JPS58197235A - Method for recovering metal - Google Patents

Abstract

PURPOSE:To carry out operation with a uniform metallizing rate and high efficiency in the titled method by directly desulfurizing and reducing a substance contg. Ni-base metallic sulfide, by specifying the water content and crushing strength of raw briquettes to be charged into a circular vertical furnace to prevent the breaking of the briquettes. CONSTITUTION:A substance contg. Ni-base metallic sulfide is mixed with a carbonaceous reducing agent, Ca oxide and/or a substance forming Ca oxide, and Na salt, and the mixture is briquetted. The briquettes are charged into a circular vertical furnace from the top. They are directly heated to 750 deg.C with a nonreducing gas contg. <=1vol% O2 fed from a lower part of the furnace to form metal, and the metal is recovered. The briquettes are raw briquettes having 2-5wt% water content and >=0.5kg/cm<2> crushing strength or 5-8wt% water content and 0.5-2kg/cm<2> crushing strength, and they are charged into the furnace without carrying out predrying.

Description

[Detailed description of the invention] This invention relates to a method for recovering metals by direct desulfurization and reduction of materials.

One of the methods for obtaining metals by directly desulfurizing and reducing metal sulfide-containing substances is the reduction method using hydrogen.Trans. Me
t. Soc. 'A Engineering MK. :15 (/949) /
727, a hydrogen reduction method for copper, nickel, cobalt, and iron was reported. In this study, CaO coexisted in the reaction system and MeS + H2 d Me + H2 S
H2El produced in (1) is effectively removed by CaO2, and the reaction of formula (1) is made to proceed smoothly in the right direction. However, in order to efficiently deposit the metal through this reaction, it is necessary to provide a strong reducing atmosphere by introducing a large amount of hydrogen gas at the same time as heating. If a non-reducing gas such as heavy oil combustion gas is used for this heating, the amount of hydrogen gas used will naturally increase.
Since this is not economical, it has not been put into practical use to date.

In order to eliminate these inconveniences, the present inventors have already investigated various methods for direct desulfurization and reduction of materials containing metal sulfides, mainly nickel, and carbonaceous reduction methods to materials containing metal sulfides, mainly nickel. agent, one or both of calcium oxide and calcium oxide generating material for sulfur fixation, and thorium salt are added and mixed, and the mixture is heated with a non-reducing gas for 7 hours. We have developed a metal recovery method that includes a step of directly heating the metal to temperatures above 0.000 C, and have found that a particularly preferred embodiment is to use an annular vertical furnace as the heating furnace. (See Japanese Patent Application No. 0-77572).

In order to carry out the metal recovery method using this annular vertical furnace, a metal sulfide-containing material mainly composed of nickel, a carbonaceous reducing agent, calcium oxide and a calcium oxide-generating material or For operational purposes, it is necessary to add and mix both of these and the sodium salt, and to form this mixture into a mass such as briquette.

Generally, when the material to be roasted is processed into pellets, briquettes, etc., pre-drying is performed to give it the necessary strength to withstand the external forces it receives when moving through the furnace, and moisture is added for molding. Coagulability is strengthened by adding a caking agent to provide caking properties. This preliminary drying is carried out either outside the oven using a drying device or in the oven, which is not economically preferable.

The present inventors conducted a test in which the mixture was molded into green nodules using a briquette machine and rapidly heated to 7S00C or higher without pre-drying, and a phenomenon in which the nodules broke with a loud noise was observed.

In actual furnaces, when the nodules break down (so-called bursting), a large amount of smoke ash is mixed into the exhaust gas, and a great deal of labor and large-scale equipment is required to purify the exhaust gas and recover the smoke ash. Furthermore, if the heating furnace is of a shaft type, such as the annular vertical furnace used in the present invention, the pressure drop inside the furnace will increase, and the heating gas will not be able to pass through the furnace uniformly, making operation difficult. becomes unstable, and as a result, the firing becomes uneven, the metallization rate of the discharged nodules varies individually, and the average metallization rate also decreases.

The present invention solves the above problems and includes a metal sulfide-containing material mainly containing nickel, a carbonaceous reducing agent, one or both of calcium oxide and calcium oxide-generating material,
In this method, a mixture of salts and sodium salts is made into agglomerates, charged into a circular vertical furnace without pre-drying, and directly heated with non-reducing gas to generate and recover metals. The purpose is to provide a method for good operation.

To achieve this objective, the invention consists in treating raw materials according to the claimed method.

In order to prevent the bursting of the nodules, the inventor investigated the granulation conditions such as the particle size of the raw material, the added moisture content, the number of passes through the briquette machine, and the properties such as the crushing strength and falling strength of the produced green nodules. We investigated the relationship between bursting. As a result,
The bursting of the baby boom is closely related to the moisture content and crushing strength of the raw baby boom, and the crushing strength is 2 K97cm when the moisture content is less than 3 kg or within the range of 5 to 5 g.
It was found that bursting can be prevented if the value is 2 or less. In addition, the crushing strength in this case is the maximum lateral W of the baby boom.
It is expressed as the value obtained by dividing the load that causes the nodule to break, which is applied in the direction perpendicular to the T plane, by the area of the maximum cross-section of the nodule.

An example of the test is nickel pine) (N177.
0゜C00, FθOg, 82/, 0% by weight),
Pulverized to 20 mesh or less, and mixed with coke of 700 mesh or less, (95% total carbon), slaked lime, and 20 parts by weight of IJum per 100 parts by weight of nickel matte, each at 9.2.9ψg/100 parts by weight. And, with the twin wheel type briquette machine! 3rnjrr thickness, J51 tread width 1. ? OY
u: Long, almond-shaped nodules were produced. By adjusting the amount of water added at the time of mixing and the molding pressure at the time of making the dough, green nodules having various moisture contents and crushing strengths were obtained. The material was rapidly heated to 200° C. for 5 minutes in this fresh N2 atmosphere, and the bursting state was observed. The results are shown in FIG.

From Figure 1, in order to prevent the bursting of the baby boons, the moisture content of the raw baby boons must be below the S weight factor, or the crushing strength should be below 2x9/cm2 within the range of moisture content from 3 to g weight factor. Understand what you need.

However, in addition to bursting, the nodules are required to withstand mechanical destruction such as crushing due to load in the furnace and destruction due to movement, and from this point of view, the crushing strength of the green nodules is 0.3; Kl; l! /cm2 or less is not preferable as it will disintegrate in the furnace and cause operational problems.

In addition, if the moisture content is less than 2 parts by weight, it is difficult to form it into a green lump using a briquette machine.

Hence the temperature gradient for rapid heating? The raw nodules to be charged into the vertical annular furnace with a moisture content of 2 to S are OjK.
Compressive strength of 7 cm2 or more or moisture content of 5 to 5 g
It is necessary to have a crushing strength of 70 m2 in terms of weight.

Sodium salts can be converted to sodium oxide or N by decomposition and reaction.
You can use the one that generates a20Q. For example, carbonates, sulfites, sulfates, rogens, etc. can be used. The addition rate of the sodium salt is preferably 0.5 parts by weight or more, calculated as Na2O, per 100 parts by weight of the metal sulfide-containing material, which is mainly nickel, and more preferably 1 part by weight or more.
Wait. If the amount is 1 part by weight or more, the metallization rate will be almost saturated, so there is no need to increase it too much.

Coal, coke, charcoal, etc. can be used as the carbonaceous reducing agent, and in some cases, a liquid carbonaceous substance (eg, pitch, heavy oil, etc.) may also be used.

The amount of carbonaceous reducing agent added is determined by the following reaction formula (2) % formula % (
2) It is appropriate to set it to 72 times or more the amount theoretically calculated from .

The calcium oxide producing substance refers to a substance that is thermally decomposed to produce OaO. Suitable examples of such substances include limestone and slaked lime. Of course, quicklime can also be used, and these may be used in combination.

It is appropriate that the amount of calcium oxide, calci, or lamb oxide-forming substance added be at least 72 times the amount theoretically calculated from equation (2). However, if the amount is too large, the separation efficiency of recovered metals will deteriorate, so a range of 2 to 25 times is appropriate.

The metal sulfide-containing substance mainly composed of nickel is used after being ground into 20 meshes or less. In addition, solid forms of carbonaceous reducing agents, calcium oxides, calcium oxide generating substances, and IJium salts may be appropriately ground.

In this case, if you mix while grinding, the mixture will be even better.

The non-reducing gas used for heating is easily obtained as combustion gas of liquid fuel such as heavy oil. Such gases can also be obtained from other solid or gaseous fuels. This non-reducing gas preferably has an oxygen concentration of 1 volume or less. Otherwise, the oxidation and resulfurization reactions of the produced metal will become more active, the sulfur and oxygen concentrations of the produced metal will increase, and the carbonaceous reducing agent will be wasted.

The direct desulfurization-reduction reaction of a metal sulfide-containing substance mainly composed of nickel in the present invention is thought to occur as follows. First, the carbonaceous reducing agent reduces H2 in the combustion gas at the required temperature.
H by C, C02 and water gas reaction, Bourdois reaction, etc.
2. Generates a reducing gas such as Co, and this reducing gas reacts with metal sulfide to generate sulfide gases such as H2S and CO8 while proceeding with the desulfurization reduction reaction, and creates a reducing atmosphere. Prevents resulfurization reactions in metals. H2S
, Sulfide gas such as CO8 reacts with calcium oxide, and the sulfur content is fixed with calcium. The above-mentioned reducing gas production reaction proceeds at temperatures above about 000C, and nickel,
Since the desulfurization reduction reaction of cobalt and copper sulfides proceeds at temperatures above about 1.000C, it is possible for the reaction of equation (2) to proceed in the right direction for nickel, cobalt, and copper by heating above this temperature. However, in order to obtain a practical reaction rate, it is necessary to increase the temperature to 7SO0C or higher. The appropriate temperature for the desulfurization reduction reaction varies depending on the type of metal, and the optimum temperature for the reducing gas production reaction varies depending on the carbonaceous reducing agent used, so the combination and temperature may be selected as appropriate. For example, bituminous coal and lignite that generate large amounts of pyrolysis gas are 7JO
Suitable for ~9000C, coke is 900-/20
Suitable for use at 00C.

As the desulfurization reduction reaction progresses, the carbonaceous reducing agent is consumed, but as the residual carbon content decreases, the amount of reducing gas produced also decreases, the reducing atmosphere becomes weaker, and the resulfurization reaction occurs. Since the resulfurization reaction becomes significant when the residual carbon reaches below the weight plate, the residual carbon should be 733% by weight, preferably 20% by weight.
'It is better to make it above the weight rating. This can be determined by analyzing the heat treatment extraction force product, and the residence time in the furnace can be adjusted based on that value so that the residence time in the furnace does not become excessive.

In addition, CaS, CaC2 ash, etc. remain in the product, and the metals can be recovered by processing this product by various methods. For example, ore beneficiation methods such as flotation, magnetic separation, specific gravity separation, and electrostatic separation are effective for separating metals from other contained materials.

According to the method of the present invention described above, if the green nodules are directly charged into the annular vertical furnace without pre-drying and the metal recovery method is carried out by direct desulfurization reduction, drying and desulfurization reduction can be partially performed. Thermal efficiency can be achieved in a short time, making it more even.
The metallization rate can be improved by performing firing, and the generation of smoke ash can be reduced.

Example 1 Nickel matte (Ni 77.0. co O,1,
FeOll.

5210 (each weight%) to 20 mesh or less, and to this, 9.93.2 parts by weight or less per 700 parts by weight of coke (all carbon 9S rumatsu) of 100 mesh or less was added and mixed, and water was added to form this mixture. The moisture content was adjusted to p, s weight ratio, and the molding pressure was adjusted using a twin-wheel briquette machine, and the moisture content was adjusted to 23 lLIM thickness, Δ part width 1.70 female length, almond-shaped shape, moisture content V, s weight ratio, Crushing strength 3. Y-! 7
The mixture was molded into a green mass of /cm2. The raw nodules are continuously fed from the upper part of the annular vertical furnace, while heavy oil combustion gas is mixed with a part of the furnace exhaust gas from the lower part of the furnace at a temperature of qs.

It was blown in while adjusting the OC1 oxygen concentration and O7 capacity.

The residence time of the nodules in the furnace was 65 minutes, and the elapsed time of the temperature above 0,000 was ttS minutes. There was no crusting of nodules in the furnace. The nodules produced from the furnace were subsequently cooled in a rotary cooler and then poured into water. The water-cooled nodules are crushed into 700 mesh pieces or less using a wet ball mill.
As a result of processing this slurry with a wet magnetic separator at 7000 Gauss, Ni 9'1. ! ;, C3I, 3゜s /, o
, co2 nickel metal powder of each weight ratio was obtained. The metallization rate of nickel was related to the trade weight.

The amount of smoke ash in the exhaust gas from the annular vertical furnace was O/7% by weight of the amount of nickel matte charged.

Example 2 Nickel matte, coke, slaked lime, and sodium carbonate having the same composition and particle size as in Example 1 were mixed in the same blending ratio as in Example 1, and water was added to adjust the moisture content of this mixture to 65% by weight. 23ttW thickness 5.23ijam width, 30 crane length almond-shaped shape, moisture content S weight %, crushing strength /,
2K! It was molded into a 77 cm2 raw mass. This green nodule was continuously charged from the upper part of the annular vertical furnace and roasted under the same conditions as in Example 1. There was no bursting of nodules in the furnace. The nodules produced from the furnace were treated in the same manner as in Example 1 to obtain Ni 9tI/, Ca/J, S/, 3. C0,
3 Each weight of nickel metal powder was obtained. The metallization rate of nickel was 999% by weight. In addition, the amount of smoke ash in the exhaust gas of the annular vertical furnace is 0.0% of the amount of nickel matte charged. /, 3% by weight.

Comparative Example 1 Nickel matte, coke, slaked lime, and sodium carbonate having the same composition and particle size as Example 1 were mixed in the same mixing ratio as Example J, and water was added to bring the water content of this mixture to 5% by weight. The molding pressure was adjusted using a twin-wheel briquette machine, and 23
rlL'm thickness, :l! i rr1M width 1. '? (nLm
It was molded into a green nodule in the shape of a long almond with a moisture content of 45% by weight and a crushing strength of 30 Kq/cm2. When this green nodule was charged into an annular vertical furnace in the same manner as in Example 1, bursting occurred at the top of the furnace, the pressure loss in the furnace increased, the temperature gradient inside the furnace suddenly changed, and the produced nodule was unevenly baked. As a result, the nickel metallization rate decreased to 5% by weight. At this time, the amount of smoke ash in the exhaust gas increased to 2% by weight of the amount of nickel matte charged.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the crushing strength and moisture content of green nodules and the occurrence of bursting.

Claims (1)

[Claims] (]) A carbonaceous reducing agent, one or both of a calcium oxide and a calcium oxide generating substance, and a sodium salt are added to and mixed with a metal sulfide-containing material mainly composed of nickel, and the mixture is formed into a mass. This is charged from the upper part of the annular vertical furnace, and is made into nodules +Q7j by the non-reducing gas having an oxygen content of less than the number liter capacity coefficient and sent from the lower part of the annular vertical furnace.
In a metal recovery method in which metal is generated by direct heating to a temperature of 0.000 or more, the lump has a moisture content of 2 to 5% by weight and is 0.
．． 3 Compressive strength or moisture content t of KO/cm2 or more
-, r weight section 05~. 2. A metal recovery method characterized by charging raw nodules having a crushing strength of K9/cm2 into a furnace without pre-drying them.