JPS5928618B2 - Method for recovering valuable metals from steelmaking furnace dust, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for treating dust from steelmaking furnaces such as electric furnaces or open hearths, or similar dust, to recover valuable metals such as zinc, lead, cadmium, and iron.

The purpose is to provide an industrially advantageous method for most efficiently recovering zinc, which is the main recovered metal, and using it as a raw material source for various purposes.

The dust treated by the present invention includes steelmaking dust with a relatively high zinc content discharged from steelmaking processes such as electric furnaces and open hearths, as well as converter dust and blast furnace dust from a single ironmaking factory, which has a relatively high zinc content. It also includes analogues such as relatively high zinc-rich secondary dust generated during processing steps to obtain reduced iron from dust with low levels of zinc.

These dusts usually contain 20-30% Zn and 30-30% Fe2O.
Contains valuable metals of 0%, Pb 1-6%, Cd011-0.5%, but 1-5% CI, 0.5-1% F,
1-5% Na, 0.5-1%, 1-5% SiO
2.1-5% OaO.

It also contains 1-3% Mn.

Various methods have been proposed for recovering valuable metals from these steelmaking dusts, both wet and dry.

In other words, wet methods include leaching with aqueous ammonia or ammoniacal ammonium carbonate as a leaching agent, as seen in Japanese Patent Publication No. 42-23717, and finally recovering zinc as zinc oxide; A method for recovering zinc as zinc hydroxide using sulfuric acid as a leaching agent and chloride lime and slaked lime, JP-A-49-115
903, a method has been proposed in which dust is decomposed with acid and then aqueous ammonia is used to recover manganese, iron, and zinc.
9-52111, a method of treating zinc by adding a reducing agent in a rotary furnace, and a method of converting zinc to zinc oxide by combining reduction and volatilization with a rotary furnace and chloride volatilization, as shown in JP-A No. 49-83698. Several methods have been proposed to collect the waste, but none of them have been put into practical use industrially.
For the purpose of recovering zinc, a portion of this steelmaking dust is used in a rotary furnace to reduce and volatilize the zinc by adding coke as a reducing agent, but the reality is that most of it is discarded or deposited. be.

Recently, the problem of pollution has been brought into sharp focus, and the amount of collected steelmaking dust has increased to an enormous amount, and if it is disposed of or piled up, it will cause problems of secondary pollution, and it will also save resources. Focusing on the fact that these steelmaking dusts are one of the leading raw materials for zinc, specific proposals have been made for the purpose of recovering valuable metals from them.
(Ru.

JP-A-50-101202 is one such method, which proposes a method characterized in that steelmaking dust is sequentially treated in the steps of water washing, sintering, and alkali washing.

This method uses steelmaking dust as a powerful raw material for zinc, and involves a water washing process and a sintering process to remove harmful chlorine, fluorine, sodium, and potassium from the zinc raw material, and an alkaline cleaning process for the dust generated from that process. It is noteworthy that a large amount of water is required for washing, filtration, and drying of low-grade materials such as steelmaking dust.
In addition, the equipment and processing costs required are enormous, which is economically disadvantageous.

In addition, as mentioned above, since the crude zinc oxide partially recovered from steelmaking dust contains chlorine, fluorine, sodium, potassium, etc., it is possible to effectively and economically recover zinc, lead, etc. from this crude zinc oxide. There are various problems in doing so.
Even if a large amount of crude zinc oxide could be recovered from steelmaking dust, the reality was that it could not be processed.

The present inventors focused on this point, and if it is possible to process this crude zinc oxide to further concentrate zinc, lead, cadmium, etc., and at the same time efficiently remove chlorine, fluorine, sodium-IJium, potassium, etc., then steel production will be possible. Recognizing that a process for recovering valuable metals such as zinc and lead from dust in the most efficient and economical way would be completed, we conducted various studies and found that the crude zinc oxide was brought into contact with a dilute alkaline solution at a pH of 5 to 12, and at the same time , by adding 0.03 to 2.0% of a surfactant to crude zinc oxide and reacting it at 30°C or higher, the chlorine contained therein,
It has been discovered that while fluorine, sodium and potassium are eluted, valuable metals such as zinc and lead are concentrated, and the properties of the powder after treatment are also improved.

Immediately, the illegal practice is to improve the energy-saving technology by applying the Wertz process, which is an established technology for recovering zinc from low-grade zinc ore, to steelmaking dust, etc. At the same time as establishing the wet method, 1.
It is possible to recover zinc and other valuable metals from steelmaking dust etc. in the most effective, economical and non-polluting manner by sequential processing.

That is, the treatment method of the present invention removes chlorine, fluorine, sodium, and potassium from flat furnace steelmaking dust, etc., and recovers zinc, lead, cadmium, and iron as valuable metals economically and non-pollutingly. The purpose is to first pelletize the dust by adding water, then add a carbonaceous material as a reducing agent, and then process it in a rotary furnace for 1,000~
The process of heating at 1200℃ to reduce and volatilize zinc, lead, and cadmium and separate it from iron, calcium, silica, etc. to obtain crude zinc oxide mainly composed of zinc and clinker mainly composed of iron, and from this process The obtained clinker is subjected to magnetic separation and separated into non-magnetic material mainly composed of residual carbon and magnetic material mainly composed of iron. The crude zinc oxide obtained from the recovery process and the reduction process is added to a dilute alkaline solution at pH
5 to 12, and at the same time 0.03 of crude zinc oxide.
Add ~2.0% surfactant and react at 30°C or higher to separate chlorine, fluorine, sodium and potassium,
A method for recovering valuable metals from steelmaking dust and/or similar ducts, characterized in that it includes a step of concentrating zinc, lead, and cadmium.

Hereinafter, the present invention will be explained in detail with reference to the flow sheet of FIG. 1 showing an embodiment of the method of the present invention.

The flat furnace steelmaking dust used in the method of the present invention is made into pellets containing 7 to 15% moisture by adding water.

The pellet size is 90% from 4% to 8% with an average particle size of 6%.
A content of at least 4% is preferable, and a content of 4% or less is particularly undesirable.

The pellets are mixed with a carbonaceous reducing agent (25-35%) and charged into a rotary furnace.

As the reducing agent, coke, anthracite, recovered carbon, etc. can be used.

It is heated to 1000℃ to 1200℃ in a rotary furnace, and zinc, lead, and cadmium are reduced and volatilized, and iron, calcium,
It is separated from silica, etc., and is finally collected in a cyclone, dust barrel, etc. and recovered as an oxide.

If the reaction temperature is below 1000°C, reduction and volatilization will be insufficient, and if the reaction temperature is above 1200°C, slag will occur, which is not preferable.

At this time, most of chlorine, sodium, and potassium are volatilized at the same time and are contained in the crude zinc oxide, but fluorine is 40 to 6
0% remains in the clinker along with calcium, silica, etc.

The volatilization rate of zinc and lead is 90-95%, and that of cadmium is approximately 1o.

reach %.

Also, chlorine is 90-95%, sodium and potassium are 8%
0-90% volatilizes.

Next, the clinker discharged from the rotary furnace is cooled and then subjected to magnetic separation to separate magnetic and non-magnetic materials.

Since the non-magnetic material contains about 75% or more of unburned carbon, it is returned to the rotary furnace.

Magnetic materials are mainly composed of metallic iron and also contain calcium, silica, alumina, etc., so they are used as a raw material as an iron source for cement.

Furthermore, it is also possible to perform magnetic separation treatment to separate and recover raw materials for iron making, cement, aggregate, etc.

Next, the obtained crude zinc oxide was prepared by dissolving soda carbonate at 50°C.
A slurry of water and crude zinc oxide is made at a ratio of 5:1 with hot water at pH 7, and a surfactant of 0.1% relative to the crude zinc oxide is added and stirred for about 30 minutes.

The purpose of this cleaning step is to remove chlorine, fluorine, sodium, and potassium, suppress the elution of valuable metals such as zinc as much as possible, and concentrate valuable metals such as zinc.

A dilute alkaline solution is added to suppress the elution of zinc, etc., and a
．． It is important to add 03-2.0%, preferably 0.05-1% of surfactant and to keep the washing temperature above 30°C, preferably above 40°C.

As an alkali source for the dilute alkaline solution, in addition to soda carbonate, hydric soda, aqueous ammonia, potassium carbonate, ammonium carbonate, sodium bicarbonate, sodium silicate, etc. can be used, but soda carbonate is most preferred; in this case, pH
It is preferable to maintain the value between 6 and 9.

Anionic and nonionic surfactants are effective; for example, alkylbenzene sulfonates, aromatic sulfonates, alkylaryl phosphate salts, alkylaryl polyoxyethylene ethers, etc. can be used. .

Figure 2 shows the amount of chlorine added and the amount of chlorine added when linear sodium alkylbenzenesulfonate (LAS) is used as a surfactant.
This shows the cleaning effect of fluorine, and crude zinc oxide 200
g was added to 1 t of dilute sodium carbonate solution so that the pH was 7, and the surfactant LAS was added and the mixture was heated at 50°C for 3 ml.
The dechlorination and fluorine removal rates are shown when the sample is thoroughly filtered after stirring for 0 minutes.

From this, the amount added is 0% by weight based on crude zinc oxide.
．． 0.03% or more is required, and 0.05 to 1.0% is preferable when taking into consideration the improvement of powder properties after treatment.

FIG. 3 is a diagram similarly showing the relationship between treatment temperature and dechlorination and defluorination, and is a diagram in which 1% LASo is added.

As seen in this figure, the cleaning effect depends on the processing temperature;
A temperature of 0° C. or higher is required, and the cleaning effect gradually increases, but even if the temperature is set to 70° C. or higher, the effect does not increase significantly, so it is not economically advisable.

The cleaning effect increases as the amount of mixed water increases, but the weight ratio of crude zinc oxide to water is 1:5, as it is related to the energy for raising the temperature, the type and amount of alkali, and the type and concentration of surfactant. This is sufficient for practical use.

Next, the crude zinc oxide slurry is filtered through a filter, and the slurry has very good flowability and sedimentation properties.

For example, when the water is passed through a filter press, the water content is 20 to 25%, and depending on the conditions, it can be reduced to 20% or less.

If the purified crude zinc oxide after this washing treatment is to be used as a raw material for zinc sulfate or zinc carbonate, it can be dissolved as is, but if it is to be used for electrolytic zinc or distilled zinc, it must be dried to an appropriate moisture content. be.

A known dryer can be used for this drying process, but substances containing tetranormal sulfates, chlorides, etc. tend to stick to the dryer, which often causes operational problems. The purified crude zinc oxide treated by this method has improved powder surface properties, so it does not stick and has improved thermal efficiency.

Table 1 also compares the powder properties of untreated crude zinc oxide and dried purified crude zinc oxide.

As shown in Table 1, the dried purified crude zinc oxide has improved angle of repose, adhesion, and cohesiveness, making it significantly easier to handle in subsequent steps.

Although the dried purified crude zinc oxide still contains some chlorine, fluorine, sodium and potassium, it is possible to easily produce electrolytic zinc and distilled zinc by using conventionally known methods, and as mentioned above, readily zinc sulfate,
Zinc derivatives such as zinc carbonate and zinc white can also be produced.

As explained above in detail, the method of the present invention has the following features.

1. Refined crude zinc oxide recovered from steelmaking dust, etc. has a quality that can be used as a zinc raw material in any direction.

2. The method of the present invention first concentrates the valuable metals contained in steelmaking dust etc. as crude zinc oxide, and then washes and removes chlorine, fluorine, sodium and potassium. The removal efficiency is far superior, and the amount of washing water is only 1/2 to 1/3.

3. The iron-based clinker separated in the rotary furnace is treated with magnetic separation to recycle the residual carbon content, and the magnetic material can be used as raw materials for cement, raw materials for iron manufacturing, etc., and the overall use of resources is reduced. It can be used effectively without leaving any secondary pollution sources.

4. The process is simple and the equipment can be made compact, so it is an economical method for recovering valuable metals from steelmaking dust, etc.

5. Waste water, exhaust gas, etc. are non-polluting processes that can be easily rendered harmless by treating them using conventional, well-known methods.

Next, examples of the present invention will be described.

Example 1 Steelmaking dust 9 to 100 (Zn27.3%, PE25.0
%, C! do, 05%, Na 2.1%, KO, 8%
, CI 3.0%, Fo, 8%) and pelletized with 9% moisture using a granulator (particle size: 4-8% 95%).

8-10% 5%) 110 kg was obtained.

This was mixed with 24 kg of Coke Please as a reducing agent and 7 kg of recovered carbon (078%), and the mixture was charged into a rotary furnace and reacted at 1150°C.

As a result, crude zinc oxide (Zn55.0
%, Fe1.1%, Pb5.9%, ca o, i%
, Na 3.9%, 152%, CI 6.9%,
Fo, 43%) 46 kg and mainly iron (crushed clinker (Zn 3.3%, Fe 40.3%, Pb 0.5%, Na
O, 5%, KO, 17%, 010.33%, Fo, 67
%, 012%) 60 kg was obtained.

The recovery rate of zinc, lead, and cadmium was 92.7% each.
They were 90% and 99%.

Example 2 Clinker (Fe42.0%, SiO□12.0%.

When 100 kg of C11,0%) was separated using a magnetic separator, a magnetic material mainly composed of iron (Fe47.6%, 5iO21
27%, C1.7%) 87.8 kg, and a non-magnetic material whose main component is green coke (Fe1.5%, 5iO27%).

078%) 12.2'ky was obtained.

It was confirmed that the non-magnetic material has a sufficient function as a reducing agent.

The recovery rate of C was 86.4%.

Example 3 Crude zinc oxide (Zn55.0%, Pb6.3%, Fe1.
1%, CI 9.5%, Fo, 42%, Na 3.5%.

K1.6%) 100kg was added to a soda carbonate solution (109g/
1) Added to 500 tons and the slurry pH became 7.2.

The liquid temperature was set to 50° C., 100 g of n-dodecylbenzenesulfonic acid salt was added as a surfactant, stirred for 30 minutes, and then filtered using a filter press.

As a result, the cake had a water content of 21.5%, was dry and powdery, and weighed 108:3 kg.

The zinc content in the sap was 337119/l, and the zinc elution rate was 0.
It was 0.3%.

The cake was further dried in an indirect heating dryer Q, resulting in 85 kg of purified crude zinc oxide (Zn64.7%, Pb
7.3%, pel, 3%, CIo, 7%, Fo, 15%
tNa (145%, KO, 08%) was obtained.

The removal rates of chlorine, fluorine, sodium, and potassium were 93.8%, 69.8%, and 89.1%, respectively.

and 95.7%.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of the method of recovering valuable metals from flat furnace steelmaking dust, etc. of the present invention. FIG. 2 shows the relationship between the amount of surfactant added and dechlorination and defluorination when crude zinc oxide is treated by the method of the present invention. FIG. 3 similarly shows the relationship between treatment temperature and dechlorination and defluorination.

Claims (1)

[Claims] 1. Zinc, lead,
In the method of recovering cadmium and iron as valuable metals, steelmaking dust and/or similar dust is pelletized, a carbonaceous material is added as a reducing agent, and then heated to a temperature of 1000 to 1200°C in a rotary furnace to remove zinc. , a step in which lead and cadmium are reduced and volatilized to separate them from iron, calcium, silica, etc. to obtain a clinker mainly composed of crude zinc oxide containing zinc, and the clinker obtained from this step is subjected to magnetic separation. A process of separating the non-magnetic material mainly consisting of residual carbon and the magnetic material mainly consisting of iron, recycling the non-magnetic material into a rotary furnace as a partial substitute for the reducing agent and recovering the iron as a magnetic material, and further reduction. The crude zinc oxide obtained from the process is brought into contact with a dilute alkaline solution at pH 6 to 12, and at the same time, a surfactant of 0.03 to 2.0% of the crude zinc oxide is added and reacted at a temperature of 30°C or higher. , separating chlorine, fluorine, sodium, and potassium and concentrating zinc, lead, and cadmium. A method for recovering valuable metals from steelmaking dust and/or similar dust.