A condensate combined circulation system and method for improving boiler cold re-steam supply capacity

Abstract

The present invention discloses a condensate combined circulation system and method for improving the cold re-steam supply capacity of a boiler, including a steam pipeline isolation valve, a heat recovery heat exchanger, a flow regulating orifice plate, a water inlet isolation valve, a water outlet isolation valve, a bypass isolation valve, a water-water heat exchanger, and a circulation pump. The cold re-steam enters the heat recovery heat exchanger through a steam pipeline, and the cold re-steam is mixed with the original steam through a steam return pipe after heat exchange and cooling. A flow regulating orifice plate is newly arranged on the cold re-steam pipeline to balance the steam flow, and the closed-loop circulating water absorbs the heat in the heat recovery device and is transported to the water-water heat exchanger by the circulation pump. The condensate at the outlet of the shaft seal heater enters the water-water heat exchanger after passing through the water inlet isolation valve. The system can effectively improve the cold re-steam supply capacity of the boiler and reduce the risk of overheating of the boiler reheater, and can be put into operation and shut down online. The system can effectively increase the flow rate of the cold re-steam supply of the unit and thus improve the economy of the unit.

Description

[Technical field]

[0001] The invention belongs to the technical field of comprehensive energy utilization, and relates to a condensate combined circulation system and method for improving the cold re-steam supply capacity of a boiler. [Background technology]

[0002] External industrial steam supply can effectively reduce the energy consumption index of thermal power generating units, and is also one of the important profit directions of generating units. On the basis of meeting the steam parameter requirements of industrial steam supply users, using steam of lower quality as much as possible is beneficial to the economic operation of the unit. Therefore, increasing the industrial steam supply volume and reducing the steam supply parameters as much as possible are the directions to improve the economic efficiency of industrial steam supply of the unit.

[0003] At present, most industrial steam supply units use cold reheat steam as the steam source. However, if too much cold reheat steam is extracted, the boiler reheater is prone to overheating. Therefore, the extraction volume of cold reheat steam in many units is greatly restricted and cannot fully meet the needs of users. They can only use reheat steam with higher steam quality, which leads to poor heating economy of the unit. In addition, the temperature of cold reheat steam is generally several tens of degrees higher than the user's demand, and a large amount of cooling water needs to be sprayed for cooling. If the temperature of cold reheat steam is reasonably reduced through technical means, and the excess heat is transferred to the low-pressure heater for full utilization, the risk of overheating of the boiler reheater will be effectively reduced, and the steam supply of the unit cold reheat can be greatly increased. [Summary of the invention]

[0004] The purpose of the present invention is to solve the problems in the prior art and to provide a condensate combined circulation system and method for improving the cold re-steam supply capacity of the boiler. The present invention uses the condensate at the inlet of the low-pressure heater as a cooling source to cool part of the cold re-steam, thereby lowering the cold re-steam temperature of the unit, reducing the risk of overheating of the boiler reheater, and improving the cold re-steam supply capacity of the industrial steam.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A condensate combined circulation system for improving the cold re-steam supply capacity of a boiler comprises a high-pressure cylinder, a steam pipeline and a steam return pipeline;

[0007] The cold re-steam of the high-pressure cylinder enters the steam pipe, and a closed circulating water system is arranged between the steam pipe and the steam return pipe; a shaft seal heater and a low-pressure heater are arranged on the steam return pipe, and part of the heat of the cold re-steam is exchanged with the closed circulating water system, and the closed circulating water system also exchanges heat with the condensed water in the steam return pipe. The condensed water after heat exchange is transported to the low-pressure heater for further heating.

[0008] The present invention is further improved in that:

[0009] The closed circulating water system includes a heat recovery heat exchanger and a water-water heat exchanger. The circulating water forms a closed loop between the heat recovery heat exchanger and the water-water heat exchanger. A circulating pump is provided between the heat recovery heat exchanger and the water-water heat exchanger to provide power for the circulating water system.

[0010] The outlet of the shaft seal heater is connected to the cold side inlet of the water-water heat exchanger, and the cold side outlet of the water-water heat exchanger is connected to the low-pressure heater. The condensate of the shaft seal heater is heated by the water-water heat exchanger and then transported to the low-pressure heater.

[0011] The water-water heat exchanger is also connected in parallel with a bypass pipeline, and a bypass isolation valve is arranged on the bypass pipeline.

[0012] The steam pipeline is provided with a flow regulating orifice plate, and a heat recovery heat exchanger is connected in parallel to the flow regulating orifice plate. The cold re-steam enters the heat recovery heat exchanger through the first steam pipeline isolation valve for heat exchange. The cold re-steam after heat exchange passes through the second steam pipeline isolation valve and merges with the cold re-steam passing through the flow regulating orifice plate. A part of the merged cold re-steam is output as industrial steam supply, and the other part is output to the boiler reheater.

[0013] The inlet of the water-water heat exchanger is provided with a water inlet isolation valve, the outlet of the water-water heat exchanger is provided with a water outlet isolation valve, and the bypass pipeline is connected in parallel to both ends of the water inlet isolation valve, the water-water heat exchanger and the water outlet isolation valve.

[0014] A condensate combined circulation method for improving the cold re-steam supply capacity of a boiler comprises the following steps:

[0015] During normal operation, open the steam pipeline isolation valve, steam pipeline isolation valve, water inlet isolation valve and water outlet isolation valve, close the bypass isolation valve, and start the circulation pump; a part of the cold re-steam of the high-pressure cylinder of the steam turbine passes through the steam pipeline isolation valve, the heat recovery heat exchanger and the steam pipeline isolation valve, and then merges with the other part of the cold re-steam that passes through the flow regulating orifice plate and has not been heat exchanged; the closed circulating water completes the heat exchange process after passing through the heat recovery heat exchanger, the circulation pump and the water-water heat exchanger; the outlet condensate of the shaft seal heater passes through the water inlet isolation valve, the water-water heat exchanger and the water outlet isolation valve, and is heated by the closed circulating water, and the heated condensate enters the low-pressure heater;

[0016] When the unit does not use cold steam to supply steam to the outside, close the steam pipe isolation valve and the steam pipe isolation valve, open the bypass isolation valve, the heat recovery heat exchanger is in a shutdown state, and the circulation pump is turned off.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention transfers part of the heat of the cold re-steam to the low-pressure heater inlet water through a heat recovery heat exchanger. On the one hand, it can reduce the temperature of the cold re-steam by more than 30°C and increase the cold re-steam industrial steam supply by 200%. The unit will be more economical due to the improvement of external steam supply capacity and the reduction of high-quality steam use, and the use of industrial steam supply cooling water can also be reduced.

[0019] The present invention is provided with a heat recovery heat exchanger and a water-water heat exchanger double circuit, and utilizes part of the cold re-steam to heat the condensate at the inlet of the low-pressure heater to achieve energy joint transfer and utilization, thereby reducing the risk of boiler reheater overheating, increasing the maximum heating capacity of cold re-steam, reducing the amount of cold re-steam cooling water used, and improving the unit operation economy. The present invention can be applied to secondary reheating power generation units for external industrial steam supply, and utilizes part of the heat of cold re-steam into the condensate at the inlet of the low-pressure heater through heat exchange, reducing the temperature of cold re-steam and external industrial steam supply, reducing the risk of reheater overheating when the boiler cold re-steam supplies steam to the outside, improving the maximum capacity of cold re-steam for external industrial steam supply, reducing the use of high-quality steam such as reheat steam, reducing the use of industrial steam cooling water, improving the unit operation economy, and reducing coal consumption for power generation.

Brief Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is a schematic diagram of the system structure of the present invention.

[0022] Among them, 1-turbine high-pressure cylinder; 2-first steam pipe isolation valve; 3-shaft seal heater; 4-water-water heat exchanger; 5-second steam pipe isolation valve; 6-flow regulating orifice plate; 7-water inlet isolation valve; 8-water outlet isolation valve; 9-bypass isolation valve; 10-heat recovery heat exchanger; 11-circulating pump; 12-low-pressure heater. [Specific implementation method]

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0030] See also Figure 1 The condensate combined circulation system for improving the cold re-steam supply capacity of the boiler of the present invention comprises a steam turbine high-pressure cylinder 1, a steam pipe and a steam return pipe; the cold re-steam of the steam turbine high-pressure cylinder 1 enters the steam pipe, and a closed circulating water system is arranged between the steam pipe and the steam return pipe.

[0031] The closed circulating water system includes a heat recovery heat exchanger 4 and a water-water heat exchanger 10. The circulating water heat recovery heat exchanger 4 and the water-water heat exchanger 10 are in a closed cycle. A circulating pump 11 is arranged between the heat recovery heat exchanger 4 and the water-water heat exchanger 10 to provide power for the circulating water system.

[0032] The outlet of the shaft seal heater 3 is connected to the cold side inlet of the water-water heat exchanger 10, and the cold side outlet of the water-water heat exchanger 10 is connected to the low-pressure heater 12. The condensed water of the shaft seal heater 3 is heated by the water-water heat exchanger 10 and then transported to the low-pressure heater 12. A bypass pipe is also connected in parallel to the water-water heat exchanger 10, and a bypass isolation valve 9 is provided on the bypass pipe.

[0033] A flow regulating orifice plate 6 is provided on the steam pipeline, and a heat recovery heat exchanger 4 is connected in parallel to the flow regulating orifice plate 6. The cold re-steam enters the heat recovery heat exchanger 4 through the first steam pipeline isolation valve 2 for heat exchange. The cold re-steam after heat exchange passes through the second steam pipeline isolation valve 5 and merges with the cold re-steam passing through the flow regulating orifice plate 6. A part of the merged cold re-steam is output as industrial steam supply, and the other part is output to the boiler reheater.

[0034] An inlet isolation valve 7 is provided at the inlet of the water-water heat exchanger 10 , and an outlet isolation valve 8 is provided at the outlet. A bypass pipeline is connected in parallel to both ends of the inlet isolation valve 7 , the water-water heat exchanger 10 and the outlet isolation valve 8 .

[0035] Principle of the present invention:

[0036] The present invention transfers part of the heat of the cold re-steam to the low-pressure heater inlet water through the heat recovery heat exchanger 4, which can reduce the temperature of the cold re-steam by more than 30°C, reduce the risk of overheating of the boiler reheater, and thus increase the cold re-steam industrial steam supply by about 200%, which can reduce the commissioning of the unit's cold re-steam desuperheating water. The increase in industrial steam supply will greatly improve the unit's economic indicators.

[0037] Working process of the present invention:

[0038] A part of the cold re-steam of the high-pressure cylinder of the steam turbine of the present invention passes through the steam pipe isolation valve 2, the heat recovery heat exchanger 4 and the steam pipe isolation valve 5, and then merges with the other part of the cold re-steam that passes through the flow regulating orifice plate 6 and has not undergone heat exchange; the closed circulating water completes the heat exchange process after passing through the heat recovery heat exchanger 4, the circulating pump 11 and the water-water heat exchanger 10; the outlet condensate of the shaft seal heater 3 passes through the water inlet isolation valve 7, the water-water heat exchanger 10 and the water outlet isolation valve 8, and is heated by the closed circulating water, and the heated condensate enters the low-pressure heater.

[0039] During normal operation, the steam pipe isolation valve 2, the steam pipe isolation valve 5, the water inlet isolation valve 7, and the water outlet isolation valve 8 are all in the open state, the bypass isolation valve 9 is in the closed state, and the circulating pump 11 is in the running state; when the unit does not use cold steam to supply steam to the outside, the steam pipe isolation valve 2 and the steam pipe isolation valve 5 are closed in sequence, and then the bypass isolation valve 9 is gradually opened, the heat recovery heat exchanger 4 is in the shutdown state, and the circulating pump 11 is shut down.

[0040] The present invention has a clear principle, a simple system, low maintenance, can be put into operation and shut down online, and is suitable for all secondary reheat power generating units. It is an innovative technology for increasing the cold reheat industrial steam supply of the reheat unit, reducing the risk of boiler reheater overtemperature, and improving the heating economy of the unit.

[0041] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A condensate combined circulation system for improving boiler cold re-steam supply capacity, characterized in that: It comprises a high-pressure cylinder (1), a steam pipeline and a steam return pipeline; The cold re-steam of the high-pressure cylinder (1) enters the steam pipe, and a closed circulating water system is provided between the steam pipe and the steam return pipe; a shaft seal heater (3) and a low-pressure heater (12) are provided on the steam return pipe, and part of the heat of the cold re-steam is exchanged with the closed circulating water system, and the closed circulating water system simultaneously exchanges heat with condensed water in the steam return pipe, and the condensed water after the heat exchange is transported to the low-pressure heater (12) for further heating; The closed circulating water system comprises a heat recovery heat exchanger (4) and a water-water heat exchanger (10), the circulating water forms a closed loop between the heat recovery heat exchanger (4) and the water-water heat exchanger (10), and a circulating pump (11) is provided between the heat recovery heat exchanger (4) and the water-water heat exchanger (10) for providing power to the circulating water system; The outlet of the shaft seal heater (3) is connected to the cold side inlet of the water-water heat exchanger (10), and the cold side outlet of the water-water heat exchanger (10) is connected to the low-pressure heater (12). Condensate from the shaft seal heater (3) is heated by the water-water heat exchanger (10) and then transported to the low-pressure heater (12).

2. The condensate combined circulation system for improving boiler cold re-steam supply capacity according to claim 1, characterized in that: The water-water heat exchanger (10) is also connected in parallel with a bypass pipeline, and a bypass isolation valve (9) is provided on the bypass pipeline.

3. The condensate combined circulation system for improving boiler cold re-steam supply capacity according to claim 1, characterized in that: The steam pipeline is provided with a flow regulating orifice plate (6), and the heat recovery heat exchanger (4) is connected in parallel to the flow regulating orifice plate (6). The cold re-steam enters the heat recovery heat exchanger (4) through the first steam pipeline isolation valve (2) for heat exchange. After the heat exchange, the cold re-steam passes through the second steam pipeline isolation valve (5) and merges with the cold re-steam that passes through the flow regulating orifice plate (6). A portion of the merged cold re-steam is output as industrial steam supply, and the other portion is output to the boiler reheater.

4. The condensate combined circulation system for improving boiler cold re-steam supply capacity according to claim 1, characterized in that: A water inlet isolation valve (7) is provided at the inlet of the water-water heat exchanger (10), and a water outlet isolation valve (8) is provided at the outlet; a bypass pipeline is connected in parallel to both ends of the water inlet isolation valve (7), the water-water heat exchanger (10) and the water outlet isolation valve (8).

5. A condensate combined circulation method for improving boiler cold re-steam supply capacity using the system according to any one of claims 1 to 4, characterized in that: The following steps are involved: During normal operation, the first steam pipeline isolation valve (2), the second steam pipeline isolation valve (5), the water inlet isolation valve (7) and the water outlet isolation valve (8) are opened, the bypass isolation valve (9) is closed, and the circulating pump (11) is started; a portion of the cold re-steam of the high-pressure cylinder of the steam turbine passes through the first steam pipeline isolation valve (2), the heat recovery heat exchanger (4) and the second steam pipeline isolation valve (5), and then merges with the other portion of the cold re-steam that passes through the flow regulating orifice plate (6) and has not undergone heat exchange; the closed circulating water passes through the heat recovery heat exchanger (4), the circulating pump (11) and the water-water heat exchanger (10) to complete the heat exchange process; the outlet condensate of the shaft seal heater (3) passes through the water inlet isolation valve (7), the water-water heat exchanger (10) and the water outlet isolation valve (8), and is heated by the closed circulating water, and the heated condensate enters the low-pressure heater (12); When the unit does not use cold steam to supply steam to the outside, the first steam pipeline isolation valve (2) and the second steam pipeline isolation valve (5) are closed, the bypass isolation valve (9) is opened, the heat recovery heat exchanger (4) is in a shutdown state, and the circulation pump (11) is turned off.

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