WO2020246907A1

WO2020246907A1 - Method of removing phosphorus from iron ore concentrates and a plant for carrying out said method

Info

Publication number: WO2020246907A1
Application number: PCT/RU2019/000407
Authority: WO
Inventors: Лик Анварович Зайнуллин; Артем Юрьевич Епишин; Дмитрий Анатольевич Артов; Владислав Георгиевич Карелин; Роман Ликович ЗАЙНУЛЛИН
Original assignee: Лик Анварович Зайнуллин
Priority date: 2019-06-07
Filing date: 2019-06-07
Publication date: 2020-12-10

Abstract

The group of inventions can be used in preparing iron ore concentrates for metallurgical treatment, for which unacceptable concentrations of phosphorus are generally more than 0.25-0.30%. A method comprises oxidative roasting in a furnace at a temperature of 800-1000°С, cooling the roasted concentrate, leaching phosphorus from the concentrate with an aqueous solution of a mineral acid, and separating the leached concentrate from the solution, wherein the roasted iron ore concentrate is cooled and leached with an aqueous solution of a mineral acid. A plant comprises a roasting furnace, an apparatus for simultaneous cooling and leaching of the roasted concentrate, said apparatus being designed so that an aqueous solution of a mineral acid can be fed continuously into same, a device for continuously feeding roasted concentrate into the apparatus immediately upon unloading from the roasting furnace, as well as a device for separating the leached concentrate from the solution and unloading it, with subsequent neutralizing of the acid solution and flushing of the concentrate therefrom, said device being arranged on the side where the solution is drained.

Description

Method for purification of iron ore concentrates from phosphorus and

method installation

Technology area

The group of inventions relates to the technology of thermochemical purification of iron ore concentrates from harmful impurities, in particular, phosphorus, using mineral acids and can be used in the preparation of iron ore concentrates for metallurgical processing, for which unacceptable phosphorus concentrations are, as a rule, more than 0.25-0 ,thirty%.

Prior art

For blast-furnace smelting, the phosphorus content in iron ore concentrate is considered acceptable if it does not exceed 0.25-0.30%. When enriching ores with a phosphorus content of 0.7-1.0%, the degree of removal by conventional methods does not provide the required phosphorus concentration.

Various methods are known for removing phosphorus from ore or concentrate using various chemical reagents by leaching phosphorus into solution. Most of them are either economically ineffective or environmentally unsuitable. Known methods for removing phosphorus into slag when smelting steel in pyrometallurgical units with obligatory intermediate slag downloading. These methods are economically uncompetitive over other methods of obtaining pure steel in terms of harmful impurities.

There are known methods of chemical leaching of phosphorus, the efficiency of which increases with the use of preliminary heat treatment, which consists in roasting the concentrate at a temperature of 500-600 ° C for 1-1.5 hours, (Dukino R.D., England V.M. "Phosphorus in the iron ores of the Hemersley Ridge" (Australian Institute of Mining and metallurgy / Avstral. 1MM /, 5/97, pp. 197-202) [1]. For leaching, sulfuric acid is used in an amount of at least 110-150% of stoichiometric in relation to phosphorus, at a temperature of 60-80 ° C, the ratio S: W = 1: 3-1: 5. The leaching time in this case is 2-3 hours The residual phosphorus content in the concentrate in an amount of up to 40% of the initial, indicates a low degree of phosphorus removal.

Closest to the claimed method is a method for purifying iron ore concentrate from phosphorus (RU 2184158, publ. 27.06.2002) [2].

This method includes oxidative roasting of iron ore concentrate at a temperature of 800-1000 ° C with a holding time of no more than 1 hour, preliminary cooling of the cold concentrate, leaching of the concentrate with mineral acid at the given parameters of the leaching process, separation of the liquid phase from the solid, followed by neutralization of the solution and washing the solid phase ...

Depending on the mineralogical composition of the iron ore concentrate, sulfuric or nitric acid is used as a mineral acid for leaching. The leaching process is carried out with sulfuric or nitric acid at a ratio of S: W = 1: (1-2) and a temperature of 20-50 ° C, controlled by the final acidity of the solution and completed when the acidity value reaches 6-10 g / l. After washing on a filter and drying, a concentrate is obtained with a residual phosphorus content of up to 0.15%.

The main disadvantages of this method include: long, at least 1 hour, leaching time, relatively high consumption heat resources, significant consumption of mineral acid and the need for equipment for preliminary cooling of the fired concentrate.

Disclosure of invention

The objective of the present invention is to create a more economical and simpler in implementation method of purification of iron ore concentrate from phosphorus when achieving the properties of the concentrate, increased or comparable to the properties of products obtained by the method according to the prototype.

To solve the problem, a method is proposed for purifying iron ore concentrate from phosphorus, which includes oxidative roasting in a furnace at a temperature of 800-1000 ° C, cooling the fired concentrate, leaching phosphorus from the concentrate with an aqueous solution of mineral acid, separating the leached concentrate from the solution, followed by neutralization and washing the concentrate ... In contrast to the prototype, the roasted iron ore concentrate is cooled and leached with an aqueous solution of mineral acid directly during the unloading of the concentrate from the roasting furnace into the acid leaching apparatus.

When the fired hot iron ore concentrate with a temperature of 950 ° C is immersed in a container with an aqueous solution of mineral acid to a great depth, due to the increased pressure in its lower layers, the temperature of this solution reaches 100 ° C or more. Boiling water in this solution will provide intensive mixing of hot particles of iron ore concentrate and maximally intensify the process of leaching phosphorus from iron ore concentrate, without requiring additional heat input for heating water, as well as water consumption for

s cooling and special equipment for separate cooling and leaching.

Known installations designed to implement the method of iron ore concentrate from phosphorus, in which the processes of cooling and leaching of roasted iron ore concentrate are combined, have not been identified.

The proposed installation contains a roasting furnace, an apparatus for simultaneous cooling and leaching of the roasted concentrate, configured to _. continuous supply of an aqueous solution of mineral acid to it, a device for continuous supply of the fired concentrate to the apparatus directly during unloading from the roasting furnace, as well as a device for separating the leached concentrate from the solution and unloading it, followed by neutralization of the acid solution and washing the concentrate from it, located on the side draining the solution.

The claimed method, carried out in a new installation, provides heating of the mineral acid solution due to the physical heat of the fired concentrate without additional costs for heat. To cool the roasted concentrate, the potential of a cold mineral acid solution is used, eliminating the additional costs for expensive clean water, while cooling and leaching of the concentrate is carried out in one apparatus. In the same apparatus, the spent mineral acid solution is neutralized with an alkaline solution and the concentrate is washed from it. Leach time is shortened by using the heat of the highly heated particles of the roasted iron ore concentrate. A small amount of steam generated during cooling of the fired concentrate is completely condensed by a neutralizing alkaline solution. Due to the complete condensation of steam with residues of acid and sulfur compounds, emissions of sulfur compounds into the atmosphere are excluded. Thus, the claimed group of inventions makes it possible to significantly simplify the scheme for removing phosphorus from iron ore concentrates, reducing the equipment to two main units, namely a roasting furnace and an apparatus in which the fired concentrate is cooled and leached. The same apparatus provides for the neutralization of the spent mineral acid solution, washing the concentrate from it, condensing the contaminated steam and unloading the dehydrated concentrate. Drying of the de-phosphorized concentrate due to the heat of flue gases with a temperature of 300 - 400 ° C is carried out in a separate drum dryer, if necessary. The claimed solution allows to accelerate the leaching rate from 2 to 5 times (5-10 minutes), which reduces the weight and dimensions of the equipment, does not require expensive equipment for washing, filtration, neutralization and purification of acid compounds. The technology makes it possible to use the heat of the exhaust gases of the roasting furnace for drying the concentrate. In addition, flue gas cleaning can be organized by flushing with neutralizing water in a scrubber.

Brief Description of Drawings

Figure 1 shows an installation for the purification of iron ore concentrate from phosphorus; figure 2 - a device for separating the concentrate from the acid solution and its unloading, side view; in Fig.Z - a fragment of the device for separating the concentrate from the acid solution and its unloading.

Implementation of the invention

The installation contains a kiln 1 with a loading head 2, a feeder - dispenser 3 with a loading funnel 4 connected to a belt conveyor for feeding iron ore concentrate 5. Loading head 2 is equipped with a gas outlet 6 and a smoke exhauster 7. On the unloading side, furnace 1 has an unloading head 8, a burner 9, tray 10 unloading fired concentrate connected to the drum 11 for cooling and leaching the fired concentrate with an aqueous solution of mineral acid, inside which is mounted at least one spiral of Archimedes 12. The drum 11 is equipped with a system 13 for feeding an aqueous solution of mineral acid. From the discharge side, the drum 11 is equipped with a device 14 for separating the concentrate from the mineral acid solution and unloading it. The device 14 is made in the form of peripheral elevator buckets with the possibility of unloading the concentrate into the tray 15 connected to the dryer 16 of the leached concentrate, made in the form of a rotating drum with the possibility of feeding into it the concentrate and flue gases separated from the spent solution from the roasting furnace (hereinafter referred to as the drum dryer). In addition, the drum 11 from the unloading side is connected to a vertical scrubber 17, which has at the top a branch pipe 18 for exhausting gases connected to a fan 19, as well as an alkaline solution supply system 20, and at the bottom - a settler 21 with a device 22 for discharging solid sediment of fine concentrate into a receiver 23. An alkaline solution is supplied to the scrubber 17 and drum 11 before unloading the concentrate and draining the spent mineral acid solution from the system 20 to neutralize the steam and the spent acid solution, respectively.

The drum dryer 16 is equipped with an unloading head 24, a fan 25 for supplying hot flue gases, an unloading hopper 26, a finished concentrate feeder 27, a conveyor 28 for transferring the concentrate to a warehouse (not indicated in the diagram). Pipe 29 serves to remove exhaust gases into the atmosphere.

Purification of iron ore concentrate from phosphorus in the claimed installation is carried out as follows.

The roasting of iron ore concentrate is carried out in a rotary kiln 1, where it is fed through a loading head 2, equipped with a spill collector in the lower part. The concentrate is loaded with a dispenser 3 of

b loading funnel 4, where it is fed by a belt conveyor 5. Exhaust flue gases from the roasting furnace 1 enter the loading head 2 and through the branch pipe 6 are sucked by the fan 7 into the chimney or into the dryer 16 by the fan 25, after which the gases enter the scrubber 17 and, washed with an alkaline water from the system 20, are sucked through the branch pipe 18 by the fan 19 into the chimney 29. From the opposite side of the drum 11, by means of the burner 9, the heat carrier for the concentrate roasting is supplied to the furnace 1. Passing through the rotary kiln 1, the concentrate is dried, heated to the firing temperature and kept at a constant temperature for a specified amount of time. After that, the concentrate enters the rotary drum 11 for leaching through the inclined tray 10, where simultaneously an aqueous solution of mineral acid is fed from the system 13 to leach phosphorus from the concentrate. This solution, mixing with the fired concentrate, cools it and leaches phosphorus during mixing and movement along the channel formed by the Archimedes spiral 12. After the Archimedes spiral 12, the concentrate and the mineral acid solution enter the neutralization zone with an alkaline solution, which is supplied from the system 20 using a spray heads. The resulting slurry enters the device 14, where in the elevator buckets with filter walls rotating with the drum 11, the concentrate settles to the bottom of each bucket and slowly rises in a circle. In the process of this movement, when the ladles are tilted, the liquid phase from the surface is discharged into the drum 11, and at the top point from the inverted ladle the concentrate is discharged into the inclined tray 15, from where it enters the drum dryer 16 through a slide, where the dewatered concentrate is dried with exhaust gases supplied by the fan 25 from the kiln 1. The dried concentrate from the dryer 16 through the unloading head 24 enters the intermediate hopper 26, from where it is unloaded by the feeder 27 onto the belt conveyor 28 to transfer the finished product to the warehouse. Exhaust gases from the dryer 16 enter the scrubber 17, where they are washed with alkaline water from the system 20 in an upward flow, then they are sucked out through the nozzle 18 by the fan 19 and discharged into the atmosphere through the chimney 29. The scrubber 17, located between the drum 11 of the dryer 16, provides washing, cooling hot flue gases and neutralization of the acid waste solution, acting as a neutralizer and gas purifier. In its lower part, the scrubber 17 collects the liquid phase and settles the solid particles in the hopper 21, from where the neutralized liquid phase is poured into the corresponding settler, and the solid phase in a thickened form is removed by the unloading device 22 into the receiver 23.

The claimed method for purifying iron ore concentrate from phosphorus has been tested in laboratory conditions. Roasting of the concentrate with phosphorus content up to 0.7-0.9% was carried out in a stationary layer in a muffle furnace at a given temperature. Before firing, the material was preliminarily dried in a drying oven until the external (adsorption) moisture was completely removed at 105 ° C. Empirically, the value of weight loss on ignition (PMPP,%) in the test concentrate was established. To obtain a given mass of the sample after firing and proceed to the leaching process, we recalculated the sample loaded into the furnace taking into account the PMPP.

For firing, a sample of the dried concentrate was taken, placed in a cylindrical glass made of heat-resistant steel, and a thermocouple was placed in the center of the layer. The glass with the material was loaded into a preheated furnace, and after reaching a predetermined temperature by a thermocouple in the layer, the exposure was carried out for 60 minutes. After firing, the glass was removed with metal tongs from the working space of the muffle furnace. The fired concentrate weighing 350 g was poured hot into a ceramic beaker with a prepared aqueous solution of sulfuric acid room temperature and weighing 700 g. Such a solution consists of 35 g of chemically pure sulfuric acid and 665 g of distilled water, and the mass concentration of sulfuric acid in an aqueous solution is 5%. The ratio of solid to liquid in the pulp is S: W = 1: 2.

Once the concentrate was completely discharged into the solution, an overhead stirrer impeller was placed in the slurry and active stirring was performed at a shaft rotation speed of 250 rpm. Leaching was carried out for a specified time from the moment of complete discharge of the hot concentrate into an aqueous solution of sulfuric acid.

The leached concentrate was sampled in small portions weighing about 30 g at a given time, the concentrate was washed with distilled water, the sample was dried in an oven, and the resulting product was analyzed for the content of total iron and residual phosphorus impurities.

The results of purification of iron ore concentrate from phosphorus impurities are shown in the table.

Table

As can be seen from the table, within a leaching time of up to 5 minutes, a residual phosphorus content of up to 0.20% is achieved, within up to 10 minutes - up to 0.13%, and within up to 15 minutes - up to 0.12%, while when leaching cooled in a separate refrigerator (according to the prototype), the concentrate is leached to a residual phosphorus content of up to 0.12% within 30 minutes, and up to 0.15% within 60 minutes.

Thus, the leaching efficiency of hot concentrate with a temperature of up to 950 ° C and higher is achieved more than six times. In addition, the need for a separate cooler is eliminated, and it becomes possible to simultaneously neutralize the slurry directly in the leaching apparatus, as well as to separate the liquid and solid phases by short-term settling in lift ladles combined with the leaching apparatus. It becomes possible to use the heat of flue gases for drying the concentrate, excluding the vacuum filters used in the prototype technology. Also, the use of a scrubber for neutralizing vapors and water allows for flushing (cleaning) of flue gases used in the drying drum, which makes it possible to abandon the use of a special cleaning system in the form of bag filters or electrostatic precipitators in the prototype technology.

The use of hot leaching of fired bulk materials has not been found in the known technologies.

Claims

Claim

1. A method for purifying iron ore concentrate from phosphorus, including oxidative roasting in a furnace at a temperature of 800-1000 ° C, cooling the roasted concentrate, leaching phosphorus from the concentrate with an aqueous solution of mineral acid, separating the leached concentrate from the solution, characterized in that the roasted iron ore concentrate is cooled and leached with an aqueous solution of mineral acid.

2. The method according to claim 1, characterized in that the simultaneous cooling and leaching of the concentrate is carried out in a rotating drum.

3. The method according to claim 1, characterized in that the leaching of phosphorus is carried out in an aqueous solution of mineral acid having a temperature of up to 100 ° C.

4. The method according to claim 1, characterized in that to achieve residual phosphorus up to 0.2%, leaching is carried out for up to 5 minutes.

5. The method according to claim 1, characterized in that in order to achieve residual phosphorus up to 0.13%, the leaching is carried out for up to 10 minutes.

6. The method according to claim 1, characterized in that to achieve the residual phosphorus up to 0.12%, the leaching is carried out for up to 15 minutes.

7. The method according to claim 1, characterized in that after completion of the leaching process, the spent aqueous mineral acid solution is subjected to neutralization with an alkaline solution.

8. The method according to claim 1.7, characterized in that the leached concentrate is separated from the aqueous mineral acid solution after it has been neutralized with an alkaline solution.

9. The method according to claim 1, 7, 8, characterized in that the leached concentrate is dried by off-gases from the roasting furnace.

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SUBSTITUTE SHEET (RULE 26)

10. A method according to claim 1, characterized in that the steam generated during the cooling and leaching of the roasted concentrate is subjected to condensation.

1 1. The method according to PP. 1,10, characterized in that the steam generated during the cooling and leaching of the roasted concentrate is subjected to condensation by sprinkling with fine spray of alkalized cold water.

12. Installation for purification of iron ore concentrate from phosphorus, containing a roasting furnace, an apparatus for simultaneous cooling and leaching of the roasted concentrate, made with the possibility of continuous supply of an aqueous solution of mineral acid to it, a device for continuous supply of the roasted concentrate to the apparatus directly when unloading from the roasting furnace, and also a device for separating the leached concentrate from the solution and unloading it, followed by neutralizing the acid solution and washing the concentrate from it, located on the side of the solution discharge.

13. Installation according to claim 12, characterized in that the apparatus for simultaneous cooling and leaching of the roasted concentrate is made in the form of a rotating drum.

14. Installation according to claims 12, 13, characterized in that the apparatus for simultaneous cooling and leaching of the roasted concentrate is made in the form of a rotating drum, inside which is mounted at least one Archimedes spiral.

15. Installation according to claims 12, 13, characterized in that the device for separating and unloading the leached concentrate is equipped with elevator buckets located along the inner perimeter at the end of the drum and an inclined chute located under the concentrate unloading point.

16. Installation according to claim 12, 13, 15, characterized in that the device for separating and unloading the leached concentrate is made in the form of annular lift ladles with filter walls.

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SUBSTITUTE SHEET (RULE 26)

17. Installation according to clauses 12,13, characterized in that the drum for simultaneous cooling and leaching of the roasted concentrate from the unloading side is connected to a vertical scrubber equipped at the top with a branch pipe for exhausting gases, and at the bottom with a settling tank with a device for unloading fine solid sediment concentrate.

18. Installation according to claim 12, characterized in that it is equipped with a leached concentrate dryer made in the form of a rotating drum with the possibility of supplying to it concentrate separated from the spent solution and flue gases from the roasting furnace.

19. Installation according to claim 12, characterized in that it is provided with a pipeline for feeding the alkaline solution to the cooling and leaching drum before the device for separating and discharging the leached concentrate.

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SUBSTITUTE SHEET (RULE 26)