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Section 3. Materials Science
https://doi.org/10.29013/AJT-21-3.4-17-27
Izet Ibrahimi, E-mail: [email protected] Zarife Bajraktari-Gashi, E-mail: [email protected]
Arber Zeqiraj, University IsaBoletiniMitrovice, Faculty of Geosciences, Mitrovice, Kosove E-mail: [email protected]
NEWFERRONICKEL PRODUCTION TECHNOLOGIES OPPORTUNITY FOR SUSTAINABLE ECONOMIC DEVELOPMENT
Abstract. During the last century, ferroalloys, especially steel were the dominant materials on which industrial development and generally technological progress were based. Global demand for ferroalloys is expected to increase significantly in the coming years, partly due to the dynamic economic growth in China and India, but also due to developing countries. However, so far there has been a disproportion between the exploitation of natural resources, economic growth and technological progress. This has resulted in irrational exploitation of natural resources and with a high level of greenhouse gas emissions, where as a result our climate is changing. According to the co-government panel on Climate Change, for this, the world is warmer for 0.6 °C and in the worst case scenario, temperatures could rise to 5.8 °C by the end of this century. The most complex part of ferronickel extraction is the refining process. From the data of this case study, as well as from the quantitative and qualitative analysis, as and XRD analysis of the Fe-Ni refining process, there are technological possibilities and high economic benefits if the electro arc furnace (EAF) with desulfurizer injection system, would be installed how intermediate process of the but also descriptive data and comparative models from good practices of refining processes. The obj ective of this study is the most appropriate selection of the technological route of ferronickel production, which would result with rational exploitation natural resources, increase of energy efficiency, improvement of the metal utilization coefficient, reduction ofproduction costs, and generally the reduction of pollution and a sustainable economic development.
Keywords: New technology, Fe-Ni, converter route, cost reduction, sustainable development.
1. Introduction ic development, they are also the largest consumer of
As the ferroalloy industry, especially the steel in- energy and environmental pollution. Although, dur-dustry, continues to be the main indicator of econom- ing 2019 there was a decline in ferro-alloy production,
nevertheless world production of crude steel was 1869.9 million tons, where China alone accounting for 53.3% of world production [1]. At the same time, China was the largest contributor to greenhouse gas emissions, which in 2018 alone it burned 4 billion tons of coal, as much as the rest of the world [3].
After the Kosovo Energy Corporation, the New-Co "Ferronickel" is actually the largest generator of employment and exports in the country, as well as one of the most important factors for the sustainable economic development of Kosovo. Until recently nickel was considered a precious metal, mainly due to the limited use of it, while today it is considered a widely used metal in the machine building industry, for the production of special steelsand other branches of industry. Evaluated by its strategic role in the World Industry, as well as the good possibilities ofexploitation and processing of ore, but and according to the actually demand trends for ferronickel, it is expected that NewCo "Ferronickel" will have this cash flow, up to 10% of GDP Kosovo [4]. Despite the great demands in the world market for Ni and ferroalloys, as well as despite its numerous reserves of metal ores, Kosovo is still with a low level of production, and with a metallurgical industry, which is being forwarded from low technical progress. This has resulted in a marked imbalance between: rational use of natural resources, environmental protection and economic development. Despite the initiatives of various countries for the development of new technological routes, so far in developing countries, including Kosovo, there has been little attention to such agendas.Only through a significant technological progress in the metallurgical industry and the transition to a new regime of exploitation and processing of ores, Kosovo could promote a favorable climate for investment, increase development opportunities and would rise an environmentally friendly industry.
Realization of objectives of this study program, namely promoting the "High Power- Low Cost" approach and "Conveter Route" in the NewCo "Ferronickel" would mark the beginning of a transition
to a new regime technology of the metallurgical industry in Kosovo. The first stages of transition to the new technological regime would be the creation of technological conditions for the development of de-sulfurization outside the furnace - the integration of an intermediate process in the actualy refining scheme according to the "Converter Route with desulfuriza-tion aystem Integrated in the Electro-Arc Furnace with reagent injection". This new technological regime would be the creation of industrial conditions for a rational exploitation of natural resources, improvement of energy efficiency, increase of effectiveness, increased quality control, reduction of costs and maximization ofproduction capacities. From the review of the technological parameters of the refining process in the converter department in NewCo "Ferronikeli" as well as from the study data it is technologically possible to integrate this intermediate process.
1. Research methodology
This study is based on chemical analyzes of raw materials, electric furnace of ferronickel, chemical composition ofmetal and slag according desul-phurization of EF Fe-Ni stages, gases, chemical and granulometric composition of desufulrator and other technological materials. Based on these data andprocess operational indicators of desulphuriza-tion outside the furnace or LD convertor, we have determined the C, Si, P, and S separation coefficient as a key determinant ofdesulphurization effectiveness of EF Fe-Ni in the electroreducing furnce with the system for injection of the desulphurizer. This study program will follow the standard research diagram are shown in (Figure 1).
For the needs of this study we have used the new practices of ferronickel production in PT Inco (Indonesia), Cerro Matoso (Colombia) and SNNC (South Korea) and the industrial practices of obtaining "cleen steels" with lower oxygen content than 1 ppm and sulfur content below 1 ppm.Also are determined the other performance indicators of this intermediate process at the"Ferronickel Foundry" in Drenas, according to the comparative and statistical method.
Figure 1. Flowchart for research methodology
Comparison of outputs, process parameters, and production practices, are based on review the production period November 2019 and January 2021.Evaluation of desulphurization efficiency and measurement ofprocess indicators are supported by chemical and technological analysis of furnace metal and slag, metal and slag of converters, chemical and granulometric composition of CaCO3, as and content and amount other technological materials, which are used during the production process in the "Ferronickel Foundry"Whereas theeffectiveness of desulphurization according to these operating parameters is compared with theoretical parameters, assuming the development of desulphurization effectiveness of EF Fe-Ni in the electroreducing furnce with the system for injection of the desulphurizer.
3. New Fe-ni production and refining technologies
Production of ferro-nickel from relatively Ni-de-pleted ores, as in the case of Kosovo laterite ores, the pyrometallurgical process according to the technological scheme; rotary klin-electric furnace and LD converters has been shown to be the most success-
ful.For this route lateritic ore is screened, crushed and blended to produce a consistent process plant feed with defined ratios of iron and nickel as well as SiO2 and Mg O. This feed is charged into a rotary kiln where it is calcined and prereduced by coal or powdered coke. Afterwards the calcine and residual coke is charged into the electric furnace (also named submerged arc furnace (SAF)). Here it is melted by electric energy and reduced yielding crude FeNi with Ni contents usually between 13 and 25%. Unreduced components (mainly FeO, SiO2, MgO) are removed as slag whereas crude FeNi metal is tapped semi-continuously into ladles [5, 10].
The rotary-klin electric furnace (RKEF) proces has long been the most commonly employed means of recovering nickel from suprolitic laterite ores. While other technologies such as Xstrata's NST process are emerging and blast furnace FeNi production has made somwhat pf a comeback, much scope remains for increasing the productivity and efficiency of RKEF plants [3]. To achieve the optimization of the production, the ferronickel in-
The scientists and professionals especially has at- ergy efficiency of energy over the years, as show tention to increased furnace power levels and en- in (Figure 2):
This was achieved by a combination of several technological developments, most importantly the adoption of "shielded-arc" smelting (to replace the traditional immersed electrode mode of operation), and the installation of water-cooled copper cooling elements in the furnace sidewalls [3].These technologies have advanced the production capacity, when one rotary-kiln could have a capacity of 160 t/h of calcine to a single, and 80 MW furnace can process approximately 1.3 million tons per year of new laterite ore. This has been well proven at PT Inco (Indonesia), Cerro Matoso (Colombia) and SNNC (South Korea), and is the standard for high power furnace operation [3]. The reasons for the increase of the capacities of the rotary kiln and the electric furnace were the reduction of the production costs, the improvement of the metal utilization coefficient as well as the reduction of the greenhouse gases. So as to meet these objectives, particular attention must be paid to:
• Adequate measurement and control including:
- Calcine feed rates;
- Calcine compositions;
Figure 2. Evolution of furnace power over time
- Furnace level measurements (hearth build-up, bath levels, calcine levels);
- Metal and slag temperatures;
- Furnace crucible condition (temperatures, heat fluxes, brick thickness, expansion).
• Competent design of the crucible including:
- Appropriate cooling;
- Appropriate expansion allowances and bindings.
• Design and maintenance of feeding, off gas and metal/slag handling to ensure that upstream and downstream processes do not negatively affect furnace operating factor.
• Careful selection of FeNi grade to be produced and corresponding selection of appropriate operating parameters [3].
During pyrometallurgical processing the converter is one of the most important aggregates to produce and to refine ferronickel. The oxygen blowing process is necessary to decrease the sulphur, phosphorus, carbon, silicon and the iron content in the FeNi metal to the requested levels [2; 7; 9].
Production of ferronickel from "high powr-low cost" technologies, which have integrated ladle furnace route, must be developed in accord to reflective costs-avvailable costs, quality control and environmentally friendly behavior.In the "ladle furnace route" [12] the entire metallurgical treatment is done
Table 1. - Process steps
The main advantage in this production route is that only the treatment ladle is used during the entire process from tapping to granulation. This means less refractory lined equipment will be in operation resulting in lower total refractory consumption as well as low temperature losses [5].
Desulfurization ofEF metal, which is produced in the Foundry of "Ferronikel" in Drenas, due to the poor quality of Kosovo lignite which is used as a reducer in the electric furnace, it would be important to define technical performance indicators according to the new technologies, known as the "converter route". In this
One of the most advanced methods that could be used for the part of industrial examinations is the desulfurization of iron through mixture of Na2CO3 and
in only one vessel, namely the ladle. It is used e.g. In the ferro-nickel plants of Loma de Niquel (Venezuela), Barro Alto (Brazil), Onca Puma (Brazil) and contains the following main process steps. Table 1 shows steps the treatment of electric furnace metal according to process steps in ladle furnace route [5].
in ladle furnace route [5]
case of particular interest would be the theoretical-experimental review of ferronickel desulfurization schemes according to; converter route, ladles-converter, electric arc or ladle furnace. This route is used e.g. at FeNi Industries (Macedonia), Larco (Greece) [5]. But in the case of the NewCo "Ferronickeli" (Kosovo) the refining process would provide more advantages, if will applied to the converter route, similar to those used e.g. at FeNi Industries (Macedonia), Larco (Greece), with some modifications and integration of electro-arc furnace with powder reagent injection system. Again the main process steps are described below:
FeSO4. In this case it would be important to examine the mechanism of the reactions between the metal and the slag. According to theoretical data, the ad-
Process step Aim
1. Tapping from electric furnace into the ladle
2. Oxygen blowing during tapping using blowing Chemical heating station Chemical heating Removal ofcarbon, silicon, phosphorus
3. Deslagging Removal of Fe2O3, SiO2 and P2O5 rich slag
4. Ladle furnace treatment Deoxidation and desulphurization Electrical heating
5. Optional oxygen blowing Final decarburisation
6. Granulation
Table 2.- Process steps of converter route, [5]
Process step Aim
1. Tapping from electric furnace into the transport ladle
2. Oxygen blowing in the converter Enrichment of nickel Removal of carbon, silicon, phosphorus
3. Deslagging Removal of Fe2O3, SiO2 and P2O5 rich slag
4. Electric arc or ladle furnace treatment Deoxidation and desulphurization Electrical heating
5. Granulation
dition of FeSO4 to the Na2CO3 powder mixture would result in increased desulfurization efficiency and with increased economic effects of the process, namely advancement of technical-technological parameters, based on energy efficiency and reduce of the production cost [7; 10].
Such technologies have shown good results in technological schemes which include; the blaste furnace, EAF, ladle furnace route, convertor route will remain the future process leader for the production of high grade steels and other ferroalloys, especially for ferronickel products. However, according to the composition of the ore, EF metal, as well as the existing infrastructure in the converters department in NewCo "Ferronickeli" (Kosovo), "cornveter route", which includ one combination of desulphurization
outside the ferronickel - "desulphurization in the electric arc furnace with the system for injection of reagents" would enable reflective costs and generally will optimize production process.
4. Results and discussion
4.1 High power, low cost
The low utilization of production capacities in NewCo "Ferronickeli (Kosovo) is one of the main problems. The application of" High power-low cost "variants, as in the case of PT Inco (Indonesia), Cerro Matoso (Colombia) and SNNC (South Korea)), would result with increase capacity of at least 50% from those of the actual level.Industrial practices according to the "high power low cost" variant in these foundries have brought the benefits ofhigh capacity, reliable process units are illustrated in Table 3.
Table 3.- Benefits of high power, high intensity furnaces [5]
Parameter Units Current options for processing 1.3 Mtpy of dry ore compared to present "state of theart" 80 MW shielded-arc furnace Furnace for 2 Mtpy of dry ore RKEF line
Low Power High Power, Low Intensity High Power, High Intensity (State of the art) Ultra High Power, High Intensity
1 2 3 4 5 6
No. of Funace 2 1 1 1
Furnace Power MW 40 80 80 120
Calcine Production t/h 159 161 166 250
million t/y 1.18 1.20 1.24 1.86
Hearth Area m2 225 450 225 350
Power Density kW/m2 175 175 350 350
Total Surface Area 2 m2 1640 1420 820 1150
Thermal Losses MW 8.4 7.6 4.9 6.8
Electrical Losses (Electrodes, LV Bus, Transformer) MW 2.0 2.0 1.6 2.4
Total Losses MW 10.4 9.6 6.5 9.2
Approx crucible(s) weight(refractory, steel, coppercoolers) tones 4500 4300 2400 3400
Furnace Installed Cost* $ million 65 45 40 45
1 2 3 4 5 6
Capital cost per annual tonne of calcine smelted * $/t calcine 55 38 32 24
Cost of energy loss ** $/ t calcine $7.67 $7.00 $4.57 $4.33
* Furnace only (excludes offgas, feed system, utilities, building etc);
** Assuming a power cost of $0.10/kWh
In this case, capital cost savings of up to $25 mil- According to the actual version at NewCo "Fer-
lion dollars for the furnace alone (plus additional ronickeli" (Kosovo), electric energy, technological
savings due to smaller buildings etc) can be realized resources and refractory materials not only make up
by employing a high powered, intense furnace pro- the bulk of the costs, but they are also key indicators
cess [5]. of performance (Figure 3).
Figure 3. Participation of energy, technological materials and others in the cost of Fe-Ni production [%] in NewCo "Ferronikeli"
4.2 Research steps in "Converter route with de-sulfurization system integrated in the electro-arc furnace with reagent injection" and cost structure
Ferronickel of electric furnace of Ferronickel "Foundry" in Drenas (Kosovo), is followed by various impurities, such as: silicon, chromium, copper, carbon, sulfur, phosphorus, phosphorus, cobalt, etc., Tabla 4. Table 4.- Average of chemical composition of ferronickel
As Fe Si Cr C P S Ni Co Cu
0.03 72.5-84 2.7-4.0 0.25-0.76 0.3-0.6 0.07-0.2 0.7-2.0 11.22-17 0.5-0.74 0.03-0.05
Of all the impurities, sulphur, has the greatest negative impact on ferronickel properties, when is used for the production of steel, and its removal proceeds slowly and is followed by high energy costs and high pro-
duce costs. Thus, the desulfurization of Fe-Ni is quite complex, and usually preceded by desulphurization in "ladle furnace route", "converter route" or in the case of NewCo Ferronickel (Kosovo) it would be good to
develop according to the "converter route with desul-furization system integrated in the electro-arc furnace with reagent injection", were used different reagents and then continued in LD converters during the oxygen refining process.Theoretically, ifdesulphurization was carried out offurnace, namely through "converter route with integration of EAF with powder reagent
injection system", using desulphurizer Mg, Na2CO3, synthetic slag or any similar desulphurizer the desulphurization rate during this intermediate phase would have to be 40-60% [S], removed from the electric furnace of ferronickel [2]. According to the theoretical converter route reviews, the main steps of which are described in Table 4:
Table 4.- Process steps in converter route with desulfurization system integrated in the electro-arc furnace with reagent injection
Process step Aim
1. Casting from electric furnace EF metal
2. Oxygen blowing and addition CaO during casting Chemical heating Removal of carbon, silicon, and phosphorus
3. Deslagging Removal of SiO2 and P2O5 rich slag
4. EAF - electrical energy treatment EF metal (Ni = = 15-25%, Si - 2-3%, S = 0.5-1,8%, C = 0.5-1.5%) and addition CaO Deoxidation and desulfurisation
Electrical heating
5. Deslagging Removal of Fe2O3, SiO2 and P2O5 rich slag
6. Optional oxygen blowing Decarburisation
7. Electrical energy and addition CaCO3 + CaO Deoxidation and desulfurisation
and powder reagent Electrical heating
8. Deslagging Removal of FeO, S through slag and gases
9. Electrical energy Deoxidation, decarburisation and desulfurisation
10. Deslagging Removal of FeO, FeS, Cr2O3, etc.
11. Refining in converter (Ni = 25-45%, S = 0.04%, C = 0.01%, Si = 0.01%, Cr = 0.01%) Final removal; Si, Cr, P, etc.
12. Deslagging Removal of FeO, FeS, Cr2O3, etc.
13. Granulation
The oxidation reaction ofSi during time ofcasting of metal from the electric furnace would be used to improve the thermal conditions. Thus in support of the chemical heating, which comes from the oxidation reactions of Si, P, C and Fe as well as that from the electric arc, will:
• prevents the appearance of "cold metal" in the ladle by eliminating the physical losses of the base metal;
• affected the speed of chemical reactions that take place between the metal-slag phasesl;
• also wil be enabled the processing of the cooled metal of the EF channel, scrap, as other metal wherever it appears in the ward, thus increasing the utilization rate of ferronchiel.
The technical construction of the desulphurizer injection station may be equipped with two spears, one for the injection of powdered or molten desul-phurizers and one for the blowing of oxygen and
the electromagnetic mixer between which the com- structure of costsfor desulfurization of ferronickel
ponents participating in the desulphurisation are according to the variant for converter route with
deliberately subjected to mixing. Table 5 shows the desulfurization system integrated in the electro-arc
main technical-technological parameters with the furnace with reagent injection.
Table 5.- The main technical-technological parameters with the cost structure for converter route with desulfurization system integrated in the electro-arc furnace with reagent injection
Stages of the process Conc. i Si dhe S [%] Temp. of phase. [0C] Time of phase [min] Cost [$/t] Othres
Casting (Fe-Ni from Electric Furnace 2.8 Si 1.28 S 1350 25
Transportation 1340 5
oxidation Si, C in "converter route" 0.05 Si 0.05 C 1650 40 5 1500kg CaCO3 10 kg R.m./t ' 5 t scrap
Deslaggin and addition of CaO 1490 10 6 500kg CaO
Addition ofAl 0.4 Al 1625 20 12.5 175 kg Al
Temperature measurement - 1625 10
Injection desulfurization (first degree) 0.1 S 1520 16 10 800 kg CaO
Removal of slag, for control the temp.and addit. CaO 1510 15 5 400 kg CaO
Heating through EAF 1620 30 55x 1200 kwh energy
Injection desulfurization (second degree) 0.04 S 1570 8 5 400 kg CaO
Deslagging and additon CaO 1560 10 5 400 kg CaO
Injection defosorption 0.04 P 1480 16 17.5 80 kg(40% CaO 40% FeO 20% Ca 20% CaF2 Consumption of spears
Deslagging 1470 10 64 1400 kWh
TOTAL REFINING COST 245 197
The results of the this research have proved that for the crude Fe-Ni compositions from the "Fer-ronikel" Foundry of Drenas, the integration of this intermediate process in the technological refining scheme would show favorable economic indicators and rational use of natural resources.
5. Conclusions
Ladle based refinery plants have been successfully installed for the refining of crude FeNi produced by the RRK-EF-LD "conveter route". Refining operation using oxygen blowing during tapping and by integration of EAT with the desulphurization injector treatment afterwards are flexible to cope with
varying compositions ofthe crude metal.According to the current refining technologies in the NewCo "Ferronckeli", electrical energy and refractory materials are the main determinants in the structure of production costs, so the integration of such technologies as between stages of the refining process in addition to minimizing heat loss and and reducing costs for refractory materials, they would enable the increase of production capacities, improve the utilization coefficient of metal, reduce production costs as well as guarantee a high quality controll.
Acknowledgements
Authors thank their colleagues from NewCoFer-ronikeli, who supported and greatly assisted us during the researchwork.
Conflicts of interest
The authors declare no conflict of interest.This research did not receive any specific grant from funding agencies in the public, commercial, or not-forprofit sectors.
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