JPH11325452A - Method and apparatus for processing waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect, when condensation is produced owing to a change in properties of waste gas, the condensation from pressure loss through a bag filter, and hence raise waste gas cooling temperature for prevention of the condensation, and further effectually exfoliate an adherant on the surface of the bag filter, by improving a removal rate of harmful matter by cooling the waste gas at relatively low temperature. SOLUTION: The present apparatus includes an incinerator 1 for incinerating waste and the like, a gas condenser 2 for cooling waste gas G1 produced in the incinerator 1, a first detector 8 for detecting temperature of the waste gas cooled in the gas condenser 2, a bag filter 6 for separating dust and the like in the waste gas, a second detector 9 for detecting pressure loss in the waste gas passing through the bag filter 6, and control means 10 for outputting a control signal for waste gas cooling temperature. Herein, signals from the first detector 8 and the second detector 9 are inputted into the control means 10, and cooling temperature of the waste gas in the gas condenser 2 is controlled with a control signal V4 from the control means 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating exhaust gas, and more particularly, to a method for combusting a decomposed gas produced by burning waste or the like or thermally decomposing waste or the like with a combustible component. The present invention relates to a method for treating exhaust gas generated by combustion and an apparatus for carrying out the method.

[0002]

2. Description of the Related Art Generally, pyrolysis gas generated by burning general waste such as municipal solid waste or combustible waste such as industrial waste such as waste plastic, or by pyrolyzing such waste. Exhaust gas generated by burning oxygen and combustible components (mainly carbon) is cooled by a gas cooler and then supplied with a chemical agent such as an alkali reactant or an auxiliary agent, and supplied to a dust collector to remove dust and gas. Cleaning is to be performed.

That is, as shown in FIG. 3, an exhaust gas G ₁ generated by burning waste in the incinerator ₁ is about 90%.
At a high temperature of about 0 ° C., sulfur oxides and for containing toxic substances such as hydrogen chloride or heavy metal compounds, the relatively low temperature of about 200 ° C. is cooled by the gas cooler 2 gas G ₂
Next, the exhaust gas G agent a such ₂ alkaline reactant and activated carbon and aids such as slaked lime is introduced, it is supplied to the dust collector 3, such as bag filter thereafter. Then, the injected chemicals and dust are separated, and the clean exhaust gas G is removed.
It is emitted to the atmosphere from chimney 4 as ₃ . As the gas cooler 2, a waste heat boiler, an air preheater, or a cooling tower as a heat recovery device is appropriately selected.

[0004]

However, in the above-mentioned method for treating exhaust gas, it is not always possible to sufficiently remove harmful substances contained in the exhaust gas, in particular, dioxin, which has recently been regarded as a problem. There's a problem. That is, FIG. 4 shows the relationship between the temperature of the exhaust gas and the dioxin removal rate. As is clear from FIG. 4, the dioxin removal rate increases when the temperature falls below 170 ° C. or lower. For this reason, there is a problem that, when the operation is performed with the exhaust gas cooling temperature set at around 200 ° C. as in the related art, this harmful substance cannot be sufficiently removed.

In view of the above, it is conceivable to operate the exhaust gas at a low cooling temperature, for example, at a temperature of 170 ° C. or lower. In this case, moisture in the exhaust gas is condensed to cause low temperature corrosion and clogging of the bag filter. May occur. By the way, the temperature at which the moisture in the exhaust gas is condensed, that is, the dew point temperature is, as is clear from FIGS. 5 and 6, the moisture content and the sulfur oxide concentration or the moisture content and the hydrogen chloride content in the exhaust gas. It changes depending on the concentration. The amount of water and the concentration of sulfur oxides or hydrogen chloride in the exhaust gas constantly change depending on the properties of the waste to be incinerated. Therefore, it is practically difficult to obtain the dew point temperature of the exhaust gas and control the gas cooling temperature to follow the dew point temperature.

SUMMARY OF THE INVENTION It is an object of the present invention to increase the removal rate of harmful substances by cooling exhaust gas to a relatively low temperature, and to detect the occurrence of condensation due to a change in the properties of the exhaust gas by detecting the pressure loss of a bag filter. It is an object of the present invention to provide a method and an apparatus for treating exhaust gas, which can prevent the formation of dew by increasing the cooling temperature of the exhaust gas and can efficiently remove the deposits on the bag filter surface.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, a first invention is to cool an exhaust gas generated by burning wastes and the like, and then add an alkali reactant and an auxiliary agent to form a bug. An exhaust gas treatment method for supplying to a filter and separating the alkali reactant, the auxiliary agent, and dust by the bag filter, wherein a pressure loss of the exhaust gas passing through the bag filter is detected to cool the exhaust gas. It is an object of the present invention to provide a method for treating exhaust gas whose degree is controlled.
Then, the exhaust gas is heated to a temperature of 170 ° C. or lower, preferably 100 ° C., which is slightly higher than a predicted dew point temperature of the exhaust gas.
The temperature is set so as to be cooled to 150 to 150 ° C., and when the pressure loss of the exhaust gas passing through the bag filter becomes larger than a predetermined value, the cooling temperature of the exhaust gas is controlled to be higher than the predetermined temperature.

According to such an exhaust gas treatment method, since the cooling temperature of the exhaust gas can be kept low, the removal rate of harmful substances can be increased, and when dew condensation occurs due to a change in the properties of the exhaust gas, This is detected by an increase in the pressure loss, and the cooling temperature of the exhaust gas is increased to prevent dew condensation and to dry the attached matter attached to the bag filter. As a result, when the bag filter peels off the deposits by pulse cleaning or the like, the peelability is improved.

A second invention is an apparatus for carrying out the first invention, comprising: an incinerator for burning waste and the like;
A gas cooler for cooling the exhaust gas generated in the incinerator, a first detector for detecting a temperature of the exhaust gas cooled by the gas cooler, a bag filter for separating dust and the like in the exhaust gas, A second detector for detecting a pressure loss of the exhaust gas passing through the bag filter; and control means for outputting a control signal for the exhaust gas cooling temperature. The controller detects signals from the first detector and the second detector. It is an object of the present invention to provide an exhaust gas treatment device which is inputted to the control means and controls a cooling temperature of exhaust gas in the gas cooler in accordance with a control signal from the control means. In this case, it is preferable that a cooling tower is selected as the gas cooler and the supply amount of the cooling water supplied to the cooling tower is controlled.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of an apparatus for implementing an exhaust gas treatment method according to the present invention, and FIG. 2 is a system diagram of waste treatment measures according to the present invention. In FIGS. 1 and 2, the same reference numerals as those in FIG. 3 denote the same names.

FIG. 1 is a system diagram of an apparatus for carrying out a method of treating exhaust gas according to the present invention, and shows a high-temperature exhaust gas G generated at a temperature of, for example, about 900 ° C. generated by burning wastes in an incinerator 1. ₁ is supplied to the gas cooler 2.
The gas cooler 2, for example, a reduced cooling tower, is spray cooling water W is supplied from the cooling water supply pipe 5, the high temperature exhaust gas G ₁ to a predetermined temperature, for example 170 ° C. or less, preferably Cool to a set temperature between 100 ° C and 150 ° C. The exhaust gas G ₂ cooled to the predetermined temperature is supplied to the bag filter 6, where dust and the like are removed, and the exhaust gas G ₂ becomes a low-temperature clean exhaust gas G ₃ and the chimney 4.
Is released into the atmosphere.

More specifically, the control valve 7 is connected to the cooling water supply pipe 5.
Is provided, and a thermometer 8 as a first detector is arranged in a _first exhaust gas line L1 for guiding the exhaust gas G2 cooled from the gas cooler ₂ to the bag filter 6. The first exhaust gas line L ₁ and the second exhaust gas line L ₂ for guiding the clean exhaust gas G ₃ removed by the bag filter 6 to the chimney 4 are connected via a differential pressure gauge 9 as a second detector. It is connected by the line L ₃ Te. Reference numeral 10 denotes a control device, which is a storage device, a first comparator 12, a second comparator 13,
It comprises a corrector 14, a control signal generator 15 and a calculator 16.

In such a configuration, the storage device 11 constituting the control unit 10 has a predetermined exhaust gas cooling temperature,
Specifically, it is 170 ° C. or less, preferably 100 ° C. to 150 ° C.
℃ and cooling temperature T of the exhaust gas is set within the range of the pressure loss of the predetermined exhaust gas G ₃ in the bag filter 6, for example a pressure loss S tolerance which is set within a predetermined range is input.

When the exhaust gas G ₁ cooled by the gas cooler 2 flows through the first exhaust gas line L ₁ , its temperature T 1
₁ is detected by the thermometer 8, and the signal V ₁ is input to the first comparator 12. Then, in the first comparator 12 is compared with the signal V ₂ of the cooling temperature T of the storage device 11, when there is no deviation of the signal V ₃ the control signal generator 1
5 is inputted to, wherein the control signal V ₄ which has been created in is led to the control valve 7, a predetermined cooling water W is sprayed is supplied to the gas cooler 2.

When there is a difference between the predetermined cooling temperature T and the temperature T ₁ of the exhaust gas G ₂ , the deviation symbol V ₅ is guided from the first comparator 12 to the computing unit 16, and is calculated by the computing unit 16. The obtained signal V ₆ of the amount of the cooling water W is supplied to the control signal generator 15.
To generate a control signal V ₄ , which controls the control valve 7.

On the other hand, the pressure loss S ₁ of the exhaust gas G ₃ in the bag filter 6 detected by the differential pressure gauge 9 as the second detector is inputted to the second comparator 13 as a symbol V ₇ ,
Here, it is input to the storage device 11. It is compared with the signal V ₈ of a predetermined pressure loss S, when there is a deviation, the deviation symbol V ₉ is input into the correction unit 14, the storage device 11 from the first comparator 12 the signal V ₂ is corrected derived Is done.

That is, a temperature slightly higher than the dew point temperature of the exhaust gas, specifically 170 ° C. or less, preferably 100 ° C.
From the range of ~ 150 ° C, the exhaust gas is cooled to a selected predetermined temperature, and during the waste treatment operation,
Due to the change in the waste to be incinerated, the properties of the exhaust gas change and the dew point temperature rises. When the dew point temperature exceeds the predetermined cooling temperature, moisture in the exhaust gas condenses, and together with dust and chemicals, the bag filter 6 has Adheres to the outer surface of the Such deposits are less likely to be peeled off by ordinary pulse cleaning, thus increasing the pressure loss.

Therefore, as described above, the pressure loss S ₁ is detected by the differential pressure gauge 9 as the second detector, and when the pressure loss becomes larger than the predetermined pressure loss S, the exhaust gas G ₂ , The supply amount of the cooling water W is reduced. As a result, the temperature of the exhaust gas G ₂ rises, and dew condensation can be prevented, and the exhaust gas G ₂ having the increased temperature dries dust and the like attached to the surface of the bag filter 6. By performing the washing, the attached matter can be easily peeled off. Of course, the peeling of such deposits is carried out, the pressure loss S ₁ in this bag filter becomes a predetermined one, to return to normal operation.

In the above-described embodiment, the case where dust removal and gas cleaning are performed by one bag filter 6 has been described. However, the first bag filter and the second bag filter are used, and dust removal is performed by the first bag filter. It is obvious that in the method of performing gas cleaning with the second bag filter, the exhaust gas treatment method according to the present invention may be adopted for at least one of the bag filters.

Next, an embodiment of a waste disposal measure to which the method of the present invention is applied will be described. FIG. 2 is a system diagram of the waste treatment measure 50 according to the present invention. In the waste treatment apparatus 50, a crusher 52 is a crusher of, for example, a biaxial shearing type disposed in a receiving yard.
Is supplied to this crusher 52, where it is crushed into, for example, 150 mm square or less. The crushed waste a is charged by a second conveyor 53 and supplied to a pyrolysis reactor 55 via a screw feeder 54. The thermal decomposition reactor 55 uses, for example, a horizontal rotating drum, and its interior is kept in a low oxygen atmosphere by a sealing mechanism (not shown), and is disposed on the downstream side of the combustion melting furnace 63 as a combustor. heated air heated by the heat exchanger 68 is supplied from the line L _1.

The waste a supplied into the pyrolysis reactor 55 is heated to 300 ° C. to 600 ° C., usually about 450 ° C. by the heated air. Thus, this waste a is thermally decomposed, the thermal decomposition gas G _1, primarily to produce a pyrolysis residue b nonvolatile. Then, this thermal cracking reactor pyrolysis gas G ₁ and the pyrolysis residue produced in the 55 b are separated by the discharge device 56, the pyrolysis gases G ₁
Is supplied to the burner 62 of the burning melting furnace 63 through a line L ₁ is a pyrolysis gas pipe.

Although the pyrolysis residue b varies depending on the type of the waste a, in the case of municipal solid waste in Japan, according to the knowledge of the present inventor, most of the flammable content of relatively fine particles is 10 to 60%. It has been found that relatively fine ash content is 5 to 40%, coarse metal component is 7 to 50%, and that coarse rubble, pottery, concrete, etc. are composed of 10 to 60%.

Pyrolysis residue b having such components
Is discharged at a relatively high temperature of about 450 ° C., and is cooled to about 80 ° C. by the cooling device 57 and guided to the separating device 58, where it is separated into the combustible component c and the non-combustible component d. As the separation device 58, for example, a known separator of a magnetic separation type, a centrifugal type or a wind separation type is used. The combustible component c from which the non-combustible component d has been separated and removed as described above is supplied to the crusher 6.
0 is supplied. The crusher 60 is suitably of a roll type, a tube mill type, a rod mill type, a ball mill type or the like, and is appropriately selected depending on the properties of the waste to be treated.

[0024] Then, the combustion component c in this grinder 60 is preferably ground to all 1mm or less, the ground combustible component c is supplied to the burner 62 of the burning melting furnace 63 through a line L ₁ You. On the other hand, the combustion air and the pyrolysis gas G ₁ supplied from the line L ₁ by the blower 61 and the combustible component c are mixed in the combustion melting furnace 63 by 1300.
The combustion ash generated from the relatively fine ash content of the combustible component c is melted by the combustion in a high temperature range of about ° C. to form a molten slag f.

The non-combustible component d is stored in a container 59. Unburned waste c is fed towards the possible under the combustion melting furnace 63 through a line L _1. At this time, the non-combustible waste e is 1 m in order to improve the combustion and melting efficiency.
m or less and preferably heated. Therefore, crusher provided in the line L _1, crushing provided a pulverizer 64 and a heater 65, it is being fed to the combustion melting furnace 63 is a processing such as grinding and heating. Therefore, heated air heated by the heat exchanger 68 disposed on the downstream side of the combustion melting furnace 63, and is supplied to the heater 65 via a line L _1.

Further, the non-combustible waste e is melted in the combustion melting furnace 63 to become slag g, mixed with the molten slag f formed by the combustion ash, dropped from the slag discharge port 66 into the water tank 67, and granulated. It is slag. The granulated slag is blocked or granulated in a predetermined shape by a device (not shown), and can be reused as a building material or a pavement material. In this case, the non-combustible waste e may be mixed into the molten slag f without melting as required.

The combustion melting furnace 6 of such a waste disposal apparatus
The combustion exhaust gas G ₁ generated by 3 is the heat recovery in the heat exchanger 68, further after being heat recovered by the waste heat boiler 69 through line L _1, dust 7 by the first exhaust gas treatment device 71
2 after collecting dust, the second exhaust gas treatment device (bag filter)
After being desalted and desulfurized at 73 and discharging the desalination residue 74, it becomes low-temperature clean exhaust gas G ₃ , and is discharged from a chimney 76 to the atmosphere via an induction blower 75. A part of the exhaust gas G ₃ are supplied to the cooling device 57 via a line L ₇ by the blower 77. Dust 72 collected in the first exhaust gas treatment device 71 is returned by the line L ₉ to the combustion melting furnace 63, is mixed melted and into the slag. Incidentally, steam generated in the waste heat boiler 69 is fed to the generator 70 to the steam turbine to work, also, part of it is sent to the heater 65 by a line L _8.

In the present embodiment, the gas cooler 2 is provided upstream of the second exhaust gas processor (bag filter) 73, and the first exhaust gas processor 71 and the second exhaust gas processor 73 are connected to each other. As shown in FIG. 1, a connecting line L ₆ is provided with a thermometer 8 as a first detector, and a difference detector as a second detector for detecting a pressure loss in a second exhaust gas treatment device 73. A pressure gauge 9 is provided, and a signal V ₁ and a signal V ₇ of the thermometer 8 and the differential pressure gauge 9 are transmitted to the
Is the input control signal V ₄ to be created, by controlling the control valve 7 by the control signal V _4, to control the amount of cooling water W supplied to the gas cooler 2. This control method is similar to that of the above embodiment, and will not be described again here.

[0029]

As is clear from the above description, according to the method and apparatus for treating exhaust gas according to the present invention, the exhaust gas is cooled down to a relatively low temperature by the gas cooler, so that the harmful substance removal rate can be reduced. Can be enhanced,
If condensation occurs due to a change in the properties of the exhaust gas, this is detected by the pressure loss of the bag filter, and the cooling temperature of the exhaust gas can be increased to prevent dew condensation and efficiently remove substances adhering to the bag filter surface. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a system diagram of an apparatus for implementing an exhaust gas treatment method according to the present invention.

FIG. 2 is a system diagram of a waste disposal measure according to the present invention.

FIG. 3 is a system diagram showing a general flue gas treatment system.

FIG. 4 is a diagram showing the relationship between the temperature of exhaust gas and the dioxin removal rate.

FIG. 5 is a diagram showing the relationship between the dew point temperature at which moisture in the exhaust gas is condensed, the amount of moisture in the exhaust gas, and the concentration of sulfur oxides.

FIG. 6 is a diagram showing the relationship between the dew point temperature at which moisture in the exhaust gas is condensed, the amount of moisture contained in the exhaust gas, and the concentration of hydrogen chloride.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incinerator 2 Gas cooler 4 Chimney 5 Cooling water supply pipe 6 Bag filter 7 Control valve 8 Thermometer 9 Differential pressure gauge 10 Control device 11 Memory measure 12 First comparator 13 Second comparator 14 Corrector 15 Control signal Creator 16 Computing unit 50 Waste treatment measures 51 First conveyor 52 Crusher 53 Second conveyor 54 Screw feeder 55 Pyrolysis reactor 56 Discharge device 57 Cooling device 58 Separator 59 Container 60 Crusher 61 Blower 62 Burner 63 Combustion melting furnace 64 Crusher 65 Heater 66 Slag discharge port 67 Water tank 68 Heat exchanger 69 Waste heat boiler 70 Generator 71 First exhaust gas processor 72 Dust 73 Second exhaust gas processor (bag filter) 74 Desalination residue 75 Induction blower 76 Chimney 77 Blower

Claims (5)

[Claims] After cooling waste gas generated by burning waste, an alkali reactant and an auxiliary agent are charged and supplied to a bag filter, and the alkali reaction agent, the auxiliary agent, and dust are separated by the bag filter. An exhaust gas processing method for separating exhaust gas, wherein a pressure loss of the exhaust gas passing through the bag filter is detected, and a degree of cooling of the exhaust gas is controlled. . 2. The exhaust gas is cooled to 170 ° C. or lower, preferably 100 ° C. to 150 ° C.
The method for treating exhaust gas described in 1. 3. The exhaust gas according to claim 1, wherein a cooling temperature of the exhaust gas is raised above a predetermined temperature when a pressure loss of the exhaust gas passing through the bag filter becomes larger than a predetermined value. Processing method. 4. An incinerator for incinerating waste and the like, a gas cooler for cooling exhaust gas generated in the incinerator, and a first detector for detecting a temperature of the exhaust gas cooled by the gas cooler. A bag filter for separating dust and the like in the exhaust gas, a second detector for detecting a pressure loss of the exhaust gas passing through the bag filter, and control means for outputting a control signal of the exhaust gas cooling temperature, Signals of the first detector and the second detector are input to the control means, and a control signal from the control means controls a cooling temperature of exhaust gas in the gas cooler. Exhaust gas treatment equipment. 5. The exhaust gas treatment apparatus according to claim 4, wherein the gas cooler is constituted by a cooling tower, and the supply amount of cooling water supplied to the cooling tower is controlled.