JPH02277709A - Method for recovering raw material for phosphatic fertilizer from molten iron pretreatment slag - Google Patents

Abstract

PURPOSE:To minimize a unit requirement of a pretreating agent and to recover the raw material for phosphatic fertilizer from the slag by pretreating molten iron at low basicity and recovering the slag having specified calculated contents of F and P2O5 in the generated slag. CONSTITUTION:When molten iron is treated with the pretreating agent contg. a desulfurizing agent and a desiliconizing agent, desulfurization and desiliconization are carried out at the low basicity of (CaO/SiO2)<=3.0 as the pretreatment. Consequently, good-quality slag having a low content of F is formed, and the unit requirement of the pretreating agent is reduced. The slag in the formed molten iron pretreatment slag contg. <=1.5% F and >=3.5% P2O5 calculated from the equations, F%=alphaXWspar/Wslog and P2 O5%=(0.0229X(Po-Pr)+R.P2O5/100XWR)X100/Wslog, is recovered as the raw material for phosphatic fertilizer (F is the F% in the slag, alpha is F% in fluorite, Wspar is fluorite amt. kg/molten slag ton, Wslog is slag amt. kg/molten slag ton, P2O5 is the P2O5% in slag, Po and Pr are P concn. (X10<-3>%) at before and after treating, R.P2O5 is P2O5% in the residual slag and WR is residual slag amt. kg/molten iron ton).

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for recovering raw material for phosphoric acid fertilizer from hot metal pre-treated slag.

<Prior Art> In conventional converter operation using the top-blowing method, the pretreatment of the hot metal was mainly performed by desulfurization because St in the hot metal was used as a heat source. However, in recent years, a combined blowing method of bottom blowing and top and bottom blowing has been implemented, and hot metal pretreatment requires desulfurization, desiliconization, and dephosphorization, each of which requires different types of hot metal blowing. Hot metal pretreatment is now performed separately for each of the above treatments using a pretreatment agent.

That is, a CaO-based material is used as a desulfurization agent, an iron oxide source such as iron ore powder, mill scale, dust collected in the steel industry is used as a desiliconization agent, and CaO-CaF! is used as a dephosphorization agent. - The usual method is to separately inject pretreatment agents such as iron oxide through lances, but soda ash-based fluxes are also used for phosphorization and desulfurization treatments.

Dephosphorization and desulfurization treatments using lime-based fluxes have the problem of increasing flux costs and slag treatment costs, and contaminating the hot metal container, especially since a large amount of quicklime is used in the desulfurization treatment. Dephosphorization and desulfurization treatment using soda ash-based flux simultaneously performs desiliconization and dephosphorization treatment using soda ash and iron oxide.
Soda ash reacts with 5i(h and P2O), and the amount of effective soda ash that reacts with subsequent S decreases.As a result, the unit consumption of expensive soda ash increases, which becomes a major cause of high costs.

Furthermore, when using soda ash, there are problems such as significant damage to the refractories of the hot metal container.

By the way, when dephosphorizing slag produced during the dephosphorizing treatment of hot metal is conventionally used as a raw material for phosphoric acid fertilizer, the fluorine (F) i11 degree in the dephosphorizing slag based on fluorite (CaFt) as a pretreatment agent is When the temperature increases, citric acid-soluble phosphoric acid (
It is known that the concentration of P2O3) decreases and it no longer plays the role of a phosphoric acid fertilizer.

The citric acid solubility rate (%) of P2O in the slag is P,0
．． In other words, it is a method to confirm the fertilizing effect of phosphoric acid fertilizer in a short period of time.A material containing phosphoric acid (HAS) is immersed in a 2% citric acid solution at 30'C for 1 hour, and the p in the phosphorous material is confirmed. ,o,
The amount eluted into the citric acid solution is expressed as a percentage.

On the other hand, when pre-treating hot metal using the simultaneous dephosphorization and desulfurization method, it is necessary to ensure the slag basicity (Cab/5ift) to be 4 or higher, thereby ensuring the reactivity of the slag and its discharge from the pig iron mixing car. It was being processed.

<Problem to be solved by the invention> However, when the slag basicity is 4 or more, the pzos of the slag
If the F concentration of the slag is reduced by suppressing the addition of fluorite (CaFz) to increase the concentration, the reaction efficiency will decrease and the inside of the pig iron car will be contaminated with slag due to adhesion.
There was a problem that the i degree could not be lowered.

Therefore, JP-A-56-127717 proposes a method of adding a portion of fluorite instead of calcium chloride (CaC1g) without making P2O3 insoluble. However, Caclx has a problem in that it is difficult to handle and expensive because it is hygroscopic.

The present invention solves the above-mentioned problems, minimizes the unit consumption of the pretreatment agent, reduces the Fm degree in the slag without deteriorating the reactivity of the slag and the slag discharge performance, and reduces the P,
0. The purpose of the present invention is to provide a method for recovering raw materials for phosphoric acid fertilizer from hot metal preliminary slag, which can ensure the following.

Means for Solving the Problems> The method for recovering raw materials for phosphoric acid fertilizers from hot metal preliminary slag of the present invention which achieves the above objects is a method for recovering raw materials for phosphorous fertilizers from hot metal pretreated slag. (CaO/SiO
2) Pre-treated with a low basicity of ≦3.0, and in the hot metal pre-treated slag produced in the pre-treatment, fluorine (F) 1 degree calculated based on the following formula is 1.5% or less and phosphoric acid ( P2
O3) This method is characterized in that hot metal pre-treated slag that does not satisfy the condition that the m degree is 3.5% or more is recovered as a raw material for phosphoric acid fertilizer.

(%F) = a XWspar/Wslog(%
PZO5) = (0,0229X (POPF) +
R-P2O3/100XW*) X100/Wsl
og Here, F Fluorine concentration in Nislag (%) α:
Fluorine concentration in fluorite amount (%) Hspar: Firefly amount (kg/L hot metal) Wslog Amount of varnish slag (kg/L hot metal) P2O3 Phosphoric acid concentration in varnish slag (%) Po: Phosphorus concentration in hot metal before treatment (X 10- %) Pr: Phosphorus concentration of hot metal after treatment (X 10
- ”%) R-P, O,: Phosphoric acid concentration in residual slag (
%) Wl: Residual slag amount (kg/hot metal)
In pre-treating hot metal with a slag-forming agent, a blowing lance is immersed in the hot metal in a container for mixed car washing, etc., and through the lance, quicklime (Cab) as a main ingredient is mixed with an oxidizing agent such as iron oxide and a reaction. For the purpose of promoting the melting point depressant of the slag, a slag forming agent mixed with fluorspar (caFz) is blown in together with an inert gas, and the basicity (CaFz) of the produced slag is increased.
O/SiO2) is 3.0 or less, preferably 2.0 to 3.0.
Desilicate by maintaining the temperature at 0.

By carrying out dephosphorization treatment, not only the desired amount of hot metal removal can be obtained, but also the slag discharge efficiency can be improved even if the amount of fluorite added is reduced and the degree of fluorine (F) in the slag is lowered. Since the slag does not deteriorate and there is no slag adhesion to the pig iron mixer car, etc., it is possible to prevent a decrease in the filling amount of the pig iron mixer car.

That is, first, the following reaction causes desiliconization and simultaneous dephosphorization.

SI +O□=SiOz −・・
・・・・−・−(+)Sing + 2 CaO= 2
CaO-5iOz ------- (2) In this case, 0□ required for desiliconization according to formula (1) is removed (3)
The value of 02M acting on dephosphorization according to the formula expressed in NJ per hot metal is taken as the desiliconization external 0□ basic unit, and the Cab/Si island is varied from 1.0 to over 3.0 to □Basic unit (
The results of investigating the relationship between M/l) and the amount of dephosphorization (XIO-'%) are shown in FIG.

As is clear from Figure 1, CaO/SiO□ is 1,0
~2.0 is 0.0. Although the amount of dephosphorization relative to the basic unit is low, in the range of CaO/SiO*-2.0 to 2.5, the non-siliconizing Ot basic unit is 3.0 to 4.0, and 60 at Nil/t.
It is possible to secure a dephosphorization amount of ~80 (×10″2%), and when CaO/S+Ot=2.5 to 3.0, the dephosphorization increases, but even more CaO/SiO□−3 ，
Even if it exceeds 0, de1ffi increases slightly, but the effect is only a slight increase, so for the purpose of the present invention, the basicity Ca0ZSi island is set to 3.0 or less, preferably 2.
．． Desiliconization and dephosphorization treatment are performed by adjusting the temperature to 0 to 3.0.

Next, in the desulfurization process using soda ash (Na2CO3) after the desiliconization and dephosphorization treatments, not only the desulfurization reaction but also the following reactions occur simultaneously.

NaxCOt+5i=NazO・5iOz+C----
---(4)3 Na2CO3+ 2 P = (Na
zO)i'I'2O3+CO+ 2 CNa zc
O* + S = NazS + Co + O-・-
--(6) NazCOs + 2 C-2Na + 3
CO-.---(7) Therefore, in order to effectively utilize the amount of soda ash consumed in the desulfurization reaction represented by formula (6) to a minimum, it is necessary to suppress other reactions as much as possible. To this end, in the desiliconization and dephosphorization process, as much as possible
It is preferable to proceed to the desulfurization step after desiliconizing and dephosphorizing by promoting the reaction of formula (3) 0 For example, Si≦0 in hot metal
．． 03% and P≦0.03-0.04%, and after desiliconization and dephosphorization are completed, if desulfurization treatment with soda ash is performed, the soda consumed according to equations (4) and (5) will be There is very little ash, and the desulfurization reaction efficiency with soda ash can be improved.

In the present invention, the slag basicity (CaO/
When pre-treating hot metal with S i Ot ) of 3.0 or less, the slag should be prepared so that the reactivity of the slag is maintained and the slag does not cause the amount of filling in the container due to deterioration of the slag discharge performance from the container such as a pig iron mixing vehicle. The F' (Q degree and P2O34
The degree is calculated and estimated from the slag component.

Figure 2 shows F in slag? The graph shows the relationship between the degree of a (%) and the reduction in the amount of mixed iron car filling ffi (t/vehicle) due to slag adhesion. This shows that even if the F concentration in the metal is reduced to about 0.2%, the reactivity of hot metal pretreatment and the slag discharge performance from the pig iron mixer car will not deteriorate, and therefore the filling amount of the pig iron mixer car will not be reduced. This shows that increasing the basicity is effective.

FiJ degree (%) in slag and citric acid soluble P20 determined by calculation based on fluorite (CaFz) introduced in hot metal pretreatment. The relationship with the conversion rate is shown in Figure 3. That is, as the F concentration in the slag increases, citric acid-soluble P20. By reducing the calculated slag F concentration to 1.5% or less, the citric acid-soluble P20. The conversion rate can be increased to over 90%, but if the F concentration exceeds 1.5%, the conversion rate of citric acid-soluble P2O3 will decrease rapidly and the fertilizer effect will be insufficient, so the F concentration in the slag should be reduced to 1.5%. It is important to keep it below 5%.

Furthermore, Figure 4 shows the relationship between the calculated P2O51 degree (%) in the slag and the actual Iff P10% concentration (%) determined by analysis. Therefore, in the present invention, the concentration of P2O in the slag can be quickly determined by calculation without analysis.

Figure 5 shows the relationship between the calculated slag P2O concentration (%) and the citric acid-soluble PtOs concentration (%). By setting the calculated Pt0sfj4 degree to 3.5% or more, the citric acid soluble P20. It can be seen that the concentration can be increased to 3.0 or higher and that it can be recovered as a phosphoric acid fertilizer.

Pre-treatment of hot metal in a storage container using a mixer car etc. is carried out in a batch manner, so the slag produced by desiliconization, dephosphorization and desulfurization of hot metal at a low basicity of CaO/SiO≦3.0 is F. The concentration and P2O3fi degree are estimated by calculation. Thus, the estimated Fi11 degree is 1.5! Itff
Slag from batches that satisfy the conditions of i% or less and PxOsfA degree of 3.5% or more is recovered as a raw material for phosphoric acid fertilizer, and slag from batches that do not meet these conditions are used for other purposes or disposed of.

When estimating the F concentration and PTOSI 11 degrees of the generated slag by calculation, first calculate the amount of generated slag (Wslog) based on the following formula (81) from the amount of residual slag and the slag forming agent used.

0, 13 (Mn@Mnr) ---
--(a) Here, 6: Residual slag amount (kg/
Hot metal) -51□: Added lime (kg/Hot metal) Ws
par: Added fluorite (kg/?9 tons)'A Ns
l CO2: Added soda ash (kg/hot metal) Sto
: Silicon concentration (%) of hot metal on the treated surface, then F concentration and P, 0
．． The concentration is calculated using equations (b) and (C) below.

(%F) Estimation -cr ・Wspar/Wslog
−−−−−(b) Here, α: Fluorite amount Fi
Using 11 degrees (%) iron oxide and quicklime, and using fluorite, the Si concentration after desiliconization and dephosphorization treatment is 0.03%.
After confirming that the amount of injection has reached the following amount, add quicklime.

Injection of iron oxide, etc. was stopped. Subsequently, desulfurization treatment using soda ash was performed.

The hot metal components before and after pretreatment are as shown in Table 1.

Table 1 Estimated (%F) calculated by formula (b) above is 1.5%
Below, and (%hos) calculated by formula (b) is 3
．． The generated slag that satisfies conditions 5 or more is recovered as a raw material for phosphoric acid fertilizer. (Thus, a fertilizer with a citric acid soluble P2O3m degree of 3.0% or more can be obtained.

<Example> C: 4.5%, Si: 0.1 housed in a pig iron mixing car
For hot metal with 0% P: 0.11% and SF 0.030%, the basicity of the slag before the start of pretreatment was adjusted to 2.3 using quicklime. As shown in Table 1, the initial desiliconization 1 dephosphorization rate is as high as 80%, 78%
By increasing the desulfurization rate, P: 0.020. S:
It was possible to supply 0.008 g of hot metal to the converter.

In the hot metal pretreatment, the amount of residual slag (Wll) -
3 kg/L, and the basic unit of the pretreatment agent required to calculate the amount of slag produced by the above formula (a) is quicklime (WL).
+xt) -10kg/L, Fluorite (Wspar
) = 0.4 kg/l, soda ash (NazCOi)
= 6 kg/t.

Also, as shown in Table 1, Sl. -10,Pa-100,P
Since F = 20 Mno = 2s Mny = 15, when these values are applied to equation (a) and calculated, the amount of slag produced (Wslog) -22.15 kg/molten metal is obtained.

Also, the Ffi degree (%) of Hotaru Fuchu was -39%, so from equation (b) (%F) estimation = 39X (0,4/22
．． 15) -0.70%, and further hO in the residual slag
Since s1 degree (%) was 5.0%, (from formula C1, (
%hos) estimate -9,0 is obtained.

The estimate (%F) thus obtained is -0,70° (%
P2O3) estimated = 9.0 is based on the conditions for using the phosphoric acid fertilizer raw material, that is, (%F)≦1.5 and (%P2O3)≧3.
5, it was recovered and used as a raw material for phosphoric acid fertilizer.

<Effects of the Invention> As explained above, according to the present invention, hot metal pre-treated slag can be recovered as a raw material for phosphoric acid fertilizer, which greatly contributes to the effective utilization of slag.

[Brief explanation of drawings]

Figure 1 shows the amount of phosphorus removed during pretreatment of hot metal and the amount of 0% desiliconization. A graph showing the relationship between slag basicity in relation to the basic unit; Part 2 is a graph showing the relationship between slag basicity in relation to the F concentration in slag and the amount charged in the pig iron car; and Fig. 3 shows the slag F concentration under calculation. and citric acid soluble P, 0. Figure 4 is a graph showing the relationship between conversion rate and P under calculation, 0. A graph showing the correspondence between the concentration and the actual slag concentration, Figure 5 is the slag P2 under calculation.
It is a graph showing the relationship between O3fA degree and citric acid-soluble PtOs concentration.

Claims (1)

[Claims] A method for recovering raw materials for phosphoric acid fertilizer from hot metal pre-treated slag, which comprises pre-treating hot metal with a low basicity of (CaO/SiO_2)≦3.0 and using the hot metal produced in the pre-treatment. The pre-treated slag has a fluorine (F) concentration of 1.5% or less and a phosphoric acid (P_2O_5) concentration of 3.0% or less, calculated based on the following formula.
A method for recovering a raw material for phosphoric acid fertilizer from hot metal pre-treated slag, characterized in that hot metal pre-treated slag satisfying a condition of 5% or more is recovered as a raw material for phosphoric acid fertilizer. (%F)=α×Wspar/Wslog (%P_2O_5)={0.0229×(P_0-P_
F)+R・P_2O_3/100×W_R}×100/
Wslog Where, F: Fluorine concentration in slag (%) α: Fluorine concentration in fluorite (%) Wspar: Fluorite amount (kg/t hot metal) Wslog: Slag amount (kg/t hot metal) P_2O_5: In slag Phosphoric acid concentration (%) P_0: Phosphorus concentration of hot metal before treatment (×10^-^3%) P_
F: Phosphorus concentration of hot metal after treatment (×10^-^3%) R・P_
2O_3: Phosphoric acid concentration in residual slag (%) W_R: Amount of residual slag (kg/ton of hot metal)