JPS6322874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to energy recovery type waste treatment equipment, in particular, to recover energy from waste by using a combination of pyrolysis treatment and fermentation treatment, and to reduce the volume of materials ultimately discharged from the waste treatment equipment. This invention relates to waste treatment equipment that can be made significantly smaller.

Currently, urban solid waste (so-called municipal waste) is
Most of it is disposed of by landfill or incineration. It is well known that in recent years, such waste has been reconsidered as a renewable energy resource. As one type of municipal waste processing equipment suitable for this purpose, a system that uses both thermal decomposition and fermentation processing of waste is being developed. The details of this combination system will be referred to later in the description of an embodiment of the present invention, but the outline is as follows. First, in the pre-processing stage, the collected garbage is separated into a group consisting mainly of kitchen waste and other organic substances, mainly plastics and paper.
Digestion gas (methane gas + carbon dioxide gas) is recovered from the former waste through anaerobic fermentation. In addition, digestion sludge is generated at this time.

The latter waste is decomposed into produced gas and charred matter by thermal decomposition, and flammable oil (plastic oil and cellulose oil) is separated and purified from the produced gas.

Digestion gas and combustible oil recovered in this way are used as energy sources, but the problem in this case is the digestion sludge produced during fermentation and the combustible oil produced during pyrolysis. This is the treatment with the resulting carbide. For example, in conventional pyrolysis furnaces, the carbide discharged from the furnace is left in the open air for a while and, after waiting for the temperature to drop, is disposed of in a landfill or the like. However, due to the lack of landfill space and other reasons, this disposal method has its limits, and charred materials that cannot be disposed of are often left behind. Therefore, in order to treat a large amount of municipal waste by pyrolysis, it is necessary to take appropriate measures to treat this charred material, especially to reduce its volume (volume reduction). If this is not achieved, waste disposal may be restricted in this respect.

On the other hand, fermentation treatment has been widely used in sewage treatment, industrial wastewater treatment, etc., and the sludge discharged from these fields is generally treated by landfilling or incineration. However, when incinerated, sludge has an extremely high moisture content of over 75% by weight, and if incinerated in this state, the combustion temperature will be extremely low, causing odor and
Gas containing harmful gases, water vapor, etc. (hereinafter referred to as mixed gas) will be generated. Suratji,
The generation of mixed gas can be prevented by incinerating at a high combustion temperature, such as by pre-drying using an external heat source or by using auxiliary fuel during incineration. However, in either case, a large amount of energy is consumed, which is not preferable.

As one of the countermeasures, there is a method of pre-drying the sludge before it is put into the incinerator by exchanging heat with the combustion exhaust gas from the incinerator that incinerates the sludge. 48−
78782). In this method, if the amount of heat generated in the incinerator and the amount of heat consumed during heat exchange cannot be properly balanced, the waste will not be sufficiently dried, and as a result, the combustion temperature in the incinerator will drop, eventually reaching a sufficiently high temperature. Auxiliary fuel will be required to achieve combustion temperature. However, as a concept, it is possible to apply this system to the treatment of digested sludge in a waste treatment facility that uses both pyrolysis treatment and fermentation treatment, to which the present invention is applied, as described above.

By the way, even if the above-mentioned method is applied to the above-mentioned waste treatment equipment, it is only a local solution that merely processes the digested sludge within the fermentation treatment system, and it does not affect the overall waste treatment equipment. There is no practical solution. This is because the carbide produced by thermal decomposition remains untreated, and its sensible heat is not utilized at all.

This invention has been made in view of the above points, and its purpose is to reduce the amount of waste that is ultimately discharged from waste treatment equipment that uses both thermal decomposition treatment and fermentation treatment of waste. The object of the present invention is to provide a new energy recovery type waste treatment facility equipped with an exhaust treatment system that can efficiently treat waste and achieve significant volume reduction.

The gist of this invention is to dry the digested sludge discharged from the fermentation treatment system using the sensible heat of the charred matter discharged from the pyrolysis treatment system and convert it into something easily combustible. The aim is to combust carbides together.

Due to the co-combustion of char, the combustion temperature during incineration is raised to almost the same level as in a normal waste incinerator, and therefore both substances eventually become incineration ash, which undergoes both thermal decomposition and fermentation. It is possible to significantly reduce the volume of waste from the treatment system.

Furthermore, as mentioned above, since the combustion temperature during incineration is quite high, the flue gas therefrom can be used for further drying of the digester sludge.

A detailed explanation will be given below with reference to the drawings.

FIG. 1 shows a schematic configuration of garbage processing equipment according to an embodiment of the present invention. In addition, in the figure, each substance such as garbage, waste, oil, gas, water, etc. is transferred between various devices by appropriate transportation means such as pipes or other transportation equipment, but in the figure, all of the above substances are transferred between various devices. The flow is shown by a solid line with an arrow. Among them, thin solid lines indicate the flow of gas or gaseous substances, and other substances are indicated by thick solid lines. However, in the following description, the respective reference numbers may indicate the conveyance means in question, or the substances themselves transferred by the means.

In the figure, reference numeral 1 indicates a pre-processing device, which converts collected waste 2 into waste 3 suitable for thermal decomposition such as paper and plastics (garbage that is not suitable for fermentation or can only be processed by thermal decomposition). including)
and Garbage 4, which is mainly kitchen waste and is suitable for fermentation processing. Various methods have been proposed for sorting, but a typical method is to first remove empty cans and other metals from the thrown garbage 2 using a device that uses magnetic force, and then use wind power or the specific gravity of the garbage to remove empty cans and other metals. There is a device that performs the above-mentioned sorting using .
The waste thus separated is supplied to a thermal decomposition treatment system and a fermentation treatment system, respectively.

The main components of the pyrolysis treatment system are a pyrolysis furnace 5 and an oil separation and purification device 6. Although the pyrolysis furnace 5 is described as a fluidized bed type pyrolysis furnace in this embodiment, the present invention is not limited to the type of pyrolysis furnace. Here, to briefly explain about the fluidized bed type furnace, sand is put into the furnace, and the sand is fluidized by blowing air 8 from the bottom of the furnace with the blower 7. The waste 3 is thrown into the tank and thermally decomposed. In the furnace, garbage is fluidized together with sand, so
Uniform heat can be applied even to non-uniform materials such as municipal waste. The pyrolysis furnace 5 is usually
It operates in a temperature range of 450 to 550℃ and thermally decomposes waste 3.

The gas generated by the thermal decomposition is taken out from a pipe 9 at the top of the furnace. This generated gas 9 contains gaseous flammable oil. The extracted generated gas 9 is guided to the oil separation and purification device 6 . This device 6 uses water to cool the produced gas 9 and separate and recover the flammable oil 10. The remaining gas components are discharged into the atmosphere as off-gas 11 after being subjected to necessary exhaust gas treatment. In addition, the pyrolysis furnace 5 collects carbide generated during the pyrolysis treatment of the garbage that is successively fed into the overflow pipe 1 along with some sand.
Discharge from 2. This waste 12 is led to a separator 13, where it is separated into sand 14 and carbide 15. The sand 14 is returned to the pyrolysis furnace 5 and reused for the fluidized bed. The carbide 15 is transferred to an exhaust treatment system to be described later.

The main component of the fermentation treatment system is fermentation treatment equipment 1.
It is 6. This device 16 anaerobically ferments the waste 4 using, for example, methane-fermenting bacteria. The resulting digestion gas 17 is drained and then stored. Digested sludge produced by fermentation treatment 18
The water used for this purpose is discharged as waste water 19. The digested sludge 18 is transferred to a waste treatment system to be described later. Further, the wastewater 19 is sent to a wastewater treatment device 21 along with wastewater 20 from the oil separation and purification device 6.
After being treated there, it is discharged as effluent water 22.

The waste treatment system for supplying the above-mentioned charred material 15 and digested sludge is constructed as follows. Both effluents are first led to a drying device 23.
The carbide 15 discharged from the pyrolysis furnace 5 has a temperature substantially close to the operating temperature of the pyrolysis furnace (450 to 550°C). Therefore, the drying device 23
Using sensible heat, heat exchange is performed with the digested sludge 18, and the digested sludge 18 is dried. The simplest method of heat exchange is to mix both effluents. That is, the charred material 15 having the above-mentioned temperature is mixed with the digested sludge 18,
By stirring well, heat exchange occurs through direct contact between the two substances. As a result, the water in the digested sludge 18 is evaporated and dried. At that time, the mixed gas 24 containing odor etc.
is generated, which is deodorized by the deodorizing device 25 and then released into the atmosphere as a discharged gas 26. Note that the mixing means used here is one in which the temperature of the substances to be mixed is not very high.
It is possible to use devices of this kind that are known in the art.

The mixture 27 from the drying device 23 is led to an incinerator 28 where it is incinerated. The combustion exhaust gas 29 generated by this incineration process is subjected to well-known exhaust gas treatment and released into the atmosphere. Incinerator 28
Since the discharge from the pyrolysis furnace 5 (that is, the final discharge from the waste treatment equipment) 30 is incineration ash, it is compared with the charred material 15 and digested sludge 18 which are discharge from the pyrolysis furnace 5 and the fermentation treatment equipment 16. , resulting in a significant decrease in its volume. In addition, charcoal 15 is used to dry digested sludge 18 which has a high moisture content.
Since the system utilizes the sensible heat possessed by the waste, there is no need to supplement energy from the outside, and the waste treatment facility as a whole achieves highly efficient waste treatment.

By the way, in the above embodiment, the digestion sludge 18 was dried by heat exchange through direct contact with the carbonized material 15 having sensible heat. This method is extremely simple in terms of structure, and is also the quickest method in that the digested sludge 18 is co-fired with the carbide 15 in the end. However, if sufficient consideration is not taken, there is a risk that the mixture 27 fed into the incinerator 28 will have uneven drying.

One of the reasons for this is that, unlike mixing and drying while always obtaining constant thermal energy from the outside, the method uses the thermal energy of one of the substances itself to be mixed. A situation like this occurs. That is, the drying device 23
When freshly supplied char (and therefore has sufficient drying capacity) comes into contact with digester sludge, which is also completely freshly supplied (and therefore has undergone little drying), both substances Since there is a large temperature difference between them, a considerable amount of heat is taken away from the carbide. Although the digested sludge may then undergo sufficient drying, the char will greatly reduce its drying capacity and the digested sludge that comes into contact with the char will not be sufficiently dried during the subsequent mixing process. On the other hand, if the newly supplied carbide comes into contact with a part that has already been mixed and stirred for a while in the drying equipment, the temperature difference between the two substances is not very large, so a large amount of heat may be taken away. Therefore, the carbide will continue to maintain a considerable drying ability.
In this way, localized areas of sufficient drying and areas of insufficient drying are created in the mixture.

Another reason is as follows. Even if there is uneven drying as described above, if uniform mixing is possible, for example when fluids are mixed together, considerable uniformity can be achieved through sufficient mixing. However, it is difficult to mix char and digested sludge completely homogeneously, as in the case of fluids. As a result, the drying unevenness generated as described above remains in the mixture fed into the incinerator.

Since such drying unevenness makes combustion in the incinerator unstable, it is better to prevent its occurrence as much as possible. For this purpose, we clearly distinguish the drying process in the drying device into a heat exchange process and a mixing process.
In the heat exchange process, heat exchange is performed effectively without direct contact between the char and the digested sludge, and then the two substances are mixed. A schematic configuration for this purpose is shown in FIG. In addition,
The figure shows only the structure inside the drying device 23, where 23a is a heat exchange device and 23b is a mixing device. Other reference numbers indicate the same as in FIG. However, the charred material and digested sludge discharged from the heat exchanger 23a are shown as 15' and 16', respectively. In this case as well, a well-known mixing device can be used as the mixing device 23b, as described in the previous embodiment. An example of an effective configuration for the heat exchange device 23a in this case is shown in FIG. 3.

In the figure, the casing 3 of the heat exchange device 23a
Within 5, two suitable transport devices 36, 37 are provided, for example belt conveyors. One device 36 is a device for transferring the carbide 15 discharged from the pyrolysis furnace 5, and transfers the carbide 15 charged from the input port 38 toward the discharge port 39. The other device 37 is provided in a space almost directly above the transfer device 36, and transfers the digested sludge 18 from the fermentation treatment device 16 from its input port 40 to its discharge port 41. With this configuration, the digested sludge 18 moving in the upper stage receives radiant heat from the charred material 15 moving in the lower stage during the movement process, is gradually dried, and is discharged from the discharge port 41. The gas 24 containing odor, water vapor, etc. generated at this time is led to the deodorizing device 25 through an exhaust port 42 provided at the upper part of the casing 35.

In addition, as shown by the arrow in the figure,
The carbide 15 and the digested sludge 18 are moved in opposite directions. This has the following effects. The temperature distribution of the carbide 15 on the moving device 36 appears to decrease almost linearly from the input port 38 toward the discharge port 39, that is, along the direction of movement of the carbide 15. The digested sludge 18 on the moving device 37 is initially preheated at a low temperature when it is supplied from the input port 40, and is exposed to a gradually higher temperature as it moves toward the discharge port 41 side. Therefore, the temperature distribution appears to increase almost linearly along the direction of movement. As a result, the temperature difference between the digested sludge 18 moving in the upper stage and the charred material 15 moving in the opposite direction in the lower stage is approximately equal over the entire distance of movement of both substances. This allows uniform heating and sufficient drying of the digested sludge 18.

Note that the heat exchange device shown in FIG. 3 shows an example of a desirable embodiment, and the heat exchange device applicable to the present invention is not limited to this.

The digested sludge 18' from the outlet 41 dried as described above is mixed with the carbonized material 1 from the outlet 39.
5' and mixed by the mixing device 23b and guided to the incinerator 28. In this case, the digestive sludge 1
8' is so well dried that, depending on its degree of drying, it is not necessarily necessary to mix it with the charred material 15' after it has been discharged from the heat exchanger 23a, but to separate both materials into the incinerator. 28 for co-firing. However, for more uniform combustion within the incinerator 28 and for reasons described below, it is desirable to mix both materials before charging them into the incinerator 28, as described above. That is, by this mixing, the moisture content of the combustion material in the incinerator 28 (not the moisture content of the digested sludge itself) is further reduced, making it easier to burn. For example, let A (Kg) be the amount of carbide 15' discharged from the heat exchanger 23a per unit time, and B (Kg) be the amount of the digested sludge 18'. Further, although the digested sludge 18' is dried in the heat exchanger 23a, its moisture content does not become zero. Therefore, if this water content is α, the amount of water entering the mixing device 23b is αB (Kg). On the other hand, the total amount produced by mixing is A+B (Kg). Therefore, the moisture content of the mixture discharged from the mixing device 23b (i.e., the combusted material fed into the incinerator 28) is αB/(A+B), which is more clearly than the moisture content α of the digested sludge 18' itself. becomes smaller. From this, it can be understood that combustion is easier when the digested sludge 18' is burned as a mixture than when it is burned itself.

By the way, in the embodiment shown in FIG.
The combustion exhaust gas 29 from the incinerator 28 has been subjected to appropriate exhaust gas treatment and released into the atmosphere. However, here, the dried digestive sludge 1
It should be noted that upon combustion of 8', carbide 15' is also combusted. That is,
As mentioned above, in the present invention, the combustion material incinerated in the incinerator 28 is more combustible than the dried digested sludge 18' itself. Therefore, the combustion temperature in the incinerator 28 becomes sufficiently high, and is almost close to the combustion temperature in a normal garbage incinerator. Generally, waste incineration processing is performed at considerably higher temperatures than thermal decomposition processing. Its temperature is approximately 900℃.
The combustion exhaust gas from the incinerator 28 operated at such a high temperature also has a temperature almost similar to that.

On the other hand, the temperature of the carbide 15 used for heat exchange with the digestion sludge 18 in the above-described embodiment is approximately close to 500° C., which is the operating temperature of the pyrolysis furnace 5. Therefore, the combustion exhaust gas 29 can be used to further dry the digestion sludge 18 (or the mixture thereof with the char 15) after heat exchange with the char 15.

The embodiment shown in FIG. 4 is constructed based on this idea. The figure shows only the drying and incineration process, but the other parts are the same as the embodiment shown in FIG. Further, in the figures, the same components as those in FIG. 1 are designated with the same reference numbers. In order to realize the above idea, this embodiment uses a drying device 3 that performs the second heat exchange.
1 (hereinafter referred to as a second drying device). In this second drying device 31, heat exchange between the mixture 27 from the drying device 23 (hereinafter referred to as the first drying device in this embodiment) and the combustion exhaust gas 29 led from the incinerator 28 is performed. The mixture 27 is further dried. After this heat exchange, the combustion exhaust gas 29 is subjected to necessary exhaust gas treatment and released into the atmosphere. The further dried mixture 32 is transferred to the incinerator 28,
Incinerated. Also, during heat exchange in the second drying device 31, a mixed gas 33 is generated, which is led to the deodorizing device 25 together with the mixed gas 24 similarly generated in the first drying device 23, where it is deodorized. It is then released into the atmosphere.

Also in this embodiment, a heat exchange device as shown in FIG. 3 can be used as the first drying device 23. In this case, the first drying device 23
There are two possible cases for the substance to be transferred from the dryer to the second drying device 31.

One of them is the carbonized material 15' discharged from the heat exchange device in the first drying device 23 and the digested sludge 1.
8' and then sending the mixture to the second drying device 31, the other method is to transfer only the digested sludge 18' discharged from the heat exchange device to the second drying device 31.
After the digested sludge 18' is discharged from the second drying device 31, the charred material 1
This is the case where it is mixed with 5'. The schematic configurations in each case are shown in FIGS. 5a and 5b. The figure shows only a portion of the drying device, and the other portions are similar to the structure shown in FIG. 1. Further, the reference numbers in the drawings are the same as those used in the previous drawings, so explanations will be omitted.

In the case of FIG. 5a, there is no need to install any other device between the second drying device 31 and the incinerator 28, so the combustion exhaust gas can be transported from the incinerator 28 to the second drying device 31 by the shortest distance. 29 can be guided, and heat loss between them can be reduced. However, on the other hand, in the second drying device 31, heat is absorbed not only by the digested sludge 18' to be dried but also by the charred material 15' which does not originally need to be dried.

In the case of FIG. 5b, a mixing device is installed between the second drying device 31 and the incinerator 28, and the path of the combustion exhaust gas 29 becomes somewhat longer, increasing heat loss. Instead, in the second drying device 31, the combustion exhaust gas 29 exchanges heat only with the digestion sludge 18' that needs to be dried, which is efficient. In any case, both methods have advantages and disadvantages, and which method to use should be determined based on the specifications of each device, their installation status, and other factors.

As detailed above, according to this invention, energy can be effectively recovered from municipal waste, and the final volume of waste can be extremely reduced without receiving any energy supply from outside. It is possible to realize a new energy recovery type waste treatment facility that can perform the following tasks.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a schematic configuration of an energy recovery type waste treatment facility that is an embodiment of the present invention, Fig. 2 is a diagram showing an improved example of the drying device in the above embodiment, and Fig. 3 is similar to Fig. A diagram showing a specific configuration of a heat exchange device suitable for use in the improved example shown,
FIG. 4 is a diagram schematically showing a partial configuration of an energy recovery type waste treatment facility according to another embodiment of the present invention;
FIGS. 5a and 5b are views showing a modification of the drying device portion in the other embodiment described above. Explanation of main symbols, 1: Pretreatment device, 5: Pyrolysis furnace, 6: Oil separation and purification device, 10: Recovered combustible oil, 13: Sand/char separator, 16: Fermentation treatment device, 17: Digestion gas to be recovered, 21: wastewater treatment device, 23: drying device, 23a: heat exchange device,
23b: Mixing device, 25: Deodorizing device, 28: Incinerator, 31: Second drying device.

Claims (1)

[Claims] 1. Pretreatment means for separating collected waste into waste suitable for pyrolysis treatment and waste suitable for fermentation treatment, and converting the waste suitable for pyrolysis treatment into generated gas and charred matter. A pyrolysis treatment means for separating and recovering combustible oil from the generated gas and discharging the charred material to the outside; A fermentation treatment means for discharging the digested sludge produced at that time to the outside; an incineration treatment means for co-incinerating the discharged charred material and the digested sludge; 1. An energy recovery type waste treatment facility comprising: drying means for drying the digested sludge by exchanging heat between the sludge and the sludge. 2. According to claim 1, the drying means includes a mixing device, and mixes the charred material and the digested sludge to effect heat exchange between the two substances through direct contact. Energy recovery type waste treatment equipment. 3. In the description of claim 1, the drying means has a heat exchange device and a mixing device, and the charred material and the digested sludge exchange heat in the heat exchange device without coming into direct contact with each other. The energy recovery type waste processing equipment is characterized in that the energy recovery type waste processing equipment is mixed in the mixing device after the mixing. 4. According to claim 3, the heat exchange device includes a first transfer device for moving the char, and a second transfer device for moving the digested sludge, which is located in a space substantially above the first transfer device. 1. An energy recovery type waste processing facility, comprising a transfer device, and these two transfer devices are operated such that the moving directions of the substances they respectively move are opposite to each other. 5. Pretreatment means for separating the collected waste into waste suitable for pyrolysis treatment and waste suitable for fermentation treatment, and pyrolysis of the waste suitable for pyrolysis treatment into a product gas and charred matter to generate the product gas. a pyrolysis treatment means for separating and recovering combustible oil from the waste and discharging the charred matter to the outside; and a pyrolysis treatment means for anaerobically fermenting the waste suitable for the fermentation treatment, recovering the digestion gas generated from the anaerobic fermentation, and recovering the digestion sludge produced at that time. A fermentation treatment means for discharging to the outside, an incineration treatment means for co-combusting the discharged charred material and the digested sludge, and a heat exchange between the two substances before the charred material and the digested sludge are supplied to the incineration treatment means. heat exchange between the first drying means for drying the digested sludge and the combustion exhaust gas led from the incineration treatment means for the substance discharged from the first drying means, and then the incineration treatment. and a second drying means for supplying energy to the drying means. 6. In the description of claim 5, the first drying means has a mixing device, and mixes the charred material and the digestion sludge to perform heat exchange between the two substances through direct contact. Energy recovery type waste treatment equipment featuring: 7. In claim 5, the first drying means has a heat exchange device and a mixing device, and the char and the digested sludge exchange heat in the heat exchange device without coming into direct contact with each other. An energy recovery type waste processing facility characterized in that after performing the above steps, the waste is mixed in the mixing device. 8. In the description of claim 5, the first drying means has a heat exchange device, and performs heat exchange between the charred material and the digestion sludge without bringing them into direct contact with each other, Further, the second drying means is supplied with only the digestion sludge from the first drying means, exchanges heat with the combustion exhaust gas, and then mixes it with the char. Energy recovery type waste treatment equipment. 9. In claim 7 or 8, the heat exchange device in the first drying means includes a first transfer device for moving the carbide and a space substantially above the first transfer device. and a second transfer device located therein for moving the digested sludge, wherein the two transfer devices are operated such that the directions of movement of the substances to be moved are opposite to each other. Collection type garbage processing equipment.