JP7154368B2 - Hydrogen recovery method and hydrogen recovery device - Google Patents

Description

TECHNICAL FIELD 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 in a sewage treatment plant, night soil sludge generated in a night soil treatment plant, meat-and-bone meal, livestock manure, and the like.

For example, sewage sludge generated at a sewage treatment plant and night soil sludge generated at a night soil treatment plant contain high concentrations of phosphorus. Conventional methods for recovering phosphorus include a method of recovering phosphoric acid dissolved in water as HAP (basic calcium phosphate) or MAP (magnesium ammonium phosphate) in advanced treatment of anaerobic digestion liquid or sewage. , an ash-alkali extraction method in which phosphorus is extracted and precipitated from incinerated ash after sludge incineration with an alkaline chemical, and the like is known.

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 method for extracting phosphorus using carbon dioxide. Non-Patent Document 2 describes that carbon dioxide has the effect of extracting sparingly soluble phosphates such as tricalcium phosphate, that the form of the extracted phosphorus is hydrogen carbonate "CaHPO ₄ ", that carbonic acid It is also described that the concentrations of heavy metals containing phosphorus extracted as hydrogen salts are lower compared to other acid extractions. However, Non-Patent Document 1 describes low profitability due to increased construction costs, chemical costs, maintenance and management costs, etc. of the phosphorus resource recovery facility compared to the income from selling the recovered phosphorus resources, and low profitability due to increased phosphorus resource distribution. It is also stated that there are issues such as In other words, the recovery of phosphorus resources using carbon dioxide has a cost problem.

On the other hand, various countermeasures against adhesion and accumulation of incinerator ash caused by melting of low-melting phosphorus compounds have been studied. In incinerating sewage sludge, it is desired to maintain the incineration 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 incinerated ash to an incinerator can be prevented by increasing the amount of ferric polysulfate added to sludge. However, according to Non-Patent Document 3, sewage sludge contains a phosphorus compound with a relatively low melting point (40° C. to 500° C.). It is also described that problems such as adhesion and deposition of incinerated ash to the incinerator due to the melting of the compound occur.

On the other hand, in Patent Document 1, a compound containing a basic component such as Fe ₂ O ₃ , K ₂ O or MgO, or Ca ions such as calcium carbonate, slaked lime or quicklime is added to phosphorus in sludge. It describes a method of increasing the melting point of the incineration ash by adding the compound contained in it to phosphorus at an equivalent ratio of about 1:1 before incineration to increase the basicity of the incineration ash. Further, in Patent Document 1, phosphorus is recovered as crystals of calcium phosphate by adding a compound containing Ca ions to incineration ash.

JP 2015-120164 A

Guidance on Phosphorus Recycling in Sewage (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 (Takefumi Toyama, College of Science and Technology, Nihon University, "The 14th Phosphorus Resource Recycling Symposium" materials; July 21, 2016) Issues and countermeasures for both promotion of advanced treatment and countermeasures against global warming (Tokyo Metropolitan Government Bureau of Sewerage Technical Survey 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, so the form of the obtained phosphorus compound is the melting point. 975° C. of calcium metaphosphate “Ca(PO ₃ ) ₂ ”. Therefore, if the incineration temperature further rises in the incinerator or localized high-temperature spots occur, there is a concern that the inside of the incinerator will exceed the melting point of calcium metaphosphate. Therefore, the method described in Patent Literature 1 is insufficient to prevent adhesion of the phosphorus compound to the incinerator due to melting and clogging of the incinerator due to the melting in the pyrolysis treatment and combustion treatment. Further, in the method described in Patent Document 1, it is necessary to constantly analyze the components of the sludge in order to set the equivalent ratio of the compound to phosphorus to about 1:1. Also, in order to recover phosphorus as calcium phosphate, it is necessary to add a compound containing Ca ions in two stages, before and after incinerating the sludge.

One aspect of the present invention is to recover phosphorus from phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, night soil sludge generated at a night soil treatment plant, meat-and-bone meal, livestock manure, etc., as tricalcium phosphate, which is a high melting point compound. , a main object of which is to provide a phosphorus recovery method and a phosphorus recovery apparatus.

The inventor mixed an inorganic calcium compound with phosphorus-containing biomass and separated the products obtained by thermal decomposition reaction and combustion reaction to recover phosphorus as tricalcium phosphate, which is a high-melting compound. The present inventors have found that it is possible to complete the present invention.

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 a mixing step of mixing an inorganic calcium compound with the phosphorus-containing biomass, and thermally decomposing the mixture obtained in the mixing step in the presence of steam. Phosphorus recovery comprising a thermal decomposition step, a combustion step of burning the thermal decomposition products obtained in the thermal decomposition step, and a separation step of separating tricalcium phosphate from the combustion products 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 inorganic calcium compound is mixed per 1 kg of dry weight of phosphorus-containing biomass.

[3] The method for recovering phosphorus 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 hour to 2 hours.

[4] The method for recovering phosphorus according to any one of [1] to [3], further comprising a step of producing phosphoric acid by adding acid to the tricalcium phosphate separated in the separation step to obtain phosphoric acid.

[5] The method for recovering phosphorus according to any one of [1] to [4], wherein carbon dioxide is separated in the separation step from the combustion gas obtained together with combustion products 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 products in the combustion step, and the carbon dioxide is used as an acid in the phosphoric acid production step. Method.

[7] The method for recovering phosphorus according to [4], further comprising a dehydration step of dehydrating the mixture, wherein the water separated in the dehydration step is used in the phosphoric acid production step.

[8] Further comprising 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 method for recovering phosphorus according to any one of [7].

[9] A phosphorus recovery apparatus for recovering phosphorus from phosphorus-containing biomass, comprising: a mixing apparatus for mixing an inorganic calcium compound with the phosphorus-containing biomass; a thermal decomposition apparatus for thermally decomposing the mixture obtained by the mixing apparatus; A phosphorus recovery device comprising: a combustion device for burning pyrolysis products obtained in the pyrolysis device; and a separation device for separating tricalcium phosphate from the combustion products obtained in the combustion device.

[10] further comprising a reformer for producing a fuel gas with a hydrogen concentration higher than that of the fuel gas by steam reforming using calcium oxide from the fuel gas obtained in the pyrolyzer, [9] Phosphorus recovery device according to.

According to one aspect of the present invention, phosphorus is extracted from phosphorus-containing biomass such as sewage sludge generated at a sewage treatment plant, night soil sludge generated at a night soil treatment plant, meat and bone meal, and livestock manure as tricalcium phosphate, which is a high-melting compound. It has the effect of being able to be collected.

1 is a block diagram showing a schematic configuration of a phosphorus recovery device according to an embodiment of the present invention; FIG. FIG. 4 is a block diagram showing a schematic configuration of a phosphorus recovery device according to another embodiment of the present invention; FIG. 3 is a block diagram showing a schematic configuration of a phosphorus recovery device according to still another embodiment of the present invention; FIG. 3 is a block diagram showing a schematic configuration of a phosphorus recovery device according to still another embodiment of the present invention; FIG. 3 is a block diagram showing a schematic configuration of a phosphorus recovery device according to still another embodiment of the present invention; FIG. 3 is a block diagram showing a schematic configuration of a phosphorus recovery device according to still another embodiment of the present invention;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to this, and various modifications are possible within the scope described, and embodiments obtained by appropriately combining technical means disclosed in different embodiments are also present. included in the technical scope of In this 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 device]
A phosphorus recovery device according to an embodiment of the present invention comprises a mixing device for mixing an inorganic calcium compound with a phosphorus-containing biomass, a thermal decomposition device for thermally decomposing the mixture obtained by the mixing device, and and a separation device for separating tricalcium phosphate from the combustion products obtained in 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, night soil sludge generated at a human waste treatment plant, meat and bone meal, livestock manure, and the like. The form of phosphorus contained in the phosphorus-containing biomass includes, for example, organic phosphorus derived from living organisms, phosphoric acid-form phosphorus, and the like. However, the phosphorus-containing biomass is not limited to the phosphorus-containing biomass exemplified above. In the following description, sludge slurry, which is sewage sludge and night soil sludge, is taken as an example of phosphorus-containing biomass.

As shown in FIG. 1, the phosphorus recovery apparatus according to one embodiment of the present invention includes a dehydrator 1 that also serves as a mixer, a drying apparatus 2, a thermal decomposition apparatus 3, a reforming apparatus 4, a combustion apparatus 5, a calcium oxide At least a (CaO) separation device 6 , a phosphorus separation device 7 and a phosphoric acid production device 8 are provided. Each device is connected to each other by a device (not shown) having a transport function so that phosphorus recovery can be performed continuously. 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 recovery apparatus.

Hereinafter, each device constituting the phosphorus recovery device according to one embodiment of the present invention will be described with reference to FIG.

<Dehydrator 1>
The dehydrator 1 removes a separated liquid containing water from the sludge slurry (phosphorus-containing biomass) supplied through the sludge slurry supply path 13 to obtain dehydrated sludge slurry, and then feeds the obtained dehydrated sludge slurry to the dehydrated sludge slurry. It feeds the drying device 2 through the passage 15 . The dehydrator 1 also discharges the separated liquid containing water to the outside through the separated liquid discharge path 16 .

The dehydrator 1 may be any device capable of removing a separated liquid containing water from the sludge slurry, and examples thereof include a pressurized dehydrator such as a belt press or a mechanical dehydrator such as a centrifugal dehydrator.

Further, the dehydrator 1 also functions as a mixing device for mixing the sludge slurry with the inorganic calcium compound supplied from the inorganic calcium compound supply channel 14 . Therefore, the dehydrated sludge slurry supplied to the drying device 2 is a mixture of the sludge slurry and the inorganic calcium compound.

The timing of mixing the inorganic calcium compound with the sludge slurry may be before the separation liquid is removed from the sludge slurry, during the removal, or after the removal. Multiple times may be combined. 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 separated liquid.

(Inorganic calcium compound)
The inorganic calcium compound serves as a source of calcium for tricalcium phosphate “Ca ₃ (PO ₄ ) ₂ ” and also acts as a dehydration aid that promotes dehydration of sludge slurry. Therefore, by adding an inorganic calcium compound to the sludge slurry, it is possible to improve the dehydration property more than the normal dehydration method.

The inorganic calcium compound is preferably at least one selected from calcium carbonate “CaCO ₃ ”, slaked lime “Ca(OH) ₂ ”, quicklime “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, inorganic calcium compounds play multiple roles such as fluid media, carbon dioxide absorption media, heat sources for the gasification process (sensible heat media and carbon dioxide absorption reaction heat) and phosphorus melting inhibitors. . Furthermore, inorganic calcium compounds also have a secondary function of contributing to the production of high-concentration hydrogen.

The inorganic calcium compound may be supplied to the dehydrator 1 in its entirety supplied to the phosphorus recovery device, and a part thereof may be supplied to any of the thermal decomposition device 3, the reformer 4, and the combustion device 5 as described later. may be supplied to

The amount W (mol/kg-dry weight (DS)) of the inorganic calcium compound to be mixed with the sludge slurry is stoichiometrically represented by the following formula (1). That is, the amount W to be added should be at least the amount that can recover the phosphorus and sulfur contents 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)
Therefore, 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 with 1 kg of dry weight of sludge slurry (phosphorus-containing biomass). In particular, by mixing an excessive amount of the inorganic calcium compound with the sludge slurry, it is possible to more effectively prevent adhesion of the phosphorous compound to the incinerator due to melting and clogging 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 dewatering device 1 . The drying device 2 supplies a part of the evaporated moisture as dry steam to the thermal decomposition device 3 through the heat exchanger 11 and the thermal decomposition steam supply channel 18, and the rest is discharged to the outside through the dry steam discharge channel 17. Discharge. The dry steam supplied to the pyrolyzer 3 is used for pyrolyzing the mixture. Then, the drying device 2 supplies the dried mixture from which water is removed to the thermal decomposition device 3 through the dry sludge supply channel 19 . In addition, the drying device 2 supplies part of the mixture from which moisture has been removed and dried to the combustion device 5 through the dry sludge supply path 20 for the heat source, if necessary. The mixture supplied to the combustion device 5 is combusted as a heat source.

The drying device 2 is not particularly limited as long as it is a device capable of drying the mixture. Moreover, when the amount of water in the mixture obtained by the dehydrator 1 is small, the drying device 2 does not necessarily have to be provided. In that case, the mixture may be supplied from the dehydrator 1 to the thermal cracker 3 .

<Pyrolyzer 3>
The thermal decomposition unit 3 heats the mixture supplied from the dehydrator 1 or the drying unit 2 at 400° C. to 900° C., more preferably 600° C. to 800° C. in the presence of steam for 0.1 hour to 2 hours. It is thermally decomposed by holding for 1 hour, more preferably 0.5 hour to 1 hour. The thermal decomposition device 3 supplies thermal decomposition products obtained by thermal decomposition to the combustion device 5 through the thermal decomposition product supply passage 21 . Then, the thermal decomposition device 3 supplies the fuel gas, which is the thermal decomposition gas obtained by thermal decomposition, to the reformer 4 through the fuel gas supply passage 26 . In addition, calcium oxide “CaO” is supplied (circulated) from the reformer 4 to the thermal decomposition apparatus 3 through the supply channel 28, and, if necessary, a part of the new inorganic calcium compound is supplied. .

The thermal decomposition device 3 is not particularly limited as long as it can thermally decompose the mixture.

In the thermal decomposition device 3, thermal decomposition is performed by the following reaction to generate fuel gas. That is, the mixture is thermally decomposed in the presence of steam by the reaction represented by the following formula (2) and converted into thermal decomposition gas and solid residue. The pyrolysis gases _are hydrogen "H2", carbon monoxide "CO", carbon dioxide " _CO2 ", hydrogen sulfide " _H2S " and ammonia " _NH3 ", as well as methane " _CH4 ", a hydrocarbonaceous It contains as a main component a hydrocarbon-based gas “C _m H _n ” containing gas and tar components. Solid residues include charcoal and ash.

Mixture (C, H, O, _N , S) + _H2O → pyrolysis gas (H2, CO, _CO2 , _CmHn , _H2S , _NH3 ) ₊ C(charcoal) + ash...( 2)
Here, ash is a compound containing P, Si, Al, Fe, Mg, Ca, Na, K and the like.

A portion of the charcoal also reacts with water vapor and is converted to carbon dioxide and hydrogen as shown in formula (3) below.

C(charcoal) + 2H2O → _{CO2 + 2H2} (3)
Further, 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, which is an inorganic calcium compound added to the mixture and is mainly generated by heating, and as shown in the following formula (5), calcium sulfide becomes fixed. Most of the hydrogen sulfide contained in the pyrolysis gas is thus immobilized as calcium sulfide, resulting in an increase in the concentration of hydrogen in the pyrolysis gas.

CaO+ _H2S →CaS+ _H2O (5)
Then, the carbon dioxide generated by the reactions represented by the above formulas (2) to (4) reacts with calcium oxide to become calcium carbonate “CaCO ₃ ” as represented by the following formula (6), and is immobilized. 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 a high A fuel gas containing a concentration of hydrogen is produced.

CaO+ _CO2 → _CaCO3 (6)
On the other hand, the phosphorus contained in the ash 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 the present embodiment, the amount of inorganic calcium compound added to the sludge slurry is extremely large, and a large amount of calcium exists inside the thermal decomposition device 3 (reaction field). Phosphorus can therefore be converted to tricalcium phosphate, a high-melting phosphorus compound with a melting point of 1390°C.

Therefore, by thermal decomposition in the thermal decomposition apparatus 3, tricalcium phosphate, calcium sulfide, charcoal, calcium carbonate, unreacted inorganic calcium compounds, ash, etc. are removed from the mixture as solid components (solid residues). Pyrolysis products containing are obtained.

Since the tricalcium phosphate is a main component of phosphate ore resources, it can be reused as ore resources. In addition, since the melting point of tricalcium phosphate is as high as 1390° C., it is possible to prevent adhesion of the phosphorus compound to the incinerator due to melting of the phosphorus compound in the thermal decomposition device 3 and the combustion device 5 and clogging of the incinerator. Therefore, it becomes possible to operate the phosphorus recovery apparatus more stably and continuously.

<Reformer 4>
The reformer 4 performs steam reforming using calcium oxide from the fuel gas supplied from the thermal cracker 3 to produce a second fuel gas with a higher hydrogen concentration than the fuel gas, The second fuel gas is discharged through the fuel gas discharge passage 27 . The discharged second fuel gas is cooled by the heat exchanger 9 and recovered as gas containing high-concentration hydrogen. As a result, the phosphorus recovery device can be used as an energy conversion device that simultaneously recovers phosphorus and produces hydrogen. The heat recovered by heat exchanger 9 is supplied via line 35 to drying device 2 and heat exchangers 11,12.

In addition, calcium oxide "CaO" is supplied (circulated) from the calcium oxide separator 6 to the reformer 4 through a circulating calcium oxide supply channel 24, and if necessary, a part of a new inorganic calcium compound is supplied. Further, the reformer 4 supplies (circulates) calcium oxide to the pyrolyzer 3 through the supply path 28 .

The reformer 4 is not particularly limited as long as it is a device capable of steam reforming the fuel gas.

In the reformer 4, the fuel gas is steam-reformed by the following reaction to produce hydrogen of high concentration. That is, the fuel gas contains hydrogen and carbon monoxide, as well as methane “CH ₄ ”, a hydrocarbon-based gas “C _m H _n ” containing hydrocarbon-based gas and tar components. 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 produced carbon dioxide is absorbed by calcium oxide as shown in the above formula (6). As a result, a second fuel gas with a further increased hydrogen concentration, that is, a gas containing high-concentration hydrogen is obtained from the fuel gas.

<Combustion device 5>
The combustion device 5 burns the thermal decomposition products supplied from the thermal decomposition device 3 to produce combustion products and combustion gas, which are supplied to the calcium oxide separation device 6 through the combustion product supply passage 23 . Combustion gas serving as a heat source is externally supplied to the combustion device 5 through the heat exchanger 12 and the combustion gas supply passage 22 together with air or oxygen-containing gas. In addition, part of the new inorganic calcium compound is supplied to the pyrolyzer 3 as needed.

Further, the combustion device 5 is supplied with the mixture from the drying device 2 through the heat source dry sludge supply path 20 as required. The mixture is combusted as a heat source when it is difficult to combust the pyrolysis products in the combustor 5 only with the amount of heat generated by combustion of 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 is not particularly limited as long as it is a device capable of burning the thermal decomposition products.

In the combustion device 5, combustion products and combustion gas are produced by the following reactions. That is, as shown in the following formula (8), the charcoal contained in the pyrolysis products is combusted into carbon dioxide by air or an oxygen-containing gas. Moreover, as shown in the following formula (9), calcium carbonate contained in the thermal decomposition products is regenerated by becoming calcium oxide. Further, as shown in the following formula (10), the calcium sulfide contained in the thermal decomposition products is converted into gypsum (calcium sulfate) "CaSO ₄ " by air or an oxygen-containing gas.

C(charcoal)+ _O2 → _CO2 (8)
_CaCO3 →CaO+ _CO2 (9)
CaS+ _2O2 → _CaSO4 (10)
The reactions represented by the above formulas (8) and (10) are exothermic reactions, and the reaction heat generated by the reactions becomes sensible heat of the circulated calcium oxide, and the thermal decomposition device 3, the reformer 4, and the 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 produced by the reactions represented by the above formulas (8) to (10) and, if necessary, combustion of the mixture supplied from the drying device 2. Combustion products are obtained which are solid components containing. In addition, a combustion gas containing a high concentration of carbon dioxide is obtained together with the combustion products.

<Calcium oxide separator 6>
The calcium oxide separation device 6 separates particles containing calcium oxide as a main component and solid components containing tricalcium phosphate, gypsum, ash, etc. from the combustion products and combustion gas supplied from the combustion device 5. (combustion products other than calcium oxide) and combustion gases. The calcium oxide separator 6 then supplies the separated product and combustion gas, which are solid-gas mixtures, to the phosphorus separator 7 through the separated product supply path 25 . _The separated products include, as calcium phosphate compounds, tricalcium phosphate " _{Ca3 (} PO4) ₂ ", _P2O5 , _{CaPO4 ,} Ca _{( PO3)2 , Ca2P2O7} , _CaHPO4 and the like are included. The separated product has a smaller particle size than the particles containing calcium oxide as a main component.

On the other hand, the calcium oxide separator 6 supplies particles containing calcium oxide as a main component to the reformer 4 through the circulating calcium oxide supply channel 24 . As a result, the calcium oxide circulates through the reformer 4, the thermal decomposition device 3, the combustion device 5, and the calcium oxide separation device 6, is used repeatedly, and performs the multiple functions described above.

The calcium oxide separation device 6 may be any device that can separate combustion products into particles containing calcium oxide as a main component and other combustion products, and includes, for example, a cyclone. is not particularly limited.

<Phosphorus separator 7>
The phosphorus separator 7 separates the separation product and the combustion gas (solid-gas mixture) supplied from the calcium oxide separation device 6 into the separation product and the combustion gas. The phosphorus separator 7 discharges the separated combustion gas through the combustion gas discharge passage 29 . The exhausted combustion gas is cooled by the heat exchanger 10 and recovered as gas containing high-concentration carbon dioxide. As a result, it is possible to reduce greenhouse gas emissions in the phosphorus recovery apparatus. The heat recovered by heat exchanger 10 is supplied via line 34 to dryer 2 and heat exchangers 11,12.

The phosphorus separator 7 also supplies the separated product containing tricalcium phosphate to the phosphoric acid production apparatus 8 through the separated product supply line 30 . As a result, in the phosphorus recovery apparatus according to the embodiment of the present invention, phosphorus can be recovered as tricalcium phosphate, which is a high melting point compound. A part of the separated product separated by the phosphorus separator 7 may be supplied (circulated) to the reformer 4 through the supply passage 31 as necessary. As a result, the ratio of tricalcium phosphate to the circulating calcium oxide can be increased, so that the concentration of tricalcium phosphate in the separation 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 separation product and a combustion gas, and examples include a cyclone, bag filter, or ceramic filter, but the configuration is particularly limited. not.

<Phosphoric acid production device 8>
The phosphoric acid production device 8 adds the acid supplied through the acid supply channel 38 to the separated product containing tricalcium phosphate supplied from the phosphorus separation device 7 to react with the tricalcium phosphate to produce phosphorous. Acids and soluble phosphate compounds such as calcium dihydrogen phosphate are produced. The phosphoric acid production apparatus 8 supplies the produced soluble phosphoric acid compound to the outside through the soluble phosphoric acid compound discharge channel 32 . Further, the phosphoric acid manufacturing apparatus 8 discharges solid components (solid residue) containing calcium oxide, gypsum, ash, etc. contained in the separation product to the outside through the discharge path 33 .

Acids added to the separated product include, for example, inorganic acids such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid and carbon dioxide.

In the phosphoric acid manufacturing 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. occur.

_{Ca3 (} PO4) _{2 + 3H2SO4} → _3CaSO4 ↓+ _{2H3PO4 (} phosphoric acid)
…(11)
Ca3(PO4) ₂ + _2H2SO4 → _2CaSO4 ↓ ₊ Ca _{( H2PO4} ) _{2 (} calcium dihydrogen phosphate) ( ₁₂ )
The reactions shown in formulas (11) and (12) are similar to the reaction for obtaining soluble phosphorus from phosphate ore. Here, the mixture of gypsum and calcium dihydrogen phosphate obtained by the reaction shown in formula (12) is called superphosphate, and is the fertilizer with the highest production volume among phosphorus fertilizers (phosphate fertilizers). is. That is, the phosphoric acid production device 8 can produce a phosphorous fertilizer from tricalcium phosphate.

In addition, when carbon dioxide is used as the acid to be added, the effect of extracting sparingly soluble phosphates such as tricalcium phosphate is obtained, and the form of extracted phosphorus is hydrogen carbonate " _CHPO4 is known to be When carbon dioxide is used as an acid, the concentration of heavy metals contained in phosphorus extracted as a hydrogen carbonate becomes lower than when other acids are used.

In the phosphoric acid production apparatus 8, various soluble phosphoric acid compounds that serve as phosphoric fertilizers can be produced by reactions between tricalcium phosphate and various acids. Specific examples include acid-decomposed phosphate powder, ammonium phosphate, ammonium nitrophosphate, and calcium phosphate, in addition to the phosphoric acid, calcium dihydrogen phosphate, and lime superphosphate.

The ash contained in the separated product contains oxides such as Fe ₂ O ₃ , SiO ₂ or Al ₂ O ₃ that do not react with acids such as sulfuric acid to form sparingly soluble salts. When mixed with calcium dihydrogen oxide or the like, the resulting phosphorus fertilizer may not satisfy product standards. In this case, by supplying an alkaline agent such as NaOH to the phosphoric acid production apparatus 8 through the acid supply channel 38 (or other supply channel) and adjusting the pH and temperature of the produced soluble phosphoric acid compound, The oxide may be separated.

[Phosphorus recovery method]
A phosphorus recovery method in one embodiment of the present invention includes a mixing step of mixing an inorganic calcium compound with a phosphorus-containing biomass, a pyrolysis step of pyrolyzing the mixture obtained in the mixing step in the presence of steam, A method comprising a combustion step of burning thermal decomposition products obtained in the pyrolysis step, and a separation step of separating tricalcium phosphate from the combustion products obtained in the combustion step.

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

Hereinafter, each step constituting the phosphorus recovery method according to one embodiment of the present invention will be described. However, with respect to the content that overlaps with the content described in the phosphorus recovery apparatus described above, the description will be simplified or omitted.

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

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

A specific mixing method for mixing the sludge slurry and the inorganic calcium compound and a specific dewatering method for dewatering the mixture of the sludge slurry and the inorganic calcium compound are not particularly 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 portion of the evaporated water is used as dry steam for pyrolysis of the mixture in the pyrolysis step, and the rest is discharged to the outside. The dried mixture is subjected to the next pyrolysis step. Also, part of the dried mixture is combusted as a heat source in the combustion process, if desired.

A specific drying method for drying the mixture is not particularly limited. Moreover, when the amount of water in the mixture obtained in the dehydration step is small, the drying step is not necessarily required. In that case, the mixture obtained through the dehydration step may be subjected to the thermal decomposition step.

<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 heated in the presence of steam at 400°C to 900°C, more preferably at 600°C to 800°C. It is thermally decomposed by being kept under heating for 0.1 hour to 2 hours, more preferably 0.5 hour to 1 hour. 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 hour to 2 hours, more preferably 0.5 hour to 1 hour. is.

In the thermal decomposition step, thermal decomposition is performed by the reaction described above to generate fuel gas, which is thermal decomposition gas. The thermal decomposition products obtained by thermal decomposition are subjected to the combustion process. Then, the fuel gas obtained by thermal decomposition is supplied to the next reforming process. In addition, in the thermal decomposition step, the calcium oxide “CaO” used in the reforming step is supplied (circulated), and if necessary, a part of the new inorganic calcium compound is supplied.

A specific thermal decomposition method for thermally decomposing the mixture is not particularly limited.

Since the melting point of tricalcium phosphate contained in the thermal decomposition products is as high as 1390°C, it is necessary to prevent phosphorus compounds from sticking to the incinerator due to melting and clogging the incinerator during the thermal decomposition process and the following combustion process. can be done. Therefore, it becomes possible to operate the phosphorus recovery method more stably and continuously.

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

As a result, the method for recovering phosphorus according to one embodiment of the present invention can be used as a production method for recovering phosphorus and producing hydrogen at the same time. Heat recovered from the second fuel gas is supplied to the drying, pyrolysis and combustion processes.

In addition, in the reforming step, the calcium oxide “CaO” separated in the calcium oxide separating step is supplied (circulated), and if necessary, a part of the new inorganic calcium compound is supplied. Furthermore, the calcium oxide used in the reforming step is supplied (circulated) to the thermal decomposition step.

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

<Combustion process>
In the combustion step, the above reaction is performed by burning the thermal decomposition products obtained in the thermal decomposition step to obtain combustion products and combustion gas. Combustion products and combustion gases are fed to a subsequent calcium oxide separation step. 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 the combustion process, a part of the fresh inorganic calcium compound is supplied as necessary.

Furthermore, in the combustion step, the mixture described above is supplied from the drying step as required. The mixture is combusted as a heat source when it is difficult to combust the thermal decomposition products only by the amount of heat generated by combusting 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 thermal decomposition product is not particularly limited.

<Calcium oxide separation step>
In the calcium oxide separation step, particles containing calcium oxide as the main component and separation products (oxidation combustion products other than calcium) and combustion gases. 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. As a result, the calcium oxide is cycled through the reforming process, the thermal decomposition process, the combustion process and the calcium oxide separation process, is repeatedly used, and performs the multiple functions described above.

Although a specific separation method for separating combustion products into particles containing calcium oxide as a main component and other combustion products is not particularly limited, a separation method using a cyclone, for example, is preferable.

<Phosphorus separation step>
In the phosphorus separation step, the separation product and the combustion gas (solid-gas mixture) separated through the calcium oxide separation step are separated into the separation product and the combustion gas. The separated combustion gas is cooled and recovered as a gas containing high concentrations of carbon dioxide. As a result, the method for recovering phosphorus according to the embodiment of the present invention can reduce greenhouse gas emissions. Heat recovered from the combustion gases is supplied to the drying, pyrolysis and combustion processes.

The separated product containing tricalcium phosphate is fed to a subsequent phosphoric acid production unit. Thus, in the method for recovering phosphorus according to one embodiment of the present invention, phosphorus can be 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, if necessary. As a result, the ratio of tricalcium phosphate to circulating calcium oxide can be increased, so that the concentration of tricalcium phosphate in the separation product separated in the phosphorus separation step can be increased.

A specific separation method for separating the solid-gas mixture into the separation product and the combustion gas is not particularly limited, but a separation method using, for example, a cyclone, bag filter, or ceramic filter is preferable.

<Phosphoric acid manufacturing process>
In the phosphoric acid production step, the acid described above is added to the separated product obtained in the phosphorus separation step, and the reaction described above is performed. That is, in the phosphoric acid production step, the acid and tricalcium phosphate contained in the separated product are reacted to produce phosphoric acid and a soluble phosphoric acid compound such as calcium dihydrogen phosphate. In addition, solid components (solid residue) containing calcium oxide, gypsum, ash, etc. contained in the separated product are discharged to the outside.

In the phosphoric acid production process, various soluble phosphoric acid compounds that serve as phosphorus fertilizers can be produced by reacting tricalcium phosphate with various acids.

If 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 sparingly soluble salt, The oxide may be separated by supplying an alkaline agent to the phosphoric acid production process and adjusting the pH and temperature of the produced soluble phosphoric acid compound.

A specific reaction method for reacting the separated product and the acid is not particularly limited.

〔Example〕
Examples using the above-described phosphorus recovery apparatus and phosphorus recovery method will be described below.

<Conditions>
Table 1 summarizes an example of the properties of the raw sludge. The ash composition in Table 1 is an oxide conversion value. Table 2 summarizes an example of implementation conditions. As shown in Table 2, the amount of sludge supplied is 50 t-DS / d (DS: dry weight), and the water content of the sludge before dehydration is 97% by weight (Table 1), so the amount of sludge slurry is , 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, the operating conditions of the phosphorus separator 7 are set so that the amount of circulating calcium oxide circulating among the thermal decomposition device 3, the combustion device 5, the calcium oxide separation device 6 and the reformer 4 is 1. In addition, the sludge was set to have an ash content of 0.25. That is, a part of the separated product separated by the phosphorus separator 7 was supplied (circulated) to the reformer 4 through the supply channel 31, and tricalcium phosphate was set to circulate in the phosphorus recovery apparatus.

<Implementation result>
Table 3 shows each compound contained in the thermal decomposition product, the combustion product and the separated product in the present embodiment and the recovery amount thereof, based on the chemical equilibrium calculation results using commercially available process simulation software.

As shown in Table 3, tricalcium phosphate is the only form of calcium phosphate compound contained in the thermal decomposition products. Therefore, it is judged that calcium phosphate compounds other than tricalcium phosphate are unlikely to be produced in the thermal decomposition apparatus 3 . Therefore, almost all of the phosphorus contained in the sludge becomes tricalcium phosphate with a melting point of 1390° C. in the pyrolysis device 3, which prevents the melting of the phosphorus compound from adhering to the incinerator and clogging the incinerator. I know it can be done.

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

Incidentally, when 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 57 t/h, 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, it is possible to provide 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.

[Embodiment 2]
[Phosphorus recovery device]
As compared with the phosphorus recovery device in the first embodiment, the phosphorus recovery device in another embodiment of the present invention has a high concentration of carbon dioxide discharged through the combustion gas discharge passage 29 as shown in FIG. The configuration further includes a carbon dioxide supply path 36 for supplying the containing gas to the phosphoric acid production apparatus 8 . In other words, the phosphorus recovery apparatus according to the present embodiment uses carbon dioxide contained in the combustion gas generated by the combustion apparatus 5 to produce phosphoric acid when the acid supplied to the phosphoric acid production apparatus 8 is carbon dioxide. It has a configuration to use.

As a result, the phosphorus recovery apparatus according to the present embodiment can produce phosphoric acid at a much lower cost than the phosphorus recovery apparatus according to the first embodiment. In addition, it is possible to reduce the emission of carbon dioxide, which is a greenhouse gas. Furthermore, since the gas discharged through the combustion gas discharge path 29 has a higher concentration of carbon dioxide than the exhaust gas discharged from a normal sludge incinerator, the phosphoric acid production apparatus 8 can be made smaller.

Note that the combustion gas supplied to the combustion device 5 through the combustion gas supply passage 22 is not air or an oxygen-containing gas, but pure oxygen generated by, for example, a PSA (gas generator: Pressure Swing Adsorption). At this time, the concentration of carbon dioxide contained in the gas supplied to the phosphoric acid manufacturing apparatus 8 through the carbon dioxide supply channel 36 becomes even higher. Therefore, further miniaturization of the phosphoric acid manufacturing apparatus 8 is possible.

[Phosphorus recovery method]
The method for recovering phosphorus according to another embodiment of the present invention differs from the method for recovering phosphorus according to the first embodiment. It is designed to supply to That is, in the method for recovering phosphorus according to the present embodiment, carbon dioxide contained in the combustion gas generated in the combustion step is used for the production of phosphoric acid when the acid used in the phosphoric acid production step is carbon dioxide.

As a result, the phosphorus recovery method according to the present embodiment can produce phosphoric acid at a much lower cost than the phosphorus recovery method according to the first embodiment. In addition, it is possible to reduce the emission of carbon dioxide, which is a greenhouse gas.

[Embodiment 3]
[Phosphorus recovery device]
In a phosphorus recovery device according to still another embodiment of the present invention, as compared with the phosphorus recovery device in the first embodiment, as shown in FIG. The configuration further includes a separated liquid supply path 37 for supplying a part of the separated liquid containing moisture to the phosphoric acid manufacturing apparatus 8 . That is, the phosphorus recovery apparatus according to the present embodiment has a configuration in which part of the separated liquid discharged from the dehydrator 1 is supplied to the phosphoric acid production apparatus 8 as a raw material.

The separated liquid contains components such as Ca, P, N, K and Na, which are raw materials for fertilizers. Therefore, by supplying the separated liquid to the phosphoric acid manufacturing apparatus 8, these components can be recovered and used as raw materials. Therefore, the phosphorus recovery apparatus according to the present embodiment can produce phosphoric acid at a much lower cost than the phosphorus recovery apparatus according to the first embodiment. In addition, since the amount of separated liquid to be treated as waste liquid is reduced, the cost for waste liquid treatment can be reduced.

Incidentally, the phosphorus recovery device in the second embodiment and the phosphorus recovery device in the third embodiment can be combined.

[Phosphorus recovery method]
In the method for recovering phosphorus according to another embodiment of the present invention, unlike the method for recovering phosphorus according to the first embodiment, part of the separated liquid discharged in the dehydration step is supplied to the phosphoric acid production step as a raw material. It's like That is, in the method for recovering phosphorus according to the present embodiment, part of the separated liquid discharged in the dehydration step is used for manufacturing phosphorus fertilizer (phosphate fertilizer).

The separated liquid contains components such as Ca, P, N, K and Na, which are raw materials for fertilizers. Therefore, by supplying the separated liquid to the phosphoric acid production process, these components can be recovered and used as raw materials. Therefore, the phosphorus recovery method according to the present embodiment can produce phosphoric acid at a much lower cost than the phosphorus recovery method according to the first embodiment. In addition, since the amount of separated liquid to be treated as waste liquid is reduced, the cost for waste liquid treatment can be reduced.

It should be noted that the phosphorus recovery method in the second embodiment and the phosphorus recovery method in the third embodiment can be used together.

[Embodiment 4]
[Phosphorus recovery device]
A phosphorus recovery apparatus according to still another embodiment of the present invention does not include a phosphoric acid production apparatus 8 and a supply path 31 as shown in FIG. , a circulating calcium oxide supply path 39 is further provided. The circulating calcium oxide supply path 39 supplies particles containing calcium oxide as a main component obtained in the calcium oxide separator 6 to the dehydrator 1 .

Calcium oxide “CaO” is supplied (circulated) from the calcium oxide separator 6 to the dehydrator 1 through a circulating calcium oxide supply path 39 . That is, the calcium oxide separator 6 supplies (circulates) calcium oxide to the dehydrator 1 in addition to the reformer 4 . As a result, calcium oxide circulates through the reformer 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 used repeatedly, and performs the multiple functions described above.

The calcium oxide separation device 6 supplies (circulates) calcium oxide also to the dehydrator 1, thereby reducing the amount of inorganic calcium compound supplied to the sludge slurry from the inorganic calcium compound supply channel 14, or reducing the amount of inorganic calcium compound supplied to the sludge slurry. It is possible to eliminate the need to supply the inorganic calcium compound from the calcium compound supply channel 14 .

The phosphorus recovery apparatus according to the present embodiment can recover the separated product containing tricalcium phosphate as phosphorus-containing ash. It can be used as a device. That is, the phosphorus recovery device according to the present embodiment may be a device that recovers only hydrogen. When phosphorus is not recovered, the phosphorus separator 7 separates the solid-gas mixture supplied from the calcium oxide separator 6 into ash and gas containing high concentration carbon dioxide to obtain gas containing high concentration carbon dioxide. It functions as an ash separator to obtain.

[Method for recovering phosphorus]
The phosphorus recovery method according to another embodiment of the present invention does not include a phosphoric acid production step, unlike the phosphorus recovery method according to the first embodiment. Also, part of the particles containing calcium oxide as a main component obtained in the calcium oxide separation step is supplied to the mixing step.

As a result, the phosphorus recovery method according to the present embodiment can reduce the supply amount of the inorganic calcium compound supplied to the sludge slurry in the mixing step, or the inorganic Calcium compounds can be dispensed with.

The phosphorus recovery method according to the present embodiment can recover the separated product containing tricalcium phosphate as phosphorus-containing ash, but the main purpose is to recover hydrogen without recovering phosphorus. It can be used as a method. That is, the method for recovering phosphorus according to the present embodiment may be a method for recovering only hydrogen. When phosphorus is not recovered, the phosphorus separation step separates the solid-gas mixture supplied from the calcium oxide separation step into 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 device]
As compared with the phosphorus recovery device in the fourth embodiment, the phosphorus recovery device in still another embodiment of the present invention has a carbon dioxide supply passage 42, a carbonation device 40, a carbonation A calcium supply channel 41 is further provided. The carbon dioxide supply path 42 supplies part of the gas containing high-concentration carbon dioxide discharged through the combustion gas discharge path 29 to the carbonation device 40 . The carbonation device 40 reacts calcium oxide with carbon dioxide in the gas containing high-concentration carbon dioxide supplied from the carbon dioxide supply channel 42 by the reaction shown in the above formula (6) to form calcium carbonate. convert. The calcium carbonate supply path 41 supplies the calcium carbonate obtained in the carbonation device 40 to the dehydrator 1 . In this embodiment, the circulating calcium oxide supply path 39 supplies particles containing calcium oxide as the main component to the carbonation device 40 .

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

CaO+ _H2O →Ca(OH) ₂ (13)
Since the slaked calcification reaction represented by the 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 mineralization reaction is not separated from the calcium in the drying device 2, but is separated at the stage brought into the thermal decomposition device 3 to become water vapor. For this reason, there is concern that the hydroxyl group taken into calcium by the slaked calcification reaction lowers the temperature inside the thermal decomposition device 3, and as a result, the fuel gas recovery efficiency is lowered.

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 shown in formula (13) can be reduced. By reducing heat generation, the operation control of the dehydrator 1 can be stabilized. In addition, since calcium carbonate does not lower the temperature inside the thermal decomposition device 3, it is possible to suppress a decrease in the recovery efficiency of the fuel gas.

With the configuration described above, the phosphorus recovery apparatus according to the present embodiment can reduce the amount of slaked lime compared to the phosphorus recovery apparatus according to the fourth embodiment. A decrease in recovery efficiency can be suppressed.

[Method for recovering phosphorus]
The phosphorus recovery method according to another embodiment of the present invention is different from the phosphorus recovery method according to the fourth embodiment. It further includes a carbonation step of reacting with carbon dioxide to convert it to calcium carbonate. That is, calcium oxide is converted to calcium carbonate before being used in the mixing process.

As a result, the phosphorus recovery method according to the present embodiment can further suppress a decrease in fuel gas recovery efficiency as compared with the phosphorus recovery method according to the fourth embodiment.

[Embodiment 6]
[Phosphorus recovery device]
A phosphorus recovery apparatus according to still another embodiment of the present invention further includes a carbon dioxide supply line 42, as shown in FIG. 6, compared to the phosphorus recovery apparatus according to the fourth embodiment. The carbon dioxide supply path 42 supplies part of the gas containing high-concentration carbon dioxide discharged through the combustion gas discharge path 29 to the dehydrator 1 .

As a result, the phosphorus recovery device according to the present embodiment can reduce the amount of slaked lime generated by the slaked lime reaction shown in the formula (13) compared to the phosphorus recovery device in the fourth embodiment. As a result, it is possible to suppress the decrease in fuel gas recovery efficiency.

[Method for recovering phosphorus]
In the phosphorus recovery method according to another embodiment of the present invention, unlike the phosphorus recovery method according to the fourth embodiment, the gas containing high-concentration carbon dioxide obtained in the phosphorus separation step is supplied to the mixing step. It has become.

As a result, the phosphorus recovery method according to the present embodiment can further suppress a decrease in fuel gas recovery efficiency 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 for recovering only hydrogen or a method for producing only hydrogen.

One aspect 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, night soil sludge generated at a night soil treatment plant, meat and bone meal, and livestock manure. It also aims to

In order to solve the above problems, a hydrogen recovery device according to one aspect of the present invention is a hydrogen recovery device for recovering hydrogen from phosphorus-containing biomass, comprising: a mixing device for mixing an inorganic calcium compound with the phosphorus-containing biomass; a thermal decomposition device for thermally decomposing the mixture obtained in the mixing device; a combustion device for burning the thermal decomposition products obtained in the thermal decomposition 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 in the pyrolyzer; including.

In order to solve the above problems, a hydrogen recovery method according to one aspect of the present invention is a hydrogen recovery method for recovering hydrogen from phosphorus-containing biomass, comprising a mixing step of mixing an inorganic calcium compound with the phosphorus-containing biomass; A thermal decomposition step of thermally decomposing the mixture obtained in the mixing step in the presence of steam, a combustion step of burning the thermal decomposition product obtained in the thermal decomposition step, and a combustion product obtained in the combustion step A separation step of separating tricalcium phosphate from the substance, and steam reforming using calcium oxide from the fuel gas obtained in the thermal decomposition step to produce a fuel gas with a hydrogen concentration higher than that of the fuel gas. and a reforming step.

According to one aspect 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, night soil sludge generated at a night soil treatment plant, meat-and-bone meal, livestock manure, and the like.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be 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 device according to one embodiment of the present invention are included in phosphorus-containing biomass such as sewage sludge generated at sewage treatment plants, night soil sludge generated at night soil treatment plants, meat and bone meal, livestock manure, and the like. It is preferably used in the recovery of phosphorus.

1 Dewatering device (mixing device)
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 separation device)
8 Phosphoric acid manufacturing equipment

Claims (8)

A hydrogen recovery method for recovering hydrogen from phosphorus-containing biomass, comprising:
A mixing step of mixing an inorganic calcium compound with the phosphorus-containing biomass;
a thermal decomposition step of thermally decomposing the mixture obtained in the mixing step in the presence of water vapor using the inorganic calcium compound as a fluid medium;
a combustion step of burning the thermal decomposition products obtained in the thermal decomposition step;
a separation step of separating tricalcium phosphate from the combustion products obtained in the combustion step;
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 thermal decomposition step;
including
The addition amount W (mol/kg-dry weight (DS)) of the inorganic calcium compound with respect to the dry weight of the phosphorus-containing biomass is W (mol/kg-DS) ≧ (3/2) × P (mol/kg- DS) + S (mol/kg-DS), the hydrogen recovery method. The hydrogen recovery method according to claim 1, wherein in the mixing step, 0.06 kg to 0.8 kg of inorganic calcium compound is mixed per 1 kg of dry weight of phosphorus-containing biomass. 3. The method for recovering hydrogen according to claim 1, wherein the heating temperature of the mixture in the thermal decomposition step is 400° C. to 900° C., and the residence time is 0.1 hour to 2 hours. The hydrogen recovery method according to any one of claims 1 to 3, further comprising a phosphoric acid production step of adding an acid to the tricalcium phosphate separated in the separation step to obtain phosphoric acid. The hydrogen recovery method according to any one of claims 1 to 4, wherein carbon dioxide is separated in said separation step from combustion gas obtained together with combustion products in said combustion step. 5. The method for recovering hydrogen according to claim 4, wherein carbon dioxide is separated in said separation step from the combustion gas obtained together with combustion products in said combustion step, and said carbon dioxide is used as an acid in said phosphoric acid production step. 5. The method for recovering hydrogen according to claim 4, further comprising a dehydration step of dehydrating said mixture, wherein water separated in said dehydration step is used in said phosphoric acid production step. A hydrogen recovery device for recovering hydrogen from phosphorus-containing biomass,
a mixing device for mixing an inorganic calcium compound with the phosphorus-containing biomass;
a thermal decomposition device that thermally decomposes the mixture obtained in the mixing device in the presence of water vapor using the inorganic calcium compound as a fluid medium;
a combustion device for burning the pyrolysis products obtained in the pyrolysis device;
a separation device for separating tricalcium phosphate from combustion products obtained in the combustion device;
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 in the pyrolyzer;
including
The addition amount W (mol/kg-dry weight (DS)) of the inorganic calcium compound with respect to the dry weight of the phosphorus-containing biomass is W (mol/kg-DS) ≧ (3/2) × P (mol/kg- DS) + S (mol/kg-DS).

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