold material to be added,thus being available to absorb excess smelting heatas a consequence of the relatively high level ofoxygen enrichment used. Thus, with the two chan-ges mentioned above, an oxygen enrichment level of63% is allowed to close the heat balance and obtaina slag temperature of 1180�C.

RESULTS

Tables III and IV show the results of energy andfossil fuel consumption for the Noranda Reactor andthe BBS furnace cases, respectively. Separate col-umns for electric energy, expressed in kWh/t ofanode copper, and fuel, expressed in MJ/t of anodecopper, are provided in these tables. The fuelequivalents of electrical energy were calculated us-ing a power plant efficiency of 38%.9 In the tables,the numbers for items such as fuel, oxygen, com-pressed air, secondary gases, and fugitive gasescorrespond to respectively overall smelter con-sumption or production.

Fig. 6. Model flowsheet configuration used for the Noranda flowsheet and the BBS flowsheet.

Coursol, Mackey, Kapusta, and Valencia1072

Table III. Energy requirements for the Noranda reactor case with Peirce–Smith converters and slagflotation (slightly modified from Ref. 10 for consistency with following BBS furnace case)

Item

ElectricalFuel Total

kWh/t Eq MJ/t MJ/t MJ/t

Fuel 0 0 4088 4088Tonnage oxygen 256 2427 0 2427High pressure air 135 1276 0 1276Process gas handling 61 576 0 576Secondary and fugitive gas handling 76 720 0 720Supplies, steel, etc. 2 17 39 56Milling slag 160 1515 0 1515Acid production 401 3800 0 3800Lighting and miscellaneous 30 284 0 284

1120 10,614 4127 14,741Steam credit �176 �1669 �1669

944 8946 13,072

Table IV. Energy requirements for the BBS furnace case with Peirce–Smith converters and slag flotation

Item

ElectricalFuel Total

kWh/t Eq MJ/t MJ/t MJ/t

Fuel 0 0 2331 2331Tonnage oxygen 298 2824 0 2824High-pressure air 133 1255 0 1255Process gas handling 48 459 0 459Secondary and fugitive gas handling 76 720 0 720Supplies, steel, etc. 1 12 39 51Milling slag 160 1518 0 1518Acid production 360 3413 0 3413Lighting and miscellaneous 30 284 0 284

1107 10,486 2370 12,857Steam credit �129 �1223 �1223

978 9263 11,634

The calculations performed in this study and selected data from previous studies9,10 are shown in Table V.

Table V. Comparison between energy consumption for copper production (concentrate to anode) for thereverberatory furnace and for selected modern copper smelting technologies

Processing route Electric energya Fossil fuela Totala

KH-hot calcine reverberatory8 2173 15,935 18,108Flash smelting–flash converting–slag flotation9 9266 1518 10,784Isasmelt–Peirce–Smith converting-rotary slag cleaning9 6903 4175 11,078Mitsubishi Process (Mitsubishi Materials Corporation, Tokyo, Japan)9 8508 2498 11,006Noranda–Teniente with dry feed + slag flotation9 10,088 2657 12,746Noranda reactor (filter cake) + PSCs + slag flotation 8946 4127 13,072Bottom blowing smelting (filter cake) + PSCs + slag flotation 9263 2370 11,634

aAll energies are expressed in MJ/t of anode copper.

Energy Consumption in Copper Smelting: A New Asian Horse in the Race 1073

CONCLUSION

From an energy perspective, our calculationsindicate the BBS/SKS technology to be superior to theNoranda/Teniente smelting vessels and to be nearlyequivalent to other highly efficient technologies:flash smelting, Isasmelt, and the Mitsubishi Process.

The calculated specific energy data presented inTable V are not only for smelting but also fortreating concentrate through to anode copper;hence, the results of all technologies can be im-proved by optimizing peripheral equipment. Theauthors believe that more work needs to be doneregarding better converting technologies and anodefurnace design to further reduce energy usage.Oxygen enrichment, a dominant aspect in improv-ing energy efficiency, has been incorporated in mostmodern technologies, and the industry now has tosearch elsewhere while reaching even higher en-richment levels. Converting, fire refining, wasteheat recovery, and oxygen/acid production are allkey areas to allow further improvements in energyefficiency and energy usage.

The Noranda Reactor and Teniente Converterhave been work horses in Canada and Chile duringthe last 40 years. Much attention has been placed inincreasing productivity but with no major change invessel configuration or injector technology. Thecurrent practical limitation in oxygen enrichmentwith low-pressure, nonshrouded tuyeres is consid-ered near to 45% O2. It is believed that high-pres-sure injectors and/or shrouded tuyeres added to theNoranda–Teniente Converter can provide sig-nificant benefits in terms of energy efficiency, withattendant improvements in environmental perfor-mance. Using this approach, such vessels located inChile could improve operational and environmentalperformance and better energy efficiency with likelya low capital investment.

ACKNOWLEDGEMENT

The authors would like to acknowledge the con-tribution of Dr. Carlos Diaz in previous publicationson energy efficiency, which paved the way for thepresent study.

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