JP2007100621A - Stop control method for pressurized fluidized bed plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stop control method for a pressurized fluidized bed plant capable of shortening work time for stopping the pressurized fluidized bed plant and reducing power cost. <P>SOLUTION: A emergency hot water tank heater is stopped when load of a generator drops to a predetermined value. Bed material circulation cooling is performed during gas turbine operation in a boiler extinguish cooling process. Temperature of gas turbine bearing cooling water is established lower than gas turbine parallel off process after a gas turbine parallel off process. A supply pump is stopped when supply water temperature of a water supply system drops to predetermined temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stop control method for stopping a power plant equipped with a pressurized fluidized bed boiler, and more particularly, to a pressurized fluidized bed plant capable of stopping a boiler early without imposing a burden on boiler equipment. The present invention relates to a stop control method.

  Conventionally, in a power plant equipped with a pressurized fluidized bed boiler, it is necessary to cool various facilities because fuel remains in the boiler even when the plant is stopped. In addition, when cooling is performed rapidly, a burden is placed on the cooling pipe and the cooling pipe or the like may be damaged.

  Therefore, in order to stop the boiler for equipment inspection or the like, it is necessary to gradually cool so as not to put a burden on the boiler equipment, and it takes a long time to stop the boiler. Furthermore, in the cooling process, power is required to circulate the cooling water. If a long time is required for the boiler stop process, the power cost increases accordingly.

Therefore, various stop control methods for stopping a power plant equipped with a pressurized fluidized bed boiler have been proposed.
For example, in Japanese Patent Application Laid-Open No. 2000-213306, “Pressurized Fluidized Bed Combined Power Plant” (Patent Document 1), when the pressurized fluidized bed combined power plant is stopped, a low temperature exhaust heat recovery heat exchanger, a high temperature exhaust heat recovery heat exchange There has been proposed a technique for preventing steam condensate at the outlet of the vessel and steaming of the feed water to improve the reliability of the plant and reduce the power in the station at the time of stoppage.

  The “pressurized fluidized bed combined power plant” described in Patent Document 1 includes an air compressor, a pressurized fluidized bed boiler, a gas turbine driven by the high temperature gas of the pressurized fluidized bed boiler, and a pressurized fluidized bed. Multiple steam turbines driven by floor boiler steam, condensate pumps and feed pumps that supply feedwater from the condenser to the pressurized fluidized bed boiler, feedwater heaters that heat the feedwater, and high / low temperature waste heat recovery In a pressurized fluidized bed combined power plant consisting of a heat exchanger and a deaerator, air and hot gas from the outlet of the air compressor to the gas turbine inlet valve are supplied to the gas turbine outlet piping during normal or emergency shutdown of the plant. A high-temperature gas discharge pipe for discharging and a high-temperature gas discharge valve are provided.

  Further, Japanese Patent Application Laid-Open No. 11-159305 “Pressurized Fluidized Bed Combined Cycle Power Plant” (Patent Document 2) sufficiently prevents flash generated around the exhaust gas heat exchanger when the plant is started and stopped and during an emergency stop. In addition, a technology has been proposed that can ensure the protection of the device and improve the reliability.

  The “pressurized fluidized bed combined power plant” described in Patent Document 2 includes a pressurized fluidized bed boiler for generating steam, a steam turbine driven by the steam generated in the pressurized fluidized bed boiler, A gas turbine driven by exhaust gas from a fluidized bed boiler and a water supply system for supplying water from a steam turbine condenser to a pressurized fluidized bed boiler are provided, and the exhaust gas heat exchanger and water heater for heating the water supply are provided in the water supply system. In a pressurized fluidized bed combined power plant provided with a deaerator, a replacement water supply system for supplying the exhaust water of the exhaust gas heat exchanger generated in the deaerator to the exhaust water heat exchanger in the feed water system The replacement water supply system is provided with a pump and an adjustment valve for adjusting the flow rate.

JP 2000-213306 A JP 11-159305 A

However, as described above, if rapid cooling is performed when the boiler is stopped, the boiler equipment is burdened, and in the worst case, the boiler equipment may be damaged. For this reason, in the conventional stop control method for a pressurized fluidized bed plant including the techniques described in Patent Document 1 and Patent Document 2, it is assumed that it takes a long time to stop the boiler.
In this regard, when stopping the boiler for equipment inspection, etc., if the time required for the boiler stop process can be shortened, the restart of the boiler can be accelerated, and the power cost related to the boiler stop process Can be reduced.

  The present invention has been proposed in view of the above-described circumstances, and is capable of reducing the working time when stopping the pressurized fluidized bed plant and reducing the power cost. The purpose is to provide.

The stop control method for a pressurized fluidized bed plant according to the present invention includes the following features in order to achieve the above-described object.
That is, the pressurized fluidized-bed plant stop control method of the present invention is a method for stopping a power plant equipped with a pressurized fluidized-bed boiler, and the bed material circulation during the gas turbine operation in the boiler fire extinguishing and cooling process Cooling is performed.

Moreover, in the stop control method for the pressurized fluidized bed plant, it is preferable to stop the emergency hot water tank heater when the load on the generator is reduced to a predetermined value.
Moreover, in the stop control method of the pressurized fluidized bed plant, it is preferable that the temperature of the turbine bearing cooling water is set lower than that in the gas turbine disconnection process after the gas turbine disconnection process.

  Moreover, in the stop control method for the pressurized fluidized bed plant, it is preferable to stop the feed water pump when the feed water temperature of the feed water system drops to a predetermined temperature. At this time, it is preferable to stop the feed water pump when the boiler temperature and the feed water temperature coincide.

  According to the stop control method for a pressurized fluidized bed plant of the present invention, the working time for stopping the pressurized fluidized bed plant can be shortened without imposing a burden on the boiler equipment. Moreover, since the boiler stop process is shortened, the power cost for circulating the coolant can be reduced.

Hereinafter, an embodiment of a stop control method for a pressurized fluidized bed plant according to the present invention will be described with reference to the drawings.
1 to 3 are time tables showing the procedure of a stop control method for a pressurized fluidized bed plant according to an embodiment of the present invention, and FIG. 4 is a stop control method for a pressurized fluidized bed plant according to an embodiment of the present invention. FIG. 5 is an explanatory view showing a schematic configuration of a power plant to which the stop control method for a pressurized fluidized bed plant according to an embodiment of the present invention is applied.

<Power plant>
A power generation plant to which a pressurized fluidized bed plant stop control method according to an embodiment of the present invention is applied is a power plant that employs a pressurized fluidized bed combined power generation system (PFBC), and a pressure vessel A steam turbine is driven by steam generated from a fluidized bed boiler housed therein, and a gas turbine is driven by exhaust gas from the boiler.

  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 can be kept low (about 860 ° C.), so that the generation of nitrogen oxides (NOx) can be kept low.

Hereinafter, the power plant to which this embodiment is applied will be described in detail.
As shown in FIG. 5, the power plant to which the present embodiment is applied includes two boilers 10, 20. CWP is introduced into the furnaces 11, 21 of the boilers 10, 20 and burned, and heat exchange is performed. The generated steam is guided to the high-pressure turbine 31, the intermediate-pressure turbine 32, and the low-pressure turbine 33 to rotate each turbine, thereby driving the generator 41 to generate electric 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 water and steam pipes 71 are provided in the furnaces 11 and 21, respectively. It is inserted. The water / steam pipe 71 is first guided into the B furnace 21 to perform heat exchange, and then routed in the order of the A furnace 11, the brackish water separator 72, the A furnace 11, the B furnace 21, and the A furnace 11. Then, it is guided 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 pipe 77 between the condenser 50 and the boilers 10 and 20 passes through two exhaust heat recovery exchangers 91 and 93 provided in an exhaust gas system, which will be described in detail later. Heat exchange is performed.

  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 of the furnaces 11 and 21 and the gas turbine 34, non-catalytic denitration devices 82a and 82b for performing denitration, and a primary cyclone 83 and a secondary cyclone 84 for removing dust are disposed. Yes. Note that the dust collected by the primary cyclone 83 and the secondary cyclone 84 is sent to the ash treatment apparatus via the ash hoppers 85 and 86.

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.
An activation motor 43 is attached to activate the gas turbine 34 and the compressor 35.

  The exhaust gas after rotating the gas turbine 34 passes through a first exhaust heat recovery exchanger 91, a denitration device 92 for performing denitration, a second exhaust heat recovery exchanger 93, and a bag filter 94, and from a chimney 95. Dissipated into the atmosphere.

  BM tanks 13 and 23 for collecting BM are connected to the A furnace 11 and the B furnace 21 in communication. In the example shown in FIG. 5, one BM tank 13, 23 is provided for each boiler 10, 20. However, 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.

  A dust collection pipe 101 for collecting the dust deposited in each of the furnaces 11 and 21 is connected to the lower part of the A furnace 11 and the B furnace 21, and the collected dust is ashed through the ash hoppers 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.

<Procedure for stopping control of pressurized fluidized bed plant>
With reference to FIGS. 1-4, the procedure of the stop control method of the pressurized fluidized-bed plant which concerns on embodiment of this invention is demonstrated.
In the pressurized fluidized bed plant, the internal inspection of the boilers 10 and 20, the internal inspection of the gas turbine 34, the internal inspection of the primary cyclone 83 and the secondary cyclone 84 are periodically performed. In order to carry out these inspections, the manhole leading to the flue must be opened and workers must enter the facility, so the boilers 10, 20, the gas turbine 34, the primary cyclone 83, the secondary cyclone 84, etc. It needs to be cooled.

  In order to stop the pressurized fluidized bed plant, as shown in FIG. 1 to FIG. 3, the first load reduction process, the second load reduction process, the boiler fire extinguishing and cooling process, the gas turbine (GT) disconnection process, the forced The cooling / storage chemical injection operation process and the auxiliary machine stopping process are performed in this order.

  In the stop control method of the pressurized fluidized bed plant according to the embodiment of the present invention, when the load of the generators 41 and 42 is reduced to a predetermined value, the heater of the emergency hot water tank 14 is stopped and the gas turbine in the boiler fire extinguishing and cooling process. The bed material circulation cooling (BM circulation cooling) is performed during the operation of the gas turbine 34, and the temperature of the turbine bearing cooling water is set lower than that of the gas turbine 34 disconnection process after the gas turbine 34 disconnection process. When the temperature drops to a predetermined temperature, the stop time of the plant is shortened by stopping the feed water pump 76.

Hereinafter, these stop control procedures will be specifically described.
<Start time of BM circulation cooling>
While the plant is stopped, BM exists in the BM tanks 13 and 23, and the temperature may rise to, for example, about 700 to 800 ° C. due to retained heat. Further, there is no shut-off valve in the BM supply line and the extraction line.

  Therefore, the heat retained in the BM tanks 13 and 23 flows out to the flue and takes time for cooling. Furthermore, when the BM temperature is 400 ° C. or higher, harmful gases such as CO may be generated, and it is necessary to cool early in order to make the working environment in the furnace appropriate.

In this regard, in the conventional plant stop control procedure, BM circulation cooling was performed at the time of N ₂ circulation cooling after the gas turbine 34 was stopped. However, since the air source at this timing is a nitrogen gas circulation fan, the amount of air is small. It was a factor that took time to cool down.

  Therefore, in this embodiment, the BM cooling time is shortened by the abundant air volume from the compressor 35 by performing BM circulation cooling during operation of the gas turbine 34 in the boiler fire extinguishing cooling process. Specifically, when the furnace bed height reaches the minimum required level of about 0.6 m, the BM is moved in the boilers 10 and 20 by the air blown from the compressor 35 while continuing the operation of the gas turbine 34. By circulating the BM between the BM tanks 13 and 23 and the boilers 10 and 20, the BM is circulated and cooled. In the BM circulation cooling process, it is necessary to perform control so that the furnace layer height does not become about 0.6 m or less in order to prevent GT surging.

The furnace bed height at which the BM circulation cooling is started is not limited to the above-mentioned standard, and can be appropriately changed according to the scale of the plant including the boilers 10 and 20 and the like.
By performing BM circulation cooling in such a procedure, the temperature of the BM tanks 13 and 23 could be lowered to 300 ° C. or less at an early stage.

<Emergency hot water tank heater power off>
An emergency hot water tank 14 is installed on the roof of the boiler building. The emergency hot water tank 14 is a tank for storing cooling water supplied to the boilers 10 and 20 by water head pressure from the boiler roof. That is, when the boiler water supply system is stopped, the fuel supplied to the boilers 10 and 20 is shut off, but the residual fuel burns in the boilers 10 and 20 to prevent burning of water wall pipes, etc. Cooling water is supplied from the emergency hot water tank 14.

  During normal operation, water is supplied to the boilers 10 and 20 by the water supply pump 76. However, if the water supply system is stopped for some reason, water is not supplied into the boilers 10 and 20 and an overheating state occurs. Therefore, the cooling water is supplied from the emergency hot water tank 14 to prevent the boilers 10 and 20 from being heated. In this emergency hot water tank 14, the cooling water stored inside is heated to about 300 ° C. using a heater (not shown) in order to prevent tube damage due to overcooling.

When the plant is stopped, the cooling water stored in the emergency hot water tank 14 is supplied into the boilers 10 and 20, but the cooling water heated to about 300 ° C. is supplied into the boilers 10 and 20, This hinders boiler cooling.
Therefore, in this embodiment, when the generator load becomes about 50% of normal operation (for example, 125 MW output), the heater power supply of the emergency hot water tank 14 is turned off to supercool the boiler equipment. The cooling water temperature is lowered to promote boiler cooling within the range where there is no influence.

In addition, the timing which turns off the heater power supply of the emergency hot water tank 14 is not limited to the above-mentioned standard, and can be appropriately changed according to the scale of the plant including the boilers 10 and 20. .
<Early stop of water supply pump>
In the conventional plant stop control procedure, the forced cooling / storage chemical injection operation process is completed, and the water supply pump 76 is stopped when entering the auxiliary machine stop process.

However, as shown in FIG. 4, the boiler temperature and the feed water temperature gradually decrease with time, but when the boiler temperature reaches about 70 ° C., the feed water temperature also reaches about 70 ° C., and thereafter the boiler The water supply temperature continues to be higher than the temperature. That is, after the boiler temperature reaches 70 ° C., the boilers 10 and 20 are heated by water supply.
Therefore, in this embodiment, the cooling time is shortened by stopping the feed water pump 76 when the feed water temperature of the feed water system drops to a predetermined temperature (for example, about 70 ° C.).

  In addition, the boiler temperature which stops the feed water pump 76 is not limited to the reference | standard mentioned above, It can change suitably according to the scale etc. of the plant containing the boilers 10 and 20.

<Bearing coolant temperature setting change>
While the plant is stopped, cooling is performed by circulating air through a boiler cooling system (primary cyclone 83, secondary cyclone 84, etc.) using a nitrogen gas circulation fan (not shown). A nitrogen gas circulation cooler (not shown) is disposed on the upstream side of the nitrogen gas circulation fan, and a cooling effect is achieved by exchanging heat between the air circulated by the nitrogen gas circulation fan and the bearing cooling water. Is increasing.

Therefore, in the present embodiment, in the N ₂ circulation cooling step, the temperature of the bearing cooling water set to about 30 ° C. during normal operation is set to an appropriate value (for example, 27 ° C.), thereby Cooling time is shortened.
Note that the set temperature of the bearing cooling water is not limited to the above-described standard, and can be appropriately changed according to the scale of the plant including the boilers 10 and 20.

<Stop operation time>
In the conventional stop control method of a pressurized fluidized bed plant, it took about 110 hours from the ST disconnection until the stop operation was completed.
On the other hand, according to the stop control method of the pressurized fluidized bed plant according to the embodiment of the present invention, as shown in FIGS. 1 to 3, about 56 hours from the ST disconnection until the stop operation is completed. We were able to.

  That is, by adopting the stop control method of the pressurized fluidized bed plant according to the embodiment of the present invention, the time required for the stop operation can be shortened to about half of the conventional time, so that the start time of the inspection work is advanced. Can do. Moreover, the restart of operation of the boilers 10 and 20 is accelerated, and the power cost related to the stop processing of the boilers 10 and 20 can be reduced.

  The present invention can mainly be used as a stop control method when stopping a power plant including the pressurized fluidized bed boilers 10 and 20, but any plant including the pressurized fluidized bed boilers 10 and 20 can be used. It can also be applied to plants other than power plants.

It is a timetable which shows the procedure of the stop control method of the pressurized fluidized bed plant which concerns on embodiment of this invention. It is a timetable which shows the procedure of the stop control method of the pressurized fluidized bed plant which concerns on embodiment of this invention. It is a timetable which shows the procedure of the stop control method of the pressurized fluidized bed plant which concerns on embodiment of this invention. It is explanatory drawing which shows the stop timing of a feed water pump in the stop control method of the pressurized fluidized bed plant which concerns on embodiment of this invention. It is explanatory drawing which shows schematic structure of the power plant to which the stop control method of the pressurized fluidized bed plant which concerns on embodiment of this invention is applied.

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 pipe 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 Braking water separator 73 Condensate pumps 74a-74e Feed water heater 75 Deaerator 76 Feed water pump 77 Condensate pipe 81 Exhaust gas pipe 82a, 82b Non-catalytic denitration device 83 Primary cyclone 84 Secondary cyclone 85, 86 Ash hopper 91, 93 Waste heat recovery exchanger 92 Denitration device 94 Bug Filter 95 Chimney 101 Dust collection Tube 102,103 Ash hopper

Claims (5)

A method for stopping a power plant equipped with a pressurized fluidized bed boiler,
A stop control method for a pressurized fluidized bed plant, wherein bed material circulation cooling is performed during gas turbine operation in a boiler fire extinguishing and cooling process.   The method for controlling stoppage of a pressurized fluidized bed plant according to claim 1, wherein the emergency hot water tank heater is stopped when the load on the generator is reduced to a predetermined value.   The method for controlling stoppage of a pressurized fluidized bed plant according to claim 1 or 2, wherein the temperature of the turbine bearing cooling water is set to be lower than that of the gas turbine disconnection process after the gas turbine disconnection process.   The stop control method for a pressurized fluidized bed plant according to any one of claims 1 to 3, wherein the feed water pump is stopped when the feed water temperature of the feed water system drops to a predetermined temperature.   The stop control method for a pressurized fluidized bed plant according to claim 4, wherein the feed water pump is stopped when the boiler temperature and the feed water temperature coincide with each other.

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