JPH08117555A - Method and apparatus for treating mercury vapor - Google Patents

Abstract

PURPOSE: To treat exhaust gas containing mercury vapor in an extremely safe manner at low reaction temp. without generating the explosive reaction with mercury vapor by collecting mercury vapor in a form of mercurous chloride even in any state of mercury vapor by reacting exhaust gas containing mercury vapor with a specific treatment agent to collect obtained mercurous chloride. CONSTITUTION: Exhaust gas containing mercury vapor is reacted with at least one kind of an aq. soln. containing SnCl4 -HCl, CuCl2 -HCl, FeCl3 -HCl or NiCl2 -HCl at 25-80 deg.C to collect obtained mercurous chloride. As a reactor, a Tellerette packed column type device sufficient in gas-liquid contact is desirable in order to bring gaseous mercury vapor into contact with a liquid treatment agent. As the material quality of the reactor, a metal coated with a resin material is desirable because the treatment agent uses metal chloride. This treatment method is extremely low in running cost and suitable for treatment of an industrial scale and high in practicality because an apparatus to be used is structurally simple.

Description

Detailed Description of the Invention

[0001]

[Industrial application] Mercury is used in extremely large quantities such as fluorescent materials for fluorescent lamps and conducting materials for batteries. This takes advantage of the fact that the reaction between mercury and other compounds is difficult. On the other hand, mercury vapor is extremely stable in the atmosphere, dissolves only slightly in water, and has a TLV value of 0.05 mg.
It is a toxic vapor of / m ³ , and the waste treatment facility of an industrial waste treatment plant that generates mercury vapor needs to remove the mercury vapor when it is exhausted. The present invention relates to such a mercury vapor removal method.

[0002]

2. Description of the Related Art The following two methods are known for removing mercury vapor by using a solid adsorbent. (1) Method of reacting with SnCl ₄ -KCL supported on activated carbon The reaction formula in this method is as follows: Hg (mercury vapor) + C (activated carbon) → C-Hg C-Hg + SnCl ₄ → Hg ₂ Cl ₂ + SnCl ₂ + C (activated carbon) KCL: Electrochemical reaction promoter and chloride additive First, mercury vapor is captured by activated carbon as shown in the formula, and then the captured mercury vapor is supported by Sn as shown in the formula.
Cl ₄ gradually becomes sweetened (Hg ₂ Cl ₂ ). In this case, when the amount of SnCl ₄ and KCL supported on the activated carbon is small and the concentration of mercury vapor is high, the mercury adsorbent is dead and activated immediately, and there are various problems that the mercury vapor cannot cope.

(2) Method of reacting with MeS supported on activated carbon (Me: Fe, Sn, Cu) The reaction formula in this method is as follows: Hg (mercury vapor) + C (activated carbon) → C-Hg C -Hg + MeS → HgS ↓ + C (activated carbon) First, the mercury vapor is captured by the activated carbon according to the formula, and then the captured mercury vapor is supported on the Me according to the formula.
S gradually becomes cinnabar (HgS). In this case, when the amount of MeS supported on the activated carbon is small and the concentration of mercury vapor is high, the mercury adsorbent is immediately dead and activated, and there are various problems that the mercury vapor cannot be processed.

[0004]

The present invention provides an industrial method of removing mercury vapor which eliminates the above-mentioned problems of the conventional method. Specifically, the present invention provides an exhaust gas containing mercury vapor. SnCl ₄ -HCl, CuCl ₂ -HCl, FeC
l _3-HCl, characterized in that collecting is reacted with at least one and a range of 25 to 80 ° C. selected from among aqueous solutions, such as NiCl 2-HCl, mercurous chloride obtained by _{(Hg 2} Cl 2) It is a method of removing mercury vapor. The present invention comprises a step of reacting mercury vapor with a treating agent to obtain mercuric chloride, and a step of collecting the obtained mercuric chloride, and the treating agent used in the first step is There is no problem that even high-concentration mercury vapor reacts easily, and mercury vapor that is immediately dead and activated cannot be discarded. Further, mercury vapor can be captured in the form of mercuric chloride in any state of mercury vapor (amalgam), and at a reaction temperature of 25 to 80 ° C., an explosive reaction with mercury vapor is also possible. No, it is extremely safe.

The treating agent used is an optimal treating agent because metal chloride is inexpensive in terms of price. The mercury vapor treated in the present invention may be liquid mercury or mercury vapor diluted with various gases, as a matter of course. Although the reaction temperature varies depending on the treating agent and type used, it is generally 25 to 80 ° C, preferably 30 to 60 ° C. Further, the contact time is 0.
It may be appropriately selected within the range of 1 to 10 minutes. Further, the pressure is not particularly limited because it can remove harm at a sufficient rate even under pressure, atmospheric pressure or reduced pressure. As a reactor,
There is no particular problem as long as it makes contact with gas (mercury vapor) and liquid (treatment agent), but it is more preferable if it is a device (terraret packed column type) or the like in which gas-liquid contact is sufficient. In addition, since the treatment agent uses a metal chloride as the material, a resin coating material is desirable for the metal.

The mercuric chloride (precipitate) produced in the first-step reaction is stored as a solid in the chemical bath. It was confirmed that the principle was to capture mercury vapor by the following reaction.

I The reaction of mercury vapor with ferric chloride causes ferric ions to oxidize mercury to mercuric chloride on the surface of mercury, producing green ferrous chloride. 2FeCl ₃ + 2Hg → 2FeCl ₂ + Hg ₂ Cl ₂ ↓ In the treatment liquid, mercuric chloride is further oxidized to mercuric chloride. 2FeCl ₃ + Hg ₂ Cl ₂ ↓ → 2FeCl ₂ + 2HgCl ₂ ↓ When mercuric chloride is generated in the treatment liquid, HgCl ₂ + Hg → Hg ₂ Cl ₂ ↓. Further, what has become ferrous chloride becomes ferric chloride by adding hydrochloric acid. Since FeCl ₂ + HCl → FeCl ₃ or more, mercury vapor can be treated according to the amount of HCl added.

II The reaction of mercury vapor with stannic chloride causes stannic ions to oxidize mercury at the mercury surface to mercuric chloride, producing colorless stannous chloride. SnCl ₄ + 2Hg → SnCl ₂ + Hg ₂ Cl ₂ ↓ In the treatment liquid, mercuric chloride is further oxidized to mercuric chloride. SnCl ₄ + Hg ₂ Cl ₂ ↓ → SnCl ₂ + 2HgCl ₂ ↓ When mercuric chloride is generated in the treatment solution, HgCl ₂ + Hg → Hg ₂ Cl ₂ ↓. Moreover, what became stannous chloride becomes stannic chloride by adding hydrochloric acid. Since SnCl ₂ + 2HCl → SnCl ₄ or more, mercury vapor can be treated according to the amount of HCl added.

III. The reaction of mercury vapor with cupric chloride causes cupric ions to oxidize mercury at the mercury surface to mercuric chloride, producing colorless cuprous chloride. 2CuCl ₂ + 2Hg → 2CuCl + Hg ₂ Cl ₂ ↓ In the treatment liquid, mercuric chloride is further oxidized to mercuric chloride. 2CuCl ₂ + Hg ₂ Cl ₂ ↓ → CuCl + 2HgCl ₂ ↓ When mercuric chloride is generated in the treatment liquid, HgCl ₂ + Hg → Hg ₂ Cl ₂ ↓. Further, what has become cuprous chloride becomes cupric chloride by adding hydrochloric acid. Since CuCl + 2HCl → CuCl ₂ + H ₂ or more, mercury vapor can be treated according to the amount of HCl added.

[0010]

Example 1 FeCl ₃ as a treating agent: 400 parts
s, HCl: 50 parts, water: 50 parts with a chemical solution was used to wash mercury vapor (concentration 50 mg / m ³ ) in the exhaust gas with an air flow of 10 l / min, and the outlet concentration of mercury vapor in the exhaust gas was 0.03 mg / m ³ or less. Becomes

[0011]

Example 2 CuCl ₂ as a treating agent: 400 parts
s, HCl: 50 parts, water: 50 parts with a chemical solution was used to wash mercury vapor (concentration 50 mg / m ³ ) in the exhaust gas with an air flow of 10 l / min, and the outlet concentration of mercury vapor in the exhaust gas was 0.03 mg / m ³ or less. Becomes

[0012]

Example 3 SnCl ₄ as a treating agent: 400 parts
s, HCl: 50 parts, water: 50 parts with a chemical solution was used to wash mercury vapor (concentration: 50 mg / m ³ ) in the exhaust gas at an air flow rate of 10 l / min, and the outlet concentration of mercury vapor in the exhaust gas was 0.08 mg / m ³ . Become.

[0013]

Example 4 FeCl ₃ as a treating agent: 300 parts
s, HCl: 50 parts, water: 150 parts with a chemical solution was used to wash mercury vapor (concentration 50 mg / m ³ ) in the exhaust gas at an air flow rate of 10 l / min, and the outlet concentration of mercury vapor in the exhaust gas was 0.08 mg / m ³ . Become.

[0014]

Fifth Embodiment CuCl ₂ as a treating agent: 300 parts
s, HCl: 50 parts, water: 150 parts with a chemical solution was used to clean mercury vapor (concentration 50 mg / m ³ ) in the exhaust gas at an air flow rate of 10 l / min, and the outlet concentration of mercury vapor in the exhaust gas was 0.06 mg / m ³ . Become.

[0015]

Example 6 FeCl ₃ : 150 parts as a treating agent
s, HCl: 50 parts, water: 300 parts with a chemical solution was used to wash mercury vapor (concentration 50 mg / m ³ ) in the exhaust gas at an air flow rate of 10 l / min, and the outlet concentration of mercury vapor in the exhaust gas was 0.5 mg / m ³ . Become.

[0016]

Example 7: CuCl ₂ as a treating agent: 150 parts
s, HCl: 50 parts, water: 300 parts with a chemical solution was used to wash mercury vapor (concentration: 50 mg / m ³ ) in the exhaust gas at an air flow rate of 10 l / min, and the outlet concentration of mercury vapor in the exhaust gas was 0.6 mg / m ³ . Become.

As described above, it has been confirmed by experiments that the mercury vapor concentration in the exhaust gas can be treated to a gradual amount or less as the metal chloride concentration increases, and further mercury vapor can be treated by supplementing the hydrochloric acid solution. .

Next, the processing equipment used for the mercury vapor processing will be described. FIG. 1 shows the structure of this equipment, and this processing apparatus 1 comprises an apparatus main body 2 and a control box 3. The apparatus main body 2 has a bag filter 4 which is used for switching, the processing tower has a terraret tower 5, an absorption tank 6, a circulation pump 7, a mist separator 8, a hydrochloric acid (hydrochloric acid 35% solution) purge tank 9, a metal chloride. An object purge tank 10 is provided.
The absorption tank is equipped with a salt concentration meter 11.

Taking the case of use in a treatment tower as an example, the mercury vapor exhaust gas to be treated is discharged from a waste treatment facility or the like of an industrial waste treatment plant. First, the exhaust gas enters the bag filter, removes dust such as dust, and only mercury vapor is supplied to the treatment tower. In the treatment tower, the metal salt compound-hydrochloric acid system is brought into gas-liquid contact with the terraret layer to form a precipitate (first chloride). Mercury vapor can be treated instead of mercury, and the exhaust gas entrained with mist (hydrochloric acid) can be removed by the mist with a mist separator and discharged. In addition, industrial water or metal chloride-hydrochloric acid solution is replenished to reduce the amount of the absorbing solution accompanied by mist.
In that case, when the concentration of the salt concentration meter installed in the absorption liquid tank becomes low, metal chloride-hydrochloric acid is replenished from the purge tank, and when the concentration of the salt concentration meter becomes high, it is installed. It is controlled so that the working water is replenished to the absorption liquid tank.

Next, the exhaust gas temperature in the mercury vapor exhaust gas discharged from the waste treatment facility of the industrial waste treatment plant will be described. The mercury vapor exhaust gas proceeds through an ionic reaction with the metal chloride-hydrochloric acid solution system, and the ionic reaction rate becomes faster as the temperature rises. Further, when the temperature of the exhaust gas reaction rises, the metal chloride-hydrochloric acid solution easily evaporates, but the evaporated water condenses in the mist separator, so there is not much problem.

Next, the operation at the time of power failure will be described. When a power failure occurs during processing, the fan stops and the circulation pump only stops, and there is no problem in terms of static pressure. The absorption tower, valves, instruments, and piping necessary for operation are functionally contained in the processing box. This processing box is provided with an exhaust fan, an air intake port, and an exhaust port, and the exhaust port is connected to the exhaust duct at the installation site.

Since the metal chloride-hydrochloric acid solution is a liquid that reacts with metals fairly easily, it is made of a material in which the absorption tower, circulation pump, duct and pipe joints are covered with all plastics.

Next, a specific example in which the present invention is carried out and mercury vapor discharged from a waste treatment facility of an industrial waste treatment plant is treated will be described.

Concrete Example 1 Mercury vapor having a concentration of 1000 mg / m ³ was used at an exhaust gas temperature of 40
C, reaction pressure 1 atm flow rate SV500-1000 (1 / H
The results of treatment with r) are shown in Table 1. L (absorption liquid amount) /
G (flue gas amount) = 3 to 15 is used for gas-liquid contact. As can be seen from the table, the mercury vapor concentration is 0.01 mg / m ³ or less. A ferric chloride-hydrochloric acid solution was used as the absorbing solution.

Specific Example 2 Mercury vapor having a concentration of 100 mg / m ³ was used at an exhaust gas temperature of 50 ° C.
Reaction pressure 1 atm flow rate SV500-1000 (1 / Hr)
Table 2 shows the results of the treatment with. L (absorption liquid amount) / G
Gas-liquid contact is performed at (amount of exhaust gas) = 3 to 15. As can be seen from the table, the mercury vapor concentration is 0.01 mg / m ³ or less. The absorbing solution used was a cupric chloride-hydrochloric acid solution.

Specific Example 3 Mercury vapor having a concentration of 100 mg / m ³ was used at an exhaust gas temperature of 60 ° C.
Reaction pressure 1 atm flow rate SV500-1000 (1 / Hr)
Table 3 shows the results of the treatment with. L (absorption liquid amount) / G
Gas-liquid contact is performed at (amount of exhaust gas) = 3 to 15. As can be seen from the table, the mercury vapor concentration is 0.01 mg / m ³ or less. A stannic chloride-hydrochloric acid solution was used as the absorbing solution.

[0027]

As is apparent from the above description, according to the present invention, it is possible to convert mercury vapor, which exists as mercury vapor even at room temperature and has high toxicity, into water-insoluble mercuric chloride. became. The treatment method of the present invention has a very low running cost as compared with other methods and is suitable for treatment on an industrial scale, and its apparatus is structurally simple and highly practical.

[0028]

[0029]

[0030]

[0031]

[Brief description of drawings]

[Figure 1] Mercury treatment process flow sheet

[Explanation of symbols]

 1 Processing Equipment 2 Equipment Main Body 3 Control Box 4 Bag Filter 5 Terralet Tower 6 Absorption Tank 7 Circulation Pump 8 Mist Separator 9 Hydrochloric Acid Purge Tank 10 Metal Chloride Purge Tank 11 Salt Concentration Meter

Claims (4)

[Claims] 1. A gas containing mercury vapor is added to SnCl ₄ -HC.
_{l, CuCL 2 -HCl, FeCl 3} -HCl, NiC
at least 1 selected from aqueous solutions such as l ₂ -HCl
A treatment method characterized by reacting with a seed in the range of 25 to 80 ° C. and collecting the resulting mercury vapor. 2. Mercury in a metal amalgam, which is easily decomposed, contains SnCl ₄ --HCl, CuCL ₂ --HCl, FeCl.
Reacting with at least one selected from an aqueous solution of ₃ -HCl, NiCl ₂ HCl or the like in the range of 25 to 80 ° C.
Treatment method characterized by collecting with a stable compound 3. Mercury vapor generated from a waste treatment facility of an industrial waste treatment plant is converted into SnCl ₄ -HCl, CuC.
_{L 2 -HCl, FeCl 3 -HCl,} NiCl 2 -HC
at least one selected from aqueous solutions such as 1 and 25 to
By oxidizing the mercury vapor by contacting it at 80 ° C, it is absorbed by the metal chloride up to the mercury concentration in the exhaust gas below the limit amount, and then harmful mercury vapor is supplemented with a hydrochloric acid solution to the metal chloride. Mercury vapor treatment method that enables treatment of any mercury vapor 4. SnCl ₄ —HCl, CuCL ₂ —HC
l, FeCl ₃ -HCl, NiCl ₂ -HCl, etc., at least one chemical solution selected from the aqueous solution, a chemical solution tank installed below the packing layer, and the chemical solution in the chemical solution tank are pumped up. It has a pump and a spray nozzle that sprays the pumped chemical solution to the packed bed.When the mercury vapor generated from the industrial waste treatment plant is introduced and the packed bed passes through it, it is contacted with the chemical solution to oxidize and remove the mercury vapor. Device to
The hydrochloric acid solution in the chemical solution is a device that requires timely replenishment of the hydrochloric acid solution because it reacts with the amount of generated mercury and decreases, and the reacted mercury compound in the chemical solution accumulates as a precipitate in the chemical solution tank.