JP4787528B2 - Wet raw material drying apparatus and drying method - Google Patents

Description

  The present invention relates to a wet raw material drying apparatus and a drying method for drying a wet raw material such as coal charged in a coke oven with a fluidized bed dryer.

  In coke production, for the purpose of improving the quality of coke and improving the productivity in the coke oven, the charging coal is dried before charging the coke oven. The water content of the coke oven coal is usually about 9 to 13% before drying, but this coal is dried to 5 to 6% with a coal dryer. In general, it is known that the amount of fine powder separated from coal increases as the moisture in the coal decreases.

  It has been known to use a fluidized bed dryer for drying coal. Patent Document 1 introduces coke oven flue flue gas as a heat source and fluidized gas into a fluidized bed dryer to dry the coal. A method is disclosed. Most of the coal powder charged in the fluidized bed dryer is discharged from a discharge chute that communicates with the fluidized bed and is conveyed to a coke oven. Further, fine powder is generated by drying the coal powder, and the fine powder is discharged together with the exhaust gas from the exhaust gas outlet above the fluidized bed, and is collected by a dust collector provided in the exhaust gas pipe.

  Here, the exhaust gas temperature of the coke oven used as the heat source and fluidizing gas of the fluidized bed dryer varies depending on the operation load status, fuel properties, and combustion control status of the coke oven. For example, when the production of a coke oven is temporarily reduced, exhaust gas having a temperature significantly higher than the temperature condition at the time of designing the dryer may flow in. As a result, the amount of fine powder generated from the coal increases because the moisture in the coal is dried more than at the time of design, and the amount of fine powder recovered by the dust collector also increases. Further, when the calorific value of the coke oven fuel is temporarily reduced, exhaust gas having a temperature significantly lower than the temperature condition at the time of designing the dryer may flow in. Thereby, the amount of fine powder generated from the coal is reduced, and the amount of fine powder collected by the dust collector is also reduced. Thus, when using the exhaust gas of a coke oven as a heat source and fluidizing gas of a fluidized bed dryer, the gas temperature may fluctuate. As a result, the amount of fine powder generated from the coal fluctuates with variation in the degree of drying of the wet raw material in the fluidized bed dryer, and the amount of fine powder collected and discharged by the dust collector also varies.

  Further, the coke oven usually has two combustion gas systems for each furnace group, and when the usage time in one system reaches a predetermined time, the system is switched to the other system. System switching is usually performed once every 15 to 30 minutes. At the time of switching the combustion gas system, as shown in FIG. 4, the combustion gas flow rate of the system (system A) that has been used so far is sequentially decreased, and when the flow rate becomes zero, the system to be used next (system B) ) Is gradually increased. Therefore, when the combustion gas system is switched, the amount of exhaust gas in the coke oven decreases, becomes zero, and increases again. The time during which the gas flow rate fluctuates with switching of the combustion gas system is generally 0.5 to 3 minutes.

  Thus, when using the exhaust gas of a coke oven as a heat source and fluidizing gas of a fluidized bed dryer, the amount of exhaust gas in the coke oven decreases when the combustion gas system of the coke oven is switched. The technology maintains the fluidized state of the fluidized bed by circulating the gas discharged from the fluidized bed dryer and reusing it as the fluidized gas of the fluidized bed dryer when the supply of exhaust gas from the coke oven stops or decreases. Like to do. However, since the gas discharged from the fluidized bed dryer is the gas that has been used for drying the coal powder, the temperature of the gas is of course considerably lower than the temperature of the exhaust gas from the coke oven. At the time of switching, as shown in FIG. 4, the temperature of the gas flowing into the fluidized bed of the fluidized bed dryer is lowered. As a result, the dryness of the wet raw material decreases, and the amount of fine powder generated by drying and collected by the dust collector decreases. On the other hand, it is conceivable to provide a hot air generating furnace, etc. separately, to make up for the shortage of heat by burning when switching the combustion gas system, and to make the amount of fine powder recovered constant. As described above, the switching of the combustion gas system is normally performed once every 15 to 30 minutes, and the time for the change of the gas flow rate accompanying the switching is as short as about 0.5 to 3 minutes. It is not realistic to operate the hot air generating furnace to supplement the amount of heat necessary for drying the wet raw material.

On the other hand, in order to prevent dust scattering from the dust discharged from the dust collector of the fluidized bed coal dryer for drying the coal charged in the coke oven and carbon adhesion to the coke oven wall, it is heavy on the collected dust. A method of granulating by adding oil has been devised as Patent Document 2, but in this patent, it does not take into account fluctuations in the gas flow rate and gas temperature of hot air such as exhaust gas from a coke oven, As described, the amount of heavy oil added is constant at about 250 kg / hr for a fine powder amount of about 95 t / hr.
JP 2001-55582 A Japanese Patent Publication No.49-28241

  The problem to be solved by the present invention is that supply of coke oven exhaust gas, which is a high-temperature gas supplied to a fluidized bed dryer as a heat source and fluidizing gas, is stopped, reduced or increased, or the temperature of the gas changes. As a result, even if the amount of fine powder discharged and recovered from the fluidized bed dryer increases or decreases, by mixing at a constant ratio with the binder necessary for kneading and granulating fine powder, dust scattering and coke oven walls are achieved. This is to reliably prevent carbon adhesion.

The present invention includes a fluidized bed dryer for drying a wet raw material, a duct and a blower for introducing exhaust gas from a coke oven into the fluidized bed dryer, and a dust collector for collecting fine powder accompanying the exhaust gas from the fluidized bed dryer. In a wet raw material drying apparatus that uses exhaust gas from a coke oven as a heat source and fluidizing gas for a fluidized bed dryer , a change in the amount of exhaust gas supplied from the coke oven or a change in exhaust gas temperature is detected, and Corresponding to the detection signal, it has a binder addition device equipped with a binder addition amount control device that adjusts the binder addition amount so that the binder addition amount becomes a fixed ratio to the fine powder amount discharged from the dust collector. And

Further, the present invention detects that the supply of exhaust gas from the coke oven stops or decreases in the drying device, and the binder addition amount is constant with respect to the fine powder amount discharged from the dust collector in response to the detection signal. It has a binder addition apparatus provided with the binder addition amount control apparatus which adjusts a binder addition amount so that it may become this ratio .

According to the present invention, in the method of drying wet material by the drying device, variations in the supply amount of the exhaust gas from the coke oven, or detects a variation in the temperature of the exhaust gas, in response to the detection signal, the amount of added binder precipitator It is characterized by adjusting the amount of binder added so as to be a constant ratio with respect to the amount of fine powder discharged from the container .

Further, the present invention detects that the supply of exhaust gas from the coke oven stops or decreases in the drying method of the wet raw material by the drying device, and the amount of binder added is discharged from the dust collector in response to the detection signal. The additive amount of the binder is adjusted so as to be a constant ratio with respect to the fine powder amount .

  In the present invention, it is possible to detect from the signal from the coke oven that the supply of the exhaust gas from the coke oven supplied to the fluidized bed dryer is stopped, decreased or increased, or the exhaust gas temperature fluctuates.

  In the present invention, when the supply of exhaust gas from the coke oven is stopped or reduced, the gas discharged from the fluidized bed dryer can be circulated and reused as the fluidized gas of the fluidized bed dryer. Further, it is possible to detect that the supply of exhaust gas from the coke oven is stopped or decreased by a prediction signal or a start signal for switching the combustion system of the coke oven.

  According to the present invention, the coke oven exhaust gas supplied to the fluidized bed dryer as a heat source / fluidizing gas is discharged together with the gas from the fluidized bed dryer due to the stop, decrease or increase of the supply of the coke oven exhaust gas or the temperature fluctuation of the coke oven exhaust gas. Even if the amount of fine powder recovered varies, the supply, discharge, or increase of coke oven exhaust gas supply is detected, or changes in coke oven exhaust gas temperature are detected or predicted, and the increase or decrease in the amount of fine powder recovered by the dust collector is anticipated. Therefore, the mixing ratio of the fine powder and the binder can always be maintained at an optimum ratio. Therefore, by adding a sufficient amount of binder to the fine powder, dust scattering and carbon adhesion to the coke oven wall can be prevented, and problems such as contamination of the conveyance path due to excessive binder and waste of the binder can be solved.

  Hereinafter, embodiments of the present invention will be described based on examples in which the present invention is applied to drying of coal powder for coke ovens (hereinafter simply referred to as “coal powder”).

  FIG. 1 is a schematic block diagram showing an embodiment of the drying apparatus of the present invention.

  In the figure, the combustion exhaust gas of the coke oven generated in the coke oven 1 passes through the flue 2 and is emitted from the coke oven chimney 3 to the atmosphere. The temperature of the flue exhaust gas (coke oven exhaust gas) 4 passing through the flue 2 is about 150 to 250 ° C. The coke oven exhaust gas 4 flows through the gas supply pipe 5 branched from the coke oven flue 2, is pressurized by the blower 6, and is then supplied from the lower part of the fluidized bed dryer 8 as the heat source / fluidizing gas 7.

  The exhaust gas 9 discharged from the fluidized bed dryer 8 is diffused into the atmosphere from the chimney 13 via the dust collector 11 and the blower 12 by the exhaust gas pipe 10.

  Further, the gas circulation pipe 14 is branched from the exhaust gas pipe 10 and the tip thereof is connected to the gas supply pipe 5 so that the exhaust gas 9 of the fluidized bed dryer 8 is circulated to recycle the fluidized gas of the fluidized bed dryer 8. As it can be used as.

  Coal powder, which is a wet raw material, is charged into the fluidized bed dryer 8 by the charging chute 15 and forms a fluidized bed 16 by the upward flow of the heat source / fluidized gas 7 introduced from the lower part of the fluidized bed dryer 8. To do. The coal powder is dried in the fluidized bed 16, the coal powder is adjusted to a predetermined temperature and moisture content, and most of the coal powder is discharged by the discharge chute 17. The coal powder discharged from the discharge chute 17 is transported to the coke oven through a transport path (not shown). On the other hand, fine powder is generated by drying the coal powder in the fluidized bed 16, and this fine powder is discharged together with the gas from the upper part of the fluidized bed dryer 8 and is collected by the dust collector 11 provided in the exhaust gas pipe 10.

  A binder such as heavy oil is added to the collected fine powder by a binder addition device 18, and after being kneaded and granulated by a kneading granulator 19, it is conveyed to a coke oven through a conveying path (not shown). The amount of binder added by the binder addition device 18 is adjusted by the binder addition control device 20. Of course, the binder addition control device 20 can be incorporated in the binder addition device 18. In addition, when adjusting the binder addition apparatus 18 manually, the binder addition control apparatus 20 is unnecessary.

  The above-described coke oven flue 2 is provided with an exhaust gas flow meter 21, the gas supply pipe 5 is provided with a flow meter 23 and a first control valve 24, the exhaust gas pipe 10 is provided with a second control valve 25, and a gas circulation pipe. 14 is provided with a third control valve 26. The exhaust gas flow meter 21 is not essential, and the exhaust gas flow rate can also be estimated by the combustion calculation of the coke oven. The opening degree or flow rate of the first to third control valves 24 to 26 can be adjusted by the control valve control devices 27 to 29, respectively.

  In this embodiment, the mixing ratio of the fine powder recovered by the dust collector 11 and the binder is always set to an optimal ratio by adjusting the binder adding device 18 in accordance with the change in the exhaust gas temperature or flow rate of the coke oven. A specific description will be given with reference to FIG.

  Since the amount of fine powder discharged from the dust collector 11 is constant in the steady state, the amount of binder added is constant, and a mechanism for adjusting the binder adding device 18 is not necessary. As a result of intensive studies on the optimum mixing ratio of the fine powder and the binder by the present inventors, it has been found that the optimum ratio is 0.1 to 15% of the binder with respect to the fine powder 1.

  On the other hand, when the flow rate or temperature of the coke oven exhaust gas 4 introduced into the fluidized bed dryer 8 is changed for some reason, such as a sudden change in the production amount or a change in the calorific value of the coke oven fuel in the coke oven, it is described above. The amount of fine powder collected by the dust collector 11 also changes depending on the reason. As described above, a binder necessary for kneading and granulation is added to the recovered fine powder. However, if the same amount of binder as that in steady operation is added when the exhaust gas property of the coke oven is changed, the binder is excessive. Or the binder is insufficient. On the other hand, in the present invention, the change in the flow rate or temperature of the coke oven exhaust gas is obtained by grasping the amount of fine powder recovered by the dust collector 11 that changes with the change in the flow rate or temperature of the coke oven exhaust gas. Accordingly, the binder adding device 18 can be adjusted manually or automatically to keep the mixing ratio between the amount of fine powder discharged from the dust collector 11 and the binder constant, problems such as contamination of the conveyance path due to excessive binder, It is possible to prevent dust generation in the conveyance path due to the shortage or carbon adhesion in the coke oven.

  As a method for adjusting the binder adding device 18, the property change of the coke oven exhaust gas can be detected or predicted and manually performed. However, the property of the coke oven exhaust gas sent from the coke oven may change. The binder addition amount is automatically adjusted by detecting signals (a signal indicating increase / decrease in coke oven production, a signal indicating increase / decrease in calorific value of coke oven fuel) by the binder addition control device 20 shown in the figure. It is also possible to do this.

  FIG. 2 is a schematic configuration diagram showing another embodiment of the drying apparatus of the present invention.

  In the figure, the combustion exhaust gas of the coke oven generated in the coke oven 1 passes through the flue 2 and is emitted from the coke oven chimney 3 to the atmosphere. The temperature of the coke oven exhaust gas 4 passing through the flue 2 is about 150 to 250 ° C. The coke oven exhaust gas 4 flows through the gas supply pipe 5 branched from the coke oven flue 2, is pressurized by the blower 6, and is then supplied from the lower part of the fluidized bed dryer 8 as the heat source / fluidizing gas 7.

  The exhaust gas 9 discharged from the fluidized bed dryer 8 is diffused into the atmosphere from the chimney 13 via the dust collector 11 and the blower 12 by the exhaust gas pipe 10.

  Further, the gas circulation pipe 14 is branched from the exhaust gas pipe 10 and the tip thereof is connected to the gas supply pipe 5 so that the exhaust gas 9 of the fluidized bed dryer 8 is circulated to recycle the fluidized gas of the fluidized bed dryer 8. As it can be used as.

  Coal powder, which is a wet raw material, is charged into the fluidized bed dryer 8 by the charging chute 15 and forms a fluidized bed 16 by the upward flow of the heat source / fluidized gas 7 introduced from the lower part of the fluidized bed dryer 8. To do. The coal powder is dried in the fluidized bed 16, the coal powder is adjusted to a predetermined temperature and moisture content, and most of the coal powder is discharged by the discharge chute 17. The coal powder discharged from the discharge chute 17 is transported to the coke oven through a transport path (not shown). On the other hand, fine powder is generated by drying of the coal powder in the fluidized bed 16, and this powder is discharged from the upper part of the fluidized bed dryer 8 together with the gas and collected by the dust collector 11 provided in the exhaust gas pipe 10.

  A binder such as heavy oil is added to the collected fine powder by a binder addition device 18, and after being kneaded and granulated by a kneading granulator 19, it is conveyed to a coke oven through a conveying path (not shown). The amount of binder added by the binder addition device 18 is adjusted by the binder addition control device 20. Of course, the binder addition control device 20 can be incorporated in the binder addition device 18.

  The above-described coke oven flue 2 is provided with an exhaust gas flow meter 21, the gas supply pipe 5 is provided with a flow meter 23 and a first control valve 24, the exhaust gas pipe 10 is provided with a second control valve 25, and a gas circulation pipe. 14 is provided with a third control valve 26. The exhaust gas flow meter 21 is not essential, and the exhaust gas flow rate can also be estimated by the combustion calculation of the coke oven. The opening degree or flow rate of the first to third control valves 24 to 26 can be adjusted by the control valve control devices 27 to 29, respectively. Furthermore, a gas circulation system control device 30 is provided, and the control of the circulation gas amount is performed by giving control commands to the control devices 27 to 29 of the first to third control valves 24 to 26.

  As described above in the background art section, the coke oven 1 normally has two combustion gas systems for each furnace group, and when the usage time in one system reaches a predetermined time, the other Switch to the system. System switching is usually performed once every 15 to 30 minutes.

  At the time of switching the combustion gas system, as shown in FIG. 4, the combustion gas flow rate of the system (system A) that has been used so far is sequentially decreased, and when the flow rate becomes zero, the system to be used next (system B) ) Is gradually increased. Therefore, when switching the combustion gas system, the amount of exhaust gas in the coke oven decreases and increases again. The time required for switching the combustion gas system is generally 0.5 to 3 minutes.

  In this embodiment, when the supply of exhaust gas from the coke oven is stopped or reduced, the exhaust gas discharged from the fluidized bed dryer 8 is circulated through the gas circulation pipe 14 as fluidized gas of the fluidized bed dryer 8. Use again. A specific description will be given with reference to FIGS. 2 and 3 as follows.

  The third control valve 26 disposed in the gas circulation pipe 14 is fully closed or slightly opened during steady operation. That is, when the exhaust gas temperature of the coke oven is too high during steady operation, it is effective to lower the gas temperature by mixing the low-temperature circulating gas slightly, and the water content of the supplied coal powder fluctuated. Circulating gas can also be used to adjust the drying capacity.

  At the start of the combustion gas system switching in the coke oven, the third control valve 26 is fully closed or opened from a slightly open state to a certain opening degree. As a result, the circulating gas 31 flows through the gas circulation pipe 14 by the action of the blower 6 and the blower 12 to generate a recycle flow. The opening degree of the first control valve 24 is gradually reduced at a timing when a constant amount of the circulation gas 31 is secured. As a result, the coke oven exhaust gas 4 that has been supplied to the fluidized bed dryer 8 gradually decreases, and conversely, the flow rate to the coke oven chimney 3 increases. The opening / closing operation speed of the first control valve 24 is not necessarily constant, and the amount of combustion exhaust gas (flue exhaust gas amount) varies depending on the operation degree of the coke oven 1 and the combustion state of the coke oven 1. It is necessary to decide on an individual basis.

  The first to third control valves 24 to 26 are controlled by the control valve control devices 27 to 29 controlling the control valves based on commands from the gas circulation system control device 30. Of course, part or all of the gas circulation system control device 30 and the control valve control devices 27 to 29 can be integrated into a single control device. Each control valve control device can also be incorporated in each control valve.

  The control for changing the gas supplied to the fluidized bed dryer 8 at the time of switching the combustion gas system of the coke oven is started by receiving a start signal for switching the combustion gas system from the coke oven 1, and the exhaust gas flow meter of the flue 2 A method of starting based on the change in the flow rate of 21 can be used. Further, as shown in FIG. 3, a prediction signal is received from the coke oven 1 for a predetermined time before the combustion gas system switching is started, and supply gas change control to the fluidized bed dryer 8 is started based on this prediction signal. You can also. For example, a prediction signal is received one minute before the exhaust gas flow rate becomes the opening, and waste recycling via the gas circulation pipe 14 is started. As a result, it is possible to avoid a situation where the amount of gas supplied to the fluidized bed dryer 8 (heat source / fluidized gas amount) is insufficient due to insufficient waste recycling.

  Since the circulating gas 31 used when switching the combustion gas system of the coke oven is a gas after being used for drying the coal powder in the fluidized bed dryer 8, the gas temperature is naturally lower than that of the coke oven exhaust gas 4. Therefore, when the combustion gas system of the coke oven is switched, the temperature of the gas flowing into the fluidized bed of the fluidized bed dryer decreases as shown in FIG. As a result, the dryness of the wet raw material decreases, and the amount of fine powder generated by drying and collected by the dust collector decreases.

  As described above, the binder required for kneading and granulation is added to the recovered fine powder, but when the amount of fine powder decreases when switching the combustion gas system of the coke oven, the same amount of binder as in steady operation is added. Addition results in excessive binder. On the other hand, in the present invention, the switching of the combustion gas system of the coke oven is detected, and the binder addition amount is reduced after anticipating the decrease in the fine powder amount (see the lowermost stage in FIG. 3). As shown in FIG. 3, the detection of switching of the combustion gas system can be performed by receiving a prediction signal from the coke oven for a predetermined time before starting the switching of the combustion gas system. When the binder addition control device 20 receives this prediction signal, it predicts that the amount of fine powder will decrease every t seconds, and the binder added by the binder addition device 18 so that the ratio of fine powder to binder becomes the same as in steady operation. Reduce the amount added. As a result, the fine powder and the binder can always be mixed at a constant rate, and problems such as contamination of the conveyance path due to excessive binder do not occur.

  Detection of switching of the combustion gas system can also be performed by receiving a start signal for switching of the combustion gas system from the coke oven 1. In this case, the time required to start the adjustment of the binder addition amount is shorter than that in the detection based on the prediction signal, but it can be sufficiently handled in actual operation.

  The present invention can be applied not only to drying coal powder charged into a coke oven, but also to drying other wet raw materials such as granulated slag and limestone.

It is a schematic block diagram which shows one Example of the drying apparatus of this invention. It is a schematic block diagram which shows the other Example of the drying apparatus of this invention. It is a figure which shows the switching condition of the combustion exhaust gas system | strain of the coke oven in this invention. It is a figure which shows the switching condition of the combustion exhaust gas system | strain of the coke oven in a prior art.

Explanation of symbols

1 Coke oven 2 Flue 3 Coke oven chimney 4 Flue exhaust gas (Coke oven exhaust gas)
5 Gas supply pipe 6 Blower 7 Heat source / fluidized gas 8 Fluidized bed dryer 9 Exhaust gas 10 Exhaust gas pipe 11 Dust collector 12 Blower 13 Chimney 14 Gas circulation pipe 15 Charge chute 16 Fluidized bed 17 Discharge chute 18 Binder addition device 19 Kneading granulation Machine 20 Binder addition control device 21 Exhaust gas flow meter 23 Flow meter 24 First control valve 25 Second control valve 26 Third control valve 27-29 Control valve control device 30 Gas circulation system control device 31 Circulating gas

Claims (5)

Fluidized bed dryer for drying wet raw materials, ducts and blowers for introducing the coke oven exhaust gas into the fluidized bed dryer, and a dust collector for collecting fine powder accompanying the exhaust gas from the fluidized bed dryer Detects fluctuations in the amount of exhaust gas supplied from the coke oven or fluctuations in the temperature of the exhaust gas, and responds to the detection signal in the wet raw material drying equipment that uses the coke oven exhaust gas as the heat source and fluidizing gas for the layer dryer. A wet raw material comprising a binder addition device having a binder addition amount control device that adjusts the binder addition amount so that the binder addition amount becomes a constant ratio to the fine powder amount discharged from the dust collector Drying equipment. Fluidized bed dryer for drying wet raw materials, ducts and blowers for introducing the coke oven exhaust gas into the fluidized bed dryer, and a dust collector for collecting fine powder accompanying the exhaust gas from the fluidized bed dryer In a wet raw material drying device that uses coke oven exhaust gas as a heat source and fluidizing gas for a layer dryer, it is detected that the supply of exhaust gas from the coke oven is stopped or reduced, and in response to the detection signal, a binder A wet raw material drying apparatus comprising a binder addition device having a binder addition amount control device for adjusting a binder addition amount so that the addition amount becomes a constant ratio with respect to the fine powder amount discharged from the dust collector . Gas circulation piping for recirculating the gas discharged from the fluidized bed dryer and supplying it to the fluidized bed dryer, and the gas discharged from the fluidized bed dryer when the supply of exhaust gas from the coke oven stops or decreases The wet raw material drying apparatus according to claim 1, further comprising a gas circulation system control device that performs control so as to circulate and reuse the fluidized gas of the fluidized bed dryer . Fluidized bed dryer for drying wet raw materials, ducts and blowers for introducing the coke oven exhaust gas into the fluidized bed dryer, and a dust collector for collecting fine powder accompanying the exhaust gas from the fluidized bed dryer In a wet raw material drying method using a coke oven exhaust gas as a heat source and fluidizing gas for a layer dryer, a change in the amount of exhaust gas supplied from the coke oven or a change in exhaust gas temperature is detected. A method for drying a wet raw material, characterized in that, in response to the detection signal, the amount of binder added is adjusted so that the amount of added binder becomes a constant ratio to the amount of fine powder discharged from the dust collector . Fluidized bed dryer for drying wet raw materials, ducts and blowers for introducing the coke oven exhaust gas into the fluidized bed dryer, and a dust collector for collecting fine powder accompanying the exhaust gas from the fluidized bed dryer In the drying method of wet raw material by the wet raw material dryer using the coke oven exhaust gas as the heat source and fluidizing gas of the bed dryer, it detects that the exhaust gas supply from the coke oven stops or decreases, and the detection signal In accordance with the above, a method for drying a wet raw material is characterized in that the binder addition amount is adjusted so that the binder addition amount becomes a constant ratio to the fine powder amount discharged from the dust collector .

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