JP2013007533A - Control method of once-through boiler and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable improvement of thermal efficiency and reduction of equipment cost and power cost by decreasing an amount of circulating water while capable of maintaining integrity of a furnace wall in a control method of the once-through boiler and a device therefor.SOLUTION: The once-through boiler producing superheated steam which is generated by a heat exchange with an inner heat source by supplying water to a heat transfer tube 53 in boiler 10 includes: a water supply pump 52 for supplying water to the heat transfer tube 53; and a control device 67 for adjusting water supply to the heat transfer tube 53 by the water supply pump 52 based on quality of the steam.

Description

  The present invention relates to a once-through boiler that is configured by a pipe and forcibly circulates and supplies water from one end, sequentially repeats heating and evaporation, and takes out superheated steam from the other end. The present invention relates to a control method and apparatus.

  In the once-through boiler, a large number of heat transfer tubes are arranged on the wall of the furnace, water is supplied to the heat transfer tubes, a flame is generated inside the furnace by a burner, and steam is heated by heating the water in the heat transfer tubes by the flame. The superheated steam is generated and the superheated steam is taken out, and the superheated steam is supplied to, for example, a steam turbine to generate power.

  In such a once-through boiler, usually, when a predetermined amount of water is supplied to the heat transfer pipe of the boiler by a feed water pump, the water is heated by the boiler, so that the whole amount becomes steam and is taken out as superheated steam. However, when the amount of heating in the boiler is low, such as immediately after the startup of the boiler, the entire amount of water cannot be converted into steam by the boiler, and the water separated by the steam separator is returned to the water supply line. In this case, when the water separated by the steam separator is returned to the water supply line, the heat amount of the water heated by the boiler is discarded, and the thermal efficiency is not good. Moreover, in order to return the water separated by the steam separator to the water supply line, a separate pump is required, resulting in an increase in equipment cost and power cost. Therefore, it is desirable to set the amount of water supply corresponding to the heating amount of the boiler.

  As such a conventional once-through boiler control method, there is one described in Patent Document 1 below. The control method and control device for a once-through boiler described in Patent Document 1 are configured to heat a boiler feed water at a economizer and a furnace water wall at the start-up operation or stop operation of the boiler, and the heated furnace water wall outlet The fluid is separated into steam and water with a steam separator, and the steam is supplied to the superheater and heated.After the water is stored in the water storage tank, it is recirculated to the furnace water wall by the recirculation system. When the boiler recirculation system cannot be used and the furnace water wall heat transfer tube temperature is normal, the water supply through the furnace water wall is reduced from that during normal operation and the circulating water is supplied to the boiler recirculation pump. It is recirculated from the upstream side to the furnace water wall through the condensate system.

Japanese Patent No. 2880558

  In the conventional once-through boiler control method and control device described above, the furnace water wall passage water supply amount is normally set on condition that the furnace water wall heat transfer tube temperature is normal when the boiler recirculation system cannot be used. It is described that it is reduced from the time of operation. However, it is desirable to reduce the amount of water supplied to the heat transfer tube (water wall) of the boiler (furnace), so that the amount of water supplied corresponds to the amount of heating of the boiler. However, a certain amount of water is supplied to the boiler (heat transfer tube). Without ensuring, it becomes difficult to maintain the soundness of the furnace wall. That is, if the amount of water supplied to the boiler (heat transfer tube) is reduced, the boiling state of the water in the heat transfer tube transitions from nucleate boiling to film boiling, thereby increasing the metal temperature of the heat transfer tube. It is difficult to set the optimum conditions for the flow rate that prevents water from transitioning from nucleate boiling to nucleate boiling limit (DNB) to film boiling beyond the boiling point, depending on the pressure and heat flux in the heat transfer tube. It has become a thing.

  The present invention solves the above-described problems, and it is possible to improve the thermal efficiency, reduce the equipment cost and the power cost by reducing the amount of circulating water and to maintain the soundness of the furnace wall. It is an object to provide a control method and apparatus.

  In order to achieve the above object, a method for controlling a once-through boiler according to the present invention provides a method for controlling a once-through boiler in a once-through boiler that supplies water to a heat transfer tube of a boiler and takes out superheated steam generated by heat exchange with an internal heat source. The amount of water supplied is adjusted based on the quality of the steam.

  Therefore, the amount of water supplied to the heat transfer tubes of the boiler is adjusted based on the quality of the steam, so that the transition from nucleate boiling to film boiling due to a decrease in the amount of water supplied can be prevented, and the amount of recirculation caused by an increase in the amount of water supplied By setting the optimal conditions for the water supply volume, the circulating water volume can be reduced to improve thermal efficiency, reduce equipment costs and power costs, and maintain the integrity of the furnace wall Can be possible.

  In the once-through boiler control method of the present invention, an upper limit value of quality capable of maintaining the nucleate boiling state of water in the heat transfer tube is set in advance, and a lower limit of the amount of water supplied to the heat transfer tube corresponding to the upper limit value of the quality A value is set, and when the boiler is started, the amount of water supplied to the heat transfer tube is adjusted to a lower limit value of the amount of water supplied.

  Therefore, at the time of boiler startup, the transition from nucleate boiling to film boiling due to a decrease in the water supply amount is achieved by adjusting the water supply amount to the heat transfer tube to the lower limit value of the water supply amount obtained from the upper limit value of the quality. In addition to being able to prevent, an increase in the amount of recirculation due to an increase in the amount of water supply can be prevented.

  In the once-through boiler control method of the present invention, the current steam quality is determined based on at least two of the amount of water supplied to the heat transfer pipe, the amount of steam generated, and the amount of recirculated water separated from the steam and returned to the water supply side. It is characterized by calculating.

  Therefore, the quality of the steam can be easily calculated based on the amount of water supplied to the heat transfer tube, the amount of steam, and the amount of recirculated water.

  Further, the control device for the once-through boiler of the present invention includes a feed water pump for supplying water to the heat transfer tube in the once-through boiler for supplying water to the heat transfer tube of the boiler and taking out superheated steam generated by heat exchange with an internal heat source. And a pump control unit that adjusts the amount of water supplied to the heat transfer pipe by the water supply pump based on the quality of the steam.

  Therefore, since the pump control unit adjusts the amount of water supplied to the heat transfer pipe by the water supply pump based on the quality of the steam, it can prevent the transition from nucleate boiling to film boiling due to the decrease in the amount of water supplied, and the amount of water supplied Increase in the amount of recirculation due to an increase in the amount of water can be prevented, and by setting the optimum conditions for the amount of water supply, the amount of circulating water can be reduced to improve thermal efficiency and reduce equipment costs. Sex can be maintained.

  In the once-through boiler control apparatus according to the present invention, the pump control unit sets an upper limit value of quality that can maintain the nucleate boiling state of water in the heat transfer tube in advance, and the heat transfer tube corresponding to the upper limit value of the quality The lower limit value of the water supply amount is set, and when the boiler is started, the water supply amount to the heat transfer pipe is adjusted to the lower limit value of the water supply amount.

  Therefore, at the time of boiler startup, the transition from nucleate boiling to film boiling due to a decrease in the water supply amount is achieved by adjusting the water supply amount to the heat transfer tube to the lower limit value of the water supply amount obtained from the upper limit value of the quality. In addition to being able to prevent, an increase in the amount of recirculation due to an increase in the amount of water supply can be prevented.

  In the once-through boiler control device of the present invention, a feed water amount sensor for measuring the feed water amount to the heat transfer pipe, and a recirculation water amount sensor for measuring the recirculation water amount separated from the steam and returned to the feed water side are provided, The pump control unit is characterized in that the current steam quality is calculated based on the water supply amount and the recirculated water amount.

  Therefore, the current steam quality is calculated based on the water supply amount measured by the water supply amount sensor and the recirculation water amount measured by the recirculation water amount sensor, and the steam quality can be easily calculated with high accuracy. .

  In the once-through boiler control apparatus according to the present invention, the steam-water separator that separates the steam heated by the boiler into moisture and steam, and the moisture separated by the steam-water separator is returned to the downstream side of the water supply pump. It is characterized by providing a circulation path.

  Therefore, the reduction | decrease in thermal efficiency can be suppressed by returning the water | moisture content isolate | separated by the steam separator to the downstream of a feed water pump by the circulation path.

  According to the control method and apparatus for the once-through boiler of the present invention, the amount of water supplied to the heat transfer pipe is adjusted based on the quality of the steam, so that the heat efficiency is improved by reducing the amount of circulating water, and the equipment cost and the power cost are reduced. It is possible to maintain the soundness of the furnace wall.

FIG. 1 is a schematic diagram illustrating a once-through boiler control apparatus according to Embodiment 1 of the present invention. FIG. 2 is a graph showing the vapor mass velocity versus vapor quality. FIG. 3 is a graph showing the boiler water supply amount with respect to the boiler load. FIG. 4 is a schematic configuration diagram illustrating the once-through boiler of the first embodiment. FIG. 5 is a schematic diagram illustrating a once-through boiler control apparatus according to Embodiment 2 of the present invention.

  Exemplary embodiments of a method and apparatus for controlling a once-through boiler according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example, Moreover, when there exists multiple Example, what comprises combining each Example is also included.

  FIG. 1 is a schematic configuration diagram showing a once-through boiler control apparatus according to Embodiment 1 of the present invention, FIG. 2 is a graph showing steam mass velocity with respect to steam quality, and FIG. 3 shows boiler feed water amount with respect to boiler load. FIG. 4 is a schematic configuration diagram illustrating the once-through boiler of the first embodiment.

  In Example 1, as shown in FIG. 1, the once-through boiler 10 uses, for example, pulverized coal obtained by pulverizing coal as pulverized fuel, burns the pulverized coal with a combustion burner, and recovers heat generated by the combustion. It is a pulverized coal fired boiler that can.

  The once-through boiler 10 is a conventional boiler, and includes a furnace 11 and a combustion device 12. The furnace 11 has a rectangular hollow shape and is installed along the vertical direction. A combustion device 12 is provided at the lower part of the furnace wall constituting the furnace 11. The furnace 11 is sealed with a furnace wall formed by a number of heat transfer tubes (not shown).

  The combustion device 12 has a plurality of combustion burners 21, 22, 23, 24, 25 mounted on the furnace wall. In this embodiment, the combustion burners 21, 22, 23, 24, and 25 are arranged as four sets at equal intervals along the circumferential direction, and 5 sets along the vertical direction. Five stages are arranged.

  Each combustion burner 21, 22, 23, 24, 25 is connected to a pulverized coal machine (mill) 31, 32, 33, 34, 35 via a pulverized coal supply pipe 26, 27, 28, 29, 30. ing. Although not shown, the pulverized coal machines 31, 32, 33, 34, and 35 are supported in a housing so that the pulverization table can be driven to rotate with a rotation axis along the vertical direction, and face the upper side of the pulverization table. A plurality of crushing rollers are configured to be rotatably supported in conjunction with the rotation of the crushing table. Therefore, when coal is introduced between a plurality of crushing rollers and a crushing table, the pulverized coal supplied to the pulverized coal supply pipes 26 and 27 is pulverized to a predetermined size and classified by carrier air (primary air). , 28, 29, 30 can be supplied to the combustion burners 21, 22, 23, 24, 25.

  Further, the furnace 11 is provided with a wind box 36 at the mounting position of each combustion burner 21, 22, 23, 24, 25, and one end portion of an air duct 37 is connected to the wind box 36, and this air The duct 37 has a blower 38 attached to the other end. Therefore, the combustion air (secondary air) sent by the blower 38 is supplied from the air duct 37 to the wind box 36 and supplied from the wind box 36 to the combustion burners 21, 22, 23, 24, 25. Can do.

  Therefore, in the combustion apparatus 12, each combustion burner 21, 22, 23, 24, 25 can inject a pulverized fuel mixture obtained by mixing pulverized coal and primary air into the furnace 11 and secondary air. Can be blown into the furnace 11, and a flame can be formed by igniting the pulverized fuel mixture with an ignition torch (not shown).

  In general, when the boiler is started, each combustion burner 21, 22, 23, 24, 25 injects oil fuel into the furnace 11 to form a flame.

  The furnace 11 has a flue 40 connected to the upper portion thereof, and a superheater (superheater) 41 and 42 for recovering heat of exhaust gas as a convection heat transfer section, and a reheater 43 and 44 in the flue 40. The economizers 45, 46 and 47 are provided, and heat exchange is performed between the exhaust gas generated by the combustion in the furnace 11 and water.

  The flue (exhaust gas passage) 40 is connected to an exhaust gas pipe 48 through which the exhaust gas subjected to heat exchange is discharged downstream. This exhaust gas pipe 48 is provided with an air heater 49 between the air duct 37 and performs heat exchange between the air flowing through the air duct 37 and the exhaust gas flowing through the exhaust gas pipe 48, and the combustion burners 21, 22, 23, The temperature of the combustion air supplied to 24 and 25 can be raised.

  Although not shown, the exhaust gas pipe 48 is provided with a denitration device, an electrostatic precipitator, an induction blower, and a desulfurization device, and a chimney is provided at the downstream end.

  Accordingly, when the pulverized coal machines 31, 32, 33, 34, and 35 are driven, the generated pulverized coal together with the conveying air passes through the pulverized coal supply pipes 26, 27, 28, 29, and 30 and the combustion burners 21, 22, 23, 24, 25. Also, heated combustion air is supplied from the air duct 37 to the combustion burners 21, 22, 23, 24, 25 via the wind box 36. Then, the combustion burners 21, 22, 23, 24, and 25 blow the pulverized fuel mixture mixed with the pulverized coal and the carrier air into the furnace 11 and blow the combustion air into the furnace 11 and ignite at this time. Can form a flame. In the furnace 11, the pulverized fuel mixture and the combustion air are burned to generate a flame. When a flame is generated in the lower part of the furnace 11, the combustion gas (exhaust gas) rises in the furnace 11, and the flue 40 is discharged.

  At this time, water supplied from a water supply pump (not shown) is preheated by the economizers 45, 46 and 47, and then supplied to each heat transfer tube (not shown) constituting the furnace wall, where it is heated. It becomes steam. Further, the steam is introduced into the superheaters 41 and 42 and is heated by the combustion gas. The superheated steam generated by the superheaters 41 and 42 is supplied to a power plant (not shown) (for example, a steam turbine). Further, the steam taken out in the middle of the expansion process in the steam turbine is introduced into the reheaters 43 and 44, overheated again, and returned to the turbine.

  Thereafter, the exhaust gas that has passed through the economizers 45, 46, and 47 of the flue 40 is subjected to removal of harmful substances such as NOx by a catalyst in a denitration device (not shown) in the exhaust gas pipe 48, and the particulate matter is collected by an electric dust collector Is removed, and after the sulfur content is removed by the desulfurizer, it is discharged from the chimney into the atmosphere.

  Here, the flow of water and steam in the once-through boiler 10 described above will be described. As shown in FIG. 1, the water supply line 51 is equipped with a water supply pump 52, and a downstream portion is connected to a economizer 45 (46, 47), and the economizer 45 constitutes a furnace wall of the furnace 11. It is connected to the heat transfer tube 53. The heat transfer pipe 53 is connected to a steam / water separator 54 at a downstream portion, and the steam / water separator 54 is connected to a steam turbine 56 and a turbine bypass valve 57 via a steam line 55. The steam turbine 56 is connected to a condenser 59 by a discharge line 58, and the condenser 59 is connected to an upstream portion of the water supply line 51. The steam separator 54 is connected to the downstream side of the water supply pump 52 in the water supply line 51 by a recirculation line (recirculation path) 60. A drain tank 61 and a recirculation water pump 62 are attached to the recirculation line 60.

  Therefore, when the feed water pump 52 is driven, a predetermined amount of water is heated from the feed water line 51 by the economizer 45 and then supplied to the heat transfer pipe 53, and is heated by exchanging heat in the boiler to generate steam. . This steam is separated into steam and moisture by the steam separator 54, and the superheated steam is supplied to the steam turbine 56 via the steam line 55, and the steam turbine 56 is driven to generate electricity. Then, the steam that has worked in the steam turbine 56 is sent to the condenser 59 through the discharge line 58, where it is cooled to become condensed water and returned to the water supply line 51. On the other hand, the water separated from the superheated steam by the steam separator 54 is temporarily stored in the drain tank 61 from the recirculation line 60, and returned from the drain tank 61 to the water supply line 51 by the recirculation water pump 62.

  In the once-through boiler 10 configured as described above, the amount of water supplied to the heat transfer pipe 53 by the water supply pump 52 is adjusted based on the quality (dryness) of the steam. That is, a water supply sensor 65 that measures the amount of water supplied to the heat transfer pipe 53, a recirculation water amount sensor 66 that measures the amount of recirculated water separated from the steam (wet steam) and returned to the water supply line 51, and A control device (pump control unit) 67 is provided that calculates the current steam quality based on the circulating water amount and adjusts the water supply amount to the heat transfer pipe 53 by the feed water pump 52 based on the steam quality.

  And this control apparatus 67 sets the upper limit of the quality which can maintain the nucleate boiling state of the water in the heat exchanger tube 53 previously, and sets the lower limit of the amount of water supply to the heat exchanger tube 53 corresponding to this upper limit of this quality. The water supply amount to the heat transfer pipe 53 is adjusted to the lower limit value of the water supply amount when the boiler is activated.

  More specifically, when the once-through boiler 10 is activated, the water supply pump 52 operates to supply water to the furnace 11 as described above. At this time, when the load of the boiler 10 is operating at 100% and the inlet water supply amount to the economizer 45 is 100, if the load of the boiler 10 is 25%, the inlet water supply to the economizer 45 An amount of 25 is required, and this inlet water supply amount 25 is a total amount of the water supply amount and the recirculation amount. In addition, when the boiler 10 is started, the amount of water supplied to the economizer 45 is less than 25.

  Conventionally, immediately after this boiler 10 is started, that is, before the load reaches 25%, the heat transfer pipe 53 in the furnace 11 has a small amount of water evaporation. Even in this case, the economizer 45 by the feed water pump 52 is used. The amount of water supply to the inlet is controlled to be 25. Therefore, in the boiler 10, the water supply amount 25 cannot be all converted to steam, and the steam separated from the water by the steam separator 54 is sent to the steam turbine 56 via the superheater 41, but cannot be evaporated. The water (saturated water) separated from the steam by the steam separator 54 is returned to the water supply line 51 by the recirculation water pump 62 and supplied to the furnace 11 again. That is, when the boiler 10 is started, only 5 of the water supply amount 25 supplied to the furnace 11 is evaporated and sent to the steam turbine 56, and 20 is recirculated. When the load on the boiler 10 reaches 25%, the recirculation water pump 62 is stopped, and the inlet water supply amount to the economizer 45 by the water supply pump 52 is increased to 100 as the load increases.

  In this case, since the evaporation amount in the furnace 11 is 5, if the inlet water supply amount to the economizer 45 can be set to 5, the recirculation water pump 62 is eliminated without generating the recirculation amount 20. However, if a certain amount of water supply is not ensured for the furnace 11, the heat transfer tube 53 of the furnace wall transitions from nucleate boiling to film boiling, thereby raising the metal temperature and improving the soundness of the furnace wall. Cannot be maintained.

  Therefore, in the once-through boiler 10 of the first embodiment, as described above, the amount of water supplied to the heat transfer pipe 53 by the water supply pump 52 is adjusted based on the quality of the steam. That is, if the amount of flowing water in the heat transfer tube 53 in the furnace 11 decreases, the quality (vapor dryness) increases. When this quality exceeds a certain value (upper limit), the boiling state of the water flowing through the heat transfer tube 53 transitions from nucleate boiling to the film boiling beyond the nucleate boiling limit (DNB) point, so that the heat in the heat transfer tube 53 is increased. The transfer rate is lowered, the metal temperature of the heat transfer tube 53 is rapidly increased, and the soundness of the furnace wall cannot be maintained.

  Therefore, the upper limit value of the quality that can maintain the nucleate boiling of the water flowing through the heat transfer tube 53 (the lower limit value of the amount of flowing water in the heat transfer tube 53) was grasped by experiments, and the transition condition from nucleate boiling to film boiling was predicted. That is, in the boiler 10, as shown in FIG. 2, from the relationship between the quality (steam quality) and the mass velocity, the upper limit value of the quality, that is, the lower limit value of the amount of flowing water in the heat transfer tube 53, in other words, At startup, the minimum flow rate required by the furnace 11 can be predicted, and the amount of water supplied at this time can be greatly reduced.

  Conventionally, the upper limit value (the lower limit value of the flowing water amount) that can maintain nucleate boiling cannot be predicted, and even if it can be predicted, the accuracy is low. For this reason, the amount of water supplied to the heat transfer pipe 53 of the furnace 11, that is, the inlet water supply to the economizer 45 has been secured excessively until the load reaches 25% after the boiler 10 is started. However, as described above, in this embodiment, since the upper limit value of the quality of the water in the heat transfer tube 53 can be predicted with high accuracy, the inlet to the economizer 45 can be controlled by controlling the feed water pump 52. It became possible to greatly reduce the amount of water supply.

  That is, as shown in FIG. 3, the boiler water supply amount (inlet water supply amount to the economizer 45) from when the boiler 10 is started until the load reaches 25% is conventionally 25. In Example 1, it can be made lower than 25. As a result, the amount of water flowing from the steam separator 54 to the recirculation line 60 can be reduced, and the capacity of the recirculation pump 62 can be reduced and the size can be reduced. Further, since the recirculated water that has not evaporated is very small, the recirculation pump 62 can be eliminated by draining the recirculated water.

  More specifically, the control device 67 drives and controls the feed water pump 52 when the boiler 10 is started, so that the amount of water supplied to the heat transfer tube 53 of the furnace 11 via the economizer 45 is increased. The upper limit value of the quality that can maintain the nucleate boiling of the water flowing through 53, that is, the lower limit value of the flowing water amount in the heat transfer tube 53 is set. The lower limit value of the flowing water amount is obtained in advance by an experiment according to the form of the boiler 10.

  Then, the amount of water supplied to the heat transfer tube 53 is increased as the load of the boiler 10 increases. At this time, the heat transfer tube is adjusted so that the flow rate of the recirculated water separated by the steam separator 54 becomes an appropriate amount. The amount of water supply to 53 is controlled. That is, the control device 67 measures the amount of water supplied to the heat transfer pipe 53 by the water supply amount sensor 65, and measures the amount of recirculated water that is separated from the steam (wet steam) and returned to the water supply line 51 by the circulating water amount sensor 66. The current steam quality is calculated based on the amount of water supplied and the amount of recirculated water. And the control apparatus 67 adjusts the amount of water supply to the heat exchanger tube 53 by the water supply pump 52 so that the quality of this steam may not exceed the upper limit of quality.

  Therefore, when the water supply amount at the time of starting the boiler 10 in the related art is 25, 5 of them are evaporated and the remaining 20 are recirculated. However, in this embodiment, the water supply amount at the start of the boiler 10 is The amount of recirculated water may be small even if the amount of evaporation is the same. For example, if the amount of water supply can be reduced to 10, the amount of recirculated water can be 5 even if the evaporation amount is the same. As a result, the capacity of the recirculation water pump 62 can be reduced, or the recirculation water pump 62 can be eliminated because the recirculation water that has not evaporated is small.

  As described above, in the once-through boiler control apparatus according to the first embodiment, in the once-through boiler that supplies water to the heat transfer tube 53 of the boiler 10 and extracts the superheated steam generated by heat exchange with the internal heat source, the heat transfer tube 53 is provided. A water supply pump 52 that supplies water to the heat transfer pipe 52 and a control device 67 that adjusts the amount of water supplied to the heat transfer pipe 53 by the water supply pump 52 based on the quality of the steam are provided.

  Therefore, since the control device 67 adjusts the amount of water supplied to the heat transfer pipe 53 by the water supply pump 52 based on the quality of the steam, it can prevent the transition from nucleate boiling to film boiling due to the decrease in the amount of water supplied, An increase in the amount of recirculation due to an increase in the amount of water supply can be prevented, and by setting the optimum conditions for the amount of water supply, the amount of circulating water can be reduced to improve thermal efficiency and reduce equipment costs. It is possible to maintain the soundness.

  Further, in the once-through boiler control device of the first embodiment, the control device 67 sets an upper limit value of the quality that can maintain the nucleate boiling state of the water in the heat transfer tube 53 in advance, and the heat transfer tube corresponding to the upper limit value of this quality The lower limit value of the water supply amount to 53 is set, and the water supply amount to the heat transfer pipe 53 is adjusted to the lower limit value of this water supply amount when the boiler 10 is started. Therefore, when the boiler 10 is started, the amount of water supplied to the heat transfer tube 53 is adjusted to the lower limit value of the water supply amount to the heat transfer tube 53 obtained from the upper limit value of the quality, so that the film boiling from the nucleate boiling due to the decrease of the water supply amount Can be prevented, and an increase in the amount of recirculation due to an increase in the amount of water supply can be prevented.

  In the once-through boiler control apparatus according to the first embodiment, the water supply sensor 66 that measures the amount of water supplied to the heat transfer pipe 53 and the circulating water sensor 66 that measures the amount of circulating water separated from the steam and returned to the water supply side are provided. The control device 67 calculates the current steam quality based on the water supply amount and the circulating water amount. Accordingly, the current steam quality is calculated based on the water supply amount measured by the water supply amount sensor 65 and the circulating water amount measured by the circulating water amount sensor 66, and the steam quality can be easily calculated with high accuracy. .

  In the once-through boiler control apparatus according to the first embodiment, the steam-water separator 54 that separates the steam (wet steam) heated by the boiler 10 into moisture and steam, and the moisture separated by the steam-water separator 54 is used. A recirculation line 60 that returns to the downstream side of the feed water pump 52 is provided. Therefore, by returning the water separated by the steam separator 54 to the downstream side of the water supply pump 52 in the water supply line 51 by the recirculation line 60, it is possible to suppress a decrease in thermal efficiency.

  In the once-through boiler control method according to the first embodiment, the amount of water supplied to the heat transfer pipe 53 is adjusted based on the quality of the steam. Therefore, it is possible to reduce the amount of recirculated water, improve the thermal efficiency and reduce the equipment cost, and maintain the soundness of the furnace wall.

  Moreover, in the control method of the once-through boiler of Example 1, based on at least two of the amount of water supplied to the heat transfer pipe 53, the amount of generated steam, and the amount of circulating water separated from the steam (wet steam) and returned to the water supply side. The current steam quality is calculated. Therefore, the quality of the steam can be easily calculated based on the amount of water supplied to the heat transfer pipe 53, the amount of superheated steam, and the amount of circulating water.

  FIG. 5 is a schematic configuration diagram illustrating a once-through boiler control apparatus according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the member which has the function similar to the Example mentioned above, and detailed description is abbreviate | omitted.

  In the once-through boiler control apparatus according to the second embodiment, as shown in FIG. 5, the feed water line 51 is equipped with a feed water pump 52, and the downstream portion is connected to the heat transfer pipe 53 of the furnace 11 through the economizer 45. Yes. The heat transfer pipe 53 has a downstream portion connected to a steam / water separator 54, and the steam / water separator 54 is connected to a steam turbine 56 via a steam line 55. The steam turbine 56 is connected to a condenser 59 by a discharge line 58, and the condenser 59 is connected to an upstream portion of the water supply line 51. The steam separator 54 is connected to the downstream side of the water supply pump 52 in the water supply line 51 by a recirculation line (recirculation path) 70. A drain tank 61 is attached to the recirculation line 70.

  Therefore, when the feed water pump 52 is driven, a predetermined amount of water is heated from the feed water line 51 by the economizer 45 and then supplied to the heat transfer pipe 53, and is heated by steam exchange to become steam. The steam is separated from moisture by the steam separator 54 and supplied to the steam turbine 56 via the steam line 55 to generate electricity. Then, the steam that has worked in the steam turbine 56 is sent to the condenser 59 through the discharge line 58, where it is cooled to become condensed water and returned to the water supply line 51. On the other hand, the water separated from the superheated steam by the steam separator 54 is temporarily stored in the drain tank 61 from the recirculation line 70 and returned to the water supply line 51.

  In the once-through boiler 10 configured as described above, the amount of water supplied to the heat transfer pipe 53 by the water supply pump 52 is adjusted based on the quality of the steam as in the first embodiment. The control device 67 calculates the current steam quality based on the water supply amount and the circulating water amount, and adjusts the water supply amount to the heat transfer pipe 53 by the water supply pump 52 based on the steam quality. In this case, the control device 67 sets an upper limit value of the quality that can maintain the nucleate boiling state of the water in the heat transfer tube 53 in advance, and sets the lower limit value of the amount of water supplied to the heat transfer tube 53 corresponding to the upper limit value of the quality. It sets and adjusts the amount of water supplied to the heat transfer pipe 53 to the lower limit of the amount of water supplied when the boiler is started.

  In addition, Example 2 is the same as the structure of Example 1 except that the recirculation line 70 is connected to the downstream side of the water supply pump 52 in the water supply line 51 and there is no recirculation water pump. Since this is the same, detailed description is omitted.

  Thus, in the control apparatus for the once-through boiler according to the second embodiment, the recirculation line 70 is provided to return the water, from which the steam is extracted by the steam separator 54, to the downstream side of the water supply pump 52 in the water supply line 51. . Therefore, the recirculated water is returned to the water supply line 51 by the water supply pump 52, and the recirculated water pump 62 can be eliminated.

  In each of the above-described embodiments, a water supply amount sensor 65 that measures the amount of water supplied to the heat transfer tube 53 and a recirculation amount of water that measures the amount of recirculation water separated from the steam (wet steam) and returned to the water supply line 51. A sensor 66 is provided, and the control device 67 calculates the current steam quality based on the measured water supply amount and the recirculated water amount, and determines the water supply amount to the heat transfer pipe 53 by the water supply pump 52 based on the steam quality. Although it adjusted, it is not limited to this structure. The control apparatus for the once-through boiler of the present invention is based on at least two of the amount of water supplied to the heat transfer pipe 53, the amount of steam generated, and the amount of recirculated water separated from the steam (wet steam) and returned to the water supply side. The current steam quality is calculated.

  Further, in each of the above-described embodiments, the recirculation lines 60 and 70, the drain tank 61, and the recirculation water pump 62 that return from the steam / water separator 54 to the feed water line 51 are provided. If the amount of recirculated water can be eliminated, these may not be provided.

11 furnace 41, 42 superheater 43, 44 reheater 45, 46, 47 economizer 51 feed water line 52 feed water pump 53 heat transfer pipe 54 steam separator 55 steam line 56 steam turbine 57 turbine bypass valve 58 discharge line 59 recovery Water 60,70 Recirculation line 61 Drain tank 62 Recirculation water pump

Claims (7)

In a once-through boiler that feeds water to the heat transfer pipe of the boiler and takes out superheated steam generated by heat exchange with the internal heat source,
Adjusting the amount of water supplied to the heat transfer tube based on the quality of the steam;
A control method for a once-through boiler, characterized in that.   The upper limit value of the quality that can maintain the nucleate boiling state of the water in the heat transfer tube is set in advance, the lower limit value of the amount of water supplied to the heat transfer tube corresponding to the upper limit value of the quality is set, and when the boiler is started, The method for controlling a once-through boiler according to claim 1, wherein the amount of water supplied to the heat transfer pipe is adjusted to a lower limit value of the amount of water supplied.   The current steam quality is calculated based on at least two of the amount of water supplied to the heat transfer pipe, the amount of generated steam, and the amount of circulating water separated from the steam and returned to the water supply side. The method for controlling the once-through boiler according to 2. In a once-through boiler that feeds water to the heat transfer pipe of the boiler and takes out superheated steam generated by heat exchange with the internal heat source,
A water supply pump for supplying water to the heat transfer pipe;
A pump controller that adjusts the amount of water supplied to the heat transfer pipe by the feed water pump based on the quality of the steam;
A once-through boiler control device.   The pump control unit previously sets an upper limit value of quality that can maintain the nucleate boiling state of water in the heat transfer tube, and sets a lower limit value of the amount of water supplied to the heat transfer tube corresponding to the upper limit value of the quality. 5. The once-through boiler control device according to claim 4, wherein when the boiler is started, the amount of water supplied to the heat transfer pipe is adjusted to a lower limit value of the amount of water supplied.   A water supply sensor for measuring the amount of water supplied to the heat transfer pipe and a recirculation water amount sensor for measuring the amount of recirculated water separated from the steam and returned to the water supply side are provided. 6. The once-through boiler control device according to claim 4, wherein the current steam quality is calculated based on the amount of water.   A steam / water separator that separates steam heated by the boiler into moisture and steam, and a recirculation path that returns the moisture separated by the steam / water separator to the downstream side of the feed water pump are provided. The once-through boiler control device according to any one of claims 4 to 6.

Images