JP4242859B2 - Gasification and melting system - Google Patents

Description

  The present invention relates to a gasification and melting system for treating waste such as municipal waste and industrial waste.

  As a gasification and melting system for treating waste such as municipal waste and industrial waste, for example, Patent Document 1 discloses that a fluidized bed made of a fluidized medium is formed in a furnace, and the combustible material that has been introduced is fluidized. Disclosed is a fluidized bed gasification and melt combustion method and apparatus technique in which the combustible gas is gasified into a combustible gas while circulating in the bed, and the combustible gas burns at high temperature to melt the ash. ing.

  Here, in the system of FIG. 10 of this patent document 1, the gas discharge part of the melting combustion furnace 41 which is a high temperature combustion apparatus containing a melting furnace and the waste heat boiler 31 of the latter stage are connected.

For example, in a small-scale waste treatment facility provided in a local city with a small population, the waste heat boiler 31 for waste heat recovery is omitted, and the gas of a high-temperature combustion apparatus including a melting furnace is used instead. In some cases, a system in which a discharge unit and a subsequent temperature reduction tower are connected via a duct is employed. However, in the system of FIG. 11 of Patent Document 1, a gas that is a temperature reduction tower instead of the waste heat boiler 31 is used. A cooler 280 is provided, and a gas discharge unit of a molten combustion furnace 41 that is a high-temperature combustion apparatus including a melting furnace and a gas cooler 280 at a subsequent stage are connected via a duct 278.
JP-A-7-332614

  However, in the system disclosed in FIG. 11 of Patent Document 1, an air preheater 188 that is a first air preheater that preheats combustion air for combusting combustible components in the pyrolysis gas generated in the gasification furnace. However, since it is provided downstream of the gas cooler 280, which is a temperature reducing tower, the temperature of the exhaust gas that can be recovered by the preheater 188 is low. As a result, the heat transfer area of the preheater 188 tends to increase. For this reason, the first air preheater cannot be made compact.

  Further, in the system disclosed in FIG. 10 of Patent Document 1, an air preheater 186 that preheats the forced air is also provided downstream of the waste heat boiler 31, so the temperature of the exhaust gas that can be recovered by the preheater 186. As a result, the heat transfer area of the preheater 186 tends to increase. For this reason, an air preheater that preheats other air such as forced air cannot be made compact.

  In addition, since the temperature of the exhaust gas from which each preheater recovers heat is low, dioxins are generated in the heat recovery portion of each preheater, and as a result, dioxins discharged from the system are generated. There is a problem that there is a limit in reducing the total amount of emissions.

  Moreover, if the preheater 186 or the preheater 188 is installed downstream of the waste heat boiler 31 and downstream of the gas cooler 280, a space for the preheater 188 is required, which reduces the installation area and construction cost of the entire gasification melting system. There was a limit.

  Furthermore, when an air preheater is provided in a range where the exhaust gas temperature is low in this way, a heat transfer surface such as a plate may be interpolated in order to increase the heat transfer area. As the ash adheres to the exhaust gas and blocks the exhaust gas flow path, it is necessary to periodically clean the inside of the preheater, which makes it impossible to perform continuous operation over a long period of time. In this case, it is difficult to clean the ash adhering to the inside of the preheater, and there is a concern about deterioration of the working environment. Furthermore, in the case of providing equipment for mechanically removing the attached ash, the equipment becomes complicated and the cost increases.

  The present invention has been made in view of such circumstances, and includes a heat transfer area of a first air preheater that preheats combustion air in a gasification and melting system, and a second preheater for other air such as a forced air preheater. The purpose is to reduce the heat transfer area of the two-air preheater to make these preheaters more compact and to further reduce the installation area by reducing the construction cost.

  Another object is to reduce the total amount of dioxins emitted from the system.

  In addition, ash is prevented from adhering to the heat transfer surface of the air preheater and blocking the exhaust gas flow path, and gasification and melting with a simple structure eliminates the need for cleaning and mechanical removal of the attached ash. The purpose is to realize the system.

As means for solving the above-mentioned problems, the present invention provides a fluidized bed type gasification furnace in which a fluidized bed of fluidized particles is formed on a hearth and pyrolyzes an object to be processed to generate pyrolysis gas, It includes a melting furnace that burns combustible components in the pyrolysis gas generated in the bed type gasification furnace and melts the ash in the gas, and discharges the molten slag, and discharges from this high-temperature combustion apparatus In a gasification and melting system comprising a temperature-decreasing tower for cooling the gas to be discharged , the gas-discharging unit is directly connected to the gas-discharging unit at a position downstream of the gas-discharging unit of the high-temperature combustion apparatus and upstream of the temperature-decreasing tower. Combusting the exhaust gas flowing through the gas discharge part and the combustible component in the pyrolysis gas generated in the fluidized bed gasifier in order from the upstream side in the flow direction of the exhaust gas flowing through the gas discharge part , connected via a flange Combustion air for A first air preheater for preheating the combustion air by heat exchange, is connected via a flanged directly to the first air preheater, the fluidized bed gasification furnace and the exhaust gas flowing through the gas outlet portion A second air preheater that preheats the pushed air by exchanging heat with the pushed air for feeding into the furnace bottom is continuously connected to the high-temperature combustion apparatus.

  According to the above configuration, the first air preheater and the second air preheater are continuously located at a position downstream of the gas discharge portion of the high temperature combustion apparatus and upstream of the temperature reducing tower, and then the high temperature combustion apparatus. Since each of the preheaters can recover heat from the high-temperature exhaust gas, the heat transfer area of each preheater can be reduced. As a result, the first air preheater and the second air preheater can be made more compact.

  Moreover, since the temperature of the exhaust gas for recovering heat in each preheater is high, the production of dioxins in this heat recovery portion is small. That is, the production of dioxins in the heat recovery portion of the preheater can be reduced as compared with the case where these preheaters are arranged in the low temperature portion of the exhaust gas. As a result, the total amount of dioxins discharged from the system can be reduced.

  Moreover, according to this structure, since an installation area can be made smaller than the case where a preheater is installed separately, a construction cost can be suppressed.

  In addition, the second air preheater preheats the compressed air by exchanging heat between the exhaust gas flowing through the gas discharge unit and the compressed air fed into the bottom of the fluidized bed gasifier, As a result that the second air preheater can recover heat from the high-temperature exhaust gas, the heat transfer area of the second air preheater can be reduced. As a result, the second air preheater can be made more compact.

  Moreover, since the temperature of the exhaust gas from which heat is recovered in the second air preheater is high, the production of dioxins in the heat recovery portion can be reduced.

  Furthermore, according to this structure, since an installation area can be made smaller than the case where a 2nd air preheater is installed separately, a construction cost can be suppressed.

  Here, the first air preheater and the second air preheater are connected to the high temperature combustion device at a position above the molten slag discharge part of the high temperature combustion device, and the first air preheater and the second air preheater are connected to the high temperature combustion device. It is preferable that the ash conveyed to the air preheater is dropped and melted inside the high temperature combustion apparatus and discharged from the high temperature combustion apparatus as molten slag.

According to this configuration, the first air preheater and the second air preheater are connected to the high temperature combustion device at a position above the molten slag discharge portion of the high temperature combustion device, and the first air preheater and the second air preheater are connected to the high temperature combustion device. Since the ash conveyed to the air preheater falls and melts inside the high temperature combustion device and is discharged from the high temperature combustion device as molten slag, the ash adhering to the inside of each preheater is separately collected. No need to process. Moreover, it can be set as the gasification melting system with the high slag generation rate and volume reduction rate of the whole ash content to generate | occur | produce.

  In addition, since the first air preheater and the second air preheater are provided directly and continuously, and the duct between them is omitted, there is no heat dissipation between the preheaters. It can be used.

  Further, in this gasification and melting system, an exhaust gas cooling section for cooling the exhaust gas at a position upstream of the two preheaters in the exhaust gas flow direction is provided in the gas discharge section of the high-temperature combustion apparatus. Is preferred.

  According to this configuration, since the exhaust gas cooling unit that cools the exhaust gas is provided in the gas discharge unit of the high-temperature combustion apparatus, the exhaust gas temperature at the inlets of both preheaters can be lowered, and as a result Can reduce equipment damage.

  Moreover, it is preferable that the said exhaust gas cooling part contains the water cooling jacket which cools the refractory which comprises the inner wall of the said gas discharge part.

  According to this configuration, the refractory constituting the inner wall of the gas discharge unit can be cooled by the water cooling jacket, so that the exhaust gas temperature at the entrance of both preheaters can be lowered, and the inner wall of the gas discharge unit can be made of ash. It becomes possible to cool below the softening / fixing temperature.

As described above, according to the present invention, the first air preheater is directly connected to the gas discharge portion of the high-temperature combustion apparatus via the flange, and the second air preheater that is a forced air preheater is connected to the first air preheater. Since the heaters are continuously connected directly via the flange , each preheater can recover heat from the high-temperature exhaust gas. As a result, the heat transfer area of each preheater can be reduced. As a result, the first air preheater and the second air preheater can be made more compact.

  In addition, since the temperature of the exhaust gas from which each preheater recovers heat is high, the dioxins in the heat recovery part of the preheater are compared with the case where these preheaters are arranged in the low temperature part of the exhaust gas. Production can be reduced. As a result, the total amount of dioxins discharged from the system can be reduced.

  Moreover, according to this invention, since an installation area can be made smaller than the case where a preheater is installed separately, a construction cost can be suppressed.

  In addition, ash is prevented from adhering to the heat transfer surface of the air preheater and blocking the exhaust gas flow path, and gasification and melting with a simple structure eliminates the need for cleaning and mechanical removal of the attached ash. A system can be realized.

  In addition, the second air preheater preheats the compressed air by exchanging heat between the exhaust gas flowing through the gas discharge unit and the compressed air fed into the bottom of the fluidized bed gasifier, As a result that the second air preheater can recover heat from the high-temperature exhaust gas, the heat transfer area of the second air preheater can be reduced. As a result, the second air preheater can be made more compact.

  A preferred embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of a gasification and melting system 100 according to the first embodiment of the present invention, and FIG. 2 shows a first air preheater 34 and a forced air preheater 35 of the gasification and melting system 100. It is a schematic sectional side view which shows this structure.

A gasification and melting system 100 according to the first embodiment shown in FIG. 1 includes a dust feeder 10, a fluidized bed gasification furnace 12, a high-temperature combustion apparatus 14, and a first temperature reduction in order from the front side. A tower 16, a second temperature reducing tower 20, a bag filter 22, an induction fan 24, and a chimney 26 are provided. Moreover, the 1st air preheater 34 which preheats combustion air in order from the upstream of the flow direction of the waste gas G which flows through this gas discharge part 32a downstream from the gas discharge part 32a of the high temperature combustion apparatus 14, and other air As a second air preheater for preheating, a push air preheater 35 is continuously connected to the high temperature combustion device 14.

  The dust feeder 10 has a waste hopper 11 and quantitatively supplies the waste introduced into the waste hopper 11 to the fluidized bed gasifier 12 by a screw conveyor.

  A fluidized bed 28 made of fluidized particles such as sand is formed on the hearth of the fluidized bed gasification furnace 12, and the fluidized bed 28 is charged into the fluidized bed 28 while maintaining the temperature of the fluidized bed 28 at, for example, 450 to 650 ° C. An operation is performed in which the generated waste is subjected to low-temperature pyrolysis, that is, primary combustion. Incombustible substances contained in the garbage are extracted from the bottom of the furnace together with the fluidized particles, and separated from the fluidized particles in the subsequent stage. The separated fluidized particles are returned to the fluidized bed 28 and reused.

  The high-temperature combustion apparatus 14 has a configuration in which a melting furnace 30 extending in the vertical direction and a secondary combustion chamber 32 at the subsequent stage are arranged in parallel.

  In the melting furnace 30, the pyrolysis gas sent from the fluidized bed gasification furnace 12 is further burned under the condition of a total air ratio of 1.3, for example. Specifically, a swirling flow is formed in the melting furnace 30 by combustion air and high-temperature combustion of about 1300 ° C. or more is performed, and the ash in the pyrolysis gas is melted on the furnace wall by the heat. It becomes slag and is discharged from the outlet 36 at the bottom of the high-temperature combustion apparatus 14 through the furnace wall. The molten slag is subjected to a cooling process by the slag water cooling device 38 or the like, and then is discharged from the molten slag discharge unit 39 and collected to a specific location.

  The secondary combustion chamber 32 is provided on the opposite side of the melting furnace 30 with the tap hole 36 interposed therebetween, and plays a role of further secondary combustion of the gas introduced from the melting furnace 30.

  The first air preheater 34 exchanges heat between the exhaust gas G flowing through the gas discharge portion 32a of the high-temperature combustion apparatus 14 and the combustion air A2 for burning the combustible components in the pyrolysis gas generated in the gasification furnace 12. By this, this combustion air A2 is preheated.

  As shown in FIG. 2, the first air preheater 34 is a radiant heat exchanger, and has a flange directly on the secondary combustion chamber 32 downstream of the secondary combustion chamber 32 and on the upper side thereof. Connected through. The first air preheater 34 reduces the exhaust gas G by exchanging heat between the exhaust gas G that rises from the secondary combustion chamber 32 and the air sent from the secondary blower 50 (FIG. 1). The temperature of the air is raised to 300 to 500 ° C. and the combustion air A2 is obtained. Further, the combustion air A <b> 2 heated here is supplied to appropriate places of the fluidized bed gasification furnace 12 and the melting furnace 30.

  The forced air preheater 35 (corresponding to the second air preheater) is also forced air A1 for burning the exhaust gas G flowing through the gas discharge part 32a and the combustible component in the pyrolysis gas generated in the gasification furnace 12. This air is preheated by exchanging heat with each other.

  As shown in FIG. 2, the pushed air preheater 35 is directly connected to the first air preheater 34 via a flange on the downstream side, that is, the upper side of the first air preheater 34. The forced air preheater 35 is also a radiant heat exchanger similar to the first air preheater 34, and exhaust gas G rising from the secondary combustion chamber 32 is sent from the forced air blower 52 (FIG. 1). By exchanging heat with air, the temperature of the exhaust gas G is reduced to 800 to 1200 ° C. and the temperature of the air is increased to 150 to 200 ° C. to serve as the forced air A2. Further, the temperature of the pushed-in air A2 raised here is supplied to the bottom of the fluidized bed gasifier 12 as a fluidizing gas.

  Thus, the first air preheater 34 and the forced air preheater 35 are formed integrally with the high temperature combustion device 14 at a position above the molten slag discharge part 39 of the high temperature combustion device 14, and these first air The ash conveyed to the preheater 34 and the forced air preheater 35 falls into the high temperature combustion device 14 and is melted and discharged from the high temperature combustion device 14 as molten slag.

  A gas discharge port 40 is provided on the downstream side, that is, the upper side of the forced air preheater 35, and the gas discharge port 40 and the gas inlet 42 at the top of the first temperature reducing tower 16 are connected via a duct 60. It is connected.

  The first temperature-decreasing tower 16 causes the high-temperature combustion gas introduced from the gas inlet 42 to flow down while being in contact with cooling water, and reduces the temperature of the gas to, for example, about 300 ° C. to 400 ° C. Drain to tower 20.

  The second temperature reducing tower 20 further cools the introduced exhaust gas G to about 150 ° C. to 200 ° C., and the cooled exhaust gas G is then sent to the bag filter 22 and the induction blower 24. From the system through the chimney 26.

  In the gasification and melting system 100 shown above, the first air preheater 34 and the forced air preheater 35 (second air preheater) are continuously arranged downstream of the gas discharge portion 32a of the high-temperature combustion apparatus 14. Since it is connected to the high-temperature combustion apparatus, each of the preheaters 34 and 35 can recover heat from the high-temperature exhaust gas G. As a result, the heat transfer area of each of the preheaters 34 and 35 can be reduced. . As a result, the first air preheater 34 and the push air preheater 35 can be made more compact.

  Further, since the temperature of the exhaust gas G for recovering heat in each of the preheaters 34 and 35 is high, the production of dioxins in this heat recovery portion is small. That is, compared with the case where these preheaters 34 and 35 are disposed in the low temperature portion of the exhaust gas, the production of dioxins in the heat recovery portion of the preheaters 34 and 35 can be reduced. As a result, the total amount of dioxins discharged from the system can be reduced.

  Moreover, according to this structure, since an installation area can be made smaller than the case where the preheaters 34 and 35 are installed separately, a construction cost can be suppressed.

  Furthermore, according to this structure, the 1st air preheater 34 and the pushing air preheater 35 are integrally formed with the high temperature combustion apparatus 14 in the position above the molten slag discharge part 39 of the high temperature combustion apparatus 14, The ash transferred to the first air preheater 34 and the second air preheater such as the forced air preheater 35 falls into the high temperature combustion device 14 and is melted and discharged from the high temperature combustion device 14 as molten slag. Therefore, it becomes unnecessary to separately collect and process the ash adhering to the inside of each preheater 34, 35. Moreover, it can be set as the gasification melting system 100 with the high slag formation rate and volume reduction rate of the whole ash content to generate | occur | produce.

  And since the 1st air preheater 34 and the pushing air preheater 35 are provided directly continuously, and the duct between these is abbreviate | omitted, as a result of no heat radiation between the preheaters 34 and 35, exhaust gas G It is possible to effectively use the amount of heat possessed by.

  Next, a second embodiment of the gasification melting system of the present invention will be described with reference to FIG. FIG. 3 is an overall configuration diagram of the gasification and melting system 200 according to the second embodiment of the present invention. In addition, the same code | symbol is attached | subjected about the structure similar to the gasification melting system 100 which concerns on 1st Embodiment, and the duplication of description shall be avoided.

  As shown in FIG. 3, in the gasification and melting system 200 according to the second embodiment of the present invention, the flow direction of the exhaust gas G to the gas discharge part 32 a of the high-temperature combustion device 14 rather than both the preheaters 34 and 35. An exhaust gas cooling unit 37 that cools the exhaust gas G is provided at an upstream position.

  And this exhaust gas cooling part 37 cools the exhaust gas G of the high temperature combustion apparatus 14 from 900-1400 degreeC to 800-1300 degreeC by the structure containing the water cooling jacket which cools the refractory which comprises the inner wall of the gas discharge part 32a. It is supposed to be.

  Thus, according to this structure, since the exhaust gas cooling part 37 which cools the exhaust gas G is provided in the gas discharge part 32a of the high temperature combustion apparatus 14, the exhaust gas G temperature at the inlets of both the preheaters 34 and 35 is set. As a result of being able to lower, device damage due to the heat of both preheaters 34 and 35 can be reduced.

  Further, by cooling the refractory constituting the inner wall of the gas discharge part 32a with a water cooling jacket, the refractory in the gas discharge part 32a can be cooled below the softening / fixing temperature of ash with a small heat transfer area. In addition to preventing ash softening and sticking in the refractory of the gas discharge part 32a, it is also possible to prevent ash softening and sticking in the preheaters 34 and 35 provided in the gas discharge part 32a. Become.

  The above-described embodiment is merely a preferred specific example of the present invention, and the present invention is not limited to the above-described embodiment.

  For example, the configuration of the gasification and melting system 100 is not necessarily limited to the configuration of FIG. 1, and the configuration of the gasification and melting system 200 is not necessarily limited to the configuration of FIG.

  In the present invention, the second temperature reducing tower 20 is not necessarily required. If the gas temperature can be sufficiently lowered in the first temperature reducing tower 16, the bag filter 22 is directly connected from the first temperature reducing tower 16. You may do it.

  As described above, the gasification melting systems 100 and 200 include a fluidized bed gasification furnace 12 that thermally decomposes a workpiece to generate a pyrolysis gas, and a pyrolysis generated in the fluidized bed gasification furnace 12. If the gasification melting system includes a melting furnace 30 that burns combustible components in the gas and melts the ash in the gas, and includes a high-temperature combustion device 14 that discharges the molten slag, various design changes can be made. Is possible.

  In addition, various design changes can be made to the types, shapes, specifications, operating conditions, and the like of the individual devices of the gasification and melting systems 100 and 200.

For example, the types of the first air preheater 34 and the forced air preheater 35 are not necessarily limited to the radiant heat exchanger. Various design changes can be made as long as the air is preheated by exchanging heat between the exhaust gas G flowing through the gas discharge portion 32a and each air. For example, FIG. 4 is a schematic side sectional view showing a modification of the first air preheater 34 of the gasification melting system 100.

  In FIG. 4, the first air preheater 34 is changed to a multi-tube heat exchanger using a U-shaped tube 34a.

  According to this configuration, since the U-shaped tube 34a is employed in the heat transfer section, the thermal stress due to the temperature difference between the high temperature side fluid and the low temperature side fluid can be suppressed to a small value.

  Thus, the 1st air preheater 34 and the pushing air preheater 35 can each be changed, and the plate type thing etc. which inserted the plate inside are also employable.

  Moreover, the cooling fluid for cooling the exhaust gas cooling unit 37 (FIG. 3) is not limited to water, and various fluids can be used as appropriate. Alternatively, it is effective to wind the cooling water pipe on the outer surface of the gas discharge part 32a.

  Various configurations of the high-temperature combustion apparatus 14 can be employed. For example, the melting furnace 30, the tap port 36, and the secondary combustion chamber 32 of the high-temperature combustion apparatus 14 have a structure in which the secondary combustion chamber 32 is located above the tap port 36 as shown in FIG. The bottom of the melting furnace 30 and the secondary combustion chamber 32 as shown in FIG. 5B is not inclined toward the tap port 36, and the bottom of the secondary combustion chamber 32 as shown in FIG. Various design changes, such as a structure inclined toward the tap opening 36, are possible.

  In addition, various design changes are possible within the scope of the claims of the present invention.

1 is an overall configuration diagram of a gasification melting system according to an embodiment of the present invention. It is a schematic sectional side view which shows the structure of the 1st air preheater and forced air preheater of a gasification melting system. It is a whole block diagram of the gasification melting system which concerns on the 2nd Embodiment of this invention. It is a schematic sectional side view which shows the modification of the 1st air preheater of a gasification melting system. It is explanatory drawing which shows the modification of a high temperature combustion apparatus, Fig.5 (a) is a structure which has a secondary combustion chamber in the upper part of a taphole, FIG.5 (b) is a bottom part of a melting furnace and a secondary combustion chamber However, FIG. 5 (c) shows a structure in which the bottom of the secondary combustion chamber is inclined toward the tap outlet, respectively.

Explanation of symbols

A1 Pressurized air A2 Combustion air G Exhaust gas 12 Fluidized bed gasifier 14 High-temperature combustion device 28 Fluidized bed 30 Melting furnace 32a Gas exhaust part 34 First air preheater 35 Pressurized air preheater (second air preheater)
37 Exhaust gas cooling unit 39 Molten slag discharge unit 100, 200 Gasification melting system

Claims (4)

A fluidized bed gasification furnace in which a fluidized bed of fluidized particles is formed on the hearth and pyrolyzes the object to be processed to generate pyrolysis gas, and the pyrolysis gas generated in the fluidized bed gasification furnace A gas comprising a melting furnace that burns combustible components to melt ash in the gas, a high-temperature combustion device that discharges the molten slag, and a temperature-decreasing tower that cools the gas discharged from the high-temperature combustion device In the fusing system,
At a position downstream of the gas discharge section of the high-temperature combustion apparatus and upstream of the temperature reducing tower, the gas discharge section is directly connected to the gas discharge section in order from the upstream side in the flow direction of the exhaust gas flowing through the gas discharge section. The combustion air is preheated by exchanging heat between the exhaust gas flowing through the gas discharge section and the combustion air for burning the combustible components in the pyrolysis gas generated in the fluidized bed gasifier. 1 air preheater, and this 1st air preheater are directly connected via the flange, and heat exchange is carried out between the exhaust gas flowing through the gas discharge part and the forced air for feeding into the bottom of the fluidized bed gasifier Thus, the gasification and melting system is characterized in that the second air preheater for preheating the forced air is continuously connected to the high-temperature combustion apparatus. The gasification melting system according to claim 1 , wherein the first air preheater and the second air preheater are connected to the high temperature combustion device at a position above the molten slag discharge portion of the high temperature combustion device, Gasification and melting characterized in that the ash transferred to the first air preheater and the second air preheater falls and melts inside the high temperature combustion device and is discharged from the high temperature combustion device as molten slag. system. In gasification and melting system of claim 1 or claim 2, wherein the gas outlet portion of the hot combustion apparatus, the exhaust gas cooling portion than both preheater cooling the exhaust gas at the position of the flow direction upstream side of the exhaust gas A gasification and melting system characterized in that is provided. 4. The gasification and melting system according to claim 3 , wherein the exhaust gas cooling unit includes a water-cooling jacket that cools a refractory that forms an inner wall of the gas discharge unit. 5.

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