JP5465747B2 - Start-up method of pressurized fluidized bed combined power plant - Google Patents

Description

  The present invention relates to a startup method of a pressurized fluidized bed combined power plant, and more particularly to a startup method of a pressurized fluidized bed combined power plant that performs a backflow prevention operation when starting a gas turbine.

  A pressurized fluidized bed combined power plant uses a pressurized fluidized bed boiler in which a furnace is installed in a pressure vessel to generate steam, drive a steam turbine, drive a gas turbine with combustion gas, and generate electricity. It is a plant. Since the pressurized fluidized bed boiler fluidizes the fluid medium in the boiler and combusts the supplied coal while fluidizing it, the combustion temperature is as low as about 870 ° C. As a result, the generation of nitrogen oxides is suppressed, and further, the use of limestone as the fluid medium has the advantage that in-furnace desulfurization is simultaneously performed.

  In starting a pressurized fluidized bed combined power plant (sometimes referred to as a unit), it is necessary to start and parallel a gas turbine prior to boiler ignition in order to supply air necessary for boiler ignition. By starting and paralleling the gas turbine, it is possible to supply combustion air from the air compressor connected to the gas turbine to the pressurized fluidized bed boiler.

  To start the gas turbine, compressed air is sent to the gas turbine starting combustor, and the gas turbine is started by generating combustor combustion gas (starting gas) using light oil or the like as fuel. At this time, if the starting gas flows backward to the furnace side, the fluid medium in the furnace falls to the wind box through the dispersion nozzle and accumulates.

  A high-temperature gas control valve and a high-temperature gas stop valve for preventing the start-up gas from flowing into the furnace side are provided upstream of the gas turbine start-up combustor, but the start-up gas is high-temperature and high-pressure. The hot gas control valve and hot gas stop valve cannot be completely shut off. In order to prevent this, a backflow prevention operation is performed in which a certain amount of backflow prevention air is supplied to the pressure vessel and the furnace. In some cases, the backflow prevention air is provided with a booster fan in addition to the in-house air (see, for example, Patent Document 1).

  When it becomes possible to supply combustion air from the air compressor connected to the gas turbine to the pressurized fluidized bed boiler, the boiler ignition preparation process is started. Thereafter, boiler ignition / temperature increase / pressure increase, steam turbine startup preparation, steam After starting the turbine, paralleling the steam turbine, increasing the load, and reaching the rated load, the unit is started.

Japanese Patent Laid-Open No. 10-9512

  The start-up of the unit is performed in such a way that the computer sequentially advances each process, and the backflow prevention operation is also incorporated in the unit start-up process. In the backflow prevention operation, it is necessary to supply a large amount of air to the furnace. Therefore, when the in-house air is used as the backflow prevention air, it is necessary to operate a plurality of in-house air compressors. For this reason, when some in-house air compressors are in an inoperable state, the backflow preventing air cannot be sufficiently supplied. Further, when the number of in-house air compressors is a condition for proceeding with the backflow prevention operation, the unit cannot be activated if some of the in-house air compressors are in an inoperable state.

  If a dedicated booster fan is provided as in the pressurized fluidized bed combined power plant described in Patent Document 1, the above problem does not occur, but the backflow prevention operation is an operation performed only when the unit is started. It is not economical to provide a booster fan only for such an operation.

  An object of the present invention is to provide a method for starting up a pressurized fluidized bed combined power plant that can start up the pressurized fluidized bed combined power plant even when the air supply capacity of the in-house air system is reduced.

The present invention relates to a pressurized fluidized bed that performs a backflow prevention operation for supplying backflow prevention air to a pressurized fluidized bed boiler in order to prevent the combustor combustion gas from flowing back to the pressurized fluidized bed boiler when the gas turbine is started. In the combined power plant startup method, the pressurized fluidized bed combined power plant includes an in-house air system, a control air system, and a backup system that supplies the air in the in-house air system to the control air system as backup air. a, a, characterized in that using the backup system in the opposite direction, to produce a mixed air feed air to the house air line from the control air system, to use the mixed air in the backflow preventing air This is a method for starting up a pressurized fluidized bed combined power plant.

  Further, in the start-up method of the pressurized fluidized bed combined power plant according to the present invention, the backflow prevention operation using the mixed air may be performed by compressing some of the in-house air compressors out of a plurality of in-house air compressors. It is performed when the machine cannot be operated.

  In the method for starting a pressurized fluidized bed combined power plant according to the present invention, the mixed air of the air in the in-house air system and the air in the control air system is used for the backflow prevention operation when starting the gas turbine. The pressurized fluidized bed combined power plant can be started up by replenishing the air in the in-house air system with the air in the control air system even when the supply amount of is reduced. At this time, if replenishment of air from the control air system to the in-house air system is performed using the backup system in the reverse direction, the pressurized fluidized bed of the present invention can be used without improving the existing pressurized fluidized bed combined power plant. A method for starting a combined power plant can be implemented.

It is a figure which shows schematic structure of the pressurized fluidized bed combined power plant which uses the starting method of the pressurized fluidized bed combined power plant as one Embodiment of this invention. It is a figure which shows schematic structure of the air supply equipment 100 of the pressurized fluidized bed combined power plant of FIG. It is a flowchart which shows the starting procedure of the pressurized fluidized bed combined power plant of FIG. 2 is a time chart when a backflow prevention operation is performed while replenishing in-house air system 101 with air in control air system 111 of the pressurized fluidized bed combined power plant of FIG. 1.

  FIG. 1 is a diagram showing a schematic configuration of a pressurized fluidized bed combined power plant using a method for starting up a pressurized fluidized bed combined power plant as one embodiment of the present invention. After describing the overall configuration of the pressurized fluidized bed combined power plant, the startup method (procedure) and backflow prevention operation of the pressurized fluidized bed combined power plant will be described.

  The Pressurized Fluidized Bed Combined Cycle (PFBC) plant uses a pressurized fluidized bed boiler to generate steam from the combustion heat of combustion of coal and to drive the steam turbine. Is a combined power plant that generates electricity by driving.

In this power plant, the inside of a pressurized fluidized bed boiler is maintained in a pressurized state with combustion air from an air compressor, and limestone is used as a fluid medium (BM: sometimes referred to as BM). CWP can be efficiently combusted by supplying coal / water paste (CWP: Coal Water Paste) as fuel. Further, since it is possible to desulfurize in the furnace by adopting the limestone flowing medium, it is possible to suppress the generation of sulfur sulfide (SO _x). Furthermore, since fluidized bed combustion has a low combustion temperature of about 870 ° C., generation of nitrogen oxides (NO _x ) can be kept low.

  The two pressurized fluidized bed boilers 10 and 20 are provided with furnaces 11 and 21 in pressure vessels 12 and 22, respectively. The furnaces 11 and 21 each hold limestone as a fluid medium, and the bottom of the furnaces 11 and 21. Combustion air is fed into the furnaces 11 and 21. As a result, the fluidized medium is fluidized, and a fluidized bed is formed in the furnaces 11 and 21. Here, in order to distinguish between the two furnaces, the left side is referred to as A furnace and the right side as B furnace.

  The combustion air is supplied into the pressure vessels 12 and 22, respectively, and then sent into the furnaces 11 and 21, and the furnaces 11 and 21 and the pressure vessels 12 and 22 are maintained in a pressurized state. The fuel is supplied to the bottoms of the furnaces 11 and 21 as CWP made of coal, limestone and water adjusted to a predetermined particle size. Coal burns in a fluidized state in the furnaces 11 and 21, and the sulfur oxide generated by the combustion reacts with limestone to become gypsum.

  The water / steam pipe 25 is disposed across the two pressurized fluidized bed boilers 10 and 20, and the feed water is heated in the B furnace 21 and the A furnace 11, and then in a brackish water separator (not shown). Water is separated, and the steam is further heated in the order of A furnace 11, B furnace 21, and A furnace 11, and sent to a high-pressure turbine (not shown). The steam that has driven the high-pressure turbine is guided again to the B furnace 21 and reheated, and then is guided to an intermediate-pressure turbine (not shown) and a low-pressure turbine (not shown) to drive these turbines. A generator (not shown) is coaxially connected to the high-pressure turbine, the medium-pressure turbine, and the low-pressure turbine, and power is generated by driving each turbine. The steam that has driven the turbine is condensate by a condenser (not shown), and then sent to the furnace 21 as feed water via a feed water heater (not shown).

  High-temperature and high-pressure combustion gas generated by burning coal in the furnaces 11 and 21 is sent to the gas turbine 41 through the combustion gas pipes 30, 31 and 36 connected to the upper parts of the furnaces 11 and 21, and rotates the gas turbine 41. To drive. In the middle of the combustion gas pipes 30, 31, primary cyclones 32, 33 and secondary cyclones 34, 35 for removing dust contained in the combustion gas are provided.

  The gas turbine 41 is connected to an air compressor 51 and a generator 42 that produce combustion air on the same axis, and the gas turbine 41 is driven to generate power and produce combustion air. 22 is supplied.

  A combustion gas pipe 36 that sends combustion gas to the gas turbine 41 is provided with a high temperature gas stop valve 44, a high temperature gas control valve 45, and a gas turbine starting combustor 43 in order from the upstream side. Further, a gas turbine bypass pipe 46 that bypasses the high temperature gas stop valve 44, the high temperature gas control valve 45, the gas turbine start combustor 43 and the gas turbine 41 and connects the combustion gas pipe 36 and the exhaust gas pipe 37 is provided. . A gas turbine first bypass valve 47 and a gas turbine second bypass valve 48 are interposed in the gas turbine bypass pipe 46.

  The air compressor 51 supplies combustion air to the pressure vessels 12 and 22 through the air supply pipe 52. A compressor outlet valve 53 is provided in the middle of the air supply pipe 52. Further, a compressed air bypass pipe 54 that sends compressed air to the combustor 43 for starting the gas turbine is connected between the air compressor 51 and the compressor outlet valve 53. A compressed air bypass valve 55 is interposed in the compressed air bypass pipe 54. The hot gas stop valve 44, the hot gas control valve 45, the compressor outlet valve 53 and the compressed air bypass valve 55 are referred to as a system valve 56. The starter motor 58 is connected to the air compressor 51.

  Further, a backflow prevention air supply pipe 61 that supplies backflow prevention air used during backflow prevention operation is connected to the air supply pipe 52 that connects the compressor outlet valve 53 and the pressure vessels 12 and 22. A backflow prevention air supply pipe 61 is provided with an in-house air furnace supply flow rate adjustment valve 62.

  The furnaces 11 and 21 are provided with fluidized medium tanks (BM tanks) 71 and 72 for storing a fluidized medium for adjusting the height (bed height) of the fluidized bed. In addition, furnace bottom extraction pipes 81 and 82 for discharging a fluid medium containing dust deposited in the furnaces 11 and 21 are connected to the bottoms of the furnaces 11 and 21.

  Although not shown, temperature detectors and pressure detectors are installed in various places including A furnace 11 and B furnace 21, primary cyclones 32 and 33, and secondary cyclones 34 and 35. These data are sent to an operation control device (not shown). The operation control device controls the operation based on data sent from each detection device and measuring instrument including the temperature and pressure.

  FIG. 2 is a diagram illustrating a schematic configuration of the air supply facility 100 of the pressurized fluidized bed combined power plant. The air supply facility 100 includes an in-house air system 101 and a control air system 111. The in-house air system 101 is a system that supplies compressed air as it is without being dehumidified by a dehumidifier. Working air used in the plant, for example, air used when flushing the inside of a pipe, operation of an air operating tool Used for air etc. Further, the in-house air is used as backflow prevention air during backflow prevention operation. The control air system 111 is a system that supplies compressed air (control air) dehumidified by the dehumidifier 120, and is used as instrumentation and control air such as control valve drive air.

  The in-house air system 101 includes three in-house air compressors 102, 103, 104, an air storage tank 105 that stores compressed air, and an air that connects the in-house air compressors 102, 103, 104 and the air storage tank 105. It has supply pipes 106, 107, and 108, and an air supply pipe 109 that is connected to the air storage tank 105 and supplies in-house air. The backflow preventing air supply pipe 61 is connected to the air supply pipe 109 via an air header (not shown). The three in-house air compressors 102, 103, and 104 perform load operation and no-load operation according to the pressure of the air storage tank 105.

  The control air system 111 connects two control air compressors 112 and 113, an air storage tank 115 that stores compressed air, a dehumidifier 120, the control air compressors 112 and 113, and the air storage tank 115. Air supply pipes 116 and 117, an air supply pipe 119 connecting the air storage tank 115 and the dehumidifier 120, and an air supply pipe 121 connected to the dehumidifier 120 and supplying control air. The two control air compressors 112 and 113 perform a load operation and a no-load operation according to the pressure of the air storage tank 115. The air compressor 113 is a spare machine.

  The air supply facility 100 further includes a backup system 130 that communicates the in-house air system 101 and the control air system 111. The backup system 130 is a system for securing the air amount of the control air system 111 by sending the in-house air to the control air system 111 when the control air system is short of air.

  The backup system 130 connects the air supply pipe 109 of the in-house air system and the air supply pipe 119 of the control air system with a backup air supply pipe 131. The backup air supply pipe 131 is provided with a check valve 132 and a backup valve 133 that can supply in-house air to the control air system 111. Further, the backup air supply pipe 131 is provided with a bypass pipe 134 that is provided with a backup valve bypass valve 135 that bypasses the check valve 132 and the backup valve 133.

  The backup valve 133 is an automatic control valve, and opens when the air supply pipe 119 of the control air system drops to a predetermined pressure, and closes when the air supply pipe 119 of the control air system rises to a predetermined pressure. The opening / closing control of the backup valve 133 is performed by the pressure regulator 122 provided in the air supply pipe 119. The backup valve bypass valve 135 is a manual valve, and is used for emergency evacuation when the check valve 132 and / or the backup valve 133 is malfunctioning and the in-house air cannot be supplied to the control air system 111.

  Next, the startup procedure of the pressurized fluidized bed combined power plant will be described. FIG. 3 is a flowchart showing the startup procedure of the pressurized fluidized bed combined power plant. The startup of the pressurized fluidized bed combined power plant (unit) consists of a plurality of steps, and each step proceeds according to a procedure predetermined by a computer.

  In the start-up operation of the pressurized fluidized bed combined power plant, unit start-up preparation (step S1) is performed to check the operation and status of common facilities and equipment necessary for unit start-up, and then water without impurities (water quality is controlled). The condensate system and the water supply system are washed and filled (step S2), and the pressurized fluidized bed boilers (hereinafter referred to as boilers) 10 and 20 are washed and filled (step S3).

  When cleaning and water filling of the boilers 10 and 20 are completed, the gas turbine 41 is started to enable supply of air necessary for boiler ignition prior to ignition of the boilers 10 and 20 (step S4). The gas turbine 41 is started using a gas turbine starting combustor 43. After the gas turbine 41 is started, the gas turbines 41 are paralleled (step S5). During the parallel operation of the gas turbine 41 from the start of the gas turbine 41, the backflow prevention operation is performed. Details of the start-up, the parallel operation, and the backflow prevention operation of the gas turbine 41 will be described later.

  When it becomes possible to drive the gas turbine 41 and supply ignition air from the connected air compressor 51, the boiler ignition preparation (step S6), the boiler ignition / temperature increase / pressure increase process (step S7), The steam necessary for the starting condition of the steam turbine is created.

  Thereafter, preparation for starting the steam turbine (step S8), starting of the steam turbine (step S9), starting the power generation in parallel with the system, and the steam turbine parallel / load increasing process for increasing the generator output to the rated output (step 10) Then, the unit activation operation is completed (Step S12) upon completion of reaching the rated load (Step S11).

  The start-up of the gas turbine 41, the parallel operation, and the backflow prevention operation performed accompanying the operation will be described. The gas turbine 41 is started using a gas turbine starting combustor 43. Specifically, the air compressor 51 is driven via the starter motor 58, the compressed air is sent to the gas turbine starter combustor 43 through the compressed air bypass pipe 54, and the combustor combustion gas (startup) using light oil or the like as fuel. Gas) is generated and the gas turbine 41 is started. At this time, the hot gas stop valve 44 and the hot gas control valve 45 are fully closed so that the starting gas does not flow into the furnaces 11 and 21. The compressor outlet valve 53 is also fully closed.

  Since the starting gas is high temperature and high pressure, it cannot be completely shut off by the high temperature gas control valve 45 and the high temperature gas stop valve 44 and leaks to the furnaces 11 and 21 side. When the starting gas flows backward to the furnaces 11 and 21, the fluid medium in the furnaces 11 and 21 falls and accumulates in a wind box (not shown) through a dispersion nozzle (not shown). In order to prevent this, a backflow prevention operation is performed in which a certain amount of backflow prevention air is supplied to the pressure vessels 12 and 22 and the furnaces 11 and 21.

  The backflow prevention operation is performed by supplying a predetermined amount of backflow prevention air to the pressure vessels 12 and 22 through the backflow prevention air supply pipe 61 and the air supply pipe 52. At this time, the gas turbine first bypass valve 47 and the gas turbine first bypass valve 48 interposed in the gas turbine bypass pipe 46 are fully opened.

  The backflow prevention air supplied to the pressure vessels 12 and 22 passes through the furnaces 11 and 21, and the combustion gas pipes 30, 31, the primary cyclones 32, 33, the secondary cyclones 34, 35, the combustion gas pipe 36, and the gas. It is discharged from the chimney through the turbine bypass pipe 46. The starting gas leaking from the hot gas stop valve 44 and the hot gas control valve 45 is led to the chimney from the gas turbine bypass pipe 46 together with the backflow prevention air. As a result, the backflow of the starting gas is prevented.

  The backflow prevention operation is performed as follows. A computer that controls unit startup is performed in accordance with gas turbine startup, gas turbine parallel, and the like in the unit startup process. On the condition that the three in-house air compressors 102, 103, and 104 are in operation, the computer prepares for ventilation system gas turbine startup, gas turbine startup, gas turbine parallel, gas turbine system valve switching, gas turbine The process proceeds in the order of system valve switching completion. During this time, in-house air is supplied from the in-house air system 101 to the furnaces 11 and 21 as backflow prevention air.

  Since the backflow prevention operation constitutes a system with a sequence master and is a master completion condition, a “traffic jam” warning is issued if it is not completed. An example of the air flow rate supplied in the backflow prevention operation is 15.84 ton / h or more. At this time, the pressure in the pressure vessels 12 and 22 becomes 0.12 MPa (gauge pressure), and the secondary cyclone 34, The gas temperature after the 35 joining (point of a in FIG. 1) is 300 ° C. or less. Note that the temperature of the starting gas that leaks through the high-temperature gas stop valve 44 at the time of starting the gas turbine (the point B in FIG. 1) is about 200 to 240 ° C.

  In the backflow prevention operation performed in association with the start-up and parallel operation of the gas turbine 41 as described above, the compressed air of the in-house air system 101 is used as the backflow prevention air. If one of the machines 102, 103, 104 fails and becomes inoperable, even if the remaining two in-house air compressors 102, 103 are healthy, a predetermined amount of backflow prevention air cannot be supplied. . Furthermore, since the unit activation condition cannot be satisfied, the unit cannot be activated.

  In such a case, the back-up prevention operation is performed by using the backup system 130 in the opposite direction to the original method of use and replenishing the in-house air system 101 with air from the control air system 111. FIG. 4 is a time chart when the backflow prevention operation is performed while replenishing the in-house air system 101 with air from the control air system 111.

  The spare air compressor 113 of the control air system 111 is activated, and a simulation signal is input to the computer to establish the condition for operating three on-site air compressors, which is a unit activation condition.

  The backup system 130 is a system for ensuring the amount of air in the control air system 111 by sending air from the in-house air system 101 to the control air system 111. The in-house air system 101 and the control air system Since the check air valve 132 is provided in the backup air supply pipe 131 that connects to the air 111, the air in the control air system 111 cannot be supplied to the indoor air system 101 through the backup air supply pipe 131.

  In the present embodiment, air is sent from the control air system 111 to the in-house air system 101 using the bypass pipe 134 that bypasses the check valve 132 and the backup valve 133. At this time, the backup valve bypass valve 135 is fully opened. In such an air supply facility 100, the control air system 111 and the in-house air system 101 communicate with each other. Therefore, when the pressure of the in-house air system 101 is lower than the pressure of the control air system 111, The air in the industrial air system 111 flows into the in-house air system 101. Conversely, when the pressure in the in-house air system 101 is higher than the pressure in the control air system 111, the air in the in-house air system 101 flows into the control air system 111.

  In the state where the in-house air system 101 and the control air system 111 are communicated with each other via the bypass pipe 134, two in-house air compressors and two in-control air compressors are operated to execute the unit starting process. Then, during the gas turbine starting process, the air in the in-house air system is supplied to the pressure vessels 12 and 22 as backflow prevention air. Since the backflow prevention air is a large flow of air, the two in-house air compressors operate continuously.

  Since a large amount of air is supplied as backflow prevention air from the in-house air system 101 connected to the backflow prevention air supply pipe 61, the pressure of the in-house air system 101 is compared with the pressure of the control air system 111. Become lower. Therefore, the air in the control air system 111 naturally flows into the in-house air system 101 through the bypass pipe 134.

  The two air compressors of the control air system 111 perform load / no-load automatic operation so that the control air system 111 has a predetermined pressure. When the gas turbines 41 are arranged in parallel and the switching of the system valve 56 of the gas turbine 41 is completed, air is supplied from the air compressor 51 connected to the gas turbine 41 through the original route. Decrease significantly. The switching of the system valve 56 is an operation of opening the hot gas stop valve 44, the hot gas control valve 45 and the compressor outlet valve 53 and closing the compressed air bypass valve 55. In conjunction with the switching of the system valve 56, the gas turbine first bypass valve 47 and the gas turbine second bypass valve 48 are closed. After completion of the backflow prevention operation, the backup valve bypass valve 135 is closed, the preliminary air compressor 103 of the control air system 111 is stopped, and the original form is obtained.

  As described above, the start-up method of the pressurized fluidized bed combined power plant according to the present invention is such that the control air is supplied to the in-house air system 101 when the supply amount of the in-house air decreases in the backflow prevention operation at the start of the gas turbine. Since the air of the system 111 is fed and used as the backflow prevention air, the pressurized fluidized bed combined power plant can be started even if some of the in-house air compressors fail. Further, since the bypass pipe 134 of the backup system 130 is used for replenishing the air from the control air system 111 to the in-house air system 101, the existing pressurized fluidized bed combined power plant can be implemented without improvement.

  The start-up method of the pressurized fluidized bed combined power plant according to the present invention is not limited to the above embodiment, and can be changed and used without changing the gist. For example, the backup valve bypass valve 135 is provided with a limit switch that is turned on when the valve is fully opened, and the ON signal of the limit switch is transmitted to the computer as the operation signal of the in-house air compressor. As a result, even if one of the in-house air compressors fails, by opening the backup valve bypass valve 135, the conditions on the computer side are automatically established, and the air amount in the in-house air system 101 is also secured. A pressurized fluidized bed combined power plant can be activated.

10, 20 Pressurized fluidized bed boiler 11, 21 Furnace 12, 22 Pressure vessel 41 Gas turbine 42 Generator 43 Gas turbine start combustor 44 Hot gas stop valve 45 Hot gas control valve 46 Gas turbine bypass pipe 47 Gas turbine first Bypass valve 48 Gas turbine second bypass valve 51 Air compressor 52 Air supply pipe 53 Compressor outlet valve 54 Compressed air bypass pipe 55 Compressed air bypass valve 58 Motor for starting 61 Air supply pipe for preventing backflow 62 In-house air furnace supply flow rate Control valve 100 Air supply facility 101 In-house air system 102, 103, 104 In-house air compressor 105 Air storage tank 106, 107, 108, 109 Air supply pipe 111 Control air system 112, 113 Control air compressor 115 Air storage tank 116, 117, 119, 121 Air supply pipe 120 Humidifier 122 pressure adjusting meter 130 Backup system 131 Backup air supply pipe 132 check valve 133 back up valve 134 bypass pipe 135 backup valve bypass valve

Claims (2)

In order to prevent the combustor combustion gas from flowing back to the pressurized fluidized bed boiler when the gas turbine is started, a pressurized fluidized bed combined power plant that performs a backflow preventing operation for supplying backflow preventing air to the pressurized fluidized bed boiler. In the startup method,
The pressurized fluidized bed combined power plant has an in-house air system, a control air system, and a backup system that supplies air from the in-house air system to the control air system as backup air,
Using said backup system in the opposite direction, to produce a mixed air feed air to the house air line from the control air system, pressurization, which comprises using the mixed air in the backflow preventing air How to start a fluidized bed combined power plant. The backflow prevention operation using the mixed air is performed when some of the in-house air compressors in the in-house air system cannot be operated. Item 2. A method for starting up a pressurized fluidized bed combined power plant according to item 1 .

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