JPS581054A - Raw material for ferroalloy - Google Patents

Abstract

PURPOSE:To provide a raw material which consists of reduction-neutralized chromium slag of specified contents of chromium, valuable components of iron and chromium and sodium respectively and which is extremely suitable for production of chromium-congt. alloys. CONSTITUTION:The chromium-contg. slag which is byproduced in the stage of producing Na2CrO4 from chromium ore is prepared. More specifically, the chromium-contg. slag having respective component contents of about >=10wt%, more particularly >=12wt% chromium in terms of oxide, about >=20wt%, more particularly, >=30wt% valuable components of iron and chromium, and about <=5wt%, more particularly <=3wt% sodium is preferable. Such chromium-contg. slag is reduction-neutralized by, for example, a wet method. More specifically, a reducing agent of an oxidation reduction equiv. to acid and Cr<6+> or above is added to the slurry of the chromium ore under agitation and these are allowed to react until the final pH of the slurry attains <=4. The product of reaction is subjected to solid-liquid sepn., and after the filter cake is washed, it is dried and is finished to the intended raw material for ferroalloy. It is possible to granulate this by adding a suitable binder to the cake in the stage of said drying.

Description

Detailed Description of the Invention The present invention uses raw materials for ferroalloys, particularly chromium-containing slag produced as a by-product when producing sodium chromate from chromium ore, through chemical treatment, as a raw material for producing chromium-containing ferroalloys. Regarding effective utilization -1 Generally, industrial production of sodium chromate is made by mixing chromium ore with an alkaline agent such as soda ash and caustic soda, and further adding lime, inert fillers, etc. as necessary. oxidized and roasted at high temperature,
Next, a method is adopted in which a sodium chromate aqueous solution is obtained by leaching the roasted product with water. On the other hand, at this time, a large amount of chromium-containing leaching residue, chromium-containing slag, is generated as a by-product, and its composition varies depending on the roasting conditions, type of ore, presence or absence of lime addition, etc. Among these, Cr2O3 components are mainly 3 Although it exists as valent chromium, it also contains about 3,000 to 15,000 ppM of hexavalent chromium.

Furthermore, since most of the Na20 component exists as a compound that is poorly soluble or insoluble in water, it is not eluted by normal leaching operations.

Conventionally, such chromium slag has been found to have little practical utility after recovering as much chromate as possible by increasing the leaching efficiency. Therefore, although it is normal to reduce the hexavalent chromium in the slag to trivalent chromium using a reducing agent such as ferrous sulfate and dispose of it in a landfill, active and effective use of chromium-containing slag has not been studied. The following are typical proposals that have been made, rather than just the wrong ideas.

First, after adding and mixing chromium-containing slag with silicic acid and a reducing agent and granulating it, the granulated product is fired at a high temperature to form a granular porous silicate, which is used as a lightweight aggregate for civil engineering. use for purposes. (Special Publication No. 52-10094) Second, by applying acid to chromium-containing slag, Fe2O3
, At203 and components such as j, J g○ are partially dissolved, and an aqueous solution of these salts is used as a sewage water treatment agent. (Japanese Unexamined Patent Publication No. 110.10/1982) However, among these methods, the former method for making lightweight aggregates requires large-scale production in order to add a large amount of silicic acid and heat it at a high temperature close to the melting point. It has the disadvantage of requiring a large amount of energy (1M) to set up, and in addition, even if such an economic sacrifice is required, the added value is low and it is not always used, so it cannot be called an industrial method. In addition, the latter method of providing water treatment agents is not a rational method because only one component in the chromium-containing slag is used.

In any case, chromium-containing slag has not been actively and effectively utilized for its characteristics.
In view of this situation, as a result of various studies and examinations on more effective and efficient utilization methods that give rise to the characteristics of chromium slag, we have found that a specific composition of chromium slag can be obtained by chemically treating the chromium slag. The present invention was completed by discovering that the treated product is extremely suitable as a raw material for producing chromium-containing iron alloys.

That is, the present invention is a reduced-neutralized product of chromium-containing slag produced as a by-product when producing sodium chromate from chromium ore, which contains at least 10% by weight of chromium in terms of oxide, and contains valuable components of iron and chromium. The vehicle weight for ferroalloy is 20% by weight, and the soda content is 5% by weight, and the content of each component is as follows.

According to the study results of the present inventors, chromium-containing slag generally contains significant amounts of hexavalent chromium and Na2O components, causing environmental pollution, and may also contain large amounts of CaO components. , itself is not suitable as a raw material for ferroalloys. Also, even if you dare to use it, a large amount of Ca
Since the O component lowers the content of valuable components such as chromium and iron, more slag is produced than necessary in the process of producing ferroalloy, resulting in an increase in energy. However, it has been found that such slag, which has been reduced and neutralized with mineral acid, can be effectively used as a raw material for ferroalloy, which has the characteristics of chromium slag.

Therefore, in the present invention, the reduced and neutralized product of chromium-containing slag means that the basic components of chromium-containing slag are neutralized with an acid and at the same time, the hexavalent chromium contained therein is reduced to substantially contain hexavalent chromium. refers to processed materials that have not been processed. In the present invention, among the above-mentioned reduction-neutralized products, those particularly applicable as raw materials for ferroalloys have a chromium content of about 10% by weight or more, preferably 12% by weight or more in terms of oxide, and valuable components of iron and chromium. is about 20% by weight or more, preferably 30% by weight
It is necessary to have a content of each component above and below about 5% by weight, preferably below 3% by weight. The reason for this is that the raw material for ferroalloy according to the present invention can be used by itself or in combination with other raw materials for iron manufacturing to effectively recover valuable components, and if it deviates from this range, the slag component may be too large, This is because large quantities cannot be used because it may damage the furnace materials.

Various chromium-containing slags can be used in the present invention regardless of their history, but due to their properties, it is preferable to have as much chromium as possible and as little alkali and calcium as possible.

On the other hand, the acid is made by modifying chromium-containing slag 1 and making it a ferroalloy Kawahara'#).
However, depending on the processing method described below, the hexavalent chromium in the slag can be reduced to 3.
A reducing agent is used in combination to reduce it to valent chromium. Examples of such reducing agents include ferrous sulfate, sodium sulfide, sulfite, sulfites, thiosulfates, sulfur, activated carbon, glyoxal, and hydrazine. In addition, acid elutes poorly soluble Na and 20 components that cannot be eluted by simple water washing, and dissolves excess CaO, MgO, and slag components such as At203 to increase the content of valuable components Cr2O and Fe203. Examples include mineral acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as formic acid and acetic acid. Therefore, for example, industrial waste fluids discarded from various chemical factories or metallurgical processes, such as waste acid containing divalent iron produced as a by-product during the production of titanium oxide, are inexpensive and practical from the viewpoint of resource conservation, and are therefore preferable.

The raw material for the ferroalloy according to the present invention can be industrially produced as follows. Specifically, there are two methods: a wet method in which chromium-containing slag, an acid, and a reducing agent are reacted in a slurry form for modification, and a dry method in which a mixture of the slag and acid is directly calcined, and then soluble components are leached out. are representative examples.

In the wet method, a slurry of chromium-containing slag is first added with an acid and a reducing agent having an oxidation-reduction equivalent or more for hexavalent chromium while stirring, and the reaction is carried out until the final pH of the slurry becomes 4 or less. Neutralize by adding alkali as necessary. The reaction is accelerated by heating. After the reaction is completed, solid-liquid separation is performed, and the filter cake is then washed and dried to produce a raw material for ferroalloy. During this drying, a suitable binder can be added to form granules.

Next, in the dry method, acid is added to the chromium-containing slag in the presence of an appropriate amount of water, stirred or kneaded to mix uniformly, and then
This mixture is heated to 400-1000°C in a heating furnace.

As a result, hexavalent chromium is substantially reduced, and after heating,
It is washed with water to separate and remove soluble components such as Na2O, and further dried in the same manner as described above to be finished as a raw material for ferroalloy.

Therefore, in this method, since hexavalent chromium is reduced by heating, a reducing agent is not necessarily a necessary agent, but it can be used as appropriate depending on the properties of the slag to be treated and the firing conditions.Amount of acid in this method The pH of the slurry is about 4 or less, which is the same as in the wet method.

In addition, in the reduction-neutralization treatment, by-products generated from various factories containing chromium oxides and hydrous oxides, and acidic substances containing chromium can be effectively used together as required.

Also, when drying, in any case.

It is more preferable to mix carbon materials such as coke, dust and scales generated during iron manufacturing, steel manufacturing, or metal processing with the treated material and pelletize it, since by-products can be effectively recovered. In this way, regardless of the method used, the reduced and neutralized product has alkali and other soluble components substantially separated and removed, and valuable components such as chromium and iron are more concentrated than in chromium-containing slag, while other components are Mainly A40. .

MgO and CaO are slag-forming components in steelmaking, and these are particularly easily soluble and have a tendency to form highly fluid slag to facilitate refining operations, making them effective as raw materials for ferroalloys. It can be used for both purposes.

As described above, according to the present invention, the chromium content including the most problematic hexavalent chromium in chromium-containing slag can be reduced to Fe20. Since the chromium-containing slag is completely recovered as a valuable resource along with other components, and other components are also used as slag forming agents, the chromium-containing slag is not only rendered harmless, but its characteristics are fully utilized and the recovery of useful resources is effective. Accomplished by Vine.

Therefore, it can be said that it is the most appropriate purpose and has great industrial significance in these days when resource saving is being called for.

Next, examples of the present invention will be shown.

Example Chromium-containing slag powder (particle size 175 μm) shown in Table 1 10
After reacting 0 parts by weight with 7.3 parts by weight of sulfuric acid, 90 parts by weight of ferrous sulfate, and 200 parts by weight of water in a tank, the solid and liquid are separated. The obtained solid is washed with about 5 times the amount of water and then dried in a rotary kiln.

The rotary kiln was operated at a maximum temperature of 250° C. and an average residence time of 15 hours. This is raw material A for ferroalloy.
shall be. The separated liquid was treated under normal wastewater treatment conditions.

Next, chromium-containing slag powder (particle size 175 μm) shown in Table 2
Uniformly mix 125 parts by weight of lo o and 125 parts by weight of sulfuric acid,
Maximum temperature 800℃ in rotary kiln Average residence time 2
Fired under certain conditions. After washing the baked product with 10 times the amount of water, the solid material was heated to a maximum temperature of 250°C in a rotary kiln.
The average residence time was 5 hours. This is designated as raw material B for ferroalloy.

After mixing 18 parts by weight of silica, 10 parts by weight of quicklime, and 17 parts by weight of coke with 100 parts by weight of each of the raw materials A and B for ferroalloy obtained above, this mixture was placed in a Soederberg electric furnace. Approximately 1641 o'
It was melted and treated at c. The obtained treated products and recovery rate are the third
It was as shown in the table.

As is clear from the results shown in Table 3, most of the chromium in the chromium-containing slag was recovered as ferrochrome, which was found to be effective as a raw material for ferroalloys.

Claims (1)

[Scope of Claims] 1'1) A reduced and neutralized product of chromium-containing slag produced as a by-product during the production of sodium chromate from chromium ore, comprising:
A raw material for a ferroalloy characterized by having a chromium content of at least 10% by weight or more, a valuable component of iron and chromium at least 20% by weight, and a soda content of at least 5% by weight (calculated as an oxide). 2) The raw material for a ferroalloy according to claim 1, wherein the reduced and neutralized product is wet-treated. (3) The raw material for a ferroalloy according to claim 1, wherein the reduction-neutralized product is dry-treated. (4) The raw material for a ferroalloy according to claim 1, wherein the reduced and neutralized product is in the form of pellets.