JP5127220B2 - Slurry viscosity control method with coal type switching in fluidized bed boiler - Google Patents

Description

  The present invention relates to a method for managing the viscosity of a slurry accompanying the change of coal type in a fluidized bed boiler, and in particular, when the viscosity of the slurry changes due to the change of coal type, the fluidized bed boiler is controlled by performing a quick and accurate response operation. The present invention relates to a technology capable of stable operation.

  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 viscosity of the slurry changes when the coal type supplied to the pressurized fluidized bed boiler is switched. Then, when the viscosity of the slurry changes with the change of the coal type, it is necessary to perform a corresponding operation so that the viscosity of the slurry becomes an appropriate management value in order to perform stable operation.

  Conventionally, there is no clear standard for the handling operation for setting the viscosity of the slurry to an appropriate control value, and there is a side 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 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 the type of raw coal to be charged in a fluidized bed boiler is switched, the management standard for the viscosity of the slurry is clarified, so that it can be quickly and appropriately performed. An object of the present invention is to provide a method for managing the viscosity of a slurry accompanying the change of coal types in a fluidized bed boiler capable of performing a corresponding operation to achieve a stable operation and reducing the burden on the operator.

In order to achieve the above-described object, the slurry viscosity management method associated with the coal type switching in the fluidized bed boiler according to the present invention has the following features.
That is, the viscosity management method of the slurry accompanying the coal type switching in the fluidized bed boiler according to the present invention is a method for appropriately managing the viscosity of the slurry when the type of the raw coal supplied in the fluidized bed boiler is switched. Thus, the method includes a step of determining the viscosity of the slurry, and a step of correcting the viscosity of the slurry to an appropriate value based on the determination result of the viscosity of the slurry. The slurry is a coal paste pulverized using a fine pulverizer while mixing water into the coal powder pulverized by the coarse pulverizer.

  Here, it is preferable that the step of correcting the viscosity of the slurry to an appropriate value corrects the viscosity of the slurry to an appropriate value by performing moisture correction according to the viscosity of the slurry.

  The step of correcting the viscosity of the slurry to an appropriate value includes reducing the water content when the slurry viscosity falls below a predetermined value range, and containing the slurry when the slurry viscosity exceeds a predetermined value range. It is preferable to correct the slurry viscosity to an appropriate value by increasing the amount of moisture.

The range of the predetermined value V (Pa · S) of the viscosity of the slurry is preferably 110 <V <130.
In the step of correcting the viscosity of the slurry to an appropriate value, the moisture correction allowable value is preferably within plus or minus 1%.

  In the method for managing the viscosity of the slurry accompanying the switching of the coal type in the fluidized bed boiler according to the present invention, the viscosity of the slurry supplied to the kneader is determined, and the viscosity of the slurry is corrected to an appropriate value based on the determination result. Specifically, the viscosity of the slurry is decreased by decreasing the water content when the slurry viscosity falls below a predetermined value range and by increasing the water content when the slurry viscosity exceeds a predetermined value range. Correct to an appropriate value. As a result, the management standard of slurry viscosity becomes clear, and stable operation can be achieved by promptly and appropriately responding operations according to the coal type switching in the fluidized bed boiler, while reducing the burden on the operator. can do.

Hereinafter, with reference to the drawings, an embodiment of a slurry viscosity management method associated with coal type switching in a fluidized bed boiler according to the present invention will be described.
The slurry viscosity management method associated with coal type switching in the fluidized bed boiler according to the embodiment of the present invention is applied to, for example, a power plant that employs 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 illustrating a schematic configuration of a power plant to which a slurry viscosity 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 to which the slurry viscosity management method associated with the coal type switching in the fluidized bed boiler according to the present embodiment includes two boilers 10 and 20, and a furnace for the boilers 10 and 20. The CWP is injected into the cylinders 11 and 21 and combusted, 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.

  Further, the combustion 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 combustion 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 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. Heat exchange is performed.

  An exhaust gas pipe 81 is connected to the upper parts of the A furnace 11 and the B furnace 21 so that the combustion 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. . An emergency hot water tank 14 is disposed above 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.

  Dust collection pipes 111 and 121 for collecting the dust deposited in each of the furnaces 11 and 21 are connected to the lower part of the A furnace 11 and the B furnace 21, and the collected dust passes through the ash coolers 112 and 122. Then, it is sent to the ash treatment 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.

<Slurry viscosity control method>
Next, a description will be given of a slurry viscosity management method associated with coal type switching in a fluidized bed boiler according to an embodiment of the present invention. FIG. 1 is a flowchart showing a procedure of a slurry viscosity 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 viscosity of the slurry that changes as the coal type is switched, information on the viscosity of the slurry is first acquired (S1).
Then, it is determined whether or not the viscosity of the slurry is below a predetermined lower limit value (for example, 110 Pa · s) (S2), and if the viscosity of the slurry is below a predetermined lower limit value (for example, 110 Pa · s) Then, by correcting the water content by reducing the water content of the slurry, the viscosity of the slurry is corrected to an appropriate value (S3), and continuous monitoring is performed.

  On the other hand, if the viscosity of the slurry is not lower than a predetermined lower limit (for example, 110 Pa · s), it is determined whether the viscosity of the slurry is higher than a predetermined upper limit (for example, 130 Pa · s) (S4). If the slurry viscosity exceeds a predetermined upper limit (for example, 130 Pa · s), the slurry viscosity is corrected to an appropriate value by increasing the moisture content of the slurry and performing moisture correction. (S5) Continuous monitoring is performed.

  In addition, when the viscosity V (Pa · s) of the slurry is within a predetermined range (for example, 110 <V <130), the operation is in an appropriate state, and therefore 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 target viscosity value V (Pa · s) of the slurry is in the range of 110 <V <130. That is, when the slurry viscosity target value V falls below the lower limit value, the combustion efficiency decreases. On the other hand, when the target viscosity value V of the slurry exceeds the upper limit value, the CWP conveyance efficiency decreases.
At this time, it is preferable that the moisture correction allowable value is within plus or minus 1% in order to prevent disturbance of boiler operation management due to a sudden change. In addition, the value regarding the viscosity of slurry can be acquired by conducting a sampling survey, for example. 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 slurry viscosity management method associated with the coal type switching in the fluidized bed boiler according to the present invention is, for example, when the viscosity of the slurry is changed by switching the coal type in a pressurized fluidized bed boiler used in a power plant or the like. It can be used when the boiler is operated stably.

It is a flowchart which shows the procedure of the viscosity management method of the slurry accompanying the coal type switching in the fluidized bed boiler which concerns on embodiment of this invention. It is a mimetic diagram showing the schematic structure of the power plant which applies the viscosity management method of the slurry accompanying the coal type change in the fluidized bed boiler concerning the 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 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 Waste heat recovery Heat exchanger 92 Denitration equipment 4 bag filter 95 chimney 111, 121 dust collecting pipe 112,122 ash cooler

Claims (2)

A method for appropriately managing the viscosity of a slurry when the type of coking coal to be input in a fluidized bed boiler is switched.
Determining the viscosity of the slurry;
Based on the determination result of the viscosity of the slurry, the step of correcting the viscosity of the slurry to an appropriate value,
The step of correcting the slurry viscosity to an appropriate value includes:
When the viscosity of the slurry is less than the range of 110 <V <130 as the predetermined value V (Pa · S), the water content is decreased, and when the viscosity of the slurry exceeds the range of the predetermined value, the water content is decreased. A method for managing the viscosity of a slurry accompanying a change in coal type in a fluidized bed boiler , wherein the viscosity of the slurry is corrected to an appropriate value by increasing the viscosity.   2. The slurry viscosity management according to the change of coal type in a fluidized bed boiler according to claim 1, wherein in the step of correcting the slurry viscosity to an appropriate value, a moisture correction allowable value is within ± 1%. Method.

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