A cleaner production assessment of the ultra-fine coal waste generated in South Africa

Transcription

1 SAIMM_Dec_55-60:Templte Joul 12/6/07 8:03 AM Pge 811 Syopsis A clee poductio ssessmet of the ult-fie col wste geeted i South Afic by J.F. Reddick*, H. vo Blottitz, d B. Kothuis The South Afic col miig idusty is cuetly disposig of bout 10 millio tos of ult-fie col (<150 µm) pe ye. Oce discded, these sulphu-cotiig ult-fies cotibute to sevel eviometl poblems. As pt of poject iitited by the Wte Resech Commissio to ivestigte the use of Clee Poductio (CP) i the miig idusty, study ws cied out to detemie whethe CP ppoch could be used to idetify oppotuities to educe this col wste, d to detemie which of these oppotuities would be most fesible. I ode to do this, CP ssessmet ws coducted t thee cse study collieies i the South Afic Witbk colfield. Mss-blcig d smplig, followed by lbotoy chcteistio tests d site suveys, wee used to detemie the qutity, qulity d souces of the ult-fie col t the thee collieies. Litetue eviews, bistomig sessios d iteviews the followed to geete the CP optios. A eviometl, ecoomic d techicl fesibility ssessmet ws the peped fo ech optio, to detemie the most vible itevetios fo implemettio. A umbe of oppotuities wee idetified though the ssessmet. By pevetig cose col fom beig discded with the ult-fie col, the qutity of col disposed of could be decesed t ll thee collieies, d by up to 24% i oe cse. Icesig the cushe top size would educe the mout of col tht is milled to less th 150 µm, so tht less is wsted. The ult-fies tht hve ledy bee disposed of o sluy dms c be completely eclimed d coveted ito vluble poduct, which c be sold s powe sttio feedstock. The ewly pocessed ult-fies could be beeficited usig flottio d expoted togethe with the cose col. The esults of the ssessmets thus suggested tht wokble CP oppotuities to educe ult-fie col wstge exist t the sites ivestigted, d tht thei fesibility is colliey-specific. The ssocited ficil beefits of the poposed optios suggested tht CP is elistic ppoch to ddessig eviometl poblems. Keywods: Clee Poductio; col miig; col-wshig; ultfies eve highe. Oce discded, these sulphucotiig ult-fies cotibute to sevel eviometl poblems, icludig cid mie dige, dust elese d spoteous combustio. Thus, isted of beig viewed s commodity, col of good qulity is beig discded i lge qutities evey ye, theeby cotibutig to the eviometl dmge doe by the idusty. As pt of poject iitited by the WRC to itoduce Clee Poductio (CP) i the miig idusty, study ws cied out by the Uivesity of Cpe Tow s Deptmet of Chemicl Egieeig d BECO the Istitute fo Sustible Busiess to detemie whethe CP ppoch could be used to fid wys to educe o miimize this col wste, d to detemie which of these e the most fesible. The poject ws ispied by the successful itoductio of CP to sevel South Afic idusties, most otbly metl fiishig d textiles2,3. Clee Poductio i the cotext of the miig idusty I the miig idusty, whee eviometl degdtio is uvoidble side-effect, CP is descibed s cotiuous pevettive eviometl ppoch with the ultimte gol of educig wstes t souce. Thee e my othe, lbeit simil, defiitios of CP, but it is outside the scope of this ppe to udetke compehesive lysis of CP temiology. The ctul ppoch to CP c be pplied t physicl, mgeil d legisltive levels4 vi five techiques tht e show i Figue 1. T s c t i o P p e Itoductio The South Afic col miig idusty is cuetly disposig of ove 10 millio tos of ult-fie (<150 µm) col pe ye,1 becuse the idusty believes tht the high cost of dewteig the ult-fie col exceeds its vlue. Howeve, the qulity of this col is geelly equivlet to tht of the u-of-mie (ROM) col, d t some mies the qulity is * Deptmet of Chemicl Egieeig, Uivesity of Cpe Tow, South Afic. Uivesity of Cpe Tow, South Afic. BECO Istitute fo Sustible Busiess, South Afic. The Southe Afic Istitute of Miig d Metllugy, SA ISSN X/ Ppe eceived Nov. 2006; evised ppe eceived Aug The Joul of The Southe Afic Istitute of Miig d Metllugy VOLUME 107 REFEREED PAPER DECEMBER

2 SAIMM_Dec_55-60:Templte Joul 12/6/07 8:03 AM Pge 812 A clee poductio ssessmet of the ult-fie col wste Figue 1 The 5 key CP techiques 6 Good housekeepig, w mteil substitutio, techology chge, poduct chge d itel ecyclig e the five geelly ccepted ules fo chievig CP. Poduct chge icopotes esouce use optimiztio5 d y modifictios to the poducts. Good housekeepig ivolves impovemets i opetiol pocedues d mgemet, such s tiig d moitoig. Techology chges iclude impoved pocess utomtio d substitutio, while itel ecyclig efes to y w mteil e-use o ecyclig tht occus o-site. Sice the cocept of CP seeks to educe wste emissios, the costs elted to delig with the wste (i.e. disposl, w mteils, eegy, lbou, wte, tspot, cle-up, stoge, mgemet time etc.) e lso lesseed. Thus CP bigs bout svigs s well s lowe eviometl impcts. Method I ode to obti cuet dt bout the idusty, CP ssessmet ws coducted t thee collieies (efeed to s A, B d C) i the Witbk colfield, South Afic. Tble I displys cuet ifomtio petiig to ech colliey. I the fist step of the esech, the qutity, qulity d souces of the ult-fie col hd to be estblished t ech of the thee collieies. Site suveys d flow sheet lyses wee used to detemie the souces of wstes. Poductio sttistics fomed the bsis fo developig mss blce clcultios, d these wee suppoted by smplig d lbotoy chcteiztio of compositio, cloific vlue d pticle size distibutio. I the ext step, litetue eviews, bistomig sessios d iteviews wee used to geete CP optios. Ech ws the submitted to fesibility ssessmet to detemie the itevetios tht would be most pcticble to implemet t the collieies. The fesibility ssessmet pocedue is illustted i Figue 2. As depicted, the optios wee fist subjected to sc to ssess thei fesibility, fist o techicl d eviometl gouds, d the o ecoomic citei. The fesible optios tht equied low cpitl ivestmets could be implemeted, whilst those tht equied high cpitl ivestmets wee the submitted to ecoomic ssessmet. If two mutully exclusive optios wee both deemed vible, the moe pofitble would be give pefeece. Though this pocess, fesible CP itevetios could be idetified d ecommeded thoughout the idusty. CP optios to miimize the wstge of ult-fie col Thee e thee geel methods of educig ult-fie col wste. These e listed below d the discussed: Pevet the uecessy geetio of ult-fie col Pevet cose col fom beig discded with the ult-fie col Covet the emiig ult-fie col ito useful poduct. The lst method is cosideed CP itevetio becuse, by utilizig the ult-fies d covetig them ito poduct, wste is beig educed o eve elimited. This type of itevetio is kow s poduct chge i tems of the five CP techiques show i Figue 1. Pevet the uecessy geetio of ult-fie col Extctio of col udegoud is oe of the mi cuses of ult-fie col geetio. Mode mechized miig methods esult i the poductio of moe ult-fie col th mul miig methods. It is, howeve, highly ulikely tht the idusty would be willig to evet to mul miig, becuse of the sigifict ficil beefits of mechiztio. Cushig is the othe mi cuse of ult-fie geetio: Figue 2 Fesibility ssessmet pocedue Tble I Relevt cse study colliey ifomtio Colliey Type of mie Qutity of col Method of ult- % of Mied col discded Cloific vlue: ult-fies A Udegoud mied (tp) fies disposl s ult-fies (MJ/kg) i dy A Udegoud Udegoud 5 % 22.7 B Udegoud Sluy Dm 4 % 23.7 C Udegoud Sluy Dm 4 % DECEMBER 2007 VOLUME 107 REFEREED PAPER The Joul of The Southe Afic Istitute of Miig d Metllugy

3 SAIMM_Dec_55-60:Templte Joul 12/6/07 8:03 AM Pge 813 A clee poductio ssessmet of the ult-fie col wste othes, such s mteil hdlig, e egligible by compiso. Icesig the top, o mximum, size to which the col is cushed would seve to decese the mout of ult-fie d icese the popotio of cose col poduced. The mied col is cushed to top size of 40, 50 d 80 mm t collieies A, B d C espectively. The cose col pocessig equipmet is desiged to hdle col up to 100 mm i size. Theefoe, the cushig top size could be icesed while still emiig withi the equipmet s opetig size ge. Sice colliey C is cuetly cushig to lge top size, this optio is moe pplicble to collieies A d B. Plt tils should be coducted to esue tht icesig the top size does ot compomise the qulity of the poduct. Pevet cose col fom beig discded with the ult-fie col Col tht is lge th 150 µm should ot be puged with the ult-fies, s it c esily be upgded d dewteed t ech of the mies. It is theefoe uecessy fo +150 µm col to be discded with the ult-fies. Pevetig this fom hppeig will educe the mout of col tht is wsted. Figue 3 displys the pticle size distibutio of the col discded s ult-fies fo the cse study collieies (with the 95% cofidece limits show). Bsed o this ifomtio, Tble II lists the pecetge of col cose th 150 µm tht is discded, to withi 95% cofidece. The ifomtio idictes tht oughly oe-qute of the col discded t colliey A should ot hve bee disposed of i the fist plce. Although ot s sigifict, thee is lso otble wstge t the othe mies. The clssifyig cycloes o the mies e esposible fo septig the col ito the cose d fie th 150 µm size fctios. It c theefoe be cocluded tht the cycloes, pticully t colliey A, e ot opetig optimlly. A CP optio is theefoe to impove the opetio of the clssifyig cycloes. Covet the emiig ult-fie col ito useful poduct Utilizig the ult-fie wste d covetig it ito poduct is cosideed CP itevetio becuse the wste is beig educed o eve elimited. Thee e sevel diffeet methods of covetig the ult-fies ito useful poduct. These e listed d the discussed: Beeficite, dewte d expot the ult-fies Dewte d sell the ult-fies Covet the ult-fies to low-smoke fuel Solubilize the ult-fies to poduce methe d polymes Poduce col-wte sluy fom the ult-fies Combust the ult-fies i fluidized bed combusto Owig to the ogoig developmets of techologies fo sluy utiliztio wold-wide, it is likely tht sevel othe optios e cuetly vilble o will become so i the futue. Beeficite, dewte d expot the ult-fies This optio etils the upgdig of the ult-fies by beeficitio d the dewteig of the high-qulity poduct. Dewteig is dvtgeous fo sevel esos, icludig educig tspot d pot costs d impovig the cloific vlue of the col d cosequetly its mket vlue. Flottio is the oly effective method of beeficitig ult-fie col,7 d my mjo col poducig couties, such s Austli, commoly opete flottio plts. I South Afic, the techicl fesibility of usig flottio to beeficite the ultfies fom the Witbk colfield hs bee cofimed.8 I 2000, oughly 12% of the SA col pocessig plts utilized flottio to beeficite the ult-fies.9 I tems of dewteig, thee e sevel kids of equipmet suitble fo the pupose, icludig scee-bowl cetifuges, hoizotl belt filtes d theml dyig. Despite cuet South Afic peceptios, ecet study cocluded tht theml dyig to oe pecet sufce moistue is the most ecoomicl method of dewteig the ult-fies.10 The combitio of flottio Tble II Volume fctio of the ult-fie wste tht is cose th 150 m Colliey A B C Volume % cose th 150 m 24 ± 3 18 ± ± 1.4 T s c t i o P p e Cumultive volume % Mie A Mie B Mie C Pticle size (μm) Figue 3 Pticle size distibutio of the discded ult-fie col The Joul of The Southe Afic Istitute of Miig d Metllugy VOLUME 107 REFEREED PAPER DECEMBER

4 SAIMM_Dec_55-60:Templte Joul 12/6/07 8:03 AM Pge 814 A clee poductio ssessmet of the ult-fie col wste d theml dyig c esult i 75% covesio of the ult-fies to vluble poduct, depedig o the qulity of the col. Thee is o miimum limit o the size fctio of the col tht c be expoted by y of the thee mies. Theefoe the beeficited d dewteed ult-fies c be dded to the cose col, d c be sold to the ledy estblished expot mket. I the cse of colliey A, ll of the poduct col is expoted. Oly potio of tht poduced t the two othe collieies is set bod. Dewte d sell the ult-fies This optio ivolves dewteig ubeeficited ult-fies to sell the esult s low-qulity col fo electicity geetio. Theml dyig of ubeeficited col is ulikely to be ecoomiclly fesible owig to the low vlue of the col. Theefoe moe cost-effective dyig method should be cosideed. A locl BEE pivte compy, Wste Eegy Recovey d Mgemet (WERM), hs pteted pocess of dyig d ecoveig ult-fies fom sluy dms usig sol eegy. Evey two to thee dys the top 300 mm lye of the dm is ploughed d stockpiled. The ult-fies e died to betwee 12 18% moistue becuse they become difficult to hdle outside this ge.11 Oce dy, the col is ot esily e-wet if it is stockpiled. This ebles the dyig pocess to occu duig the iy seso, lthough 30 40% decese i yield is expeieced. The died ult-fie mteil is bleded with ewshed cose wste ock d is sold to the Hedi o Mjub powe sttios, s othe powe sttios e ot equipped to hdle the fie mteil.11 The pupose of bledig the wste ock with the ult-fies is to lowe the ovell moistue cotet. This pocess covets ll of the ult-fies to vluble poduct becuse WERM opetes util the sluy dm is empty. Typiclly this tkes up to five yes pe mie.11 This is theefoe shot-tem optio utilizig the col tht hs ledy bee discded i the dms. Othe optios to utilize the ult-fies s they ise fom the plt should be cosideed. The beefits of educig the poblem of cid mie dige cused by discd dumps, d of poducig electicity fom col tht does ot equie to be mied, idicte tht this optio is eviometlly pefeble to the cuet sceio. Howeve, i-depth ivestigtio should be coducted to estblish the eviometl impcts cused by buig ult-fies d ewshed wste ock to geete electicity. This optio does ot pply to colliey A, s this mie cuetly disposes of its ult-fies udegoud the th i dms. Covet the ult-fies to low-smoke fuel This CP optio etils covetig the ult-fie col to low smoke fuel (LSF). These e fuels tht elese low levels of smoke emissio whe but. They e widely used i my couties, icludig the Uited Kigdom, Pold d Idi. LSF could povide solutio to the vst mout of i pollutio bought bout by the buig of col fo domestic usge, pticully i ifoml settlemets. I ode to covet ult-fie col ito low smoke fuel, the col should fist be gglometed to mke it moe esy to hdle. Vious methods of gglometio e vilble, icludig pelletizig, extusio, bide d bideless biquettig. The ltte ws foud to be the most ecoomiclly vible12. To covet the col ito low-smoke fuel, the biquettes e devoltised t high tempetues. Pilot d lbotoy tests hve bee coducted t Kleikopje Colliey by Coltech 2020 to estblish the techicl fesibility of the poductio of low-smoke fuels fom ultfies i South Afic. The tests cofimed tht the pocess is techiclly fesible with South Afic col.13 A study by Egld12 cocluded tht the costs of biquettig e much highe th the pice of D-gde col. Theefoe it is ulikely tht low-smoke fuels will be dopted by the domestic secto uless subsidized o mdted by lw. Theefoe, this optio is ot likely to be ecoomiclly fesible t peset. Solubilize the ult-fies to poduce methe d polymes Col solubiliztio is the pocess though which col is coveted by mico-ogisms d ezymes ito solutio of col mcomolecules. These i tu c be coveted ito vious poducts, such s methe o polymes.14 Low-k cols, such s ligite, e moe susceptible to solubiliztio becuse of thei highe moistue cotet, moe suitble stuctue, smlle poes, softess d susceptibility to wetheig.15 Howeve, ceti mico-ogisms c solubilize highe-k col.16 The lck of stddiztio of esech wok i this field is hideig the pogess d developmet of the pocess. I South Afic this techology is ot commecilly vilble t peset, lthough esech wok is beig udetke t locl uivesities to optimize d commecilize this pocess. Poduce col-wte sluy fom the ult-fies Col-wte sluies (CWS), lso kow s col-wte fuels (CWF) o col-wte mixtues (CWM), e cocetted suspesios of highly beeficited ult-fie col i wte. The CWS must be betwee 65 70% solids d thee to fou % sh. The CWS c be poduced fom the ult-fie sluy by udegoig extesive cushig d gidig to impove libetio of the high-gde col so tht the low sh equiemets c be met.7 The CWS is piped diectly to powe sttios whee it is bued s hevy oil, the th beig dded to the cose col. Col-wte sluies hve sevel dvtges ove tditiol dy col. The poblems of spoteous combustio d dust geetio duig stoge d tspottio of dy col e elimited. The cost of dyig d dewteig e sigifictly educed, d colwte sluies e moe esily hdled becuse, beig queous, they equie o lge-scle tspottio o hdlig fcilities.7 Howeve, thee e cuetly o powe sttios i South Afic tht c utilize col-wte sluies becuse they e limited to hdlig dy col. Theefoe, util thee is use fo the CWS, this optio is ot ecoomiclly fesible. Combust the ult-fies i fluidised bed combusto A fluidized bed ecto is combusto i which the col pticles e suspeded i bed by updfts of gs tht keep the col i tubulet stte.17 Resech by the CSIR18 hs 814 DECEMBER 2007 VOLUME 107 REFEREED PAPER The Joul of The Southe Afic Istitute of Miig d Metllugy

5 SAIMM_Dec_55-60:Templte Joul 12/6/07 8:03 AM Pge 815 A clee poductio ssessmet of the ult-fie col wste Tble III Fesibility Sc Optio o Techicl Fesibility Is it pove techology? C the techology be implemeted i SA t peset? N/A Eviometl Fesibility Is it likely to esult i et eductio of eviometl impcts?? Is thee eductio i wstge of col? Ecoomic Fesibility Is it potetilly ficilly fesible t peset? T s c t i o estblished tht it is techiclly fesible to combust ult-fie col sluies of 63% moistue i fluidized bed combustio boile. Covetiol pulveized fuel boiles equie tht the feed col cotis t most te pecet moistue. Theefoe the cost of dewteig the ult-fie col is getly educed fo the fluidized bed ecto. Although eltively low theml efficiecy of 67% is chieved, the costs of obtiig this wste col e lso low. Tspot othe th vi pipelies is ot fesible, s the sluy is ot sufficietly stble.18 Thee e cuetly o commecil fluidized bed combustio powe sttios i South Afic tht u o col, lthough Eskom pls to istll d opete them i the uspecified futue. Theefoe this optio is ot cuetly ecoomiclly fesible, but it my become so ove time. Fesibility of the CP optios The vious CP optios tht hve bee suggested fo the ult-fies e summized below: Icese the cushe top size Optimize the pefomce of the clssifyig cycloes Beeficite usig flottio, + theml dyig, d expot the ult-fies Dewte the uwshed ult-fies d supply to locl powe sttios Covet the ult-fies to low-smoke fuel Solubilize the ult-fies to poduce methe o polymes Covet the ult-fies ito Col-Wte Sluy (CWS) Combust the ult-fies i fluidized bed combusto Due to bette pefomces t colliey C, optios 1 d 2 e moe pplicble to collieies A d B. As descibed i the Method sectio, ech optio ws subjected to fesibility ssessmet, commecig with the fesibility sc to discd y optios tht do ot meet ceti citei. The citei e show i the left-hd colum of Tble III. Negtive swes ( ) sigify tht the optio is usuitble, d will ot be cosideed y futhe. The optio umbes i Tble III coespod with the optio umbes listed bove. The ifomtio povided i the pevious sectio ws used to complete this sc. The esults of the sc wee the sme fo ll thee mies, with the exceptio tht optio 4 cot be implemeted t colliey A s ult-fies e disposed of udegoud. Tble III idictes tht optios 5 8 will o loge be cosideed fo implemettio, s they e ot cuetly vible. Howeve, they should ot be completely dismissed becuse they my become wokble i the futue. The emiig optios (1 4) e ll cosideed techiclly fesible d eviometlly pefeble (with some ucetities emiig ove optio 4), s they hve stisfied the citei i the left-hd colum of Tble III. Owig to the fct tht optios 1 d 2 equie o o low cpitl ivestmets, these optios did ot equie ecoomic fesibility study, s pe the pocedue outlied i the Method sectio. Sice these optios e ot mutully exclusive, they c be implemeted immeditely. Optios 3 d 4 e both high-cost optios, d wee theefoe submitted to geelized ecoomic fesibility ssessmet. The esults fo optio 3, flottio d theml dyig of the ult-fies, e summized i Tble IV, d the ssumptios e listed i Tble V. Opetig d cpitl costs wee bsed o those used by de Kote7. The et peset vlues (NPV) idicted i Tble IV eflect the diffeece betwee the cuet pofits d those tht would esult if optio 3 ws implemeted. The vlues idicte tht icese i NPV of t lest R50 millio could be chieved ove te-ye peiod by implemetig optio 3 t y of the mies. This ifomtio idictes tht optio 3 is ficilly, s well s eviometlly, stogly beeficil. With egd to optio 4 (cotctig idepedet opeto to sol-dy the ult-fies) the esults Tble IV Net Peset Vlue (NPV) d cpitl ivestmets fo optio 3 Colliey A B C NPV (10 yes) R 100,000,000 R 200,000,000 R 50,000,000 Cpitl R 10,000,000 R 10,000,000 R 6,000,000 Tble V Optio 3 Assumptios Flottio yield5 75 % Flottio poduct i-dy CV5 28 MJ/kg Reveue fom col expot sles A: R278/t; B: R279/t; C: R297/t Cost of ilge, tuckge A: R 58/t; B: R 59/t; C: R 81/t d pot fees Discout te 15% Avege vlues fo 2005 fo the espective collieies P p e The Joul of The Southe Afic Istitute of Miig d Metllugy VOLUME 107 REFEREED PAPER DECEMBER

6 SAIMM_Dec_55-60:Templte Joul 12/6/07 8:03 AM Pge 816 A clee poductio ssessmet of the ult-fie col wste Tble VI Net Peset Vlue (NPV) fo optio 4 Colliey B C NPV R 50,000,000 R 15,000,000 Peiod of Cotct 5 yes 2 yes Refeeces 1. DME; Ntiol Ivetoy Discd d Duff Col, Summy Repot, BARCLAY, S.J. Applicbility of wste miimistio clubs i South Afic: Results fom pilot studies, Wte Resech Commissio Repot No. TT 161/02, 2001, Dub. Tble V Optio 4 Assumptios Poduct poduced pe moth Mie B: t*; Mie C: t* Reveue fom col sles R 60 / poduct to* Cotctig cost R 42.5 / poduct to* Cost of discds disposl R 2 / to of discds5 Yield of the ewshed wste ock 50 %* Tx 29 % Discout Rte 15 % * Bsed o uofficil ough quote fom WERM 3. HANKS, J. d JANISCH, C. Evlutio of Clee Poductio ctivities i South Afic, Evlutio Missio Repot, DANIDA, Dish Embssy, 2003, Petoi. 4. HILSON, G. Defiig clee poductio d pollutio pevetio i the miig cotext, Miels Egieeig 16, 2003, pp VAN BERKEL, R. Eco-efficiecy d eco-iovtio: oppotuities fo sustible d sustiig col busiesses; t the 2004 Techicl Exchge Meetig betwee the CRC fo Col i Sustible Developmet d the Jp Powe Idusty Resech Istitute, Newcstle, 28 Jue 2004, Dowloded fom: of the ecoomic ssessmet e summized i Tble VI, d the ssumptios listed i Tble VII. Colliey A hs ot bee icluded i the ssessmet s this optio is ot suitble fo this mie. Tble VI idictes tht optio 4 is ecoomiclly stogly vible t both of the othe collieies. Howeve, the fesibility of optio 4 ultimtely depeds o whethe o ot the collieies e ble to estblish cotct geemet with Eskom. While futhe, moe itesive fesibility ssessmets should be coducted befoe optios 3 d 4 e implemeted, it is cle tht CP could educe the dumpig of the ult-fies t the colleies sigifictly. Coclusios CP ssessmets hve bee peped fo thee collieies i the Witbk colfield, tht wee thought to be sufficietly typicl of pctices i the South Afic col miig idusty fo the esults to hve geel sigificce. The ssessmets foud tht thee e techiclly d ecoomiclly fesible optios fo educig the eviometl hzds bought bout by the commo pctice of dumpig ult-fie col i South Afic. The fidigs idicted tht the geetio of this wste o of cose col cotied i it could be educed, t low cost, by optimizig cushe d cycloe pefomce. The emiig ult-fie col wste c be ecoomiclly upgded o ecoveed d sold, eithe ito the expot mket o loclly, with ttctive etus o ivestmet. Howeve, the fesibility of ech optio, s the cse study ssessmets hve idicted, depeds o the colliey. The ssocited ficil beefits of the poposed optios suggested tht CP offes elistic ppoch to ddessig eviometl poblems. Ackowledgemets The uthos would like to ckowledge the bckig of the Wte Resech Commissio fo iititig d fudig the poject (K5/1553) fom which the epoted esults emted, s well s the suppot eceived t the thee collieies. 6. UNEP, Govemet Sttegies d Policies fo Clee Poductio, UNEP Idusty d Eviomet, 1994, Pis. 7. LASKOWSKI, J.S. Col Flottio d Fie Col Utiliztio; Developmets i Miel Pocessig, Fuesteu, D.W. (ed.), vol. 14, 2001, Elsevie. 8. HAND, P.E. Col Flottio d Dyig i the Witbk Colfield; Isdl Col Cosultig cc; Repot fo Coltech 2020, 1998, p. 6.; Dowloded fom: 9. DE KORTE, G.J. South Afic Col Peptio Plts; Dtbse fo Coltech 2020, DE KORTE, G.J. Dewteig of Fie Col Pogess Repot No. 2, Repot fo Coltech 2020, BLENKINSOP, M. Mgig Diecto of Wste Eegy Recovey d Mgemet; Pesol commuictio, Novembe ENGLAND, T. The ecoomic gglometio of fie col fo idustil d commecil use; Repot fo Coltech 2020, MANGENA, S.J. d DE KORTE, G.J. Developmet of Pocess fo Poducig Low Smoke Fuels fom Col Discds, Repot, Divisio of Miig Techology, CSIR, CATCHESIDE, D.E.A. d RALPH, J.P., Biologicl Pocessig of Col, Appl Micobil Biotechol, 1999, vol. 52, pp FAISON, B.D. The chemisty of low k col d its eltioship to the biochemicl mechisms of col biotsfomtio; Micobil Tsfomtios of Low Rk Cols, Cwfod, D.L. (ed.), CRC Pess, Boc Rto, 1993, Fl pp KLEIN, J. et l. (eds.) Biologicl pocessig of fossil fuels: Resumé of the Biocovesio Sessio of ICCS 97, Appl Micobiol Biotechol, 1999, vol. 52, pp Efficiet Powe Geetio; Accessed 14 Mch NORTH, B.C. Combustio of Low-Gde Sluies; Divisio of Eegy Techology, CSIR; Repot No. ENER-C 90088, 1990, Petoi. 816 DECEMBER 2007 VOLUME 107 REFEREED PAPER The Joul of The Southe Afic Istitute of Miig d Metllugy