Preliminary Beneficiation Test Work on Macedonian Iron Ore

Transcription

1 Eastern Finland Office C/MT/2014/23 Outokumpu Preliminary Beneficiation Test Work on Macedonian Iron Ore Tero Korhonen

2 GEOLOGICAL SURVEY OF FINLAND Authors Tero Korhonen DOCUMENTATION PAGE Date / Rec. no Type of report Research Report Commissioned by Ecofer Oy Title of report Preliminary Beneficiation Test Work on Macedonian Iron Ore Abstract Ecofer Oy ordered a preliminary bench scale beneficiation test work on Macedonian iron ore. The main interest was to find out would it be possible to enrich iron by using only crushing, grinding and magnetic separation. Also other beneficiation methods like flotation and roasting were investigated. The original target grade for the iron concentrate was 6065 % Fe with low phosphorus content < 0.06 %. These laboratory scale studies were carried out at Mineral Processing laboratory of the Geological Survey of Finland (GTK) in Outokumpu. According to the mineralogical studies the ore contains mainly siderite, chlorite, muscovite, goethite, magnetite, quartz, apatite and Fesulphide. The magnetite seemed to occur in very fine particle size about 62 % of the mag to the results it is netite was totally liberated in 20µ m particle size after 60 minutes grinding D80~89 µm. The best results were achieved when magnetic separation and flotation were applied. According feasible to achieve the following iron concentrates: 50 Fe % with 6469 % recovery, 52 Fe % with 5559 % recovery and 55 % Fe with 40 % recovery, then the recoveries will fall down rapidly. Probably in the closed circuit iron recoveries might be improved. The highest quality iron concentrate had 66.6 % Fe grade with ~8 % recovery, the corresponding magnetite recovery was 62 % with 69 % grade. The harmful elements in the concentrate were SiO %, Al 2 O % P 0.10 %. According to mineralogical observations most of the silicates were carried by chlorite both in mixed and liberated grains. Keywords iron, magnetite, siderite, goethite, magnetic separation, flotation Geographical area Map sheet Other information Report serial Archive code C/MT/2014/23 Total pages Appendices Language English Price Confidentiality confidential Unit and section Eastern Finland Office/ section 407 Signature/name Asse Marjasvaara Project code Macedonia Signature/name Tero Korhonen

3 Contents Documentation page 1 INTRODUCTION 2 ORE SAMPLES 2.1 Sample preparation 2.2 Chemical analyses 3 MINERALOGICAL STUDIES 3.1 The modal mineralogy 3.2 The degrees of liberation 4 TEST PROGRAM 4.1 Grinding tests 4.2 Beneficiation tests 5 TEST RESULTS 5.1 Mineralogical observations 6 CONCLUSIONS APPENDICES Appendix 1. Bench Scale Tests, Results. Appendix 2. Bench Scale Tests, Flowsheets and Test Conditions. Appendix 3. Chemical Analyses, Feed Sample. Appendix 4. Chemical Analyses, Bench Scale Tests.

4 1 1 INTRODUCTION Ecofer Oy ordered a preliminary bench scale beneficiation test work on Macedonian iron ore sam Now this mine ples. After the disintergration of Jugoslavia this particular iron ore mine was closed. has a new owner and they are interested to continue production. Anyhow some research work is needed to find out the best beneficiation process. In the past both gravity and magnetic separation were used to concentrate iron ore. The client s main interest was to find out would it be possible to enrich iron by using only crushing, grinding and magnetic separation. Also some other beneficiation methods like flotation and roasting were investigated in this test work. The target grade for the iron concentrate was 6065 % Fe with low phosphorus content < 0.06 %. These bench scale tests were carried out at Mineral Processing laboratory of the Geological Survey of Finland (GTK) in town of Outokumpu. 2 ORE SAMPLES 2.1 Sample preparation Ecofer Oy delivered ~100 kg ore samples. The ore samples were crushed to < 1.5 mm particle size. After the crushing material was homogenized by mixing and divided into 1.5 kg sub samples for laboratory tests. 2.2 Chemical analyses The main feed analyses are shown in Table 1. The complete analyses are presented in Appendix 1. The iron content was 43 %. The other main elements in the ore sample were: SiO %, Al 2 O %, MgO 1.2 %, CaO 2.7 %, P 2 O %, C 3.3 %. The sulphur grade was low 0.2 %. The meas ured Satmagan value was 6.4 % which indicates the magnetite content in the feed. Table 1. The main feed analyses Fe SiO 2 Al 2 O 3 MgO CaO P 2 O 5 P S % % % % % % % % C Satmagan % % The ore samples were analyzed by following methods: XRF: overall composition Eltra analyzer: S, C Satmagan: magnetite

5 2 3 MINERALOGICAL STUDIES Mineralogical studies of the feed material were done for 60 minutes ground material (D80 ~89 µm). The modal mineralogy was determined by Mineral Liberation Analyzer (MLA) and XRD. The mineralogical content was determined also by using the chemical assays. The liberation degrees of magnetite and goethite were determined by MLA. 3.1 The modal mineralogy The modal mineralogy of the feed material determined by MLA and XRD is presented in Tables 2 and 3. The feed sample contains mainly siderite, chlorite, muscovite, goethite, magnetite, quartz, apatite and Fesulphide. The sample seems to be mineralogically very simple. However, to deter siderite and goe mine the modal mineralogy utilizing the MLA method is very challenging because thite have almost identical EDspectra and hence the identification is not reliable. Because of that reason, the Rietveld method was used for quantitative XRD analysis. Table 2. The modal mineralogy determined by MLA. Mineral +75 µm 4575 µm 2045 µm 20 µm Head Wt% Wt% Wt% Wt% Wt% Magnetite Ilmenite Rutile Goethite Siderite Chlorite Muscovite Biotite Clay Serpentine Quartz Monazite(Ce) Apatite Pyrite Arsenopyrite Total Table 3. The modal mineralogy determined by XRD Rietveld method. Mineral +75 Wt% 4575 Wt % 2045 Wt % 20 Wt % Head Wt % Siderite Magnetite Goethite Quartz Montmorillonite(Cs) Chlorite IIb Muscovite 3T Apatite(CaOH,CaF) Total

6 3 The distribution of iron was calculated theoretically by using the chemical feed assays and the iron contents in the literature (Table 4). Magnetite is carrying 11 % of the total iron. The most of the iron are in goethite, siderite and chlorite. Theoretically if the all magnetitee and goethite could be recovered without any other minerals the iron grade in this concentrate would be about 65 % with 43 % recovery. If the all magnetite, goe thite and siderite could be recovered without any other minerals the iron grade in this concentrate would be about 55 % with 75 % recovery. Based on this fact it can t be expected the high iron grades with high iron recoveries. Table 4. The distribution of iron. Mineral Feed Distribution of Fe wt.% % Magnetite Goethite Siderite Chlorite(Fe) Muscovite 2.4 Quartz 6.5 Apatite 4.9 Pyrite Total The degrees of liberation The liberation degrees of magnetite and goethite in different sieve fractions are presented in Figures 13 and 67. The liberation degree of magnetite was quite poor after 60 minutes grinding. About 33 % of the magnetite was totally liberated, in +75 µm size fraction only 5 %, in 20 µm size fraction the liberation degree was higher 62 %. For example some quartz, chlorite, siderite, apatite and clay were noticed in mixed grain magnetite particles. The liberation degree of goethitee was poor too. After 60 minutes grinding about 36 % of the goe 54 %. Quartz, thite was totally liberated, in +75 µm size fraction 23 % and in 20 µm size fraction chlorite, siderite, magnetite, apatite and clay were noticed in mixed grain magnetite particles.

7 4 Figure 1. The liberation degrees of magnetite in different sieve fractions. The orange line corre sponds the liberation degree of the combined, total magnetite. Figure 2. The magnetite particles in +75 µm size fraction (MLA).

8 5 Figure 3. The magnetite particles in 2045 µm size fraction (MLA).

9 6 Figure 4.. The typical magnetite in the feed material.

10 7 Figure 5. The liberation degrees of goethite in different sieve fractions. The orange line corresponds the liberation degree of the combined, total goethite. Figure 6. The goethite particles in +75 µm size fraction (MLA).

11 8 Figure 7. The goethite particles in 2045 µm size fraction (MLA).

12 9 4 TEST PROGRAM The main interest was to find out would it be possible to enrich the Macedonian iron ore sample only by crushing and grinding. Anyhow some flotation and roasting tests were done too. The bench scale testwork was started with grinding tests. 4.1 Grinding tests Grinding tests were done with the mild steel ball mill with ~63 % slurry density, ore sample 1.5 kg and water 0.9 l. The particle size distributions for the ground material were determined by wet and dry sieving. At first, wet sieving with 20µm screen was done and after this the overflow of the wet sieving phase was sieved as dry by RoTap sieve shaker. The results from the grinding tests are shown in Figure 8 and Table 5. Passing, % Grinding Tests Particle Size Distributions Screen size, µm Ground 30 min Ground 45 min Ground 60 min Ground 90 min Ground 120 min Ground 180 min Figure 8. Particle size distributions in grinding tests.

13 10 Table 5. Particle size distributions in grinding tests. Screen Ground 30 min Ground 45 min Ground 60 min Ground 90 min Ground 120 min size Passing Passing Passing Passing Passing µm % % % % % D80 µm Ground 180 min Passing % The used primary grinding times in the beneficiation tests varied from 45 to 180 minutes and the corresponding grinding fineness were from D80~150 µm to D80~22 µm. The chemical analyses were made for 90 minutes ground and sieved material (Table 6). The iron content was slightly higher in the +20µm size fractions Fe 4445 % compared to 20µm material Fe 42 %. Anyhow the iron and the other elements were not really concentrated in any size fraction. Table 6. Chemical analyses, 90 minutes ground material. Screen size Mass Fe SiO 2 Al 2 O 3 P 2 O 5 P C S µm % % Rec. % % Rec. % % Rec. % % Rec. % % Rec. % % Rec. % % Rec. % Calc. feed

14 Beneficiation tests Several bench scale beneficiation tests were done in order to find favourable process conditions. The low, medium, and high intensity magnetic separation tests were done. Also some flotation tests were done both for magnetic concentrates and tailings. The each test is described below, the used test conditions and the flowsheets are presented in Appendix 2. Test 1 The used grinding fineness was D80 ~89µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T and high intensity mag LIMS 0.07 T netic separations HGMS 0.1 T and 0.3 T. Test 2 The used grinding fineness was D80 ~51µm. The low intensity magnetic separation was made followed by medium intensity magnetic separation MIMS 0.3 T and high intensity magmade in the four liter netic separations HGMS 0.05 T and 0.1 T. Test 3 The used grinding fineness was D80 ~51µm. After the grinding desliming was flotation cell by applying the Stoke`s law. The specific gravity ~3.20 kg/dm 3 was determined for the crushed 1.5 mm ore. Desliming was made because it was noticed that the iron content was a little bit higher in the coarser screen sizes compared to 20 µm size fraction (Table 6). After the desliming the low intensity magnetic separation 0.07 T was made for the non slime mateintensity magnetic rial followed by 15 minutes regrinding and one cleaning stage. The medium separation 0.3 T was made for the non magnetic product LIMS 0.07 T NM2. The non magnetic product LIMS 0.07 T NM1 was reground 20 minutes followed by low intensity magnetic separa magnetic separa tion 0.07 T, medium intensity magnetic separation MIMS 0.3 T and high intensity tion HGMS 0.1 T. The high intensity magnetic separation HGMS 0.1 T was made also for the slimes. Test 4 The used grinding fineness was D80 ~89µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The magnetic products LIMS 0.07 T M1 and MIMS 0.3 T M1 were combined and reground 15 minutes followed by the low and medium intensity magnetic separations. Then the magnetic products LIMS 0.07 T M2 and MIMS 0.3 T were combined and reground again 15 minutes followed by the low and medium in LIMS 0.07 T tensity magnetic separations. At the end it was tried to clean the magnetic concentrate M3 by flotation. Lilaflot 811M was used as collector chemical. Test 1B The used grinding fineness was D80 ~89µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T and high intensity magnetic separations HGMS 0.1 T and 0.3 T. The magnetic concentrate LIMS 0.07 T M1 was cleaned once after it was tried to clean by flotation. Lilaflot 811M was used as collector chemical, dekstrin as iron depressant and NaOH as ph regulator. Test 1B was continuation test based on the results in Test 1. The magnetic concentratee LIMS 0.07 T M1 from the Test 1 was used in Test 1B.

15 12 Test 2B The used grinding fineness was D80 ~51µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T and high intensity magnetic separations HGMS 0.05 T and 0.1 T. The magnetic concentrate LIMS 0.07 T M1 was cleaned once after it was tried to clean by flotation. Atrac 1563 and Lilaflot 811M were used as collector chemicals, dekstrin was used to depress the iron and NaOH was used as ph regulator. Test 2B was continuation test based on the results in Test 2. The magnetic concentrate LIMS 0.07 T M1 from the Test 2 was used in Test 1B. Test 5 The used grinding fineness was D80 ~89µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The magnetic product LIMS 0.07 T M1 was reground 30 minutes and cleaned once. Then the cleaned magnetic product LIMS 0.07 T M2 was reground again 30 minutes and cleaned four times. At the end the magnetic product LIMS 0.07 R M6 was tried to upgrade by flotation. Aero 845 was used as collector chemi cal and starch to depress the iron. Test 1C The used grinding fineness was D80 ~89µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The non magnetic prod four hours in uct MIMS 0.3 T NM1 from the medium intensity magnetic separation was roasted 600 C temperature. At least a part of the siderite should become as secondary magnetite. After the roasting the low and mediumm intensity magnetic separations with cleanings were made for the roasted material. Test 1C was continuation test based on the results in Test 1. The non magnetic product MIMS 0.3 T NM1 from the Test 1 was used in Test 1C. Test 6 The used grinding fineness was D80 ~89µm. The low intensity magnetic separation LIMS 0.07 T was made then the magnetic product LIMS 0.07 T M1 was reground 60 minutes and cleaned four times. Test 8 The used grinding fineness was D80 ~32µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The magnetic product 0.07 T M1 was reground 60 minutes and cleaned five times followed by cleaning flotation. The non magnetic product MIMS 0.3 T NM1 was delivered to the high gradient magnetic separation HGMS 0.1 T and 0.3 T. The both magnetic concentrates HGMS 0.1 T and 0.3 T were cleaned once. Test 1E The used grinding fineness was D80 ~89µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The non magnetic prod eight hours in uct MIMS 0.3 T NM1 from the medium intensity magnetic separation was roasted 600 C temperature. At least a part of the siderite should become as secondary magnetite. After the roasting the low and mediumm intensity magnetic separations were made with cleanings for the roasted material. Test 1E was continuation test based on the results in Test 1. The non magnetic product MIMS 0.3 T NM1 from the Test 1 was used in Test 1E.

16 13 Test 9 The used grinding fineness was D80 ~22µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The magnetic product LIMS 0.07 T M1 was cleaned once and then reground 120 minutes followed by five cleanings. The magnetic product MIMS 0.3 T M1 was cleaned once. The non magnetic product MIMS 0.3 T NM1 was reported to high gradient magnetic separation HGMS 0.1 T and 0.3 T. The both magnetic prod ucts HGMS 0.1 T M1 and 0.3 T M1 were cleaned once. Test 9B The used grinding fineness was D80 ~22µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The magnetic product LIMS 0.07 T M1 was cleaned once and then reground 120 minutes followed by five cleanings. The magnetic product MIMS 0.3 T M1 was cleaned once. The non magnetic product MIMS 0.3 T NM1 was reported to reverse flotation in which the gangue minerals like apatite and quartz was floated and iron was depressed into flotation tailings. The used collector chemicals were Atrac 1563 and Lilaflot 811M, dekstrin was used to depress the iron and soda ash was used as ph regulator and dis magnetic product pergant. Test 9B was continuation test based on the results in Test 9. The nonn MIMS 0.3 T NM1 from the Test 9 was used in Test 9B. Test 9D The used grinding fineness was D80 ~22µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The magnetic product LIMS 0.07 T M1 was cleaned once and then reground 120 minutes followed by five cleanings. The magnetic product MIMS 0.3 T M1 was cleaned once. The non magnetic product MIMS 0.3 T NM1 was reported to reverse flotation in which the gangue minerals like apatite and quartz was floated and iron was depressed into flotation tailings. The used flotation chemicals were same like in the Test 9B except the dekstrin dosages were higher. Test 9D was continuation test based on the results in Test 9. The non magnetic product MIMS 0.3 T NM1 from the Test 9 was used in Test 9D. Test 10 The used grinding fineness was D80 ~150µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The non magnetic prodminerals like apatite uct MIMS 0.3 T NM1 was reported to reverse flotation in which the gangue and quartz was floated and iron was depressed into flotation tailings. The used collector chemicals were Atrac 1563 and Lilaflot 811M, dekstrin was used to depress the iron and soda ash was used as ph regulator and dispergant. Test 8X The used grinding fineness was D80 ~32µm. The low intensity magnetic separation LIMS 0.07 T was made followed by medium intensity magnetic separation MIMS 0.3 T. The magnetic product 0.07 T M1 was reground 60 minutes and cleaned five times followed by cleaning flotation. The non magnetic product MIMS 0.3 T NM1 was reported to reverse flotation in which the gangue minerals like apatite and quartz was floated and iron was depressed into flotation tailings. The used collector chemicals were Atrac 1563 and Lilaflot 811M, dekstrin was used to depress the iron and soda ash was used as ph regulator and dispergant. Test 8X was continuation test based on the results in the Test 8. The non magnetic concentrate MIMS 0.3 T NM1 from the Test 8 was used in Test 8X.

17 14 5 TEST RESULTS The detailed test results are presented in Appendix 1 and chemical assays in Appendix 4. The main results from the beneficiation tests are shown in Figures 912 and in Table 7. The best results were achieved when magnetic separation and flotation were applied (Tests 9B, 9D, 10 and 8X). In the Table are shown some iron concentrate combinations from Tests 9B and 8X. According to the results it is feasible to achieve the following iron concentrates: 50 Fe % with % recovery, 52 Fe % with 5559 % recovery and 55 % Fe with 40 % recovery, then the recoveries will fall down rapidly. The high gradient magnetic separation was applied in many tests for the non magnetic product from medium intensity magnetic separation. According to the results the high gradient magnetic separa followed by low tion was not as selective like flotation the iron grades were not much upgraded. The roasting of non magnetic product from medium intensity magnetic separation and medium intensity magnetic separations improved the iron recoveries (Figure 12). Fe recovery % Iron Grades and Recoveries Beneficiation Tests on Macedonian Iron Ore Fe % Test 1 Test 2 Test 3 Test 4 Test 1B Test 2B Test 5 Test 1C Test 6 Test 8 Test 1E Test 9 Test 9B Test 9D Test 10 Test 8X Figure 9. Iron grades and recoveries in beneficiation tests

18 15 Table 7. The main results, tests 9B and 8X. Test Products Mass % 9B LIMS 0.07 T M7 5.5 LIMS 0.07T M3+MIMS 0.3T M2 8.7 LIMS 0.07T M2+Tails 32.5 LIMS 0.07T M1+MIMS 0.3T M2+RT LIMS 0.07T M1+MIMS 0.3T M1+RT Calculated Feed X LIMS 0.07 T M6/RT4 7.1 LIMS 0.07 T M5+MIMS 0.3T M2 9.8 LIMS 0.07 T M2+RT LIMS 0.07 T M1+MIMS 0.3 T M1+RT LIMS 0.07 T M1+MIMS 0.3 T M1+RT Calculated Feed Fe Satmagan SiO 2 Al 2O 3 P 2O 5 P S % Rec. % % Rec. % % Rec. % % Rec. % % Rec. % % Rec. % % Rec. % The highest quality iron concentrate was produced in Tests 9 (9&9B&9D) with 66.6 % Fe grade and ~8 % recovery, the corresponding magnetite recovery was 62 % with 69 % grade. The harmful elements in the concentrate weree SiO %, Al 2 O % P 0.10 %. According to mineralogical observations most of the silicatess were carried by chlorite. The magnetite grades and recoveries in the bench scale tests are shown in Figure 10. The magnetite recoveries were higher compared to the iron recoveries because most of the iron occurs in the other minerals, goethite, siderite and chlorite. Satmagan recovery % Magnetite Grades and Recoveries Beneficiation Tests on Macedonian Iron Ore Satmagan % Test 1 Test 2 Test 1B Test 2B Test 5 Test 1C Test 6 Test 8 Test 1E Test 9 Test 9B Test 9D Test 10 Test 8X Figure 10. Magnetite grades and recoveries in beneficiation tests.

19 16 Fe recovery % Mass vs. Iron Recoveries Beneficiation Tests on Macedonian Iron Ore Mass recovery % Test 1 Test 2 Test 3 Test 4 Test 1B Test 2B Test 5 Test 1C Test 6 Test 8 Test 1E Test 9 Test 9B Test 9D Test 10 Test 8X Figure 11. The mass recoveries vs. iron recoveries. The iron recoveries tend to depend very much on the mass recoveries which also indicate that the separation of the iron minerals was not very selective (Figure 11). The effect of grinding fineness and roasting to iron grades and recoveries are presented in Figure 12. The grades and recoveries denon magnetic prod pend on the grinding fineness. Also it was noticed that after the roasting of the uct the iron recoveries were increased. The part of the siderite was become as secondary magnetite Iron Grades and Recoveries Effect of Grinding Fineness and Roasting Test 1: D80~89µm, LIMS+MIMS Test 2: D80~51µm, LIMS+MIMS Fe recovery % Test 1C: D80~89µm, LIMS+MIMS+Roasting 30 Test 1E: D80~89µm, LIMS+MIMS+Roasting 20 Test 8: D80~32µm, LIMS+MIMS 10 Test 9: D80 ~22µm, LIMS+MIMS Test 10: D80 ~150µm, LIMS+MIMS Fe % Figure 12. The effect of grindingg fineness and roasting to iron grades and recoveries in low and medium intensity magnetic separation.

20 Mineralogical observations Some mineralogical observationss by optical microscope from Test 1 are presented in Figures Magnetite, goethite and some pyrite was seen in magnetic product LIMS 0.07 T M1. The magnetite occurred mostly in mixed grains. There was not much magnetite in products from medium intensity magnetic separation. Figure 13. Test 1, the magnetic product LIMS 0.07 T M1. Figure 14. Test 1, the magnetic product MIMS 0.3 T M1.

21 18 Figure 15. Test 1, the non magnetic product MIMS 0.3 T NM1. The magnetic product LIMS 0.07 T M6 from test 9 (9&9B&9D) was investigated too, the purpose was to found out how the impurities like quartz and apatite are occurring in the sample (Figures 16 18). The backscattered electron image (BSE) shows magnetite as white and gangue as grey. The main gangue mineral is ironrich chlorite. All of the magnetitegangue composite grains are actually magnetitechlorite composite grains. These Xray maps illustrate the distribution of magnetite, chlorite, quartz and apatite in the sample. The Xray map of iron shows magnetite as bright yellow. The dark yellow areas of the Fe map cor ironrich chlorite. relate rather well with the bright red areas of the Al map which in turn represent The bright red of the Al map correlates quite well with the bright green of Si as well. Some of the brightest green spots on the Si map, however, do not correlate with Al. Hence they represent quartz. The bright blue spots on the P map represent apatite.

22 19 BSE Fe Al Si P Figure 16. Test 9 magnetic product LIMS 0.07 T M6, backscattered electron image and Xray maps of iron, aluminum, silicon and phosphorus.

23 20 Figure 17. Test 9 magnetic product LIMS 0.07 T M6. Figure 18. Test 9 magnetic product LIMS 0.07 T M6.

24 21 6 CONCLUSIONS According to the mineralogical studies the ore contains mainly siderite, chlorite, muscovite, goein very fine particle thite, magnetite, quartz, apatite and Fesulphide. The magnetite seemed to occur size about 62 % of the magnetitee was totally liberated in 20µm particle size after 60 minutes grind According to ing D80~89 µm. The best results were achieved when magnetic separation and flotation were applied. the results it is feasible to achieve the following iron concentrates: 50 Fe % with 6469 % recovery, 52 Fe % with 5559 % recovery and 55 % Fe with 40 % recovery, then the recoveries will fall down rapidly. Probably in the closed circuit iron recoveries might be improved. The highest quality iron concentrate had 66.6 % Fe grade with ~8 % recovery, the corresponding magnetite recovery was 62 % with 69 % grade. The harmful elements in the concentrate were SiO %, Al 2 O % P 0.10 %. According to mineralogical observations most of the silicates were carried by chlorite both in mixed and liberated grains. The iron recoveries tend to depend on the mass recoveries which also indicate that the separation of the iron minerals was not very selective. Also the iron grades and recoveries are depending on the grinding fineness. After the roasting of the non magnetic product the iron recoveries were increased, part of the side rite was became as secondary magnetite. Most of the magnetite is possible to recover by magnetic separation but other iron minerals like siderite and goethite need to be recovered other way. According to the test results it seems that the best process combination could be magnetic separation together with flotation. Anyhow it would be worthwhile to do more testwork in order to optimize the flotation conditions. The selective separa tion of magnetite, siderite and goethite with low phosphorus content will be very challenging.