A method for recovering phosphates and nitrogen from sewage sludge and, in some cases, biological waste, by combining them.

Abstract

The present invention relates to a method for combined recovery of phosphate and nitrogen from sewage sludge. The core objective of the present invention is to recover phosphorus from sewage sludge ash and convert phosphorus into NP fertilizer diammonium phosphate using steam from sewage sludge drying and nitrogen from liquid manure.

Description

Technical Field

[0001] Subject matter of the invention The present invention relates to a method for recovering phosphate and nitrogen in combination from biological waste such as sewage sludge and optionally liquid manure, which contains an aqueous liquid phase. The core problem of the present invention is to recover phosphorus from sewage sludge ash and to convert phosphorus into ammonium dihydrogen phosphate of NP fertilizer using nitrogen from steam in sewage sludge drying and liquid manure.

Background Art

[0002] Background of the invention Phosphorus in all compounds is essential for life. Humans, animals, and plants rely on its availability. However, phosphates are mainly extracted from phosphate-containing rocks in sedimentary deposits (Morocco, China, United States). Germany relies 100% on imports. The problem arising from this is that these deposits are finite and heavy metal pollution by cadmium and uranium increases as the mining depth increases. For reasons of resource and environmental protection, the recycling of phosphorus is an essential step.

[0003] Sewage sludge as a resource has the highest potential for phosphorus recycling. Against this background, new political and legal framework conditions have been created at the federal level by amending the Sewage Sludge Waste Ordinance (AbfKlarV). In the future, it will be extremely important and legally obligatory to recover phosphorus in the process of sewage sludge treatment in Germany.

[0004] The applicant's German Patent Invention No. 102013018650, German Patent Application Publication No. 102013018652, and German Patent Invention No. 102014006278 disclose methods for recovering phosphorus from sewage sludge ash.

[0005] The October 3, 2017 amendment to the Sewage Sludge Ordinance (AbfKlarV) aims to significantly reduce the use of sewage sludge in relation to soil, particularly in order to more comprehensively return the valuable components (phosphorus) of sewage sludge to the economic cycle, while simultaneously further reducing the amount of contaminants in the soil. According to AbfKlarV, all sewage treatment operators are obligated to recycle phosphorus. In the future, agricultural use will only be permitted to a limited extent.

[0006] Therefore, it is desirable to economically process sewage sludge or sewage sludge ash while simultaneously recovering the valuable phosphates and nitrogen contained therein. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Problem to be solved by the invention: Therefore, the objective of this invention became to provide a method for recovering phosphate and nitrogen in combination from sewage sludge or sewage sludge ash.

[0008] Summary of the invention: As described above, the core objective of the present invention is to recover phosphorus from sewage sludge ash and to convert phosphorus into diammonium phosphate NP fertilizer using steam from sewage sludge drying and nitrogen from liquid fertilizer. The present invention offers the enormous advantage of providing for the first time a combined and integrated method for recovering phosphates and nitrogen from sewage sludge or sewage sludge ash.

[0009] In the recovery of phosphorus from sewage sludge, the recovery of nitrogen from liquid fertilizer is also a central component of the method of the present invention, in which NH3 is obtained by stripping. This is then converted to diammonium phosphate using the obtained phosphoric acid together with the NH3-containing vapor from the post-drying of sewage sludge. The applicant's German Patent Invention No. DE102016122869 describes a method for processing liquid fertilizer.

[0010] The generation of sewage sludge ash is an essential component of phosphorus recycling, based on the intersection and synergistic effects of matter and energy. Next, phosphorus is obtained from this ash in the form of phosphoric acid, which is a fundamental chemical at the heart of the phosphorus industry. In addition to phosphoric acid, by-products such as gypsum and metal salts (iron, aluminum) are also recovered. Valuable materials are used in the building materials industry (gypsum) and as precipitants in sewage treatment plants (metal salts). The ash remaining at the end of the process is used as aggregate in the building materials industry.

[0011] During the post-drying process of sewage sludge to approximately 40% DM (dry matter), which is necessary for incineration, NH3-rich steam is generated. This steam is then condensed and directly converted by phosphoric acid in a phosphate deoxidation unit (Riesler). The resulting diammonium phosphate is an approximately 10% aqueous solution and is either used directly locally as a fertilizer, or it is crystallized by evaporation, concentration, and cooling, then dried and granulated to become a common NP fertilizer.

[0012] The liquid fertilizer is used throughout the integrated process. In a pressure vessel, the liquid fertilizer is treated with CO2 under pressure, and the contained phosphates are transferred from the solid particle phase to the liquid phase. After relaxation, the solids are separated by centrifugation. The phosphorus and nitrogen contained in the fertilizer are concentrated in the liquid phase here. By alkalizing with lime milk (Ca(OH)2) and, if necessary, by introducing steam, NH3 is stripped and phosphorus precipitates as tricalcium phosphate (apatite). As described above, the NH3 is converted to diammonium phosphate in the same facility (e.g., in a deoxidation unit) along with the NH3-rich steam from the post-drying of sewage sludge. The precipitated tricalcium phosphate is heat-treated together with the dried sewage sludge at a planned sewage sludge incineration facility and then sent together to a phosphorus recovery process. At the end of the processing process, a residual liquid fertilizer remains, which contains only trace amounts of phosphorus and nitrogen and is rich in potassium, and can be used for irrigation or treated so that it can be returned to the water cycle through a purification process. The dehydrated solid phase can be further used in biogas facilities or directly used for soil remediation. [Brief explanation of the drawing]

[0013] [Figure 1] This diagram illustrates the key steps of method (1). [Modes for carrying out the invention]

[0014] Detailed description of the invention: According to the present invention, the above problems are solved by a method for recovering a combination of phosphate and nitrogen from (and regenerating) biological waste such as sewage sludge and, in some cases, liquid fertilizers containing an aqueous liquid phase. In this case, method (1) recovers a combination of phosphate and nitrogen from sewage sludge only. In combination method (2), the regeneration of a combination of phosphate and nitrogen from sewage sludge is carried out in combination with the regeneration treatment of biological waste containing an aqueous liquid phase, and the biological waste is particularly liquid fertilizer, aqueous fertilizer, and fermentation residue from biogas facilities.

[0015] In one aspect (1) of the present invention, the present invention relates to a method (1) for recovering a combination of phosphate and nitrogen from sewage sludge, comprising the following method steps. Stage (1A1): The sewage sludge is optionally crushed, Stage (1A2): The sewage sludge is dried, producing NH3-rich steam and dried sewage sludge. Stage (1B1): The NH3-rich vapor from Stage (1A2) is optionally condensed. Step (1B2): Release ammonia [NH3], optionally alkalize the NH3-rich vapor condensed from Step (1B1) (especially using CaO or Ca(OH)2 (lime milk), and possibly mixed with NaOH), and expel the ammonia [NH3] under heating and / or by applying negative pressure and / or by using an airflow or vaporflow (ammonia stripping 1). Stage (1D2): The dried sewage sludge from Stage (1A) is incinerated to produce sewage sludge ash. Stage (1D3): The sewage sludge ash from Stage (1D2) is treated with phosphoric acid. Stage (1D4): The acid-insoluble portion of the treated sewage sludge ash from Stage (1D3) is separated, thereby producing a filtrate or supernatant in the form of a phosphate-containing liquid. Step (1D5): Optionally return at least a portion of the phosphoric acid-containing solution from Step (1D4) for use in Step (1D3). Step (1D6): The phosphate-containing solution from Step (1D4) is purified by adding sulfuric acid to the phosphate-containing solution from Step (1D4), thereby obtaining and separating a calcium sulfate precipitate, and / or by applying ion exchange or liquid-liquid extraction, a purified phosphate-containing solution is obtained. Step (1D7): At least a portion of the purified phosphate-containing solution from Step (1D6) is optionally concentrated, thereby obtaining and separating the phosphate. Step (1E): The condensed NH3-rich vapor from Step (1B1) and / or the ammonia [NH3] obtained in Step (1B2) are reacted with the phosphoric acid-containing liquid from Step (1D4), the purified phosphoric acid-containing liquid from Step (1D6), and / or phosphoric acid [H3PO4] in the form of phosphoric acid from Step (1D7) to obtain ammonium phosphate compounds, particularly diammonium hydrogen phosphate [(NH4)2HPO4], and the obtained ammonium phosphate compounds are optionally separated.

[0016] Figure 1 (Fig. 1) illustrates and describes the key steps of Method (1) as described above.

[0017] In another aspect (2) of the present invention, the present invention relates to a combined method (2) for recovering phosphates and nitrogen together from sewage sludge and biological waste, which comprises the following method steps, and which includes an aqueous liquid phase containing at least urea and ammonium compounds and inorganic and organic bound phosphates dissolved and / or in the form of particles, namely, Stage (2A1): The sewage sludge is optionally crushed, Stage (2A2): The sewage sludge is dried, producing NH3-rich steam and dried sewage sludge. Stage (2B1): The NH3-rich vapor from Stage (2A2) is optionally condensed. Step (2B2): Release ammonia [NH3], optionally alkalize the condensed NH3-rich vapor from step (2B1), and expel ammonia [NH3] under heating and / or by applying a negative pressure and / or using an air stream or a vapor stream (ammonia stripping 2), Step (2C1): Separate the solids of the bio-derived waste from the liquid phase, Step (2C1): Introduce carbon dioxide gas [CO2] under high pressure or supercritical carbon dioxide into the liquid phase of the bio-derived waste to dissolve the particle-bound phosphate, Step (2C2): Reduce the CO2 content in the liquid phase from step (2C1) by acidifying the liquid phase and expelling the dissolved CO2 and / or the CO2 bound as carbonate, Step (2C4): Release ammonia [NH3], alkalize the liquid phase from step (2C2) or (2C3), and expel ammonia [NH3] under heating and / or by applying a negative pressure and / or using an air stream or a vapor stream (ammonia stripping 3), Step (2C5): Precipitate and separate calcium-phosphate from the liquid phase from step (2C4), Step (2D1): Mix the precipitated and separated calcium-phosphate from step (2C5) with the dried sewage sludge from step (2A), Step (2D2): Incinerate the mixture of the precipitated and separated calcium-phosphate from step (2C4) and the dried sewage sludge from step (2A2) to obtain sewage sludge ash, Step (2D3): Treat the sewage sludge ash from step (2D2) with phosphoric acid, Step (2D4): Separate the acid-insoluble part of the treated sewage sludge ash from step (2D3), thereby producing an acid-insoluble part and a filtrate or supernatant in the form of a phosphoric acid-containing liquid, Step (2D5): Optionally return at least a part of the phosphoric acid-containing liquid from step (2D4) for use in step (2D3), Step (2D6): The phosphate-containing solution from Step (2D4) is purified by adding sulfuric acid to the phosphate-containing solution from Step (2D4), thereby obtaining and separating a calcium sulfate precipitate, and / or by applying ion exchange or liquid-liquid extraction, a purified phosphate-containing solution is obtained. Step (2D7): At least a portion of the purified phosphate-containing solution from Step (2D6) is optionally concentrated, thereby obtaining and separating the phosphate. Step (2E): The condensed NH3-rich vapor from step (2B1) and / or the ammonia [NH3] obtained in step (2B2), and the ammonia [NH3] obtained in step (2C4) are reacted with the phosphoric acid-containing liquid from step (2D4), the purified phosphoric acid-containing liquid from step (2D6), and / or phosphoric acid [H3PO4] in the form of phosphoric acid from step (2D7) to obtain an ammonium phosphate compound, and the obtained ammonium phosphate compound is optionally separated.

[0018] Preferred embodiments of aspect (1) and / or aspect (2) are described below, but it should be noted that they can be combined with each other, for example, one particularly preferred embodiment of one step can be combined with at least one other preferred embodiment of one or more steps.

[0019] In a preferred embodiment of aspect (1) of the present invention, the method (1) for recovering phosphate and nitrogen together from sewage sludge is such that the sewage sludge ash of step (1D2) is only the ash produced by incinerating the sewage sludge initially used from steps (1A1) and (1A2). This is phosphate-containing sewage sludge. In one embodiment of aspect (1) of the present invention, the method (1) for recovering phosphate and nitrogen together from sewage sludge is also such that other phosphate-containing ash may be added to the sewage sludge ash of step (1D2), for example, any ash obtained by incinerating phosphate-containing sewage sludge, biodegradable waste, biological waste and / or animal waste in a waste incineration facility. Sewage sludge ash resulting from the incineration of stage (1D2) sewage sludge (used in stages (1A1) and (1A2)) has a phosphate content (measured in P2O5) of >3 wt%, >5 wt%, >7 wt%, >10 wt%, >15 wt%, or >20 wt% (phosphate content (measured in P2O5) of >40 wt% or >35 wt%) is rare), or a phosphorus content (P) of >1 wt%, >2 wt%, >3 wt%, >5 wt%, >8 wt%, or >10 wt% (phosphorus content (measured in P) of >15 wt% or >14 wt%) is rare).

[0020] In a preferred embodiment of aspect (2) of the present invention, in a combined method (2) for recovering phosphate and nitrogen in combination from both sewage sludge and bio-derived waste, the bio-derived waste is preferably liquid fertilizer, water fertilizer and / or fermentation residue from a biogas facility. In a preferred embodiment of aspect (2) of the present invention, in a combined method (2) for recovering phosphate and nitrogen in combination from both sewage sludge and bio-derived waste, the sewage sludge ash of step (2D2) is only the ash produced by incinerating the initially used sewage sludge from steps (2A1) and (2A2). This is phosphate-containing sewage sludge. In one embodiment, other phosphate-containing ash, such as any ash obtained by incinerating phosphate-containing sewage sludge, biodegradable waste, bio-derived waste and / or animal waste in a waste incineration facility, may also be added to the sewage sludge ash of step (2D2). In that case, in principle, sewage sludge ash may also include other (phosphate-containing) ash, such as ash obtained by incinerating phosphate-containing sewage sludge, biodegradable waste, biological waste and / or animal waste in a waste incineration facility. Sewage sludge ash resulting from the incineration of sewage sludge (used in stages (2A1) and (2A2)) in stage (2D2) has a phosphate content (measured in P2O5) of >3 wt%, >5 wt%, >7 wt%, >10 wt%, >15 wt%, or >20 wt% (phosphate content (measured in P2O5) of >40 wt% or >35 wt%) is rare), or a phosphorus content (P) of >1 wt%, >2 wt%, >3 wt%, >5 wt%, >8 wt%, or >10 wt% (phosphorus content (measured in P) of >15 wt% or >14 wt%) is rare). In a preferred embodiment of aspect (2) of the present invention, in combination method (2), urea contained in the liquid phase of a biological waste having an aqueous liquid phase is hydrolyzed by adding the enzyme urease to obtain ammonia and / or ammonium.

[0021] In a preferred embodiment, the step of crushing the sewage sludge (1A1) or (2A1) is performed before step (1A2) or (2A2), and step (1A1) or (2A1) is performed preferably by mechanical treatment (e.g., using a ball mill), by ultrasonic treatment, and / or under high pressure and high temperature. Crushing increases the ammonia yield in the vapor produced by drying in step (1A2) or (2A2).

[0022] In a preferred embodiment of stage (1A2) or (2A2), the drying of the sewage sludge is carried out at a high temperature, and / or the NH3-rich steam produced by the drying is collected directly at the drying site. Typically, (mechanically) dewatered sewage sludge has about 25% DM (dry matter, wt%). For incineration, the sewage sludge needs to be dried to about 40% DM (dry matter, wt%). This is done at this stage, and can be done using, for example, a belt dryer or a fluidized bed dryer, and temperatures such as 40°C to 95°C, 50°C to 80°C, or 60°C to 70°C are used.

[0023] In a preferred embodiment of step (1B1) or (2B1), the condensation of the NH3-rich vapor from step (1A2) or (2A2) is preferably carried out directly in a dry place. These steps can be omitted if the vapor is already liquid.

[0024] In a preferred embodiment of the optional step (1B2) or (2B2), alkalization of the condensed NH3-rich vapor from step (1B1) or (2B1) is not optional but follows step (1B1) or (2B1). In a preferred embodiment of step (1B2) or (2B2), alkalization of the condensed NH3-rich vapor from step (1B1) or (2B1) is carried out by adding NaOH, optionally further adding CaO or Ca(OH)2 (lime milk), and especially optionally further adding Ca(OH)2 (lime milk). In a preferred embodiment of step (1B2) or (2B2), ammonia [NH3] removal (ammonia stripping 1 or 2) is carried out under heating. In a preferred embodiment of step (1B2) or (2B2), ammonia [NH3] removal (ammonia stripping 1 or 2) is carried out by applying negative pressure. In a preferred embodiment of step (1B2) or (2B2), the removal of ammonia [NH3] (ammonia stripping 1 or 2) is carried out using an airflow or vapor flow. In a preferred embodiment of step (1B2) or (2B2), the removal of ammonia [NH3] (ammonia stripping 1 or 2) is carried out under heating using an airflow or vapor flow. The release and removal of ammonia from the liquid phase in step (1B2) or (2B2) of the method according to the present invention is basically known. According to the present invention, this is carried out by alkalizing the liquid phase using, for example, CaO or Ca(OH)2 (lime milk), and optionally by mixing with NaOH, and the removal of gaseous ammonia is carried out under heating and / or by applying negative pressure and / or using an airflow or vapor flow. In this case, the liquid phase can be alkalized to a pH value of 9 to 14, especially 10 to 13, and particularly preferably 11 to 12. The removed gaseous ammonia can be absorbed by mineral acid or water (ammonia water).

[0025] In a preferred embodiment, in step (2C1), solid matter of the bio-waste (if present, e.g., plant remains or straw) can be separated from the liquid phase by mechanical separation. This can be done, for example, by sieving, raking, sedimentation, filtration, centrifugation, or a combination thereof. Alternatively or additionally, the coarse solid matter can be mechanically crushed, for example, by chopping, grinding, or an equivalent suitable method to generate fluidity in the starting material. In particular, the separation is carried out by centrifugation. In one embodiment, the step (1C1) or (2C1) of separating solid matter of the bio-waste from the liquid phase is performed after step (2C2).

[0026] In a preferred embodiment of step (2C2), the introduction of carbon dioxide gas [CO2] or supercritical carbon dioxide under high pressure into the liquid phase of the bio-derived waste is carried out in a pressure vessel. The purpose is to dissolve the particulate phosphates. A method for obtaining phosphates from sewage sludge products by introducing carbon dioxide gas (CO2) or supercritical carbon dioxide under high pressure into the liquid phase is known from German Patent Application Publication No. 102009020745, which is incorporated herein by reference. The method described therein can be appropriately applied in step (2C2) of the method according to the present invention to dissolve particulate phosphates according to the present invention.

[0027] In a preferred embodiment of step (2C3), the reduction of the CO2 content in the liquid phase from step (2C2) is achieved by acidifying the liquid phase with an inorganic acid. This successfully expels the dissolved CO2 and / or CO2 bound as carbonate from the liquid phase. In step (2C4) of ammonia stripping (3), when the pH value is increased by alkalizing with NH3 and / or CaO or Ca(OH)2, the high CO2 content in the liquid phase results in the formation and precipitation of not only desirable calcium phosphate but also undesirable calcium carbonate in high proportions. Therefore, according to the present invention, before alkalizing the liquid phase for ammonia stripping in the next step (2C4), the CO2 content in the liquid phase is reduced by acidifying the liquid phase and expelling the dissolved CO2 and / or CO2 bound as carbonate. Acidification is preferably carried out using phosphoric acid. The expulsion of CO2 can be advantageously accelerated by increasing the temperature and / or by stirring or otherwise moving the reaction mixture.

[0028] In a preferred embodiment of step (2C4), alkalization of the liquid phase from step (2C3) is carried out by adding NaOH, and optionally by further adding CaO or Ca(OH)2 (lime milk), and especially optionally by further adding Ca(OH)2 (lime milk). In a preferred embodiment of step (2C4), the removal of ammonia [NH3] (ammonia stripping 3) is carried out under heating. In a preferred embodiment of step (2C4), the removal of ammonia [NH3] (ammonia stripping 3) is carried out by applying negative pressure. In a preferred embodiment of step (2C4), the removal of ammonia [NH3] (ammonia stripping 3) is carried out using an airflow or vapor flow. In a preferred embodiment of step (2C4), the removal of ammonia [NH3] (ammonia stripping 3) is carried out under heating and using an airflow or vapor flow (ammonia stripping 3). The release and removal of ammonia from the liquid phase in step (2C4) of the method according to the present invention, so-called ammonia stripping, is known in principle. According to the present invention, this is carried out by alkalizing the liquid phase using, for example, CaO or Ca(OH)2 (lime milk), and optionally by mixing it with NaOH. The expulsion of gaseous ammonia is carried out under heating, and / or by applying negative pressure, and / or by using an airflow or vaporflow. In this case, the liquid phase can be alkalized to a pH value of 9-14, especially 10-13, and particularly preferably 11-12. The expelled gaseous ammonia can be absorbed by mineral acid or water (ammonia water).

[0029] In a preferred embodiment of step (2C5), in which calcium phosphate is precipitated and separated from the liquid phase from step (2C4), the calcium phosphate exists particularly as tricalcium phosphate [Ca3(PO4)2] or hydroxyapatite [Ca5(PO4)3(OH)]. However, in this case, the calcium phosphate includes Ca3(PO4)2), CaHPO4, Ca5(PO4)3(OH), and Ca(H2PO4)2. In a preferred embodiment of step (2C5), the separation of calcium phosphate from the liquid phase is carried out by filtration, centrifugation, sedimentation, or a combination of the aforementioned methods.

[0030] In a preferred embodiment of step (2D1), the calcium phosphate precipitated and separated from step (2C5) is mixed with the dried sewage sludge from step (2A), in which case various methods can be used for mixing. The purpose of this mixing is usually to remove any organic residues associated with the calcium phosphate from step (2C5) by incineration in the next step (2D2).

[0031] In a preferred embodiment of step (2D2), a mixture of calcium phosphate precipitated and separated from step (2C4) and dried sewage sludge from step (2A2) is incinerated, in which case any organic residue attached to the calcium phosphate from step (2C4) is also incinerated. In a preferred embodiment of step (2D2), the incineration of the mixture of calcium phosphate precipitated and separated from step (2C4) and dried sewage sludge from step (2A2) is carried out in a waste incineration facility at 600°C to 1,200°C, preferably 800°C to 900°C.

[0032] In a preferred embodiment of step (1D2), the dried sewage sludge from step (1A2) is incinerated to produce sewage sludge ash, in which case organic residues are particularly incinerated. In a preferred embodiment of step (1D2), the incineration of the sewage sludge from step (1A2) to sewage sludge ash is carried out at a waste incineration facility at 600°C to 1,200°C, particularly at 800°C to 900°C.

[0033] In a preferred embodiment of step (1D3) or (2D3), the sewage sludge ash from step (1D2) or (2D2) is treated with phosphoric acid. In particular, this treatment is carried out for less than 5 minutes, or less than 2 minutes, or 5 to 45 minutes, or 2 to 300 minutes, especially 10 to 60 minutes, or 2 to 20 minutes, and in particular this treatment is carried out at a temperature above 40°C, or above 50°C, or 20°C to 90°C, especially 60°C to 80°C, or 20°C to 80°C, or 25°C to 50°C. In particular, the acid is present at a concentration of 5% to 50% by weight, especially 10% to 30% by weight (diluted with water), and / or the sewage sludge ash in the reactor is treated with the acid, and / or the ratio of sewage sludge ash to acid is 5% to 50% by weight, especially 20% to 30% by weight, or 25% to 35% by weight. Particularly preferred, the treatment of sewage sludge ash from step (1D2) or (2D2) with phosphoric acid is carried out at a temperature of 20-80°C or 25-50°C for less than 2 minutes or 2-20 minutes, the acid is present at a concentration of 10%-30% by weight (in the aqueous dilution), and the ratio of sewage sludge ash to acid is 20%-30% by weight or 25%-35% by weight. Particularly preferred, the treatment of sewage sludge ash from step (1D2) or (2D2) with phosphoric acid is carried out at a temperature of 25-50°C for 2-20 minutes, the acid is present at a concentration of 10%-30% by weight (in the aqueous dilution), and the ratio of sewage sludge ash to acid is 25%-35% by weight.

[0034] In a preferred embodiment of step (2D4), the acid-insoluble portion of the treated sewage sludge ash from step (1D3) or (2D3) is separated, thereby yielding a filtrate or supernatant in the form of the acid-insoluble portion and a phosphate-containing liquid. In a preferred embodiment of the present invention, the acid-insoluble portion of the treated sewage sludge ash from step (1D3) or (2D3) is separated by mechanical filtration and / or dewatering. In a preferred embodiment of the present invention, the separation of the acid-insoluble portion of the treated sewage sludge ash from step (1D3) or (2D3) is performed by a dewatering unit (e.g., vacuum belt filter, chamber filter press, membrane filter press, belt filter press, centrifuge). In a preferred embodiment of the present invention, the separation of the acid-insoluble portion of the treated sewage sludge ash from step (1D3) or (2D3) is performed by a vacuum belt filter. In a preferred embodiment of the present invention, after the separation of the acid-insoluble portion of the treated sewage sludge ash from step (1D3) or (2D3), the residue in the filter unit is washed with water, and the wash water is returned to step (1D3) or (2D3).

[0035] In a preferred embodiment of step (1D5) or (2D5), at least a portion of the phosphoric acid-containing solution from step (1D4) or (2D4) is returned for use in step (1D3) or (2D3). In particular, at least 10%, especially preferably at least 20%, more preferably 20% to 80%, and most preferably 40% to 60%, of the total content of the phosphoric acid-containing solution from step (1D4) or (2D4) is returned for use in step (1D3) or (2D3). In a preferred embodiment of step (1D5) or (2D5), this step is performed after step (1D6) or after step (2D6) and before step (1D7) or (2D7).

[0036] In a preferred embodiment of step (1D6) or (2D6), the phosphoric acid-containing solution from step (1D4) or (2D4) is purified by adding sulfuric acid to the phosphoric acid-containing solution from step (1D4) or (2D4), thereby obtaining and separating a calcium sulfate precipitate. In preferred embodiments only, this may be followed by the application of ion exchange or liquid-liquid extraction, where ion exchange is preferred (particularly the use of ion exchange resin and regeneration with mineral acid). In either case, a purified phosphoric acid-containing solution is obtained.

[0037] Regarding the purification by adding sulfuric acid to the phosphoric acid-containing solution from step (1D4) or (2D4), the addition of sulfuric acid is carried out in particular in a stirred reactor. Furthermore, sulfuric acid is preferably added in a stirred reactor at a dilution of 10 to 98% by weight, particularly 40 to 80% by weight, and the sulfuric acid is preferably added at a dissolved calcium concentration of 0.5Ca to 1.5SO4, particularly in a molar ratio corresponding to 1.0Ca to 1.0SO4. In this case, the residence time in the stirred reactor after the addition of sulfuric acid is 5 to 60 minutes, particularly 10 to 30 minutes, and / or the reaction temperature in the stirred reactor (precipitation of calcium sulfate after sulfuric acid addition) is 20°C to 90°C, preferably 60 to 90°C. Furthermore, the calcium sulfate precipitate is preferably obtained and separated by mechanical filtration and / or dehydration. Preferably, the separation of the calcium sulfate precipitate is carried out using a dehydration unit (e.g., vacuum belt filter, chamber filter press, membrane filter press, belt filter press, centrifuge). Particularly preferably, the separation of the calcium sulfate precipitate is carried out using a vacuum belt filter. In particular, after the separation of the calcium sulfate precipitate, the residue in the filter unit is washed with water, and the wash water is returned for use in step (1D3) or (2D3).

[0038] In a preferred embodiment of step (1D7) or (2D7), at least a portion of the purified phosphoric acid-containing solution from step (1D6) or (2D6) is concentrated to obtain and separate the phosphoric acid, which is preferably done by evaporation concentration.

[0039] In a preferred embodiment of step (2E), the ammonia [NH3] obtained in step (2B2) and / or the ammonia [NH3] obtained in step (2C4) are reacted with phosphoric acid [H3PO4] in the form of phosphoric acid from step (2D4), the purified phosphoric acid from step (2D6), and / or phosphoric acid from step (2D7) to obtain an ammonium phosphate compound. In particular, the ammonium phosphate compound is diammonium hydrogen phosphate [(NH4)2HPO4] (fertilizer). The resulting diammonium phosphate is an aqueous solution of about 10% and can be used directly on-site as a fertilizer, or it can be crystallized by evaporation, concentration and cooling, and then dried and granulated to become a general NP fertilizer, and the obtained ammonium phosphate compound can be optionally separated. In particular, phosphoric acid is added in the form of phosphoric acid-containing solution from step (1D4) or the purified phosphoric acid-containing solution from step (1D6). In particular, phosphoric acid is added in the form of phosphoric acid-containing solution from step (1D4). In particular, phosphoric acid is added in the form of a purified phosphoric acid-containing solution from step (1D6), especially after the precipitation of calcium sulfate precipitate CaSO4. In particular, phosphoric acid is used at a concentration of 10-15%. Phosphoric acid [H3PO4] can also be used at a concentration of 40-89% by weight, or 50-75% by weight. In particular, ammonia is used in the form of aqueous ammonia. In particular, ammonia is used at a concentration of about 25%. In particular, ammonia is used in the form of aqueous ammonia at a concentration of about 25%. In particular, ammonia is reacted with phosphoric acid in a deoxidation apparatus (phosphoric acid deoxidation apparatus). In a preferred embodiment, in step (2E), the ammonia obtained in steps (2B2) and (2C4) is reacted with phosphoric acid. In particular, phosphoric acid is used in the form of a purified phosphoric acid-containing solution from step (2D6) and / or phosphoric acid from step (2D7).

[0040] In a preferred embodiment of step (1E), the ammonia [NH3] obtained in step (1B2) is reacted with phosphoric acid [H3PO4] in the form of a phosphoric acid-containing solution from step (1D4), a purified phosphoric acid-containing solution from step (1D6), and / or phosphoric acid from step (1D7) to obtain an ammonium phosphate compound. In particular, the ammonium phosphate compound is diammonium hydrogen phosphate [(NH4)2HPO4] (fertilizer). The resulting diammonium phosphate is an aqueous solution of about 10% and can be used directly in-situ as a fertilizer, or it can be crystallized by evaporation, concentration and cooling, and then dried and granulated to become a general NP fertilizer, and the obtained ammonium phosphate compound can be optionally separated. In particular, phosphoric acid is added in the form of a phosphoric acid-containing solution from step (1D4) or a purified phosphoric acid-containing solution from step (1D6). In particular, phosphoric acid is added in the form of a phosphoric acid-containing solution from step (1D4). In particular, phosphoric acid is added in the form of a purified phosphoric acid-containing solution from step (1D6), especially after the precipitation of calcium sulfate precipitate CaSO4. In particular, phosphoric acid is used at a concentration of 10-15%. Phosphoric acid [H3PO4] can also be used at a concentration of 40-89% by weight, or 50-75% by weight. In particular, ammonia is used in the form of aqueous ammonia. In particular, ammonia is used at a concentration of about 25%. In particular, ammonia is used in the form of aqueous ammonia at a concentration of about 25%. In particular, ammonia is reacted with phosphoric acid in a deoxidation apparatus (phosphoric acid deoxidation apparatus). In a preferred embodiment, the ammonia obtained in step (1B2) is reacted with phosphoric acid in step (1E). In particular, phosphoric acid is used in the form of a purified phosphoric acid-containing solution from step (1D6) and / or phosphoric acid from step (1D7).

[0041] Definition: In the context of this invention, the term "calcium phosphate" includes Ca3(PO4)2, CaHPO4, Ca5(PO4)3(OH), and Ca(H2PO4)2.

[0042] In the sense of this invention, the term "ash" refers to any residual solids from the incineration of organic materials. In the sense of this invention, this is particularly the residual solids from the incineration of sewage sludge. However, in principle, this can also be biodegradable waste, biological waste and / or animal waste, waste from meat processing plants, for example, residual solids from the incineration of meat and bone meal. Ash is, among other things, Al2O3, CaO, Fe2O3, MgO, MnO, P2O5, P4O 10 It consists of various metal oxides and (bi)carbonates such as K2O, SiO2, Na2CO3, and NaHCO3.

[0043] In the sense of this invention, the term "phosphate-containing ash" refers to ash as defined herein, which contains at least one phosphate as defined herein.

[0044] In the meaning of this invention, the term "phosphate" refers to P2O5 and P4O 10 This refers to [the above]. On the other hand, the term "phosphate" further refers to salts and esters of orthophosphate (H3PO4), and clearly includes condensates (polymers) of orthophosphate and its esters. In particular, the term "phosphate" refers to the metal salt of phosphoric acid of the general formula X(Y)m(PO4)n, where X and selectively Y are metals selected from the group consisting of aluminum, beryllium, bismuth, lead, cadmium, chromium, iron, gallium, indium, potassium, cobalt, copper, magnesium, manganese, molybdenum, sodium, nickel, osmium, palladium, rhodium, ruthenium, strontium, titanium, vanadium, tungsten, zinc, and tin.

[0045] In the sense of the present invention, the term “precipitate” refers to the removal of a dissolved substance from a solution as a solid, which is usually caused by the addition of a suitable substance (precipitant). In particular, the term includes any completely or partially insoluble precipitate in any microcrystalline, crystalline, or amorphous form, in the form of flakes, droplets, or crystalline material. The term “precipitate” explicitly includes any further processing, modification, purification, etc., of the precipitate obtained by the method according to the present invention into powder, fine powder, dust, bulk material, granular material, grit, etc.

[0046] In the context of this invention, the term "waste incineration facility" refers to all facilities, equipment, etc., suitable for incinerating the air-combustible components of all types of waste.

[0047] In the sense of the present invention, the term "sewage sludge" refers to any suspension of finely dispersed solid particles in a liquid. Sewage sludge can exist as primary sludge, raw sludge, excess sludge, or as treated and / or stabilized sewage sludge (aerobic / anaerobic). In particular, this is (mechanically) dewatered sewage sludge and / or particularly / preferably sewage sludge containing 15% to 30% dry matter, especially about 25% (DM, dry matter).

[0048] In a preferred embodiment, the liquid in which the particles are suspended is wastewater as defined herein.

[0049] In the context of this invention, the term "wastewater" refers to all liquids having aqueous and / or organic properties, or mixtures thereof, that do not possess the qualities of drinking water in the sense of the Drinking Water Regulations (TrinkwV) and / or national and / or international drinking water standards (e.g., Germany's DIN2000). The term "wastewater" further includes all wastewater as defined in Article 54, paragraph 1 of the Water Management Act (WHG).

[0050] In preferred embodiments, wastewater as defined in this invention is water that has been contaminated by use or whose properties or composition have been altered. Furthermore, the term “wastewater” as defined in this invention includes water whose properties have been altered by domestic, commercial, agricultural, or other uses, as well as water that flows out with it in dry weather (sewage), and water that is collected and flows out by precipitation from urban or paved areas (rainwater). Liquids discharged and collected from facilities that process, store, and dispose of waste are also considered sewage. Sewage includes domestic wastewater from toilets (fecal water or toilet wastewater), sanitation facilities, kitchens and washing machines (laundry water or household wastewater), and wastewater from business activities discharged into public sewer systems (commercial wastewater or industrial wastewater). Hot water from cooling systems is also considered wastewater. Wastewater generated by the wide variety of purification and treatment technologies of water treatment plants belongs to wastewater as defined in this invention.

Claims

1. A method for recovering phosphates and nitrogen from sewage sludge, comprising the following steps, namely Stage (1A2): The sewage sludge is dried and NH ３ This generates steam rich in nutrients and dried sewage sludge. Stage (1B1): NH from Stage (1A2) ３ Condensing the steam rich in nutrients, Stage (1D2): The dried sewage sludge from Stage (1A2) is incinerated to obtain sewage sludge ash. Stage (1D3): The sewage sludge ash from Stage (1D2) is treated with phosphoric acid. Stage (1D4): The acid-insoluble portion of the treated sewage sludge ash from Stage (1D3) is separated, thereby producing a filtrate or supernatant liquid in the form of a phosphoric acid-containing liquid. Step (1D6): Purify the phosphoric acid-containing solution from Step (1D4) by adding sulfuric acid, thereby obtaining and separating a calcium sulfate precipitate, and / or obtain a purified phosphoric acid-containing solution by applying ion exchange or liquid-liquid extraction. Stage (1E): The condensed NH from Stage (1B1) ３ A vapor rich in phosphoric acid is used to obtain phosphoric acid in the form of the phosphoric acid-containing liquid from step (1D4) and / or the purified phosphoric acid-containing liquid from step (1D6) [H ３ PO ４ This is reacted with ] to obtain an ammonium phosphate compound. method.

2. A method for recovering phosphates and nitrogen in combination from sewage sludge and biological waste, which includes an aqueous liquid phase containing at least urea and ammonium compounds and inorganic and organic bound phosphates in dissolved and / or particulate form, comprising the following steps: Stage (2A2): The sewage sludge is dried and NH ３ This generates steam rich in nutrients and dried sewage sludge. Stage (2B1): The NH from Stage (2A2) ３ Condensing the steam rich in nutrients, Stage (2C2): To dissolve the particle-bound phosphates, carbon dioxide gas [CO2] under high pressure, or supercritical carbon dioxide, is introduced into the liquid phase of the bio-derived waste. Step (2C3): Acidify the liquid phase and expel the CO ２ dissolved and / or the CO bound as carbonate ２ to reduce the CO2 content in the liquid phase from step (2C2), Stage (2C4): The ammonia [NH ３ By releasing ], the liquid phase from step (2C3) is alkalized, and under heating and / or by applying negative pressure and / or by using an airflow or vapor flow, the ammonia [NH ３ ] to expel (ammonia stripping 3), Stage (2C5): Separate the calcium phosphate by precipitating it from the liquid phase from Stage (2C4). Stage (2D1): The calcium phosphate separated by sedimentation from Stage (2C5) is mixed with the dried sewage sludge from Stage (2A). Stage (2D2): The mixture of the calcium phosphate precipitated and separated from Stage (2C4) and the dried sewage sludge from Stage (2A) is incinerated to obtain sewage sludge ash. Stage (2D3): The sewage sludge ash from Stage (2D2) is treated with phosphoric acid. Stage (2D4): The acid-insoluble portion of the treated sewage sludge ash from Stage (2D3) is separated, thereby producing a filtrate or supernatant in the form of the acid-insoluble portion and a phosphate-containing liquid. Step (2D6): Purify the phosphate-containing solution from Step (2D4) by adding sulfuric acid, thereby obtaining and separating a calcium sulfate precipitate, and / or obtain a purified phosphate-containing solution by applying ion exchange or liquid-liquid extraction. Step (2E): The condensed NH3-rich steam from step (2B1) and the ammonia [NH3] obtained in step (2C4) ３ ] Phosphoric acid [H ３ PO ４ This is reacted with ] to obtain an ammonium phosphate compound. method.

3. The method according to claim 1, wherein a step (1D5) is performed in which the phosphoric acid-containing solution from step (1D4) is returned for use in step (1D3).

4. The method according to claim 2, wherein a step (2D5) is performed in which the phosphoric acid-containing solution from step (2D4) is returned for use in step (2D3).

5. The method according to claim 1 or 3, wherein a step (1A1) of crushing the sewage sludge is performed before step (1A2).

6. The method according to claim 2 or 4, wherein a step (2A1) of crushing the sewage sludge is performed before step (2A2).

7. The condensed NH from stage (1B1) ３ The method according to any one of claims 1, 3, or 5, wherein a step (1B2) of alkalizing a vapor rich in [unclear] is performed.

8. The condensed NH from stage (2B1) ３ The method according to any one of claims 2, 4, or 6, wherein a step (2B2) of alkalizing a vapor rich in [unclear] is performed.

9. The method according to any one of claims 1, 3, 5, or 7, wherein step (1D7) is performed, in which at least a portion of the purified phosphoric acid-containing solution from step (1D6) is concentrated so that phosphoric acid is obtained and separated.

10. The method according to any one of claims 2, 4, 6, or 8, wherein step (2D7) is performed, in which at least a portion of the purified phosphoric acid-containing solution from step (2D6) is concentrated so that phosphoric acid is obtained and separated.

11. The method according to any one of claims 1, 3, 5, 7, or 9, wherein a step (1D6) is performed from step (1D4) to purify the phosphoric acid-containing solution by adding sulfuric acid, thereby obtaining and separating a calcium sulfate precipitate, and producing the purified phosphoric acid-containing solution.

12. The method according to any one of claims 2, 4, 6, 8, or 10, wherein a step (2D6) is performed from step (2D4) to purify the phosphoric acid-containing solution by adding sulfuric acid, thereby obtaining and separating a calcium sulfate precipitate, and producing the purified phosphoric acid-containing solution.

13. The method according to claim 11, wherein in step (1D6), the purification of the phosphoric acid-containing solution from step (1D4) by adding sulfuric acid is followed by further purification by applying ion exchange or liquid-liquid extraction.

14. The method according to claim 12, wherein in step (2D6), the purification of the phosphoric acid-containing solution from step (2D4) by adding sulfuric acid is followed by further purification by applying ion exchange or liquid-liquid extraction.

15. The method according to any one of claims 1, 3, 5, 7, 9, 11, or 13, wherein in step (1E), the ammonia obtained in step (1B2) is reacted with phosphoric acid.

16. The method according to any one of claims 2, 4, 6, 8, 10, 12, or 14, wherein in step (2E), the ammonia obtained in step (2B2) and the ammonia obtained in step (2C4) are reacted with phosphoric acid.

17. The method according to any one of claims 2, 4, 6, 8, 10, 12, 14, or 16, wherein the step of separating the solid matter of the biological waste from the liquid phase (2C1) is performed before step (2C2).

18. Stage (1A1): The sewage sludge is crushed and / or Stage (1B2): After Stage (1B1), ammonia [NH ３ ] is released, and the condensed NH from step (1B1) ３ The ammonia [NH4] is alkalized by alkalizing the vapor rich in NH4, and by heating and / or by applying negative pressure and / or by using an airflow or vapor flow. ３ ] to expel (ammonia stripping 1), and / or Step (1D5): After step (1D4), at least a portion of the phosphoric acid-containing solution from step (1D4) is returned for use in step (1D3), and / or Step (1D7): After step (1D6), at least a portion of the purified phosphoric acid-containing solution from step (1D6) is concentrated so that phosphoric acid is obtained and separated, and / or At the end of step (1E), the obtained ammonium phosphate compound is separated. The method according to any one of claims 1, 3, 5, 7, 9, 11, 13, or 15, comprising at least one of the steps of the following:

19. It encompasses at least stages (1B2) and (1D7), and as an alternative to stage (1E), Stage (1E'): The condensed NH from Stage (1B1) ３ A vapor rich in and / or the ammonia [NH] obtained in step (1B2) ３ ] the phosphoric acid-containing solution from step (1D4), the purified phosphoric acid-containing solution from step (1D6), and / or phosphoric acid in the form of the phosphoric acid from step (1D7) [H ３ PO ４ The ammonium phosphate compound is reacted with [ ] to obtain an ammonium phosphate compound, and the obtained ammonium phosphate compound is separated. The method according to claim 18, comprising the above.

20. Stage (2A1): The sewage sludge is broken down and / or Stage (2B2): After Stage (2B1), ammonia [NH ３ ] is released, and the condensed NH from step (2B1) ３ The ammonia [NH4] is alkalized by alkalizing the vapor rich in NH4, and by heating and / or by applying negative pressure and / or by using an airflow or vapor flow. ３ ] expel (ammonia stripping 2), and / or Stage (2C1): Before Stage (2C2), separate the solids of the biological waste from the liquid phase, and / or Step (2D5): After step (2D4), return at least a portion of the phosphoric acid-containing solution from step (2D4) for use in step (2D3), and / or Step (2D7): After step (2D6), at least a portion of the purified phosphoric acid-containing solution from step (2D6) is concentrated, thereby obtaining and separating phosphoric acid, and / or At the end of step (2E), the obtained ammonium phosphate compound is separated. The method according to any one of claims 2, 4, 6, 8, 10, 12, 14, 16, or 17, comprising at least one of the steps of:

21. It encompasses at least stages (2B2) and (2D7), and as an alternative to stage (2E), Stage (2E'): The condensed NH from Stage (2B1) ３ A vapor rich in and / or the ammonia [NH] obtained in step (2B2) ３ ] and the ammonia [NH obtained in step (2C4) ３ ] the phosphoric acid-containing solution from step (2D4), the purified phosphoric acid-containing solution from step (2D6), and / or phosphoric acid in the form of the phosphoric acid from step (2D7) [H ３ PO ４ The ammonium phosphate compound is reacted with [ ] to obtain an ammonium phosphate compound, and the obtained ammonium phosphate compound is separated. The method according to claim 20, comprising:

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