JP3765542B2 - Molten exhaust gas treatment method - Google Patents

Description

  The present invention relates to a molten exhaust gas treatment method in which exhaust gas from an ash melting furnace such as a plasma melting furnace is subjected to purification treatment while being sequentially passed through a temperature reducing device, a bag filter, and a wet smoke cleaning facility.

FIG. 3 is a system diagram showing an example of an examination technique for an exhaust gas treatment system of a plasma melting furnace provided in combination with a waste incinerator.
In FIG. 3, 1 is a plasma melting furnace, 8 is a hopper for introducing a combustion treated product such as industrial waste into the melting furnace 1, 10 is an exhaust gas pipe from the plasma melting furnace 1, and 17 is a residue discharge pipe. .
Reference numeral 2 denotes a temperature reducing device for lowering the exhaust gas temperature, which is connected to the plasma melting furnace 1 through the exhaust gas pipe 10. 3 is a bag filter that removes the melting furnace fly ash and the like in the gas, and is provided with a heater 31 and a fly ash carrying conveyor 32, and carries the removed fly ash to a fly ash treatment facility (not shown). Reference numeral 19 denotes an exhaust gas pipe for connecting the temperature reducing device 2 and the bag filter 3.

Reference numeral 4 denotes a wet smoke-washing tower that removes high-concentration acidic gas components in the exhaust gas, and deposits salts by making wet contact with the high-concentration acidic gas components with alkaline water added from the NaOH tank 41. Reference numeral 11 denotes an exhaust gas pipe connecting the bag filter 3 and the wet smoke cleaning tower 4, and the exhaust gas pipe 11 is provided with an exhaust gas fan 7 for exhaust gas pressure feeding.
Reference numeral 18 denotes an exhaust gas pipe connected to the outlet of the wet smoke cleaning tower 4.
A waste water treatment apparatus 6 removes heavy metals and the like in the drained water drawn from the wet smoke squeezing tower 4.
5 is a water supply tank in which the temperature-reduced water supplied to the temperature reducing device 2 is accommodated, and 9 is a temperature-reducing water pipe connecting the water supply tank 5 and the temperature reducing device 2.

During operation of the melting furnace exhaust gas treatment system, the exhaust gas discharged from the plasma melting furnace 1 is introduced into the temperature reducing device 2 through the exhaust gas pipe 10.
In the temperature reducing device 2, the temperature-reducing water introduced from the water tank 5 through the temperature-reducing water pipe 9 is sprayed into the exhaust gas, and the exhaust gas temperature is set to the required inlet temperature of the bag filter 3 (preferably about 150 to 160 ° C.) Allow to cool down.
The exhaust gas that has passed through the temperature reducing device 2 is introduced into the bag filter 3 via the exhaust gas pipe 19 to remove the melting furnace fly ash and the like, and the fly ash is sent to the fly ash treatment equipment (not shown) via the fly ash conveyor 32. Transport to.

The exhaust gas that has passed through the bag filter 3 is sent by the exhaust gas fan 7 through the exhaust gas pipe 11 to the wet smoking tower 4, where high-concentration acidic gas components are removed, and then through the exhaust gas pipe 18, an incinerator (non-reactor). It is combined with the exhaust gas on the side) or discharged to the outside.
The drainage discharged from the wet smoke tower 4 is discharged or sent to an incinerator-side wastewater treatment device (not shown) after heavy metals are removed by the wastewater treatment device 6.

Patent Document 1 discloses a technique in which a bag filter and a washing tower are attached to a melting and solidifying apparatus that melts and solidifies fly ash in a garbage incinerator.
JP-A-9-276651

  In the exhaust gas treatment system for a plasma melting furnace shown in FIG. 3, when a large wet smoke tower is installed on the waste incinerator (not shown) side of the plasma melting furnace, the bag filter 3 The melting furnace exhaust gas after the gradual dusting in the furnace is mixed with the exhaust gas on the incinerator side, and then batch processing is performed in the wet smoke cleaning tower 4.

  However, in the case where only the dry type exhaust gas treatment facility is installed on the incinerator side, the wet scrubbing tower 4 is provided alone in the exhaust gas treatment system on the plasma melting furnace 1 side as shown in FIG. Cost.

  For this reason, in the system in which the wet smoke tower 4 is provided in the exhaust gas treatment system on the side of the plasma melting furnace 1 as described above, it is simple if the waste water can be discharged into the sewer as it is withdrawn from the smoke tower 4. It is only necessary to remove heavy metals in the wastewater with a simple wastewater treatment device. However, when the discharge is impossible, complicated maintenance is required for the drainage drainage channel of the wet smoke tower 4, and a wide range of substances can be removed. It is necessary to provide a wastewater treatment device 6 having a removal function, and the structure of the wastewater treatment device 6 is complicated and large, resulting in high costs.

  Further, in such an exhaust gas treatment system for a melting furnace, water is sprayed in the temperature reducing device 2 in order to lower the temperature (reducing the temperature) to the required exhaust gas temperature at the bag filter 3 inlet. However, there is a problem that low temperature corrosion occurs due to acid gas components.

  In view of such a problem, the present invention provides an exhaust gas treatment system for treating exhaust gas from an ash melting furnace via a temperature reducing device, a bag filter, and a wet smoke washing facility, and drainage for extraction drainage treatment from the wet smoke washing facility. An object of the present invention is to simplify the structure of the processing apparatus to reduce the apparatus cost and to prevent the occurrence of low temperature corrosion in the bag filter.

  Therefore, in order to solve such a problem, the present invention provides, as its first invention, a temperature reducing device for reducing the temperature of the exhaust gas from the ash melting furnace with the temperature-decreasing water supplied from the water tank, the bag filter, and the wet smoke cleaning equipment. When the purification treatment is carried out while sequentially passing through, the drainage drainage of the wet smoke cleaning equipment is introduced into the water tank, supplied from the water tank to the temperature reducing device, and sprayed as temperature-reduced water. An exhaust gas treatment method is proposed.

  The wet smoke cleaning equipment is preferably installed in the exhaust gas line on the ash melting furnace side, but may also be used as the wet smoke cleaning equipment on the combustion furnace side. In view of this, the second invention is characterized in that the exhaust gas from the ash melting furnace is mixed with the exhaust gas on the combustion furnace side and introduced into the wet smoke-washing tower.

Further, the third invention relates to an exhaust gas treatment method using the exhaust gas treatment apparatus according to the first invention. More specifically, a base component such as NaOH or NaHCO ₃ is added to the dewarmed water, specifically, a water supply tank to reduce the alkalinity. The hot water is supplied to the temperature reducing device.

According to the first and second aspects of the present invention, the drainage drained from the wet smoke cleaning equipment is introduced into the water tank after being subjected to the heavy metal removal treatment by the waste water treatment apparatus or is directly reduced in the water tank. Mixed with warm water. (If a closed circuit is configured, the heavy metal removal process may not be performed.)
Then, this mixed temperature-reduced water is sent to a temperature reducing device and sprayed into the exhaust gas, and the exhaust gas temperature is lowered to the required inlet temperature of the bag filter.

  The mixed dewarmed water sprayed by the dewarming device has been subjected to alkali treatment in the wet smoke cleaning equipment, and therefore, salts in the extracted drainage are mixed. It is sent to the bag filter together with the exhaust gas mixed with the spray of hot water and is removed together with the melting furnace fly ash by the bag filter. Thereby, it is only necessary to remove heavy metals in the waste water treatment apparatus.

  Therefore, according to this invention, the extraction waste water of the wet smoke cleaning equipment is mixed with the temperature-reduced water and sent to the temperature reducing device, and the mixed temperature-reduced water is sprayed into the exhaust gas, so that (precipitated) salts in the extraction waste water are reduced. It is mixed into the exhaust gas by spraying the mixed dewarmed water in the temperature device, sent to the bag filter, and reliably removed together with the fly ash in the melting furnace.

As a result, the wastewater treatment apparatus for treating the drained wastewater from the wet smoke cleaning facility only needs to remove a simple heavy metal, and the wastewater treatment apparatus may be simple in structure and small in size. In addition, when the drained waste water is circulated and used, heavy metal treatment may be performed when it is discharged to the outside.
In addition, according to the present invention, it is possible to continuously discharge (deposited) salts contained in the drained waste water from the smoke-washing tower to the outside of the system by the above-described treatment, and prevent concentration of salts in the exhaust gas treatment system. be able to.

Further, according to the third invention, by adding an appropriate amount of NaOH to the temperature-reduced water, the temperature-reduced water becomes alkaline and is sprayed into the exhaust gas by the temperature-reducing device, and wet contact with the high-concentration acidic gas component by the alkaline temperature-reduced water. To precipitate salts and weakly acidify high-concentration acidic gas components.
The weakly acidified melting furnace exhaust gas is sent to the bag filter together with the precipitated salts, and the bag filter removes the precipitated salts and suppresses low temperature corrosion due to the exhaust gas.

  That is, according to the present invention, an appropriate amount of NaOH is added to the temperature-reduced water to make the temperature-reduced water alkaline, and this is sprayed into exhaust gas to weakly acidify high-concentration acidic gas components and precipitate salts. By flowing through the bag filter, the salt can be removed from the bag filter and the low temperature corrosion due to the acid gas of the bag filter can be prevented.

Furthermore, instead of NaOH, NaHCO ₃ (baking soda) is used in the temperature-reduced water sprayed by the temperature reducing device
And this may be converted into alkaline temperature-reduced water and supplied to the temperature-reducing device.

Further, according to the invention, when the wet smoke cleaning equipment is installed on the incinerator side, an appropriate amount of NaHCO ₃ is added to the temperature-decreasing water and sprayed into the exhaust gas by the temperature-decreasing device to make it alkaline, and the bag filter. By feeding, the low temperature corrosion by acid gas components, such as a bag filter, can be prevented with precipitation of salts similarly to the above.
It is obvious that the same effect can be obtained even if other basic components are added in place of NaOH or NaHCO ₃ .

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

FIG. 1 is a system diagram of a molten exhaust gas treatment apparatus for a plasma melting furnace according to a first embodiment of the present invention.
In FIG. 1, 1 is a plasma melting furnace, 8 is a hopper for introducing a combustion treated product such as industrial waste into the melting furnace 1, 10 is an exhaust gas pipe from the plasma melting furnace 1, and 17 is a residue discharge pipe. . Reference numeral 2 denotes a temperature reducing device for lowering the exhaust gas temperature, which is connected to the plasma melting furnace 1 through the exhaust gas pipe 10.
3 is a bug filter for removing fly ash and precipitated salts in the exhaust gas, which is provided with a heater 31 and a fly ash transport conveyor 32, and transports the fly ash after removal to a fly ash treatment facility (not shown). Reference numeral 19 denotes an exhaust gas pipe for connecting the temperature reducing device 2 and the bag filter 3.

Reference numeral 4 denotes a wet smoke-washing tower that removes high-concentration acidic gas components in the exhaust gas, and deposits salts by making wet contact with the high-concentration acidic gas components with alkaline water added from the NaOH tank 41. Reference numeral 11 denotes an exhaust gas pipe connecting the bag filter 3 and the wet smoke cleaning tower 4, and the exhaust gas pipe 11 is provided with an exhaust gas fan 7 for exhaust gas pressure feeding.
Reference numeral 18 denotes an exhaust gas pipe connected to the outlet of the wet smoke cleaning tower.
5 is a water supply tank in which the temperature-reduced water supplied to the temperature reducing device 2 is accommodated, and 9 is a temperature-reducing water pipe connecting the water supply tank 5 and the temperature reducing device 2.
The above configuration is the same as that of the prior art shown in FIG.

In the first embodiment of the present invention, the system for treating the drained waste water of the wet smoke-flushing tower 4 is improved.
That is, in FIG. 1, 6 is a waste water treatment device, and as described above, the waste water discharged from the wet smoke cleaning tower 4 is introduced to remove heavy metals in the waste water. The outlet of the treated waste water of the device 6 is connected to the water supply tank 5 through a drain pipe 15.
Further, NaOH is added to the water supply tank 5 together with the withdrawing waste water so that the temperature-reduced water is made into alkaline temperature-reduced water.

During operation of an exhaust gas treatment system for a plasma melting furnace having such a configuration,
The drainage drained from the wet smoke cleaning tower 4 is sent to a wastewater treatment device 6 where heavy metals in the wastewater are removed.
The extracted waste water from which heavy metals have been removed by the waste water treatment device 6 is sent to the water tank 5 through the drain pipe 15 and mixed with the dewarmed water in the water tank 5.
In addition, a small amount of NaOH (sodium hydroxide) is also mixed in the water supply tank 5 to make the temperature-reduced water alkaline, as will be described later.

Then, the mixed temperature-reduced water in the water supply tank 5, that is, the temperature-reduced water mixed with the extraction waste water and NaOH, is sent to the temperature-reducing device 2 through the temperature-reduced water pipe 9.
On the other hand, the exhaust gas discharged from the plasma melting furnace 1 is introduced into the temperature reducing device 2 through the exhaust gas pipe 10.

In the temperature reducing device 2, the mixed temperature-reduced water introduced from the water tank 5 through the temperature-reducing water pipe 9 is sprayed into the exhaust gas, and the exhaust gas temperature is changed to the required inlet temperature (150 ° C. to 160 ° C.) of the bag filter 3. Since the temperature-reduced water becomes alkaline and is sprayed into the exhaust gas by the temperature-reducing device 2, the high-concentration acidic gas component in the exhaust gas is brought into wet contact with the exhaust gas by the alkaline-temperature-reduced water. Is weakly acidified to precipitate salts.
The exhaust gas that has passed through the temperature reducing device 2 is introduced into the bag filter 3 through the exhaust gas pipe 19 together with the precipitated salts and fly ash, where the precipitated salts and fly ash are removed.

When the bag filter 3 is operated, the mixed dewarmed water sprayed into the exhaust gas by the dewarming device 2 dissolves the salts in the drained effluent from the wet smoke cleaning tower 4 with alkaline dewarmed water again. It is deposited by the temperature reducing device 2 and sent to the bag filter 3.
In the bag filter 3, solid components such as the salts and fly ash are removed, and these are transferred to the fly ash treatment facility via the fly ash transfer conveyor 32.

Therefore, the wastewater treatment device 6 for treating the drainage wastewater from the wet smoke cleaning tower 4 needs only to remove simple heavy metals, and the wastewater treatment device 6 is simple in structure and small in size.
In addition, since the salts contained in the drainage waste water from the smoke tower 4 and the high-concentration acidic gas components in the exhaust gas are neutralized and precipitated are continuously discharged out of the system by the treatment as described above. , Salt concentration in the exhaust gas treatment system can be prevented.

  After the above operation, the exhaust gas exiting the bag filter 3 is sent to the wet smoke tower 4 through the exhaust gas pipe 11 by the exhaust gas fan 7, where acid gas components and the like are completely removed and then passed through the exhaust gas pipe 18. Then, it is combined with the exhaust gas on the incinerator (not shown) side or discharged to the outside.

  Further, by adding an appropriate amount (a small amount) of NaOH to the temperature-reduced water in the water supply tank 5, the high-concentration acidic gas component in the exhaust gas is weakly acidic by making wet contact with the exhaust gas with alkaline temperature-reduced water in the temperature-reducing device 2. And sent to the bag filter 3 to suppress low temperature corrosion caused by acid gas in the bag filter 3.

  In the above embodiment, in order to avoid clogging of the spray nozzle of the temperature reducing device 2, the salt content contained in the drainage waste water is once dissolved as an alkaline solution by adding NaOH supplied in the water tank 5, and then reduced. It is necessary to supply the temperature device 2 and neutralize the high-concentration acidic gas component in the exhaust gas with the temperature decrease device 2 so as to precipitate salts. It is preferable to make the degree of weak alkalinity, to suppress the alkalinity of the temperature-reduced water in the water tank 5 as low as possible, and to prevent the formation of salts in the water tank 5.

FIG. 2 is a system diagram of an exhaust gas treatment system for a plasma melting furnace showing a second embodiment of the present invention.
In this embodiment, the wet smoke cleaning tower 4 and the waste water treatment device 6 attached thereto are installed on the incinerator (not shown) side in the first embodiment.

Therefore, in this embodiment, the wet smoke tower 4, the waste water treatment device 6, and the drain pipe 15 connecting the waste water treatment device 6 and the water tank 5 are removed from the apparatus of FIG. The exhaust gas that has passed through is mixed with the exhaust gas on the combustion furnace side and introduced into the wet smoke cleaning tower 40.
Also, an appropriate amount (small amount) of NaHCO ₃ (sodium bicarbonate) is added to the dewarmed water in the water tank 5.
Structures other than the above are the same as those of the first embodiment of FIG. 1, and the same members are denoted by the same reference numerals.

Also in this embodiment, a small amount of NaHCO ₃ is added to the temperature-decreasing water to the temperature reducing device 5 to make it alkaline, and this is sprayed into the exhaust gas by the temperature reducing device 2, thereby causing an acid gas component such as the bag filter 3. In addition to preventing low temperature corrosion, the temperature-reduced water becomes alkaline and is sprayed into the exhaust gas by the temperature-reducing device 2, so that the high-concentration acidic gas component in the exhaust gas is weakened by wet contact with the exhaust gas by the alkaline temperature-reduced water. Acidify to precipitate the salts.
The exhaust gas that has passed through the temperature reducing device 2 is introduced into the bag filter 3 through the exhaust gas pipe 19 together with the precipitated salts and fly ash, where the precipitated salts and fly ash are removed.

  As described above, according to the first and second aspects of the invention, the drainage waste water from the wet smoke squeezing tower is mixed with the temperature-decreasing water and sent to the temperature-decreasing device. The salt in the drained waste water is mixed into the exhaust gas by spraying the mixed temperature-reduced water in the temperature reducing device, sent to the bag filter, and reliably removed by the bag filter.

  As a result, the wastewater treatment apparatus for treating the drained wastewater from the wet smoke cleaning tower only needs to remove a simple heavy metal, and the structure of the wastewater treatment apparatus is simplified and miniaturized to reduce the apparatus cost.

  In addition, it is possible to continuously discharge the salt contained in the drainage drained from the smoke tower by the treatment with the temperature reducing device and the bag filter, thereby preventing the concentration of the salt in the exhaust gas treatment system. Can do.

According to the third and fourth aspects of the invention, an appropriate amount of a base such as NaOH or NaHCO ₃ is added to the temperature-reduced water to make the temperature-reduced water alkaline, and this is sprayed into the exhaust gas to flow through the bag filter. As a result, the alkaline spray is sent to the bag filter, whereby low temperature corrosion due to the acid gas of the bag filter can be prevented.

  Further, even when the wet smoke cleaning tower is installed on the incinerator side, low temperature corrosion due to acidic gas components such as a bag filter can be similarly prevented.

1 is a system diagram of an exhaust gas treatment system for a plasma melting furnace according to a first embodiment of the present invention. It is a figure corresponding to FIG. 1 which shows 2nd Example of this invention. It is a figure corresponding to FIG. 1 which shows the prior art which this applicant examined.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma melting furnace 2 Temperature reduction apparatus 3 Bag filter 4 Wet smoke-wash tower 5 Water supply tank 6 Waste water treatment device 7 Exhaust gas fan 9 Temperature-reduction water pipe 10, 11, 19 Exhaust gas pipe 15 Drain pipe 40 Wet smoke washing equipment (incinerator side)

Claims (4)

  When the exhaust gas from the ash melting furnace is subjected to purification treatment while passing through a temperature reducing device, a bag filter, and a wet smoke cleaning equipment in order, with the temperature reduction water supplied from the water tank, the wet smoke cleaning equipment is pulled out. A molten exhaust gas treatment method, wherein waste water is introduced into the water tank, supplied to the temperature reducing device from the water tank, and sprayed as temperature-reduced water.   The molten exhaust gas treatment method according to claim 1, wherein the exhaust gas from the ash melting furnace is mixed with the exhaust gas on the combustion furnace side and introduced into a wet smoke tower. The molten exhaust gas treatment method according to claim 1 or 2, wherein a base component such as NaOH or NaHCO ₃ is added to the temperature-reduced water to form alkaline temperature-reduced water, which is supplied to the temperature decrease device. The molten exhaust gas treatment method according to claim 1 or 2, wherein a base component such as NaOH or NaHCO ₃ is added to the water tank to form alkaline temperature-reduced water, and then supplied to the temperature decrease device as temperature-reduced water.

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