JPH1089601A - Method of preventing adhesion of dust against waste heat boiler and self-melting furnace employing this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a good state of operating condition at water pipes in a waste heat boiler for a long period of time. SOLUTION: Side walls, for example, of a settler 3 of a self-melting furnace (a reaction shaft 2, the settler 3 and an up-take 5) are provided with oxidizing gas blowing-in ports 4. Under an operation of the furnace, raw material of ores are reacted, dropped and accumulated at the lower section of the furnace while they are being separated into a slug phase 7 and a mat phase 9. However, mat components of dust particles floating together with discharged gas without falling down are oxidized by oxidizing gas, thereafter they are sent to a water tube waste heat boiler. The dusts can be removed more easily than in the case of the conventional process even if the dusts adhere to the water tubes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing dust in exhaust gas discharged in an air-introduction type mat smelting process employed in ore dry smelting from adhering to a waste heat boiler. In particular, the present invention relates to a method for preventing dust in exhaust gas from adhering to a waste heat boiler, which can be advantageously applied to a flash furnace.

[0002]

2. Description of the Related Art In a mat smelting operation using a smelting furnace, a solvent (SiO ₂ ) is prepared by using (pulverized) concentrate obtained by pre-treating sulfide ore while blowing air or oxygen-enriched air. ) Together with the smelting furnace to cause a reaction in the gas phase, and oxidize unnecessary parts in the concentrate, especially most of Fe, and combine it with SiO ₂ added as a solvent to form slag, And Ni are concentrated as a sulfide melt mat. At this time, when an air feeding type smelting furnace is used, a large amount of exhaust gas is emitted. The exhaust gas is an aerosol and is a gas (SO ₂ , CO, CO ₂ , N ₂ , H ₂ O, etc.)
And dust (including fumes) carried out on the gas stream. Of these, Pb,
In addition to those in which volatile components such as Zn are volatilized, those in which some raw material particles and their reaction products are mechanically scattered are included.

Since exhaust gas leaves the smelting furnace at a high temperature, sensible heat of the gas is recovered, and SO ₂ and dust are also recovered to prevent air pollution. Sensible heat recovery is roughly classified into two methods: preheating raw ore and air charged into the furnace by heat exchange, and generating superheated steam through a waste heat boiler and using it for power generation and heating. However, when the latter method is adopted, since exhaust gas contains dust, a water tube type waste heat boiler is usually used. In this case, the dust is settled and separated from the exhaust gas in the waste heat boiler, but part of the dust adheres to the water pipe and reduces the cooling efficiency of the waste heat boiler, and as a result, reduces the amount of steam generated in the waste heat boiler And results in an increase in the gas temperature at the outlet of the waste heat boiler. In order to remove such adverse effects as much as possible, in order to remove dust adhering to the water pipe, installation of a hammering device and measures for preventing dust adhesion by a suit blow are currently being implemented.

[0004] However, even if the charging rate of the sulfide ore, usually pretreated sulfide concentrate, to the smelting furnace is constant,
Changes in the reaction conditions in the smelting furnace significantly increased the dust generation rate per unit ore treatment amount and increased the amount of dust attached to the water pipe, or significantly increased the charging speed of the concentrate. In this case, the amount of dust generated due to the mechanical scattering of a part of the reacted raw material greatly increases, and the amount of dust attached to the water pipe also increases, resulting in the waste heat boiler. Since the outlet gas temperature will increase, the above-mentioned dust adhesion prevention measures are not sufficient, and in order to surely remove the dust adhering to the water pipe, the operation of the smelting furnace is periodically stopped and manual operation is performed. At present, dust removal is being carried out.

[0005] Such dust removal operations result in a loss of productivity due to an interruption of the smelting operation, in addition to an increase in human costs. Further, this is a factor that hinders an increase in the amount of ore processed per furnace, that is, mass production.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a waste heat boiler which minimizes dust from adhering to the water pipe of a waste heat boiler and enables a long-term maintenance of a good operating state of mat smelting. It is an object of the present invention to provide a method for preventing dust from adhering to a surface. Another object of the present invention is to provide a simple and economical method for preventing dust from adhering to a waste heat boiler.

Another object of the present invention is to provide a flash smelting furnace to which the above-described dust adhesion preventing method is applied.

[0008]

SUMMARY OF THE INVENTION As a result of earnest studies, the present inventors have found that dust suspended in exhaust gas in a smelting furnace is generated by a reaction of charged concentrate. Dust adhered to the water pipe of the waste heat boiler, whereas mat components and slag components composed of sulfides such as copper sulfide were mainly scattered mechanically without falling. In boiler dust, since almost all of the mat component particles are sulfated, it is found that the sulfide mat component particles are sent to a waste heat boiler, where they are oxidized by free air, etc., and further turned into sulfate oxides. Based on the findings, the mat component particles cause an oxidative exothermic reaction in the waste heat boiler, increasing the heat load on the waste heat boiler, and partially oxidizing on the surface of the water pipe after reaching the water pipe surface. The reaction caused the reaction product by heat generated at that time reaches the estimated and was probably led to the result that adheres strongly to the water pipe.

As long as the absolute amount of the sulfide-containing dust scattered into the waste heat boiler is smaller than the waste heat boiler capacity, the ratio of the calorific value of the dust to the heat input to the boiler is small. Does not. However, when the dust generation rate per unit ore processing amount is significantly increased, or when the ore processing speed is significantly increased, the absolute amount of generated dust is increased. The effects of the oxidative exothermic reaction of water, especially the effects on water tubes, cannot be ignored.

[0010] Based on the above knowledge and estimation, the inventor of the present invention has determined that even if dust adheres to the surface of a water pipe of a waste heat boiler, if the mat component particles that cause an oxidative exothermic reaction in the dust are previously oxidized, For example, once dust reaches the surface of the water pipe, it does not cause an oxidative exothermic reaction on the water pipe, so it does not adhere strongly to the water pipe. We believe that it is possible to reduce the amount of dust adhering to the water pipe, and as a result, it is possible to operate the smelting furnace continuously for a long time,
After various experiments including experiments under actual operation, the following method has been proposed as an effective method for preventing dust from adhering to a waste heat boiler, particularly to a water pipe.

That is, the method for preventing dust from adhering to a waste heat boiler according to the present invention is characterized in that an oxidizing gas is blown into exhaust gas from an air-introduction type mat smelting to remove mats, ie, sulfides, contained in dust in the exhaust gas. After the oxidation, the exhaust gas is passed through a waste heat boiler. A preferred embodiment of the method is a flash smelting furnace for mat smelting, wherein the settler is provided with a blowing port for oxidizing gas.

Since the method of the present invention significantly reduces the heat load on the waste heat boiler, the method is not particularly limited to the water tube type waste heat boiler. It goes without saying that a smelting furnace provided as an auxiliary equipment can be advantageously applied.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention for preventing dust from adhering to a waste heat boiler is used in the mat smelting of ore, typically sulfide ore, of an air-feeding type. Examples of the air feeding type include a flash smelting furnace, a smelting furnace, and a reverberatory furnace. The air may be oxygen-enriched air or hot air. In the case of air-injection type, a large amount of exhaust gas is emitted, and in particular, the flash smelting furnace is subjected to considerable oxidation, which generates a large amount of dust. Will be an important issue.

As the oxidizing gas, air, oxygen-enriched air or the like is used. Preferably, the oxidizing gas is blown directly toward the exhaust gas in the smelting furnace.

FIG. 1 schematically shows the structure of a flash smelting furnace when the method of the present invention is applied to a flash smelting furnace. FIG.
Is a side sectional view of the flash smelting furnace, and FIG. 1b is a front cross sectional view of the flash smelting furnace cut along the line AA ′ shown in FIG. 1a. In both figures, 1 is a concentrate burner, 2 is a reaction shaft, 3 is a settler, 4 is an oxidizing gas inlet, 5
Denotes an uptake, 6 denotes a slag hole, 7 denotes a slag, 8 denotes a mat hole, and 9 denotes a mat.

The reaction shaft 2 is provided with one to three concentrate burners 1 (here, two). From the concentrate burner 1 toward the reaction shaft 2, dry fine concentrate is blown together with oxygen-enriched air or high-temperature hot air, where instantaneous oxidation reaction occurs, reaction products drop, and slag as a melt is obtained. It is stored in the lower part of the furnace, separated from each other as 7 and mat 9. Since this furnace is air-feeding type,
A large amount of high-temperature exhaust gas containing dust is also generated. Especially,
In the case of a flash furnace, dust is generated in a large amount because it is considerably oxidized. The generated exhaust gas is then passed through a waste heat boiler. Although not shown here, the waste heat boiler is usually of a water tube type because the amount of dust is large in the case of a flash furnace. When exhaust gas is passed through a waste heat boiler, steam is generated there. Furthermore, in the case of a flash furnace, S
Since O ₂ is generated, the cooled exhaust gas is passed through a cotter (not shown) and further through a mist cotter (not shown) to remove the generated SO ₃ mist, and is converted in the presence of a catalyst to form SO 2. ₃ is generated.

An important feature of the flash smelting furnace is that the oxidizing gas injection port 4 is provided on the side wall of the settler 3. The oxidizing gas for oxidizing the sulfide in the dust may be blown in at the inlet of the waste heat boiler, but in that case, the flow speed of the gas in the waste heat boiler becomes slow, and part of the dust in the exhaust gas becomes gaseous. Since it is separated from the stream by gravity, the oxidizing efficiency of oxidizing gas decreases when trying to oxidize sulfide in all dust including these separated dust, and as a result, the oxidizing gas is removed by settler. A larger amount and an excess of oxidizing gas than in the case of blowing are required. If unreacted oxygen gas is contained in the exhaust gas, SO ₂ contained in the exhaust gas is similarly oxidized to form a sulfuric acid mist, which may cause an increase in the rate of waste acid generation in the sulfuric acid production process. . On the other hand, as shown in FIG. 1, when the setler 3 is provided with an oxidizing gas injection port,
Since there is almost no separation between dust and gas, sulfides contained in dust can be efficiently oxidized in the flash furnace up to the waste heat boiler inlet, significantly reducing the waste acid generation rate in the sulfuric acid production process. The unreacted oxygen gas is not brought into the waste heat boiler as much as possible. Therefore, even if the amount of dust scattered in the waste heat boiler increases, there is no adverse effect in the sulfuric acid production process as described above.

In the flash smelting furnace shown in FIG. 1, the oxidizing gas inlet is provided at two places on the side wall of the settler, but the position of the inlet is not limited to the side wall of the settler. It may be the ceiling. Further, the number of the blowing ports is not limited to two.

The amount of oxygen in the oxidizing gas blown by the settler is determined by the amount of sulfide contained in the dust when the dust generation rate per unit ore processing amount in the flash smelting furnace or the ore processing speed is constant. Since the amount does not greatly change, it may be substantially constant. In the case of a large change, the amount of oxygen contained in the oxidizing gas may be changed or the blowing amount of the oxidizing gas itself may be changed. The amount of oxidizing gas blown is
The oxygen concentration in the exhaust gas is measured during the uptake of the flash furnace, and control can be performed based on the measured data.

In the case of using the flash furnace having the structure shown in FIG. 1, even if dust adheres to the water pipe, the dust is easily detached. Since the measures to prevent dust adhesion by suit blow are effectively implemented, the frequency of dust removal work performed manually after the operation of the smelting furnace is stopped is greatly reduced as compared with the conventional case.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to an embodiment (operation) using a flash smelting furnace (provided with a conventional water tube type waste heat boiler as an accessory equipment) shown in FIG. However, the scope of the present invention is not limited by the description of the examples.

[0022] From operation examples concentrate burner 1 according to the method of the present invention, the raw material ore (sulfide copper concentrate) 145
t / h, and oxygen-enriched air (O ₂ : about 75
%) At a flow rate of 440 m ³ / min. Further, air (O ₂ : about 21%) is used as an oxidizing gas,
Was injected at a flow rate of 75 m ³ / min through the oxidizing gas injection ports 4 provided at two places on the side wall of the oxidizing gas. After the start of the operation, dust contained in the exhaust gas discharged from the exit of the uptake 5 was rapidly cooled in water and collected. Table 1 shows the chemical analysis values of the collected dust. FIG. 2 shows an optical microscope photograph (magnification: 200 times) of a section in which the collected dust is embedded in a resin, cut and polished.

[Table 1] As shown in Table 1, the S (sulfur) content in the dust that was to be sent to the waste heat boiler as it was was about 0.9% by weight. Further, as shown in FIG. 2, a mat, that is, Cu ₂ S—FeS remains in a part of the dust particles, but most of the dust particles are white glue (Cu
₂ S), metallic copper (Cu), copper-iron composite oxide (CuFe
O ₂ ), magnetite (Fe ₃ O ₄ ) and slag (Fe ₂ S)
iO ₄ ). From these results, it was found that copper sulfide and iron sulfide, which were components of the mat, were almost completely oxidized. The temperature of the exhaust gas at the outlet of the waste heat boiler was 390 ° C. From operation examples concentrate burner 1 of the comparative example, the same ore as used in operation example according to the method of the present invention (sulfide copper concentrate) was charged at a rate of 125t / h, oxygen-enriched air (O ₂ : About 73%) at a flow rate of 410 m ³ / min. However, no oxidizing gas was blown. Then, dust was collected and evaluated in the same manner as in the operation example according to the present invention described above. Table 2 shows the chemical analysis values of the collected dust. Further, FIG. 3 shows an optical microscope photograph (magnification: 200 times) of a cross section obtained by embedding the collected dust in a resin and cutting and polishing the resin.

[Table 2] As shown in Table 2, the amount of S (sulfur) in the dust that was to be sent to the waste heat boiler as it was was as high as 8.8% by weight. Further, as shown in FIG. 3, the dust particles are matte (Cu ₂ S—FeS) and white glue (Cu
₂ S), magnetite (Fe ₃ O ₄ ) and slag (Fe ₂ S)
iO ₄ etc.) and contained a considerable amount of matte components. Since the dust particles have substantially the same shape as the falling particles collected from the inside of the reaction shaft 2, it was found that the dust particles were mechanically scattered without falling into the settler bath. Also, the temperature of the exhaust gas at the outlet of the waste heat boiler suddenly rose at the rear of the waste heat boiler,
Eventually it was 450 ° C. The upper limit of the control value, which is the temperature that can be controlled at the outlet of the waste heat boiler, is currently 400
Since the temperature of the exhaust gas is high, the operation becomes difficult. Therefore, in order to continue the operation of the flash smelting furnace, it is necessary to reduce the charged amount of the raw ore from 125 t / h to about 110 t / h, which is a conventionally used charged amount. In a conventional flash smelting furnace that performs mat smelting without blowing oxidizing gas, the charged amount of the raw material ore is about 110 t / h, and the flow rate of the oxygen-enriched air blown together with the raw material ore is 360 m at maximum. It was about ³ / min. The temperature of the exhaust gas at the outlet of the waste heat boiler is 370
° C.

According to the method of the present invention, a waste heat boiler,
In particular, dust can be efficiently prevented from adhering to the water pipe. Therefore, it is possible to further increase the amount of ore processed per smelting furnace, that is, to open the way to mass production of mats.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the structure of a flash smelting furnace when the method of the present invention is applied to a flash smelting furnace, FIG. 1a is a cross-sectional view of the side of the flash smelting furnace, and FIG. Line AA ′ shown in 1a
FIG. 3 is a cross-sectional view of the front of the flash smelting furnace taken along the line.

FIG. 2 is a photograph showing a particle structure of dust particles in exhaust gas collected in an example.

FIG. 3 is a photograph showing a particle structure of dust particles in exhaust gas collected in a comparative example.

[Explanation of symbols]

1: concentrate burner, 2: reaction shaft, 3: settler, 4: oxidizing gas inlet, 5: uptake, 6: slag hole, 7: slag, 8: mat hole, 9: mat

Claims (2)

[Claims] An oxidizing gas is blown into exhaust gas from an air-introduction type mat smelter to oxidize sulfide contained in dust in the exhaust gas, and then the exhaust gas is passed through a waste heat boiler. To prevent dust from adhering to waste heat boilers. 2. A flash smelting furnace for mat smelting, wherein a oxidizing gas injection port is provided in a settler.