JP2011117709A - Method and equipment for treating exhaust gas in water-granulation of slag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating an exhaust gas generated in water-granulation of slag discharged from a non-ferrous metal smelting furnace, and to further provide an exhaust gas treatment equipment. <P>SOLUTION: This method for treating the exhaust gas 5 including water vapor generated in water-granulating the slag discharged from the non-ferrous metal smelting furnace as its main component, and including metal fume, includes a process for treating the exhaust gas by a wet-electrical dust collector 9. The exhaust gas treatment equipment includes an exhaust gas collecting means 7, an exhaust gas passage 8, and the electrical dust collector 9, the exhaust gas collecting means 7 is disposed at the upper part of an exhaust gas generation part, and the exhaust gas collecting means 7 and the wet-electrical dust collector 9 are connected by an exhaust gas passage 8. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for treating exhaust gas generated when water slag discharged from a non-ferrous metal smelting furnace is granulated, and more particularly to a method for treating metal fume contained in the exhaust gas. The present invention also relates to a facility for treating exhaust gas generated when water slag discharged from a non-ferrous metal smelting furnace is granulated, and more particularly, to a facility for treating metal fume contained in the exhaust gas.

  In the smelting process of non-ferrous metals such as copper, lead, zinc and nickel, a slag which is a mixture of impure metal sulfides and slag which is a non-metallic composition is generated by a smelting reaction in a smelting furnace. The mat and slag are separated and discharged from the smelting furnace. For example, in the copper smelting process, copper sulfide ore concentrate is charged into a smelting furnace such as a blast furnace, a reflection furnace, or a flash smelting furnace, heated and melted, and a mat containing a large amount of copper, iron and silicic acid as the main components Slag is generated and discharged separately. The mat becomes crude copper by oxidizing and blowing in a converter. In general, slag is crushed to a size that is easy to handle using high-pressure seawater or industrial water, and then landfilled or effectively used as a civil engineering material.

  When the high-temperature slag discharged from the smelting furnace is granulated, exhaust gas containing a large amount of water vapor is generated. As a method for treating exhaust gas generated during slag granulation, several methods are known that target exhaust gas generated when granulating slag discharged from a blast furnace during iron smelting.

For example, in Japanese Patent Laid-Open No. 8-245243 (Patent Document 1), when hot water discharged from a blast furnace is supplied with cold water and subjected to a water granulation treatment, from a large amount of exhaust gas generated by the water granulation treatment, A method for removing H ₂ S gas and SO ₂ gas which are generated and mixed when cold water reacts with cold water is described.

The above method reduces the temperature of the exhaust gas by spraying cooling water on the exhaust gas containing H ₂ S gas or SO ₂ gas and cooling the exhaust gas, condenses water vapor in the exhaust gas, and separates the condensed water. The exhaust gas is brought into a saturated state, and then fine water droplets floating in the exhaust gas are removed to form a saturated vapor gas body, and the gas body is returned to the blast furnace to contain H ₂ S gas or SO ₂ gas. Is characterized by being hatched by desulfurization reaction in the blast furnace (Claim 1). As a means for removing fine water droplets floating in the exhaust gas to form a saturated vapor gas body, a wet electrostatic precipitator is cited.

In addition, US Pat. No. 5,540,895 (Patent Document 2) describes the steam and gas containing H ₂ S and SO ₂ generated when granulating the blast furnace slag by granulation. A method of treating by spraying alkaline water is described.

JP-A-8-245243 US Pat. No. 5,540,895

  All of the above methods are intended for the treatment of exhaust gas generated during the slag granulation in the iron smelting process, and treat the exhaust gas generated when the slag discharged from the non-ferrous metal smelting furnace is granulated. No method is disclosed. Until now, it has not been thought that components that require special treatment are contained in the exhaust gas generated when water slag discharged from non-ferrous metal smelters is granulated, and it is released into the atmosphere as it is. It was normal. Therefore, there was no case where the component was analyzed in detail, and the component which should be processed was not clarified.

  Then, this invention makes it one subject to provide the method of processing the waste gas generated when the slag discharged | emitted from a nonferrous metal smelting furnace is granulated. Another object of the present invention is to provide a facility for treating exhaust gas generated when water slag discharged from a non-ferrous metal smelting furnace is granulated.

  The present inventor analyzed the exhaust gas generated when the slag discharged from the non-ferrous metal smelting furnace was granulated, and found that a trace amount of metal fumes such as iron and arsenic was contained in a large amount of water vapor. . The metal fume is a fine particle formed by agglomeration of metal vapor, and it is preferable to prevent release into the atmosphere from the viewpoint of working environment and environmental protection.

  Metal fume generally has a fine particle size and is considered to be mostly 1 μm or less. These submicron particles are unlikely to be collected in water droplets due to inertial collision, and can only be expected to be collected by Brownian diffusion. For this reason, it is generally difficult to collect 90% or more in the collection by a spray tower having a small water droplet diameter. In addition, due to suspended solids (SS) contained in the spray water, the water droplet size cannot be stably maintained, and there is a risk that the collection efficiency will be reduced. In addition, there will be a scale on the piping, and maintenance of the spray tower will occur. There is a concern that the frequency will increase.

  On the other hand, collection by a wet electrostatic precipitator (mistcottrel) can achieve a dust collection efficiency of 80% or more even for particles of submicron diameter, so metal fume is removed by using a wet electrostatic precipitator. Is possible. Although it is known that metal fume can be collected with a wet electric dust collector, the inventor is an example of applying a wet electric dust collector to the treatment of exhaust gas generated when water slag discharged from a nonferrous metal smelting furnace is granulated. As far as I know, it doesn't exist and the need for it was not recognized.

  Therefore, in one aspect, the present invention is a method for treating an exhaust gas containing metal fume mainly containing water vapor generated when water slag discharged from a non-ferrous metal smelting furnace is granulated. It is a method including the process of processing with a wet-type electrostatic precipitator.

  In one embodiment of the method according to the invention, the non-ferrous metal is copper.

  In another embodiment of the method according to the invention, the exhaust gas contains one or more metal fumes selected from Cu, Zn, Ni and Fe.

  In still another embodiment of the method according to the present invention, the method further includes a step of filtering the waste water containing the metal component discharged from the wet electrostatic precipitator and then returning the residue to the smelting furnace.

  Another aspect of the present invention is an equipment for treating exhaust gas containing metal fume mainly containing water vapor generated when water slag discharged from a non-ferrous metal smelting furnace is granulated, comprising exhaust gas collecting means And an exhaust gas passage and a wet electric dust collector, the exhaust gas collecting means is provided above the exhaust gas generation location, and the exhaust gas collecting means and the wet electric dust collector are connected by the exhaust gas passage.

  In one embodiment of the equipment according to the invention, the non-ferrous metal is copper.

  In another embodiment of the equipment according to the invention, the exhaust gas contains one or more metal fumes selected from Cu, Zn, Ni and Fe.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to remove a metal fume from the waste gas which generate | occur | produces when the slag discharged | emitted from a nonferrous metal smelting furnace is granulated.

FIG. 1 shows an example of an exhaust gas treatment scheme according to the present invention.

  Hereinafter, a preferred embodiment of an exhaust gas treatment method according to the present invention will be described with reference to FIG. The slag discharged from the smelting furnace 1 such as an electric smelting furnace flows into the granulated slag 4 through the slag slag 3, and is crushed by the granulated water 2 flowing down the slag slag, It falls into the granulation tank 6 as slag. The granulated slag is scooped up by a bucket elevator (not shown) provided in the granulated tank and transported out of the system.

Varies depending on the type of non-ferrous metals smelting, for example, the composition of the slag discharged from the smelting furnace in a copper smelting process, typically Fe: 35 to 45 wt%, Fe ₃ O _4: 3~15 wt%, SiO ₂ : 25 to 35% by mass, Cu: 0.5 to 3% by mass. The non-ferrous metal that is the subject of the present invention is not particularly limited, and examples thereof include copper, zinc, and nickel.

The slag before water granulation is usually at a high temperature of about 1150 to 1300 ° C., and a large amount of water vapor is generated as exhaust gas 5 from the vicinity of the water granule 4 and the water granulation tank 6 where the slag is in contact with water. The generated water vapor contains a small amount of metal fume, covers the upper part of the water granule 4 and the water granulation tank 6, and is preferably movable in the vertical and horizontal directions. ). The flue gas at the time of water granulation contains metal fumes such as Cu, Zn and Fe, and is generally contained at a concentration of about 0.1 to 10 mg / m ³ . However, the composition of metal fume differs depending on the metal to be smelted. For example, in the case of copper smelting, the concentration of Zn is higher than that of other metals, and is generally about 1 to 10 mg / m ³ . The exhaust gas temperature in the smoke collection hood is typically about 80 to 90 ° C.

  Next, the exhaust gas 5 mainly composed of water vapor collected by the smoke collection hood 7 is introduced into the wet electric dust collector 9 through the flue 8 (exhaust gas passage). While passing through the flue 8, the water vapor partially condenses naturally. The exhaust gas temperature at the inlet of the wet electrostatic precipitator 9 is typically about 30 to 80 ° C. In the present invention, no means (such as a cooling tower) for spraying cooling water to the exhaust gas is required from the smoke collection hood to the wet electric dust collector.

  In general, the wet electrostatic precipitator 9 applies corona discharge by applying a high voltage between the discharge electrode and the collection electrode to charge particles floating in the gas, and further to the collection electrode by Coulomb force generated by an electric field. This is a device that collects particles and then discharges the collected particles as waste water by washing them with spray water. Metal fume is fine particles formed by agglomeration of metal vapor, and can be recovered by a wet electrostatic precipitator. However, since most metal fume is 1 μm or smaller, operation on the high voltage side is desirable in order to obtain a sufficient recovery rate.

  Typical operating conditions of a wet electrostatic precipitator are a voltage of about 10 to 50 kV and a current of about 30 to 100 mA.

  As the wet type electrostatic precipitator 9, a known one may be appropriately selected and used. For example, a parallel type in which the discharge electrode and the dust collecting electrode are arranged in parallel to the gas flow, or a dust collecting electrode And a cross flow type (e.g., Nylft type) in which discharge electrodes are arranged so as to be orthogonal to the gas flow.

  The exhaust gas 10 exiting the wet electrostatic precipitator 9 can be released to the atmosphere. The exhaust gas temperature is about 20 to 40 ° C. at the outlet of the wet electrostatic precipitator 9. On the other hand, the wastewater 11 containing the recovered metal discharged from the wet electrostatic precipitator 9 is collected in the drainage tank 12 and then sent to a general wastewater treatment plant by a pump. After neutralization treatment, the wastewater 11 is filtered by a fuller press. The metal recovered as a residue can be returned to the smelting furnace as a mixed ore.

  Examples of the present invention will be described below, but the examples are for illustrative purposes and are not intended to limit the invention.

Example 1
In this example, in the copper smelting, the exhaust gas generated when the high-temperature slag discharged from the electric smelting furnace attached to the flash smelting furnace was granulated was treated. An exhaust gas treatment facility according to the exhaust gas treatment scheme of FIG. 1 was constructed. The slag discharged from the electric smelting furnace flows into the granulated slag through the slag slag, is crushed by the crushed water flowing down the slag slag, and falls into the slag tank as granulated slag. . Exhaust gas accompanied with a large amount of water vapor generated during the water granulation was collected with a smoke collecting hood that covers the water granule and the water granulation tank. The exhaust gas temperature in the smoke collection hood was about 80 to 90 ° C. The exhaust gas collected in the smoke collection hood entered the flue through the flue port at the top of the smoke collection hood and sent to the wet electric dust collector. The exhaust gas temperature flowing into the wet electrostatic precipitator was about 30 to 80 ° C., and the exhaust gas temperature discharged from the wet electrostatic precipitator was about 20 to 40 ° C.

Slag granulation conditions were as follows.
・ Slag crushed 2.5t / min
・ Slag temperature before granulation 1150-1300 ° C
・ Granulated water amount 20t / min

  Table 1 shows the results of measuring the metal concentration (mass%) in the slag by the metal analysis method in the exhaust gas in accordance with JIS K0083.

The operating conditions of the exhaust gas treatment facility were as follows.
・ Exhaust gas recovery amount in smoke collection hood 300m ³ / min
-Wet electrostatic precipitator specification-Manufacturer: Eldeck's Noilft type-Voltage: 15-25kV
-Current: 60-100 mA
-Spray water amount: about 20 L / min

  Table 2 shows the metal concentration (dust collector inlet concentration) in the exhaust gas collected by the smoke collection hood, the metal concentration (dust collector outlet concentration) in the exhaust gas after being treated by the wet electric dust collector, and the recovery rate (%). The metal concentration was measured by a method for analyzing metal in JIS K0083 exhaust gas.

(Example 2)
As in Example 1, in copper smelting, exhaust gas generated when high-temperature slag discharged from an electric smelting furnace attached to the flash smelting furnace was subjected to water granulation was treated. However, in Example 2, the amount of exhaust gas recovered in the smoke collection hood was increased as compared with Example 1.

Slag granulation conditions were as follows.
・ Slag crushed 2.5t / min
・ Slag temperature before granulation 1150-1300 ° C
・ Granulated water amount 20t / min

The operating conditions of the exhaust gas treatment facility were as follows.
・ Exhaust gas recovery amount in smoke collection hood 500m ³ / min
-Wet electrostatic precipitator specification-Manufacturer: Eldeck noilft type (2 wards, 3 stages)
Section: The number of sections because each section is charged by a separate high-voltage power supply.
Stage: The number of stages installed in the gas flow direction with one pair of discharge electrode and dust collecting electrode as one stage.
-Voltage: 30 to 35 kV (first and second ward)
-Current: 110 to 150 mA (first ward), 140 to 180 mA (second ward),
-Spray water amount: about 10 L / min

Table 3 shows the temperature, flow rate, metal fume collection weight, metal fume concentration, and dust collection efficiency (%) at the inlet and outlet of the dust collector. Table 4 shows the concentrations of exhaust gas at the inlet and outlet of the dust collector and the recovery rate (%) of the fumes of Cu, Zn, and Fe among the metal fumes. It can be seen that the metal fume in the exhaust gas can be recovered with high efficiency. The measurement of metal fume and metal concentration was performed based on the metal analysis method in JIS K0083 exhaust gas.

DESCRIPTION OF SYMBOLS 1 Smelting furnace 2 Granulated water 3 Slag tank 4 Granulated tank 5 Exhaust gas 6 Granulated tank 7 Smoke collection hood 8 Flue 9 Wet electric dust collector 10 Exhaust gas 11 Drainage 12 Drainage tank 13 Drainage

Claims (7)

  A method for treating an exhaust gas containing metal fume mainly containing water vapor generated when water slag discharged from a non-ferrous metal smelting furnace is granulated, comprising a step of treating the exhaust gas with a wet electrostatic precipitator Method.   The method of claim 1, wherein the non-ferrous metal is copper.   The method according to claim 1 or 2, wherein the exhaust gas contains one or more metal fumes selected from Cu, Zn, Ni and Fe.   The method according to any one of claims 1 to 3, further comprising a step of neutralizing the waste water containing the metal component discharged from the wet electrostatic precipitator, filtering the waste water, and returning the residue to the smelting furnace.   A facility for treating exhaust gas containing metal fume, mainly composed of water vapor generated when the slag discharged from a non-ferrous metal smelting furnace is granulated, comprising an exhaust gas collecting means, an exhaust gas passage, and a wet electric dust collector. The exhaust gas collecting means is provided above the exhaust gas generation location, and the exhaust gas collecting means and the wet electric dust collector are connected by an exhaust gas passage.   The facility according to claim 5, wherein the non-ferrous metal is copper.   The equipment according to claim 5 or 6, wherein the exhaust gas contains one or more metal fumes selected from Cu, Zn, Ni and Fe.

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