JP2007322070A - Furnace bed temperature/bed height management method following coal type switching in fluidized bed boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out stable operation, and to reduce a burden on an operator by clarifying management criteria of a bed temperature/bed height of a fluidized bed boiler and carrying out quick and appropriate responsive operation when switching the type of raw material coal to be input in a fluidized bed boiler. <P>SOLUTION: The method includes steps S2, S6 of judging a state of the furnace bed temperature, steps S3, S7 of judging a state of the bed height, and a step of correcting the bed temperature and the bed height to appropriate values on the basis of state judgements of the bed temperature and the bed height. In the step of correcting the bed temperature and the bed height to the appropriate values, by fluctuating a bed material amount or a mixing ratio of limestone and coal in response to the bed temperature and the bed height (S4, S5, S8, S9), the bed temperature and the bed height are changed to the appropriate values. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a furnace bed temperature / bed height management method associated with coal type switching in a fluidized bed boiler, and in particular, when a layer temperature / bed height of a furnace changes due to coal type switching, a quick and accurate operation is performed. The present invention relates to a technique that can stably operate a fluidized bed 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 bed temperature and bed height change when the type of coal supplied to the pressurized fluidized bed boiler is switched. And when layer temperature and bed height changed with coal type change, in order to perform stable operation, it was necessary to perform corresponding operation that bed temperature and bed height become suitable management values.

  Conventionally, there is no clear standard for the corresponding operation for setting the layer temperature and the layer height to appropriate control values, and there is an aspect that relies on the experience and intuition of a skilled operator. That is, monitoring items and corresponding operations for performing stable operation at the time of coal type switching 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, although the "coal supply method and apparatus to a bunker" described in the said patent document 1 aims at labor-saving at the time of mixing and using a some coal type, in order to perform a stable operation There is no mention of any clear criteria.

  The present invention has been proposed in view of the above-described circumstances, and when the type of raw coal to be charged in a fluidized bed boiler is switched, the management standards for the bed temperature and bed height of the fluidized bed boiler are clarified. A furnace bed temperature and bed height management method that accompanies the change of coal type in a fluidized bed boiler that can reduce the burden on the operator as well as being able to perform stable and prompt operations by responding quickly and appropriately. The purpose is to provide.

In order to achieve the above-described object, the furnace bed temperature / bed height management method accompanying the coal type switching in the fluidized bed boiler according to the present invention has the following features.
That is, the furnace bed temperature / bed height management method associated with the coal type switching in the fluidized bed boiler according to the present invention is the method of switching the type of raw coal supplied to the fluidized bed boiler, A method for appropriately controlling the bed height, the step of determining the state of the furnace bed temperature, the step of judging the state of the bed height, and the bed temperature and And a step of correcting the layer height to an appropriate value.

  Here, the step of correcting the bed temperature and bed height to appropriate values is performed by changing the mixing ratio of limestone and coal or the amount of fluidized medium according to the bed temperature and bed height. Is preferably an appropriate value.

  In addition, the step of correcting the bed temperature and bed height to appropriate values is performed by supplying a fluid medium into the furnace when the bed temperature rises and the bed height is lowered. When the layer temperature rises and the layer height does not decrease, the layer temperature and the layer height are increased by increasing the proportion of limestone when mixing the limestone and coal supplied to the furnace. When the layer temperature decreases and the layer height increases, the step of setting the layer temperature and the layer height to appropriate values by extracting the fluid medium from the furnace, and the layer temperature decreases and the layer height decreases. If the limestone does not rise, it is preferable to include a step of setting the layer temperature and the layer height to appropriate values by reducing the ratio of limestone when mixing the limestone and coal supplied to the furnace.

  Further, in the step of correcting the bed temperature and bed height to appropriate values, when the bed temperature and bed height are not stable and there are a plurality of boilers, the fuel input amount for each boiler is changed. Therefore, it is preferable to stabilize the layer temperature and the layer height. Note that changing the fuel input amount for each boiler means, for example, changing the fuel bias for each boiler.

  Further, in the step of correcting the bed temperature and bed height to appropriate values, if the bed temperature and bed height cannot be set to appropriate values, the load of the fluidized bed boiler is reduced to reduce the bed temperature and bed height. It is preferable to set the layer height to an appropriate value.

  The furnace bed temperature / bed height management method associated with the coal type switching in the fluidized bed boiler according to the present invention specifies that the state of the furnace bed temperature and bed height is determined, and that a predetermined operation is performed based on the determination result. By adjusting the bed temperature and bed height to appropriate values, the management standards for bed temperature and bed height of the fluidized bed boiler become clear. 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, an embodiment of a furnace bed temperature / bed height management method associated with coal type switching in a fluidized bed boiler according to the present invention will be described with reference to the drawings.
The furnace bed temperature / bed height management method associated with 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. Is done.

  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 furnace bed temperature / bed height management method according to 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 furnace bed temperature / bed height management method associated with the coal type switching in the fluidized bed boiler according to this embodiment includes two boilers 10, 20. CWP is introduced into 20 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 generating 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 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 boiler 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. Heat exchange is performed.

  An exhaust gas pipe 81 is connected to the upper part of the A furnace 11 and the B furnace 21, and the high pressure gas generated in each of 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.

<Furnace layer temperature and height control method>
Next, a furnace bed temperature / bed height management method associated with coal type switching in a fluidized bed boiler according to an embodiment of the present invention will be described. FIG. 1 is a flowchart showing a procedure of a furnace bed temperature / bed height 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 manage the bed temperature and bed height that change with the change of coal type, first, information on the bed temperature and bed height is acquired (S1). Then, it is determined whether or not the layer temperature has risen from a management value (for example, 900 ° C.) (S2). If the layer temperature has risen from the management value, the layer height has a management value (for example, 4.2 m). It is judged whether it has fallen from (S3).

  Then, when the bed height is lower than the management value, BM (bed material) is supplied (S4), and continuous monitoring is performed. On the other hand, when the bed height has not decreased from the control value, L / C (mixing ratio of limestone and coal) is changed to a predetermined value (for example, 12 or less) (S5), and continuous monitoring is performed. In addition, in the change of L / C, when the limestone supplied to a furnace and coal are mixed, the ratio of limestone is raised.

  If the layer temperature has not risen from the control value (for example, 900 ° C.), it is determined whether the layer temperature has decreased from the control value (for example, 900 ° C.) (S6). In the case where the height has decreased, it is determined whether or not the bed height has increased from a management value (for example, 4.2 m) (S7).

  Then, when the bed height is rising from the management value, BM (bed material) is extracted (S8), and continuous monitoring is performed. On the other hand, when the bed height has not risen from the control value, L / C (mixing ratio of limestone and coal) is changed to a predetermined value (for example, 12 or less) (S9), and continuous monitoring is performed. In addition, in the change of L / C, when the limestone supplied to a furnace and coal are mixed, the ratio of limestone is reduced.

  In addition, when the bed temperature and the bed height are within the range of the management value, it is an appropriate operation state, and thus 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, regarding the furnace layer temperature, the control value is set to 900 ° C. or lower, and when the layer temperature at a predetermined location is 930 ° C. or higher, MFT (main fuel trip: fuel cutoff) is performed, and the layer temperature at the predetermined location is 910 An alarm is generated when the temperature is above ℃. In addition, regarding the layer height, the management value is 4.2 m or less. Further, regarding L / C, the management value is set to 12 or less.

  Here, when the bed temperature and bed height are not stable, the bed temperature and bed height are stabilized by adjusting the bias value of the fuel supplied to each furnace. Further, when the bed temperature and bed height cannot be set to appropriate values, the bed temperature and bed height are set to appropriate values by reducing the load of the pressurized fluidized bed boiler.

  In addition, the data regarding the bed temperature and bed height can be acquired by the existing bed temperature measurement means and bed height measurement means installed in the furnace. 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 furnace bed temperature / bed height management method associated with the coal type switching in the fluidized bed boiler according to the present invention, for example, the bed temperature / bed height changed by switching the coal type in a pressurized fluidized bed boiler used in a power plant or the like. In some cases, it can be used when the fluidized bed boiler is operated stably.

It is a flowchart which shows the procedure of the furnace bed temperature and bed height 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 furnace bed temperature and bed height 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 furnace bed temperature and bed height of the fluidized bed boiler when the type of coking coal to be charged in the fluidized bed boiler is switched,
Determining the state of the layer temperature;
Determining the height of the building;
A step of correcting the bed temperature and bed height to appropriate values based on the judgment of the bed temperature and bed height state, and the furnace bed temperature and bed height management accompanying the change of coal type in a fluidized bed boiler Method.   The step of correcting the bed temperature and bed height to an appropriate value is performed by changing the mixing ratio of limestone and coal or the amount of fluidized medium according to the bed temperature and bed height, thereby adjusting the bed temperature and bed height appropriately. The furnace bed temperature / bed height management method associated with the coal type switching in the fluidized bed boiler according to claim 1, wherein The step of correcting the bed temperature and bed height to appropriate values,
When the bed temperature rises as the bed temperature rises, a step of setting the bed temperature and bed height to appropriate values by supplying a fluid medium into the furnace,
When the layer temperature rises and the layer height does not decrease, the step of setting the layer temperature and the layer height to appropriate values by increasing the proportion of limestone when mixing the limestone and coal supplied to the furnace,
When the bed temperature rises as the bed temperature falls, the step of setting the bed temperature and bed height to appropriate values by extracting the fluid medium from the furnace,
When the bed temperature decreases and the bed height does not rise, the step of setting the bed temperature and bed height to appropriate values by reducing the proportion of limestone when mixing limestone and coal supplied to the furnace, A furnace bed temperature / bed height management method associated with coal type switching in a fluidized bed boiler according to claim 1 or 2.   In the step of correcting the bed temperature and bed height to appropriate values, if the bed temperature and bed height are not stable and there are a plurality of boilers, by changing the fuel input amount for each boiler, The method for controlling the furnace bed temperature and bed height associated with coal type switching in a fluidized bed boiler according to any one of claims 1 to 3, wherein the bed temperature and bed height are stabilized. In the step of correcting the bed temperature and bed height to appropriate values, if the bed temperature and bed height cannot be set to appropriate values, the bed temperature and bed height can be reduced by reducing the load of the fluidized bed boiler. The furnace layer temperature / layer height management method associated with the coal type switching in the fluidized bed boiler according to any one of claims 1 to 4, wherein the value is an appropriate value.

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