JP4919635B2 - Bed density optimization method and bed density optimization system of fluidized medium in pressurized fluidized bed boiler - Google Patents

Description

  The present invention relates to a bed density optimization method and bed density optimization system for optimizing the bed density of a fluidized medium in a pressurized fluidized bed boiler, and in particular, to optimize the bed density of a fluidized medium easily and accurately. The present invention relates to a layer density optimization method and a layer density optimization system.

  Conventionally, steam generated from a boiler is produced by supplying a mixture of coal, limestone, and water into a fluidized bed using limestone as a fluid medium while maintaining the pressure inside the boiler with combustion air from a compressor. There is known a pressurized fluidized bed boiler in which a steam turbine is driven and a gas turbine is driven by exhaust gas from the boiler.

  In a pressurized fluidized bed boiler having such a configuration, the amount of steam generated in the boiler is adjusted by adjusting the height of the fluidized bed to increase or decrease the heat transfer area of the steam pipe buried in the fluidized bed. Yes. Therefore, in the pressurized fluidized bed boiler, the particle size management of the fluidized medium forming the fluidized bed is important.

  Conventionally, various techniques for managing a fluidized bed in a pressurized fluidized bed boiler have been proposed. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2002-174406) discloses a technique for estimating the wear rate and particle size distribution of fluidized particles in a pressurized fluidized bed combustion apparatus.

  The method for estimating the wear rate of fluidized particles in a pressurized fluidized bed combustor and the method for predicting the particle size distribution of fluidized particles in a pressurized fluidized bed combustor described in Patent Document 1 Calculating using the desulfurizing agent supply rate, the particle weight of the fluidized particles present in the fluidized bed, and the extracted weight of the desulfurizing agent, and measuring the weight fraction in advance, desulfurization in the pressurized fluidized bed boiler The particle size distribution of the agent is predicted.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-161403) discloses a technique for performing bed height calculation and monitoring of a fluid state in a fluid apparatus having a structure in a fluidized bed.
The “fluidized bed control method and control apparatus” described in Patent Document 2 corrects the measured laminar pressure loss value to the equivalent laminar pressure loss when there is no structure in the fluidized bed, and calculates the bed height Status monitoring is performed. In the correction process, the correction factor is calculated using a function having the sum of the gap lengths of the fluidized bed structure and the furnace width as parameters.

JP 2002-174406 A JP 2003-161403 A

  As described above, the particle size control of the fluidized medium that forms the fluidized bed is an important operation in a pressurized fluidized bed boiler, especially when a coarse shear occurs in the fluidized bed. Must be detected and appropriate action taken.

  However, in the technique described in Patent Document 1 described above, the calculation is performed using the desulfurization agent weight fraction, the desulfurization agent supply rate, the particle weight of the fluidized particles, and the desulfurization agent extraction weight. It is difficult to predict that the particle size distribution of the fluidized medium can be easily predicted because the measurement items are diverse and the calculation becomes complicated. In addition, since there are many measurement items, there is an increased possibility of measurement errors, and it was difficult to accurately predict the bed density of the fluid medium.

  Moreover, in the technique described in the above-mentioned Patent Document 2, correction calculation is performed using parameters based on the shape of a structure such as a heat transfer tube existing in the fluidized bed. However, the pressurized fluidized bed boilers that are subject to bed height calculation and fluidity monitoring are different in size, etc. for each plant, and parameters must be set again for each plant, which lacks versatility. There was a problem.

  The present invention has been proposed in view of the above-described circumstances, and an object thereof is to provide a layer density optimization method and a layer density optimization system that can easily and accurately optimize the layer density of a fluidized medium. .

The bed density optimization method and bed density optimization system for a fluidized medium in a pressurized fluidized bed boiler according to the present invention have the following features in order to achieve the above-described object.
That is, the fluidized medium bed density optimizing method according to the present invention is a method for optimizing the fluidized medium bed density in a pressurized fluidized bed boiler, wherein the fluidized bed is divided into a plurality of layers for each layer. A step of detecting a pressure loss, a step of predicting a layer density of the fluidized medium based on the detected pressure loss, and a layer of the fluidized medium when the predicted layer density of the fluidized medium exceeds a predetermined allowable range. It consists of a process of optimizing the density, and the process of detecting the pressure loss for each layer by dividing the fluidized bed into a plurality of layers is a part where the slip is likely to convection upward and the other part In the process of optimizing the bed density of the fluidized medium and in the process of detecting the pressure loss for each layer, the layer density of the fluidized medium at the site where the slippage is likely to convection and the other site are determined in advance. Process within tolerance It is characterized in.

A fluidized bed bed density optimization system in a pressurized fluidized bed boiler according to the present invention is a system for optimizing the bed density of a fluidized medium in a pressurized fluidized bed boiler, and the fluidized bed is divided into a plurality of layers. A plurality of pressure loss detecting means for detecting the pressure loss for each layer;
Based on the pressure loss detected by the pressure loss detecting means, a layer density predicting means for predicting the layer density of the fluid medium in each layer, and determining whether or not the predicted layer density of the fluid medium is within a predetermined allowable range. It consists of layer density judgment means, and the fluidized bed is divided into a plurality of layers, and the pressure loss detection means for each layer consists of detecting the part where slippage tends to convection upward and the other part from the dispersion plate. In the step of detecting the pressure loss for each layer in the means for optimizing the bed density of the fluidized medium, the layer density of the fluidized medium at the part where the slippage tends to convection and the exception part are processed within a predetermined allowable range. A bed density optimization system for a fluidized medium in a pressurized fluidized bed boiler.

  In the fluidized bed density optimization method and bed density optimization system in the pressurized fluidized bed boiler according to the present invention, the pressure loss in the fluidized bed is detected, and the bed density of the fluidized medium is predicted by performing a predetermined calculation. Therefore, it is possible to easily and accurately control the particle size of the fluidized medium forming the fluidized bed.

  In addition, the calculation formula used to predict the bed density of the fluidized medium is a simple formula that uses pressure loss, fluidized bed height, and gravitational acceleration. Since no time is required, even when a coarse shift occurs in the fluidized bed, it is possible to detect that fact immediately and take appropriate measures.

Hereinafter, with reference to the drawings, an embodiment of a bed density optimizing method and a bed density optimizing system of a fluidized medium in a pressurized fluidized bed boiler according to the present invention will be described.
1 is a block diagram showing a schematic configuration of a fluidized medium bed density optimization system in a pressurized fluidized bed boiler according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a BM circulation path in the pressurized fluidized bed boiler, FIG. 3 is a schematic diagram for explaining the influence of the bed density on the plant, and FIG. 4 is a flowchart showing the procedure of the bed density optimization method of the fluidized medium in the pressurized fluidized bed boiler according to the embodiment of the present invention. FIG. 5 is an explanatory diagram showing a schematic configuration of a power plant to which a fluidized bed density optimization method and a bed density optimization system are applied in a pressurized fluidized bed boiler according to an embodiment of the present invention.

<Power plant>
A power plant to which a bed density optimization method and bed density optimization system of a fluidized medium in a pressurized fluidized bed boiler according to an embodiment of the present invention is applied is a pressurized fluidized bed combined power generation system (PFBC). ), A steam turbine is driven by steam generated from a fluidized bed boiler housed in a pressure vessel, 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 is kept low (about 870 ° C.), so that the generation of nitrogen oxides (NOx) can be kept low.

Hereinafter, a power plant to which a fluid density bed density optimization method and a bed density optimization system in a pressurized fluidized bed boiler according to the present embodiment are specifically described.
As shown in FIG. 5, the power plant to which the bed density optimization method and bed density optimization system of the fluidized medium in the pressurized fluidized bed boiler according to the present embodiment includes two boilers 10 and 20, By introducing CWP into the furnaces 11 and 21 of the boilers 10 and 20 and burning them, and introducing steam generated by heat exchange to the high-pressure turbine 31, the intermediate-pressure turbine 32, and the low-pressure turbine 33 to rotate the turbines, The generator 41 is driven 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 to the high pressure turbine 31 after being routed in the order of the A furnace 11, the B furnace 21, and the furnace 11.

  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 device via the ash coolers 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.
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 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 temporarily storing BM to be circulated are connected to A furnace 11 and 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.

  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, 21. 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.

<BM circulation system>
Next, the BM circulation system will be described in detail with reference to FIG.
In the A furnace 11 disposed in the boiler 10, 0.2 m, 0.4 m, 0.6 m, 1.5 m, 2.6 m, 3.55 m, and 7.8 m upward from the dispersion plate. Pressure gauges 111a to 111g are respectively disposed at positions, and in the B furnace 21 disposed in the boiler 20, 0.2 m, 0.4 m, 0.6 m, Pressure gauges 111a to 111g are disposed at positions of 1.15 m, 2.425 m, 3.55 m, and 7.8 m, respectively.

  A hot blast furnace 150 and a BM furnace bottom extraction system 140 are connected to the lower part of the furnaces 11 and 21, and high temperature gas generated in the furnaces 11 and 21 is discharged to the upper part of the furnaces 11 and 21. For this purpose, a hot gas pipe 130 is connected in communication. A BM return pipe 161 and a BM supply pipe 162 are disposed between the furnaces 11 and 21 and the BM tanks 13 and 23. The BM tanks 13 and 23, the BM supply pipe 162, the furnaces 11 and 21, The BM circulates in the order of the BM furnace bottom extraction system 140 and the BM return pipe 161. In FIG. 2, reference numeral 120 indicates a fluidized bed.

<Relationship between layer density and plant impact>
Next, with reference to FIG. 3, the influence which the layer density in the furnaces 11 and 21 has on the plant will be described. 3A is a schematic diagram showing a state where the layer density is high, FIG. 3B is a schematic diagram showing a state where the layer density is good, and FIG. 3C is a schematic diagram showing a state where the layer density is low. FIG.

  In the state shown in FIG. 3A, since the BM particle size is small and the gap is small, the pressure loss in the furnaces 11 and 21 is high and the layer density is high. In such a state, the BM fluidity in the furnaces 11 and 21, the heat transfer properties of the boilers 10 and 20, the desulfurization performance in the furnaces, and the like are excellent, but the BM particle size is small, so the wake of the boilers 10 and 20 BM tends to scatter to the side, and not only the amount of ash collected by the cyclone increases, but also the layer height maintainability deteriorates.

  In the state shown in FIG. 3C, since the BM particle size is large and the gaps are large, the pressure loss in the furnaces 11 and 21 is low and the layer density is low. In such a state, the shear concentration becomes high, and the BM fluidity in the furnaces 11 and 21, the heat conductivity of the boilers 10 and 20, the desulfurization performance in the furnaces 11 and 21, and the like deteriorate. Furthermore, in order to maintain the output, the fuel tends to increase, and the unburned portion increases as the bed temperature increases. For this reason, cyclone blockage and heat transfer tube wear due to coarse particles are likely to occur.

  In contrast to such a state, in the state shown in FIG. 3 (b), the BM particle size and the gap are appropriate, so that a favorable operation can be performed. However, when operating in a high load zone, there is a feature that the BM particle size gradually increases, and it is necessary to periodically extract the bottom of the furnace and adjust the layer density within the control value.

<Layer density optimization system>
Next, with reference to FIG. 1, a fluidized medium bed density optimization system in a pressurized fluidized bed boiler according to an embodiment of the present invention will be described.
As shown in FIG. 1, the fluidized bed density optimization system 200 in the pressurized fluidized bed boiler according to the embodiment of the present invention includes a plurality of pressure gauges 111 a to 111 g and layers disposed in the furnaces 11 and 21. The density predicting unit 201, the layer density determining unit 202, and the layer density optimizing unit 203 are main components. Each means of the present embodiment is composed of a computer and its peripheral devices, and functions as each means are exhibited when a CPU or the like constituting the computer operates according to an application program.

The pressure gauges 111a to 111g are for detecting pressure loss in the fluidized bed. As described above, in the A furnace 11, from the dispersion plate upward, 0.2 m, 0.4 m, 0.6 m, 1.5 m, 2.6 m, 3.55 m, and 7.8 m, respectively. In the B furnace 21, 0.2 m, 0.4 m, 0.6 m, .15m, 2.425m, 3.55m, and 7.8m, respectively.
In the present embodiment, the pressure gauges 111a, 111b, and 111c disposed at 0.2 m, 0.4 m, and 0.6 m are used, and 0.2 m to 0.4 m and 0.4 m, which are sites where slippage is likely to convect. The layer density at ˜0.6 m is managed. In addition, according to the shape etc. of the pressurization fluidized bed boiler 10 and 20, you may manage layer density using the other pressure gauges 111d-111g.

The layer density predicting unit 201 is a unit for predicting the layer density of the fluidized medium based on the pressure loss detected by the pressure gauges 111a, 111b, and 111c. This layer density predicting means 201 calculates and predicts the layer density of the fluid medium using the following equation (1).
ρf = ΔP / (h × g) (1)
However,
ρf: Layer density (kg / m ³ )
ΔP: Pressure loss h: Fluidized bed height g: Gravity acceleration

The layer density determination unit 202 is a unit for determining whether or not the predicted layer density of the fluidized medium is within a predetermined allowable range. In this embodiment, the allowable range of the layer density at 0.2 m to 0.4 m is 1,100 to 1,200 kg / m ^3, and the allowable range of the layer density at 0.4 m to 0.6 m is 900 to 1,000 kg. / M ³ . The allowable range of the bed density can be appropriately changed and set according to the shape of the pressurized fluidized bed boilers 10 and 20.

  The layer density optimizing unit 203 is a unit for optimizing the layer density of the BM when the layer density determining unit 202 determines that the layer density of the fluidized medium exceeds a predetermined allowable range. This layer density optimizing means 203 operates the BM furnace bottom extraction system 140 to extract BM from the furnaces 11 and 21, or changes the operating state of the hot stove 150 and supplies it to the furnaces 11 and 21. By changing the amount of combustion air, the flow state of BM in the fluidized bed is changed, and the bed density is adjusted within a predetermined allowable range. Note that both the BM extraction operation and the combustion air amount increase / decrease operation may be performed at the same time or only one of the operations may be performed in accordance with the operating conditions of the pressurized fluidized bed boilers 10 and 20. .

<Layer density optimization method>
Next, with reference to FIG. 4, the procedure of the layer density optimization method of the fluid medium in the pressurized fluidized bed boiler according to the embodiment of the present invention will be described.
As shown in FIG. 4, the method for optimizing the bed density of a fluidized medium in a pressurized fluidized bed boiler according to an embodiment of the present invention detects a pressure loss in a fluidized bed (S1), and performs BM based on the detected pressure loss. The layer density of the BM is predicted (S2), and it is determined whether the predicted layer density of the BM is within a predetermined allowable range (S3).

When the predicted layer density of the BM exceeds a predetermined allowable range, the BM is extracted from the furnaces 11 and 21 or the amount of combustion air supplied to the furnaces 11 and 21 is increased or decreased. The layer density of BM is optimized (S4).
Thus, according to the fluidized bed density optimization method and the bed density optimization system of this embodiment, the particle size management of the BM forming the fluidized bed can be performed easily and accurately.

  The present invention can be used mainly for optimizing the bed density of the fluidized medium in the pressurized fluidized bed boilers 10 and 20 constituting the power plant, but the pressurized fluidized bed boilers 10 and 20 are provided. If it is a plant, it is applicable also to plants other than a power plant.

It is a block diagram which shows schematic structure of the bed density optimization system of the fluidized medium in the pressurized fluidized bed boiler which concerns on embodiment of this invention. It is explanatory drawing of the BM circulation path | route in embodiment of this invention. It is a schematic diagram for demonstrating the influence which a layer density has on a plant. It is a flowchart which shows the procedure of the layer density optimization method of the fluidized medium in the pressurized fluidized bed boiler which concerns on embodiment of this invention. It is explanatory drawing which shows schematic structure of the power plant which applies the bed density optimization method and bed density optimization system of the fluidized medium in the pressurized fluidized bed boiler which concerns on embodiment of this 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 pipe 81 Exhaust gas pipe 82a, 82b Non-catalytic denitration device 83 Primary cyclone 84 Secondary cyclone 85, 86 Ash cooler 91, 93 Waste heat recovery exchanger 92 Denitration device 94 Bug Filter 95 Chimney 101 Dust collection pipe DESCRIPTION OF SYMBOLS 102,103 Ash cooler 111a-111g Pressure gauge 120 Fluidized bed 130 High temperature gas pipe 140 BM furnace bottom extraction system 150 Hot blast furnace 161 BM return pipe 162 BM supply pipe 200 Layer density optimization system 201 Layer density prediction means 202 Layer density judgment Means 203 Layer density optimization means

Claims (2)

A method for optimizing the bed density of a fluid medium in a pressurized fluidized bed boiler,
Dividing the fluidized bed into a plurality of layers and detecting pressure loss for each layer;
Predicting the bed density of the fluid medium in each bed based on the detected pressure loss;
When the predicted bed density of the fluidized medium exceeds a predetermined allowable range, the step of optimizing the bed density of the fluidized medium comprises
The step of dividing the fluidized bed into a plurality of layers and detecting the pressure loss for each layer detects the part where the slip is likely to convection upward and the other part from the dispersion plate,
In the step of optimizing the bed density of the fluid medium, in the step of detecting the pressure loss for each layer, the layer density of the fluid medium at the site where slippage is likely to convection and the other part are processed within a predetermined allowable range. A method for optimizing the bed density of a fluidized medium in a pressurized fluidized bed boiler.
A system for optimizing the bed density of a fluidized medium in a pressurized fluidized bed boiler,
A plurality of pressure loss detection means for detecting the pressure loss for each layer by dividing the fluidized bed into a plurality of layers;
A bed density prediction means for predicting a bed density of the fluidized medium in each bed based on the pressure loss detected by the pressure loss detection means;
It comprises a layer density judgment means for judging whether or not the predicted bed density of the fluid medium is within a predetermined allowable range,
The fluidized bed is divided into a plurality of layers, and the pressure loss detection means for each layer consists of detecting a portion where slippage tends to convection upward and other portions from the dispersion plate,
In the means for optimizing the layer density of the fluidized medium, in the step of detecting the pressure loss for each layer, the layer density of the fluidized medium where the slippage tends to convect and the exceptional part are processed within a predetermined allowable range. A system for optimizing the bed density of a fluidized medium in a pressurized fluidized bed boiler.

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