JP4507098B2 - Fluid circulation operation equipment and operation method for supercritical constant pressure once-through boiler - Google Patents

Description

  The present invention relates to a supercritical pressure constant pressure once-through boiler of a thermal power plant, and a part of the fluid is returned to the boiler feed water from the furnace wall outlet and circulated to ensure the flow rate through the furnace wall, and the minimum operable output is achieved. The present invention relates to a fluid circulation operation control circuit (equipment) of a supercritical pressure constant pressure once-through boiler suitable for lowering and a control method thereof.

  The minimum load restriction in the supercritical pressure constant pressure once-through boiler to which the present invention is applied is mostly due to the restriction of the flow rate of the minimum passage fluid required for the boiler furnace wall. To put it simply, the boiler furnace wall has a large number of heat transfer tubes arranged in parallel on the fluid path.If the fluid flow rate decreases, the differential pressure on the furnace wall decreases, and the difference in fluid flow rate that occurs between the heat transfer tubes The heat transfer tube, which becomes large and difficult to flow, overheats and causes tube leak.

  When operating at a load lower than the minimum load limit caused by the furnace wall fluid flow restriction, the amount of fluid flowing from the furnace wall outlet is reduced to reduce the evaporation while maintaining the furnace wall fluid flow rate above the minimum passage flow restriction. A method of circulating the furnace wall by returning the part to the boiler inlet has been filed in the past.

  Japanese Patent Publication No. 39-18455, Japanese Patent Publication No. Sho 56-16002, and Japanese Patent Publication No. Sho 62-44161 show a circulation system for returning a part of fluid from the furnace outlet to the furnace inlet. This is a method in which a pump is installed not in a circulation system but in a system of main fluid flow paths so that a part of the fluid is circulated from the furnace outlet to the furnace inlet. For this reason, the forced circulation pump needs to have a capacity that is equal to or greater than the furnace minimum passage flow rate, and a large pump capacity is required. Japanese Examined Patent Publication No. 39-18456 discloses a method of installing and circulating an ejector pump in a system that circulates from the furnace outlet to the furnace inlet, but only describes that it is feasible.

  None of these patent application inventions describes means for ensuring the required amount of fluid to be circulated from the furnace outlet to the furnace inlet. When there is a load change in the boiler, the fluid enthalpy fluctuates dynamically at both the furnace inlet and outlet, and the furnace inlet flow rate, enthalpy and furnace heat recovery amount change due to the influence of circulating water even at the start of circulation operation. Also changes.

  In addition, pump characteristics change if the fluid temperature condition changes in any type of pump, so if the fluid state quantity fluctuates, the circulation flow rate will fluctuate. Means for ensuring the necessary circulating flow rate are not considered.

  In the invention described in Japanese Patent Publication No. 6-50163, as the starting system of the transformer once-through boiler, all of the furnace outlet fluid is passed through the brackish water separator, and the saturated water and the saturated steam are separated from the fluid. The structure which returns to boiler feed water with a circulation pump is described. In order to prevent saturated water from causing cavitation in the boiler circulation pump, a certain amount of low-temperature water in front of the high-pressure feed water heater is placed in the fluid at the boiler recirculation pump inlet to bring the boiler recirculation pump inlet water into a subcooled state. Yes.

The technology of this patent application invention is used in the subcritical state of the transformer once-through boiler, the boiler recirculation pump is flow controlled at the level of the brackish water separator, and the system is completely different from the constant pressure once-through boiler, but for saturated water If a certain amount of cold water is added, it will surely be in a subcooled state, and the boiler recirculation pump inlet fluid will not always fluctuate much at a temperature slightly lower than the saturation temperature. That is, in the variable once-through boiler, it is not necessary or considered that the fluid specific volume at the inlet of the boiler recirculation pump dynamically varies.
Japanese Examined Patent Publication No. 39-18455 Japanese Patent Laid-Open No. 56-16002 Japanese Examined Patent Publication No. 62-44161 Japanese Examined Patent Publication No. 39-18456 Japanese Examined Patent Publication No. 6-50163

  What is common to the prior art is that changes in pump characteristics that occur when the boiler state quantity fluctuates dynamically, such as when a load changes or when a circulation operation starts, are not taken into account. Therefore, when the prior art is applied to the constant pressure once-through boiler that is the subject of the present invention, there is a drawback that the circulating flow rate of the fluid fluctuates.

  In a constant-pressure once-through boiler, the enthalpy of the fluid flowing into the boiler recirculation pump is also high because the enthalpy is high without steam separation and the fluid with fluctuations in the boiler state is circulated into the furnace inlet or boiler inlet. It may be used in an area where the specific volume is high and changes. When entering the region where the specific volume of the fluid is increased, the discharge pressure and flow rate characteristics of the boiler recirculation pump are lowered, and in some cases, the boiler recirculation pump without sufficient tolerance may not discharge. In that case, since the minimum feed water flow rate to the boiler cannot be secured, the boiler is urgently stopped.

  An object of the present invention is to provide a fluid circulation operation facility and a method for operating a supercritical pressure constant pressure once-through boiler that controls the fluid conditions flowing into the boiler recirculation pump and ensures the minimum feed water flow rate required for the furnace. It is.

In order to solve the above problems, the present invention uses the following solution means.
The invention according to claim 1 includes a plurality of heat transfer tubes including a economizer disposed in a furnace, a furnace wall and an evaporator and a superheater disposed in the furnace, the economizer, the furnace wall, and the evaporation A boiler feed pipe (2) for sequentially supplying water for steam generation to the heat transfer pipe including the heater and superheater, and boiler recirculation water from the furnace wall outlet in the supercritical pressure state or the heat transfer pipe at the downstream position. In a fluid circulation operation facility of a critical pressure constant pressure once-through boiler for obtaining constant pressure steam in a supercritical pressure state having a boiler recirculation pump (21) for recirculation to a boiler feed pipe (2), the boiler recirculation pump In order to extract the boiler recirculation water, which is a part of the fluid that cannot be separated by brackish water in a supercritical pressure state, from the heat transfer pipe at the furnace wall outlet using (21) and return it to the boiler feed pipe (2), Boiler recirculation pump (from downstream heat transfer tube) A boiler recirculation extraction pipe (30, 31) connected to the inlet of 1), a boiler recirculation pump outlet pipe (22, 23) connecting the outlet of the boiler recirculation pump (21) and the boiler feed pipe (2); Boiler recirculation which extracts cooling water which is a part of the feed water branched from the boiler water supply pipe (20) and connects to the middle of the boiler recirculation discharge pipe (30, 31) or the inlet of the boiler recirculation pump (21) A water cooling pipe (10, 11), flow rate detection means (14, 26, 34) provided in at least two of the three pipes (30, 31; 22, 23; 10, 11), This is a fluid circulation operation facility of a supercritical pressure constant pressure once-through boiler provided with fluid flow rate adjusting means (12, 24) provided in two pipes.

In the first aspect of the invention, the flow rate of the three pipes (30, 31; 22, 23; 10, 11) is measured for the flow rate of the fluid.
Cooling water flow rate (102) + boiler recirculation water flow rate (103)
= Boiler recirculation pump discharge flow rate (104)
Therefore, since the flow rate of the remaining one pipe can be understood no matter which two pipes are measured, in the present invention, the flow rate is measured with at least two pipes. In practice, a flow meter is attached to the pipe whose flow rate is to be controlled. In FIG. 12, the boiler recirculation flow rate control valve 24 is attached to the pipes 22 and 23 to adjust the flow rate of the boiler recirculation pump discharge water (W4). Therefore, the flow meter (33) is attached to the boiler recirculation extraction pipe (30, 31).

  On the other hand, the flow rate adjusting valve is provided on at least two of the three pipes (30, 31, 22, 23, 10, 11) in the same manner as the flow meter, so that the flow rate of the three pipes can be adjusted. First, the boiler recirculation pump flow rate control valve (24) attached to the outlet side of the boiler recirculation pump (21) is essential. This is because, for example, when the flow rate is adjusted at two locations of the cooling water flow rate control valve (12) and the flow rate control valve attached to the boiler recirculation extraction pipe (30), the boiler recirculation pump ( 21) The boiler recirculation pump discharge water (W4) is adjusted by lowering the inlet pressure of 21), but if this is actually done, cavitation occurs due to the pressure drop at the inlet of the pump (21), Damage to the pump (21) occurs. Special care is required here because of its high enthalpy.

  Accordingly, (a): a combination of a pump recirculation flow rate control valve (24) and a cooling water flow rate control valve (12), or (b): a pump recirculation flow rate control valve (24) and a boiler recirculation extraction pipe (30, 31). ) Will be one of the valves installed. However, (b) cannot be realized. This is because the boiler feed pipe (2) is the boiler inlet and has a higher pressure than the furnace outlet from which the boiler recirculation extraction pipe (31) is taken out. The mixing ratio of the cooling water (W2) and the boiler recirculation water (W3) can be adjusted only by inserting the flow rate adjusting valve (12) into the boiler recirculation water cooling pipe (10, 11) having a higher pressure and throttling. If the cooling water flow control valve (12) is removed and the valve is inserted into the lower pressure boiler recirculation extraction pipe (30, 31), only the cooling water (W2) flows and the boiler recirculation water (W3) does not flow. It cannot be recycled.

  The invention described in claim 2 includes a economizer disposed in the furnace, a furnace wall, a plurality of heat transfer tubes including an evaporator and a superheater disposed in the furnace, the economizer, the furnace wall, the evaporation A boiler feed pipe (2) for sequentially supplying water for steam generation to the heat transfer pipe including the heater and superheater, and boiler recirculation water from the furnace wall outlet in the supercritical pressure state or the heat transfer pipe at the downstream position. In the fluid circulation operation facility of a critical pressure constant pressure once-through boiler for obtaining constant pressure steam in a supercritical pressure state equipped with a boiler recirculation pump (21) for recirculation to a boiler feed pipe (2), the boiler recirculation The pump (21) is a pump having a fluid flow rate adjusting function, and the boiler recirculation that is a part of the fluid that cannot be subjected to brackish water separation in a supercritical pressure state from the heat transfer pipe at the furnace wall outlet using the boiler recirculation pump (21). Remove water and return to boiler feed pipe (2) Therefore, a boiler recirculation extraction pipe (30, 31) connected to the inlet of the boiler recirculation pump (21) from the furnace wall outlet or the heat transfer pipe at a downstream position thereof, the outlet of the boiler recirculation pump (21), and the boiler feed water A boiler recirculation pump outlet pipe (22, 23) connected to the pipe (2) and a cooling water which is a part of the feed water branched from the boiler feed water pipe (2) to extract the boiler recirculation discharge pipe (30, 31) ) Or the boiler recirculation water cooling pipe (10, 11) connected to the inlet of the boiler recirculation pump (21) and the boiler recirculation extraction pipe (30, 31) or the boiler recirculation water cooling pipe (10, 11). 11) is a fluid circulation operation facility of a supercritical pressure constant pressure once-through boiler provided with a fluid flow rate adjusting means (12) provided in at least one of the pipes.

  The invention described in claim 3 is a method for operating the fluid circulation facility of the supercritical pressure constant pressure once-through boiler according to claim 1 or 2, wherein the fluid for returning boiler recirculation water from the furnace wall outlet to the boiler feed pipe (2) In the circulation operation state, the flow rates of the boiler recirculation water with high enthalpy and the low-temperature cooling water that cannot be separated by brackish water with supercritical pressure are changed to the boiler recirculation pump (21) and the three pipes (30, 31; 22, 23). The fluid flow rate adjusting means (12, 24 or 34) provided in at least one of the pipes 10 and 11) to adjust the flow rate of the fluid to ensure the necessary boiler recirculation water flow rate, This is a method for operating a fluid circulation facility of a supercritical pressure constant pressure once-through boiler having a function of suppressing the fluid temperature (109) at the inlet of the recirculation pump (21) to a specified value or less.

  The invention according to claim 4 is the boiler recirculation water flow rate flowing through the boiler recirculation extraction pipe (30, 31), the boiler recirculation pump outlet pipe (22, 23) and the boiler recirculation water cooling pipe (10, 11), respectively. (103), adjusting at least two of the discharge flow rate (104) and the cooling water flow rate (102) of the boiler recirculation pump (21) to the respective flow rate target values, and the respective flow rate target values are circulated. The supercritical pressure according to claim 3, wherein a minimum feed water flow rate required for the furnace wall is secured over the entire range, and the inlet fluid temperature (109) of the boiler recirculation pump (21) is maintained in a temperature range of 380 ° C or lower. This is a method for operating a fluid circulation facility of a constant pressure once-through boiler.

According to the fifth aspect of the present invention, when the boiler recirculation pump inlet fluid temperature (109: signal 29) becomes higher than the set value, (a) a predetermined value obtained in accordance with the boiler output command (50) is determined. The opening of the cooling water flow rate adjusting means (12) is increased so that the deviation (signal 55) between the cooling water flow rate setting value (signal 52) and the actual cooling water flow rate (signal 16) becomes zero, and the cooling water flow rate (102 : Control to increase signal 16), or (b) Control of cooling water flow rate (102: signal 16) by the control of (a) and predetermined according to boiler output command (50) When the actual boiler recirculation pump inlet fluid temperature (109: signal 29) is larger than the boiler recirculation pump inlet temperature upper limit setting value (signal 67), the boiler recirculation pump inlet temperature upper limit setting value (signal 67) And the boiler recirculation pump inlet fluid temperature (signal 72) according to the deviation (signal 70) between the actual boiler recirculation pump inlet fluid temperature (109: signal 29) (signal 70). 109: Signal 29) is used in combination with control for increasing the cooling water flow rate (102: signal 16) until the boiler recirculation pump inlet temperature upper limit set value (signal 67) is lowered. The operation method of the fluid circulation facility of the supercritical pressure constant pressure once-through boiler according to claim 4, which has a function of increasing the signal 16).

  According to the sixth aspect of the present invention, when the boiler recirculation pump inlet fluid temperature (109: signal 29) is increased and the cooling water flow rate (102: signal 16) is increased, (a) the actual boiler recirculation pump When the inlet fluid temperature (109: signal 29) is larger than the boiler recirculation pump inlet temperature upper limit setting value (signal 67), boiler recirculation determined in advance based on both the temperature deviations (signal 70). Deviation between a pump inlet fluid temperature correction value (signal 72) between a boiler recirculation pump discharge flow rate setting value (signal 81) and an actual boiler recirculation pump discharge flow rate (signal 28) determined in advance according to the output command (50). (B) added to (signal 84), or (b) boiler recirculation pump inlet having a value of 0 to 1 preset in the boiler recirculation pump inlet fluid temperature correction value (signal 72) The correction value (signal 96) obtained by multiplying the degree correction control gain (signal 94) is added to the deviation value (signal 84) of the boiler recirculation pump discharge flow rate (104: signal 28), thereby discharging the boiler recirculation pump. 6. The boiler recirculation pump discharge flow rate (104: signal 28) is increased by an amount equal to or less than the amount of increase in the cooling water flow rate by correcting the water discharge flow rate (104: signal 29) in the increasing direction. It is an operation method of the fluid circulation facility of the described supercritical pressure constant pressure once-through boiler.

  According to the seventh aspect of the present invention, the cooling water flow rate adjusting means (12) sets the cooling water flow rate lower limit value (signal 74) predetermined in accordance with the output command (50) as the lower limit value (102: signal The operation method of the fluid circulation facility of the supercritical pressure constant-pressure once-through boiler according to any one of claims 4 to 6, wherein 16) is controlled.

  According to the eighth aspect of the present invention, a predetermined inlet temperature setting value (signal 76) of the boiler recirculation pump (21) corresponding to the boiler output command (50) and the inlet fluid temperature (109 of the actual boiler recirculation pump 21). : The deviation (signal 77) from the signal 29) becomes zero, and the cooling water flow rate adjusting means (signal 79) is set based on the predetermined upper limit setting value (signal 79) of the cooling water flow rate (102: signal 16). The operation of the fluid circulation facility of the supercritical pressure constant pressure once-through boiler according to claim 3, wherein the boiler recirculation pump inlet fluid temperature (109: signal 29) is controlled by adjusting the cooling water flow rate (102: signal 16) according to 12). Is the method.

  The invention according to claim 9 is: (a) the boiler recirculation water flow detection means (34) provided in the boiler recirculation discharge pipe (30) directly detects the boiler recirculation water flow (signal 35); Or (b) the boiler recirculation pump discharge water flow rate (104: signal 28) detected by the boiler recirculation pump discharge flow rate detection means (26) provided in the boiler recirculation pump outlet pipe (22, 23). The cooling water flow rate (102: signal 16) detected by the cooling water flow rate detection means (14) provided in the recirculation water cooling pipe (10, 11) is subtracted to obtain the boiler recirculation water flow rate (103: signal 35). Thus, the obtained boiler recirculation water flow rate (103: signal 35) matches the boiler recirculation flow rate setting value (signal 98) determined in advance according to the boiler output command (50). Boiler recirculation flow rate control means (24) according to boiler recirculation pump discharge water flow rate (104: the signal 92) is a third aspect supercritical pressure once-through boiler operation method of fluid circulation equipment according to regulate.

  A tenth aspect of the present invention is an operation method of a fluid circulation operation facility for a supercritical pressure constant pressure once-through boiler according to the first or second aspect, wherein a constant flow of cooling water is supplied to a boiler recirculation water cooling pipe (10, 11). A supercritical pressure constant pressure once-through boiler in which two or more predetermined fixed opening setting values (signals 59, 60, 61) used for flowing (W2) are provided in the cooling water flow rate adjusting means (12). This is an operation method of the fluid circulation facility.

  According to the eleventh aspect of the present invention, at the start of the boiler recirculation water circulation operation, the flow rate adjustment performed by the cooling water flow rate adjusting means (12) is set to a predetermined initial set value (signal 59), and the boiler recirculation pump ( 21) After starting the cooling water flow rate adjusting means (12) at the timing when the boiler recirculation water temperature (108) obtained by mixing the cooling water (W2) with the boiler recirculation water (W3) tends to increase. The set value (signal 59) is switched to a set value (signal 60) that has a relatively higher flow rate than the initial set value (signal 59), and the circulation operation of the boiler recirculation water (W3) is stopped to perform a once-through operation. When switching to, the flow rate adjustment performed by the cooling water flow rate adjustment means (12) remains at the set value (signal 60), and then the flow rate performed by the boiler recirculation pump flow rate adjustment means (24). The operation is performed at the lowest flow rate at a predetermined initial setting value (signal 88), the flow rate adjustment performed by the boiler recirculation pump flow rate adjusting means (24) is stopped (signal 87) after the state is stabilized, and then the boiler After the recirculation pump (21) is stopped and the initial set value (signal 88) of the boiler recirculation pump flow rate adjusting means (24) is selected in the middle of its operation, the cooling water flow rate adjusting means (12) The operation method of the fluid circulation equipment of the supercritical pressure constant pressure once-through boiler according to claim 10, wherein the set value (signal 60) is switched to a predetermined opening degree setting value (signal 61).

  According to the first aspect of the present invention, it is possible to perform a fluid circulation operation of a supercritical pressure constant pressure once-through boiler that can perform a circulation operation that is stable and resistant to disturbance, and can obtain a wide output operation range as compared with a once-through state.

  According to the invention described in claim 1, by using the boiler recirculation pump (21) having a fluid flow rate adjustment function, the fluid flow rate adjustment function (boiler recirculation extraction pipe (30, 31) or boiler recirculation water) By controlling the fluid flow rate adjusting means (12 or 24) provided in at least one of the cooling pipes (10, 11)), the fluid circulation operation of the boiler can be controlled.

  According to the second aspect of the present invention, when the boiler recirculation pump (21) itself is a pump having a fluid flow rate adjusting function, the recirculation pump discharge flow rate (104) is controlled by controlling the rotational speed of the boiler recirculation pump (21). ) Can be adjusted, the boiler recirculation pump flow control valve (24) can be omitted. In that case, the control circuit for controlling the opening degree of the boiler recirculation pump flow rate control valve (24) according to the first aspect of the present invention can be used as it is as a control circuit for controlling the rotational speed of the recirculation pump (21).

  According to the invention described in claim 3, in the fluid circulation operation state in which the boiler recirculation water is returned from the furnace wall outlet to the boiler feed pipe (2), the flow rate of the fluid passing through the furnace wall is the lowest flow rate even if the boiler operation output is lowered. It can be reliably maintained above the limit.

  According to the invention described in claim 4, in addition to the effect of the invention described in claim 3, the inlet fluid temperature of the boiler recirculation pump (21) can be made relatively small in change in specific volume.

  According to the fifth aspect of the invention, in addition to the effect of the fourth aspect of the invention, when the boiler recirculation pump inlet fluid temperature (109) becomes higher than the set value, the temperature can be effectively lowered. it can.

   According to the sixth aspect of the invention, in addition to the effect of the fifth aspect of the invention, when the boiler recirculation pump inlet fluid temperature (109) is increased and the cooling water flow rate is increased, the furnace wall fluid flow rate is increased. Can be suppressed.

  According to the invention of claim 7, in addition to the effect of the invention of any of claims 4 to 6, it is prevented that the cooling water flow rate is unnecessarily lowered and the boiler circulation pump inlet fluid temperature is raised. can do.

  According to the eighth aspect of the present invention, the boiler recirculation pump inlet fluid temperature (109) can be maintained at the specified value (temperature setting with a small change in specific volume) by the cooling water flow rate adjusting means (12).

According to invention of Claim 9, a boiler recirculation water flow rate (103) is securable.
According to the invention of claim 10, two or more predetermined fixed opening set values (signals 59, 60, 61) provided with two or more different set values provided in the cooling water flow rate adjusting means (12). Can be switched according to operating conditions and state quantities at the start / end of the circulation operation, and the temperature change of the boiler recirculation pump inlet fluid can be reduced.

   According to the eleventh aspect of the present invention, at the start of the circulating operation of the boiler recirculation water, the cooling water flow rate is the timing at which the boiler recirculation water temperature (108) obtained by mixing the cooling water with the boiler recirculation water tends to increase. Is increased from the initial setting value (signal 59) to the settling setting value (signal 60), as shown in FIG. 6, the boiler recirculation water mixing is performed without changing the boiler recirculation pump inlet fluid temperature 109. It is possible to shift from the initial mixed state to a balanced state after circulation, and when the circulation operation of the boiler recirculation water is stopped and switched to the once-through operation, the flow rate adjustment performed by the cooling water flow rate adjustment means (12) is performed. The settling value (signal 60) remains unchanged, and then the flow rate adjustment performed by the boiler recirculation pump flow rate adjusting means (24) is performed at the minimum flow rate with the initial setting value (signal 88). After the state is stabilized, the flow rate adjustment performed by the boiler recirculation pump flow rate adjusting means (24) is stopped, and then the boiler recirculation pump (21) is stopped. During the operation, the boiler recirculation pump flow rate adjustment means (24) After the initial set value (signal 88) is selected, the setting value (signal 60) of the cooling water flow rate adjusting means (12) is switched to the predetermined end opening set value (signal 61). The boiler recirculation pump inlet fluid temperature 109 does not change much as shown in FIG. 9 and can be gradually stabilized at the warming water temperature.

Hereinafter, a fluid circulation operation facility and its control of a supercritical pressure constant pressure once-through boiler according to an embodiment of the present invention will be described.
FIG. 1 shows a schematic diagram of a main part of a fluid circulation operation facility for a boiler according to this embodiment, and FIG. 2 shows a flow rate balance during the fluid circulation operation according to this embodiment.

  In the boiler fluid circulation operation facility shown in FIG. 1, water supplied to the boiler enters the economizer (not shown) from the economizer inlet header 6 and is heated by the economizer, and then the economizer outlet pipe. Entering the furnace wall 1 (formed by the furnace water wall made of a plate material connecting the plurality of heat transfer tubes and the heat transfer tubes) from the header 7 sequentially through the water wall downcomer 5 and the furnace wall inlet tube header 114, After being heated by the furnace wall 1, the furnace wall outlet header 8 (the furnace wall outlet 8 shown in FIG. 1 hits the position of the primary superheater inlet header 9, but has the same fluid conditions as the furnace wall outlet header 8. ) To the primary superheater inlet header 9, heated by the primary superheater, further heated by the secondary superheater (not shown), supplied to the steam turbine, and used for power generation.

The fluid circulation operation facility of the embodiment shown in FIG. 1 includes boiler recirculation extraction pipes 30 and 31 that branch the high-temperature boiler recirculation water W3 from the furnace wall outlet header 8 and send it to the mixer 20; A boiler recirculation check valve 32 provided between the pipes 30 and 31, a boiler recirculation water cooling pipe 10 and 11 that branches from the boiler feed water pipe 2 and sends the cooling water W2 to the mixer 20, Cooling water flow rate control valve 12 for adjusting the flow rate of cooling water W2 provided in pipes 10 and 11, cooling water flow meter 13 for measuring flow rate, and fluid mixed in mixer 20 (boiler recirculation pump inlet water 47) A boiler recirculation pump (BRP) 21 that introduces and boosts the pressure, and a boiler recirculation pump outlet pipe 22 that feeds the boiler recirculation pump discharge water W4 boosted by the pump 21 to the boiler feed water pipe 2, 3, a boiler recirculation pump flow rate adjustment valve 24 for adjusting the flow rate of boiler recirculation pump discharge water W4 provided in the pipes 22 and 23, a boiler recirculation pump discharge flow meter 25, and the cooling water flow rate adjustment valve 12 The control circuit S2 and the control circuit S2 of the boiler recirculation pump flow rate adjustment valve 24 are provided.
It should be noted that elements, valve drive mechanisms, stop valves, and the like attached to the device alone, such as a BRP circulation valve, are not shown and explanation of the operation is omitted.

  When circulating the fluid of the boiler in the above configuration, the boiler recirculation water W3 is returned from the furnace wall outlet header 8 to the boiler feed water pipe 2 by the discharge pressure of the boiler recirculation pump 21. However, since the boiler recirculation water W3 is high temperature and has a large specific volume, if it is returned to the boiler recirculation pump 21 as it is, the boiler recirculation pump 21 needs to be enlarged. Therefore, the mixer 20 is provided on the inlet side of the boiler recirculation pump 21 to mix the hot boiler recirculation water W3 and the low temperature boiler feed water W1 to lower the temperature of the boiler recirculation water W3. Put in.

  The boiler recirculation pump 21 may be a rotational speed control type pump having a fluid flow rate adjusting function. In this case, the recirculation pump discharge flow rate 104 is controlled by the rotational speed control of the boiler recirculation pump 21. Therefore, the boiler recirculation pump flow rate adjustment valve 24 can be omitted. In that case, the control circuit for controlling the opening degree of the boiler recirculation pump flow rate control valve 24 becomes the control circuit for controlling the rotational speed of the recirculation pump 21 as it is.

Adjustment of each circulation flow rate of the cooling water flow rate 102, the boiler recirculation water flow rate 103, and the boiler recirculation pump discharge flow rate 104 shown in FIG. 2 is performed as follows.
That is, the boiler recirculation pump discharge flow rate 104 is controlled by the boiler recirculation pump flow rate adjustment valve 24, the cooling water flow rate 102 is controlled by the cooling water flow rate adjustment valve 12, and the boiler recirculation water flow rate 103 is discharged from the boiler recirculation pump flow rate. It is determined as a flow rate difference between the flow rate 104 and the cooling water flow rate 102.

  Here, the flow rate balance during the fluid circulation operation will be described with reference to FIG. The horizontal axis of the graph of FIG. 2 is a boiler output command. For example, in the case of a thermal power plant, a target value or a command value of a generator output (actually, a signal when the power plant receives the output command is a generator output command). There are various types of signals up to the output target signal used for control, but it is preferable to use an output command before the correction signal due to the frequency or power flow of the power system is applied.

  FIG. 2 shows an example in which the boiler output command 25% is a switching output between the circulation operation and the once-through operation, and the once-through / circulation switching operation is performed at the boiler output of 25%, and the circulation operation is performed when the output is 25% or less.

  Since the boiler recirculation water W3 returns from the furnace wall outlet header 8 to the boiler feed pipe 2, the boiler inlet feed water flow rate 101 passing through the furnace wall 1 is the total flow rate of the feed water pump feed water flow rate 111 and the boiler recirculation water flow rate 103. . The boiler recirculation pump discharge flow rate 104 is the sum of the boiler recirculation water flow rate 103 and the cooling water flow rate 102, and the cooling water flow rate 102 is supplied from the boiler recirculation water cooling pipe 11 branched from the boiler feed pipe 2 to the mixer 20. Since it returns to the boiler feed pipe 2 via the boiler recirculation pump 21, it does not affect the water supply balance of the boiler body.

  That is, in this supercritical pressure constant pressure boiler, it is necessary to ensure the amount of water supply so that the minimum amount of water flows through the furnace wall 1 even during low load operation, so when the 25% output is the minimum amount of water supply. If the load is further reduced to 15%, the water supply amount W1 and the boiler furnace fuel supply amount are also reduced from 25% to an amount corresponding to 15%, but it is necessary to secure the minimum water supply amount. Therefore, the boiler recirculation pump 21 extracts 10% (= 25-15)% of the output from the boiler recirculation water extraction pipes 30 and 31 branched from the furnace wall outlet header 8, and the circulation operation is performed. At this time, since the boiler recirculation water extracted from the boiler recirculation water extraction pipes 30 and 31 returns to the feed water pipe 2, the above-mentioned amount discharged from the boiler while maintaining the flow rate flowing through the furnace wall 1 at 25%, the boiler output is 15%.

  In the feed water flow characteristics in each output state shown in FIG. 2, the boiler feed water flow rate 101 can secure the minimum feed water flow rate to the boiler body, and the specific volume changes at the inlet fluid temperature 109 of the boiler recirculation pump 21. It is planned to be balanced so that it is kept in a low temperature range.

The fluid circulation operation equipment, control circuit, and signal behavior of the supercritical constant pressure once-through boiler of this embodiment will be described below.
First, a basic control method during fluid circulation operation will be described with reference to FIGS. Regarding the control of the boiler recirculation pump flow rate adjustment valve 24, the boiler recirculation pump flow rate adjustment is performed so that the planned fluid flow rate can be obtained with the planned flow rate of the boiler recirculation pump discharge flow rate 104 as shown in FIG. The opening degree of the valve 24 is automatically controlled. Specifically, a boiler recirculation pump discharge flow rate setting signal 81 corresponding to the boiler output command 50 is generated in the boiler recirculation pump discharge flow rate setting function 80, and the boiler recirculation pump discharge flow rate measuring device 26 using the adder / subtractor 83. The controller 85 generates a boiler recirculation pump discharge flow rate deviation signal 84 by taking the difference from the boiler recirculation pump discharge flow rate signal 28 obtained in step S3 so that the boiler recirculation pump discharge flow rate deviation signal 84 becomes zero. Feedback control is performed, and the boiler recirculation pump discharge flow rate 104 is controlled by the boiler recirculation pump flow rate adjustment valve 24.

  Similarly, for the cooling water flow rate control, the opening degree of the cooling water flow rate control valve 12 is automatically controlled so that the planned flow rate as shown in FIG. Specifically, a cooling water flow rate setting signal 52 corresponding to the boiler output command 50 is generated in the cooling water flow rate setting function 51, and the cooling water flow rate signal 16 obtained by the cooling water flow rate measuring instrument 14 using the adder / subtractor 54. The cooling water flow deviation signal 55 is generated by taking the difference between the above and the feedback control by the controller 56 so that the cooling water flow deviation signal 55 becomes zero, and the cooling water flow control valve 12 controls the cooling water flow 102. The

  In the case of using the above-described control method with the planned flow rate as a control target, each flow rate (boiler inlet water supply flow rate 101, cooling water flow rate 102, The behavioral analysis of the boiler recirculation water flow rate 103, the boiler recirculation pump discharge flow rate 104, and the feed water feed water flow rate 111) is shown, and FIG. 4 shows the flow rates corresponding to the output command 100 when a load drop is performed during fluid circulation operation. The behavioral analysis of is shown.

  Each of the flow rates shown in FIGS. 3 and 4 smoothly transitions, and there is little overshoot or undershoot in both the temperature 109 of the boiler recirculation pump inlet fluid and the specific volume 110 of the boiler recirculation pump inlet fluid. This is an appropriate control method.

  However, when actually operating the plant, it is necessary to consider how to deal with disturbances and fluctuations. Although the above control method controls only the flow rate of the fluid, it needs to be incorporated into the control in consideration of the case where the boiler recirculation pump inlet fluid temperature 109 temporarily rises.

  In the embodiment shown in FIG. 1, a boiler recirculation pump inlet temperature upper limit setting signal 67 is generated according to the boiler output command 50 by a boiler recirculation pump inlet temperature upper limit function 66, and the recirculation pump inlet temperature upper limit setting signal 67 is added or subtracted. The difference between the boiler recirculation pump inlet fluid temperature signal 29 obtained by the boiler recirculation pump inlet temperature measuring device 27 using the condenser 69 is taken as a boiler recirculation pump inlet temperature upper limit deviation 70, and the boiler recirculation pump inlet fluid is obtained. When the value of the temperature signal 29 is larger than the value of the boiler recirculation pump inlet temperature upper limit setting signal 67, the boiler recirculation pump inlet fluid temperature correction signal 72 (+ signal) is added / subtracted by the feedback control by the controller 71. In addition, until the boiler recirculation pump inlet fluid temperature signal 29 decreases to the boiler recirculation pump inlet temperature upper limit setting signal 67 Corrected-ring water flow rate control valve position command 65 in the increasing direction to increase the cooling water flow rate 102.

  The boiler recirculation pump inlet temperature upper limit setting signal 67 is preferably set to 380 ° C. or lower, and is preferably set to 360 ° C. or lower (eg, 350 ° C.) due to fluctuations in control and an increasing tendency of the specific volume.

  Here, since the boiler recirculation water flow rate 103 is the difference between the boiler recirculation pump discharge flow rate 104 and the cooling water flow rate 102 as described above, the cooling water flow rate 102 increases while the boiler recirculation pump discharge flow rate 104 remains constant. As a result, the boiler recirculation water flow rate 103 decreases. Therefore, in order to simultaneously increase the boiler recirculation pump discharge flow rate 104, the boiler recirculation pump inlet fluid temperature correction signal 72 is also added to the adder / subtractor 83 to correct the boiler recirculation pump flow rate control valve opening command 92 in the increasing direction. Thus, a decrease in the boiler recirculation water flow rate 103 can be prevented.

  However, when the boiler recirculation pump inlet fluid temperature 109 is suppressed, the boiler recirculation pump inlet fluid temperature 109 is suppressed by reducing the high-temperature boiler recirculation water flow rate 103 within an allowable range rather than keeping it constant. The increase in the boiler recirculation pump discharge flow rate 104 required for the operation is small. Therefore, before adding the boiler recirculation pump inlet fluid temperature correction signal 72 to the adder / subtractor 83, the boiler recirculation consisting of a value of 0 to 1 generated by the boiler recirculation pump inlet temperature correction control gain setting 93 using the multiplier 95. A small correction is added to the adder / subtractor 83 by multiplying the circulation pump inlet temperature correction control gain 94.

  Further, even if the boiler recirculation pump discharge flow rate 104 is constant, if the cooling water flow rate 102 decreases, the boiler recirculation water flow rate 103 increases, the boiler recirculation pump inlet fluid temperature 109 rises, and the boiler recirculation pump inlet flow increases. Since the fluid specific volume 110 increases, the discharge pressure and discharge amount characteristics of the boiler recirculation pump 21 deteriorate.

  FIG. 5 is a behavioral analysis when the cooling water flow rate 102 is gradually decreased with the boiler recirculation pump discharge flow rate 104 kept constant. When the cooling water flow rate 102 decreases, the boiler recirculation pump inlet fluid specific volume 110 increases, so that the boiler recirculation pump flow rate control valve opening command 92 is increased to compensate for the decrease in discharge capacity of the boiler recirculation pump 21. Since the boiler recirculation pump flow rate control valve opening command 92 becomes a fully open command value at the time of (A) in the figure, the discharge capacity of the boiler recirculation pump 21 becomes insufficient thereafter, and the boiler recirculation pump discharge flow rate. 104 cannot be maintained. Therefore, the cooling water flow rate control valve opening command 65 (equivalent to 38% in FIG. 5) at the time of (A) in the figure is set as the lower limit value of the cooling water flow rate control valve opening command 65 in the output state, and is reduced to a lower value. By restricting the opening degree of the cooling water flow rate control valve 12 so as to prevent the operation, the boiler recirculation pump discharge capability can be prevented from operating even with respect to the boiler state and dynamic fluctuations in control. It becomes. As a circuit for this purpose, a cooling water flow rate control valve opening lower limit signal 74 is generated according to the output command 50 by the cooling water flow rate control valve opening lower limit setting 73 of FIG. 1 and is given to the controller 56 as a lower limit value. Thus, the cooling water flow rate control valve automatic opening command 57 can be maintained at the cooling water flow rate control valve opening lower limit signal 74 or higher.

Next, the case of switching between reflux / circulation operation during plant operation will be described below.
When switching from the once-through operation to the circulation operation, the circulation start operation is performed during the constant output operation with the boiler output to be switched (25% boiler output in the example of FIG. 2). The circulation start operation and the behavior at the time of switching will be described with reference to FIGS.

   First, a warming water control valve 40 provided in a boiler recirculation water pump warming pipe 42 branched from the water wall downcomer 5 and connected to the boiler recirculation water pump 21 and a water branched from the boiler recirculation extraction pipe 30 are connected. The warming water relief valve 43 provided in the ming water relief pipe 45 is closed, and the warming is finished. At this stage, the boiler recirculation pump 21, the boiler recirculation water cooling pipe 10, and the boiler recirculation extraction pipes 30 and 31 are warmed in the economizer outlet fluid, but the boiler recirculation water cooling pipe 11 and the boiler recirculation The extraction tube 31 is not warmed.

   Until then, the cooling water flow rate control valve opening command 65 was set to the cooling water flow rate control valve closing setting 58 (zero command) by the switches 62 and 64 and was fully closed. The control valve initial opening setting 59 is selected by the switches 62 and 64, and the opening of the cooling water flow rate control valves 12 and 24 is set to the initial opening. Thereafter, the boiler recirculation pump 21 is activated and the boiler recirculation pump flow rate adjustment valve 24 starts to flow the prescribed boiler recirculation pump discharge flow rate 104.

   By the way, the boiler recirculation extraction pipes 30 and 31 initially contain water having a lower temperature than the fluid of the furnace wall outlet header 8 and the temperature of the pipe itself is also low. 108 does not rise for a while. As for the cooling water temperature 107 entering the mixing unit 20, the water in the boiler recirculation water cooling pipe 10 warmed first flows in, but the water in the boiler recirculation water cooling pipe 11 that has not been warmed immediately Then, boiler feed water W1 having a lower temperature enters.

   Naturally, the change in the temperature of each fluid entering the mixer 20 is determined by the flow rate of the fluid flowing through each, and for example, the change starts quickly when the flow rate is high. Therefore, the cooling water flow rate control valve initial opening setting 59 is set to a cooling water flow rate 102 in which the temperature rise timing of the mixing section inlet boiler recirculation water temperature 108 and the temperature drop timing of the mixing section inlet cooling water temperature 107 substantially overlap. What is necessary is just to set it as the setting different from the cooling water flow control valve set opening setting 60 corresponding to the balance flow after switching. In the example shown in FIG. 6, the cooling water flow control valve initial opening setting 59 corresponds to 5% opening, and the cooling water flow control valve set opening setting 60 corresponds to 9%.

   When the mixing part inlet boiler recirculation water temperature 108 tends to rise, switching from the cooling water flow control valve initial opening setting 59 to the larger cooling water flow control valve set opening setting 60 is performed as shown in FIG. As shown in FIG. 6, the boiler recirculation pump inlet fluid temperature 109 can shift from the initial state to the balanced state after circulation without much fluctuation.

   FIG. 7 shows the characteristics at the start of the circulation operation when the cooling water flow rate control valve opening setting is only the set opening setting 60 (opening 9%). If the opening degree command of the cooling water flow rate control valve 24 is set to 9% from the beginning, the boiler recirculation pump inlet fluid temperature 109 is once greatly reduced and the temperature is increased, and the temperature fluctuation range is large and the boiler recirculation pump 21 is increased. The stress on the thermal stress applied to

   FIG. 8 shows the characteristics at the start of the circulation operation when the cooling water flow rate control valve opening setting is only the initial opening setting 59. If the opening command of the cooling water flow rate control valve 24 is kept at 5% until automatic control is started, the cooling water becomes a little balance, so the boiler is recirculated before entering the automatic control. As a result, the pump inlet fluid temperature 109 rises above the balance temperature. From the above results, the opening setting before the cooling water flow rate control valve 12 is switched to the automatic control is preferably two steps.

Next, the operation of stopping the circulation operation and switching to the once-through operation will be described with reference to FIGS. 1 and 9.
With the circulation / through-flow switching output (25% output state in FIG. 2), the output is kept constant, the automatic control of the cooling water flow control valve 12 is canceled, and the cooling valve opening command 65 is set to open the cooling water flow control valve. The degree setting 60 (9% opening in FIG. 9) is selected, but the state quantity hardly fluctuates because of the opening setting that maintains the settling balance. Thereafter, the automatic control of the boiler recirculation pump flow rate adjustment valve 24 is canceled, and the boiler recirculation pump flow rate adjustment valve opening command 92 is selected as the boiler recirculation pump flow rate adjustment valve initial opening setting 88, and the operation becomes the minimum flow rate. After the state is stabilized, the boiler recirculation pump flow control valve closing setting 87 (zero opening) is selected, the boiler recirculation pump flow control valve 24 is fully closed, and the boiler recirculation pump 21 is stopped. During the operation, after the boiler recirculation pump flow rate control valve initial opening setting 88 is selected as the boiler recirculation pump flow rate control valve opening command 92, the cooling water flow rate control valve opening command 65 is changed to the cooling water flow rate control valve. By switching from the set opening setting 60 (9% opening in FIG. 9) to the cooling water flow valve end opening setting 61 (6% opening in FIG. 9), the boiler recirculation pump inlet fluid temperature 109 is changed to FIG. As shown, it does not fluctuate so much and shows the characteristic of gradually stabilizing to the warming water temperature.

   FIG. 10 shows the characteristics at the end of the circulation operation if the cooling water flow rate control valve opening setting is only the cooling water flow rate control valve setting opening setting 60. Since the opening degree command of the cooling water flow rate adjustment valve 24 is 9% constant, when the boiler recirculation pump flow rate adjustment valve initial opening degree setting 88 is selected in the process of stopping the boiler recirculation pump 21, the boiler recirculation water flow rate is selected. The balance between the flow rate 103 and the cooling water flow rate 102 is lost, and the boiler recirculation pump inlet fluid temperature 109 is once greatly lowered and stopped, and the boiler recirculation pump 21 is subjected to stress due to temperature change. From the above results, it is preferable that the opening setting after the automatic control of the cooling water flow rate control valve is canceled is set in two stages. However, it is rare that the cooling water flow rate control valve initial opening setting 59 and the cooling water flow valve end opening setting 61 are individually set so that the operation is so severe that it is practical to use both.

   As another embodiment of the present invention, a method of controlling the boiler recirculation pump inlet fluid temperature 109 at a specified value (temperature setting with a small change in specific volume) by the cooling water flow rate control valve 12 will be described below with reference to FIG. I will explain.

  In the boiler recirculation pump inlet temperature setting function 75 shown in FIG. 11, a boiler recirculation pump inlet temperature setting signal 76 corresponding to the boiler output command 50 is generated, and the boiler recirculation pump is used by using the temperature setting signal 76 and the adder / subtractor 69. The controller 56 takes the difference from the boiler recirculation pump inlet fluid temperature signal 29 obtained by the inlet temperature measuring instrument 27 and sets the boiler recirculation pump inlet temperature deviation 77 as zero as the boiler recirculation pump inlet temperature deviation 77. Feedback control is performed, and the boiler recirculation pump inlet fluid temperature 109 is automatically controlled by the cooling flow rate control valve 12.

At this time, since it takes time for the temperature to change, the preceding signal generated by the cooling flow rate control valve preceding signal setting function 78 is added to the controller 56 to improve controllability.
Further, when the cooling water flow rate 102 is increased, the boiler circulation pump discharge flow rate 104 is increased in order to maintain the boiler recirculation water flow rate 103. However, the cooling water flow rate control valve is set so as not to exceed the discharge capacity of the boiler circulation pump 21. An opening degree upper limit setting 79 is provided and given to the controller 56 as an upper limit.

   The boiler circulation pump flow rate control valve 24 includes a boiler recirculation water flow signal 35 which is a difference between the boiler circulation pump discharge flow rate signal 28 and the cooling water flow rate signal 16 and a boiler recirculation flow rate generated by the boiler recirculation flow rate setting function 97. Feedback control is performed by the controller 85 so that the boiler recirculation flow rate deviation 99, which is the difference from the setting signal 98, becomes zero, thereby ensuring the necessary boiler recirculation water flow rate 103.

As another embodiment of the present invention, a method of controlling the boiler recirculation water flow rate 103 to the target flow rate by the boiler recirculation pump flow rate control valve 24 will be described with reference to FIG.
A boiler recirculation water flow meter 33 is installed in the boiler recirculation extraction pipe 30, and the boiler recirculation water flow signal 35 obtained by the boiler recirculation water flow detector 34 is output from the boiler recirculation flow setting function 97 as a boiler output command. 50, feedback control is performed by the controller 85 so as to coincide with the boiler recirculation flow rate setting signal 98 generated in accordance with 50, and the boiler recirculation pump discharge flow rate 104 is adjusted by the boiler recirculation flow rate adjustment valve 24, thereby the boiler. The recirculated water flow rate 103 is controlled to the target flow rate.

  The boiler recirculation water flow signal 35 may be obtained by subtracting the cooling water flow signal 16 from the boiler recirculation pump discharge flow signal 28 as shown in FIG.

  According to the present invention, a fluid circulation operation of a supercritical pressure constant pressure once-through boiler capable of obtaining a stable and strong disturbance operation and obtaining a wider output operation range than a once-through state can be performed.

It is a figure which shows the installation and control circuit which concern on embodiment of this invention. It is a figure which shows the basic operation in connection with this invention. It is a figure which shows the behavior at the time of load increase in this invention. It is a figure which shows the behavior at the time of load drop in this invention. It is a figure which shows a behavior when cooling water is decreased gradually in this invention. It is a figure which shows the behavior when the circulation driving | operation is started in this invention. It is a figure which shows a behavior when the circulation driving | operation is started with the circuit which does not depend on this invention. It is a figure which shows a behavior when the circulation driving | operation is started with the circuit which does not depend on this invention. It is a figure which shows the behavior when a circulation driving | operation is complete | finished in this invention. It is a figure which shows a behavior when a circulation driving | operation is complete | finished with the circuit which does not depend on this invention. It is a figure which shows the control circuit by the other Example by this invention. It is a figure which shows the control circuit by the other Example by this invention.

Explanation of symbols

W1: Boiler feed water W2: Cooling water W3: Boiler recirculation water W4: Boiler recirculation pump discharge water 1 Furnace wall 2 Boiler feed pipe 5 Water wall precipitating pipe 6 Charcoal inlet inlet header 7 Fuel saving outlet outlet header 8 Furnace Wall outlet header 9 Primary superheater inlet header 10 Boiler recirculation water cooling pipe 11 Boiler recirculation water cooling pipe 12 Cooling water flow rate control valve 13 Cooling water flow meter 14 Cooling water flow meter 16 Cooling water flow signal 20 Mixer 21 Boiler Recirculation Pump 22 Boiler Recirculation Pump Outlet Pipe 23 Boiler Recirculation Pump Outlet Pipe 24 Boiler Recirculation Pump Flow Control Valve 25 Boiler Recirculation Pump Discharge Flowmeter 26 Boiler Recirculation Pump Discharge Flowmeter 27 Boiler Recirculation Pump Inlet Temperature measuring instrument 28 Boiler recirculation pump discharge flow signal 29 Boiler recirculation pump input Port temperature signal 30 Boiler recirculation extraction pipe 31 Boiler recirculation extraction pipe 32 Boiler recirculation check valve 33 Boiler recirculation water flow meter 34 Boiler recirculation water flow detector 35 Boiler recirculation water flow signal 40 Warming water adjustment valve 41 Boiler recirculation water cooling pipe warming pipe 42 Boiler recirculation pump warming pipe 43 Boiler recirculation pump warming water relief valve 45 Boiler recirculation pump warming water relief pipe 47 Boiler recirculation pump inlet water 50 Boiler output command 51 Cooling water flow rate setting function 52 Cooling water flow rate setting signal 54 Adder / subtractor 55 Cooling water flow rate deviation signal 56 Controller (PID control)
57 Cooling water flow control valve automatic opening command 58 Cooling water flow control valve closing setting 59 Cooling water flow control valve initial opening setting 60 Cooling water flow control valve set opening setting 61 Cooling water flow control valve end opening setting 62 Switching 63 Cooling water flow control valve specified opening command 64 Switch 65 Cooling water flow control valve opening command 66 Boiler recirculation pump inlet temperature upper limit function 67 Boiler recirculation pump inlet temperature upper limit setting signal 69 Adder / subtractor 70 Boiler recirculation pump Inlet temperature upper limit deviation 71 Controller (PID control)
72 Boiler recirculation pump inlet fluid temperature correction signal 73 Cooling water flow rate control valve opening lower limit setting 74 Cooling water flow rate control valve opening lower limit signal 75 Boiler recirculation pump inlet temperature setting function 76 Boiler recirculation pump inlet temperature setting signal 77 Boiler Recirculation pump inlet temperature deviation 78 Cooling flow rate control valve leading signal setting function 79 Cooling water flow rate control valve opening upper limit setting 80 Boiler recirculation pump discharge flow rate setting function 81 Boiler recirculation pump discharge flow rate setting signal 83 Adder / subtractor 84 Boiler recirculation Pump discharge flow rate deviation signal 85 Controller (PID control)
86 Boiler recirculation pump flow rate control valve automatic opening command 87 Boiler recirculation pump flow rate control valve closing setting 88 Boiler recirculation pump flow rate control valve initial opening setting 89 Switch
90 Boiler recirculation pump flow rate control valve specified opening command 91 Switch 92 Boiler recirculation pump flow rate control valve opening command 93 Boiler recirculation pump inlet temperature correction control gain setting 94 Boiler recirculation pump inlet temperature correction control gain 95 Multiplier 96 Boiler recirculation pump inlet fluid temperature setting correction signal 97 Boiler recirculation flow rate setting function 98 Boiler recirculation flow rate setting signal 99 Boiler recirculation flow rate deviation 100 Output command 101 Boiler inlet water supply flow rate 102 Cooling water flow rate 103 Boiler recirculation water flow rate 104 Boiler recirculation pump discharge flow rate 107 Mixer inlet cooling water temperature 108 Mixer inlet boiler recirculation water temperature 109 Boiler recirculation pump inlet fluid temperature 110 Boiler recirculation pump inlet fluid specific volume 111 Feed water pump feed flow rate 114 Furnace wall inlet header

Claims (11)

A plurality of heat transfer tubes including a economizer disposed in the furnace, a furnace wall and an evaporator and a superheater disposed in the furnace, and the economizer including the economizer, the furnace wall, the evaporator and the superheater. Boiler feed pipe (2) that supplies steam generation water to the heat transfer pipe in sequence, and boiler recirculation water from the furnace wall outlet in the supercritical pressure state or the heat transfer pipe at the downstream position are recirculated to the boiler feed pipe (2). In a fluid circulation operation facility of a critical pressure constant pressure once-through boiler for obtaining a constant pressure steam in a supercritical pressure state equipped with a boiler recirculation pump (21) for circulation,
In order to extract boiler recirculation water, which is part of the fluid that cannot be separated by brackish water under supercritical pressure, from the heat transfer pipe at the furnace wall outlet using the boiler recirculation pump (21) and return it to the boiler feed pipe (2) A boiler recirculation extraction pipe (30, 31) connected to the inlet of the boiler recirculation pump (21) from the wall outlet or a heat transfer pipe located downstream thereof;
A boiler recirculation pump outlet pipe (22, 23) connecting the outlet of the boiler recirculation pump (21) and the boiler feed pipe (2);
Cooling water, which is a part of feed water branched from the boiler feed pipe (2), is extracted and connected to the boiler recirculation draw pipe (30, 31) or the inlet of the boiler recirculation pump (21). Cooling pipes (10, 11);
Of the three pipes (30, 31; 22, 23; 10, 11), flow rate detection means (14, 26, 34) provided in at least two pipes;
A fluid circulation operation facility for a supercritical pressure constant pressure once-through boiler, comprising fluid flow rate adjusting means (12, 24) provided in the at least two pipes. A plurality of heat transfer tubes including a economizer disposed in the furnace, a furnace wall and an evaporator and a superheater disposed in the furnace, and the economizer including the economizer, the furnace wall, the evaporator and the superheater. Boiler feed pipe (2) that supplies steam generation water to the heat transfer pipe in sequence, and boiler recirculation water from the furnace wall outlet in the supercritical pressure state or the heat transfer pipe at the downstream position are recirculated to the boiler feed pipe (2). In a fluid circulation operation facility of a critical pressure constant pressure once-through boiler for obtaining a constant pressure steam in a supercritical pressure state equipped with a boiler recirculation pump (21) for circulation,
The boiler recirculation pump (21) is a pump having a fluid flow rate adjusting function,
In order to extract the boiler recirculation water, which is part of the fluid that cannot be subjected to brackish water separation in a supercritical pressure state, from the heat transfer pipe at the furnace wall outlet using the boiler recirculation pump (21) and return it to the boiler feed pipe (2), A boiler recirculation extraction pipe (30, 31) connected to the inlet of the boiler recirculation pump (21) from the furnace wall outlet or a heat transfer pipe located downstream thereof;
A boiler recirculation pump outlet pipe (22, 23) connecting the outlet of the boiler recirculation pump (21) and the boiler feed pipe (2);
Cooling water, which is a part of feed water branched from the boiler feed pipe (2), is extracted and connected to the boiler recirculation draw pipe (30, 31) or the inlet of the boiler recirculation pump (21). Cooling pipes (10, 11);
Fluid flow rate adjusting means (12) provided in at least one of the boiler recirculation extraction pipe (30, 31) or the boiler recirculation water cooling pipe (10, 11). Fluid circulation operation facility for supercritical and constant pressure once-through boilers. An operation method of the fluid circulation operation facility of the supercritical pressure constant pressure once-through boiler according to claim 1 or 2,
In the fluid circulation operation state in which the boiler recirculation water is returned from the furnace wall outlet to the boiler feed pipe (2), each flow rate of the boiler recirculation water with high enthalpy and low temperature cooling water that cannot be separated by brackish water at supercritical pressure is Fluid using the circulation pump (21) and the fluid flow rate adjusting means (12, 24 or 34) provided in at least one of the three pipes (30, 31; 22, 23; 10, 11) The supercritical pressure is characterized in that it has a function of controlling the fluid temperature (109) at the inlet of the boiler recirculation pump (21) to a specified value or less by adjusting the flow rate of the boiler and ensuring the necessary boiler recirculation water flow rate. Operation method of fluid circulation equipment of constant pressure once-through boiler.    Boiler recirculation extraction pipes (30, 31), boiler recirculation pump outlet pipes (22, 23), boiler recirculation water cooling pipes (10, 11), boiler recirculation water flow rate (103), boiler recirculation pump, respectively At least two of the discharge flow rate (104) and the cooling water flow rate (102) of (21) are adjusted to the respective flow rate target values, and each flow rate target value is necessary for the furnace wall throughout the circulation operation range. The supercritical pressure constant pressure once-through boiler according to claim 3, wherein the minimum feed water flow rate is secured and the inlet fluid temperature (109) of the boiler recirculation pump (21) is maintained in a temperature range of 380 ° C or lower. Of operating the fluid circulation facility. When the boiler recirculation pump inlet fluid temperature (109: signal 29) becomes higher than the set value,
(A) Cooling so that a deviation (signal 55) between a predetermined cooling water flow rate setting value (signal 52) obtained in response to the boiler output command (50) and the actual cooling water flow rate (signal 16) becomes zero. The control is performed to increase the opening of the water flow rate adjusting means (12) to increase the cooling water flow rate (102: signal 16), or (b) the cooling water flow rate (102: signal 16) by the control of (a) above. And the actual boiler recirculation pump inlet fluid temperature (109: signal 29) is larger than the boiler recirculation pump inlet temperature upper limit setting value (signal 67) determined in advance according to the boiler output command (50), Boiler recirculation pump inlet flow according to the deviation (signal 70) between the boiler recirculation pump inlet temperature upper limit setting value (signal 67) and the actual boiler recirculation pump inlet fluid temperature (109: signal 29) Based on the body temperature correction value (signal 72), the cooling water flow rate (102: signal 16) until the boiler recirculation pump inlet fluid temperature (109: signal 29) decreases to the boiler recirculation pump inlet temperature upper limit set value (signal 67). ) In combination with the control to correct in the increasing direction,
The operation method of the fluid circulation facility of the supercritical pressure constant pressure once-through boiler according to claim 4, which has a function of increasing a cooling water flow rate (102: signal 16). When the boiler recirculation pump inlet fluid temperature (109: signal 29) is increased and the cooling water flow rate (102: signal 16) is increased,
(A) When the actual boiler recirculation pump inlet fluid temperature (109: signal 29) is larger than the boiler recirculation pump inlet temperature upper limit setting value (signal 67), both the temperature deviations (signal 70) are Based on the boiler recirculation pump inlet fluid temperature correction value (signal 72) determined in advance based on the output command (50), the boiler recirculation pump discharge flow rate setting value (signal 81) and the actual boiler recirculation pump discharge Adding to the deviation (signal 84) from the flow rate (signal 28), or (b) boiler recirculation consisting of a value of 0 to 1 preset in the boiler recirculation pump inlet fluid temperature correction value (signal 72) A correction value (signal 96) obtained by multiplying the pump inlet temperature correction control gain (signal 94) is added to the deviation value (signal 84) of the boiler recirculation pump discharge flow rate (104: signal 28). That
By correcting the boiler recirculation pump discharge water discharge flow rate (104: signal 28) in the increasing direction, the boiler recirculation pump discharge flow rate (104: signal 28) is equal to or less than the increase in the cooling water flow rate. The method of operating a fluid circulation facility for a supercritical pressure constant pressure once-through boiler according to claim 5, wherein:    The cooling water flow rate adjusting means (12) controls the cooling water flow rate (102: signal 16) with the cooling water flow rate lower limit value (signal 74) predetermined according to the output command (50) as the lower limit value. A method for operating a fluid circulation facility of a supercritical pressure constant pressure once-through boiler according to any one of claims 4 to 6. Deviation between a predetermined inlet temperature setting value (signal 76) of the boiler recirculation pump (21) corresponding to the boiler output command (50) and an inlet fluid temperature (109: signal 29) of the actual boiler recirculation pump 21 ( The cooling water flow rate (102: signal 77) is set by the cooling flow rate adjusting means (12) based on a predetermined upper limit set value (signal 79) of the cooling water flow rate (102: signal 16). 4. The method of operating a fluid circulation facility of a supercritical constant pressure once-through boiler according to claim 3, wherein the boiler recirculation pump inlet fluid temperature (109: signal 29) is controlled by adjusting the signal 16). (A) the boiler recirculation water flow rate detection means (34) provided in the boiler recirculation water extraction pipe (30) directly detects the boiler recirculation water flow rate (signal 35), or
(B) Boiler recirculation from the boiler recirculation pump discharge water flow rate (104: signal 28) detected by the boiler recirculation pump discharge flow rate detection means (26) provided in the boiler recirculation pump outlet pipe (22, 23). The cooling water flow rate (102: signal 16) detected by the cooling water flow rate detection means (14) provided in the water cooling pipe (10, 11) is subtracted to obtain the boiler recirculation water flow rate (103: signal 35).
Boiler recirculation flow rate adjusting means so that the obtained boiler recirculation water flow rate (103: signal 35) matches the boiler recirculation flow rate setting value (signal 98) determined in advance in accordance with the boiler output command (50). The operation method of the fluid circulation facility of the supercritical pressure constant pressure once-through boiler according to claim 3, wherein the flow rate (104: signal 92) of the boiler recirculation pump discharged from (24) is adjusted. A method for operating a fluid circulation facility of a supercritical constant pressure once-through boiler according to claim 1 or 2,
Two or more predetermined fixed opening setting values (signals 59, 60, 61) having different setting values used for flowing a constant flow of cooling water (W2) through the boiler recirculation water cooling pipes (10, 11). A method for operating a fluid circulation facility for a supercritical pressure constant pressure once-through boiler, which is provided in a cooling water flow rate adjusting means (12). At the start of the boiler recirculation water circulation operation, the flow rate adjustment performed by the cooling water flow rate adjustment means (12) is set to a predetermined initial set value (signal 59), and the boiler recirculation pump (21) is started and then cooled. From the initial set value (signal 59) of the cooling water flow rate adjusting means (12) at the timing when the boiler recirculation water temperature (108) in which water (W2) is mixed with the boiler recirculation water (W3) tends to increase. Switching to a settling setpoint (signal 60) that relatively increases the flow rate from the initial setpoint (signal 59),
Further, when the circulation operation of the boiler recirculation water (W3) is stopped and switched to the once-through operation, the flow rate adjustment performed by the cooling water flow rate adjustment means (12) remains at the set value (signal 60), and then the boiler recirculation is performed. The flow rate adjustment performed by the circulation pump flow rate adjustment means (24) is performed at the minimum flow rate with a predetermined initial setting value (signal 88), and the flow rate adjustment performed by the boiler recirculation pump flow rate adjustment means (24) after the state is stabilized. After the boiler recirculation pump (21) is stopped and the initial set value (signal 88) of the boiler recirculation pump flow rate adjusting means (24) is selected during the operation. The switching setting value (signal 60) of the cooling water flow rate adjusting means (12) is switched to a predetermined opening degree setting value (signal 61). The operation method of the fluid circulation facility of the described supercritical pressure constant pressure once-through boiler.

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