JPH05263160A - Method for recovering noble metal - Google Patents

Abstract

PURPOSE:To rapidly and simply detect the progress of an oxidation reaction and to surely recover noble metals by oxidizing the molten noble lead contg. noble metals to obtain the oxides of lead, etc., to be removable and measuring the oxygen partial pressure of the metal in the melt. CONSTITUTION:A noble lead contg. noble metals is heated and melted. The molten metal is air-blown and oxidized. Consequently, the lead and impurities are converted to their oxides, and the oxides a entrained by the slag and removed or volatilzed to recover the noble metals. In this case, the oxygen partial pressure of the metal in the melt is measured, the grade of the noble metal in the metal is obtained from the measured value and the relation between the previously obtained oxygen partial pressure in the metal and the grade of the noble metal in the metal, and oxidation is carried out. Consequently, the end point of oxidation is accurately determined, and the noble metal recovering operation precisely and efficiently controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the removal or volatilization of lead and other impurity elements in slag from a noble metal-containing lead (referred to as noble lead) obtained by treating slime generated by electrolytic refining of copper and lead. It relates to a method of removing gold and silver to recover them.

[0002]

In the dry smelting of copper or lead concentrates, precious metals in ores and melts are absorbed in crude copper and crude lead and finally concentrated in anode slime produced during electrolytic refining.
Then, the precious metal is recovered from the precious lead obtained from this anode slime.

In this recovery, when the raw material is copper electrolytic slime, the slime is sulphated roasted and extracted with water to separate copper, and the obtained residue is roasted by oxidation to selenium volatilize and separate, Then, the obtained roasted product and a reducing agent are mixed and heated to melt to concentrate the noble metal in the noble lead, and the noble lead thus obtained is treated.
When the raw material is lead electrolytic slime, the precious metal is concentrated in the precious lead by directly melting the slime, and the obtained precious lead is treated. Further, when the zinc crust obtained by the Perks method is used as a raw material, the noble lead obtained by distilling the zinc of the zinc crust is treated.

To recover the noble metal from the noble lead, the noble lead is heated and melted to form a melt, and air is blown to the melt to sequentially remove the lead and impurities in the noble lead by oxidation. Usually, this oxidation removal is carried out in a reverberatory furnace called a weight separating furnace. Recently, a method of using a top-blown rotary furnace (TBRC) to improve the oxidation efficiency and a method of blowing oxygen from the bottom of the melt using a special lance have been proposed and put into practical use. ..

Regardless of which type of furnace is used, as a reaction, each element in the noble lead is oxidized and volatilized or removed from the metal as slag according to the order in which it is easily oxidized. Also, depending on the composition of the noble lead to be treated, slag is discharged when the oxidation reaction has progressed to some extent, additional noble lead is charged, the generated slag is separated and discharged to the outside of the furnace, and tellurium is removed. It is also the same that an alkali or alkaline earth compound may be added to do so, or lead may be added to accelerate decoppering.

By the way, it is indispensable to accurately grasp the progress of the reaction in order to efficiently perform each operation such as the separate discharge of the slag during the reaction. Further, at the end of the oxidation reaction, the quality of the precious metal in the metal becomes extremely high, and the quality of the precious metal in the slag changes drastically. Therefore, if the end point is erroneously determined, excessive oxidation will result in severe loss of precious metal to the slag, or insufficient oxidation will result in deterioration of the quality of the crude silver product, and subsequent recovery of precious metal from the crude silver. It will cause problems.

Therefore, it is important to stop the reaction when the quality of the noble metal in the metal reaches a predetermined value. For this reason, it is an important control point to accurately grasp the progress of the reaction.

Conventionally, the following method has been adopted to estimate or measure the progress of this reaction.

(1) The oxygen efficiency is evaluated based on the past operation results, and the progress of the reaction is estimated from the air flow rate and the expected oxygen efficiency.

(2) Estimated from the generation rate of slag.

This is based on the phenomenon that, in a certain reaction stage, under a certain oxidizing condition, the rate of slag generation becomes faster or slower depending on the kind of the element to be oxidized.

(3) The quality of the produced slag is estimated from the properties such as fluidity and color.

(4) A metal sample is taken, its color and properties are observed, and the composition is estimated.

(5) A metal sample is taken and analyzed.

However, the method (1) has a problem that the result varies depending on the variation of the oxidation efficiency.
The methods (3) and (4) have a problem that a skilled person is required, and the method (5) has a problem that it is not suitable for operation management on site because it takes too much time.

[0016]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method capable of rapidly and simply measuring the progress of an oxidation reaction when recovering a noble metal from a noble lead.

[0017]

Means for Solving the Problems As a result of studying the oxidation process of molten noble lead in the molten metal, the present inventors have found that there is a clear relationship between the composition of the metal in the molten metal and the oxygen partial pressure. This led to the present invention.

The method of the present invention for solving the above-mentioned problems is a method of oxidizing precious lead containing a noble metal into a liquid, oxidizing the lead to form an oxide in a slag, and recovering the precious metal into a metal. Oxygen partial pressure of the metal is measured, and the oxidation treatment is performed while obtaining the ratio of the noble metal in the metal from the obtained oxygen partial pressure measurement value and the relationship between the oxygen partial pressure and the noble metal grade in the metal that have been obtained in advance. It is something to do.

In the present invention, the oxygen partial pressure is measured by an oxygen sensor using an oxygen concentration battery. The oxygen partial pressure may be measured continuously, or may be measured intermittently using a consumable sensor.

[0020]

In the present invention, the main component of the noble metal to be recovered is silver. This silver will contain gold, platinum, and palladium. When obtaining the relationship between the oxygen partial pressure in the metal and the noble metal quality in advance, it may be obtained by actually performing a test using noble lead, or may be obtained by a thermodynamic calculation. The present invention will be described below with reference to the drawings.

FIG. 1 shows Ag: 25 to 32% by weight, Au:
2 to 4% by weight, Bi: 25 to 30% by weight, Pb: 10
Noble lead of various compositions in the range of 15 wt%, Cu: 7 to 12 wt%, Sb: 9 to 13 wt% was put into an alumina crucible in an amount of 2 kg each, and the mixture was heated and melted at about 1000 ° C. Blow oxygen-enriched air into the metal to oxidize the metal,
The oxygen partial pressure obtained by immersing the consumable oxygen sensor in the metal and measuring it, and the contents of the gold grade and the silver grade in the metal at that time (hereinafter referred to as "precious metal grade"). It shows the relationship of.

FIG. 1 shows that there is a clear correlation between the oxygen partial pressure in the metal and the noble metal quality in the metal. Therefore, if this relationship is utilized, the quality of the precious metal in the metal can be estimated only by measuring the oxygen partial pressure of the metal in the oxidation process. Oxygen partial pressure obtained depending on the type and quality of the accompanying elements in the noble lead may differ from the noble metal quality curve.However, in such a case, the noble lead of the composition to be pretreated should be used. It is sufficient to obtain the oxygen partial pressure and the precious metal quality.

Since the method for measuring the oxygen partial pressure is described in detail in Japanese Patent Laid-Open No. 61-261445, its description is omitted.

[0024]

EXAMPLES Next, examples of the present invention will be described. [Example 1] Beaker test: Au + Ag: 30.1% by weight, Pb:
19.6% by weight, Sb: 10.1% by weight, Bi: 29.
2 kg of precious lead containing 5 wt% and Cu: 6.59 wt% was put into an alumina crucible and heated to 1000 ° C. to melt, and 0.51 of oxygen-enriched air containing 80 vol% oxygen was added to the obtained melt. / M
Pb, Sb, contained in noble lead, blown in at a ratio of in
Bi, Cu, etc. were oxidized and removed to slag. The oxygen partial pressure of the metal in the molten metal when the noble lead is completely melted is
The value when converted to 1000 ° C. is 10 ^−9.28 atm. Met.

With a consumable oxygen sensor (manufactured by Yamazato Electronite Co., Ltd.) that uses magnesia-stabilized zirconia as the solid electrolyte and Fe-FeO as the reference electrode, the oxygen partial pressure of the metal during the reaction is determined every predetermined time. It was measured. 220 minutes after the start of blowing oxygen-enriched air, the oxygen partial pressure of the metal is 10 when converted to 1000 ° C.
^-6.98 atm. Met.

From the results of FIG. 1 and the oxygen partial pressure, it was estimated that the noble metal grade in the metal was 50%, and a small amount of the metal was sampled and analyzed. Sampling was performed by suctioning into an opaque quartz tube having an inner diameter of 8 mm. Then the slag was discharged.

As a result of metal analysis, Au + Ag was 50.
It was 5% by weight, which was almost the same as the estimated value. Also, P
b was 0.58% by weight and Sb was 0.5% by weight or less. Removal rate of lead and antimony in precious lead is 95%
It was found that almost all was removed.

Next, Bi, T remaining in the metal
In order to sequentially remove e and Cu by oxidation, oxygen-enriched air was continuously blown into the metal for 180 minutes at the same rate. 10
Oxygen partial pressure in metal converted to 00 ℃ is 10 ^-2.04 at
m. At that point, the blowing of oxygen-enriched air was stopped. The estimated value of noble metal grade from FIG. 1 is 95% by weight.

After the melt was cooled and solidified, the slag and the metal were separated and the metal was analyzed. Au + in metal
Ag is 97.2% by weight, Pb is <0.5% by weight, Sb is <0.5% by weight, Bi is 0.5% by weight, Cu is 1.21%.
% By weight. The quality of the noble metal is close to the expected value, the removal rate of Bi is 95% or more, and it can be seen that almost all is oxidized. The relationship between the noble metal grade in the metal obtained in this example and the oxygen partial pressure is shown by the black circles in FIG.

Example 2 Actual furnace test: Au + Ag: 28.0% by weight, Pb: 1
0.0% by weight, Sb: 12.8% by weight, Bi: 25.6
2 t of noble lead containing 1% by weight, Te: 3.7% by weight, Cu: 7.2% by weight, volume 0.25 m ³ , surface area of the melt 3.11.
It was charged into a m ² reverberatory furnace and heated and melted using a heavy oil burner. The oxygen partial pressure of the metal in the molten metal when the noble lead is completely melted is 10 ^-14.5 when converted to 1000 ° C.
atm. Met. The quality of the metal at this time is Au +
Ag: 32.0 wt%, Pb: 12.6 wt%, Sb:
10.5% by weight, Bi: 30.0% by weight, Te: 3.4
% By weight and Cu: 7.0% by weight. After that, air was blown onto the surface of the molten metal from the upper blowing lance at a rate of 15 Nm ³ / min, and Sb, Pb, Bi, T
The operation started to oxidize and remove e, Cu and the like.

6 hours after the start of operation, precious lead was added while scraping off the slag and slag generated on the surface as needed. When the oxygen partial pressure in the metal was measured 8 hours after the start of operation, it was 1
The value when converted to 000 ° C. is 10 ^−7.0 atm. Met. From this result, it was judged that the removal of Pb and Sb was almost completed, and a small amount of metal was sampled and analyzed. The grade of metal is Au + Ag: 35.1% by weight, P
b: 5.0% by weight, Sb: 0.3% by weight, Bi: 37.
6% by weight, Te: 4.6% by weight, Cu: 9.0% by weight. The removal of Pb and Sb is remarkable, and the removal of Sb is 95% or more.

Next, in order to remove Bi in the metal, the oxidation by blowing air was continued, and the slag was discharged while charging the precious lead at any time. When 4.6 t was added in total, the amount of slag generated decreased and the slag receiving container became full. At this point, the oxygen partial pressure in the metal was measured. As a result, the value when converted to 1000 ° C is 10
^-5.5 atm. Met. From this result, it was judged that the removal of Bi was almost completed, and all the slag in the furnace was discharged,
A small amount of metal was sampled and analyzed.

The grades of metal are Au + Ag: 86.7% by weight, Pb: 0.1% by weight, Sb: <0.1% by weight, B
i: 1.4% by weight, Te: 5.4% by weight, Cu: 4.4
% By weight, and the removal of Bi is 95% or more.
In addition, this slag serves as Bi raw material as Bi honey.

Then, in order to remove Te, soda ash was charged, and the slag produced at any time was discharged. During this period, oxidation by blowing air was continued. The oxygen partial pressure in the metal was measured 48 hours after the start of operation. As a result, 100
The value when converted to 0 ° C. is 10 ^−3.5 atm. Met.
From this result, it was judged that the removal of Te was almost completed, the charging of soda ash was stopped, all the slag in the furnace was discharged, and a small amount of metal was sampled and analyzed. The grade of metal is Au + Ag: 95.0% by weight, Pb: 0.1
% By weight, Sb: <0.1% by weight, Bi: 0.4% by weight,
Te: 0.1% by weight, Cu: 3.2% by weight, Te
Removal is over 95%.

Next, in order to remove Cu remaining in the metal, 300 kg of lead was additionally charged, and further oxidation by blowing air was continued. Oxygen partial pressure is 1000
The value when converted to ° C is 10 ^-2.5 atm. Therefore, it was judged that the oxidation and refining of the metal had been completed, the slag was discharged from the furnace, and the metal was cast into the anode for silver electrolysis. The grade of metal is Au + Ag: 98.2% by weight, P
b: 0.1% by weight, Sb: <0.1% by weight, Bi: 0.
1% by weight, Te: 0.02% by weight, Cu: 0.4% by weight
And the metal quality was as expected. In addition,
The relationship between the noble metal grade and the oxygen partial pressure in the metal obtained in this example is shown by the white circles in FIG.

[Example 3] Thermodynamic calculation: Ag: 33.8% by weight, Pb: 14.9
%, Sb: 10.9% by weight, Bi: 27.6% by weight, Te: 3.2% by weight, Cu: 9.5% by weight Then, the composition of slag and metal, which is thought to be considered, was calculated, and the relationship between the oxygen partial pressure in the metal and the silver grade was calculated. At the time of calculation, the amount of each element existing in the molten system (slag + metal), the temperature and pressure of the system are given, the generated phases and constituents are assumed, and the free energy of the system is minimized. Thus, the amount of each produced component was determined. The phases considered were two phases, slag and metal, and the gas phase was not considered. The metal is assumed to be composed only of the above elements, and the slag is assumed to consist only of stable oxides of those elements. In addition, both slag and metal are considered to be ideal solutions, and the free energy of formation of compounds required for calculation is “Nonferrous metal smelting (edited by the Japan Institute of Metals,
80 years) ". The oxygen partial pressure indicated by the system is M + n /, where M is an arbitrary metal element contained in the system.
It was determined from the equilibrium relationship of 2 O ₂ = MO _n .

The obtained 1273K, 1 atm. The calculation result in Table 3 is shown in FIG. This result is similar to that of FIG. 1, and it was found that a so-called calibration curve can be calculated.

[0038]

As described above, according to the method of the present invention, the progress of the noble lead oxidation reaction can be easily and easily grasped, and efficient and accurate operation control can be performed based on this. it can.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the oxygen partial pressure in metal, which is obtained by oxidizing noble lead having various compositions, and the noble metal grade.

FIG. 2 is a graph showing the relationship between the oxygen partial pressure in the metal obtained in the example of the present invention and the noble metal grade, the black circles are the results of the beaker test, and the white circles are the test results in the actual furnace. Is.

FIG. 3 is a graph showing the relationship between the oxygen partial pressure in metal and the noble metal quality obtained by thermodynamic calculation.

Claims (1)

[Claims] 1. A method of oxidizing noble lead containing noble metal into a liquid, oxidizing the noble metal into a slag and recovering the noble metal into a metal, and measuring the oxygen partial pressure of the metal in the melt. The obtained oxygen partial pressure measurement value and the relationship between the oxygen partial pressure of the metal and the precious metal grade in the metal obtained in advance are used to perform oxidation treatment while determining the precious metal grade in the metal. Recovery method.