JPH06257714A - Device and method for supplying slurry fuel of mixed coas and water for pressurized fluidized bed type boiler - Google Patents

Abstract

PURPOSE:To keep a desired combustion performance of a pressurized fluidized bed type boiler by a method wherein an unstable state of flow rate of supplying CWP or a closing trouble in a supplying pipe is prevented. CONSTITUTION:An increased viscosity caused by a variation in nature of a coal water mixed slurry (CWP) and a pressure loss in a CWP supplying pipe 3 are detected by a pressure difference sensor 10. As they become predetermined dangerous values, water is fed and controlled to be supplied to the corresponding locations with a water feeding pipe 12, thereby an unstable state of a flow rate of CWP supplying during an operation of the pressurized fluidized bed type boiler 101 is eliminated and a closing of the supplying pipe 3 can be prevented, so that a combustion performance of the boiler 101 is not substantially influenced. Although a closing trouble of the sensor device itself for the pressure loss can be expected during supplying of CWP 120 of high viscosity, even in that case, a water supplying control for the supplying pipe 3 is carried out under a combination of O2 and NOx concentration sensor 14 for the discharged gas of the boiler 101, resulting that back-up for the device may easily be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device, which is a main device of a pressurized fluidized bed boiler, and particularly to a slurry fluid (Coal W) prepared by mixing coal particles and water in a supply pipe.
By adjusting the viscosity of ater Paste (hereinafter referred to as CWP), it is possible to prevent clogging in the supply pipe before it occurs and to supply CWP fuel suitable for stabilizing the CWP supply amount to the pressurized fluidized bed boiler. It relates to the device.

[0002]

2. Description of the Related Art As a method for supplying coal fuel to a pressurized fluidized bed boiler, 1) a lock hopper for stepwise increasing the pressure to the coal supply destination by a plurality of containers in which dried coal particles are connected in series. A dry supply system for supplying coal to a pressurized fluidized bed boiler using an air transportation system for pneumatically transporting coal, and 2) supplying CWP to the pressurized fluidized bed boiler by using CWP as fuel and using a pump as a pressure increasing and pumping means. There is a wet supply system. On the other hand, the pressurized fluid Doso boiler generally to 10~15kg / cm ² · g at the time of the maximum load pressure of the combustion chamber, at the time of minimum load is operated at about 4~6kg / cm ² · g, coal fueling The device needs to follow the pressure of the pressurized fluidized bed boiler of this supply destination.

That is, in the dry supply method, the pressure of the lock hopper needs to be adjusted in accordance with the change in the pressure of the supply destination, which complicates the operation operation and also increases the equipment cost of the control device and the like. Since there are many disadvantages such as the above, and since dry coal is supplied, an imbalance occurs in the temperature in the combustion chamber (hereinafter referred to as bed temperature), which is not preferable. Compared to the dry supply method, in the wet supply method, the CWP is boosted and pressure-fed by the pump, but the discharge pressure of the pump is determined by the pressure of the supply destination.
It has the advantage of being able to respond smoothly to changes in pressure at the supply destination. Also, since it is a wet type, the combustion time of coal fuel is long,
Since there is an advantage that an imbalance of bed temperature is unlikely to occur, a pressurized fluidized bed boiler is often adopted by a wet supply system.

Hereinafter, a schematic system of a wet supply system for supplying CWP to the pressurized fluidized bed boiler in a wet manner will be described with reference to FIG. The pressurized fluidized bed boiler 101 housed in the pressure vessel 104 is provided with an air dispersion plate 105 at the bottom thereof, and fluid medium particles 102 are filled on the air dispersion plate 105. The compressed air 106 is supplied to the pressure vessel 104 and then supplied as combustion air 107 through the air dispersion plate 105 into the pressurized fluidized bed boiler 101 to fluidize the fluidized medium particles 102 to form a fluidized bed 109. To do. On the other hand, fuel coal 11
4 is a CWP adjustment tank 11 adjusted to a predetermined particle size distribution
1 is continuously charged, and further, water 116 and a limestone 11 for desulfurization in a fluidized bed at a predetermined ratio to the amount of coal 114 supplied.
5 are continuously charged. This coal 114, limestone 11
5 and water 116 are mixed by a stirring blade 113 rotated by an electric motor 112 in the CWP adjustment tank 111,
After being stirred, it is sent to the CWP tank 121 and stored. In the CWP tank 121 as well, in order to prevent the coal 114 and the water 116 of the CWP 120 from being separated, the stirring blade 123 that is rotated by the electric motor 122 is agitated. The pressurized fluidized bed boiler 101 includes a CWP pump 1
CWP12 from the CWP tank 121 boosted by
0 is transported through the supply pipe 3 and the CWP nozzle 110
Is blown into the fluidized bed 109. The combustion exhaust gas discharged from the pressurized fluidized bed boiler 101 is introduced into a gas turbine (not shown) through an exhaust gas pipe 108 after dust is removed by a cyclone 103.

During normal operation, the CWP 120 opens the valve 2 of the CWP tank 121 and is supplied from the CWP nozzle 110 of the pressurized fluidized bed boiler 101 to the fluidized bed 109 through the supply pipe 3 and the three-way valve 4 by the CWP pump 1. . A three-way valve 4 and a CWP return pipe 5 are provided for warming when the supply of the CWP 120 to the pressurized fluidized bed boiler 101 is started or for purging the supply pipe 3 of the CWP 120. However, in the case of producing the CWP 120 in which the coal 114 and the water 116 are mixed, in order to reduce the evaporation sensible heat of the water 116 from the viewpoint of combustion performance, it is desirable that the moisture content be as low as possible and set at a predetermined ratio with respect to the amount of coal. Water 1
16 is added. However, since the properties of the coal 114 (particularly the water content adhering to the coal) depend on the storage condition and the atmospheric condition, it is almost impossible to manufacture a uniform CWP120, and the properties of the CWP120 change from moment to moment.

Therefore, during transportation, CWP120
When the coal concentration in the inside increases (the water concentration decreases), its viscosity increases, the pressure loss of the supply pipe 3 increases, and the supply pipe 3 becomes slightly blocked. In this case, the supply amount of CWP 120 is insufficient, and in the worst case, the supply pipe 3 is blocked. In particular, the CWP 12 during operation of the pressurized fluidized bed boiler 101
0 fuel supply instability or instantaneous supply stop
Since the combustion state of No. 01 is drastically changed, the emission concentration of NOx and SOx in the combustion exhaust gas is influenced, and the environmental protection performance is seriously affected.

[0007]

The above prior art does not take into consideration the fact that a stable amount of CWP 120 is maintained during the operation of the pressurized fluidized bed boiler 101, and the CWP is not considered.
The property changes (the viscosity of CWP increases), and CWP120
Instability of the supply flow rate, and in the worst case, the supply pipe 3 may be blocked, which may have a significant effect on the combustion performance of the pressurized fluidized bed boiler 101. An object of the present invention is to provide a CWP to a pressurized fluidized bed boiler while the CWP is being supplied.
Even if the viscosity of CWP increases due to property changes, the sign is detected in advance to prevent instability of the CWP supply flow rate and the trouble of blockage of the supply pipe, and to determine the combustion performance of the pressurized fluidized bed boiler. It is to provide a CWP fuel supply device that can maintain

[0008]

The above object of the present invention can be achieved by the following constitutions. That is, a pump for pumping a mixed slurry fuel of coal and water and a supply pipe for transporting the fuel are provided, and a coal water mixed slurry fuel supply of a pressurized fluidized bed boiler for supplying the coal water mixed slurry fuel to the pressurized fluidized bed boiler is provided. In the apparatus, a differential pressure detector and a water injection pipe are provided in the middle of the coal water mixed slurry fuel supply pipe, and at least one of oxygen concentration and nitrogen oxide concentration detector is provided at the exhaust gas outlet of the pressurized fluidized bed boiler. A deviation signal between the differential pressure detection signal and the differential pressure setting signal from the differential pressure detector, and a deviation signal between the setting signal corresponding to at least one of the oxygen concentration and nitrogen oxide concentration detectors. Coal in a pressurized fluidized bed boiler equipped with a water injection control device that controls the amount of water injected into the supply pipe to adjust the viscosity of the coal-water mixed slurry fuel in the fuel transportation system. Mixing a slurry fuel supply system. Here, it is desirable that the differential pressure detector is provided in at least one blockage danger point of the supply pipe, and in addition, in case the pressure abnormality is present in the supply pipe upstream from the fuel pressure pump, the differential pressure detector is installed. It can be configured such that it is provided in the supply pipe near the outlet of the fuel pressure pump and the water injection port to the supply pipe is arranged in the supply pipe upstream of the fuel pressure pump.

Further, when the deviation signal between the differential pressure detection signal from the differential pressure detector and the differential pressure setting signal shows an abnormal value, the water injection control device performs the primary water injection control to the supply pipe and further oxygen When the deviation signal between the oxygen concentration and nitrogen oxide concentration detection signal from the concentration and nitrogen oxide concentration detector and the deviation signal of oxygen concentration and nitrogen oxide concentration setting signal shows an abnormal value, the secondary water injection control to the supply pipe is performed. It can be configured. Further, the water injection control device may prioritize water injection control based on detection signals from the oxygen concentration and nitrogen oxide concentration detectors when the differential pressure detector is out of order. At this time, it is also possible to perform the sequential water injection control from the blockage risk location where the differential pressure detector on the downstream side is provided to the blockage danger location where the differential pressure detector on the upstream side is provided.

The above object of the present invention can also be achieved by the following configuration. That is, in the coal water mixed slurry fuel supply method of the pressurized fluidized bed boiler, which supplies the coal water mixed slurry fuel to the pressurized fluidized bed boiler while pumping the mixed slurry fuel of coal and water, during the coal water mixed slurry fuel supply. Of the coal water mixture in the fuel transportation system by controlling the amount of water injected into the fuel during the supply depending on the abnormality in the pressure in the exhaust gas or the abnormality in at least one of the oxygen concentration and the nitrogen oxide concentration in the exhaust gas of the pressurized fluidized bed boiler. It is a coal water mixed slurry fuel supply method for a pressurized fluidized bed boiler that adjusts the viscosity of the slurry fuel. Here, primary control of water injection is performed due to abnormal pressure during coal water mixed slurry fuel supply, and secondary control of water injection is performed according to abnormal oxygen concentration and nitrogen oxide concentration in boiler exhaust gas. Slurry fuel supply method,
Alternatively, when the detection of the pressure during the coal water mixed slurry fuel supply is unsuccessful, a coal water mixed slurry fuel supply method that prioritizes the water injection control due to the abnormal oxygen concentration and nitrogen oxide concentration in the boiler exhaust gas can also be used. . At this time, it is also possible to carry out sequential water injection control from the blockage risk point on the downstream side to the blockage danger point on the upstream side.

[0011]

[Action]

(1) Since the pressure loss of the CWP supply pipe is monitored,
Viscosity increase due to changes in CWP properties can be easily detected by pressure loss, and when a preset dangerous value is reached, water injection control (water injection may be pulsed) is applied to that portion to prevent the increase in pressure fluidized bed boiler operation. Since the instability of the CWP supply flow rate can be eliminated and the CWP supply pipe can be prevented from being blocked, the combustion performance of the pressurized fluidized bed boiler is not significantly affected. (2) Since water injection can be controlled for each CWP supply pipe, the minimum amount of water injection is sufficient, so that an increase in excess water is small, and an increase in evaporation sensible heat of water in combustion of the pressurized fluidized bed boiler is also small. (3) When supplying high-viscosity CWP, it is naturally expected that the pressure loss detection device itself will be clogged, but even in that case, oxygen (O ₂ ) and nitrogen oxidation in the exhaust gas of the pressurized fluidized bed boiler will occur. Since the water injection control to the CWP supply pipe is performed in combination with the device that monitors changes in the concentration of NOx (NOx), backup can be easily performed. That is, in the combustion performance of the pressurized fluidized bed boiler, considering a case where the supply flow rate of the CWP fuel is insufficient, for example, below a predetermined supply amount, the O _{2 in the} exhaust gas is discharged faster than the decrease in the bed temperature. , NOx concentration changes appear. Therefore, by monitoring the change in O ₂ and NOx concentrations in the exhaust gas and combining them with water injection control, it is possible to deal with them very quickly.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Example 1 In FIG. 1, 10 is a differential pressure detector, 11 is a control device,
2 is a water injection pipe, 13 is a water injection valve, 14 is O ₂ , NOx
Concentration detector, 15 is differential pressure detection signal, 16 is O ₂ , NOx
Concentration detection signal, 17a differential pressure setting signal, 17b O ₂
NOx setting signal, 18 is a control signal for the water injection valve 13,
Regarding other members, the same members as those shown in FIG. 4 are designated by the same reference numerals. Although FIG. 1 shows an example in which the supply pipe 3 is arranged at a bend part which is a blockage danger point due to CWP fuel, it may be provided at any position of the supply pipe 3.

Next, before explaining this embodiment, O ₂ , N
O ₂ and NOx concentration detection signal 1 from the Ox concentration detector 14
The reason why 6 is used as the control factor will be described. The compressed air 106 pressurized by a compressor directly connected to a gas turbine (not shown) is first supplied to the pressure vessel 104 and then supplied to the pressurized fluidized bed boiler 101 as combustion air 107. The flow rate control of the combustion air 107 is usually controlled so as to have a constant ratio with respect to the fuel amount (CWP amount here), and the O ₂ concentration in the exhaust gas of the pressurized fluidized bed boiler 101 is measured. It is controlled so as to correct the deviation from the set value. However, for example, when the supply of the CWP 120 to the pressurized fluidized bed boiler 101 suddenly stops, the flow rate of the combustion air 107 is naturally adjusted, but since the volume of the pressure vessel 104 becomes a buffer tank, It is not possible to quickly follow the flow rate of combustion air.
Therefore, the combustion state of the pressurized fluidized bed boiler 101 causes an excessive amount of air, resulting in an increase in O ₂ and NOx concentrations in the exhaust gas, and an increase in the NOx concentration leads to a problem that a predetermined environmental protection performance cannot be secured.

On the other hand, from the supply pipe 3 to the CWP nozzle 110
The supply amount of the CWP 120 supplied to the CMP 120 is controlled by an output request to the pressurized fluidized bed boiler 101, etc. The actual amount of the CWP 120 supplied is determined by a flow meter in the middle of the supply pipe 3. It is possible to grasp to some extent by providing the above or by investigating the flow rate characteristic of the CWP pump 1 (relationship between the output of the CWP pump 1 and the CWP supply amount) in advance. However, unlike a fluid such as air, the CWP 120 is difficult to measure the flow rate itself, and C
Since the properties of the WP 120 change from moment to moment, the flow rate characteristic of the CWP pump 1 also has a problem in accuracy. Therefore, CWP
120 tends to become clogged in the supply pipe 3, and the CWP12
There may be cases where the supply amount of 0 has decreased, but this has not been measured. In this case, even if the CWP 120 that does not appear as a differential pressure abnormality in the differential pressure detector 10 of the supply pipe 3 is reduced, the predetermined ratio of the CWP supply amount and the combustion air collapses, so the outlet of the pressurized fluidized bed boiler 101. The increase in O ₂ and NOx concentrations can be detected by the O ₂ and NOx concentration detector 14 provided in the exhaust gas pipe 108.

Therefore, in the present embodiment, the exhaust gas pipe 108 is provided with the O ₂ and NOx concentration detector 14, and the O ₂
The O ₂ and NOx concentration detection signals 16 from the NOx concentration detector 14 were also used as control factors. Therefore, as shown in FIG. 1, the differential pressure detector 10 provided in the middle of the supply pipe 3 continuously monitors the differential pressure of the supply pipe 3 to check whether the differential pressure detection signal 15 and the differential pressure setting signal 17a are abnormal. Presence / absence control device 11
If the dangerous value is reached, the water injection valve 13 is controlled by the control signal 18 to inject water from the water injection pipe 12 into the supply pipe 3. Further, the O ₂ and NOx concentration detector 14 in the exhaust gas provided in the exhaust gas pipe 108 at the outlet of the pressurized fluidized bed boiler 101 gives an O ₂ and NOx concentration detection signal 16 to the control device 11 to back up the water injection control. . By the water injection control based on these two types of detection signals, the viscosity of the CWP 120 in the supply pipe 3 can be reduced, the pressure loss in the supply pipe 3 can be reduced, and the CWP supply flow rate can be stabilized. The blockage in the pipe 3 can be prevented in advance.

Embodiment 2 FIG. 2 is an explanatory view of another embodiment of the present invention. The same members as those in FIG. 1 are indicated by the same numbers. In the present embodiment, a countermeasure is taken in the case where there is a danger of blockage such as a bend portion due to the actual arrangement of the supply pipe 3. In this case as well, the differential pressure detectors 10a, 10b, 10c are provided at the blockage danger point, and if the pressure loss in the supply pipe 3 becomes a dangerous value, it is controlled which of the detectors 10a, 10b, 10c is the danger point. The device 11 makes a judgment, and the water injection valve 13 automatically
A, 13b, and 13c are controlled to inject water. At this time, the abnormality determination in the control device 11 is backed up by the O ₂ and NOx concentration detector 14 in the exhaust gas as in the first embodiment shown in FIG. The differential pressure detector 10
When any of a, 10b, and 10c is out of order, the differential pressure detector 10 is out of order due to abnormal O ₂ and NOx concentrations in the exhaust gas.
The control device 11 performs control to inject water by prioritizing the blockage danger point provided with the other blockage danger point. Further, when all of the differential pressure detectors 10 are out of order, it is possible to perform sequential water injection control from the blockage danger point where the differential pressure detectors 10 on the downstream side are provided to that on the upstream side. It is possible.

Embodiment 3 FIG. 3 shows an explanatory view of the system of this embodiment. The same members as those in FIG. 1 are indicated by the same numbers. This embodiment is effective when the supply of the CWP 120 becomes unstable on the upstream side of the CWP pump 1. In the present embodiment, when the supply of the CWP 120 on the upstream side of the CWP pump 1 becomes unstable, it is expected that the pressure loss in the supply pipe 3 on the upstream side is hardly detected. The control device 11 determines the presence or absence of a dangerous place by the differential pressure detector 10 provided at the outlet of the CWP pump 1 that can detect the relatively reliably, and controls the injection of water into the supply pipe 3 on the upstream side of the CWP pump 1. The subsequent operation is the same as that of the embodiment shown in FIGS. 1 and 2.

[0018]

According to the present invention, the instability of the CWP supply amount can be eliminated even when the CWP property changes during operation, and the worst supply pipe blockage can be prevented in advance. It does not seriously affect the combustion performance of the single-layer boiler. In addition, especially CWP due to a decrease in water content adhering to coal
The CWP supply side can cope with fluctuations in CWP properties such as an increase in viscosity, and the CWP supply pipe can be flexibly arranged.

[Brief description of drawings]

FIG. 1 is a schematic system diagram of a pressurized fluidized bed boiler according to a first embodiment of the present invention.

FIG. 2 is a schematic system diagram of a pressurized fluidized bed boiler according to a second embodiment of the present invention.

FIG. 3 is a schematic system diagram of a pressurized fluidized bed boiler according to a third embodiment of the present invention.

FIG. 4 is a schematic system diagram of a pressurized fluidized bed boiler according to a conventional wet feed system.

[Explanation of symbols]

1 ... CWP pump, 3 ... supply pipe, 10 ... differential pressure detector,
11 ... Control device, 12 ... Water injection pipe, 13 ... Water injection valve,
14 ... O ₂ , NOx concentration detector, 15 ... Differential pressure detection signal,
16 ... O ₂ , NOx concentration detection signal, 17a ... Differential pressure setting signal, 17b ... O ₂ , NOx setting signal, 18 ... Control signal,
101 ... Pressurized fluidized bed boiler, 102 ... Fluid medium particles, 1
03 ... Cyclone, 104 ... Pressure vessel, 105 ... Air dispersion plate, 106 ... Pressurized air, 107 ... Combustion air, 108
... Exhaust gas piping, 109 ... Fluidized bed, 110 ... CWP nozzle, 111 ... CWP adjustment tank, 112 ... Electric motor, 11
3 ... Stirrer, 114 ... Coal, 115 ... Limestone, 116 ...
Water, 120 ... CWP, 121 ... CWP tank, 122 ...
Electric motor, 123 ... stirring blade

Claims (10)

[Claims] 1. A coal-water mixture for a pressurized fluidized bed boiler, which is provided with a pump for pumping a mixed slurry fuel of coal and water and a supply pipe for transporting the fuel, and supplies the coal-water mixed slurry fuel to the pressurized fluidized bed boiler. In the slurry fuel supply device, a differential pressure detector and a water injection pipe are provided in the middle of the coal water mixed slurry fuel supply pipe, and at least one of oxygen concentration and nitrogen oxide concentration detector is provided at the exhaust gas outlet of the pressurized fluidized bed boiler. And a deviation signal between the differential pressure detection signal and the differential pressure setting signal from the differential pressure detector, and a setting signal corresponding to at least one of the oxygen concentration and nitrogen oxide concentration detector detection signals. An additional feature is to provide a water injection control device that controls the amount of water injected into the supply pipe by the deviation signal to adjust the viscosity of the coal-water mixed slurry fuel in the fuel transportation system. Coal water slurry mixture fuel supply system of the fluidized bed boiler. 2. The coal water mixed slurry fuel supply system for a pressurized fluidized bed boiler according to claim 1, wherein the differential pressure detector is provided at at least one blockage danger point of the supply pipe. 3. The differential pressure detector is provided in a supply pipe near an outlet of the fuel pressure pump, and a water injection port to the supply pipe is arranged in a supply pipe upstream of the fuel pressure pump. A coal water mixed slurry fuel supply system for a pressurized fluidized bed boiler as described above. 4. The water injection control device, when the deviation signal between the differential pressure detection signal from the differential pressure detector and the differential pressure setting signal indicates an abnormal value,
When the primary water injection control to the supply pipe is performed and further the deviation signal of at least one of the detection signal from the oxygen concentration and nitrogen oxide concentration detector and the oxygen concentration and nitrogen oxide concentration setting signal shows an abnormal value. The coal water mixed slurry fuel supply device for a pressurized fluidized bed boiler according to claim 1, 2 or 3, wherein secondary water injection control to the supply pipe is performed. 5. The water injection control device prioritizes water injection control by at least one detection signal from the oxygen concentration and nitrogen oxide concentration detectors when the differential pressure detector is out of order. 1. A coal water mixed slurry fuel supply device for a pressurized fluidized bed boiler according to 1, 2, or 3. 6. The water injection control is performed in sequence from the blockage danger point where the differential pressure detector on the downstream side is provided to the blockage danger point where the differential pressure detector on the upstream side is provided. The coal water mixed slurry fuel supply device for a pressurized fluidized bed boiler according to claim 5. 7. A coal water mixed slurry fuel supply method for a pressurized fluidized bed boiler, which supplies a coal water mixed slurry fuel to a pressurized fluidized bed boiler while pumping a coal and water mixed slurry fuel. It is in the fuel transportation system by controlling the amount of water injected into the fuel during the supply depending on the abnormality in the pressure during the fuel supply or the abnormality in at least one of the oxygen concentration and the nitrogen oxide concentration in the exhaust gas of the pressurized fluidized bed boiler. A coal water mixed slurry fuel supply method for a pressurized fluidized bed boiler, which comprises adjusting the viscosity of a coal water mixed slurry fuel. 8. The secondary control of water injection is performed by primary control of water injection due to abnormal pressure during coal-water mixed slurry fuel supply, and further due to abnormalities of at least one of oxygen concentration and nitrogen oxide concentration in boiler exhaust gas. The coal water mixed slurry fuel supply method for a pressurized fluidized bed boiler according to claim 7, wherein the following control is performed. 9. When the detection of the pressure during the supply of the coal water mixed slurry fuel is unsuccessful, priority is given to the water injection control by the abnormality of at least one of the oxygen concentration and the nitrogen oxide concentration in the boiler exhaust gas. Item 7. A coal water mixed slurry fuel supply method for a pressurized fluidized bed boiler according to Item 7 or 8. 10. The coal-water mixed slurry fuel for a pressurized fluidized bed boiler according to claim 9, wherein water injection control is sequentially performed from the downstream danger point on the downstream side toward the upstream danger point on the upstream side. Supply method.