JP4031771B2 - Fly ash delivery method and system - Google Patents

Description

    The present invention is a combustion furnace mainly using heavy oil or coal as a fuel, and carries out the stored materials from a plurality of hoppers storing fly ash (fly ash) one by one to the next process using a gas conveyor. The present invention relates to a carry-out method and a carry-out system for fly ash. The present invention is effective as a countermeasure against ratholes that occur during carry-out of fly ash.

    An outline of a fly ash carry-out system in a coal combustion furnace such as a thermal power plant will be described with reference to FIGS. 1 and 2. Although the coal used as the fuel for the combustion furnace varies depending on the coal type and brand, it generally contains 5 to 30% incombustible content, and a part of the incombustible content, about 10 to 20%, becomes clinker ash and the combustion furnace. 11 is dropped from the bottom of 11 and collected by clinker hopper 12. The remaining incombustible matter becomes fly ash and is accompanied by the combustion waste gas 13 and discharged outside the furnace. The fly ash discharged to the outside of the furnace passes through a economizer (ECO) 14 and an air preheater (AH) 15 and partly settles in ash hoppers 1a and 1b provided at the lower portions of the fly ash. Separated. The combustion waste gas is further sent to an electric dust collector (EP) 16 utilizing a corona discharge or a bag filter, and the remaining fly ash is separated. The separated fly ash is stored in an ash hopper 1c (usually a plurality of units) attached to the lower part of the dust collector. The fly ash stored in each of the hoppers 1 is sequentially carried out to the next process such as the ash silo 7 and processed.

  Since these fly ash is continuously generated during the operation of the combustion furnace, it is necessary to carry out the ash removal continuously and stably, and the processing system must be highly reliable. Various means have been put to practical use as means for carrying out fly ash stored in the hopper, but in Japan, an air flow conveying system that generally uses a gas conveyor is adopted. There are a pressure feeding type, a suction type, and a combined type in the air flow conveyance. FIG. 2 illustrates a suction type and FIG. 2 illustrates a pressure feeding type fly ash carry-out system by a flow sheet.

  An air operated flap valve called an ash intake valve 2 is usually attached to an ash outlet provided at the bottom of each hopper 1. The fly ash stored in each hopper by the opening / closing operation is sequentially carried out through the gas conveyor 3, separated from the carrier gas in the gas-solid separator 6 such as a cyclone, and conveyed to, for example, the silo 7. In this example, the root blowers 4 and 5 are used for the suction drive device or the pressure drive device of the gas conveyor.

  The open / close control of the ash intake valve is a mechanism that adjusts the carry-out speed of the fly ash to be almost constant by measuring the suction pressure or the pressure feed pressure of the gas conveyor. In the case of a suction-type gas conveyor, the ash discharge amount from the hopper increases and the ash intake valve is closed when the inside of the conveyor becomes a high vacuum, and it opens when the discharge amount decreases and becomes a low vacuum. Usually, the ash intake valve is opened and closed several to several tens of times from the start of fly ash carry-out of one hopper to completion. When the fly ash carrying out in the hopper is completed, the inside of the conveyor is in a low vacuum, and when the low vacuum state continues for a certain time, it is shifted to carrying out from the next hopper. In the case of the pressurization type, the ash intake valve is closed when the pressure inside the conveyor is high, and is opened when the pressure is low. Moreover, since the inside of a conveyor will become a low pressure when fly ash carrying out is completed, it will be made to transfer to the next hopper carrying out when the low pressure state continues for a fixed time.

    It is a problem of the rathole that must be noted when taking out the fly ash from the hopper 1. The rat hole 21 (refer to FIG. 3) is also referred to as “channeling” or “blow-off”, and means that a gas blow-out passage is formed in the fly ash layer while the fly ash 23 is being taken out from the bottom of the hopper 22 and cannot be taken out. Fly ash is easy to form a rat hole, and can easily lead to troublesome troubles. When a rat hole is generated, in the suction type, gas blows through and the discharge of fly ash stops, and the degree of vacuum decreases. In the pressure-feed type, gas flows out of the conveyor and the pressure decreases. Conventionally, since the generation of the rat hole and the completion of the unloading could not be identified, it was determined that the unloading operation was completed because the hopper was empty due to the generation of the rat hole, and the unloading operation was completed in a shorter time than usual. Even though fly ash remains, the process proceeds to the next hopper carry-out process. Then, high-temperature fly ash was newly added on the remaining fly ash.

  When the residual fly ash accumulates one after another in this way and is left in a high temperature state for a long time, they stick to each other and become largely solidified. Then, the effective volume of the hopper is reduced, or a large hard lump is peeled off, which hinders carrying out and leads to a stop. If it is minor, it can be recovered by hitting the hopper with a hammer on the outer wall, but if the amount increases, the manhole must be opened and the artificially fixed part must be crushed, peeled off, discharged and recovered.

  Conventionally, measures such as attaching a powder level measuring device to a key point in the hopper and detecting the weight of the hopper have been taken or studied, but the fly ash is hot and the equipment remodeling cost becomes excessive. Because of this, solving the problem was not easy. The present invention has been completed as a result of research and trial-and-error studies on a method and system that can prevent the above-described troubles caused by ratholes in advance and stably carry out fly ash.

    In order to solve the above-mentioned problems, the present invention is a method of carrying out fly ash from a plurality of fly ash hoppers one by one by a gas conveyor to the next process in order, and carrying out once for each hopper. The average carry-out time is calculated by averaging all hoppers, and the value obtained by multiplying the calculated average carry-out time by an adjustment factor K of 1 or less is used as the threshold time, while fly ash is being carried out. The pressure fluctuation in the gas conveyor is monitored, and if it is detected that the pressure in the gas conveyor has deviated from the normal range before the threshold time has elapsed since the start of carry-out of fly ash, an abnormal event is transmitted. When it is detected that the pressure in the gas conveyor has deviated from the normal range after the threshold time has been reached, the unloading operation of the hopper is completed and the operation of the next fly ash in the hopper is performed. Shifting to start out, it discloses a fly ash method out of said.

  In addition, the present invention is a method of carrying out fly ash from a plurality of fly ash hoppers one by one by a gas conveyor to the next process in sequence, and the effective time required for one carry-out for each hopper. The value obtained by setting an adjustment coefficient K of 1 or less for each hopper and multiplying the effective time is the threshold time of the hopper, while monitoring the pressure fluctuation in the gas conveyor during the fly ash carry-out When it is detected that the pressure in the gas conveyor has deviated from the normal range before the threshold time has elapsed since the start of ash unloading, an abnormality is generated, and after the threshold time has been reached, When it is detected that the pressure is out of the normal range, the unloading operation of the hopper is completed and the operation is shifted to the start of unloading of fly ash in the next hopper. It discloses a method of unloading fly ash.

  The gas conveyor may be either a suction type or a pressure feed type. In the present invention, the rat hole breaker is operated by the abnormal transmission described above, and the rat hole is extinguished every time and the carry-out is continued, and the carry-out can be continued until the hopper is empty.

  Further, the present invention provides a plurality of fly ash hoppers 1a, 1b, 1c, an ash intake valve 2 for taking out the contents attached to the opening at the bottom of each hopper, and a fly ash carry-out connected to the valve. Connected to the gas conveyor 3, the gas conveyor suction drive device 4 or the pressure feed drive device 5, the gas-solid separator 6 that is connected to the gas conveyor and separates fly ash from the air flow, and the gas-solid separator. The fly ash tank 7, the pressure measurement transmitter 8 in the conveyor attached to the gas conveyor, and the effective time T required to carry the fly ash out of the hopper is multiplied by an adjustment factor K of 1 or less. On the other hand, the pressure fluctuation in the gas conveyor is monitored, and the gas code is measured before the threshold time is reached from the start of fly ash carry-out. When it is detected that the pressure in the bear has deviated from the normal range, the occurrence of an abnormality is transmitted, and when it is detected that the pressure in the gas conveyor has deviated from the normal range after reaching the threshold time A fly ash unloading system comprising: a sequence control device that completes the unloading operation of the hopper and shifts the operation to the start of unloading of fly ash in the next hopper.

  In the present invention, the measurement or detection of the pressure or pressure fluctuation in the gas conveyor is not limited to means for directly measuring the pressure in the gas conveyor, and includes the following cases. That is, the suction drive device gas suction pressure after separating fly ash in the case of suction type, and the pressure feed before mixing fly ash in the case of pressure feed type, for reasons such as avoiding troubles caused by the measurement of solid-gas mixed fluid The object of the present invention can also be achieved by measuring and detecting the drive device gas discharge pressure. An example is shown in FIGS.

    By using the present invention, the occurrence of an abnormality such as a rat hole is quickly detected, and the rat hole breaker is operated each time the phenomenon is slight. In each case, the rat hole is extinguished and the carrying out is continued, and the hopper is empty. Unloading can be continued until Then, it is possible to prevent the remaining fly ash from developing into a trouble that is stuck in a high temperature state for a long time and hinders carrying out.

    The fly ash carry-out method and system according to the present invention will be specifically described with reference to FIGS. 1 and 2 illustrate a typical large coal combustion furnace as an example, FIG. 1 illustrates a suction-type fly ash carry-out system in FIG.

  As described above, the present invention smoothly carries out fly ash stored in a plurality of hoppers by performing sequence control using a gas conveyor. The above sequence control sets the threshold time based on the effective time required for normal fly ash unloading, and the pressure fluctuation of the gas conveyor that occurs within the threshold time and the pressure fluctuation that occurs after the threshold time elapses The pressure fluctuation that occurs within the time is determined as an abnormal situation due to the rat hole, etc., and is dealt with to resolve it, and the pressure fluctuation that occurs after the time has passed is determined to be due to completion of fly ash carry-out. The next operation is performed.

  In general, fly ash accompanying combustion waste gas such as a coal combustion furnace is separated from the combustion waste gas and provided below the economizer 14, the air preheater 15, and the electric dust collector 16 (or bag filter, etc.). It is stored in the hoppers 1a, 1b, 1c. Of these, a plurality of hoppers 1 c are often provided below the electric dust collector 16. Moreover, in this example, the fly ash stored in each hopper 1a, 1b, 1c is carried out to the fly ash tank 7 by the one-system gas conveyor 3 without distinction, but the fly ash stored in each hopper. Since the ash particle size is coarser toward the upstream side, depending on the purpose of use, the fly ash in each hopper 1a, 1b may be separately carried out, and the present invention may be implemented for a plurality of hoppers provided at the lower part of the electric dust collector. .

  The fly ash stored in the hoppers 1a, 1b, and 1c is sequentially carried out to the next process, for example, the fly ash tank 7, for each hopper. In order to implement the present invention, first, for each hopper 1a, 1b, 1c, the effective carry-out time T required to empty the storage fly ash for one time during normal operation is measured. Ideally, fly ash is continuously discharged from the hopper 1, but as described above, the ash intake valve 2 is opened and closed several to several tens of times from the start to the end of discharge in order to operate the gas conveyor 3 smoothly. The amount of emissions is controlled. The effective carry-out time T is the total time during which fly ash flows while the ash intake valve 2 is opened. This is because the time during which the valve is closed fluctuates every time, so that errors caused by adopting the apparent carry-out time are eliminated.

Next, an average effective carry-out time (ΣTn / N, where N = number of target hoppers) of the entire target hopper (assuming n groups) is calculated. A value obtained by multiplying the obtained average carry-out time by a coefficient K of 1 or less (0.8 (0.0 to 1.0 variable)) is defined as a threshold time (K · ΣTn / N). In the case of an abnormality such as a rathole, a large amount of air flows into the gas conveyor, and the degree of vacuum in the gas conveyor is greatly reduced in the same way as at the end of carry-out. In the case of the pressure-feed type, the fly ash is not supplied to the gas conveyor, so that the gas blows through the conveyor and the pressure is greatly reduced in the same manner as at the end of carrying out. This is because there is a margin against the fact that the total discharge time is not always constant due to variations in the received fly ash, habit of the hopper, and the like.
Therefore, in the present invention, the pressure state in the gas conveyor 3 is monitored, and when a large pressure fluctuation is detected before the threshold time is reached before the threshold time is reached, that is, a decrease in the degree of vacuum in the suction type and a decrease in the conveyance pressure in the pressure type. Considering that a rathole has occurred, start the corresponding operation. Although the corresponding operation is not the same depending on the device, for example, an attempt is made to extinguish the rat hole by operating a rat hole breaker such as a vibrator or knocker attached to the hopper. When the rat hole disappears, the fly ash is taken out and the pressure in the gas conveyor returns to the normal value. If the pressure does not return to the normal value by repeating the corresponding operation 3 to 4 times, it is highly possible that the rathole will not disappear or the hopper is empty. It will be. If a low vacuum condition occurs for a time exceeding the threshold, confirm that the condition has continued for a certain period of time, and assume that the entire discharge of the hopper has been completed. Migrate to

    INDUSTRIAL APPLICABILITY The present invention is effective as a countermeasure against troubles such as a rat hole that occurs when a stored material is carried out from a hopper that stores fly ash to the next process. Specifically, it is possible to quickly detect the occurrence of an abnormality such as a rat hole, operate the rat hole breaker each time the phenomenon is minor, and continue to carry out until the rat hole disappears and the hopper is empty . As a result, it is possible to prevent the remaining fly ash from developing into a large trouble that is stuck in a high temperature state for a long time, and it is possible to carry out the fly ash stably. In a boiler of a power plant that uses heavy oil or coal as fuel, the fly ash can be effectively used in a process for carrying out the processing.

Flow sheet showing an example of a suction fly ash carry-out system Flow sheet showing an example of a pressure-feed type fly ash carry-out system Illustration of the rat hole

Explanation of symbols

1: Fly ash hopper (multiple hoppers)
(1a: for ECO, 1b: for AH, 1c: for EP)
2: Ash intake valve 3: Gas conveyor for carrying out fly ash 4: Suction drive device (this example: Roots blower)
5: Pressure feeding device (this example: Roots blower)
6: Gas-solid separator (bag filter, etc.)
7: Fly ash tank 8: Transmitter for pressure measurement in gas conveyor 11: Combustion furnace 12: Clinker hopper 13: Combustion waste gas 14: Eco-saving device (ECO)
15: Air preheater (AH) 16: Electric dust collector (EP) or bag filter 21: Rathole 22: Hopper 23: Fly ash

Claims (6)

    It is a method of carrying out fly ash from multiple fly ash hoppers one by one by gas conveyor to the next process in sequence, and obtaining the effective time required for one carry-out for each hopper, and averaging all hoppers The average unloading time is calculated, and the value obtained by multiplying the calculated average unloading time by an adjustment factor K of 1 or less is used as the threshold time. On the other hand, the pressure fluctuation in the gas conveyor during the fly ash unloading is monitored, and the fly When it is detected that the pressure in the gas conveyor has deviated from the normal range before the threshold time has elapsed since the start of ash unloading, an abnormality is generated, and after the threshold time has been reached, When it is detected that the pressure is out of the normal range, the unloading operation of the hopper is completed and the operation is shifted to the start of unloading of fly ash in the next hopper. Fly ash method of carrying out that.     This is a method of carrying out fly ash from a plurality of fly ash hoppers one by one by a gas conveyor to the next process in sequence. The effective time required for one hopper is calculated for each hopper. A value obtained by setting the following adjustment coefficient K and multiplying the effective time is set as the threshold time of the hopper, while monitoring the pressure fluctuation in the gas conveyor during fly ash carry-out, and from the start of fly ash carry-out If it is detected that the pressure in the gas conveyor has deviated from the normal range before the threshold time has been reached, an error will be generated and the pressure in the gas conveyor will deviate from the normal range after the threshold time has been reached. A fly ash characterized in that when the operation is detected, the carry-out operation of the hopper is completed and the operation is shifted to the start of carry-out of the fly ash in the next hopper. Carry-out method.     The method for carrying out fly ash according to claim 1 or 2, wherein the gas conveyor is a suction type.     The method for carrying out fly ash according to claim 1 or 2, wherein the gas conveyor is of a pressure feed type.     5. The fly ash carry-out method according to any one of claims 1 to 4, wherein the occurrence of abnormality is caused by rat hole generation in the fly ash hopper, and the rat hole breaker is operated according to a predetermined procedure. A plurality of fly ash hoppers (1a, 1b, 1c), an ash intake valve (2) for taking out the contents attached to the opening at the bottom of each hopper, and a gas for carrying out fly ash connected to the valves A conveyor (3), a suction drive device (4) or a pressure drive device (5) of a gas conveyor, a gas-solid separator (6) connected to the gas conveyor to separate fly ash from a conveyed air current, The fly ash tank (7) connected to the gas-solid separator, the pressure measurement transmitter (8) in the conveyor attached to the gas conveyor, and the effective time T required to carry out fly ash from the hopper is 1 or less. KT multiplied by the adjustment factor K is input as a threshold time, while the pressure fluctuation in the gas conveyor is monitored, and the above threshold time from the start of fly ash carry-out When it is detected that the pressure in the gas conveyor has deviated from the normal range before reaching, the occurrence of an abnormality is transmitted, and it is detected that the pressure in the gas conveyor has deviated from the normal range after reaching the threshold time. A fly ash unloading system comprising: a sequence control device that completes the unloading operation of the hopper and shifts the operation to the start of unloading of fly ash in the next hopper.

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