JP2019034301A - Phosphorus recovery method and phosphorus recovery apparatus - Google Patents

Abstract

To provide a phosphorus recovery method and a phosphorus recovery apparatus for recovering phosphorus from phosphorus-containing biomass as a high melting point compound, tricalcium phosphate.SOLUTION: The phosphorus recovery apparatus comprises a dehydrating device (1) which also functions as a mixing device for mixing an inorganic calcium compound with phosphorus-containing biomass, a thermal decomposition device (3) for thermally decomposing the mixture obtained by the dehydrating device (1), a combustion device (5) for burning the thermal decomposition product obtained by the decomposition device (3), and a phosphorus separation device (7) for separating tricalcium phosphate from the combustion product obtained by the combustion device (5).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a phosphorus recovery method and a phosphorus recovery apparatus for recovering phosphorus from phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, human waste sludge generated at a human waste treatment plant, meat-and-bone meal, and animal manure.

  For example, sewage sludge generated at a sewage treatment plant and human waste sludge generated at a human waste treatment plant contain high concentrations of phosphorus. As a method of recovering phosphorus, conventionally, in advanced treatment of anaerobic digestion and detachment liquid or sewage, a method of recovering phosphoric acid dissolved in water as HAP (basic calcium phosphate) or MAP (magnesium ammonium phosphate) An ash-alkali extraction method is known in which phosphorus is extracted and precipitated from an incinerated ash after incineration with sludge using an alkali chemical.

As a method for recovering phosphorus, Non-Patent Document 1 describes a method for recovering phosphoric acid from incinerated ash of sewage sludge by a carbon dioxide blowing method. Non-Patent Document 2 also describes a phosphorus extraction method using carbon dioxide. In Non-Patent Document 2, there is an effect of extracting a poorly soluble phosphate such as tricalcium phosphate into carbon dioxide, the form of the extracted phosphorus is bicarbonate “CaHPO ₄ ”, It is also described that the concentration of phosphorus-containing heavy metals extracted as hydrogen salts is lower than other acid extractions. However, Non-Patent Document 1 describes the low profitability due to the increased construction costs, chemical costs, maintenance costs, etc. of phosphorus resource facilities, and the distribution of phosphorus resources, compared to the proceeds from sales of recovered phosphorus resources. It is also described that these are issues. That is, recovery of phosphorus resources using carbon dioxide has a problem in terms of cost.

On the other hand, various countermeasures against adhesion and deposition of incinerator ash resulting from melting of a low melting point phosphorus compound have been studied. In the incineration treatment of sewage sludge, it is desired to maintain the incineration treatment temperature at about 850 ° C. to 900 ° C. from the viewpoint of preventing the generation of N ₂ O, which is a greenhouse gas. For example, Non-Patent Document 3 describes that adhesion of incineration ash to an incinerator can be prevented by increasing the amount of polyferric sulfate added to sludge. However, in Non-Patent Document 3, since a relatively low melting point phosphorus compound (40 ° C. to 500 ° C.) is contained in sewage sludge, if the sewage sludge is incinerated at a high temperature of 850 ° C. or higher, for example, low melting point phosphorus It is also described that problems such as adhesion and deposition of incinerator ash due to melting of the compound to the incinerator occur.

On the other hand, Patent Document 1 discloses compounds containing basic components such as Fe ₂ O ₃ , K ₂ O or MgO, or Ca ions such as calcium carbonate, slaked lime or quick lime with respect to phosphorus in sludge. It describes a method for increasing the melting point of the incinerated ash by adding the compound to be contained before incineration so as to have an equivalent ratio of about 1: 1 with phosphorus and increasing the basicity of the incinerated ash. Moreover, in patent document 1, phosphorus is collect | recovered as a crystal of calcium phosphate by adding the compound containing Ca ion to incineration ash.

JP, 2015-120164, A

Guide to recycling phosphorus in sewers (Ministry of Land, Infrastructure, Transport and Tourism, Urban and Regional Development Bureau, Sewerage Department; March 2010) Development of phosphoric acid recovery technology from sewage sludge incineration ash (Nihon University, Faculty of Science and Technology, Takeshi Toyama, "14th Phosphorus Resource Recycling Symposium", July 21, 2016) Challenges and responses for coexistence of advanced treatment and global warming countermeasures (Tokyo Sewerage Bureau Technical Research Annual Report; 2014, vol. 38)

However, in the method described in Patent Document 1, a basic component or a compound containing Ca ions is added so as to have an equivalent ratio of about 1: 1 with phosphorus. It becomes calcium metaphosphate “Ca (PO ₃ ) ₂ ” at 975 ° C. For this reason, when the incineration temperature is further increased in the incinerator, or a local high temperature portion is generated, there is a concern that the inside of the incinerator exceeds the melting point of calcium metaphosphate. Therefore, the method described in Patent Document 1 is insufficient to prevent adhesion of the phosphorus compound to the incinerator and the accompanying blockage of the incinerator during the pyrolysis process and the combustion process. In addition, in the method described in Patent Document 1, it is necessary to always perform a component analysis of sludge in order to make the equivalent ratio of the compound and phosphorus about 1: 1. Moreover, in order to collect phosphorus as calcium phosphate, it is necessary to add a compound containing Ca ions in two stages before and after incineration of sludge.

  One embodiment of the present invention recovers phosphorus as tricalcium phosphate, which is a high melting point compound, from phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, human waste sludge generated at a human waste treatment plant, meat-and-bone meal, and animal manure. The main object is to provide a phosphorus recovery method and a phosphorus recovery apparatus.

  The inventor collects phosphorus as tricalcium phosphate, which is a high melting point compound, by mixing an inorganic calcium compound with phosphorus-containing biomass and separating the products obtained by the pyrolysis reaction and combustion reaction. As a result, the present invention has been completed.

  That is, the present invention includes the inventions described in [1] to [10] below.

  [1] A phosphorus recovery method for recovering phosphorus from phosphorus-containing biomass, comprising mixing a phosphorus-containing biomass with an inorganic calcium compound, and thermally decomposing the mixture obtained in the mixing step in the presence of water vapor Phosphorus recovery including a pyrolysis step, a combustion step for burning the pyrolysis product obtained in the pyrolysis step, and a separation step for separating tricalcium phosphate from the combustion product obtained in the combustion step Method.

  [2] The phosphorus recovery method according to [1], wherein in the mixing step, 0.06 kg to 0.8 kg of an inorganic calcium compound is mixed per 1 kg of phosphorus-containing biomass dry weight.

  [3] The phosphorus recovery method according to [1] or [2], wherein the heating temperature of the mixture in the pyrolysis step is 400 ° C to 900 ° C, and the residence time is 0.1 hours to 2 hours.

  [4] The phosphorus recovery method according to any one of [1] to [3], further including a phosphoric acid production step in which phosphoric acid is obtained by adding an acid to the tricalcium phosphate separated in the separation step.

  [5] The phosphorus recovery method according to any one of [1] to [4], wherein carbon dioxide is separated in the separation step from the combustion gas obtained together with the combustion product in the combustion step.

  [6] The phosphorus recovery according to [4], wherein carbon dioxide is separated in the separation step from the combustion gas obtained together with the combustion product in the combustion step, and the carbon dioxide is used as an acid in the phosphoric acid production step. Method.

  [7] The phosphorus recovery method according to [4], further including a dehydration step of dehydrating the mixture, and using water separated in the dehydration step in the phosphoric acid production step.

  [8] The method further includes a reforming step of producing a fuel gas having a hydrogen concentration higher than that of the fuel gas by steam reforming using calcium oxide from the fuel gas obtained in the pyrolysis step. [1] -The phosphorus collection | recovery method in any one of [7].

  [9] A phosphorus recovery device that recovers phosphorus from phosphorus-containing biomass, a mixing device that mixes an inorganic calcium compound with the phosphorus-containing biomass, and a thermal decomposition device that thermally decomposes the mixture obtained by the mixing device; The phosphorus collection | recovery apparatus containing the combustion apparatus which burns the pyrolysis product obtained with the said pyrolysis apparatus, and the separation apparatus which isolate | separates tricalcium phosphate from the combustion product obtained with the said combustion apparatus.

  [10] A reformer that further produces a fuel gas having a hydrogen concentration higher than that of the fuel gas by steam reforming using calcium oxide from the fuel gas obtained by the pyrolysis device. [9] The phosphorus collection | recovery apparatus as described in.

  According to one aspect of the present invention, phosphorus is added as tricalcium phosphate, which is a high melting point compound, from phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, human waste sludge generated at a human waste treatment plant, meat-and-bone meal, and animal manure. The effect that it can collect | recover is produced.

It is a block diagram which shows the schematic structure of the phosphorus collection | recovery apparatus which concerns on one embodiment of this invention. It is a block diagram which shows the schematic structure of the phosphorus collection | recovery apparatus which concerns on other embodiment of this invention. It is a block diagram which shows the structure of the outline of the phosphorus collection | recovery apparatus which concerns on other embodiment of this invention. It is a block diagram which shows the structure of the outline of the phosphorus collection | recovery apparatus which concerns on other embodiment of this invention. It is a block diagram which shows the structure of the outline of the phosphorus collection | recovery apparatus which concerns on other embodiment of this invention. It is a block diagram which shows the structure of the outline of the phosphorus collection | recovery apparatus which concerns on other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to this, and various modifications can be made within the scope described, and the present invention also relates to embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is included in the technical scope. In the present specification, unless otherwise specified, “A to B” representing a numerical range means “A or more and B or less”. Also, “mass” and “weight” are considered synonymous.

[Embodiment 1]
[Phosphorus recovery equipment]
The phosphorus recovery apparatus in one embodiment of the present invention is obtained by a mixing apparatus that mixes an inorganic calcium compound with phosphorus-containing biomass, a thermal decomposition apparatus that thermally decomposes the mixture obtained by the mixing apparatus, and the thermal decomposition apparatus. And a separation device for separating tricalcium phosphate from the combustion product obtained by the combustion device.

  Examples of the phosphorus-containing biomass supplied to the phosphorus recovery apparatus include phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, human waste sludge generated at a human waste treatment plant, meat and bone meal, and livestock excreta. Examples of the form of phosphorus contained in the phosphorus-containing biomass include living body-derived organic phosphorus and phosphate phosphorus. However, the phosphorus-containing biomass is not limited to the phosphorous biomass exemplified above. In the following description, sludge slurry that is sewage sludge or human waste sludge is taken as an example of phosphorus-containing biomass.

  As shown in FIG. 1, a phosphorus recovery apparatus according to an embodiment of the present invention includes a dehydrator 1, a dryer 2, a pyrolyzer 3, a reformer 4, a combustion device 5, and calcium oxide that also serve as a mixing device. (CaO) Separation device 6, phosphorus separation device 7, and phosphoric acid production device 8 are provided at least. The apparatuses are connected to each other by an apparatus (not shown) having a transport function so that phosphorus can be continuously collected. That is, the phosphorus recovery device is composed of a plurality of fluidized bed devices so that phosphorus can be recovered continuously. However, the phosphorus recovery apparatus of the present invention is not limited to a fluidized bed type recovery apparatus.

  Hereafter, each apparatus which comprises the phosphorus collection | recovery apparatus in one embodiment of this invention is demonstrated, referring FIG.

<Dehydration device 1>
The dewatering device 1 removes the liquid containing water from the sludge slurry (phosphorus-containing biomass) supplied through the sludge slurry supply path 13 to obtain a dehydrated sludge slurry, and then supplies the obtained dehydrated sludge slurry to the dehydrated sludge slurry. Supply to the drying apparatus 2 through the path 15. Further, the dehydrator 1 discharges the separation liquid containing moisture to the outside through the separation liquid discharge path 16.

  The dehydrating device 1 may be any device that can remove the separation liquid containing moisture from the sludge slurry, and examples thereof include a pressure dehydrator such as a belt press or a mechanical dehydrator such as a centrifugal dehydrator.

  Furthermore, the dehydrating apparatus 1 also has a function as a mixing apparatus that mixes the inorganic calcium compound supplied from the inorganic calcium compound supply path 14 with the sludge slurry. Therefore, the dewatered sludge slurry supplied to the drying device 2 is a mixture of the sludge slurry and the inorganic calcium compound.

  The time when the inorganic calcium compound is mixed with the sludge slurry may be before the separation liquid is removed from the sludge slurry, may be in the middle of the removal, may be after the removal, and these You may combine multiple times. However, as shown below, since the inorganic calcium compound acts as a dehydration aid, it is more preferable to mix the inorganic calcium compound with the sludge slurry before removing the separation liquid.

(Inorganic calcium compound)
The inorganic calcium compound serves as a calcium base of tricalcium phosphate “Ca ₃ (PO ₄ ) ₂ ” and also acts as a dehydration aid for promoting dewatering of the sludge slurry. Therefore, by adding an inorganic calcium compound to the sludge slurry, the dehydrating property can be improved as compared with a normal dehydrating method.

The inorganic calcium compound is preferably at least one selected from calcium carbonate “CaCO ₃ ”, slaked lime “Ca (OH) ₂ ”, quick lime “CaO”, and dolomite “Ca · Mg (CO ₃ ) ₂ ”. . The particle size of the inorganic calcium compound is preferably 200 μm to 500 μm.

  In addition to acting as a dehydration aid, the inorganic calcium compound plays multiple roles such as a fluid medium, a carbon dioxide absorption medium, a heat source for the gasification process (sensible heat medium and carbon dioxide absorption reaction heat), and a phosphorus melting inhibitor. . Furthermore, inorganic calcium compounds also have a secondary function of contributing to the production of high-concentration hydrogen.

  The entire amount of the inorganic calcium compound supplied to the phosphorus recovery device may be supplied to the dehydration device 1, and a part of the inorganic calcium compound is any of the thermal decomposition device 3, the reforming device 4, and the combustion device 5 as will be described later. May be supplied.

The added amount W (mol / kg-dry weight (DS)) of the inorganic calcium compound to be mixed with the sludge slurry is quantitatively expressed by the following formula (1). That is, the added amount W may be an amount that can recover the phosphorus and sulfur content in the sludge slurry as tricalcium phosphate “Ca ₃ (PO ₄ ) ₂ ” and gypsum “CaSO ₄ ”.

W (mol / kg-DS) ≧ (3/2) × P (mol / kg-DS) + S (mol / kg-DS) (1)
Accordingly, the amount of the inorganic calcium compound added to the sludge slurry is not particularly limited as long as it satisfies the formula (1). Specifically, 0.06 kg to 0.8 kg, more preferably 0.1 kg to 0.5 kg of inorganic calcium compound may be mixed per 1 kg of sludge slurry (phosphorus-containing biomass) dry weight. In particular, by excessively mixing the inorganic calcium compound with the sludge slurry, it is possible to more effectively prevent adhesion of the phosphorus compound to the incinerator due to melting of the phosphorus compound and the accompanying blockage of the incinerator.

<Drying device 2>
The drying device 2 evaporates part or all of the water contained in the mixture of the sludge slurry and the inorganic calcium compound supplied from the dehydrating device 1. The drying apparatus 2 supplies the evaporated water as dry steam, a part of which is supplied to the thermal decomposition apparatus 3 through the heat exchanger 11 and the thermal decomposition steam supply path 18, and the rest through the dry steam discharge path 17. Discharge. The dry steam supplied to the thermal decomposition apparatus 3 is used for thermal decomposition of the mixture. Then, the drying device 2 supplies the dried mixture from which moisture has been removed to the pyrolysis device 3 through the dried sludge supply path 19. Moreover, the drying apparatus 2 supplies a part of the mixture from which moisture has been removed to the combustion apparatus 5 through the heat source dry sludge supply path 20 as necessary. The mixture supplied to the combustion device 5 is burned as a heat source.

  The drying device 2 may be any device that can dry the mixture, and the configuration thereof is not particularly limited. Further, when the amount of water in the mixture obtained by the dehydrating apparatus 1 is small, the drying apparatus 2 is not necessarily provided. In that case, the mixture may be supplied from the dehydrating apparatus 1 to the thermal decomposition apparatus 3.

<Thermal decomposition device 3>
The thermal decomposition apparatus 3 is used for 0.1 hour to 2 while heating the mixture supplied from the dehydration apparatus 1 or the drying apparatus 2 in the presence of water vapor at 400 ° C to 900 ° C, more preferably 600 ° C to 800 ° C. Thermal decomposition is carried out by retaining for a period of time, more preferably 0.5 to 1 hour. The thermal decomposition apparatus 3 supplies the thermal decomposition product obtained by thermal decomposition to the combustion apparatus 5 through the thermal decomposition product supply path 21. The pyrolysis device 3 supplies fuel gas, which is pyrolysis gas obtained by pyrolysis, to the reforming device 4 through the fuel gas supply path 26. In addition, calcium oxide “CaO” is supplied (circulated) from the reformer 4 through the supply path 28 to the thermal decomposition apparatus 3, and a part of a new inorganic calcium compound is supplied as necessary. .

  The thermal decomposition apparatus 3 should just be an apparatus which can thermally decompose the said mixture, and the structure is not specifically limited.

In the thermal decomposition apparatus 3, thermal decomposition is performed by the following reaction to generate fuel gas. That is, the mixture is pyrolyzed in the presence of water vapor by the reaction shown in the following formula (2), and converted into pyrolysis gas and solid residue. Pyrolysis gas includes hydrogen “H ₂ ”, carbon monoxide “CO”, carbon dioxide “CO ₂ ”, hydrogen sulfide “H ₂ S” and ammonia “NH ₃ ”, and methane “CH ₄ ”, hydrocarbon-based A hydrocarbon-based gas “C _m H _n ” containing a gas and a tar component is included as a main component. The solid residue contains charcoal and ash.

Mixture (C, H, O, N, S) + H ₂ O → Pyrolysis gas (H ₂ , CO, CO ₂ , C _m H _n , H ₂ S, NH ₃ ) + C (charcoal) + Ash content ( 2)
Here, ash is a compound containing P, Si, Al, Fe, Mg, Ca, Na, K and the like.
Moreover, a part of charcoal reacts with water vapor, and is converted into carbon dioxide and hydrogen as shown in the following formula (3).

C (charcoal) + 2H ₂ O → CO ₂ + 2H ₂ (3)
Furthermore, carbon monoxide contained in the pyrolysis gas reacts with water vapor and is converted to carbon dioxide as shown in the following formula (4).

_{CO + H 2 O → CO 2} + H 2 ... (4)
Most of the hydrogen sulfide contained in the pyrolysis gas reacts with calcium oxide generated mainly by heating, which is an inorganic calcium compound added to the mixture, and as shown in the following formula (5), calcium sulfide And fixed. As described above, most of the hydrogen sulfide contained in the pyrolysis gas is fixed as calcium sulfide, resulting in an increase in the hydrogen concentration in the pyrolysis gas.

CaO + H ₂ S → CaS + H ₂ O (5)
The carbon dioxide generated by the reactions shown in the above formulas (2) to (4) reacts with calcium oxide to become calcium carbonate “CaCO ₃ ” and is fixed as shown in the following formula (6). Since only carbon dioxide is absorbed by calcium oxide and extracted from the pyrolysis gas by the reaction shown in formula (6), a rightward equilibrium shift occurs in the reactions shown in formulas (2) to (4), resulting in high A fuel gas containing a concentration of hydrogen is produced.

CaO + CO ₂ → CaCO ₃ (6)
On the other hand, phosphorus contained in the ash content of the solid residue reacts with the inorganic calcium compound in the thermal decomposition apparatus 3 to become tricalcium phosphate “Ca ₃ (PO ₄ ) ₂ ”. In this Embodiment, the addition amount of the inorganic calcium compound mixed with a sludge slurry is very large, and many calcium exists in the thermal decomposition apparatus 3 (reaction field). Therefore, phosphorus can be converted to tricalcium phosphate, which is a high melting point phosphorus compound with a melting point of 1390 ° C.

  Therefore, by pyrolysis in the pyrolysis apparatus 3, tricalcium phosphate, calcium sulfide, charcoal, calcium carbonate, unreacted inorganic calcium compound, ash, etc. are obtained from the mixture as solid components (solid residue). A thermal decomposition product containing is obtained.

  Since the tricalcium phosphate is a main component of the phosphate ore resource, it can be reused as an ore resource. In addition, since the melting point of tricalcium phosphate is as high as 1390 ° C., it is possible to prevent the pyrolysis apparatus 3 and the combustion apparatus 5 from adhering to the incinerator due to the melting of the phosphorus compound and the accompanying blockage of the incinerator. Therefore, it becomes possible to operate the phosphorus recovery apparatus more stably and continuously.

<Reformer 4>
The reformer 4 produces a second fuel gas having a hydrogen concentration higher than that of the fuel gas by performing steam reforming using calcium oxide from the fuel gas supplied from the pyrolysis device 3. The second fuel gas is discharged through the fuel gas discharge path 27. The discharged second fuel gas is cooled by the heat exchanger 9 and recovered as a gas containing high-concentration hydrogen. Thereby, a phosphorus collection | recovery apparatus can be used as the energy conversion apparatus which manufactures hydrogen simultaneously with collection | recovery of phosphorus. The heat recovered by the heat exchanger 9 is supplied to the drying device 2 and the heat exchangers 11 and 12 via the line 35.

  In addition, the reformer 4 is supplied (circulated) with calcium oxide “CaO” from the calcium oxide separator 6 through the circulating calcium oxide supply path 24 and, if necessary, a part of a new inorganic calcium compound. Is supplied. Further, the reformer 4 supplies (circulates) calcium oxide to the thermal decomposition apparatus 3 through the supply path 28.

  The reformer 4 may be any device that can steam reform the fuel gas, and its configuration is not particularly limited.

In the reformer 4, steam reforming of the fuel gas is performed by the following reaction, and high concentration hydrogen is generated. That is, the fuel gas contains hydrogen and carbon monoxide, and methane “CH ₄ ”, a hydrocarbon gas, and a hydrocarbon gas “C _m H _n ” containing a tar component. The hydrocarbon-based gas contained in the fuel gas is reformed into hydrogen and carbon dioxide by steam reforming using calcium oxide as a catalyst, as shown in the above formula (4) and the following formula (7).

_{C m H n + H 2 O} → H 2 + CO 2 ... (7)
The generated carbon dioxide is absorbed by calcium oxide as shown in the formula (6). As a result, a second fuel gas having a higher hydrogen concentration, that is, a gas containing a high concentration of hydrogen is obtained from the fuel gas.

<Combustion device 5>
The combustion device 5 burns the pyrolysis product supplied from the pyrolysis device 3 into a combustion product and a combustion gas, and supplies the combustion product and combustion gas to the calcium oxide separation device 6 through the combustion product supply path 23. Combustion gas serving as a heat source is supplied to the combustion apparatus 5 from the outside through the heat exchanger 12 and the combustion gas supply path 22 together with air or oxygen-containing gas. Moreover, a part of new inorganic calcium compound is supplied to the thermal decomposition apparatus 3 as needed.

  Furthermore, the mixture is supplied to the combustion device 5 from the drying device 2 through the dry sludge supply path 20 for heat source as necessary. The mixture is burned as a heat source when it is difficult for the combustion apparatus 5 to burn the pyrolysis product with only the amount of heat generated by the combustion gas. By burning the mixture, the amount of combustion gas supplied from the outside can be reduced, so that the amount of energy used can be reduced.

  The combustion device 5 may be any device that can burn the pyrolysis product, and its configuration is not particularly limited.

In the combustion device 5, combustion products and combustion gases are generated by the following reaction. That is, as shown in the following formula (8), charcoal contained in the thermal decomposition product is burned into carbon dioxide by air or oxygen-containing gas. Moreover, as shown in the following formula (9), calcium carbonate contained in the thermal decomposition product is regenerated by becoming calcium oxide. Further, as shown in the following formula (10), the calcium sulfide contained in the thermal decomposition product becomes gypsum (calcium sulfate) “CaSO ₄ ” by the air or the oxygen-containing gas.

C (charcoal) + O ₂ → CO ₂ (8)
CaCO ₃ → CaO + CO ₂ (9)
CaS + 2O ₂ → CaSO ₄ (10)
The reactions shown in the formulas (8) and (10) are exothermic reactions, and the reaction heat generated in the reactions becomes sensible heat of the circulating calcium oxide, and the thermal decomposition apparatus 3, the reforming apparatus 4 and It is used as a heat source for the combustion device 5.

  In the combustion device 5, calcium oxide, tricalcium phosphate, gypsum, ash, etc. are obtained by the reactions shown in the above formulas (8) to (10) and, if necessary, combustion of the mixture supplied from the drying device 2. A combustion product that is a solid component is obtained. In addition, a combustion gas containing a high concentration of carbon dioxide is obtained together with the combustion product.

<Calcium oxide separator 6>
The calcium oxide separation device 6 is a separation product that is a solid component containing particles containing calcium oxide as a main component, tricalcium phosphate, gypsum, ash, and the like from the combustion product and combustion gas supplied from the combustion device 5. (Combustion products other than calcium oxide) and combustion gas are separated. Then, the calcium oxide separation device 6 supplies the separation product and the combustion gas, which are a solid-gas mixture, to the phosphorus separation device 7 through the separation product supply path 25. In addition to tricalcium phosphate “Ca ₃ (PO ₄ ) ₂ ”, the separated product includes P ₂ O ₅ , CaPO ₄ , Ca (PO ₃ ) ₂ , Ca ₂ P ₂ O ₇ , as a calcium phosphate compound. CaHPO _{4 and the} like are included. The separated product has a smaller particle size than particles containing calcium oxide as a main component.

  On the other hand, the calcium oxide separation device 6 supplies particles containing calcium oxide as a main component to the reforming device 4 through the circulating calcium oxide supply path 24. Thereby, calcium oxide circulates through the reforming device 4, the thermal decomposition device 3, the combustion device 5, and the calcium oxide separation device 6, is repeatedly used, and plays a plurality of roles as described above.

  The calcium oxide separation device 6 may be any device that can separate the combustion product into particles containing calcium oxide as a main component and other combustion products. Is not particularly limited.

<Phosphorus separator 7>
The phosphorus separation device 7 separates the separation product and the combustion gas (solid gas mixture) supplied from the calcium oxide separation device 6 into a separation product and a combustion gas. The phosphorus separator 7 discharges the separated combustion gas through the combustion gas discharge path 29. The discharged combustion gas is cooled by the heat exchanger 10 and recovered as a gas containing high-concentration carbon dioxide. Thereby, the amount of greenhouse gas emissions in the phosphorus recovery apparatus can be reduced. The heat recovered by the heat exchanger 10 is supplied to the drying device 2 and the heat exchangers 11 and 12 via the line 34.

  Further, the phosphorus separation device 7 supplies a separation product containing tricalcium phosphate to the phosphoric acid production device 8 through the separation product supply path 30. Thereby, in the phosphorus collection | recovery apparatus in one embodiment of this invention, phosphorus can be collect | recovered as tricalcium phosphate which is a high melting-point compound. A part of the separation product separated by the phosphorus separation device 7 may be supplied (circulated) to the reforming device 4 through the supply path 31 as necessary. Thereby, since the ratio of the tricalcium phosphate with respect to the circulating calcium oxide can be increased, the concentration of the tricalcium phosphate in the separated product separated by the phosphorus separator 7 can be increased.

  The phosphorus separation device 7 may be any device that can separate the solid-gas mixture into a separated product and a combustion gas. For example, a cyclone, a bag filter, or a ceramic filter may be used, but its configuration is particularly limited. Not.

<Phosphoric acid production apparatus 8>
The phosphoric acid production apparatus 8 adds the acid supplied through the acid supply path 38 to the separation product containing tricalcium phosphate supplied from the phosphorus separation apparatus 7, reacts with the tricalcium phosphate, and reacts with phosphorus. A soluble phosphate compound such as acid and calcium dihydrogen phosphate is produced. The phosphoric acid production apparatus 8 supplies the produced soluble phosphate compound to the outside through the soluble phosphate compound discharge passage 32. Moreover, the phosphoric acid manufacturing apparatus 8 discharges the solid component (solid residue) containing calcium oxide, gypsum, ash, and the like contained in the separated product to the outside through the discharge path 33.

  Examples of the acid added to the separation product include inorganic acids such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, and carbon dioxide.

In the phosphoric acid production apparatus 8, a soluble phosphoric acid compound is produced by the following reaction. That is, when sulfuric acid is used as the acid to be added, as an example of the reaction between tricalcium phosphate “Ca ₃ (PO ₄ ) ₂ ” and sulfuric acid, the reactions shown in the following formulas (11) and (12) are performed. Arise.

Ca ₃ (PO ₄ ) ₂ + 3H ₂ SO ₄ → 3CaSO ₄ ↓ + 2H ₃ PO ₄ (phosphoric acid) (11)
Ca ₃ (PO ₄ ) ₂ + 2H ₂ SO ₄ → 2CaSO ₄ ↓ + Ca (H ₂ PO ₄ ) ₂ (calcium dihydrogen phosphate) (12)
The reactions shown in Formula (11) and Formula (12) are the same reactions as those for obtaining soluble phosphorus from phosphorus ore. Here, the mixture of gypsum and calcium dihydrogen phosphate obtained by the reaction shown in the formula (12) is referred to as superphosphate lime, and the fertilizer having the largest production amount among phosphorus fertilizers (phosphate fertilizers). It is. That is, the phosphoric acid fertilizer can be produced from the tricalcium phosphate by the phosphoric acid production apparatus 8.

In addition, when carbon dioxide is used as the acid to be added, an effect of extracting a poorly soluble phosphate such as tricalcium phosphate can be obtained, and the form of the extracted phosphorus is bicarbonate “CHPO _4. It is known that When carbon dioxide is used as the acid, the concentration of heavy metals contained in phosphorus extracted as the bicarbonate is reduced compared to the case where other acids are used.

  In the phosphoric acid production apparatus 8, various soluble phosphoric acid compounds that become phosphorus fertilizers can be produced by the reaction of tricalcium phosphate with various acids. Specifically, in addition to the phosphoric acid, calcium dihydrogen phosphate, and superphosphate lime, for example, acid-decomposed phosphorus mineral powder, phosphate, nitrophosphate, and calcium phosphate can be mentioned.

The ash contained in the separated product contains an oxide such as Fe ₂ O ₃ , SiO _2, or Al ₂ O ₃ that does not react with an acid such as sulfuric acid to form a hardly soluble salt. When mixed in calcium dihydrogen oxide or the like, the obtained phosphorus fertilizer may not satisfy the product standard. In this case, by supplying an alkaline agent such as NaOH to the phosphoric acid production apparatus 8 through the acid supply path 38 (or other supply path), and adjusting the pH and temperature of the produced soluble phosphoric acid compound, What is necessary is just to isolate | separate the said oxide.

[Phosphorus recovery method]
The phosphorus recovery method in one embodiment of the present invention includes a mixing step of mixing an inorganic calcium compound with phosphorus-containing biomass, a pyrolysis step of thermally decomposing the mixture obtained in the mixing step in the presence of water vapor, It is a method including a combustion step of burning the pyrolysis product obtained in the pyrolysis step, and a separation step of separating tricalcium phosphate from the combustion product obtained in the combustion step.

  More specifically, the phosphorus recovery method in one embodiment of the present invention mainly includes a mixing step, a dehydration step, a drying step, a thermal decomposition step, a reforming step, a combustion step, a calcium oxide separation step, and a phosphorus separation step. , And a phosphoric acid manufacturing process. In addition, the phosphorus recovery method includes a transport step between the steps so that phosphorus can be recovered continuously.

  Hereinafter, each process which comprises the phosphorus collection | recovery method in one embodiment of this invention is demonstrated. However, the description overlapping with the content described in the above-described phosphorus recovery apparatus will be simplified or omitted.

<Mixing process and dehydration process>
In a mixing process, the inorganic calcium compound mentioned above is mixed with sludge slurry (phosphorus content biomass). Although the order of performing the mixing step and the dehydrating step is not particularly limited, the dehydrating property can be improved as compared with a normal dehydrating method by performing the mixing step before the dehydrating step. The amount of inorganic calcium compound added to the sludge slurry is as described above.

  In the dehydration step, the mixture of the sludge slurry and the inorganic calcium compound obtained in the mixing step is dehydrated. That is, the separation liquid containing moisture is removed from the sludge slurry. The mixture from which the separated liquid has been removed is subjected to the next drying step.

  In addition, the specific mixing method which mixes a sludge slurry and an inorganic calcium compound, and the specific dehydration method which dehydrates the mixture of a sludge slurry and an inorganic calcium compound are not specifically limited.

<Drying process>
In the drying step, part or all of the water contained in the mixture obtained through the dehydration step is evaporated. A part of the evaporated water is used as dry water vapor for the thermal decomposition of the mixture in the thermal decomposition step, and the rest is discharged to the outside. The dried mixture is subjected to the next pyrolysis step. In addition, a part of the dried mixture is burned as a heat source in a combustion process, if necessary.

  The specific drying method for drying the mixture is not particularly limited. In addition, when the amount of water in the mixture obtained in the dehydration step is small, the drying step is not necessarily provided. In that case, what is necessary is just to use for the said thermal decomposition process the said mixture obtained through the dehydration process.

<Thermal decomposition process>
In the thermal decomposition step, the mixture obtained through the dehydration step, or the mixture dried through the dehydration step and the drying step is 400 ° C to 900 ° C, more preferably 600 ° C to 800 ° C in the presence of water vapor. Thermal decomposition is carried out by retaining for 0.1 to 2 hours, more preferably 0.5 to 1 hour while heating. That is, the heating temperature of the mixture in the pyrolysis step is 400 ° C to 900 ° C, more preferably 600 ° C to 800 ° C, and the residence time is 0.1 hours to 2 hours, more preferably 0.5 hours to 1 hour. It is.

  In the pyrolysis step, pyrolysis is performed by the above-described reaction to generate fuel gas that is pyrolysis gas. The pyrolysis product obtained by pyrolysis is subjected to a combustion process. And the fuel gas obtained by thermal decomposition is used for the next reforming step. In the pyrolysis step, the calcium oxide “CaO” used in the reforming step is supplied (circulated), and a part of a new inorganic calcium compound is supplied as necessary.

  In addition, the specific thermal decomposition method of thermally decomposing a mixture is not specifically limited.

  Since the melting point of tricalcium phosphate contained in the pyrolysis product is as high as 1390 ° C, the adhesion to the incinerator due to the melting of the phosphorus compound and the accompanying blockage of the incinerator are prevented in the pyrolysis process and the following combustion process. Can do. Therefore, the phosphorus recovery method can be operated more stably and continuously.

<Reforming process>
In the reforming step, the above-described reaction is performed by performing steam reforming using calcium oxide from the fuel gas obtained in the pyrolysis step, and a second fuel gas having a higher hydrogen concentration than the fuel gas is obtained. To manufacture. The produced second fuel gas is cooled and recovered as a gas containing high-concentration hydrogen.

  Thereby, the phosphorus collection | recovery method in one embodiment of this invention can be used as a manufacturing method which manufactures hydrogen simultaneously with collection | recovery of phosphorus. The heat recovered from the second fuel gas is supplied to the drying process, the pyrolysis process, and the combustion process.

  In the reforming step, the calcium oxide “CaO” separated in the calcium oxide separation step is supplied (circulated), and a part of a new inorganic calcium compound is supplied as necessary. Further, the calcium oxide used in the reforming process is supplied (circulated) to the pyrolysis process.

  A specific reforming method for steam reforming the fuel gas is not particularly limited.

<Combustion process>
In the combustion process, the above-described reaction is performed by burning the thermal decomposition product obtained in the thermal decomposition process, and a combustion product and a combustion gas are obtained. The combustion products and combustion gases are supplied to the next calcium oxide separation process. The combustion gas contains a high concentration of carbon dioxide. In the combustion process, a combustion gas serving as a heat source is supplied from the outside together with air or an oxygen-containing gas. Moreover, in a combustion process, a part of new inorganic calcium compound is supplied as needed.

  Further, in the combustion process, the mixture described above is supplied from the drying process as necessary. The mixture is burned as a heat source when it is difficult to burn the pyrolysis product with only the amount of heat generated by burning the combustion gas in the combustion process. By burning the mixture, the amount of combustion gas supplied from the outside can be reduced, so that the amount of energy used can be reduced.

  A specific combustion method for burning the pyrolysis product is not particularly limited.

<Calcium oxide separation process>
In the calcium oxide separation step, the separation product (oxidation) is a solid component containing particles containing calcium oxide as a main component and tricalcium phosphate, gypsum and ash, etc., from the combustion product and combustion gas obtained in the combustion step. Combustion products other than calcium) and combustion gases are separated. The separated product and combustion gas are subjected to the next phosphorus separation step.

  On the other hand, particles containing calcium oxide as a main component are supplied to the modification step. Thereby, calcium oxide circulates through the reforming step, the thermal decomposition step, the combustion step, and the calcium oxide separation step, is repeatedly used, and plays a plurality of roles as described above.

  In addition, although the specific separation method which isolate | separates a combustion product into the particle | grains which contain a calcium oxide as a main component, and other combustion products is not specifically limited, For example, the separation method using a cyclone is preferable.

<Phosphorus separation process>
In the phosphorus separation step, the separated product and the combustion gas (solid gas mixture) separated through the calcium oxide separation step are separated into a separated product and a combustion gas. The separated combustion gas is cooled and recovered as a gas containing a high concentration of carbon dioxide. Thereby, in the phosphorus collection | recovery method in one embodiment of this invention, the emission amount of greenhouse gas can be reduced. The heat recovered from the combustion gas is supplied to the drying process, the pyrolysis process, and the combustion process.

  The separated product containing tricalcium phosphate is supplied to the next phosphoric acid production apparatus. Thereby, in the phosphorus collection | recovery method in one embodiment of this invention, phosphorus can be collect | recovered as tricalcium phosphate which is a high melting-point compound. A part of the separated product separated in the phosphorus separation step may be supplied (circulated) to the reforming step as necessary. Thereby, since the ratio of the tricalcium phosphate with respect to the circulating calcium oxide can be raised, the density | concentration of the tricalcium phosphate in the separation product isolate | separated in a phosphorus separation process can be raised.

  In addition, although the specific separation method which isolate | separates the said solid-gas mixture into a separation product and combustion gas is not specifically limited, For example, the separation method using a cyclone, a bag filter, or a ceramic filter is preferable.

<Phosphate production process>
In the phosphoric acid production process, the above-described reaction is performed by adding the above-described acid to the separated product obtained in the phosphorus separation process. That is, in the phosphoric acid production process, the acid and tricalcium phosphate contained in the separation product are reacted to produce a soluble phosphoric acid compound such as phosphoric acid and calcium dihydrogen phosphate. Moreover, the solid component (solid residue) containing calcium oxide, gypsum and ash contained in the separated product is discharged to the outside.

  In the phosphoric acid production process, various soluble phosphoric acid compounds that become phosphorus fertilizers can be produced by reaction of tricalcium phosphate with various acids.

When the ash contained in the separated product contains an oxide such as Fe ₂ O ₃ , SiO ₂ or Al ₂ O ₃ that does not react with an acid such as sulfuric acid to form a hardly soluble salt, as necessary The oxide may be separated by supplying an alkaline agent to the phosphoric acid production step and adjusting the pH and temperature of the produced soluble phosphoric acid compound.

  The specific reaction method for reacting the separated product with the acid is not particularly limited.

〔Example〕
Hereinafter, examples using the above-described phosphorus recovery apparatus and phosphorus recovery method will be described.

<Conditions for implementation>
An example of the properties of the sludge as a raw material is shown in Table 1. The ash composition in Table 1 is an oxide equivalent value. An example of the implementation conditions is summarized in Table 2. As shown in Table 2, the amount of sludge supplied is 50 t-DS / d (DS: dry weight), and the moisture content of the sludge before dehydration is 97% by weight (Table 1). 1667 t / d.

  Slaked lime was used as the inorganic calcium compound, and the raw material supply amount was 3.2 t / d (Table 2). The operating conditions of the calcium oxide separator 6 were set so that the calcium oxide recovery rate was 90%.

  As shown in Table 2, when the operating condition of the phosphorus separation device 7 is 1, the amount of circulating calcium oxide circulating between the thermal decomposition device 3, the combustion device 5, the calcium oxide separation device 6 and the reforming device 4 is 1. The sludge ash content was set to 0.25. That is, a part of the separated product separated by the phosphorus separation device 7 was supplied (circulated) to the reforming device 4 through the supply path 31 so that tricalcium phosphate was circulated in the phosphorus recovery device.

<Results>
Table 3 shows each compound contained in the pyrolysis product, the combustion product, and the separation product in the present embodiment based on the chemical equilibrium calculation result using commercially available process simulation software, and the amount recovered.

  As shown in Table 3, the form of the calcium phosphate compound contained in the thermal decomposition product is only tricalcium phosphate. Therefore, in the thermal decomposition apparatus 3, it is judged that calcium phosphate compounds other than tricalcium phosphate are difficult to be generated. Accordingly, almost all of the phosphorus contained in the sludge becomes tricalcium phosphate having a melting point of 1390 ° C. in the thermal decomposition apparatus 3, thereby preventing adhesion of the phosphorus compound to the incinerator and accompanying clogging of the incinerator. I can see that

  The tricalcium phosphate contained in the separated product is 4.40 t / d (Table 3).

In addition, when the amount of circulating calcium oxide circulating between the thermal decomposition apparatus 3, the combustion apparatus 5, the calcium oxide separation apparatus 6, and the reforming apparatus 4 is 57 t / h, it is recovered from the fuel gas discharge passage 27. The concentration of hydrogen contained in the second fuel gas was 80% by volume (dry), and the production amount was 38,000 Nm ³ -H ₂ / d.

  From the above results, it was found that according to one aspect of the present invention, a phosphorus recovery apparatus and a phosphorus recovery method capable of recovering phosphorus from sludge as tricalcium phosphate, which is a high melting point compound, can be provided.

[Embodiment 2]
[Phosphorus recovery equipment]
Compared with the phosphorus recovery apparatus in the first embodiment, the phosphorus recovery apparatus in another embodiment of the present invention emits high-concentration carbon dioxide discharged through the combustion gas discharge passage 29 as shown in FIG. It is the structure further equipped with the carbon dioxide supply path 36 which supplies the gas which contains to the phosphoric acid manufacturing apparatus 8. FIG. That is, in the phosphorus recovery apparatus according to the present embodiment, when the acid supplied to the phosphoric acid production apparatus 8 is carbon dioxide, the carbon dioxide contained in the combustion gas generated by the combustion apparatus 5 is used to produce phosphoric acid. It has a configuration to use.

  Thereby, the phosphorus collection | recovery apparatus which concerns on this Embodiment can manufacture phosphoric acid still more cheaply compared with the phosphorus collection | recovery apparatus in the said Embodiment 1. FIG. In addition, emission of carbon dioxide, which is a greenhouse gas, can be reduced. Furthermore, since the gas discharged through the combustion gas discharge passage 29 has a higher carbon dioxide concentration than the exhaust gas discharged from a normal sludge incinerator, the phosphoric acid production apparatus 8 can be downsized.

  Note that the combustion gas supplied to the combustion device 5 through the combustion gas supply path 22 is not pure air or oxygen-containing gas but pure oxygen generated by, for example, PSA (Pressure Swing Adsorption) or the like. The concentration of carbon dioxide contained in the gas supplied to the phosphoric acid production apparatus 8 through the carbon dioxide supply path 36 is further increased. Therefore, the phosphoric acid production apparatus 8 can be further downsized.

[Phosphorus recovery method]
The phosphorus recovery method according to another embodiment of the present invention differs from the phosphorus recovery method according to the first embodiment in that the combustion gas containing a high concentration of carbon dioxide discharged in the phosphorus separation step is used as the phosphoric acid production step. To supply. That is, in the phosphorus recovery method according to the present embodiment, when the acid used in the phosphoric acid manufacturing process is carbon dioxide, carbon dioxide contained in the combustion gas generated in the combustion process is used for manufacturing phosphoric acid.

  Thereby, the phosphorus collection | recovery method which concerns on this Embodiment can manufacture phosphoric acid still more cheaply compared with the phosphorus collection | recovery method in the said Embodiment 1. FIG. In addition, emission of carbon dioxide, which is a greenhouse gas, can be reduced.

[Embodiment 3]
[Phosphorus recovery equipment]
Compared with the phosphorus recovery apparatus in the first embodiment, the phosphorus recovery apparatus in still another embodiment of the present invention is discharged from the dehydrator 1 to the outside through the separation liquid discharge passage 16 as shown in FIG. The separation liquid supply path 37 for supplying a part of the liquid-containing separation liquid to the phosphoric acid production apparatus 8 is further provided. That is, the phosphorus recovery apparatus according to the present embodiment has a configuration in which a part of the separation liquid discharged from the dehydration apparatus 1 is supplied to the phosphoric acid production apparatus 8 as a raw material.

  The separation liquid contains components that are raw materials for fertilizer, such as Ca, P, N, K, and Na. Therefore, by supplying the separation liquid to the phosphoric acid production apparatus 8, these components can be recovered and used as raw materials. Therefore, the phosphorus recovery apparatus according to the present embodiment can manufacture phosphoric acid at a lower cost than the phosphorus recovery apparatus in the first embodiment. Moreover, since the amount of the separation liquid to be processed as the waste liquid is reduced, the cost related to the waste liquid processing can be reduced.

  In addition, the phosphorus collection | recovery apparatus in the said Embodiment 2 and the phosphorus collection | recovery apparatus in Embodiment 3 can also be combined.

[Phosphorus recovery method]
Unlike the phosphorus recovery method in the first embodiment, the phosphorus recovery method in another embodiment of the present invention supplies a part of the separated liquid discharged in the dehydration process as a raw material to the phosphoric acid manufacturing process. It is like that. That is, in the phosphorus recovery method according to the present embodiment, a part of the separation liquid discharged in the dehydration step is used for manufacturing phosphorus fertilizer (phosphate fertilizer).

  The separation liquid contains components that are raw materials for fertilizer, such as Ca, P, N, K, and Na. Therefore, these components can be recovered and used as raw materials by supplying the separation liquid to the phosphoric acid production process. Therefore, the phosphorus recovery method according to the present embodiment can produce phosphoric acid at a lower cost than the phosphorus recovery method according to the first embodiment. Moreover, since the amount of the separation liquid to be processed as the waste liquid is reduced, the cost related to the waste liquid processing can be reduced.

  The phosphorus recovery method in the second embodiment and the phosphorus recovery method in the third embodiment can be used in combination.

[Embodiment 4]
[Phosphorus recovery equipment]
As shown in FIG. 4, the phosphorus recovery apparatus in still another embodiment of the present invention does not include the phosphoric acid production apparatus 8 and the supply path 31 as compared with the phosphorus recovery apparatus in the first embodiment. The configuration further includes a circulating calcium oxide supply passage 39. The circulating calcium oxide supply path 39 supplies the dehydration apparatus 1 with particles containing calcium oxide as a main component obtained by the calcium oxide separation apparatus 6.

  Calcium oxide “CaO” is supplied (circulated) from the calcium oxide separator 6 through the circulating calcium oxide supply path 39 to the dehydrator 1. That is, the calcium oxide separator 6 supplies (circulates) calcium oxide to the dehydrator 1 in addition to the reformer 4. Thereby, calcium oxide circulates through the reforming device 4, the thermal decomposition device 3, the combustion device 5, the calcium oxide separation device 6, the dehydration device 1 and the drying device 2, is repeatedly used, and plays a plurality of roles as described above.

  The calcium oxide separation device 6 reduces the supply amount of the inorganic calcium compound supplied to the sludge slurry from the inorganic calcium compound supply channel 14 by supplying (circulating) calcium oxide to the dehydrating device 1 or inorganic. The supply of the inorganic calcium compound from the calcium compound supply path 14 can be made unnecessary.

  The phosphorus recovery apparatus according to the present embodiment can recover the separation product containing tricalcium phosphate as phosphorus-containing ash, but does not recover phosphorus but recovers hydrogen as a main purpose. It may be used as a device. That is, the phosphorus recovery apparatus according to the present embodiment may be an apparatus that recovers only hydrogen. In the case where phosphorus is not recovered, the phosphorus separation device 7 separates the solid-gas mixture supplied from the calcium oxide separation device 6 from the gas containing high concentration carbon dioxide by separating the ash and the gas containing high concentration carbon dioxide. Functions as an ash separator to obtain.

[Phosphorus recovery method]
Unlike the phosphorus recovery method in the first embodiment, the phosphorus recovery method in another embodiment of the present invention does not include a phosphoric acid production step. Moreover, a part of particle | grains which have the calcium oxide obtained by the calcium oxide isolation | separation process as a main component are supplied to a mixing process.

  Thereby, the phosphorus collection | recovery method which concerns on this Embodiment reduces the supply amount of the inorganic calcium compound supplied to a sludge slurry by a mixing process compared with the phosphorus collection | recovery method in the said Embodiment 1, or inorganic Supply of a calcium compound can be made unnecessary.

  The phosphorus recovery method according to the present embodiment can recover the separation product containing tricalcium phosphate as phosphorus-containing ash, but does not recover phosphorus, but recovers hydrogen for the main purpose of recovering hydrogen. It may be used as a method. That is, the phosphorus recovery method according to the present embodiment may be a method of recovering only hydrogen. When phosphorus is not recovered, the phosphorus separation step separates the solid-gas mixture supplied from the calcium oxide separation step from ash and gas containing high concentration carbon dioxide to obtain gas containing high concentration carbon dioxide. It becomes a separation process.

[Embodiment 5]
[Phosphorus recovery equipment]
As shown in FIG. 5, the phosphorus recovery apparatus in yet another embodiment of the present invention is compared with the phosphorus recovery apparatus in the fourth embodiment, as shown in FIG. And a calcium supply path 41. The carbon dioxide supply path 42 supplies a part of the gas containing high-concentration carbon dioxide discharged through the combustion gas discharge path 29 to the carbonator 40. The carbonation device 40 reacts calcium oxide with carbon dioxide in a gas containing high-concentration carbon dioxide supplied from the carbon dioxide supply path 42 by the reaction shown in the above formula (6), thereby converting the calcium carbonate into calcium carbonate. Convert. The calcium carbonate supply path 41 supplies the calcium carbonate obtained by the carbonator 40 to the dehydrator 1. In the present embodiment, the circulating calcium oxide supply channel 39 supplies particles containing calcium oxide as a main component to the carbonator 40.

When calcium oxide is directly supplied to the dehydrator 1 from the inorganic calcium compound supply path 14 or the circulating calcium oxide supply path 39, a part of the calcium oxide reacts with water, as shown in the following formula (13). Moreover, it may be converted to slaked lime (Ca (OH) ₂ ).

CaO + H ₂ O → Ca (OH) ₂ (13)
Since the slaked calcification reaction shown in Formula (13) is an exothermic reaction, the operation control of the dehydrator 1 may be unstable. Moreover, the hydroxyl group taken into calcium by the slaked calcification reaction is not separated from calcium in the drying device 2 but separated at the stage when it is brought into the thermal decomposition device 3 to become water vapor. For this reason, the hydroxyl group taken into calcium by the slaked calcification reaction lowers the temperature in the thermal decomposition apparatus 3, and there is a concern that the recovery efficiency of the fuel gas may be lowered as a result.

  When the inorganic calcium compound supplied to the dehydrator 1 is calcium carbonate, unlike calcium oxide, the reaction with water (slaked calcification reaction) as shown in Formula (13) can be suppressed.

  Therefore, when the inorganic calcium compound is calcium carbonate, heat generation due to the slaked calcification reaction represented by the formula (13) can be reduced. By reducing the heat generation, the operation control of the dehydrating apparatus 1 can be stabilized. Moreover, since calcium carbonate does not reduce the temperature in the thermal decomposition apparatus 3, it can suppress that the recovery efficiency of fuel gas falls as a result.

  With the above-described configuration, the phosphorus recovery apparatus according to the present embodiment can reduce the amount of slaked lime as compared with the phosphorus recovery apparatus in the fourth embodiment. It can suppress that recovery efficiency falls.

[Phosphorus recovery method]
The phosphorus recovery method according to another embodiment of the present invention is different from the phosphorus recovery method according to the fourth embodiment, in the gas containing calcium oxide and high concentration carbon dioxide supplied from the carbon dioxide supply path 42. It further includes a carbonation step of reacting with carbon dioxide to convert it into calcium carbonate. That is, calcium oxide is used in the mixing step after being converted to calcium carbonate.

  Thereby, the phosphorus recovery method according to the present embodiment can further suppress the reduction in the recovery efficiency of the fuel gas as compared with the phosphorus recovery method according to the fourth embodiment.

[Embodiment 6]
[Phosphorus recovery equipment]
Compared with the phosphorus collection | recovery apparatus in the said Embodiment 4, the phosphorus collection | recovery apparatus in further another embodiment of this invention is further provided with the carbon dioxide supply path 42, as shown in FIG. The carbon dioxide supply path 42 supplies a part of the gas containing high-concentration carbon dioxide discharged through the combustion gas discharge path 29 to the dehydrator 1.

  Thereby, since the phosphorus collection | recovery apparatus which concerns on this Embodiment can reduce the quantity of the slaked lime produced by the slaked calcification reaction shown to Formula (13) compared with the phosphorus collection | recovery apparatus in the said Embodiment 4, As a result, the fuel gas recovery efficiency can be prevented from decreasing.

[Phosphorus recovery method]
Unlike the phosphorus recovery method in the fourth embodiment, the phosphorus recovery method in another embodiment of the present invention supplies the gas containing high-concentration carbon dioxide obtained in the phosphorus separation step to the mixing step. It has become.

  Thereby, the phosphorus recovery method according to the present embodiment can further suppress the reduction in the recovery efficiency of the fuel gas as compared with the phosphorus recovery method according to the fourth embodiment.

[Embodiment 7]
As described above in Embodiment 4, one embodiment of the present invention may be an apparatus that recovers only hydrogen or a method that produces only hydrogen.

  One embodiment of the present invention provides a hydrogen recovery method and a hydrogen recovery apparatus for producing hydrogen from phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, human waste sludge generated at a human waste treatment plant, meat and bone meal, and livestock excrement. It is also aimed to do.

  In order to solve the above problems, a hydrogen recovery apparatus according to an aspect of the present invention is a hydrogen recovery apparatus that recovers hydrogen from phosphorus-containing biomass, and a mixing apparatus that mixes an inorganic calcium compound with the phosphorus-containing biomass; A pyrolysis device for pyrolyzing the mixture obtained by the mixing device, a combustion device for burning the pyrolysis product obtained by the pyrolysis device, and a phosphoric acid trioxide from the combustion product obtained by the combustion device. A separator for separating calcium; a reformer for producing a fuel gas having a hydrogen concentration higher than that of the fuel gas by steam reforming using calcium oxide from the fuel gas obtained by the thermal decomposition apparatus; including.

  In order to solve the above problems, a hydrogen recovery method according to an aspect of the present invention is a hydrogen recovery method of recovering hydrogen from phosphorus-containing biomass, and a mixing step of mixing an inorganic calcium compound with the phosphorus-containing biomass; A pyrolysis step in which the mixture obtained in the mixing step is pyrolyzed in the presence of water vapor, a combustion step in which the pyrolysis product obtained in the pyrolysis step is burned, and a combustion product obtained in the combustion step A fuel gas having a hydrogen concentration higher than that of the fuel gas is produced from the fuel gas obtained in the pyrolysis step using a separation step for separating tricalcium phosphate from the product by steam reforming using calcium oxide. A reforming step.

  According to one embodiment of the present invention, there is an effect that hydrogen can be recovered from phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, human waste sludge generated at a human waste treatment plant, meat-and-bone meal, and animal manure.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The phosphorus recovery method and the phosphorus recovery apparatus according to an embodiment of the present invention are included in, for example, phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, human waste sludge generated at a human waste treatment plant, meat-and-bone meal, and animal manure. It is preferably used in the recovery of phosphorus.

1 Dehydrator (mixer)
2 Drying device 3 Thermal decomposition device 4 Reforming device 5 Combustion device 6 Calcium oxide (CaO) separation device 7 Phosphorus separation device (separation device, ash content separation device)
8 Phosphoric acid production equipment

Claims (10)

A phosphorus recovery method for recovering phosphorus from phosphorus-containing biomass,
A mixing step of mixing an inorganic calcium compound with the phosphorus-containing biomass;
A pyrolysis step of pyrolyzing the mixture obtained in the mixing step in the presence of water vapor;
A combustion step of burning the pyrolysis product obtained in the pyrolysis step;
A separation step of separating tricalcium phosphate from the combustion product obtained in the combustion step;
A method for recovering phosphorus.   The phosphorus recovery method according to claim 1, wherein in the mixing step, 0.06 kg to 0.8 kg of an inorganic calcium compound is mixed per 1 kg of phosphorus-containing biomass dry weight.   The phosphorus recovery method according to claim 1 or 2, wherein the heating temperature of the mixture in the pyrolysis step is 400 ° C to 900 ° C, and the residence time is 0.1 hours to 2 hours.   The phosphorus collection | recovery method as described in any one of Claims 1-3 which further includes the phosphoric acid manufacturing process which adds an acid to the tricalcium phosphate isolate | separated at the said isolation | separation process, and obtains phosphoric acid.   The phosphorus recovery method according to any one of claims 1 to 4, wherein carbon dioxide is separated in the separation step from the combustion gas obtained together with the combustion product in the combustion step.   The phosphorus collection | recovery method of Claim 4 which isolate | separates a carbon dioxide from the combustion gas obtained with the combustion product at the said combustion process at the said separation process, and uses the said carbon dioxide as an acid for the said phosphoric acid manufacturing process.   The phosphorus recovery method according to claim 4, further comprising a dehydration step of dehydrating the mixture, wherein water separated in the dehydration step is used in the phosphoric acid production step.   The fuel gas obtained in the pyrolysis step further includes a reforming step of producing a fuel gas having a hydrogen concentration higher than that of the fuel gas by steam reforming using calcium oxide. The method for recovering phosphorus according to any one of the above. A phosphorus recovery device for recovering phosphorus from phosphorus-containing biomass,
A mixing device for mixing an inorganic calcium compound with the phosphorus-containing biomass;
A pyrolysis device for pyrolyzing the mixture obtained by the mixing device;
A combustion apparatus for burning the pyrolysis product obtained by the pyrolysis apparatus;
A separation device for separating tricalcium phosphate from the combustion product obtained by the combustion device;
Containing phosphorus recovery equipment.   10. The reformer according to claim 9, further comprising a reformer that produces a fuel gas having a hydrogen concentration higher than that of the fuel gas by steam reforming using calcium oxide from the fuel gas obtained by the thermal decomposition apparatus. Phosphorus recovery device.

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