Alternative technologies for the production of high carbon ferromanganese: A techno-economic Evaluation

Sithole, Ntokozo Aphelele (2020-12)

Thesis (MEng)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: The manganese resource (land-based) in South Africa is currently the largest, accounting for 75% of the global resource. Ore exporting has increased from 50% of the total sales in 1997 to around 85% in 2016 and the trend seems to be increasing (Directorate Mineral Economics, 2017). Furthermore, manganese smelters have either reduced capacity or shut down completely due to operational costs. Van Zyl (2017) explored the various aspects that limit growth in the mineral value chain (Van Zyl, 2017). One of the barriers that were identified in the beneficiation of manganese is the high cost of electricity required for ore smelting. Ferromanganese in South Africa is produced using Submerged-arc furnace (SAF) technology which relies heavily on electricity during production. The current study aimed to identify and compare alternative furnace technologies that can or could produce HCFeMn. The main criterion is to substantially reduce the reliance on electricity during production. The objective of the study was to make use of a literature review in the ferromanganese industry and the ironmaking industry to identify suitable alternative furnace technologies. Alternative technologies will then be compared using a techno-economic evaluation to assess the financial performance of each furnace when compared to the current technology the SAF. The evaluation consisted of mass and energy balances of the HCFeMn process and economic models. Furthermore, the sensitivity of the economic model results in response to deviations in CAPEX and OPEX estimates was investigated. The SAF was compared to the BF that was identified in the ferromanganese industry and the COREX® that was identified in the ironmaking industry. Both technologies commercially produce FeMn and/or pig iron. The BF relies on coke and the COREX® relies on coal. Mass and energy balance model results indicate that SAF recovers the least amount of manganese at 82.8% and the COREX®recovers the most at 84.1%. Fixed capital costs make the SAF the most attractive, the COREX® and BF cost 35% and 37% more, respectively. Annual production costs per ton of alloy for the COREX® on average over the project life are over 26% lower than both furnaces. The COREX® had the highest NPV (R 11 430.46) and IRR (33.11%) with the lowest discounted payback period of 7 years. The SAF NPV was 33% lower, IRR 5.04% lower, and DPBP 1 year longer than the COREX®. The BF performed the worst financially. In all three scenarios, the COREX® yielded a positive NPV, meaning the probability of a 15% return is 1. Furthermore, manganese recoveries as low as 79.7% still yield an NPV 38% higher than the SAF base case. Sourcing of technical and economic data was a challenge, the BF model had outdated HCFeMn process data available. The COREX® has no data published for the HCFeMn process, data can be obtained from thermochemical modelling, laboratory or pilot plant scale tests. Process data specific for the COREX® could improve the quality of the model outcomes of the. Collaborations with Mintek and industry partners are recommended to obtain better quality technical and economic data.

AFRIKAANSE OPSOMMING: Die mangaanhulpbron in Suid-Afrika (landgebaseerde) is volgens berigte die grootste en is verantwoordelik vir 75% van die wêreld se bronne. Ertsuitvoere het toegeneem van 50% van totale produksie in 1997 tot ongeveer 85% in 2016 en dit blyk asof die neiging toeneem (Directorate Mineral Economics, 2017). Verder het die smelters met mangaanlegerings óf die kapasiteit verlaag óf, weens die toename in bedryfskoste, heeltemal gesluit. Van Zyl (2017) het die verskillende aspekte ondersoek wat groei in die minerale waardeketting beperk. Een van die hindernisse watidentifiseer is vir die veredeling van mangaan, is die koste van elektrisiteit wat benodig word vir die smelt van erts. Ferromangaanlegerings in Suid-Afrika word vervaardig met behulp van dompelboog-oondtegnologie wat tydens produksie baie afhanklik is van elektrisiteit.Die doel van die huidige studie was om alternatiewe oondtegnologieë te identifiseer en te vergelyk wat FeMn moontlik kan produseer. Die belangrikste kriteria is om die afhanklikheid van elektrisiteit tydens produksie aansienlik te verminder. Die doel van die studie was om gebruik te maak van 'n literatuuroorsig van die ferromangaan-industrie en die ysterbedryf om geskikte alternatiewe oondtegnologieë te identifiseer. Alternatiewe tegnologieë word dan met behulp van 'n tegno-ekonomiese evaluering vergelyk om die finansiële prestasie van elke oond te beoordeel in vergelyking met die huidige dompelboogoond tegnologie. Die evaluering het bestaan uit massa- en energiebalanse van die proses vir die produksie van hoëkoolstof ferromangaanlegerings, en 'n ekonomiese model. Die dompelboogoond is vergelyk met die hoogoond wat in die ferromangaan-industrie geïdentifiseer is, en die COREX®wat in die ysterbedryf geïdentifiseer is. Beide tegnologieë produseer ferromangaanleregings en/of ruyster. Die hoogoond maak staat op kooks en die COREX® maak staat op steenkool. Die resultate van die massa- en energiebalansmodel dui aan dat die dompelboogoond die kleinste hoeveelheid mangaan op 82.8% herwin en dat die COREX® die meeste op 84.1%.Kapitaalkoste maak die dompelboogoond die aantreklikste; die COREX® en hoogoond kos onderskeidelik 35% en 37% meer. Die jaarlikse produksiekoste per ton legering vir die COREX® is gemiddeld 26% laer as vir die ander twee oonde.Die COREX® die hoogste netto huidigewaarde (R 11 430.46) en interne rendement(33.11%) met die laagste terugbetalingstydperk van 7 jaar. Die dompelboogoond se netto huidigewaarde was 33% laer, interne rendement 5.04% laer en met ‘nterugbetalingstydperk 1 jaar langer as dié van die COREX®. Die hoogoond het finansieël die slegste gevaar. Die COREX® 'n positiewe NPV gelewer in alle scenario's, wat impliseer dat die waarskynlikheid van 15% opbrengs 1 is. Verder lewer mangaan verhaling so laag as 79.7% steeds 'n netto huidigewaarde wat 38% hoër is as die dompelboogoondop die basis geval. Die verkrying van tegniese en ekonomiese insette tot hierdie modelle was 'n uitdaging. Die hoogoond-model het gebruik gemaak van effens verouderde prosesdata vir die produksie van hoëkoolstof ferromangaanlegerings. Die COREX®het geen data wat vir die produksie van hoëkoolstof ferromangaanlegerings- publiseer is nie. Die verkryging van hierdie data deur middel van termodinamiese modellering, laboratorium- of loodsaanlegte, kan die kwaliteit van die modeluitkomste verbeter. Samewerking tussen Mintek en bedrysvennote word aanbeveel om tegniese en ekonomiese data van beter gehalte te bekom.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/109233
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