metallurgical and mining requirements

8/3/2019 Metallurgical and Mining Requirements

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Presiden tia l Address

T h e e n e r g y r e q u i r e m e n t s o f t h em in in g a n d m e t a l lu r g i c a l in d u s t r yin S o u t h A f r i c a

b y P . R . J O C H E N S * . P r . E n g . . B .S e . ( E n g . ) (W i ts . ) . M .S e . ( E n g . ) (W i t s . ) . P h .D . (W its . )SYNOPSISSouth Africa depends to a considerable m easure on the exploitation of m ineral reserves and the processing ofthese m inerals. One of the prim e requirem ents for the m ining and m etallurgical industry to continue in this vitalrole is a cc ess to su fficie nt en erg y in a suita ble fo rm . H en ce , fou r im portan t qu estio ns are d iscu sse d:D oes S outh A frica have sufficient energy for the processing of its m inerals and m etals!W ill the cost of energy allow S outh A frica's m inerals and m etals to com pete on w orld m arkets?

C an m in in g a nd meta llu rg ic al p ro ce ss es b ec ome mor e e ne rg y- ef fic ie nc lC an m ining and m etallurgical processes be adapted to the various form s of energy that m ay have to be utilizedin th e f utu re ?It is concluded that about 26 per cent of the extractable reserves of coal would be required in the m ining andpro ce ssin g o f 5 0 pe r ce nt of S ou th A frica 's re serv es o f g old , p la tinu m-g ro up m etals , c op per, iron , fe rro ch rom ium ,and ferrom anganese. However, the reducing agents required exceed the extractable reserves but not the totale stim ate s o f m in ea ble i n s it u res ou rce s o f m eta llu rg ical c oa l an d an th racitic c oa l. E ven u nde r th e sev ere c on strain tthat coal could becom e virtually the sole source of energy, only about three-quarters of the extractable reserveso f coa l would have been consumed b y t he y ea r 2 02 5.The reasonably assured resources of uranium m etal that can be recovered at less than $80 per kilogram are con-sid era ble an d, at c urr en t c on versio n eff ic ien cies to e lec tr ic ity, are eq uiva le nt to o ne-fifth of the ex tr acta ble res erv esof coal. The rate of exportation of energy in the form of U 30. w as about five tim es that of coal in 1978.It is pointed o ut t ha t t he p ri ce o f e ne rg y h as a d ir ec t e ff ec t o n t he c ompet iti ve ne ss o f met al s, a nd , a lt ho ug h c on -stituting only a sm all proportion of the selling price of precious m etals, it represents a significant proportion of theselling price of copper and m etals recovered from oxide ores.The sc op e fo r th e c on se rv atio n o f e ner gy a pp ear s to be g re ate r in th e e xtra ctio n a nd co nv er sio n o f p rim aryene rgy-ca rr ie rs to e le ct ri ca l ene rgy than in o ther mining o r me ta llurgica l f ie ld s.P ro vi de d t ha t a lt er na ti ve s ou rc es o f e ne rg y ca n be c on ver ted to e le ctr ica l en er gy , th ey c an b e ap plie d to th em ining and m etallurgical industries. T he decision as to w hich type of energy should be used in specific m ining andmetallurgical situations is c omp li ca te d, a nd i s l ik el y t o b e s ub je ct ed t o c lo se r s cr ut in y t ha n i n th e past.T he hope is expressed that the tentative conclusions reached w ill give rise to m ore-quantitative analyses fromthose qualified to undertake such an exercise. Inevitably, the questions asked at the outset give rise to m ore ques-tions, and the m ore interesting ones are posed in the context of each conclusion.SAMEVATTINGSuid-A frika is in 'n groot mate afhanklik van die ontginning van sy mineraalreserwes en die verwerking van hierdiem inerale. E en van die prim ere vereistes vir die m ynbou- en m etallurgiese bedryf om hierdie belangrike rol te kanve rv ul, is d ie b ek om baa rhe id va n vo ldo en de e ne rg ie in 'n geskikte vorm . In die lig hiervan is daar vier belangrikesake wat bespreek word:Het Suid-Afrika genoeg energie vir die verwerking van sy minerale en metale?S al S uid -A frik a se m in erale e n m eta le in d ie lig v an d ie en erg iek os te op die w ereld ma rkte k an m eed in g?Kan mynbou- en meta llu rg ie se p ro se ss e e ne rg ie m ee r d oe ltr ef fe nd g eb ru ik !Kan mynbou- en m etallurgiese prosesse aangepas w ord by die verskillende vorm s van energie w at m oontlikin die toekoms gebruik sal moet word!Die slotsom is dat ongeveer 26 persent van die ekstraheerbare steenkoolreserwes nodig sal wees vir die ont-ginning en verw erking van 50 persent van Suid-Afrika se reserwes van g ou d, p la tin um gro epm eta le , ko pe r, yste r,fe rro ch ro om e n fe rro ma ng aa n. D ie re du se erm id de ls wat nodig is oorskry e gt er d ie e ks tr ah ee rb ar e r es erw es , m aa rnie die to ta le r am in gs van ter plaatse ontginbare bronne van m etallurgiese steenkool en antrasietkool n ie . S elfs

m et die e rns tig e be lemm ering d at stee nk ool fe itlik d ie e nig ste bron van energie kan word sal daar net ongeveerd rie-k wa rt v an die ek stra he erb are stee nk oolre serw es te en d ie jaar 2 02 5 v er br uik w ee s.Die redelik versekerde bronne van uraanmetaal wat teen koste van minder as $80 per kilogram herwin kan wordis aansienlik, en is m et die huidige rendem ent v an d ie om setting in e le ktris ite it g ely k aan e en -vy fd e va n die ekstra-heerbare steenkoolreserwes. D ie uitvoertem po van energie in die vorm van U30. was in 1978 ongeveer vyf m aald ie v an s te en ko ol.Daar word op gewys dat die prys van energie 'n d ir ek te u itw er kin g op die m ededingingsverm oe van m etale hete n h oewe l d it s le gs 'n k le in g ed ee lte v an d ie verkoopprys van edelmeta le ui tmaak, verteenwoordig d it 'n b ed uid en dedeel van die ve rko op prys v an k op er e n meta le w at uit oksiedertse herw in w ord.Die geleentheid vir die behoud van energie is blykbaar groter in die ekstraksie en omsetting v an p rim er e e ne rg ie -d ra er s in e le kt rie se energie as op ander m ynbou- of meta ll urg ie se t er re in e .M its altern atie we e ne rgie bro nne in elek tries e en erg ie om ge sit ka n w ord ka n hu lle in die m yn bo u- en m etallurg ie sebed ry f g eb ru ik word. D ie besluit oor die tipe energie om in 'n b ep aa ld e m yn bo u- e n meta llu rg ie se s itu as ie te g eb ru ikis in gewik ke ld e n s al w aa rs ky nlik n ou ke ur ig er a an dag a s in die ve rle de g en ie t.D ie v er tr ou e word u it ge spreek dat die t en ta ti ewe gevo lg trekk ing s w at g em aa k word, sal lei tot m eer kw antita-tiewe ontledings deur diegene wat bevoeg is om sulke ontledings te doen. Die vrae w at aan die b eg in g es te l is , le ionverm ydelik tot nog vrae en die interessantstes daarvan w ord in sam ehang m et elke gevolgtrekking gestel.

*Deputy President, National Institute for Metallurgy, Private Bag X3015, Randburg, 2125 Transvaal. @ 1980.JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY S EP TE MB ER 1980 33 1


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.Estimated contained Estimated average E stim ated c oa l re qu ire dMetal metal or alloy in consum ption per M treserves of ore ton of metal

t Energy* Coal* As elect ric ity t A s co altMW.h tGold 20 000' 20000 11 2P la tin um -g ro up m eta ls 306464 20000 17 1Copper 64000003 1O,6t 19Iron 5 700 000 0003 1, 0 2850Ferrochromium I 240 000 0004 3,7 0,9 1284 55 8Ferromanganese 12000000003 2,7 0,8 90 7 48 0

Sub-totals 2493 3888Total 6381

IntroductionAs stated repeatedly, the standard of living of all the

inhabitants of South Africa depends to a considerablemeasure on the exploitation of mineral reserves and theprocessing of these minerals. The mining and metal-lurgical industry provides employment for about onem illion people, m akes the country independent of almostall m ineral and metal imports, provides a secure basisfor future industrial developm ent by ensuring the supplyof raw materials, confers a considerable degree ofstrategic importance on the subcontinent, encouragesgrowth points in underdeveloped areas, and, in con-stantly dem anding industrial and technical equipm ent,assists in creating sophisticated secondary industries. A san example, revenue from mineral and metal salescurrently represents about 65 per cent of all foreignexchange earned by South African exports abroad, andthe contribution to the Gross Domestic Product in 1979was about RIO 000 million 1.One of the prime requirements (apart from adequate

capital and trained manpower) for the m ining andmetallurgical industries to continue in this vital role isaccess to sufficient energy in a suitable form . Hence,the follow ing rather naive, but nevertheless im portant,questions should be asked:(1) Does South Africa have sufficient energy for the

processing of its minerals and m etals?(2) W ill the cost of energy allow South Africa's mineralsand metals to compete on world markets?(3) Can mining and metallurgical processes becomemore energy-ef fi cien t?(4) Can mining and metallurgical processes be adaptedto the various forms of energy that may have to beutilized in the future?

One could doubtless adopt several sophisticatedapproaches in attempting to answer anyone of thesequestions in detail. In fact, each question deserves anintensive investigation by persons with the necessaryexpertise, and several organizations and committees areknow n to be considering various facets of the local energysituation. I do not pretend to supply quantitativeansw ers, but merely attem pt, from the non-confidential

information that is available, to arrive at qualitativetrends that may be found sufficiently interesting toinitiate discussion and to motivate an in-depth study ofthe questions posed. The energy-supply industry andthe m ining and metallurgical industry are extremelylarge, technically complex, and capital-intensive, andchanges cannot therefore be made rapidly. Long-termplanning is indicated, which in turn directs attention tothe questions posed above.1. Does South Africa have sufficient energy for theprocessing of its m inerals and metals?Energy for P roduction of M etalsThe most simplistic approach to this question wouldprobably involve the identification of known reserves of

ores, the arbitrary assumption that 50 per cent will bemined and processed locally, and a determination of thetotal amount of energy consumed in the production ofmetal commodities from 50 per cent of the reserves. Thevalue for the total consumption of energy per unit ofmetal produced would have to include the sum of theenergies consum ed during m ining, beneficiation, hydro-m etallurgical or pyrom etallurgical processing, refining,shaping, and transportation on site, together w ith energyconsumed in the commodites and services used duringany of these activites. In Table I, I have attempted todo this for some of the metals produced in South Africa.The energy consumed per ton of metal produced can beregarded as low because only the operations associatedwith known consumptions of energy on site were con-sidered. In addition, the reducing agents required foroxide ores are included in the total coal required for theprocessing of 50 per cent of the metal in the ore reserves.It is appreciated that the list of minerals and metals

in Table I is by no means complete. However, as thenext most important consumer of electrical energy in1978 used only half that of copper, which was the lowestconsumer on the list, the list is sufficient for the purposesof this discussion. It is interesting to note that coalm ining itself consumed 1078000 MW .h in 19785, whichplaces it slightly ahead of the copper-m ining industry interm s of annual energy consum ption.

TABLE IESTIMATED COAL REQUIREMENTS FOR THE MINING AND PROCESSING OF 50 PER CENT OF THE RESERVES OF SOME METALS

* E stim ates based on available inform ation (see text)t 0,56 t of coal = 1MW.hot Total energy consumption is expressed in electrical units for the purpose of this calculation.Note: The superscript numbers refer to the list of references on p. 342.33 2 SEPTEM BER 1980 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF M INING AND METAL LURGY


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Metal 19 78 to 2 00 0 1 97 8 to 20 25Gold ** **P la tin um -g ro up m eta ls 10 45Copper ** **Iron


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in the economy, and to meet the increased energydemand as a result of the phenomenal increase inpopulation and in per ca pita consumption that hasbeen forec as t. )(e) Coal exports w ill average 40 M t per annum through-out the period under consideration. (A ll indicationsare that export quotas and railage facilities w illenable such an amount to be exported within thenext few years.)Table II gives the proportions of the present reservesthat would have been extracted at annual growth ratesof 4 per cent to the year 2000 and 2025.

Because of the trend that is established between thereserve of a commodity and the rate of its exploitationat any given time, the growth rate of 4 per cent perannum for gold and copper is completely unrealistic.For example, the most recent predictions for gold 2 arethat, until 1987, the production of gold will remainrelatively close to the present levels of around 700 t perannum and then fall off gradually to about 350 t at theturn of the century. In fact, at a real gold price close tothat at present, the existing mines are expected toproduce over 15000 t of gold in the next 50 years. Newmines can be expected to add another 5000t.By the year 2000 the reserves of the ores from whichiron, ferrochromium, and ferromanganese are producedwould have been little affected, in that less than 5 percent of each would have been mined and processedlocally. The platinum-bearing reserves would also havebeen relatively unaffected, in that about 10 per centwould have been m ined and processed. By the year 2025,the situation would have undergone relatively littlefurther change; that is, over three-quarters of each ofthe oxide ores w ill not have been processed locally(significant proportions may have been exported) andover half the ores containing platinum-group metals w illstill be in the ground.On the previous assumptions of a growth rate in localcoal consumption of 6,8 per cent from 1978 to 2000 and4 per cent thereafter, and of an annual average coalexport figure of 40 Mt, it can be calculated that theproportions of the extractable reserves (24891 M t) that

w ill have been consumed will be 18 per cent by 2000 and76 per cent by 2025. Therefore, in the context of theassumptions that were m ade, there should be no shortageof coal by the year 2025, and there should be adequatetime to perm it the development and introduction ofalternative sources of energy.Ura nium Reso urc esAt this stage, you will be justified in wonderingwhether I am going to consider nuclear power. Of course,I am. South Africa's reasonably assured resources ofuranium metal that can be recovered at less than $80per kilogram are estimated9 to be 247 kt. The currentconventional nuclear-power stations would be capableof generating at least about 8744 X 1 06 M W.h from sucha quantity of uranium. (Depending on the load factorand on fuel cycle param eters, a conventional reactor cangenerate at least 30 MW.h from 1 kg of U3Og.) Therefore,if all these rea 10nably assured resources of uranium wereutilized in conventional reactors, the electrical-energycontent w ould represent about one-fifth of the electrical-energy content in the extractable reserves of coal.33 4 SEPTEMBER 1980 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

Like the reserves of coal (and several metals), thereasonably assured resources of uranium metal are alsolikely to increase with time; for example, the inclusionof reasonably assured resources of uranium recoverableat $80 to $130 per kilogram brings the total to 391 kt9.It is possible that, at som e future date, unless alternativdenergy-producing processes are developed, fast-breederor thermal-breeder nuclear-power plants may be in-evitable. If the total reasonably assured resources ofuranium (391 kt) were to be used in fast-breeder reactorsand not in present-generation conventional thermalreactors, the energy content of the uranium would in-crease by a factor of 60 to 70 - equivalent to about 20times the energy content of the extractable reserves ofcoal. Presumably it is important to have sufficient con-ventional power until these newer power-generatingf aci litie s b ec ome a va ila ble .W hen I referred previously to the export of coal fromSouth Africa, I assumed, for the purpose of the energybalance, that coal exports would soon reach a figureof 40 Mt per annum . In 1978, coal exports had attaineda figure of 15,4 M t per annum , earning foreign-exchangeto the value of R325 million3. In 1978, the produc-tion of uranium was 4674 t of U3Og, w ith a foreign-exchange earning of about R335 m illion9. On thebasis of the electrical energy that can be generated fromcoal and uranium in conventional electrical-generatingplants, the energy in the uranium exported representsabout five times that in the coal exported if it is assumedthat the major proportion of the uranium is exported.From the above it is also evident that energy containedin coal is purchased at a price several times greater thanthat contained in uranium. M ore im portant, calculatedon the basis of the present efficiency in the conversionof these prim ary energy-carriers to electrical energy, theenergy in the coal and uranium exported represents m orethan tw ice the primary energy-carrier required togenerate the electricity supplied by Escom for the sameperiod. Hence, it can be reasoned that the export ofenergy in the form of these primary-energy carriers farexceeds the energy consumed in the processing of thee xp or te d m eta ls.As mentioned previously, the rate of production ofgold is expected to decrease gradually after 1987,

although the industry is likely to exhibit a good level ofactivity until up to and beyond 2030. Of the reasonablyassured resources of uranium, less than 10 per cent is tobe found outside the greater W itwatersrand Basin.Therefore, it can be argued that, by the year 2000, overhalf of the uranium resources could have been extractedalong with gold. Similarly, by the year 2030, up to 90per cent of the uranium reserves could have been ex-tracted. The current expansion of uranium -extractionfacilities makes the assumption a reasonable one. Atpresent, the major proportion of the U3Og produced isexported, and the local present rate of installation ofnuclear-pow er generating plants indicates that the m ajorproportion may continue to be exported for many yearsto com e.Energy Used in G old M iningThe gold-m ining industry holds a unique position inrelation to the energy consumed during the m ining and

processing of metals, apart from the fact that it is by


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far the greatest consumer of electricity. So far, all theuranium has been produced as a byproduct or co-productof gold, the production ratioIO in 1978 having been6,5 kg of U3Os for every kilogram of gold produced.The ratio of U 3 0 S to gold is expected to increase rapidlyto 8,5 as present expansion program mes are im plementedand new mines are opened. However, even at the presentratio, it can be calculated that the U3O s recovered bythe gold-m ining industry would be capable of generating195 MW .h for each kilogram of gold mined. Therefore,although 20 MW.h were consumed for each kilogram ofgold produced, the byproduct contained the equivalentuseful electrical energy of 195 MW.h. In fact, althoughthe gold-m ining industry is the largest single consumerof electrical power, it produced as a byproduct or co-product a primary energy-carrier with an energy contentalmost twice the energy that was required by Escom in1978.2. W ill the cost of energy allow South Africa'sm inerals and metals to compete on world markets?

An attempt to provide some qualitative answers tothis question requires consideration of at least twoaspects: the proportion of a commodity's selling pricethat is attributable to the cost of the energy component,and the situation of competing countries with respect toraw m aterials and energy.

Table III gives estimates for 1978 of the cost ofelectrical energy as a proportion of the selling price ofmetals. It can be seen that, for gold and the platinum-group metals, the cost of electrical energy contributesabout 5 per cent to the selling price. All other thingsbeing equal, a country producing gold and platinum-group metals that has electrical energy at half theSouth African price would have an advantage of onlyabout 2,5 per cent. Perhaps it could be argued that evensuch a major advantage in electrical energy by onecompetitor should not significantly affect the com-petitiveness of the other, because the difference shouldbe within the profit margin of either. However, theabsolute price of local electrical energy does have aneffect on the mining of marginal ores and on the ultimaterecovery during processing. Hence, if consideration isgiven only to the cost of energy and the extent ofreserves, South Africa should be able to retain its com-petitiveness on overseas markets in respect of gold andplatinum -group m etals. (South Africa's gold reserves are51 per cent of the world's reserves, and its platinum

TABLE IIIESTIMATED COST OF ELECTRICAL ENERGY AS A PROPORTION OF

THE SELLING PRICE OF THE METAL IN 1978.

Metal C os t o f electrical en erg yas percentage of selling price ofmetalGoldP latin um -g ro up m eta lsCopperSteelFerrochromiumFerromanganese

55.*1815

* The cost of energy for the production of these metals is notprim arily dependent on the price of electricity (see text).

reserves are 75 per centll.) At the risk of making a self.evident statement, I can say that the ore w ill always beprocessed locally, irrespective of whether the prices offoreign energy are significantly less than those per-taining locally, because the transportation costs of theore would exceed any cost advantage provided by theenergy used in the processing of the mined ore.Energy C ost for C opper

The total energy consumption per ton of copper is high,as noted in Table I, and therefore the cost of energy as aproportion of the selling price of copper will be high. Ifall the energy requirements were met by electricalenergy, the estimated cost of this electrical energy as aproportion of the selling price would be about 15 percent. However, it is common practice for pulverized coalto be used to fire the reverberatory furnaces (a costsaving), but a very considerable additional cost inenergy is incurred by the use of liquid fuels to power thelarge vehicles used in open-pit m ines. The local reservesof copper are relatively small (about 2 per cent of theworld's reserves) and the cost of energy is a significantproportion of the selling price. Several types of energycan be used, and careful evaluation of the lowest overallcost is essential to ensure future com petitiveness.E ne rg y C os t fo r F er ro -a llo ys

The costs of electrical energy represent about 17 percent of the selling price of ferrochromium and ferro-manganese, and a competitor could have a very definiteadvantage if his energy costs were significantly lower.Even a relatively small advantage in the price of energycould affect market penetration in the over-supplysituation that exists from time to time. Also, it willremain economically feasible for competitors to importores and process them, provided that the cost of theirenergy is not significantly higher than that of the countryfrom which the ore is imported. The vast reserves ofores and large reserves of energy should ensure that theseimportant alloys continue to be exported to an increas-ing extent. Indeed, increased further processing offerrochromium to stainless-steel ingots and hot-rolledbands can be visualized, which would take advantage ofenergy-conservation m easures within a large integratedplant for the production of ferrochromium and stainlesssteel. If the cost of electrical energy in South Africa wereto show an increase disproportionate to that of othercountries, not only would the ability of the local ferro-alloy producers to compete be seriously affected, but itis not inconceivable that, when w ishing to expand andto rem ain com petitive, they w ould contem plate exportingthe ore to countries in which they could take advantageof lower energy costs.E nergy Cost for Steel

Although by far the greatest proportion of virgin steelin South Africa is produced in blast furnaces, an in-creasing amount of steel is being produced in electric-smelting furnaces, and this latter steel is even moresusceptible to the price of electricity than are the ferro-alloys.

This significant dependence on the price of electricityis demonstrated by the existence of rotary kilns forprereduction or metallization, which prepare the raw

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material for electric smelting or melting and so decreasethe consumption of electrical energy by using coal for aportion of the energy requirem ents.C ost of E le ctric al E ne rgyTherefore, the cost of electrical energy can affect to a

relatively small degree the life of a precious-metal m ineand the recovery of the metal m ined, or can affect to avery considerable degree a producer's ability to competein the electric-sm elting industry. The record of electricalenergy costs in South Africa shows that the averagetariff increase from 1950 to 1975 was 4,4 per cent perannum, which compares favourably w ith the inflationrate. This increase was followed by increases of 30 percent in 1976, 48 per cent in 1977, and 16,5 per cent in19785. The quite extraordinary tariff adjustments in1976, 1977, and 1978 reflected the necessity for thisincome to be used for the financing of expansion bymeans of the Capital Development Fund. The 1979 and1980 tariff adjustments appear to indicate a return toEscom 's traditional price stability as shown in the periodbefore 1976. If such a trend can be maintained, it isdifficult to visualize that the price of electrical energywould place South African mining and metallurgicalindustries in a disadvantageous position.Those metals for which certain unit operations utilizecoal directly as a primary source of energy are likely to

continue to benefit from the comparatively low prices ofcoal; competitiveness should therefore be assured in thisrespect.The effect of the rapid price increases in liquid fuels islikely to affect most producers in W estern countries to a

sim ilar degree. However, their change to alternativetypes of primary energy-carriers may not be as flexibleas in South Africa.The sudden dramatic increase in the price of oil hashad a tremendous world-wide effect on the price of thealternative primary energy-carriers coal and uranium .It is interesting to note that the increased demand forthese sources of energy has had a very beneficial effecton So uth A frica's foreig n-exchan ge earnings by increasingboth the quantities and the prices of coal and uraniumexports. On the negative side, it can be expected that,in the long term , this new supply-and~demand situationwill also affect the local prices of these sources of energy.However, the price of electrical energy is not so much afunction of the cost of the primary energy-carrier (coalor uranium), but rather of the cost and amortization ofthe electricity-generating plant and its associated equip-ment. It will be interesting to see how long primaryenergy-carriers w ill be controlled by free-enterprise andsupply-and-dem and forces before various States initiatesome form of control to ensure sufficient local suppliesat favourable prices to promote other sectors of theireconomies.3. Can mining and metallurgical processes becomemo re ene rgy- ef fi ci en t?The energy-efficiency of a mine and an extractive-

metallurgical recovery plant depends on a number offactors, and a distinction has to be made between themetals that occur in very small concentrations (forexample, the precious m etals) and those which, although33 6 SEPTEM BER 1980 JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY

present in high concentrations, occur as compoundshaving high free energies of formation (for example,chromite).P roduction of G oldIn 1978, the gold-and-uranium mines of the Chamber

of M ines milled 78,2 M t of rock to produce 691,4 tonsof goldlo, and purchased about 15,8 million MW .hof electrical energy. This represents a consumptionof about 200 kW .h per ton milled, or about 20 MW .h perkilogram of gold. It was forecast12 in 1975 that thecontinuing programme on the improvement of theunderground-mining environment through better ven-tilation practices and the use of refrigeration wouldincrease the consumption of electrical energy. The im-plementation of the planned long-term mechanizationof underground-mining operations will further increasethe consumption, as w ill the cooling of this machinery,which will represent an additional increase of 40 per cent.The power for pumping is not expected to increasemeasurably as the depth of m ining increases, because thewater to be pumped is fissure water originating in theupper levels, but the power required for hoisting in-creases at a rate faster than the increase in depth ofmining.The necessity for improved strata control as the depthof m ining is increased may result in the hoisting of lower

tonnages of rock (less by up to 30 per cent) if the wasterock is used to refill worked-out areas. In addition, moreselective mining could decrease the tonnages of rock to behoisted (by up to 25 per cent), and would also decreasethe tonnages to be treated in the reduction works (whichaccount for almost 20 per cent of the total energy con-sumed in the mining and extraction of gold12). L ittlechange is expected in the consumption of energy per tontreated in the reduction works, and this includes theintroduction of gold-recovery processes based on theadsorption of gold on activated carbon.It is expected that the proposed process for the con-

centration of gold and other valuable minerals under-ground, which would perm it about 60 per cent ofthe ton-nage mined to be replaced in the excavation, could effectsavings in energy, although this is not the prim e motiva-tion for this novel concept13.P roduc tion o f P la tin um -group M etalsThe consum ption of electrical energy for the platinum -group metals and gold is sim ilar - about 20 MW .h per

kilogram . Because the ore reserves are adequate and thegeothermal gradients are relatively high, the platinummines are shallow. If the Merensky Reef has to befollowed to much greater depths or the lower UG-2 Reefis m ined, hoisting and pumping are likely to increaseproportionately, and the cooling requirements could beeven more significant. When the UG-2 Reef is m ined,the consumption of electricity during matte smeltingcould be very much lower than for M erensky ore, in thatthe grade of the flotation concentrate is often muchhigher - three to five times higher than that of con-centrate from the Merensky Reef. The effect on energysaving could be considerable; at present, matte smeltingis estim ated to account for as much as 25 per cent of theenergy consumed in the production of the platinum-group metals. In terms of specific power consumption


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during the smelting of matte, detailed heat balances forthe smelting of Merensky Reef concentrates in electric-smelting furnaces clearly indicate the potential benefit(perhaps a saving of up to 25 per cenP4) to be derivedfrom the feeding of dry concentrate, the reduction of theslag volume by the minimum of flux additions, and theimprovement of thermal insulation as a result of thecorrect cover of raw material over the slag.P roduc tion o f C oppe rCopper produced from open-pit m ines via conven-tional m illing circuits, reverberatory furnaces, andelectrorefining requires energy equivalent to between10 and 11 MW .h per ton of copperl5 . Modern develop-ments in smelting can considerably decrease the energycon,.'mmed during that process step, but the effect on theoverall consumption of energy is unlikely to exceed15 per cent.

Much has been said about the possibility that theenergy required in the hydrometallurgical recovery ofcopper may be less than that consumed in pyrometal-lurgical p rocessing. H ow ever, the m ajority ofthe pro posedh yd rometa llu rg ica l p ro ce sse s in co rp orate e lec tro win nin gfor the final recovery, and this consumes about 2,2 M W.hper ton, com pared w ith about 0,3 MW.h per ton for electro-refining by the conventional pyrom etallurgical routesl6.This leads one to suggest that, for high-purity copper,hydrometallurgical processing is unlikely to be lessenergy consuming than pyrometallurgical processing.It is recognized that cement copper from dump leachingcan be obtained at a saving in energy of more than 20per cenp5 of the energy required in the conventionalpy rom etallurgical process. H ow ever, the pro duct req uiresf urth er r ef in in g.P rodu ction of Ste el

The production of steel slabs by the smelting of ore in apig-iron blast furnace and refining of the hot metal tosteel in a basic oxygen furnace consumes energy equiva-lent to slightly more than that in 1 t of coal15, most of itin the form of coke. This is the process that is used mostfor the processing of iron ore, and has the lowest energyconsumption. In fact, the energy consumption is low com-pared with that used in other metallurgical processes,indicating that steelmaking is a relatively efficientprocess that benefits from the availability of high-gradeores.

The advantages to be gaiaed from the recycling ofscrap are also clearly shown in the case of steel (althoughnowhere nearly as spectacularly as for the preciousmetals) in that the energy consumed (in the form ofelectricity) for the remelting of scrap in the electric-arcfurnace is only half that required for the production ofsteel from orel5.

In the production of steel, there is a slow but steadyincrease in the use of the direct-reduction process, inwhich ore is reduced with a gas or solid reducing agentfollowed by electric melting. Several advantages can beclaimed for such a process, but lower consumption ofenergy does not appear to be one of them .P ro du ct io n o f F er ro -a ll oy s

Detailed heat and mass balances have shown that thetheoretical m inim um energy consum ption 17 in the pro-

duction of ferrochrom ium from standard raw materialsand by a standard process in large units is about 3,2MW.h/t, and it was recently shown that, w ith modernfurnace technology, process optim ization, and com putercontrol, a consumption of 3,6 MW.h/t can be attained.Little further reduction in the consumption of electricalenergy can be predicted. The heat lost during the tappingof molten alloy and slag is unlikely to be recovered,except in integrated plants in which the hot alloy canbe transferred to the process for the making of stainlesssteel. Particularly in the ferrochromium process (butalso relevant to other electric-smelting processes), theoff-gases are rich in carbon monoxide because they areproduced by the reduction reaction and very little of thecarbon monoxide participates in prereduction. Heatbalances for a 48 MV A furnace operating at 38 MW forone hour show that the carbon monoxide in the off-gasstream at 1O00C is equivalent to about 15 MW .h at aconversion efficiency of 100 per centIs. There appears tobe little doubt that the rapidly increasing cost of energywill warrant capital expenditure on the utilization ofthis source of energy in large plants, either for thegeneration of electric power or the preheating and pre.reduction of the ore (and other raw materials). Betterutilization of off-peak power should be attempted, eitherby sophisticated control strategy or by the installationof an additional process that can operate w ith a supplyof interru pted electrical energ y.

An interesting aspect is that the partial prereductionof chromite ore w ith carbon fines prior to smelting canlower the electrical energy required for smelting fromabout 4 MW.h/t to about 2,4 MW.h/t. However, theoverall consumption of cnergy per ton of alloy is unlikelyto b e altered significantly, since, altho ugh the g enerationof electricity is an inefficient process, it burns the coal tocarbon dioxide, w hereas the rotary-kiln process convertsthe coal predom inantly to carbon monoxide.

In respect of the carbonaceous reducing agent, theefficiency of chemical utilization is about 90 per cent,and little improvement can be expected beyond thefurther utilization of the carbon monoxide off-gases.

It is perhaps interesting to note that research anddevelopment on the applicability of plasma-arc tech.nology to the large-tonnage production of ferro-alloys ismaking slow but steady progress. Although it has severaladvantages, particularly the ability to sm elt fines direct,there has been no evidence that its speciiic energy con-sumption is likely to be significantly less than in theconventional process. Some attention has also beenfocused on the use of m odified blast-furnace technology.Short shafts, which would perm it the use of non-cokingcoals, and high degrees of oxygen enrichment may makesuch a process economically attractive, but the overallconsumption of energy is likely to be sim ilar.

Sim ilar reasoning can be applied to the production offerrom anganese, provided it is recognized that the higheroxides of manganese can be reduced by carbon monoxide.

Very interesting econom ic calculations could be under-taken to show whether the production process shoulduse less-expensive coal involving increased capitalexpenditure (for example, rotary kilns for preheatingand prereduction), or whether the process should be

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based on a lower capital investment, all the energy beingsupplied by electricity, which is relatively more expen-sive. Such calculations w ould be particularly valuable inthe local ferro-alloy industry, which has access to coaland to coal-based electrical energy at reasonable prices.E f f e c t o f E ne rg y C ost o n R eco ve ry

In most mining and metallurgical operations, the per-centage recovery is affected by the costs incurred in therecovery of additional values. Hence, the cost of energycan also, and often does, have som e sm all but quantifiableeffect on the recovery: for example, finer grinding canincrease the recovery slightly by improving the libera-tion. On the other hand, the overall consumption ofenergy per unit mass of metal can be reduced if theincremental energy per unit mass of metal requiredto effect the additional recovery is less than the presentconsumption of energy; for example, if the recoveryof the platinum-group metals by flotation can beimproved from the present 85 per cent to over 90 percent at a similar grade.The rapidly increasing cost of energy will focus in-creasing attention on the need to improve the efficiency ofmining and metallurgical processes as regards energyconsumption. However, rapid changes are not possiblebecause of the capital-intensive nature of the industry.Also, although energy savings can be accomplished incertain processes, such savings are not likely to total morethan 10 to 15 per cent. A militating factor in severalinstances is the decreasing grade of raw m aterials, whichimplies an increasing consumption of energy per ton offin al m eta l p ro du ct.E ffic ie nc y o f E ne rg y P ro du ctio n from Coa lIn this context, perhaps it would be useful to considerthe efficiency of energy production in the same way asthe production of metals was considered above; therecovery and efficiency of conversion of the primaryenergy-carriers assumes a greater role because there isan 'energy crisis' but not yet a 'metal crisis'. Until thebeginning of the 'energy crisis', a 30 per cent recovery ofextractable coal deposits in South A frica w as a com monlyaccepted ratiol9. The increasing use of open-cast miningmethods for relatively shallow and thick coal seams, andof panel and longwall m ining methods for deeper coalseam s, together w ith improvem ents in bord-and-pillarm ining methods, is contributing to an averall increase incoal extraction during mining. However, it has beensuggested that bord-and-pillar m ining is likely to remainthe most important method of coal extraction for manyyears, and it has been calculated that about 60 per cent ofthe country's coal reserves could fall within the scope ofbord-and-pillar mining with a coal loss of 40 per cent20.O verall, the extraction ratio is determ ined by economic,legislative, technical, and geological considerations, ofw hich the first is still the most important.

T he average conversion efficiency of coal to electricityby Escom's modern single-reheat stations is about 37per cent21. From this must be subtracted, firstly, theelectricity used for auxiliaries, which is about 5 per centof the power generated, and, secondly, the loss duringtransm ission, which amounts to about 7 per cent of thepower sent out to the point of sale of the units7. There-fore, on the assum ption that these figures are reasonably33 8

representative, and that the efficiency of mining extrac-tion is 40 per cent, the average overall efficiency in theprovision of electrical energy from coal in the ground tothe point of consumption is about 13 per cent.

As already mentioned, the efficiency of m ining ex-traction is improving and will continue to improve, butrelatively little improvement is taking place in theefficiency of conversion to electricity. This is not a localproblem; indeed, Escom 's new large power stations arecomparable with the best in the world. Efficienciessignificantly higher than those of the conventional powerstation do not appear to be practical because thesewould require an increase in the pressure and tempera-ture of the steam entering the turbines. T he m etallurgicalconstraints on operation at higher temperatures and theeconomic constraints on operation at higher pressuresare such that alternative concepts for electricity-generating stations may be sought.

One of the most prom ising developments is that of thecombined gas-turbinejsteam-turbine cycle, whichachieves a higher efficiency than that of the steam or gasturbine on its own. W ith the present technology for com-bined cycles, thermal efficiencies as high as 44 per centcan be attained. As the technology advances to perm itan increase in turbine inlet temperatures to 12000 andhigher, thermal efficiencies of 50 per cent may bepossible21. T he fuel requirem ent of such com bined-cyclepower stations will be clean fuel (gas or oil) and, in theSouth African context, the gasification of coal will be aprerequisite. (It has been demonstrated that a com bined-cycle installation could be supplied direct from a pres-surized fluidized-bed combustor. However, it appearsunlikely that full advantage could be taken of highergas-turbine operating temperatures; the combustiontemperature would be lim ited to about 9000 because ofproblems with ash fusion and deposition on the turbineblades.) Gasification is the topic of research-and-development projects throughout the world, and con-tinuous advancement can be expected. A gasificationplant feeding a com bined-cycle electricity-generatingplant would perm it the production of a wide range ofhydrocarbon byproducts, and could form the basis of anintegrated power station and chemical complex pro-ducing liquid fuels and chemical products, as well aselectricity from coal. An additional advantage in thegasification of coal as fuel for a combined-cycle genera-ting plant is that the quality of the coal in terms of ashcontent and size need not be as good as in other power-station applications. This would make possible a betterrec()very and utilization of coal.

Therefore, it can be seen that both mining and con-version efficiencies are capable of im provem ent, depend-ing on the usual technological and financial limitations.E ffic ie nc y o f Ene rg y P roductio n from U raniumThe other primary source of energy that is to beutilized in the immediate future for the generation ofelectricity is uranium (the first of tw o nuclear-poweredelectricity-generating plants under construction is to becommissioned in 1982), and should be considered alongthe same lines as w as coal. M ining at gold-and-uraniummines has been governed predominantly by a desire forthe recovery of the maximum amount of gold, and

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extraction efficiencies of 85 per cent and higher arebelieved to be generally achieved. The attitude is pre-sumably different for the deposits outside the greaterW itwatersrand Basin, namely, the southern Karoo, thenorthern Cape Province, and the uraniferous coal de-posits of the northern Transvaal. There, the recoveryduring mining will be determined predominantly by theprevailing price of uranium , w hich will also determ ine thegrade below which m ining and processing are uneco-nomic.However, attention could be focused on the efficientextraction of uranium from ore that has been minedpredominantly for the recovery of gold. (V irtually allcurrent uranium production falls into this category, andit should be borne in mind that less than 10 per cent ofthe known reserves that can be recovered at a cost of lessthan $80 per kilogram of uranium do not occur in thegreater Witwatersrand Basin.) The efficiencies in theextraction of uranium by leaching with sulphuric acidcan be as low as 75 per cent, but several plants achieve85 per cent. However, it can be predicted that there willbe a considerable increase in leaching efficiency when useis m ade of higher tem peratu res, increased con centrationsof ferric ions and acid, and pressure leaching.

Continuing research and developm ent are being under-taken in South Africa to decrease the cost and increasethe recovery of the uranium-extraction process, and toperm it the econom ic exploitation of ores w ith low er headvalues. A good example is the recent industry-w ideintroduction of continuous countercurrent ion-exchangeprocesses for the treatm ent of unclarified solutions. H igh-density resins will permit feeds with higher solids con-centrations or increased flow-rates to such plants, andit is predicted that resin-in-pulp plants m ay be successfuli n c er ta in a pp li ca ti on s.A lthough uranium recoveries during mining and pro-cessing are com paratively high, the present com mercialreactors are poor converters and burn less than 1 percent22 of the natural uranium required to run them. Thisis therefore the area on which attention is being focused.The first step is likely to be the recycling of plutonium,which is not yet carried out in general; when it is, theproportion of uranium burnt w ill increase to 2 per cent22,and the efficiency of providing electrical energy fromuranium in the ground to the point of consumption willthen approach 1 per cent.

T he nuclear variant o f the gas-turbine/steam -turb inecycle, namely the high-temperature gas-cooled reactor(HTR) using an all-ceramic core and helium as thecooling agent, is under development. It may becomecom mercially available tow ards the end of this century,and could be used for the generation of electricity(either via the combined cycle or the direct helium gas-tu rbine cycle), or po ssibly for direct therm al ap plications.Fast-breeder reactors hold the greatest promise forthe good utilization of nuclear fuel. Such reactors pro-duce more fresh fissile fuel than the primary fuel de-~troyed, and it should be possible for fast-breederreactors to be designed so that, over a lifetime of thirtyyears, they will fuel two similar additional units (i.e., adoubling tim e of fifteen years). Several prototypes exist,and com mercial dem onstration units are under construc-

tion. TechnicaHy, the most pressing problems ot suchreactors are related to the performance of the fuel rodsand the integrity of the structural material. However,recent w orld-w ide indications are that teehnical develop-ment may not be the rate-determining step in the intro-duetion of nuclear reactors, but rather the inereasingopposition to such reactors based on their possibleimpact on the environment, possible accidents, and thepossible susceptibility of the nuclear-fuel eycle toexplo itation by local or in tern ational terrorists.Low E ff ic ie nc yAlthough the energy-generating cycles for coal(mining and conversion) and uranium (mining, extrac-tion, conversion, and recycling) have relatively lowoverall efficiencies, it is only low efficiency in the con-version of coal to electrical energy that represents adefinite permanent loss. A lmost all the other lossesincurred as a result of deviations from ultimate effi-ciencies can be recovered as a function of increasingprice of energy and technological developm ents. C ertain-ly, the production of energy seems to offer more scopefor the conservation of energy than does the utilizationof energy by the m ining and m etallurgical industry.4. Can minin~ and metallur~ical processes beadapted to the various forms of ener~y that mayhave to be utilized in the future?

As is apparent from what I said earlier, electricalenergy constitutes the major proportion of the energyutilized by the local m ining and m etallurgical industries.Furthermore, there appear to be no technical reasonsw hy m ining activities and m etallurgical processes shouldnot be adapted so that their total energy requirementscan be supplied by electricity. It can therefore be arguedthat, provided alternative sources of energy can beconverted to electrical energy, they can be applied tothe mining and metallurgical industries. However, thelikelihood that alternative sources of energy can beapplied direct should be exam ined.A lte rnativ e Sourc es of E ner gyAlternative sources of energy, such as those providedby the action of w ind, tides, and waves, could be applieddirect to mechanical devices in the m ining and metal-lurgical industries, but remote geographical locationsand non-assured continuity of supply would probablymilitate against this, and the conversion to electricalenergy may be the obvious solution. Some alternativesources of energy, such as those provided by thermalgradients in the earth and oceans, geysers, and hotsprings, do not provide a sufficiently intense directsource of heat for pyrometallurgical operations, butcould be used to provide a continuous supply of heat atthe tem peratures required by hydro m etallurgical opera-tions. In general, these sources of energy are also likelyto be converted to electrical energy. It has been demon-strated that solar energy can be utilized direct to providetemperatures sufficiently high for all types of pyro-m etallurgical applications. However, large-scale pyro-m etallurgical operations are essentially continuous, theobject being the conservation of energy (apart from theoptim um utilization of capital-intensive equipm ent), andit is therefore suggested that even solar energy will

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generally be converted to electrical energy. (Solarevaporation is an obvious exception.)Although these alternative sources of energy are

likely to be converted to electrical energy for use in them ining and metallurgical industries, it is expected thattheir contribution will be relatively small for the fore-s eeab le f ut ur e.E lectricity th e B est V eh iclePerhaps a more important consideration is whetherelectricity is always the best vehicle for the energycontent of coal and uranium when this energy is to beused in the m ining and metallurgical industries.The mining industry generally requires energy in the

form of electrical energy, except possibly for nuclearexplosive devices for underground rock shattering as aprelim inary to solution mining. It should also be notedthat, traditionally, liquid fuels (mainly diesel) are usedto pow er the large vehicles in open-pit m ines. D ependenceon this source of energy has given rise to rapidly escala-ting mining costs. For example, a local copper producerstated23 that the cost of diesel fuel per ton of copperproduced was about R58 in 1978, and that this figurewould reach R215 per ton of copper produced in 1979.Because no decrease can be expected in the cost of liquidfuels, even when they are produced locally from coal inlarge quantities, serious consideration will be given tothe electrification of m ine transportation systems if theadditional capital expense can be recouped over are aso na ble p erio d.In the m ajority of m etallurgical operations, electricityis either essential or already established as the optim um

form of energy. However, the blast furnace for theproduction of molten iron, using coke as the source offuel and as the reducing agent, is an example of a processthat not only uses less energy than alternative processes,but is also associated with lower production costs. Themotivation to explore the application of blast furnaces(so modified as to perm it the use of reducing agentsother than coke) for the production of ferro-alloys isbased predominantly on the economics of iron produc-tion. Sim ilarly, consideration is being given to the partialprereduction of oxide ores by the use of pulverized-coalfiring in rotary kilns to decrease the consumption ofelectrical energy during smelting or melting by the useof cheaper coal at additional capital expense.The rmal E ne rg yIt can be reasoned that thermal energy from nuclearfission could be utilized direct instead of being converted

to electrical energy first. The thermal energy could betransferred direct from the nuclear pile to, for instance,a molten metal from which the heat could be transferredby heat exchange to a pyrometallurgical operation.Attention is also being focused on utilization of thereactor cooling load to produce reducing gases at hightem perature and pressure.F usion E nerg yIt has been stated that the supplies of fuel for fusionenergy (as opposed to fission energy) are so large as to be

considered inexhaustible. However, a vast range oftechnical problem s, including the high ignition tem pera-ture (the lowest is 50 X 106 K for the deuterium-tritium

reaction), containment of the high temperatures, and asufficiently high product of particle density and con-fin em en t tim e, m ust be so lved b efo re electricity -g enera-ting stations based on fusion becom e viable. T here is littleoptim ism that industrial units can be considered in thiscentury, and it may not be until the m iddle of thetwenty-first century that a significant proportion ofelectrical energy can be provided by this means.Carb on ac eo us R ed uc in g Age ntsO bviously, coal (or electricity derived from it), apart

from constituting a major source of energy to the m iningand m etallurgical industries, has an even m ore im portantrole as a carbonaceous reducing agent for local oxideores; that is, here the emphasis is on the reactive chemicalproperties of coal rather than on its energy potential.Table IV shows the estimated amounts of reducingagents required to process 50 per cent of South Africa'sreserves of oxide ores. The calculations w ere based on theassumption that 50 per cent of the reserves of iron,chromium, and manganese ore will be processed locally,that the minimum quantity of carbon required isgoverned by the stoichiometric requirements of thechemical reactions, and that the average fixed-carboncontent of the reducing agent is 55 per cent. From thesefigures, it can be seen that about 1981 Mt of coal suitablefor use as a reducing agent would be required. TheReport of the Petrick Commission6 classified 705 M t ofmetallurgical coal and 375 Mt of anthracitic coal asextractable reserves. Certainly, the sum of these two isonly about half of the requirement predicted above. TheC ommission 's fig ures for to tal m etallurgical coal (w ashed )and anthracitic coal (washed) are 3451 M t and 744 M trespectively, but these totals include proven, indicated,and inferred categories on the basis that the in situreserves of m ineable coal are 81 274 M t.Although these requirements for reducing agentsconstitute a relatively small proportion of the coalreserves, pyrom etallurgical processes require coal w ithm ore closely defined specific characteristics than thoserequired for coal that is to be converted to electricity orliquid fuels; that is, not only are the properties of thecoal specific with reference to its coking and charringproperties, but the ash content and its composition arealso very important, and the contents of sulphur andphosphorus have to be below certain levels. It has notyet been possible to identify which of the know n depositsof coal are suitable for use as reducing agents, nor whatfractions of other coal deposits could be rendered suitableby coal-processing operations. It should be noted thatthe minimum required properties of coal for use asreducing agenti'! could be decreased as a result of m odified

TABLE IVREDUCING AGENTS REQUIRED FOR THE PROCESSING OF HALF

SOUTH AFRICA'S RESERVES OF OXIDE ORE

Oxide ore C oa l r eq uire d fo r re du ctio nMt94 355 848 0

IronChromiumManganeseTotal 1981

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pyrometallurgical processes and processed reducingagents like form coke. Iron oxides can be completelyreduced, and manganese and chromite ore partiallyreduced, by carbon monoxide, and therefore the issueof coal quality can be circumvented to a degree by coalgasification. In the long-term future, a hydrogen-basedenergy cycle could perhaps lead to an alternative re-d uc in g a ge nt.Choice of EnergyIt might be argued that, because there is no legislationrequiring that m ining and metallurgical operations (in

fact any operation) should be efficient in terms of energyutilization, the type of energy used and the efficiency ofits utilization will be determ ined by the price to theconsumer of a particular form of energy. Several metal-lurgical operations can be identified where either coal orelectricity (derived from coal or uranium), or both, canbe utilized. Also, there are certain operations on minesand m etallurgical plants, particularly transport system s,in which electrical energy or liquid fuels (both are pro-duced locally from coal) can be utilized. The com parisonbetween the use, on the one hand, of cheaper energyinvolving an increase in capital costs, and the use, onthe other hand, of more-expensive energy involvinglower capital costs will continue to be an interesting one.A number of complicated factors must be considered insu ch an an aly sis:(a) the long-term availability of a particular type of

energy (particularly m etallurgical-quality coal),(b) the future efficiency with which coal and uraniumare converted to electricity, and coal to liquid fuels,(c) the future capital cost per annual unit of capacityof the various conversion installations (electricityand liquid fuels from coal, and electricity fromuranium),(d) the efficiency with which the mining and metal-lurgical industries utilize various types of energy onsite,(e) the on-site capital costs associated with each typeof energy in relation to the cost of purchased energy,an d(f) the effect of incremental expansion of mining andm etallurgical operations on the cost of the additionale ne rgy r equi re d.

ConclusionsFrom my qualitative discussion of four important

energy-related questions affecting the mining andmetallurgical industries, I can draw the followingtentative conclusions. If they are wrong, my excuse isthat I avoided the use of confidential information, that,in several instances, the required information was notavailable, and, especially, that my interpretation issubjective. Also, the conclusions may encourage more-quantitative analyses from those qualified to undertakethem. Inevitably, the questions asked at the outset havegiven rise to more questions, and the more interestingones are posed in the context of each conclusion.(1) The mining and processing in South Africa of 50

per cent of the reserves of gold, platinum-groupmetals, copper, iron, ferrochromium, and ferro-manganese would require about 26 per cent of the

extractable reserves of coal. On the assumption thatcoal could become virtually the sole source of energyfor a prolonged period, the proportion of coalreserves utilized annually in the mining and metal-lurgical industries w ithin the next few decades maybe lower than that required to ensure that 50 percent of the reserves of ores are ultimately mined andprocessed locally. However, even under thesesevere constraints, about three-quarters of theextractable reserves of coal would have beenconsumed by the year 2025, i.e., sufficient time isavailable to make major changes in the energy-supply industry and the mining and metallurgicalindustries. At that stage, the reserves of gold andcopper as estimated in the past would be close toexhaustion, while over half the platinum-groupmetals would still be in the ground, and over three-quarters of the oxide ores would not have beenp ro cessed lo cally . H en ce ,(a) although South Africa has an enviable record

in the planning and utilization of energy(namely, the supply of adequate electricalenergy, the recovery and beneficiation of ura-nium, and the conversion of coal to liquidproducts) is sufficient effort being devoted toensure that alternative sources of energy will beavailable locally on a sufficient scale duringthe 21st century1(b) is there any reason to change the establishedpolicy of exporting both oxide ores and metalsw hile e nco ura gin g in cre ased lo cal p ro cessin g1

(2) The reserves of uranium are considerable and, atpresent conversion efficiencies to electricity, areequivalent to one-fifth of the coal reserves. Bothcoal and uranium have shown such rapid increasesin demand, and hence price, that they contributesignificantly to foreign-exchange earnings; that is,R325 million and R335 million respectively in 1978.On the basis of the contained energy at presentconversion efficiencies and on the assumption thatthe major proportion of the U 30 S is exported, therate of exportation of energy in the form of U 30 Swas about five times that of coal in 1978. In relationto their respected reserves, the rate of exportationof energy via U3Os was about twenty-five timesgreater than that of coal.Hence,(a) although the predicted annual exportation ofcoal will soon reach 40 M t, should the figure be

encouraged to increase or decrease w ith time?(b) is the local and international nuclear-energyprogramme sufficiently defined for an assess-ment to be made of the period for which themajor proportion of the annual production ofU 30 S can be exported 1

(3) The price of energy w ill always affect the overallrecovery of metals. For precious metals, the cost ofelectrical energy constitutes a sufficiently smallproportion of the final price of the metals for theircompetitiveness not to be affected. However, as thecost of energy represents a significant proportion ofthe production costs of copper and of metals and

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al1oys trom oxIde ores, the iocai prIce of energy has adirect effect on their com petitiveness. There are indi-catioll'3 that the local costs of energy should not hin-der expansion in the exportation of minerals andm eta ls. H en ce ,(a) for what period of time is the relatively low

cost of electrical energy assured to the miningand m etallurgical ind ustry?(b) as several major processors of raw materialsdepend on the importation both of rawmaterials and of primary energy-carriers, cansuch producers continue to compete with pro-ducers in countries that have reserves of botht he se commodi ti es ?

(4) C onsiderable attention is being focused on increasedefficiency in the utilization of energy in the miningand metallurgical i:--.dustrics. Although there areseveral process steps in which the efficiency can beincreased by 10 to 15 per ccnt, the specific con-sumption of energy per unit of metal can be expectedto increase in several instances because of a decreasein ore grade and an increase in depths of mining.However, scope for the conservation of energyappears to be greater in the extraction and con-version of primary energy-carriers to electricalenergy than in other mining or metallurgical fields.Hence,(a) is sufficient co-ordinated planning, research,

development, and on-site improvement beingundertaken to decrease the consumption ofenergy per unit of metal and to increase theefficiency of extraction and conversion of coaland uranium to electrical energy?

(b) as, theoretically, only the conversion of coal toelectrical energy is associated w ith a perm anentloss, is this the area that should receive mostattention, or are there other areas of loss inwhich subsequent recovery is unlikely or theapplication of effort would have more chanceo f succe ss ?

(5) If other sources of energy can be converted toelectrical energy, they can be used in the mining andm etallurgical industry, but their direct applicationis not likely to be common. The decision as to whichtype of energy should be used in specific mining andm eta llu rg ic al situ atio ns is c om plic ate d.Hence,(a) can a meaningful study be undertaken of the

optimum types of energy for the various miningand metallurgical operations so that, not onlythe minimum energy is consumed, but theminimum capital requirements (on a plant anda national basis) are also assured?(b) can it be deduced that the cost of liquid fuelsderiv ed lo cally from coal w ill follo w the exam pleof local electrical energy and be relatively lowin the future since their reserves are not subjectto the same short-term horizons as are theliq1.:id fuels derived from crude oil(6) The reducing agents required for the local processing

of 50 per cent of the oxide ores exceed the extract-able reserves but not the total estimates of mineable3 4 2 S E P T E M B E R 1980 JOURNA L O F THE SOU TH A FR IC AN IN ST IT UTE O F M IN ING AND METAL LURGY

in situ resources of meta lIu rg ica i c oa l a nd an th rad tIccoal.Hence,(a) are sufficient attempts being made to ensure

that the comparatively limited reserves of coalsuitable as reducing agents are identified andreserved for this application and, further, thatthe maximum amount of suitable fractions arerecovered from other coal deposits before thecoal is used for other purposes?(b) are sufficient research-and-development pro-grammes being undertaken to ensure thatlower-grade and alternative reducing agentscan be utilized by the pyrometallurgicalindustries?Finally, although South Africa has been endowed

with an absolute treasure-chest of minerals and prim aryenergy-carriers (except, apparently, oil), a tentative m assand energy balance of raw materials shows that manwill have to use his ingenuity, both technical andeconomic, to ensure that these resources are exploited inthe best possible way and for as long as possible, to thebenefit of all the inhabitants. In particular, the foresightand detailed planning that have characterized pastdevelopments in this context in South Africa are evenmore important for the future.

References1. Processing, Feb. 1980. pp. 11, 13, and 14.2. ANON. Cham ber of M ines B ulletin, vol. 3 , no. 1. 12th Feb.,6 pp.3. M inerals Bureau, Johannesburg. Private communication,N ov. 1979.4. VON GRUENENWALDT, G. An evaluation of the mineralresources of the Bushveld Complex. Institute for GeologicalResearch of the Bushveld Complex, R esea rch R ep ort, no. 3 .

Sep. 1976.5. ELECTRICITY SUPPLY COMMISSION. Annual Report 1978.Sandton, the Commission, 1978.6. Report of the Commission of Enquiry into the Coal Reservesof the Republic of South Africa. Republic of South Africa,RP. 63/1975.7. DUTKIEWICZ, R . K . Coal requirements of the electric andchemical industries. Paper presented at Conference: Energyand Its Future in Southern Africa, Cape Town, 1975.8. COHEN, R. L. The econom ics of coal liquefaction. Paperpresented at Conference: Energy and Its Future in SouthernAfrica, Cape Town, 1975.9 . ATOMIC ENERGY BOARD OF SOUTH AFRICA . Annual report1979. Pelindaba, the Board, 1979.10. CHAMBER OF MINES OF SOUTH AFRICA. Annual Report1978. Johannesburg, the Chamber, 1978.11. NEETHLING, D., and ROSSI, G. World mineral supplysituation. 1975 vs 1977. The role of South Africa. Johannes-burg, M inerals B ureau Internal R eport 29, Nov. 1978.12. W HIL LIE R, A. , and LLOYD, P. J. Possible changes in theuse of energy in the mining industry . Paper presented at Con-ference: Energy and Its Future in Southern Africa, CapeTown, 1975.13. LLOYD, P. J. An integral m ining and extraction system foruse on W itwatersrand mines. J. S. A fr. Inst. M in. M etall.,vol. 79, no. 6 . Jan. 1979. pp. 135-148.14. RENNIE, M . S. Randburg, National Institute for Metal-lurgy. Private communication, Jun. 1979.15. BATELLE COLUM BUS LABORATORIES. Energy use patternsin metallurgical and non-metallic mineral processing (Phase4 - Energy data and flow -sheets, high-priority commodities).D .S. Department of Commerce, National Technical In-fo rm ation S ervic e, P.13. 245 759. 27th Jun., 1975.16. PAYNTER, J. C . A review of copper hydrometallurgy.J. S. Afr. Inst. M in. M etall., vol. 74, no. 4. Nov. 1973. pp.158~170.17. BARCZA, N. A . Randburg, National Institute for Metal-lurgy. Private communication, Oct. 1979.18. CURR, T. Randburg, National Institute for Metallurgy.Private communication, Oct. 1979.


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19. KING, P. Long term trends in South African coal m ining.Coa l, G old , B as e M in er ., M ar. 1979. pp. 37-45.20. WAGNER, H . Pillar design in coal m ines. J. S. Afr. Inst.M in . M eta ll. , vol. 80, no. 1. Jan. 1980.21. SHEER, T. J. Electricity generation by combined-cyclepow er stations incorporating coal gasification. Paper pre-sented at Conference: Energy and Its Future in SouthernA frica, C ape T ow n, 1975.

22. BR OWN, K. T. A review of nuclear power technology. Pa.perpresented at Conference: Energy and Its Future in SouthernA frica, C ape T ow n, 1975.23. PALA BORAM INING COMPA NY LIM ITED. Interim report tomembers and debenture holders for the six months ended30th June, 1979. Phalaborwa, the Company, 1979.

Graduate studies programme at W itsThe U niversity of the W itw atersrand offers a Graduate

Diploma in Engineering (GDE) and the follow ing higherdegrees:Master of Science in Engineering M .sc. (Eng.)Doctor of P hilosophy Ph.D .Doctor of Science in Engineering D .Sc. (Eng.)Doctor of E ngineering D . Eng.The Faculty of Engineering is introducing a specialized

programme of coursework and research leading to theM .sc. (Eng.) in the field of physical metallurgy, whichis open to candidates who have a three-year Bacheloror Science degree w ith suitable physics of chemistrym ajo r s ub je cts .G raduate D iploma in EngineeringA candidate for the diploma must hold the degree of

B.sc. (Eng.) (or the degree of B.sc. (Hons.) with anappropriate grouping of subjects) of the University or anequivalen t qu alification from another in stitu tio n.The curriculum extends over one year of full-time

study, or up to three years part-time, and comprises aprogramme of A-level (graduate level) and B-level(undergraduate level) engineering courses or under-graduate courses offered in other faculties. (Such coursesmay each be rated as equivalent to more than one B-levelcourse.) The credit point-rating system for courses isexplained below . The University will take into account acandidate's previous training and experience whenapproving a student's proposed curriculum . Exemptionwill not be granted on the grounds of attendance atprevious courses of a sim ilar nature, nor will a student beperm itted to register for a course substantially the sameas one previously com pleted. No dissertation is required,except when converting to an M .Sc. (Eng.). It should benoted that, for this conversion to take place, all GDEcourses must have been passed at the first attempt.Occa s ional coursesCourses may also be attended by graduates on an

occasiorutl basis, L e. not for degree pu rposes.

Credit point ratings for coursew ork for G DECandidates admitted to study for the Graduate

Diploma in Engineering shall complete courses withcredit points totalling not less than 24, of which not lessthan 18 shall be derived from A-level courses.Credit point ratings for coursework for M Bc. (Eng.)Candidates admitted to study for the degree of Masterof Science in Engineering by a programme of coursework

and research or development shall complete either(i) a set of courses w ith credit points totalling not lessthan 18, together w ith a report on a project equiva-lent to not less than six months of full-time work(counting an additional 18 points),

or(ii) a set of courses with credit points totalling not lessthan 24, together with a report on a project equiva-lent to not less than four months of full-time work(counting an additional 12 points).

At least 18 credit points shall be derived from A-levelcourses. A candidate shall be required to completeevery course at the first attempt.The credit point ratings of each course offered are

listed below after the A or B designation of the course.A -level (3 p oints each):37510 G eostatistical m ethods in m ineral evaluation3 7566 M ining finance37568 Econom ics of energy resources37536 M echanics and design of major rock slopes3 75 69 M ec ha nize d ea rthmo vin g37543 Mine design - open-pi t wo rk ings3 7556 T herm al environm ents u ndergroundB-level (2 points each):37612 Introduction to m ineral econom ics37614 Exploitation systems (Part 2)Any enquiries should be directed to Mr M . J. M artin-son, Department of M ining Engineering, M ining &Geology Building, University of the W itwatersrand, JanSmuts Avenue, Johannesburg. (Tel. 39-4011, ext. 559.)

JOURNAL OF THE SOUTH AFRICAN INSTITUTE OF MINING AND METALLURGY SEPTEM BER 1980 3 4 3

metallurgical and mining requirements

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