DE102011014221A1 - Process for recovering heavy metals from soot water - Google Patents

Abstract

Process for the recovery of heavy metals, especially vanadium, from an aqueous suspension containing soot and ash particles, in particular from soot water obtained from the partial oxidation of hydrocarbons, by treating the suspension with ultrasound, filtering off the soot and ash particles and precipitating the heavy metals from the Filtrate by setting the precipitation conditions.

Description

Field of the invention

The invention relates to a process for recovering heavy metals, in particular vanadium, from an aqueous suspension containing soot particles and ash particles, in particular from soot water obtained in the partial oxidation of hydrocarbons.

State of the art

In Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Volume 15, Chapt. 3.2.2 is the Lurgi MPG ^® process for the production of synthesis gas by partial oxidation of hydrocarbons, such. As heavy oil, as well as the MARS (Metals Ash Recovery System) said process for the treatment of the resulting in the scrubbing of the synthesis gas, referred to as soot and containing substantially soot and ash particles, aqueous suspension described. The main purpose of the MARS process is to recover the vanadium derived from the hydrocarbons used.

Of the heavy metals contained in the hydrocarbons used, mainly iron, nickel and vanadium, the recovery of vanadium is of economic interest in the first place.

The MARS process provides a vanadium-rich solid product that can be used in metal production. For this purpose, the soot and ash particles are filtered out of the soot water and the retentate, the filter cake is ashed in a multi-deck oven to the above-mentioned vanadium-rich solid product. The carbon black contained in the filter chamber serves as an energy source.

When ashing in the multi-level oven, like the EP 0 542 322 B1 It can be seen to be avoided by a precise temperature control and adjustment of the oxygen partial pressure in the conversion of these oxides of vanadium (V) oxide (V ₂ O _5), as this tends to form in the oven caking. However, the lead in accordance with EP 0 542 322 B1 required, low process temperatures to a slow process and thus to large furnace dimensions and a high carbon monoxide content in the exhaust gas, which requires a complex gas purification.

In order to consistently exploit the carbon monoxide formation is described in the patent DE 101 52 686 B4 proposed to convert the resulting in the partial oxidation of carbon black, which is largely carbon, by addition of oxygen and water in synthesis gas. For this purpose, two variants are described in this document.

In a variant, as with the MARS process, a filter cake filtered out of soot water is used, which, after being dried, is introduced into a fly-flow reactor in which, with the addition of oxygen and water, the carbon black present in the filter cake is converted into synthesis gas. The present in the synthesis gas, loaded with vanadium solids are then separated from the gas.

In the other, in the patent DE 101 52 686 B4 variant described, the synthesis gas produced by partial oxidation is not washed with water. The soot and other solids are dry separated from the gas and, with the addition of oxygen and water, preferably in the form of water vapor, placed in a Rußvergasungsreaktor. From the resulting synthesis gas, the vanadium loaded solids are separated.

These mentioned processes have the disadvantage that the very different valuable substances contained in the solid mixture produced as a by-product of the partial oxidation, namely carbon black and vanadium, have to be treated in a common working step, whereby procedural compromises are required, so that neither for carbon black nor for Vanadium optimal processing conditions are adjustable.

It is an object of the present invention to provide a process for processing the solid mixture resulting from the partial oxidation, which enables optimum processing of carbon black and vanadium and the most efficient possible recovery of the vanadium.

Description of the invention

The object underlying the invention is achieved essentially by the entirety of the features of claim 1. Further advantageous embodiments of the method according to the invention can be found in the dependent claims.

In the method according to the invention, it is provided to separate off the heavy metals bound on or in the carbon black and ash particles, in particular vanadium, before the carbon black / ash mixture is further treated. Surprisingly, this is achieved by treating the soot and ash particle containing suspension, the so-called soot water, by treatment with ultrasound.

It has long been known that superficial adhesions and substances bound to surfaces by adsorption can be dissolved or desorbed by ultrasound. As is known, ultrasound is used for cleaning baths.

In the article by A. Profumo et al., Talanta 61 (2003), pp. 465-472 describes how the type and extent of nickel contamination in airborne dust is measured. In the process, the air is filtered and nickel is dissolved from the dust adhering to the filter by means of multistage ultrasonic treatment. The work is limited to the separation and subsequent analytical determination of nickel on filter dusts.

The dissertation Brüggemann, Freiberg, 2010, ch. 6.3.2 describes a method for the analytical determination of adsorbed on solid gasification residues nickel, iron and vanadium. To remove the metals from the residues, the residues are dispersed in water and sonicated, thereby separating the metals, at least in part, from the residues. This work is also directed to the analytical determination of various metal species, including vanadium.

Surprisingly, it has been found that even on an industrial scale the separation of metals from gasification residues known hitherto only from analytics succeeds by means of ultrasound treatment and can thus be used in a large-scale process for the recovery of heavy metals, in particular vanadium, from residues of partial oxidation. It is advantageous that the major part of the vanadium is converted into a form that can be fed to the metal recovery.

• a) Bereitstellen einer wässrigen, im Wesentlichen Ruß- und Aschepartikel enthaltenden Suspension,
• b) Behandeln der Suspension mit Ultraschall, wobei die auf oder in den suspendierten Ruß- und Aschepartikeln gebundenen adsorbierten Schwermetalle, insbesondere Vanadium, mindestens teilweise in die wässrige Phase übergehen,
• c) Abtrennung der an Schwermetallen verarmten Ruß- und Aschepartikel als Retentat von der wässrigen Phase mittels eines mechanischen Trennverfahrens,
• d) Ausfällen der Schwermetalle, insbesondere des Vanadiums, aus dem Filtrat durch Einstellung von Fällungsbedingungen,
• e) Thermische Behandlung des Retentats zu einer Schwermetalle, insbesondere Vanadium enthaltenden Asche.

The process according to the invention for the separation of heavy metals, in particular vanadium-containing residues, from the scrubbing water laden with soot particles and ash particles obtained in the scrubbing of raw synthesis gas, comprises the following process steps:

• a) providing an aqueous suspension containing substantially carbon black and ash particles,
• b) treating the suspension with ultrasound, wherein the adsorbed heavy metals bound on or in the suspended carbon black and ash particles, in particular vanadium, at least partially pass into the aqueous phase,
• c) separation of the heavy metal-depleted soot and ash particles as retentate from the aqueous phase by means of a mechanical separation process,
• d) precipitating the heavy metals, in particular the vanadium, from the filtrate by setting precipitation conditions,
• e) Thermal treatment of the retentate to a heavy metal, in particular vanadium-containing ash.

In a preferred embodiment of the method according to the invention, it is provided to provide an aqueous suspension containing essentially carbon black and ash particles, which is obtained as carbon black in the gasification or partial oxidation of hydrocarbons.

The ultrasound treatment may be carried out by ultrasound generators mounted on the outside of the treatment vessel or immersed in the suspension. Preference is given to the outside of the treatment vessel mounted ultrasonic generator for cleaning and corrosion protection reasons. By setting suitable pH values in the aqueous phase, the transition of the heavy metals in the ultrasonic treatment can be further improved.

A preferred embodiment of the invention is characterized in that the suspension is first thickened and the resulting thick sludge according to process steps b) to e) of claim 1 is treated. By this procedure, the utilization of the introduced sound energy can be increased.

Preferably, the removal of the soot-depleted soot and ash particles takes place as a retentate of the aqueous phase by means of filtration.

A further preferred embodiment of the invention is characterized in that the thermal treatment of the retentate in process step e) takes place under gasification conditions. For this purpose, oxygen, air, oxygen-enriched air and / or water, preferably in the form of steam, are added to the retentate and, under gasification conditions, a crude synthesis gas comprising carbon oxides and hydrogen is produced. This procedure has the advantage that in the thermal processing of the retentate, the carbon black is not only processed to a cost-causing exhaust gas, but to a usable Rohsynthesegas. It is particularly advantageous to provide this embodiment in the processing of soot water from the partial oxidation of hydrocarbons, since the crude synthesis gas obtained by the gasification of the carbonaceous retentate can be further processed together with the synthesis gas obtained by the partial oxidation.

The heavy metal-containing ash obtained in process step e) can be landfilled or to be led back. An advantageous embodiment of the method according to the invention provides that these heavy metal-containing ashes at least partially to process step b), ie to the ultrasonic treatment, due. The combination of the thermal treatment in process step e) and the renewed ultrasound treatment in process step b), a further proportion of heavy metals, such as vanadium, recovered in process step d). The heavy metal precipitate obtained in process step d) can be separated off and further processed in a manner known to those skilled in the art and subsequently supplied to landfill or metal recovery.

The precipitation of the dissolved heavy metals in process step d) can in principle be carried out in any manner known to those skilled in the art; Examples are the precipitation as metal hydroxides or metal sulfides by adding appropriate precipitant. It is also possible to use complex-forming precipitants such as EDTA. By appropriate adjustment of the pH during the precipitation, this can also be fractionated, so that different metals can be obtained as enriched fractions. The resultant heavy metal-containing, in particular vanadium-containing precipitate can subsequently be used in metal production.

The inventive method can also be carried out according to a further advantageous embodiment, that the thermal treatment of the retentate in step e) takes place under combustion or Verschwelungsbedingungen, wherein the thermal treatment step is then advantageously preceded by a drying step.

embodiments

Further developments, advantages and applications of the invention will become apparent from the following description of exemplary embodiments and the drawings. All described and / or illustrated features alone or in any combination form the invention, regardless of their combination in the claims or their dependency.

Show it

1 a schematic representation of the method according to the invention according to a first embodiment,

2 a schematic representation of the method according to the invention according to a second embodiment.

At the in 1 and 2 A suspension containing carbon black and ash particles is obtained as a by-product in the partial oxidation of heavy oil according to the ^MPG® process. This suspension, also referred to as soot water ( 1 ) is placed in an ultrasonic treatment plant ( 2 ), in which the heavy metals bound to or in the suspended solid particles, in particular vanadium, are separated by means of ultrasound and pass into the aqueous phase. The suspension treated in this way ( 3 ) is subjected to filtration ( 4 ) in the solid particles such as soot and ash particles as retentate ( 11 ) are separated from the suspension. The filtrate ( 5 ), in which the heavy metals are dissolved, is placed in a precipitation stage ( 6 ) in which the heavy metals are precipitated by addition of a suitable precipitant and, if appropriate, after the setting of a suitable pH as precipitate (US Pat. 10 ) are separated from the aqueous phase. The aqueous phase leaves as clear water ( 7 ) the precipitation stage ( 6 ) and is the wastewater treatment ( 8th ) and / or back to the scrubbing of the crude synthesis gas ( 9 ) guided. The heavy metal-containing or vanadium-containing precipitate ( 10 ) is given to a further work-up process, which is not the subject of the inventive method, and worked up so that it can be used as a raw material in metal extraction.

The carbon black and ash particles containing retentate ( 11 ) is transferred as a filter cake in a drying step ( 12 ) and subsequently dried ( 14 ) in a thermal treatment plant ( 15 ). The thermal treatment plant is designed as combustion in the present example. There the retentate ( 14 ) into a heavy metal-containing or vanadium-containing ash ( 17 ), wherein the soot contained in the retentate in exhaust gas ( 16 ) is converted. The exhaust gas ( 16 ) is optionally supplied to an exhaust treatment not shown in the figure. The ash ( 17 ) can be used as a raw material in metal production. It can also be added to the ultrasonic treatment system ( 2 ) are recycled to convert a further portion of the heavy metals into the aqueous phase.

In the embodiment of the invention according to 2 the suspension ( 1 ) first into a thickening stage ( 18 ). The clear-water ( 19 ) of the thickening stage is led to a wastewater treatment, not shown, electricity ( 8th' ), and / or returned to gas scrubbing, power ( 9 ' ). The clarification of the thickening stage ( 19 ) with the clear water ( 7 ) the precipitation stage ( 6 ), as in 2 presented, treated together, but also a separate treatment is possible. The one in the thickening stage ( 18 ) produced Dickschlamm ( 20 ) is introduced into the ultrasonic treatment plant ( 2 ), in which by means of ultrasound on the or in the suspended solid particles bound heavy metals, in particular vanadium, are separated and pass into the aqueous phase. The suspension treated in this way ( 3 ' ) is subjected to filtration ( 4 ) in the solid particles such as soot and ash particles as retentate ( 11 ) are separated from the suspension. From the filtrate ( 5 ) is in the precipitate ( 6 ) a heavy metal-containing precipitate ( 10 ) precipitated.

Unlike the in 1 illustrated embodiment, the carbon black and ash particles containing retentate ( 11 ) not dried, but with adherent residual moisture directly the thermal treatment ( 15 ' ). This is designed as a gasification stage, in which the retentate ( 14 ) contained free carbon by the addition of oxygen ( 22 ) and water ( 21 ), preferably as water vapor, is partially oxidized to a crude synthesis gas mainly containing carbon monoxide and hydrogen. It is advantageous that the metered amount of water, due to the residual moisture of the retentate, can be reduced, whereby the energy consumption of the process for the evaporation of water and the overheating of the water vapor decreases. At the same time, in the gasification stage ( 15 ' ) converted the remaining solids content into a heavy metal-containing ash. The mixture of raw synthesis gas and ash ( 23 ) is poured into a solids deposit ( 24 ), in which the crude synthesis gas ( 25 ) of the ashes ( 17 ) is separated. The ash may optionally be wholly or preferably partially to the ultrasound treatment ( 2 ) (not in 2 shown) and run through this one more time, so that a further proportion of the heavy metals is transferred into the aqueous phase and subsequently recovered by precipitation. The raw synthesis gas ( 25 ) is combined with the crude synthesis gas from the partial oxidation of heavy oil and worked up together with this further. To the further processing steps to the skilled person include well-known process steps such as the CO conversion, the synthesis gas scrubbing ^® example, by the Rectisol process, for removing acid gas components and the pressure swing adsorption to separate a hydrogen-rich fraction of the synthesis gas.

Industrial Applicability

The invention thus provides a process which makes it possible in a simple manner to obtain the heavy metals which accumulate in the partial oxidation of hydrocarbons, for example in the gasification of heavy oil, with the ash, in particular the vanadium estimated in the production of stainless steels to gain enriched fraction. Due to the use of ultrasound to promote the transition of the heavy metals from the soot or ash particles in the aqueous phase, it is possible to carry out the inventive method with lower energy consumption and reduced use of aggressive chemicals than in the case of already known in the prior art method of the case is.

LIST OF REFERENCE NUMBERS

1

Suspension (also referred to as soot water)

2

Ultrasonic treatment plant

3, 3 '

treated suspension, treated thick sludge

4

filtration

5

filtrate

6

precipitation

7

Clear running of the precipitation stage

8, 8 '

Clear water for wastewater treatment

9, 9 '

Clear run for washing the crude synthesis gas

10

heavy metal-containing precipitate

11

retentate

12

drying stage

13

Retentate (filter cake), moist

14

Retentate (filter cake), dried

15, 15 '

Thermal treatment plant

16

exhaust

17

Ash, containing heavy metals

18

thickening

19

Clear running of the thickening stage

20

thick sludge

21

adding water

22

oxygen addition

23

Ash-containing crude synthesis gas

24

Solids separation

25

raw synthesis gas

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0542322 B1 [0005, 0005]
• DE 10152686 B4 [0006, 0008]

Cited non-patent literature

• Ullmann's Encyclopedia of Industrial Chemistry, 6th Edition, Volume 15, Chapt. 3.2.2 [0002]
• A. Profumo et al., Talanta 61 (2003), pp. 465-472 [0014]
• Brüggemann, Freiberg, 2010, ch. 6.3.2 [0015]

Claims (10)

Process for the recovery of heavy metals, in particular vanadium, from suspensions containing aqueous particles containing soot and ash, the heavy metals being bound to or in the carbon black and ash particles, comprising the following process steps: a) providing an aqueous suspension containing substantially carbon black and ash particles, b) treating the suspension with ultrasound, wherein the adsorbed heavy metals bound on or in the suspended carbon black and ash particles, in particular vanadium, at least partially pass into the aqueous phase, c) separation of the heavy metal-depleted soot and ash particles as retentate from the aqueous phase by means of a mechanical separation process, d) precipitating the heavy metals, in particular vanadium, from the filtrate by adjusting precipitation conditions, and recovering a precipitate containing heavy metals, e) Thermal treatment of the retentate to a heavy metal, in particular vanadium-containing ash. A method according to claim 1, characterized in that the aqueous suspension containing substantially carbon black and ash particles is obtained as soot water in the partial oxidation of hydrocarbons. A process according to claim 1 or 2, wherein the suspension is first thickened and the thick sludge thus obtained is treated according to process steps b) to e) of claim 1. A method according to claim 1 to 3, characterized in that the separation of the heavy metals depleted soot and ash particles as a retentate from the aqueous phase by means of filtration. Method according to one of the preceding claims, characterized in that the thermal treatment of the retentate in process step e) takes place under gasification conditions, wherein a crude synthesis gas is obtained. A method according to claim 2 and 5, characterized in that the crude synthesis gas obtained by gasification of the retentate is further processed together with the synthesis gas obtained in the partial oxidation of hydrocarbons. Method according to one of the preceding claims, characterized in that the heavy metal-containing ashes obtained in process step e) is at least partially recycled to process step b). A method according to claim 1 to 4, characterized in that the thermal treatment of the retentate in step e) takes place under combustion or Verschwelungsbedingungen, wherein the thermal treatment step is preceded by a drying step. Heavy metal-containing, in particular vanadium-containing precipitate obtainable by a process according to Claims 1 to 8. Use of the heavy metal-containing, in particular vanadium-containing precipitate according to claim 9 for metal production.

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