JP6665443B2 - Operating method of flash smelting furnace - Google Patents

Description

  The present invention relates to a method for operating a flash smelting furnace. More specifically, a self-smelting smelting furnace that can suppress the occurrence of forming in the melt when burning copper concentrate in a self-smelting smelting furnace to form a melt and separating the melt into specific gravity into karami and kava Related to the operation method.

  In a flash smelting furnace used for copper smelting, a raw material composed of copper concentrate and a flux and a reaction air are blown into a reaction tower, and the sulfur in the copper concentrate is burned to melt the raw material. Then, the melt is separated into karami and kawa by a settler.

If the combustion reaction is not completed in the reaction tower, the combustion reaction continues in the settler. Then, a smelting gas such as sulfur dioxide (SO ₂ ) is generated. When the smelting gas is generated in the melt in the settler, the melt foams and porous, low bulk specific gravity appears on the melt surface layer. The phenomenon in which the melt foams is called forming (Patent Document 1).

  If forming occurs excessively, the height of the melt surface in the settler rises, and the melt leaks out of the heat retention burner holes provided in the settler, and the pressure inside the self-melting smelting furnace can be maintained at a negative pressure. There is a problem of disappearing.

  In order to reduce the height of the melt surface in the settler, it is conceivable to reduce the amount of raw material charged. However, there is a problem in that the operation efficiency of the flash smelting furnace is reduced when the charged amount of the raw material is reduced.

JP 2006-188738 A

  In view of the above circumstances, an object of the present invention is to provide a method for operating a flash smelting furnace capable of suppressing the occurrence of forming.

The method for operating a flash smelting furnace according to the first invention is a method for operating a flash smelting furnace in which at least copper concentrate and silica sand are charged as raw materials. When the threshold value is exceeded, the ratio of silica sand in the raw material is reduced .

According to the present invention, by reducing the proportion of silica sand in the raw material, silicon dioxide derived from silica sand is reduced, and the viscosity of lumps in the settler can be reduced. As a result, the occurrence of forming can be suppressed.

It is a graph which shows the relationship of the thickness of a forming layer with respect to the weight ratio of silica sand in a raw material. It is a graph which shows the time series change of the weight ratio of the silica sand in a raw material, and the thickness of a forming layer. It is explanatory drawing of the flash smelting furnace FF.

Next, an embodiment of the present invention will be described with reference to the drawings.
(Self-melting furnace)
First, a flash smelting furnace used for copper smelting will be described.
As shown in FIG. 3, the flash smelting furnace FF includes a settler S, a reaction tower R and a flue gas U erected on the upper surface of the settler S, and a concentrate burner B provided at an upper end of the reaction tower R. It is composed of The settler S is provided with a cutout opening P1 and a lint removal opening P2.

Copper smelting using the flash smelting furnace FF is performed as follows.
From the concentrate burner B, a powdery raw material and reaction air (oxygen-enriched air) are blown into the reaction tower R. The raw material contains at least copper concentrate and silica sand, and may contain a cold material as needed. Silica sand is used as a flux to produce good quality karami.

  The raw material blown into the reaction tower R is heated by the heat of the auxiliary burner, the radiant heat in the furnace wall of the reaction tower R, and the like, and the sulfur in the copper concentrate burns to form a melt. The melt is stored in the settler S. The melt is separated into Karami and Kawa in the settler S due to a difference in specific gravity. Then, the kava is discharged from the cutout port P1, and the lumps are discharged from the cutout port P2. The high-temperature exhaust gas generated in the reaction tower R is discharged from the flash smelting furnace FF through the settler S and the flue gas U.

(Forming)
If the combustion reaction of the raw materials is not completed in the reaction tower R, the combustion reaction continues in the settler S. Then, a smelting gas such as sulfur dioxide (SO ₂ ) is generated. When the smelting gas is generated in the melt in the settler S, the melt foams, and porous and low bulk specific gravity appears on the surface of the melt. This phenomenon is so-called forming.

  In order to monitor the operation state of the flash smelting furnace FF, the thickness of each layer of the melt in the settler S is measured. In the process, the thickness of the forming layer is also measured.

The thickness of each layer of the melt in the settler S is measured, for example, as follows.
A measuring bar (a long iron bar) is inserted from the ceiling of the settler S. When the tip of the measuring rod reaches the bottom of the settler S, remove the measuring rod. The height of the bottom of the settler S can be determined from the length of the test bar inserted into the settler S. Further, the thickness of the melt can be determined from the length of the melt attached to the measuring rod. Further, the boundary between the karami and the kawa is determined from the properties of the melt adhered to the measuring rod, and the thickness of each layer of the karami and the kawa is determined. Of the kalami layers, the forming layer contains bubbles and is porous, whereas the kalami layer without forming has a dense composition. The forming layer is determined from the difference in the properties, and the thickness of the forming layer is determined.

  The measurement of the thickness of each layer using a measuring rod includes a measurement error. Therefore, the same measurement is performed at several tens of places of the settler S, and the average value of the measurement values measured in one day is obtained. It is general to determine the operation status based on the obtained average value.

  For example, if the average thickness of the forming layer is 180 mm or more per day, it is determined that excessive forming has occurred. In this case, due to an increase in the height of the surface of the melt in the settler S, the melt leaks from the heat retaining burner holes provided in the settler S, or a negative pressure is generated in the self-melting smelting furnace. May not be maintained.

The present inventor has found that the reason why forming occurs is as follows.
In other words, if the viscosity of the melt is high, the smelting gas generated inside the melt cannot escape from the melt and remains as bubbles in the melt. This causes forming.

The inventor of the present application sampled a lump with forming and a lump without forming from the flash smelting furnace FF, and measured the respective compositions. As a result, there was a tendency that the Karami with the forming had a lower Fe / SiO ₂ ratio than the Karami without the forming. Here, the “Fe / SiO ₂ ratio” means a weight ratio of iron (Fe) to silicon dioxide (SiO ₂ ) contained in karami.

The Fe / SiO ₂ ratio indicates the basicity of kalami, and is known as a parameter used to monitor the properties of kalami in the operation of the flash smelting furnace FF. Generally, an oxide having a low basicity has a high viscosity. Therefore, it is considered that the leach of the smelting furnace FF has a high viscosity when the basicity is low. From this, it is considered that the lower the Fe / SiO ₂ ratio of the lumps, the higher the viscosity of the lumps and the easier the forming to occur.

The raw material charged into the flash smelting furnace FF is adjusted so that the Fe / SiO ₂ ratio maintains a certain value. Specifically, if the SiO ₂ grade of the copper concentrate is high, the charge of silica sand is reduced, and if the SiO ₂ grade of the copper concentrate is low, the charge of silica sand is increased.

The particle size of copper concentrate is 10-300 μm, while the particle size of silica sand is 50-2,000 μm. That is, silica sand has a larger particle size than copper concentrate. Since the silica sand has a large particle diameter, it may not completely melt in the reaction tower R. Unmelted silica sand will be melted in the settler S. However, since it takes time for the SiO _2, which is the main component of silica sand, to diffuse throughout the larch, the surface layer of the melt contains a large amount of SiO ₂ and the Fe / SiO ₂ ratio decreases. As a result, the viscosity of the surface layer of Karami increases. For the above reasons, forming is more likely to occur as the proportion of silica sand in the raw material is higher.

  FIG. 1 shows the relationship between the weight percentage of silica sand in the raw material and the average daily value of the thickness of the forming layer. Here, the weight ratio of silica sand in the raw material means the weight ratio of the charged amount of silica sand to the charged amounts of all raw materials including copper concentrate, silica sand, and cold materials. The average daily value of the thickness of the forming layer is an average daily value of the thickness of the forming layer measured with a measuring rod as described above.

  FIG. 1 shows that the forming layer becomes thicker as the weight ratio of silica sand in the raw material increases. From this, it was confirmed that the higher the proportion of silica sand in the raw material, the easier the forming was to occur. In addition, it can be seen that the average daily thickness of the forming layer can be suppressed to 180 mm or less when the weight ratio of the silica sand in the raw material is 6% or less.

(Operation method)
Therefore, by operating the flash smelting furnace FF as described below, it is possible to suppress the occurrence of forming.
First, the thickness of the forming layer of the melt in the settler S is measured. The measuring method is not particularly limited, and includes, for example, a measuring method using a measuring rod as described above.

  The thickness of the forming layer is measured regularly or irregularly. Then, when the thickness of the forming layer exceeds a predetermined threshold, the ratio of silica sand in the raw material is reduced. Here, the upper limit of the thickness of the forming layer (for example, 180 mm) may be set as the threshold, or a value lower than the upper limit may be set by providing a margin to the upper limit.

It is preferable that the Fe / SiO ₂ ratio of the entire raw material be maintained at a desired value, since good quality karami can be obtained. Therefore, when reducing the charging amount of silica sand, copper concentrate with high SiO ₂ grade is selected as a raw material. By doing so, the Fe / SiO ₂ ratio of the raw material can be adjusted to a desired value.

  As described above, instead of the method of adjusting the ratio of silica sand in the raw material based on the measurement result of the thickness of the forming layer, in advance, the weight ratio of silica sand in the raw material may be adjusted to be equal to or less than a predetermined value. Good. When the weight ratio of silica sand in the raw material is set to 6% or less, the thickness of the forming layer can be set to 180 mm or less.

Also in this case, it is preferable to select a copper concentrate having a high SiO ₂ grade in order to maintain the Fe / SiO ₂ ratio of the entire raw material at a desired value.

  According to the above-described operation method, by reducing the ratio of silica sand in the raw material, silicon dioxide derived from silica sand is reduced, and the viscosity of the lumps in the settler S can be reduced. As a result, the occurrence of forming can be suppressed. In addition, since it is not necessary to reduce the amount of raw materials charged, the operation efficiency of the flash smelting furnace FF can be maintained at a high level.

Next, an embodiment will be described.
Copper smelting operation was carried out in a flash smelting furnace FF. The charge amount of copper concentrate to the flash smelting furnace FF was 4,000 tons / day. During the operation period, the weight ratio of silica sand in the raw material was adjusted to 6% or more in the first half, and the weight ratio of silica sand in the raw material was adjusted to 6% or less in the second half. Further, during the operation, the thickness of the forming layer was measured using a measuring rod.

  The result is shown in FIG. As can be seen from FIG. 2, the thickness of the forming layer exceeded 180 mm in the first half when the weight ratio of silica sand in the raw material was adjusted to 6% or more. On the other hand, the thickness of the forming layer was less than 180 mm in the latter half when the weight ratio of the silica sand in the raw material was adjusted to 6% or less.

  From the above, it was confirmed that the thickness of the forming layer could be suppressed to 180 mm or less by adjusting the weight ratio of the silica sand in the raw material to 6% or less.

FF Self-melting smelting furnace S Settler R Reaction tower U Flue gas B Concentrate burner

Claims (1)

An operation method of a flash smelting furnace that charges at least copper concentrate and silica sand as raw materials,
A method for operating a self-melting smelting furnace, characterized in that when the thickness of a forming layer of a melt in a settler exceeds a threshold value, the proportion of silica sand in a raw material is reduced.