Boiling type coal economizer tube group denitration inlet flue gas temperature lifting system and lifting method

Abstract

The application provides a denitration inlet flue gas temperature lifting system of a boiling type economizer tube group, which comprises a feedwater main pipeline and a first feedwater branch pipeline; a first economizer tube group and a second economizer tube group are sequentially arranged on the feedwater main pipeline, and a first valve is arranged on the upstream side of the first economizer tube group on the feedwater main pipeline; the upstream end of the first feedwater branch pipeline is connected to the feedwater branch pipeline, and the connection position is located on the upstream side of the first valve; the downstream end of the first feedwater branch pipeline is connected to the feedwater branch pipeline, and the connection position is located between the first economizer tube group and the second economizer tube group; a second regulating valve is arranged on the first feedwater branch pipeline. Under high load conditions, the feedwater absorbs more heat through all the economizer tube groups; under low load conditions, the first economizer tube group is shielded, and the heat absorption amount of the feedwater is reduced. Therefore, the application can shield different economizers, reduce the heat absorption amount of the feedwater in the economizer, increase the flue gas temperature at the economizer outlet, and adjust the denitration inlet flue gas temperature.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation system technology, and in particular to a denitrification inlet flue gas temperature enhancement system and method for a fluidized bed economizer tube group. Background Technology

[0002] Currently, thermal power units are frequently operating under peak shaving conditions. During the deep peak shaving phase, the flue gas temperature at the denitrification inlet does not meet the operating requirements. Common methods to increase the flue gas temperature at the denitrification inlet include: flue gas bypass, economizer grading, economizer water-side bypass, hot water recirculation, and No. 0 high-pressure heater.

[0003] The methods mentioned above have various problems in terms of economy and unit performance, and cannot make step-by-step adjustments based on the changing flue gas temperature at the denitrification inlet under different unit loads. Summary of the Invention

[0004] The purpose of this invention is to provide a denitrification inlet flue gas temperature enhancement system and method for a fluidized bed economizer tube group, which can adjust the denitrification inlet flue gas temperature in stages for different operating conditions of the unit, such as high load, low load and even lower load.

[0005] This invention provides a denitrification inlet flue gas temperature enhancement system for a boiling economizer tube group, comprising a main water supply pipeline and a first water supply branch pipeline; a first economizer tube group and a second economizer tube group are sequentially arranged on the main water supply pipeline, and a first valve is provided on the upstream side of the first economizer tube group on the main water supply pipeline; the upstream end of the first water supply branch pipeline is connected to the water supply branch pipe, and the connection point is located upstream of the first valve; the downstream end of the first water supply branch pipeline is connected to the water supply branch pipe, and the connection point is located between the first economizer tube group and the second economizer tube group; a second regulating valve is provided on the first water supply branch pipeline.

[0006] Furthermore, it also includes a second water supply branch pipeline, the upstream end of which is connected to the first water supply branch pipeline, and the connection point is located upstream of the second regulating valve; the downstream end of the second water supply branch pipeline is connected to the main water supply pipeline, and the connection point is located downstream of the second economizer tube group; a fourth regulating valve is provided on the second water supply branch pipeline.

[0007] Furthermore, an economizer inlet header is connected to the main water supply line, and the economizer inlet header is located between the first valve and the first economizer pipe assembly.

[0008] Furthermore, an economizer intermediate header is connected to the main water supply pipeline, and the economizer intermediate header is located between the first economizer pipe group and the second economizer pipe group, and the first water supply branch pipeline is connected to the economizer intermediate header.

[0009] Furthermore, the main water supply pipeline is connected to an economizer outlet mixing header, and the economizer outlet mixing header is located downstream of the second economizer pipe group. The second water supply branch pipeline is connected to the economizer outlet mixing header, and a temperature measuring point is provided on the economizer outlet mixing header.

[0010] Furthermore, a first regulating pipeline is connected to the main water supply pipeline, and the two ends of the first regulating pipeline are respectively connected to the upstream side and the downstream side of the first valve. A first regulating valve is provided on the first regulating pipeline.

[0011] Furthermore, a second regulating pipe is connected to the first water supply branch pipe, and the two ends of the second regulating pipe are respectively connected to the upstream side and the downstream side of the second regulating valve. A third regulating valve is provided on the second regulating pipe.

[0012] The present invention also provides a method for raising the denitrification inlet flue gas temperature of the boiling economizer tube group. Under high load conditions, when the denitrification inlet flue gas temperature can meet the denitrification requirements, the first valve is opened and the second and fourth regulating valves are closed. The feedwater passes through the first economizer tube group and the second economizer tube group in sequence along the feedwater main pipeline and enters the economizer outlet header.

[0013] Furthermore, under low-load conditions, when the denitrification inlet flue gas temperature is low and deviates little from the normal operating temperature of the catalyst, the first economizer pipe group is shielded by the following steps: close the first valve and the fourth regulating valve, open the second regulating valve, and allow feedwater to enter the main feedwater pipeline along the first feedwater branch pipeline, and then enter the economizer outlet header through the second economizer pipe group; under even lower load conditions, when the denitrification inlet flue gas temperature deviates significantly from the normal operating temperature of the catalyst, the first and second economizer pipe groups are shielded by the following steps: open the fourth regulating valve, close the first valve and the second regulating valve, and allow feedwater to enter the second regulating branch pipeline along the first regulating branch pipeline, and then enter the economizer outlet header.

[0014] Furthermore, under lower load conditions, the third regulating valve is opened simultaneously to ensure that water can flow smoothly back into the first economizer tube group; when the first valve is closed to shield the economizer tube group, the first regulating valve is opened to control part of the feedwater to flow through the economizer tube group to prevent steam lock.

[0015] The technical solution of this invention involves installing a first economizer tube group and a second economizer tube group (or more) on the main feedwater pipeline. Under high-load conditions, when the denitrification inlet flue gas temperature meets the denitrification requirements, the feedwater passes through all economizer tube groups sequentially, absorbing a significant amount of heat. Under low-load conditions, when the denitrification inlet flue gas temperature is lower and deviates only slightly from the normal operating temperature of the catalyst, the first valve can be closed and the second regulating valve opened, allowing the feedwater to enter the main feedwater pipeline through the first feedwater branch pipeline and then pass through the second economizer tube group. This effectively shields the first economizer tube group, reducing the heat absorbed by the feedwater within it. Therefore, this invention can address different operating conditions of the unit under high and low loads by shielding different economizers, thereby reducing the heat absorbed by the feedwater in the economizers and ultimately increasing the economizer outlet flue gas temperature. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the overall system of the present invention;

[0018] Explanation of reference numerals in the attached figures:

[0019] 1-Main water supply line; 201-First water supply branch line; 202-Second water supply branch line; 3-First economizer pipe group; 4-Second economizer pipe group; 5-First valve; 6-First regulating valve; 7-Second regulating valve; 8-Third regulating valve; 9-Fourth regulating valve; 10-Stop valve; 11-Economizer inlet header; 12-Economizer intermediate header; 13-Economizer outlet mixing header; 14-Temperature measuring point; 15-Economizer outlet header; 16-Water supply. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0023] Example 1

[0024] like Figure 1 As shown, the present invention provides a denitrification inlet flue gas temperature enhancement system for a boiling economizer tube group, including a main water supply pipeline 1 and a first water supply branch pipeline 201; a first economizer tube group 3 and a second economizer tube group 4 are sequentially arranged on the main water supply pipeline 1, and a first valve 5 is provided on the upstream side of the first economizer tube group 3 on the main water supply pipeline 1; the upstream end of the first water supply branch pipeline 201 is connected to the water supply branch pipe, and the connection point is located upstream of the first valve 5; the downstream end of the first water supply branch pipeline 201 is connected to the water supply branch pipe, and the connection point is located between the first economizer tube group 3 and the second economizer tube group 4; a second regulating valve 7 is provided on the first water supply branch pipeline 201.

[0025] Specifically, in this invention, the economizer inlet water supply pipeline has at least two water supply lines:

[0026] Under high-load conditions, when the denitrification inlet flue gas temperature meets the denitrification requirements, the first valve 5 (gate valve) is opened, and the first regulating valve 6, the second regulating valve 7, the third regulating valve 8, and the fourth regulating valve 9 (all electrically operated regulating valves) are closed, along with the electrically operated shut-off valves 10 installed upstream and downstream of the first regulating valve 6, the second regulating valve 7, the third regulating valve 8, and the fourth regulating valve 9. Feedwater 16 flows sequentially through the economizer inlet header 11, the first economizer tube group 3, the economizer intermediate header 12, the second economizer tube group 4, and the economizer suspension pipe along the main feedwater pipeline 1, finally entering the economizer outlet header 15. In this process, feedwater 16 absorbs heat from the first economizer tube group 3 and the second economizer tube group 4, maintaining the denitrification inlet flue gas temperature without a relative increase.

[0027] Under low-load conditions, when the denitrification inlet flue gas temperature is relatively low and deviates only slightly from the normal operating temperature of the catalyst, only the first economizer tube group 3 needs to be shielded. This requires closing the first valve 5 (gate valve), the third regulating valve 8, the fourth regulating valve 9, and the corresponding electric shut-off valve 10, while opening the second regulating valve 7 and the corresponding electric shut-off valve 10. This allows the feedwater to pass through the economizer intermediate header 12, the second economizer tube group 4, and the economizer suspension pipe into the economizer outlet header 15. In this process, the feedwater 16 only absorbs heat from the second economizer tube group 4 (the first economizer tube group 3 is shielded), thus reducing the heat absorption of the feedwater 16 in the economizer. Consequently, the economizer outlet flue gas temperature increases, while the denitrification inlet flue gas temperature increases relatively slightly.

[0028] Example 2

[0029] It also includes a second water supply branch pipe 202, the upstream end of which is connected to the first water supply branch pipe 201, and the connection point is located upstream of the second regulating valve 7; the downstream end of the second water supply branch pipe 202 is connected to the main water supply pipe 1, and the connection point is located downstream of the second economizer pipe group 4; a fourth regulating valve 9 is provided on the second water supply branch pipe 202.

[0030] Specifically, the second water supply branch pipe 202 is used to shield the second economizer pipe group 4. When more economizer pipe groups are set, more water supply branch pipes can also be set accordingly.

[0031] Under lower load conditions (very low load before and after unit grid connection), when the denitrification inlet flue gas temperature deviates significantly from the normal catalyst operating temperature, it is necessary to simultaneously shield the first economizer tube group 3 and the second economizer tube group 4. This requires opening the fourth regulating valve 9 and its corresponding electric shut-off valve 10, while closing the first valve 5 (gate valve), the second regulating valve 7, and its corresponding electric shut-off valve 10. This allows feedwater 16 to enter the economizer tube group outlet mixing header and then, through the economizer suspension pipe, into the economizer outlet header 15. In this process, feedwater 16 does not absorb heat from the first economizer tube group 3 and the second economizer tube group 4 (both are shielded), further reducing the heat absorption of feedwater 16 in the economizer. Consequently, the economizer outlet flue gas temperature increases further, resulting in a relatively large increase in the denitrification inlet flue gas temperature.

[0032] Example 3

[0033] An economizer inlet header 11 is connected to the main water supply line 1, and the economizer inlet header 11 is located between the first valve 5 and the first economizer tube group 3. An economizer intermediate header 12 is connected to the main water supply line 1, and the economizer intermediate header 12 is located between the first economizer tube group 3 and the second economizer tube group 4. The first water supply branch line 201 is connected to the economizer intermediate header 12. An economizer outlet mixing header 13 is connected to the main water supply line 1, and the economizer outlet mixing header 13 is located downstream of the second economizer tube group 4. The second water supply branch line 202 is connected to the economizer outlet mixing header 13. A temperature measuring point 14 is provided on the economizer outlet mixing header 13. The temperature of the economizer outlet mixing header 13 can be detected through the temperature measuring point 14, and the shielding of the first economizer tube group 3 and the second economizer tube group 4 can be adjusted according to the temperature. A first regulating pipe is connected to the main water supply pipeline 1. The two ends of the first regulating pipe are connected to the upstream and downstream sides of the first valve 5, respectively. A first regulating valve 6 is installed on the first regulating pipe. A second regulating pipe is connected to the first water supply branch pipeline 201. The two ends of the second regulating pipe are connected to the upstream and downstream sides of the second regulating valve 7, respectively. A third regulating valve 8 is installed on the second regulating pipe.

[0034] Specifically, by simultaneously opening the third regulating valve 8 and the corresponding electric shut-off valve 10 through the first and second regulating pipelines, water can be smoothly backflowed into the first economizer tube group 3. When the first valve 5 is closed to shield the economizer tube group, the first regulating valve 6 and the corresponding electric shut-off valve 10 are opened to control a smaller flow of feedwater 16 through the economizer tube group to prevent steam lock.

[0035] This invention effectively prevents thermal shock to the economizer tube assembly caused by the large temperature difference between the feedwater 16 and the economizer tube wall when switching between two feedwater lines. When the economizer tube assembly is shielded, feedwater is backflowed into the economizer tube assembly through the economizer intermediate header 12 or the economizer outlet header 15 to prevent the economizer tube assembly from dry burning, thereby avoiding strong shock during feedwater line switching. When switching from one or two bypass economizers to the normal feedwater flow during unit load increase, the temperature of the economizer tube assembly can be effectively reduced by gradually opening the bypass regulating valve before switching, avoiding thermal shock caused by temperature difference. The unit load reduction process is the opposite.

[0036] Example 4

[0037] The present invention also provides a method for raising the denitrification inlet flue gas temperature of the boiling economizer tube group. Under high load conditions, when the denitrification inlet flue gas temperature can meet the denitrification requirements, the first valve 5 is opened, the second regulating valve 7 and the fourth regulating valve 9 are closed, and the feedwater enters the economizer outlet header 15 through the first economizer tube group 3 and the second economizer tube group 4 along the feedwater main pipeline 1. Under low load conditions, when the denitrification inlet flue gas temperature is low and deviates little from the normal operating temperature of the catalyst, the first economizer pipe group 3 is shielded by the following steps: close the first valve 5 and the fourth regulating valve 9, open the second regulating valve 7, and feedwater enters the feedwater main pipe 1 along the first feedwater branch pipe 201, and then enters the economizer outlet header 15 through the second economizer pipe group 4; under even lower load conditions, when the denitrification inlet flue gas temperature deviates significantly from the normal operating temperature of the catalyst, the first economizer pipe group 3 and the second economizer pipe group 4 are shielded by the following steps: open the fourth regulating valve 9, close the first valve 5 and the second regulating valve 7, and feedwater enters the second regulating branch pipe along the first regulating branch pipe, and then enters the economizer outlet header 15.

[0038] Specifically, under high-load conditions, when the denitrification inlet flue gas temperature meets the denitrification requirements, the first valve 5 (gate valve) is opened, and the first regulating valve 6, the second regulating valve 7, the third regulating valve 8, and the fourth regulating valve 9 (all electrically operated regulating valves) are closed, along with the electrically operated shut-off valves 10 installed upstream and downstream of the first regulating valve 6, the second regulating valve 7, the third regulating valve 8, and the fourth regulating valve 9. The feedwater flows sequentially through the economizer inlet header 11, the first economizer pipe group 3, the economizer intermediate header 12, the second economizer pipe group 4, and the economizer suspension pipe along the main feedwater pipeline 1, finally entering the economizer outlet header 15. In this process, the feedwater 16 absorbs heat from the first economizer pipe group 3 and the second economizer pipe group 4, maintaining the denitrification inlet flue gas temperature without a relative increase.

[0039] Under low-load conditions, when the denitrification inlet flue gas temperature is low and deviates only slightly from the normal operating temperature of the catalyst, only the first economizer tube group 3 needs to be shielded. This requires closing the first valve 5 (gate valve), the third regulating valve 8, the fourth regulating valve 9, and the corresponding electric shut-off valve 10, while opening the second regulating valve 7 and the corresponding electric shut-off valve 10. This allows feedwater to pass through the economizer intermediate header 12, the second economizer tube group 4, and the economizer suspension pipe into the economizer outlet header 15. In this process, the feedwater only absorbs heat from the second economizer tube group 4 (the first economizer tube group 3 is shielded), thus reducing the heat absorption of the feedwater 16 in the economizer. This results in an increase in the economizer outlet flue gas temperature and a relatively small increase in the denitrification inlet flue gas temperature.

[0040] Under lower load conditions (very low load before and after unit grid connection), when the denitrification inlet flue gas temperature deviates significantly from the normal catalyst operating temperature, it is necessary to simultaneously shield the first economizer tube group 3 and the second economizer tube group 4. This requires opening the fourth regulating valve 9 and its corresponding electric shut-off valve 10, while closing the first valve 5 (gate valve), the second regulating valve 7, and its corresponding electric shut-off valve 10. This allows feedwater to enter the economizer tube group outlet mixing header and then, through the economizer suspension pipe, into the economizer outlet header 15. In this process, the feedwater does not absorb heat from the first economizer tube group 3 and the second economizer tube group 4 (both are shielded), further reducing the heat absorption of the feedwater 16 in the economizer. Consequently, the economizer outlet flue gas temperature increases further, resulting in a relatively large increase in the denitrification inlet flue gas temperature.

[0041] This invention proposes a denitrification inlet flue gas temperature enhancement system and method for thermal power units with multiple economizer tube groups in the boiler tail flue. Depending on the load, the air preheater outlet flue gas temperature varies. By shielding the first economizer tube group 3 or simultaneously shielding the first economizer tube group 3 and the second economizer tube group 4, the feedwater 16 flowing through the economizer is partially or completely short-circuited, reducing the heat absorption of the feedwater in the economizer, thereby increasing the economizer outlet flue gas temperature.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A denitrification inlet flue gas temperature enhancement system for a fluidized bed economizer tube assembly, characterized in that, This includes the main water supply pipeline and the first branch water supply pipeline; The main water supply line is provided with a first economizer pipe group and a second economizer pipe group in sequence, and a first valve is provided on the main water supply line upstream of the first economizer pipe group. The upstream end of the first water supply branch pipe is connected to the main water supply pipe, and the connection point is located upstream of the first valve; the downstream end of the first water supply branch pipe is connected to the main water supply pipe, and the connection point is located between the first economizer pipe group and the second economizer pipe group; a second regulating valve is provided on the first water supply branch pipe; It also includes a second water supply branch pipeline, the upstream end of which is connected to the first water supply branch pipeline, and the connection point is located upstream of the second regulating valve; the downstream end of the second water supply branch pipeline is connected to the main water supply pipeline, and the connection point is located downstream of the second economizer tube group; a fourth regulating valve is provided on the second water supply branch pipeline. The main water supply pipeline is connected to a first regulating pipeline, the two ends of which are respectively connected to the upstream side and the downstream side of the first valve, and the first regulating pipeline is equipped with a first regulating valve. The first water supply branch pipe is connected to a second regulating pipe, the two ends of which are respectively connected to the upstream side and the downstream side of the second regulating valve, and a third regulating valve is provided on the second regulating pipe; When the first valve is closed to shield the economizer tube group via the first and second regulating pipelines, the third regulating valve and the corresponding electric shut-off valve are opened simultaneously. The first regulating valve and the corresponding electric shut-off valve are opened to control a smaller flow rate of feedwater to flow back to the first economizer tube group through the economizer intermediate header, preventing the economizer tube group from dry burning and preventing steam lock, thereby avoiding strong impacts when switching the feedwater pipeline.

2. The denitrification inlet flue gas temperature enhancement system for the fluidized bed economizer tube group according to claim 1, characterized in that, An economizer inlet header is connected to the main water supply line, and the economizer inlet header is located between the first valve and the first economizer pipe assembly.

3. The denitrification inlet flue gas temperature enhancement system for the fluidized bed economizer tube group according to claim 1, characterized in that, An economizer intermediate header is connected to the main water supply pipeline, and the economizer intermediate header is located between the first economizer pipe group and the second economizer pipe group. The first water supply branch pipeline is connected to the economizer intermediate header.

4. The denitrification inlet flue gas temperature enhancement system for the fluidized bed economizer tube group according to claim 1, characterized in that, The main water supply pipeline is connected to an economizer outlet mixing header, which is located downstream of the second economizer pipe group. The second water supply branch pipeline is connected to the economizer outlet mixing header, and a temperature measuring point is provided on the economizer outlet mixing header.

5. A method for raising the inlet flue gas temperature of the denitrification system based on the fluidized bed economizer tube group as described in claim 1, characterized in that, Under high load conditions, when the flue gas temperature at the denitrification inlet meets the denitrification requirements, the first valve is opened and the second and fourth regulating valves are closed. The feedwater flows along the main feedwater pipeline through the first economizer pipe group and the second economizer pipe group in sequence into the economizer outlet header.

6. The method for raising the inlet flue gas temperature of the denitrification system for the fluidized bed economizer tube group according to claim 5, characterized in that, Under low load conditions, when the inlet flue gas temperature of the denitrification system is low and deviates little from the normal operating temperature of the catalyst, the first economizer pipe group is shielded by the following steps: close the first valve and the fourth regulating valve, open the second regulating valve, and feedwater enters the main feedwater pipeline along the first feedwater branch pipeline, and then enters the economizer outlet header through the second economizer pipe group. When the flue gas temperature at the denitrification inlet deviates significantly from the normal operating temperature of the catalyst under lower load conditions, the first and second economizer tube groups should be shielded by following these steps: Open the fourth regulating valve, close the first and second regulating valves, and allow the feedwater to enter the second regulating branch pipe along the first regulating branch pipe and then into the economizer outlet header.

7. The method for raising the inlet flue gas temperature of the denitrification system for the fluidized bed economizer tube group according to claim 6, characterized in that, Under lower load conditions, the third regulating valve is opened simultaneously to ensure that water can be smoothly backflowed into the first economizer tube group; when the first valve is closed to shield the economizer tube group, the first regulating valve is opened to control part of the feedwater to flow through the economizer tube group to prevent steam lock.

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