JPS6157526B2 - - Google Patents

Description

[Detailed description of the invention]

Field of the Invention The present invention relates to a melting device for melting water treatment sludge or ash or dust discharged from an incinerator to form slag, and more specifically, the present invention relates to a melting device for melting water treatment sludge or ash and dust discharged from an incinerator to form slag, and more specifically, The present invention relates to a melting device equipped with a structure for effectively collecting low-boiling point dust. Description of Prior Art In equipment for incinerating municipal waste, in order to solidify incineration residue and recovered dust, an incinerator is installed in the downstream process of the incinerator, and after the incineration residue and recovered dust are turned into molten slag, Cooling, solidification, and evacuation are widely practiced. In addition, water treatment sludge and the like are directly turned into molten slag in an incinerator, cooled and solidified, and then discharged. FIG. 1 shows a flow diagram of a conventional melting apparatus for carrying out the melting process as described above. Waste 1 collected from the city is once stored in a storage pit and then incinerated in an incinerator. Incineration residue 2 such as ash or incombustible materials and exhaust gas 3 are discharged from the incinerator. Of these, the incineration residue 2 is introduced into a melting furnace heated to a predetermined temperature, turned into molten slag, and then cooled and solidified to form solid slag 7.
is discharged from the system as On the other hand, the exhaust gas 3 is cooled by passing through an exhaust gas cooling section A (for example, a sprinkler type cooling device), and after dust in the exhaust gas is removed in the dust collection section A, it is discharged to the outside of the system. Further, the dust 4 collected in the dust collection section A is introduced into the melting furnace, and is turned into molten slag together with the incineration residue 2. Furthermore, in the melting furnace, incineration residue 2
And the exhaust gas 5 generated when melting the collected dust 4 is introduced into a heat exchanger and cooled, and then
The dust is combined with the incinerator exhaust gas 3 through the line 6 and supplied to the dust collection section A, where the dust is collected again. However, the chloride or dust components generated or recovered in the above-mentioned melting equipment include, for example, ZnCl ₂ , PbCl ₂ , CdCl ₂ , KCl, NaCl
It also contains components with a boiling point lower than the temperature inside the melting furnace, such as _FeCl2 . These low-boiling point dusts are vaporized in the melting furnace and discharged together with the exhaust gas, and cannot be solidified as slag. When such a gaseous low-boiling point component is cooled by a heat exchanger or the like, it solidifies again and becomes dust, which is collected in the dust collecting section A. Therefore, it is reinjected into the melting furnace again. However, the internal temperature of the melting furnace is
Since the boiling point is higher than that of such low-boiling components, the low-boiling components are vaporized again and circulated within the system. In this way, the low-boiling components are kept circulating within the recovery system and are not discharged outside the system. Therefore, as this type of melting equipment continues to operate for a long period of time, low-boiling point dust accumulates in the recovery system, and a considerable amount adheres to the pipes and heat exchangers through which the melting furnace exhaust gas 5 flows, causing blockages or malfunctions. There was a problem with inviting people. Therefore, the inventor of the present application proposed a configuration for solving the above-mentioned problems in an earlier application, that is, Japanese Patent Application No. 100119/1983, which has not yet been published. Here, a separate dust collection section is provided in the exhaust gas line 6 of the melting furnace, and the low boiling point dust collected in this dust collection section is introduced into a separately designed remelting furnace with a low furnace temperature. A structure is disclosed in which the molten slag is turned into molten slag and discharged outside the system. However, even with this improved melting device, there were problems such as the relatively complicated structure and the high cost of operating the newly introduced remelting furnace. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a melting device that can efficiently discharge low-boiling point dust out of the system, has a relatively simple structure, and has low operating costs. . In summary, the present invention provides an incinerator for incinerating waste, a melting furnace for melting incineration residue discharged from the incinerator into slag, and a slag discharged from the incinerator and recovered. A first dust supply line for supplying dust to a melting furnace, and an exhaust gas duct branched from a slag discharge port of the melting furnace, and a dust collection section is provided in the exhaust gas duct via an exhaust gas cooling section. In the melting apparatus, a low temperature melting section is provided in the exhaust gas duct upstream of the exhaust gas cooling section, a cooling means is disposed for cooling the slag discharged from the low temperature melting section, and the slag is further collected in the dust collection section. A second dust supply line for returning the collected dust to the low temperature melting section and a third dust supply line branched from the first dust supply line and connected to the second dust supply line are provided. This is a melting device characterized by: Other features of the invention will become clear from the following description of the embodiments. DESCRIPTION OF EMBODIMENTS FIG. 2 is a flow explanatory diagram of a melting apparatus according to an embodiment of the present invention. As is clear from Figure 2,
The melting apparatus of this embodiment consists of an incineration processing portion surrounded by a dashed line X and a melting processing portion surrounded by a dashed dotted line Y. In the following description, symbol A indicates a structure that is also provided in the conventional device shown in FIG. 1, and symbol B indicates a device that is provided for the first time in this embodiment. Waste 11 to be incinerated is stored in a storage pit 12.
The waste is then stored in the incinerator 13. The waste 11 is incinerated in the incinerator 13, and incineration residue 14 and exhaust gas 15 are generated. The incineration residue 14 is supplied to a melting processing section Y, which will be described later.
On the other hand, the exhaust gas 15 generated in the incinerator 13 is cooled in the exhaust gas cooling section A16, and then transferred to the exhaust gas processing section 1.
Guided by 7. The exhaust gas treatment section 17 includes an HCl absorption section 18 and a dust collection section A19. HCl absorption part 1
At 8, in the incinerator 13, for example, HCl generated by combustion of PVC products is absorbed or adsorbed and removed. In addition, when absorbing HCl, CaCO ₃ , Ca(OH) ₂ , CaO, NaOH, etc. are used in a dry method or a wet method. As a result of the absorption reaction, CaCl ₂ or NaCl (hereinafter referred to as chloride) is produced. On the other hand, dust in exhaust gas is
The dust is captured by the dust collecting section A19. Chlorides generated in the HCl absorption section 18 and dust captured in the dust collection section A19 are collected and supplied to the melting furnace 22 via the first dust supply line 21. Note that from this first dust supply line 21, another third dust supply line 23 is branched off. The third dust supply line 23 is led to a low temperature melting section 29 of the melting section Y, as will be described later. The incineration residue 14 and the chlorides and dust in the exhaust gas are both put into the melting furnace 22 and turned into molten slag, then cooled and solidified in the slag cooling section A25, and discharged to the outside of the system as solidified slag. By the way, the melting furnace 22 is normally maintained at a relatively high temperature of 1300°C to 1500°C. Therefore, the exhaust gas generated in the melting furnace 22 contains a large amount of vaporized low-boiling point component dust as described above. This vaporized material is cooled and solidified in an exhaust gas cooling section B26 provided in the exhaust gas dust, and then captured in a dust collecting section B27. The low-boiling point dust captured by the dust collection section B27 is fed into the low-temperature melting section 29 together with the dust from the third dust supply line 23 via the second dust supply line 28. As is clear from FIG. 2, the low temperature melting section 29 is arranged upstream of the exhaust gas cooling section B26. Therefore, the low-temperature melting section 29 is supplied with exhaust gas having a calorific value discharged from the melting furnace 22, and the low-boiling point dust is melted by the calorific value of this exhaust gas. As a result, the low boiling point component becomes molten slag 30 and is discharged from the slag cooling section B31 as solidified slag to the outside of the system. In the apparatus shown in FIG. 2 described above, the incinerator 13 was placed upstream of the melting furnace 22. However, when the waste to be treated is water treatment sludge, as shown by the imaginary line in FIG. can do. In this case, the dust supplied to the low-temperature melting section 29 is only that captured by the dust collecting section B27. However, a part of the slag discharged from the slag cooling section A25 may be supplied to the low-temperature melting section 29 along with the dust from the dust collecting section B27 through the slag supply line 49 (indicated by an imaginary line). Next, the specific configuration of the melting device of this example is as follows.
This will be explained along with FIG. The most important feature of this device is that it has a low-temperature melting section that directly utilizes the sensible heat of the exhaust gas generated in the melting furnace, without constructing a low-temperature melting section that requires a separate heat source as in the previously unknown invention. The goal is to prepare for Referring to FIG. 3, the melting apparatus of this embodiment is as follows:
Melting furnace 22, low temperature melting section 29, melting furnace slag cooling water tank 25 low temperature melting section slag cooling water tank 31 (corresponds to slag cooling section B31 in the previous flow diagram), exhaust gas cooling section B26, dust collection section B27
Consists of etc. A hopper H is attached to the upper part of the melting furnace 22. Wastes such as crushed waste from the storage pit 12, incinerated ash from the incinerator 13, recovered chloride from the HCl absorption section 18, and collected dust from the dust collection section A19 are thrown into this hopper H all at once. Ru. As described above, when treating waste such as water treatment sludge, the water treatment sludge is directly charged into the hopper H and subjected to a melting device as described below. The waste to be treated inputted from the hopper H is melted by flame heat from burners 34, 34 provided approximately at the center of the upper fireproof wall 33 of the flame chamber 32 of the melting furnace 22. A reburning chamber 35 is provided at the bottom of the melting furnace 22.
is formed. The re-combustion chamber 35 functions as a fall path for the molten slag and re-combusts the exhaust gas (incompletely combusted exhaust gas containing H ₂ , CO, etc.) generated in the melting furnace. The molten slag 36 is located at the inclined bottom 3 of the reburning chamber 35.
7 falls on top. Incidentally, in this embodiment, an inclined slag chute 38 is provided so as to cover the surface of the inclined bottom portion 37. Inclined slag chute 3
8 is made of, for example, a stainless steel plate with excellent corrosion resistance and heat resistance. Further, above the inclined slag chute 38, a cooling water supply port 39 is provided in the side wall of the reburning chamber 35, and cooling water is supplied from the cooling water supply port 39 onto the inclined slag chute 38. Therefore, the molten slag 3 that has fallen into the reburning chamber 35
6 falls onto the inclined slag chute 38 without directly contacting the inclined bottom 37. Therefore, damage to the inclined bottom portion 37 due to the heat of the molten slag 36 can be prevented.
It can be effectively prevented. Further, since the impact when the molten slag 36 falls is also alleviated by the inclined slag chute 38, damage to the inclined bottom portion 37 caused by the falling molten slag 36 can be avoided. The molten slag that has flown down from the inclined slag chute 38 together with the cooling water is solidified in the cooling water tank 25 and discharged to the outside of the system by the conveyor 42. In addition, the cooling water supply port 39 and the cooling water recovery path 43a
Surplus cooling water circulation paths Aa and Ab are provided between the cooling water supply port 39 and the inclined slag chute 38 . In this case, part of the cooling water stored in the cooling water tank 25 is used as the cooling water. That is, the water that is circulated as cooling water uses overflow water that has flowed into a surplus cooling water recovery channel 43a attached to the upper part of the cooling water tank 25, and the surplus cooling water that has flowed into the recovery channel 43a is pumped. 44 and sent to the heat exchanger 45 from the cooling water circulation path Aa. After being cooled by the heat exchanger 45, this water is passed through the cooling water circulation path.
The water is guided to the cooling water supply port 39 via Aa. The cooling water discharged from the cooling water supply port 39 is
It flows into the cooling water tank 25 through the inclined slag chute 38 and overflows into the surplus cooling water recovery path 43a again. In this way, the cooling water is circulated, the cooling water is always supplied onto the inclined slag chute 38, and the falling molten slag 36 is smoothly swept away toward the cooling water tank 25 and is cooled at the same time. Therefore, as mentioned above, the inclined bottom 37
The problem of being heated up can be effectively solved. Note that the molten slag 36 is cooled by cooling water on the inclined slag chute 38 to generate water vapor. However, since the cooling water is constantly flowing over the inclined slag chute 38, it will be understood that the location where water vapor is actually generated is the lower portion of the communication passage 46. Further, the cooling water flowing down the inclined slag chute 38 forms an inclined water film, that is, a water curtain in the communication passage 46 portion. Therefore, the water vapor generated in the cooling water tank 25 is prevented from rising by this water curtain. Therefore, there is no fear that water vapor will flow into the afterburning chamber 35, and the temperature inside the afterburning chamber 35 can be kept constant. On the other hand, a cooling medium such as water continues to be supplied to the heat exchanger 45 from the pipes Ba and Bb in order to cool the cooling water sent from the pump 44. That is, the cooling medium is supplied from the storage tank 51 to the heat exchanger 45 by the pump 52, and after being heat exchanged in the heat exchanger 45, it is discharged from the pipe Bb. The cooling medium, that is, the heated cooling medium, sent out from the pipe line Bb is appropriately supplied to end equipment for utilizing residual heat. This makes it possible to effectively utilize waste heat. Next, the treatment of dust in exhaust gas, which is a characteristic feature of the present invention, will be explained. The incompletely combusted exhaust gas generated in the melting furnace 22 is completely combusted by a recombustion burner 53 provided within the recombustion chamber 35 .
The completely combusted exhaust gas is introduced into the exhaust gas cooling section B26 via the exhaust gas duct 54 branched from the re-combustion chamber 35. In the exhaust gas cooling section B26,
Low boiling point dust vapors in the exhaust gas are solidified by cooling. Therefore, these solidified dusts are collected in the dust collecting section B27, and the cleaned exhaust gas is discharged to the outside of the system. On the other hand, the exhaust gas cooling section B26 of the exhaust gas duct 54
A low temperature melting section 29 is inserted on the upstream side. The low-temperature melting section 29 has a structure in which a silo-shaped insertion tube 55 whose outer surface is covered with a refractory material and a pot 56 are suspended below the silo-shaped insertion tube 55. A water seal type low temperature melting section slag cooling water tank 31 is provided below the low temperature melting section 29 . The dust collected by the dust collecting section B27 as described above is fed into the low temperature melting section 29 via the second dust supply line 28. By the way, a mixer 58 is provided in the middle of this dust supply line 28. The mixer 58 is also connected to a third dust supply line 23 branched from the first dust supply line 21 which runs from the HCl absorption section 18 and dust collection section A19 of the incineration processing section to the melting furnace 22. Furthermore, an introduction line 60 for adding FeSO ₄ is also connected to the mixer 58 . Therefore, to the low temperature melting section 29,
The structure is such that these dusts, FeSO ₄ , etc. are injected all at once. In the mixer 58,
A configuration is provided that can set the blending ratio of dust supplied from the dust supply lines 28 and 23 to a predetermined value, thereby making it possible to set the dust blending ratio to a preferable value as described later. Further, when supplying the dust to the low-temperature melting section 29, it is desirable that each dust is uniformly mixed in the mixer 58. For this purpose, the mixer 5
8, for example, hot water supplied from the residual heat utilization water pipe Bb described above may be introduced, and each dust and FeSO ₄ may be kneaded by an arbitrary stirring means. Furthermore, it goes without saying that water may be mixed instead of hot water. As the stirring means, a known mechanical stirring device or air bubbling may be used. Furthermore, if the gas discharged from the dust collection part B27 is used to perform air bubbling, the apparatus can be simplified. The reason why the mixer 58 is provided in this way to mix the dust supplied from the third dust supply line 23 from the incineration processing section will be explained in detail later. Since the dust introduced into the low-temperature melting section 29 is in the form of a paste, it flows down inside the silo-shaped insertion tube 55 . At this time, since the tip of the silo-shaped insertion tube 55 is inserted into the exhaust gas duct 54, it is heated by the high temperature exhaust gas flowing inside the exhaust gas duct 54.
The temperature is gradually increased. By the way, the exhaust gas duct 54
The temperature of the exhaust gas flowing therein is lower than the temperature in the melting furnace 22 and the afterburning chamber 35, and does not have a temperature high enough to vaporize low-boiling point dust. Therefore,
The low boiling point dust is reliably melted in the low temperature melting section 29, collected in the steel 56, overflows from the edge of the pan 56, and falls into the cooling water tank 31. The molten slag is cooled and solidified in the cooling water tank 31 and discharged to the outside by the conveyor 61. In the above-mentioned melting apparatus, in order to convert high boiling point dust such as incineration ash into molten slag, the melting furnace 2 is used.
The temperature inside 2 has been raised to approximately 1350°C. However, the temperature of the exhaust gas that has reached the low-temperature melting section 29 from the melting furnace 22 via the re-combustion chamber 35 and the exhaust gas duct 54 is about 1000°C to 1200°C. Therefore, the temperature of the dust inside the insertion tube 55 heated by the exhaust gas is only raised to 900°C to 950°C at most, and the low-boiling point dust inside the insertion pipe 55 is only melted and not vaporized. . Therefore, the low boiling point dust becomes molten slag and falls into the cooling water tank 31. The melting device of this embodiment selectively extracts low-boiling point dust and melts it into slag at a temperature above the melting point and below the boiling point, and is designed to use the heat retained in the exhaust gas as a heat source, and to The feature is that the dust from the dust supply line is also introduced into the low temperature melting section. Therefore, it can be seen that low boiling point dust can be economically converted into slag. Next, mixing of the dust supplied from the dust supply line 28 and the dust supplied from the dust supply line 23 in the above-mentioned agitator 58 will be explained. First, it should be pointed out that the mixer 58 is not an essential component of the present invention. That is,
The structure may be such that the mixer 58 is removed. It will be understood that even in this case, the low boiling point dust is turned into molten slag due to the retained heat of the exhaust gas flowing in the exhaust gas duct 54, and therefore the low boiling point dust can be reliably discharged to the outside of the system. Dew. However, preferably, the mixer 58 is provided as described above, the dust supply line 23 from the incineration processing section and the FeSO ₄ introduction line 60 are connected, and the mixed dust is supplied to the low temperature melting section 29. The reason for this will be explained in detail based on the following examples. FIG. 4 shows the dust supplied from the second dust supply line 28 and the third dust supply line 23.
It is a graph showing changes in the melting point of mixed dust when changing the mixing ratio with dust supplied from. As is clear from FIG. 4, when the blending ratio of the dust supplied from the second dust supply line 28 to the dust supplied from the third dust supply line 23 exceeds 1:2, the melting point of the mixed dust 900℃
It will be understood that it exceeds Therefore, if this mixing ratio is exceeded, low boiling point dust such as chloride will be vaporized and it will no longer be possible to form molten slag. Therefore, the mixing ratio of the dust supplied from the second dust supply line 28 and the dust supplied from the third dust supply line 23 is required to be 1:2 or less.
Preferably, this ratio is 1:0.9 or less. Thereby the melting point of the mixed dust
This is because the temperature can be lowered to 800°C or less, and vaporization of low-boiling point dust can be reliably prevented. By the way, the fundamental reason for processing it as mixed dust is that the low temperature melting section 29 and the slag cooling water tank 31
Heavy metals from slag solidified by cooling, e.g.
This is to prevent elution of Cd, Pb, etc. In other words, experiments have shown that heavy metals such as Cd and Pb can be eluted in the slag obtained by feeding only the low-boiling point dust collected in the dust collection section B27 into the low-temperature melting section 29 from the second dust supply line 28. It has been confirmed. In order to prevent this, the dust from the third dust supply line 23 is mixed in the mixer 58 as described above. When experiments were repeated under various conditions using the melting apparatus of this example,
The following results are known. Table 1 shows the results regarding heavy metal elution from the obtained slag.

[Table] As is clear from Table 1, the blending ratio of the molten dust supplied from the second dust supply line 28 and the incinerated dust supplied from the third dust supply line 23 is 1:0.7. ~1:0.9 condition,
It will be appreciated that the elution amount of Pb and Cd can be kept low. However, ignoring Cd,
It will be understood that this blending ratio may be in the range of 1:0.5 to 1:0.9 as long as the amount of Pb eluted is only suppressed to 3.0 PPM or less. On the other hand, it should be understood that if Pb can be ignored and the only requirement is to suppress the elution amount of Cd to 0.3 PPM or less, this mixing ratio should be 1:0.6 or more. Dew. As is clear from the results in Table 1 above, by mixing the dust from the incineration section from the third dust supply line 23 in the mixer 58, the dust formed in the low temperature melting zone 29 and the slag cooling water tank 31 is Elution of heavy metals from slag can be effectively prevented. Next, in the mixer 58, FeSO ₄ introduction line 6
The advantage of connecting 0 will be explained. In Table 2,
Experimental results when FeSO ₄ is mixed are shown.

[Table] As is clear from Table 2, it is understood that when 1% FeSO ₄ is added, the amount of Cd and Pb eluted can be reduced more effectively than when it is not added. Will. Furthermore, by adding FeSO ₄ , the mixed dust kneaded in the stirrer 58 can be made more uniform, and therefore a mixed dust with a stable composition can be obtained, and the amount of heavy metals eluted from the slag can be reliably kept constant. It has also been confirmed that it is possible to lower the value below this value. Effects of the Invention This invention provides a low-temperature melting section upstream of the exhaust gas cooling section of the exhaust gas duct, a cooling means for cooling the slag discharged from the low-temperature melting section, and further collects the slag in the dust collection section. a second dust supply line for returning dust to the low-temperature melting section; and a third dust supply line branched from the first dust supply line for supplying dust from the incinerator to the melting furnace and connected to the second dust supply line. Because the structure has a dust supply line, it is possible to economically convert low-boiling point dust into slag, and since dust does not accumulate in the system, there is no possibility of blockages in ducts or dust collectors. It is possible to reliably prevent such accidents.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of a conventional waste melter system. FIG. 2 is a flow diagram of a system incorporating a melting device according to an embodiment of the present invention.
FIG. 3 is a schematic sectional view showing the specific structure of the melting device shown in FIG. 2. FIG. Figure 4 shows the blending ratio of the dust supplied to the low temperature melting section from the second dust supply line and the dust supplied to the low temperature melting section from the third dust supply line, and the ratio of dust supplied to the low temperature melting section from the second dust supply line. It is a figure showing the relationship with the melting point of dust. 13... Incinerator, 21... First dust supply line, 22... Melting furnace, 23... Third dust supply line, 26... Exhaust guy cooling section, 27... Dust collection section, 28... Second dust supply line, 29...
Low temperature melting section, 31... Cooling water tank as a cooling means, 54... Exhaust gas duct.

Claims (1)

[Scope of Claims] 1. An incinerator for incinerating waste, a melting furnace for melting incineration residue discharged from the incinerator into slag, and dust discharged and recovered by the incinerator. a first for supplying the melting furnace to the melting furnace;
A melting device comprising: a dust supply line; and an exhaust gas duct branched from a slag discharge port of the melting furnace, the exhaust gas duct being provided with a dust collection section via an exhaust gas cooling section; A low-temperature melting section is provided upstream of the cooling section, a cooling means is arranged to cool the slag discharged from the low-temperature melting section, and the dust collected in the dust collecting section is sent to the low-temperature melting section. A second dust supply line for returning the dust, and a third dust supply line branched from the first dust supply line and connected to the second dust supply line. Device.