JP2000070663A - Exhaust gas cooling and harmful substance removing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas cooling and harmful substance removing method capable of simultaneously performing the cooling of exhaust gas and the removal of a harmful substance by one apparatus, capable of keeping the removal ratio of the harmful substance high, also preventing the re-synthesis of dioxin, not taking an apparatus arranging space and capable of suppressing equipment cost or running cost relatively low. SOLUTION: In a method for cooling exhaust gas and removing a harmful substance in the exhaust gas, a fluidized bed treatment apparatus 1 is used and, in such a state that the fluidizing chamber 2 of this apparatus 1 is packed, for example, with granular activated carbon with a size of 0.3-4.0 mm, the exhaust gas is sent into the fluidizing chamber 2 to fluidize activated carbon and a cooling liquid is sprayed and dripped on activated carbon to remove the heat of the exhaust gas to lower the temp. thereof and the harmful substance in the exhaust gas is bonded to activated carbon to remove the harmful substance from the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cooling exhaust gas from a garbage incinerator or the like and removing harmful substances from the exhaust gas.

[0002]

BACKGROUND OF THE INVENTION In recent years, harmful substances such as dioxins generated from exhaust gas from garbage incinerators have become a problem, and there is a technical problem how to reduce such harmful substances such as dioxins. As the treatment of exhaust gas from current garbage incinerators, the exhaust gas is cooled and harmful substances in the exhaust gas are removed, thereby preventing generation and emission of harmful substances such as dioxins.

[0003] First, a method of cooling exhaust gas will be described.
The reason why the exhaust gas is cooled (quenched) is that dioxins are easily resynthesized in a temperature range of 200 to 500 ° C., so that the exhaust gas temperature does not remain in this temperature range. The above exhaust gas is rapidly cooled to 200 ° C. or less at a stretch. Conventional refuse incinerator cooling methods for this purpose include water spray,
There are methods using a scrubber, air dilution, and a heat exchanger. In addition, the applicant has filed a patent application filed in Japanese Patent Application
A method using a fluidized bed treatment apparatus as disclosed in JP-A-88012 has also been proposed.

However, the above-described exhaust gas cooling method has the following problems. That is, in the conventional cooling method, the size of the apparatus as a whole is increased due to the necessity of related auxiliaries and the like, and equipment for performing wastewater treatment is required. Further, there is a problem that dioxins are easily re-synthesized because dioxins themselves are not removed by the cooling method alone, but only the generation environment is eliminated. Further, the aforementioned Japanese Patent Application No. Hei 10-88012
No. 2 shows an embodiment in which a medium sphere such as an alumina ball is fluidized in a fluidized bed of a fluidized-bed processing apparatus, and an alkali solution or the like is supplied thereto and exhaust gas is passed therethrough. However, it has a high pressure loss in the fluidized bed portion and has a cost increase factor in that the power of the exhaust fan must be increased.

On the other hand, as a conventional method of removing harmful substances, quick lime is put into an incinerator, slaked lime and activated carbon are blown into exhaust gas and collected with a bag filter, and the exhaust gas is further discharged into an activated carbon adsorption tower or a catalyst tower. The method of passing is adopted. However, the method for removing harmful substances in exhaust gas as described above has the following problems. That is, in the conventional method for removing harmful substances, for example, in collecting bugs, the removal rate of dioxins is about 80%, and the removal ability is not sufficient. In addition, the removal apparatus such as the activated carbon adsorption tower and the catalyst tower has a problem that the equipment cost is large because the apparatus takes a large space and a separate cooling device is required.

[0006]

[Technical Problems Attempted to Be Developed] The present invention has been made in view of such a background, and a single device can simultaneously cool exhaust gas and remove harmful substances, and maintain a high harmful substance removal rate. A new exhaust gas cooling and harmful substance removal method that can prevent the resynthesis of dioxins, prevent the installation space of equipment, and keep the equipment cost and running cost relatively low. It is.

[0007]

According to a first aspect of the present invention, there is provided a method for cooling exhaust gas and removing harmful substances, the method comprising the steps of: The exhaust gas is sent into the fluidized chamber with the activated carbon in the chamber, and the activated carbon is fluidized by the exhaust gas, and at the same time, the temperature of the exhaust gas is lowered by removing the heat of the exhaust gas by the cooling liquid supplied into the fluidized bed, The method is characterized by removing harmful substances from exhaust gas by attaching harmful substances in the exhaust gas.

The method for cooling exhaust gas and removing harmful substances according to claim 2 is characterized in that, in addition to the above requirements, the activated carbon is granular.

Further, the method for cooling exhaust gas and removing harmful substances according to claim 3 is characterized in that, in addition to the requirements described in claim 2, the size of the particles of the activated carbon is 0.3 to 4.0 mm. It consists of.

According to a fourth aspect of the present invention, there is provided a method for cooling exhaust gas and removing harmful substances, wherein the activated carbon has a particle size distribution of 0.5 to 1.0 m.
m.

Further, the method for cooling exhaust gas and removing harmful substances according to claim 5 is the same as that of claim 1, 2, 3, or 4.
In addition to the stated requirements, the exhaust gas is exhaust gas exhausted from an incinerator.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. In the following description, first, an apparatus used for the method for cooling exhaust gas and removing harmful substances according to the present invention will be described, and then the method for cooling exhaust gas and removing harmful substances according to the present invention will be described together with the operation mode of this apparatus. In this embodiment, an embodiment is shown in which harmful substances such as dioxins in the exhaust gas of an incinerator are removed and the temperature of the exhaust gas is cooled to 200 ° C. or lower.

An apparatus indicated by reference numeral 1 in FIG. 1 is a fluidized bed treatment apparatus, which cools exhaust gas and removes harmful substances in the exhaust gas. The fluidized bed processing apparatus 1 has a substantially tower shape, has a fluid chamber 2 at an intermediate stage, and has an exhaust gas blowing chamber 4 below which exhaust gas from an incinerator is blown from a blowing port 4a. Further, an exhaust chamber 3 for exhausting exhaust gas from which harmful substances have been removed is provided above the flow chamber 2. The flow chamber 2 and the exhaust gas blowing chamber 4 are separated by a perforated plate 2A having a plurality of perforations. Activated granular carbon is put in the fluidized chamber 2 and is made to flow by exhaust gas. Reference numeral 7 denotes a liquid supply device for supplying a cooling liquid. In this embodiment, water is used as the cooling liquid. In addition, a liquid that neutralizes harmful substances in exhaust gas, for example, an alkaline solution is used. You may do so. Further, a stirring device for stirring the activated carbon, a circulating device for circulating water falling from the flow chamber 2 to the exhaust gas blowing chamber 4 to the flow chamber 2 again, and the like may be appropriately provided in the flow chamber 2.

The exhaust chamber 3 in the fluidized bed processing apparatus 1 includes:
A bag filter 6 is connected, where dust in exhaust gas and powder from activated carbon are further collected and exhausted through an exhaust fan 8. The foreign matter collected by the bag filter 6 is taken out from a lower outlet 6a.

The liquid supply device 7 will be described. The liquid supply device 7 includes a liquid tank 7A for storing a cooling liquid, a valve 7
B and a liquid supply pump 7C. A supply pipe extends from the bottom of the liquid pump to the fluidized bed processing apparatus 1, and a cooling liquid is sprayed or dropped from a nozzle 5 in the fluidized chamber 2 toward the fluidized bed.

The specific form of the apparatus used in the method for cooling exhaust gas and removing harmful substances according to the present invention is as described above, and the method for cooling exhaust gas and removing harmful substances according to the present invention will be described together with the operation mode. Will be described. Exhaust gas discharged from the incinerator is supplied to the inlet 4 of the fluidized bed treatment apparatus 1.
a is ejected into the flow chamber 2 through the perforated plate 2A.
Activated carbon is contained in the flow chamber 2, and these are made to flow by the exhaust gas. Here, the cooling liquid is sprayed or dropped and adheres to the surface of the activated carbon. Since the activated carbon to which moisture has adhered is in a fluid state and comes into contact with the exhaust gas very efficiently, the exhaust gas is quenched to 200 ° C. or less, while harmful substances such as dioxins in the exhaust gas are adsorbed by the activated carbon. Then, the purified exhaust gas is discharged from the exhaust chamber 3 to the bag filter 6. The solid matter is removed in the bag filter 6 and exhausted through the exhaust fan 8. Exhaust gas is rapidly cooled to 200 ° C. or lower, and precursors involved in the synthesis of dioxins are also removed, so that dioxins are not resynthesized. Since activated carbon has a low specific gravity, the fluidized bed pressure loss is smaller than when alumina balls are used as a fluidized medium, and therefore, the power of the exhaust fan 8 can be suppressed to a small value.

[0017]

Next, specific experimental examples using the method for cooling exhaust gas and removing harmful substances according to the present invention will be described with reference to data obtained at this time. As shown in FIG.
The devices used in the experiments of the present invention are basically the same as those described in the above-described embodiment, and are provided with devices for producing gas assuming exhaust gas and various measuring instruments. Become.

Devices other than the fluidized bed processing device 1, the bag filter 6, the liquid supply device 7, and the like will be described.
The device indicated by reference numeral 9 is a blower fan for introducing outside air. The flow rate of the outside air introduced by the blowing fan 9 is measured by the orifice 10. Some of this outside air is directly blown into the blowing port 4a of the fluidized bed processing apparatus 1, and the remaining outside air is supplied to two heaters 11A,
It is heated by 11B and is blown into the blowing port 4a.

The device denoted by reference numeral 12 is a burette, and monochlorobenzene, which is a substitute for dioxin, is supplied to the blow-in port 4a of the fluidized bed processing apparatus 1 while measuring a predetermined amount. Since monochlorobenzene is also one of the precursors of dioxin, it is shown that dioxin is reduced if it is removed according to the present invention.

The device denoted by reference numeral 13 is a weighing scale.
Measure the water supply weight. Further, a thermometer is provided in each of the exhaust chamber 3 and the exhaust gas blowing chamber 4 to measure the temperature of the inspection gas. The device indicated by reference numeral 14 is a fluidized-bed pressure-loss measuring device using, for example, a water column pressure gauge and the like, for inspecting a pressure loss caused by a test gas passing through a fluidized bed.

The fluidized bed processing apparatus 1 has a fluidized bed area of 0.1.
05 m ² , and the temperature of the exhaust gas
And the test gas is cooled by spraying a cooling liquid so that the temperature of the exhaust chamber 3 becomes 150 ° C. In the experiment, a fluidized medium was a column of activated carbon (upper and lower surfaces having a diameter of 3 mm and a height of 3 mm) and crushed activated carbon (having a particle size of 0.5 to 1.7 mm).
And two types of 0.36 to 0.85 mm) and alumina balls (diameter: 2 mm). The fluidized bed pressure loss and the removal rate of monochlorobenzene were inspected by changing the input amounts for each.

The results are as shown in Table 1 below. The best removal rate of monochlorobenzene was obtained when the removal rate of Run3 was 99%. At this time, 6.8 kg of granular activated carbon having a particle size of 0.5 to 1.7 mm was charged and the experiment was performed. . At this time, the concentration of monochlorobenzene, which had been set to 26 ppm at the time of blowing, was reduced to 0.3 ppm, and the pressure loss of the fluidized bed material was 136 mm.
Aq.

When alumina balls were used as the fluid medium, the concentration of monochlorobenzene did not decrease as shown in Run 1. Alumina balls have a large pressure loss in the fluidized bed material, and if the amount is further reduced, the dispersion of water becomes worse. The upper and lower surfaces are 3 mm in diameter and 3 to 8 mm in height
In the case of using columnar activated carbon, Run7 or Run
As shown in FIG. 8, the removal rate of morochlorobenzene was smaller than that of Runs 2 to 6 using the crushed charcoal, which had similar conditions.

[0024]

[Table 1]

[0025]

According to the method for cooling exhaust gas and removing harmful substances according to the first aspect of the present invention, the exhaust gas is fed into the fluid chamber 2 using the fluidized bed treatment apparatus 1 while the activated carbon is put in the fluid chamber 2. Since the activated carbon is fluidized and the cooling liquid is sprayed or dropped thereon, the exhaust gas is rapidly cooled and harmful substances such as dioxins can be removed from the exhaust gas by adsorbing the activated carbon. In addition, the heat of the exhaust gas is quickly taken away to lower the temperature, and the precursors (harmful substances) involved in the synthesis of dioxins are removed, so that the dioxins are resynthesized after the exhaust gas is cooled. Is also prevented. Despite the improved performance of each unit, which has both cooling and harmful substance removal functions, it can be provided as a relatively compact unit. The equipment does not become large like a toxic substance removal equipment such as a tower.

According to the method for cooling exhaust gas and removing harmful substances according to the second aspect, since the activated carbon is granular, the fluidized bed pressure loss can be reduced as compared with the case where alumina balls are used as the fluidized medium. The power can be kept small. Also, the adsorption surface area of activated carbon is large, and the removal rate of harmful substances is also large.

According to the method for cooling exhaust gas and removing harmful substances according to the third aspect, the size of the activated carbon particles is 0.3 to
Since it is 4.0 mm, the flow state of the activated carbon is good, the harmful substance removal rate is excellent, and the fluidized bed pressure loss is small.

According to the method for cooling exhaust gas and removing harmful substances according to the fourth aspect, the particle size distribution of the activated carbon is adjusted to 0.5 to 0.5%.
Since it is within the range of 1.0 mm, the activated carbon is uniformly dispersed in the fluidized bed, the harmful substance removal rate is further excellent, and the fluidized bed pressure loss is reduced.

According to the method for cooling exhaust gas and removing harmful substances according to the fifth aspect, since dioxins are mostly generated from a garbage incinerator, the present invention is applied to an incinerator to reduce dioxins. Generation is largely prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of a method for cooling exhaust gas and removing harmful substances according to the present invention.

FIG. 2 is an explanatory view showing an embodiment of the method for cooling exhaust gas and removing harmful substances according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluidized bed processing apparatus 2 Fluid chamber 2A Perforated plate 3 Exhaust chamber 4 Exhaust gas blowing chamber 4a Inlet 5 Nozzle 6 Bag filter 6a Outlet 7 Liquid supply device 7A Liquid tank 7B Valve 7C Liquid supply pump 8 Exhaust fan 9 Blow fan 10 Orifice 11A Heater 11B Heater 12 Bullet 13 Weight scale 14 Fluidized bed pressure loss measuring instrument

Continued on front page F term (reference) 4D002 AA21 AC04 BA04 BA12 BA13 BA14 CA01 CA09 DA35 DA41 GA02 GA03 GB01 GB02 GB03 GB04 GB06 GB12 HA08 4D012 CA12 CC14 CE01 CE02 CF02 CF03 CF04 CF05 CF06 CG05 CH01 CJ05 CK01

Claims (5)

[Claims] 1. A method for cooling effluent gas and removing harmful substances in the effluent gas, using a fluidized bed treatment apparatus, sending the effluent gas into the fluidized chamber with the activated carbon contained in the fluidized chamber, Fluidize,
At the same time, the temperature of the exhaust gas is lowered by depriving the heat of the exhaust gas by the cooling liquid supplied into the fluidized bed, and the harmful substance is removed from the exhaust gas by attaching the harmful substance in the exhaust gas to the activated carbon. Method of cooling exhaust gas and removing harmful substances. 2. The method for cooling exhaust gas and removing harmful substances according to claim 1, wherein said activated carbon is granular. 3. The activated carbon has a grain size of 0.3 to 0.3.
3. The method for cooling exhaust gas and removing harmful substances according to claim 2, wherein the diameter is 4.0 mm. 4. The particle size distribution of said activated carbon is 0.5 to 1.
4. The method for cooling exhaust gas and removing harmful substances according to claim 2, wherein the diameter is within a range of 0 mm. 5. The exhaust gas according to claim 1, wherein the exhaust gas is exhaust gas exhausted from an incinerator.
The method for cooling exhaust gas and removing harmful substances according to the above.