Coal-fired unit 20% load feed water flow control system

Abstract

The utility model discloses a 20% load feed water flow control system for a coal-fired unit, which belongs to the technical field of coal-fired power generation automatic control and comprises a deaerator (9), a first operating pump (4), a second operating pump (5), a start standby pump (6), a first operating pump circulating valve (1), a second operating pump circulating valve (2), a start standby pump circulating valve (3), a high-pressure heater (10), a main feed water valve (7), a bypass feed water valve (8) and a coal economizer (11). The system provided by the utility model is reasonable in structure, and can accurately adjust the feed water flow of the boiler unit, so that the unit is safer, more stable and more reliable in operation.

Description

TECHNICAL FIELD

[0001] The utility model relates to coal-fired power generation automatic control technical field, more specifically relates to a coal-fired unit 20% load feed water flow control system. BACKGROUND

[0002] Wind power and solar power as the representative of renewable energy develop rapidly, but its output power has randomness, intermittence and instability, easily causes the frequent fluctuation of power grid load, this proposes new requirements to the peak shaving capacity of coal-fired unit as the ballast of power system. Meanwhile, a number of policies of encouraging coal-fired power plant to dig the peak shaving capacity and carry out flexible transformation are successively introduced in each region, through compensated peak shaving auxiliary temperature adjustment, spot trading etc. the enthusiasm of coal-fired unit deep peak shaving is stimulated. It has become the inevitable means to improve the market competitiveness of coal power enterprise to realize deep peak shaving as soon as possible and improve the operation flexibility of unit.

[0003] At present, most thermal power unit is usually operated in the range of 50% to 100% conventional load, and the thermal power unit is generally not suitable for fast rate and variable condition operation in the load interval below 50% due to the limitation of thermal system structure and original control strategy. Compared with conventional load condition (50% to 100% rated power), the device state and operating parameters of thermal system in deep peak shaving load condition will change, resulting in obvious difference in controlled object characteristics, increase in operation amount of emergency response of operation personnel, and lack of guarantee for safety and economy of unit. Without equipment modification, the lower limit of power generation load adjustment in normal condition is expanded to 30% rated power, 20% rated power or even lower through control system optimization, thereby effectively relieving the peak shaving pressure of power grid and greatly improving the new energy consumption capacity of power grid.

[0004] The existing control technology has low automation level of the feed water system of most coal-fired units under 20% load of coal-fired unit, each single operation of the feed water system needs to be performed one by one, and the operation is complex, resulting in long overall operation period. The operation mode of the feed water pump changes, and the parallel operation and exit operation of the feed water pump cannot be automatically controlled and need manual operation. If not handled properly, it is easy to cause water stealing between two steam-driven feed water pumps or even tripping of the feed water pump.

[0005] Therefore, how to provide a coal-fired unit 20% load feed water flow control system to solve the problems in the prior art is a problem to be solved by those skilled in the art. UTILITY MODEL CONTENTS

[0006] Therefore, the utility model provides a coal-fired unit 20% load feed water flow control system, the system structure is reasonable, can accurately adjust the feed water flow of boiler unit, makes the unit operation more safe, stable and reliable.

[0007] In order to achieve the above object, the utility model adopts the following technical scheme:

[0008] A coal-fired unit 20% load feed water flow control system, including: deaerator, running pump one, running pump two, starting standby pump, running pump one circulating valve, running pump two circulating valve, starting standby pump circulating valve, high pressure heater, main feed water valve, bypass feed water valve, coal economizer;

[0009] The inlet of the running pump one, the inlet of the running pump two and the inlet of the starting standby pump are connected with the outlet of the deaerator;

[0010] The first outlet of the running pump one, the first outlet of the running pump two and the first outlet of the starting standby pump are connected with the inlet of the high pressure heater;

[0011] The second outlet of the running pump one is connected with the inlet of the running pump one circulating valve, the second outlet of the running pump two is connected with the inlet of the running pump two circulating valve, and the second outlet of the starting standby pump is connected with the inlet of the starting standby pump circulating valve;

[0012] The outlet of the running pump one circulating valve, the outlet of the running pump two circulating valve and the outlet of the starting standby pump circulating valve are connected with the feed water inlet of the deaerator;

[0013] The outlet of the high pressure heater is connected with the inlet of the main feed water valve and the inlet of the bypass feed water valve respectively;

[0014] The outlet of the main feed water valve and the outlet of the bypass feed water valve are connected with the inlet of the coal economizer.

[0015] Preferably, the running pump one and the running pump two are steam-driven feed water pumps with 50% of the rated capacity of the boiler, and the starting standby pump is an electric feed water pump with 50% of the rated capacity of the boiler.

[0016] Preferably, the high pressure heater is provided with two columns in parallel, which are an A column high pressure heater and a B column high pressure heater respectively.

[0017] The A column high pressure heater comprises A1 high pressure heater, A2 high pressure heater, A3 high pressure heater, A4 high pressure heater and A5 high pressure heater arranged in series.

[0018] The B column high pressure heater comprises B1 high pressure heater, B2 high pressure heater, B3 high pressure heater, B4 high pressure heater and B5 high pressure heater arranged in series.

[0019] Preferably, the deaerator is a rotating film deaerator, which comprises a shell, a steam-water separator, a rotating film device, a water spraying grate and a heat storage filler liquid-vapor net.

[0020] Preferably, the coal economizer is arranged in two stages by adopting a serpentine light pipe, wherein the second-stage coal economizer is arranged above and the first-stage coal economizer is arranged below.

[0021] Compared with the prior art, the utility model discloses provide a kind of coal-fired unit 20% load feedwater flow control system, with following beneficial effect: without needing to reconstruct equipment, the feedwater of coal-fired unit 20% load depth peak shaving can be realized Whole course automatic regulation;Water pump of feedwater control system and pump / pump process are stable, and the automatic regulation precision of feedwater flow, outlet pressure is high, effectively avoid the occurrence of the water of two feedwater pumps between, improve the operation safety of unit;System structure is reasonable, can accurately regulate the feedwater flow of boiler unit, so that unit operates more safely, stably, reliably. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or prior art, the following will briefly introduce the drawings needed to be used in embodiment or prior art description, obviously, the drawings in the following description are only embodiments of the utility model, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creating labor.

[0023] Figure 1 The utility model provides a kind of coal-fired unit 20% load feedwater flow control system overall structure schematic view;

[0024] Mark explanation:

[0025] 1 is running pump one circulating valve;2 is running pump two circulating valve;3 is starting standby pump circulating valve;4 is running pump one;5 is running pump two;6 is running pump three;7 is main feedwater valve;8 is bypass feedwater valve;9 is deaerator;10 is high-pressure heater;11 is economizer. DETAILED DESCRIPTION

[0026] The technical scheme in the embodiments of the utility model will be clearly and completely described in the drawings in the embodiments of the utility model, obviously, the described embodiments are only a part of the embodiments of the utility model, not all the embodiments.Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creating labor are within the scope of the utility model.

[0027] The utility model embodiment discloses a kind of coal-fired unit 20% load feedwater flow control system, refer to Figure 1 As shown in the figure, including: deaerator 9, running pump one 4, running pump two 5, starting standby pump 6, running pump one circulating valve 1, running pump two circulating valve 2, starting standby pump circulating valve 3, high-pressure heater 10, main feedwater valve 7, bypass feedwater valve 8, economizer 11;

[0028] The inlet of the running pump 4, the inlet of the running pump 5 and the inlet of the starting standby pump 6 are connected with the outlet of the deaerator 9;

[0029] The first outlet of the running pump 4, the first outlet of the running pump 5 and the first outlet of the starting standby pump 6 are connected with the inlet of the high-pressure heater 10;

[0030] The second outlet of the running pump 4 is connected with the inlet of the running pump one circulating valve 1, the second outlet of the running pump 5 is connected with the inlet of the running pump two circulating valve 2 and the second outlet of the starting standby pump 6 is connected with the inlet of the starting standby pump circulating valve 3;

[0031] The outlet of the running pump one circulating valve 1, the outlet of the running pump two circulating valve 2 and the outlet of the starting standby pump circulating valve 3 are connected with the feedwater inlet of the deaerator 9;

[0032] The outlet of the high-pressure heater 10 is connected with the inlet of the main feedwater valve 7 and the inlet of the bypass feedwater valve 8 respectively;

[0033] The outlet of the main feedwater valve 7 and the outlet of the bypass feedwater valve 8 are connected with the inlet of the economizer 11.

[0034] Further, the running pump 4 and the running pump 5 are steam-driven feedwater pumps with 50% of the rated capacity of the boiler and the starting standby pump 6 is an electric feedwater pump with 50% of the rated capacity of the boiler;

[0035] Further, the rotation speed of the running pump 4 and the running pump 5 is automatically controlled to jointly adjust the feedwater flow; meanwhile, the opening degree of the running pump one circulating valve 1 and the running pump two circulating valve 2 is automatically set according to the deep peak load variation of the unit to ensure that the rotation speed of the running pump 4 and the running pump 5 and the feedwater flow are in a good linear adjustment range and the inlet flow of the running pump 4 and the running pump 5 is not lower than the minimum flow;

[0036] Further, when the unit is reduced from 50% of the rated power to 20% of the rated power, only the running pump one circulating valve 1 of the running pump 4 is automatically opened to reduce the rotation speed of the steam-driven feedwater pump on the basis of ensuring the minimum flow of the steam-driven feedwater pump and enter the hot standby state, the pump inlet flow is fully recirculated and the running pump two circulating valve 2 of the running pump 5 is kept closed to automatically adjust the feedwater flow;

[0037] When the unit is increased from 20% of the rated power to 50% of the rated power, the rotation speed of the running pump 4 is automatically increased to automatically close the running pump one circulating valve 1 on the basis of ensuring the minimum flow of the pump and automatically enter the parallel operation of the double feedwater pumps to jointly adjust the feedwater flow.

[0038] Further, the high-pressure heater 10 has two columns and is arranged in parallel, which are the A column high-pressure heater and the B column high-pressure heater;

[0039] The A column high-pressure heater comprises an A1 high-pressure heater, an A2 high-pressure heater, an A3 high-pressure heater, an A4 high-pressure heater and an A5 high-pressure heater arranged in series;

[0040] The B column high-pressure heater comprises a B1 high-pressure heater, a B2 high-pressure heater, a B3 high-pressure heater, a B4 high-pressure heater and a B5 high-pressure heater arranged in series;

[0041] Furthermore, each high-pressure heater in the A column high-pressure heater and the B column high-pressure heater is provided with a corresponding liquid level transmitter and two drainage pipes, wherein the liquid level transmitter is used for measuring the drainage water level of the corresponding high-pressure heater;

[0042] In the A1 high-pressure heater, the A2 high-pressure heater, the A3 high-pressure heater, the A4 high-pressure heater, the B1 high-pressure heater, the B2 high-pressure heater, the B3 high-pressure heater and the B4 high-pressure heater, one of the two drainage pipes is a normal drainage pipe, which is connected to the next high-pressure heater in series, and the other is an accident drainage pipe, which is connected to a drainage riser; in the A5 high-pressure heater and the B5 high-pressure heater, one of the two drainage pipes is a normal drainage pipe connected to the deaerator 9, and the other is an accident drainage pipe.

[0043] Furthermore, the deaerator 9 is a rotating film deaerator, which comprises a shell, a steam-water separator, a rotating film device, a water spraying grate and a heat storage filler liquid-vapor net;

[0044] Furthermore, the shell is made of a cylinder body and a stamping elliptical head, and is provided with a manhole for maintenance; the steam-water separator replaces the old-style deaerator with a grass hat cone structure design, so that the deaerator 9 eliminates the phenomenon of steam with water; the rotating film device comprises a water chamber, a steam chamber, a rotating film tube, a condensate water connecting pipe, a supplementary water connecting pipe and a primary steam inlet connecting pipe, the condensate water, the chemical supplementary water and the primary heating steam are sprayed out in a spiral shape at a certain angle through the rotating film device, to form a water film skirt and exchange heat with the heating steam introduced through the primary heating steam connecting pipe, so as to achieve primary deaeration; the feed water is heated to a temperature close to the saturation temperature under the working pressure of the deaerator 9, i.e. 2-3℃ lower than the saturation temperature, through the contact with the rising secondary heating steam through the water spraying grate, to achieve coarse deaeration, and generally about 90%-95% of the oxygen content in the feed water can be removed through the rotating film section; the water spraying grate is made of a plurality of layers of staggered angular steel, and the feed water that has been coarsely deaerated through the rotating film section is evenly distributed and falls on the liquid-vapor net below in a uniform rain-like manner; the heat storage filler liquid-vapor net is composed of a plurality of mutually spaced flat steel belts and a cylindrical body, and a specially designed stainless steel mesh is arranged in the cylindrical body, so that the feed water is fully contacted with the secondary steam and heated to the saturation temperature for the purpose of deep deaeration.

[0045] Further, the coal economizer 11 is arranged in two stages by a serpentine light pipe, the second stage coal economizer is above, and the first stage coal economizer is below.

[0046] Further, the first stage coal economizer is arranged in four groups in horizontal order, on the basis of the existing SNCR denitration system, in combination with the requirements of the emission index and the combined denitration efficiency, two layers of SCR denitration layers are arranged at the position of the tail flue economizer 11, in combination with the optimal reaction temperature range (300-420℃) of the SCR denitration, the catalyst layer is arranged at the position from the middle of the second group to the outlet of the third group; there is a 1350mm maintenance space between the third group and the fourth group.

[0047] In one specific embodiment, the boiler is a supercritical variable pressure once-through boiler produced by Shanghai Boiler Co., Ltd. by introducing ALSTOM technology, the model is SG-3005 / 29.30-M7008, the type is single furnace, double tangential combustion, once intermediate reheat, balanced draft, semi-outdoor arrangement, solid slagging, all-steel frame, full-suspension structure Π type pulverized coal boiler, the coal economizer is arranged in stages; the steam turbine is a 1000MW supercritical, once intermediate reheat, single shaft, four-cylinder four-steam, double back pressure, condensing type steam turbine produced by Shanghai Steam Turbine Co., Ltd. by introducing German Siemens technology, the model is C1000-28 / 600 / 620, the unit adopts nine-stage regenerative extraction. The denitration system adopts honeycomb catalyst and vortex mixing ammonia injection mode to achieve ultra-low NOx emission; the control system adopts Ovation of Emerson in Shanghai;

[0048] The test is divided into three stages of 30% load stable condition, 20% load stable condition and 15% load stable condition: the speed of the two steam-driven feed water pumps is automatically controlled to jointly adjust the feed water flow; at the same time, the opening degree of the recirculation valve of the two steam-driven feed water pumps is automatically set according to the change of the deep peak load of the unit, to ensure that the steam-driven feed water pump speed and the feed water flow are in a good linear adjustment range, and the steam-driven feed water pump inlet flow is not less than the minimum flow; during the process of reducing the load from 50% rated power to 15% rated power, only one steam-driven feed water pump automatically opens the recirculation valve, reduces the speed of the steam-driven feed water pump on the basis of ensuring the minimum flow, and enters the hot standby state, the pump inlet flow is fully recirculated, and the recirculation valve of the other steam-driven feed water pump remains closed to automatically adjust the feed water flow; during the process of increasing the load from 15% rated power to 50% rated power, one steam-driven feed water pump in hot standby automatically increases the speed, automatically closes the recirculation valve on the basis of ensuring the minimum flow, and automatically enters the parallel operation of the double feed water pumps to jointly adjust the feed water flow.

[0049] Key investigation: the control of the temperature of flue gas at the inlet of the denitration system and the NOx emission index under this condition; the economic index of the main / reheated steam of the boiler under this condition; the operation stability of the related auxiliary machines of the boiler under this condition; the metal wall temperature of the heating surface of each region of the boiler under this condition; the operation stability of the main auxiliary machines on the machine side under this condition; the extraction capacity of the steam turbine and the change of the body parameters under this condition; the actual situation of the low-load parallel operation of the two steam pumps under this condition;

[0050] The test result is better than the requirement of "the deep peaking capacity reaching 20% of the rated output of the unit", and the minimum value reaches 15% of the load. During the test, the unit runs stably, the boiler burns stably, and the environmental protection index is normal. The lower limit of the deep peaking of the million unit is broken, and valuable experience is accumulated for the exploration of the deep peaking of the million unit.

[0051] Each of the embodiments in the specification is described in a progressive manner, and the same and similar parts of each embodiment can be referred to each other. Each embodiment mainly describes the difference from other embodiments. Especially, for the system or system embodiment, since it is basically similar to the method embodiment, it is described more simply, and the related part can be referred to the part of the method embodiment. The above-described system and system embodiment are only illustrative, and the units described as separate components can be or can not be physically separated, and the components shown as units can be or can not be physical units, that is, they can be located in one place, or can be distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the embodiment scheme according to the actual needs. Those skilled in the art can understand and implement without creative labor.

[0052] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the utility model. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the utility model. Therefore, the utility model will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A coal-fired unit 20% load feedwater flow control system characterized by, Comprise: Deaerator (9), running pump one (4), running pump two (5), starting standby pump (6), running pump one circulating valve (1), running pump two circulating valve (2), starting standby pump circulating valve (3), high pressure heater (10), main feed water valve (7), bypass feed water valve (8), economizer (11); The inlet of running pump one (4), the inlet of running pump two (5), the inlet of starting standby pump (6) are connected with the outlet of deaerator (9); The first outlet of running pump one (4), the first outlet of running pump two (5) and the first outlet of starting standby pump (6) are connected with the inlet of high pressure heater (10); The second outlet of running pump one (4) is connected with the inlet of running pump one circulating valve (1), the second outlet of running pump two (5) is connected with the inlet of running pump two circulating valve (2), the second outlet of starting standby pump (6) is connected with the inlet of starting standby pump circulating valve (3); The outlet of running pump one circulating valve (1), the outlet of running pump two circulating valve (2) and the outlet of starting standby pump circulating valve (3) are connected with the feed water inlet of deaerator (9); The outlet of high pressure heater (10) is connected with the inlet of main feed water valve (7) and the inlet of bypass feed water valve (8) respectively; The outlet of main feed water valve (7) and the outlet of bypass feed water valve (8) are connected with the inlet of economizer (11).

2. The 20% load feed water flow control system of coal-fired unit according to claim 1, wherein, Running pump one (4) and running pump two (5) are steam-driven feed water pumps with 50% of the rated capacity of the boiler, and starting standby pump (6) is an electric feed water pump with 50% of the rated capacity of the boiler.

3. The 20% load feed water flow control system of coal-fired unit according to claim 1, wherein, High pressure heater (10) has two columns and is arranged in parallel, which are column A high pressure heater and column B high pressure heater respectively; Column A high pressure heater comprises A1 high pressure heater, A2 high pressure heater, A3 high pressure heater, A4 high pressure heater and A5 high pressure heater arranged in series; Column B high pressure heater comprises B1 high pressure heater, B2 high pressure heater, B3 high pressure heater, B4 high pressure heater and B5 high pressure heater arranged in series.

4. The 20% load feed water flow control system of coal-fired unit according to claim 1, wherein, Deaerator (9) is a rotating film deaerator, which comprises a shell, a steam-water separator, a rotating film device, a water spraying grate and a heat storage filler liquid-vapor net.

5. The 20% load feed water flow control system of coal-fired unit according to claim 1, wherein, Economizer (11) is arranged in two stages by adopting serpentine light pipes, with the second stage economizer on the top and the first stage economizer on the bottom.

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