DE112017006996B4 - Integrated process for recycling sludge for the production of iron oxide and carbon - Google Patents

Abstract

A method for extracting iron and carbon components from sludge comprising the steps of: i) providing a sludge containing iron and carbon components, ii) adding hydrochloric acid to the sludge and carrying out a reaction such that an acidic aqueous phase rich in iron and a carbon-rich phase is obtained, iii) separating the acidic aqueous iron-rich phase from the carbon-rich phase, andiv) processing the acidic aqueous iron-rich phase so that the iron component is obtained, the processing ( Step iv)) either comprises the following steps: v) adding an oxidizing agent to the acidic aqueous iron-rich phase so that an oxidized iron-rich phase is obtained, vi) adding the precipitated agent to the oxidized iron-rich phase so that a Iron-enriched phase and iron-depleted phase is obtained, vii) separating the iron-enriched phase from the iron-depleted P rabbit, andviii) drying the iron-enriched phase at least in a roasting oven, so that the iron component is obtainedix) wherein the iron-depleted phase is subjected to a regeneration process at least with a spray rusting oven, so that a regenerated hydrochloric acid is obtained, the regenerated one Hydrochloric acid is preferably returned to the process; or wherein the processing (step iv)) alternatively comprises the following steps: v) reducing the acidic aqueous iron-rich phase with a reducing agent so that a reduced iron-rich phase is obtained, vi) separating the reduced iron-rich phase into an iron enriched and an iron-depleted phase by means of a first ion exchange column, in particular a lead and zinc-selective ion exchange column, vii) oxidizing the iron-enriched phase with an oxidizing agent so that an oxidized iron-enriched phase is obtained, andviii) separating one oxidized, pure iron-enriched phase from the oxidized iron-enriched phase by means of a second ion exchange column, in particular an iron (III) -selective ion exchange column, undix) subjecting the oxidized, pure iron-enriched phase to a regeneration process, at least with a spray rust oven, so that a regenerated hydrochloric acid and the iron components nte is obtained, the regenerated hydrochloric acid preferably being returned to the process.

Description

Technical field

The present invention relates to a method for obtaining iron and carbon components from sludge and a plant for carrying out the method according to the invention.

Technical background

Steel production produces large quantities of sludge every year, which currently has to be landfilled due to the partly toxic composition. As the landfill capacities are approaching their maximum absorption capacity and stricter environmental standards can still be expected, alternatives are currently being sought.

Possibilities for removing zinc and lead from sludge are discussed in the prior art, for example in the publication "HERCK, Peter [et. al.]: Zinc and lead removal from blast furnace sludge with a hydrometallurgical process. In: Environmental science & technology, Vol. 34, 2000, No. 17, pp. 3802-3808. - ISSN 0013-936X ".

Summary of the invention

The present invention is therefore based on the object of providing a method with which the quantities of sludge that accumulate can be worked up to such an extent that costly landfilling can be dispensed with.

This object is achieved by a method with the features of patent claim 1 and an installation for carrying out the method according to the invention with the features of patent claim 4.

Advantageous refinements and variants of the invention result from the dependent claims and the following description.

According to the invention, it is provided that the method for obtaining iron and carbon components from sludge comprises the following steps.

First, a sludge containing iron and carbon components is provided, preferably from a tank. In addition to the main components of iron, preferably in an amount> 5% by weight and carbon, preferably in an amount> 20% by weight, the sludge also contains other components such as zinc and lead, which can also be recycled if necessary by adapting the process can be.

In a next step, the gout sludge is mixed with an acidic solution, namely hydrochloric acid, and reacted with it. Here, the iron components present in the sludge are dissolved so that an acidic aqueous phase rich in iron is obtained. The predominantly insoluble organic residue, in particular the carbon components, then form a carbon-rich phase.

The heterogeneous mixture containing the acidic aqueous iron-rich phase and the carbon-rich phase is then separated from one another, preferably by means of a thickener.

The separated acidic aqueous iron-rich phase is worked up so that the iron component is obtained. The iron component obtained is preferably an Fe- (III) -containing solution, more preferably dried iron oxide (Fe ₂ O ₃ ).

The separated carbon-rich phase is preferably fed to a filter unit in order to remove the remaining water. Any chlorides contained can be removed beforehand using a rinsing step. A filter press, a belt filter system, a filter chute, a centrifugal disc filter, a lamella separator or a hydrocyclone are preferred as the filter unit.

According to a preferred embodiment variant, the reaction is carried out at a temperature in the range from 30 to 100 ° C., more preferably 60 to 80 ° C. and a time in the range from 5 to 60 minutes, more preferably 5 to 15 minutes. The reaction time depends on the temperature and concentration of the acidic solution selected in the reactor.

If hydrochloric acid is used as the acidic solution, the concentration in the reactor is preferably 5-20%.

In order to further shorten the reaction time, further homogenization methods can be carried out if necessary. The response time can preferably be significantly reduced by using ultrasound.

In addition to hydrochloric acid, other acidic solutions, preferably selected from the group of mineral acids, are also conceivable.

According to the invention, the preparation of the acidic aqueous iron-rich phase comprises the following steps in a first alternative. The acidic aqueous iron-rich phase is first mixed with an oxidizing agent, so that an oxidized iron-rich phase is obtained.

If appropriate, the acidic aqueous iron-rich phase can first be further acidified to a pH in the range from 0.5 to 1.5 before it is mixed with the oxidizing agent. A hydrogen peroxide solution is preferably used as the oxidizing agent. The iron present in the form of Fe- (II) is oxidized in Fe- (III).

A precipitant is then added to the oxidized iron-rich phase. Lime milk or an ammonia solution are preferred as possible precipitants. After the precipitation reaction has been carried out, an iron-enriched phase and iron-depleted phase are obtained. The iron-enriched phase here preferably comprises iron hydroxide.

The two phases are then separated from one another, preferably by means of a thickener. The iron-enriched phase is dried so that iron (III) oxide is obtained.

In the first alternative, the iron-depleted phase is subjected to a regeneration process to obtain the acidic solution.

According to the invention, the processing of the acidic aqueous iron-rich phase comprises the following steps in a second alternative. The acidic aqueous iron-rich phase is first reduced with a reducing agent, so that a reduced iron-rich phase is obtained. The iron present in the acidic aqueous iron-rich phase in Fe- (II) / (III) is preferably reduced to Fe- (II). The reduced iron-rich phase is then separated into an iron-enriched and an iron-depleted phase by means of a first ion exchange column, in particular a lead and zinc-selective ion exchange column. The iron-depleted phase, consisting essentially of lead and zinc, can preferably be separated into a lead and a zinc phase via a further ion exchange column. The iron-enriched phase is then oxidized with an oxidizing agent. so that an oxidized iron-enriched phase is obtained. The iron present in the iron-enriched phase in the form of Fe- (II) is oxidized to Fe- (III). In a further step, a pure iron-enriched phase is separated off by means of a second ion exchange column, in particular an iron (III) -selective ion exchange column, and subjected to a regeneration process. In the regeneration process, a regenerated acidic solution and the iron component, preferably an iron (III) oxide, are obtained.

According to the invention, the regenerated acidic solution is preferably returned to the process.

According to a further aspect, the present invention relates to a plant for the extraction of iron and carbon components from sludge comprising a first reactor for mixing a sludge with an acidic solution, a first separation unit for separating an acidic iron-rich phase from a carbon rich phase and a processing unit for processing the acidic aqueous iron-rich phase.

According to a first alternative, the processing unit according to the invention contains an oxidation unit for oxidizing the acidic aqueous iron-rich phase, a second reactor for precipitating an iron-enriched phase from the oxidized acidic aqueous iron-rich phase, and a second Separation unit for separating the iron-enriched phase from an iron-depleted phase and a drying unit for drying the iron-enriched phase and, if appropriate, a regeneration unit for obtaining a regenerated acidic solution.

According to the invention, the drying unit contains a roasting oven, a drum dryer, a fluid bed dryer or a vibration fluidized bed dryer.

According to a second alternative, the processing unit according to the invention contains a reduction unit, a first ion exchange column, in particular a lead and zinc selective ion exchange column, an oxidation unit, a second ion exchange column, in particular an iron (III) selective ion exchange column and a regeneration unit for obtaining a regenerated acidic solution , which can preferably be fed back into the process.

The regeneration unit preferably contains a spray grate furnace.

The separation unit is preferably a thickener.

Figure list

• 1 eine schematische Darstellung einer ersten Ausführungsform des erfindungsgemäßen Verfahrens,
• 2 eine schematische Darstellung einer ersten Ausführungsvariante einer Aufbereitungseinheit, und
• 3 eine schematische Darstellung einer zweiten Ausführungsvariante der Aufbereitungseinheit.

The invention is explained in more detail below with reference to drawings and examples. Show in detail:

• 1 1 shows a schematic representation of a first embodiment of the method according to the invention,
• 2nd a schematic representation of a first embodiment variant of a processing unit, and
• 3rd a schematic representation of a second embodiment of the processing unit.

1 shows a schematic representation of a first embodiment of the method according to the invention using an example. Via a screw conveyor (not shown) with a mass flow of 1000 kg / h sludge 11 from a tank 10th a first reactor 20th fed. The gout sludge 11 essentially contains iron, carbon, silicon, zinc, lead as well as alkaline, alkaline earth and transition metal impurities. In the reactor 20th becomes the gout sludge 11 with an acidic solution 22 , for example, hydrochloric acid mixed to the reactor 20th from a tank 21st is supplied via lines and pumps (not shown) with a mass flow of 300-500 kg / h. At a temperature in the range of 60 - 80 ° C and a residence time in the range of 5 - 15 min, they go in the sludge 11 contained metals in solution. The predominantly insoluble organic components, however, remain in the residue as a solid. After the reaction has been carried out, an acidic aqueous iron-rich phase and a carbon-rich phase 24th receive. Both phases then become a first separation unit 23 , for example, a thickener, in which the acidic aqueous iron-rich phase from the carbon-rich phase 24th is separated. The carbon-rich phase is fed to a filtration unit, such as a filter press (not shown), to remove the remaining water. Any chlorides contained can be removed beforehand using a rinsing step. The table below shows the composition of the dried carbon-rich phase obtained 24th shown. The acidic aqueous iron-rich phase becomes a processing unit 30th supplied, in which the iron present in solution is converted into iron (III) oxide and the hydrochloric acid is regenerated. The technical grade hydrochloric acid is used in the tank 21st fed again. The iron (III) oxide fraction obtained has the composition shown in the table, depending on the preparation 31 , 32 on.

2nd shows a schematic representation of a first embodiment variant of the processing unit 30th . The processing unit 30th supplied acidic aqueous iron-rich phase is first further acidified to a pH in the range from 0.5 to 1.5 and an oxidation unit 33 fed. Here the acidic aqueous iron-rich phase with an oxidizing agent 35 , for example a hydrogen peroxide solution, from a tank 34 transferred. The iron in the form of Fe- (II) is oxidized in Fe- (III). The oxidation unit 33 can be implemented in the simplest case in the form of a line through which the acidic aqueous iron-rich phase flows. The oxidized iron-rich phase then obtained becomes a second reactor 36 fed in which the oxidized iron-rich phase with a precipitant 38 , for example lime milk, from a tank 37 is mixed in a mass flow ratio of 1: 3 to 1: 4. After iron (III) hydroxide has precipitated, it is separated from the residue, an iron-depleted phase. For this purpose, the mixture of iron (III) hydroxide and the residue of a second separation unit 39 , for example a thickener. The separated iron (III) hydroxide is then a drying unit 40 fed in which the iron (III) hydroxide first a filtration unit (not shown), for example passes through a filter press to remove the water and is then fed to a roasting oven (not shown). In the roasting furnace, the iron (III) hydroxide is roasted to iron (III) oxide. The iron (III) oxide fraction obtained has the composition shown in the table 31 on. The iron-depleted phase is used to obtain the acidic solution 22 a regeneration unit 41 fed. For this purpose, the iron-depleted phase is fed to a spray grate furnace, by means of which the hydrogen chloride gas is expelled from the iron-depleted phase. The hydrogen chloride gas is then dissolved in water and the tank as technical hydrochloric acid 21st fed. The remaining residue contains approx. 90% by weight calcium oxide and oxides of alkaline, alkaline earth and transition metals. If necessary, this can be worked up to obtain lime milk 42 and fed back into the process.

3rd shows a schematic representation of a second embodiment variant of the processing unit 30th . The processing unit 30th supplied acidic aqueous iron-rich phase is first adjusted to a pH in the range from 1.5 to 2.5 and a reduction unit 43 fed. Here, the acidic aqueous iron-rich phase is mixed with a reducing agent, for example using hydroxylammonium chloride (not shown). The Fe- (III) present in the iron-rich phase is reduced to Fe- (II). The reduction unit 43 can be realized in the simplest case in the form of a line through which the acidic aqueous iron-rich phase flows. The reduced iron-rich phase is then a first ion exchange column 44 , in particular a lead and zinc selective ion exchange column. By means of the first ion exchange column 44 the reduced iron-rich phase is freed from the lead and zinc components present in solution. The iron-enriched phase obtained is now in an oxidation unit 45 oxidized (not shown) with an oxidizing agent, for example a hydrogen peroxide solution, so that the Fe- (II) present in solution is converted into Fe- (III) and in a subsequent second ion exchange column 46 , in particular an iron (III) selective ion exchange column, is separated from the oxidized iron-enriched phase. The oxidation unit 45 can be implemented in the simplest case in the form of a line. The resulting oxidized, pure iron-enriched phase, which essentially consists of Fe (III) chloride dissolved in hydrochloric acid, then becomes a regeneration unit 47 fed to obtain a regenerated acidic solution. For this purpose, the oxidized, pure iron-enriched phase is fed to a spray grate by means of which the hydrogen chloride gas is expelled from the oxidized, pure iron-enriched phase.

The hydrogen chloride gas is then dissolved in water and the tank as technical hydrochloric acid 21st fed. The remaining residue 32 contains 99.1% by weight of iron (III) oxide. Table: composition 22 31 32 component Share in% by weight C. 75.5 - - SiO ₂ 15.4 - - Fe 2.7 - - Fe ₂ O ₃ - 87.3 99.1 Al ₂ O ₃ - 9.9 - rest 6.4 2.8 0.9

Reference symbol list

10th

tank

11

Gout sludge

20th

first reactor

21st

tank

22

acid halide solution

23

first separation unit

24th

Carbon-enriched phase

30th

Processing unit

31

composition

32

composition

33

Oxidation unit

34

tank

35

Oxidizing agent

36

second reactor

37

tank

38

Precipitant

39

second separation unit

40

Drying unit

41

Regeneration unit

42

Lime milk production unit

43

Reduction unit

44

first ion exchange column

45

Oxidation unit

46

second ion exchange column

47

Regeneration unit

Claims (6)

A method for extracting iron and carbon components from sludge comprising the steps of: i) providing a sludge containing iron and carbon components, ii) adding hydrochloric acid to the sludge and carrying out a reaction such that an acidic aqueous phase rich in iron and a carbon-rich phase is obtained, iii) separating the acidic aqueous iron-rich phase from the carbon-rich phase, and iv) processing the acidic aqueous iron-rich phase so that the iron component is obtained, the processing (Step iv)) either comprises the following steps: v) adding an oxidizing agent to the acidic aqueous iron-rich phase so that an oxidized iron-rich phase is obtained, vi) adding the precipitating agent to the oxidized iron-rich phase so that an iron-enriched phase and iron-depleted phase is obtained, vii) separating the iron-enriched phase from the iron-depleted area first phase, and viii) drying the iron-enriched phase at least in a roasting oven, so that the iron component is obtained ix) the iron-depleted phase being subjected to a regeneration process at least with a spray oven, so that a regenerated hydrochloric acid is obtained, wherein the regenerated hydrochloric acid is preferably returned to the process; or wherein the processing (step iv)) alternatively comprises the following steps: v) reducing the acidic aqueous iron-rich phase with a reducing agent so that a reduced iron-rich phase is obtained, vi) separating the reduced iron-rich phase into one Iron-enriched and an iron-depleted phase by means of a first ion exchange column, in particular a lead and zinc-selective ion exchange column, vii) oxidizing the iron-enriched phase with an oxidizing agent, so that an oxidized iron-enriched phase is obtained, and viii) Separating an oxidized, pure iron-enriched phase from the oxidized iron-enriched phase by means of a second ion exchange column, in particular an iron (III) -selective ion exchange column, and ix) subjecting the oxidized, pure iron-enriched phase to a regeneration process, at least with a spray furnace, so that a regenerated hydrochloric acid and the iron component are obtained, the regenerated hydrochloric acid preferably being returned to the process. Procedure according to Claim 1 , wherein the reaction in step ii) is carried out at a temperature in the range from 30 to 100 ° C. and a time in the range from 5 to 60 minutes and, if appropriate, using a homogenization method. Procedure according to Claim 1 or after Claim 2 , the regenerated hydrochloric acid being fed back to the process in step ii). Plant for the extraction of iron and carbon components from sludge comprising: i) a first reactor for mixing a top sludge with a hydrochloric acid, ii) a first separation unit for separating an acidic aqueous iron-rich phase from a carbon-rich phase, and iii) a processing unit for processing the acidic aqueous iron-rich phase. being the processing unit iv) an oxidation unit for the oxidation of the acidic aqueous iron-rich phase, v) a second reactor for precipitating an iron-enriched phase from the oxidized acidic aqueous iron-rich phase, vi) a second separation unit for separating the iron-enriched phase from an iron-depleted phase, and vii) a drying unit with a roasting oven, a drum dryer, a fluid bed dryer or a vibrating fluidized bed dryer for drying the iron-enriched phase, and if appropriate viii) contains a regeneration unit, preferably with a spray grate furnace, for obtaining regenerated hydrochloric acid, or being the processing unit iv) a reduction unit, v) a first ion exchange column, in particular a lead and zinc selective ion exchange column, vi) an oxidation unit, vii) a second ion exchange column, in particular an iron (III) selective ion exchange column, and viii) contains a regeneration unit with a spray grate furnace for obtaining a regenerated hydrochloric acid, the regenerated acidic solution preferably being able to be fed back into the process. Plant after Claim 4 , wherein the regenerated hydrochloric acid can be fed to the first reactor. Plant after Claim 4 or after Claim 5 , wherein the separation unit is a thickener.

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