JP2007315686A - Fly ash amount management method following coal type changing in fluidized bed boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out stable operation, and to reduce a burden of an operator even if a fly ash amount changes when changing the type of raw material coal inputted in a fluidized bed boiler. <P>SOLUTION: This fly ash amount management method includes a step (S2) of determining the change of a cyclone delivery interval, and a step of properly managing the discharge of fly ash according to the change of the delivery interval when the cyclone delivery interval is changed. The step of properly managing the discharge of fly ash includes a step (S6) of raising a rotational frequency of a screw feeder on condition that an ash temperature of a screw feeder inlet and a temperature of a cyclone hopper have dropped, a step (S7) of carrying out the soot blowing of a cyclone, and a step (S8) of purging an inlet seat arranged between an outlet of the cyclone and the inlet of the screw feeder. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fly ash ash amount management method associated with coal type switching in a fluidized bed boiler, and in particular, when a fly ash ash amount changes due to coal type switching, a fluidized bed can be obtained by performing a quick and accurate operation. The present invention relates to a technology capable of stably operating a boiler.

  A pressurized fluidized bed boiler, which is a type of fluidized bed boiler, is a CWP (Coal Water) in a fluidized bed using limestone as a fluidized medium (BM: bed material) while keeping the boiler pressurized with combustion air from a compressor. Paste: a boiler in which CWP is burned by introducing a fuel (a mixture of coal, limestone and water).

  Conventionally, in a thermal power plant equipped with such a pressurized fluidized bed boiler, in order to reduce the environmental load as much as possible and to increase the energy efficiency and perform stable operation, it is necessary to use multiple types of coking coal while switching. Yes. At this time, since the water content, calorific value, contained components, etc. are different for each coal type of the raw coal, the operation of the pressurized fluidized bed boiler is appropriate depending on the coal type of the raw coal supplied to the pressurized fluidized bed boiler. There was a need to manage.

  As such a coal type management method, when a different type of coal is used as a fuel by mixing it with “a method and apparatus for supplying coal to a bunker” (Japanese Patent Laid-Open No. 8-258960: Patent Document 1), a mixed coal is previously used. There has been disclosed a technique for saving labor by eliminating the step of mixing different types of coal in a hopper.

  The “coal supply method and apparatus to a bunker” described in Patent Document 1 supplies different types of coal to bunker units at a predetermined ratio from a conveyor provided in a plurality of systems when supplying coal to a bunker unit. The process of mixing the coal in the coal hopper is omitted by comprehensively mixing the fuel coal at a predetermined ratio when the bunker is introduced into the boiler.

JP-A-8-258960

  By the way, it is known that the amount of fly ash ash changes when the type of coal supplied to the pressurized fluidized bed boiler is switched. And when the amount of fly ash ash changed with coal type change, in order to perform stable operation, it was necessary to perform corresponding operation which makes discharge of fly ash appropriate.

  In the past, there was no clear standard for handling operations to make fly ash discharge appropriate, and there were aspects that relied on the experience and intuition of skilled operators. That is, monitoring items and corresponding operations for performing stable operation at the time of switching coal types may differ depending on the operator. As described above, even if different handling operations are performed for each operator, stable operation can be performed as a result, but in order to perform even more stable operation, it was desired to set a clear standard. . In addition, when the operation is performed based on the experience and intuition of the operator without being based on a clear standard, there is a problem that the monitoring burden on the operator and the corresponding operation burden increase.

  In addition, the "coal supply method and apparatus to a bunker" described in the above-mentioned Patent Document 1 is for the purpose of saving labor when using a mixture of a plurality of coal types, and for performing stable operation. There is no mention of clear criteria.

  The present invention has been proposed in view of the above-described circumstances, and when switching the type of raw coal supplied in a fluidized bed boiler, it is possible to achieve stable operation by appropriately managing the discharge of fly ash. An object of the present invention is to provide a fly ash ash amount management method associated with coal type switching in a fluidized bed boiler capable of reducing the burden on the operator.

The fly ash ash amount management method accompanying the coal type switching in the fluidized bed boiler according to the present invention has the following features in order to achieve the above-described object.
That is, the fly ash amount management method associated with the coal type switching in the fluidized bed boiler according to the present invention is for appropriately managing the discharge of fly ash when the type of the raw coal supplied in the fluidized bed boiler is switched. A method comprising: determining a change in a cyclone payout interval; and appropriately managing fly ash discharge according to the change in the payout interval when the cyclone payout interval is changed. It is characterized by.
The cyclone is a device for collecting fly ash discharged from the furnace.

Here, the step of appropriately managing the discharge of fly ash appropriately manages the discharge of fly ash by eliminating fly ash accumulation in the cyclone according to the ash temperature of the screw feeder inlet and the temperature of the cyclone hopper. It is preferable to do.
The screw feeder is a device for taking out the fly ash collected by the cyclone, and the cyclone hopper is a device for temporarily storing the fly ash collected by the cyclone.

  In addition, the step of appropriately managing the discharge of the fly ash includes the steps of increasing the rotational speed of the screw feeder on condition that the ash temperature of the screw feeder inlet and the temperature of the cyclone hopper have decreased, and the step of soot blowing the cyclone And purging a deposit account disposed between the outlet of the cyclone and the inlet of the screw feeder.

  Further, in the step of appropriately managing the discharge of fly ash, if the fly ash accumulation is not eliminated, it is preferable to appropriately manage the discharge of fly ash by performing an emergency discharge of fly ash.

  Moreover, when fly ash accumulation is not eliminated even if emergency discharge of the fly ash is performed, it is preferable to achieve proper operation of the fluidized bed boiler by reducing the load of the fluidized bed boiler.

  The fly ash ash amount management method accompanying the coal type switching in the fluidized bed boiler according to the present invention determines a change in the cyclone payout interval, and when the cyclone payout interval is changed, a predetermined value is set according to the change in the payout interval. By performing this operation, fly ash discharge is properly managed. Therefore, according to the coal type switching in the fluidized bed boiler, it is possible to perform a prompt and appropriate response operation to achieve stable operation, and to reduce the burden on the operator.

Hereinafter, with reference to the drawings, an embodiment of a fly ash ash amount management method associated with coal type switching in a fluidized bed boiler according to the present invention will be described.
The fly ash ash amount management method accompanying the coal type switching in the fluidized bed boiler according to the embodiment of the present invention is applied to, for example, a power plant adopting a pressurized fluidized bed combined power generation (PFBC) system. .

  In this power plant, CWP (Coal Water Paste: coal, limestone, and water) is placed in a fluidized bed using limestone as a fluid medium (BM: bed material) while the boiler is kept pressurized with combustion air from the compressor. CWP can be burned efficiently by introducing the mixed fuel). Moreover, since it can desulfurize in a furnace by employ | adopting limestone as a fluid medium, generation | occurrence | production of sulfur oxide (SOx) can be suppressed low. Furthermore, in fluidized bed combustion, the combustion temperature is kept low (about 870 ° C.), so that the generation of nitrogen oxides (NOx) can be kept low.

<Power plant with pressurized fluidized bed boiler>
FIG. 2 is a schematic diagram showing a schematic configuration of a power plant to which a fly ash ash amount management method associated with coal type switching in a fluidized bed boiler according to an embodiment of the present invention is applied.
As shown in FIG. 2, the power plant that applies the fly ash ash amount management method associated with the coal type switching in the fluidized bed boiler according to the present embodiment includes two boilers 10, 20. CWP is introduced into the furnaces 11 and 21 and burned, and steam generated by heat exchange is guided to the high-pressure turbine 31, the intermediate-pressure turbine 32, and the low-pressure turbine 33 to rotate the turbines, thereby driving the generator 41. To generate power. The steam after rotating the low-pressure turbine 33 is condensed by the condenser 50 and guided again into the boilers 10 and 20.

  The high pressure gas generated in the boilers 10 and 20 is guided to the gas turbine 34 to rotate the gas turbine 34, thereby driving the generator 42 to generate electric power. Further, the high pressure gas drives a compressor 35 connected coaxially to the gas turbine 34 to supply combustion air to the boilers 10 and 20.

  The fuel supply system that supplies fuel to the boilers 10 and 20 includes a coal hopper 61 that supplies coal, a coarse pulverizer 62 that roughly pulverizes the coal supplied from the coal hopper 61, and coal pulverized by the coarse pulverizer 62. A classifier 63 for classifying the powder, a relay hopper 64 for relaying the coal powder classified by the classifier 63, and a fine pulverizer 65 for further pulverizing the coal powder pulverized by the coarse pulverizer 62 while mixing water. A limestone hopper 66 for supplying limestone, a kneader 67 for kneading water, coal powder pulverized by the coarse pulverizer 62, coal paste pulverized while mixing water by the fine pulverizer 65, and limestone; A fuel tank 68 for temporarily storing the CWP kneaded by the machine 67 and a fuel pump 69 for sending the CWP from the fuel tank 68 into the furnaces 11 and 21 are provided.

  The two boilers 10 and 20 include pressure vessels 12 and 22 and furnaces 11 and 21 accommodated in the pressure vessels 12 and 22, respectively, and a water / steam pipe 71 is provided in the furnaces 11 and 21. It is inserted. The water / steam pipe 71 from the condenser 50 is first led into the B furnace 21 and then into the A furnace 11 for heat exchange, and is led to the brackish water separator 72 for steam and water. Are separated. The water / steam pipe 71 from the brackish water separator 72 is led in the order of the A furnace 11, the B furnace 21, and the A furnace 11, and then led to the high pressure turbine 31.

  The high-pressure turbine 31 is rotated by the steam supplied from the water / steam pipe 71. The steam after rotating the high-pressure turbine 31 is guided again to the B furnace 21 and reheated, guided to the intermediate-pressure turbine 32 to rotate the intermediate-pressure turbine 32, and further guided to the low-pressure turbine 33 to be low-pressure turbine. 33 is rotated. A generator 41 is coaxially connected to the high-pressure turbine 31, the intermediate-pressure turbine 32, and the low-pressure turbine 33, and the generator 41 is driven by the rotation of the turbines 31, 32, and 33 to generate power. .

  The steam that has rotated the low-pressure turbine 33 is led to the condenser 50 to be condensed. A cooling water pipe 51 is disposed in the condenser 50. The cooling water pipe 51 is guided by deep-sea water, and the sea water is subjected to heat exchange in the condenser 50 and then discharged again into the sea.

  On the downstream side of the condenser 50, a condensate pump 73, a first feed water heater 74a, a second feed water heater 74b, a third feed water heater 74c, a deaerator 75, a feed pump 76, and a fifth feed water heater. 74d and the 6th feed water heater 74e are arrange | positioned, and the condensate is heated and deaerated. A condensate water supply pipe 77 between the condenser 50 and the boilers 10 and 20 passes through two exhaust heat recovery heat exchangers 91 and 93 provided in an exhaust gas system, which will be described in detail later, and Heat exchange is performed between them.

  An exhaust gas pipe 81 is connected to the upper portions of the A furnace 11 and the B furnace 21 so that high-pressure gas generated in the furnaces 11 and 21 is supplied to the gas turbine 34. Further, between each furnace 11, 21 and the gas turbine 34, there are non-catalytic denitration devices 82a, 82b for performing denitration, primary cyclones 83a, 83b and secondary cyclones 84a, 84b for removing dust. It is arranged. The dust collected by the primary cyclones 83a and 83b and the secondary cyclones 84a and 84b is sent to the ash treatment apparatus via the ash coolers 85a, 85b, 86a, and 86b.

A generator 42 and a compressor 35 are coaxially connected to the gas turbine 34. When the gas turbine 34 rotates, the generator 42 is driven to generate power, and the compressor 35 is driven to generate combustion air. It feeds into the boilers 10 and 20.
A starter motor 43 for driving the compressor 35 and sending combustion air to the boilers 10 and 20 when the plant is started is attached to the compressor 35.
The exhaust gas after rotating the gas turbine 34 passes through a first exhaust heat recovery heat exchanger 91, a denitration device 92 for performing denitration, a second exhaust heat recovery heat exchanger 93, and a bag filter 94, and then a chimney. 95 is released into the atmosphere.

  BM tanks 13 and 23 for temporarily storing BM to be circulated are connected to A furnace 11 and B furnace 21 in communication. In the example shown in FIG. 2, one BM tank 13, 23 is provided for each boiler 10, 20, but two BM tanks 13, 23 may be provided for each boiler 10, 20. . Further, an emergency hot water tank 14 is disposed above each of the boilers 10 and 20. This emergency hot water tank 14 is a device for preventing water wall pipes and the like from being damaged by combustion of residual fuel in the boilers 10 and 20 when the boiler water supply system is stopped. Water is supplied to 10 and 20.

  The lower part of the A furnace 11 and the B furnace 21 is connected to a dust recovery pipe 101 for recovering the dust deposited in each of the furnaces 11 and 21, and the recovered dust is ashed through the ash coolers 102 and 103. It is sent to the processing device. The A furnace 11 and the B furnace 21 are supplied with light oil for heating the furnaces 11 and 21 when the boilers 10 and 20 are started.

<Fly ash amount control method>
Next, the fly ash ash amount management method accompanying the coal type switching in the fluidized bed boiler according to the embodiment of the present invention will be described. FIG. 1 is a flowchart showing a procedure of a fly ash amount management method associated with coal type switching in a fluidized bed boiler according to an embodiment of the present invention.

  As shown in FIG. 1, in order to appropriately manage the collection of fly ash according to the amount of fly ash ash that changes with the change of coal type, first, information on the cyclone dispensing interval is acquired (S1). . Then, it is determined whether or not the cyclone payout interval has changed (extended or shortened) (S2). If the cyclone payout interval has changed, that is, if the cyclone payout interval has been extended or shortened, the screw Information on the ash temperature at the feeder inlet and information on the temperature of the cyclone hopper are acquired (S3, S4).

  Then, it is determined whether or not the ash temperature at the screw feeder inlet and the temperature of the cyclone hopper have decreased (S5). Here, when the ash temperature at the screw feeder inlet and the temperature of the cyclone hopper are lowered, fly ash accumulation is eliminated by performing at least one of the following three operations. That is, in order to eliminate the accumulation of fly ash, the rotational speed of the screw feeder is increased (S6), the cyclone is soot blown (S7), and the account is arranged between the outlet of the cyclone and the inlet of the screw feeder. Is purged (S8).

  Subsequently, it is determined whether or not the fly ash accumulation has been eliminated (S9). If the fly ash accumulation has been eliminated, the rotation speed of the screw feeder is adjusted (S10), and the continuation monitoring is performed. .

  On the other hand, if the fly ash accumulation has not been eliminated, emergency payout is performed (S11) to eliminate the fly ash accumulation. Thereafter, it is judged again whether or not the fly ash accumulation has been eliminated (S12). If the fly ash accumulation has been eliminated, the rotation speed of the screw feeder is adjusted (S10), and the continuous monitoring is performed. Do.

On the other hand, if the fly ash accumulation is not eliminated even after the emergency payout, the load drop of the fluidized bed boiler is started (S13), and the fluidized bed boiler is properly operated.
In addition, when the payout interval of the cyclone does not change, since it is an appropriate operating state, continuous monitoring is performed without performing the above-described operation.

<Monitor item>
Next, specific monitoring items in the present embodiment will be described.
In the present embodiment, the rotational speed of the screw feeder is adjusted as shown in Table 1 below.

なお、本実施形態では、２次サイクロンにおけるスクリューフィーダの回転数のみについて調整を行っている。

In the present embodiment, adjustment is made only for the rotational speed of the screw feeder in the secondary cyclone.

Moreover, regarding the outlet temperature of a screw feeder, a management value shall be 320 degrees C or less. Further, regarding the relay hopper temperature, the management value is set to 425 ° C. or lower.
In addition, the data regarding the ash temperature in the inlet of a screw feeder, the temperature of a cyclone hopper, etc. can be acquired by the temperature measurement means installed in the applicable location. Moreover, the specific numerical value in the monitoring item mentioned above is an example, and of course, it can change and implement suitably according to the scale of the fluidized bed boiler, the operating condition, etc.

  The fly ash ash amount management method accompanying the coal type switching in the fluidized bed boiler according to the present invention, for example, when the fly ash ash amount is changed by switching the coal type in the pressurized fluidized bed boiler used for a power plant or the like, It can be used when the fluidized bed boiler is operated stably.

It is a flowchart which shows the procedure of the fly ash ash amount management method accompanying the coal type switching in the fluidized bed boiler which concerns on embodiment of this invention. It is a mimetic diagram showing a schematic structure of a power plant which applies a fly ash ash amount management method accompanying coal type change in a fluidized bed boiler concerning an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 Boiler 11,21 Furnace 12,22 Pressure vessel 13,23 BM tank 14 Emergency hot water tank 31 High pressure turbine 32 Medium pressure turbine 33 Low pressure turbine 34 Gas turbine 35 Compressor 41, 42 Generator 43 Start motor 50 Condensate Equipment 51 Cooling water piping 61 Coal hopper 62 Coarse pulverizer 63 Classifier 64 Relay hopper 65 Fine pulverizer 66 Limestone hopper 67 Kneading machine 68 Fuel tank 69 Fuel pump 71 Water / steam pipe 72 Brackish water separator 73 Condensate pumps 74a-74e Feed water heater 75 Deaerator 76 Feed water pump 77 Condensate feed water pipe 81 Exhaust gas pipe 82a, 82b Non-catalytic denitration device 83a, 83b Primary cyclone 84a, 84b Secondary cyclone 85a, 85b, 86a, 86b Ash cooler 91, 93 Exhaust Heat recovery heat exchanger 92 Denitration equipment Device 94 Bag filter 95 Chimney 101 Dust collection pipe 102,103 Ash cooler

Claims (5)

A method for appropriately managing the discharge of fly ash when the type of coking coal to be input in a fluidized bed boiler is switched,
Determining a change in the payout interval of the cyclone;
Fly ash ash associated with coal type switching in a fluidized bed boiler, comprising: appropriately managing the discharge of fly ash according to the change in the payout interval when the payout interval of the cyclone is changed Quantity management method. Properly managing the discharge of fly ash,
The fluidized bed boiler according to claim 1, wherein the discharge of fly ash is appropriately managed by eliminating fly ash accumulation in the cyclone according to the ash temperature at the inlet of the screw feeder and the temperature of the cyclone hopper. Of fly ash ash management method for coal type switching in Japan. The step of appropriately managing the discharge of fly ash is based on the condition that the ash temperature at the screw feeder inlet and the temperature of the cyclone hopper have decreased.
Increasing the rotational speed of the screw feeder;
A step of sootblowing the cyclone;
And a step of purging a deposit account disposed between an outlet of the cyclone and an inlet of the screw feeder, and fly ash accompanying coal type switching in a fluidized bed boiler according to claim 1 or 2. Ash amount management method.   The fly ash discharge is appropriately managed by performing an emergency discharge of fly ash when fly ash accumulation is not eliminated in the step of appropriately managing the discharge of fly ash. The fly ash ash amount management method accompanying coal type switching in the fluidized bed boiler according to any one of? 5. The proper operation of the fluidized bed boiler is achieved by reducing the load of the fluidized bed boiler when fly ash accumulation is not eliminated even after the emergency discharge of the fly ash is performed. The fly ash ash amount management method accompanying the coal type change in the fluidized bed boiler.

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