JPS5826422B2 - Manufacturing method of Ferronitskel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing ferronickel through a combination of a calcination process using a calcination furnace such as a rotary kiln and a melting process using a reduction melting furnace such as an electric furnace.

Various methods have been used to produce ferronickel using nickel oxide ore as a raw material, such as the electric furnace method, the blast furnace method, and the Kurtzprene method, but recently the electric furnace method has become the main method.

The electric furnace method is a method in which nickel oxide ore is calcined in a calcining furnace such as a rotary kiln, and then charged into an electric furnace to obtain ferronickel.

In this electric furnace method, for the purpose of increasing the usage efficiency of the electric furnace, that is, reducing the energy consumption rate and reducing the cost of the ferronickel manufacturing process, the raw material ore is not only calcined in a rotary kiln etc., but also the nickel contained therein is It is said to be advantageous to reduce some or all of the iron beforehand and then process it in an electric furnace.

Several methods have been proposed for this purpose.

For example, fine ore is charged into a fluidized bed and high-temperature reducing gas is blown into it, or lump ore treated with aggregates is charged from the top of a vertical furnace and high-temperature reducing gas is injected from the bottom. There was a way to inject it.

However, these methods require the installation of reducing gas production equipment, which reduces the cost advantage of preliminary reduction treatment before charging the electric furnace, and the utilization rate of reducing gas is low, resulting in reducing gas being contained in the exhaust gas. It was also necessary to treat the exhaust gas.

Yet another method has been proposed, in which a mixture of ore treated with ore ore and a carbonaceous reducing agent is charged from the top of a vertical furnace, and high-temperature combustion gas as heating fuel is blown from the bottom. .

However, this method requires sizing of the charge, which requires a large amount of expense for pretreatment.

As before, exhaust gas treatment equipment was required to treat the reducing gas contained in the exhaust gas in small amounts.

Still another method is to mix ore treated with ore with a solid carbonaceous reducing agent and charge it into a rotary kiln. A method of restitution was proposed.

Although this method is advantageous in terms of equipment, it is difficult to mix the ore and reducing agent uniformly, and the degree of reduction of the ore discharged from the kiln varies widely, and the oxygen contained in the combustion gas of the fuel This presented a serious drawback in that reoxidation of the reduced ore occurred.

Recently, it has been reported that for the purpose of uniform mixing, a liquid carbonaceous reducing agent such as heavy oil is added to ore and carbonaceous material, granulated, and then charged into a rotary kiln, fluidized roasting furnace, etc. (Sho 49-64503).

However, this method had a fatal drawback in that the strength of the resulting aggregates was weakened because the granulation was performed by adding a liquid carbonaceous reducing agent such as heavy oil.

Since the strength of the briquettes is low, there is a strong tendency for the charged briquettes to become powder during roasting, resulting in a significant increase in the rate of dust generation.

Furthermore, when a rotary kiln is used, the added heavy oil volatilizes before reaching the reduction zone in the kiln, so its utilization efficiency as a reducing agent is low, and extra addition is required.

Another serious drawback is that when reduced ore with a low melting point passes through the highest temperature range in the kiln, it becomes an extremely viscous semi-molten material that adheres to the inner surface of the kiln, inevitably causing so-called ring trouble. Occurs during this period, making operations extremely unstable.

Another drawback is that it is not possible to avoid reoxidation of the reduced ore by oxygen contained in the combustion gas near the ore release date.

In order to solve these problems, the inventors first attempted to inject a reducing agent such as heavy oil directly into the rotary kiln.

However, simply spraying heavy oil deep inside the rotary kiln onto the ore does not solve the ring druffle and reoxidation problem described above, although the problem of dust generation can be alleviated.

Simply spraying heavy oil onto the ore did not necessarily result in good contact between the heavy oil and the ore, even though the ore was rolling in the kiln, and penetration of the heavy oil was not as rapid as expected.

Furthermore, an additional drawback was found in that the heavy oil injection lance extends into a high temperature range and is easily damaged.

As a result of various studies, the present inventor found that nickel oxide ore can be easily reduced by heavy oil or the like if kept at a temperature of about 500° C. or higher.

To confirm this, nickel ore was charged into an alumina crucible, heated to a predetermined temperature in an electric test furnace, and C heavy oil was added as a reducing agent through an alumina pipe that penetrated the ore layer while maintaining the predetermined temperature. The reduction rate of nickel and iron contained in the ore was investigated by adding nickel and iron.

The contact time between heavy oil and ore in this experiment was about 10 minutes, but as shown in the table below, if the raw ore is at a temperature of 500°C or higher, a reduction rate of about 9% for nickel and 10% iron can be obtained. I found out that it can be done.

In calcining furnaces such as regular rotary kilns, there is usually a temperature zone of 500°C or higher near the ore outlet, so if the reduction reaction is carried out in that zone, several of the problems mentioned above will be solved at once. Confirmed that it is resolved.

Briefly, the present invention relates to a method for producing ferronickel by calcining nickel oxide ore in a calcining furnace and then reducing and melting it in a reduction melting furnace.

Heavy oil,
A method for producing ferronickel, which comprises adding a carbonaceous reducing fluid such as natural gas to reduce some or all of the nickel oxide and iron oxide in the ore, and charging the resulting post-reduction melting furnace. I will provide a.

In particular, it is preferable to add the reducing fluid to the ore through a lance embedded in the ore.

Furthermore, as will be described later, it has been found that similar results can be obtained even if heavy oil is added in the process from the calciner outlet to the reduction melting furnace, for example in the surge hopper.

The method of the present invention will be specifically explained below.

In the present invention, nickel oxide ore is first mixed with about 3 to 5% of a solid carbonaceous reducing agent and charged into a calcining furnace such as a rotary kiln in the same manner as conventional calcining. Ru.

The charged ore advances to the highest temperature zone in the furnace and is sufficiently calcined during its progress.

In this process, no reducing fluid is added, and therefore, the ore is sufficiently calcined without causing problems such as the ring druffle described above.

After passing through the highest temperature zone, the calcined ore advances toward the ore outlet.

For example, 75? ? In the case of a Z-length rotary kiln, the distance from the highest temperature zone to the ore outlet is generally 1 to 10 mm. ? Z
That's about it.

A reducing fluid such as heavy oil or natural gas is added while the calcined ore is maintained at 500° C. or higher in the zone from the highest temperature zone to the ore outlet.

A reducing fluid injection lance extends into the furnace from the ore tap at a short distance from the furnace bottom so that it is embedded in the ore.

In a rotary kiln, the ore is
Since it is customary that the lance occupies sections 0 to 15, the lance may be appropriately positioned so that it is buried in the ore.

In the present invention, since the addition of heavy oil etc. is done inside the ore pile layer, compared to the method of spraying onto the surface of the ore pile layer,
A sufficient reduction effect is brought to the ore inside the sedimentary layer.

The unreacted reducing gas that rises through the gaps between ore grains reacts with oxygen in the combustion gas on the surface of the ore and burns, thereby preventing re-oxidation of the reduced ore and increasing the ore temperature. Promote giving back.

When heavy oil is used as a reducing fluid, decomposed carbon adheres to the surface of ore grains, but this carbon is extremely active and reacts with carbon dioxide and water produced by ore reduction to produce carbon monoxide, hydrogen, etc. and provide an additional contribution to the reduction action.

Reducing gases such as heavy oil and natural gas can be used as the carbonaceous reducing fluid, and conditions such as the amount of injection and the required contact time depend on the characteristics of the furnace, the temperature and type of ore, and the injection amount. It is necessary to select it appropriately depending on the input pressure and the desired degree of reduction.

For example, using heavy oil, the reduction rate of iron at 700°C is 16 times when the contact time is 5 minutes, 21 times when the contact time is 10 minutes,
In 15 minutes, there are 23 stations, but in the case of 8000C, there are 26 stations, 29 stations, and 31 stations, respectively, in the above time.

The lance for injecting the reducing fluid is not particularly limited, and a commonly used water-cooled lance pipe is sufficient.

Since the lance is not extended deep into the furnace, a conventional lance is sufficient in terms of strength.

According to the present invention, the carbonaceous reducing fluid is added outside the highest temperature zone in the furnace, so the ring trouble described above does not occur, and the reoxidation problem does not occur.

Since the reducing fluid is not added up to the maximum temperature range, stable calcining can be performed without generating dust.

Since the injection lance is extended from the ore outlet into the furnace while being embedded in the ore, the efficiency of contact between the reducing fluid and the ore is good, and there is no problem with damage to the lance.

In particular, the fact that the ring trouble problem seen in the prior art does not occur is noteworthy as an effect of the present invention, considering that when such trouble occurs, it is necessary to shut down the furnace and remove troublesome deposits. be.

In the above description, the carbonaceous reducing fluid is added to the zone from the ore outlet to the highest temperature zone in the furnace while the ore is maintained at 500° C. or higher.

However, in the present invention, when the residence time of ore from the highest temperature zone to the ore outlet in the calcining furnace is short, a chamber for adding carbonaceous reducing fluid is provided outside the furnace or on an extension of the furnace. It also includes performing reduction processing within the system.

If the temperature of the calcined ore is maintained at 500°C or higher, the intended purpose can be satisfactorily achieved.

Furthermore, this idea can be extended to bring the reducing fluid into contact with the calcined ore during the transportation or storage process of the calcined ore from the calciner outlet to the reduction melting furnace.

Generally, the calcined ore discharged from the outlet of the calciner is received in a collection container such as a surge tank and then sent to a hopper located above the electric furnace for reduction and melting.

Reduction equipment may be interposed between the ore outlet and the collection vessel or between the collection vessel and the hopper, or the reduction may be carried out within the collection vessel such as a surge tank or the hopper itself.

By inserting a spray lance into the bottom of a storage tank such as a surge tank or hopper and spouting heavy oil, etc. into the calcined ore accumulation layer, it is possible to substantially exceed the addition of heavy oil, etc. in the calciner mentioned above. Such contact effects can be obtained.

In this case, since the reducing fluid is added outside the furnace, the above-mentioned problems will not occur at all.

In another way, in order to increase the contact efficiency between the reducing fluid and the calcined ore, in addition to direct injection of heavy oil, etc., reducing fluid may be sprayed across the falling calcined ore flow, or conventional methods may be used. Gas-solid and liquid-solid contact methods can also be applied as appropriate.

Needless to say, a location where reducing gas generated by injection of heavy oil or the like can be sucked and recovered is desirable.

Examples of the present invention will be shown below.

Example 1 A mixture of nickel oxide ore from Celebes and 35 kg of coal per ton based on its dry weight was charged into a rotary kiln of 74 m length x 3.5 m diameter.

The rotary kiln's ore outlet is equipped with a water-cooled lancing pipe that can spout heavy oil into the ore deposits over a range of 2m deep inside the furnace.

This 2m range corresponded to about 10 minutes of ore residence time.

C heavy oil was injected from the Lansing pipe at a rate of 61 tons per ton of ore on a dry basis.

The amount of heavy oil for heating was 707 per dry ton of ore.

When the calcined reduced ore recovered from the kiln was analyzed using the bromo-methanol method, the following values were obtained.

The composition of the test ore and the composition of the calcined ore produced by the conventional method are also shown.

Example 2 Nickel oxide ore from New Caledonia and coal were mixed in the same ratio as in Example 1 and charged into a rotary kiln with a length of 80 m and a diameter of 3.5 mTM, and kiln burning was performed. .

Heavy oil C was injected at the kiln outlet under the same conditions as in Example 1.

The composition of the obtained reduced ore and the composition of the raw ore are shown.

For comparison purposes, the composition of calcined ore produced by the conventional method is also shown.

It will be seen from Examples 1 and 2 that the preliminary reduction rate by the method of the present invention is significantly improved compared to the conventional method.

Although the operation continued for a long period of time, there were no problems related to ring troubles or strikes that required the furnace to be shut down.

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Claims (1)

[Claims] 1. In a method of producing ferronickel by calcining nickel oxide ore in a calcining furnace and then reducing and melting it in a reduction melting furnace, in the zone from the highest temperature zone in the calcining furnace to the ore outlet or In the process from the ore outlet to the reduction melting furnace, a carbonaceous reducing fluid is injected into the accumulated layer of the calcined ore while the calcined ore is maintained at 500°C or higher. A method for producing ferronickel, characterized in that the ore is subjected to a preliminary reduction treatment and then charged into the reduction melting furnace.