JP2003001062A - Method of removing mercury contained in exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of removing a mercury component by which the mercury component contained in an exhaust gas discharged from a refining furnace for refining ores containing sulfur can be easily and effectively removed. SOLUTION: The method of removing the mercury component has been developed by improving a conventional method for removing mercury contained in the exhaust gas generated from the refining furnace 11 for refining the ores containing sulfur, and comprises a gas cleaning process 12 for separating the exhaust gas into a gas mainly containing SO2 and waste water by washing the exhaust gas discharged from the refining furnace with cleaning water containing 3 to 5 wt.% hydrochloric acid, a solid/liquid separation process 14 for separating a solid content in the waste water, a mercury component removing process 17 for removing the mercury component by bringing the waste water into contact with a mercury removing agent, a primary waste water treating process 18 for separating a sulfuric acid component by adding CaCO3 into the waste water from which the mercury component has been removed, and a secondary waste water treating process 21 for separating heavy metals contained in the waste water as the secondary sludge by adding a portion of the raw water sludge separated at the solid/liquid separation process 14 and Ca(OH)2 to the waste water from which the sulfuric acid component has been removed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for simply and effectively removing mercury components contained in exhaust gas discharged from a smelting furnace for smelting ores containing sulfur.

[0002]

2. Description of the Related Art Conventionally, exhaust gas from boilers that use metal smelting, petroleum, and coal as fuel contains harmful heavy metals such as mercury. Therefore, strict emission standards have been set. Smoke and wastewater from power plants, etc. are completely controlled and discharged so as not to exceed this emission standard. For example, as a method of treating exhaust gas in the smelting of copper, as shown in FIG. 4, smelting ore containing sulfur is smelted using a fuel mainly containing coal or heavy oil. Smelting furnace 1 by smelting
From this, exhaust gas containing sulfur components including SO ₂ gas, SO ₃ , MSO ₄ (M is a heavy metal), mercury components, etc. is generated. This exhaust gas is sent to a gas cleaning step 2, where it is brought into contact with an adsorbent or gas-liquid in the presence of water, whereby a gas containing SO ₂ gas as a main component and SO ₃ or MSO other than SO ₂ gas.
Separated into wastewater containing sulfur and mercury components including ₄ and others. That is, in the gas cleaning step 2, the cleaning water is made to absorb sulfur components including SO ₃ , MSO _{4 and the} like other than SO ₂ gas and mercury components. Of these, SO ₃ reacts with washing water to form sulfuric acid (H ₂ SO ₄ ). SO separated in gas cleaning step 2
_The gas containing ₂ gas as a main component is obtained by removing and recovering SO ₂ gas as sulfuric acid or gypsum, and is discharged out of the system in a state where all harmful substances are regulated to below the emission standard. Also, the gas cleaning step 2
A large amount of mercury component exists in the wastewater separated in step 1. However, since the mercury component is large in the solid content contained in the wastewater (pH 1 or less), it is separated into solid content and wastewater in the solid-liquid separation step 4. Specifically, the wastewater is concentrated with a thickener or the like, and the concentrated raw water slurry is subjected to solid-liquid separation to separate the solid content from the wastewater. The separated solid content is raw water sludge, and this raw water sludge is re-supplied to the smelting furnace 1, a part of the raw water sludge is supplied to the waste water secondary treatment step 7 described later as the raw water slurry, or outside the system. And discharge (bleed off).

Wastewater from which solids have been separated in the solid-liquid separation step 4 is treated with calcium carbonate (C) in the wastewater primary treatment step 5.
The pH of the wastewater is adjusted to 2 to 4 by adding aCO ₃ ).
Is adjusted to fix only the sulfuric acid component of the sulfur component, and the sulfuric acid component is separated and recovered as gypsum (CaSO ₄ ) by solid-liquid separation. At this time, the mercury dissolved in the waste water is separated together with the sulfuric acid component and transferred to gypsum. In the wastewater secondary treatment step 7, the wastewater from which the gypsum was separated in the wastewater primary treatment step 5 was mixed with a portion of the raw water sludge separated in the solid-liquid separation step 4 (raw water slurry state) and calcium hydroxide (Ca (OH)). By adding ₂ ), the pH of the wastewater is adjusted to 11 to 12 to fix the heavy metals mainly contained in the wastewater together with the mercury contained in the raw water sludge (raw water slurry), and the heavy metals are not included by solid-liquid separation. Get drainage. Wastewater is discharged to the outside of the system with all harmful substances regulated to below the emission standard. The solid content fixed in the waste water secondary treatment step 7 is re-supplied to the smelting furnace 1 as secondary sludge.

Like the above method, the technology for removing harmful substances contained in these exhaust gases has been almost established, but various improved technologies have been proposed (Japanese Patent Laid-Open Nos. 7-308542 and 9-308817, Japanese Patent Laid-Open No. 9-308817). Kaihei 10-216476).
Japanese Patent Application Laid-Open No. 7-308542 discloses a mixture of lead concentrate or artificially synthesized lead sulfide (PbS) and a mixture of naturally occurring pyrite (FeS ₂ ) such as iron sulfide or synthesized iron sulfide. A method for removing mercury in exhaust gas by adsorbing and removing mercury by passing exhaust gas accompanied by gaseous or mist-like mercury through an absorbent composed of a substance supported on a substance carrier is disclosed. In this method, the absorbent supported on the porous material carrier by mixing iron sulfide with lead sulfide can be used stably for a long time, and also has a good mercury adsorption efficiency and a mercury removing ability per unit weight of the absorbent. Since it is high, there is an effect that the filling layer for filling the absorbent can be downsized. Further, Japanese Patent Laid-Open No. 9-308817 discloses an improved technique for removing harmful substances by absorbing, filtering or capturing harmful substances in a powder layer on the surface of a bag filter cloth by a bag filter formed by supplying powder particles. Is measured, and one or more of the concentrations of harmful substances in the exhaust gas at the bag filter outlet are measured, and based on the increase / decrease in the concentration, the supply of the granular material used for forming the granular layer on the surface of the bag filter. By increasing or decreasing the amount, it becomes possible to minimize the amount of powder to be blown in for removing harmful substances in the exhaust gas. Japanese Patent Laid-Open No. 10-216476
In the gazette, a mercury removing agent is added to at least one of the circulating liquid used in the desulfurization device, the absorbing liquid, the feed water used in the wet electrostatic precipitator, the circulating water, the water in the dust collector body, and the exhaust gas at the dust collector inlet. The method of addition is shown. With this method, a large amount of mercury is emitted from the emission source, and the mercury concentration is 10 μg.
/ Nm ³ or less of ultra-low concentration mercury in exhaust gas,
In particular, metallic mercury vapor can be removed.

[0005]

However, Japanese Patent Laid-Open No. 7-3
The technique disclosed in Japanese Patent No. 08542 discloses that mercury is adsorbed and removed by passing exhaust gas accompanied by gaseous or mist-like mercury through an absorbent, but the mercury component in the gas phase is removed. Since the technology is used, the cost is high. Further, in the technique disclosed in Japanese Patent Laid-Open No. 9-308817, a bag filter is used to remove mercury,
When the filter cloth of the bag filter is damaged, it is feared that the dust concentration in the exhaust gas will increase. In addition, the method using this bag filter has a low mercury removal efficiency, which may increase the cost. Further, the technique disclosed in Japanese Patent Laid-Open No. 10-216476 uses an electric dust collector for removing mercury, but the electric dust collector has a problem in dust-removing property, and the mercury removing effect is simply improved by improving the performance of the dust collector. If it is raised, the dust collection area becomes too large, which is not only economically inefficient, but also requires a large site area.

An object of the present invention is to remove mercury contained in exhaust gas by a simple method and effectively remove the mercury component contained in exhaust gas discharged from a smelting furnace for smelting ores containing sulfur. To provide.

[0007]

The invention according to claim 1 is
It is an improvement of a method for removing mercury contained in exhaust gas discharged from a smelting furnace for smelting ores containing sulfur. As shown in FIG. 1, its characteristic configuration is that the exhaust gas discharged from the smelting furnace 11 is washed with wash water containing 3 to 5% by weight of hydrochloric acid to produce gas containing SO ₂ gas as a main component and waste water. Gas cleaning step 12 for separating into solids, solid-liquid separation step 14 for separating solids contained in wastewater as raw water sludge, and wastewater from which solids have been separated are contacted with a mercury removing agent to remove mercury components contained in the wastewater. The mercury component removal step 17 for removing water, the wastewater primary treatment step 18 for adding calcium carbonate to the wastewater from which the mercury component has been removed to separate the sulfuric acid component out of the sulfur components contained in the wastewater as gypsum, and the wastewater from which the sulfur component has been separated This is to include a wastewater secondary treatment step 21 in which a part of the raw water sludge separated in the solid-liquid separation step 14 and calcium hydroxide are added to separate heavy metals mainly contained in the wastewater as secondary sludge.

In the invention according to claim 1, since the exhaust gas is cleaned in the gas cleaning step 12 with the cleaning water containing hydrochloric acid of 3 to 5% by weight, the mercury component contained in the exhaust gas is dissolved in soluble mercury (II) chloride (HgCl). ₂ ) and transfer more to the drainage side, and a mercury component removal step 17 is provided between the solid-liquid separation step 14 and the wastewater primary treatment step 18, and this mercury component removal step 17
The mercury component contained in the wastewater is removed by bringing the wastewater into contact with the mercury removing agent to effectively remove the mercury component by a simple method.

The invention according to claim 2 is the invention according to claim 1, wherein a part of the wastewater from which the mercury component has been removed by the mercury removing agent in the mercury component removing step 17 is a SO ₂ gas in the gas cleaning step 12. This is a method of removing mercury that is reused in cleaning water. In the invention according to claim 2, the mercury component removing step 17
By reusing a part of the wastewater from which the mercury component has been removed in step S12 as water for cleaning the SO ₂ gas,
The concentration of mercury contained in the cleaning water is reduced, and the gas cleaning step 12
Reduce the mercury load on. In addition, the concentration of mercury component contained in the gas containing SO ₂ gas as a main component can be reduced.

The invention according to claim 3 is the invention according to claim 1, wherein before the mercury component is removed in the mercury component removal step 17, the drainage is passed through a layer made of sand, and the solid content contained in the drainage. The method for removing mercury further comprises a sand filtration step 16 of filtering the remainder. In the invention according to claim 3, the wastewater is passed through the sand layer in the sand filtration step 16, thereby preventing clogging due to the remaining solid content contained in the wastewater in the subsequent mercury component removal step 17.

The invention according to claim 4 is the invention according to claim 1, wherein the mercury removing agent is activated carbon, and the activated carbon adsorbs 5 to 20% by weight of a mercury component with respect to 100% by weight of activated carbon. It is a method of removing mercury that has the ability. The invention according to claim 5 is the invention according to claim 1, which is a method for removing mercury in which the refining furnace 11 is a reflection furnace.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to the drawings by taking a method for removing mercury contained in exhaust gas as an example of exhaust gas generated by smelting copper. Figure 1
As shown in, when smelting ore containing sulfur, smelting furnace 11
The exhaust gas generated from, SO ₂ gas, SO _3, MSO ₄
Sulfur components including (M is heavy metals), mercury components, etc. are included. By the exhaust gas is sent to the gas washing step 12, where it is gas-liquid contact in the presence of wash water containing 3-5% by weight hydrochloric acid, gas and SO ₂ mainly composed of SO ₂ gas
Separated into sewage containing sulfur components other than gas such as SO ₃ and MSO _4, and mercury components. That is, the gas cleaning step 12
Then, the cleaning water is made to absorb sulfur components including SO ₃ and MSO ₄ other than SO ₂ gas and mercury components. Of these, SO ₃
Reacts with wash water to form sulfuric acid (H ₂ SO ₄ ). In the gas cleaning step 12, the cleaning water is subdivided into a large number of fine droplets by a nozzle or the like, and these are dispersed in the exhaust gas passing through the superficial column to suspend solids or liquids such as heavy metals other than mercury or dust floating in the exhaust gas. It is performed by a spray type scrubber that captures fine particles of mercury. When the exhaust gas is washed with cleaning water containing 3 to 5% by weight of hydrochloric acid, the mercury component contained in the exhaust gas becomes soluble mercury (II) chloride (HgCl ₂ ) and more of it migrates to the drainage side. S in this gas cleaning step 12
The concentration of the O ₂ gas cleaning water is adjusted so that it always contains 3 to 5% by weight of hydrochloric acid. The hydrochloric acid concentration is defined to be 3 to 5% by weight because if it is less than the lower limit value, the amount of mercury component transferred to the drainage side does not increase, and if it exceeds the upper limit value, a large amount of hydrochloric acid is used, Mercury component removal step 17
This is because mercury will not be adsorbed on the activated carbon, and the amount of calcium carbonate used will increase in the wastewater primary treatment step 18, resulting in problems. The gas containing SO ₂ gas as the main component separated in the gas cleaning step 12 removes SO ₂ gas as sulfuric acid or gypsum and collects it, and discharges it out of the system in a state where all harmful substances are regulated to below the emission standard. To be done.

Wastewater having strong acidity (including hydrofluoric acid, hydrochloric acid, sulfuric acid) containing sulfur components such as SO ₃ and MSO ₄ other than SO ₂ gas separated in the gas cleaning step 12 and mercury components, Since the solid content is contained, the solid-liquid separation step 14 separates the solid content and the waste water. Specifically, the wastewater is concentrated with a thickener or the like, and the concentrated raw water slurry is subjected to solid-liquid separation to separate the solid content from the wastewater. The separated solid content is raw water sludge, and this raw water sludge is re-supplied to the smelting furnace 11 or a part of the raw water sludge is supplied to the waste water secondary treatment step 21 described below as a raw water slurry. The wastewater from which solids have been separated in the solid-liquid separation step 12 is sent to the sand filtration step 16, where the wastewater is passed through a layer of sand to filter the remaining solids contained in the wastewater. By performing the sand filtration step 16, in the subsequent mercury component removal step 17, clogging due to the remaining solid content contained in the wastewater is prevented.

In the mercury component removing step 17, the wastewater from which the solid content has been separated is brought into contact with the mercury removing agent to remove the mercury component contained in the wastewater. This mercury component removal step 1
Due to 7, most of the mercury components contained in the waste water are adsorbed by the mercury removing agent. Since the wastewater is a liquid exhibiting acidity with a pH of 1 or less, activated carbon, fly ash or the like is used as the mercury removing agent. In particular, activated carbon is preferable because it has a high adsorption capacity. The particle size of the mercury removing agent is 6 to 100 mesh, preferably 10 to 30 mesh. When activated carbon is used as a mercury removing agent, the activated carbon has an ability to adsorb 5 to 20% by weight of a mercury component with respect to 100% by weight of activated carbon, depending on the quality of the activated carbon. Before sending the wastewater from which the mercury component has been removed to the wastewater primary treatment step 18, a part of the wastewater from which the mercury component has been removed is supplied to the water for cleaning the SO ₂ gas in the gas cleaning step 12 for reuse. By supplying the waste water to the water for cleaning the SO ₂ gas, the concentration of the mercury component contained in the cleaning water is lowered, and the concentration of the mercury component contained in the gas containing SO ₂ gas as the main component can also be reduced. In the subsequent recovery of SO ₂ , for example, the mercury load of the waste gypsum plant can also be reduced. Further, since the mercury component concentration of the wastewater sent to the subsequent wastewater treatment is also reduced, the mercury component concentration of gypsum obtained by neutralizing the sulfuric acid content in the wastewater can be reduced.

In the wastewater primary treatment step 18, the wastewater from which the mercury component has been removed is adjusted to pH 2 to 4 by adding calcium carbonate (CaCO ₃ ) to fix only the sulfuric acid component of the sulfur component. The sulfuric acid component is separated as gypsum (CaSO ₄ ) by solidification and solid-liquid separation.

The waste water from which the sulfuric acid component has been separated in the waste water primary treatment step 18 is treated with calcium hydroxide (a raw water slurry state) together with a part of the raw water sludge separated in the solid-liquid separation step 14 in the waste water secondary treatment step 21. Ca (O
H) ₂ ) is added to adjust the pH of the wastewater to 11 to 12
Adjusted to fix the heavy metals mainly contained in the wastewater along with mercury contained in the raw water sludge (raw water slurry),
By performing solid-liquid separation, heavy metals are separated as solids. Wastewater is discharged to the outside of the system with all harmful substances regulated to below the emission standard. The solid content fixed in the wastewater secondary treatment step 21 is re-supplied to the smelting furnace 11 as secondary sludge.

Next, the distribution ratio of mercury contained in the exhaust gas will be described using the mercury removing method of the present invention and the conventional method. A case where the exhaust gas generated by smelting is treated by the conventional mercury removal method will be described. As shown in FIG. 3, first, assuming that the ratio of the mercury component contained in the exhaust gas initially generated from the smelting furnace is 100%, a part of the mercury component contained in the exhaust gas is combined with selenium contained in the exhaust gas. Form mercury (II) selenide (HgSe) that is insoluble in water and remain in the gas even after gas cleaning, so all mercury components do not move to wastewater A mercury component is distributed at a ratio of 10% to the separated gas containing SO ₂ gas as a main component, and is distributed at a ratio of 90% to waste water. In the solid-liquid separation step, the mercury component contained in the wastewater is transferred to the raw water sludge at a rate of 90% and to the wastewater at a rate of 10%. Therefore, of the 90% mercury contained in the wastewater, 81% is on the raw water sludge side and 9% is on the drainage side.
Will be changed at the rate of each. The mercury component transferred to the drainage side is 9% in the wastewater primary treatment step, and almost all the mercury component is contained in the gypsum together with the sulfuric acid component. If 81% of the mercury component transferred to the raw water sludge is a and the rest is 1-a,
The distribution rate of mercury components supplied to the wastewater secondary treatment process is (1
-A) x 81% and the balance is a x 81%. The mercury component supplied to the wastewater secondary treatment process moves to the secondary sludge as a solid content, and the rest of the raw water sludge and the secondary sludge are re-supplied to the smelting furnace. The rate is 81%.

Next, when the distribution rate of the mercury component contained in the exhaust gas continuously generated is [+ α], the ratio of the mercury component sent to the gas cleaning step is [81% + α]. In this gas cleaning step, as described above, the gas containing SO ₂ gas as the main component is transferred at a rate of 10%, and the waste water is transferred at a rate of 90%.
[81% + α] x on the gas side containing SO ₂ gas as the main component
0.1 and [81% + α] × 0.9 at the drain side respectively. In the solid-liquid separation step, the mercury component contained in the wastewater migrates to the raw water sludge at a rate of 81% and to the wastewater at a rate of 9%, respectively. Therefore, of the mercury component contained in the wastewater [81% + α] × 0.9, [81% + α] × 0.81 for raw water sludge side, [81% + α] × for drainage side
It shifts at a rate of 0.09. The mercury component transferred to the wastewater side is [81% + α] × in the wastewater primary treatment process.
0.09 Almost all mercury components are separated as solid components together with sulfuric acid components and contained in gypsum. Of the mercury component [81% + α] x 0.81 transferred to the raw water sludge, if a part of the raw water sludge is a and the rest is 1-a, the mercury component supplied to the wastewater secondary treatment process The distribution rate of
(1-a) x [81% + α] x 0.81 with the balance a x
It becomes [81% + α] × 0.81. The mercury component supplied to the wastewater secondary treatment process moves to the secondary sludge as a solid content, and the rest of the raw water sludge and the secondary sludge are re-supplied to the smelting furnace. Distribution rate
It becomes [81% + α] × 0.81. If the mercury distribution ratio [+ α] of the exhaust gas that is continuously generated is 100%, which is the same as the mercury distribution ratio of the exhaust gas that is first generated, the mercury component that returns to the smelting furnace again exceeds 100%. Therefore, every time the mercury component is re-supplied to the smelting furnace, there arises a problem that the mercury component concentration increases.

The case where the exhaust gas generated by smelting is treated by the method for removing mercury of the present invention will be described.
As shown in FIG. 2, first, assuming that the ratio of the mercury component contained in the exhaust gas initially generated from the smelting furnace is 100%, when the conventional mercury removal method is used, one of the mercury components contained in the exhaust gas is The part combines with selenium contained in the exhaust gas to form water-insoluble mercury selenide (II), which remains in the gas even after gas cleaning. 10% on the gas side containing SO ₂ gas that has been separated in the gas cleaning process as the main component, and 90% on the drainage side.
In the present invention, since the exhaust gas is washed with cleaning water containing 3 to 5% by weight of hydrochloric acid in the gas cleaning step, the mercury component contained in the exhaust gas becomes soluble mercury (II) chloride, Migrate to the drain side. Therefore, more mercury components contained in the exhaust gas can be transferred to the drain side than in the conventional method, and 5% to the gas side containing SO ₂ gas as the main component and 95% to the drain side. . In the solid-liquid separation step, the mercury component contained in the wastewater is transferred to the raw water sludge at a rate of 10% and to the wastewater at a rate of 90%. Therefore, the mercury component contained in the wastewater is 95
%, 9.5% on the raw water sludge side and 85.% on the drainage side.
It will be transferred at a rate of 5%. The mercury component transferred to the drainage side is 85.5% in the mercury component removing step, and almost all the mercury component is removed by the mercury removing agent. Assuming that part of the raw water sludge is ‘a’ and the rest is 1−a among 9.5% of the mercury components transferred to the raw water sludge,
The distribution rate of mercury components supplied to the wastewater secondary treatment process is (1
-A) x 9.5% and the balance a x 9.5%.
The mercury component supplied to the wastewater secondary treatment process moves to the secondary sludge as a solid content, and the rest of the raw water sludge and the secondary sludge are re-supplied to the smelting furnace. The rate is 9.5%.

Next, assuming that the distribution rate of the mercury component contained in the exhaust gas continuously generated is [+ α], the ratio of the mercury component sent to the gas cleaning step is [9.5% + α]. 5% to the gas side of the main component as SO ₂ gas described above in the gas washing step, the process proceeds at a rate of 95% in the waste water side, the gas side composed mainly of SO ₂ gas [9 0.5% +
α] × 0.05, [9.5% + α] × 0.95 on the drain side
Will be changed at the rate of each. In the solid-liquid separation process, the mercury component contained in the wastewater is 1% in the raw water sludge.
0% and 90% to the wastewater, respectively, so of the mercury components [9.5% + α] × 0.95 contained in the wastewater, [9.5% + α] × 0. 095,
Transfer to the drainage side at a rate of [9.5% + α] × 0.855. In the mercury component removal step, the mercury component transferred to the drainage side is [9.5% + α] × 0.855 Almost all of the mercury component is removed by the mercury removing agent. Of the mercury component [9.5% + α] x 0.095 transferred to the raw water sludge, a part of the raw water sludge is assumed to be a and the rest is 1
-A, the distribution rate of the mercury component supplied to the wastewater secondary treatment process is (1-a) x [9.5% + α] x 0.095, and the balance is a x [9.5% + α]. It becomes × 0.095. The mercury component supplied to the wastewater secondary treatment process moves to the secondary sludge as a solid content, and the rest of the raw water sludge and the secondary sludge are re-supplied to the smelting furnace. The distribution rate is [9.5% + α] × 0.095.

As described above, since the distribution rate of the mercury component returned to the smelting furnace decreases every time it is re-supplied, the SO ₂ separated in the gas cleaning step and the gypsum separated in the wastewater primary treatment step are separated. The concentration of the mercury component contained in each is also reduced. Although not shown in FIG. 2, a part of the wastewater from which the mercury component was removed in the mercury component removal step was reused as water for cleaning SO ₂ in the gas cleaning step, and thus was separated by the gas cleaning step. The distribution rate of mercury contained in the wastewater is smaller than the value shown in Fig. 2.

[0022]

As described above, according to the present invention, in the method for removing mercury contained in the exhaust gas generated by smelting, the exhaust gas is washed in the gas cleaning step with the cleaning water containing 3 to 5% by weight of hydrochloric acid. For cleaning, the mercury component contained in the exhaust gas is converted to soluble mercury chloride and transferred to the drainage side, and a mercury component removal process is provided between the solid-liquid separation process and the wastewater primary treatment process. The gypsum separated in the subsequent wastewater primary treatment step contains almost no mercury component by removing the mercury component contained in the wastewater by contacting with the mercury removing agent. Further, since a part of the wastewater from which the mercury component has been removed in the mercury component removal step is reused as water for cleaning SO ₂ in the gas cleaning step, it is included in the gas containing SO ₂ as the main component separated in the gas cleaning step. The distribution rate of mercury components contained in the wastewater separated in the gas cleaning process can be reduced, and the mercury content in gypsum produced using the recovered sulfur components can be minimized. be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing a method for removing mercury contained in exhaust gas according to the present invention.

FIG. 2 is a diagram showing the distribution ratio of mercury when treated using the method for removing mercury of the present invention.

FIG. 3 is a diagram showing a distribution ratio of mercury when treated using a conventional mercury removal method.

FIG. 4 is a diagram showing a conventional method for removing mercury contained in exhaust gas.

[Explanation of symbols]

11 Smelting furnace 12 gas cleaning process 14 Solid-liquid separation process 17 Mercury component removal process 18 Wastewater primary treatment process 21 Wastewater secondary treatment process

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C02F 1/28 C22B 43/00 102 1/58 B01D 53/34 136A 1/62 ZAB C22B 3/24 23 / 16 7/00 29/08 520A 43/00 102 540A C22B 3/00 K (72) Inventor Yuji Nakagawa One of Nagisa Ichibanchi, Onahama, Iwaki City, Fukushima Prefecture F term (reference) 4D002 AA29 AC10 BA02 DA26 EA07 GA01 GB08 4D024 AA04 AB18 BA02 DB03 DB20 4D038 AA08 AB36 AB73 BA04 BB06 BB13 BB17 4D041 BB04 CA03 CA07 CB04 4K001 AA09 AA14 AA20 AA30 BA18 BA24 CA02 CA07 DB23 DB35 GA04 GB09

Claims (5)

[Claims] 1. A smelting furnace for smelting ores containing sulfur (11)
In the method for removing mercury contained in exhaust gas discharged from the exhaust gas, the exhaust gas discharged from the smelting furnace (11) is washed with cleaning water containing 3 to 5% by weight of hydrochloric acid to contain SO ₂ gas as a main component. A gas cleaning step (12) for separating gas and wastewater to be separated, a solid-liquid separation step (14) for separating solids contained in the wastewater as raw water sludge, and the wastewater from which the solids have been separated is used as a mercury removing agent. Mercury component removal step of contacting to remove the mercury component contained in the wastewater
(17), a wastewater primary treatment step (18) of adding calcium carbonate to the wastewater from which the mercury component has been removed to separate the sulfuric acid component of the sulfur component contained in the wastewater as gypsum, and separating the sulfuric acid component A wastewater secondary treatment step (21) in which a part of the raw water sludge separated in the solid-liquid separation step (14) and calcium hydroxide are added to the wastewater to separate the heavy metals mainly contained in the wastewater as secondary sludge (21). A method for removing mercury contained in exhaust gas, which comprises: 2. The mercury according to claim 1, wherein a part of the waste water from which the mercury component has been removed by the mercury removing agent in the mercury component removing step (17) is reused as the SO ₂ gas cleaning water in the gas cleaning step (12). Removal method. 3. The method further comprises a sand filtration step (16) of passing the wastewater through a layer of sand to filter the remainder of solids contained in the wastewater before removing the mercury component in the mercury component removal step (17). The method for removing mercury according to claim 1. 4. The method for removing mercury according to claim 1, wherein the mercury removing agent is activated carbon, and the activated carbon has an ability to adsorb 5 to 20% by weight of a mercury component with respect to 100% by weight of the activated carbon. 5. The method for removing mercury according to claim 1, wherein the smelting furnace (11) is a reverberatory furnace.