JP3495902B2 - Cooling system for incineration flue gas - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in which a flue is provided with a bag filter for removing air pollutants discharged from an incinerator. In general, when high-temperature exhaust gas discharged from an incinerator contains chlorine gas, if the temperature of the exhaust gas is maintained at 300 to 500 ° C. for several seconds, there is a possibility that dioxin is generated. It is said that there is. Therefore, measures taken to reduce dioxins in smoke are:
This means that the combustion gas is cooled at once from a high temperature range of 500 ° C. or higher to a low temperature range of 200 ° C. or lower. Specifically, a heat exchanger is used. On the other hand, when dioxin once generated is to be removed by a calcareous chemical deposited on the bag filter, the dioxin is led to the bag filter by keeping the high temperature side close to the dioxin generation temperature even in the low temperature region. Is preferred. [0003] However, a wet heat exchanger using water as a cooling medium has a large heat absorption capacity and is suitable for downsizing the apparatus or rapidly cooling the exhaust gas. It was difficult to quickly adjust the amount of heat absorption, which caused a large fluctuation in the temperature of the exhaust gas. On the other hand, a dry heat exchanger using air as the refrigerant can quickly adjust the outlet temperature by controlling the flow rate of the cooling air, but has a disadvantage that the amount of heat absorbed is small and the device becomes large. Was. [0004] The above object is achieved by providing a bag filter in a flue connected to an incinerator, and providing a water-cooled first heat exchanger and an air-cooled type upstream of the bag filter in the flue. The problem is solved by arranging the second heat exchanger in series and interposing the second heat exchanger, and configuring the flow rate of the cooling air sent to the second heat exchanger located on the downstream side to be adjustable. A controller that operates depending on the flow rate of the cooling air sent to the second heat exchanger located on the downstream side depending on the output of a temperature sensor provided in the flue on the outlet side of the second heat exchanger. It is preferable to control the temperature to be substantially constant. [0005] The high-temperature flue gas discharged from the incinerator is efficiently cooled by the first water-cooled heat exchanger to lower its temperature. By adjusting the amount of cooling air flowing to the second heat exchanger, the amount of heat absorbed from the exhaust gas by the second heat exchanger changes quickly. That is, the exhaust gas is cooled at once by the first heat exchanger, and is accurately controlled to the predetermined temperature by the second heat exchanger. The [0006] controller, if higher than the outlet temperature is predetermined temperature of the second heat exchanger cooling air volume is increased, the amount of cooling air if lower than predetermined temperature is controlled so as to reduce. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. In FIG. 1, reference numeral 10 denotes an incinerator using the present invention. The incinerator 10 has a flue 12 connected to an incinerator 11. The stack 12 has a water-cooled first heat exchanger 13 for cooling the high-temperature combustion gas discharged from the incinerator 11.
And an air-cooled second heat exchanger 20 are provided.
The high-temperature combustion gas (exhaust gas) discharged from 1 is cooled at a time, and the time during which the chlorine gas contained in the exhaust gas is kept in the temperature range where dioxin is generated is shortened. Reference numeral 15 denotes a well-known bag filter provided downstream of the heat exchangers 13 and 20. Reference numeral 16 denotes an exhaust fan including a large-sized blower. The discharged exhaust gas is discharged into the atmosphere via a chimney 17. Reference numeral 19 denotes slaked lime supply means for introducing slaked lime to the upstream side of the bag filter 15. [0008] The first heat exchanger 13 is a fire tube boiler type using water as a refrigerant, and the exhaust gas passes through a large number of fire tubes arranged in a lateral direction and is cooled by water filled around the fire tubes. As a result, the heat of the exhaust gas is absorbed by the water, and the heated water is released into the atmosphere from the steam stack 14 as steam. The second heat exchanger 20 uses air as a refrigerant, and as shown in FIGS. 5 and 6, a large number of smoke tubes 2 extending vertically in a box 21 made of a steel plate and having a rectangular shape.
2, 22 are supported. Exhaust gas inflow chamber 23 partitioned by partitions 23, 23 at the upper and lower parts of box 21.
a and an outflow chamber 23b are provided, and one end of the smoke tube 22 is opened to the inflow chamber 23a and the other end is opened to the outflow chamber 23b. Reference numerals 23c and 23d denote an inlet and an outlet, respectively, for connecting the inflow chamber 23a, the outflow chamber 23b, and an external pipe. The flue 22 thus forms part of the flue 12. A cooling air passage 30 is formed between the partition walls 23, 23, and has an inlet 21a and an outlet 21b.
Cooling air is introduced from outside through the cooling air. The cooling air passage 30 is formed between the lower inlet 21a and the upper outlet 21b, and is indicated by arrows in FIG. 6 by upper and lower partition plates 21c and 21d protruding from one wall surface toward the other wall surface. Thus, it is formed in a zigzag. In other words, the heat absorbing effect is enhanced by a so-called three-pass method in which the outer surface of the smoke tube 22 is traversed three times. One end of the cooling air passage 30 is connected to an outlet 21.
The other end is connected to a blower 31 provided outside through an inlet 21a. The blower 31 has a drive motor 32 integrally, and the drive motor 3
2 is a commercial product that can increase or decrease the amount of air blow by changing the rotation speed. The drive motor 32 is connected to an inverter power supply, and the rotation speed can be increased or decreased by changing the frequency of the power supply. 33 is a controller for the drive motor 32, 34 is the exhaust gas outlet 23d
Is a temperature-sensitive sensor provided for detecting exhaust gas temperature. FIG. 8 is a flowchart showing the operation of the controller 33 for controlling the drive motor 32. Incinerator 1
When 0 operates, exhaust gas flows through the flue 12 and the temperature sensor 34 detects the temperature. The temperature of the exhaust gas discharged from the second heat exchanger 20 is set to a predetermined value T ° C., in this embodiment, 150 ° C. The exhaust gas temperature is compared with a predetermined value T ° C. every predetermined time s seconds, for example, every 10 seconds. At the beginning of the operation of the apparatus 10, the exhaust gas temperature t ° C. is T
The drive motor 32 remains stopped until the temperature reaches ° C. When the detected temperature t ° C. reaches T ° C., the drive motor 32 is driven, and cooling air is sent to the cooling air passage 30. If the state of T <t still continues after 10 seconds, the rotational speed of the drive motor 32 is increased each time to a speed that increases the blowing amount by a predetermined amount, for example, 6%. Exhaust gas temperature t ° C decreases and T ° C
When the temperature reaches> t ° C., the drive motor 32 is reduced to a speed that reduces the air flow by 6%. That is, the drive motor 32 determines whether or not the exhaust gas temperature t ° C. exceeds the predetermined value T ° C., and controls the exhaust gas temperature by increasing or decreasing the air blowing amount by 6% every predetermined time s seconds. In this embodiment, as means for adjusting the amount of cooling air for cooling the flue gas in the second heat exchanger 20, the amount of air discharged from the blower 31 is increased or decreased as shown in FIG. However, this configuration is not an essential requirement for the configuration of the invention, and as shown in FIG. Of course, the air volume may be increased or decreased by increasing or decreasing the degree. According to the first aspect of the present invention, it is possible to obtain an apparatus having a small installation area of the heat exchanger and excellent responsiveness. Further , the controller has a simple structure, and an excellent device which is inexpensive and practical can be obtained. And so on.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart of an incinerator using one embodiment of the present invention. FIG. 2 is a plan view of a second heat exchanger that forms a main part of the present invention. FIG. 3 is a view as viewed in the direction of arrows in FIG. 2; FIG. 4 is an IV view taken in the direction of arrow in FIG. 2; FIG. 5 is a sectional view taken along line VV in FIG. 4; FIG. 6 is a sectional view taken along the line VI-VI in FIG. 4; FIG. 7 is an external view showing a cooling air blower, and FIG.
Is an example of using a variable speed blower to adjust the air flow,
(B) is an example using a damper. FIG. 8 is a flowchart for adjusting exhaust gas temperature. DESCRIPTION OF SYMBOLS 10 incinerator 11 incinerator 12 flue 13 first heat exchanger 14 steam chimney 15 bag filter 16 exhaust fan 17 chimney 19 slaked lime supply means 20 second heat exchanger 21 boxes 21 c, 21 d partition plate 22 Smoke tube 23 Partition wall 23a Inflow chamber 23b Outflow chamber 23c Inflow port 23d Outflow port 30 Cooling air passage 31 Blower 32 Drive motor 33 Controller 34 Temperature sensor 35 Damper

   ────────────────────────────────────────────────── ─── Continuation of front page       (56) References JP-A-9-42646 (JP, A)                 JP-A-63-315122 (JP, A)                 JP-A-8-210617 (JP, A)                 JP-A-2-237483 (JP, A)                 JP-A-9-122438 (JP, A)                 JP-A-6-42728 (JP, A)                 Actual opening 1979-144458 (JP, U)                 Actual opening Hei 4-115234 (JP, U)

Claims (1)

(57) [Claims 1] A water-cooled type in which a bag filter is provided in a flue connected to an incinerator, and a smoke tube forming a part of the flue is cooled by water upstream of the bag filter. The first heat exchanger and an air-cooled second heat exchanger that cools a flue tube forming a part of the flue with air are sequentially arranged in series in this order, and are interposed in the second heat exchanger. The flow rate of the cooling air to be blown is configured to be adjustable, and the second heat exchanger is further provided with an inflow chamber and an outflow chamber of the exhaust gas which are respectively partitioned by upper and lower parts by partitions. between these partition walls to form a passage of the cooling air, the lower portion and upper portion of the passageway, an inlet and an outlet of the cooling air <br/> formed respectively, in the second heat exchanger Is formed zigzag by upper and lower partition plates, and this second heat exchange Flue gas temperature detected by the temperature-sensitive sensor disposed on the outlet side of the flue of the vessel stops the drive motor of the variable speed type blower for blowing the cooling air to reach a starting initial predetermined value of the incinerator On the other hand, when the flue gas temperature detected by the temperature sensor reaches a predetermined value, the drive motor is driven, and the air is blown to the second heat exchanger so that the flue gas temperature becomes constant at a predetermined value. And a controller for controlling a flow rate of the cooling air.