JPS5980739A - Fluidized reduction method of nickel oxide - Google Patents

Abstract

PURPOSE:To reduce NiO by a solid phase reduction to metallic Ni having high purity at a low cost by using kerosene contg. S in a small amt. as fuel in the stage of reducing NiO powder coated externally with MgO to Ni in a fluidized bed. CONSTITUTION:Powder of NiO of 35-70 mesh which is coated externally with MgO and contains <=0.005% S is charged into a reduction furnace 1 from the upper part thereof. The furnace 1 is beforehand maintained at 800-1,000 deg.C. Kerosene contg. <0.02% S is fed as fuel oil together with air at <=0.131 ratio of the amt. of NiO into the furnace according to the amt. of the NiO to be charged and the temp. in the furnace is maintained at the above-mentioned temp. The fuel oil is decomposed to generate reducing gas which reduces NiO to a powdery metal having high purity without melting the same. The formed Ni is prevented from sticking on the wall of the reduction furnace by the thin MgO coating layer and the Ni contg. an extremely small amt. of S is produced at a low cost without conglomeration of the powdery metallic Ni by the effect of said coating layer.

Description

[Detailed description of the invention] The present invention relates to a method for fluid reduction of nickel oxide.

More specifically, the present invention relates to a method of obtaining high-grade reduced nickel with a low sulfur content using magnesium oxide-coated nickel oxide.

Due to advances in manufacturing technology for special steels such as stainless steel and alloy steel, as well as the need to conserve resources and energy, there is a desire to develop a method that can stably supply inexpensive, high-grade nickel.

Conventionally, many sources of nickel have been known, such as nickel oxide, electrolytic nickel, ferronickel, and nickel metal, but nickel sources other than nickel oxide are expensive because they require the use of large amounts of electricity. The goal of energy conservation cannot be achieved.

On the other hand, nickel oxide is a cheap and stable source of nickel, but because it is an oxide, nickel and oxygen are mixed together in melting furnaces used to produce, for example, stainless steel. Extra heat is required for decomposition, which may lead to increased power consumption and loss of chromium.

Furthermore, even when reusing the dust in dust collectors installed as dust pollution countermeasures, the amount of dust used is limited because most of it is in the form of oxides, and the use of other oxides is limited. The production method of a nickel source that can solve these problems and stably supply nickel at low cost is to produce nickel oxide without going through the process of melting nickel oxide. Many proposals have been made for this type of method. For example, there is a method of reduction using hydrogen or a gas such as carbon monoxide in a fluidized bed furnace, or a method of direct reduction with hydrogen or natural gas or the like in a rotating moving bed furnace.

However, most of these known methods cause problems of adhesion agglomeration between the reduced nickel particles and adhesion on the walls of the reduction furnace. Furthermore, hydrogen gas, carbon oxide gas, etc. are expensive and dangerous gases that require a pouring window to handle, so they require large and powerful equipment. This is disadvantageous in that it requires preheating or combustion, which increases costs and complicates the process.

In addition, when using a rotating moving bed furnace, contact between the gas and the material to be reduced is insufficient, and a large amount of reducing agent is required.
Moreover, the equipment is also large-scale.

Many solutions have been proposed to solve this problem of interparticle adhesion as well as adhesion to the furnace walls. One was to optimize the reduction rate and rate while minimizing particle mechanical problems based on the correlation between reduction temperature and particle size distribution. It has also been proposed to provide inert particles and use them as a mechanical buffer phase to avoid the problem of adhesion between metal surfaces.

However, to achieve effective anti-fouling,
The presence of large amounts of inert particles is believed to be necessary. Furthermore, such a method causes problems such as segregation of inert particles and scattering during fluidized reduction, and furthermore requires a sorting step to remove the inert particles afterwards, making handling complicated. It is also known (Canadian Patent No. 869.475) to try to solve the adhesion problem by using small amounts of very fine inert particles and high purity nickel oxide. However, the Canadian patent describes II
ISg - is necessary, and since it involves the use of hydrogen as a reducing agent, it is economically disadvantageous, and the process is unavoidably complicated.

On the other hand, Japanese Patent Publication No. 55-9932 proposes forming an anti-agglomeration coating on nickel oxide particles in order to overcome the problem of adhesion. The method has a sulfur content of 0.00
A moving bed comprising 5 to 0.5% of non-ferrous metal oxide particles (e.g. nickel oxide, cobalt oxide) and at least one additive which is calcium oxide, magnesia or an insulator which can be thermally decomposed to these oxides. forming and contacting the coating with a reducing atmosphere at a temperature sufficient to reduce the non-ferrous metal oxide particles, the anti-agglomeration coating being formed under said reducing conditions.

However, even in the method described in Japanese Patent Publication No. 55-9932, the sulfur content in the coated nonferrous metal oxide is 0.0.
0.05% to 0.5%, so when fluid reduction is performed by injecting fuel oil, the reduction rate decreases because decomposition of the fuel oil is inhibited by sulfur: 1i Temperature below 1000°C However, under these conditions, the adhesion of the coating layer is insufficient, the coverage is poor, and desulfurization tends to be incomplete: 111 Reduction using coated nickel oxide with a high sulfur content If this is done, the nickel particles become brittle and more dust is generated.Therefore, there is still room for improvement.

Under these circumstances, the inventors of the present invention discovered a new method of coating nickel oxide particles as a result of various studies to further improve the known method, and filed a separate patent application on the same date as the present application.

This nickel oxide coating method is characterized by blowing a soluble magnesium compound solution into a fluidized bed of nickel oxide or its precursor at a high temperature of 1000° C. or higher.

The present inventors have discovered that this magnesium oxide-coated nickel oxide is extremely effective in preventing the adhesion of nickel particles from agglomeration and adhesion to the furnace wall during reduction, and that it is also highly effective in preventing the use of fuel oil with an extremely low sulfur content. The present inventors have discovered that effective fluidized reduction can be achieved, and have completed the present invention.

Therefore, the main purpose of the present invention is to provide a method for obtaining high-grade reduced nickel economically and productively by effectively avoiding adhesion between reduced nickel oxide particles and their adhesion to the furnace wall. .

Other objects and features of the invention will become more apparent from the following description.

That is, the present invention injects low sulfur fuel oil into a fluidized bed,
The present invention relates to a method for obtaining reduced nickel with a low sulfur content and high quality, which includes a step of fluidically reducing magnesium oxide-coated nickel oxide with a low sulfur content at a high temperature in the range of 800'C to 1000 t::.

First, the coating of nickel oxide particles is carried out according to the method described above. The nickel oxide source may be of any origin, and its precursor can be exemplified, particularly after primary desulfurization treatment during desulfurization of nickel sulfide. As soluble magnesium compounds that can be used, magnesium sulfate, magnesium thiosulfate, magnesium acetate, etc. can be used alone or as a mixture.
It is usually best to use it as an aqueous solution. The concentration of the solution used is preferably in the range of 10 to 25% by weight, and the solution is such that the weight of magnesium to be formed in the phosphorous layer is 0 based on nickel oxide.
．． It is used in an amount of 2-0.3%.

By sniffing, coated nickel oxide particles with a sulfur content of 0.005% or less and a magnesium content of 0.2% or more can be obtained, and these can be directly transferred to the subsequent reduction step without cooling treatment. , economically advantageous.

The reduction method of the present invention involves blowing air through the lining of the hearth to fluidize the charge in the furnace, and then injecting fuel oil into it and causing partial combustion to generate heat to maintain the temperature in the furnace within a predetermined range. The process includes a step of reducing nickel oxide using a reducing gas generated by partially burning the fuel oil.

In order to implement this method efficiently, it is necessary to pay attention to the following points.

(a) Maintain good flow conditions at all times; (b)
Decompose fuel oil so that reducing gas is generated most efficiently; (C) Reduce as much as possible the components that inhibit the decomposition of fuel oil and the components that may interfere with reduction.

To explain these important requirements in more detail, requirement (a) is related to nickel oxide as a raw material, and as mentioned above, the nickel particles produced by the reduction of nickel oxide adhere and form agglomerates. The biggest cause of trouble is that it sticks to the furnace walls. However, this problem can be effectively prevented by using nickel oxide particles coated with magnesium oxide by the method described above.

Furthermore, this requirement is also influenced by the conditions of the air to be blown. Such incomplete flow in the hearth caused by blown air can be prevented by increasing the number of tuyere to be installed in the hearth as much as possible and by adjusting the blowing direction of the tuyere. It is desirable that the blowing direction of the tuyeres be directed diagonally downward. This is effective in allowing the particles around the tuyere to flow without stagnation and at the same time preventing the particles in the fluidized bed from flowing back from the tuyere.

In order to improve fluidity, the particle size distribution of nickel oxide is preferably between 10 mesh and 100 mesh, preferably between 35 mesh and 70 mesh. The greater the proportion of particles with a mesh size of 35 or more, the more difficult it becomes to achieve uniform flow, and the greater the proportion of particles with a mesh size of 70 or less increases, the worse the yield of nickel particles becomes. There is no relationship between the particle size distribution of nickel oxide and the space velocity of the blown air.In the above particle size distribution, the space velocity of the blown air is about 152 ctn/sec~2
A range of 13 cm/see is desirable.

This is because if the space velocity becomes less than about 152tYn/SeC, the flow condition deteriorates and the flow becomes uneven, and about 213c7
This is because at a space velocity of n/SeC or more, particles in the furnace are entrained in the blown air, resulting in poor yield.

In order to meet the requirement of the next K (b), that is, to decompose fuel oil so that reducing gas is generated most efficiently, first, a burner having a structure that can make the droplet diameter of fuel oil as fine as possible, For example, sufficient atomization should be carried out using a high-pressure air flow burner, a hydraulic spray burner, or the like. Furthermore,
Temperature is also an important factor to promote cracking and gasification of fuel oil, and to achieve the specified purpose, 800
Temperatures in the range ˜1000° C. are suitable. A temperature lower than 800° C. is not preferable because the efficiency of decomposition and gasification of fuel oil is poor, a large amount of soot is generated, and as a result, the reduction rate decreases. Furthermore, at temperatures higher than 1000℃, the amount of fuel oil required to maintain the high temperature increases, which not only wastes energy, but also increases the rate of wear and tear on the furnace walls, siding, burners, etc. This is not desirable.

In order to meet the third requirement (C), that is, to minimize the amount of components that inhibit the decomposition and reduction of fuel oil, the sulfur content in nickel oxide and in the fuel oil must be minimized. It is. It is also important not to use water, steam, etc. to adjust the temperature.

As shown in Example 2, the presence of sulfur, even in a small amount, inhibits the decomposition of the fuel oil blown into the fluidized bed in the reduction process and reduces the efficiency of generating hydrogen and carbon oxides as reducing agents. , soot, and hydrocarbons that hardly contribute to reduction.

Also, since most of the sulfur remains in the reduced nickel,
When reduced nickel is used as a raw material for producing special steel, etc., it is highly likely that it will have an adverse effect as an impurity.

According to research conducted by the present inventors, it has been found that the sulfur content in the nickel oxide to be reduced is desirably 0.005% or less. If the sulfur content is higher than this, the decomposition of the fuel oil will be inhibited, the generation rate of soot and hydrocarbons will increase, and as a result, the reduction efficiency will also decrease.

For similar reasons, it is preferable to use fuel oil with a low sulfur content, and it is most desirable to use kerosene because it is less dangerous to handle.

In the present invention, the amount of fuel oil used is 0.131 or less in weight ratio to nickel oxide. Thereby, reduced nickel can be obtained continuously and with high productivity with a degree of reduction of 88 coefficients or higher.

The reduction furnace used in the present invention is not particularly limited, and for example, a bed type fluidized bed furnace, an upper conical type fluidized bed furnace, a lower conical type fluidized bed furnace, etc. can be used, and either a batch type or a continuous type method can be used. You can also do it.

Hereinafter, preferred embodiments of the reduction method of the present invention will be explained with reference to the attached drawings.

The nickel oxide coated with magnesium oxide is allowed to fall by gravity from an input hole at the top or side of the reduction furnace 1, or is mechanically blown into the furnace. Refund・Door 1 is 8 in advance
The temperature is maintained between 00°C and 1000°C, and the amount of fuel oil and air are adjusted according to the amount of nickel oxide added to maintain the specified temperature. Blow inside.

Air should have a space velocity of approximately 152-2 for optimal flow.
Feed through the hearth tuyere in an amount such that 13 Cm/sec.

Fuel oil is added in accordance with the amount of nickel oxide added so that the furnace temperature reaches a predetermined temperature, but a weight ratio of 0.131 or less to nickel oxide is sufficient.

The reduced nickel is transferred to the cooler 2, where it is cooled under a controlled atmosphere of inert gas such as nitrogen or furnace exhaust gas.

The cooler 2 is not particularly limited and can be, for example, a fluidized cooling furnace, an external water-cooled rotary moving bed furnace, a water-cooled mixer, etc., but the atmosphere must be adjusted so that the reduced high-temperature nickel does not re-oxidize. There is a need.

The exhaust gases from the reduction furnace 1 and the cooler 2 are collected in a flue 4, further passed through an exhaust gas cooling and cleaning device 3, and then released.

Thus, by following the method of the present invention, many effects can be achieved, such as the following.

1. Since the heat source and reducing agent utilize partial combustion of fuel oil, they are highly safe, inexpensive, and require less strict airtightness than hydrogen gas, carbon oxide gas, etc.

2. Since the gasification and decomposition reactions of fuel oil can be performed simultaneously in the fluidized fluidized reduction furnace, there is no need for a special preheating chamber or combustion chamber, and it is sufficient to simply inject the fuel oil into the furnace.

3. If you choose kerosene as your fuel oil, it will have a lower sulfur content, and its price will be monitored to reflect the impact on the lives of the general public, and supply and demand will be controlled by the government and consumers. Stability,
There is a public nature of price.

4. Compared to melting and refining, electricity is extremely low.

5. When looking at the cost comprehensively, the fuel cost is low, the electric power is low, and there is no need for auxiliary materials such as slag-forming agents required in melting and refining, so the cost is very low.

6. No special power is required for the equipment, and it can be used as is in places that have a fluidized roasting furnace, and the equipment investment is very low.

Although the Z product is granular, it has a wide range of uses, such as blowing into AOD furnaces, raw material for electrolytic nickel, and electric furnaces.
It is also suitable for operations with high scrap content.

8. In this method, the amount of dust generated during fluidized reduction is extremely small, and not only is the yield very high, but compared to melting and refining, there is less nickel loss, and the nickel generated as dust can be recycled and reused. .

9. Reduction operation is easy and productivity is high for the equipment scale.

10. If conditions are selected, it is also possible to reform fuel oil with steam, making it possible to further reduce costs.

Next, the present invention will be explained in more detail with reference to Examples.

Examples 1 and 3 are good examples of implementation using this method.

In Example 2, the sulfur content in nickel oxide was 0.00
A comparison between the case of 5% and the case of more than 5% is shown, and when the sulfur content is 0.005% or more, the degree of reduction is poor and the productivity is also bad.

This is because, as is clear from the exhaust gas analysis values in Table 8, sulfur worsens the decomposition of fuel oil, increases hydrocarbons such as methane, and decreases Co and H2 necessary for reduction.

Example: Magnesium oxide coated nickel oxide having the chemical composition shown in Table 1 and the particle size distribution shown in Table 2 was used and heated at 900°C.
Fluid reduction was performed. The operating conditions at this time are shown in Table 3.

The chemical composition and particle size distribution of the obtained reduced nickel are shown in Tables 4 and 5, respectively.

1st - oxidizer, 7 no iku 4 舅tan - one catch Ieku conversion - and four Qi servings - regret 76.79. i,ol 0
．． 110.390.0050.27 Table 2 Particle size distribution of nickel oxide coated with magnesium oxide 29.16
68.23 2.15 0.46 Reduction temperature 900℃ Air ratio *' 0.383 Fuel ratio *2 0.131 Hearth area fi productivity 48.8) n/m2・day reduction degree 91.5 ratio * 1 Air ratio is the ratio between the amount of air required for complete combustion of fuel oil and the amount of input air. 0 *2 Fuel ratio is the weight ratio of fuel to input raw materials.

Contact 95.501.220-140.520.0070
．． 3.7 Table 5 Particle size distribution of reduced nickel Example 2 Using two types of magnesium oxide-coated nickel oxide having the chemical compositions shown in Table 6, fluidized reduction was carried out at 900°C. The operating conditions at this time are shown in Table 7, and the exhaust gas analysis values are shown in Table 8.

The chemical composition of the obtained reduced nickel is shown in Table 9: O f%, N, i-, -Co, Cu, -Fe,
,-,,,,S--,,M,g-176,791,0
10,110,390,0050,27276,781
,010,110,390,0+110.27Table 7
Operating condition number 12 Reduction temperature 1: 900 900
Air ratio 0.3830.356 Fuel ratio 0.1310.140 Productivity tons per hearth area/m2-8 48.8
45.5 Reduction level 91.0 7
6.9 Example 3 Magnesium-coated nickel oxide having the chemical composition shown in Table 10 was fluidized at 894°C. The operating conditions at this time are shown in Table 11.

The chemical composition of the obtained reduced nickel is shown in Table 12.

Person in charge 76.79 1.01 0.11 0.590.0
050.27 Reduction temperature 894℃ Air ratio 0.392 Fuel ratio 0.127 Hearth area productivity 50.1 tons/m2・day reduction degree 88.7 Width 95.01.250.1.40.4B 0.007
0.33

[Brief explanation of drawings]

The attached drawing is a diagram showing an example of a process diagram for carrying out the method of the present invention.

Claims (1)

[Scope of Claims] (1) Magnesium oxide coated nickel oxide with a low sulfur content is charged into a fluidized bed, fuel oil with a low sulfur content is blown into the fluidized bed, and fuel oil with a low sulfur content is injected into the fluidized bed and partially combusted.
A method for producing high-grade reduced nickel with a low sulfur content, comprising a step of dynamically reducing the nickel oxide at a high temperature within the range of 0°C. (2) The amount of fuel oil used is based on the weight of nickel oxide. The method according to claim 1, wherein the ratio is 0.131 or less. (3) Claim No. (1) or (2) characterized in that the sulfur content of the fuel oil is 0.02% or less.
The method described in section 2). (4) The method according to claim (3), wherein the fuel oil is kerosene. (5) Claim 10, wherein the sulfur content of the magnesium-coated nickel oxide is 0.005% or less.
The method according to any one of (4) to (4).