JP2023139359A - Temperature raising method of smelting furnace - Google Patents

Abstract

To provide a temperature raising method capable of shortening a temperature raising time without generating local overheating in a furnace, by smoothly igniting a shaft burner, and stabilizing a burner flame even after ignition of the shaft burner.SOLUTION: A method for raising a temperature at the time of startup of a smelting furnace for smelting non-ferrous metals, such as a self-melting furnace used in a smelting process of pyrometallurgical copper smelting, wherein after the inside of the smelting furnace is substituted by air of higher oxygen concentration than the air introduced via a gas introduction part formed of a window box for example in the smelting furnace, a burner of the smelting furnace is ignited.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for raising the temperature of a smelting furnace, and more particularly to a method for raising the temperature of a smelting furnace used in the smelting process of non-ferrous metal smelting, typified by copper smelting.

The dry copper smelting process uses copper concentrate with a copper grade of about 30% obtained by beneficiation of mined ore as raw material.The copper concentrate charged into a smelting furnace is oxidized and melted to produce a copper grade of 60%. A smelting process that produces matte with a copper content of about 65%, a copper manufacturing process that produces blister copper with a copper grade of about 99.8% by further oxidizing the resulting matte, and electrolytic refining of the blister copper obtained. It mainly consists of a refining process that produces refined copper (pure copper) with a copper grade of 99.99% or higher.

As the above-mentioned smelting furnace, an Outokump type self-smelting furnace is generally often used. A flash-melting furnace consists of a vertical cylindrical reaction shaft that oxidizes copper concentrate introduced from an upper burner using air or oxygen-enriched air, and a matte produced by the oxidation reaction located below the reaction shaft. and a settler that separates slag based on the difference in specific gravity; and an uptake located on the opposite side of the reaction shaft at the top of the settler and that discharges high temperature exhaust gas of about 1300°C containing SO ₂ generated during the oxidation reaction. It is mainly composed of.

As mentioned above, high-temperature exhaust gas containing a high concentration of _SO2 gas is stably discharged from the uptake of the flash-melting furnace, so this exhaust gas is used as a raw material for sulfuric acid after its heat is recovered in the waste heat boiler. and sent to a sulfuric acid manufacturing plant. The waste heat boiler uses the recovered heat to generate steam, which is used to power the turbine generator included in the auxiliary equipment. This turbine generator undergoes periodic government inspections about once every two years, so the flash-melting furnace also shuts down at the same time. The refractories of the flash-melting furnace are then inspected and repaired as necessary during this period of shutdown.

When starting up the flash melting furnace after the end of the above-mentioned shutdown period, it is necessary to increase the temperature of the flash melting furnace over a period of about one week before charging copper concentrate as a raw material. The reason for this is that the refractory expands rapidly if the temperature rises without taking a long time, which can damage the bricks, especially in areas that have been renewed during the outage period, or cause excessive molten material to fill the gaps between the bricks due to rapid expansion. This is because there is a risk of problems such as the water flowing into the water. Further, if copper concentrate is introduced from the burner without sufficiently raising the temperature of the flash melting furnace, there is a risk that the copper concentrate will not ignite well due to lack of heat.

The temperature rise during startup of the above-mentioned flash melting furnace is achieved by a burner installed at the top of the reaction shaft (hereinafter also referred to as a shaft burner or concentrate burner) and multiple burners installed in the settler (hereinafter also referred to as settler burner). ) heating method is generally adopted by burning heavy oil. For example, Patent Document 1 describes how to maintain or raise the temperature of the flash smelting furnace body when the flash smelting furnace stops operating, or to raise the temperature when starting up the flash smelting furnace after repair. Techniques have been disclosed for heating materials using concentrate burners in which materials are introduced with fuel and air or oxygen-enriched air and burned. Specifically, coke breeze is introduced from a concentrate burner together with air or oxygen-enriched air, and a portion of the coke breeze is scattered and burned in an unburned state in a settler, thereby keeping the entire furnace at a predetermined temperature. It maintains or raises the temperature.

Japanese Patent Application Publication No. 2000-199019

By using the technology of Patent Document 1 mentioned above, coke powder can be supplied together with air etc. from the concentrate burner installed at one location on the top of the reaction shaft without the need to specifically provide a burner for heat retention or temperature increase. It is said that it is advantageous in terms of equipment management because it can keep or raise the temperature of the entire inside of the furnace, and that it can also reduce damage to bricks due to local heating and cracks in bricks due to uneven thermal expansion, etc. . Furthermore, when maintaining the temperature of the melt in the settler during operation, by using coke powder, the amount of steam generated by the waste heat boiler can be reduced to about 30% of normal operation compared to when heavy oil is used. It is stated that the amount of steam can be increased by about 50% from 100 to 100%, and that by raising the temperature using coke breeze after furnace repair, about three times as much steam can be obtained compared to using only heavy oil.

However, the technology of Patent Document 1 uses coke breeze in addition to heavy oil, which is generally used as an auxiliary fuel during normal operations, and requires separate equipment for storage, quantitative cutting, transportation, etc., which increases equipment costs. It takes time to handle it.

Additionally, when starting up a flash-melting furnace in an atmospheric environment, the temperature inside the furnace is raised from a state where it is left to cool. It was difficult to ignite the burner, and even when it was ignited, the flame of the burner was unstable, so heavy oil sometimes entered the furnace unburned. In addition, even after the shaft burner is ignited, the flame is difficult to extend due to incomplete combustion in the shaft burner and multiple settler burners, and as a result, the gas temperature does not rise sufficiently, causing local overheating in the furnace and slowing down the temperature rise rate. Problems sometimes occurred. Under such circumstances, if the supply flow rate of heavy oil is forcibly increased to approach the ideal temperature rise curve, there is a risk that the burner will undergo incomplete combustion. For this reason, the supply flow rate of heavy oil cannot be increased until the temperature of the refractories in the furnace rises to a certain extent, which poses a problem in that it takes a long time to raise the temperature.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to smoothly ignite a shaft burner when the temperature rises at the time of starting up a smelting furnace, and to stabilize the burner frame even after the shaft burner is ignited. The object of the present invention is to provide a heating method that can shorten the heating time without causing local overheating in a furnace.

In order to achieve the above object, a method for increasing the temperature of a smelting furnace according to the present invention is a method for increasing the temperature at the time of startup of a smelting furnace for smelting non-ferrous metals, the method includes: The method is characterized in that the burner of the smelting furnace is ignited after the interior of the smelting furnace is replaced with a gas having a higher oxygen concentration than the air introduced through the smelting furnace.

According to the present invention, the shaft burner can be ignited smoothly when the temperature rises at the start-up of the smelting furnace, and the burner frame can be stabilized even after the shaft burner is ignited, so that The heating time can be shortened without causing local overheating.

FIG. 2 is a schematic flow diagram of a self-melting furnace and its exhaust gas treatment equipment whose temperature is raised by a temperature raising method according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of a specific example of a shaft burner included in the flash furnace of FIG. 1. FIG. It is a graph which shows the temperature rise profile of the self-melting furnace which temperature rose in the Example of this invention.

EMBODIMENT OF THE INVENTION Hereinafter, the embodiment of the temperature raising method of the smelting furnace based on this invention is described concretely. The method for increasing the temperature of a smelting furnace according to an embodiment of the present invention is aimed at a smelting furnace in which non-ferrous metals such as copper, zinc, lead, nickel, and tin are smelted, and the smelting furnace is inspected and In order to restart the operation of the smelting furnace, which had been shut down due to suspension of raw material charging due to repairs and repair of ancillary equipment, the temperature of the smelting furnace was increased from a state where the inside of the furnace was allowed to cool. This method is characterized by replacing the inside of the smelting furnace with a gas having a higher oxygen concentration than the air introduced into the smelting furnace through the gas introduction part, and then igniting the burner of the smelting furnace. It is said that

To explain specifically, first, a gas with a higher oxygen concentration than air (hereinafter referred to as high oxygen concentration gas) is introduced into the furnace of the smelting furnace through the gas introduction part, and the inside of the furnace is filled with this high oxygen concentration. Replace with concentrated gas. Examples of the supply source of this high oxygen concentration gas include oxygen production equipment such as a PSA (pressure swing adsorption) type oxygen gas generator and a cryogenic air separation device.

This high oxygen concentration gas preferably has an oxygen concentration of 80% by volume or more. If this oxygen concentration is less than 80% by volume, the oxygen concentration when replacing the inside of the furnace will be lower than the desired oxygen concentration, making it difficult to ignite the burner smoothly, or after igniting the burner. There is a high possibility that the burner frame becomes unstable, and the effects of the present invention may be difficult to fully exhibit.

The burner is ignited when the above replacement is completed and the high oxygen concentration gas is distributed throughout the furnace. The burner ignited here is, in the case of a flash-melting furnace, a shaft burner that is installed on the ceiling of the reaction shaft and uses heavy oil as fuel, for example. Furthermore, if necessary, in addition to this shaft burner, settler burners, preferably about 6 to 12 settler burners, which are provided in the settler of the flash-melting furnace, may be ignited.

When igniting the burner mentioned above, oxygen is present in the furnace at a higher concentration than air overall, so even when starting up from a state where the inside of the furnace has been left to cool, the burner can be easily ignited. can do. Furthermore, the shape of the frame can be stabilized after the burner is ignited. This makes it possible to make the gas temperature within the furnace substantially uniform throughout the furnace, so that the temperature can be raised substantially uniformly throughout the furnace without locally heating the furnace wall. Therefore, when starting up a smelting furnace in an air atmosphere like in the past, problems such as the burner not igniting smoothly or the flame becoming unstable even when ignited are less likely to occur, so the burner does not ignite. The problem of heavy oil introduced into the burner dripping without being ignited and collecting at the bottom of the furnace, which occurs due to this, is almost eliminated. In addition, the problem of local overheating caused by the flame becoming too short or unstable after ignition becomes less likely to occur.

Note that the above-mentioned state in which the high oxygen concentration gas is pervasive in the furnace is a state in which the oxygen concentration exceeds at least 21% by volume in all parts of the furnace. It may be determined that the gas has been distributed by detecting that the oxygen concentration exceeds 21% by volume with a gas concentration meter installed at the exhaust gas outlet of the furnace, or alternatively, the volume inside the furnace may be determined by adjusting the supply flow rate of high oxygen concentration gas. It may be determined that the gas has been distributed because the time calculated by dividing by It may be concluded that this has been achieved.

After the above burner is ignited, the temperature measured with a thermometer installed in the refractory installed inside the furnace or a thermometer for measuring the gas temperature inside the furnace will rise to a temperature that has been prepared in advance. It is preferable to raise the temperature along a curve, and this can be adjusted by adjusting the flow rate of heavy oil supplied to the burner. Generally, inside a smelting furnace, thermometers are installed at four or more but eight or less locations on the refractory lined as a lining material, and thermometers are installed at around 4 or more and 8 or less locations on the refractory lining. To measure the temperature, thermometers are also provided at two locations, for example in the center of the settler and at the bottom of the uptake. Therefore, it is possible to accurately grasp the state of temperature increase in the furnace based on the indicated values of these thermometers.

The temperature raising method of the embodiment of the present invention can be well applied to a smelting furnace for non-ferrous metals, and can be suitably applied to the above-mentioned Outokumpu flash-smelting furnace, but is not limited thereto. , an ausmelt TSL (Top Submerged Lance) furnace in which a lance into which fuel, air, etc. are introduced is inserted from the top into a vertical approximately cylindrical furnace, and the tip of the lance is immersed in a slag layer to perform melting. Furnaces of various shapes, such as reverberatory furnaces, which have a rectangular wide and shallow hearth with a burner at one end and an arched ceiling, and perform melting using reflections from the ceiling. Applicable.

FIG. 1 schematically shows a flash melting furnace 1 comprising a reaction shaft 11, a settler 12, and an uptake 13. This flash-melting furnace 1 is provided with one shaft burner 20 at the top of a reaction shaft 11, and the settler 12 has five shaft burners on each side wall parallel to the longitudinal direction, and two shaft burners on the side wall on the reaction shaft side. A total of 12 settler burners 30 are provided. The high-temperature exhaust gas discharged from the reaction shaft 11 is sent to the sulfuric acid production plant 3 after its heat is recovered by the waste heat boiler 2 . High pressure steam generated by heat recovery in the waste heat boiler 2 is sent to the steam turbine 4 and used there as a power source.

The gas introduction part is not particularly limited as long as it can introduce high oxygen concentration gas into the furnace at a desired supply flow rate, but in the case of the flash-melting furnace 1, it is preferable to use a wind box of the shaft burner 20. Specifically, as shown in FIG. 2, the shaft burner 20 provided at the top of the reaction shaft 11 has a substantially cylindrical burner cone 21 that passes through the top of the reaction shaft 11, and a burner cone 21 that is similar to the burner cone 21. A substantially conical wind box 22 is provided in the shape of a core shaft and communicates with the upper end of the burner cone 21, and a cylindrical concentrate chute serves as a supply pipe for copper concentrate and flux. 23, an oxyfuel burner 24 that is provided concentrically inside the concentrate chute 23 and plays the role of introducing fuel such as heavy oil, and an oxyfuel burner 24 that surrounds the concentrate chute 23 and can freely reciprocate in the axial direction. It mainly consists of a wind speed regulator 25 provided.

During normal operation, concentrate supplied from the upper end of the concentrate chute 23 is introduced into the burner cone 21 in free fall, while reaction air is introduced into the slit between the wind box 22 and the wind speed regulator 25. It is blown into the burner cone 21 from there. Thereby, the concentrate and reaction air are introduced into the reaction shaft 11 in a mixed state within the burner cone 21. By using the wind box 22 and the burner cone 21 connected to the lower end thereof as the introduction section for the high oxygen concentration gas, the high oxygen concentration gas introduced into the flash furnace 1 is transferred to the reaction shaft 11, the settler 12 and uptake 13 flow in one direction inside the furnace and are discharged from the upper exhaust port of uptake 13, so that the inside of the furnace can be efficiently replaced with high oxygen concentration gas.

In the temperature raising method according to the embodiment of the present invention, the flow rate of air introduced into the burner to raise the temperature of the furnace is smaller than the theoretical combustion air amount of the fuel introduced into the burner (i.e., the theoretical combustion air amount is less than the theoretical combustion air amount). (based on the amount) is preferably less than 100%. As a result, the burner undergoes incomplete combustion and some unburned fuel spreads into the smelting furnace, so it is necessary to burn the unburned fuel that has spread inside the furnace in a place away from the burner. Therefore, the temperature inside the furnace can be raised more uniformly. Note that the lower limit of the air supply flow rate is preferably 70% or more of the theoretical combustion air amount. If this supply flow rate is less than 70% of the theoretical combustion air amount, combustion in the burner body becomes difficult.

As explained above, by adopting the temperature raising method of the embodiment of the present invention, the burner can be ignited smoothly when the temperature is raised at the time of startup of the smelting furnace, and after the burner is ignited, Since the frame shape of the burner can be stabilized, the temperature can be raised in a relatively short time without causing local overheating inside the furnace. In particular, the temperature raising method according to the embodiment of the present invention is more noticeable in the temperature increase when the furnace is started up from a state where the inside of the furnace is from about room temperature to about 300°C due to the operation of the smelting furnace being stopped for a long period of time. The effect is produced. Such long-term shutdowns may be necessary, for example, when large-scale repairs are being made to the refractories of the smelting furnace, or when the waste heat boiler or steam turbine power generation equipment attached to the smelting furnace is being shut down periodically. One example is when operations are shut down in conjunction with inspections.

[Example]
In order to restart the operation of the flash smelting furnace 1 for copper smelting, which has a structure as shown in FIG. A high oxygen concentration gas of 85-91% by volume was introduced. This high oxygen concentration gas is generated by a PSA (pressure swing adsorption) type oxygen gas generator and introduced into the wind box 22 of the shaft burner 20 as shown in FIG. 2, which is installed on the ceiling of the reaction shaft 11. Then, it was introduced into the flash-melting furnace 1 via the burner cone 21.

Approximately 2 hours, which is the time calculated by dividing the volume of the flash melting furnace 1 by the supply flow rate of the high oxygen concentration gas, has elapsed since the introduction of the high oxygen concentration gas. It was determined that the amount of oxygen had gone through, so the introduction of high oxygen concentration gas was stopped, and instead heavy oil and air were supplied to the shaft burner 20 and ignited. At this time, the air supply flow rate was set to be 80% of the theoretical combustion air amount of heavy oil. As a result, it was possible to ignite smoothly. Subsequently, 8 of the 12 settler burners 30 were similarly ignited under the condition of 80% of the theoretical combustion air amount, and were able to be ignited smoothly.

After the shaft burner 20 and settler burner 30 were ignited, the shapes of the frames of these burners were visually checked through the viewing window of the flash melting furnace 1, and were found to be stable without being particularly short. Therefore, there was no problem of local overheating or problems of heavy oil dripping and accumulating at the bottom of the furnace due to non-smooth ignition. In addition, by adjusting the supply flow rate of heavy oil while checking the readings on the thermometer installed in the center of the settler, it is possible to control the temperature throughout the entire furnace without deviating from the pre-planned temperature rise curve. The temperature could be raised uniformly and at approximately the same rate. The temperature of the automelting furnace 1 was raised twice at different times under the same conditions as above. As a result, the burner was able to ignite smoothly even during these two temperature increases, and the shape of the burner frame after ignition was stabilized, so problems such as local heating and heavy oil dripping did not occur. .

[Comparative example]
The temperature of the flash melting furnace 1 was raised in the same manner as in the above example except that the interior of the flash melting furnace 1 was not replaced with the high oxygen concentration gas introduced from the wind box 22 before igniting the burner. As a result, it was difficult to ignite the burner smoothly, and even when the burner was ignited, the shape of the flame became unstable. Additionally, when ignition did not occur smoothly, heavy oil that dripped from the burner would accumulate at the bottom of the furnace. This problem occurred not only in the shaft burner 20 but also in the eight settler burners 30 that were ignited.

In addition, after igniting the shaft burner 20 and settler burner 30, we visually checked the shape of the frame of these burners through the viewing window, and found that some of the frames were short in length and others had unstable frame shapes. , local overheating occurred inside the furnace. Furthermore, if the burner frame shape is unstable, there is a risk of excessive incomplete combustion, so it is not possible to increase the fuel oil supply flow rate until the temperature of the refractory in the furnace rises to a certain extent, and it takes time. However, the temperature had to be increased. As a result, variations in temperature and variations in heating rate were observed depending on the position within the furnace.

While checking the readings of the thermometer installed in the center of the settler, for the three temperature increases (Case 1 to 3) in the above example and the one temperature increase (Case 4) in the comparative example, FIG. 3 and Table 1 show the results of temperature increase when an attempt was made to increase the temperature along a pre-planned temperature increase curve by adjusting the supply flow rate of heavy oil.

As can be seen from Table 1 above, in Cases 1 to 3 of the Examples, the temperature increase rate was 1.13 to 1.34 times faster than that of Case 4 of the Comparative Example. In addition, in these Cases 1 to 3, the temperature increase rate per unit amount of heavy oil was 1.38 to 1.77 times faster than in Case 4. Therefore, it can be seen that by raising the temperature of the flash-melting furnace using a method that satisfies the requirements of the present invention, the temperature can be raised more quickly and efficiently than in the past.

1 Flash melting furnace 2 Waste heat boiler 4 Steam turbine 11 Reaction shaft 12 Settler 13 Uptake 20 Shaft burner 21 Burner cone 22 Wind box 23 Concentrate chute 24 Oxyfuel burner 25 Wind speed regulator 30 Settler burner

Claims (4)

A method for raising the temperature at startup of a smelting furnace for smelting nonferrous metals, the inside of the smelting furnace being heated by a gas having a higher oxygen concentration than the air introduced into the smelting furnace through a gas introduction part. A method for increasing the temperature of a smelting furnace, which comprises igniting a burner of the smelting furnace after the substitution. 2. The method for increasing the temperature of a smelting furnace according to claim 1, wherein the smelting furnace is a self-smelting furnace, and the gas introduction section is a wind box. 3. The method for increasing the temperature of a smelting furnace according to claim 1, wherein the temperature increase at the time of startup is a temperature increase from a state where the inside of the furnace is left to cool. The smelting furnace riser according to any one of claims 1 to 3, characterized in that the flow rate of air introduced into the burner is smaller than the theoretical combustion air amount of the fuel introduced into the burner. Warm method.

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