UA92729C2 - Method and plant for production of titanium slag from ilmenite - Google Patents

Abstract

In a process for producing titania slag from ilmenite, granular ilmenite first is partially reduced with a reducing agent in a reduction reactor, then the hot material with an inlet temperature of at least 550 °C is transferred into an electric furnace and molten there in the presence of a reducing agent by forming liquid pig iron and titania slag. The reduction reactor consists of a circulating fluidized-bed reactor.

Description

cooled, carbon dioxide formed during the partial reduction of ilmenite is removed from it in the CO absorber, then it is heated in the next gas heater and, finally, it is again fed to the reduction reactor and, possibly, to the coking reactor as a fluidizing gas.

It was found that when the raw ilmenite used has a relatively high content of Eeo, it is advisable to subject it to a preliminary oxidation treatment before partial reduction a) in order to fully oxidize BeO to EeOz. This is a certain advantage, since ReO is present in such a crystal structure that is very resistant to the action of gaseous reducing agents, while the crystal structure of RegOz, which is formed during the post-oxidation of BeO, allows the gas to diffuse into the pores of the material. Usually post-oxidation is carried out in such a way that the content of GeO in the processed material does not exceed 5 wt.95, and even better - it is less than 3 wt.95.

According to the invention, the oxidation of raw ilmenite, as well as its partial reduction, is proposed to be carried out in a circulating fluidized bed, preferably at temperatures between 600 and 100070.

In particular, it turned out that when using chromite-containing ilmenite as a starting material, and coal and/or semi-coke as a reducing agent, it is advisable to carry out magnetic separation of the partially reduced ilmenite before it enters the electric furnace in order to separate the titanium dioxide enriched in the magnetic fraction from the non-magnetic fraction , which contains mainly chromite, resins and semi-coke, if it is used as a reducing agent, and therefore only the magnetic fraction obtained in this way should be placed in the electric furnace. In this case, it is desirable that the temperature of the partially reduced material during magnetic separation is at least 600°C, even better - at least 675°C, and best of all - around 700760.

It is especially desirable that the further transfer of the magnetic fraction to the electric furnace takes place without cooling or heating. Thus, the energy required to cool the partially reduced material, on the one hand, and the energy required to heat the material fed to the electric furnace to the operating temperatures of the furnace, on the other hand, are minimized without significant additional oxidation of the partially reduced material, which may occur before entering the electric furnace. The non-magnetic fraction can be subjected to further processing and the semi-coke contained in this non-magnetic fraction can be reused in the technological process, that is, as a starting material.

The titanium slag removed from the electric furnace contains, mainly, from 75 to 90 wt.95, and better - about 85 wt.Oo of titanium dioxide, and liquid cast iron contains more than 94 of metallic iron.

According to the invention, the installation, which can be used in particular to implement the method described above, includes a coking reactor consisting of a reactor with a stationary fluidized bed for coking coal with simultaneous heating of ilmenite, a reduction reactor with a circulating fluidized bed for partial reduction of ilmenite and an electric stove.

It is desirable that the coking reactor is connected to the reducing reactor by means of a connecting channel, so that the suspension of solid particles in the gas can pass from the upper part of the coking reactor to the lower part of the reducing reactor, and at the outlet of the reducing reactor there is a cyclone, which provides separation of the solid phase from the suspension of solid particles in the gas, as well as a pipeline for the return of solid particles from the cyclone to the coking reactor.

According to the method of implementation of the invention, it is proposed to apply at least one heating stage, which involves the presence of a heat exchanger for the suspension of solid particles in the gas and a cyclone placed between the output of the reduction reactor and the input of the coking reactor, in which the ilmenite is heated to temperatures from 500 to 900 "C, preferably - up to 600-850"С, and best of all - up to a temperature of about 800"С before loading it into the reactor for coking. According to the method of implementation of the invention, it is proposed to provide means for circulating the fluidized bed in the installation.

According to the method of implementation of this invention, the installation additionally includes a magnetic separator.

Next, the invention will be described in detail with references to its implementation and schemes. All details explaining the essence of the invention, each in particular, or in any combination, regardless of whether they are included in the claims, or the sequence of reference to them, are described and/or illustrated by diagrams.

A brief description of the illustrations.

In fig. 1 shows a block diagram of the method and installation in accordance with the first embodiment of the present invention, and in fig. 2 shows a block diagram of the method and installation in accordance with the second embodiment of the present invention.

As shown in fig. 1, in the process of producing titanium slag from ilmenite, a mixture of semi-coke and ilmenite, which are loaded from tanks 2, C and mixed in the mixing tank 4, is continuously fed through a special pipeline 1 for supplying solid particles to the heat exchanger for the suspension 5 of the first heating stage, in which most of the material is suspended and heated by the gas (16) released in the second heating stage. Next, the suspension enters the cyclone b with the help of a gas flow, in which solid particles are separated from the gas. Then, the separated solid particles are supplied through the pipeline 7 to the second heat exchanger for the suspension of the venturi type 8, where they are further heated to a temperature of about 8007 and in the outlet cyclone 9 are again separated from the gas stream. The raw material heated in this way is fed through a special pipeline for solid particles 1' to the coking reactor 10, into which coal with a particle size of less than 5 mm and oxygen is also fed through a pipeline for solid particles 7". In addition, the fluidizing gas consisting of 70 vol.9o of carbon monoxide and 30 vol.9o of molecular hydrogen and has a temperature of about 600"C, is supplied to the coking reactor 10 through the gas line 11 in order to fluidize the solid particles in the reactor 10, thus creating a stationary fluidized bed. The rate of supply of oxygen and fluidizing gas, as well as the residence time of solid particles in the reactor 10, are selected so that a temperature of about 105070 is provided in the fluidized bed and a sufficient degree of coal coking is achieved. Coal fed through the pipeline 7" can be cleaned and/or coked using an additional device before feeding it to the reactor 10.

The mixture of gas and solid particles continuously flows from the coking reactor 10 through the connecting channel 12 to the reduction reactor 13, in which the solid particles are fluidized with the help of fluidizing gas supplied through the gas line 11", forming a circulating fluidized bed, and ilmenite is reduced with the help of reducing agents, in particular carbon monoxide, until reaching a degree of metallization in terms of iron content of about 7095. The suspension is then fed by a gas stream to cyclone 14, which is located at the outlet of reduction reactor 13, and in this cyclone solid particles are separated from gas ( 16). After that, the separated solid particles are returned through the return pipeline 15 to the coking reactor 10, at the same time, the released gas, which contains CO 1 and CO 2 with a temperature of about 1000 °C, is transferred through the gas pipeline 16 first to the heat exchanger for hang from the second heating cascade, and from there through cyclone 9 and gas pipeline 16' - to the heat exchanger for heating 5 of the first heating stage, where it cools down to a temperature of about 500"C. Through a 16" pipeline, the gas obtained after the separation of solid particles in the cyclone 6 located at the outlet of the heat exchanger for the suspension 5 first passes through a boiler that uses the heat of the separated gases (not shown), where it is cooled to about 2007 by the formation of steam ( 4 bar), and then it is cleaned of dust in the gas purifier 17 and cooled to a temperature of about 30"C. The solid/liquid sludge formed in the gas purifier (particles of ore and carbon) can be used further, that is, after its granulation, as raw material for the mixing tank 4 and/or reactor 10, reactor 13 or furnace 22. Further, carbon dioxide is separated from of the released gas in the CO absorber 18, and the gas mixture purified in this way, which can be heated in the heat exchanger, i.e. gas from the pipeline 16, is heated to a temperature of about 600 °C in the gas heater 19, and then returned as a fluidizing gas to the coking reactor 10 and the reducing reactor 13 via lines 11, 11". In addition, the amount of hydrogen and/or water and/or water vapor in the circulating gas stream can be controlled, for example, by means of a hydrogen-permeable membrane, a water cooler/absorber or a water vaporizer.

From the reduction reactor 13, a mixture of partially reduced ilmenite and semi-coke at a temperature of about 10007" is continuously removed through a pneumatic product discharge pipeline 20, cooled to a temperature of about 7007 in a heat exchanger (not shown) and at this temperature is fed to a magnetic separator 21, in which the fraction enriched with dioxide titanium, as a magnetic substance, is separated from the non-magnetic fraction, which contains a significant amount of chromite, resins and semi-coke, and then the magnetic fraction is loaded into the electric furnace 22.

In the electric furnace 22, the temperature of which is about 1600"C, the final products are titanium slag with a titanium dioxide content of 75 to 90 wt.9o and liquid cast iron with a metallic iron content of more than 94 wt. furnace, contains more than 90 mab.9o of carbon monoxide; after dust removal, it is burned in an afterburner (not shown), and the resulting hot flue gas is used in the gas heater 19 to heat the fluidized gas. In addition, part of the circulating gas stream can also be burned and used in the gas heater 19.

In contrast to the installation described above, the installation shown in fig. 2, additionally includes an oxidation reactor 23 placed at the entrance to the coking reactor 10. The raw material heated in the heat exchangers for heating the suspension 5, C is fed to the oxidation reactor 23 through the pipeline for solid particles 1 and fluidized with the help of the incoming fluidizing gas through the gas line 11" after its heating in the heat exchanger 24 with the help of exhaust gases coming from the cyclone 14, located in front of the reactor for recovery 13, thanks to the formation of a circulating fluidized bed. In addition, fuel is supplied to the reactor for oxidation 23 through the pipeline 16 ". The suspension is carried by the gas flow into the cyclone 25 located in front of the oxidation reactor 23, in which the solid phase is separated from the gas. Part of the solid phase is fed again to the reactor for oxidation 23, and the other part - through the pipeline for supplying solid particles 7" enters the reactor for coking 10.

The gas leaving the cyclone 25 through the gas line 26 is fed to the heat exchanger for heating the suspension of the second heating stage 8, and from there through the cyclone 9 - to the heat exchanger for heating the suspension of the first heating stage 5 and through the cyclone 6 - to the exhaust gas cleaning device (not shown).

The essence of the invention will be explained below with reference to an example that illustrates the invention, but does not limit it.

Example

In the installation corresponding to fig. 2, the heat exchanger for heating the suspension 5 is loaded with the initial ilmenite (12 kg/h) in the form of particles with a size smaller than 1 mm and the following composition through the pipeline for the supply of solid particles 1:

TO" 50.04 mass.

EegOz 13.4 4 wt. 95

EeO 32.79 wt.9o

Mpo 0.58 wt.

BIO" 0.62 wt.9o

AI25Oz 0.53 wt.9o

MOO 0.68 wt.

Sao 0.05 wt.

From 0 wt. vol

C 0 wt.

Others 0.37 wt.9o

Combustion losses (I ОЙ) 0.90 wt.9o

Total 100.00 wt. 9o

Total Those 30 wt. 9o

Total He 34.90 wt.9o

After passing through the first and second stages of heating, the heated ore was introduced through pipeline 7 into the oxidation reactor 23 in order to almost completely oxidize BeO to RegOz. In addition, fuel and fluidizing gas were supplied to the oxidation reactor 23 through the pipeline 11". After the separation of the solid phase from the gas in the cyclone 25 located at the entrance to the oxidation reactor 23, the solid phase through the pipeline for supplying solid particles 7" entered the reactor for coking 10. The oxygen content in the spent gas of cyclone 25 would be 95% by mass. In addition, oxygen and 7.5 kg/h of coal (Viaig AgNOI,

Спх: 6295), corresponding to the ratio Re:Спх, equal to 1, were supplied to the coking reactor 10 through a pipeline for supplying solid particles 7", in the reactor 10, the particles of the solid phase were fluidized with a gas mixture consisting of 70 wt.9o of carbon monoxide and 30 wt.9o of hydrogen, by forming a stationary fluidized bed.From the coking reactor 10, a mixture of solid particles and gas was fed through the connecting channel 12 to the reduction reactor 13, in which the oxidized ilmenite was partially reduced to the degree of metallization of 7090 in terms of iron content.

The solid phase discharged from the reduction reactor 13 through the pipeline 20 was first separated using a magnetic separator 21, after which the magnetic fraction obtained in this way was fed to the electric furnace 22. The installed capacity of the transformer of the furnace 22 was 2 MVA.

Titanium slag was unloaded from the furnace every 2 hours, and sponge iron - twice a day.

According to the data of chemical analysis, the composition of titanium slag and sponge iron obtained in this way are shown in Table 1. The estimated electricity consumption of the process is 1.004kWh per ton of slag.

Table 1

The chemical composition of titanium slag and sponge iron obtained, respectively, in the example and prototype

Pre-reduced ilmenite Unprocessed ilmenite oo Titanovyishlak.u/ ІІ 77777771 о Gubchastezalvo./// | 77777711

Electricity consumption 1.004 kWh per ton of slag 2.050 kWh per ton (calculation) of slag

Prototype.

For comparison, untreated ilmenite of the above composition, which was not subjected to either oxidation or partial reduction, was placed instead of pre-reduced ilmenite in the electric furnace 22 described in the above example and melted.

The composition of titanium slag and sponge iron obtained in this way are given in Table 1.

The estimated electricity consumption of the process is 2,050 kWh per ton of slag.

List of designations: 1 - special pipeline for supplying solid particles 2 - tank for semi-coke

C - tank for ilmenite 4 - mixing tank - heat exchanger for heating the suspension of the first stage of heating 6 - cyclone of the first stage of preheating 7, 7.7" - pipeline for supplying solid particles 8 - heat exchanger for heating the suspension of the second stage of heating 9 - cyclone of the second stage heating - (coking) reactor 11, 11, 11" - pipeline for supplying fluidizing gas 12 - connecting channel

13 - reduction reactor 14 - cyclone of the reduction reactor - return pipeline of solid particles 16, 16, 16" - gas pipeline 17 - gas purifier 18 - CO absorber 19 - gas heater - product discharge pipeline 21 - magnetic separator 22 - electric furnace 23 - reactor - oxidizer 24 - heat exchanger - reactor-oxidizer cyclone 2 6 - pipeline for discharge of spent gas iz 165 LI shi t ii oi | i v NoschU 81 OO v p pgoyai NI CHNU, shi sche ! Eh li B dia i te a | dinia Y And eats at 7-8

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