System for reconstructing thermodynamic system to improve low-load thermal efficiency in unit

Abstract

The utility model discloses a system for improving low-load thermal efficiency in a unit by reconstructing a thermodynamic system, which comprises at least one pressure matcher, and a steam extraction source input end of the pressure matcher is connected with a steam exhaust side of a low-pressure cylinder or a steam exhaust condensing device. The driving steam source input end of the pressure matcher is connected with the steam exhaust side of the high-pressure cylinder or the regenerative steam extraction of the medium-pressure cylinder, and the steam output end of the pressure matcher is connected with the steam input side of the low-pressure heater corresponding to the high-grade regenerative steam extraction pipeline through a regenerative steam extraction replacement pipeline. The driving steam source input end of the pressure matcher is connected with a driving steam source shut-off door, a normal steam extraction shut-off door is arranged on the high-grade regenerative steam extraction pipeline, and a substitute steam extraction shut-off door is arranged on the regenerative steam extraction substitute pipeline. The low-pressure cylinder is fully utilized to exhaust steam, cold source loss is reduced, the heat economy of a low-load unit in the unit is improved, the device is suitable for a newly-built unit and an active-service unit, and the technical and economic feasibility is high.

Description

TECHNICAL FIELD

[0001] The utility model belongs to coal-fired power generation technical field, and concretely relates to a system of thermal system reconstruction to improve the thermal efficiency of unit in low load. BACKGROUND

[0002] Traditional coal power mainly considers the high efficiency under rated working condition, and unit coal consumption is significantly increased under medium and low load working condition. Taking a million kilowatt wet cooling unit as an example, the power supply coal consumption under rated working condition is 275g / kWh, the power supply coal consumption under 30% rated working condition is 326g / kWh, and the power supply coal consumption under 20% rated working condition reaches 375g / kWh.

[0003] The unit efficiency mainly depends on the boiler efficiency and the absolute internal efficiency of the steam turbine. With the decrease of load, the general boiler efficiency does not decrease much, but the absolute internal efficiency of the steam turbine will significantly decrease. Taking a million kilowatt wet cooling unit as an example, the boiler efficiency decreases from 95.4% under rated working condition to 94.63% under 30% rated working condition; the absolute internal efficiency of the steam turbine decreases from 51.4% under rated working condition to 46.6% under 30% rated working condition and 44.5% under 20% rated working condition. As can be seen from the above, the focus of improving the medium and low load efficiency of the unit lies in improving the absolute internal efficiency of the steam turbine under medium and low load.

[0004] The absolute internal efficiency of the steam turbine reflects the actual thermal efficiency of the steam turbine unit. The heat input into the steam turbine by the boiler is the cold source loss, that is, the heat released to the environment by the exhaust steam of the low-pressure cylinder of the steam turbine through the condensing device. The low thermal efficiency of the unit under medium and low load means that the cold source loss is large. The factors determining the thermal efficiency of the steam turbine unit mainly include the initial parameters of the unit, the exhaust back pressure, the thermal system (the number of regenerative system stages and the number of reheating times), etc. With the decrease of the initial parameters of the unit, the unit efficiency continuously decreases and the cold source loss continuously increases.

[0005] Improving the economy of the unit under medium and low load and realizing high efficiency under full working condition are one of the key technologies of new generation coal power. Therefore, a new type of thermal system of coal power unit needs to be designed to improve the economy of the unit under medium and low load and realize high efficiency under full working condition. UTILITY MODEL CONTENTS

[0006] The technical problem to be solved by the utility model is to provide a system of thermal system reconstruction to improve the thermal efficiency of unit under medium and low load, solve the problems of low unit efficiency and large cold source loss of coal-fired power generation unit under medium and low load working condition, fully utilize the exhaust heat of the steam turbine, reduce the cold source loss, improve the economy of the unit under medium and low load, and realize high efficiency under full working condition through innovation and reconstruction of the thermal system.

[0007] The utility model provides a kind of thermal system reconstruction to improve the system of low load thermal efficiency in unit, including sequentially connected boiler, high-pressure cylinder, middle-pressure cylinder, low-pressure cylinder, exhaust condensing device, low-pressure heater group, deaerator and high-pressure heater group, low-pressure heater group includes multiple low-pressure heaters being arranged in series, wherein the steam input side of at least one low-pressure heater is connected with middle-pressure cylinder by high-grade regenerative extraction steam pipeline;Further include at least one pressure matcher, the steam source input end of the drive of pressure matcher is connected with low-pressure cylinder exhaust side or exhaust condensing device, the drive steam source input end of pressure matcher is connected with high-pressure cylinder exhaust side or middle-pressure cylinder regenerative extraction steam, the steam output end of pressure matcher is connected with the steam input side of the corresponding low-pressure heater of high-grade regenerative extraction steam pipeline by regenerative extraction steam alternative pipeline, the drive steam source input end of pressure matcher is connected with drive steam source shutoff door, high-grade regenerative extraction steam pipeline is provided with normal extraction shutoff door, regenerative extraction steam alternative pipeline is provided with alternative extraction shutoff door.

[0008] Further, the pressure matcher includes a primary pressure matcher and a secondary pressure matcher;The steam source input end of the primary pressure matcher is connected with low-pressure cylinder exhaust side or exhaust condensing device, the drive steam source input end of the primary pressure matcher is connected with high-pressure cylinder exhaust side or middle-pressure cylinder regenerative extraction steam, the steam output end of the primary pressure matcher is connected with the steam input side of the corresponding low-pressure heater of high-grade regenerative extraction steam pipeline by regenerative extraction steam alternative pipeline;The steam source input end of the secondary pressure matcher is connected with the steam output end of the primary pressure matcher, the drive steam source input end of the secondary pressure matcher is connected with high-pressure cylinder exhaust side or middle-pressure cylinder regenerative extraction steam, the steam output end of the secondary pressure matcher is connected with regenerative extraction steam alternative pipeline.

[0009] Further, the corresponding low-pressure heater of high-grade regenerative extraction steam pipeline is No. five low-pressure heater.

[0010] Further, the drive steam source input end of the pressure matcher is connected with high-pressure cylinder exhaust side.

[0011] Further, high-pressure cylinder exhaust side is connected with boiler by steam reheating pipeline, steam reheating pipeline is led out with drive steam source pipeline, drive steam source pipeline is connected with the drive steam source input end of pressure matcher, and drive steam source shutoff door is arranged on drive steam source pipeline.

[0012] Further, the high-pressure heater group comprises a first high-pressure heater, a second high-pressure heater and a third high-pressure heater arranged in series; the steam input side of the first high-pressure heater is connected with the high-pressure cylinder, the steam input side of the second high-pressure heater is connected with the steam reheating pipeline, and the steam input side of the third high-pressure heater is connected with the intermediate-pressure cylinder; the low-pressure heater group comprises a fifth low-pressure heater, a sixth low-pressure heater and a seventh low-pressure heater arranged in series; the steam input side of the fifth low-pressure heater is connected with the exhaust side of the intermediate-pressure cylinder, the steam input side of the sixth low-pressure heater is connected with the low-pressure cylinder, and the steam input side of the seventh low-pressure heater is connected with the low-pressure cylinder; the low-pressure heater corresponding to the high-grade regenerative extraction pipeline is the fifth low-pressure heater.

[0013] Further, the steam input side of the deaerator is connected with the intermediate-pressure cylinder, and the water output side of the deaerator is connected with the water input end of the third high-pressure heater through a feed water pump pre-pump and a feed water pump.

[0014] Further, a condensate pump, a condensate polishing device and a steam seal cooler are sequentially arranged between the exhaust condensing device and the low-pressure heater group.

[0015] According to the technical scheme of the utility model, the utility model also provides a kind of method for reconstructing heat system to improve the thermal efficiency of unit in low load, which uses the system for reconstructing heat system to improve the thermal efficiency of unit in low load of the utility model, which includes the following contents:

[0016] When load is higher than set threshold, it is operated in normal mode, the state of driving steam source shutoff door and alternative extraction shutoff door is off, the state of normal extraction shutoff door is on, primary pressure matcher does not work, and the steam input side of low-pressure heater corresponding to high-grade regenerative extraction pipeline receives normal extraction of corresponding intermediate-pressure cylinder;

[0017] When load is equal to or lower than set threshold, it is operated in low load mode, the state of driving steam source shutoff door and alternative extraction shutoff door is on, the state of normal extraction shutoff door is off, pressure matcher works, extraction steam of low-pressure cylinder is extracted and pressurized to obtain steam, the steam input side of low-pressure heater corresponding to high-grade regenerative extraction pipeline receives steam to replace normal extraction in normal mode, and the steam corresponding to the replaced normal extraction will continue to work in steam turbine to generate electricity.

[0018] Further, set threshold is 50%.

[0019] Compared with prior art, the utility model has the beneficial technical effects as follows:

[0020] The utility model fits reasonable setting pressure matching ware, utilizes the high pressure steam extraction low pressure cylinder exhaust steam, preparation parameter suitable medium pressure steam, replaces parameter suitable unit backheating system extraction steam, backheating system utilizes the sensible heat and latent heat of unit extraction steam to heat condensate or feed water, reduces cold source loss, the utility model utilizes pressure matching ware extraction low pressure cylinder exhaust steam preparation steam heating condensate or feed water, utilizes low pressure cylinder exhaust steam heat (mainly latent heat) at the same time, the replaced unit interstage extraction steam continues to work in steam turbine and generates electricity, improves unit thermal efficiency, when designing, backheating system normal extraction steam is parallel with pressure matching ware, considering that pressure matching ware capacity is according to medium low load design, therefore under medium low load, the steam of pressure matching ware is put into to replace unit interstage extraction steam, the utility model makes full use of low pressure cylinder exhaust steam, reduces cold source loss, aims at improving unit medium low load unit thermal economy, is not only applicable to new unit, also applicable to active unit, is not limited to unit parameter, capacity, cold end type etc., is the innovation and reconstruction of thermal system, technical and economic feasibility is strong, has development value and demonstration significance, has milestone significance to the progress of electric power industry, is worth developing and promoting, preliminary estimation shows that under 50% load, the unit coal consumption is reduced 1.5g / kWh when cutting off 5 section extraction steam and putting into pressure matching ware system. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is the system structure schematic drawing provided by the utility model.

[0022] Figure 2 It is the system structure schematic drawing of another embodiment provided by the utility model.

[0023] Explanation of reference numerals in the drawings:

[0024] 1, boiler;2, high pressure cylinder;3, medium pressure cylinder;4, low pressure cylinder;5, exhaust steam condensing device;6, deaerator;7, high grade backheating extraction pipe line;8, pressure matching ware;81, primary pressure matching ware;82, secondary pressure matching ware;9, backheating extraction replacement pipe line;10, driving steam source shutoff door;11, normal extraction shutoff door;12, replacement extraction shutoff door;13, steam reheating pipe line;14, driving steam source pipe line;15, No. 1 high pressure heater;16, No. 2 high pressure heater;17, No. 3 high pressure heater;18, No. 5 low pressure heater;19, No. 6 low pressure heater;20, No. 7 low pressure heater;21, feed water pump pre-pump;22, feed water pump;23, condensate pump;24, condensate fine treatment device;25, steam seal cooler;26, extraction steam source shutoff door. DETAILED DESCRIPTION

[0025] The utility model provides a kind of thermal system reconstruction to improve the system of low load heat efficiency in unit, solve the problem of low efficiency of coal-fired generator set and large cold source loss under low load working condition, by innovation, reconstructing thermal system, fully utilizing steam turbine exhaust heat, reducing cold source loss, improving unit low load economy, realizing high efficiency in full working condition.

[0026] Please refer to Figure 1 、 Figure 2 The utility model provides a kind of thermal system reconstruction to improve the system of low load heat efficiency in unit, including the boiler 1 of sequentially connected high-pressure cylinder 2, middle-pressure cylinder 3, low-pressure cylinder 4, exhaust condensing device 5, low-pressure heater group, deaerator 6 and high-pressure heater group.The high-pressure cylinder 2, middle-pressure cylinder 3, low-pressure cylinder 4 and generator are the component parts of steam turbine.The low-pressure heater group includes a plurality of low-pressure heaters arranged in series, wherein at least one low-pressure heater steam input side is connected to the middle-pressure cylinder 3 through high-grade regenerative extraction steam pipeline 7.In other words, the steam input side of each low-pressure heater is connected to a regenerative extraction steam pipeline, and at least one regenerative extraction steam pipeline is connected to the high-pressure cylinder 2 or the middle-pressure cylinder 3 (usually connected to the middle-pressure cylinder 3), and then high-grade extraction steam is used for regenerative extraction, which is called high-grade regenerative extraction steam pipeline 7.

[0027] The above structure is a common structure (part) in existing coal-fired generator set, and the main improvement point of the utility model is Figure 1 、 Figure 2 The part of pipeline highlighted in bold, i.e., further includes at least one pressure matcher 8, the extraction steam source input end of the pressure matcher 8 is connected to the exhaust side of the low-pressure cylinder 4 or the exhaust condensing device 5, the driving steam source input end of the pressure matcher 8 is connected to the exhaust side of the high-pressure cylinder 2 or the regenerative extraction steam of the middle-pressure cylinder 3 (connected to the regenerative extraction steam pipeline on the middle-pressure cylinder, for example, middle-pressure cylinder 4 stage extraction steam or 5 stage extraction steam), and the steam output end of the pressure matcher 8 is connected to the steam input side of the corresponding low-pressure heater of the high-grade regenerative extraction steam pipeline 7 through the regenerative extraction steam replacement pipeline 9.The pipeline also has a valve group (such as an electric shut-off door) corresponding to the pressure matcher 8, including the driving steam source shut-off door 10 connected to the driving steam source input end of the pressure matcher 8, the normal extraction steam shut-off door 11 provided on the high-grade regenerative extraction steam pipeline 7, the replacement extraction steam shut-off door 12 provided on the regenerative extraction steam replacement pipeline 9, and the extraction steam source shut-off door 26 connected to the extraction steam source input end of the pressure matcher 8.

[0028] The pressure matcher is a mature industrial equipment in power station, and the water jet air ejector for unit vacuum extraction is an application scene of the pressure matcher. The working principle is that the high-pressure driving steam is used as a power source, a high-speed jet flow is formed through a nozzle, a low-pressure area is generated at the throat of the nozzle, a pressure difference is formed with the low-pressure steam to be extracted, the low-pressure steam is extracted, the high-pressure steam and the low-pressure steam are mixed and expanded, the output pressure is higher than the pressure of the low-pressure steam to be extracted, and thus the purpose of the low-pressure steam pressure increasing is achieved. In the utility model, the pressure matcher is used, the high-grade steam of the high-pressure cylinder or the medium-pressure cylinder is used as the driving steam source, the low-pressure cylinder exhaust (waste steam) is extracted, the product steam with appropriate parameters is prepared, and the product steam is used as the steam source of the low-pressure heater to replace the original high-grade extraction steam, so that the cold source loss is reduced, and the thermal efficiency of the unit at low load is improved.

[0029] The pressure matcher needs to be matched and designed according to the driving steam source parameters, the extraction steam source parameters and the required product steam parameters (pressure, flow and the like). In a specific project, a reasonable pressure matcher system needs to be set according to the coal saving requirement of the medium and low load, the characteristics of the unit regenerative system and the investment economy, and the pressure matcher system includes the regenerative extraction grade (specific regenerative stage, which can be one stage or multiple stages) replaced by the pressure matcher, the driving steam source selection of the pressure matcher and the stage number of the pressure matcher.

[0030] For example Figure 1 In the embodiment shown in the figure, the pressure matcher 8 includes a first-stage pressure matcher 81 and a second-stage pressure matcher 82. For another example Figure 2 In the embodiment shown in the figure, the pressure matcher 8 only has one stage. In Figure 1 , Figure 2 , only one pressure matcher is shown, and the steam source of one low-pressure heater is optimized and replaced. In other feasible embodiments, multiple groups of pressure matchers are arranged, the steam sources of multiple low-pressure heaters are optimized and replaced, each group of pressure matchers can be selected as one stage, two stages or more stages according to requirements, and the product steam of one group of pressure matchers can be output to two or more low-pressure heaters. The basic principle is that if the product parameters of the first-stage pressure matcher cannot meet the requirements, the second-stage pressure matcher can be arranged; the product steam of the first-stage pressure matcher is used as the suction steam source, and the driving steam source can be unchanged. The following is a more specific description with reference to the embodiment shown in Figure 1

[0031] Figure 1 ​In the shown embodiment, the pressure matcher 8 comprises a first pressure matcher 81 and a second pressure matcher 82. The steam extraction source input end of the first pressure matcher 81 is connected with the exhaust steam side of the low-pressure cylinder 4 or the exhaust steam condenser 5 (in the shown embodiment, specifically connected with the exhaust steam condenser 5), the driving steam source input end of the first pressure matcher 81 is connected with the exhaust steam side of the high-pressure cylinder 2 or the regenerative extraction of the intermediate-pressure cylinder 3, and the steam output end of the first pressure matcher 81 is connected with the steam input side of the corresponding low-pressure heater of the high-grade regenerative extraction pipeline 7 through the regenerative extraction replacement pipeline 9. The steam extraction source input end of the second pressure matcher 82 is connected with the steam output end of the first pressure matcher 81, the driving steam source input end of the second pressure matcher 82 is connected with the exhaust steam side of the high-pressure cylinder 2 or the regenerative extraction of the intermediate-pressure cylinder 3, and the steam output end of the second pressure matcher 82 is connected with the regenerative extraction replacement pipeline 9. For a common regenerative system scheme, the high-grade regenerative extraction pipeline 7 can be selected as the fifth low-pressure heater 18 corresponding to the low-pressure heater. In other embodiments, the low-pressure heater below the fifth low-pressure heater can also be selected, such as the sixth low-pressure heater or the seventh low-pressure heater, etc.

[0032] More specifically, the high-grade regenerative extraction pipeline 7 is connected with the intermediate-pressure cylinder 3, and the originally used heating steam of the corresponding low-pressure heater is derived from the exhaust steam of the intermediate-pressure cylinder. The exhaust steam of the intermediate-pressure cylinder still has a lot of available energy. If it is replaced by the product steam formed by the exhaust steam of the low-pressure cylinder, the originally part of the exhaust steam of the intermediate-pressure cylinder can continue to enter the low-pressure cylinder for power generation instead of being used for regenerative, thereby improving the thermal efficiency. The driving steam source input end of the pressure matcher 8 is connected with the exhaust steam side of the high-pressure cylinder 2, that is, the exhaust steam of the high-pressure cylinder is used as the driving steam source of the pressure matcher. For the second pressure matcher, the first pressure matcher 81 and the second pressure matcher 82 can both be selected as the driving steam source of the pressure matcher. The extraction mode of the exhaust steam of the high-pressure cylinder is specifically, for example, the exhaust steam side of the high-pressure cylinder 2 is connected with the boiler 1 through the steam reheating pipeline 13. The steam reheating pipeline is provided in the prior art. In the present scheme, the driving steam source pipeline 14 is led out on the steam reheating pipeline 13, the driving steam source pipeline 14 is connected with the driving steam source input end of the pressure matcher 8, and the driving steam source shut-off door 10 is arranged on the driving steam source pipeline 14.

[0033] The high-pressure heater group comprises a first high-pressure heater 15, a second high-pressure heater 16 and a third high-pressure heater 17 arranged in series. The steam input side of the first high-pressure heater 15 is connected to the high-pressure cylinder 2 (through the pipeline marked with the number 1 in the figure), the steam input side of the second high-pressure heater 16 is connected to the steam reheating pipeline 13 (through the pipeline marked with the number 2 in the figure), and the steam input side of the third high-pressure heater 17 is connected to the intermediate-pressure cylinder 3 (through the pipeline marked with the number 3 in the figure). The low-pressure heater group comprises a fifth low-pressure heater 18, a sixth low-pressure heater 19 and a seventh low-pressure heater 20 arranged in series. The steam input side of the fifth low-pressure heater 18 is connected to the exhaust side of the intermediate-pressure cylinder 3 (through the pipeline marked with the number 5 in the figure), the steam input side of the sixth low-pressure heater 19 is connected to the low-pressure cylinder 4 (through the pipeline marked with the number 6 in the figure), and the steam input side of the seventh low-pressure heater 20 is connected to the low-pressure cylinder 4 (through the pipeline marked with the number 7 in the figure). In the illustrated embodiment, the low-pressure heater corresponding to the high-grade regenerative extraction pipeline 7 is the fifth low-pressure heater 18, and the pipeline marked with the number 5 in the figure is the high-grade regenerative extraction pipeline 7 which is added and improved.

[0034] Further, the steam input side of the deaerator 6 is connected to the intermediate-pressure cylinder 3 (through the pipeline marked with the number 4 in the figure), and the water output side of the deaerator 6 is connected to the water input end of the third high-pressure heater 17 through the feed water pump pre-pump 21 and the feed water pump 22. The condensate pump 23, the condensate polishing device 24 and the steam seal cooler 25 are further arranged in sequence between the exhaust condensing device 5 and the low-pressure heater group. The exhaust steam of the low-pressure cylinder 4 is converted from gaseous state to liquid state after passing through the exhaust condensing device 5, enters the pipeline of the regenerative system, and sequentially passes through the condensate pump 23, the condensate polishing device 24, the steam seal cooler 25, the seventh low-pressure heater 20, the sixth low-pressure heater 19, the fifth low-pressure heater 18, the deaerator 6, the feed water pump pre-pump 21, the feed water pump 22, the third high-pressure heater 17, the second high-pressure heater 16, the first high-pressure heater 15, and then returns to the boiler 1, forming a water circulation.

[0035] Based on the above system structure of the utility model, the utility model provides a kind of method for reconstructing thermodynamic system to improve the thermal efficiency of unit medium-low load, which uses the system for reconstructing thermodynamic system to improve the thermal efficiency of unit medium-low load of the utility model, which includes the following contents:

[0036] When load is higher than set threshold, it is operated in normal mode, the state of driving steam source shutoff door 10, alternative extraction shutoff door 12 (and extraction steam source shutoff door 26) is off, the state of normal extraction shutoff door 11 is on, first-stage pressure matcher 81 does not work, and the steam input side of the low-pressure heater corresponding to high-grade regenerative extraction pipeline 7 receives corresponding normal extraction of intermediate-pressure cylinder 3.

[0037] When the load is equal to or lower than the set threshold, the unit is operated in the low-medium load mode, the state of the driving steam source shutoff door 10 and the substitute extraction steam shutoff door 12 (and the extraction steam source shutoff door 26) is open, the state of the normal extraction steam shutoff door 11 is closed, the pressure matcher 8 works, the exhaust steam of the low-pressure cylinder 4 is extracted and pressurized to generate steam, the high-grade regenerative extraction steam pipeline 7 receives the generated steam at the steam input side of the corresponding low-pressure heater, and the generated steam substitutes the normal extraction steam in the normal mode, and the steam corresponding to the substituted normal extraction steam will continue to work in the steam turbine to generate power.

[0038] Preferably, the set threshold is 50%, for example.

[0039] In a typical embodiment, taking a regenerative system of a unit as an example, it is assumed that the pressure matcher system is put into operation when the unit load is 50% or lower. The high-pressure cylinder exhaust steam is used as the driving steam source, the low-pressure cylinder exhaust steam (waste steam) is extracted, and the product steam with appropriate parameters is prepared to be used as the steam source of the No. 5 low-pressure heater to replace the No. 5 extraction steam. When the pressure matcher is designed, the required product steam pressure and mass flow are designed as the design conditions to meet the steam parameters of the No. 5 low-pressure heater at 50% load. The pressure matcher system and the No. 5 extraction steam system are arranged side by side and are isolated by a valve group. When the load is higher than 50%, the regenerative system is normally operated; when the load is 50% or lower, the No. 5 extraction steam is cut off, and the pressure matcher system is put into operation. According to preliminary calculation, when the pressure matcher system is put into operation and the No. 5 extraction steam is cut off at 50% load, the unit coal consumption is reduced by 1.5 g / kWh.

[0040] In summary, the utility model makes full use of the low-pressure cylinder exhaust steam and reduces the loss of cold source, aims to replace the regenerative extraction steam with the low-pressure cylinder exhaust steam (waste steam) to reduce the loss of cold source and improve the economic efficiency of the unit at low-medium load. The utility model has a wide range of applications, is suitable for new units and active units, is suitable for heating units and pure condensing units, is not limited to unit parameters, capacity and cold end type, is an innovation and reconstruction of the thermal system, has strong technical and economic feasibility, has development value and demonstration significance, has a milestone significance for the progress of the electric power industry, and is worth developing and promoting.

[0041] Finally should be explained is: above only to the main improvement points of the utility model have carried on the detailed explanation, the rest is not explained in detail the part is common sense content or can use the prior art or adopt similar technical scheme, thereby realizing the required function, therefore need not to repeat; The above examples are only used to illustrate the technical scheme of the utility model, but not limit it; Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of the utility model protection; In order to facilitate the description, only the part related to the utility model is shown in the drawings. In the case of no conflict, the embodiments in the utility model and the features in the embodiments can be combined with each other; The technical scheme recorded in the foregoing embodiments is modified, or some technical features are replaced, and the essence of the corresponding technical scheme does not deviate from the spirit and scope of the technical scheme of the utility model embodiments.

Claims

1. A system for reconfiguring a thermal system to improve the thermal efficiency of a unit under low load, comprising a boiler (1), a high-pressure cylinder (2), an intermediate-pressure cylinder (3), a low-pressure cylinder (4), an exhaust steam condenser (5), a low-pressure heater group, a deaerator (6), and a high-pressure heater group connected in sequence, wherein the low-pressure heater group comprises multiple low-pressure heaters arranged in series, wherein at least one low-pressure heater has its steam input side connected to the intermediate-pressure cylinder (3) via a high-grade regenerative steam extraction pipeline (7); characterized in that, It also includes at least one pressure matching device (8), the steam source input end of the pressure matching device (8) is connected to the exhaust side of the low-pressure cylinder (4) or the exhaust steam condensing device (5), the driving steam source input end of the pressure matching device (8) is connected to the exhaust side of the high-pressure cylinder (2) or the regenerative steam extraction of the medium-pressure cylinder (3), the steam output end of the pressure matching device (8) is connected to the steam input side of the corresponding low-pressure heater of the high-grade regenerative steam extraction pipeline (7) through the regenerative steam extraction substitution pipeline (9), the driving steam source input end of the pressure matching device (8) is connected to a driving steam source shut-off valve (10), a normal steam extraction shut-off valve (11) is provided on the high-grade regenerative steam extraction pipeline (7), and a substitute steam extraction shut-off valve (12) is provided on the regenerative steam extraction substitution pipeline (9).

2. The system for reconfiguring the thermal system according to claim 1 to improve the thermal efficiency of a unit at low loads, characterized in that, The pressure matcher (8) includes a primary pressure matcher (81) and a secondary pressure matcher (82). The steam source input end of the first-stage pressure matching device (81) is connected to the exhaust side of the low-pressure cylinder (4) or the exhaust condensing device (5). The driving steam source input end of the first-stage pressure matching device (81) is connected to the exhaust side of the high-pressure cylinder (2) or the regenerative steam extraction of the medium-pressure cylinder (3). The steam output end of the first-stage pressure matching device (81) is connected to the steam input side of the corresponding low-pressure heater of the high-grade regenerative steam extraction pipeline (7) through the regenerative steam extraction replacement pipeline (9). The steam source input end of the secondary pressure matcher (82) is connected to the steam output end of the primary pressure matcher (81), the driving steam source input end of the secondary pressure matcher (82) is connected to the exhaust side of the high pressure cylinder (2) or the reheat extraction of the intermediate pressure cylinder (3), and the steam output end of the secondary pressure matcher (82) is connected to the reheat extraction replacement pipeline (9).

3. The system for reconfiguring the thermal system according to claim 1 to improve the thermal efficiency of the unit at low loads, characterized in that, The corresponding low-pressure heater for the high-grade regenerative steam extraction pipeline (7) is the No. 5 low-pressure heater (18).

4. The system for reconfiguring the thermal system according to claim 1 or 2 to improve the thermal efficiency of the unit at low loads, characterized in that, The driving steam source input end of the pressure matching device (8) is connected to the exhaust side of the high-pressure cylinder (2).

5. The system for reconfiguring the thermal system according to claim 4 to improve the thermal efficiency of the unit at low loads, characterized in that, The exhaust side of the high-pressure cylinder (2) is connected to the boiler (1) through the steam reheat pipeline (13). A driving steam source pipeline (14) is led out from the steam reheat pipeline (13). The driving steam source pipeline (14) is connected to the driving steam source input end of the pressure matching device (8). The driving steam source shut-off valve (10) is set on the driving steam source pipeline (14).

6. The system for reconfiguring the thermal system according to claim 5 to improve the thermal efficiency of the unit at low loads, characterized in that, The high-pressure heater group includes a No. 1 high-pressure heater (15), a No. 2 high-pressure heater (16), and a No. 3 high-pressure heater (17) connected in series. The steam input side of the No. 1 high-pressure heater (15) is connected to the high-pressure cylinder (2), the steam input side of the No. 2 high-pressure heater (16) is connected to the steam reheat pipeline (13), and the steam input side of the No. 3 high-pressure heater (17) is connected to the intermediate-pressure cylinder (3). The low-pressure heater group includes a No. 5 low-pressure heater (18), a No. 6 low-pressure heater (19), and a No. 7 low-pressure heater (20) connected in series. The steam input side of the No. 5 low-pressure heater (18) is connected to the exhaust side of the intermediate-pressure cylinder (3), the steam input side of the No. 6 low-pressure heater (19) is connected to the low-pressure cylinder (4), and the steam input side of the No. 7 low-pressure heater (20) is connected to the low-pressure cylinder (4). The corresponding low-pressure heater of the high-grade regenerative steam extraction pipeline (7) is the No. 5 low-pressure heater (18).

7. The system for reconfiguring the thermal system according to claim 6 to improve the thermal efficiency of a unit at low loads, characterized in that, The steam input side of the deaerator (6) is connected to the intermediate pressure cylinder (3), and the water output side of the deaerator (6) is connected to the water input end of the No. 3 high pressure heater (17) through the feed water pump pre-pump (21) and the feed water pump (22).

8. The system for reconfiguring the thermal system according to claim 6 to improve the thermal efficiency of the unit at low loads, characterized in that, A condensate pump (23), a condensate polishing device (24), and a steam seal cooler (25) are also installed sequentially between the exhaust steam condensing device (5) and the low-pressure heater group.

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