A process for the reduction roasting of manganese ores and a device therefor

Abstract: Manganese ore, solid carbonaceous reductant and water are mixed. The mixture is formed into a bed on a grate. The top surface is ignited to incandescence while maintaining suction below the grate and then the top surface is sealed against entry of air while continuing the said suction. The combustion of the solid reductant proceeds drawing the oxygen from the ore itself, resulting in high reduction. The product is cooled either by direct water quenching or by indirect means. The equipment employed is either a batch type pot or a continuous strand with sealing devices and material handling systems.

Description: This invention relates to a process for the reduction roasting of manganese ore and device therefor. Manganese ores form the starting material for the production of manganese based chemicals such as electrolytic manganese dioxide (EMD), electrolytic manganese metal (EMM), chemical manganese dioxide (CMD) or manganese sulphate. Low carbon-ferro manganese, high carbon ferro manganese and silico manganese are some of the ferro alloys produced from manganese ores. For the production of manganese based chemicals or ferro alloys such as low carbon ferro-manganese, naturally occurring manganese ores have to be first subjected to reduction roasting to convert the ores from higher oxides into lower oxides. For the production of high carbon ferro-manganese, naturally occurring manganese ores can be used directly provided such ores contain manganese and iron at least in 5:1 ratio. In ferruginous ores (that is naturally occurring manganese ores with high iron content) the manganese to iron ratio is generally less than 5:1 and hence removal of iron therefrom is necessary for further processing. When ferruginous manganese ores are subjected to reduction roasting, the higher iron oxide minerals also get reduced to lower oxide form and are amenable to removal by magnetic separation thereby improving the manganese to iron ratio. The lower iron manganese ores thus obtained can be used as a starting material for the production of manganese based chemicals or ferro alloys. Lower oxides of manganese produced by reduction roasting are soluble in solvents like sulphuric acid or hydrochloric acid whereas naturally occurring manganese oxide ores are insoluble in such solvents. Therefore, dissolution efficiency of reduction roasted manganese ores is dependent on the degree of reduction. Hence the lower the degree of reduction, higher the wastage of manganese minerals during the production of manganese based chemicals. Conventional process for the reduction roasting of manganese ores comprises grinding manganese ores to fines of size generally up to 0.075 mm., reducing the manganese ore fines generally in a rotary kiln or fluidised bed roaster using a reducing agent at elevated temperature (generally about 1000°C) and cooling the reduced ore fines out of contact with air. The size of the manganese ore fines obtained by the conventional process of reduction roasting will also be generally up to 0.075mm. Grinding of manganese ores which are highly abrasive into fines is very expensive. The reducing agent generally used is petroleum based fuel such as oil or gas. Furthermore heating of the fines during reduction is also done generally using a petroleum based fuel such as oil or gas. Thus considerable petroleum based fuel such as oil or gas which is very expensive is required for the reduction roasting. Besides, during grinding there is a loss of the valuable ore in the form of dust which also creates pollution problems. Burning of petroleum based fuels generates obnoxious fumes which also creates pollution problem. The reducing atmosphere requires to be very carefully controlled by adjusting the fuel to air ratio. Sophisticated air controls are required to control the air. The reduced fines are prone to reoxidation while being cooled due to their inherent large exposed surface area. In the conventional processes,the conversion of manganese dioxide (MnO 2 ) present in the natural ore to manganous oxide (MnO) is generally up to 50% of the raw feed. The conventional processes of reduction' roasting are thus expensive, difficult to carry out, less efficient, result in wastage of valuable mineral wealth, require to be very carefully controlled and create pollution problems. JP-A-53095117 discloses a method for the spontaneous combustion of manganese dust cake. FR-A-2318938 discloses reduction of manganese oxides in which a non-oxidizing gas is passed into and through an initial bed of combustible carbonaceous solid and manganese mineral which has been at least partially reduced to MnO, and the resulting hot reduction gas mixture is directed to a contiguous bed of unreduced manganese mineral mixed with combustible carbonaceous solids. FR-A-2246640 discloses apparatus for treating iron minerals which has a main conduit for feeding to one or more hoods air drawn through the charge, injecting combustible gas into the main conduit, means for measuring the amount of air transversing the main conduit, and means for regulating the amount of gas injected into the air to maintain it below the limits of inflammability. An object of the present invention is to provide a process for reduction roasting of manganese ores which process is more economical and efficient and is simple and easy to carry out and safe and pollution-free. Another object of the present invention is to provide a device for carrying out such process for the reduction roasting of manganese ores. According to the present invention there is provided a process for the reduction roasting of manganese ores,said process comprising mixing manganese ore fines and solid fuel fines with water and forming the resulting mixture into a bed, the solid fuel fines used being from 8 to 38% by weight of the manganese ore fines and the water used being 5 to 10% by weight of the total of the manganese ore fines and solid fuel fines; igniting the top surface of the bed in the presence of air and under suction from below until the top surface thereof becomes incandescent; sealing the bed whose top surface has become incandescent against entry of air, the heat front formed by ignition liberating inherent or combined oxygen of the manganese ore fines for combustion of the solid fuel fines and thereby sustaining the flame front formed by ignition to achieve a high degree of reduction roasting of the manganese ore fines; continuing suction to draw the heat front and flame front along with the combustion products down through the bed until reduction roasting is over; disintegrating the resulting reduced mass; and cooling the resulting reduction roasted manganese ores. The reduction roasted manganese ore obtained by the process of the invention can be processed in known manner for the production of manganese based chemicals or ferro alloys. Combustion products include water vapour, carbon monoxide, carbon dioxide and oxygen. Manganese ore fines contemplated for the process of the present invention can be fines generally up to -6 mm and include run of mine fines or plant fines. Solid fuel fines contemplated for the process of the present invention are carbonaceous matter fines such as coke, coal or charcoal fines generally up to -6 mm size. Depending upon the quality of the solid fuel fines and the degree of reduction roasting desired, the percentage of solid fuel fines will vary. The solid fuel fines used may be from 8 to 38 % by weight of the manganese ore fines. Water contemplated for the process of the present invention includes water (moisture) present in the manganese ore fines and/or solid fuel fines. Water may be 5 - 10 % by weight of the total of the manganese ore fines and solid fuel fines. According to the present invention there is also provided a device for the reduction roasting of manganese ores, said device comprising a pair of vertically disposed bunkers, each of the said bunkers being open at its upper end and provided with an outlet at its lower end, one of said bunkers being for receiving and discharging manganese ores fines through its open upper end and lower outlet respectively and the other of said bunkers being for receiving and discharging solid fuel fines through its open upper end and its lower outlet end respectively, the outlet of each of said bunkers being provided with a regulator to regulate the discharge of manganese ore fines and solid fuel fines therethrough respectively; a first endless conveyor horizontally disposed below the outlets of said bunkers and travelling forward in the horizontal plane, said first endless conveyor being so disposed that manganese ore fines and solid fuel fines being discharged through the outlets of said bunkers fall down thereon; a mixer for said ore and fuel fines and water vertically disposed in the proximity of the discharge end of said first endless conveyor, said mixer having an inlet and outlet, said mixer being so disposed in the proximity of the discharge end of said first endless conveyor that the discharge end of said first endless conveyor communicates with said inlet of said mixer to transfer the manganese ore fines and solid fuel fines on said first endless conveyor into said mixer; means for supplying water into said mixer through said outlet or inlet of said mixer; a second, endless conveyor horizontally disposed at an inclination with respect to the horizontal plane such that its inlet end is below the outlet of said mixer and the mixture of manganese ore fines, solid fuel fines and water falls down thereon, said second endless conveyor travelling forward at an inclination with respect to the horizontal plane; a reduction roasting unit, the inlet of which is disposed below the discharge end of the second endless conveyor such the said mixture falls thereinto to form a bed in said reduction roasting unit, said reduction roasting unit having means for carrying said bed, a discharge end, means for igniting the top surface of said bed in the presence of air until incandescence, means for sealing said bed against entry of air after ignition to incandescence, and means for creating suction below said bed from the inception of ignition of the top surface of said bed until reduction roasting of said bed is over within the zone in which said bed is sealed against the entry of air; a disintegrator unit comprising a rotor provided with blades, said rotor with blades being disposed in an airtight casing vertically disposed in the proximity of the discharge end of said reduction roasting unit and provided with an inlet and an outlet, the inlet of said airtight casing communicating with the discharge end of said reduction roasting unit such that the reduction roasted mass enters said disintegrator unit on being discharged; cooling means disposed below said airtight casing and provided with an inlet and an outlet, the inlet of said cooling means being connected to said outlet of said airtight casing such that the disintegrated reduction roasted manganese ores from said disintegrator unit fall thereinto; and drive means connected to said first and second endless conveyors, reduction roasting unit and rotor. The following is a detailed description of embodiments of the present invention with reference to the accompanying drawings in which : Fig. 1 is schematic view of a device for the reduction roasting of manganes ores according to an embodiment of the present invention without cooling means; Fig. 2 is schematic view of a device for the reduction roasting of manganese ores according to another embodiment of the present invention without cooling means; Fig.3 is schematic view of an indirect type cooling means (indirect rotary drum cooler) for the device of fig. 1 or fig. 2; and Fig. 4 is schematic view of a direct type cooling means (spiral or rake classifier) for the device of fig. 1 or 2. Refering to Fig. 1 the device is for the reduction roasting of manganese ores in a continuous manner and consists of a pair of vertically disposed bunkers 1 and 2, whose upper ends are open and whose lower ends are provided with outlets 3 and 4. Outlets 3 and 4 are provided with regulators 5 and 6 respectively. Bunker 1 receives manganese ore fines (not shown) through its upper open end and discharges the manganese ore fines through outlet 3 at its lower end continuously. Regulator 5 is for regulating the discharge rate of manganese ore fines through outlet 3. Bunker 2 receives solid fuel fines through its open upper end and discharges solid fuel fines through its outlet 4 at its lower end continuously. Regulator 6 is for regulating the discharge rate of solid fuel fines through outlet 4. A first endless conveyor 7 is horizontally disposed below the outlets 3 and 4 of bunkers 1 and 2 respectively. Conveyor 7 is so disposed that manganese ore fines and solid fuel fines being discharged through outlets 3 and 4 of bunkers 1 and 2 fall down thereon. Conveyor 7 travels forward in the horizontal plane in the direction of arrow X towards mixer 8 which is vertically disposed in the proximity of the discharge end 7b of conveyor 7. The inlet end of conveyor 7 is marked 7a. Mixer 8 is provided with an inlet 9 and outlet 10. Mixer 8 is so disposed in the proximity of the discharge end 7b of conveyor 7 that conveyor 7 communicates with inlet 9 of mixer 8 to transfer the manganese ore fines and solid fuel fines on conveyor 7 into mixer 8. Mixer 8 mixes the manganese ore fines and solid fuel fines with water and forms a mixture (not shown) thereof. Water for mixing is supplied into mixer 8 through outlet 10 thereof continously. Water for mixing can also be supplied through inlet 9 of mixer 8 continously instead of through its outlet 10. A second endless conveyor 11, is horizontally disposed at an inclination with respect to the horizontal plane and with its inlet end 11a below the outlet 10 of mixer 8 such that the mixture of manganese ore fines and solid fuel fines with water falls down thereon continuously. Conveyor 11 travels forward at an inclination with respect to the horizontal plane in the direction of arrow Y. 12 is a series of horizontally disposed pallets, inlet end 12a of which is disposed below the discharge end 11b of conveyor 11. The pallets 12 travel forward in the horizontal plane in the direction of the arrow Z. A hopper 13 is vertically disposed below the discharge end 11b of conveyor 11 and above the inlet end 12a of pallets 12 such that said mixture falls down into hopper 13 and from hopper 13 onto pallets 12 and forms a bed (not shown) thereon continuously. A fuel fired burner 14 is disposed above pallets 12 such that burner 14 ignites the top surface of said bed, until incandescence, in the presence of air. The air inlet and fuel inlet of burner 14 are 15 and 16 repectively. Air sealing means 17 is disposed above pallets 12 to seal against entry of air said bed whose top suface has been ignited to incandescence by burner 14. A suction box 18 is provided below pallets 12. Suction box 18 is connected to exhaust stack 28 through suction line 29. Suction fan 30 and dust trap 31 are provided in suction line 29. Suction fan 30 creates suction through said bed from the inception of ignition of the top surface of said bed until reduction roasting of said bed is over within the zone covered by air sealing means 17, the heat front formed by ignition liberating inherent or combined oxygen of said manganese ore fines within said zone for combustion of said solid fuel fines thereby sustaining the flame front formed by ignition to achieve a high degree of reduction roasting of said manganese ore fines, said suction drawing the combustion products along with the heat front and flame front through said bed. A rotor 19 is provided with blades 19a and disposed in an airtight casing 20. Casing 20 is vertically disposed below the discharge end 12b of pallets 12 and is provided with an inlet 21 and outlet 22. Casing 20 is so disposed that the discharge end 12b of pallets 12 communicates with inlet 21 of casing 20 and the reduction roasted manganese ore mass from pallets 12 falls continuously down into casing 12 where it is disintegrated by rotor 19 and its blades 19a and discharges through outlet 22 into the cooling arrangement of fig. 3 or fig. 4 described hereinafter. Dust trap 31 is provided with an opening 32 at its lower end. A third endless conveyor 33 is horizontally disposed at an inclination with respect to the horizontal plane such that its inlet end 33a is below dust collector 31 and its discharge end 33b is above bunker 1. Conveyor 33 is so disposed that manganese ore dust trapped in trap 31 falls down on conveyor 33 through opening 32 and that from conveyor 33 the manganese ore dust falls down into bunker 1 continuously. Manganese ore dust-free gases are let out through stack 28. The conveyors 7,11 and 33, pallets 12, rotor 19, fan 30 and mixer 8 are driven by prime mover(s) such as electric motor(s), (not shown) by connecting them to the prime mover(s) in known manner using known means such as sprockets, shafts, chains,spur gears or belts (not shown). The sprockets driving conveyors 7, 11 and 33 and pallets 12 are marked 34 and 35, 36 and 37, 38 and 39 and 40 and 41 respectively. Referring to Fig. 2 the device is for reduction roasting of manganese ore in a batchwise manner and is similar to the device of Fig. 1 except as follows : A pot 42 with a removable perforated bottom is vertically disposed and movable in the horizontal plane. Pot 42 can occupy four position viz. filling position (first position), ignition positon (second position), reduction roasting position (third position) and discharge position (fourth position) in sequence as indicated by 43a, 43b, 43c and 43d. In the filling position 43a, pot 42 comes directly below the discharge end 11b of conveyor 11 with its perforated bottom in closed position and said mixture falls down into pot 42 and forms a bed (not shown). After being filled, pot 42 is moved to the ignition position 43b. In the ignition position pot 42 comes below burner 14 such that burner 14 ignites the top surface of said bed until incandescence. After ignition the pot is moved to the reduction roasting position 43c. In the reduction roasting position, pot 42 is made air tight by air sealing means 17a provided at its top. Suction boxes 18 a are provided below positions 43b and 43c. Fan 30 creates suction through said bed from the inception of ignition of the top surface of said bed in position 43b and during reduction roasting of said bed in positon 43c, the heat front formed by ignition liberating inherent or combined oxygen from said manganese ore fines in pot 42, for combustion of said solid fuel fines in pot 42 thereby sustaining the flame front formed by ignition to achieve a high degree of reduction roasting of said manganese ore fines, suction drawing the combustion products along with the heat front and flame front through said bed. After reduction roasting is completed, pot 42 is moved to the discharge position in which it is connected to inlet 21 of casing 20. In the discharge position, the perforated bottom of pot 42 is removed so that the reduction roasted manganese ores from pot 42 fall down into casing 20. Pot 42 can be moved manually or automatically. When pot 42 is moved mechanically, drive to pot 42 is taken from said prime mover(s) in known manner using known means such as those mentioned above. Referring to Fig. 3 the cooling arrangement is of the indirect cooling type, namely an indirect rotary drum cooler. The rotary drum 23 is provided with an inlet 24 and outlet 25. The inlet 24 of rotary drum 23 and outlet 22 of casing 20 are interconnected by pipe 26 (see Figs. 1 and 3 or 2 and 3) so that the disintegrated reduction roasted manganese ores fall down into drum 23 from casing 20. The disintegrated reduction roasted manganese ores are indirectly cooled in drum 23 by spraying water through sprayers or diffusers 27 provided outside the drum 23 so that the cooling water does not come into contact with the disintegrated reduction roasted manganese ores being cooled. Therefore, the cooled ores being discharged through outlet 25 of drum 23 will be dry and can be processed further in known manner. Referring to Fig. 4, the cooling arrangement is of the direct cooling type, namely a spiral or rake classifier. A quenching tank 46 of the spiral or rake classifier is inclined with respect to the horizontal plane and has a pool of water (not shown) at its bottom. Entry port 47 of tank 46 is connected to the inlet 22 of casing 20 by pipe 26 (see Figs. 1 and 4 or 2 and 4) so that the disintegrated reduction roasted manganese ores fall down into tank 46 from casing 20. In tank 46 rapid cooling of the ores takes place. A raking mechanism 48 continously moves the cooled ores upwards to the top discharge opening 49 of tank 46. A continuous spray 50 of cold water cools and washes the disintegrated reduction roasted manganese ores and removes the water soluble fraction thereof. Water in tank 46 continuously overflows through exit port 51 thereof and carries with it heat as well as the dissolved fraction. The cooled and washed ores are discharged from opening 49 of tank 46 in a wet condition. The cooled and washed ores are dried in known manner, if necessary, and processed further in known manner. The size of the manganese ores obtained by the process of the present invention is preferably up to 75mm. Similarly the following examples are also illustrative of the process of the present invention. EXAMPLE - 1 The following mixture was reduction roasted in a batchwise manner as per the present invention :- Mn Ore (-4 mm size) 68.6 parts by weight Coal (-3 mm size) 24.3 parts by weight Water 7.1 parts by weight 100 parts by weight Chemical composition of the Mn ore prior to reduction roasting was as follows : Assay % by Wt. Mn (total) 46.8 Fe 9.4 MnO 2 67.82 Manganese soluble in 8 % dilute sulphuric acid. Nil Ignition was carried out using liquified petroleum gas. Ignition time was 1 minute. Reduction roasting time was 15 minutes. Vaccum applied was 0.99kPa (100mm WG-Water Gauge). Air flow during reduction roasting was nil. Reduction roasted ore was leached with 8 % dilute sulphuric acid, MnO 2 , the form in which manganese is present in the ore prior to reduction, is insoluble. The MnO fraction produced by reduction of MnO 2 during reduction roasting is soluble. Reduction roasted materials produced conventionally and by the invention from the same ore were chemically analysed before acid leaching and the solid residue after leaching was also analysed, and by difference the Mn (soluble) was computed for both routes. The results are as follows. Material Assay % Mn (Total) Soluble Mn % Mn(Sol) / Mn (Total) X 100 - Reduction roasted product by conventional process 49.91 46.1 - Reduction roasted product by process of invention 53.55 91.0 Note The difference in Mn (Total) is due to lower product weight as a result of oxygen loss during the reduction roasting. The loss of oxygen is higher in the process of the invention during the reduction roasting. EXAMPLE - II. The following mixture was reduction roasted in a batchwise manner as per the present invention. Mn Ore (-4 mm size) 85.2 parts by weight Coal (-3 mm size) 7.4 parts by weight Water 7.4 parts by weight 100 parts by weight Chemical composition of the Mn ore prior to reduction roasting was as follows Assay % by weight Mn (total) 46.0 Fe 13.24 Mn/Fe 3.47 Ignition was carried out using liquified petroeum gas. Ignition time was 1 minute. Reduction roasting time was 10 mins. Vacuum applied was 1.48 kPa (150mm WG). Air flow during reduction roasting was nil. Reduction roasted ore was subjected to magnetic separation and the results were as under : Assay % by Wt. Ratio. Wt. %. Mn. Fe. Mn/Fe. Magnetic fraction 40.8 43 23.0 1.87 Non-magnetic 59.2 55.1 8.6 6.45 100.0 The magnetic fraction can be used as feed in blast furnaces as it is rich in iron and contains a good amount of manganese. The non-magnetic fraction can be directly used for the production of low carbon ferro-manganese or after sintering for the production of high carbon ferro-manganese. In ferro-manganese production an Mn:Fe ratio of 6.45 is excellent. EXAMPLE - III The following mixture was reduction roasted in a batchwise manner as per the present invention: Mn Ore (-4 mm size) 68.6 parts by weight Coal (-3 mm size) 24.3 parts by weight Water 7.1 parts by weight 100 parts by weight Chemical composition of the Mn ore prior to reduction Assay % by wt. Mn (total) 47.2 Fe 9.0 K 2 O 0.6 Ignition was carried out using liquified petroleum gas. Ignition time was 1 minute. Reduction roasting time was 15 mins. Vacuum applied was 0.99 kPa (100mm WG). Air flow during reduction roasting was nil. Reduction roasted ore was air cooled and after drawing a sample was quenched in water. After dewatering the solids were analysed for potassium. The sample drawn before quenching was also analysed. By difference in potassium content before and after quenching soluble potassium was computed. Soluble potassium percentage with respect to total potassium content before quenching was calculated. The results are as follows :- Compared to the conventional process of reduction roasting of manganese ores, the process of the present invention has the following advantages : 1. No grinding of the manganese ores is required prior to reduction roasting and therefore dust loss resulting from grinding is avoided. The novel process is, therefore, economical and pollution free. 2. Expensive and scarce petroleum based fuel such as gas or oil is not required either as reducing agent or for heating until reduction roasting is over and, in the place of such petroelum based fuel, cheap and abundantly available solid fuel fines such as those of coke, coal or charcoal are used, petroleum based fuel being required only to ignite the top surface of the mixture of the manganese ore fines and solid fuel fines with water until incandescence. The process, therefore, is economical. 3. Heat required for the reduction roasting is generated within the mixture of manganese ore fines and solid fuel fines with water (whereas heat required for the reduction roasting by the conventional process is supplied externally). Consequently during the process heat utilisation is maximum and heat loss is minimum thereby rendering the process more efficient. 4. Since oxygen inherent in the mnaganese ore fines (that is oxygen in the compound form) is liberated and fully utilised for combustion of solid fuel fines, the process achieves an almost completely reducing atmosphere thereby achieving a very high degree of reduction roasting (whereas in the conventional process a certain amount of air is always employed for combustion and hence the atmosphere is only partially reducing). 5. Since no air is employed during reduction roasting, the sophisticated air controls required in the conventional process are unnecessary with the result that the process is simple and easy to cary out and economical. 6. Since there is no grinding of manganese ores and since burning of petroleum based fuel is only for a short period (that is, only up to the stage of igniting the top surface of the mixture to incandescence), generation of hazardous dust and emission of obnoxious fumes is eliminated thereby rendering the process economical, safe and pollution free. 7. Since the manganese ores used for and obtained after reduction roasting are of coarse size (that is, generally up to 6 mm), the exposed surface area thereof is small compared to that of an equal quantity of manganese ores fines (of 0.075mm size) used for and obtained by the conventional process. The exposed area of the reduction roasted ores being small, reoxidation (which is proportional to exposed surface area) of the ores during cooling is low. 8. In contrast to the conventional process in which nitrogen from the certain amount of air employed during reduction roasting carries away sensible heat, the reduction roasting is carried out in airless conditions so that no such loss of sensible heat takes place and the process is more efficient. 9. Potassium, if present in the manganese ores in water insoluble form, gets converted into water soluble form during reduction roasting with the result that potassium which is an undesirable impurity in certain manganese based chemicals such as EMD or CMD can be easily removed by dissolution during cooling of the reduction roasted manganese ores, directly with water. 10. Since the process can produce reduced material which can be easily agglomerated by a conventional process of sintering and then can be charged to an electric arc smelting furnace directly, considerable saving in electric power during smelting can be achieved in the production of high carbon ferromanganese. The lowering of oxygen level in the reduced material also brings about considerable saving in the consumption of reductants in a smelting furnace and makes the furnace operation smoother. 11. In the case of ferruginous manganese ores the process of the invention has the following additional advantages: Since a high degree of reduction roasting of manganese ore is achieved, reduction of higher oxides of iron to lower oxides of iron will also be correspondingly high with the result that better magnetic separation of iron minerals from manganese mineral in the reduction roasted ores in possible. Since the manganese ores used for and obtained by reduction roasting are of coarse size, they are amenable to fusion by sintering, whereas the manganese ores used for and obtained by reduction roasting by the conventional process (being microfines of 75 microns) can be fused/agglomerated only by the expenssive pelletization method. Due to the high degree of reduction roasting loss of oxygen is correspondingly high. Therefore, the manganese content in the reduction roasted manganese ores is high and correspondingly high manganese to iron ratios are achievable. The manganese ores after being reduction roasted and after being subjected to magnetic separation can be used for the production of ferroalloys such as low carbon ferro-manganese. The manganese ore after being reduction roasted and after being subject to magnetic separation can be advantageously used for the production of manganese based chemicals such as EMD or EMM as removal of iron by magnetic separation reduces the load on the chemical process by which iron also had to be removed for the production of such chemicals.

Claims: A process for the reduction roasting of manganese ores,said process comprising mixing manganese ore fines and solid fuel fines with water and forming the resulting mixture into a bed, the solid fuel fines used being from 8 to 38% by weight of the manganese ore fines and the water used being 5 to 10% by weight of the total of the manganese ore fines and solid fuel fines; igniting the top surface of the bed in the presence of air and under suction from below until the top surface thereof becomes incandescent; sealing the bed whose top surface has become incandescent against entry of air, the heat front formed by ignition liberating inherent or combined oxygen of the manganese ore fines for combustion of the solid fuel fines and thereby sustaining the flame front formed by ignition to achieve a high degree of reduction roasting of the manganese ore fines; continuing suction to draw the heat front and flame front along with the combustion products down through the bed until reduction roasting is over; disintegrating the resulting reduced mass; and cooling the resulting reduction roasted manganese ores. A device for the reduction roasting of manganese ores, said device comprising a pair of vertically disposed bunkers, each of the said bunkers being open at its upper end and provided with an outlet at its lower end, one of said bunkers being for receiving and discharging manganese ores fines through its open upper end and lower outlet respectively and the other of said bunkers being for receiving and discharging solid fuel fines through its open upper end and its lower outlet end respectively, the outlet of each of said bunkers being provided with a regulator to regulate the discharge of manganese ore fines and solid fuel fines therethrough respectively; a first endless conveyor horizontally disposed below the outlets of said bunkers and travelling forward in the horizontal plane, said first endless conveyor being so disposed that manganese ore fines and solid fuel fines being discharged through the outlets of said bunkers fall down thereon; a mixer for said ore and fuel fines and water vertically disposed in the proximity of the discharge end of said first endless conveyor, said mixer having an inlet and outlet, said mixer being so disposed in the proximity of the discharge end of said first endless conveyor that the discharge end of said first endless conveyor communicates with said inlet of said mixer to transfer the manganese ore fines and solid fuel fines on said first endless conveyor into said mixer; means for supplying water into said mixer through said outlet or inlet of said mixer; a second endless conveyor horizontally disposed at an inclination with respect to the horizontal plane such that its inlet end is below the outlet of said mixer and the mixture of manganese ore fines, solid fuel fines and water falls down thereon, said second endless conveyor travelling forward at an inclination with respect to the horizontal plane; a reduction roasting unit, the inlet of which is disposed below the discharge end of the second endless conveyor such the said mixture falls thereinto to form a bed in said reduction roasting unit, said reduction roasting unit having means for carrying said bed, a discharge end, means for igniting the top surface of said bed in the presence of air until incandescence, means for sealing said bed against entry of air after ignition to incandescence, and means for creating suction below said bed from the inception of ignition of the top surface of said bed until reduction roasting of said bed is over within the zone in which said bed is sealed against the entry of air; a disintegrator unit comprising a rotor provided with blades, said rotor with blades being disposed in an airtight casing vertically disposed in the proximity of the discharge end of said reduction roasting unit and provided with an inlet and an outlet, the inlet of said airtight casing communicating with the discharge end of said reduction roasting unit such that the reduction roasted mass enters said disintegrator unit on being discharged; cooling means disposed below said airtight casing and provided with an inlet and an outlet, the inlet of said cooling means being connected to said outlet of said airtight casing such that the disintegrated reduction roasted manganese ores from said disintegrator unit fall thereinto; and drive means connected to said first and second endless conveyors, reduction roasting unit and rotor.

Inventors: KOTHARI SUDHAKAR VINAYAK, SUBRAMANIAN NILKANTHA ANANTHA, KOTHARI, SUDHAKAR VINAYAK, SUBRAMANIAN, NILKANTHA ANANTHA
Applicants: PARAMOUNT SINTERS PRIVATE LIMI, PARAMOUNT SINTERS PRIVATE LIMITED
Application year: 1992
Main classification: C22B47
IPC codes: F27B21, C22B1, F27D15, C22B47