JPH11211065A - Apparatus and method for treating melted exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of a low temperature corrosion in a bag filter by simplifying a structure of a drain treating unit for drawing and draining from a wet type smoke cleaning facility and reducing its cost in an exhaust gas treating system for treating an exhaust gas from an ash melting furnace via a temperature lowering unit, the bag filter and the cleaning facility. SOLUTION: The apparatus for treating a melted exhaust gas comprises a temperature lowering unit 2 for lowering a temperature of an exhaust gas from an ash melting furnace 1 with a temperature lowering water supplied from a feed water tank 5, a bag filter 3 and a wet type smoke cleaning facility sequentially provided to clean it. In this case, drawn and drain water of the cleaning facility is introduced into the tank 5, and supplied as a temperature lowering water from the tank 5 to the unit 2. And, a salt content precipitated in the drain water is treated by the filter 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for purifying molten exhaust gas by passing exhaust gas from an ash melting furnace such as a plasma melting furnace through a temperature reducing device, a bag filter, and a wet smoke washing facility in order. The present invention relates to an apparatus and a processing method.

[0002]

2. Description of the Related Art FIG. 3 is a system diagram showing an example of a prior art of an exhaust gas treatment system for a plasma melting furnace attached to a waste incinerator. In FIG. 3, 1 is a plasma melting furnace, 8 is a hopper for charging a combustion treatment product such as industrial waste into the melting furnace 1, 10 is an exhaust gas pipe from the plasma melting furnace 1,
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 via the exhaust gas pipe 10. Reference numeral 3 denotes a bag filter for removing fly ash and the like from the melting furnace in the gas, which is provided with a heater 31 and a fly ash transport conveyor 32, and transports fly ash after removal to fly ash processing equipment (not shown). Reference numeral 19 denotes an exhaust gas pipe connecting the temperature reducing device 2 and the bag filter 3.

[0003] Reference numeral 4 denotes a wet-type smoke washing tower for removing high-concentration acidic gas components in the exhaust gas, which is brought into wet contact with the high-concentration acidic gas components by alkaline water added from a NaOH tank 41 to precipitate salts. Reference numeral 11 denotes an exhaust gas pipe for connecting the bag filter 3 and the wet-type smoke washing tower 4, and the exhaust gas pipe 11 is provided with an exhaust gas fan 7 for sending exhaust gas under pressure. 18
Is an exhaust gas pipe connected to the outlet of the wet smoke washing tower 4.
Reference numeral 6 denotes a wastewater treatment device for removing heavy metals and the like in the wastewater drawn out from the wet-type smoke washing tower 4.
Reference numeral 5 denotes a water supply tank in which the temperature-reducing water to be supplied to the temperature-reducing device 2 is stored.

When the exhaust gas treatment system of the melting furnace is operated, 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, temperature-reduced water introduced from the water supply tank 5 through the temperature-reducing water pipe 9 is sprayed into the exhaust gas to adjust the exhaust gas temperature to a required inlet temperature of the bag filter 3 (preferably about 150 ° C. to 160 ° C.). Let cool down. Exhaust gas that has passed through the temperature reducing device 2 is introduced into the bag filter 3 through an exhaust gas pipe 19 to remove fly ash and the like in the melting furnace, and the fly ash is supplied to a fly ash treatment facility (not shown) via a fly ash conveyor 32. Transport to

The exhaust gas having passed through the bag filter 3 is sent by an exhaust gas fan 7 through an exhaust gas pipe 11 to a wet-type smoke washing tower 4 where high-concentration acidic gas components are removed. It is combined with the exhaust gas on the furnace (not shown) side or discharged outside. The wet smoke tower 4
After the heavy metals are removed in the wastewater treatment device 6, the wastewater extracted from the wastewater is discharged or sent to an incinerator-side wastewater treatment device (not shown).

[0006]

In such an exhaust gas treatment system for a plasma melting furnace, a large wet-type smoke cleaning tower is installed on the side of a waste incinerator (not shown) provided with the plasma melting furnace. After mixing the flue gas from the melting furnace after dust reduction in the bag filter 3 with the flue gas on the incinerator side, batch treatment is performed in the wet smoke washing tower 4.

However, in the case where only a dry type exhaust gas treatment facility is installed on the incinerator side, FIG.
As shown in the figure, it is necessary to provide the wet smoke washing tower 4 alone in the exhaust gas treatment system on the plasma melting furnace 1 side.

For this reason, the plasma melting furnace 1 as described above
In a system in which a wet-type smoke washing tower 4 is provided in the exhaust gas treatment system on the side, if heavy water is removed from the smoke washing tower 4 and the wastewater can be discharged to the sewer as it is, removal of heavy metals in the wastewater by a simple wastewater treatment device However, if the discharge is not possible, the drainage drain of the wet-type smoke washing tower 4 requires complicated maintenance and is provided with a wastewater treatment device 6 having a function of removing a wide range of substances. And the structure of the wastewater treatment device 6 becomes complicated and large, resulting in high cost.

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 (reduce) the temperature of the exhaust gas to the required exhaust gas temperature at the inlet of the bag filter 3. There is a problem that low-temperature corrosion due to acid gas components occurs in such devices.

In view of the above-mentioned problems of the prior art, the present invention provides an exhaust gas treatment system for treating exhaust gas from an ash melting furnace through a temperature reducing device, a bag filter, and a wet smoke cleaning device. It is an object of the present invention to simplify the structure of a wastewater treatment device for drawing wastewater treatment, reduce the cost of the device, and prevent low-temperature corrosion in the bag filter.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides, as a first invention, a temperature-reducing device for lowering the temperature of exhaust gas from an ash melting furnace by using temperature-reducing water supplied from a water supply tank, A filter and a molten flue gas treatment device that performs purification treatment by interposing a wet smoke cleaning facility in this order, and introducing drainage drainage of the wet smoke cleaning facility to the water supply tank,
The present invention proposes a molten exhaust gas treatment apparatus characterized in that the apparatus is configured to supply water as desuperheated water from the water supply tank to the desuperheater.

The wet smoke cleaning equipment is preferably installed in the exhaust gas pipe on the ash melting furnace side, but may be used also as the wet smoke cleaning equipment on the combustion furnace side.

According to the invention, the drainage water drawn out from the wet-type smoke cleaning equipment is introduced into the water tank after the heavy metal removal treatment is performed by the wastewater treatment device or as it is, and the temperature-reduced water and the water are discharged from the water tank. Mixed. (If a closed circuit is configured, the heavy metal removal process may not be performed.) Then, the mixed deheated water is sent to the deheater and sprayed into the exhaust gas, and the temperature of the exhaust gas is lowered to the required inlet temperature of the bag filter. Let it.

[0014] The mixed temperature-reduced water sprayed by the temperature-reducing device has been subjected to alkali treatment in the wet-type smoke-cleaning facility, so that salts in the extracted wastewater are mixed in. The salts (precipitated salts) are: The spray of the mixed temperature-reduced water is sent to the bag filter together with the mixed exhaust gas, and is removed together with the fly ash by the bag filter. Thus, the wastewater treatment device only needs to remove heavy metals.

Therefore, according to the invention, the drainage from the wet-type smoke washing facility is mixed with the desuperheated water and sent to the desuperheater.
By spraying the mixed temperature-reduced water into the exhaust gas, the (precipitated) salts in the drawn wastewater are mixed into the exhaust gas by the spray of the mixed temperature-reduced water in the temperature reduction device, sent to the bag filter, and sent to the bag filter. It is surely removed together with the fly ash.

Thus, the wastewater treatment device for treating the drainage water drawn from the wet-type smoke washing facility only needs to perform simple heavy metal removal, and the wastewater treatment device has a simple structure.
And a small one is enough. In the case where the drawn wastewater is circulated and used, a heavy metal treatment may be performed when the drawn wastewater is discharged outside. Further, according to the present invention, the (precipitated) salts contained in the drainage drawn from the smoke washing tower can be continuously discharged out of the system by the above treatment, and the concentration of the salts in the exhaust gas treatment system is prevented. be able to.

Further, a second invention relates to an exhaust gas treatment method using the exhaust gas treatment apparatus according to the first invention, wherein the temperature of the exhaust gas from the ash melting furnace is lowered by desuperheated water supplied from a water supply tank. At the time of purifying treatment through the temperature reducing device, the bag filter, and the wet-type smoke cleaning equipment, in this order, the drainage of the wet-type smoke cleaning equipment is introduced into the water supply tank, and supplied from the water supply tank to the temperature reducing apparatus. And sprayed as desuperheated water, and NaOH is added to the desuperheated water to form alkaline desuperheated water and supplied to the above-mentioned desuperheater.

According to the invention, an appropriate amount of Na
By adding OH, the desuperheated water becomes alkaline and is sprayed into the exhaust gas by the desuperheater, and the alkaline desuperheated water is brought into wet contact with the high-concentration acidic gas component to precipitate salts, and the high-concentration acidic gas component Is slightly acidified. 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 desuperheated water to make the desuperheated water alkaline, and this is sprayed into exhaust gas to weakly acidify high-concentration acidic gas components and to remove salts. By causing the bag filter to precipitate and flow through the bag filter, the salts can be removed from the bag filter and low-temperature corrosion of the bag filter due to the acidic gas can be prevented.

Further, NaHCO ₃ (baking soda) is added to the temperature-reduced water sprayed by the temperature-reducing device instead of NaOH.
This may be supplied to the temperature reducing device as alkaline temperature-reduced water.

According to this invention, when a wet smoke washing facility is installed on the incinerator side, an appropriate amount of NaHCO ₃ is added to the desuperheated water, and the deheated device is sprayed into the exhaust gas to make it alkaline, and the By sending the filter to the filter, it is possible to prevent salt precipitation and low-temperature corrosion due to an acidic gas component such as a bag filter in the same manner as described above. In addition, NaOH or Na
It is obvious that the same effect can be obtained by adding another basic component instead of HCO ₃ .

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now 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, and are merely illustrative examples. Only.

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, reference numeral 1 denotes a plasma melting furnace, 8 denotes a hopper for charging combustion products such as industrial wastes into the melting furnace 1, 10 denotes an exhaust gas pipe from the plasma melting furnace 1, and 17 denotes 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 via the exhaust gas pipe 10. Reference numeral 3 denotes a bag 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 removed fly ash to a fly ash processing facility (not shown). Reference numeral 19 denotes an exhaust gas pipe connecting the temperature reducing device 2 and the bag filter 3.

Reference numeral 4 denotes a wet smoke washing tower for removing high-concentration acidic gas components in the exhaust gas, which is brought into wet contact with the high-concentration acidic gas components by alkaline water added from the NaOH tank 41 to precipitate salts. Reference numeral 11 denotes an exhaust gas pipe for connecting the bag filter 3 and the wet-type smoke washing tower 4, and the exhaust gas pipe 11 is provided with an exhaust gas fan 7 for feeding exhaust gas under pressure. 18
Is an exhaust gas pipe connected to the outlet of the wet-type smoke washing tower. 5
Numeral 9 denotes a water supply tank for storing the temperature-reducing water to be supplied to the temperature-reducing device 2, and numeral 9 denotes 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 drainage of the wet smoke washing tower 4 is improved. That is, in FIG. 1, 6 is a wastewater treatment device,
As described above, the drainage drained from the wet-type smoke washing tower 4 is introduced to remove heavy metals in the drainage. It is connected to the water supply tank 5 through the above. Further, NaOH is added to the water supply tank 5 together with the drawn drainage so that the temperature-reduced water becomes alkaline temperature-reduced water.

During operation of the exhaust gas treatment system of the plasma melting furnace having the above-mentioned configuration, the drainage water extracted from the wet-type smoke washing tower 4 is sent to the wastewater treatment device 6, where heavy metals in the wastewater are removed. The drawn wastewater from which heavy metals have been removed by the wastewater treatment device 6 is sent to the water supply tank 5 through the drainage pipe 15 and mixed with the temperature-reduced water in the water supply tank 5. The water tank 5 contains a small amount of N as described later.
aOH (sodium hydroxide) is also mixed in, so that the temperature-reduced water becomes alkaline temperature-reduced water.

The mixed temperature-reduced water in the water supply tank 5, that is, the temperature-reduced water mixed with the drawn drainage 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 supply tank 5 through the temperature-reducing water pipe 9 is sprayed into the exhaust gas, and the temperature of the exhaust gas is adjusted to the required inlet temperature of the bag filter 3 (150 ° C.). (Approximately 160 ° C. is preferable), and the temperature-reduced water becomes alkaline and is sprayed into the exhaust gas by the temperature-reducing device 2. The acid gas component is weakly acidified to precipitate salts. The exhaust gas having 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,
In the mixed temperature-reduced water sprayed into the exhaust gas by the temperature-reducing device 2, the salts in the wastewater drawn out from the wet-type smoke washing tower 4 are also alkali-dissolved by the alkaline temperature-reduced water and precipitated again by the temperature-reducing device 2. It is sent to the bag filter 3. And
In the bag filter 3, solid components such as the salts and fly ash are removed, and these are transported to the fly ash processing equipment via the fly ash transport conveyor 32.

Therefore, the wastewater treatment apparatus 6 for treating the drainage water extracted from the wet-type smoke washing tower 4 only requires simple heavy metal removal. The wastewater treatment apparatus 6 has a simple structure and a small size. Is enough. Further, the salts contained in the wastewater drawn out from the smoke washing tower 4 and the salts precipitated by neutralizing the high-concentration acidic gas components in the exhaust gas are continuously discharged out of the system by the treatment as described above. In addition, the concentration of salts in the exhaust gas treatment system can be prevented.

After the above operation, the exhaust gas that has exited the bag filter 3 is sent by the exhaust gas fan 7 through the exhaust gas pipe 11 to the wet-type smoke washing tower 4 where acid gas and the like are completely removed. After passing through 18, the waste gas is combined with the exhaust gas from the incinerator (not shown) or discharged outside.

The temperature-reduced water in the water supply tank 5 contains NaOH.
Is added in an appropriate amount (small amount) to bring the exhaust gas into wet contact with the exhaust gas in the desuperheater 2 with alkaline deheated water, whereby the high-concentration acidic gas component in the exhaust gas is weakly acidified and sent to the bag filter 3, where Low temperature corrosion due to acid gas in the filter 3 is suppressed.

In the above-described embodiment, in order to avoid clogging of the spray nozzle of the temperature reducing device 2, the salt contained in the drawn drainage is once dissolved as an alkaline solution by adding NaOH supplied in the water supply tank 5. After that, it is necessary to supply the mixture to the temperature reducing device 2 to neutralize the high-concentration acidic gas component in the exhaust gas to precipitate salts. It is preferable that the degree of alkalinity of the hot water is set to a weak alkali level, the alkalinity of the desuperheated water in the water supply tank 5 is kept as low as possible, and the generation of salts in the water supply tank 5 is prevented.

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

Accordingly, in this embodiment, the wet-type smoke washing tower 4, the wastewater treatment device 6, and the drainage pipe 15 connecting the wastewater treatment device 6 and the water supply tank 5 are removed from the device shown in FIG. The exhaust gas having passed through the blower 7 is mixed with the exhaust gas on the combustion furnace side and introduced into the wet smoke washing tower 40. Also,
An appropriate amount (a small amount) of NaHCO ₃ (baking soda) is added to the temperature-reduced water in the water supply tank 5. The configuration other than the above is the first configuration in FIG.
This is the same as the embodiment, 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-reduced water to the temperature-reducing device 5 to make it alkaline.
By spraying this into the exhaust gas with the temperature reducing device 2,
In addition to preventing low-temperature corrosion caused by acidic gas components such as the bag filter 3, the temperature-reduced water becomes alkaline and the temperature-reducing device 2
Is sprayed into the exhaust gas, so that the high-concentration acidic gas component in the exhaust gas is weakly acidified by wet contact with the exhaust gas by the alkaline temperature-reduced water to precipitate salts. The exhaust gas that has passed through the temperature reducing device 2 is mixed with precipitated salts and fly ash together with the exhaust gas pipe 1.
9 to the bag filter 3, where the precipitated salts and fly ash are removed.

[0037]

As described above, according to the first aspect of the present invention, the extracted wastewater from the wet-type smoke washing tower is mixed with deheated water and sent to a deheater, and the mixed deheated water is sprayed into exhaust gas. With this configuration, the salts in the drawn wastewater are mixed into the exhaust gas by spraying the mixed deheated water in the desuperheater, sent to the bag filter, and reliably removed by the bag filter.

Thus, in the wastewater treatment apparatus for treating the wastewater extracted from the wet-type smoke washing tower, it is only necessary to perform simple removal of heavy metals, and the structure of the wastewater treatment apparatus is simplified, the size of the wastewater treatment apparatus is reduced, and the cost of the apparatus is reduced. Is done.

Further, it is possible to continuously discharge the salts contained in the drainage water drawn out from the smoke washing tower to the outside of the system by the treatment with the temperature reducing device and the bag filter. Can be prevented.

[0040] According to the invention of claim 2, the alkaline reducer warm water by adding an appropriate amount of NaOH and NaHCO ₃ and the like of bases in reduced hot water, flowing through the bag filter which was sprayed into the exhaust gas As a result, the alkaline spray is sent to the bag filter, whereby low-temperature corrosion of the bag filter due to acidic gas can be prevented.

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

[Brief description of the drawings]

FIG. 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.

FIG. 2 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 3 is a diagram corresponding to FIG. 1 showing a conventional technique.

[Explanation of symbols]

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

Claims (2)

[Claims] 1. A molten exhaust gas for purifying exhaust gas from an ash melting furnace by interposing a temperature reducing device for lowering the temperature of the exhaust gas from the ash melting furnace with deheated water supplied from a water supply tank, a bag filter, and a wet smoke cleaning facility in this order. In the treatment apparatus, a molten exhaust gas treatment apparatus is configured to introduce drawn wastewater from the wet-type smoke cleaning facility into the water supply tank and supply the wastewater from the water supply tank to the temperature reduction device as desuperheated water. 2. A process for purifying exhaust gas from an ash melting furnace by sequentially passing the exhaust gas from a ash melting furnace through a temperature-reducing device for lowering the temperature of the exhaust gas from a water tank, a bag filter, and a wet-type smoke cleaning facility. The drainage water from the smoke washing facility is introduced into the water tank, and supplied from the water tank to the temperature reducing device to be sprayed as temperature-reduced water, and a basic component such as NaOH or NaHCO ₃ is added to the temperature-reduced water to add alkaline water. A method for treating molten exhaust gas, wherein the method is supplied as desuperheated water to the desuperheater.