JP2008014505A - Viscosity management method of cwp (coal water paste) accompanying change of kind of coal in fluidized bed boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably perform an operation by quickly and properly performing responding operation, and to reduce an operator's load by defining management criterion of the viscosity of CWP in changing the kind of material coal to be charged into a fluidized bed boiler. <P>SOLUTION: The viscosity management method comprises: steps (S2, S4) of judging the viscosity of CWP; and a step for correcting the viscosity of CWP to a proper value on the basis of a result of judgement of the viscosity of CWP. In the step of correcting the viscosity of CWP to the proper value, a flow rate in charging water to a kneading machine is decreased by increasing moisture correction bias of coarsely-ground coal (S3), when the viscosity of CWP is lower than a range of a prescribed value, and the flow rate in charging water to the kneading machine is increased by reducing moisture correction bias of the coarsely-ground coal (S5), when the viscosity of CWP is higher than the range of prescribed value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a CWP viscosity management method associated with coal type switching in a fluidized bed boiler, and in particular, when the viscosity of CWP changes due to coal type switching, a fluidized bed boiler is controlled by performing a quick and accurate 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, has a CWP (Coal Water) in a fluidized bed using limestone as a fluidized medium (BM: bed material) while keeping the boiler in a pressurized state 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 CWP changes when the type of coal supplied to the pressurized fluidized bed boiler is switched. And when the viscosity of CWP changed with coal type switching, in order to perform stable operation, it was necessary to perform a corresponding operation so that the viscosity of CWP becomes an appropriate management value.

  Conventionally, there is no clear standard for the handling operation for setting the viscosity of the CWP to an appropriate management value, 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 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. When the type of raw coal to be input in a fluidized bed boiler is switched, the management standard of the viscosity of CWP is clarified, so that it is quick and appropriate. It is an object of the present invention to provide a CWP viscosity management method associated with coal type switching in a fluidized bed boiler capable of performing a corresponding operation to achieve stable operation and reducing the burden on the operator.

In order to achieve the above-mentioned object, the CWP 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 CWP viscosity management method associated with the coal type switching in the fluidized bed boiler according to the present invention is a method for appropriately managing the viscosity of the CWP when the type of raw coal input in the fluidized bed boiler is switched. Thus, the method includes a step of determining the viscosity of the CWP and a step of correcting the viscosity of the CWP to an appropriate value based on the determination result of the viscosity of the CWP. CWP (Coal Water Paste) is a fuel in which coal, limestone, and water are mixed.

  Here, in the step of correcting the viscosity of the CWP to an appropriate value, the flow rate of water injected into the kneader is adjusted by operating the moisture correction bias of the coarsely pulverized coal according to the viscosity of the CWP, and the viscosity of the CWP is adjusted. It is preferable to correct to an appropriate value.

  Further, in the step of correcting the viscosity of the CWP to an appropriate value, when the viscosity of the CWP falls below a predetermined value range, the flow rate of water injected into the kneader is decreased, and the viscosity of the CWP exceeds the predetermined value range. In this case, it is preferable to correct the viscosity of CWP to an appropriate value by increasing the flow rate of water injected into the kneader.

  The range of the predetermined value V (Pa · S) of the viscosity of the CWP is preferably 8 <V <10.

  In the CWP viscosity management method associated with coal type switching in the fluidized bed boiler according to the present invention, the viscosity of the CWP supplied to the furnace is determined, and the viscosity of the CWP is corrected to an appropriate value based on the determination result. Specifically, when the viscosity of CWP falls below a predetermined value range, the flow rate of water injected into the kneader is decreased by increasing the moisture correction bias of the coarsely pulverized coal, and the viscosity of CWP falls within the predetermined value range. Is exceeded, the flow rate of water injection to the kneader is increased by reducing the moisture correction bias of the coarsely pulverized coal, and the viscosity of the CWP is corrected to an appropriate value. As a result, the management standard of CWP viscosity becomes clear, and stable operation can be achieved by performing prompt and appropriate response 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 CWP viscosity management method associated with coal type switching in a fluidized bed boiler according to the present invention will be described.
The CWP viscosity management method associated with coal type switching in a fluidized bed boiler according to an 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 showing a schematic configuration of a power plant to which a CWP 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 that applies the CWP viscosity management method associated with the coal type switching in the fluidized bed boiler according to the present embodiment includes two boilers 10, 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.

  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. Further, a condensate water supply 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 at

  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 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. 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.

<CWP viscosity control method>
Next, a CWP viscosity 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 CWP 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 CWP that changes as the coal type is switched, first, information on the viscosity of CWP is acquired (S1).
Then, it is determined whether or not the viscosity of CWP is lower than a predetermined lower limit value (for example, 8 Pa · s) (S2), and when the viscosity of CWP is lower than a predetermined lower limit value (for example, 8 Pa · s) By increasing the moisture correction bias of the coarsely pulverized coal, the flow rate of water injected into the kneader is decreased, the viscosity of the CWP is corrected to an appropriate value (S3), and continuous monitoring is performed.

  On the other hand, when the viscosity of CWP is not lower than a predetermined lower limit (for example, 8 Pa · s), it is determined whether or not the viscosity of CWP is higher than a predetermined upper limit (for example, 10 Pa · s) (S4). When the viscosity of CWP is higher than a predetermined upper limit value (for example, 10 Pa · s), by decreasing the moisture correction bias of the coarsely pulverized coal, the water injection flow rate to the kneader is increased and the viscosity of CWP is increased. Is corrected to an appropriate value (S5), and continuous monitoring is performed.

  In addition, when the viscosity V (Pa · s) of CWP is within a predetermined range (for example, 8 <V <10), since it is an appropriate operation state, continuous monitoring is performed without performing the above-described operation.

<Monitor item>
Next, specific monitoring items in the present embodiment will be described.
In this embodiment, the viscosity target value V (Pa · s) of CWP is set to a range of 8 <V <10. That is, when the CWP viscosity target value V falls below the lower limit value, the combustion efficiency decreases. On the other hand, when the CWP viscosity target value V exceeds the upper limit value, the CWP conveyance efficiency decreases.
In addition, the value regarding the viscosity of CWP can be acquired by performing a sampling investigation, 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 viscosity management method for CWP associated with coal type switching in the fluidized bed boiler according to the present invention is, for example, when the viscosity of CWP changes 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 CWP 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 to which a viscosity management method of CWP accompanying coal type change in a fluidized bed boiler concerning an embodiment of the present 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 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 exchanger 92 Denitration equipment 94 Bag filter 95 Chimney 101 Dust collection pipe 102,103 Ash cooler

Claims (4)

A method for appropriately managing the viscosity of CWP when the type of raw coal to be charged in a fluidized bed boiler is switched.
Determining the viscosity of the CWP;
And a step of correcting the viscosity of the CWP to an appropriate value based on the determination result of the viscosity of the CWP, and a method of managing the viscosity of the CWP accompanying the change of the coal type in the fluidized bed boiler. The step of correcting the viscosity of the CWP to an appropriate value is as follows:
The flow according to claim 1, wherein the flow rate of water injected into the kneader is adjusted by operating a moisture correction bias of the coarsely pulverized coal according to the viscosity of the CWP, and the viscosity of the CWP is corrected to an appropriate value. CWP viscosity management method associated with coal type switching in a floor boiler. The step of correcting the viscosity of the CWP to an appropriate value is as follows:
When the viscosity of CWP falls below a predetermined value range, the flow rate of water injected into the kneader is decreased, and when the viscosity of CWP exceeds the range of predetermined value, the flow rate of water injected into the kneader is increased. The viscosity management method according to claim 2, wherein the viscosity is corrected to an appropriate value. The range of the predetermined value V (Pa · S) of the viscosity of the CWP is 8 <V <10. The method for managing the viscosity of the CWP according to coal type switching in the fluidized bed boiler according to claim 3.

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