METHOD FOR SEPARING PHOSPHORUS AND / OR PHOSPHORUS COMPOUNDS FROM IRON(OXIDE)-CONTAINING PHOSPHORUS AND / OR PHOSPHATE CARRIERS

Description

[0001] The invention relates to a method for separating phosphorus and / or phosphorus compounds from iron(oxide)-containing phosphorus and / or phosphate carriers, and to devices for carrying out such a method.

[0002] Publications JP 2001-198546 A, CN 101659406 A, EP 2 428 493 A1 and WO 2018 / 122599 A1 relate to the subject matter of the present invention.

[0003] Elemental iron-phosphorus carriers (iron phosphides or ferrophosphides) are formed, for example, in the Wähler process during the processing of apatite or during the reduction of phosphate-rich melts in a carbonaceous iron bath (as described, for example, in WO 2005 / 113840 A1). Ferrophosphides are also formed during the processing of organic waste materials with the addition of chlorine carriers and subsequent substoichiometric combustion to oxidize the waste materials to form metal chlorides and reduce the remaining fraction to obtain elemental phosphorus, as described in EP 2 640 531 B1. Iron (oxide)-containing phosphate carriers are also generated in large quantities in industry and especially in municipal wastewater treatment plants, and their disposal is becoming an increasing problem.

[0004] The inventive process for separating phosphorus and / or phosphorus compounds from such iron (oxide)-containing phosphorus and / or phosphate carriers is particularly suitable for processing sewage sludge and sewage sludge ash, animal meal and animal meal ash, liquid manure, food waste, flame-retardant plastics, pharmaceuticals, metallurgical slags, lubricant residues, used lithium-ion batteries and electronic waste by separating the phosphorus and / or its compounds from the aforementioned phosphate carriers, whereby the phosphorus content can be used for further processing in the chemical industry, for example for the production of fertilizers or phosphoric acid, and the iron content can be used, for example, in the cement industry or for iron production.

[0005] Cement plants in particular are increasingly being required by law to utilize sewage sludge and sewage sludge ash, creating a need to efficiently and safely process waste materials such as sewage sludge and similar substances.

[0006] To solve this problem, the method according to the invention comprises at least the following steps: a) Melting metallurgical reduction of the iron(oxide)-containing phosphorus and / or phosphate carriers to form slag melt and a melt of iron phosphides, in particular FeP, Fe2P and / or Fe3P, and b1) Oxidation of the melt of iron phosphides in the presence of Ca and Al carriers to form gaseous P2O5 and lime-aluminium-iron compounds, in particular brownmillerite, and / or b2) Melting metallurgical reaction of the melt of iron phosphides in the presence of elemental sulfur and / or sulfur carriers to form iron sulfides and elemental phosphorus.

[0007] The melt metallurgical processes of reduction according to step a) are preferably carried out in or on an inductively heated retort made of carbon supports, i.e. a column of carbon supports such as coke, charcoal or lumpy graphite.

[0008] Whenever the present application refers to phosphorus, phosphate, phosphate slag, phosphate carriers and the like, in case of doubt, this generally means phosphorus in different modifications and oxidation states.

[0009] In the metallurgical reduction process according to step a), the phosphorus content (phosphorus and / or phosphate) is reduced to iron phosphides (ferrophosphorus), and the remaining iron is converted to a cement-compatible slag melt. The slag melt is separated from the iron phosphides, and the iron phosphides are subsequently subjected to metallurgical oxidation of the iron phosphide melt with calcium and aluminum carriers to achieve the most complete possible separation of the phosphorus content from the iron content. This oxidation process produces volatile P₂O₅ (gaseous). Furthermore, the calcium and aluminum carriers, together with the iron content, form calcium-aluminum-iron compounds, and in particular, brownmillerite. These calcium-aluminum-iron compounds exhibit no chemical affinity for phosphorus, thus ensuring complete separation.Calcium and aluminum carriers must be added if calcium (Ca) and aluminum (Al) are not already present in the process. For example, the slag melt formed in step a) typically consists largely of calcium silicates and can therefore be used as a calcium carrier in step a). In the additional or alternative reaction of the iron phosphide melt with elemental sulfur and / or sulfur carriers, iron sulfides and elemental phosphorus are formed, with the elemental phosphorus again showing no affinity for the insoluble iron sulfides. In an additional or alternative, non-inventive oxidation of the iron phosphide melt in the presence of oxygen, iron oxides and P₂O₅ are formed, with P₂O₅ again showing no affinity for the iron oxides at a temperature of at least 1100°C.If oxygen is present only in substoichiometric amounts for this reaction, P₂ is additionally formed. Thus, in all mechanisms under step b1) or b2) of the process according to the invention, chemical iron species are formed that have no affinity for the respective phosphorus fractions.

[0010] The process according to the invention makes it possible to form a cement-compatible product, which contains no phosphorus, through the oxidative reaction of the molten iron phosphides with calcium and aluminum supports according to step b1), and, on the other hand, to form gaseous P₂O₅, which can subsequently be used for further phosphorus modifications. Therefore, valuable materials for both the cement and chemical industries are recovered from the aforementioned waste materials using the process according to the invention, so that a synergistic and economically profitable processing method is provided under future legal regulations for the acceptance of sewage sludge by cement plants.Alternatively or additionally, highly reactive but economically valuable elemental phosphorus can be directly obtained through the metallurgical reaction of molten iron phosphides in the presence of elemental sulfur and / or sulfur carriers. This reaction can be understood as an oxidative anion exchange with sulfur as the oxidizing agent, in the sense that the iron in the iron phosphides releases its phosphorus in favor of the sulfur. At the same time, iron sulfides are regenerated and made available for the reaction of the molten iron phosphides. The redox reaction with sulfur can be described, for example, as follows: 2e -< + S 0< → S 2-< (Reduktion des Schwefels) P 3< - → P 0< + 3e -< (Oxidation des Phosphors) bzw. P 5-< → P 0< + 5e -<

[0011] Alternatively, the iron sulfides can be reacted with oxygen to form iron oxide for the steel industry and sulfur dioxide, whereby the sulfur dioxide is in turn available for the melt metallurgical conversion (step b2) of the melts from step a) to iron sulfides and elemental phosphorus.

[0012] While the iron phosphides formed in reduction step a) are in equilibrium with the calcium-aluminum-iron compounds during the oxidation of the melt of iron phosphides in the presence of Ca and Al carriers to form P2O5 and calcium-aluminum-iron compounds, the reaction (oxidation) in the presence of elemental sulfur and / or sulfur carriers (sulfur compounds) results in a quantitative release of elemental phosphorus.

[0013] According to a preferred embodiment of the present invention, the P₂O₅ formed in step b1) is fed to step a) to form elemental phosphorus. In this case, the P₂O₅ formed is again fed to reduction step a) and reduced there to elemental phosphorus.

[0014] In step a), it is preferred that coal dust and oxygen are used at a substoichiometric combustion oxygen ratio, preferably at a combustion oxygen ratio of λ =0.2 to λ =0.8, preferred λ =0.4, thereby reducing the consumption of relatively expensive carbon carriers such as metallurgical coke, graphite, or charcoal, which are required as inductively coupled carbon carriers in the inventive process as a melt metallurgical process in an inductively heated retort. Depending on the combustion oxygen ratio and the reaction temperature at which the reduction is carried out, the coal dust is oxidatively gasified to carbon monoxide and is thus available for energy generation by combustion.

[0015] It is further preferred to supply elemental hydrogen in step a), which can advantageously provide approximately one-third of the total required reduction potential. During the reduction to water, the hydrogen is oxidized and can subsequently react with carbon in an endothermic reaction to form carbon monoxide and, again, hydrogen (heterogeneous water-gas reaction). The hydrogen can thus be regenerated for the reduction of the iron(oxide)-containing phosphorus and / or phosphate carriers, and due to the endothermic nature of the reaction of water with carbon to form carbon monoxide and hydrogen, the cooling requirement of the process gas in the process according to the invention can be reduced and utilized effectively.

[0016] To keep the slag melt as fluid as possible during the reduction, the process according to the invention is preferably further developed in such a way that in step a) the basicity (CaO / SiO 2 ) of the slag melt is adjusted to a value of 0.75 to 1.45, preferably 0.8 to 1.4, by adding Ca carriers and / or Si carriers.

[0017] The aforementioned iron(oxide)-containing phosphate carriers often contain a number of undesirable and problematic accompanying substances, which must be removed before the reduction step for waste management reasons and also to prevent blockages and chemical cycles in the reduction devices. The process according to the invention is therefore preferably further developed in such a way that, prior to the reduction according to step a), a pre-oxidation of accompanying substances of the iron(oxide)-containing phosphorus and / or phosphate carriers takes place, such as organics, heavy metals, halogens, alkalis, and sulfur compounds, forming a melt of the iron(oxide)-containing phosphorus and / or phosphate carriers and drawing off the gas phase containing the accompanying substances, wherein the melt of the iron(oxide)-containing phosphorus and / or phosphate carriers is subjected to the reduction according to step a).

[0018] For pre-oxidation in the case of processing sewage sludge with a dry matter content of approximately 65%, oxidation is carried out with the addition of lime carriers, in particular limestone, bone meal, steel slag and / or cement kiln bypass dust, wherein the pre-oxidation takes place in a combustion chamber with the introduction of the iron (oxide)-containing phosphorus and / or phosphate carriers by means of an oxygen-containing gas, as corresponds to a preferred embodiment of the present invention. The combustion oxygen ratio is preferably λ =0.8 to λ =1.2. The melt of the iron(oxide)-containing phosphorus and / or phosphate carriers is separated at a temperature of approximately 1500°C, and the gas phase containing the accompanying substances is drawn off at approximately 1600°C. Depending on the starting material, the exhaust gas contains H₂O, CO₂, CO, H₂, N₂, NOₓ, heavy metal vapors, chlorine and chlorides and other halogens or halides, alkalis, especially sodium, lithium, and potassium, SO₂, and the like.

[0019] To utilize the exergy, i.e., the sensible heat, of the hot exhaust gas, the process according to the invention is preferably further developed by subjecting the gas phase containing the accompanying substances to a cooling step by bringing the gas phase into contact with organic waste, such as waste plastics, electrical and electronic waste, biomass, digestate, and shredder light fraction, and / or by bringing the gas phase into contact with limestone, marl, cement clinker meal, and / or kaolin. This cooling step utilizes the heat from the pre-oxidation exhaust gas to process further waste materials, with the complete conversion of the waste materials preferably taking place in a entrained-flow gasifier. Alternatively or additionally, the heat from the pre-oxidation exhaust gas can preferably also be used for the calcination of limestone, marl, cement clinker meal, and / or kaolin.

[0020] The exhaust gas temperature is preferably reduced to approximately 600°C, after which the exhaust gas from the cooling step is preferably used for steam generation and solid residues of gaseous H₂ and / or CO are filtered out. The filtered residues can include zinc, copper, cadmium, mercury, lead, chlorine, sodium, SOₓ, alkalis, alkaline earth metals, and the like, and are collected in the filter as a concentrate and can be further purified according to processes known in metallurgy. H₂ and CO form so-called synthesis gas, which can be used in a known manner by combustion or as a metallurgical reducing agent, as well as for methanol synthesis or in Fischer-Tropsch synthesis, or also in a partial cycle for reduction in the reduction step according to step a) of the process according to the invention.

[0021] Alternatively, the exhaust gas from the cooling step can be converted to H2 and CO2 in a water-gas shift reaction, and solid residues of H2 and CO2 can be filtered out, whereby the residues are again obtained as a concentrate, as described above, and H2 and CO are obtained as synthesis gas.

[0022] The pre-oxidation step can be separated from the reduction and oxidation steps according to the invention by cooling and preferably granulating the melt of the iron(oxide)-containing phosphorus and / or phosphate carriers before the reduction of step a), as corresponds to a preferred embodiment of the process according to the invention. In this way, the hot phosphate slag melt becomes a solid intermediate that is easy to handle and can also be further processed at another location if handling phosphorus, particularly in elemental form, is not desired or possible at the site of receipt of iron(oxide)-containing phosphate carriers, such as sewage sludge, for regulatory reasons. The cooling and preferably granulation of the melt can, for example, be carried out on a tin bath, as described in AT 521769 A1.

[0023] According to a preferred embodiment of the present invention, the reduction according to step a) is carried out using a reductive column made of carbon carriers, preferably coke, charcoal, graphite and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds, for the iron(oxide)-containing phosphorus and / or phosphate carriers. Such reductive columns made of carbon carriers are already known in the art and are maintained at high temperatures for melt metallurgical reduction, for example inductively. Depending on the process, carbon may need to be continuously replenished to compensate for losses due to gasification processes and the actual reduction processes.

[0024] Preferably, the reductive column is maintained at reaction temperature by blowing in oxygen, whereby the oxygen is, of course, only blown in an amount that is conducive to maintaining the reaction temperature but does not impair the reduction potential of the carbon column for the phosphate and iron (oxide) fractions. Alternatively, it is also preferred that the reductive column is maintained at reaction temperature by electromagnetic induction, as corresponds to a preferred embodiment of the present invention.Induction can be chosen in addition to the injection of oxygen or as the sole means of maintaining the high temperatures required for the reduction processes, whereby inductive heating of the carbon column leads to a higher yield of elemental phosphorus by reducing the proportion of CO and increasing the P2 partial pressure in the process gas.

[0025] Preferably, the reaction products of the reduction according to step a) are P4 and CO in the gas phase, as well as the melt of iron phosphides and the slag melt at the bottom of the column, whereby, as already mentioned, the proportion of CO can be higher or lower depending on how the reaction temperature in the reductive column is maintained. In this embodiment, a portion of the phosphorus or phosphates is thus obtained as elemental phosphorus in the gas phase, separated from the iron components, already in the reduction step.

[0026] In addition to the possibility of carrying out the oxidation of the iron phosphides with elemental oxygen or sulfur directly in the melt bath or in a separate metallurgical ladle by blowing in O₂ or sulfur via lances or bottom nozzles, whereby sulfur can be introduced both as a solid and as sulfur vapor, with regard to steps b1) and / or b2) of the process according to the invention, a preferred embodiment of the present invention proceeds in such a way that steps b1) and / or b2) are carried out in a fluidized-flow reactor by atomizing the melt of iron phosphides by means of a gas stream, preferably consisting of or containing oxygen carriers such as O₂, H₂O, air and / or CO₂, and preferably with the addition of Ca and Al carriers and / or elemental sulfur and / or sulfur carriers.As in step a), the aim is to achieve fine atomization of the reactants to be oxidized, so that the iron phosphides are present with the largest possible surface area in the oxidizing environment of the entrained-flow reactor and come into intensive contact with the added calcium and aluminum carriers or the elemental sulfur and / or the sulfur carriers. An entrained-flow reactor for use in this oxidation step is shown, for example, in Austrian patent AT 518 979 B1, although the disclosure therein must be adapted with regard to the addition of calcium and aluminum carriers or the elemental sulfur and / or the sulfur carriers. However, it is essential that the molten iron phosphides are drawn from a tundish or a refractory-lined storage container.a casting ladle can be discharged via a spout, which for example includes a weir pipe, into a fluidized bed reactor, wherein, in contrast to the disclosure of AT 518 979 B1, in the present process oxidizing conditions are set by adding O 2 or oxygen carriers such as air, O 2 or H 2 O or sulfur, and the necessary selectivity of the process for separating the phosphorus compounds from the iron compounds is ensured by further addition of Ca and Al carriers and / or elemental sulfur and / or sulfur carriers.

[0027] The process according to the invention is preferably designed such that P₂O₅ is separated from lime-aluminum-iron compounds, in particular brownmillerite, as reaction products of the oxidation according to step b1). As already mentioned, the lime-aluminum-iron compounds, and in particular brownmillerite, have no chemical affinity for P₂O₅, so that a quantitative separation of these compounds from the phosphorus components takes place. Phosphorus and phosphorus oxides can subsequently be further processed according to known methods, and the lime-aluminum-iron compounds can, for example, be incorporated into Portland clinker as sintering aids in the cement industry.

[0028] The process according to the invention is further preferably designed such that iron sulfides are separated from elemental phosphorus as reaction products of the reaction according to step b2). The iron sulfides have no affinity for the elemental phosphorus, so that a quantitative separation of these compounds from the phosphorus fractions takes place.

[0029] Preferably, the separation of P₂O₅ from calcium-aluminum-iron compounds and / or the separation of iron sulfides from elemental phosphorus is carried out using a cyclone. This also represents a different procedure than that shown in Austrian patent AT 518 979 B1, but does not pose a significant problem for a person skilled in the art. For example, this can also be carried out externally in an oxidizing melt bath, as described above.

[0030] As an alternative to carrying out the oxidation step according to step b1) in an entrained-flow or direct oxidation reactor, step b1) can preferably also be carried out in such a way that the oxidation of the melt of iron phosphides to P₂O₅ and the formation of calcium-aluminum-iron compounds, in particular brownmillerite, takes place in a bottom region of the reductive column by blowing a gaseous oxygen carrier, preferably containing at least one aluminum carrier, through the melt of iron phosphides and thus reacting the iron phosphides with slag melt from step a) floating on the melt of iron phosphides to form P₂O₅ and calcium-aluminum-iron compounds, preferably brownmillerite.are brought into contact. In this case, the reductive column is reductive for the phosphate and iron(oxide) components in the area where the iron(oxide)-containing phosphorus and / or phosphate carriers are introduced, and retains these reductive properties in a section extending downwards from the introduction area for the complete conversion of the phosphate and iron(oxide) components to form the melts of iron phosphides and slag. Only at the bottom of the column is an oxidizing environment for the iron phosphides created by blowing in oxygen carriers. This blowing in results in a mechanical mixing of the melts of iron phosphides and the slag melt, and in this way, in the presence of aluminum carriers, the slag melt is converted to calcium-aluminum-iron compounds, especially brownmillerite, which, as already mentioned several times,exhibits no chemical affinity for the phosphorus fractions oxidized to P₂O₅ by the injection of oxygen carriers. The oxidation of the molten iron phosphide to P₂O₅ is preferably carried out at temperatures of at least 1350°C. The selective separation of P₂O₅ and its compounds from the lime-aluminum-iron compounds thus takes place in a single, continuously operable process step. The P₂O₅ formed subsequently flows into the reductive column and is reduced there to P₂. An excess of O₂ can be used at this stage.

[0031] According to a preferred embodiment of this alternative process according to the invention, P₂O₅ is converted to P₂ and CO in the reductive column, and the P₂ and CO are withdrawn in the gas phase when the P₂O₅ formed at the bottom of the column rises in the reductive column further up and is reduced there to elemental phosphorus. By appropriately adding O₂ to the reductive column, which, as already mentioned, may also be necessary to maintain a suitable reaction temperature, the proportions of P₂ and CO in the gas phase can be adjusted over a certain range.

[0032] According to a first alternative, a device according to the invention for carrying out the method according to the invention is for processing, if applicable,granulated, melt of the phosphate and iron(oxide) components, as described above, is designed in such a way that it comprises a refractory-lined, longitudinally symmetrical or rotationally symmetrical housing and a column arranged in the housing, which is reductive for the iron(oxide)-containing phosphorus and / or phosphate carriers, preferably made of inductively heated carbon carriers, preferably of coke, graphite and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds, wherein the housing has a region along the longitudinal axis with a discontinuous increase in diameter forming an annular space between the housing and the column, wherein the device according to the invention is characterized in that at least one feed device for melts of the iron(oxide)-containing phosphorus and / or phosphate carriers opens into the annular space in the region of the discontinuous increase in diameter.The melts of the iron(oxide)-containing phosphorus and / or phosphate carriers are also referred to as pre-slag melts in connection with the present invention. This device according to the invention thus provides a reactor with a reductive column arranged therein, which, due to the abrupt increase in diameter, provides an annular space into which the melt of the iron(oxide)-containing phosphorus and / or phosphate carriers from the pre-oxidation can be introduced for reduction. The surface of the column in the annular space below a compact section of the column, which serves as a preheating zone for the carbon carriers and optionally for granulated, oxidized pre-slag melt, can thus be considered a reduction hearth, at or in which the reactants introduced in solid or molten form, namely the melts of the iron(oxide)-containing phosphorus and / or phosphate carriers, are optionally melted and reduced upon entering the column.Due to gravity, the iron phosphides and their precursors migrate downwards in the column and are completely reduced, accumulating at the bottom. To compensate for carbon losses due to gasification and reduction reactions, coke, graphite, or similar carbon carriers, as previously described, are introduced at the top of the device according to the invention, i.e., at the top of the compact section of the reductive column. These carriers are preheated and heated by the gasification processes in this region, so that the necessary reaction temperature for reduction is already available in the annular space. In addition to preheating, endothermic reactions take place in this compact section of the reductive column, such as pre-reduction of the reactants or heterogeneous water-gas reactions.

[0033] To ensure the distribution of solid and / or molten phosphate and iron oxide fractions on the surface of the reductive column in the region of the aforementioned reduction focus, the at least one feeding device can be equipped with a plurality of nozzles arranged radially in the region with a rapidly increasing diameter and directed tangentially into the annular space for the introduction of an oxygen-containing gas and preferably coal dust, as corresponds to a preferred embodiment of the present invention. The oxygen-containing gas introduced through the nozzles, optionally mixed with coal dust or sewage sludge ash, ensures a uniform shearing or distribution of the powdery or molten reactants in the annular space, so that they are distributed throughout the entire annular space and thus uniformly applied to the reductive column.In this way, blockages, caking and the formation of chimneys in the reductive column are avoided, and a uniform and effective reduction of the solid or molten starting materials is ensured.

[0034] To ensure uniform flow conditions along the entire length of the device according to the invention, a preferred embodiment of the present invention provides for a central cylinder to form an annular column in the region with the increased diameter. The arrangement of a central cylinder to form an annular column prevents, firstly, the reductive column from having a significantly increased effective cross-section for the passage of reaction gases in the region after the abrupt increase in diameter, which may be necessary for establishing uniform and thus defined pressure conditions throughout the entire device according to the invention. Secondly, it reduces the overall requirement for carbon supports in the device according to the invention, since, of course, no carbon supports need to be provided within the volume of the central cylinder.Furthermore, the carbon supports can only be heated by induction to a certain radial depth, so the formation of an annular column ensures uniform heating of the carbon supports by induction. The cylinder is preferably made of the same material as the housing itself and is, of course, also lined with a refractory material. The cylinder is covered at its upper end and preferably has a conical or hemispherical cover.

[0035] In order to adjust the reduction conditions and to maintain the necessary reaction temperature in the region of the annular column, a preferred embodiment of the present invention may provide that the central cylinder has a plurality of openings for blowing an oxygen-containing gas into the annular column.

[0036] According to a preferred embodiment of the present invention, an induction device may further be arranged in the central cylinder. This serves to additionally heat the reductive column inductively from the inside, which may be necessary for a correspondingly large column.

[0037] Preferably, a further area with a rapidly increasing diameter is arranged at the bottom of the housing, forming an annular space between the housing and the annular column. This area is designed for tapping or drawing off melts, preferably into a forehearth for separating the melts. This further area with its rapidly increasing diameter thus forms a kind of tundish, melting cup, or casting ladle at the bottom of the housing or annular column and serves to collect and capture the reaction products formed during the reduction.

[0038] As already described in connection with a preferred embodiment of the method according to the invention, steps b1) and b2) of the method according to the invention can be integrated in this device according to the invention if the further area with a rapidly increased diameter is formed with nozzles for blowing an oxygen-containing gas, preferably with at least one aluminum support, through the melt of iron phosphides, as corresponds to a preferred embodiment of the present invention.In this single-stage variant, the oxidation of the iron phosphides takes place at the bottom of the column, which is otherwise reductive for phosphate components. The iron phosphides come into contact with the slag melt above, which is mixed with aluminum supports if necessary, thereby forming the selective lime-aluminum-iron compounds, especially brownmillerite, and P2O5 rises through the column and is reduced to P2 and CO.

[0039] According to a preferred embodiment of the present invention, the further section with a significantly increased diameter can be equipped with nozzles for blowing elemental hydrogen through it. In this preferred variant, the reduction potential of the reductive column can thus be adjusted accordingly, as already described above, and in particular up to one-third of the reduction potential intended for the reduction can be provided by hydrogen.

[0040] Another preferred embodiment of the present invention provides that a plurality of refractory-lined, tubular housing sections, each symmetrical along a longitudinal axis, are connected to the section with the enlarged diameter. These tubular sections contain reductive columns for the iron(oxide)-containing phosphorus and / or phosphate carriers, consisting of carbon carriers, preferably coke and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds. This means that the reductive column is divided into a plurality of individual reductive columns, thereby providing a relatively high reduction rate with simultaneously small diameters of the reductive carbon carrier bed. The preferred diameter of the tubular housing sections is between 600 mm and 1000 mm to ensure satisfactory coupling by induction of the individual columns.This has advantages regarding the flow conditions in the individual reductive columns, and also allows the individual columns to be heated inductively, ensuring sufficiently high reaction temperatures even at high throughputs.

[0041] For this purpose, the tubular parts of the housing can each be enclosed by an induction coil, as is the case in a preferred embodiment of the present invention. In this way, a large total amount of the reductive column can be inductively heated.

[0042] An alternative apparatus for carrying out the method according to the invention comprises a refractory-lined housing and a column made of carbon carriers, preferably coke and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds, arranged in the housing and preferably inductively heated for the iron(oxide)-containing phosphorus and / or phosphate carriers, and is characterized according to the invention in that the housing has a step, preferably a bend, along its longitudinal axis, forming a cavity between the housing and the column, wherein at least one feed device for liquid melt of the iron(oxide)-containing phosphorus and / or phosphate carriers opens into the cavity in the area of ​​the step.This variant of an apparatus according to the invention for carrying out the method according to the invention thus represents a modification of the previously described variant of a reduction reactor with a significantly increased diameter of the housing, in which, however, no annular space is formed, but only a cavity is formed in the area of ​​the step between the housing and the reductive column, into which molten products of the pre-oxidation, and thus liquid reactants of the reduction, can be applied to the surface of the reductive column, whereby a reduction focus is formed in the same way on the surface of the column, in which the phosphate components are reduced to iron phosphides and move downwards through the column due to gravity and collect at the bottom. In the area above the step, a preheating zone for the carbon supports and, if applicable,Phosphate slag granules are provided, as already described in connection with the preceding device according to the invention. Thus, lumpy carbon supports and solid phosphate slag granules can be introduced into this area.

[0043] To maintain the required reaction temperature for the reduction, the housing preferably has a plurality of openings for injecting an oxygen-containing gas into the column or the carbon bed, thereby maintaining endothermic reduction processes in the carbon bed of the reductive column. Alternatively or additionally, according to a preferred embodiment of the present invention, an induction device for the reductive carbon bed of the reductive column may be arranged in the area below the offset of the housing.

[0044] According to a preferred embodiment of the present invention, a further offset of the housing is arranged at the bottom of the housing, forming a cavity between the housing and the column, which is designed for withdrawing or tapping off melts, preferably into a forehearth for separating the melts.

[0045] Preferably, nozzles for blowing a gaseous oxygen carrier, preferably interspersed with at least one aluminum carrier, through the melt of iron phosphides are arranged in the area of ​​the further offset. This offers the possibility, as already described above, of carrying out the oxidation in the presence of Ca and Al carriers with the otherwise reductively configured carbon carrier bed in the device.

[0046] Alternatively or additionally, the further area with a significantly increased diameter can be equipped with nozzles for blowing elemental hydrogen through it, as corresponds to a preferred embodiment of the present invention. In this way, as already described above, elemental hydrogen can be supplied to the reduction step of the iron(oxide)-containing phosphorus and / or phosphate carriers, advantageously providing approximately one-third of the total required reduction potential. During the reduction of the iron(oxide)-containing phosphorus and / or phosphate carriers to water, the hydrogen is oxidized and can subsequently react with carbon in an endothermic reaction to form carbon monoxide and, again, hydrogen.The hydrogen can thus be regenerated to reduce the iron(oxide)-containing phosphorus and / or phosphate carriers, and due to the endothermic nature of the reaction of water with carbon to carbon monoxide and hydrogen, the cooling requirement of the process gas of the process according to the invention can be reduced.

[0047] A further device according to the invention for carrying out the process according to the invention is intended to serve to bring the melts formed in the pre-oxidation step, the melting step or in step a) of the process according to the invention to the reduction device or to receive them from the reduction device, so that the melt can be transferred to another location for step b1) or b2) of the process according to the invention, for example to the location of the operation of the entrained flow reactor for the oxidation of the melts to form P 2 O 5 and calcium-aluminum-iron compounds and / or for reaction in the presence of elemental sulfur and / or sulfur carriers to form iron sulfides and elemental phosphorus.This is because, in the process according to the invention, elemental phosphorus can be formed in steps a) and b2), which is in itself highly problematic to handle. Therefore, it may be desirable to be able to separate the locations of the individual process steps and to maintain or adjust the required temperatures of the melts during transport between these locations. Additionally, it may be desirable to be able to selectively control the slag chemistry.

[0048] For this reason, the device according to the invention for receiving melts preferably comprises a refractory-lined housing rotatably mounted about a pivot axis, with at least one induction device spanning a portion of the housing and at least one opening opposite the at least one induction device. The melts can be received in this device and kept at temperature by means of an inductively heated tin bath held in the device in the region of the induction device, in order to subsequently be reduced or subjected to step b1) or b2) in the entrained flow reactor. The tin melt of the tin bath is maintained at temperatures of approximately 1500°C to 1600°C and exhibits no affinity for the iron phosphates of the oxidized pre-melt (phosphate melt) or for the iron phosphides.

[0049] Preferably, at least one opening for blowing in purge gas, preferably nitrogen, is arranged in the area of ​​the induction device, whereby superheated tin droplets from the tin bath are driven into the melt of iron phosphides. Due to the very large interface between the tin droplets and the melt of iron phosphides, very efficient heat transfer from the superheated tin to the melt of iron phosphides takes place.

[0050] Likewise, in this device according to the invention, the temperature and / or the chemical properties of the slags or melts can be adjusted.

[0051] The invention is explained in more detail below with reference to an exemplary embodiment schematically illustrated in the drawing. This shows Fig. 1 an overview scheme of the method according to the invention, Fig. 2 a first variant of a device according to the invention for carrying out the method according to the invention, Fig. 3 a second variant of a device according to the invention for carrying out the method according to the invention, Fig. 4 a device for carrying out step b1) or b2) of the method according to the invention, Fig. 5 a preferred further development of the first variant of the device according to Fig. 2 , Fig. 6a a third variant of a device according to the invention for carrying out step a) of the method according to the invention in longitudinal section and Fig. 6b a cross-section of the device according to Fig. 6a and Fig. 7 a device according to the invention for receiving the melt of iron phosphides or the oxidized phosphate slag melt formed in step a).

[0052] In the scheme according to Fig. 1 It can be seen that the iron(oxide)-containing phosphorus and / or phosphate carriers can, in a first step, either undergo optional pre-oxidation to remove accompanying substances such as organics, heavy metals, alkalis, halogens, sulfur compounds, and the like, or be directly subjected to reduction. If the iron(oxide)-containing phosphorus and / or phosphate carriers include sewage sludge or dried sewage sludge, animal meal and animal meal ash, or food waste, pre-oxidation is recommended in any case. The exhaust gas from the pre-oxidation can, as described above, be cooled by contacting it with organic waste, such as plastics, biomass, and similar materials. The cooled exhaust gas is then filtered, removing residual substances such as heavy metals, halogens, alkalis, sulfur compounds, and the like.The cooled gas can be separated from the iron(oxide)-containing phosphorus and / or phosphate carriers, which can be used as synthesis gas for energy production, as a reducing agent, or as a raw material for the chemical industry (Fischer-Tropsch synthesis, methanol production). After optional pre-oxidation, the melt of the iron(oxide)-containing phosphorus and / or phosphate carriers is optionally subjected to cooling and preferably to granulation, or the melts are directly fed to reduction. A key aspect of the invention is that the iron(oxide)-containing phosphorus and / or phosphate carriers are subjected to reduction, whereby, with the addition of carbon carriers, P₂ / P₄ and CO as well as H₂ are formed in the gas phase, and an iron phosphide melt and a slag melt are also formed. The slag melt can then be granulated, and the heat generated in this process can again be used for energy production.Likewise, the exergy of the slag can preferably be used to produce charcoal, thereby potentially covering the entire carbon requirement of the reduction step. This results in an extremely favorable CO₂ balance for the process according to the invention. The iron phosphide melt can subsequently be subjected to oxidation according to step b1), whereby P₂O₅ is formed in the gas phase and the iron content of the iron phosphide melt is converted to calcium-aluminum-iron compounds, and in particular brownmillerite, due to the addition of aluminum carriers and optionally calcium carriers, if calcium is not already present, for example in the form of the slag melt. These can then be incorporated into Portland clinker. Alternatively or additionally, the melts can be converted to iron sulfides and elemental phosphorus in the presence of elemental sulfur and / or sulfur carriers.Alternatively or additionally, the melts can be converted to iron oxides and P2O5 in the presence of oxygen.

[0053] As from Fig. 2 As can be seen, a first embodiment of a device 1 according to the invention for carrying out the method according to the invention comprises a housing 2 in which a reductive column 3 made of carbon supports is arranged for the iron(oxide)-containing phosphorus and / or phosphate supports. The housing 2 has a region 5 with a discontinuously increased diameter along the longitudinal axis 4, thereby forming an annular space 6 between the housing 2 and the column 3. This creates the possibility in the region 5 to construct a Fig. 5 The illustrated feed device 7 is designed for feeding melts of iron(oxide)-containing phosphorus and / or phosphate carriers into the annular space 6. The feed device 7 is supplemented by a plurality of nozzles 8 arranged radially in region 5 with a significantly increased diameter and directed tangentially into the annular space for an oxygen-containing gas and optionally coal dust or sewage sludge ash. A central cylinder 9 is arranged in the region 5 with the increased diameter, which is lined with a refractory material inside the device 1. The column 3 is therefore extended to an annular column 3' in this region. An induction device is designated by reference numeral 34. A further region 11 with a significantly increased diameter is arranged at the bottom 10 of the housing 2, which serves for drawing off or tapping off melt, preferably into a forehearth 12 for separating the melts.Nozzles 13 can be arranged at the bottom 10 of the column for blowing an oxygen-containing gas through the molten iron phosphide 14, which may preferably be mixed with an aluminum support. In this way, the molten iron phosphide 14 is brought into contact with the overlying slag melt 15, enabling the oxidation to P₂O₅ and the formation of calcium-aluminum-iron compounds, preferably brownmillerite, to take place in this apparatus. The P₂O₅ rises in gaseous form through the annular column 3' and the column 3 and is converted there to P₂. P₂ and CO can be drawn off at the fume hood 16 of the apparatus 1. Reference numeral 17 designates a feed device for carbon carriers, such as coke, and phosphate slag granules.

[0054] In Fig. 3 Identical parts are provided with the same reference numerals, and a variant of an apparatus 1 according to the invention for carrying out the method according to the invention is shown. The apparatus 1 is again formed by a housing 2 and a reductive column 3 arranged therein for the iron(oxide)-containing phosphorus and / or phosphate carriers, wherein the housing 2 has a projection 18 along its longitudinal axis 4, whereby a cavity 6 is formed between the housing 2 and the column 3. For better clarity, in Fig. 3 No induction device is apparent, however one can be used analogously. Fig. 2 The device is provided for heating the reductive column 3. Reference numeral 19 designates a feed device for preferably molten reactants of the reduction, which molten reactants, i.e., the melt of the iron(oxide)-containing phosphorus and / or phosphate carriers, can be applied to the column 3. After the reduction, the melt of the iron phosphides 14 and the slag melt 15 collect again at the bottom 10 of the housing 2 and the column 3, respectively, and can either be drawn off into a forehearth (not shown) or, as previously described, brought into contact with each other by blowing an oxygen-containing gas through the melts 14 and 15 from nozzles 13, to form P₂O₅ and calcium-aluminum-iron compounds. The P₂O₅ rises again in gaseous form through the reductive column 3 and can be drawn off at the fume hood 16 after conversion to P₄ together with CO. Consumed carbon is replaced via the feed device 17.The addition of solid, possibly granulated, phosphate slag granules can also take place at the feed device 17.

[0055] In Fig. 4 A fluidized-flow gasifier 20 for the separate conversion of iron phosphides according to steps b1), b2), and b3) is shown. The fluidized-flow gasifier 20 has a tundish or ladle 21 for the melts 14 and 15, wherein a weir tube 21' can be lowered into the tundish 21 to form an annular gap 22 for the passage of the melts 14 and 15 into a direct oxidation reactor. The wall 24 of the oxidation device can be cooled by an airflow, which is operated by means of a fan 25, wherein the heated and thereby expanded gas can be expanded in a turbine 26 to generate energy. An oxygen-containing gas or another oxidizing gas such as O 2 , O 2 -H 2 O , air, CO 2 or a sulfur-containing gas or sulfur vapor with high kinetic energy is blown in via a lance 27 to atomize the melts 14 and 15 as they pass through the annular gap 22.Reference numeral 28 denotes a feed device for Ca and / or Al carriers and / or elemental sulfur and / or sulfur carriers. The reaction products are drawn off at the fume hood 29 and fed, for example, to a cyclone 30 for the separation of the gas phase from brownmillerite, iron sulfides and / or iron oxides. The cyclone 30 has a fume hood 31 for the gaseous P₂O₅ and / or elemental phosphorus, as well as a rotary valve 32 for the discharge of the calcium-aluminum-iron compounds.

[0056] In Fig. 5 Identical parts are again provided with the same reference numerals, and it is evident that in the area 5 with a rapidly increased diameter, thereby forming an annular space 6 between the housing 2 and the column 3, a feed device 7 is arranged for feeding melts of the iron(oxide)-containing phosphorus and / or phosphate carriers into the annular space 6. The feed device 7 is designed as an annular melting pan, which has at least one opening 7' at its bottom that can be opened and closed by a metering plunger 7" . The phosphate- and iron(oxide)-containing slag melt is held in the melting pan and fed into the annular space 6, and thus onto the column 3, in a controlled manner by moving the metering plunger 7" in the direction of the double arrow 33. An induction device 34 is arranged both inside and outside the annular column 3' to maintain the reductive column 3 or 3' at a suitable reaction temperature.At the base 10 of the housing 2, a further section 11 with a significantly increased diameter is arranged, with a further annular tundish 33 or annular melting pan 33 for receiving the molten iron phosphide and the slag melt being arranged below section 11. Hydrogen can be blown into section 11. In addition, coal dust and / or oxygen can also be blown into the annular space 6.

[0057] In Fig. 6a und 6b The figure shows that a plurality of refractory-lined tubular parts 2' of the housing 2, arranged symmetrically along the longitudinal axis, are connected to the area 11 with the enlarged diameter, with carbon support columns 3" arranged in the tubular parts 2' that are reductive for the iron(oxide)-containing phosphorus and / or phosphate carriers, and each of these columns being surrounded by induction devices 34.

[0058] In Fig. 7 A rotatably mounted housing 35 with an opening 36 and an induction device 37 is shown. An opening 35' for blowing in purge gas, for example nitrogen, is arranged in the area of ​​the induction device 37. A tin bath 38 is maintained at temperatures of 1500°C to 1600°C in the area of ​​the induction device 37. This bath, supported by the purge gas, maintains the overlying pre-oxidized slag melt 39 and, if applicable, the slag melt itself at a suitable reaction temperature. In the device according to Fig. 7 Furthermore, the temperature and chemical properties of the pre-oxidized slag melt 39 can be adjusted as described above. Another advantage of using a device according to Fig. 7 The advantage lies in the fact that flow fluctuations in the previously described process stages of pre-oxidation or step a) can be compensated for by providing a collection volume.

Claims

1. Method for separating phosphorus and / or phosphorus compounds from iron(oxide)-containing phosphorus and / or phosphate carriers, such as sewage sludge and sewage sludge ash, animal meal and animal meal ash, liquid manure, food residues, flame-retardant plastics, medications, metallurgical slags, lubricant residues, used lithium-ion batteries, electronic waste and the like, comprising at least the following steps: a) melt-metallurgical reduction of the iron(oxide)-containing phosphorus and / or phosphate carriers to form a slag melt and a melt of iron phosphides, in particular FeP, Fe2P and / or Fe3P and b1) oxidation of the melt of iron phosphides in the presence of Ca and Al carriers to form gaseous P2O5 and lime-aluminum-iron compounds, in particular brownmillerite, and / or b2) melt-metallurgical conversion of the melt of iron phosphides in the presence of elemental sulfur and / or sulfur carriers to form iron sulfides and elemental phosphorus.

2. Method according to claim 1, characterized in that the P2O5 formed in step b1) is supplied to step a) to form elemental phosphorus.

3. Method according to claim 1 or 2, characterized in that in step a) coal dust and oxygen are supplied at a substoichiometric combustion oxygen ratio, preferably at a combustion oxygen ratio of λ=0.2 to λ=0.8, preferably A=0.4.

4. Method according to claim 1, 2 or 3, characterized in that in step a) elemental hydrogen is supplied.

5. Method according to any one of claims 1 to 4, characterized in that in step a) the basicity (CaO / SiO2) of the slag melt is adjusted to a value of 0.75 to 1.45, preferably 0.8 to 1.4, by adding Ca carriers and / or Si carriers.

6. Method according to any one of claims 1 to 5, characterized in that prior to the reduction as per step a), a pre-oxidation of accompanying substances of the iron(oxide)-containing phosphorus and / or phosphate carriers takes place, such as e.g. organics, heavy metals, halogens, alkalis, and sulfur compounds, to form a melt of the iron(oxide)-containing phosphorus and / or phosphate carriers as well as withdrawing the gas phase containing the accompanying substances, wherein the melt of the iron(oxide)-containing phosphorus and / or phosphate carriers is subjected to the reduction as per step a).

7. Method according to claim 6, characterized in that the pre-oxidation takes place in a combustion chamber while supplying the iron(oxide)-containing phosphorus and / or phosphate carriers by means of an oxygen-containing gas.

8. Method according to claim 6 or 7, characterized in that the gas phase containing the accompanying substances is subjected to a cooling step by contacting the gas phase with organic waste, such as waste plastic, electrical and electronic waste, biomass, fermentation residues, and shredder light fraction, and / or by contacting the gas phase with limestone, lime marl, cement clinker raw meal, and / or kaolin.

9. Method according to claim 8, characterized in that the exhaust gas of the cooling step is used for steam generation and solid residues are filtered off from gaseous H2 and / or CO.

10. Method according to claim 8, characterized in that the exhaust gas of the cooling step is converted into H2 and CO2 in a water-gas shift reaction and solid residues are filtered off from H2 and CO2.

11. Method according to any one of claims 6 to 10, characterized in that the melt of the iron(oxide)-containing phosphorus and / or phosphate carriers is cooled and preferably granulated prior to the reduction of step a).

12. Method according to any one of claims 1 to 11, characterized in that the reduction as per step a) takes place by means of a column of carbon carriers that is reductive for the iron(oxide)-containing phosphorus and / or phosphate carriers, preferably of coke, charcoal, graphite, and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds.

13. Method according to claim 12, characterized in that the reductive column is maintained at reaction temperature by blowing in oxygen.

14. Method according to claim 12 or 13, characterized in that the reductive column is maintained at reaction temperature by electromagnetic induction.

15. Method according to any one of claims 12 to 14, characterized in that P4 as well as CO in the gas phase and the melt of iron phosphides as well as the slag melt are withdrawn at the bottom of the column as reaction products of the reduction as per step a).

16. Method according to any one of claims 1 to 15, characterized in that the steps b1) and / or b2) take place in an entrained flow reactor by atomization of the melt of iron phosphides by means of a gas stream, preferably consisting of or containing O2, H2O, air, and / or CO2, and preferably with the addition of Ca and Al carriers and / or elemental sulfur and / or sulfur carriers.

17. Method according to any one of claims 1 to 16, characterized in that, as reaction products of the oxidation as per step b1), P2O5 in the gas phase is separated from lime-aluminum-iron compounds, in particular brownmillerite.

18. Method according to any one of claims 1 to 16, characterized in that, as reaction products of the conversion as per step b2), iron sulfides are separated from elemental phosphorus.

19. Method according to claim 17 or 18, characterized in that the separation of P2O5 from lime-aluminum-iron compounds and / or the separation of iron sulfides from elemental phosphorus takes place by means of a cyclone.

20. Method according to any one of claims 12 to 15, characterized in that the oxidation of the melt of iron phosphides to P2O5 and the formation of lime-aluminum-iron compounds, in particular brownmillerite, takes place in a bottom region of the reductive column in that a gaseous oxygen carrier, preferably mixed with at least one aluminum carrier, is blown through the melt of iron phosphides and the iron phosphides are in this way brought into contact with a slag melt from step a) floating on the melt of iron phosphides to form P2O5 and lime-aluminum-iron compounds, preferably brownmillerite.

21. Method according to claim 20, characterized in that P2O5 is converted into P2 and CO in the reductive column and P4 and CO are withdrawn in the gas phase.

22. Device for carrying out a method according to any one of claims 1 to 21, comprising a refractory-lined housing (2), symmetrical or rotationally symmetrical along a longitudinal axis (4), and a column (3) arranged in the housing (2), preferably inductively heated, reductive for the iron(oxide)-containing phosphorus and / or phosphate carriers, of carbon carriers, preferably from coke, graphite and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds, wherein the housing (2) has along the longitudinal axis (4) a region (11) with abruptly enlarged diameter with formation of an annular space (6) between the housing (2) and the column (3), characterized in that in the region (11) of the abrupt enlargement of the diameter at least one feeding device (7) for melt of the iron(oxide)-containing phosphorus and / or phosphate carriers opens into the annular space (6).

23. Device according to claim 22, characterized in that the at least one feeding device (7) cooperates with a plurality of nozzles (8) arranged radially in the region (11) with the abruptly enlarged diameter and directed tangentially into the annular space (6) for the introduction of an oxygen-containing gas and preferably coal dust.

24. Device according to claim 22 or 23, characterized in that a central cylinder (9) for forming an annular column (3') is arranged in the region (11) with the enlarged diameter.

25. Device according to claim 24, characterized in that the central cylinder (9) has a plurality of openings for blowing in an oxygen-containing gas into the annular column (3').

26. Device according to claim 24 or 25, characterized in that an induction device (34) is arranged in the central cylinder (9).

27. Device according to any one of claims 22 to 26, characterized in that at the bottom (10) of the housing (2) a further region (11) with an abruptly enlarged diameter is arranged, forming an annular space between the housing (2) and the annular column (3'), which is configured for withdrawing or tapping melts, preferably into a forehearth (12) for separating the melts.

28. Device according to claim 27, characterized in that the further region (11) with the abruptly enlarged diameter is configured with nozzles for blowing an oxygen-containing gas, preferably mixed with at least one aluminum carrier, through the melt of iron phosphides.

29. Device according to claim 27 or 28, characterized in that the further region (11) with the abruptly enlarged diameter is configured with nozzles for blowing elemental hydrogen through.

30. Device according to claim 22 or 23, characterized in that a plurality of refractory-lined tubular parts of the housing (2'), each arranged symmetrically along a longitudinal axis, with reductive columns (3'') of carbon carriers arranged in the tubular parts, reductive for the iron(oxide)-containing phosphorus and / or phosphate carriers, preferably of coke and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds, connects to the region with the enlarged diameter.

31. Device according to claim 30, characterized in that the tubular parts of the housing (2'') are each surrounded by an induction coil (34).

32. Device for carrying out a method according to any one of claims 1 to 21, comprising a refractory-lined housing (2) and a column (3) arranged in the housing (2), preferably inductively heated, reductive for the iron(oxide)-containing phosphorus and / or phosphate carriers, of carbon carriers, preferably of coke and / or coal dust, preferably mixed with biomass and / or pyrolysate of organic compounds, characterized in that the housing (2) has an offset (18), preferably a cranked portion, along its longitudinal axis (4), forming a cavity (6) between the housing (2) and the column (3), wherein in the region of the offset (18) at least one feeding device (19) for liquid melts of the iron(oxide)-containing phosphorus and / or phosphate carriers opens into the cavity (6).

33. Device according to claim 32, characterized in that the housing (2) has a plurality of openings for blowing an oxygen-containing gas into the column (3).

34. Device according to claim 32 or 33, characterized in that at the bottom (10) of the housing (2) a further offset (11) of the housing (2) is arranged, forming a cavity between the housing (2) and the column (3), which is configured for withdrawing or tapping melts, preferably into a forehearth (12) for separating the melts.

35. Device according to claim 34, characterized in that in the region of the further offset (11), nozzles (13) are arranged for blowing a gaseous oxygen carrier, preferably mixed with at least one aluminum carrier, through the melt of iron phosphides.