JPS59145740A - Treatment of zinc leached slag - Google Patents

Abstract

PURPOSE:To suppress the amt. of the by-product sulfuric acid and the waste slag to be produced and to perform selective sulfatization by adding solid fuel to zinc-leached slag, blowing the same into a fluidized roasting furnace, and introducing the gaseous mixture composed of the smelting waste gas contg. an adjusted amt. of SO2 and oxygen into the furnace. CONSTITUTION:Granular fuel and pyrite of 5-20wt% of zinc-leached slag are added to hydrous filter cake consisting of the zinc leached slag under agitation. The slurry thereof is ejected with high-pressure gas or the like into the fluidized bed of a fluidized roasting furnace. A gaseous mixture of smelting waste gas contg. SO2 and oxygen is introduced in the furnace to maintain the fluidized bed. The amt. of the solid fuel in this case is adjusted to the amt. enough to maintain 650-700 deg.C suitable for selective sulfation of Zn, Cu and Cd in the zinc-leached slag. The total amt. of oxygen in the gaseous mixture is so adjusted that the concn. of O2 in the waste gas from the fluidized furnace is made >=1 times of the concn. of the SO2 after oxygen is consumed for sulfation reaction and combustion. The valuable metal in the leached slag is converted efficiently to a water-soluble sulfate by the above-mentioned treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to the use of leaching slag (
The present invention relates to an improvement in a treatment method in which zinc leaching slag (hereinafter referred to as zinc leaching slag) is sulfated and roasted to convert valuable metals such as zinc, copper, and cadmium contained in zinc leaching slag into water-soluble sulfate.

In normal wet zinc smelting, zinc concentrate is oxidized and roasted, and the zinc oxide produced is leached out with an acidic sulfuric acid solution (usually electrolytic waste), and zinc is electrowinning.

During the roasting, iron in the raw material combines with zinc to form insoluble zinc ferrite (zinc ferrite), so the so-called zinc leaching slag contains 15 to 25 zinc.

One method for recovering this zinc is high-temperature, high-acid leaching. In this method, ferrite is decomposed and eluted using excess sulfuric acid at high temperatures, and a large amount of iron as well as zinc is eluted. A step to generate crystals is required.

On the other hand, the sulfation roasting method (Patent No. 537551) converts zinc, copper, and cadmium in the zinc leaching slag into sulfates (hereinafter referred to as sulfation), but most of the iron does not elute and the above This method leaches only valuable metals.

However, since iron sulfide concentrate is used as the sulfur source and heat source for sulfuric roasting, which is approximately the same amount as the zinc leaching slag, the roasting equipment, sulfuric acid plant, etc. have to be large-sized, and large amounts of sulfuric acid are produced as by-products and the waste slag is This includes problems such as a large amount of

A method is also known in which zinc leaching slag and concentrated sulfuric acid are mixed and then roasted to selectively sulfate only valuable elements such as zinc. In this case, the amount of leaching residue generated is significantly reduced compared to the sulfated roasting method, but on the other hand, it requires fuel as a heat source for heating, and it also contains sulfur compounds such as SO, SO, etc. Since exhaust gas is generated, these sulfur compounds have to be treated to eliminate them, which has many disadvantages.

The purpose of the present invention is to solve the above-mentioned drawbacks of the conventional method, to process zinc leaching slag in a fluidized fluidized furnace, using smelting exhaust gas containing
Another object of the present invention is to provide a method for treating zinc leaching slag that makes it possible to suppress the amount of by-product sulfuric acid and waste slag. That is, according to the present invention, zinc leaching slag containing zinc in the form of zinc ferrite is selectively sulfated and roasted to convert zinc, copper, and cadmium in the leaching slag into water-soluble sulfates. In the sludge processing method, granular solid fuel is added to the water-containing filter cake made of the leaching slag and stirred to form a slurry, and the slurry is blown into the fluidized bed of a fluidized roasting furnace via high-pressure air or high-pressure steam, The fluidized bed is maintained by introducing a mixed gas of smelting exhaust gas and industrial oxygen containing go, and the amount of the solid fuel controls the temperature of the fluidized torrefaction furnace and the zinc and copper in the leaching slag. , 650 at a temperature suitable for selective sulfation of cadmium.
After the total amount of oxygen in the mixed gas is consumed in the combustion of the solid fuel, the oxygen concentration in the exhaust gas of the fluidized bed furnace reaches SOtg degree. There is obtained a method for treating zinc leaching slag, characterized in that the zinc leaching slag is at least one time or more.

Next, the present invention will be explained with reference to drawings.

FIG. 1 is a float sheet diagram of one embodiment of the method of the present invention. Generally, in the wet zinc smelting process, the zinc leaching slag is thoroughly washed and filtered to obtain a filter cake containing 25 to 4 (l) of moisture. Even if 10 to 20 parts of solid auxiliary raw materials are mixed, it can be made into a slurry by stirring.

As described above, the fluidized roasting method, which allows raw materials to be supplied in a slurry state, has the advantage of eliminating the need for a pretreatment step for drying the filter cake. As auxiliary raw materials to be added, sodium salts such as sodium sulfate, sodium carbonate, or sodium hydroxide are used as auxiliary agents to improve the sulfation rate of valuable metals to be recovered from solid fuel, zinc, steel, and cadmium.

The amount of the solid fuel added will be described later, but the amount of the sodium salt added is 0.1 to 1.0 weight t based on the zinc leaching slag. The slurry thus obtained is atomized and fed into the fluidized bed by high pressure air or high pressure steam through a feed gun installed at the level of the fluidized bed of the fluidized torrefaction furnace. In this way, the slurry is mixed with high pressure air! By spraying with high-pressure steam or spraying, the slurry is dispersed within the fluidized bed, rapidly evaporating water, and raising the temperature, which prevents partial temperature drop and partial fluidization failure in the fluidized bed. can. In addition, due to the slurry spraying, the zinc leaching slag, which is the raw material, forms secondary particles with a relatively large particle size, so some of them are decomposed into fine primary particles in the fluidized bed, but there is carryover. Most of it remains in the fluidized bed, ensuring the residence time necessary for sulfation of zinc and the like.

A portion of the calcine becomes a carryover and is discharged outside the furnace together with the exhaust gas, and a portion is extracted from the overflow outlet.

The fluidized roasting furnace is also supplied with a mixed gas consisting of smelting exhaust gas containing SO2 and industrial oxygen in order to maintain the fluidized bed and generate SO1 necessary for sulfating zinc and the like. Zinc concentrate is normally oxidized and roasted in a fluidized roasting furnace, and the exhaust gas from the roasting furnace is cooled to approximately 350°C, dusted with a hot cotterel, and then sent to a sulfuric acid factory, so it can be used separately. I can do it.゛In other words, the composition of the exhaust gas is SO28~l
Ovol qi), 0°3-5 vol%,
In order to secure oxygen for fuel combustion and to maintain an oxygen concentration such that a sufficient 'SO8 partial pressure is obtained for flow oxidation of the zinc leaching slag, industrial oxygen is used as a mixture. The sulfation reaction in the fluidized bed is accomplished by the following equation.

Fe, 03 ZnO@Fe, 03+SO,'-+ znso, +F
e, O, @@@@ f2) CuO"F6203 +so
, −+ cuso, + F6203 ”” (3
) CdO@Fe2O3+SO3→Cd50. +Fe, 0
The temperature of the s-6@6 T41 fluidized bed is preferably 600°C or higher to prevent oxidation of iron, and a temperature of 650 to 700°C provides a high sulfation rate of copper and zinc. Figure 2 shows experimental data showing the relationship between roasting temperature and the sulfation rate of copper and zinc.

In order to maintain the temperature of the fluidized bed, a solid fuel, such as pulverized coal or coke, is added to the zinc leaching slag. In order to suppress fuel consumption as much as possible and prevent an increase in the amount of waste gas, highly concentrated industrial oxygen is used instead of air for the oxygen required for combustion. Industrial oxygen is mixed with the SO-containing waste gas and supplied to the wind box of the fluidized bed furnace (hereinafter referred to as blowing gas). Free oxygen in the fall gas is consumed by the generation of SOI and combustion of solid fuel in the fluidized bed. Therefore, in order to increase the oxygen partial pressure in the furnace, it is effective to add excess industrial oxygen.

A portion of the calcine is discharged outside the furnace as a carryover and collected in a cooler, hot cotterel, etc., and a portion is directly extracted from the fluidized bed as an overflow.

These are sent together to the leaching process, where zinc, cadmium, copper, etc. are leached and recovered using the washing water (hereinafter referred to as process water) in the smelting process.The main components of the leaching slag (hereinafter referred to as slag) are Although it is hematite, the silver in the zinc concentrate is concentrated, so it is recovered as silver concentrate through flotation, and the tailings are discarded.

After removing dust from the fluidized torrefaction furnace exhaust gas, it is sent to the sulfuric acid factory together with the main oxidation roaster exhaust gas. The gas composition at the furnace outlet varies depending on the composition of the blown gas and fuel consumption.
The S03 content is about 1%, the So content is 3-6%, and the content is 0.4-8% (based on dry gas), making it suitable for sulfuric acid raw materials. In addition, as shown in Figure 1, the gas blown into the sulfation roasting furnace is a branched part of the smelting exhaust gas that should be sent to the sulfuric acid factory. There is no difference in the sulfuric acid plant capacity compared to the case where the oxidation roasting is not carried out.Therefore, the capacity of the sulfuric acid plant is also almost the same as the case where the awakening roasting is not carried out. Since it forms roots and binds and fixes zinc and copper, the amount of sulfuric acid produced at the sulfuric acid factory is reduced accordingly.

In the method of the present invention, 5 to 20 layers of pyrite is further added to the zinc leaching slag, and industrial oxygen containing the amount of oxygen necessary for converting the pyrite to (2) is added to the blown gas. Therefore, it is possible to increase the temperature in the fluidized bed and promote the sulfation reaction.

The required amount of pyrite in the above-mentioned patent No. 537551 is about 100 parts by weight for the zinc leaching slag, but in the method of the present invention, the temperature control of the fluidized bed is separately performed using fuel, so the method of the present invention The amount of pyrite added in is the amount of zinc in the zinc leaching slag.

The amount is extremely small because it is determined to be the amount necessary to supply part or all of the amount of S02 required for the sulfation of copper and cadmium and to slightly increase the S02 concentration of the furnace exhaust gas.

Since the oxygen necessary for the oxidation of pyrite is supplied by industrial oxygen, the gases produced by the oxidation of pyrite are mostly SO1 and only a small amount of N and gas as impurities in the industrial oxygen. By the way, when using 0.92% industrial oxygen, the gas produced is 5O290, N
It is about 210 people.

Since these 802 gases are fixed as sulfate radicals through reactions (1) to (4), the increase in exhaust gas amount is due to N.

It is only a minute, and it is small.

Furthermore, in the fluidized bed, a considerable amount of unfixed S03 is produced by the sulfation reaction of zinc, copper, and cadmium. 6
The theoretical conversion rate of SO to SO3 at 50 to 700'C is 40 to 50 degrees, but the conversion rate in the sulfation roaster is much lower than this, and SO3 is present in the sulfation roaster exhaust gas. It contains around 1%.

Such free SO1 is removed in an exhaust gas scrubbing tower and sent to a wastewater neutralization plant. Therefore, as long as the amount of pyrite is controlled according to the criteria described above, the increase in sulfation roasting furnace exhaust gas due to the use of pyrite is negligible. In addition, by adding pyrite, it is possible to increase the amount of SO2 supplied without increasing the amount of exhaust gas as shown in the above explanation, increasing SO and purity in the reaction system and promoting the sulfation reaction. and improve efficiency.

In carrying out the method of the present invention, a portion of the zinc leaching slag, 1
It is also possible to stabilize the fluidized bed by granulating approximately 0 to 20% to a size of 0.1 to 3 mm and g and directly supplying it to the fluidized bed VC. When extremely fine-grained raw materials are reacted in a fluidized bed, in order to stabilize the fluidized bed, some of the auxiliary charge with relatively large particle sizes is discharged from the furnace together with the calcine, and is mixed into the calcine. Therefore, it must be something that does not affect the processes after leaching. From this point of view, it is most suitable to use the raw material itself after granulating it.

The effects of the present invention are as follows.

(1) Since highlight is not used or only a small amount is used, the amount of by-product sulfuric acid and waste slag generated is significantly suppressed.

(2) Since cheap solid fuel is used, the energy cost for maintaining the temperature of the fluidized bed is small, and on the other hand, the total gas loss to be processed is significantly reduced due to the miniaturization of the fluidized bed compared to conventional methods. Longer life by reducing energy consumption.

(3) Overall equipment costs are reduced because fluidized bed-related equipment and exhaust gas treatment equipment are downsized.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 A fluidized fluidized furnace with a diameter of 4 m (inner dimension) was used, and the temperature inside the furnace was set to 6 m in advance.
The temperature was raised to 80°C, and the dried zinc leaching slag was used as a bed, and the zinc leaching slag filter cake (moisture 28 parts) having the composition shown in Table 1 was coated with powdered coal of 90 kp/T on a dry basis (heat generation 1-6500 km). /kA') was mixed to form a slurry, which was supplied to the fluidized bed furnace through two feed guns. At the same time, 4500 Nm"/4 of oxidizing roaster exhaust gas with 5027 cm, 0.6.5 cm, and 15 cm moisture and 37 ONm"/hour of industrial oxygen with 0.9296 cm were supplied to the wind box to maintain the fluidized bed. The supply t of the removal slurry is 2.5 Tz4 in terms of zinc leaching slag on a dry leaf basis. The temperature of the fluidized bed is 65
It was maintained at 0-680'C. The height of the fluidized bed is approximately 2.5
m, the average residence time of the charge is approximately 14 hours. The overflow and carryover were combined into the calsign.

Table 1 shows an example of analysis of the main components. The sulfurized @ decommissioned reactor exhaust gas was treated with SO□ + 80.3.5%, 0.3.5%, to remove dust in a cleaning tower, and then sent to the sulfuric acid factory. The amount of gas is approximately 530 ONm37 hours in terms of dry amount. Calcine was leached out in the process water. An example of analysis of tailings is shown in Table 1. Leaching rate is Zn85
%, Cd 85%, Cu 80%.

Table 1 Example 2 Zinc leaching slag filter cake with the composition shown in Table 2 (moisture 35 parts) was mixed with powdered coal of 5.8 parts dry weight (calorific value 6500 parts).
kcaL/kP) and 20% pyrite were added to form a slurry. Powdered coal has a moisture content of 20 parts, pyrite has a moisture content of 10 parts, and the slurry concentration is 69 parts (moisture content 31 parts).

The sulfuric acid factory drying tower outlet gas (So, 8.15
%, 028.0%) 4000 Nm”/R,.

While supplying a mixed gas of 0□92% industrial oxygen at 130 ONms/hour to the wind box, the slurry was supplied by two guns at a rate of 5.2 T/hour based on the dry weight of the zinc leaching slag. At this time, the amount of pyrite supplied is 1.0T4°, and the amount of coal is 0.3
T/? It is j.

The calculated amount of S02 required for sulfation of zinc leaching slag is as follows. However, the sulfation rate is 2.5 for Fe and 5 for Zn.
, Cd was 90%, and pb and cu were 1 (10%).

Generation of cuso4 3.9 Nm3SOz /T
ZnSO4〃60.7〃CdS04” 0.3 //
Fev (804) t” 3.7
ttPbSO4〃8.1〃Ca S 04 " 6.0〃Produced from zinc leaching slag -31,5// Total 51.2 Nm"SO,/, contains p Ag, and is converted into pyrite by flotation. You can collect the snake.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet diagram of an embodiment of the present invention, and FIG. 2 is a graph diagram showing the relationship between the sulfation rate and temperature of steel and zinc. Patent applicant Mitsubishi Metals Co., Ltd. Representative Yoshi Shirakawa $/m Dorojin 550 600 6raQ 'IQO750
Wandering attack/Q/

Claims (3)

[Claims] (1) A method for treating zinc leaching slag in which zinc leaching slag containing zinc in the form of zinc ferrite is selectively sulfated and roasted, and zinc, copper, and cadmium in the leaching slag are each converted into water-soluble sulfates. , granular solid fuel is added to the water-containing filter cake consisting of the leaching slag and stirred to form a slurry, and the slurry is blown into a fluidized bed of a fluidized roasting furnace via high pressure air or high pressure steam to produce SO. The sulfur layer is maintained by introducing a mixture of smelting exhaust gas and industrial oxygen containing The total amount of oxygen in the mixed gas is adjusted to be necessary and sufficient to maintain the temperature in the range of 650 to 700'C, which is suitable for the selective sulfation of the solid fuel, and the total amount of oxygen in the mixed gas is After being consumed, 0.00. concentration is S0
2. A method for treating zinc leaching slag characterized by having low concentrations (both of which are 1 times or more). (2) In a method for treating zinc leaching slag, in which zinc leaching slag containing zinc in the form of zinc ferrite is selectively sulfated and roasted, and zinc, copper, and cadmium in the leaching slag are converted into water-soluble sulfates, respectively. , Add granular solid fuel and 5 to 20 weight range of pyrite from the zinc leaching slag to a water-containing filter cake made of the leaching slag, stirring to form a slurry, and fluidizing the slurry through high-pressure air or high-pressure steam. A mixed gas of smelting exhaust gas containing S02 and industrial oxygen is blown into the fluidized bed of the furnace to maintain the fluidized bed, and the amount of the solid fuel is adjusted to the temperature of the fluidized torrefaction furnace to maintain the fluidized bed. 650 suitable for selective sulfation of zinc, copper, and cadmium in the slag and oxidation of the pyrite
After the total amount of oxygen in the gas mixture has been consumed in the sulfation reaction and the combustion of the solid fuel and the oxidation of the pyrite, the temperature is adjusted to be necessary and sufficient to maintain a temperature range of ~700°C. The O1 yield in the exhaust gas of the fluidized bed furnace is s
1. A method for treating zinc leaching slag, characterized in that the concentration is at least one times that of 02. (3) 10 to 20% by weight of the zinc leaching slag is 0.1
The method for treating zinc leaching slag according to claim f1) or (2), wherein the granules are granulated to a size of ~3 mmy5 and charged into the fluidized bed.