WO2001027533A1

WO2001027533A1 - Refuse exhaust gas treating system and treating method

Info

Publication number: WO2001027533A1
Application number: PCT/JP1999/005638
Authority: WO
Inventors: Tsutomu Okusawa; Satoru Nomoto; Terufumi Kawasaki; Masanori Takahashi; Osamu Yokomizo; Hitoshi Ishimaru; Kazuhito Koyama; Susumu Yamashita; Kazumi Iwai
Original assignee: Hitachi, Ltd.
Priority date: 1999-10-13
Filing date: 1999-10-13
Publication date: 2001-04-19
Also published as: AU6121999A

Abstract

A refuse exhaust gas treating system and treating method that are capable of reducing the amount of dioxin in exhaust gas without having to use drain water treating equipment. The refuse exhaust gas treating system is characterized by comprising a combustor for burning the incineration gas from incineration of refuse, a heat exchanger disposed downstream of the combustor to effect indirect heat exchange between the incineration gas and combustion gas flowing down from the combustor so as to cool the combustion gas, and a cooler disposed downstream of the heat exchanger to further cool the combustion gas that has passed through the heat exchanger.

Description

Specification

Waste gas treatment system and treatment method

The present invention relates to a waste gas treatment system and a treatment method for treating waste gas generated by incinerating waste or waste. Background art

Various devices have been proposed to decompose dioxins contained in incineration exhaust gas discharged from waste incinerators. For example, as a conventional apparatus, there is a technique described in Japanese Patent Application Laid-Open No. 10-26331. In this publication, a part of the exhaust gas of an incinerator is heated with a burner and a high-temperature heat source (100 ° C As described above, a combustion device is disclosed in which a waste gas sent to a heat exchanger and heated through a dust collector is heated to decompose dioxin, and the decomposed waste gas is rapidly cooled by a cooling device.

In the device described in JP-A-10-26331, the exhaust gas is cooled by using a quenching device that publishes the exhaust gas in a cooling water tank in which the cooling water is stored, thereby suppressing dioxin regeneration. I have. However, the temperature of the exhaust gas to be cooled is in a high temperature state of 700 ° C or higher, and in order to rapidly cool this exhaust gas to a low temperature state of 300 ° C or lower, this device is applied particularly to large-scale incineration equipment. This requires a large amount of cooling water, and a separate wastewater treatment device must be installed to purify the cooling water discharged from the quenching device. The present invention has been made in view of the above points, and has as its object to provide a waste gas treatment system and a treatment method capable of reducing dioxin in exhaust gas without using a wastewater treatment device. And there. Disclosure of the invention

In order to achieve the above object, the present invention provides the following waste gas treatment system.

That is, the refuse exhaust gas treatment system of the present invention comprises a combustor for burning incineration gas obtained by incinerating refuse, and indirectly exchanging heat between the combustion gas burned in the combustor and the incineration gas. And a cooler for further cooling the combustion gas from the heat exchanger.

In order to achieve the above object, the present invention provides the following waste gas treatment method.

The exhaust gas treatment system of the present invention is characterized in that incineration gas obtained by incinerating refuse is burned in a combustor to decompose dioxin contained in the incineration gas, and the combustion gas discharged from the combustor is led to a heat exchanger. The combustion gas is cooled by indirectly exchanging heat with the incineration gas supplied to the combustor, and the combustion gas cooled by the heat exchanger is indirectly heat-exchanged by a cooler to remove the exhaust gas. Further cooling.

As described above, according to the present invention, it is possible to decompose dioxin contained in refuse incineration gas and to suppress regeneration of dioxin. In addition, since the combustion gas generated by combustion in the combustor is cooled by indirect heat exchange, dioxin can be reduced without a wastewater treatment device. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 shows a waste gas treatment system according to one embodiment of the present invention. FIG. 2, _c 3 illustrates a waste gas treatment system according to another embodiment of the present invention, <4 shows a waste gas treatment system according to another embodiment of the present invention, the present invention _t 5 shows a waste gas treatment system which is another embodiment, _t 6 illustrates a waste gas treatment system according to another embodiment of the present invention, experimental results of dioxin regeneration amount according to this embodiment Is shown. FIG. 7 is a graph showing the relationship between the dust concentration and the dioxin concentration.

Fig. 8 shows the emission control values of dioxin in waste incinerators.

Figure 9 shows the average values of the exhaust gas flow rate and dioxin concentration in a typical waste incineration plant.

FIG. 10 is a diagram showing rated performance values of the dust collector.

FIG. 11 is a diagram showing the relationship between exhaust gas combustion temperature and residence time. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a system diagram of a waste gas treatment system according to one embodiment of the present invention. The scale of the waste gas treatment system in this example is an incinerator with a waste treatment amount of 4 tZh or more. For example, the waste gas amount is 7800 kgZh, and the waste incineration scale is 100%. t Z h, dioxin emission concentration 15 ng—This is assumed to be an incinerator with a scale of TE QZm ³ N. Incidentally, the discharge limits for dioxins in incineration scale 4 t / h or more furnace, in existing furnace 1 ng- TEQ / m ³ N, in the new furnace that has been defined as O. lng- TE QZm ³ N. Note that used as the unit of dioxin emission concentration described above - ng of [ng TEQ / m ³ N] is, 1 0- ⁹ g, TEQ is, Toxicity

Abbreviation for Equivalency Quantity, the most toxic of dioxins 2,3,7,8 Tetraclonal dibenzodioxin means the amount when converted to toxicity, and m ³ N indicates the exhaust gas volume under standard conditions.

Dioxins are generated by incineration of refuse or waste, especially by incomplete combustion of organic substances (plastics) containing chlorine. The aggregation of multiple unburned hydrocarbons (soot, pure carbon, and part of the benzene ring) generated by incomplete combustion forms polycyclic hydrocarbons, which are aggregates of benzene rings. You. This is reacted with hydrochloric acid by the catalytic action of dust to form a dioxin precursor, which is said to combine with each other to produce dioxin.

In this patent, the dust concentration refers to the concentration measured by the method specified by JIS, and the dioxin concentration refers to the concentration measured by the method specified in the country. The residence time (for combustion pyrolysis and cooling of the heat exchanger) was calculated from the gas volume flow rate, the cross-sectional area of the flow path, and the gas temperature under the standard conditions, and the time was calculated using the following flow rate. ing.

Flow rate = Flow rate (m ³ NZ h) Flow area (m ² ) 2 7 3 .15 x (Temperature + 27 ³ .15)

The waste gas treatment system shown in Fig. 1 consists of an incinerator 1 that burns waste, and a dust collector cooler 13 3 that exchanges heat with flue gas 2 generated by burning waste to reduce the temperature of flue gas 2. A dust collector 3 that collects dust in the cooled exhaust gas 2, and a mixer 5 that mixes air 7 with the exhaust gas 30 from which dust is collected by the dust collector 3 to form an aerated exhaust gas 28. It has. The waste gas treatment system according to the present embodiment includes a combustor 9 that burns fuel 8 using the aerated exhaust gas 25 and the combustion air 20 as an oxidant, and an exhaust gas 26 that is combusted by the combustor 9. A heat exchanger 10 for exchanging heat with the aerated exhaust gas 28 and an evaporator 14 for cooling the exhaust gas 27 cooled by the heat exchanger 10 are provided. I have.

The blower 4 is provided to supply the exhaust gas 30 collected by the dust collector 3 to the mixer 5. The blower 6 supplies the air 7 mixed with the exhaust gas 30 to the mixer 5 and at the same time supplies the air 7 to the combustor 9 as combustion air 20. Further, water 105 is supplied to the evaporator 14 as an indirect cooling medium by a pump 101.

Fig. 8 shows the emission control values of dioxin in waste incinerators that came into effect in February 1997. As shown in Fig. 8, dioxin emission control conditions differ depending on the incinerator scale and whether the incinerator is an existing furnace or a new one. For existing furnaces, it is obliged to achieve the above regulation values within five years from the enforcement date (February 1, 1997). Fig. 9 shows the average of the exhaust gas flow rate and dioxin concentration in typical waste incineration facilities, and shows them by incinerator incineration scale in comparison with the national regulation values.

Also, the rated performance of the dust collector 3 for removing dust in the combustion exhaust gas 2 is as shown in FIG. 10 respectively. The performance of the dust collector 3 to be actually used may be a device capable of collecting dust having a particle size of 10 μιη or more, but preferably a device capable of completely collecting dust having a particle size of 1 μππ or more. What is collected is desirable. In the waste gas treatment system configured as described above, first, waste is incinerated in the incinerator 1 to generate high-temperature combustion exhaust gas 2 of about 850 ° C or more, which is incineration gas containing dioxin. Is done. The flue gas 2 is led to a desuperheater 13 via a pipe 2a, where it is cooled to a temperature of about 150 to 230 ° C or near. As means for cooling the flue gas 2, it is also possible to cool it by spraying water upstream of the dust collector 3 or in the incinerator 1. Figure 7 shows the results of a verification test using the exhaust gas from the facility. The vertical axis shows the dioxin concentration at the outlet when a cooler is used to cool the reburn exhaust gas, and the horizontal axis shows the dust concentration.

The concentration of dioxin is about 100 times higher than that before the cooler. Among these, the reason why the concentration of dioxin is plateau when the concentration of dust is 0.1 gZm ³ N or more is that the surface area of dust that mediates the dioxin regeneration reaction is more than necessary for the reaction and saturates. For this reason, dioxin can be reduced to 0.25 ng-TEQ / m ³ N or less only when the dust concentration is 0.1 g / m ³ N or less. This value, given the 2 0 0 percent measurement accuracy 5 0 die Okishin at very low concentrations, 0. 1 ng - since it is the upper limit to be considered a TEQ / m ^3, the subject of the I Li present invention thereto The dust concentration of the exhaust gas was set to 0.1 g Zm ³ N or less.

In the case of an electric dust collector, which is widely used in existing waste incineration facilities, it is known that the higher the exhaust gas temperature, the lower the electrical resistance of the dust. For this reason, in order to reduce the electric power, which is the product of the corona current and the corona voltage, with almost the same dust collection performance, use it at about 300 ° C or less, where there is no disadvantage of gas volume expansion due to high temperature It is desirable. The reason that the exhaust gas temperature at the inlet of the dust collector 3 is cooled to about 150 to 230 ° C by the desuperheater 13 is that if the temperature is lower than this temperature, dioxin is completely regenerated. The reason for this is that the regeneration of dioxin can be suppressed because the temperature is outside the growth temperature range. Therefore, in this embodiment, the temperature of the exhaust gas at the inlet of the dust collector 3 is reduced to about 150 to 230 ° C. by the desuperheater 13 so that the dust can be efficiently collected by the electric dust collector. I'm doing it. Since the purpose here is solely for dust collection, suppression of dioxin regeneration is performed in a separate step described later. In this way, the combustion exhaust gas 2 cooled to a temperature of about 150 to 230 ° C. is supplied to the dust collector 3 through the pipe 2 b, where the fly ash of the combustion exhaust gas 2 is ashed. (dust) concentration 0. 1 g Z m ³ N following conditions, dust is collected in earthenware pots by comprising, for example, 0. 0 0 1 ~ 0. 1 gZm 3 N. The exhaust gas 30 that has passed through the dust collector 3 is guided to the blower 4 via the pipe 3a, and further supplied to the mixer 5 via the pipe 30a. Here, the temperature of the exhaust gas 30 supplied to the mixer 5 by the blower 4 is about 200 ° C. or lower. The dioxin concentration in the exhaust gas 30 passing through the dust collector 3 is 15 ng—TEQ / m ³ N. The lower the dust concentration here, the more room is allowed in the cooling process in which later dioxin regeneration occurs, and the longer the cooling time can be.

The exhaust gas 30 is supplied to the mixer 5 by the blower 4 via the pipe 30a. On the other hand, a part of the air 7 supplied from the pipe 7 a is supplied to the mixer 5 by the blower 6 via the pipe 5 a. In the mixer 5, the supplied exhaust gas 30 and the air 7 are mixed to form an aerated exhaust gas 28. In the mixer 5, the exhaust gas 30 and a part of the air 7 are mixed, and the exhaust gas 30 is diluted with air to adjust the oxygen concentration or the dust concentration (fly ash concentration). The concentration of dioxin in the aerated exhaust gas 28 mixed with air 7 remains at 15 ng-TEQ / m ³ N. The aerated exhaust gas 28 coming out of the mixer 5 is supplied to the heat exchanger 10 via a pipe 28a. In the heat exchanger 10, heat exchange is performed with a high-temperature exhaust gas 26 guided from a combustor 9 described later, and the temperature of the aerated exhaust gas 28 is raised to a temperature of about 600 ° C. Exhaust gas 26 from vessel 9 is being cooled. The aerated exhaust gas 25 heated in the heat exchanger 10 is supplied to the combustor 9 via the pipe 25. The combustor 9 is supplied with the aerated exhaust gas 25 heated by the heat exchanger 10. On the other hand, fuel 8 (city gas, kerosene, heavy oil, etc.) or reformed fuel is supplied to the combustor 9 through the pipe 8a, and air 7 is used as combustion air for the fuel 8. A part of the combustion air 20 is supplied via a pipe 20a. Further, in the combustor 9, a part of the steam 102 generated in the evaporator 14, which will be described later, is passed through the pipe 102 a via the pipe 104 a, and the NO. Supplied as steam 104 for x reduction. In the combustor 9, the fuel 8 and the combustion air 20 supplied to the combustor 9 are burned while injecting steam 104, and the dioxin is decomposed into the aerated exhaust gas 25 at about 600 ° C. The heating is performed to a temperature of about 750 ° C or more, preferably about 850 ° C or more. Here, the higher the temperature of the combustion air 20 and the air-mixed exhaust gas 25 entering the combustor 9, the more the fuel 8 to be charged can be saved, and therefore it is desirable that these are high in temperature. The rest of the steam 102 guided from the evaporator 14 is supplied to other steam utilization equipment via the pipe 103a. The exhaust gas 26 heated to a high temperature in the combustor 9 is guided to the heat exchanger 10 via a pipe 26 a provided downstream of the combustor 9. Here, in the region including the combustor 9 and the pipe 26 a provided downstream of the combustor 9, the exhaust gas 26 heated in the combustor 9 is maintained at a high temperature while the exhaust gas 26 is separated from the exhaust gas 26. It stays in the high temperature area for about 1 second or more, preferably about 1.6 seconds or more, so that it is exposed to high temperature. As described above, the dioxin in the exhaust gas 26 is thermally decomposed by exposing the exhaust gas 26 to the high-temperature region for about 1 second or more, desirably about 1.6 seconds or more. Here, the time for exposing the exhaust gas 26 to a high temperature region of about 75 ° C. or more, preferably about 850 ° C. or more, is about 1 second or more, and preferably about 1.6 seconds or more. This is based on the results of the verification experiment shown in Fig. 11.

The decomposition temperature and residence time of dioxin are determined by Enviro miien ta l in the United States. The technical literature published by the Protection Agency, which is the pyrolysis of dioxin. '| 文献 ί Ru 文献, DS Duval and WA Rubey, Laboratory

Evaluation of High—Tem erature Destruction of Polichl or inate Biphenyls and Related Compounds (Laboratory evaluation of high-temperature decomposition of polychlorinated biphenylenole and its related compounds), EPA—600Z2—77—28 8, page 1 8-1 (1 9 7 7) When displayed in an easy-to-understand manner based on the contents described in (1), the dioxin concentration is reduced to 0.1 (11-£ £ (3 1 ^ ³ 1) or less. The decomposition temperature and residence time required to reduce the temperature are summarized as shown in Fig. 11. At the same time, the results of the verification tests conducted by the inventors are also shown in the right column of Fig. 11. This is the basis for the conditions for dioxin degradation.

Here, the longer the residence time of the exhaust gas 26 in the high-temperature region, the more the decomposition of dioxin progresses to the limit. Therefore, the longer the residence time, the more advantageous in terms of dioxin thermal decomposition.

At this time, the inner wall of the piping arranged downstream of the combustor 9, including the high-temperature region including the combustor 9 and the piping 26a, is made of a material that does not contribute to the regeneration of dioxin, such as stainless steel or S By using i C ceramics, a high decomposition rate can be secured. Further, by providing a baffle plate in the high temperature region, for example, a weir inside the pipe 26a, the time during which the exhaust gas 26 stays in the high temperature region can be extended. Also, by providing a turbulence promoting part on the surface or inside of the pipe 26a, for example, an uneven part on the surface of the pipe 26a, and by making the pipe 26a a curved pipe or a scaled pipe, exhaust gas 26 can be homogenized at a high temperature to improve the dioxin decomposition rate.

As described above, the flue gas 2 generated in the incinerator 1 is dedusted in the dust collector 3, mixed with air in the mixer 5, and heated to a high temperature in the combustor 9. This makes it possible to decompose dioxin in the exhaust gas 26 by 99.9% or more. In addition, the dioxin concentration at this time is reduced to 0.0 lng—TEQZ m ³ N level or less. Of course, the lower the concentration of dust in the exhaust gas 30, the lower the concentration of redoxin can be reduced.However, since the exhaust gas 26 in which dioxin has been decomposed to a low concentration is in a high temperature state, It cannot be released from the chimney without cooling. This is because dust (fly ash) remains in the exhaust gas 30 after being collected by the dust collector 3 although it has a low concentration, and this acts as a dioxin regeneration catalyst when cooling the exhaust gas 26. Because. Regarding the regeneration of dioxin, the temperature range of about 200 to 400 ° C is the regeneration range, and especially the temperature range of about 330 to 380 ° C is more remarkable.頜 area. Regeneration of dioxin is mainly defined by the concentration of dust in the exhaust gas and the cooling rate of the exhaust gas.

Hereinafter, the exhaust gas cooling equipment will be described. In this embodiment, first, the exhaust gas 26 after being heated to a high temperature in the combustor 9 to decompose dioxin is supplied to the heat exchanger 10 via the flue 26a. The high-temperature exhaust gas 26 guided to the heat exchanger 10 undergoes heat exchange with the low-temperature aerated exhaust gas 28 that is the first cooling medium supplied from the mixer 5 and is regenerated. Is cooled to around 400 ° C, where almost no occurrence occurs. As described above, almost no regeneration occurs in the heat exchanger 10, and therefore, the heat exchanger 10 is not restricted by the residence time of the exhaust gas 26. Therefore, the latest heat exchange technology can be applied to the heat exchanger 10. Wear.

The exhaust gas 27 cooled to about 400 ° C. in the heat exchanger 10 is supplied to the evaporator 14 via a pipe 27 a provided downstream of the heat exchanger 10. Water 105 supplied from a separately installed system is supplied by pump 101. Then, the pressure of the water is increased and the water 15 passed through the pump 101 is supplied to the evaporator 14 via the pipe 15a. In the evaporator 14, the exhaust gas 27 guided from the heat exchanger 10 undergoes heat exchange with water 15 as the second cooling medium, and the temperature of the exhaust gas 27 is maintained in the dioxin regeneration temperature region. It has been cooled to a certain temperature of 200 ° C or less.

Here, the evaporator 14 cools the exhaust gas 27 guided from the heat exchanger 10 from 400 ° C to 200 ° C or less within about 5 seconds, and discharges it from the evaporator 14 outlet. The dioxin concentration in the exhaust gas is reduced to less than 0.1 ng—TEQZ m ³ N level. The cooling time of the exhaust gas 27 is desirably within about 3.5 seconds, and more desirably, from 38 ° C to 33 ° C within 1 second. Dioxin regeneration can be further suppressed. The exhaust gas cooled to 200 ° C. or less in the evaporator 14 is discharged from a chimney (not shown).

In the evaporator 14, the water 15 supplied by the pump 101 is heat-exchanged with the exhaust gas 27 to generate steam 102. The steam 102 generated in the evaporator i 4 is supplied to the combustor 9 or another steam utilization device via the pipe 102 a.

As described above, in the present embodiment shown in FIG. 1, the exhaust gas heated to a high temperature in the combustor 9 is first cooled by the heat exchanger 10, which is the first cooling means, to a temperature equal to or higher than the dioxin regeneration temperature range. By cooling to a temperature and then rapidly cooling the evaporator 14 as the second cooling means so as to pass through the regeneration temperature range in a short time, the amount of dioxin regeneration is further suppressed.

FIG. 6 shows the experimental results of the amount of dioxin regeneration according to this example. The experimental results shown in this figure are based on general waste incineration exhaust gas components, and the waste incineration exhaust gas is once added to 850 ° C (750 ° C or more). Heating and holding for 1 second or more, and then, when cooling from 850 ° C (750 ° C or more) to 200 ° C with a heat exchanger, including the temperature range for promoting dioxin regeneration It shows the relationship between the residence time in the temperature range of 400 ° C to 200 ° C estimated from the above and the dioxin concentration.

The points (1) and (2) shown in the figure are the results of a test performed under conditions where ash was not deposited inside the heat exchanger, and only the flow velocity was different. As for ◊, the retention time and dioxin are linearly related, as can be seen from the results of the basic experiment conducted in the three cases where ash was not deposited in the interior. This indicates that to achieve 0.1 (ng—TEQ / m ³ N) or less, it is necessary to set the time to 5.5 seconds or less. Is expected to exceed ^{- (TEQ / m 3 N ng} ) 5. When staying more than 5 seconds in this temperature range regeneration amount increases 0.1.

Ginseng is the result of simulating the situation where ash was deposited and attached to the cooling pipe due to aging, and was obtained by a demonstration facility. From this result, considering that the heat exchanger has changed over time, it is necessary to set the heat exchanger to 3.5 seconds or less to achieve 0.1 l (ng—TE QZm ³ N) or less. In addition, a basic experiment at the test tube level revealed that the temperature range for promoting dioxin regeneration could be narrowed to 380 to 330 ° C. residence time 3.5 seconds, the 3 8 0-3 3 becomes 0 ° 〇 in 1 second _£ Incidentally, the experimental results shown in FIG. 6 is, 2 0 0 ° the exhaust gas temperature from 4 0 0 ° C Experimental results using a heat exchanger as a means of cooling to C are shown, but the use of an evaporator 14 as shown in Fig. 1 further reduces the time required to cool the exhaust gas. It can be done. Therefore, the amount of regenerated dioxin can be further reduced, and the dioxin concentration can be reduced below the national regulation value.

As described above, in the present embodiment, the temperature is increased to more than 75 Exhaust gas 26 is first cooled by heat exchanger 10. At this time, as a heat exchange medium for the exhaust gas 26, an aerated exhaust gas 28 in which air 5 is mixed into the exhaust gas 30 from the incinerator 1 that collects fly ash is used. Therefore, by heat exchange with the high-temperature exhaust gas 26 from the combustor 9, the aerated exhaust gas 28 can be supplied to the combustor 9 after being heated to a higher temperature. In a temperature range from 75 ° C or higher to 400 ° C, where dioxin regeneration is only slight, the exhaust gas 26 from the combustor is cooled by the heat exchanger 10 and the exhaust heat of the exhaust gas 26. We are collecting. Therefore, the amount of fuel 8 supplied to the combustor 9 can be reduced, and the economic efficiency can be improved. In addition, by applying an evaporator 14 having a higher cooling rate than the heat exchanger to the dioxin regeneration temperature range of 400 to 200 ° C, it is possible to suppress the regeneration of dioxin. it can.

There is no time limit for cooling the exhaust gas temperature from the combustor 9 to about 400 ° C. The reason for this is that the temperature of about 600 ° C or more is the thermal decomposition area of dioxin, and the temperature area of 400 ° C to 600 ° C stays because of the equilibrium area of regeneration and decomposition. This is because the length of time has little effect on regeneration.

Here, in the device described in Japanese Patent Application Laid-Open No. 10-26331, the exhaust gas is cooled using a quenching device that publishes the exhaust gas in a cooling water tank in which the cooling water is stored. In this conventional device, the exhaust gas of 700 ° 〇 or more was cooled by a single quenching device to 300 ° C, so when applying it to a large-scale incinerator, a large amount of cooling water was required. There was a possibility that a purification device for purifying the cooling water separately from the quenching device might be required.

On the other hand, in the present embodiment, the water for cooling the exhaust gas performs indirect heat exchange, so that a purification device is not required. Further, in this embodiment, heat exchange with exhaust gas is performed. The steam generated by the exchange is supplied to the combustor, and can be used for NOx reduction in the combustor.

As described above, according to the present embodiment, dioxin contained in exhaust gas can be reduced, and regeneration of dioxin can be suppressed, so that an inexpensive waste gas treatment system can be provided.

Figure 2 is not described here further embodiment _t Note showing a waste gas treatment system which is the same configuration and operation as the first drawing in the following description of the present invention.

In this embodiment shown in FIG. 2, the high-temperature exhaust gas 26 from the combustor 9 is cooled by only one heat exchanger 10. This heat exchanger 10 is provided with two heat exchange sections, and the exhaust gas 26 is firstly separated from the aerated exhaust gas 28 supplied from the mixer 5 by the first heat exchange section 10a. The heat is indirectly exchanged, and the exhaust gas heated to a high temperature of more than 750 ° C in the combustor 9 is cooled to a temperature of about 400 ° C. The exhaust gas cooled in the first heat exchange unit 10a is led to the second heat exchange unit 1Ob installed in the same flow path as the first heat exchange unit 10a, The heat exchange is performed indirectly with the water 105 supplied to the heat exchange unit 1 Ob of No. 2, and the exhaust gas is further cooled to a temperature of 200 ° C. or lower.

That is, in this embodiment, the exhaust gas 26 heated to a high temperature in the combustor 9 is firstly separated by the first heat exchange unit 10a into a temperature range of dioxin decomposition (about 600 ° C. or more). Alternatively, the dioxin is cooled to a temperature within a temperature range (about 400 ° C. to 600 ° C.) in which the dioxin regeneration and decomposition are equilibrated, and the dioxin is further reduced by the second heat exchange unit 1 Ob. The system reduces the exhaust gas temperature to a temperature even lower than the regeneration temperature range (400 to 200 ° C).

At this time, the temperature of the exhaust gas from the combustor 9 is reduced in the first heat exchange section 10a. Although there is no particular need to set a time limit for cooling to about 400 ° C., in the second heat exchange section 10b, as in the evaporator 14 shown in FIG. 7 from 400 ° C to below 200 ° C within about 5 seconds, preferably within about 3.5 seconds, and more preferably from 38 ° C to 330 ° C By cooling to within 1 second, the dioxin concentration in the exhaust gas can be reduced to O.lng—TE QZm ³ N level or less.

In the second heat exchange section 1 Ob, steam 105 is generated by heat exchange of water 15 supplied by the pump 101 with exhaust gas 26. The steam 102 generated in the second heat exchange section 1 Ob is supplied to the combustor 9 via the pipe 102 a and the pipe 104 a to reduce NOx in the combustor 9. It is supplied as steam 104 or as steam 103 to other steam utilization equipment via piping 103a.

As described above, according to the present embodiment, dioxin contained in exhaust gas can be reduced, and regeneration of dioxin can be suppressed, so that an inexpensive waste gas treatment system can be provided. Further, in this embodiment, the exhaust gas is cooled by one heat exchanger 10, so that the entire apparatus can be made more compact than that shown in FIG. Space can be increased.

Figure 3 will be omitted for another embodiment _c Note showing a waste gas treatment system which is the same configuration and operation as the first drawing in the following description of the present invention.

In the present embodiment, an air preheater 11 for preheating the combustion air 20 is added downstream of the combustor 9. With this addition, a combustion air pipe is provided between the blower 6 and the air preheater 11. 105 a was also provided. The-part of the air leaving the blower 6 enters the air preheater 11 via the pipe 105a and rises to around 300 ° C. It is heated and supplied to the combustor 9 as combustion air 20 via a pipe 20a. In this example, the air preheater 11 and the heat exchanger 10 cover the temperature range of about 850 to 400 ° C., which is a temperature range where dioxin regeneration is only slight, and the dioxin regeneration temperature range Approximately 400 to 200 ° C. is applied to the evaporator 14. In addition, the air preheater 11 can absorb the temperature fluctuation of the combustor as the temperature of the combustion air 20, so that the time fluctuation can be made uniform.

As described above, according to the present embodiment, not only can the fuel consumption be reduced than in the embodiment of FIG. 1, the dioxin in the exhaust gas can be decomposed to a low concentration, and the heat exchanger of the prior art can be decomposed. It can be used to recover waste heat and reduce fuel by applying from 850 ° C to 400 ° C in the temperature range where dioxin regeneration is very small, and the evaporator of the prior art (cooling speed is faster than heat exchanger) ) Is applied to the dioxin regeneration temperature range of 400 ° C to 200 ° C, and the regeneration can be suppressed, and the temperature fluctuation of the combustor 9 can be made uniform, so that the dioxin reduction performance is high and the price is low. There is an effect that a suitable dioxin purification device can be provided.

Figure 4 will be omitted for another embodiment _c Note showing a waste gas treatment system is an example, the same structures and operations as those described above in the following description of the present invention.

This embodiment has a configuration in which a superheater 17 is installed downstream of the combustor 9 and upstream of the evaporator 14 in addition to the one shown in FIG. The water 105 is supplied to the evaporator 14 by the pump 101, where it becomes steam 102 at around 300 ° C, and to the superheater 17 via the pipe 102 a. Part of superheated steam 106 passes through piping 106a as superheated steam 106 or more at 400 ° C or more, and is supplied to pipeline 104 as a countermeasure against NOx, and the remaining steam 1 0 3 goes through piping 103 a to the steam utilization equipment or is discarded. In the present embodiment, the The super-heater 17, air pre-heater 11 and heat exchanger 10 cover the temperature range of about 850 to 400 ° C, where there is little syn regeneration, and it is the dioxin regeneration temperature range Approximately 400 to 200 ° C. is covered with an evaporator 14. By changing the set temperature of the superheater 17 and the air preheater 11, the exhaust gas temperature at the evaporator 14 inlet can be adjusted, so that dioxin regeneration can be performed in response to fluctuations in combustion temperature. Deterrence can be prevented.

As described above, according to the present embodiment, not only can the fuel be reduced than in the embodiment of FIG. 3, the dioxin in the exhaust gas can be decomposed to a low concentration, and the dioxin is regenerated by the heat exchanger. The temperature range where there is only a slight temperature is about 850 to 400 ° C, waste heat can be recovered and fuel can be reduced, and the evaporator with a higher cooling rate than the heat exchanger is used as a dioxin regeneration temperature range. Is about 400

Since it can be applied to a temperature of 200 ° C. and can suppress regeneration, and can cope with fluctuations, there is an effect that a dioxin purifying apparatus with high dioxin reduction performance can be provided at a low cost.

FIG. 5 shows a waste gas treatment system according to another embodiment of the present invention. In the following description, the same configuration and operation as those described above will not be described.

In the present embodiment, power is generated by using steam 103 as surplus steam from the heater 17 and steam 53 generated in the incinerator 1. Therefore, in this embodiment, the steam turbine 24 driven by the generated steam and the generator

3 4, A condenser 35 for condensing the steam after work, and a condensate pump 38 for sending condensed condensate. Further, the incinerator 1 is provided with an economizer 21, an evaporator 22 and superheaters 23 a and 23 b, and steam is generated by utilizing the heat of the incinerator 1. The hot water 51 generated in the economizer 21 is supplied to the evaporator 22 via the pipe 51a, becomes steam, and becomes a superheater. Superheated after passing through 23a and 23b, it becomes superheated steam 53 and merges with a part of superheated steam 106 sent through piping 53a and piping 103a to overheat. The steam is supplied to the steam turbine 24 through the pipe 5 2 a.

Drive 3 4 to generate electricity. The steam that has completed its work in the steam turbine 24 is returned to water in the condenser 35. The condensed water is supplied to the economizer 21 and the evaporator 14 by the feedwater pump 38 via the pipes 21a and 15a, respectively. The water 15 supplied to the evaporator 14 is turned into steam in the evaporator 14, then superheated in the superheater 17 to become superheated steam 106, and a part of the combustor passes through the steam pipe 106 a. The remaining part is supplied to the pipe 52a via the pipe 103a. The water sent to the combustor 9 is lost from the system, so a pump 46 that supplies water is provided in the condensate line.

Since the power generation generates profits from the resale of electricity that the in-house power can cover, the cost of dioxin treatment can be reduced. The dioxin reduction performance is the same as that of the system shown in Fig. 4 and will not be described here.

As described above, according to this embodiment, not only the fuel consumption can be reduced, but also the cost due to power generation can be reduced, the dioxin in the exhaust gas can be decomposed to a low concentration, and the conventional method can be used. It can be used to recover waste heat and reduce fuel by applying dioxin regeneration from 850 ° C to 400 ° C in a temperature range where there is little dioxin regeneration in the heat exchanger of the technology, and the cooling rate is higher than that of the heat exchanger. Applying a fast evaporator to the dioxin regeneration temperature range from 400 ° C to 200 ° C to suppress regeneration and to cope with fluctuations, high dioxin reduction performance and inexpensive dioxin purification There is an effect that the device can be provided. Industrial applicability INDUSTRIAL APPLICABILITY The waste gas treatment system and treatment method of the present invention are used in the field of reducing dioxin in exhaust gas generated by burning waste or waste in an incinerator.

Claims

The scope of the claims

1. A combustor that burns incineration gas that has been incinerated from refuse or waste, and the combustion that is installed downstream of the combustor and indirectly exchanges heat between the incineration gas and flue gas flowing down from the combustor. A heat exchanger for cooling the exhaust gas,

A waste gas treatment system, comprising: a cooler installed downstream of the heat exchanger for further cooling the combustion exhaust gas passing through the heat exchanger.

2. Fly ash concentration 0.1 to 0.001 g Combustor for burning Z In ³ N waste incineration gas

A heat exchanger that indirectly exchanges heat between the flue gas burned in the combustor and the incinerated gas to cool the flue gas;

And a cooler for further cooling the combustion exhaust gas from the heat exchanger.

3. Air supply means for supplying air to the incineration gas generated by incinerating the refuse, and a combustor for burning the incineration gas supplied with the air;

It is installed downstream of the combustor and indirectly exchanges heat between the incineration gas and the flue gas flowing down from the combustor, thereby cooling the flue gas to a predetermined temperature, and performing the heat exchange and cooling. A waste gas treatment system, further comprising: a heat exchanger for lowering the combustion exhaust gas to a desired temperature lower than the predetermined temperature.

4. A combustor that burns incineration gas that has incinerated refuse or waste, and a heat exchanger that is installed downstream of the combustor and indirectly exchanges heat with the incineration gas and flue gas flowing down from the combustor, Exhaust gas within the temperature range of dioxin decomposition or equilibrium between dioxin regeneration and decomposition A refuse provided with a heat exchanger that cools the combustion exhaust gas cooled by heat exchange within the temperature range and further cools the exhaust gas cooled by the indirect heat exchange below the dioxin regeneration temperature range. Exhaust gas treatment system.

5. A combustor for burning the incineration gas from the incineration of the refuse,

An air preheater installed downstream of the combustor and indirectly exchanging heat between air supplied to the combustor and flue gas flowing down from the combustor to cool the flue gas;

A heat exchanger disposed downstream of the air preheater, for exchanging heat with the combustion exhaust gas flowing down from the air preheater, and cooling the combustion exhaust gas by exchanging heat with the incineration gas;

A waste gas treatment system, further comprising: a cooler installed downstream of the heat exchanger for further cooling the combustion exhaust gas passing through the air preheater.

6. A combustor that burns incineration gas obtained by incinerating organic matter containing chlorine, and indirectly exchanges heat between the incineration exhaust gas and the combustion exhaust gas flowing down from the combustor, which is installed downstream of the combustor. A first heat exchanger for cooling the flue gas;

An exhaust gas treatment comprising: a second heat exchanger installed downstream of the first heat exchanger for further cooling the combustion exhaust gas that has passed through the first heat exchanger. system.

7. A combustor for burning incineration gas obtained by incinerating organic matter containing chlorine, and a first cooling means for cooling the combustion exhaust gas downstream of the combustor by indirect heat exchange with a first cooling medium. Heat exchanger,

On the downstream side of the first heat exchanger, indirect heat exchange with the second cooling medium is performed, and the flue gas that has passed through the first heat exchanger is further cooled. An exhaust gas treatment system comprising: a second heat exchanger.

8. A combustor that burns the incineration gas from the incineration of the refuse,

A first heat exchanger for cooling the flue gas from the combustor within a temperature range of dioxin decomposition or within a temperature range in which dioxin regeneration and decomposition are balanced;

A waste heat treatment system, comprising: a second heat exchanger for further cooling the combustion exhaust gas from the first heat exchanger to a dioxin regeneration temperature range or lower.

9. The waste gas treatment system according to claim 1, further comprising holding means for holding the combustion exhaust gas flowing down from the combustor to the heat exchanger at a temperature of not less than 750 ° C for not less than 1 second. A waste gas treatment system according to any of claims 1 to 4.

10. The waste gas treatment system according to claim 9, wherein the holding means desirably holds the combustion exhaust gas at a temperature of 850 ° C or more for 1.6 seconds or more. .

1 1. An incinerator for incinerating refuse, a dust collector for collecting dust in exhaust gas discharged from the incinerator, an air supply means for supplying air to the exhaust gas in which the dust is collected, and A combustor that burns the supplied exhaust gas, and a first device that is provided downstream of the combustor and that exchanges heat between the combustion exhaust gas from the combustor and the exhaust gas supplied with air to cool the combustion exhaust gas. A heat exchanger, and a second heat exchanger installed downstream of the first heat exchanger and further cooling the combustion exhaust gas flowing down from the first heat exchanger by indirect heat exchange. A waste gas treatment system characterized by the following features:

12. The refuse exhaust gas treatment system, wherein the combustor combusts the temperature of the incinerated gas to 75 ° C. or more, A heat exchanger for exchanging heat between incineration gas led to the combustor and flue gas flowing down from the combustor, and cooling the flue gas to a temperature of 400 ° C;

The refuse according to claim 1, further comprising a cooler that cools the flue gas that has passed through the heat exchanger to a temperature of 200 ° C. within a time period of 5 seconds or less. 4. Exhaust gas treatment system.

13. The cooler preferably cools the flue gas that has passed through the heat exchanger to a temperature of 200 ° C. within 3.5 seconds. A waste gas treatment system according to item 12.

1 4. The cooler further desirably cools the combustion exhaust gas that has passed through the heat exchanger from a temperature of 380 ° C to 330 ° C within 1 second. 13. The refuse exhaust gas treatment system according to claim 12, wherein

15. The waste gas treatment system further includes a cooler that cools the combustion exhaust gas guided from the heat exchanger to the cooler at a cooling rate of 50 ° CZs or more. Or a waste gas treatment system according to item 2.

16. The cooler according to claim 15, wherein the cooler desirably cools the flue gas introduced from the heat exchanger at a cooling rate of 57 ° C / s or more. Waste gas treatment system.

17. The waste gas treatment system, wherein the cooler indirectly exchanges heat with the combustion exhaust gas passing through a heat exchanger and water to generate steam, and the steam generated by the cooler is 3. The refuse exhaust gas treatment system according to claim 1, further comprising a steam supply unit that supplies the waste gas to the combustor.

1 8. Combustion of the incineration gas from the incineration of refuse or waste in a combustor to decompose dioxin contained in the incineration gas and guide the combustion exhaust gas discharged from the combustor to a heat exchanger, Incineration gas supplied to the Heat exchange to cool the combustion exhaust gas, and indirect heat exchange to the combustion exhaust gas cooled by the heat exchanger in a cooler to further cool the combustion exhaust gas. Waste gas treatment method.

1 9. The incineration gas with the fly ash concentration of 0.1 to 0.01 g Z πl ³ N is burned in a combustor to decompose dioxin contained in the incineration gas and burned in the combustor. The discharged flue gas is guided to a heat exchanger, and indirectly exchanges heat with the incineration gas supplied to the combustor to cool the flue gas. The cooled flue gas is indirectly heat-exchanged by a cooler. Waste gas treatment method characterized by further cooling the waste gas.

20. Air is supplied to the incineration gas generated by incineration of refuse, and the incineration gas supplied with air is burned in a combustor to decompose dioxin contained in the incineration gas. The discharged flue gas is led to a heat exchanger. Air is supplied and indirectly exchanges heat with the incineration gas led to the combustor. The flue gas is cooled to a predetermined temperature, and cooled by the heat exchange. A waste gas treatment method characterized by lowering the combustion exhaust gas to a desired temperature lower than the predetermined temperature.

2 1. The incineration gas generated from the incineration of garbage is burned in a combustor to decompose dioxin contained in the incineration gas, and the combustion exhaust gas discharged from the combustor is led to a heat exchanger to supply air. Then, heat exchange is indirectly performed with the incineration gas led to the combustor to cool the combustion exhaust gas to a predetermined temperature, and the heat exchanged and cooled combustion exhaust gas is further heated to a temperature lower than the predetermined temperature. Waste gas treatment method characterized by lowering the temperature to a low desired temperature 22. Burning incineration gas obtained by incinerating waste or waste in a combustor to decompose dioxin contained in the incineration gas, and from the combustor The discharged combustion exhaust gas is led to a heat exchanger and indirectly interacts with the incineration gas supplied to the combustor. The flue gas is cooled to a temperature within a temperature range of dioxin decomposition or within a temperature range in which dioxin regeneration and decomposition are balanced. Wastewater exhaust gas treatment method, wherein the wastewater is further cooled to below the dioxin regeneration temperature range by indirect heat exchange.

23. The incineration gas from the incineration of the refuse is burned in the combustor, and the flue gas flowing down from the combustor is led to the first heat exchanger, where heat is indirectly exchanged with the incineration gas supplied to the combustor. To cool the combustion exhaust gas, conduct the combustion exhaust gas cooled by the first heat exchanger to a second heat exchanger, and further cool the combustion exhaust gas by indirect heat exchange. The waste gas treatment method.

24. The incineration gas from the incineration of the refuse is burned in a combustor, and the flue gas flowing down from the combustor is led to a first heat exchanger, where heat is indirectly exchanged with the first cooling medium to perform the heat exchange. The flue gas is cooled, the flue gas cooled in the first heat exchanger is guided to a second heat exchanger, and indirect heat exchange is performed with a second cooling medium to further cool the flue gas. A waste gas treatment method characterized by the following:

25. The incineration gas from the incineration of the refuse is burned in a combustor, and the flue gas flowing down from the combustor is led to a first heat exchanger, and the flue gas is within the temperature range of dioxin decomposition, or Cooling is performed within a temperature range where dioxin regeneration and decomposition are in equilibrium, and the flue gas cooled by the first heat exchanger is led to a second heat exchanger. A waste gas treatment method characterized by further cooling to the bottom.

26. The incineration gas generated by incineration of refuse in the incinerator is led to a dust collector, and the dust in the incineration gas is collected by the dust collector. Air is supplied to the incinerator to reduce the concentration of dust in the incineration gas to a desired concentration or less. The dioxin contained therein is decomposed, and the flue gas discharged by burning in the combustor is led to a heat exchanger, and heat is indirectly exchanged with the incineration gas supplied with air and led to the combustor, and the flue gas is discharged. A method for treating refuse exhaust gas, comprising cooling and further indirectly exchanging heat of the flue gas cooled by the heat exchanger with a cooler to cool the flue gas.

27. The waste gas treatment method according to claim 18, wherein the combustion exhaust gas flowing down from the combustor to the heat exchanger is maintained at a temperature of 75 ° C. or more for 1 second or more. A waste gas treatment method according to any of the above.

28. The method according to claim 27, wherein the combustion exhaust gas is desirably held at a temperature of 850 ° C or more for 1.6 seconds or more. 29. The waste gas treatment method, wherein the combustor burns the temperature of the incinerated gas to a temperature of 75 ° C. or higher, and the heat exchanger reduces the temperature of the combustion exhaust gas to 40 ° C. Cooling down to 'C

26. The refuse exhaust gas treatment method according to claim 18, wherein the refuse exhaust gas is cooled to a temperature of 200 ° C. within 5 seconds.

30. The method according to claim 29, wherein the cooler cools the temperature of the flue gas to 200 ° C within 3.5 seconds.

31. More preferably, the cooler cools the temperature of the flue gas from 38 ° C. to 33 ° C. within 1 second in the cooler. Waste gas treatment method.

32. The method for treating waste gas preferably comprises the step of controlling the amount of fuel introduced into the cooler. The waste gas treatment method according to any one of claims 18 to 25, wherein the combustion exhaust gas is cooled at a cooling rate of 50 ° CZs or more.

33. The method according to claim 31, wherein the combustion exhaust gas guided to the cooler is cooled at a cooling rate of 57 ° C Zs or more.

34. The refuse exhaust gas treatment system is characterized in that the cooler indirectly exchanges heat with combustion exhaust gas passing through a heat exchanger and water to generate steam, and supplies the generated steam to the combustor. The waste gas treatment method according to any one of claims 18 to 25.

35. An incinerator for incinerating refuse, a dust collector for collecting dust in incineration gas discharged from the incinerator, a combustor for burning incineration gas guided from the dust collector, and a downstream of the combustor A heat exchanger for cooling the combustion exhaust gas by indirectly exchanging heat between the incineration gas and the combustion exhaust gas flowing down from the combustor; and a heat exchanger installed downstream of the heat exchanger for heat exchange. A cooler that further cools the combustion exhaust gas that has passed through the incinerator, and a steam generator that is installed inside the incinerator and that generates heat by exchanging heat with the incineration gas generated by burning refuse in the incinerator And a steam turbine driven by the generated steam; and a generator connected to the steam turbine.

36. The incineration gas generated by burning the refuse is burned in a combustor to decompose dioxin contained in the incineration gas, and the combustion exhaust gas generated by burning in the combustor is led to a heat exchanger. The incineration gas is cooled by indirectly exchanging heat with the incineration gas supplied to the combustor, the combustion exhaust gas cooled by the heat exchanger is subjected to indirect heat exchange by a cooler, and the combustion exhaust gas is further reduced. In addition to the cooling, the incinerated gas generated by incinerating the refuse is heat-exchanged with a steam generator to produce steam. Generating the generated steam, guiding the generated steam to a steam turbine to drive the turbine, and driving a generator connected to the turbine to generate power.