JP5040324B2 - Method for cooling and cleaning copper smelting exhaust gas - Google Patents

Description

  The present invention relates to a method of cooling and cleaning smelting exhaust gas discharged from a copper smelting factory in a gas purification step, and more particularly to a method of removing mercury taken into a cooling cleaning liquid.

Conventionally, smelting exhaust gas generated in a copper smelting factory is sent to a sulfuric acid factory as a raw material, and sulfuric acid is produced through a gas purification process, a drying process, a conversion process, and an absorption process. The main component of the copper smelting exhaust gas is SO ₂ , but it contains SO ₃ and heavy metal or metal fumes as impurities, and is cooled and washed with a cooling washing liquid in a gas purification process which is the first process in a sulfuric acid factory.

For example, in a gas purification process, which is the first process in a sulfuric acid factory, the copper smelting exhaust gas is guided to a humidification tower and cooled and washed while passing through a shower of cooling cleaning liquid. By this cooling cleaning, SO ₃ and heavy metals and metal fumes contained in the copper smelting exhaust gas are taken into the cooling cleaning liquid, so the copper smelting exhaust gas becomes SO ₂ containing almost no impurities and sent to the next drying step. It is done.

On the other hand, the cooling cleaning liquid released into the humidification tower in the form of a shower is guided to the humidification tower caloron, taken out to the humidification tower pump tank via the overflow tank, and then circulated to the humidification tower again by the pump Is used repeatedly. Repeatedly used cooling cleaning liquid takes SO _{3 and} produces sulfuric acid. At the same time, impurities such as heavy metal fume and metal fume are also taken in, so it contains a lot of impurities such as mercury (Hg). Don't be.

  The cooling cleaning liquid in which heavy metals such as mercury (Hg) are taken in the gas purification step is extracted after a predetermined period of use, but it is not product sulfuric acid but is called waste acid and becomes a raw material for waste acid gypsum. Waste acid gypsum produced from waste acid contains heavy metals in the particles or has heavy metals attached to the surface. Among these heavy metals, waste acid gypsum in which Hg is mixed at a concentration higher than a predetermined concentration is a defective product.

  Since waste acid gypsum that has become defective due to high Hg concentration is difficult to separate Hg in waste acid gypsum, when waste acid gypsum with sufficiently low Hg concentration is produced, waste acid gypsum production Therefore, it is necessary to re-dissolve in the reaction tank for use to lower the entire Hg concentration to a predetermined concentration or lower, which is disadvantageous economically due to reprocessing costs. For this reason, a method for removing Hg in the obtained waste acid after completion of the gas purification step has been studied, but a method for removing Hg from the cooling washing liquid during the gas purification step is not known.

For example, Japanese Patent Laying-Open No. 2005-154196 (Patent Document 1) describes a method of removing heavy metals as sulfides from waste acid extracted from a gas purification step. However, this method dilutes the waste acid extracted from the gas purification process with water, and then adds sodium hydrosulfide to turn heavy metals into sulfides. There were problems such as costs.
JP 2005-154196 A

  In view of such a conventional situation, the present invention provides a method for cooling and cleaning a copper smelting exhaust gas capable of removing mercury incorporated in the cooling cleaning liquid in a gas purification process for cooling and cleaning the copper smelting exhaust gas. With the goal.

  In order to achieve the above object, the inventors conducted extensive research on the removal of mercury incorporated in the cooling cleaning liquid in the gas purification process. As a result, the white smoke ash collected from the dust collector of the converter smoke ash was made into a slurry and gas purified. It has been found that mercury can be easily removed at low cost by adding to the cooling washing liquid in the process.

That is, the method for cooling and cleaning copper smelting exhaust gas provided by the present invention includes a cooling cleaning liquid for cooling and cleaning the smelting exhaust gas in a gas purification process of smelting exhaust gas mainly containing SO ₂ discharged from the copper smelting process. Further, 0.05 to 0.3 g / l of white smoke ash collected from the dust collector of the converter smoke ash in the copper smelting process is added.

  ADVANTAGE OF THE INVENTION According to this invention, the mercury taken in in a cooling washing | cleaning liquid can be easily removed in the gas purification process which carries out cooling washing of copper smelting waste gas. Therefore, the cooling cleaning liquid (waste acid) after the gas purification step can be supplied as it is to the waste acid gypsum manufacturing step, and a good waste acid gypsum with a low mercury concentration can be stably manufactured.

  In the present invention, in the gas refining process for cooling and washing the copper smelting exhaust gas, a cooling washing liquid in which 0.05 to 0.3 g / l of white smoke ash collected from the dust collector of the converter smoke ash in the same copper smelting process is used. By using a cooling washing liquid in which 0.05 to 0.3 g / l of this white smoke ash was used, it became possible for the first time to remove mercury (Hg) taken into the cooling washing liquid in the gas purification step.

  Specifically, the white smoke ash is stirred with a cooling washing liquid (generally industrial water) to form a slurry of about 100 g / l and added to the cooling washing liquid so that the concentration of white smoke ash is 0.05 to 0.3 g / l. To do. When the white smoke ash concentration in the cooling washing liquid is less than 0.05 g / l or more than 0.3 g / l, it is not preferable because a sufficient Hg removal effect cannot be obtained. A more preferable white smoke ash concentration in the cooling washing liquid is in the range of 0.1 to 0.2 g / l.

The main components of white smoke ash are Pb (SO ₄ ), PbO, Pb ₃ Bi ₄ O ₉ , Zn ₂ (AsO ₄ ) (OH), Zn (OH) ₂ , CuO according to XRD qualitative analysis. is there. The reason why the addition of white smoke ash is effective for removing Hg from the cooling washing liquid is not clear, but the ionization of the white smoke ash component promotes the reaction in which Hg ions taken into the cooling washing liquid precipitate as metal Hg. It is estimated that Hg is removed.

  Next, the method of the present invention will be described in detail with reference to the drawings. It is desirable to add the white smoke ash as a slurry to the cooling cleaning liquid. For example, as shown in FIG. 1, white smoke ash and a cooling cleaning liquid (generally industrial water) are supplied to the mixing tank 1 and stirred by a stirrer 2 and air blowing, etc. adjust. In addition, when adjusting a density | concentration in the middle, what is necessary is just to add a required quantity of both or either one of white smoke ash and a cooling washing | cleaning liquid as needed.

  The white smoke ash slurry 3 is supplied to a humidification tower (see FIG. 2) that cools and cleans the copper smelting exhaust gas while circulating through the circulation pipe 4 by a circulation pump. Further, a flow rate measuring device 5 for measuring the flow rate of the white smoke ash slurry 3 is provided in the vicinity of the supply port to the humidification tower branched from the circulation pipe 4, and the white smoke ash concentration in the cooling cleaning liquid in the humidification tower is provided. The flow rate of the white smoke ash slurry 3 is controlled so that is within a predetermined range.

In the gas refining process of the copper smelting exhaust gas, as shown in FIG. 2, the copper smelting exhaust gas introduced into the humidifying tower 6 is cooled and washed while passing through the shower of the cooling cleaning liquid 7 containing white smoke ash. It becomes SO ₂ containing almost no slag, and is sent to the next drying step as a copper smelting exhaust gas after cooling and washing. The cooling washing liquid 7 is discharged and stays in the inside of the humidification tower 6 in the form of a shower, and is then led to the humidification tower calocon 8, taken out to the humidification tower pump tank 10 through the overflow tank 9, and passes through the circulation pipe 11. Then, it is repeatedly used in such a manner that it is circulated inside the humidification tower 6 again.

  The cooling cleaning liquid 7 always contains white smoke ash having a predetermined concentration by supplying and adding the white smoke ash slurry 3 from the circulation pipe 4 of FIG. For example, in the humidifying tower 6 shown in FIG. 2, the white smoke ash slurry 3 is supplied to the overflow tank 9 of the humidifying tower calocon 8, and the concentration of white smoke ash in the cooling cleaning liquid 7 is always 0.05 to 0.3 g / l. To be controlled.

The repeatedly used cooling and washing liquid takes SO ₃ to produce sulfuric acid, and is extracted as waste acid after a predetermined period of use and sent to the manufacturing process of waste acid gypsum. The concentration of sulfuric acid in the cooling cleaning liquid (waste acid) is usually about 140 to 210 g / l. The cooling washing liquid (waste acid) thus obtained has a small amount of impurities, and in particular, the mercury (Hg) content can be greatly reduced as compared with the conventional case. Therefore, it is not necessary to remove mercury as in the case of conventional waste acid, and it can be supplied to the waste acid gypsum production process as it is to produce good quality waste acid gypsum with a low mercury concentration.

  The white smoke ash slurry 3 was adjusted by mixing the white smoke ash and industrial water using the white smoke ash slurry adjusting device shown in FIG. The white smoke ash slurry 3 was supplied to the overflow tank 9 of the humidification tower 6 shown in FIG. 2 while being circulated through the circulation pipe 4, and the white smoke ash was added to the cooling cleaning liquid 7. At that time, the flow rate of the white smoke ash slurry 3 was controlled to adjust the white smoke ash concentrations in the cooling washing liquid 7 to 0.05 g / l, 0.15 g / l, and 0.3 g / l, respectively.

  The copper smelting exhaust gas was cooled and washed in the humidification tower 6 using the above three types of cooling washing liquids 7 having white smoke ash concentration. After carrying out cooling washing for a certain time, the Hg concentration in each cooling washing liquid 7 was measured, and the mercury removal rate was determined for each. The obtained mercury removal rate is shown in FIG. 3 for each white smoke ash concentration of each cooling cleaning liquid, together with the sulfuric acid concentration in each cooling cleaning liquid.

  As can be seen from the graph of FIG. 3, the mercury removal rate with the white smoke ash concentration of 0.05 g / l is about 7 to 20%, and the mercury removal rate with the white smoke ash concentration of 0.15 g / l is The mercury removal rate increased to about 30 to 50%, and the mercury removal rate at white smoke ash concentration of 0.3 g / l slightly decreased to about 30 to 40%. Moreover, although the sulfuric acid concentration in the cooling washing liquid during this period is in the range of 140 to 210 g / l, it can be seen that high mercury removal efficiency is obtained when the sulfuric acid concentration is about 200 g / l at any white smoke ash concentration. .

It is the schematic which shows the specific example of a white smoke ash slurry adjustment apparatus. It is the schematic which shows the gas purification process of the copper smelting waste gas in a humidification tower. It is the graph which showed the relationship between the mercury removal rate and the sulfuric acid concentration of the cooling cleaning liquid for each white smoke ash concentration in the cooling cleaning liquid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mixing tank 2 Stirrer 3 White smoke ash slurry 4 Circulation piping 5 Flow rate measuring device 6 Humidification tower 7 Cooling washing liquid 8 Humidification tower narrow con 9 Overflow tank 10 Humidification tower pump tank 11 Circulation piping

Claims (1)

In the gas purification process of the smelting exhaust gas mainly containing SO ₂ discharged from the copper smelting process, the white recovered from the dust collector of the converter smoke ash in the copper smelting process in the cooling cleaning liquid for cooling and cleaning the smelting exhaust gas A method for cooling and cleaning copper smelting exhaust gas, comprising adding 0.05 to 0.3 g / l of smoke ash.

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