Medium-pressure industrial steam supply system under low-load working condition

Abstract

The medium-pressure industrial steam supply system under the low-load working condition comprises a unit, a heater and a mixer, the unit comprises a boiler, a steam turbine high-pressure cylinder and a steam turbine medium-pressure cylinder, and the boiler is used for manufacturing main steam; the steam turbine is provided with a first water inlet, a high-pressure steam exhaust port communicated with a steam inlet of a high-pressure cylinder of the steam turbine, a medium-pressure steam inlet communicated with a steam exhaust port of the high-pressure cylinder of the steam turbine and a reheating steam exhaust port communicated with a steam inlet of a medium-pressure cylinder of the steam turbine; the heater is provided with a second water inlet, a first steam inlet communicated with the high-pressure steam exhaust port, and a main steam adjusting valve and a first steam exhaust port communicated with the medium-pressure steam inlet are arranged between the second water inlet and the first steam inlet; the mixer is provided with a first mixed steam inlet communicating with a steam exhaust port of a turbine high-pressure cylinder, a second mixed steam inlet communicating with the reheating steam exhaust port, a third mixed steam inlet communicating with the second steam exhaust port and a mixed steam exhaust port used for discharging industrial steam. The problems that an existing low-load thermoelectric unit is insufficient in steam supply and unstable in operation are solved.

Description

Technical Field

[0001] The invention relates to the technical field of heating of coal-fired cogeneration units, and in particular to a medium-pressure industrial steam supply system under low-load conditions. Background Art

[0002] The medium-pressure industrial steam provided by coal-fired cogeneration units generally comes from the turbine reheat steam system. When the unit is operating at a relatively high load, the parameters and extraction volume of the medium-pressure industrial steam meet the needs of industrial heat users. When the unit load is reduced to a certain load, the parameters and extraction volume of the medium-pressure industrial steam will gradually decrease, and will eventually fail to meet the needs of industrial heat users. With the development of the new energy industry, the online power generation of new energy units has increased year by year, and coal-fired cogeneration units have gradually transformed from the main power source to an auxiliary service-type regulating power source. Traditional cogeneration units are facing the situation of alternating operation under high load and ultra-low load conditions, which makes the problem of insufficient supply of medium-pressure industrial steam more prominent when operating under ultra-low load conditions.

[0003] At present, the solution to this problem includes the use of high- and low-pressure bypass combined heating technology. High- and low-pressure bypass combined heating has problems such as large local temperature difference stress and unstable operation. For medium-pressure industrial steam with a steam supply pressure of about 2Mpa, the usual steam supply method is to supply it from the unit's low-temperature reheat steam system or to extract it from the high-temperature reheat steam system. However, when the unit load drops to a certain level, the reheat steam system cannot extract enough steam. If the temperature and pressure are directly reduced from the main steam system, the steam extraction volume is also limited by the overtemperature of the boiler reheater. Summary of the invention

[0004] Based on the above description, the present invention provides a medium-pressure industrial steam supply system under low-load conditions to solve the problems of insufficient steam supply and unstable operation of existing low-load thermal power units.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: A medium-pressure industrial steam supply system under low-load conditions, comprising: A unit, comprising a boiler, a high-pressure cylinder of a steam turbine and an intermediate-pressure cylinder of a steam turbine, wherein the boiler is used to produce main steam and is provided with a first water inlet, a high-pressure exhaust port, an intermediate-pressure steam inlet and a reheat exhaust port, wherein the first water inlet is used to supply water to the boiler, the high-pressure exhaust port is communicated with the steam inlet of the high-pressure cylinder of the steam turbine, the intermediate-pressure steam inlet is communicated with the steam exhaust port of the high-pressure cylinder of the steam turbine, and the reheat exhaust port is communicated with the steam inlet of the intermediate-pressure cylinder of the steam turbine; a heater, provided with a second water inlet, a first steam inlet, a first steam exhaust port and a second steam exhaust port, wherein the second water inlet is used to supply water to the heater, the first steam inlet is connected to the high-pressure steam exhaust port, and a main steam regulating valve is provided therebetween, and the first steam exhaust port is connected to the medium-pressure steam inlet; and, The mixer is provided with a first mixing steam inlet, a second mixing steam inlet, a third mixing steam inlet and a mixing steam exhaust port. The first mixing steam inlet is connected to the exhaust port of the high-pressure cylinder of the steam turbine, the second mixing steam inlet is connected to the reheat exhaust port, the third mixing steam inlet is connected to the second exhaust port, and the mixing steam exhaust port is used to discharge industrial steam.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows: Furthermore, the unit also includes a first water supply pipe, a deaerator, a pre-pump and a water feed pump, the two ends of the first water supply pipe are respectively connected to the deaerator and the first water inlet, the pre-pump and the water feed pump are both arranged on the first water supply pipeline, and the pre-pump is located on the water inlet side of the water feed pump.

[0007] Furthermore, the medium-pressure industrial steam supply system under low-load conditions also includes a second water supply pipe and a medium-pressure water supply regulating valve, one end of the second water supply pipe is connected to the first water supply pipe and is located between the pre-pump and the water supply pump, and the other end is connected to the second water inlet, and the medium-pressure water supply regulating valve is arranged on the second water supply pipe.

[0008] Furthermore, the unit further comprises a high-pressure cylinder exhaust pipe, both ends of which are respectively connected to the exhaust port of the high-pressure cylinder of the steam turbine and the medium-pressure steam inlet; The medium-pressure industrial steam supply system under low-load conditions also includes a medium-pressure steam pipe, one end of which is connected to the high-pressure cylinder exhaust pipe, and the other end of which is connected to the first exhaust port.

[0009] Furthermore, a check valve is provided on the high-pressure cylinder exhaust pipe.

[0010] Furthermore, a stop valve is provided on the medium-pressure steam pipe.

[0011] Furthermore, a low-temperature reheat steam regulating valve is provided on the pipeline connecting the exhaust port of the high-pressure cylinder of the steam turbine and the first mixing steam inlet.

[0012] Furthermore, a high-temperature reheat steam regulating valve is provided on the pipeline connecting the reheat steam exhaust port and the second mixing steam inlet port.

[0013] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: The high-pressure exhaust port of the boiler is used to provide main steam to the high-pressure cylinder of the steam turbine. The main steam becomes low-temperature reheat steam after doing work in the high-pressure cylinder of the steam turbine. The low-temperature reheat steam is discharged from its exhaust port and enters the boiler from the medium-pressure steam inlet. After being heated again by the boiler, the low-temperature reheat steam becomes high-temperature reheat steam. The high-temperature reheat steam is discharged from the reheat exhaust port and enters the medium-pressure cylinder of the steam turbine to do work to complete the power generation of the steam turbine.

[0014] Among them, part of the main steam generated by the boiler enters the heater to heat the water in the heater into saturated steam, and the saturated steam enters the mixer from the second exhaust port; the main steam becomes medium-pressure steam after being reduced in pressure and temperature by the main steam regulating valve and the heater, and the medium-pressure steam enters the boiler from the first exhaust port. Since the medium-pressure steam further absorbs heat in the boiler reheater, it can play a role in cooling the reheater of the boiler in the boiler, without affecting the amount of reheated steam returned to the boiler, and avoiding overheating of the boiler reheater. And part of the low-temperature reheated steam and part of the reheated high-temperature steam both enter the mixer to be mixed into industrial steam in the mixer, and the industrial steam is discharged from the mixed exhaust port for users. In this way, the system is simple and the equipment investment is small; the supply of medium-pressure steam is met under the low-load condition of the turbine, and there is no equipment such as a temperature reducer and pressure reducer, which avoids the equipment operation safety problem caused by the large local temperature difference stress of the equipment caused by water spraying and cooling, and improves the stability of system operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic structural diagram of a medium-pressure industrial steam supply system under low-load conditions provided in an embodiment of the present invention.

[0016] In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1. Unit; 11. Boiler; 111. First water inlet; 112. High-pressure exhaust port; 113. Medium-pressure steam inlet; 114. Reheat exhaust port; 12. High-pressure cylinder of steam turbine; 13. Medium-pressure cylinder of steam turbine; 14. First water supply pipe; 15. Deaerator; 16. Fore pump; 17. Feedwater pump; 18. High-pressure cylinder exhaust pipe; 19. Check valve; 2. Heater; 21. Second water inlet; 22. First steam inlet; 23. First steam exhaust port; 24. Second steam exhaust port; 3. Mixer; 31. First mixed steam inlet; 32. Second mixed steam inlet; 33. Third mixed steam inlet; 34. Mixed exhaust port; 4. Second water supply pipe; 5. Medium-pressure feedwater regulating valve; 6. Medium-pressure steam pipe; 7. Stop valve; 81. Main steam regulating valve; 82. Low-temperature reheat steam regulating valve; 83. High-temperature reheat steam regulating valve. DETAILED DESCRIPTION

[0017] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0019] It will be appreciated that spatial relationship terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein to describe the relationship of an element or feature shown in the figures to other elements or features. It will be appreciated that, in addition to the orientations shown in the figures, spatial relationship terms also include different orientations of the device in use and operation. For example, if the device in the accompanying drawings is flipped, an element or feature described as "under other elements" or "under it" or "under it" will be oriented as being "above" the other elements or features. Thus, the exemplary terms "under" and "under" may include both upper and lower orientations. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptors used herein are interpreted accordingly.

[0020] It should be noted that when an element is considered to be "connected" to another element, it can be directly connected to the other element, or connected to the other element through an intermediate element. The "connection" in the following embodiments should be understood as "electrical connection", "communication connection", etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0021] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" etc. specify the presence of stated features, wholes, steps, operations, components, parts or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts or combinations thereof.

[0022] Please refer to Figure 1The present invention provides a medium-pressure industrial steam supply system under low-load conditions, comprising a unit 1, a heater 2 and a mixer 3. The unit 1 comprises a boiler 11, a turbine high-pressure cylinder 12 and a turbine medium-pressure cylinder 13. The boiler 11 is used to produce main steam and is provided with a first water inlet 111, a high-pressure exhaust port 112, a medium-pressure steam inlet 113 and a reheat exhaust port 114. The first water inlet 111 is used to supply water to the boiler 11. The high-pressure exhaust port 112 is communicated with the steam inlet of the turbine high-pressure cylinder 12, the medium-pressure steam inlet 113 is communicated with the steam exhaust port of the turbine high-pressure cylinder 12, and the reheat exhaust port 114 is communicated with the turbine medium-pressure cylinder 13. The heater 2 is provided with a second water inlet 21, a first water inlet 112, a medium-pressure steam inlet 113 and a reheat exhaust port 114. The steam port 22, the first steam exhaust port 23 and the second steam exhaust port 24, the second water inlet 21 is used to supply water to the heater 2, the first steam inlet 22 is connected to the high-pressure exhaust port 112, and a main steam regulating valve 81 is arranged between them, and the first steam exhaust port 23 is connected to the medium-pressure steam inlet 113; the mixer 3 is provided with a first mixed steam inlet 31, a second mixed steam inlet 32, a third mixed steam inlet 33 and a mixed steam exhaust port 34, the first mixed steam inlet 31 is connected to the exhaust port of the high-pressure cylinder 12 of the steam turbine, the second mixed steam inlet 32 ​​is connected to the reheat exhaust port 114, the third mixed steam inlet 33 is connected to the second steam exhaust port 24, and the mixed steam exhaust port 34 is used to discharge industrial steam.

[0023] The high-pressure steam exhaust port 112 of the boiler 11 is used to provide main steam to the high-pressure cylinder 12 of the steam turbine. The main steam becomes low-temperature reheat steam after doing work in the high-pressure cylinder 12 of the steam turbine. The low-temperature reheat steam is discharged from its exhaust port and enters the boiler 11 from the medium-pressure steam inlet 113. After being heated again by the boiler 11, the low-temperature reheat steam becomes high-temperature reheat steam, which is discharged from the reheat exhaust port 114 and enters the medium-pressure cylinder 13 of the steam turbine to do work, so as to complete the power generation of the steam turbine.

[0024] Among them, a part of the main steam generated by the boiler 11 enters the heater 2, heats the water in the heater 2 into saturated steam, and the saturated steam enters the mixer 3 from the first exhaust port 23; the main steam becomes medium-pressure steam after being reduced in pressure and temperature by the main steam regulating valve 81 and the heater 2, and the medium-pressure steam enters the boiler from the first exhaust port 23; because the medium-pressure steam further absorbs heat in the reheater of the boiler 11, it can play a role in cooling the reheater of the boiler 11 in the boiler 11, without affecting the amount of reheated steam returned to the boiler 11, and avoiding overheating of the reheater of the boiler 11. And a part of the reheated low-temperature steam and a part of the reheated high-temperature steam both enter the mixer 3 to be mixed into industrial steam in the mixer 3, and the industrial steam is discharged from the mixed exhaust port 34 for use by users. In this way, the system is simple and the equipment investment is small; the supply of medium-pressure steam is met under low-load conditions of the turbine, and there is no need for equipment such as temperature reducers and pressure reducers, thus avoiding equipment operation safety problems caused by large local temperature difference stress of the equipment caused by water spray cooling, and improving the stability of system operation.

[0025] It should be noted that the combined heating of high and low pressure bypass means that part of the main steam is cooled and decompressed by the high pressure bypass and then sent to the high pressure cylinder 12 of the steam turbine for exhaust. After being heated by the reheater of the boiler 11, steam is extracted from the low pressure bypass (the steam inlet of the medium pressure cylinder 13 of the steam turbine) for external heating. Generally, water spraying is used for cooling, which can easily lead to large local temperature difference stress of the cooling and decompression device and cause operation safety problems.

[0026] In the present invention, part of the main steam enters the heater 2 after pressure regulation by the main steam regulating valve 81, and becomes medium-pressure steam in the heater 2, and the medium-pressure steam flows back into the boiler 11 from the first steam exhaust port 23. That is, part of the main steam extracted from the boiler 11 becomes medium-pressure steam after heat exchange in the heater 2 and flows back into the boiler 11, thereby ensuring the total circulation amount of the steam in the boiler 11 and preventing the overheating of the reheater of the boiler 11. The stable operation of the system is ensured while increasing the steam supply.

[0027] Specifically, in this embodiment, the unit 1 further includes a first water supply pipe 14, a deaerator 15, a pre-pump 16 and a feed water pump 17, the two ends of the first water supply pipe 14 are respectively connected to the deaerator 15 and the first water inlet 111, the pre-pump 16 and the feed water pump 17 are both arranged on the first water supply pipe 14, and the pre-pump 16 is located on the water inlet side of the feed water pump 17. The deaerator 15 is used to provide water from which oxygen and other gases are removed. The pre-pump 16 is used to increase the pressure at the inlet of the feed water pump 17 to prevent cavitation of the feed water pump 17. The feed water pump 17 is used to pump water into the boiler 11 through the first water supply pipe 14.

[0028] More specifically, in this embodiment, the medium-pressure industrial steam supply system under low-load conditions further includes a second water supply pipe 4 and a medium-pressure water supply regulating valve 5, one end of the second water supply pipe 4 is connected to the first water supply pipe 14 and is located between the pre-pump 16 and the water supply pump 17, and the other end is connected to the second water inlet 21, and the medium-pressure water supply regulating valve 5 is arranged on the first water supply pipe 14. The pre-pump 16 increases the pressure of water so that the water can be transported to the second water supply pipe 4. The medium-pressure water supply regulating valve 5 is used to adjust the flow rate and pressure of water supply to the heater 2.

[0029] In this embodiment, the unit 1 further includes a high-pressure cylinder exhaust pipe 18, the two ends of which are respectively connected to the exhaust port of the high-pressure cylinder 12 of the steam turbine and the medium-pressure steam inlet 113, so as to introduce the low-temperature reheated steam discharged from the exhaust port of the high-pressure cylinder 12 of the steam turbine into the boiler 11 from the medium-pressure steam inlet 113. The medium-pressure industrial steam supply system under low-load conditions also includes a medium-pressure steam pipe 6, one end of which is connected to the high-pressure cylinder exhaust pipe 18, and the other end is connected to the first exhaust port 23. The medium-pressure steam pipe 6 is used to introduce part of the medium-pressure steam into the boiler 11 to cool the reheater and ensure the overall circulation amount of the steam of the boiler 11.

[0030] In this embodiment, a check valve 19 is provided on the high-pressure cylinder exhaust pipe 18 , and the check valve 19 is used to prevent the low-temperature reheated steam from flowing back into the high-pressure cylinder 12 of the steam turbine.

[0031] In this embodiment, the medium-pressure steam pipe 6 is provided with a stop valve 7, and the stop valve 7 is used to cut off or conduct the medium-pressure steam pipe 6. It can be opened when the steam turbine is in a low-load condition, so that the heater 2, the steam turbine high-pressure cylinder 12 and the steam turbine medium-pressure cylinder 13 all supply steam to the mixer 3. It is closed under other working conditions of the steam turbine, and steam is supplied by the steam turbine high-pressure cylinder 12 or the steam turbine medium-pressure cylinder 13. In this way, it is flexible to use, and the steam supply mode is adjusted according to different working conditions of the steam turbine to ensure sufficient and stable steam supply.

[0032] In this embodiment, a main steam regulating valve 81 is provided on the pipeline connecting the first steam inlet 22 and the high-pressure steam exhaust port 112 to adjust the flow rate and pressure of the main steam that needs to enter the heater 2 so that the main steam enters the heater 2 after being decompressed.

[0033] In this embodiment, a low-temperature reheat steam regulating valve 82 is provided on the pipeline connecting the exhaust port of the high-pressure cylinder 12 of the steam turbine and the first mixing steam inlet 31 .

[0034] In this embodiment, a high-temperature reheat steam regulating valve 83 is provided on the pipeline connecting the reheat steam exhaust port 114 and the second mixing steam inlet 32 ​​.

[0035] Among them, the low-temperature reheat steam regulating valve 82, the high-temperature reheat steam regulating valve 83 and the main steam regulating valve 81 are all used to adjust the flow and pressure in the corresponding pipelines, and the flow between the low-temperature reheat steam regulating valve 82, the high-temperature reheat steam regulating valve 83 and the main steam regulating valve 81 can also be adjusted, so as to flexibly adjust the pressure parameters of the industrial steam in the mixer 3.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A medium-pressure industrial steam supply system under low-load conditions, characterized in that: include: A unit, comprising a boiler, a high-pressure cylinder of a steam turbine and an intermediate-pressure cylinder of a steam turbine, wherein the boiler is used to produce main steam and is provided with a first water inlet, a high-pressure exhaust port, an intermediate-pressure steam inlet and a reheat exhaust port, wherein the first water inlet is used to supply water to the boiler, the high-pressure exhaust port is communicated with the steam inlet of the high-pressure cylinder of the steam turbine, the intermediate-pressure steam inlet is communicated with the steam exhaust port of the high-pressure cylinder of the steam turbine, and the reheat exhaust port is communicated with the steam inlet of the intermediate-pressure cylinder of the steam turbine; a heater, provided with a second water inlet, a first steam inlet, a first steam exhaust port and a second steam exhaust port, wherein the second water inlet is used to supply water to the heater, the first steam inlet is connected to the high-pressure steam exhaust port, and a main steam regulating valve is provided therebetween, and the first steam exhaust port is connected to the medium-pressure steam inlet; and, The mixer is provided with a first mixing steam inlet, a second mixing steam inlet, a third mixing steam inlet and a mixing steam exhaust port. The first mixing steam inlet is connected to the exhaust port of the high-pressure cylinder of the steam turbine, the second mixing steam inlet is connected to the reheat exhaust port, the third mixing steam inlet is connected to the second exhaust port, and the mixing steam exhaust port is used to discharge industrial steam.

2. The medium-pressure industrial steam supply system under low-load conditions according to claim 1 is characterized in that: The unit also includes a first water supply pipe, a deaerator, a pre-pump and a water feed pump. The two ends of the first water supply pipe are respectively connected to the deaerator and the first water inlet. The pre-pump and the water feed pump are both arranged on the first water supply pipeline, and the pre-pump is located on the water inlet side of the water feed pump.

3. The medium-pressure industrial steam supply system under low-load conditions according to claim 2 is characterized in that: The medium-pressure industrial steam supply system under low-load conditions also includes a second water supply pipe and a medium-pressure water supply regulating valve. One end of the second water supply pipe is connected to the first water supply pipe and is located between the pre-pump and the water supply pump, and the other end is connected to the second water inlet. The medium-pressure water supply regulating valve is arranged on the second water supply pipe.

4. The medium-pressure industrial steam supply system under low-load conditions according to claim 1 is characterized in that: The unit also includes a high-pressure cylinder exhaust pipe, both ends of which are connected to the exhaust port of the high-pressure cylinder of the steam turbine and the medium-pressure steam inlet respectively; The medium-pressure industrial steam supply system under low-load conditions also includes a medium-pressure steam pipe, one end of which is connected to the high-pressure cylinder exhaust pipe, and the other end of which is connected to the first exhaust port.

5. The medium-pressure industrial steam supply system under low-load conditions according to claim 4 is characterized in that: A check valve is provided on the high-pressure cylinder exhaust pipe.

6. The medium-pressure industrial steam supply system under low-load conditions according to claim 4, characterized in that: The medium-pressure steam pipe is provided with a stop valve.

7. The medium-pressure industrial steam supply system under low-load conditions according to claim 1, characterized in that: A low-temperature reheat steam regulating valve is provided on the pipeline connecting the exhaust port of the high-pressure cylinder of the steam turbine and the first mixed steam inlet.

8. The medium-pressure industrial steam supply system under low-load conditions according to claim 1, characterized in that: A high-temperature reheat steam regulating valve is provided on the pipeline connecting the reheat steam exhaust port and the second mixing steam inlet port.

Images