JPS602649A - Production of ferroboron by electric furnace method - Google Patents

Abstract

PURPOSE:To produce stably and effectively ferroboron in the stage of producing the ferroboron from a carbonaceous reducing agent consisting essentially of a boron source, iron source and charcoal by an electric furnace method by using specified coke for a part of the reducing agent. CONSTITUTION:Coke having>=1.10 reactivity index to be defined as follows is used as a part of a carbonaceous reducing agent consisting essentially of charcoal to be used for producing ferroboron: The reactivity index is the index expressed by the ratio of the peak width at half height on the 002 face of a diffraction chart when an X-ray diffraction is performed under the conditions using a tube bulb of copper at 45kV tube bulb voltage and 30mA tube bulb current with the slit width of 1 deg. diverting slit width, 1 deg. scattering slit width, 0.60mm. photodetecting slit width 0.55mm. monochrometer photodetecting slit width and using a curved single crystal of graphite at 4,000 counts/sec count rate of a recorder with respect to the total width, 1sec time constant, 2 deg./min scanning speed of a counter tube and 20cm/min recording chart speed of the recorder. The reactivity index when the half-width is 91.5mm. is designated as 1.00.

Description

[Detailed description of the invention] The present invention relates to a method for producing ferroboron by an electric furnace method,
In particular, the present invention relates to a method for producing ferroboron using an electric furnace method, which has stable furnace conditions and can be mass-produced at low cost.

Prior art related to the production method of 7eroboron by electric furnace method is Japanese Patent Publication No. 34-9108, Japanese Patent Publication No. 40-188.
No. 41, Special Publication No. 51-37613, etc. are known.

The method disclosed in Japanese Patent Publication No. 34-9108 is a method for producing FERROBO 0/ by charging raw materials consisting of iron powder, a boronic compound, and a carbonaceous reducing agent into an electric furnace and melting and reducing them. In order to prevent the elementary compounds from melting at low temperatures and separating from other raw materials, the iron powder and carbonaceous reducing agent are finely pulverized to 5 mesh or less, and the amount of carbonaceous reducing agent is adjusted to the level required to reduce the raw materials. It is characterized in that it is added slightly in excess of the required amount. However, this method had the following drawbacks. In other words, because this method uses an excessive amount of carbonaceous reducing agent, refractory substances tend to accumulate at the bottom of the furnace, and if operating methods are implemented to prevent this accumulation, the lining at the bottom of the furnace will be seriously damaged. In any case, it was difficult to continue stable long-term operation.

In addition, the method of Tokuko No. 51-37613 is
This is an improved method of method No. 4-9108, in which a lime component is added to prevent refractory substances from accumulating on the furnace bottom, and as a countermeasure against the fact that the lining of the furnace bottom is easily damaged as a result. It is characterized by lining the floor with a dense graphite carbon material, and is said to be able to operate for a relatively long period of time compared to conventional methods. However, since this method uses lime or the like to generate a low-melting slag, it has drawbacks such as an increase in electric power consumption and a decrease in boron yield.

The method disclosed in Japanese Patent Publication No. 40-18841 uses iron ore as the iron source, and the amount of carbonaceous reducing agent is lower than the theoretical amount, in order to prevent the accumulation of poorly soluble substances by forming easily soluble slag. In order to prevent the boron compound from melting and separating, the raw material is crushed to 5 mm or less, mixed with a small amount of water, heated to 200°C, and then put into an electric furnace. It is said that However, since this method involves the production of easily soluble slag, it has the same drawbacks as the method of Japanese Patent Publication No. 51-37613.

In addition, a common problem with the above conventional technology is that it requires pretreatment such as pulverization of the raw material, briquette, and preheating, and the use of only charcoal as the carbonaceous reducing agent makes the furnace conditions of the electric furnace extremely difficult. It was difficult to maintain constant operating conditions. (None of the conventional methods were industrially satisfactory.

An object of the present invention is to provide an effective method for producing ferroboron using an electric furnace method, which eliminates the drawbacks of the above-mentioned conventional methods for producing ferroboron using an electric furnace and enables stable mass production.

This object of the present invention is effectively achieved by the following two inventions.

The gist of the first invention is as follows. That is, boric acid, boron oxide, and one or more of the five sands are used as a boronic source, and iron scraps, iron powder,
In a method for producing ferroboron by an electric furnace method in which a mixed raw material consisting of one or more iron ores and a carbonaceous reducing agent mainly composed of charcoal is charged into an electric furnace and melted and reduced, one of the reducing agents is 1. A method for producing ferroboron by an electric furnace method, characterized in that coke having a reactivity index defined below as 1.10 or more is used.

Reactivity index Two-tube bulb Copper tube Bulb voltage 45 kV Tube current 30 mA Slit width Diverging slit width 1 degree Scattering slit width 1 degree Receiving slit width 0.60 mm Counting rate relative to the full width of optical slit width recorder 4000 counts/second hour Scanning speed of the counter: 1 second Scanning speed of the counter: 2 degrees/minute Recording paper speed of the recorder: 20 centimeters X-ray diffraction of coke was performed under the following conditions using a grafted curved single crystal, and the half-width value of the peak on the 002 plane of the diffraction chart was It is an index expressed as a ratio, and when the half width is 91.5 mm, the reactivity index is defined as 1.00.

The gist of the second invention is that, like the first invention, in addition to using coke with a reactivity index of 1.10 or more, coal or pitch with a Button index of 7 or more is used alone or in combination as a reducing agent. This is a method for producing ferroboron using the electric furnace method, which is also used as part of the process.

That is, when producing ferroboron using an electric furnace, the present invention abolishes the conventional method of using only charcoal, and instead uses coke having a certain characteristic value of reactivity as a part of the reducing agent. In addition to using coke with excellent reactivity that exceeds the value, the effects of each are synergized by using strongly caking coal and pitch with a Button index of 7 or more, either alone or in combination. The present invention was achieved by discovering that all of these can enable long-term stable operation.

First, use coke with a reactivity index of 1.10 or higher (8) Explain the purpose, effects, and usage methods.

Conventionally, in the electric furnace method for producing ferroboron, charcoal has been exclusively used as the carbonaceous reducing agent.
When operating only with charcoal, the resistance inside the furnace is too large, so the trap must have the electrode tip located close to the metal formed at the bottom of the furnace because the current continues to flow inside the furnace. In such a position, the arc will not be stable and the current will be greatly hunting, and power will not be stably supplied.
Phenomena such as a decrease in the temperature of the melt and a narrowing of the melting area occurred, making long-term stable operation impossible. When coke is added to the furnace, the coke that exists between the electrode and the metal bath acts as a conductive material (so the current flow becomes smooth, voltage and current swings are greatly reduced, and operation becomes extremely easy. The furnace conditions are stable and the consumption of raw materials and electricity is reduced.However, if the reactivity of the coke used here is poor, refractory substances will accumulate at the bottom of the furnace, so coke with a reactivity index of 1.10 or higher is If it is less than 1.10, stable furnace conditions cannot be guaranteed. Therefore, the reactivity index defined by the inventors is limited to coke having a reactivity index of 1.10 or more.

Next, regarding the amount of coke used, even if the coke has good reactivity, if too much is used, refractory substances will accumulate at the bottom of the furnace, so the amount of coke used is the amount required to deoxidize the raw materials. 30% against theoretical carbon lid
Since the desired effect can be obtained with a minimum amount of 10% or more, the amount used should be limited to 10 to 30% of the required theoretical carbon amount. Note that the amount of the return material reducing agent used needs to be slightly smaller than the theoretical amount.

As mentioned above, stable operation can be ensured by using coke with a reactivity index of 1.10 or more according to the present invention as a part of the reducing agent in addition to the conventional reducing agent consisting of only charcoal. , in addition to such coke, button index 7
It has been found that the objects of the present invention can be achieved more effectively by using the above-mentioned coals and pitches alone or in combination.

Next, the purpose and effect of using coal and pitch as part of the reducing agent will be explained.

Previously, due to the low melting point of boronic compounds, pretreatment such as crushing, briquette, and preheating of raw materials was essential to prevent them from melting and separating from other raw materials. By using strong coal and pitch, these pretreatments can be omitted. i.e. cohesive coal;
Pitch softens and melts at low temperatures below 500℃, the particles stick to each other, and then expand to form a porous coke-like substance, so it acts like an adhesive against other reducing agents, iron sources, etc. It works with shapes and connects particles. In addition, since the molten boron compound enters the pores, it is possible to prevent the separation and segregation of raw materials up to the reaction zone at the bottom of the electric furnace, thereby maintaining the stability of furnace operation. . The degree of caking of the coal and pitch used here must be strong caking with a Button index of 7 or more. Coal and pitch with a Button index of less than 7 will not achieve the purpose of the present invention. (11) Therefore, in the present invention, the use of coal and pitch with a Button index of 7 or more is limited.

The amount of coal and pitch used above should be limited to a range of 5 to 507 o relative to the linear fixed carbon amount of the charged reducing agent in terms of fixed carbon amount, either individually or in the total usage ratio, and 15 A range of 40% is most preferred. The reason for this is that if it is less than 5%, there is almost no effect of addition, and if it exceeds 50%, there will be a large amount of rapidly dry distilled coke with many pores, which will increase the electrical resistance in the furnace.
This is because the operation conditions are close to those when using charcoal alone.

By using coke with a reactivity index of 1.10 or more, the coke acts as a conductive material between the electrode and the metal, making the current flow smoother and stabilizing the furnace condition. Strongly caking coal and pitch with a button index of 7 or higher are used together as part of the reducing agent.
Not only is there no restriction on raw material size and pretreatment such as crushing and briquette is no longer necessary, but it is also possible to prevent the occurrence of separation and segregation of raw materials in the furnace, and the synergistic effect makes furnace operation (1
It has been found that 2) can be further stabilized.

By the way, in the conventional method, the problems of accumulation of dissolvable substances on the hearth and damage to the hearth refractories are contradictory issues, and if the operation is carried out under conditions where refractory substances do not accumulate, the hearth will be damaged. Long-term stable operation was not possible, but according to the method of the present invention, the arc condition at the tip of the electrode can be properly adjusted by selecting the reducing agent and mixing it properly, so the furnace condition is extremely stable and it is possible to reduce the Since no deposition occurs and the hearth is not damaged, there is no need for any special restrictions such as dense graphite for the second innings of the electric furnace.

Example particle size 5 Q mm or less boron oxide 660 parts, 200 m
820 parts of iron scrap of 5 Q mm or less, 315 parts of charcoal of 5 Q mm or less
The inner wall of the furnace was mixed with 60 parts of coke with a reactivity index of 1.15 and a particle size of 3 Q mm or less, a button index of 71/2, and 65 parts of coal with a particle size of 30 mm or less (all parts by weight). The carbon stamp paste was charged into a 600KVA Elu type electric furnace and the voltage was set to 45.
~50V, current 4000~5000A tap spacing 180
The operation was carried out in minutes.

The furnace conditions were extremely stable and operations continued smoothly, but
Three weeks later, operations were stopped to investigate the situation inside the reactor, and after cooling, the reactor was excavated. The results showed that there was almost no wear on the inner wall of the furnace, and no accumulation of hardly soluble substances was observed.

The composition of the obtained ferroboron was 13:13.3%
, Si: 1.7%, C: 0.3%, An: 0.04%
The ion yield is 80.4%, and the electricity consumption is approximately 5.
It was oooKwH/l.

As is clear from the above examples (conventionally, in the production of ferroboron by the electric furnace method, refractory substances accumulate on the hearth, making continuous operation impossible, or, if this is to be avoided, damage to the refractory material of the hearth). It has been extremely difficult to maintain long-term stable operation due to the occurrence of problems, but with the present invention, coke with a reactivity index of 1.10 or more can be used simultaneously with charcoal as a part of the reducing agent, or in addition to the use of such coke. button index 7
Strongly cohesive coal or pitch of 1 or more, either alone or in combination (1
5) By using these in combination, the following effects could be achieved.

(b) The use of coke prevents the accumulation of dissolvable substances on the hearth, ensuring a stable supply of electricity and enabling long-term stable operation.

(b) By using coal and pitch, there is no need to limit the size of raw materials, and pre-treatment of raw materials such as crushing and briquettes is not required, and separation and segregation of raw materials can be prevented, making it possible to improve furnace conditions. stability was maintained.

(!9) Since there is almost no wear and tear on the inner walls of the furnace, there is no need for especially expensive dense graphite refractory materials, and stable furnace conditions make operation extremely easy, reducing raw materials and electric power consumption, and reducing the use of boron. The improved yield has made it possible to significantly reduce manufacturing costs.

) Due to stable furnace conditions, variations in the composition of ferroboron produced were reduced, making it possible to improve product quality.

Agent: Patent Attorney Takeo Nakaji (16)

Claims (4)

[Claims] (1) One or more of boric acid, boron oxide, and silt as a boronic source; iron scraps and iron powder as an iron source;
A method for producing ferroporon by an electric furnace method in which a mixed raw material consisting of one or more iron ores and a carbonaceous reducing agent mainly composed of charcoal is charged into an electric furnace and melted and reduced. A method for producing ferroboron by an electric furnace method, characterized by using coke having a reactivity index of 1.10 or more as defined below. Reactivity index: Tube Copper tube voltage 45 kV Tube current 30 mA Slit width Diverging slit width 1 degree Scattering slit width 1 degree Receiving slit width 0.60 mm Counting rate for the full width of the optical slit width recorder 4000 volts V seconds Constant: 1 second Scanning speed of counter tube: 2 degrees/minute Recording paper speed of recorder: 20 Cr 117 minutes X-ray diffraction of coke was performed under the following conditions using a curved single crystal of graphite, and the ratio of the half-width value of the peak on the 002 plane of the diffraction chart was The anti-loyalty index is defined as 1.00 when the half width is 91.5 rrm. (2) One or more of boric acid, oxidized boron, and silt as a boronic source; iron scraps and iron powder as an iron source;
In a method for producing 7eroboron by an electric furnace method in which a mixed raw material consisting of one or more iron ores and a carbonaceous reducing agent mainly composed of charcoal is charged into an electric furnace and melted and reduced, one of the reducing agents is Production of ferroboron by an electric furnace process characterized by using coke with a reactivity index of 1.10 or more as defined below as well as coal or pitch with a Button index of 7 or more, either singly or in combination. Method. Reactivity index: Tube Copper tube voltage 45kV Tube current 3QmA Slit width Divergent slit width 1 degree Scattering slit width 1 degree Receiving slit width Q, 5Qmm Counting rate relative to the total width of the recorder 4000 force un V seconds time constant 1 second Scanning speed of counter: 2 degrees/min Recording paper speed of recorder: 20 crrr + graphite curved single crystal was used. It is assumed that the reactivity index is 1.00 when the half width is 91.5 mm. (3) The use ratio of the coke is 10 to 30% by weight based on the theoretical carbon amount required for reduction of all the raw materials. Method for producing ferroboron. (4) The usage ratio of either the coal or the pitch alone or in total is 5 to 50% by weight relative to the linear fixed carbon amount of the charged reducing agent in terms of the fixed carbon amount. A method for producing ferroboron by the electric furnace method according to item 2.