KR100729009B1 - Method for withdrawing phosphorus from sewage sludge or burned ash thereof - Google Patents

Abstract

By recovering phosphorus from sewage sludge or incineration ash of sewage sludge, the incineration ash of sewage sludge or sewage sludge can be effectively used, thereby enabling sufficient utilization of resources.

Melting of phosphorus-containing iron by melting the sewage sludge containing phosphorus or the incineration ash of sewage sludge 2 in the electric melting furnace 15, and adding the iron or iron compound to the resulting melt to separate the melt according to the specific gravity difference. Produce metal 20.

Description

How to recover phosphorus from incineration of sewage sludge or sewage sludge {METHOD FOR WITHDRAWING PHOSPHORUS FROM SEWAGE SLUDGE OR BURNED ASH THEREOF}

1 is a schematic diagram illustrating an example of an apparatus for practicing the method of the present invention.

* Explanation of symbols for main parts of drawings *

2: Sewage sludge incineration ash (sewage sludge or sewage sludge incineration ash)

10: mill scale (iron or iron compound)

15: electric melting furnace

20: molten metal

The present invention relates to a method for recovering phosphorus from sewage sludge or sewage sludge incineration.

Sludge generated by sewage treatment is increasing with the spread of sewage, but as landfills, which were the main treatment sites, have been reduced, it is now more difficult to dispose of landfill than before. Therefore, in order to reduce the amount of sludge disposal, there is an urgent need to reduce the capacity and volume of the sewage sludge.

In addition, in order to effectively use the sewage sludge or the incineration ash of sewage sludge, it is desired to establish a recycling technology in addition to the reduction of the capacity and volume. To produce aggregates used in concrete.

However, although sewage sludge and sewage sludge incineration ash contain phosphorus, the conventional resource-recycling technique cannot recover phosphorus from sewage sludge incineration ash, and thus cannot fully utilize resources.

The present invention has been made in view of the above circumstances, and an object thereof is to enable the utilization of resources by effectively using phosphorus incineration of sewage sludge or sewage sludge by recovering phosphorus from the incineration ash of sewage sludge or sewage sludge.

In the method for recovering phosphorus according to the present invention, incineration of sewage sludge or sewage sludge containing phosphorus and iron or iron compounds are melted in an electric melting furnace to generate a melt, and the material contained in the melt is converted into a specific gravity difference of the material. Separation is to produce a molten metal containing phosphorus in iron.

In addition, in the method for recovering phosphorus according to the present invention, the sewage sludge containing the phosphorus or the incineration of the sewage sludge is melted in an electric melting furnace to form a melt, and the iron or iron compound is added to the melt to gravity the material contained in the melt. Separation according to the difference produces molten metal containing phosphorus in iron.

According to the present invention, since phosphorus which is important as a mineral resource can be recovered from iron incinerator of sewage sludge or sewage sludge as iron phosphide, the effective utilization of the incineration ash of sewage sludge or sewage sludge can be expected. Can be.

Moreover, in the present invention, it is preferable to melt the sewage sludge containing the phosphorus or the incineration material of the sewage sludge in a reducing atmosphere in an electric melting furnace.

When the incineration of the sewage sludge or the sewage sludge containing phosphorus is melted in a reducing atmosphere in this manner, the iron in the melt is promoted to be converted into metal iron, and the phosphoric acid is reduced to the phosphorus monomer, thereby improving the efficiency of operation. .

In order to make the inside of a melting furnace into a reducing atmosphere, at least one of a method of using coke as a raw material, a method of using a carbon material, and a method of suppressing the inflow of air into the furnace extremely, may be used. Efficiency can be achieved.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with an illustration example.

1 shows an example of an apparatus for carrying out the method of the present invention, wherein reference numeral 1 denotes a sewage sludge incinerator hopper for accommodating incineration ashes 2 of sewage sludge generated by incineration of sewage sludge by an incinerator not shown. , 3, 4, 5, and 6 are side feed hoppers, and 7 is a raw material supply conveyor. For example, dolomite (MgO + CaO; 8) is added to the sub-material hopper 3, quicklime (CaO; 9) is applied to the sub-material hopper 4, mill scale (FeO; 10) to the sub-material hopper 5, and the sub-material hopper 6 is used. ), The coke C 11 can be accommodated as a subsidiary material, respectively.

Reference numeral 12 denotes an incineration ash (2) and a dolomite (8) of the sewage sludge discharged from the sewage sludge incinerator hopper (1) and the subsidiary hoppers (3, 4, 5, 6) and returned from the raw material supply conveyor (7). , Quicklime 9, mill scale 10, and coke 11 are each a raw material supply conveyor for conveying them as the raw material 13, and reference numeral 14 denotes a plurality of raw materials disposed below the upper horizontal portion of the raw material supply conveyor 12. The raw material supply device 15 is an electric melting furnace for melting the raw material 13 injected from the raw material supply device 14.

The electric melting furnace 15 is a direct current type electric resistance furnace. A carbon electrode 16 serving as a cathode is provided at the center of the furnace, and an iron plate serving as an anode is formed inside the brick at the bottom of the furnace. The electrode 17 is embedded and the raw material 13 such as the incineration ash 2 of the sewage sludge can be melted by generating a joule heat by flowing a current between the electrodes 16 and 17.

In addition, reference numeral 18 is included in the melt produced by the sewage sludge incineration ash 2 and the like melted in the electric melting furnace 15, and is discharged from the discharge port 19 installed above the bottom of the electric melting furnace 15. 20 is a molten slag which is included in the melt and is discharged from the bottom of the electric melting furnace 15 to the container 21 at regular time intervals, and 22 is an upper outlet 23 installed above the electric melting furnace 15. ) Is a gas discharged to the outside of the electric melting furnace 15.

Next, the operation of the illustrated example will be described.

Sewage sludge incineration ash (2) from the sewage sludge incineration hopper (1), dolomite (8), quicklime (9), mill scale (10), coke discharged from each subsidiary hopper (3, 4, 5, 6) 11 is conveyed as the raw material 13 through the raw material supply conveyor 7, and is supplied to the raw material supply conveyor 12, and conveyed to the upper part through the raw material supply conveyor 12, and supplies raw material below from the upper horizontal part. It is supplied to the apparatus 14, and it is introduced into the electric melting furnace 15 from the raw material supply apparatus 14.

Dolomite (8), quicklime (9), mill scale (10) and coke (11) may be added to the electric melting furnace (15) after the incineration ash (2) of the sewage sludge begins to melt in the electric melting furnace (15). Alternatively, it may be introduced into the electric melting furnace 15 together with the incineration ashes 2 of the sewage sludge.

The raw materials 13, such as the incineration ashes 2 of sewage sludge injected into the electric melting furnace 15, are heated and melt | dissolved by Joule heat to about 1300 to 1600 degreeC under a reducing atmosphere. Thus, the material contained in the melt in the electric melting furnace 15 produced by melting the raw material 13 is separated according to the specific gravity difference, and the comparatively light calcium oxide, silicon dioxide, aluminum oxide, and magnesium oxide, which are the main components of the stone, are separated. It moves to the upper layer of silver melt, and heavy metals, such as iron with high specific gravity, settle to the lower layer of a melt. In addition, the substance having a low boiling point is vaporized and discharged out of the electric melting furnace 15 through the upper discharge port 23 as the gas 22.

Phosphorus is reduced in the electric melting furnace 15 to become a monomer, which is then combined with iron to form iron phosphide and settles to the lower layer of the molten liquid, so that iron is easily added to the lower layer by adding iron powder such as mill scale 10 as an auxiliary material. Can be separated.

The melt of the upper layer having a light specific gravity in the melt is continuously discharged through the discharge port 19 as the molten slag 18, and is solidified by a predetermined treatment in a later step to form stones of the same level as natural stone.

The melt having a high specific gravity transferred to the lower layer is extracted from the electric melting furnace 15 at a predetermined time interval as the molten metal 20 by removing the refractory material filled in the hole formed in the bottom of the electric melting furnace 15. By the process of storing in the container 21 etc., it cools and solidifies in a post process, and iron phosphide is formed.

When various raw materials 13 such as the incineration ash 2 of sewage sludge are melted in the electric melting furnace 15 to form iron phosphide, the electric melting furnace 15 includes, for example, [Formula 1], [Formula 2], and [Formula 2]. 3], [Formula 4], [Formula 5] and the reaction is made.

P ₂ O ₅ + 5C → 2P + 5CO

Fe ₂ O ₃ + 3C → 2Fe + 3CO

FeO + C → Fe + CO

Fe + P → FeP

2Fe + P → Fe ₂ P

According to the embodiment of the present invention, since phosphorus which is important as a mineral resource can be recovered as iron phosphide from the incineration ashes 2 of sewage sludge, the incineration ashes 2 of sewage sludge can be effectively used, and sufficient utilization of resources is made. Can be planned.

The inventors of the present application conducted a basic experiment to confirm the recovery of phosphorus and the separation of phosphorus, iron, heavy metals. In other words, incineration ash, dolomite, quicklime, mill scale and coke of sewage sludge were added to a direct current electric resistance furnace, and components such as molten metal extracted by melting in a reducing atmosphere were investigated. In order to ensure that the phosphorus and iron are combined, the amount of iron added to the direct current resistance furnace was increased to about twice the amount required chemically. As a result, very good results were obtained: about 92% of the recoverable phosphorus in the molten metal, about 5% of the phosphorus remaining as a stone component in the molten slag, and about 3% of the phosphorus discharged to the outside of the furnace as exhaust gas. The molten metal contained about 78% iron and about 15% phosphorus.

In the experiment, the incineration ash of sewage sludge having the components and contents shown in [Table 1] was used, and the ratio of dolomite, quicklime, mill scale and coke to the incineration ash of sewage sludge was as shown in [Table 2]. In addition, the quantity of the product produced | generated in the melt is as Table 3, and content of an iron phosphate component is as Table 4 shows.

ingredient Content (wt%) Silicon Dioxide (SiO ₂ ) 33.2 Calcium Oxide (CaO) 10.6 Aluminum Oxide (Al ₂ O ₃ ) 16.5 Magnesium Oxide (MgO) 3.01 Fe 9.48 Phosphorus (P) 8.61 Etc 18.6

ingredient Rate (kg / kg-ash) Sewage sludge incineration 1.0 Dolomite (MgO + CaO) 0.05 Quicklime (CaO) 0.08 Mill scale (FeO) 0.35 Coke (C) 0.26

ingredient Yield (kg / kg-ash) Incineration pellets 1.73 Molten slag 0.69 Molten metal 0.40 Molten fly ash 0.035

ingredient Content (wt%) Fe 78.1 Phosphorus (P) 15.2 Etc 6.7

In order to sell phosphorus extracted from sewage sludge or melt of incineration ash of sewage sludge as a product, it is preferable that the content of phosphorus in the sewage sludge or sewage sludge incineration ash is 20 wt% or more. It is thought to be feasible by adjusting suitably.

In the embodiment of the present invention, the case where the incineration material of the sewage sludge is used as the main raw material has been described. However, in order to use the unburned sewage sludge itself and to make the inside of the electric melting furnace into a reducing atmosphere, as in the embodiment example of the present invention, the sub-raw material It is also possible to use furnace coke, carbon material, or to minimize the inflow of air into the furnace.Using carbonaceous electrodes as an electrode can improve the durability of the electrode. Coating with a carbon material can improve the durability of the electric melting furnace, and of course, various modifications can be added within the scope not departing from the gist of the present invention.

As described above, according to the method for recovering phosphorus from the incineration of the sewage sludge or the sewage sludge according to claims 1 and 2 of the present invention, phosphorus which is important as a mineral resource is ignited from the sewage sludge or the sewage sludge ash. Since it can be recovered as iron, it is possible to effectively use sewage sludge or sewage sludge incineration ash, thereby enabling the utilization of resources, and in the case of claims 3 and 4, the iron powder of the melt is made of metal iron. Since it is promoted to be converted, and further, phosphoric acid is reduced to phosphorus monomer, various excellent effects can be achieved, such as efficiency of operation.

Claims (4)

Phosphorus containing sewage sludge or sewage sludge incinerator and iron or iron compounds are heated and melted in an electric melting furnace at 1,300 ℃ ~ 1,600 ℃ in the reducing atmosphere to promote the conversion of iron in the melt into metal iron and at the same time phosphoric acid To reduce it, Combining phosphorus monomer and metal iron in the melt to form iron pyrophosphate of heavy metal having a high specific gravity, and segregating iron phosphide from the melt to the lower layer of the electric melting furnace according to the size of the specific gravity to separate from the melt, A method for recovering phosphorus from sewage sludge or sewage sludge incineration, characterized by extracting a high specific gravity melt containing iron phosphide from the bottom of the furnace of the electric melting furnace. The sewage sludge or sewage sludge incineration ash containing phosphorus is heated and melted in an electric melting furnace at 1,300 ° C. to 1,600 ° C. in an electric melting furnace, thereby promoting the reduction of phosphoric acid into a phosphorus monomer to form a melt, By adding an iron compound in the melt to promote the conversion of iron in the melt to metal iron, In the melt, the phosphorus monomer and the metal iron are combined to form iron phosphide having a high specific gravity, and the iron phosphide is precipitated and separated from the melt into the lower layer of the melting furnace according to the size of the specific gravity. A method for recovering phosphorus from sewage sludge or sewage sludge incineration, characterized by extracting a high specific gravity melt containing iron phosphide from the bottom of the furnace of the electric melting furnace. The method for recovering phosphorus from sewage sludge or sewage sludge incinerator according to claim 1 or 2, wherein the sewage sludge or sewage sludge incinerator containing phosphorus is melted in a reducing atmosphere in an electric melting furnace. The sewage sludge according to claim 3, wherein at least one of a method of using coke as a raw material, a method of using carbon material, and a method of suppressing air inflow into the furnace extremely is performed in order to make the interior of the electric melting furnace into a reducing atmosphere. Or recovery of phosphorus from sewage sludge incineration.

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