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    • 专利摘要:
    Phosphorus-containing materials are treated with inorganic acids to form leach solutions (7) containing trivalent iron, trivalent aluminum, and phosphorus. Iron and / or aluminum is extracted by adsorption in a capture substance (22) affinity for cations and by releasing iron and / or aluminum into a stripping solution during regeneration. The regeneration is carried out with hydrochloric acid (31). Anionic metal chloride complexes are extracted from the hydrochloric acid-containing stripping solution (32) by adsorption in a capture substance (42) having an affinity for anionic metal chlorides. Metal chlorides are recovered from the charged capture substance (46) by elution with water (49). Gaseous hydrogen chloride (38) is added to the raffinate (33) from the metal chloride extraction. Crystalline aluminum chloride hexahydrate (37) is separated if desired. The hydrochloric acid-containing stripping solution (31) is recycled and used for stripping the capture substance (26) loaded with iron and / or aluminum. The depleted ash slurry solution (9) is treated for phosphorus recovery and is preferably reused for dissolving a phosphorus-containing material. (Fig. 2)
    公开号:SE0950622A1
    申请号:SE0950622
    申请日:2009-08-31
    公开日:2011-03-01
    发明作者:Yariv Cohen
    申请人:Easymining Sweden Ab；
    IPC主号:
    专利说明:

    Phosphorus removal in wastewater treatment is usually based on chemical precipitation with iron or aluminum salts. Iron and aluminum are non-volatile metals that remain in the ash during the combustion of sewage sludge. Iron and aluminum are therefore large components in ash from incinerated sewage sludge, with up to 20% by weight.
    A necessary step in phosphorus recovery from ash is the dissolution of phosphorus. Dissolution with a base has a low efficiency as only a part of the phosphorus in the ash is leached out. However, the efficiency of phosphorus leaching from ash with inorganic acids is very high. For this reason, acid leaching is the most common approach. The use of inorganic acids for phosphorus leaching from ash results in a dissolution of iron and aluminum. High concentrations of iron and aluminum in ash solutions from ash are the biggest obstacle to phosphorus recycling. It is not possible to precipitate phosphorus in forms other than iron phosphate or aluminum phosphate unless iron and aluminum are separated, preferably before phosphorus recovery. Iron and aluminum phosphate have very low solubility in water and therefore cannot release phosphorus fast enough for the crops if they are used as fertilizer. The fertilization value of iron phosphate and aluminum phosphate is therefore very low. In addition, iron and aluminum phosphate cannot be processed by the phosphate industry because they interfere with the industrial process. High concentrations of iron and aluminum in ash solutions also constitute an obstacle to the recovery of phosphorus by techniques of liquid extraction or ion exchange as the efficiency of phosphorus extraction decreases with increasing metal ion concentration. In addition, it is preferred that the solution from the phosphorus extraction be recycled and used for ash dissolution to reduce acid consumption and to minimize effluent production. Such recirculation of ashtray solution results in an accumulation of iron and aluminum in the circulating solution which renders phosphorus recovery inefficient. Therefore, it is desirable to be able to separate and preferably recycle iron and aluminum from ash ash solutions to enable phosphorus recovery. It is desirable to be able to recycle the main components of the ash to reduce the costs associated with ash disposal. In addition, it is desirable to be able to recycle iron and aluminum separately and preferably in a form suitable for phosphorus precipitation in sewage treatment plants. This can enable the recirculation of iron and aluminum from ash for use in phosphorus precipitation and thereby reduce the need for externally supplied iron and aluminum salts.
    Published international patent application WO 00/50343 describes a process for recovering iron, aluminum and phosphorus from ash ash solutions using ion exchange.
    The process includes the separation of iron and aluminum from ash ash solutions with a cation exchange compound with strong acid such as Dowex Marathon C in sodium or proton form.
    Regeneration of the cation exchange mass is preferably done with an aqueous solution of sodium chloride 3, but hydrochloric acid or sulfuric acids are also mentioned as possible regeneration solutions. It is found that the eluate solution containing iron and aluminum ions can be recycled to a water treatment plant where substances containing iron and aluminum are valuable as precipitants.
    The approach presented in Preparation WO OO / 50343 has a number of serious disadvantages such as high costs due to the need for a large excess of regeneration chemicals and a limited value of the recycled iron and aluminum as these are contaminated with acids or salts. Regeneration of a cation exchange mass with strong acid takes place via a reaction with ion exchange equilibrium. The cation exchange mass affinity for trivalent cations such as iron and aluminum is much higher than the affinity for monovalent cations such as sodium or protons. A very high concentration of monovalent cations is therefore required in the regeneration solution to shift the equilibrium reaction in the ion exchanger so that trivalent iron or aluminum ions can be exchanged for monovalent sodium or protons. Therefore, the regeneration of a cation exchange compound loaded with iron and aluminum requires the use of highly concentrated salt or acid solutions. The need for salt or acid is much greater than the stoichiometric amount to form iron and aluminum salts. This makes the regeneration process costly as an excess of chemicals is needed. Furthermore, the eluate has a high content of excess acid or salt.
    Addition of concentrated acids or salts to the wastewater treatment process is undesirable.
    In addition, the process described above does not allow iron and aluminum to be recycled separately. In wastewater treatment, phosphorus precipitation is optimized for using either iron or aluminum salts. To achieve maximum efficiency of phosphorus removal, it is necessary to control the pH of the solution and to be able to adjust the ratio of metal to phosphorus during precipitation. It is therefore desirable to use precipitating chemicals with a predetermined composition and to use either iron or aluminum salts and not mixtures with varying Fe and Al content.
    The content of iron and aluminum in ash from incinerated sewage sludge varies over time. In several cases, sewage sludge is incinerated in central plants that receive sludge from several treatment plants which use either iron or aluminum as precipitation chemicals.
    Since the difference in the molecular weight of aluminum and iron is large and the relative content of iron and aluminum in ash varies over time, eluates produced in accordance with the preparation WO 00/50343 will have a very limited value as precipitating chemicals. The published international patent application WO 2008/115121 discloses a method and an arrangement for phosphorus recovery. The method is applicable for phosphorus recovery from leach solutions 4 from ash. Separation of iron and aluminum takes place with a strong cation exchange mass which is regenerated with an inorganic acid. The disadvantages are similar to those presented in WO OO / 50343 and include high costs due to the need for a large excess of regeneration chemicals, a limited value of the recycled iron and aluminum products due to contamination with acid and the fact that it is not possible to recycle iron and aluminum separately.
    Despite extensive research worldwide in the field of phosphorus recovery and attempts to use ion exchange technology and liquid extraction for this purpose, the recovery of iron and aluminum from ash solutions from ash, separately and in pure form, for use as a precipitant in wastewater treatment, has not been applied industrially.
    There is a need for an improved method for recovering iron and aluminum from ash leaching solutions, in which the continuous need for large excesses of regeneration chemicals is eliminated. There is also a need for a method which enables the recycling of iron and aluminum separately and in a pure form without contamination of heavy metals, to be used as a precipitant in water treatment / sewage treatment plants.
    Summary A general object of the present invention is to provide an efficient, cost-effective and environmentally friendly method for recovering iron and aluminum from solutions, preferably solutions obtained from dissolving phosphorus-containing materials, and in particular to provide a method for recovering iron and aluminum from leach solutions obtained by dissolving ash from incinerated sewage sludge with inorganic acids. A further object of the present invention is to provide a cost-effective method for separating iron and aluminum from ash ash solutions to enable, in a subsequent step, phosphorus recovery in a valuable form for use in agriculture. Another object of the present invention is to make it possible to recover iron and aluminum salt without the need for large excesses of regeneration chemicals. A further object of the present invention is to enable the recovery of iron and aluminum salts without contamination of heavy metals. A further object of the present invention is to enable the separation of iron from aluminum for use in separate phosphate control in the treatment of waste streams.
    The above objects are achieved by methods and devices in accordance with the appended claims. In general terms, phosphorus-containing materials are treated with inorganic acids to form a leach solution comprising anions of trivalent iron, trivalent aluminum, divalent heavy metals and phosphate. At least one trivalent metal selected from iron and aluminum is extracted from the leach solution by adsorbing at least one trivalent metal selected from iron and aluminum in a scavenger affinity scavenger and by releasing at least one trivalent metal selected from iron and aluminum. to a stripping solution during regeneration of the capture substance. The regeneration takes place with hydrochloric acid. Anionic metal chloride complexes are extracted from the hydrochloric acid stripping solution by adsorption of anionic metal chloride complexes in a capture substance having an affinity for anionic metal chlorides. Metal chlorides are recovered from the charged capture substance by elution with water and the capture substance is recycled to extract additional anionic metal chlorides. Hydrochloric acid is added to the raffinate from the step of metal chloride extraction. Crystalline aluminum chloride hexahydrate can be separated from the hydrochloric acid stripping solution if desired. The hydrochloric acid stripping solution, after metal separation, is returned and used to strip a trapping substance loaded with at least one trivalent metal selected from iron and aluminum. The ash ash solution, after separation of at least one trivalent metal selected from iron and aluminum, is treated for phosphorus recovery and is preferably reused for dissolving a phosphorus-containing material.
    An advantage of the present invention is that it enables the extraction of iron and aluminum from ash ash solutions in the form of high-quality iron chloride and aluminum chloride products in an environmentally friendly and cost-effective manner. Separation of iron and aluminum from ash solutions makes it possible to recover phosphorus in a possible subsequent step in a form suitable for use in agriculture. Iron and aluminum can thus be recycled from ashtray solutions in a simple and cost-effective way without the need for a large excess of regeneration chemicals. A further advantage of the present invention is that it makes it possible to recycle iron and aluminum separately and without contamination with heavy metals. Yet another advantage of the present invention is that precipitating chemicals used for phosphorus precipitation from waste streams can be recovered from ashes from incineration of phosphorus-containing sludge and then reused for phosphorus precipitation in wastewater streams, saving resources.
    BRIEF DESCRIPTION OF THE DRAWINGS The invention, together with further objects and advantages thereof, is best understood by reference to the following description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a block diagram of an embodiment of an arrangement for recovering phosphorus from ashes; Fig. 2 is a block diagram of an embodiment of an arrangement for recycling trivalent metals in accordance with the present invention; Fig. 3 is a graph illustrating extraction of metals from sulfuric acid using diethylhexylphosphoric acid as a function of equilibrium pH; Fig. 4 is a graph illustrating extraction of anionic metal chloride complexes with 6 trioctyl / decylamine from hydrochloric acid as a function of chloride concentration; Fig. 5 is a step-by-step flow chart of an embodiment of a method for recovering trivalent metals in accordance with the present invention; Fig. 6 is a step-by-step flow chart of an embodiment of a phosphorus recovery method; Fig. 7 is a block diagram of an embodiment of an aluminum recycling arrangement in accordance with the present invention; Fig. 8 is a block diagram of an embodiment of an iron recycling arrangement in accordance with the present invention; Fig. 9 is a block diagram of an embodiment of an arrangement for recycling iron and aluminum in accordance with the present invention; and Fig. 10 is a block diagram of another embodiment of an arrangement for recycling iron and aluminum in accordance with the present invention.
    Detailed description In all drawings the same reference numerals are used for similar or corresponding elements.
    Terminology frequently used in the present description is to be construed as follows: Capture substance - Material that has an affinity for solutes, e.g. materials that adsorb ions, by ion association or solution mechanisms. The term includes various types of extractants that are included in both solvents and ion exchange compounds.
    Solvent - A liquid phase, usually organic, which preferably dissolves extractable solutes from an aqueous solution.
    Extractant - An active component, usually organic, of a solvent that enables extraction.
    Liquid extraction - The separation of one or more solutes from a mixture by mass transport between immiscible phases of which at least one phase is typically an organic liquid.
    Di / uent- A liquid, usually organic, in which an extractant and a modifier are dissolved to form a solvent.
    Modifier - A substance that is added to the solvent to increase the solubility of the extractant, salt of the extractant or ionic species resulting from extraction or stripping. Also added to suppress emulsion formation.
    Regeneration - The transfer from the capture substance of the solutes removed from the process solution to make the capture substance ready for reuse.
    Stripping - Elution from a charged solvent.
    Scrubbing - Selective removal of impurities from a charged solvent before stripping.
    Raf fi nat - An aqueous phase from which a solute has been removed by extraction.
    The present invention is based on the understanding that by combining and adapting different process steps with a high degree of recycling of process chemicals, a whole process with a very high degree of chemical recycling can be achieved. In the present invention, by connecting two ion exchange processes with a process which is itself a recirculation system, synergy effects for the whole system can be achieved. This can be illustrated by a typical embodiment presented below.
    In a typical embodiment of the present invention, which, however, is to be construed as limiting the general scope, phosphorus-containing materials are treated with an inorganic acid to form a leach solution comprising trivalent iron, trivalent aluminum, divalent heavy metals and phosphate anions. At least one trivalent metal selected from iron and aluminum is extracted from this leach solution by adsorption of at least one metal selected from iron and aluminum in a capture substance having an affinity for cations and by releasing at least one trivalent metal selected from iron and aluminum to a stripping solution under regeneration of the capture substance. The regeneration takes place with hydrochloric acid. Anionic metal chloride complexes are extracted from the hydrochloric acid-containing stock solution by adsorbing anionic metal chloride complexes in a trapping substance having an affinity for anionic metal chlorides.
    Metal chlorides are recovered from the charged capture substance by elution with water and the capture substance is recycled to extract more anionic metal chlorides. Hydrochloric acid is added to the raffinate from the metal chloride extraction step. Crystalline aluminum chloride hexahydrate can be separated from the hydrochloric acid stock solution if desired. After the metal separation, the hydrochloric acid-containing stripping solution is recycled and used to strip a trapping substance loaded with at least one trivalent metal selected from iron and aluminum. After separation of at least one trivalent metal selected from iron and aluminum, the ash ash solution is treated to recover phosphorus and is preferably reused to dissolve a phosphorus-containing material.
    The original object of the present invention was to create a simple and cost-effective method for recovering iron and aluminum from ashtray solutions containing at least one of trivalent iron and trivalent aluminum and possibly also divalent heavy metals and phosphorus. The method makes it possible to recycle iron and aluminum separately and without being contaminated with heavy metals. Separation of iron and aluminum enables phosphorus recovery, in a subsequent step, in a form useful for use in agriculture. In addition, the method enables the production of iron and aluminum salts without the need for a large excess of regeneration chemicals.
    Various embodiments of processes for recycling iron, aluminum and phosphorus from ash from incinerated sewage sludge are described in detail below. However, the present invention is not limited to the recovery of iron and aluminum from ash from incinerated sewage sludge but is applicable to many other phosphorus-containing materials. A similar process can be used to extract, for example, iron and aluminum from ash from incinerated biomass, ash from incinerated household waste, ash from incinerated peat, ash from incinerated coal, chemical sludge from water / wastewater treatment plants, etc.
    Sewage sludge mask is the residue that is formed in an incineration plant during the incineration of dewatered sewage sludge. Sludge ash is mainly a floury material with some sand particles.
    The specific size distribution and the properties of the sludge mask largely depend on the type of combustion system and the chemicals used in the sewage treatment process.
    Sewage sludge ash consists for the most part of the elements O, Si, P, Ca, Fe and Al. Phosphorus occurs mainly in the form of various phosphate salts with metal cations, while the rest of the substances occur mainly as oxides. The phosphorus concentration in the ash is usually in the range 7 - 10% by weight. The concentration of other substances varies as follows: Si 9 - 21%, Ca 4 - 15%, Al 3 - 15% and Fe 1 - 14%. The sum of heavy metals such as Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn usually amounts to 0.1 - 0.5% by weight.
    A solution is created by dissolving ash from incinerated sewage sludge in acid in a dissolution arrangement. Strong inorganic acids such as sulfuric acid, nitric acid or hydrochloric acid can be used. The preferred acid is sulfuric acid due to its low price and that it can be obtained in concentrated form. The preferred way to dissolve ash in acid is to first mix: the ash with recycled process liquid and then maintain a low pH (pH <2) by continuously adding sulfuric acid in a controlled manner. The necessary pH level for dissolution is a function of the ash composition and is thus specific to each ash. 9 The insoluble parts of the ash, mainly silicates, undissolved metal oxides and gypsum are removed by sedimentation, filtration or centrifugation.
    The whole arrangement for ash dissolution and separation of insoluble solids can be seen as a pretreatment to provide a supply solution to the recycling device according to the invention, containing trivalent iron, trivalent aluminum, divalent heavy metals and phosphorus.
    An embodiment of a general block diagram of an arrangement 100 for recycling iron, aluminum and phosphorus from ashes is shown in Figure 1. Ash 1, acid 2, and process solution 3, preferably at least some recycled process solution, are fed to a dissolution unit 4. The dissolution unit 4 is provided for treating the phosphorus-containing material, in this embodiment, the ash 1, with the acid 2, in this embodiment inorganic acid. An effluent 5 from the dissolution unit 4 is then treated to remove insoluble material 13 in a dissolution separator 6, which is a solid matter separation unit from liquid.
    The dissolution separator 6 is thus arranged to separate solid and liquid phases of the treated phosphorus-containing material. The insoluble material 13 is typically removed by sedimentation, filtration and / or centrifugation and a residual liquid is passed as an inorganic acid solution 7 containing at least one of trivalent aluminum and trivalent iron to an inlet of a trivalent metal recovery arrangement 8. After removing a substantial portion of said at least one metal selected from iron and aluminum, the depleted leach liquid 9 leaving the trivalent metal recovery arrangement 8 is provided as an input solution to a phosphate recovery arrangement 10 in which phosphorus recovery is performed by means which such known in the prior art, such as liquid extraction, ion exchange, chemical precipitation, etc. An effluent 11 from the phosphor recovery arrangement 10 is recycled back to the dissolution unit 4 as the process solution 3, as a recirculation arrangement for recycling the leach depleted of trivalent metals and the phosphate back to the phosphate 4. An effluent 12 of the circulating process solution 3 is removed for further treatment e.g. to prevent the build-up of heavy metals and alkaline cations.
    In a preferred embodiment, after a substantial portion of iron and / or aluminum has been removed, the depleted solution 9 is treated for phosphorus recovery by extracting phosphoric acid with organic solvents such as alcohols, trialkyl phosphate etc. (eg heptanol, tributyl phosphate and mixtures of these compounds) in a liquid extraction process. This phosphorus recovery can _ e.g. carried out in accordance with the description in the published international patent application WO2008 / 115121. It has been found that such solvents extract phosphoric acid with preference over sulfuric acid, nitric acid and hydrochloric acid from ash solutions. Alternatively, sulfuric acid and phosphoric acid may be extracted together using solvents such as liquid amines and mixtures of liquid amines, tributyl phosphate and alcohols. Phosphorus can thus be recovered from such organic solvents by known means in a form suitable for use in agriculture.
    An embodiment of the arrangement 8 for recycling trivalent metals is schematically described in Figure 2. This arrangement 8 is suitable to operate for recycling iron and / or aluminum from ashtray solutions as mentioned above. This embodiment can thus be used in the arrangement 100 in Figure 1. The process water solution is the inorganic acid solution 7 comprising trivalent AL and / or trivalent Fe. The process aqueous solution is supplied via an inlet 21 to a first ion exchange unit 20. In an extraction section 27 of the first ion exchange unit 20, the process aqueous solution comprising dissolved trivalent iron and / or trivalent aluminum is exposed to the first capture substance 22 having an affinity for trivalent iron and / or trivalent aluminum. Iron and / or aluminum is thereby extracted via absorption in the first capture substance 22. The first capture substance 26 leaving the extraction unit 27 is thus loaded with trivalent iron and / or trivalent aluminum. After removal of preferably a substantial part of the iron and / or aluminum, the depleted leach solution 9 is discharged via an outlet 23 to e.g. treated for phosphorus recovery. Any capture substance that can remove trivalent iron and / or trivalent aluminum can be used. The mechanism for extraction of iron and / or aluminum is based on exchange with protons. The capture substance may be a solid ion exchange mass such as styrene divinylbenzene or acrylic divinylbenzene having functional groups of sulfonic acid or phosphoric acid, or a liquid organic extractant such as various organic derivatives of phosphoric acid e.g. diethylhexylphosphoric acid, etc.
    The use of liquid trapping substances such as diethylhexylhexylphosphoric acid is preferred as such trapping substances enable the separation of iron and aluminum from aqueous solutions by liquid extraction. Liquid extraction involves the selective transfer of solutes between two immiscible phases, an aqueous phase and an organic phase. The two immiscible phases are first mixed thoroughly to facilitate the transfer of solutes and then separated.
    It is common to dissolve organic extractants (eg diethylhexylphosphoric acid) in suitable solvents such as kerosene and to add substances to the solvent solution in order to increase the solubility of the extractant and to suppress emulsion formation. All such combinations are hereinafter referred to as liquid capture substances.
    Capture substances such as diethylhexylphosphoric acid have different affinity for different metal ions. The degree of metal extraction varies considerably with the pH of the aqueous solution. Therefore, by controlling the equilibrium pH during the liquid extraction, the capture substance can selectively extract some 11 metals before other metals. Extraction of metals from sulfuric acid with diethylhexylphosphoric acid, as a function of equilibrium pH, is shown in Figure 3. From sulfuric acid, the extraction sequence as a function of pH Fe "> Ala *> Znz *> Cd"> Ca "> Mnz *> Cu ”> Mg”> C02 *> Ni ”. It must be understood that comparisons of percentage extraction-pH curves for any cationic extractant can only be used as an indication of the pH range in which metal extraction takes place.
    The curves change with the metal concentration, the extractant concentration, phase conditions, contact time, etc. For example, an increase in the extractant concentration will shift the curves towards lower pH values.
    From Figure 3 it can be seen that by controlling the equilibrium pH during liquid extraction, trivalent iron can be effectively separated from heavy metals if trapping substances such as diethylhexylphosphoric acid are used. At a certain equilibrium pH value, diethylhexylphosphoric acid has a significant capacity for the extraction of trivalent iron and only a very limited capacity for divalent heavy metals.
    Aluminum can be co-extracted with trivalent iron in front of heavy metals or iron can first be extracted before aluminum and heavy metals and in a second extraction step with a higher pH level, aluminum can be extracted with some co-extraction of heavy metals. Different embodiments that utilize these different possibilities are presented further below. Again in Figure 2, the extraction section 27 of the first ion exchange unit 20 is therefore in this embodiment preferably provided with a pH control unit 29 for controlling the pH of the first capture substance 26 in extraction section 27 of the first ion exchange unit 20.
    The first capture substance 26 loaded with iron and / or aluminum can, if desired, be scrubbed in a scrubber 19 to remove co-extracted impurities. Thereafter, the first capture substance 26 leaving the extraction section 27 is led to a stripping section 28 in the first ion exchange unit 20. Here, the trivalent aluminum and / or trivalent iron is released from the first capture substance to a hydrochloric acid solution 31, in this embodiment recycled anhydrous hydrochloric acid having a concentration of about 6-8 N. Hardwood and heavy metals such as zinc, copper, cadmium, etc. forms anionic complexes with chlorine. This creates anionic metal chloride complexes. Trivial aluminum does not form negatively charged complexes with chlorine but remains in the form of cations. An excess of hydrochloric acid in addition to the stoichiometric ratio is used for stripping iron and / or aluminum from the first capture substance 22.
    Accordingly, the first capture substance 25 leaving the stripping section 28 is depleted of trivalent aluminum and / or trivalent iron and recycled back to the extraction section 27.
    The stripping solution leaving the stripping section 28 in the first ion exchange unit 20 is thus a hydrochloric acid solution 32 consisting of eluted metals and hydrochloric acid.
    The hydrochloric acid solution 32 containing anionic metal chloride complexes, hydrochloric acid and optionally 12 trivalent aluminum cations is then passed to a second ion exchange unit 40. An extraction section 47 of the second ion exchange unit 40 is arranged to extract the anionic metal chloride complexes from the hydrochloric acid solution 32 by adsorption in a second capture substance 42. The second capture substance 42 has an affinity for anionic metal chloride complexes. Anionic metal chloride complexes are selectively extracted into a second trapping substance, preferably before trivalent aluminum cations and hydrochloric acid remaining in the aqueous solution. The second capture substance 46 leaving the extraction section 47 in the second ion exchange unit 40 is thus charged with metal chlorides.
    All capture substances capable of removing anionic metal chloride complexes, preferably over trivalent aluminum and hydrochloric acid, can be used. The mechanism of extraction of metal chlorides is mainly based on exchange with chloride ions. The second capture substance may be a solid ion exchange compound such as styrene divinylbenzene or acrylic divinylbenzene having primary, secondary, tertiary or quaternary amine functional groups, or a liquid organic extractant such as various liquid amines, trialkyl phosphates, ketones, ethers, etc.
    The use of liquid capture substances such as liquid tertiary amines (eg trioctyl / decylamine) is preferred as such capture substances enable the separation of anionic metal chloride complexes from aqueous solutions via liquid extraction. It is common to dissolve tertiary amines in suitable diluents such as kerosene and to add substances to the solvent mixture to increase the solubility of the amines and to counteract emulsion formation. All such combinations are hereby referred to as liquid scavenger substances with an affinity for anionic metal chloride complexes. Figure 4 shows extraction of anionic metal chloride complexes with trioctyl / decylamine from hydrochloric acid solution as a function of chloride concentration. Returning to Figure 2, the raffinate 33 from the extraction section 47 is an aqueous solution of hydrochloric acid depleted in anionic metal chloride complexes. A recycle unit 34 is connected between the second ion exchange unit 40 and the first ion exchange unit 20. The recycle unit 34 is thus arranged to provide the hydrochloric acid solution depleted of anionic metal chloride complexes, i.e. the raffinate 33 to the first ion exchange unit 20 for reuse as a stripping solution 31. The strip section 28 of the first ion exchange unit 20, the extraction section 47 of the second ion exchange unit 40, the recycling unit 34 and the connections therebetween constitute a recycling system 30. However, since some of the chloride ion content metal chloride complexes, such chloride ions must be replaced. For this purpose, hydrochloric acid 38 is added to the raffinate 33 from the extraction section 47 of the recycle unit 34 and the connections therebetween to a hydrochloric acid addition agent 35. The raffinate 332 is gasified there with hydrogen chloride 38 to bring the concentration to the desired concentration of about 6-8 N HCl. 13 The raffinate 33 possibly contains aluminum, i.e. when the first ion exchange unit 20 is arranged to extract trivalent Al by adsorption in the first capture substance 22. Thus, if aluminum is present in the raffinate 33 in relatively high concentrations, the addition of hydrochloric acid in the admixture 35 results in a precipitation of crystalline aluminum chloride hexahydrate 37. In such an embodiment the recycling unit 34 also comprises a separator 36 for separating the precipitate of aluminum chloride hexahydrate 37 from the hydrochloric acid solution. At room temperature, the solubility of aluminum chloride decreases from 32% by weight in water to about 6.5% by weight in 8 N HCl (25% by weight HCl) and to about 0.7% by weight in 11 N HCl (35% by weight HCI). At 0 ° C, the solubility of aluminum chloride hexahydrate in saturated hydrochloric acid solution (35 wt /> HCl) is only 0.2 g / liter. Thus, crystalline aluminum chloride 37 is separated from the aqueous hydrochloric acid solution in the separator 36 by sedimentation, filtration or centrifugation. The hydrochloric acid-containing stripping solution 31, after metal separation, is recycled as mentioned above and used to strip the capture substance 26 which is loaded with trivalent metal of iron and / or aluminum.
    The second ion exchange unit 40 is further arranged to release the anionic metal chloride complexes from the second capture substance 46 into an aqueous solution. Metal chlorides are recovered from the charged second capture substance 46 by eluting with water 49 in a stripping section 48 in the second ion exchange unit 40. The result when the second capture substance 46, charged with metal chloride complex, is contacted with water 49 is that the anionic metal chloride complex is broken. depleted second capture substance 45 charged with chloride ions and an aqueous solution 41 containing neutral metal chloride salts. After metal chlorides are eluted, the second capture substance 45 is recycled to extract additional anionic metal chloride complexes. The resulting aqueous solution with metal chlorides 41 has a ratio, chloride to metal, which is about 1 without an excess of hydrochloric acid.
    An embodiment of a method for recovering trivalent metals from a solution is illustrated in the form of a flow chart in Figure 5. The trivalent metals are trivalent Al and / or trivalent Fe.
    The process starts in step 200. In step 210 an inorganic acid solution is provided comprising trivalent Al and / or trivalent Fe. The trivalent Al and / or trivalent Fe are extracted in step 220 by absorption in a capture substance. Preferably, this extraction comprises controlling the pH of the first capture substance. In a particular embodiment, described in more detail below, the control of the pH of the first capture substance is adapted to reduce the extraction of heavy metals to the first capture substance whereby the metal chloride complex is essentially iron chloride complex. In step 230, the trivalent Al and / or trivalent Fe are released from the first capture substance »to a hydrochloric acid solution, whereby anionic metal chloride complexes are formed. The anionic metal chloride complexes are extracted from the hydrochloric acid solution in step 240 by absorption 14 in a second capture substance. In step 250, the anionic metal chloride complexes are released from the second capture substance into an aqueous solution. In step 260, gaseous hydrochloric acid is added to the hydrochloric acid solution, depleted in anionic metal chloride complexes. In embodiments adapted for applications where the extraction step 220 comprises extracting trivalent A1 by absorption in the first capture substance, the step of adding gaseous hydrogen chloride 260 preferably comprises adding gaseous hydrogen chloride in an amount which causes precipitation of aluminum chloride hexahydrate. In such an embodiment, the method also includes an additional step 262 for separating the precipitated aluminum chloride hexahydrate from the hydrochloric acid solution. The hydrochloric acid solution depleted in anionic metal chloride complexes is returned in step 270 to be reused in step 230 to release trivalent Al and / or trivalent Fe from the first capture substance. The process ends in step 279.
    As further mentioned above, the recycling of trivalent metals described above can be used as part of a method for phosphorus recovery. An embodiment of such a method is illustrated as a flow chart in Figure 6. The method begins in step 280. In step 282, a phosphorus-containing material is treated with an inorganic acid. The phosphorus-containing material also contains Fe and / or Al. The phosphorus-containing material in this particular embodiment is ash from the incineration of sewage sludge. Solid and liquid phases of the treated phosphorus-containing material are separated in step 284. Thereby a leach solution containing phosphate and trivalent Al and / or trivalent Fe is formed. In step 286, trivalent metals are recycled In accordance with the ideas presented above, e.g. with the method illustrated in Figure 5. The leach solution is then used as the inorganic acid solution containing trivalent Al and / or trivalent Fe. In step 288, phosphorus is recovered from the leach solution. This can be done with all previously known methods e.g. in accordance with the principles described in WO 2008/115121. In step 290, the leach solution depleted of trivalent metals and phosphate is returned for reuse in step 282 where the phosphorus-containing material is treated.
    The process ends in step 299.
    The content of aluminum and iron in ash from incinerated sewage sludge can vary greatly.
    The precipitating agent used for phosphorus removal in wastewater treatment is a major factor affecting the metal content of ash from incinerated sewage sludge. Ash can generally be divided into two different types with respect to aluminum and iron concentrations: a) ash characterized by a high aluminum content and a low iron content with a greyish appearance, and b) ash characterized by a high iron content and a low aluminum content with a reddish brown appearance. In addition to iron and aluminum, the calcium content of ash from incinerated sewage sludge varies considerably and is usually between 4 - 15% by weight. The content of iron as well as aluminum varies in the same order of magnitude. The content of silicates (SiO 2) varies between 25 - 50% by weight / 0. During combustion of sewage sludge at high temperature (> 500 ° C), inorganic phosphorus compounds can recrystallize and form new compounds. Iron phosphate and aluminum phosphate can react with calcium compounds and silicon to form acid-soluble calcium phosphates (for example whitlockite (Ca3 (PO4) 2) and hydroxylapatite (Ca5 (PO4) 3OH) and sparingly soluble compounds such as hematite (FezOa), aluminas (AlzOaa) CaAlzSigOa) etc.
    During the dissolution of ash in acid, phosphorus is released almost completely (> 90%) regardless of the type of ash because most phosphate compounds (iron phosphate, aluminum phosphate and calcium phosphate) are soluble in acid. However, the release of iron (10-50%) and aluminum (40-80%) is usually limited due to the presence of sparingly soluble iron and aluminum compounds. An increase in the solution of iron and aluminum can be achieved by leaching at higher temperatures.
    In general, the alternatives for iron and / or aluminum recycling from ash solutions can be divided into three main categories. If the ash has a high aluminum content and a low iron content, there is very little interest in recycling iron because the iron content in the leach solution is usually very low. Similarly, if the ash has a high iron content and a low aluminum content, there is very little interest in recycling aluminum.
    However, if the ash originates from a central incineration plant that receives sludge from several plants that use either iron or aluminum as precipitating chemicals, there may be reasons to recycle both iron and aluminum at the same time.
    If only aluminum is to be recovered from ashtray solutions in pure form, the arrangement 8 for recovering trivalent metals from a solution may look like in the embodiment illustrated in Figure 7. Here, aluminum is found in an inorganic acid solution 7 ', e.g. from an ashtray solution.
    Aluminum is extracted from the extraction section 27 of the first ion exchange unit 20 using e.g. diethylhexylphosphoric acid. All trivalent iron will be co-extracted with aluminum. The liquid extraction in the extraction section 27 of the first ion exchange unit 20 can be operated in such a way that some heavy metals are also co-extracted together with aluminum.
    This is done by adjusting the pH during the extraction through the pH control unit 29. The charged capture substance 26 ', charged with at least Al, is then stripped with recycled aqueous solution of hydrochloric acid 31', whereby a capture substance 25 'depleted of Al is obtained.
    The stripping solution 32 'consists of eluted aluminum, possibly iron and some heavy metals as well as hydrochloric acid. The eluted iron and heavy metals form anionic complexes with chlorides and are selectively removed from the solution with a capture substance (eg tri-octyl / decylamine) 42 which removes anionic metal chloride complexes over aluminum and hydrochloric acid. Iron and heavy metals are recovered from the charged capture substance 46 'by elution with water 49 and the metal chlorides dissolved in water 41 are removed for disposal. Then, hydrochloric acid 38 to 16 is supplied to the raffinate 33 'from the extraction section 47 of the second ion exchange unit 40, which raffinate 33' comprises aluminum. The feed simultaneously precipitates aluminum chloride hexahydrate 37. Crystalline aluminum chloride is separated in the separator 36 from the aqueous hydrochloric acid solution 31 '. If desired, the aluminum chloride is treated to remove excess acid by e.g. neutralization with aluminum hydroxide. The produced solid aluminum chloride can then be used for e.g. phosphate control in the treatment of wastewater flows. The hydrochloric acid-containing stripping solution 312 after separation of aluminum is recycled and used for stripping a capture substance 26 'loaded with aluminum.
    If only iron were to be recovered from ashtray solution in a pure form, the arrangement 8 for recovering trivalent metals from a solution may look as in the embodiment illustrated in Fig. 8.
    Here, trivalent iron is provided in an inorganic acid solution 7 ", eg from the ash ash solution. Iron is extracted in the extraction section 27 of the first ion exchange unit 20 by using, for example, diethylhexylphosphoric acid. The liquid extraction in the extraction section 27 of the first ion exchange unit 20 can be driven in a manner in which iron is extracted in front of heavy metals and possibly also aluminum. This is done by adjusting the pH during the extraction through the pH control unit 29. The charged capture substance 26 ", charged with at least iron is then stripped with hydrochloric acid 31", giving a capture substance 25 "impoverished on Fe. The stripping solution 32 "consists of eluted iron and hydrochloric acid. Trivalent iron forms anionic complexes with chloride which are selectively extracted from the solution 32" with a capture substance (eg trioctyl / decylamine) 45, which removes anionic iron chloride complexes in front of hydrochloric acid, giving a charged capture substance sub 46 ". Iron chloride is recovered from the charged capture substance 46" by eluting with water 49 to iron chloride dissolved in water 41 ". This iron chloride can for example be used directly for phosphorus precipitation in sewage treatment plants. The pure iron chloride solution 41" can also be processed to form a solid ferric chloride used for phosphate control in the treatment of wastewater flows. Hydrochloric acid 38 is then added to the raffinate 33 "from the iron chloride extraction in the extraction section 47 of the second ion exchange unit 40. The hydrochloric acid solution 31", after the separation of iron and the addition of hydrochloric acid, is recycled and used to strip the Fe-charged capture substance 26 ".
    If iron and aluminum are to be recycled at the same time, there are two alternatives: a) removal of, in one extraction step, iron and aluminum with priority over heavy metals and b) removal of iron with priority over heavy metals in a first extraction step (some co-extraction of aluminum may occur ) followed by removal of aluminum with some co-extraction of heavy metals in a second extraction step. In a first alternative, illustrated by an embodiment of Figure 9, iron and aluminum are selectively extracted from an inorganic acid solution 7 "'with a capture substance (eg diethylhexylphosphoric acid) 22 22 with preference to divalent heavy metals remaining in solution 9 to a Fe- and All-charged capture substance 26 "'. The diethyl hexyl phosphoric acid is then stripped with 31 "hydrochloric acid.
    The stripping solution 32 "'consists of eluted iron and aluminum as well as hydrochloric acid. Trivalent iron forms anionic complexes with chlorine while aluminum remains in cationic form. Anionic iron chloride complexes are selectively extracted from the solution 32"' with a capture substance (eg tri-octyl / decylamine) 45 which removes anionic iron chloride complexes with preference over aluminum and hydrochloric acid. Iron chloride 41 "'is recovered from the charged capture substance 46"' by elution with water 49 and can e.g. be used directly for phosphorus precipitation in sewage treatment plants. Hydrochloric acid 38 is then added to the raffinate 33 "'from the iron chloride extraction step in the extraction section 47 of the second ion exchange unit 40 whereby aluminum chloride hexahydrate 37 precipitates simultaneously. Crystalline aluminum chloride is separated from the aqueous hydrochloric acid 33"' in separator 36. The solid aluminum chloride produced 37 can then be used. wastewater treatment. The hydrochloric acid-containing stripping solution 31 "', after separation of iron and aluminum, is recycled and used to strip a capture substance 26"' loaded with iron and aluminum.
    In a second alternative, illustrated with an embodiment in Figure 10, trivalent iron is selectively extracted in the extraction section 27 "in the first ion exchange unit 20" by a first arrangement 8 "for recycling trivalent metals from the ashtray solution 7". The extraction takes place in this embodiment with e.g. diethylhexylphosphoric acid as the first capture substance 22 in preference to heavy metals (some co-extraction with aluminum may occur). The solution 9 "depleted in iron is provided as a constituent inorganic acid solution 7 'to a second arrangement 8' for recycling of trivalent metals. In an extraction section 27 'of the first ion exchange unit 20' in the second arrangement 8 ', aluminum is removed, perhaps with some co-extraction of heavy metals, using eg diethylhexylphosphoric acid as the first capture substance 22. A solution depleted in both AL and Fe 9 'is dispensed for further processing.
    This embodiment thus consists of two serially connected arrangements for recycling trivalent metals, the first substantially recovering Fe and the second recovering Al. The selective extraction of Fe and Al takes place by controlling the pH of the respective extraction section 27 ', 27 "of the respective first ion exchange section 20', 20". In the first arrangement for the recovery of trivalent metals 8 ", the pH is adjusted so that it is adjusted to reduce the extraction of trivalent Al.
    Tertiary Al is instead extracted from the inorganic acid solution depleted in trivalent iron by absorption in a trapping substance in the second arrangement for recovering trivalent metals 8 '.
    From the first arrangement for the recovery of trivalent metals 8 ", pure iron chloride 41" is recovered by stripping the iron-charged capture substance 26 "with recycled hydrochloric acid 31", 18 extraction 47 "of anionic iron chloride complexes with eg tri-octyl / decylamine 45 to an iron chloride charged capture substance 46 ", followed by elution of iron chloride 41" with water 49. Hydrochloric acid in gaseous form 38 "is then added to the raffinate 33" from the iron chloride extraction 47 ". Any co-extracted aluminum is precipitated in the form of aluminum chloride hexahydrate 37 "and separated.
    The hydrochloric acid solution 31 ", after separation of iron and co-extracted aluminum, is recycled and used for stripping the iron-loaded capture substance 26".
    From the second arrangement for recycling of trivalent metals 8 ', pure aluminum chloride hexahydrate 37' is recovered by stripping the aluminum charged capture substance 26 'with recycled hydrochloric acid 31', separating anionic metal chloride complexes with e.g. trioctyl / decylamine 45 followed by precipitation of aluminum chloride hexahydrate 37 'by the addition 35' of hydrochloric acid in gaseous form 38 '. Aluminum chloride hexahydrate 37 'is separated from the hydrochloric acid solution. The hydrochloric acid-containing stripping solution 31 ', after the aluminum separation, is recycled and reused for stripping an aluminum-loaded capture substance 26'.
    In this way, iron and aluminum can be recycled efficiently, easily and cost-effectively from ashtray solutions without the need for an excess of regeneration chemicals. Although an excess of hydrochloric acid is required for stripping iron and aluminum from a charged capture substance, the consumption of hydrochloric acid in the method according to the invention will be approximately equal to the stoichiometric amount required to form iron and aluminum chloride salt. Thus, the cost of regenerating the capture substance is greatly reduced. In addition, the method according to the invention enables the recovery of iron and aluminum separately and without contamination of heavy metals. The recycled iron and aluminum salts are water-soluble and suitable for use as precipitants in water / wastewater treatment plants. The circulation of hydrochloric acid in a closed system in accordance with the invention results in a regeneration process which does not consume a large excess of hydrochloric acid in addition to the amounts required for the formation of the valuable iron and aluminum products.
    Precipitates used for phosphorus precipitation in sewage treatment plants can be recycled from ash from incinerated sewage sludge and reused for phosphorus precipitation in sewage treatment plants, thereby reducing the need for externally supplied iron and aluminum salts. The various sub-processes are thus combined in such a way that they give great synergy effects, especially when they are also applied in a system for phosphorus recovery.
    The detailed embodiments described above are only a few examples of how a method and an arrangement for recycling iron and aluminum can be made. In the examples described, iron and aluminum are extracted with liquid capture substances and a liquid extraction separation technique, but there are other possibilities. Iron and aluminum can be extracted from leach solutions using solid state traps with suitable separation techniques such as solid bed column procedures, etc. In summary, the embodiments described above are to be considered as illustrative examples of the present invention. One skilled in the art will appreciate that various modifications, combinations, and changes may be made to the embodiments without departing from the scope of the present invention. However, the scope of the invention is defined by the appended claims.
    权利要求:
    Claims (14)
    [1]
    A process for recovering trivalent metal from a solution, which trivalent metal is at least one of trivalent Al and trivalent Fe, comprising the steps of: providing (210) an inorganic acid solution comprising at least one of trivalent Al and trivalent Fe; extracting (220) said at least one of trivalent Al and trivalent Fe by absorption in a first capture substance; releasing (230) said at least one of trivalent Al and trivalent Fe from the first capture substance to a hydrochloric acid solution, thereby forming anionic chloride complexes; extracting (240) the anionic chloride complexes from the hydrochloric acid solution by absorption in a second capture substance; releasing (250) the anionic complexes from the second capture substance into an aqueous solution; adding (250) gaseous hydrogen chloride to the hydrochloric acid solution depleted in anionic metal chloride complexes; and reusing (270) the hydrochloric acid solution depleted in anionic metal chloride complexes in the step of releasing (230) said at least one of trivalent Al and trivalent Fe from the first capture substance.
    [2]
    The method of claim 1, characterized in that the step of extracting (220) said at least one of trivalent Al and trivalent Fe comprises controlling the pH of the first capture substance.
    [3]
    Process according to Claim 2, characterized in that the control of the pH of the first capture substance is adapted to reduce the extraction of heavy metals into the first capture substance, whereby the metal chloride complexes are substantially iron chloride complexes.
    [4]
    A method according to any one of claims 1 to 3, characterized in that the step of extracting (220) said at least one of trivalent Al and trivalent Fe comprises extracting trivalent Al by absorption in a first capture substance; and the step of adding (260) gaseous hydrogen chloride comprises adding gaseous hydrogen chloride in an amount which causes precipitation of aluminum chloride hexahydrate; which process comprises the further step of separating (262) the precipitate of aluminum chloride hexahydrate from the hydrochloric acid solution.
    [5]
    Process according to one of Claims 1 to 3, characterized in that the control of the pH of the first capture substance is adapted to reduce the extraction of trivalent Al.
    [6]
    Process according to claim 5, characterized by the further steps: extraction of trivalent Al from the inorganic acid solution depleted of trivalent Fe by absorption in a third capture substance; releasing said trivalent Al from the third capture substance to a second hydrochloric acid solution; adding gaseous hydrogen chloride to the second hydrochloric acid solution in an amount which causes precipitation of aluminum chloride hexahydrate; separating the precipitate of aluminum chloride hexahydrate from the second hydrochloric acid solution; and reusing the second hydrochloric acid solution in the step of releasing trivalent Al from the third capture substance.
    [7]
    A process for phosphorus recovery, comprising the steps of: treating (282) a phosphorus-containing material with inorganic acid, which phosphorus-containing material further contains at least one of Fe and Al; separating (284) solid and liquid phases of the treated phosphorus-containing material, thereby forming a leach solution comprising phosphate and at least one of trivalent Al and trivalent Fe; recovery (286) of trivalent metal from the leach solution according to any one of claims 1 to 6; recovery (288) of phosphate from the leach solution; and reusing (290) the leach solution depleted in trivalent metal and phosphate for the treatment step (282).
    [8]
    Process according to Claim 7, characterized in that the phosphorus-containing material is ash from the incineration of sewage sludge.
    [9]
    An arrangement (8) for recovering trivalent metal from a solution, which trivalent metal is at least one of trivalent Al and trivalent Fe, comprising: inlet (21) for an inorganic acid solution (7) comprising at least one of trivalent Al and trivalent Fe; a first ion exchange unit (20) connected to the inlet (21); said first ion exchange unit (20) arranged to extract said at least one of trivalent Al and trivalent Fe by absorption in a first capture substance (22); said first ion exchange unit (20) further arranged to release said at least one of trivalent Al and trivalent Fe from the first capture substance (22) into a hydrochloric acid solution (32), thereby forming anionic metal complexes; 22 a second ion exchange unit (40) connected to the first ion exchange unit (20); which second ion exchange unit (40) is arranged to extract the anionic metal chloride complexes from the hydrochloric acid solution (32) provided from the first ion exchange unit (20) by absorption in a second capture substance (42); said second ion exchange unit (40) is further arranged to release the anionic metal chloride complexes from the second capture substance (42) into an aqueous solution (41); recirculation unit (34) connected between the second ion exchange unit (40) and the first ion exchange unit (20); which recycle unit (34) is arranged to add gaseous hydrogen chloride to the hydrochloric acid solution depleted in anionic metal chloride complexes (33); and which recirculation unit (34) is arranged to supply the hydrochloric acid solution depleted of anionic metal chloride complexes (31) to the first ion exchange unit (20) for reuse as a stripping solution.
    [10]
    Arrangement according to claim 9, characterized in that the first ion exchange unit (20) comprises a pH control unit (29) for controlling the pH of the first capture substance (22) during extraction of said one of trivalent Al and trivalent Fe.
    [11]
    Arrangement according to claim 9 or 10, characterized in that the first ion exchange unit (20) is arranged to extract trivalent Al by absorption in the first capture substance (22); and the recirculation unit (34) is arranged to add gaseous hydrogen chloride to the hydrochloric acid solution in an amount which causes precipitation of aluminum chloride hexahydrate (37); which recycling unit (34) further comprises a separator (36) for separating said precipitated aluminum chloride hexahydrate (37) from the hydrochloric acid solution (33).
    [12]
    Arrangement according to claim 9 or 10, characterized in further comprising: a third ion exchange unit (20 ') connected to the first ion exchange unit (20 "), which third ion exchange unit (20') is arranged for extracting trivalent A1 from inorganic acid solution depleted on trivalent Fe provided from the first ion exchange unit (20 ") by absorption in a third capture substance (22 '); said third ion exchange unit (20 ') is further arranged to release said trivalent Al from the third capture substance (22') into a second hydrochloric acid solution (32 '); a second recirculation unit (34 ') connected to the third ion exchange unit (20'); which second recirculation unit (34 ') is arranged to add gaseous hydrogen chloride to the second hydrochloric acid solution (33') in an amount which causes precipitation of aluminum chlorohexahydrate (37 '); Which second recirculation unit (34 ') further comprises a second separator (26') for separating said precipitate of aluminum chloride hexahydrate (37 ') from the second hydrochloric acid solution (33'); and which second recycle unit (34 ') is arranged to supply the second hydrochloric acid solution (31') to the third ion exchange unit (20 ') for reuse as a stripping solution.
    [13]
    Arrangement (100) for phosphorus recovery, comprising: dissolution unit (4), arranged for treatment of a phosphorus-containing material with inorganic acid, which phosphorus-containing material further contains at least one of Fe and Al; a dissolution separator (6) connected to the dissolution unit (4) and arranged to separate solid and liquid phases of the treated phosphorus-containing material, thereby forming a leach solution (7) comprising phosphate and at least one of trivalent Al and trivalent Fe; an arrangement (8) for recovering trivalent metal from the leach solution (7) according to any one of claims 101 to 105; an arrangement (10) for recovering phosphate from the leach solution; and recirculation arrangement (3) arranged for recirculation of the leach solution depleted of trivalent metal and phosphate (11) to the dissolution unit (4).
    [14]
    Arrangement according to Claim 13, characterized in that the phosphorus-containing material is ash from the incineration of sewage sludge.
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    同族专利:
    公开号 | 公开日
    SE534505C2|2011-09-13|
    WO2011025440A1|2011-03-03|
    引用文献:
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    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    SE0950622A|SE534505C2|2009-08-31|2009-08-31|Recycling of aluminum from phosphorus-containing materials|SE0950622A| SE534505C2|2009-08-31|2009-08-31|Recycling of aluminum from phosphorus-containing materials|
    PCT/SE2010/050899| WO2011025440A1|2009-08-31|2010-08-20|Recovery of al from p-containing material|
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