JPS6041609B2 - How to recover vanadium from dephosphorization slag - Google Patents

Description

[Detailed description of the invention] This invention describes a method for collecting vanadium, specifically a method for collecting vanadium.

The present invention relates to a method for recovering vanadium from the so-called dephosphorization slag generated when pig iron or molten steel is desulfurized and dephosphorized using a slag forming agent containing an alkali metal carbonate as a main component. Vanadium (hereinafter referred to as V) is widely used as an additive component of alloy steel and as a raw material for catalysts in the chemical industry. The cost of harvesting is high.

The conventional process for collecting V from a V source starts with crushing the raw material, converts V into a water-soluble sodium compound through soda ash roasting, extraction filtration, neutralization precipitation, and soda ash melting. Ammonium chloride is added to the liquid obtained by extracting the compound with water to precipitate ammonium vanadate, which is separated by filtration, dehydrated and thermally decomposed.V is recovered in the form of V20. The V content in V ore is about 1% at most, and performing the above-mentioned roasting or melting treatment using soda pressure is extremely inefficient in terms of the amount of Na2CO3 used and heating fuel. That's a bad method. Now, the iron ore, coke, and heavy oil that are used as raw materials for steelmaking contain V, albeit in small amounts, and the pig iron discharged from the blast furnace contains approximately 0.1 V derived from the above raw materials.
Contained at a content rate of %.

When this pig iron is blown using a normal converter steel manufacturing method, most of the V is transferred to the converter slag, and its content reaches around 1%. Although some of the converter slag is reused as raw material for blast furnace charging, the majority of it is currently treated as waste because of its high phosphorus content. In addition, recently, hot metal before charging into a converter is treated with alkali metal carbonates (mainly Na2CO3).
A technique for removing sulfur (S) and phosphorus (P) from hot metal, the so-called hot metal dephosphorization method (simply referred to as hot metal dephosphorization in the present invention), has been proposed.

According to this method, P in pig iron (approximately 0.1 to 0.2%
) and S (approximately 0.02-0.05%) can be reduced to 0.01% and trace levels, respectively;
In the next converter blowing process, there is no need to add a large amount of slag-forming agent or special operations required for dephosphorization. However, the drawback of the hot metal dephosphorization method described above is that a large amount of relatively expensive alkali carbonate is used.
A method is needed to efficiently recover alkali metal carbonates from the slag (dephosphorization slag) generated during hot metal dephosphorization.

The present invention focuses on the fact that (2) transferred from hot metal during dephosphorization of hot metal and molten steel is concentrated to several percent in the form of alkali metal compounds, and effectively utilizes this as a source of (2). By recovering ■ from the dephosphorization slag and alkali metal carbonates as necessary, the total cost of dephosphorization of hot metal and molten steel can be drastically reduced, making it possible to implement it on an industrial scale. It is something to do.

The gist of the present invention lies in the following ① recovery method.

First, water and carbon dioxide gas are added to the dephosphorization slag produced when a slag-forming agent containing an alkali metal carbonate as the main component is added to hot metal or molten steel, and an extract solution in which the alkali metal compound of (2) is dissolved is prepared. obtain.

Adding an ammonium ion-generating ammonia compound to this extract to precipitate V as an ammonia compound,
Separate and collect. Since alkali metal carbonates are also dissolved in the extract obtained by treating the dephosphorization slag with hot water and carbon dioxide gas, the alkali metal can be extracted by concentrating the liquid before or after recovering the V mentioned above. Reusing carbonates as a slag-forming agent is extremely advantageous in reducing the cost of dephosphorization, but when recovering alkali metal carbonates for such purposes, the S in the liquid must be removed before the recovery process. It is better to remove the minute and P minutes.

This is because if a large amount of alkali metal combined with S and P is present in the recovered alkali metal carbonate, its desulfurization and dephosphorization ability decreases. The above S can be removed by adding Fe ions, and the P can be removed by adding Ca compounds. It is preferable to use a method in which FeS and Ca3(PO4)2 are precipitated and separated by addition. Hereinafter, the present invention will be described in detail using the process diagram of FIG. 1 as an example.

The process shown in FIG. 1 shows a process for treating dephosphorization slag generated when hot metal is dephosphorized using sodium carbonate (Na2CO3). Approximately 25k9 Na2c per ton of hot metal
When dephosphorization is performed by adding O3, the slag produced contains N.
Vanadate is contained in addition to the phosphate, oxide, and sulfide of a.

When this dephosphorization residue is brought into contact with water and CO2, Na phosphate, Na sulfide, and Na vanadate are eluted directly into the water, and Na oxide is converted into Na2C by the following reaction.
It's O3. In this extraction operation, the dephosphorization residue is -1
It is best to crush it to about 57r0n.

In addition, the ratio of water to dephosphorization slag (solid-liquid ratio) is 1.5 or more, and the water temperature is 6.
It is desirable to set the temperature to 0°C or higher in order to increase reaction efficiency. C
The amount of O2 (combustion waste gas containing about 10% or more of CO2 can also be used) is blown in such a range that the pH of the liquid becomes equal to 1. The undissolved residue separated from the above extract mainly consists of Fe and SiO2, and the Fe can be recovered by subjecting it to magnetic separation. Extract A after removing this undissolved content
Although the main purpose of the present invention is to recover V contained in the form of sodium vanadate, the process shown in FIG. 1 also intends to recover and reuse Na2cO3. Therefore, in order to remove the S and P components in the liquid A in advance, FesO4 and CaO are added. A reaction occurs due to these additions, and FeS. l5Ca3(P
The precipitate of O4)2 can be separated and separated. This operation is performed using Na2cO
It can be omitted if the recovery of Step 3 is not intended, or if it is not intended to be used as a slag forming agent for dephosphorization even if recovered. By concentrating extract B and performing solid-liquid separation, Na2cO
3 is separated from liquid B and collected.

Incidentally, even if Na2sO4 produced by reaction 2 above is mixed into this Na2cO3, there is no particular problem in using it as a sludge forming agent as long as the amount is up to about 10%. Na2
When an ammonium ion-generating ammonia compound such as (NlI4)2S04 is added to liquid C after cO3 has been separated, sodium vanadate (NaVO3) in the liquid is precipitated as ammonium vanadate.

If this is subjected to solid-liquid separation, part (1) can be recovered as NH4VO3.

Nlll■03 can be converted to V2O5 by thermal decomposition, and can also be reduced to pure V by further reduction. N? (2) By repeatedly subjecting the residual liquid D after separating 03 to the above-mentioned treatment together with the extract B, unrecovered components can be further recovered.

As mentioned earlier, the order of the V recovery process and the Na2cO3 recovery process does not have to be as shown in Figure 1, and the ammonium ion generating compound is added to extract A.
There is a method for carrying out the precipitation reaction of NH4VO3.

Example Using the hot metal dephosphorization slag (-15Tr0n) shown in Table 1-
Then, an extraction operation using hot water and CO2 was performed.

Ratio (weight ratio) of 1 part dephosphorization slag to 3 parts hot water (7 Offices C)
And so. The amount of CO2 blown was adjusted so that the pH of the liquid was approximately 10. Undissolved SiO2 and Fe were extracted from this extract.
Table 2 shows the concentration of each component in the liquid after filtering out the remaining components.

The extraction rate of V was about 80%, and the extraction rate of Na was about 75%.

When more than an equivalent amount of (NH4)2S04 was added to this extract, 90% or more of V in the solution was precipitated as NIil■03.

In other words, more than 70% of the ``■'' contained in the dephosphorization slag was recovered. In the above example, alkali metal carbonate (Na2CO3) was not recovered, but it is of course possible to add this recovery step.

Also, if you want to increase the extraction rate of (2), the water and CO
The extraction operation in step 2 may be repeated two or more times. Although the above explanation has mainly focused on hot metal dephosphorization slag, it goes without saying that V and, if necessary, alkali metal carbonates can be recovered from molten steel dephosphorization slag by the same treatment.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing one example of implementing the present invention.

Claims (1)

[Scope of Claims] 1. Dephosphorization slag generated when hot metal or molten steel is dephosphorized using a slag-forming agent containing an alkali metal carbonate as a main component, which is treated with water and carbon dioxide gas to form a dephosphorization slag. A method for recovering vanadium from dephosphorization slag, which comprises extracting vanadium as an alkali metal compound, adding an ammonium ion-generating ammonium compound to the extract, and separating and recovering vanadium as an ammonia compound. 2. The vanadium recovery method according to claim 1, which comprises the step of concentrating the extract before or after adding an ammonia compound, and precipitating and separating and recovering alkali metal carbonates in the solution. 3. A patent claim characterized in that Fe ions and Ca ions are added to the extract liquid prior to the step of precipitating the alkali metal carbonate, and the phosphorus content in the liquid is separated as calcium phosphate, and the sulfur content is separated as iron sulfide. The vanadium recovery method according to item 2.