JP2013142046A - Method of recovering raw material for slag phosphatic fertilizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for recovering a raw material for a slag phosphatic fertilizer by concentrating the content of POin dephosphorization slag to a level of "not less than 3.0% citric acid-soluble phosphoric acid" with an easy and low-cost method.SOLUTION: A method of recovering a raw material for slag phosphatic fertilizer containing not less than 3.0% citric acid-soluble phosphoric acid from dephosphorization slag which is generated in dephosphorization treatment of hot metal, includes carbonation-treating dephosphorization slag while introducing the slag into water in which carbon dioxide gas is dissolved and agitating it to elute the 2CaO/SiOphase in the dephosphorization slag, recovering a solid residue, and then repeating the operation of the carbonation treatment of the solid residue multiple times. The phosphorus is recovered from the treatment water subjected to the treatment at least twice.

Description

  The present invention relates to a raw material recovery method for mineral phosphate fertilizer.

The dephosphorization slag having a basicity of about 1.4 to 2.5 generated in the hot metal dephosphorization treatment contains many fertilizer components such as CaO, SiO ₂ , MgO, FeO, MnO, etc., and these fertilizer components Has been widely used as a “mineral acid fertilizer” (calcium fertilizer) for rice farming, field cropping and pasture use.

In addition, the dephosphorization slag generated in the hot metal dephosphorization treatment contains P ₂ O ₅ and there is a demand for utilization as a phosphoric acid fertilizer. In recent years, phosphorus resources have soared due to the problem of depletion of phosphate ore and the inclusion of phosphate ore in other countries. From the viewpoint that phosphorus contained in steelmaking slag has been reconsidered as a valuable phosphorus resource. Effective utilization of phosphorus contained in phosphorus slag is urgent.

However, in the fertilizer process standard established based on the Fertilizer Control Law, it contains 3.0% or more of soluble phosphoric acid as a requirement for the notation "mineral phosphoric acid fertilizer" (referring to steelmaking ore). However, since the P ₂ O ₅ content in dephosphorized slag is usually less than 3.0%, the phosphorus contained in dephosphorized slag is used as “mineral phosphate fertilizer” To do so, it is necessary to concentrate phosphorus.

Regarding the technology for concentrating and recovering P ₂ O ₅ in dephosphorized slag, for example, Patent Document 1 discloses that steelmaking slag is washed with carbonic acid-dissolved water to remove calcium, and then a mineral acid (such as hydrochloric acid or sulfuric acid). A technique for recovering P ₂ O ₅ in dephosphorized slag as high-purity phosphoric acid by extracting phosphorus from slag from which calcium has been removed using an inorganic acid) and neutralizing the extract is disclosed. .

  However, the method of extracting phosphorus from slag from which calcium has been removed using a mineral acid (inorganic acid such as hydrochloric acid or sulfuric acid) is expensive because hydrochloric acid and sulfuric acid are expensive and difficult to handle. In addition, there is a problem that the equipment cost is high, and the application to the production process of “mineral phosphate fertilizer” which only needs to be concentrated to meet the requirements of “mineral phosphate fertilizer” lacks practicality.

JP 2011-208277 A

The object of the present invention is to solve the above-mentioned problems, and to concentrate the P ₂ O ₅ content in the dephosphorized slag to a level of “containing at least 3.0% soluble phosphoric acid” by a low-cost and simple method. Thus, it is to provide a technique for recovering raw materials for slag phosphate fertilizer.

The raw material recovery method for mineral phosphite fertilizer of the present invention made to solve the above problems is for mineral phosphite fertilizer containing 3.0% or more of soluble phosphoric acid from dephosphorization slag generated by dephosphorization treatment of hot metal. A method of recovering a raw material, wherein dephosphorization slag is put into water in which carbon dioxide gas is dissolved and carbonized while stirring to elute the 2CaO.SiO ₂ phase in the dephosphorization slag, and solid After the residue is collected, the operation of carbonating the solid residue again is repeated a plurality of times, and at least phosphorus is collected from the treated water after the second time.

The invention according to claim 2 is the method for recovering raw materials for mineral phosphate fertilizer according to claim 1, wherein the phosphorus is recovered from the treated water from which the β-2CaO · SiO ₂ phase in which the phosphorus is dissolved is started to elute. It is a feature.

  The invention according to claim 3 is the method for recovering raw materials for mineral phosphate fertilizer according to claim 1 or 2, wherein the solid residue after carbonation treatment and the phosphorus recovered from the treated water are combined to make a raw material for phosphate fertilizer. It is characterized by this.

  The invention according to claim 4 is characterized in that, in the raw material recovery method for mineral phosphate fertilizer according to claim 1 or 2, the solid residue after carbonation is reused as an iron-making raw material.

  The invention according to claim 5 is characterized in that, in the raw material recovery method for mineral phosphoric acid fertilizer according to any one of claims 1 to 4, carbonation treatment is performed after pulverizing the dephosphorized slag under 2 mm. is there.

  The invention according to claim 6 is characterized in that, in the raw material recovery method for mineral phosphate fertilizer according to any one of claims 1 to 4, carbonation treatment is simultaneously performed while pulverizing dephosphorization slag to under 2 mm. Is.

The present invention is 2CaO · SiO ₂ phase present in the slag has coexist is γ-phase which is not dissolved with β-phase in solid solution with P ₂ O _5, at the time of carbonation process, P ₂ This is based on a new finding found by the present inventor that the γ phase not dissolved in O ₅ is preferentially decomposed.

According to the present invention, dephosphorization slag is poured into water in which carbon dioxide gas is dissolved and carbonized while stirring to elute the 2CaO.SiO ₂ phase in the dephosphorization slag and collect a solid residue. After that, the operation of carbonating the solid residue again is repeated a plurality of times, and at least a simple technique of recovering phosphorus from the treated water after the second time, an expensive and difficult mineral acid (such as hydrochloric acid or sulfuric acid). The concentration of P ₂ O ₅ in the dephosphorized slag is concentrated to the level of “containing at least 3.0% soluble phosphoric acid” without using the inorganic acid), and the raw material for the mineral phosphate fertilizer is recovered. Can do.

It is a schematic explanatory drawing of this invention. It is the whole apparatus explanatory drawing in the embodiment which repeats carbonation processing 5 times. It is a flowchart of the pre-processing process of dephosphorization slag performed prior to a carbonation process.

  Preferred embodiments of the present invention are shown below.

  FIG. 1 is a schematic explanatory diagram of the present invention, and FIG. 2 is an overall explanatory diagram of an apparatus configuration in an embodiment in which the carbonation treatment is repeated five times. FIG. 3 shows a flow chart of a dephosphorization slag pretreatment step performed prior to the carbonation treatment.

  The dephosphorization slag generated in the hot metal dephosphorization process is fed into the carbonation treatment tank shown in FIG. 1 through the steps shown in FIG. 3 through the steps of cooling, crushing, metal separation, crushing, and sieving. In order to efficiently perform the carbonation treatment, it is preferable that the dephosphorization slag is put into a carbonation treatment tank after being pulverized under 2 mm.

The carbonation tank is filled with dephosphorized slag and water pulverized under 2 mm, and the tank is agitated while CO ₂ gas is blown from below.

With stirring, dephosphorization slag is eluted in the tank by the following reaction.

_P 2 _{O 5} of dephosphorization slag is mainly solid-dissolved 2CaO · SiO ₂ phase, further, the 2CaO · SiO _{2 phase,} solid solution with β-phase in solid solution with P 2 _{O 5} Not γ phase coexists. During carbonation treatment, the γ-2CaO · SiO ₂ phase not dissolved in P ₂ O ₅ is preferentially decomposed, so that a solid residue mainly composed of β-2CaO · SiO ₂ phase in which phosphorus is dissolved. Is recovered, an increase in the concentration of P ₂ O ₅ in the slag is confirmed.

When this operation is repeated a plurality of times and the total time of carbonation treatment elapses for a predetermined time, elution of β-2CaO.SiO ₂ phase in which phosphorus is dissolved in the carbonation treatment tank starts to occur, and P in the treated water _{The 2} O ₅ concentration begins to increase.

From the viewpoint of effective utilization of phosphorus resources, it is preferable to recover and reuse all P ₂ O ₅ eluted in the treated water. However, the present invention concentrates phosphorus in order to utilize phosphorus contained in dephosphorized slag as “mineral phosphate fertilizer”, and is an official standard for fertilizers established based on the Fertilizer Control Law Then, since it is stipulated that 3.0% or more of soluble phosphoric acid is contained as a requirement for performing the notation “mineral phosphate fertilizer (refers to steelmaking ore)”, the P ₂ O ₅ concentration is a predetermined value. Only the treated water is recovered and reused. In the embodiment shown in FIG. 2, P ₂ O ₅ eluted in the treated water is not collected in the preceding carbonation treatment tanks 1 to 3, and P eluted in the treated water in the preceding carbonation treatment tanks 4 to 5. ₂ O ₅ is being recovered.

The P ₂ O ₅ recovered by the above process can be used alone or as a fertilizer production raw material together with the solid residue after carbonation treatment. The solid residue in which the carbonation treatment is repeated a plurality of times and the P ₂ O ₅ concentration in the slag is lowered may be reused as an iron-making raw material.

The Example of this invention is shown.
Table 1 shows the composition of the hot metal dephosphorization slag used in this example. This slag is prepared by charging blast furnace hot metal together with scrap into a converter-type furnace, using a CaO source and an oxygen source, and performing dephosphorization treatment while applying agitation. This is slag discharged from the furnace after discharging the hot metal, and after cooling, crushing, and performing magnetic separation to remove large iron particles.

Example 1
A part of this slag is pulverized, made under 2 mm, charged into a reaction vessel, stirred with an impeller, and carbonized while blowing combustion waste gas containing 20% CO ₂ and cooled to room temperature. Went.

Of the slag having the composition shown in Table 1, 5 kg was suspended in water for treatment. A slag sample was put into 250 L of water in a container provided with impeller stirring through an exhaust gas containing 20% CO ₂ in advance. Then, the process for 60 minutes was performed. Once the slag sample was filtered and separated, the newly prepared carbon dioxide gas was added to 250 L of water with impeller agitation, and further treated for 60 minutes. Mizuzan渣中P ₂ O ₅ concentration obtained at the beginning of treatment was 0%, but further were again residue P ₂ O ₅ concentration obtained after processing is 4.66%.

(Example 2)
The slag having the composition shown in Table 1 was treated 5 times at a water / slag ratio of 250/5 for 30 minutes. As a result, the final slag had a P ₂ O ₅ concentration of 5.69%. Further, the P ₂ O ₅ concentration in the residue of the extract was higher than the original slag P ₂ O ₅ concentration (2.41%) after the third time. In this case, it was set as the raw material of fertilizer manufacture using these 3rd, 4th, 5th liquid residue and post-process slag.

As described above, according to the present invention, dephosphorization slag is poured into water in which carbon dioxide gas is dissolved, and carbonation is performed while stirring, so that γ-2CaO · SiO _{2 in} which phosphorus is not solid-dissolved. The mineral acid (hydrochloric acid, sulfuric acid, etc.) that is expensive and difficult to handle is simply obtained by eluting the phase into the treated water and recovering the solid residue mainly composed of β-2CaO · SiO ₂ phase in which phosphorus is dissolved. The concentration of P ₂ O ₅ in the dephosphorized slag is concentrated to the level of “containing at least 3.0% soluble phosphoric acid” without using the inorganic acid), and the raw material for the mineral phosphate fertilizer is recovered. Can do.

Claims (6)

A method of recovering a raw material for mineral slag phosphate fertilizer containing 3.0% or more of soluble phosphoric acid from dephosphorization slag generated by dephosphorization of hot metal,
The dephosphorized slag is put into water in which carbon dioxide gas is dissolved and carbonized while stirring to elute the 2CaO.SiO ₂ phase in the dephosphorized slag and collect the solid residue. A method for recovering a raw material for slag phosphate fertilizer, characterized in that the operation of carbonating again is repeated a plurality of times, and phosphorus is recovered from at least the second and subsequent treated water. _{2. The} method for recovering raw materials for slag phosphate fertilizer according to claim 1, wherein phosphorus is recovered from the treated water from which the β-2CaO.SiO ₂ phase in which phosphorus is dissolved is started to elute.   3. The method for recovering raw materials for slag phosphate fertilizer according to claim 1 or 2, wherein the solid residue after carbonation treatment and the phosphorus recovered from the treated water are combined into a raw material for phosphate fertilizer.   The solid residue after carbonation treatment is reused as an iron-making raw material. The method for recovering raw materials for mineral phosphate fertilizer from dephosphorized slag according to claim 1 or 2.   The raw material recovery method for a mineral phosphate fertilizer according to any one of claims 1 to 4, wherein the dephosphorization slag is pulverized under 2 mm and then carbonized.   The method for recovering raw materials for slag phosphate fertilizer according to any one of claims 1 to 4, wherein carbonation treatment is simultaneously performed while pulverizing the dephosphorized slag under 2 mm.