Heat exchange system for heating flue gas through steam in boiler starting stage

Abstract

The invention relates to the technical field of boiler heat exchange equipment, in particular to a heat exchange system for heating flue gas by steam in a boiler starting stage, which comprises a boiler outlet flue, an electric adjusting baffle plate, a heat exchanger and a heat exchanger, the flue gas bypass and the boiler outlet flue are arranged in parallel, and a steam heater is arranged on the flue gas bypass; the steam bypass is arranged in parallel with the connecting pipeline from the low-temperature superheater to the platen superheater, is led out from an outlet of the low-temperature superheater, passes through the steam heater and then returns to the connecting pipeline from the low-temperature superheater to the platen superheater, and the steam heater is further arranged on the steam bypass; and outlet steam of the low-temperature superheater passes through a steam heater through a steam bypass to heat flue gas at an inlet of the denitration reactor. The low-pass outlet steam is led to the steam heater through the steam bypass system to heat the flue gas of the boiler outlet flue, so that the temperature of the flue gas is increased, denitration can be carried out as soon as possible, and the problem of screen over-temperature is solved.

Description

Technical Field

[0001] The invention relates to the technical field of boiler heat exchange equipment, and in particular to a heat exchange system for steam heating flue gas in a boiler startup phase. Background Art

[0002] my country has increasingly stringent requirements for pollutant emissions from coal-fired boilers in power plants. In recent years, it has been required that units be put into operation with denitration devices at low load or even connected to the grid to reduce pollutant emissions. The catalyst of the denitration device requires a certain flue gas temperature to catalyze the reduction reaction. When the unit is connected to the grid or running at low load, the flue gas temperature is generally low, and it is necessary to use devices such as graded economizers and feedwater bypass to increase the denitration inlet flue gas temperature.

[0003] At present, when the low-volatile supercritical π-type pulverized coal boiler without a circulating pump is ignited with less oil, the low-load pulverized coal burns out poorly and the flame center moves upward. At the same time, since the boiler startup system has no circulating pump, the water-cooled wall produces less steam, making it difficult to control the screen wall temperature, and a large amount of cooling water needs to be added. At present, there are two main forms of primary cooling water extraction. One is to extract it from the front of the water supply operation platform. The cooling water temperature is low, and there is a large thermal stress in the water spray cooling, and it is easy to cause uneven steam-water mixing and cause the screen water plug; the other is to extract it from the economizer outlet. Due to the small pressure difference in the startup stage, cooling water cannot be added in large quantities, which is easy to cause screen overheating. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problem of overheating in the startup phase of the prior art due to the small pressure difference, which makes it difficult to add a large amount of cooling water, thereby providing a heat exchange system for steam heating flue gas in the startup phase of the boiler.

[0005] In order to solve the above technical problems, the present invention provides a heat exchange system for steam heating flue gas during the startup phase of a boiler, comprising: a boiler outlet flue, on which an electric adjustment baffle is provided; a flue gas bypass, arranged in parallel with the boiler outlet flue, on which a steam heater is provided; a steam bypass, arranged in parallel with a connecting pipe from a low-temperature superheater to a platen superheater, leading out from the outlet of the low-temperature superheater, and returning to the connecting pipe from the low-temperature superheater to the platen superheater after passing through the steam heater, the steam heater being further provided on the steam bypass, and the steam from the outlet of the low-temperature superheater is used to heat the flue gas at the inlet of a denitrification reactor through the steam heater.

[0006] Furthermore, a first electric shutoff damper is provided on the boiler outlet flue, and the first electric shutoff damper is located at one end close to the denitration reactor.

[0007] Furthermore, a second electric shutoff damper is provided on the flue gas bypass.

[0008] Furthermore, there are two second electric shutoff dampers, and the two electric shutoff dampers are located on both sides of the flue gas bypass.

[0009] Furthermore, an electric switch is provided on the steam bypass. There are three electric switches, two of which are located on the steam bypass, respectively at the inlet and outlet of the steam heater, and the other electric switch is provided on the connecting pipe from the low-temperature superheater to the screen superheater.

[0010] Furthermore, the electric on-off component is an electric gate valve.

[0011] Furthermore, a temperature measuring element and a pressure measuring element are also provided on the steam bypass.

[0012] Furthermore, the temperature measuring element is a temperature sensor, and the pressure measuring element is a pressure transmitter.

[0013] The technical solution of the present invention has the following advantages:

[0014] 1. The heat exchange system for steam-heated flue gas during the startup phase of a boiler provided by the present invention comprises: a boiler outlet flue, on which an electric adjustment baffle is provided; a flue gas bypass, which is arranged in parallel with the boiler outlet flue, and on which a steam heater is provided; a steam bypass, which is arranged in parallel with a connecting pipe from a low-temperature superheater to a platen superheater, is led out from the outlet of the low-temperature superheater, passes through the steam heater, and returns to the connecting pipe from the low-temperature superheater to the platen superheater, the steam heater is also provided on the steam bypass, and the steam at the outlet of the low-temperature superheater is used to heat the flue gas at the inlet of the denitration reactor through the steam heater.

[0015] By setting an electric regulating baffle on the boiler outlet flue, the flue gas volume of the boiler outlet flue gas bypass can be adjusted by the electric regulating baffle; at the same time, a steam heater is set on the flue gas bypass, so that the steam flowing out of the low-temperature superheater is lower than the outlet steam and heats the flue gas at the inlet of the denitrification reactor through the steam heater.

[0016] The heat exchange system of steam heating flue gas in the startup phase of the boiler leads the low-pass outlet steam to the steam heater through the steam bypass system to heat the boiler outlet flue gas, thereby increasing the flue gas temperature, which is conducive to the early start of denitrification, because the flue gas temperature needs to reach a certain value for denitrification. At the same time, the screen inlet steam temperature is reduced, and the screen wall temperature can be controlled, thereby solving the problem of screen overheating. Because the heat exchange system is not put into operation at high load, a flue gas bypass and a steam bypass are set up; the steam heater is set on the flue gas bypass, and the low-pass outlet steam passes through the steam bypass during the startup phase, and the bypass flue gas is heated by the steam heater. During the normal operation phase, the steam bypass and flue gas bypass are removed.

[0017] 2. The heat exchange system for steam-heated flue gas during the startup phase of the boiler provided by the present invention is also provided with a second electric shut-off damper on the flue gas bypass. When the flue gas temperature at the boiler outlet flue meets the flue gas temperature required for denitrification or the main steam temperature needs to be increased due to the controllable screen wall temperature, thereby requiring no temperature drop at the low-temperature superheater outlet, the flue gas bypass system is cut off without any impact on the normal operation of the boiler.

[0018] 3. In the heat exchange system for steam heating flue gas during the boiler startup phase provided by the present invention, there are two second electric shutoff dampers, and the two electric shutoff dampers are located on both sides of the steam heater.

[0019] 4. The heat exchange system for steam-heated flue gas during the startup phase of the boiler provided by the present invention is provided with an electric switch on and off piece on the steam bypass. There are three electric switch on and off pieces, two of which are provided on the steam bypass, respectively at the inlet and outlet of the steam heater, and one is provided on the connecting pipe from the low-temperature superheater to the screen superheater. By providing the electric switch on and off piece, the low-temperature superheater outlet steam can be controlled on and off, ensuring that the outlet steam of the low-temperature superheater can all be heat-exchanged through the steam heater when the steam bypass is put into operation, and when the system is cut off, there is no impact on the operation of the boiler.

[0020] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the disclosure, nor is it intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 This is a schematic structural diagram of a heat exchange system for heating flue gas with steam during the startup phase of a boiler provided by the present invention.

[0023] Description of reference numerals:

[0024] 1. Boiler outlet flue; 2. Connection pipe from low-temperature superheater to platen superheater; 3. Electric adjustment damper; 4. Denitration reactor; 5. Flue gas bypass; 6. Steam heater; 7. Low-temperature superheater; 8. Steam bypass; 9. Platen superheater; 10. First electric shut-off damper; 11. Second electric shut-off damper; 12. Electric switch; 13. Temperature measuring element; 14. Water spray desuperheater; 15. Pressure measuring element;

[0025] →It is the flue gas flow direction of the boiler outlet flue; The steam flow direction is lower than the outlet steam. DETAILED DESCRIPTION

[0026] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present disclosure. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0027] In the description of the present disclosure, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present disclosure and simplifying the description, and do 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 of the present disclosure. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0028] In the description of the present disclosure, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0029] In the present disclosure, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is lower in level than the second feature.

[0030] The disclosure below provides many different embodiments or examples to realize different structures of the present disclosure. In order to simplify the disclosure of the present disclosure, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present disclosure. In addition, the present disclosure can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present disclosure provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0031] The preferred embodiments of the present disclosure are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0032] See also Figure 1 As shown, the present invention provides a heat exchange system for steam heating flue gas during the startup phase of a boiler, comprising: a boiler outlet flue 1, on which an electric adjustment damper 3 is provided; a flue gas bypass 5, which is arranged in parallel with the boiler outlet flue 1, and on which a steam heater 6 is provided; a steam bypass 8, which is arranged in parallel with a connecting pipe 2 from a low-temperature superheater to a platen superheater, is led out from the outlet of the low-temperature superheater 7, passes through the steam heater 6, and returns to the connecting pipe 2 from the low-temperature superheater to the platen superheater, the steam heater 6 is also provided on the steam bypass 8, and the steam at the outlet of the low-temperature superheater 7 is used to heat the flue gas at the inlet of the denitration reactor 4 through the steam bypass 8 via the steam heater 6.

[0033] By arranging an electric regulating baffle 3 on the boiler outlet flue 1, the flue gas volume of the boiler outlet flue gas bypass 5 can be adjusted by the electric regulating baffle 3; at the same time, a steam heater 6 is arranged on the flue gas bypass 5, so that the steam below the outlet flows out from the low-temperature superheater 7 and heats the flue gas at the inlet of the denitrification reactor 4 through the steam heater 6.

[0034] The heat exchange system for steam heating flue gas in the startup phase of the boiler, through the steam bypass 8 system, leads the low-pass outlet steam to the steam heater 6 to heat the boiler outlet flue gas, thereby increasing the flue gas temperature, which is conducive to the early start of denitrification, because the flue gas temperature needs to reach a certain value for denitrification, and at the same time reduces the screen inlet steam temperature, which can control the screen wall temperature, thereby solving the problem of screen overheating. Because the heat exchange system is not put into operation at high load, the flue gas bypass 5 and steam bypass 8 are set; the steam heater 6 is set on the flue gas bypass 5, and the low-pass outlet steam passes through the steam bypass 8 in the startup phase, and the bypass flue gas is heated by the steam heater 6. During the normal operation phase, the steam bypass 8 and the flue gas bypass 5 are removed.

[0035] The heat exchange system for steam heating flue gas during the startup phase of the boiler uses a boiler without a circulating pump that burns low-quality coal. The flue gas is heated by steam on the working medium side, mainly to protect the screen superheater 9 and to meet the demand for increasing the temperature of the denitrification flue gas.

[0036] In some optional embodiments, the boiler outlet flue 1 is further provided with a first electric shutoff damper 10, and the first electric shutoff damper 10 is located at one end close to the denitration reactor 4. The flue gas bypass 5 is further provided with a second electric shutoff damper 11.

[0037] By arranging a second electric shut-off damper 11 on the flue gas bypass 5, when the flue gas temperature at the boiler outlet flue 1 meets the flue gas temperature required for denitrification or the main steam temperature needs to be increased due to the controllable screen wall temperature, thereby requiring no temperature drop at the outlet of the low-temperature superheater 7, the system is cut off without any impact on the normal operation of the boiler at high load.

[0038] Specifically, there are two second electric shutoff baffles 11 , and the two electric shutoff baffles are located on both sides of the steam heater 6 .

[0039] In some optional embodiments, the steam bypass 8 is provided with an electric switch 12, and there are three electric switch 12, two of which are provided on the steam bypass 8, respectively at the inlet and outlet of the steam heater 6, and one is provided on the low-temperature superheater to platen superheater connecting pipe 2. Specifically, the electric switch 12 is an electric gate valve.

[0040] By setting the electric switch 12, the low-temperature superheater outlet steam can be controlled to be on and off, thereby ensuring that the low-temperature superheater 7 outlet steam can all pass through the steam heater 6 for heat exchange when the steam bypass 8 is put into operation, and when the system is cut off, there is no impact on the boiler operation.

[0041] At the same time, the steam bypass 8 is also provided with a temperature measuring element 13 and a pressure measuring element 15. The temperature measuring element 13 is a temperature sensor, and the pressure measuring element 15 is a pressure transmitter. The temperature measuring element 13 is used to detect the steam temperature at the outlet of the steam heater 6, and the pressure measuring element 15 is used to detect the steam pressure at the outlet of the steam heater 6. The combination of the two ensures that the steam has a certain degree of superheat after passing through the steam heater 6.

[0042] In some optional embodiments, a water spray desuperheater 14 is further provided on the steam bypass 8. The water spray desuperheater 14 is a component on the original equipment. When a π-type furnace without a starting circulation pump burns lean coal or other types of coal, the screen is prone to overheating during the startup phase, that is, before the start-up and during low-load operation after grid connection, and a large amount of cooling water needs to be injected using the water spray desuperheater 14.

[0043] The heat exchange system for steam heating flue gas during the boiler startup phase also includes other structures in the economizer, such as Figure 1 The green structure in the present invention is not protected in the present invention, so it will not be described in detail.

[0044] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A heat exchange system for steam heating flue gas during boiler startup, characterized in that: include: A boiler outlet flue (1), wherein an electric adjustment damper (3) is provided on the boiler outlet flue (1), a flue gas bypass (5) is arranged in parallel with the boiler outlet flue (1), and a steam heater (6) is provided on the flue gas bypass (5); The steam bypass (8) is arranged in parallel with the low-temperature superheater to platen superheater connecting pipe (2), is led out from the outlet of the low-temperature superheater (7), passes through the steam heater (6), and returns to the low-temperature superheater to platen superheater connecting pipe (2). The steam heater (6) is also arranged on the steam bypass (8), and the steam at the outlet of the low-temperature superheater (7) is used to heat the flue gas at the inlet of the denitration reactor (4) through the steam bypass (8) via the steam heater (6).

2. The heat exchange system for steam heating flue gas during boiler startup according to claim 1, characterized in that: A first electric shutoff damper (10) is also provided on the boiler outlet flue (1), and the first electric shutoff damper (10) is located at one end close to the denitration reactor (4).

3. The heat exchange system for steam heating flue gas during boiler startup according to claim 2, characterized in that: A second electric shutoff damper (11) is also provided on the flue gas bypass (5).

4. The heat exchange system for steam heating flue gas during boiler startup according to claim 3, characterized in that: There are two second electric shutoff dampers (11), which are located on both sides of the flue gas bypass (5).

5. The heat exchange system for steam heating flue gas during the boiler startup phase according to any one of claims 1 to 4, characterized in that: The steam bypass (8) is provided with an electric switch (12). There are three electric switch (12), two of which are arranged on the steam bypass (8), respectively at the inlet and outlet of the steam heater (6), and one is arranged on the connecting pipe (2) from the low-temperature superheater to the platen superheater.

6. The heat exchange system for steam heating flue gas during boiler startup according to claim 5, characterized in that: The electric on-off component (12) is an electric gate valve.

7. The heat exchange system for steam heating flue gas during boiler startup according to claim 5, characterized in that: The steam bypass (8) is also provided with a temperature measuring element (13) and a pressure measuring element (15).

8. The heat exchange system for steam heating flue gas during boiler startup according to claim 7, characterized in that: The temperature measuring element (13) is a temperature sensor, and the pressure measuring element (15) is a pressure transmitter.

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