EP2720797B1 - Equipment to prepare ore concentrate for pelletizing - Google Patents
Equipment to prepare ore concentrate for pelletizing Download PDFInfo
- Publication number
- EP2720797B1 EP2720797B1 EP12800621.0A EP12800621A EP2720797B1 EP 2720797 B1 EP2720797 B1 EP 2720797B1 EP 12800621 A EP12800621 A EP 12800621A EP 2720797 B1 EP2720797 B1 EP 2720797B1
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- EP
- European Patent Office
- Prior art keywords
- chamber
- equipment
- ore concentrate
- grinder
- grinding
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000012141 concentrate Substances 0.000 title claims description 39
- 238000005453 pelletization Methods 0.000 title claims description 9
- 239000007789 gas Substances 0.000 claims description 41
- 238000000227 grinding Methods 0.000 claims description 31
- 238000001035 drying Methods 0.000 claims description 28
- 239000008188 pellet Substances 0.000 claims description 25
- 238000005245 sintering Methods 0.000 claims description 20
- 238000003723 Smelting Methods 0.000 claims description 18
- 229910001021 Ferroalloy Inorganic materials 0.000 claims description 16
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims description 11
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 11
- 238000004519 manufacturing process Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 description 27
- 239000000463 material Substances 0.000 description 13
- 239000000654 additive Substances 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- 239000002002 slurry Substances 0.000 description 5
- 239000011230 binding agent Substances 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 4
- 239000000571 coke Substances 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 239000000428 dust Substances 0.000 description 4
- 238000010304 firing Methods 0.000 description 4
- 239000000446 fuel Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000004449 solid propellant Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 229910001868 water Inorganic materials 0.000 description 4
- 238000001914 filtration Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000006004 Quartz sand Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 229910000278 bentonite Inorganic materials 0.000 description 2
- 239000000440 bentonite Substances 0.000 description 2
- SVPXDRXYRYOSEX-UHFFFAOYSA-N bentoquatam Chemical compound O.O=[Si]=O.O=[Al]O[Al]=O SVPXDRXYRYOSEX-UHFFFAOYSA-N 0.000 description 2
- 239000004927 clay Substances 0.000 description 2
- 238000010891 electric arc Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000008240 homogeneous mixture Substances 0.000 description 2
- -1 lumpy ore Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910000604 Ferrochrome Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C19/00—Other disintegrating devices or methods
- B02C19/18—Use of auxiliary physical effects, e.g. ultrasonics, irradiation, for disintegrating
- B02C19/186—Use of cold or heat for disintegrating
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C23/00—Auxiliary methods or auxiliary devices or accessories specially adapted for crushing or disintegrating not provided for in preceding groups or not specially adapted to apparatus covered by a single preceding group
- B02C23/18—Adding fluid, other than for crushing or disintegrating by fluid energy
- B02C23/24—Passing gas through crushing or disintegrating zone
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B23/00—Heating arrangements
- F26B23/02—Heating arrangements using combustion heating
Definitions
- the invention relates to an equipment to prepare ore concentrate for pelletizing and sintering/indurating of pellets in connection with ferroalloys production.
- FIG. 1 A prior art process and equipment for the production of ferroalloys is schematically shown in Figure 1 .
- the shown prior art process may relate to the production of ferrochrome from chromite concentrates but it can also be applied to the production of other ferroalloys.
- the raw material is obtained from a mine.
- the ore concentrate is stored and initially fed to the process from a day bin 7.
- the ore concentrate has moisture content more than 1%.
- the equipment further comprises a grinder 1 for grinding the coarse ore concentrate to a predetermined grain size which is suitable for the subsequent pelletizing step.
- the grinder 1 is a wet grinder, such as a ball mill, whereto the material to be ground is fed together with the addition of water.
- a ball mill 1 is a rotating drum which is partially filled with the material to be ground and grinding medium. Different materials are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum rotates the grinding media rise with the aid of centrifugal force along with the inner surface of the drum and eventually fall on the material to be ground. Various factors, like the size of the grinding media and the rotation speed of the drum, affect to the degree of grinding.
- the wet grinder 1 is followed by a slurry mixer 8 which is arranged to mix the slurry discharged from the wet grinder 1.
- the slurry mixed in the slurry mixer is then led to filter 9, which can be a capillary-effect ceramic disc filter.
- the filter 9 is arranged to dewater the concentrate slurry by filtering to form a dewatered mineral concentrate.
- the concentrate and the additives are distributed from the intermediate bins 10 onto a conveyor 11 which conveys these materials to a mixer 12.
- the mixer 12 is arranged to mix the concentrate with solid fuel, process dust and binder to form a homogenous mixture of these. Also an amount of water can be added into the mixer 12 to ensure that the mixture has sufficient moisture content for pelletizing.
- the equipment comprises a pelletizing drum or disc 13 which is arranged to pelletize the mixture obtained from the mixer 12 to green pellets.
- the process equipment includes a roller screen 14 to ensure that uniformly sized green pellets only are fed as an even pellet bed to the endless conveyor belt of the strand sintering/indurating furnace 15.
- the pellet bed is exposed to subsequent drying, heating, sintering/firing and cooling steps, each of them having different temperature conditions, as the pellet bed is conveyed through respective zones of the furnace 15.
- the sintering/indurating furnace includes circulation gas ducts 16, 17, 18 which circulate gas from the cooling zones to the drying, heating and sintering/firing zones for the purpose of saving energy.
- the pellets are spherical, uniformly sized, hard and porous with consistent physical and chemical properties. They are ideal charging material for ferroalloy smelting in the smelting furnace 5.
- Reference number 19 also refers to bins for additives, like lumpy ore, coke, and quartz sand which together with pellets are charged to a preheating kiln 20.
- the preheating kiln 20 is arranged to preheat the pellets before charging to the smelting furnace 5.
- the smelting furnace 5 is an electric arc furnace. In the smelting furnace 5 the pellets are smelted and reduced to ferroalloy. The molten ferroalloy discharged from the smelting furnace 5 is casted to ferroalloy products suitable for further production of metal.
- the carbon monoxide rich off-gas exiting from the smelting furnace 5 is cleaned in a gas scrubber 21.
- the cleaned CO gas is used as a fuel which is burned by a burner 22 in the preheating kiln 20 to produce the sufficient heating energy for preheating of the pellets.
- the cleaned CO gas is also led to burners 23 and 24 located in the walls of the gas circulating ducts 16 and 17 of the strand sintering/indurating furnace 15 to heat the gas flowing in the ducts.
- the problem of the prior art equipment and process relates to an ever decreasing availability of good quality raw materials. More often the raw material to be processed has a very poor quality because it contains or forms very fine fractions, e.g. clay-like chromite. "Fine fractions" stands typically for that 80% of particles have a size less than 75 ⁇ m. Wet filtering of the fine fractions in order to dewater those is difficult since fine fractions tend to clog the filters. Also the time required to dewater the material with a ceramic filter is too long for the process and requires a series of filters whereby the required investment becomes vast.
- An equipment according to the preamble of claim 1 is known from JP 4 099132 A . It is an object of the invention to overcome the disadvantages of the prior art as outlined above.
- the equipment comprises a drying apparatus arranged to dry the concentrate during grinding by the grinder.
- the drying apparatus is arranged to dry ore concentrate by the heat energy obtained from burning carbon monoxide rich off-gas from a smelting furnace.
- the invention provides many advantages. By the arrangement of a drying apparatus to dry the concentrate during grinding by the grinder it is achieved that the concentrate can be dry ground and no subsequent dewatering by filters is needed. With the aid of the invention it is possible to cost-effectively utilize raw materials containing fine fractions which normally would be difficult to dewater by filtering. By utilizing the CO gas from the smelting furnace to produce the sufficient heat energy for drying is advantageous because fossil fuels are thus not needed.
- the drying apparatus comprises a burning chamber comprising a burner arranged to burn carbon monoxide and/or carbon monoxide rich off-gas to produce hot gases, and a drying chamber arranged to dry ore concentrate with said hot gases.
- the grinder comprises a grinding chamber arranged to grind the ore concentrate during conveyance the ore concentrate through the grinding chamber.
- the grinding chamber and the drying chamber are built together, so that hot gases from a separate burning chamber are led to the grinding chamber.
- the burning chamber, the drying chamber and the grinding chamber are built together so that the burner producing hot gases is attached directly to the grinder.
- the raw material is obtained from a mine.
- the raw material, ore concentrate is stored and initially fed to the process from a day bin 7.
- the ore concentrate has moisture content more than 1%.
- Equipment of the Figure 2 comprises a grinder 1 for grinding the coarse ore concentrate to a predetermined grain size which is suitable for the subsequent pelletizing step.
- the grinder 1 in the invention is dry grinder 1.
- the equipment comprises a drying apparatus into which the ore concentrate is fed from the day bin 7.
- the drying apparatus comprises a burning chamber 2 comprising a burner 3.
- the burner 3 is arranged to burn carbon monoxide and/or cleaned carbon monoxide rich off-gas obtained from the smelting furnace 5 with air to produce hot gases.
- the temperature of the cleaned CO gas is about 30°C to 60 °C.
- the resulting gas after burning comprises water, nitrogen, carbon monoxide and some oxygen.
- the temperature of these hot drying gases is about 300°C to 500°C.
- the hot gases are led to a drying chamber 4 which is arranged to dry ore concentrate with said hot gases.
- the burning chamber 2 and the drying chamber 4 are separate units.
- the drying chamber 4 may be a rotating drum which while it rotates conveys the material to be dried from the charge end to the discharge end.
- the dried ore concentrate is fed to the dry grinder 1.
- the grinder 1 comprises a grinding chamber 6 arranged to grind the ore concentrate during conveyance the ore concentrate through the grinding chamber.
- the dry grinder 1 may be a ball mill.
- a ball mill 1 is a rotating drum which is partially filled with the material to be ground and grinding medium. Different materials are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum rotates the grinding media rise with the aid of centrifugal force along with the inner surface of the drum and eventually fall on the material to be ground. Various factors, like the size of the grinding media and the rotation speed of the drum, affect to the degree of grinding.
- the temperature of the ore concentrate discharged from the dry grinder 1 is less than 100 °C.
- the process may continue in a manner as depicted in Figure 1 .
- the concentrate is conveyed to intermediate bins 10. Since the concentrate is dry, it does not have to be dewatered by any filters like in the prior art process of Figure 1 .
- solid fuel coarse which acts as a fuel in the subsequent sintering/indurating process
- process dust and binding agent bentonite clay
- the concentrate and the additives are distributed from the intermediate bins 10 onto a conveyor 11 which conveys these materials to a mixer 12.
- the mixer 12 is arranged to mix the concentrate with solid fuel, process dust and binder to form a homogenous mixture of these. Also an amount of water can be added into the mixer 12 to ensure that the mixture has sufficient moisture content for pelletizing.
- the equipment comprises a pelletizing drum 13 which is arranged to pelletize the mixture obtained from the mixer 12 to green pellets. Green pellets have a sufficient cohesiveness so that they can be conveyed and screened without breakage.
- the process equipment includes a roller screen 14 to ensure that uniformly sized green pellets only are fed as an even pellet bed to the endless conveyor belt of the strand sintering/indurating furnace 15.
- the pellet bed is exposed to subsequent drying, heating, sintering/firing and cooling steps, each of them having different temperature conditions, as the pellet bed is conveyed through respective zones of the furnace 15.
- the sintering/indurating furnace includes circulation gas ducts 16, 17, 18 which circulate gas from the cooling zones to the drying, heating and sintering/firing zones for the purpose of saving energy.
- the pellets are spherical, uniformly sized, hard and porous with consistent physical and chemical properties. They are ideal charging material for ferroalloy smelting in the smelting furnace 5.
- Reference number 19 also refers to bins for additives, like lumpy ore, coke, and quartz sand.
- the sintered/indurated pellets and additives are charged to a preheating kiln 20.
- the preheating kiln 20 is arranged to preheat the pellets before charging to the smelting furnace 5.
- the smelting furnace 5 is a closed-type electric arc furnace. In the smelting furnace 5 the pellets are smelted and reduced to ferroalloy. The molten ferroalloy discharged from the smelting furnace 5 is casted to ferroalloy products suitable for further production of metal.
- the carbon monoxide rich off-gas exiting from the smelting furnace 5 is cleaned in a gas scrubber 21.
- the gas scrubber 21 may be an ejector venturi scrubber operating by wet cleaning principle.
- the cleaned CO gas is used as a fuel which is burned by a burner 22 in the preheating kiln 20 to produce the sufficient heating energy for preheating of the pellets.
- the cleaned CO gas is also led to burners 23 and 24 located in the walls of the gas circulating ducts 16 and 17 of the strand sintering/indurating furnace 15 to heat the gas flowing in the ducts.
- the CO gas pipeline is indicated in Figure 2 with the reference marking B inside a circle.
- FIG 3 there is shown a modification of the equipment of Figure 2 .
- the grinding chamber 6 and the drying chamber 4 are built together.
- the hot gases from a separate burning chamber 2 are led to the grinding chamber 6 which also acts as a drying chamber 4.
- the burning chamber 2 is separate from the combined grinding and drying chamber 4, 6.
- the equipment and process may be similar to the one depicted in Figure 2 .
- the process may hereafter continue as indicated by the marking A inside a circle in Figure 2 .
- the CO gas pipeline as indicated with the reference marking B inside a circle may be similar to that shown in Figure 2 .
- FIG 4 there is shown a further modification of the equipment of Figure 2 .
- the burning chamber 2, the drying chamber 4 and the grinding chamber 6 are all built together.
- the burner 3 is attached directly to the grinder 1.
- the process may hereafter continue as indicated by the marking A inside a circle in Figure 2 .
- the CO gas pipeline as indicated with the reference marking B inside a circle may be similar to that shown in Figure 2 .
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Description
- The invention relates to an equipment to prepare ore concentrate for pelletizing and sintering/indurating of pellets in connection with ferroalloys production.
- A prior art process and equipment for the production of ferroalloys is schematically shown in
Figure 1 . For example, the shown prior art process may relate to the production of ferrochrome from chromite concentrates but it can also be applied to the production of other ferroalloys. - The raw material is obtained from a mine. The ore concentrate is stored and initially fed to the process from a day bin 7. Typically the ore concentrate has moisture content more than 1%. The equipment further comprises a
grinder 1 for grinding the coarse ore concentrate to a predetermined grain size which is suitable for the subsequent pelletizing step. - In prior art the
grinder 1 is a wet grinder, such as a ball mill, whereto the material to be ground is fed together with the addition of water. Aball mill 1 is a rotating drum which is partially filled with the material to be ground and grinding medium. Different materials are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum rotates the grinding media rise with the aid of centrifugal force along with the inner surface of the drum and eventually fall on the material to be ground. Various factors, like the size of the grinding media and the rotation speed of the drum, affect to the degree of grinding. - The
wet grinder 1 is followed by a slurry mixer 8 which is arranged to mix the slurry discharged from thewet grinder 1. - The slurry mixed in the slurry mixer is then led to filter 9, which can be a capillary-effect ceramic disc filter. The
filter 9 is arranged to dewater the concentrate slurry by filtering to form a dewatered mineral concentrate. - From the
filter 9 the concentrate is conveyed tointermediate bins 10. Also other additives, solid fuel (coke fine which acts as a fuel in the subsequent sintering/indurating process), process dust and binding agent (bentonite clay) are conveyed to firstintermediate bins 10. - The concentrate and the additives are distributed from the
intermediate bins 10 onto aconveyor 11 which conveys these materials to amixer 12. - The
mixer 12 is arranged to mix the concentrate with solid fuel, process dust and binder to form a homogenous mixture of these. Also an amount of water can be added into themixer 12 to ensure that the mixture has sufficient moisture content for pelletizing. - Further, the equipment comprises a pelletizing drum or
disc 13 which is arranged to pelletize the mixture obtained from themixer 12 to green pellets. - Further, the process equipment includes a
roller screen 14 to ensure that uniformly sized green pellets only are fed as an even pellet bed to the endless conveyor belt of the strand sintering/induratingfurnace 15. - In the continuously working strand sintering/indurating
furnace 15 the pellet bed is exposed to subsequent drying, heating, sintering/firing and cooling steps, each of them having different temperature conditions, as the pellet bed is conveyed through respective zones of thefurnace 15. The sintering/indurating furnace includescirculation gas ducts furnace 5. - From the strand sintering/indurating
furnace 15 the pellets are conveyed to secondintermediate bins 19.Reference number 19 also refers to bins for additives, like lumpy ore, coke, and quartz sand which together with pellets are charged to a preheating kiln 20. - The preheating kiln 20 is arranged to preheat the pellets before charging to the smelting
furnace 5. The smeltingfurnace 5 is an electric arc furnace. In the smeltingfurnace 5 the pellets are smelted and reduced to ferroalloy. The molten ferroalloy discharged from the smeltingfurnace 5 is casted to ferroalloy products suitable for further production of metal. - The carbon monoxide rich off-gas exiting from the smelting
furnace 5 is cleaned in agas scrubber 21. The cleaned CO gas is used as a fuel which is burned by a burner 22 in the preheating kiln 20 to produce the sufficient heating energy for preheating of the pellets. The cleaned CO gas is also led toburners gas circulating ducts furnace 15 to heat the gas flowing in the ducts. - The problem of the prior art equipment and process relates to an ever decreasing availability of good quality raw materials. More often the raw material to be processed has a very poor quality because it contains or forms very fine fractions, e.g. clay-like chromite. "Fine fractions" stands typically for that 80% of particles have a size less than 75 µm. Wet filtering of the fine fractions in order to dewater those is difficult since fine fractions tend to clog the filters. Also the time required to dewater the material with a ceramic filter is too long for the process and requires a series of filters whereby the required investment becomes vast. An equipment according to the preamble of
claim 1 is known fromJP 4 099132 A - According to the invention the equipment comprises a drying apparatus arranged to dry the concentrate during grinding by the grinder. The drying apparatus is arranged to dry ore concentrate by the heat energy obtained from burning carbon monoxide rich off-gas from a smelting furnace.
- The invention provides many advantages. By the arrangement of a drying apparatus to dry the concentrate during grinding by the grinder it is achieved that the concentrate can be dry ground and no subsequent dewatering by filters is needed. With the aid of the invention it is possible to cost-effectively utilize raw materials containing fine fractions which normally would be difficult to dewater by filtering. By utilizing the CO gas from the smelting furnace to produce the sufficient heat energy for drying is advantageous because fossil fuels are thus not needed.
- In one embodiment, the drying apparatus comprises a burning chamber comprising a burner arranged to burn carbon monoxide and/or carbon monoxide rich off-gas to produce hot gases, and a drying chamber arranged to dry ore concentrate with said hot gases.
- In one embodiment, the grinder comprises a grinding chamber arranged to grind the ore concentrate during conveyance the ore concentrate through the grinding chamber. The grinding chamber and the drying chamber are built together, so that hot gases from a separate burning chamber are led to the grinding chamber.
- In one embodiment, the burning chamber, the drying chamber and the grinding chamber are built together so that the burner producing hot gases is attached directly to the grinder.
- The accompanying drawings, which are included to provide a better understanding of the invention constitute part of the description, illustrate preferred embodiments of the invention and help to explain the principles of the invention.
-
Figure 1 shows a schematic flow chart of a prior art ferroalloys process and process equipment, -
Figure 2 shows a schematic flow chart of a ferroalloys process and process equipment which is not part of the invention, -
Figure 3 shows the beginning of the ferroalloys process and process equipment of a first embodiment of the invention, and -
Figure 4 shows the beginning of the ferroalloys process and process equipment of a second embodiment of the invention. - Referring to
Figure 2 , the raw material is obtained from a mine. The raw material, ore concentrate, is stored and initially fed to the process from a day bin 7. Typically the ore concentrate has moisture content more than 1%. - Equipment of the
Figure 2 comprises agrinder 1 for grinding the coarse ore concentrate to a predetermined grain size which is suitable for the subsequent pelletizing step. In contrast to the prior art equipment thegrinder 1 in the invention isdry grinder 1. In order to dry the ore concentrate before it is fed to thegrinder 1 it must be dried. For that purpose the equipment comprises a drying apparatus into which the ore concentrate is fed from the day bin 7. - The drying apparatus comprises a
burning chamber 2 comprising aburner 3. Theburner 3 is arranged to burn carbon monoxide and/or cleaned carbon monoxide rich off-gas obtained from the smeltingfurnace 5 with air to produce hot gases. The temperature of the cleaned CO gas is about 30°C to 60 °C. The resulting gas after burning comprises water, nitrogen, carbon monoxide and some oxygen. The temperature of these hot drying gases is about 300°C to 500°C. - The hot gases are led to a drying
chamber 4 which is arranged to dry ore concentrate with said hot gases. InFigure 2 the burningchamber 2 and the dryingchamber 4 are separate units. The dryingchamber 4 may be a rotating drum which while it rotates conveys the material to be dried from the charge end to the discharge end. - The dried ore concentrate is fed to the
dry grinder 1. - The
grinder 1 comprises agrinding chamber 6 arranged to grind the ore concentrate during conveyance the ore concentrate through the grinding chamber. Thedry grinder 1 may be a ball mill. Aball mill 1 is a rotating drum which is partially filled with the material to be ground and grinding medium. Different materials are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum rotates the grinding media rise with the aid of centrifugal force along with the inner surface of the drum and eventually fall on the material to be ground. Various factors, like the size of the grinding media and the rotation speed of the drum, affect to the degree of grinding. The temperature of the ore concentrate discharged from thedry grinder 1 is less than 100 °C. - After the
dry grinder 1 at point A inside a circle the process may continue in a manner as depicted inFigure 1 . From thedry grinder 1 the concentrate is conveyed tointermediate bins 10. Since the concentrate is dry, it does not have to be dewatered by any filters like in the prior art process ofFigure 1 . - Also other additives, solid fuel (coke fine which acts as a fuel in the subsequent sintering/indurating process), process dust and binding agent (bentonite clay) are conveyed to the
intermediate bins 10. - The concentrate and the additives are distributed from the
intermediate bins 10 onto aconveyor 11 which conveys these materials to amixer 12. - The
mixer 12 is arranged to mix the concentrate with solid fuel, process dust and binder to form a homogenous mixture of these. Also an amount of water can be added into themixer 12 to ensure that the mixture has sufficient moisture content for pelletizing. - Further, the equipment comprises a
pelletizing drum 13 which is arranged to pelletize the mixture obtained from themixer 12 to green pellets. Green pellets have a sufficient cohesiveness so that they can be conveyed and screened without breakage. - Further, the process equipment includes a
roller screen 14 to ensure that uniformly sized green pellets only are fed as an even pellet bed to the endless conveyor belt of the strand sintering/indurating furnace 15. - In the continuously working strand sintering/
indurating furnace 15 the pellet bed is exposed to subsequent drying, heating, sintering/firing and cooling steps, each of them having different temperature conditions, as the pellet bed is conveyed through respective zones of thefurnace 15. The sintering/indurating furnace includescirculation gas ducts smelting furnace 5. - From the strand sintering/
indurating furnace 15 the pellets are conveyed to a secondintermediate bin 19.Reference number 19 also refers to bins for additives, like lumpy ore, coke, and quartz sand. The sintered/indurated pellets and additives are charged to a preheating kiln 20. - The preheating kiln 20 is arranged to preheat the pellets before charging to the
smelting furnace 5. Thesmelting furnace 5 is a closed-type electric arc furnace. In thesmelting furnace 5 the pellets are smelted and reduced to ferroalloy. The molten ferroalloy discharged from thesmelting furnace 5 is casted to ferroalloy products suitable for further production of metal. - The carbon monoxide rich off-gas exiting from the
smelting furnace 5 is cleaned in agas scrubber 21. Thegas scrubber 21 may be an ejector venturi scrubber operating by wet cleaning principle. - The cleaned CO gas is used as a fuel which is burned by a burner 22 in the preheating kiln 20 to produce the sufficient heating energy for preheating of the pellets. The cleaned CO gas is also led to
burners gas circulating ducts indurating furnace 15 to heat the gas flowing in the ducts. The CO gas pipeline is indicated inFigure 2 with the reference marking B inside a circle. - In
Figure 3 there is shown a modification of the equipment ofFigure 2 . In this embodiment the grindingchamber 6 and the dryingchamber 4 are built together. The hot gases from aseparate burning chamber 2 are led to the grindingchamber 6 which also acts as a dryingchamber 4. The burningchamber 2 is separate from the combined grinding and dryingchamber Figure 2 . The process may hereafter continue as indicated by the marking A inside a circle inFigure 2 . The CO gas pipeline as indicated with the reference marking B inside a circle may be similar to that shown inFigure 2 . - In
Figure 4 there is shown a further modification of the equipment ofFigure 2 . In this embodiment the burningchamber 2, the dryingchamber 4 and the grindingchamber 6 are all built together. Theburner 3 is attached directly to thegrinder 1. The process may hereafter continue as indicated by the marking A inside a circle inFigure 2 . The CO gas pipeline as indicated with the reference marking B inside a circle may be similar to that shown inFigure 2 . - It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.
- It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.
Claims (4)
- An equipment to prepare ore concentrate for pelletizing and sintering/indurating of pellets in ferroalloys production, the equipment comprising a grinder (1) arranged to grind the concentrate to a predetermined grain size, characterised in that the equipment comprises a drying apparatus (2, 3, 4) arranged to dry the concentrate during grinding by the grinder (1), and that the drying apparatus (2, 3, 4) is arranged to dry ore concentrate by the heat energy obtained from burning carbon monoxide rich off-gas from a smelting furnace (5).
- The equipment according to claim 1, characterised in that the drying apparatus comprises- a burning chamber (2) comprising a burner (3) arranged to burn carbon monoxide and/or carbon monoxide rich off-gas to produce hot gases, and- a drying chamber (4) arranged to dry ore concentrate with said hot gases.
- The equipment according to claim 2, characterised in that the grinder (1) comprises a grinding chamber (6) arranged to grind the ore concentrate during conveyance the ore concentrate through the grinding chamber; and that the grinding chamber (6) and the drying chamber (4) are built together, so that hot gases from a separate burning chamber (2) are led to the grinding chamber (6).
- The equipment according to claim 2, characterised in that the burning chamber (2), the drying chamber (4) and the grinding chamber (6) are built together so that the burner (3) producing hot gases is attached directly to the grinder (1).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI20114064 | 2011-06-15 | ||
PCT/FI2012/050595 WO2012172174A1 (en) | 2011-06-15 | 2012-06-13 | Equipment to prepare ore concentrate for pelletizing |
Publications (3)
Publication Number | Publication Date |
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EP2720797A1 EP2720797A1 (en) | 2014-04-23 |
EP2720797A4 EP2720797A4 (en) | 2015-08-12 |
EP2720797B1 true EP2720797B1 (en) | 2017-09-27 |
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EP12800621.0A Active EP2720797B1 (en) | 2011-06-15 | 2012-06-13 | Equipment to prepare ore concentrate for pelletizing |
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CN111610305B (en) * | 2020-04-28 | 2021-11-09 | 北京科技大学 | Method for quantitatively evaluating crushing resistance and wear resistance of iron alloy for steelmaking by using rotary drum |
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Publication number | Priority date | Publication date | Assignee | Title |
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JPH0499132A (en) * | 1990-08-07 | 1992-03-31 | Kobe Steel Ltd | Production of pellet of iron ore containing much water of crystallization |
GB9317849D0 (en) * | 1993-08-27 | 1993-10-13 | Bpb Industries Plc | Improvements in calcination |
JP2002030351A (en) * | 2000-07-11 | 2002-01-31 | Mitsubishi Heavy Ind Ltd | Device for pretreating raw material for reduced iron |
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EP2720797A4 (en) | 2015-08-12 |
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