A combined heat recovery system

Abstract

The present invention discloses a combined heat recovery system, including a high-pressure cylinder of a steam turbine, a main steam pipeline, a conventional final-stage extraction pipeline, an additional pipeline added to the main steam pipeline, a heat exchanger using the main steam in the main steam pipeline as a heat source, a feedwater heater using the exhaust steam of the heat exchanger as a heat source, and a steam-side regulating valve arranged on the additional pipeline, which is used to regulate the main steam in the additional pipeline, so as to control the extraction pressure after the steam-side regulating valve to control the outlet temperature of the feedwater heater to meet the required final feedwater temperature. By using this system, the heat of boiler steam can be recovered during the start-up phase of the unit, and problems such as low coal powder burnout rate, black smoke from fuel oil, and low-temperature condensation, ash blockage, corrosion, etc. in the equipment such as the air preheater of the tail flue during the start-up phase can be solved.

Description

Technical Field

[0001] The invention relates to the field of thermal power generation, and in particular to a combined heat recovery system. Background Art

[0002] At present, my country's electricity is mainly peaked by thermal power generating units, and low-load operation of thermal power generating units has become the norm. With the official release of my country's "13th Five-Year Plan for Power Development (2016-2020)", "strengthening peak capacity construction and improving system flexibility" has become one of the important tasks of thermal power generating units, which means that higher requirements are put forward for the deep peaking and system flexibility of thermal power generating units. In fact, when thermal power generating units are operated at low load, there are many problems such as environmental protection, safety, and economy, including the need to withdraw the SCR denitrification device from operation, the problem of unstable boiler water power, unstable boiler combustion, and low cycle efficiency.

[0003] In order to solve the above-mentioned problems of SCR denitration needing to be shut down due to low load, boiler water dynamic instability, and low cycle thermal efficiency, Chinese patent ZL201110459533.2 discloses an adjustable feedwater heat recovery system, that is, compared with traditional steam turbine generator sets, the final stage steam extraction pressure set on the high-pressure cylinder is higher than the conventional maximum steam extraction pressure of the high-pressure cylinder; and a steam extraction regulating valve is set on the final stage steam extraction pipeline, and then the feedwater is reheated through the feedwater heater. During operation, the final stage steam extraction can be adjusted through the valve, so as to keep the pressure after the steam extraction regulating valve basically unchanged when the unit changes load, and the temperature of the boiler feedwater is maintained basically unchanged through the final stage feedwater heater.

[0004] However, the system and method provided by the patent still have shortcomings. At each load stage of the unit, the extraction steam of this stage needs to be throttled to maintain the pressure of the extraction steam regulating valve. Especially at lower loads, the extraction steam superheat will be relatively large, resulting in a large heat exchange temperature difference of the additional feedwater heater and an increase in irreversible losses. In other words, the additional adjustable final stage extraction steam is not very effectively utilized; on the other hand, due to the high extraction steam temperature of this stage, the corresponding pipe and feedwater heater costs will increase, especially as the unit parameters continue to increase, such as a 700℃ unit, due to the corresponding extraction steam temperature is too high, which will make the feedwater heater difficult to implement under the existing manufacturing process. In addition, the system and method provided by the patent also have application limitations, and cannot be directly applied to units without additional steam extraction ports in the steam turbine.

[0005] On the other hand, modern thermal power generating units are equipped with bypass systems to meet the requirements of unit start-up and shutdown, accident conditions, etc. When the unit is started, starting from the ignition of the boiler, a large amount of steam generated by consuming coal and fuel oil is finally sent to the condenser through the bypass system until the turbine steam inlet quality is qualified and the steam parameters meet the start-up conditions, the turbine starts to start, and finally to the grid, the bypass is finally closed. The cold start of traditional thermal power generating units takes about 8-10 hours from ignition to grid connection. During this period, a large amount of steam is sent to the condenser through the bypass system. Although the working fluid is recovered, the heat is lost. In addition, there are problems such as low coal powder burnout rate, black smoke from fuel oil, and low-temperature condensation, ash blockage, and corrosion in the air preheater of the tail flue during the startup stage. Summary of the invention

[0006] In view of this, in order to comprehensively solve the above-mentioned problems faced in the low load and startup stages and the shortcomings of the existing adjustable water supply heat recovery system, the present invention provides a combined heat recovery system.

[0007] The present invention provides a combined heat recovery system, characterized in that it comprises:

[0008] High-pressure cylinder of steam turbine;

[0009] Main steam pipe;

[0010] Conventional final stage steam extraction pipeline;

[0011] a heat exchanger using the main steam in the main steam pipeline as a heat source;

[0012] a feedwater heater using exhaust steam from the heat exchanger as a heat source;

[0013] An additional pipeline added to the main steam pipeline, through which the heat exchanger and the feedwater heater are connected in series;

[0014] The steam-side regulating valve arranged on the additional pipeline is used to regulate the main steam in the additional pipeline to control the extraction steam pressure after the steam-side regulating valve to control the outlet temperature of the feed water heater to meet the required final feed water temperature.

[0015] Preferably, the steam-side regulating valve is arranged on an additional pipeline between the main steam pipeline and the heat exchanger.

[0016] Preferably, the heat exchanger may be a single heat exchanger or a heat exchanger group consisting of a plurality of heat exchangers.

[0017] Preferably, the heat exchanger group may be a combination of two or more heat exchangers connected in parallel or in series, or may be a combination of three or more heat exchangers connected in series and in parallel.

[0018] Preferably, the working medium heated by the heat exchanger is boiler hot secondary air or boiler hot primary air or boiler powder feed or a combination of the three or a combination of two of them.

[0019] Preferably, a bypass is added to the heat exchanger, and isolation valves are added before and after the heat exchanger.

[0020] Preferably, it further comprises an additional hot re-pipeline added to the hot re-pipeline, wherein the additional hot re-pipeline is connected in parallel with the additional pipe added to the main steam pipe and then connected to the heat exchanger and the feedwater heater;

[0021] Preferably, the feedwater heater is a conventional final-stage feedwater heater, the additional pipeline is connected to the heat exchanger and the conventional final-stage feedwater heater, and an isolation valve is provided on the conventional final-stage steam extraction pipeline.

[0022] Preferably, the feedwater heater is an additional adjustable rear final stage feedwater heater; the additional pipeline is connected to the heat exchanger and the additional adjustable rear final stage feedwater heater;

[0023] Preferably, it further comprises at least one water-side regulating valve, and the water-side regulating valve is connected in parallel with the additional adjustable post-final-stage feedwater heater.

[0024] The combined heat recovery system of the present invention has the following advantages and effects:

[0025] 1. The present invention does not require the setting of an additional steam turbine extraction port. In the normal operation stages of the unit at different loads, the main steam is directly used for heat exchange through the heat exchanger, and then further to the additional adjustable final-stage feed water heater to supplement the heating of the feed water. After the main steam is throttled by the regulating valve, especially under low load, the steam superheat is relatively large, but since the heat exchanger is added, the steam superheat can be effectively utilized; in addition, in the low load stage, the main steam heats the boiler hot primary air and / or the boiler hot secondary air and / or the boiler powder feeding through the heat exchanger, which can realize the improvement of the drying output of the powder making system and the improvement of the boiler combustion performance, and alleviate the problems of air preheater equipment blockage and the like.

[0026] 2. After the main steam of the present invention is heat exchanged through the heat exchanger, the steam temperature is reduced. Therefore, the cost of the pipeline material after the heat exchanger and the additional adjustable final-stage feedwater heater can be greatly reduced. Especially for future high-parameter units, this method also provides a way out for solving the problem of high-parameter feedwater heaters being difficult to manufacture.

[0027] 3. The system of the present invention can be put into use during the startup phase of the unit, and can recover a portion of the heat of the large amount of steam originally sent to the condenser through the bypass system to heat the boiler air supply or boiler powder supply, directly increasing the air temperature and powder temperature during the startup phase; and further supplementing the heating of the boiler feed water, increasing the feed water temperature, and indirectly further supplementing the preheating of the entire boiler, which can greatly reduce the fuel and coal consumption during the startup phase. In addition, since the system can be put into use during the startup phase, it also solves the problems of low coal powder burnout rate, black smoke from fuel oil, and low-temperature condensation, ash blockage, corrosion, etc. in the air preheater of the tail flue during the startup phase, and can ensure that the unit can be put into the SCR denitration device before being connected to the grid, and can also extend the life of the SCR catalyst. These advantages are not available in the existing adjustable feed water heat recovery system.

[0028] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a system schematic diagram of specific embodiment 1 of the present invention.

[0030] Figure 2 It is a system schematic diagram of specific embodiment 2 of the present invention.

[0031] Figure 3 It is a system schematic diagram of specific embodiment 3 of the present invention.

[0032] Figure 4 It is a system schematic diagram of specific embodiment 4 of the present invention.

[0033] Figure 5 It is a system schematic diagram of specific embodiment 5 of the present invention.

[0034] Figure 6 It is a system schematic diagram of specific embodiment 6 of the present invention.

[0035] Figure 7 It is a system schematic diagram of specific embodiment 7 of the present invention.

[0036] Figure 8 It is a system schematic diagram of specific embodiment 8 of the present invention.

[0037] Fig. 9 It is a system schematic diagram of specific embodiment 9 of the present invention.

[0038] Fig.10 It is a system schematic diagram of specific embodiment 10 of the present invention.

[0039] Fig.11 It is a system schematic diagram of specific embodiment 11 of the present invention.

[0040] Fig.12 It is a system schematic diagram of specific embodiment 12 of the present invention.

[0041] Fig.13 It is a system schematic diagram of specific embodiment 13 of the present invention.

[0042] Fig.14 It is a system schematic diagram of specific embodiment 14 of the present invention.

[0043] Fig.15 It is a system schematic diagram of specific embodiment 15 of the present invention.

[0044] Fig.16 It is a system schematic diagram of specific embodiment 16 of the present invention.

[0045] Fig.17 It is a system schematic diagram of specific embodiment 17 of the present invention.

[0046] Fig.18 It is a system schematic diagram of specific embodiment 18 of the present invention.

[0047] Fig.19 It is a system schematic diagram of specific embodiment 19 of the present invention.

[0048] Fig. 20 It is a schematic diagram of a system of specific embodiment 20 of the present invention.

[0049] Among them: 1- conventional final stage steam extraction port; 10- conventional final stage steam extraction pipeline; 11- conventional final stage feed water heater; 2- main steam pipeline; 3- other conventional systems; 4- high pressure cylinder; 5- final feed water; 6- water side regulating valve; 7- reheater; 8- heat reheat to medium pressure cylinder; 00, 09, 9- isolating valve; 01- additional pipeline; 02- steam side regulating valve; 03, 03', 03''- heat exchanger; 04, 04', 04'' - heated working medium channel of heat exchanger; 05- additional adjustable final stage feed water heater; 06- heat exchanger inlet isolating valve; 07- heat exchanger outlet isolating valve; 08- additional heat reheat pipeline. DETAILED DESCRIPTION

[0050] Example 1

[0051] Figure 1 This is a system schematic diagram of a specific embodiment 1 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, a steam-side regulating valve 02 on the additional pipeline, a heat exchanger 03, and an additional adjustable final-stage feedwater heater 05 are added.

[0052] The additional adjustable rear final stage feedwater heater 05 is connected to the heat exchanger 03 and the main steam pipeline 2 through the additional pipeline 01, and the steam side regulating valve 02 is arranged on the additional pipeline 01 between the main steam pipeline 2 and the heat exchanger 03. The steam side regulating valve 02 is used to regulate the main steam in the additional pipeline 01, and the feedwater temperature at the outlet of the additional adjustable rear final stage feedwater heater 05 is controlled by controlling the pressure after the steam side regulating valve 02.

[0053] The control method of the present invention is described in detail by taking an example of a 1000MW unit in a power plant, wherein the steam turbine is an ultra-supercritical single-shaft, once-reheated, four-cylinder, four-exhaust condensing steam turbine.

[0054] For example, the main steam parameter under the rated condition (1000WM) of the unit is 27MPa / 600℃. During the unit operation stage, as the unit load decreases, the pressure entering the additional adjustable final feedwater heater is controlled at about 8.5MPa by adjusting the steam side regulating valve to maintain the final feedwater temperature at about 300℃. Since a heat exchanger is added to heat the boiler hot primary air or boiler hot secondary air or boiler powder feeding, the superheat of the additional adjustable final extraction steam can be effectively utilized, and the temperature after the heat exchanger can be reduced to about 360℃, and then enter the additional adjustable final feedwater heater to further heat the feedwater. This not only has all the advantages of the adjustable feedwater heat recovery system, but also reduces the steam inlet temperature of the additional adjustable rear final feedwater heater, and its investment cost can be reduced to a certain extent. In addition, the heat of the extracted steam is indirectly sent to the boiler by heating the boiler hot primary air or the boiler hot secondary air or the boiler powder, replacing part of the boiler's fuel and effectively improving the boiler's combustion conditions, which can greatly improve the unit's economy. In this embodiment, the heat exchanger can also be equipped with a bypass, and isolation valves can be added before and after the heat exchanger, so that if the heat exchanger has a leakage or other fault during operation, it can be switched to operation through the bypass.

[0055] During the startup phase of the unit, starting from the ignition of the boiler, the steam generated by consuming coal and fuel oil can enter the heat exchanger 03 through the additional pipeline 01 to heat the boiler hot primary air or boiler hot secondary air or boiler feed powder, thereby sending heat into the boiler to replace the boiler fuel, and then enter the additional adjustable rear final stage feed water heater 05 to further supplement and heat the boiler feed water, thereby increasing the feed water temperature in the startup phase and reducing the inlet enthalpy deficiency of the water-cooled wall in the startup phase, thereby solving the problem of hydrodynamic instability in the startup phase, creating favorable conditions for the rapid startup of the unit, and ultimately achieving a significant reduction in startup energy consumption, and solving the problems of low coal powder burnout rate, black smoke from fuel oil, and low-temperature condensation, ash blockage, and corrosion in the air preheater of the tail flue generated in the traditional startup phase.

[0056] Example 2

[0057] Figure 2 This is a system schematic diagram of a specific embodiment 2 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, a steam-side regulating valve 02 on the additional pipeline, a heat exchanger 03, an additional adjustable post-final-stage feedwater heater 05, and a water-side regulating valve 6 are added.

[0058] The main difference between this embodiment and embodiment 1 is that a water-side regulating valve 6 is added, which is connected in parallel with the additional adjustable final-stage feedwater heater 05. Therefore, the additional adjustable final-stage feedwater heater 05 can be designed as a partial-capacity feedwater heater to reduce the cost of the heater.

[0059] The only difference between the method of using the system of this embodiment and that of embodiment 1 is that the final feed water temperature is the feed water temperature after the outlet of the additional adjustable final feed water heater 05 is mixed with the outlet of the water side regulating valve 6. The rest is the same and will not be repeated here.

[0060] Example 3

[0061] Figure 3 This is a system schematic diagram of specific embodiment 3 of the present invention. In addition to the conventional final stage steam extraction port 1, the conventional final stage steam extraction 10, the final stage feed water heater 11 and the main steam pipeline 2, this embodiment further includes an additional pipeline 01, a steam side regulating valve 02 on the additional pipeline, a heat exchanger inlet isolation valve 06, a heat exchanger outlet isolation valve 07 and a heat exchanger 03.

[0062] The main difference between this embodiment and embodiment 1 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, as in embodiment 1, the steam heat that would have been wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0063] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feedwater heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, and the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation. To switch back to the original system, the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07 can be closed. Therefore, the online switching operation of the two-way steam to the conventional final-stage feedwater heater 11 can be fully realized through the isolation valve 09, the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07.

[0064] The rest is the same as that of Example 1 and will not be described again here.

[0065] Example 4

[0066] Figure 4 This is a system diagram of a specific embodiment 4 of the present invention. In this embodiment, on the basis of the conventional final-stage steam extraction port 1, conventional final-stage steam extraction 10, conventional final-stage feedwater heater 11, and main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam-side regulating valve 02 on the additional pipeline, a heat exchanger 03, and an additional adjustable final-stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate pressure cylinder to the heat exchanger 03.

[0067] The main difference between this embodiment and embodiment 1 is that an additional hot reheat pipe 08 is provided to the heat exchanger. Its advantage is that during the unit startup phase, in order to protect the reheater, a portion of the steam will inevitably pass through the bypass system (high bypass) and be heated by the reheater 7 to become hot reheat. Under traditional circumstances, this portion of hot reheat steam will pass through the bypass system (low bypass) to the condenser. In the scheme of the present invention, since this additional hot reheat pipe 08 is added to the heat exchanger 03, the hot reheat steam flowing through the reheater during the startup phase can be further recovered. Since the isolation valve 9 is provided, the switching operation of the two steam inlets 08 and 01 can be realized.

[0068] The rest is the same as that of Example 1 and will not be described again here.

[0069] Example 5

[0070] Figure 5 This is a system diagram of a specific embodiment 5 of the present invention. In this embodiment, on the basis of the conventional final-stage steam extraction port 1, conventional final-stage steam extraction 10, conventional final-stage feedwater heater 11, and main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam-side regulating valve 02 on the additional pipeline, a heat exchanger 03, and an additional adjustable final-stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate pressure cylinder to the heat exchanger 03.

[0071] The main difference between this embodiment and embodiment 4 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, as in embodiment 4, the steam heat that would have been wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0072] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feed water heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, the isolation valve 9 can be closed, and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation, that is, the main steam heats the boiler supply air or boiler powder through the heat exchanger 03, and further supplements the heating of the boiler feed water. To switch back to the original system, just close the heat exchanger outlet isolation valve 07.

[0073] The rest is consistent with Example 4 and will not be repeated here.

[0074] Example 6

[0075] Figure 6 This is a system schematic diagram of specific embodiment 6 of the present invention. In this embodiment, on the basis of the conventional final stage steam extraction port 1, the conventional final stage steam extraction 10, the conventional final stage feed water heater 11 and the main steam pipeline 2, an additional pipeline 01, a steam side regulating valve 02 on the additional pipeline, heat exchangers 03 and 03', and an additional adjustable post-final stage feed water heater 05 are added.

[0076] The main difference between this embodiment and embodiment 1 is that the heat exchangers 03 and 03' are connected in parallel, and the working fluids heated by the heat exchangers can be different, for example, boiler hot primary air, boiler hot secondary air, or boiler powder delivery, boiler hot primary air, or boiler powder delivery, boiler hot secondary air, etc. can be heated simultaneously.

[0077] The method of using the system of this embodiment is consistent with that of Embodiment 1 and will not be described again here.

[0078] Example 7

[0079] Figure 7This is a system schematic diagram of a specific embodiment 7 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, a steam-side regulating valve 02 on the additional pipeline, heat exchangers 03, 03' and 03", an additional adjustable final-stage feedwater heater 05, and a water-side regulating valve 6 are added.

[0080] The main difference between this embodiment and embodiment 6 is that a water-side regulating valve 6 is added, which is connected in parallel with the additional adjustable final-stage feedwater heater 05. Therefore, the additional adjustable final-stage feedwater heater 05 can be designed as a partial-capacity feedwater heater to reduce the cost of the heater.

[0081] The only difference between the method of using the system of this embodiment and that of Embodiment 6 is that the final feed water temperature is the feed water temperature after the outlet of the additional adjustable final-stage feed water heater 05 and the outlet of the water-side regulating valve 6 are mixed.

[0082] The method of using the system of this embodiment is consistent with that of Embodiment 6 and will not be repeated here.

[0083] Example 8

[0084] Figure 8 This is a system diagram of a specific embodiment 8 of the present invention. In this embodiment, on the basis of the conventional final stage steam extraction port 1, the conventional final stage steam extraction 10, the conventional final stage feed water heater 11, and the main steam pipeline 2, an additional pipeline 01, a steam side regulating valve 02 on the additional pipeline, and heat exchangers 03 and 03' are added.

[0085] The main difference between this embodiment and embodiment 6 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, it is also the same as embodiment 6, and the steam heat that was originally wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0086] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feedwater heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, and the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation, that is, the main steam passes through the heat exchangers 03 and 03' to heat the boiler hot secondary air or the boiler hot primary air or the boiler powder feed or a combination of the two, and then further supplements the heating of the boiler feed water. To switch back to the original system, close the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07. Therefore, the online switching operation of the two-way steam to the conventional final-stage feedwater heater 11 can be fully realized through the isolation valve 09, the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07.

[0087] The rest is consistent with Example 6 and will not be repeated here.

[0088] Example 9

[0089] Fig. 9 This is a system diagram of a specific embodiment 9 of the present invention. In this embodiment, on the basis of the conventional final stage steam extraction port 1, conventional final stage steam extraction 10, conventional final stage feedwater heater 11, and main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam side regulating valve 02 on the additional pipeline, heat exchangers 03, 03', and an additional adjustable final stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate pressure cylinder to the heat exchanger 03.

[0090] The main difference between this embodiment and embodiment 6 is that an additional hot reheat pipe 08 is provided to the heat exchanger. Its advantage is that during the unit startup phase, in order to protect the reheater, a portion of the steam will inevitably pass through the bypass system (high bypass) and be heated by the reheater 7 to become hot reheat. Under traditional circumstances, this portion of hot reheat steam will pass through the bypass system (low bypass) to the condenser. In the scheme of the present invention, since this additional hot reheat pipe 08 is added to the heat exchanger 03, the hot reheat steam after passing through the reheater during the startup phase can be further recovered. Since the isolation valve 9 is provided, the switching operation of the two steam inlets 08 and 01 can be realized.

[0091] The rest is consistent with Example 6 and will not be repeated here.

[0092] Example 10

[0093] Fig.10This is a system diagram of a specific embodiment 10 of the present invention. In this embodiment, on the basis of the conventional final-stage steam extraction port 1, conventional final-stage steam extraction 10, conventional final-stage feedwater heater 11, and main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam-side regulating valve 02 on the additional pipeline, heat exchangers 03 and 03', and an additional adjustable final-stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate pressure cylinder to the heat exchanger 03.

[0094] The main difference between this embodiment and embodiment 9 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, as in embodiment 4, the steam heat that would have been wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0095] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feed water heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, the isolation valve 9 can be closed, and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation, that is, the main steam heats the boiler supply air or boiler powder through the heat exchanger 03, and further supplements the heating of the boiler feed water. To switch back to the original system, just close the heat exchanger outlet isolation valve 07.

[0096] The rest is consistent with Example 9 and will not be repeated here.

[0097] Embodiment 11

[0098] Fig.11 This is a system schematic diagram of a specific embodiment 11 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, a steam-side regulating valve 02 on the additional pipeline, heat exchangers 03, 03', 03", and an additional adjustable final-stage feedwater heater 05 are added.

[0099] The main difference between this embodiment and embodiment 6 is that after the heat exchangers 03 and 03' are connected in parallel, they are then connected in series with the heat exchanger 03", and the working fluids heated by the heat exchangers can be different, for example, boiler hot primary air, boiler hot secondary air, or boiler powder feeding, boiler hot primary air, or boiler powder feeding, boiler hot secondary air, or a combination of the three can be heated at the same time.

[0100] The method of using the system of this embodiment is consistent with that of Embodiment 6 and will not be repeated here.

[0101] Example 12

[0102] Fig.12 This is a system schematic diagram of a specific embodiment 12 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, a steam-side regulating valve 02 on the additional pipeline, and heat exchangers 03, 03', and 03" are additionally provided.

[0103] The main difference between this embodiment and embodiment 11 is that a water-side regulating valve 6 is added, which is connected in parallel with the additional adjustable final-stage feedwater heater 05. Therefore, the additional adjustable final-stage feedwater heater 05 can be designed as a partial-capacity feedwater heater to reduce the cost of the heater.

[0104] The only difference between the method of using the system of this embodiment and that of Embodiment 8 is that the final feed water temperature is the feed water temperature after the outlet of the additional adjustable final feed water heater 05 is mixed with the outlet of the water side regulating valve 6. The rest is the same and will not be repeated here.

[0105] The method of using the system in this embodiment is consistent with that in Embodiment 11 and will not be repeated here.

[0106] Embodiment 13

[0107] Fig.13 This is a system schematic diagram of a specific embodiment 13 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, a steam-side regulating valve 02 on the additional pipeline, and heat exchangers 03, 03', and 03" are additionally provided.

[0108] The main difference between this embodiment and embodiment 11 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, as in embodiment 11, the steam heat that would have been wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0109] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feedwater heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, and the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation, that is, the main steam passes through the heat exchangers 03 and 03' to heat the boiler hot secondary air or the boiler hot primary air or the boiler powder feed or a combination of two or a combination of the three, and then further supplements the heating of the boiler feed water. To switch back to the original system, close the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07. Therefore, the online switching operation of the two-way steam to the conventional final-stage feedwater heater 11 can be fully realized through the isolation valve 09, the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07.

[0110] The rest is consistent with Example 11 and will not be repeated here.

[0111] Embodiment 14

[0112] Fig.14 This is a system schematic diagram of a specific embodiment 14 of the present invention. In this embodiment, on the basis of the conventional final-stage steam extraction port 1, the conventional final-stage steam extraction 10, the conventional final-stage feedwater heater 11, and the main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam-side regulating valve 02 on the additional pipeline, heat exchangers 03, 03' and 03", and an additional adjustable final-stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate-pressure cylinder to the heat exchanger 03.

[0113] The main difference between this embodiment and embodiment 11 is that an additional hot reheat pipe 08 is provided to the heat exchanger. Its advantage is that during the unit startup phase, in order to protect the reheater, a portion of the steam will inevitably pass through the bypass system (high bypass) and be heated by the reheater 7 to become hot reheat. Under traditional circumstances, this portion of hot reheat steam will pass through the bypass system (low bypass) to the condenser. In the scheme of the present invention, since this additional hot reheat pipe 08 is added to the heat exchanger 03, the hot reheat steam after passing through the reheater during the startup phase can be further recovered. Since the isolation valve 9 is provided, the switching operation of the two steam inlets 08 and 01 can be realized.

[0114] The rest is consistent with Example 11 and will not be repeated here.

[0115] Embodiment 15

[0116] Fig.15This is a system schematic diagram of a specific embodiment 15 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam-side regulating valve 02 on the additional pipeline, heat exchangers 03, 03' and 03", and an additional adjustable final-stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate-pressure cylinder to the heat exchanger 03.

[0117] The main difference between this embodiment and embodiment 14 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, as in embodiment 4, the steam heat that would have been wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0118] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feed water heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, the isolation valve 9 can be closed, and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation, that is, the main steam heats the boiler supply air or boiler powder through the heat exchanger 03, and further supplements the heating of the boiler feed water. To switch back to the original system, just close the heat exchanger outlet isolation valve 07.

[0119] The rest is consistent with Example 14 and will not be repeated here.

[0120] Example 16

[0121] Fig.16 This is a system schematic diagram of a specific embodiment 16 of the present invention. In this embodiment, on the basis of the conventional final stage steam extraction port 1, the conventional final stage steam extraction 10, the conventional final stage feed water heater 11, and the main steam pipeline 2, an additional pipeline 01, a steam side regulating valve 02 on the additional pipeline, heat exchangers 03, 03', and an additional adjustable final stage feed water heater 05 are added.

[0122] The main difference between this embodiment and embodiment 6 is that the heat exchangers 03 and 03' are not connected in parallel but in series, and the working fluids heated by the heat exchangers can be different, for example, boiler hot primary air, boiler hot secondary air, or boiler powder delivery, boiler hot primary air, or a combination of boiler powder delivery and boiler hot secondary air can be heated simultaneously.

[0123] The method of using the system of this embodiment is consistent with that of Embodiment 6 and will not be repeated here.

[0124] Embodiment 17

[0125] Fig.17 This is a system schematic diagram of a specific embodiment 17 of the present invention. In this embodiment, on the basis of a conventional final-stage steam extraction port 1, a conventional final-stage steam extraction 10, a conventional final-stage feedwater heater 11, and a main steam pipeline 2, an additional pipeline 01, a steam-side regulating valve 02 on the additional pipeline, heat exchangers 03, 03', an additional adjustable post-final-stage feedwater heater 05, and a water-side regulating valve 6 are added.

[0126] The main difference between this embodiment and embodiment 16 is that a water-side regulating valve 6 is added, which is connected in parallel with the additional adjustable final-stage feedwater heater 05. Therefore, the additional adjustable final-stage feedwater heater 05 can be designed as a partial-capacity feedwater heater to reduce the cost of the heater.

[0127] The only difference between the method of using the system of this embodiment and that of Embodiment 16 is that the final feed water temperature is the feed water temperature after the outlet of the additional adjustable final-stage feed water heater 05 is mixed with the outlet of the water-side regulating valve 6.

[0128] The method of using the system of this embodiment is consistent with that of Embodiment 16 and will not be repeated here.

[0129] Embodiment 18

[0130] Fig.18 This is a system schematic diagram of a specific embodiment 18 of the present invention. In this embodiment, on the basis of the conventional final stage steam extraction port 1, the conventional final stage steam extraction 10, the conventional final stage feed water heater 11, and the main steam pipeline 2, an additional pipeline 01, a steam side regulating valve 02 on the additional pipeline, and heat exchangers 03 and 03' are added.

[0131] The main difference between this embodiment and embodiment 16 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, as in embodiment 16, the steam heat that would have been wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0132] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feedwater heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, and the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation, that is, the main steam passes through the heat exchangers 03 and 03' to heat the boiler hot secondary air or the boiler hot primary air or the boiler powder feed or a combination of the two, and then further supplements the heating of the boiler feed water. To switch back to the original system, close the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07. Therefore, the online switching operation of the two-way steam to the conventional final-stage feedwater heater 11 can be fully realized through the isolation valve 09, the heat exchanger inlet isolation valve 06 and the heat exchanger outlet isolation valve 07.

[0133] The method of using the system of this embodiment is consistent with that of Embodiment 16 and will not be repeated here.

[0134] Embodiment 19

[0135] Fig.19 This is a system diagram of a specific embodiment 19 of the present invention. In this embodiment, on the basis of the conventional final stage steam extraction port 1, conventional final stage steam extraction 10, conventional final stage feedwater heater 11, and main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam side regulating valve 02 on the additional pipeline, heat exchangers 03, 03', and an additional adjustable final stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate pressure cylinder to the heat exchanger 03.

[0136] The main difference between this embodiment and embodiment 16 is that an additional hot reheat pipe 08 is provided to the heat exchanger. Its advantage is that during the unit startup phase, in order to protect the reheater, a portion of the steam will inevitably pass through the bypass system (high bypass) and be heated by the reheater 7 to become hot reheat. Under traditional circumstances, this portion of hot reheat steam will pass through the bypass system (low bypass) to the condenser. In the scheme of the present invention, since this additional hot reheat pipe 08 is added to the heat exchanger 03, the hot reheat steam flowing through the reheater during the startup phase can be further recovered. Since the isolation valve 9 is provided, the switching operation of the two steam inlets 08 and 01 can be realized.

[0137] The rest is consistent with Example 16 and will not be repeated here.

[0138] Embodiment 20

[0139] Fig. 20This is a system diagram of a specific embodiment 20 of the present invention. In this embodiment, on the basis of the conventional final stage steam extraction port 1, conventional final stage steam extraction 10, conventional final stage feedwater heater 11, and main steam pipeline 2, an additional pipeline 01, an isolation valve 00 and a steam side regulating valve 02 on the additional pipeline, heat exchangers 03 and 03', and an additional adjustable final stage feedwater heater 05 are added. In addition, an additional hot re-pipeline 08 is added to the steam pipeline from the hot re-pipeline to the intermediate pressure cylinder to the heat exchanger 03.

[0140] The main difference between this embodiment and embodiment 19 is that no additional adjustable post-final feedwater heater 05 is added. The steam pipe passing through the heat exchanger is directly sent to the original conventional final feedwater heater 11. Its advantage is that an additional adjustable post-final feedwater heater 05 is saved, reducing investment, and in the start-up phase of the unit, as in embodiment 4, the steam heat that would have been wasted through the bypass system can be fully recovered. On the other hand, the original conventional final feedwater heater 11 can also be used to supplement the heating of the feedwater to ensure the feedwater temperature in the start-up phase, meet the requirements of denitration, hydrodynamic stability, combustion stability and high combustion efficiency in the start-up phase, and avoid low-temperature condensation, ash blockage, corrosion and other problems.

[0141] During the normal operation of the unit, when the load is high, the original conventional final-stage extraction steam 10 can still be used to heat the conventional final-stage feed water heater 11. When the load is low to a certain level, the isolation valve 09 can be closed, the isolation valve 9 can be closed, and the heat exchanger outlet isolation valve 07 can be opened to switch to the additional system operation, that is, the main steam heats the boiler supply air or boiler powder through the heat exchanger 03, and further supplements the heating of the boiler feed water. To switch back to the original system, just close the heat exchanger outlet isolation valve 07.

[0142] The rest is consistent with Example 19 and will not be repeated here.

[0143] The above describes in detail the preferred specific embodiments of the present invention. It should be noted that the combined heat recovery system of the present invention can have a variety of combinations according to whether a water side regulating valve is configured on the water side, whether an additional adjustable rear final stage feed water heater is set, the position of the extraction regulating valve, the different capacities of the additional adjustable rear final stage feed water heater, the different heating media of the heat exchanger, the number of heat exchangers, whether isolation valves and bypasses are set before and after the heat exchanger, the connection method between different heat exchangers, and whether an additional heat re-pipeline is set to the heat exchanger.

[0144] It should be understood that ordinary technicians in this field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in this technical field through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the existing technology should be within the scope of protection determined by the claims.

Claims

1. A combined heat recovery system, Features: include High-pressure cylinder of steam turbine; Main steam pipe; Conventional final stage steam extraction pipeline; a heat exchanger using the main steam in the main steam pipeline as a heat source; a feedwater heater using exhaust steam from the heat exchanger as a heat source; An additional pipeline added to the main steam pipeline, through which the heat exchanger and the feedwater heater are connected in series; A steam-side regulating valve disposed on the additional pipeline between the main steam pipeline and the heat exchanger is used to regulate the main steam in the additional pipeline to control the extraction steam pressure after the steam-side regulating valve to control the outlet temperature of the feedwater heater to meet the required final feedwater temperature; The heat exchanger is a heat exchanger or a heat exchanger group consisting of a plurality of heat exchangers.

2. A combined heat recovery system as claimed in claim 1, Features: A heat exchanger group is a combination of two or more heat exchangers connected in parallel or in series, or three or more heat exchangers connected in series and in parallel.

3. A combined heat recovery system as claimed in claim 1, Features: The working medium heated by the heat exchanger is boiler hot secondary air or boiler hot primary air or boiler powder feed or a combination of the three or a combination of two of them.

4. A combined heat recovery system according to any one of claims 1 to 3, Features: It also includes an additional hot re-pipeline added to the hot re-pipeline. The additional hot re-pipeline is connected in parallel with the additional pipe added to the main steam pipe and then connected to the heat exchanger and the feed water heater.

5. A combined heat recovery system as claimed in claim 4, Features: The feedwater heater is a conventional final-stage feedwater heater, the additional pipeline is connected to the heat exchanger and the conventional final-stage feedwater heater, and an isolation valve is provided on the conventional final-stage steam extraction pipeline.

6. A combined heat recovery system as claimed in claim 4, Features: The feedwater heater is an additional adjustable rear final stage feedwater heater; the additional pipeline is connected to the heat exchanger and the additional adjustable rear final stage feedwater heater.

7. A combined heat recovery system as claimed in claim 6, Features: It also includes at least one water-side regulating valve, which is connected in parallel with the additional adjustable rear final-stage feedwater heater.

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