JP2009204282A - Sludge treatment method and sludge treatment system with circulating fluidized bed furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sludge treatment method and a sludge treatment system with a circulating fluidized bed furnace, capable of appropriately maintaining a pressure difference within the furnace without replenishing additional fluid media even when a fluid medium is discharged together with exhaust gas. <P>SOLUTION: In the sludge treatment method, after sludge 3 is dried by a dryer 2, dried sludge 4 is charged to the circulating fluidized bed furnace 10 and is burned while mixed with a fluid medium. In the dryer 2, drying treatment is performed to obtain the dried sludge 4 having 60-30% of a water content, and at least part of the dried sludge 4 charged to the circulating fluidized bed furnace 10 becomes block sludge particles and is circulated within the furnace 10 together with the fluid medium. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sludge treatment method in which sludge such as sewage sludge is dried with a dryer and then burned while being mixed with a fluidized medium in a circulating fluidized bed furnace, and a sludge treatment system equipped with a circulating fluidized bed furnace. .

  Conventionally, circulating fluidized bed furnaces are often used for the treatment of sludge discharged from sewage treatment plants, human waste treatment plants, wastewater treatment facilities, and the like. The circulating fluidized bed furnace burns and disperses the sludge and the fluid medium mixed with the primary air introduced from the bottom of the riser, and entrains the dispersed fluid medium to the free board by introducing the secondary air. The unburned matter is completely burned, the fluidized medium is separated from the combustion exhaust gas by a cyclone, returned to the riser, and the fluidized medium is recycled. Such a circulating fluidized bed furnace can instantly dry and incinerate sludge, thereby maintaining a fluid medium at a high temperature and enabling continuous combustion. In addition, since the heat capacity of the fluidized medium is very large, it is suitable for intermittent operation with little heat dissipation when stopped, and the fluidized medium has a high thermal conductivity, so it has a high water content such as sewage sludge. It is also suitably used for products.

In a treatment system equipped with such a circulating fluidized bed furnace, when treating sludge having a high water content, the sludge is dehydrated and dried, and then put into the circulating fluidized bed furnace for incineration. For example, Patent Document 1 (Japanese Patent Laid-Open No. 11-63458) discloses a method in which dehydrated sludge is dried with a dryer and then put into a circulating fluidized bed furnace for incineration.
Further, in Patent Document 2 (Japanese Patent No. 3790431), a dryer is provided on the upstream side of the circulating fluidized bed furnace to collect ash in the exhaust gas discharged from the circulating fluidized bed furnace, and the dryer An apparatus adapted to return to is disclosed. This apparatus generates steam by waste heat of combustion exhaust gas from a circulating fluidized bed furnace and introduces this steam into a dryer to perform a drying process, and generally has a moisture content of 80 to 90%. The dehydrated sludge was dried so as to reduce the water content to about 70 to 75%.

Japanese Patent Laid-Open No. 11-63458 Japanese Patent No. 3790431

In the above-described conventional circulating fluidized bed furnace, the fluidized medium has become smaller due to crushing accompanying the flow, and has shifted from the cyclone to the exhaust gas side. As a result, the fluid medium circulating in the furnace decreases, and the pressure difference in the furnace cannot be maintained in an appropriate range. Therefore, it is necessary to supply a new fluid medium to replenish this, and the running cost increases. On the other hand, a method of separating and recovering the fluid medium from the fly ash collected by the exhaust gas treatment and returning it to the furnace has also been proposed, but it is difficult and time-consuming to separate the fluid medium and the fly ash. .
Therefore, in view of the above-described problems of the prior art, the present invention can properly maintain the differential pressure in the furnace without replenishing a new fluid medium even when the fluid medium is exhausted along with the exhaust gas. An object is to provide a sludge treatment method and a sludge treatment system equipped with a circulating fluidized bed furnace.

Therefore, in order to solve this problem, the present invention provides:
In the sludge treatment method in which the sludge is dried with a dryer, and then the dried sludge is put into a circulating fluidized bed furnace and burned while being mixed with a fluid medium.
By drying the sludge so as to obtain a dried sludge having a water content of 60 to 30% in the dryer, at least a part of the dried sludge put into the circulating fluidized bed furnace is a lump sludge. It is characterized in that it is circulated in the furnace together with the fluid medium in the form of particles.

When the sludge dries, the moisture is lost and the fixed carbon and ash collect toward the center. The dry sludge having a moisture content of 60% to 30% increases in strength due to the collected fixed carbon and ash, so that it is difficult to reduce the particle size even if it is put into the circulating fluidized bed furnace, and it acts as a fluid medium. .
On the other hand, sludge having a water content of 60% or more starts combustion without being collected by ash when it is introduced into a circulating fluidized bed furnace. It moves to the exhaust gas side. On the other hand, sludge having a water content of 30% or less burns immediately after being introduced into a circulating fluidized bed furnace and is ashed to become a fluid medium.
Therefore, after the sludge is dried to a moisture content of 60 to 30% as in the present invention, the sludge in which fixed carbon and ash are agglomerated acts as a fluid medium by putting it in a circulating fluidized bed furnace. Even if the fluidized medium is discharged accompanying the exhaust gas, it is possible to maintain the in-furnace differential pressure within a certain appropriate range without newly supplying the fluidized medium.

In addition, after drying a part of the sludge with the dryer, the dried sludge is put into the circulating fluidized bed furnace, and the remaining sludge is directly fed into the circulating fluidized bed furnace without drying. The sludge is simultaneously burned in the circulating fluidized bed furnace.
A dryer in a circulating fluidized bed furnace often performs a drying process using waste heat of exhaust gas, and the amount of heat that can be used for drying is limited. In a circulating fluidized bed furnace equipped with a conventional dryer, when the entire amount of sludge is dried, the moisture content can be reduced only to around 70%, and the moisture content at which a granulation effect can be expected has not been achieved. Therefore, as in the present invention, the moisture content can be reduced to the above range of 60 to 30% by drying only a portion of the sludge without drying the entire amount of sludge, thereby producing the ash that is the fluidized medium. It became possible to do.

Further, the in-furnace differential pressure of the circulating fluidized bed furnace is detected, and when the in-furnace differential pressure exceeds a preset appropriate range, the fluidized medium is extracted from the circulating fluidized bed furnace. .
This is because the flow medium in the furnace increases due to the input of dry sludge dried to a moisture content of 60 to 30%. This is monitored by the pressure difference in the furnace, and the flow medium increases excessively. In this case, by extracting the fluid medium from the lower part of the furnace, the pressure difference in the furnace can be lowered to an appropriate range, and stable operation is possible.

Furthermore, the in-furnace differential pressure of the circulating fluidized bed furnace is detected, and when the in-furnace differential pressure exceeds a preset appropriate range, the fluid medium is extracted from the lower part of the riser of the circulating fluidized bed furnace,
The extracted fluidized medium is subjected to particle size separation, and the large-diameter side particles are returned to the circulating fluidized bed furnace.
The fluid medium extracted from the lower part of the riser includes those having a large particle diameter and those in which combustion has not been completed. Therefore, it is possible to reduce the amount of unburned matter generated by separating the particle size of the fluidized medium and returning the large diameter side particles containing a large amount of unburned matter to the circulating fluidized bed furnace.

In the sludge treatment system equipped with a circulating fluidized bed furnace,
A drier for drying the sludge so as to have a moisture content of 60 to 30%;
A circulating flow in which the dried sludge from the dryer is charged and combusted while mixing the dried sludge with a fluid medium, and at least a portion of the dried sludge is circulated in the furnace together with the fluid medium in the form of massive sludge particles. And a laminar furnace.
Furthermore, the dryer uses the waste heat of the combustion exhaust gas from the circulating fluidized bed furnace as a heat source,
A part of the sludge was charged into the dryer, a path for feeding the dried sludge from the dryer into the circulating fluidized bed furnace, and a path for directly feeding other sludge into the circulating fluidized bed furnace were provided. It is characterized by that.

In addition, a fluid medium extracting means for extracting a fluid medium from a lower part of the riser of the circulating fluidized bed furnace, and an in-furnace differential pressure detecting means for detecting a differential pressure between a riser top and a furnace bottom of the circulating fluidized bed furnace,
When the in-furnace differential pressure detected by the in-furnace differential pressure detection means exceeds a preset appropriate range, the fluid medium extraction means extracts the fluid medium from the lower portion of the riser.
Furthermore, a separator for separating the particle size of the fluid medium extracted from the lower part of the riser by the moving medium extraction means is provided, and a return path is provided for returning the large-diameter side particles separated by the separator to the circulating fluidized bed furnace. It is characterized by that.
Furthermore, a fluid medium extracting means for extracting a fluid medium from a lower part of the seal pot of the circulating fluidized bed furnace, and an in-furnace differential pressure detecting means for detecting a differential pressure between a riser top and a furnace bottom of the circulating fluidized bed furnace,
When the in-furnace differential pressure detected by the in-furnace differential pressure detection means exceeds a preset appropriate range, the fluid medium is extracted from the lower part of the seal pot by the fluid medium extraction means.

As described above, according to the present invention, after the sludge is dried to a moisture content of 60 to 30%, the dried sludge in which fixed carbon and ash are agglomerated in the furnace is introduced into the circulating fluidized bed furnace. Since the fluid medium acts as a fluid medium, even if the fluid medium is discharged accompanying the exhaust gas, it is possible to maintain the in-furnace differential pressure within a certain appropriate range without newly supplying the fluid medium.
In addition, by drying only a part of the sludge without drying, the moisture content can be reduced to the above range of 60 to 30% in a limited heat source. It can be manufactured.
Furthermore, the pressure difference in the furnace is monitored, and when the fluid medium increases too much, the fluid pressure medium is extracted from the lower part of the riser, so that the furnace pressure difference can be lowered to an appropriate range, and stable operation is possible.
Furthermore, the amount of unburned matter generated can be reduced by separating the particle size of the fluid medium extracted from the lower portion of the riser and returning the large diameter side particles containing a large amount of unburned matter to the circulating fluidized bed furnace.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  FIG. 1 is an overall configuration diagram illustrating the processing system according to the first embodiment. In the first embodiment, a pressure-feed pump 1 that feeds dehydrated sludge quantitatively, a dryer 2 that dries dehydrated sludge 3 fed by the pressure pump 1, and a dry sludge 4 from the dryer 2 are provided. A circulating fluidized bed furnace 10 that is charged and incinerated, and an exhaust gas treatment facility that processes combustion exhaust gas discharged from the circulating fluidized bed furnace 10 are provided. The dewatered sludge is obtained by dewatering sludge discharged from sewage treatment plants, human waste treatment plants, wastewater treatment facilities, and the like, and its water content is about 80 to 90%.

  The circulating fluidized bed furnace 10 includes a riser 11 composed of a fluidized bed 11a obtained by fluidizing a fluid medium such as silica sand filled in the furnace bottom, and a free board 11b positioned above the fluidized bed 11a. The cyclone 14 connected to the cyclone 14 that collects the fluid medium blown up from the free board 11b and discharges the exhaust gas separated from the fluid medium to the flue 21 and the cyclone 14 via the downcomer 15 is connected to the furnace. A seal pot 16 that prevents the fuel gas from blowing through the cyclone 14 and a fluid medium return pipe 17 that returns the fluid medium stored in the seal pot 16 to the riser 11 are mainly configured.

A primary air inlet 13 is provided at the bottom of the riser 11, and the fluidized medium is fluidized by the primary air introduced from the primary air inlet 13 to form a fluidized bed 11a. The riser furnace wall above the fluidized bed 11a is provided with a secondary air introduction port (not shown), and the cylinder speed of the free board 11b is maintained by the secondary air introduced from the secondary air introduction port. Unburned matter is burned.
Above the fluidized bed 11 a of the riser 11, sludge charging means 12 is provided. The sludge charging means 12 has a configuration in which dewatered sludge received from the sludge charging hopper is appropriately fed into the furnace by a supply feeder.

The circulating fluidized bed furnace 10 includes a fluid medium supply means for supplying a fluid medium into the furnace, and a desulfurization material charging means for charging the desulfurization material into the furnace as necessary. The fluid medium supply means and the desulfurization material charging means may be installed anywhere as long as the circulation system of the fluid medium. Preferably, the desulfurization material charging means is located below the secondary air inlet of the riser 11. The fluid medium supply means is positioned on the seal pot 15 side. As the desulfurizing material to be introduced into the furnace by the desulfurizing material charging means, for example, limestone (CaCO ₃ ), slaked lime (Ca (OH) ₂ ), dolomite (CaCO ₃ .MgCO ₃ ), or the like is used.

The exhaust gas treatment facility has a configuration in which an air preheater 22, a waste heat boiler 23, a gas cooling tower 24, and a bag filter 25 are arranged in series.
The air preheater 22 exchanges heat between the air introduced by the pushing fan 28 and the combustion exhaust gas from the cyclone 14, and preheats the primary air or the secondary air. The preheated primary air is introduced into the furnace through the primary air inlet 13.
The waste heat boiler 23 generates steam by heating the feed water 31 with combustion exhaust gas. The generated steam 32 is supplied to the dryer 2. The dryer 2 is effective for indirectly drying a viscous material such as sludge using steam, and dries the steam 32 generated by the waste heat boiler 23 as a heat medium. The steam used in the dryer 2 is condensed into water 33 and returned to the waste heat boiler 23 together with the feed water 31. The dryer 2 may be configured to dry the dewatered sludge using an external heat source.

The gas cooling tower 24 cools the combustion exhaust gas by heat exchange with cooling water. The bag filter 25 is a device that collects and removes fly ash in the cooled exhaust gas. The combustion exhaust gas passes through the exhaust gas treatment facility described above by the induction fan 26 installed at the rear stage of the bag filter 26 and is then discharged out of the system from the chimney 27.
Note that the exhaust gas treatment facility is not limited to the above-described configuration, and is configured by selecting a necessary apparatus as appropriate. As another configuration example, for example, there is a configuration in which an air preheater, a waste heat boiler, and a ceramic filter are arranged in series. Thus, in the exhaust gas treatment facility applied to this embodiment, the apparatus configuration is not particularly limited.

In the processing system having the above configuration, in the first embodiment, the drying sludge 3 is dried by the dryer 2 until the moisture content becomes 60 to 30%.
When the sludge dries, the moisture is lost and the fixed carbon and ash collect toward the center. When the water content is 60% or less, the strength increases due to the collected fixed carbon and ash, so even if it is put into the circulating fluidized bed furnace 10, it becomes difficult to reduce the particle size, and it acts as a fluid medium. That is, the sludge dried to the above moisture content range circulates in the furnace while having a diameter of 150 μm or more in the circulating fluidized bed furnace 10.

FIG. 4 shows the results of the sludge heating test. This is a graph obtained by measuring changes in sludge weight, temperature and the like when the sludge is heated with the test apparatus shown in FIG. In this test apparatus, the sludge 110 placed in the container 103 is installed in the electric furnace 101, the inside of the furnace is heated by the heater 102 to dry the sludge, and the weight change of the sludge is measured by the weight meter 104, The sludge temperature was detected by a temperature detector (not shown). In addition, data such as CO concentration is also measured.
In FIG. 4, in the dry region, the sludge is a black lump as seen in the photograph in the figure, and as the heating continues, the black lump sludge gradually gathers toward the center and becomes smaller. In addition, after a drying area | region, it is a combustion area | region of sludge. The photograph in the figure is a photograph taken from the direction of arrow A in FIG.

  On the other hand, when the sludge having a water content of 60% or more is put into the circulating fluidized bed furnace 10, combustion starts without assembling the ash, so that the ash collapses and becomes a small particle size and does not become a fluid medium. 14 shifts to the exhaust gas side. The sludge ash itself is very small, about 20 μm, and therefore does not circulate in the furnace. On the other hand, the sludge having a water content of 30% or less burns immediately when it is introduced into the circulating fluidized bed furnace 10 and does not form a lump and becomes a fine ash so that it does not become a fluid medium.

  Therefore, after drying the dehydrated sludge 3 to a moisture content of 60 to 30% as in Example 1, the sludge in which fixed carbon and ash are agglomerated is added to the fluidized medium by introducing it into the circulating fluidized bed furnace 10. Therefore, even if the fluid medium is discharged accompanying the exhaust gas, it is possible to maintain the in-furnace differential pressure within a certain appropriate range without newly supplying the fluid medium.

FIG. 2 shows an overall configuration diagram of the processing system according to the second embodiment. Hereinafter, in Example 2 and Example 3, the detailed description of the same configuration as that of Example 1 described above is omitted.
In Example 2, when dewatered sludge is charged into the circulating fluidized bed furnace 10, the dehydrated sludge is directly fed into the circulating fluidized bed furnace 10 (dehydrated sludge 5), and the dehydrated sludge is fed to the dryer 2. In addition, a path (dehydrated sludge 3-dried sludge 4) that is fed from the dryer 2 to the circulating fluidized bed furnace 10 is provided. Then, a part 3 of the dewatered sludge is introduced into the dryer 2 and dried, and the dried sludge 4 is put into the circulating fluidized bed furnace 10, and the remaining dewatered sludge 5 is left as it is without being dried. 10 At this time, it is preferable that the amount of dewatered sludge fed to the dryer 2 is an amount that can be dried to a moisture content of 60 to 30% by the heat recovered by the waste heat boiler 23.

The dryer 2 in the circulating fluidized bed furnace 10 often performs a drying process using the heat of exhaust gas, and the amount of heat that can be used for drying is limited. In the circulating fluidized bed furnace 10 equipped with a conventional dryer, when the entire amount of sludge was dried, the moisture content could be reduced only to around 70%, and the moisture content that could be expected to produce a granulation effect was not reached.
Therefore, as in Example 2, the moisture content can be reduced to 60 to 30% by drying a part of the sludge without drying the whole amount, thereby producing the ash as the fluidized medium. Became possible.

FIG. 3 shows an overall configuration diagram of the processing system according to the third embodiment. The third embodiment is used in combination with the configuration of the first embodiment or the second embodiment described above. FIG. 3 shows a configuration combined with the first embodiment as an example.
In the third embodiment, a fluid medium extraction portion 18 is provided at the bottom of the riser 11, and a valve (not shown) that can be opened and closed is provided at the extraction portion 18. Furthermore, pressure gauges 35 and 36 are provided at the bottom and top of the riser 11, respectively. Then, the controller 37 monitors the in-furnace differential pressure detected by the pressure gauges 35 and 36, and opens the valve when the detected in-furnace differential pressure exceeds a preset appropriate range. Then, the fluid medium is extracted from the fluid medium extraction unit 18.
This is because the amount of fluid medium in the furnace may increase due to the dried sludge dried to a moisture content of 60 to 30%. This is monitored by the pressure difference in the furnace, and the fluid medium increases excessively. By extracting the fluid medium from the lower part of the riser, the pressure difference in the furnace can be lowered to an appropriate range, and stable operation becomes possible.

In addition, a fluid medium separator 19 for separating the particle size of the fluid medium (including sludge) extracted from the lower portion of the riser 11 is provided. The fluid medium separator 19 is preferably separated by sieving, and in this case, the sieve mesh may be set to 4 to 15 mm. The fluid medium remaining on the sieve is returned to the circulating fluidized bed furnace 10. The fluid medium that has passed through the sieve mesh is stored in the fluid medium hopper 29.
The fluid medium extracted from the lower portion of the riser 11 includes those having a large particle diameter and those in which combustion has not been completed. Thus, by separating the particles by sieving, sludge particles containing a large amount of unburned matter remain on the sieve. By returning this to the circulating fluidized bed furnace 10, the amount of unburned matter generated can be reduced.

  Further, a fluid medium extraction part 37 may be provided at the lower part of the seal pot 16. Since the particles present in the seal pot 16 are particles blown up by the riser 11, the particle diameter is small. Therefore, the unburned portion is not extracted by extracting the particles from the seal pot 16. Those having a large particle size including unburned components flow until they become smaller on the riser 11 side. Thereby, when a fluid medium increases, it can prevent extraction of an unburned part by extracting a fluid medium from seal pot 16 lower part.

  According to the present invention, even when the fluid medium is exhausted along with the exhaust gas, it is possible to maintain the differential pressure in the furnace properly without replenishing a new fluid medium, and stable operation is possible. The present invention can be suitably applied to all systems equipped with a circulating fluidized bed furnace for treating various types of sludge such as sludge, human waste treatment sludge, wastewater treatment sludge and the like.

1 is an overall configuration diagram of a processing system according to Embodiment 1 of the present invention. It is a whole block diagram of the processing system which concerns on Example 2 of this invention. It is a whole block diagram of the processing system which concerns on Example 3 of this invention. It is a figure which shows the heating test result of sludge. It is the schematic which shows a heating test apparatus.

Explanation of symbols

2 Dryer 3, 5 Dewatered sludge 4 Dry sludge 10 Circulating fluidized bed furnace 11 Riser 14 Cyclone 15 Seal pot 18, 37 Fluidized medium extraction part 19 Fluidized medium separator 22 Air preheater 23 Waste heat boiler 24 Gas cooling tower 25 Bag filter 35, 36 Pressure gauge 37 Controller

Claims (9)

In the sludge treatment method in which the sludge is dried with a dryer, and then the dried sludge is put into a circulating fluidized bed furnace and burned while being mixed with a fluid medium.
By drying the sludge so as to obtain a dried sludge having a water content of 60 to 30% in the dryer, at least a part of the dried sludge put into the circulating fluidized bed furnace is a lump sludge. A sludge treatment method characterized by circulating in a furnace together with a fluid medium in the form of particles.   After drying a part of the sludge with the dryer, the dried sludge is put into the circulating fluidized bed furnace, and the remaining sludge is directly fed into the circulating fluidized bed furnace without drying, The sludge treatment method according to claim 1, wherein combustion treatment is performed simultaneously in the circulating fluidized bed furnace.   The in-furnace differential pressure of the circulating fluidized bed furnace is detected, and when the in-furnace differential pressure exceeds a preset appropriate range, the fluid medium is extracted from the circulating fluidized bed furnace. The sludge treatment method according to 1 or 2. Detecting the in-furnace differential pressure of the circulating fluidized bed furnace, when the in-furnace differential pressure exceeds a preset appropriate range, withdrawing the fluid medium from the lower part of the riser of the circulating fluidized bed furnace,
The sludge treatment method according to claim 1 or 2, wherein the extracted fluidized medium is subjected to particle size separation, and the large-diameter side particles are returned to the circulating fluidized bed furnace. A drier for drying the sludge so as to have a moisture content of 60 to 30%;
A circulating flow in which the dried sludge from the dryer is charged and combusted while mixing the dried sludge with a fluid medium, and at least a portion of the dried sludge is circulated in the furnace together with the fluid medium in the form of massive sludge particles. A sludge treatment system comprising a circulating fluidized bed furnace. The dryer uses the waste heat of combustion exhaust gas from the circulating fluidized bed furnace as a heat source,
A part of the sludge was charged into the dryer, a path for feeding the dried sludge from the dryer into the circulating fluidized bed furnace, and a path for directly feeding other sludge into the circulating fluidized bed furnace were provided. A sludge treatment system comprising the circulating fluidized bed furnace according to claim 5. A fluid medium extraction means for extracting a fluid medium from a lower part of the riser of the circulating fluidized bed furnace, and an in-furnace differential pressure detection means for detecting a differential pressure between a riser top and a furnace bottom of the circulating fluidized bed furnace,
The fluid medium is withdrawn from the lower part of the riser by the fluid medium withdrawing means when the in-furnace differential pressure detected by the in-furnace differential pressure detecting means exceeds a preset appropriate range. A sludge treatment system comprising the circulating fluidized bed furnace according to 5 or 6.   Provided with a separator that separates the particle size of the fluid medium extracted from the lower part of the riser by the moving medium extraction means, and provided a return path for returning the large-diameter side particles separated by the separator to the circulating fluidized bed furnace. A sludge treatment system comprising the circulating fluidized bed furnace according to claim 7. A fluid medium extraction means for extracting a fluid medium from a lower part of a seal pot of the circulating fluidized bed furnace, and an in-furnace differential pressure detecting means for detecting a differential pressure between a riser top and a furnace bottom of the circulating fluidized bed furnace,
When the in-furnace differential pressure detected by the in-furnace differential pressure detection means exceeds a preset appropriate range, the fluid medium is extracted from the lower part of the seal pot by the fluid medium extraction means. Item 7. A sludge treatment system comprising the circulating fluidized bed furnace according to item 5 or 6.

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