JP3649511B2 - Swelling occurrence prediction detection device and boiler water supply control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a swerling occurrence prediction detection device and a boiler water supply control device applied to a transformer once-through boiler.
[0002]
[Prior art]
A system diagram of a conventional transformer once-through boiler is shown in FIG. The water in the condenser 1 passes through a condensate booster pump 2, a condensate pump 3, a low pressure feed water superheater 4, a deaerator 5, a plurality of boiler feed water pumps 6, and a plurality of feed water control valves 17 in order, and then the high pressure feed water superheater 7. Sent to. Further, the high pressure feed water superheater 7 is sent to the high pressure turbine 12 through the economizer 8, the furnace evaporator tube 9, the furnace outlet bracking water separator 10, and the superheater 11 in this order.
[0003]
The drain of the furnace outlet brackish water separator 10 is sent to the outlet of the high pressure feed water superheater 7 through the brackish water separator drain tank 13, the furnace recirculation pump 14, and the furnace recirculation flow rate control valve 15 in this order. Further, it branches from the outlet of the drain tank 13 and is sent to the condenser 1 through a plurality of steam separator drain tank level control valves 16.
[0004]
In the figure, 51 is a furnace recirculation line, and 52 is a water supply line.
[0005]
A control device for the water supply system is shown in FIG. The output of the load indicator 21 is sent to the feed water control valve 17 or the boiler feed water pump 6 through the adder 22, the high selector 23, the subtractor 25, and the PI controller 26 in order. The output of the main steam pressure control device 20 is sent to the adder 22. Further, the output of the minimum water supply flow rate command device 24 is sent to the high selector 23.
[0006]
The output of the furnace passage flow rate detector 26 provided in the line after the merge of the water supply line 52 and the furnace recirculation line 51 is sent to the subtractor 25.
[0007]
In the above, the load indicator signal from the load indicator 21 and the boiler pressure control correction signal from the main steam pressure controller 20 are added by the adder 22.
[0008]
Next, the higher selector 23 selects the higher one of this signal and the minimum feed water flow rate command signal required for the transformer once-through boiler from the minimum flow rate commander 24 and outputs it to the subtractor 25. The subtracter 25 calculates the deviation between this signal and the furnace passage flow rate signal 26 s from the furnace passage flow rate detector 26 and sends it to the PI controller 26. A control signal is sent from the PI regulator 26 to the feed water control valve 17 or the boiler feed water pump 6, and the furnace passage flow rate is adjusted so that the deviation becomes zero.
[0009]
A control apparatus for the furnace recirculation system is shown in FIG. The output of the drain level meter 28 of the brackish water separator drain tank 13 is sent to a flow rate command function unit 29 and drain valve opening command function units 32, 33, and 34. The output of the flow rate command function unit 29 is sent to the furnace recirculation flow rate control valve 15 through the subtracter 30 and the PI controller 31 in order. The outputs of the drain valve opening command function units 32 to 34 are sent to the brackish water separator drain tank level control valves 16a to 16b.
[0010]
In the above, the flow rate command function unit 29 receives the output of the drain level meter 28 and outputs a recirculation flow rate command signal having characteristics as shown in FIG. The subtractor 30 receives this signal and the output of the recirculation flow rate detector 27 and sends a deviation signal to the PI controller 31. A recirculation valve opening degree control signal is sent from the PI controller 31 to the furnace recirculation flow rate control valve 27, and the recirculation flow rate is adjusted so that the deviation becomes zero. That is, when the drain level becomes α or more, the flow control valve 27 is opened, and when the drain level becomes more than β, the valve opening is adjusted so that the recirculation flow rate becomes 20%.
[0011]
The characteristics of the drain valve opening command function unit (for A valve) 32, (for B valve) 33, and (for C valve) 34 are as shown in FIG. 8, and the drain level is higher than L ₁ or higher. Then, the drain tank level control valve (A valve) 16a is opened, and the drain is also flowed to the condenser 1 side to adjust the level. For example, when the drain level is am, the drain tank control valves 16a (A valve) and 16b (B valve) are fully opened.
[0012]
Note that, as shown in FIG. 9, in a transformer once-through boiler that operates with the boiler pressure continuously changing from a subcritical pressure to a supercritical pressure depending on the load, water and steam are used particularly in a subcritical pressure operation region at low load. In order to protect the furnace tube by the boiling phenomenon in which the coexistence exists, a speed higher than the limit weight flow rate in the supercritical pressure region is required. For this purpose, a furnace outlet fluid, that is, a part of the drain of the brackish water separator 10 is recirculated by a circuit (not shown), mixed with the feed water from the feed water pump 6, and the flow rate passing through the furnace is kept at the limit flow rate. The relationship of the furnace water supply flow rate with respect to the load is expressed as shown in FIG. 10, and the load is kept at the so-called minimum water supply flow rate, that is, the above-mentioned limit weight flow rate up to about 30%. Thereafter, the water supply increases proportionally as the load increases, the furnace recirculation flow rate becomes zero, and the entire amount is supplied from the water supply pump 6.
[0013]
[Problems to be solved by the invention]
In general, when the boiler water is moved from the saturated water to the brackish water mixing region for a while after the burner ignition at the subcritical pressure at the start of the boiler, the specific volume of the rapidly heated bubbles increases, A so-called swelling phenomenon occurs in which the can water is pushed up and the level of the drain tank rises rapidly.
[0014]
However, after the canned water that has been pushed up is discharged by the water drain valve, the water supply in the furnace suddenly decreases, so conversely, the drain level suddenly drops, the water drain valve is fully closed, and the furnace recirculation flow rate also increases. Decrease rapidly. At this time, the above-described water supply control system operates to increase the flow rate of the water supply pump in order to ensure the minimum water supply amount, but the follow-up is delayed and consequently the minimum water supply flow rate is interrupted.
[0015]
Such a decrease in level leads to an emergency protection stop of the recirculation pump, and a decrease in the feed water flow rate leads to an emergency stop of the boiler in terms of boiler furnace protection. In order to prevent this, it is also possible to prevent the level drop and the feed water flow rate drop by manually opening the feed water control valve 17 in accordance with the signs of swelling by careful monitoring of the operator. However, the operation procedure and the like are extremely complicated and practically impossible.
[0016]
[Means for Solving the Problems]
The present invention takes the following means to solve the above problems.
[0017]
(1) A predetermined time when receiving a boiler ignition signal of a steam-flow separator drain tank, a furnace recirculation line connected to the steam-water separator drain tank and a level control line having a level control valve, and a boiler once-through boiler having a boiler water supply line A timer for outputting, a first high signal detector for receiving the opening signal of the level control valve, a first AND element for receiving outputs of the timer and the first high signal detector, and an output of the AND element A set reset device for receiving a set input, a delay timer for receiving the output of the set reset device, a second high signal detector for receiving a furnace passage flow rate signal after joining the boiler water supply line and the furnace recirculation line, A second AND element that receives the outputs of the delay timer and the second high signal detector and sends the output to the reset input of the set reset device. A swelling prediction detection device comprising a child.
[0018]
In the above, the boiler ignition signal is turned on when the boiler is started. Upon receiving this signal, the timer outputs a predetermined time corresponding to the time when the swelling occurs.
[0019]
On the other hand, since the valve opening degree of the level control valve increases with the occurrence of the swelling phenomenon, the first high signal detector that inputs this signal outputs it when the input exceeds a predetermined value. The first AND element sends a set signal to the set reset device when these signals are input simultaneously. The set reset device is set by this signal and outputs a swelling signal.
[0020]
Also, the furnace flow rate signal increases to suppress swelling. The second high signal detector that inputs this signal outputs it when the input exceeds a predetermined value.
[0021]
On the other hand, the delay timer receives the output of the set / reset device, and delays and outputs the time required for the operation of increasing the feed water pump flow rate. When these signals are input simultaneously, the second AND element sends a reset signal to the set reset device. The set reset device is reset by this signal.
[0022]
As described above, the occurrence of swelling at the start of the boiler can be easily and accurately predicted and detected.
[0023]
(2) The brackish water separator drain tank and the drain of the brackish water separator drain tank of a transformer once-through boiler having a furnace recirculation line having a flow control valve connected to the brackish water separator drain tank and a level control line having a level control valve A flow rate command function unit receiving a level signal, an output of the flow rate command function unit and a subtractor receiving a furnace recirculation flow rate signal of the furnace recirculation line, and a flow rate control of the furnace recirculation line receiving an output of the subtractor PI controller for sending a recirculation valve opening control signal to the valve, and a control system for the feed water pump that operates the feed water pump so that the flow rate of the feed water pump is increased by the amount that the flow control valve is throttled and lowered according to the input A changer with a change rate inserted between the flow rate command function unit and the subtractor, and an output of the switch with the change rate A boiler water supply control device comprising: a reduced flow rate signal device to be sent to the end; and the swering occurrence prediction detection device of (1) which sends an output to the control input end of the switch with change rate.
[0024]
In the above, normally, the changer with change rate receives and outputs the output of the flow rate command function unit, and the flow rate control valve is adjusted by the PI controller.
[0025]
When a sign of swering occurs and the output of the swering occurrence predictive detection device is sent to the switch with change rate, the switch with change rate switches the input at a predetermined rate of change and outputs the output of the reduced flow rate signal device . Since the reduced flow rate signal device outputs a flow rate command signal obtained by subtracting the feed water pump flow rate to be increased from the normal recirculation flow rate, this signal is sent to the subtractor. A deviation signal is generated by the subtractor, and a recirculation valve opening degree control signal is sent to the flow rate control valve via the PI controller. The flow control valve is throttled according to the input, and the recirculation flow rate is reduced.
[0026]
It operates so that the feed water pump flow rate is increased by this decrease. This increase proactively suppresses the level drop of the brackish water separator after completion of swering.
[0027]
In this way, the occurrence of the swelling of the boiler is prevented.
[0028]
(3) a load indicator that outputs a load indicator signal of a transformer once-through boiler having a feedwater line having a boiler feed pump and a feedwater control valve and a furnace recirculation line, a main steam pressure control device that outputs a boiler pressure correction signal, A high selector that receives the sum signal of the outputs of the load indicator and the main steam pressure controller and the output of the minimum flow indicator, a furnace passage flow signal after the merge of the feed water line and the furnace recirculation line, and the high selector In the boiler water supply control apparatus, comprising: a subtractor that receives the output of the subtractor; and a PI controller that receives the output of the subtractor and sends a control signal to the boiler feedwater pump or the feedwater control valve. A changer with change rate inserted in between, an increased flow rate signaler that sends output to the input terminal of the changer with change rate, and a control input for the changer with change rate A boiler water supply control device comprising the swering occurrence prediction detection device of (1) to be sent to the end.
[0029]
In the above, the change rate changer usually receives and outputs the output of the minimum flow rate indicator. The high selector receives this signal and the addition signal of the outputs of the load indicator and the main steam pressure control device, and outputs the higher one. The subtracter outputs a deviation signal from this signal and the output of the furnace passage flow rate detector. The PI controller outputs a control signal from this deviation signal to control the flow rate of the water supply line.
[0030]
When a sign of swering occurs and the output of the swering occurrence predictive detection device is sent to the switch with change rate, the switch with change rate switches the input at a predetermined rate of change and outputs the output of the increased flow rate signal device . The increase flow rate signal device outputs a feed water pump flow rate (minimum flow rate + α) signal to be increased.
[0031]
This output is sent to the subtractor via the high selector. A deviation signal is generated by the subtractor, and a control signal is sent to the boiler feed pump or feed control valve via the PI controller. In response to this control signal, the boiler feed pump or the feed water control valve is operated, and the flow rate of the feed water line is increased.
[0032]
This increase proactively suppresses the level drop of the brackish water separator after completion of swering.
[0033]
In this way, the occurrence of the swelling of the boiler is prevented.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
(1) An embodiment of the present invention 1 will be described with reference to FIG. In addition, the part demonstrated in the prior art example attaches | subjects the same number, description is abbreviate | omitted, and demonstrates mainly the part regarding this invention.
[0035]
The valve opening signals 16as, 16bs, 16cs of the brackish water separator drain tank level control valves 16a, 16b, 16c are sent to the first high signal detectors 40a, 40b, 40c, respectively. The outputs of the first high signal detectors 40 a to 40 c are sent to the set input terminal of the set reset device 46 via the OR element 41 and the first AND element 42. The boiler ignition signal 43 s is sent to the AND element 42 through the timer 43.
[0036]
The output of the furnace passage flow rate detector 26 is sent to the reset terminal of the set / reset device 46 via the second high signal detector 44 and the second AND element 45. The output of the set / reset device 46 is sent to the AND element 45 via the delay timer 47.
[0037]
In the above, the boiler ignition signal 43s is turned on when the boiler is started. In response to this signal, the timer 43 outputs a predetermined time corresponding to the time when swelling occurs.
[0038]
On the other hand, since the valve opening degree of each level control valve 16a-16c increases with the occurrence of the sign of swelling, the first high signal detectors 40a-40c that receive the valve opening signals 16as-16cs are input at a predetermined value. Output when above. These outputs are sent to the AND element 42 via the OR element 41. The AND element 42 sends a set signal to the set reset device 46 when the outputs of the timer 43 and the AND element 42 are simultaneously input. The set reset device 46 is set by this signal and outputs a swelling signal 46s.
[0039]
Further, the furnace passage flow rate signal 26s from the furnace passage flow rate detector 26 is increased to suppress swelling. The second high signal detector 44 to which this signal is input outputs when the input is a predetermined value or more.
[0040]
On the other hand, the delay timer 47 receives the output of the set / reset device 46 and delays the output for the time required for the feed water pump flow rate increasing operation. The second AND element 45 sends a reset signal to the set reset device 46 when these signals are input simultaneously. The set reset device 46 is reset by this signal.
[0041]
As described above, the occurrence of signs of swelling during boiler start-up can be detected easily and accurately.
[0042]
(2) An embodiment of the present invention 2 will be described with reference to FIG. In addition, the part demonstrated in the prior art example attaches | subjects the same number, description is abbreviate | omitted, and demonstrates mainly the part regarding this invention.
[0043]
The output of the flow rate command function unit 29 is sent to the subtracter 30 via the change rate switch 48. Further, the output of the reduced flow rate signal device 49 is sent to the input terminal of the switch 48 with a change rate. Further, the output 46 s of the swelling detection prediction device (1) is sent to the control input terminal of the switch 48 with a change rate.
[0044]
In the above, normally, the changer with change rate 48 receives and outputs the output of the flow rate command function unit 29, and the flow rate control valve 15 is adjusted by the PI adjuster 31.
[0045]
When the swelling occurs and the output 46s of the swelling occurrence prediction detection device is sent to the changer with change rate 48, the changer with change rate 48 switches the input at a predetermined change rate and outputs the output of the reduced flow rate signal device 49. Output. The reduced flow rate signal device 49 outputs a flow rate command signal obtained by subtracting the feed water pump flow rate to be increased from the normal recirculation flow rate (for example, 20% (recirculation flow rate) −15% = 5% when increasing 15%). Therefore, this signal is sent to the subtracter 30. A deviation signal is generated by the subtracter 30, and a recirculation valve opening degree control signal is sent to the flow rate control valve 15 via the PI controller 31. The flow control valve 15 is throttled according to the input, and the recirculation flow rate is reduced.
[0046]
On the other hand, the feed water pump 6 is operated by the control system of the boiler feed water pump 6 so that the flow rate of the feed water pump is increased by this decrease. This increased amount prevents the level drop of the brackish water separator 10 after the swering is completed.
[0047]
In this way, the occurrence of the swelling of the boiler is prevented, and a stable start-up is possible.
[0048]
(3) An embodiment of the present invention 3 will be described with reference to FIG. In addition, the part demonstrated in the prior art example attaches | subjects the same number, description is abbreviate | omitted, and demonstrates mainly the part regarding this invention.
[0049]
The output of the minimum flow rate commander 24 is sent to the high selector 23 via the changer 48 with change rate. Further, the output of the increased flow rate device 50 is sent to the input terminal of the change rate switching device 48.
[0050]
Further, the output 46 s of the swelling detection prediction device (1) is sent to the control input terminal of the switch 48 with a change rate.
[0051]
The output of the high selector 23 is sent to the boiler feed pump 6 or the feed water control valve 17 through the subtracter 25 and the PI regulator 26 in order.
[0052]
In the above, the change rate switching unit 48 normally receives and outputs the output of the minimum flow rate indicator 24. The high selector 23 receives this signal and an addition signal of the outputs of the load indicator 21 and the main steam pressure controller 20, and outputs the higher one. The subtracter 25 outputs a deviation signal from this signal and the output of the furnace passage flow rate detector 26. The PI controller 26 outputs a control signal from the deviation signal to control the flow rate of the water supply line 52.
[0053]
When a sign of swelling occurs and the output 46 s of the swelling detection prediction device is sent to the changer with change rate 48, the changer with change rate 48 switches the input at a predetermined change rate and the increase flow rate signal device 50. Output the output. The increased flow rate signal device 50 outputs a feed water pump flow rate (minimum flow rate + flow rate pushed by swering) signal to be increased.
[0054]
This output is sent to the subtracter 25 through the high selector 23. A deviation signal is generated by the subtracter 25, and a control signal is sent to the boiler feed pump 6 or the feed water control valve 17 via the PI controller 26. In response to this control signal, the boiler feed pump 6 or the feed water control valve 17 operates, and the flow rate of the feed water line 52 increases.
[0055]
This increased amount prevents the level drop of the brackish water separator 10 after the swering is completed.
[0056]
In this way, the occurrence of the swelling of the boiler is prevented, and a stable start-up is possible.
[0057]
In this embodiment, the flow rate is increased by a direct feed water pump or a control valve, whereas (2) is controlled indirectly, so that the feed water flow rate compensates for it by reducing the recirculation flow rate. Fast response. Further, the value of the feed water flow rate to be increased is limited to the so-called recirculation flow rate and the range of about 20% of the set value given by the flow rate command function unit 29, whereas the increase flow rate device 50 is limited. There is an effect that a wide range of setting values can be obtained.
[0058]
【The invention's effect】
As described above, the present invention has the following effects.
[0059]
(1) The occurrence of a swelling phenomenon is accurately predicted and detected by the swelling occurrence prediction detection device.
[0060]
(2) The flow of the water supply line is rapidly increased by the output of the swering occurrence prediction detection device, and the level drop of the brackish water separator due to the occurrence of swering is suppressed. Therefore, stable startup of the boiler can be realized.
[Brief description of the drawings]
FIG. 1 is a configuration system diagram of an embodiment of the present invention 1;
FIG. 2 is a configuration system diagram of one embodiment of the present invention 2;
FIG. 3 is a configuration system diagram of one embodiment of the present invention 3;
FIG. 4 is a system diagram of a conventional transformer once-through boiler.
FIG. 5 is a configuration system diagram of a control device for a water supply system of the conventional example.
FIG. 6 is a structural diagram of a conventional furnace recirculation system.
FIG. 7 is an operation explanatory diagram of the conventional example.
FIG. 8 is an operation explanatory diagram of the conventional example.
FIG. 9 is an operation explanatory diagram of the conventional example.
FIG. 10 is an operation explanatory diagram of the conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Condenser 2 Condensate booster pump 3 Condensate pump 4 Low-pressure feed water superheater 5 Deaerator 6 Boiler feed pump 7 High-pressure feed water heater 8 Carbon-saving device 9 Furnace evaporator 10 Furnace outlet steam separator 11 Superheater 12 High pressure Turbine 13 Steam separator drain tank 14 Furnace recirculation pump 15 Furnace recirculation pump flow control valve 16, 16a to 16c Steam separator drain tank level control valve 20 Main steam pressure control device 21 Load indicator 22 Adder 23 High selector 24 Minimum water supply flow rate command unit 25 Subtractor 26 Furnace passage flow rate detector 27 Recirculation flow meter 28, 31 PI controller 29 Flow rate command function unit 30 Subtractor 32-34 Drain valve opening command function unit 40a-40c, 44 High Signal detector 41 OR element 42, 45 AND element 43 Timer 46 Set reset device 47 Delay timer 48 Change rate switching device 49 Reduced flow rate Issue 50 increase the flow rate signal 51 furnace recirculation line 52 water supply line

Claims (3)

  A timer that has a level control line having a furnace recirculation line and a level control valve connected to the brackish water drain tank and a steam feed separator drain tank, and outputs a boiler ignition signal for a predetermined time with a boiler feed water line A first high signal detector for receiving the opening signal of the level control valve, a first AND element for receiving the outputs of the timer and the first high signal detector, and an output of the AND element as a set input A set reset device that receives the output of the set reset device, a second high signal detector that receives a furnace passage flow rate signal after joining the boiler water supply line and the furnace recirculation line, and the delay timer And a second AND element that receives the output of the second high signal detector and sends the output to the reset input of the set reset device. Ete becomes possible swelling occurrence prediction detecting apparatus according to claim. The drain level signal of the brackish water separator drain tank of the transformer once-through boiler with the brackish water separator drain tank and the furnace recirculation line with the flow control valve connected to the brackish water separator drain tank and the level control line with the level control valve. Receiving flow command function unit, subtracter receiving the output of the flow command function unit and the furnace recirculation flow rate signal of the furnace recirculation line, and receiving the output of the subtractor, re-entering the flow control valve of the furnace recirculation line A PI controller for sending a circulation valve opening control signal; and a control system for the feed water pump that operates the feed water pump so that the flow rate of the feed water pump increases by the amount that the flow rate control valve is throttled and lowered according to the input. In the boiler feedwater control device, a changer with change rate inserted between the flow rate command function unit and the subtractor, and an output is sent to the input terminal of the changer with change rate. Reduced flow signaler and the boiler feed water control device, characterized in that the output formed by a swelling occurrence prediction detecting device according to claim 1, wherein sending to the control input of the switch with the same rate of change.   A load indicator for outputting a load indicator signal of a transformer once-through boiler having a feed water line having a boiler feed pump and a feed water control valve and a furnace recirculation line, a main steam pressure control device for outputting a boiler pressure correction signal, and the load indicator A high selector that receives the sum signal of the output of the steam generator and the main steam pressure control device and the output of the minimum flow indicator, the furnace flow rate signal after the merge of the feed water line and the furnace recirculation line, and the output of the high selector Inserted between the minimum flow rate commander and the high selector in a boiler feedwater control device having a subtractor for receiving and a PI controller for receiving the output of the subtractor and sending a control signal to the boiler feedwater pump or the feedwater control valve Switch with change rate, an increased flow rate signaler that sends output to the input end of the switch with change rate, and output to the control input end of the switch with change rate Boiler feed water control apparatus characterized by comprising a swelling occurrence prediction detecting apparatus according to claim 1.

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