EP2720797A1 - Equipment to prepare ore concentrate for pelletizing - Google Patents

Equipment to prepare ore concentrate for pelletizing

Info

Publication number
EP2720797A1
EP2720797A1 EP12800621.0A EP12800621A EP2720797A1 EP 2720797 A1 EP2720797 A1 EP 2720797A1 EP 12800621 A EP12800621 A EP 12800621A EP 2720797 A1 EP2720797 A1 EP 2720797A1
Authority
EP
European Patent Office
Prior art keywords
chamber
ore concentrate
equipment
grinder
concentrate
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.)
Granted
Application number
EP12800621.0A
Other languages
German (de)
French (fr)
Other versions
EP2720797B1 (en
EP2720797A4 (en
Inventor
Marko Palander
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Outotec Finland Oy
Original Assignee
Outotec Oyj
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Outotec Oyj filed Critical Outotec Oyj
Priority claimed from PCT/FI2012/050595 external-priority patent/WO2012172174A1/en
Publication of EP2720797A1 publication Critical patent/EP2720797A1/en
Publication of EP2720797A4 publication Critical patent/EP2720797A4/en
Application granted granted Critical
Publication of EP2720797B1 publication Critical patent/EP2720797B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

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. ultrasonic waves or 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 suita- ble 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 ma ⁇ terial to be ground and grinding medium. Different ma ⁇ terials are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum ro ⁇ tates the grinding media rise with the aid of centrif- ugal force along with the inner surface of the drum and eventually fall on the material to be ground. Var ⁇ ious 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 con ⁇ veys 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 homoge ⁇ nous 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 ob ⁇ tained 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 con ⁇ veyor 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 re ⁇ spective zones of the furnace 15.
  • the sinter ⁇ ing/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 pel ⁇ lets 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 prod ⁇ ucts 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 equipment comprises a drying apparatus arranged to dry the concentrate be ⁇ fore and/or during grinding by the grinder.
  • the invention provides many advantages. By the ar ⁇ rangement of a drying apparatus to dry the concentrate before and/or 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.
  • the drying apparatus is arranged to dry ore concentrate by the heat energy obtained from burning carbon monoxide.
  • 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 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 di ⁇ rectly to the grinder.
  • 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 of a first embodiment of the invention
  • Figure 3 shows the beginning of the ferroalloys pro- cess and process equipment of a second embodiment of the invention
  • Figure 4 shows the beginning of the ferroalloys pro ⁇ cess and process equipment of a third embodiment of the invention.
  • 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 ma ⁇ terial to be dried from the charge end to the dis- charge 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 ro ⁇ tating drum which is partially filled with the material to be ground and grinding medium. Different materi ⁇ als are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum ro ⁇ tates the grinding media rise with the aid of centrif ⁇ ugal force along with the inner surface of the drum and eventually fall on the material to be ground. Var ⁇ ious 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.
  • solid fuel coarse which acts as a fuel in the subsequent sintering/indurating pro- cess
  • process dust and binding agent bentonite clay
  • the concentrate and the additives are distributed from the intermediate bins 10 onto a conveyor 11 which con ⁇ veys 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 homoge- nous 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. 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 con ⁇ veyor 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 re ⁇ spective zones of the furnace 15.
  • the sinter ⁇ ing/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 sin ⁇ tered/indurated pellets and additives are charged to a preheating kiln 20.
  • the preheating kiln 20 is arranged to preheat the pel ⁇ lets before charging to the smelting furnace 5.
  • the smelting furnace 5 is a closed-type electric arc fur ⁇ nace.
  • the pellets are smelt- ed 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 ref ⁇ erence 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 hereaf ⁇ ter 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 grind- ing 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 in ⁇ side a circle in Figure 2.
  • the CO gas pipeline as in ⁇ dicated with the reference marking B inside a circle may be similar to that shown in Figure 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 in ⁇ vention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

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  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

The invention relates to an equipment to prepare ore concentrate for pelletizing and sintering/indurating of pellets in ferroalloys production. The equipment comprises a grinder (1) arranged to grind the concentrate to a predetermined grain size. The equipment further comprises a drying apparatus (2, 3, 4) arranged to dry the concentrate before and/or during grinding by the grinder (1).

Description

EQUIPMENT TO PREPARE ORE CONCENTRATE FOR PELLETIZING
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 suita- ble 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. A ball mill 1 is a rotating drum which is partially filled with the ma¬ terial to be ground and grinding medium. Different ma¬ terials are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum ro¬ tates the grinding media rise with the aid of centrif- ugal force along with the inner surface of the drum and eventually fall on the material to be ground. Var¬ ious 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.
From the filter 9 the concentrate is conveyed to in- termediate bins 10. Also other additives, solid fuel (coke fine which acts as a fuel in the subsequent sin¬ tering/indurating process), process dust and binding agent (bentonite clay) are conveyed to first interme¬ diate bins 10.
The concentrate and the additives are distributed from the intermediate bins 10 onto a conveyor 11 which con¬ veys 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 homoge¬ nous 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. Further, the equipment comprises a pelletizing drum or disc 13 which is arranged to pelletize the mixture ob¬ tained from the mixer 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 con¬ veyor belt of the strand sintering/indurating furnace 15.
In the continuously working strand sinter¬ ing/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 re¬ spective zones of the furnace 15. The sinter¬ ing/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. After the sintering/indurating 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.
From the strand sintering/indurating furnace 15 the pellets are conveyed to second intermediate 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 pel¬ lets 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 prod¬ ucts 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 re- lates to an ever decreasing availability of good qual¬ ity 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 par- tides have a size less than 75 ym. Wet filtering of the fine fractions in order to dewater those is diffi¬ cult 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 re- quires a series of filters whereby the required in¬ vestment becomes vast. It is an object of the invention to overcome the dis¬ advantages of the prior art as outlined above.
According to the invention the equipment comprises a drying apparatus arranged to dry the concentrate be¬ fore and/or during grinding by the grinder.
The invention provides many advantages. By the ar¬ rangement of a drying apparatus to dry the concentrate before and/or 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.
In one embodiment, the drying apparatus is arranged to dry ore concentrate by the heat energy obtained from burning carbon monoxide.
In one embodiment, 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. By utilizing the CO gas from the smelting furnace to produce the sufficient heat energy for dry¬ ing 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 di¬ rectly to the grinder.
The accompanying drawings, which are included to pro¬ vide a better understanding of the invention constitute part of the description, illustrate preferred em¬ bodiments 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 of a first embodiment of the invention,
Figure 3 shows the beginning of the ferroalloys pro- cess and process equipment of a second embodiment of the invention, and Figure 4 shows the beginning of the ferroalloys pro¬ cess and process equipment of a third 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 a grinder 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 equip- ment the grinder 1 in the invention is dry grinder 1. In order to dry the ore concentrate before it is fed to the grinder 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 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. In Figure 2 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 ma¬ terial to be dried from the charge end to the dis- charge 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 ro¬ tating drum which is partially filled with the material to be ground and grinding medium. Different materi¬ als are used as grinding media, including ceramic balls, flint pebbles and steel balls. As the drum ro¬ tates the grinding media rise with the aid of centrif¬ ugal force along with the inner surface of the drum and eventually fall on the material to be ground. Var¬ ious 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.
After the dry grinder 1 at point A inside a circle the process may continue in a manner as depicted in Figure 1. From the dry grinder 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.
Also other additives, solid fuel (coke fine which acts as a fuel in the subsequent sintering/indurating pro- cess) , 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 a conveyor 11 which con¬ veys 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 homoge- nous 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.
Further, 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. 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 con¬ veyor belt of the strand sintering/indurating furnace 15.
In the continuously working strand sinter¬ ing/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 re¬ spective zones of the furnace 15. The sinter¬ ing/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. After the sintering/indurating 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.
From the strand sintering/indurating furnace 15 the pellets are conveyed to a second intermediate bin 19. Reference number 19 also refers to bins for additives, like lumpy ore, coke, and quartz sand. The sin¬ tered/indurated pellets and additives are charged to a preheating kiln 20.
The preheating kiln 20 is arranged to preheat the pel¬ lets before charging to the smelting furnace 5. The smelting furnace 5 is a closed-type electric arc fur¬ nace. In the smelting furnace 5 the pellets are smelt- ed 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 ref¬ erence marking B inside a circle.
In Figure 3 there is shown a modification of the equipment of Figure 2. In this embodiment 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. Otherwise, the equipment and process may be similar to the one depicted in Figure 2. The process may hereaf¬ ter 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.
In Figure 4 there is shown a further modification of the equipment of Figure 2. In this embodiment the burning chamber 2, the drying chamber 4 and the grind- ing 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 in¬ side a circle in Figure 2. The CO gas pipeline as in¬ dicated with the reference marking B inside a circle may be similar to that shown in Figure 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 in¬ vention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

Claims

1. 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) ar¬ ranged to dry the concentrate before and/or during grinding by the grinder (1) .
2. The equipment according to claim 1, characterised in that the drying apparatus (2, 3, 4) is arranged to dry ore concentrate by the heat energy obtained from burning carbon monoxide.
3. The equipment according to claim 2, characterised in 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) .
4. The equipment according to one or more of claims 1 to 3, 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.
5. The equipment according to claim 4, characterised in that the grinder (1) comprises a grinding chamber (6) arranged to grind the ore concentrate during con¬ veyance the ore concentrate through the grinding cham- ber; 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) .
6. The equipment according to claim 4, 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) .
EP12800621.0A 2011-06-15 2012-06-13 Equipment to prepare ore concentrate for pelletizing Active EP2720797B1 (en)

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
EP2720797A1 true EP2720797A1 (en) 2014-04-23
EP2720797A4 EP2720797A4 (en) 2015-08-12
EP2720797B1 EP2720797B1 (en) 2017-09-27

Family

ID=50288369

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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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JPH0499132A (en) * 1990-08-07 1992-03-31 Kobe Steel Ltd Production of pellet of iron ore containing much water of crystallization
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JP2002030351A (en) * 2000-07-11 2002-01-31 Mitsubishi Heavy Ind Ltd Device for pretreating raw material for reduced iron

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