JP2012132589A - Control method of exhaust gas at the time of stop of sintering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas control method capable of performing a shutdown operation safely and in a short time without causing an abrupt temperature rise of the main exhaust gas and a main exhaust gas duct crush owing to negative pressure even at the time of an abrupt stop of a sintering device.SOLUTION: When the sintering device 2 stops, operations are automatically performed in a way that operations (a) and (b) are concurrently performed first at the same time when the sintering device 2 stops and then operations (c) to (e) are concurrently performed. The following lists these operations: (a) opening a cold air intake damper 7 to a predetermined opening, (b) completely closing dampers 5 in a group of wind boxes 4 that hold a gas of 200°C or higher among the group of wind boxes 4, (c) closing an inlet damper 9 of the main exhauster 10 at a predetermined speed to a limiting opening of surging, (d) completely closing dampers 5 of the wind boxes 4 that are still open in the order from ore outlet side to the ore inlet side according to the opening of the inlet damper 9 of the main exhauster, and (e) adjusting an opening of the cold air intake damper 7 so that the gas temperature at the inlet of an electric precipitator 8 may not exceed an allowable temperature.

Description

  The present invention relates to an exhaust gas control method for protecting an electrostatic precipitator and a main exhaust gas duct in the event of a sudden stop or planned stop of a Dwightroid (DL) type sintering machine.

  The DL-type sintering machine sequentially fills a plurality of pallets that are endlessly connected and rotationally driven with a sintering raw material, and a surface layer portion of the sintering raw material packed layer (hereinafter also simply referred to as “filling layer”). The above-mentioned sintered raw material is struck in an ignition furnace, and the above-mentioned sintered raw material is sucked downward by an air box group fixed immediately below a pallet moving from the supply side to the discharge side after ignition. After firing, when the firing is completed, the operation of returning the pallet at the end portion of the exhaust ore and discharging it is repeated.

  Therefore, when the sintering machine is operating normally, the inlet damper of the main exhaust fan and all the dampers of each wind box are operated in a state of being fully opened or close thereto.

  However, when the sintering machine suddenly stops due to some trouble, if the inlet damper of the main exhaust fan and all the dampers of each wind box are left fully open or close to it, sintering is performed on the stopped pallet. As the firing of the raw material proceeds, the temperature of the exhaust gas that passes through the windbox on the supply side as well as the exhaust box (hereinafter referred to as the “gas temperature in the windbox”) rises rapidly. The exhaust gas temperature also rises rapidly. If the main exhaust gas temperature rises rapidly and becomes hot, sintered dust containing flammable substances burns in the electrostatic precipitator, and the dust collecting plate and the discharge frame may be thermally deformed. is there.

  On the other hand, in order to prevent a sudden rise in the main exhaust gas temperature, all the wind box dampers are closed at the same time or the main exhaust fan inlet dampers are rapidly squeezed in order to suppress firing of the sintered raw material on the stopped pallet. , The control delay occurs due to the inertia of the main exhaust fan, and this influence may cause a large negative pressure state in the main exhaust duct connecting the wind box group and the main exhaust fan, and the main exhaust duct may be collapsed There is.

  Therefore, when the conventional sintering machine stops, the main exhaust fan inlet damper is first throttled stepwise in the closing direction, and the dampers of each wind box are sequentially fully closed from the discharge side to the supply side. While avoiding the collapse of the main exhaust gas duct, the firing of the sintered raw material on the stopped pallet was suppressed, and the rapid increase in the main exhaust gas temperature was prevented. In addition, it is possible to prevent the rise of the main exhaust gas temperature by operating the cold air suction damper installed in the main exhaust gas duct upstream of the electrostatic precipitator in the opening direction to suck the cold air into the main exhaust gas duct. It was.

  As another method, when the sintering machine is stopped, if the soot concentration and the main exhaust gas temperature in the main exhaust gas introduced into the electric dust collector provided on the main exhaust fan inlet side are equal to or lower than the predetermined set values, A method of closing a main exhaust fan inlet damper of a sintering machine at low speed and continuously has been proposed (see Patent Document 1).

  Furthermore, as another method, when the sintering machine is stopped, the main exhaust fan inlet damper is closed to the opening within the surging generation limit, the ignition furnace is weakened within the range not to cause misfire, and the wind box damper is estimated for the completion time of the fire. Then, a method of sequentially fully closing has been proposed (see Patent Document 2).

  However, in general, a method in which the above-mentioned main exhaust fan inlet damper is gradually closed in the closing direction and the dampers of each wind box are sequentially fully closed from the discharge side to the supply side is manually performed by an operator. This was done by operating the exhaust fan inlet damper, each wind box damper and the cold air suction damper. For this reason, there are few problems if the sintering machine is to be stopped at the planned stoppage (at the time of planned shutdown), but the sintering machine suddenly stops due to an unplanned trouble, or an emergency stop occurs. If it is necessary to stop the operation (during sudden stoppage), the damper operation is likely to vary depending on the skill level of the operator, and the operation rate of the sintering machine is reduced because it takes a long time to stop the operation. In severe cases, there was a risk of causing a fire in the electrostatic precipitator and a collapse of the exhaust duct.

  In addition, the method described in Patent Document 1 discloses that the main exhaust fan inlet damper is continuously moved at a low speed if the soot concentration and the main exhaust gas temperature in the main exhaust gas introduced into the electrostatic precipitator are equal to or lower than predetermined values. By closing, it prevents the rise of gas temperature in the electrostatic precipitator and dust and smoke from the chimney, but it is necessary to close the main exhaust fan inlet damper at a low speed, so the operation can be stopped for a long time. There is a drawback that requires.

  In addition, the method described in the above-mentioned Patent Document 2 squeezes the main exhaust fan inlet damper to the opening within the surging generation limit when the sintering machine is stopped, so that a large negative pressure state is generated in the main exhaust duct. There is a high risk that the main exhaust gas duct will be crushed. Moreover, there is a possibility that the countermeasure for preventing the exhaust gas temperature rise is insufficient only by these operations.

  For this reason, there has been a strong demand for the development of an exhaust gas control method capable of stopping the operation more safely and in a shorter time without causing the above-described problems even when the sintering machine is suddenly stopped.

JP-A-8-5258 Japanese Patent Laid-Open No. 10-197160

  Therefore, the present invention makes it possible to stop the operation more safely and in a shorter time without causing a problem of collapse due to a sudden rise in the main exhaust gas temperature and a negative pressure in the main exhaust duct even when the sintering machine suddenly stops. It aims at providing the exhaust gas control method which can be performed.

The invention according to claim 1 is such that when the sintering machine is stopped, the inlet gas temperature of the electrostatic precipitator does not exceed an allowable temperature for protection of the electrostatic precipitator, and immediately below the pallet of the sintering machine. The operation of (a) to (e) is automatically performed so that the main exhaust gas duct between the fixedly arranged wind box group and the main exhaust fan is not crushed by negative pressure. This is an exhaust gas control method when the machine is stopped.
Simultaneously with the stop of the sintering machine, the following operations (a) and (b) are performed in parallel, and then the operations (c) to (e) are performed in parallel.
(A) Cold air is sucked into the main exhaust gas duct by opening the cold air suction damper provided in the main exhaust gas duct between the wind box group and the inlet of the electric dust collector to a predetermined opening.
(B) The dampers of all the wind boxes whose gas temperature in the wind box is 200 ° C. or higher in the wind box group are fully closed.
(C) The inlet damper of the main exhaust fan is closed at a predetermined speed to a limit opening where surging does not occur, and the main exhaust gas flow rate is reduced.
(D) In accordance with the opening degree of the inlet damper of the main exhauster, the dampers of the remaining wind boxes are sequentially fully closed from the discharge side to the supply side.
(E) The opening degree of the cold air suction damper is adjusted so that the inlet gas temperature of the electrostatic precipitator does not exceed the allowable temperature.

  According to the present invention, even when the sintering machine is suddenly stopped, the operation stop operation can be performed more safely and in a shorter time without causing a problem of a sudden rise in the main exhaust gas temperature and a collapse of the main exhaust gas duct. It has become possible.

It is a flowchart which shows the outline | summary of the whole structure of the sintering machine which enforces the method of this invention. It is a block diagram of damper control of the method of the present invention. In the conventional method and the method of the present invention, each time change of the cold air suction damper opening, the main exhaust fan inlet damper opening, the number of wind box dampers fully opened, the main exhaust gas flow rate, the main exhaust fan inlet gas pressure, and the electric dust collector inlet gas temperature is shown. FIG.

  Hereinafter, embodiments of the method of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a flowchart showing an outline of the overall configuration of a sintering machine for carrying out the present invention. In the figure, 1 is a raw material supply device, 2 is a pallet, 3 is an ignition furnace, 4 is a wind box, 5 is a wind box damper, 6 is a main exhaust duct, 7 is a cold air suction damper, 8 is an electric dust collector, and 9 is a main dust collector. The exhaust fan inlet damper, 10 is a main exhaust fan, 11 is a chimney, 12 is a wind box thermometer, 13 is a main exhaust gas thermometer, 14 is a main exhaust gas pressure gauge, 15 is a main controller, and 16 is a timer.

  The sintered raw material cut out from the raw material supply apparatus 1 is sequentially filled on the pallet 2 that is rotationally driven to form the raw material packed layer A. The raw material packed bed A is first ignited in the vicinity of the surface of the coke powder in the ignition furnace 3 while moving from the supply side to the discharge side as the pallet 2 moves. Next, the coke powder in the raw material packed bed A is sequentially burned by the air sucked downward by the group of wind boxes 4 fixedly arranged immediately below the pallet 2 and from the upper part to the lower part of the raw material packed bed A. Firing proceeds. And when baking is completed, the operation which returns the pallet 2 at the end of the discharge side and discharges it is repeated.

  Each wind box 4 is connected to a main exhaust gas duct 6 via each wind box damper 5, and this main exhaust gas duct 6 is further connected via an electric dust collector 8, a main exhaust fan inlet damper 9, and a main exhaust fan 10. It is connected to the chimney 11. Further, the main exhaust gas duct 6 is provided with a cold air suction damper 7 upstream of the electric dust collector 8.

  The exhaust gas sucked from the wind box 4 group by the main exhaust fan 10 is collected in the main exhaust duct 6 to become main exhaust gas. This main exhaust gas is gradually dusted by the electric dust collector 8 and further removed by a denitration device (not shown) if necessary. After being cleaned, it is discharged from the chimney 11 into the atmosphere.

  Therefore, during normal operation of the sintering machine, the inlet damper 9 of the main exhaust fan 10 and all the dampers 5 of each wind box 4 are operated in a state of being fully opened or close thereto.

  Here, a case where the sintering machine stops suddenly will be described as an example, and an exhaust gas control method when the sintering machine is stopped will be described with reference to a block diagram of damper control of the method of the present invention shown in FIG.

  (1) Stop of sintering machine (S1) Upon receiving the signal, the main controller 15 opens (a) the cold air suction damper 7 to a predetermined opening (for example, 20%), and (b) the wind box 4 The dampers 5 of all wind boxes 4 in the group whose gas temperature in the wind box 4 is 200 ° C. or higher are fully closed (S2).

  By introducing cold air (normal temperature air) into the main exhaust gas duct 6 by the operation (a) above, and blocking the flow of high temperature exhaust gas at 200 ° C. or higher into the main exhaust gas duct 6 by the operation (b) above. It is possible to prevent the main exhaust gas temperature from rising rapidly. Further, the amount of exhaust gas flowing into the main exhaust gas duct 6 is reduced by the operation of (b), but the decrease can be compensated for by the operation of (a), so that a decrease in the pressure in the main exhaust gas duct 6 is avoided. The main exhaust gas duct 6 can be prevented from being collapsed by the negative pressure.

  Here, the reason why the lower limit temperature of the gas temperature in the wind box 4 that fully closes the damper 5 by the operation (b) is set to “200 ° C.” is as follows.

  That is, the allowable temperature of the inlet gas temperature (main exhaust gas temperature) of the electrostatic precipitator 8 for protecting the electrostatic precipitator 8 is normally set to about 160 ° C., and the exhaust gas with the gas temperature in the wind box 4 of less than 200 ° C. If it exists, even if it flows into the main exhaust gas duct 6, the main exhaust gas temperature is hardly raised by the presence of the cold air (normal temperature air) sucked by the operation (a). For this reason, even if the lower limit temperature of the gas temperature in the wind box 4 that fully closes the damper 5 is further lowered below 200 ° C., the effect of preventing the rise of the main exhaust gas temperature is not improved so much, while the number of wind box dampers 5 that are fully closed This is because the amount of exhaust gas flowing into the main exhaust gas duct 6 is greatly reduced and the risk of crushing due to the negative pressure of the main exhaust gas duct 6 is increased even if cold air is sucked.

  Further, the opening degree (predetermined opening degree) of the cold air suction damper 7 in the operation of (a) is 20% in the above example. However, in order to prevent the main exhaust gas temperature and the main exhaust gas pressure from deviating from the allowable ranges, What is necessary is just to set with reference to the results when the sintering machine stopped.

  The gas temperature in each wind box 4 is a thermometer 12 installed in each wind box 4, and the main exhaust gas temperature is a thermometer installed in the main exhaust duct 6 on the inlet side (upstream side) of the electric dust collector 8. 13, the main exhaust gas pressure can be measured with a pressure gauge 14 installed on the outlet side of the electrostatic precipitator 6 and on the upstream side of the main exhaust fan inlet damper 9.

  (2) When the sintering machine 1 stops (S1), a stop signal is sent to the timer 16. In the timer 16, set values of time elapsed from the stop of the sintering machine 1 are set in the main exhaust fan inlet damper 9 and each wind box damper 5, respectively. (C) The opening degree of the main exhaust fan inlet damper 9 is set. (D) The damper 5 of the remaining wind box is moved from the ore discharge side to the supply side according to the opening degree of the main exhaust fan inlet damper 9. In this case, the cold air suction damper 7 is also used so that (e) the inlet gas temperature (main exhaust gas temperature) of the electrostatic precipitator 8 does not exceed the allowable temperature for protection of the electrostatic precipitator 8. Is adjusted (S3).

  While the main exhaust gas flow rate is sequentially decreased by the operation of (c) above, the operation of (d) is performed in parallel with this operation before the temperature of the exhaust gas sucked into each wind box 4 rapidly rises. It is intended to prevent the exhaust gas from flowing into the main exhaust gas duct 6 to prevent the main exhaust gas temperature from rising rapidly. However, since the progress of firing at the time of stopping the sintering machine varies variously, the above (c ) And (d) alone are not sufficient to adjust the main exhaust gas temperature. For this reason, if exhaust gas control is performed only by the operations of (c) and (d) above, there is an increased risk that the main exhaust gas temperature will exceed the allowable temperature when the operation stop is attempted in as short a time as possible. On the other hand, when it is attempted to complete the operation stop on the safe side so that the main exhaust gas temperature does not exceed the allowable temperature, it takes a long time to complete the operation stop.

  Therefore, in addition to the operations of (c) and (d) above, the operation of (e) is further performed to prevent the main exhaust gas temperature from exceeding the permissible temperature and complete the operation stop operation in a shorter time. Can be realized.

  In the operation of (c), the closing speed of the main exhaust fan inlet damper 9 and the timing of fully closing the remaining wind box damper 4 (that is, the time elapsed from the sintering machine 1 stop set in the timer 16). May be set within a range in which the main exhaust gas temperature does not increase rapidly and the main exhaust gas pressure does not decrease with reference to the past results of the sintering machine 1 being stopped.

  (3) Then, when the main exhaust fan inlet damper 9 reaches the limit opening where surging does not occur, the operation stop operation is completed, and the damper control is terminated (S4).

(Modification)
In the above embodiment, the set value of the timer 16 that issues a stop signal when the sintering machine stops is set not only in the main exhaust fan inlet damper 9 but also in each wind box damper 5. Although an example in which the wind box dampers 5 are fully closed based on the stop signal from the above is shown, the set value of the timer 16 is set only in the main exhaust fan inlet damper 9, and this main You may comprise so that the full closure operation of each wind box damper 5 may be performed sequentially by making the opening degree of the exhaust fan inlet damper 9 into a stop signal.

  In the above-described embodiment, an example of application when the sintering machine stops suddenly is shown. However, the present invention is naturally applicable to planned stoppage.

  Next, in order to confirm the effect of the method of the present invention, the method of the present invention was applied to an actual machine sintering machine (the number of wind boxes in the longitudinal direction of the sintering machine: 15) installed in the Kakogawa Works. The operation results at the time of sudden stop before and after application were compared.

  Prior to application of the method of the present invention, the operator manually operated each damper based on the conventional method (conventional method). On the other hand, after the application of the method of the present invention, the method described in the above embodiment (a method in which the set value of the timer 16 is set not only in the main exhaust fan inlet damper 9 but also in each wind box damper 5). Each damper was automatically controlled (invention method).

  FIG. 3 shows each time of the cold air suction damper opening, the main exhaust fan inlet damper opening, the number of open wind box dampers, the main exhaust gas flow rate, the main exhaust air inlet gas pressure, and the electric dust collector inlet gas temperature in the conventional method and the invention method. Comparison is shown.

  According to the figure, in the conventional method, by the manual operation, simultaneously with the sudden stop of the sintering machine, the cold air suction damper is opened to an opening of 20%, and the four exhaust box side wind box dampers are fully closed, Although the opening of the main exhaust gas inlet damper 9 is gradually reduced after a certain period of time, the remaining 11 windbox dampers 5 are sequentially fully closed from the discharge side to the supply side. In addition, there is a delay in the closing timing of the wind box damper 5 and the timing of raising the opening degree of the cold air suction damper is also slow, so that the main exhaust gas temperature exceeds the allowable temperature 160 ° C. for protecting the electric dust collector 8 to 171 ° C. Has also reached.

  On the other hand, in the invention method, the cold air suction damper is opened to an opening degree of 20% simultaneously with the sudden stop of the sintering machine by automatic control, and the gas temperature in the wind box is 200 ° C. or higher. After fully closing the four wind box dampers, the opening of the main exhaust gas inlet damper 9 is continuously reduced after a certain period of time, and the remaining 11 wind box dampers 5 are supplied from the discharge side to the supply side. Further, the opening degree of the cold air suction damper is controlled so that the main exhaust gas temperature is kept constant at 135 ° C. which is lower than the allowable temperature 160 ° C. for protection of the electric dust collector. The temperature does not exceed the allowable temperature.

  Note that, in both the conventional method and the invention method, the main exhaust gas pressure is in the positive direction as compared with that during steady operation, so there is no risk of the main exhaust duct being crushed by negative pressure.

DESCRIPTION OF SYMBOLS 1 ... Raw material supply apparatus 2 ... Pallet 3 ... Ignition furnace 4 ... Wind box 5 ... Wind box damper 6 ... Main exhaust gas duct 7 ... Cold-air suction damper 8 ... Electric dust collector 9 ... Main exhaust fan inlet damper 10 ... Main exhaust machine 11 ... Chimney 12 ... Wind box thermometer 13 ... Main exhaust gas thermometer 14 ... Main exhaust gas pressure gauge 15 ... Main controller 16 ... Timer

Claims (1)

When the sintering machine is stopped, an air dust box disposed so that the inlet gas temperature of the electrostatic precipitator does not exceed an allowable temperature for protection of the electrostatic precipitator and is fixed directly below the pallet of the sintering machine. An exhaust gas control method when the sintering machine is stopped, wherein the operations of (a) to (e) are automatically performed so that the main exhaust gas duct between the group and the main exhaust fan is not crushed by negative pressure.
Simultaneously with the stop of the sintering machine, the following operations (a) and (b) are performed in parallel, and then the operations (c) to (e) are performed in parallel.
(A) Cold air is sucked into the main exhaust gas duct by opening the cold air suction damper provided in the main exhaust gas duct between the wind box group and the inlet of the electric dust collector to a predetermined opening.
(B) The dampers of all the wind boxes whose gas temperature in the wind box is 200 ° C. or higher in the wind box group are fully closed.
(C) The inlet damper of the main exhaust fan is closed at a predetermined speed to a limit opening where surging does not occur, and the main exhaust gas flow rate is reduced.
(D) In accordance with the opening degree of the inlet damper of the main exhauster, the dampers of the remaining wind boxes are sequentially fully closed from the discharge side to the supply side.
(E) The opening degree of the cold air suction damper is adjusted so that the inlet gas temperature of the electrostatic precipitator does not exceed the allowable temperature.

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